FURNACE FOR SINTERING PRINTED OBJECTS

- Desktop Metal, Inc.

A furnace system for printing an object using additive manufacturing. The furnace system may include a furnace chamber; an outlet fluidly coupled to the furnace chamber for removal of an exhaust gas from the furnace chamber; a conduit fluidly coupled to the outlet; an oxygen injector fluidly coupled to the conduit; an isolation system fluidly coupled to the conduit between the furnace chamber and the oxygen injector; and a catalyst enclosure comprising an oxidizing catalyst.

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Description
CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of priority of U.S. Provisional Application No. 62/853,561, filed May 28, 2019, the entirety of which is incorporated by reference into this application.

DESCRIPTION Technical Field

Various aspects of the present disclosure relate generally to systems and methods for sintering printed objects.

Background of the Disclosure

Metal injection molding (MIM) is a metalworking process useful in creating a variety of metal objects. For example, a mixture of powdered metal and one or more binders (e.g., a polymer such as polypropylene) may form a “feedstock” capable of being molded, at a high temperature, into the shape of a desired object. The initial molded part, also referred to as a “green part,” may then undergo a chemical preliminary debinding process to remove primary binder while leaving secondary binder intact, followed by a sintering process. During sintering, the part may be brought to a temperature near the melting point of the powdered metal, which may thermally decompose any remaining binder and form the metal powder into a solid mass, thereby producing the desired metal object.

Additive manufacturing, also referred to as three-dimensional (3D) printing, includes a variety of techniques for manufacturing a three-dimensional object via a process of forming successive layers of the object. Three-dimensional printers may in some embodiments utilize a feedstock comparable to that used in MIM, thereby creating a green part without the need for a mold. The green part may then undergo debinding and sintering processes to produce the object.

In addition to MIM based additive manufacturing, there are systems using powder beds and loose powder, optical resin curing, and others. Many such methods require a furnace process to produce the final part or to enhance the properties of the part. The materials making up the part may include ceramics and composites as well as metals. Additionally, there are conventional materials that can benefit from furnace processing.

SUMMARY OF THE DISCLOSURE

Examples of the present disclosure relate to, among other things, systems and methods for sintering printed objects. Each of the examples disclosed herein may include one or more of the features described in connection with any of the other disclosed examples.

According to certain aspects of the present disclosure, systems and methods are disclosed for sintering printed objects. One embodiment provides a furnace system comprising: a furnace chamber defining an interior region, wherein the furnace chamber is configured to maintain an atmosphere substantially free of oxygen within the interior region; an outlet fluidly coupled to the furnace chamber for removal of an exhaust gas from the furnace chamber; a conduit fluidly coupled to the outlet; an oxygen injector fluidly coupled to the conduit, wherein the oxidizing injector is positioned downstream of the furnace chamber and is configured to introduce an oxidizing gas into the exhaust gas; an isolation system fluidly coupled to the conduit between the furnace chamber and the oxygen injector, wherein the isolation system is configured to prevent a backflow of the oxidizing gas into the furnace chamber; and a catalyst enclosure comprising an oxidizing catalyst, wherein the catalyst enclosure is configured to receive a mixture of the exhaust gas and the oxidizing gas.

One embodiment provides a furnace system comprising: a furnace chamber defining an interior region, wherein the furnace chamber is configured to maintain an atmosphere substantially free of oxygen within the interior region; an outlet fluidly coupled to the furnace chamber for removal of an exhaust gas from the furnace chamber; a binder trap system fluidly coupled to the outlet; an isolation system fluidly coupled to the binder trap system, wherein the isolation system is positioned downstream of the binder trap system and is configured to prevent a backflow of an oxidizing gas into the furnace chamber; a catalyst enclosure comprising an oxidizing catalyst, wherein the catalyst enclosure is positioned downstream of the isolation system and is configured to receive a mixture of the exhaust gas and the oxidizing gas; and an oxygen injector fluidly coupled to at least one of the isolation system or the catalyst enclosure, wherein the oxidizing injector is positioned downstream of the furnace chamber and is configured to introduce the oxidizing gas into the exhaust gas.

One embodiment provides a furnace system comprising: a furnace chamber defining an interior region, wherein the furnace chamber is configured to maintain an atmosphere substantially free of oxygen within the interior region; an outlet fluidly coupled to the furnace chamber for removal of an exhaust gas from the furnace chamber; an isolation system fluidly coupled to the outlet, wherein the isolation system is configured to prevent a backflow of an oxidizing gas into the furnace chamber; a binder cracking system fluidly coupled to the isolation system, wherein the binder cracking system is positioned downstream of the isolation system; a catalyst enclosure comprising an oxidizing catalyst, wherein the catalyst enclosure is positioned downstream of the isolation system and is configured to receive a mixture of the exhaust gas and the oxidizing gas; and an oxygen injector fluidly coupled to at least one of the isolation system or the catalyst enclosure, wherein the oxidizing injector is positioned downstream of the furnace chamber and is configured to introduce the oxidizing gas into the exhaust gas.

Both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the features, as claimed. As used herein, the terms “comprises,” “comprising,” “including,” “having,” or other variations thereof, are intended to cover a non-exclusive inclusion such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements, but may include other elements not expressly listed or inherent to such a process, method, article, or apparatus. Additionally, the term “exemplary” is used herein in the sense of “example,” rather than “ideal.” It should be noted that all numeric values disclosed or claimed herein (including all disclosed values, limits, and ranges) may have a variation of +/−10% (unless a different variation is specified) from the disclosed numeric value. In this disclosure, unless stated otherwise, relative terms, such as, for example, “about,” “substantially,” and “approximately” are used to indicate a possible variation of ±10% in the stated value. Moreover, in the claims, values, limits, and/or ranges of various claimed elements and/or features means the stated value, limit, and/or range +/−10%. The terms “object,” “part,” and “component,” as used herein, are intended to encompass any object fabricated using the additive manufacturing techniques described herein.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate various exemplary embodiments and together with the description, serve to explain the principles of the disclosed embodiments. There are many aspects and embodiments described herein. Those of ordinary skill in the art will readily recognize that the features of a particular aspect or embodiment may be used in conjunction with the features of any or all of the other aspects or embodiments described in this disclosure.

FIG. 1 is a block diagram of an exemplary furnace system, according to one embodiment of the disclosure.

FIG. 2A is a block diagram of an exemplary furnace system, according to one embodiment of the disclosure.

FIG. 2B depicts an exemplary isolation system, according to one embodiment of the disclosure.

FIG. 3 is a block diagram of an exemplary furnace system, according to one embodiment of the disclosure.

FIG. 4 is a block diagram of an exemplary furnace, system according to one embodiment of the disclosure.

FIG. 5 is a block diagram of an exemplary furnace system, according to one embodiment of the disclosure.

FIG. 6 is a block diagram of an exemplary furnace system, according to one embodiment of the disclosure.

FIG. 7 is a block diagram of an exemplary furnace system, according to one embodiment of the disclosure.

FIG. 8 is a block diagram of an exemplary furnace system, according to one embodiment of the disclosure.

FIG. 9A is a block diagram of an exemplary furnace system, according to one embodiment of the disclosure.

FIG. 9B is a block diagram of an exemplary furnace system, according to one embodiment of the disclosure.

FIG. 9C is a block diagram of part of the exemplary furnace system of FIG. 9B, according to one embodiment of the disclosure.

FIGS. 9D-9F depict exemplary data plots related to the part of the exemplary furnace system of FIG. 9C.

FIG. 10 is a block diagram of an exemplary furnace system, according to one embodiment of the disclosure.

FIG. 11 is a block diagram of an exemplary furnace system, according to one embodiment of the disclosure.

FIG. 12A is a block diagram of an additive manufacturing system according to some embodiments of the disclosure.

FIG. 12B illustrates an exemplary printing subsystem of the system of FIG. 12A.

FIG. 12C illustrates an exemplary debinding subsystem of the system of FIG. 12A.

FIG. 13A is a block diagram of an additive manufacturing system according to some embodiments of the disclosure.

FIG. 13B illustrates an exemplary printing subsystem of the system of FIG. 13A.

FIG. 13C illustrates another exemplary printing subsystem of the system of FIG. 13A.

FIG. 14 depicts an exemplary computer device or system, in which embodiments of the present disclosure, or portions thereof, may be implemented.

 DETAILED DESCRIPTION

Embodiments of the present disclosure include systems and methods to facilitate and improve the efficacy and/or efficiency of sintering printed objects. Reference now will be made in detail to examples of the present disclosure described above and illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts.

An additive manufacturing process may produce an initial “green” (unsintered) part, e.g., a printed part, which may undergo further processing to generate a finished part. This processing may include debinding, such as any combination of chemical debinding (i.e., removing various binder components through the use of solvents), reactive debinding (i.e., exposing the parts to material, such as a gas, that reacts or causes a reaction with binder components(s) or other materials present in the part or with the metal or other particles that make up the part to cross-link or otherwise render the binder components or other materials more easily removed), and/or thermal debinding (i.e., utilizing heat to evaporate or decompose binder components and other materials present within the part). In some instances, the further processing may be a sintering process.

A sintering process, in the context of the current disclosure, refers to when a part is heated in a furnace chamber to bring its temperature near the melting point of the powdered metal. As the green part is heated, in some embodiments, thermal debinding may first occur, during which any remaining binder components may be thermally decomposed (hereinafter referred to as a “thermal debinding process”). Then, as the part is heated to just below the melting point of the metal powder from which it is formed, the metal powder may densify into a solid mass (hereinafter referred to as a “main sintering process”), thereby producing the finished part. As used herein, “sintering process” may refer to heating a part in a furnace chamber, which may include thermal debinding, main sintering, or both. Any sintering process or furnace process may be utilized with respect to the embodiments disclosed herein. The sintering process may produce a gaseous effluent, particularly during thermal debinding, which may be pumped out of the furnace chamber and directed through an exhaust channel. In some embodiments, the gaseous effluent may include the volatilized binder components generated during the thermal debinding process. In some instances, the gaseous effluent may include hydrocarbons, carbon monoxide, hydrogen and/or other gases that may be harmful in certain conditions.

Conventional methods of filtering such gaseous effluents produced during a sintering process within a furnace chamber are generally not suitable for an office environment where air quality in the office and local outdoor environments have stringent standards. As such, there is a need for an improved method of filtering gaseous effluents produced during a sintering process and for controlling the sintering process accordingly.

Embodiments of the present disclosure may address one or more of these problems, or address other aspects of the prior art.

FIG. 1 is a block diagram of a furnace system 100 according to exemplary embodiments. The furnace system 100 may include a furnace chamber 102, an isolation system 104, an oxidizing gas source 106, an air injector 109 (also referred to as an oxygen injector, which may introduce air or oxygen gas into the system), a catalytic converter system 110, a CO detector 112, one or more pressure regulated gas sources 114, a controller 116, and a power source 118. The furnace system 100 may further include various thermocouples, valves, pressure gauges, and mass flow controllers (MFCs), as will be described in further detail below.

The furnace chamber 102 may be a sealable and insulated chamber designed to enclose a controlled atmosphere substantially free of oxygen to prevent combustion. In the context of the current disclosure, a controlled atmosphere refers to an atmosphere being controlled for one or more of temperature, composition, and pressure. In the context of the current disclosure, an atmosphere substantially free of oxygen refers to an atmosphere that is free of oxygen or has levels of oxygen below a predetermined threshold amount of oxygen. For example, the predetermined threshold amount of oxygen may be, e.g., about 100 ppm of oxygen or less, for example, about 10 ppm or about 50 ppm of oxygen. In some embodiments, the atmosphere substantially free of oxygen may include inert gases, such as argon and/or nitrogen.

The furnace chamber 102 may include one or more heating elements 122 for heating the atmosphere enclosed within the furnace chamber 102. Although two heating elements 122 are depicted in FIG. 1, any suitable number of heating elements may be used. In some embodiments, the controller 116 may be configured to draw power from the power source 118 to heat the heating elements 122 in accordance with a predetermined heating profile for the furnace chamber 102. In some embodiments, the power source 118 may be an electrical power source (e.g., single phase analog current, three phase analog current, or direct current power source). Controller 116 may also be operably coupled to one or more thermocouples and/or pressure gauges and/or other components within the furnace system 100 to measure and/or control conditions within the furnace chamber 102. For example, a part 126 may be placed within the furnace chamber 102 for a sintering process. As part of the thermal debinding process, the furnace chamber 102 may be heated to a suitable temperature in order to degrade any binder components included in the part 126. In some instances, the furnace chamber 102 may be heated up to about 370 degrees Celsius or to about 500 degrees Celsius during the thermal debinding process, by which any binder components included in the part 126 may be volatilized.

As shown in FIG. 1, the furnace chamber 102 may include a retort 124 in which the part 126 is placed for a sintering process. In some embodiments, the retort 124 may include heat-conductive walls (e.g., graphite walls) to spread heat generated by the heating elements 122 within the furnace chamber 102, thereby enhancing temperature uniformity in a region where the part 126 is located. In some embodiments, the retort may 124 include a graphite box with walls partially or fully enclosing the region where the part 126 is located. In such embodiments, the retort 124 may be utilized as a microwave applicator.

In some embodiments, the controller 116 may be configured to control the atmosphere within the furnace chamber 102, such as the pressure and/or temperature within the furnace chamber 102. For example, the pressure within the furnace chamber 102 may be atmospheric, positive, or negative (e.g., a vacuum). In some embodiments, the atmospheric pressure may be up to 3 psi. In some embodiments, the atmospheric pressure may be higher, depending on the composition of the part 126 being processed within the furnace chamber 102.

As shown in FIG. 1, the furnace system 100 may include a controller 116, which may be operably connected to the various components included in the furnace system 100. In some embodiments, the controller 116 may be configured to control one or more processes, e.g., a thermal debinding process and main sintering process (e.g., densification), in the furnace system 100. In some embodiments, the controller 116 as described herein may be configured to control one or more processes in the various furnace systems disclosed herein, including furnace systems 200-1100. In some embodiments, the various components or subsets of components included in the furnace system 100 (or furnace systems 200-1100) may be in communication with one or more controllers, to which the controller 116 may be operably connected to. In such embodiments, the one or more controllers in addition to, or as an alternative to, the controller 116 may be configured to control one or more processes, e.g., a thermal debinding process and main sintering process (e.g., densification), in the furnace system 100 (or furnace systems 200-1100). In some embodiments, the one or more controllers in addition to, or as an alternative to, the controller 116 may be configured to control one or more processes in the various furnace systems disclosed herein.

Gaseous effluent may be released into the atmosphere of the chamber 102 as the part 126 is heated during the sintering process, e.g., during the thermal debinding process. In some embodiments, the gaseous effluent may be pumped out of the furnace chamber 102, flowed through the isolation system 104, and directed towards the catalytic converter system 110. The isolation system 104 may be configured to prevent any downstream fluid (e.g., gas, particularly oxygen gas) from flowing back towards the furnace chamber 102. In some embodiments, the isolation system 104 may comprise a vacuum pump, a venturi pump, or other suitable pump configured to pump this gaseous effluent from the furnace chamber 102 via one or more furnace exhaust conduits 103 through the isolation system 104. The gaseous effluent may then be directed towards the catalytic converter system 110 to remove volatilized binder component and/or other toxic fumes from the gaseous effluent.

In some embodiments, the furnace system 100 may include the air injector 109 as shown in FIG. 1. The air injector 109 may provide air injection from the oxidizing gas source 106. The oxidizing gas that flows through the air injector 109 may be directed towards the catalytic converter system 110. The oxidizing gas may be mixed with the gaseous effluent (a process also referred to as diluting the gaseous effluent) and directed towards the catalytic converter system 110. Although the furnace chamber 102 may need to be maintained at an atmosphere substantially free of oxygen, the catalytic converter system 110 needed to remove volatized binder component from the gaseous effluent may require oxygen to function properly. Accordingly, to achieve an office-safe furnace system 100, oxygen may actually need to be introduced into the system and mixed with the gaseous effluent before introduction into the catalytic converter system 110. As such, the catalytic converter system 110 may also be referred to as an oxidizing catalytic converter. In some embodiments, the oxidizing gas may be added to the catalyst enclosed in the catalytic converter system 110 when the temperature of the catalytic converter system 110 meets or exceeds a threshold temperature. The oxidizing gas flowing through the catalyst may remove excess heat and may cool the catalytic converter system 110. In some embodiments, the air injector 109 may be an air pump, an air compressor, and/or a compressed air source (e.g., bottled gas). Air injector 109 may introduce air, pure oxygen, or a mixture of oxygen and other gases into the system.

The catalytic converter system 110 may be configured to catalyze reactions to decompose various compounds in the furnace chamber 102 exhaust, i.e., the gaseous effluent, to safer compounds, such as water and CO2. In some embodiments, catalytic converter system 110 may be configured to combust volatilized binder components present in the gaseous effluent. In some embodiments, during the sintering cycle, carbon monoxide (CO) may be produced by the reduction of metal oxides with carbon in the metal. The catalytic converter system 110 may be configured to convert this CO to CO2. The catalytic converter system 110 may use oxidizing gas to combust volatilized binder components and/or oxidize CO present in the gaseous effluent. For example, the oxidizing gas provided by the air injector 109 may be used to combust volatilized binder components and/or oxidize CO present in the gaseous effluent.

In some embodiments, the catalytic converter system 110 may include a catalyst enclosure 111a and a catalyst heater 111b. In some embodiments, the catalyst heater 111b may be used to pre-heat the catalyst contained in the catalyst enclosure 111a before a sintering process in the furnace chamber 102. The catalyst contained in the catalyst enclosure 111a may generate heat when it reacts with the compounds in the furnace exhaust. As such, the catalyst heater 111b may cease heating the catalyst once the catalyst begins to react to the compounds in the gaseous effluent. In some instances, the catalyst may become overheated. In such instances, the sintering process in the furnace chamber 102 may be stopped. Additional methods of adjusting the temperature of overheated catalyst are described in further detail with reference to FIG. 11 below.

The isolation system 104 may be configured to prevent oxidizing gas from the oxidizing gas source 106 from flowing back into the furnace chamber 102. Specifically, the isolation system 104 may be configured to prevent oxidizing gas directed to and used in the catalytic converter system 110 from flowing back into the furnace chamber 102. As described above, the furnace chamber 102 maintains a controlled atmosphere substantially free of oxygen within the chamber in order to prevent combustion within the furnace chamber 102.

In some embodiments, the isolation system 104 may comprise a vacuum pump, as described above, to pump gaseous effluent from the furnace chamber 102 via one or more furnace exhaust conduits 103 through the isolation system 104 and towards the catalytic converter system 110. In some embodiments, the vacuum pump may include a ballast to provide an air injection from the oxidizing gas source 106. In such embodiments, an oxidizing gas may be directed to the vacuum pump, e.g., to a pump chamber or a discharge port of the vacuum pump, through a ballast port. In some embodiments, the gaseous effluent flowing out of the vacuum pump exhaust towards the catalytic converter system 110 may include pump oil. In some embodiments, the furnace system 100 may comprise a demister positioned adjacent to the vacuum pump exhaust. In such embodiments, the demister may be configured to remove and drain the pump oil back to the vacuum pump. Without the demister, the pump oil present in the gaseous effluent may enter the catalytic converter system 110, which may clog the catalytic converter system 110 and cause the enclosed catalyst to overheat. Further, the continuous loss of the pump oil may cause the vacuum pump to run dry and cause the vacuum pump to overheat. An embodiments of the vacuum pump and the demister is described in further detail below with reference to FIG. 11.

In some embodiments, the isolation system 104 may be configured to capture, neutralize, and/or chemically convert (hereinafter collectively referred to as “trap”) one or more compounds of the gaseous effluent. For example, the isolation system 104 may trap at least a portion of the volatilized binder components present in the gaseous effluent. Various embodiments of the isolation system 104 are described in further detail below with reference to FIGS. 2-10. In some embodiments, the furnace system 100 may further comprise a binder trap system, as described in further detail below with reference to FIGS. 6-8. In some embodiments, the furnace system 100 may further comprise a binder cracking system, as described in further detail below with reference to FIG. 5.

The pressure regulated gas source 114 may provide one or more gases to the furnace chamber 102 through a gas inlet 115 fluidly connected to the furnace chamber 102. In some embodiments, the one or more gases may include Ar, N2, forming gases (e.g., a non-explosive mixture of Ar—H2 or N2—H2), CO2, and/or air. In some embodiments, the gas inlet 115 may include a mass flow controller (MFC) 113 for controlled input of one or more gases to the furnace chamber 102. In some embodiments, there may be more than one pressure regulated gas source, each fluidly connected to the furnace chamber 102. Each of pressure regulated gas sources may comprise one or more dedicated gas inlets and MFCs. The furnace pressure may be controlled on the outlet side of furnace chamber 102. For example, the user may set the input flow via the MFC and the inlet pressure at the regulator. The regulator pressure may be set so that if the outlet becomes inoperative (e.g., clogged), the furnace may not over-pressurize to an unsafe condition. In some embodiments, for example, the furnace chamber may comprise a ceramic tube furnace chamber. In such embodiments, a regulator pressure may be set to 3 PSI for the pressure regulated gas source 114. In some embodiments, the furnace chamber may comprise a metal walled furnace chamber. In such embodiments, a regulator pressure may be set to 10 PSI for the pressure regulated gas source 114. In some embodiments, a regulator pressure may be set to more than 30 PSI for the pressure regulated gas source 114. The CO detector 112 may be located at an outlet of the catalytic converter system 110. The CO detector 112 may be communicatively connected to the controller 116 and may be used to monitor CO flowing out of the furnace system 100. In some embodiments, controller 116 may be configured to shut down the furnace system 100 if the CO detector 112 detects CO or detects an amount of CO that meets or exceeds a threshold safety value. In some embodiments, an alarm may be initiated if CO detector 112 detects CO or detects an amount of CO that meets or exceeds a threshold value. Although a CO detector 112 is shown in FIG. 1, it should be recognized that any type of detector or combination of detectors or number of detectors may be included in furnace system 100 (or furnace systems 200 through 1100) to confirm that gaseous exhaust exiting furnace system 100 (or furnace systems 200 through 1100) meets air quality safety standards to promote a safe environment around furnace system 100.

In some embodiments, the furnace system 100 (or furnace systems 200 through 1100) may include an O2 sensor located at the outlet of the catalytic converter system 110. The O2 sensor may be communicatively connected to the controller 116 and may monitor excess O2 flowing out of the furnace system 100. In some embodiments, the gas flow within the furnace system 100 may be reconfigured based on the monitored O2 level. For example, reaction air flow from pressure-regulated gas source 114 may be set to target correct values for excess O2 or a minimum setting. In some embodiments, a monitored excess O2 level flowing out of the furnace system 100 may indicate that there is no CO flowing out of the furnace system 100 or that there is less CO flowing out of the furnace system 100.

In some embodiments, the furnace system 100 (or furnace systems 200 through 1100) may include a hydrocarbon sensor located at the outlet of the catalytic converter system 110. The hydrocarbon sensor may be communicatively connected to the controller 116. In some embodiments, controller 116 may be configured to shut down the furnace system 100 if the hydrocarbon sensor detects hydrocarbon or detects an amount of hydrocarbon that meets or exceeds a threshold value. In some embodiments, an alarm may be initiated if hydrocarbon sensor detects hydrocarbon or detects an amount of hydrocarbon that meets or exceeds a threshold value.

FIG. 2A is a block diagram of a furnace system 200 according to one embodiment. Similar components in FIG. 2A may function similarly to what is described in reference to corresponding components in FIG. 1. As shown in FIG. 2A, the isolation system 104 may include a liquid bubbler 202. In this embodiment, the oxidizing gas source 106 may be fluidly connected via MFC2 to a conduit 206 between the isolation system 104 and the catalytic converter system 110. In some embodiments, the oxidizing gas source 106 may direct oxidizing gas towards the catalytic converter system 110 using a vacuum pump and/or the air injector 109, as described in reference to FIG. 1.

The liquid bubbler 202 may isolate the furnace chamber 102 from the oxidizing gas source 106 (e.g., a blower or compressed air) as described in further detail below with reference to FIG. 2B. FIG. 2B shows an expanded view of the liquid bubbler 202 of FIG. 2A according to one embodiment. The liquid bubbler 202 may include a first chamber 210a, a second chamber 210b, the furnace exhaust conduit 103, a connecting conduit 204 between the first and second chambers 210a-b, and an outlet conduit 206 from the second chamber 210b. The second chamber may be 210b partially filled with a liquid 218 to a certain height, H. In some embodiments, the liquid 218 may include an oil or other non-volatile liquid. For example, the liquid 218 may be a low vapor pressure liquid, such as hydrocarbon or silicone pump oils of diffusion pump oils. The liquid 218 may be an oil with a density of approximately 0.9 to 1.1 g/cc. As another example, the liquid 218 may be a liquid metal, e.g., liquid tin. In yet another example, the liquid may be liquid salt.

The liquid bubbler 202 may be configured to maintain a pressure difference P across the liquid bubbler 202 proportional to the height (H) of the liquid 218, the liquid density (rho), and gravitational constant (g), where P=rho·g·H. As an example, an oil with a density of approximately 0.9 to 1.1 g/cc and a liquid height of 10 cm may provide a pressure drop of about 100 Pa or about 0.014 PSI.

The furnace exhaust conduit 103 may be fluidly connected to an upper region of the first chamber 210a. The gaseous effluent evacuated from the furnace chamber 102 may be directed into the first chamber 210a through the furnace exhaust conduit 103. The furnace exhaust conduit 103 may be heated in order to prevent any condensation of high molecular weight species in the volatilized binder components present in the gaseous effluent.

The connecting conduit 204 may include two ends, a first end 212a which extends into the first chamber 210a and a second end 212b which extends into the second chamber 210b. In use, the first end 212a may draw in the gaseous effluent contained in the first chamber 210a. The second end 212b may allow the gaseous effluent drawn in from the first chamber 210a to flow into the second chamber 210b. The second end 212b may be positioned below a top surface of the liquid 218. For example, the second end 212b may be located in a central region or in a lower region of the second chamber 210b, as shown in FIG. 2B. The height, H, of the liquid 218 may be several times larger, e.g., at least 10 times larger, than the diameter of a gas bubble formed by the gaseous effluent bubbling through the liquid 218. In some embodiments, the liquid 218 may be approximately half the height of the second chamber 210b or more than half the height of the second chamber 210b. The first end 212a may be located near the bottom of the first chamber 210a such that in the event that the liquid 218 is sucked back into the first chamber, the vapor seal is maintained.

The liquid 218 in the second chamber 210b may effectively seal against backflow of oxidizing gas that may be introduced into the furnace system 200 further downstream of the liquid bubbler 202, preventing oxidizing gas from entering the furnace chamber 102. The volume of liquid 218 in the second chamber 210b should be less than the volume of the first chamber 210a in order to prevent liquid 218 from being sucked out of the second chamber 210b, through the first chamber 210a, and back into the upstream portion of the furnace system 200 in the event that inlet gas flow into the furnace chamber 102 via the gas inlet conduit 115 is stopped during furnace cooling.

The outlet conduit 206 may be located above the top surface of the liquid 218. In some embodiments, the outlet conduit 206 may be fluidly connected to the top or to an upper region of the second chamber 210b. In some embodiments, a splash guard 222 may be located between the outlet conduit 206 and the surface of the liquid 218 such that bubbling liquid 218 does not get trapped in the outlet conduit 206 and pushed out of the second chamber 210b further downstream in the furnace system 200. In some embodiments, a low density floating granular media, e.g., plastic pellets, rubber, hollow glass, graphite, and/or metal spheres, may be disposed on the top surface of the liquid 218 to reduce the splashing of oil droplets instead of, or in addition to, the splash guard 222. In some embodiments, the low density floating granular media may have a density lower than that of the liquid 218.

In some embodiments, the first chamber 210a may be utilized as a binder trap. That is, the first chamber 210a may be used to trap volatilized binder components present in the gaseous effluent. In such embodiments, the liquid bubbler 202 may include a first cooler 220a configured to cool the first chamber 210a. The first chamber 210a may include a tortuous conduit with one end fluidly connected to the furnace exhaust conduit 103 and another end fluidly connected to the connecting conduit 204. The first cooler 220a may be configured to cool the first chamber 210a and the gaseous effluent coming through the furnace exhaust conduit 103 as it is passed through the tortuous conduit such that the effluent is chilled, and the volatilized binder components included in the effluent condenses and/or coalesces. In some embodiments, the condensed and/or coalesced binder components may be heated and drained out. For example, melted wax binder may be melted and then allowed to drain out. In some embodiments, the tortuous conduit may comprise a metal wool mesh, e.g., stainless steel or copper. In such embodiments, the condensed and/or coalesced binder components may be collected on a surface area of the metal wool mesh. The mesh may be removed, e.g., between furnace processes, and the collected binder components may be removed from the mesh. In some instances, the collected binder components may be removed using a solvent. In some embodiments, the mesh may be reattached after removing the binder components.

In some embodiments, the liquid 218 in the second chamber 210b may serve as a binder trap to collect higher molecular weight volatilized binder components, e.g., when an oil is used as the liquid 218. When the gaseous effluent comes into contact with the liquid 218, the gas may cool, thereby causing the volatilized binder components to condense. In some embodiments, volatilized binder components with higher molecular weight may form a miscible solution with certain oils. As such, the liquid bubbler 202 may collect a sufficient amount of volatilized binder components present in the gaseous effluent. In some embodiments, the collected volatilized binder components may collect in second chamber 210b, increasing the height of the fluid in second chamber 210b. In such embodiments, fluid may be removed from the second chamber 210b periodically. A cooler 220b may be used to cool the second chamber 210b, particularly if large amounts of gaseous effluent is flowed through the liquid bubbler 202, to facilitate use of second chamber 210b as a binder trap.

In some embodiments, the liquid 218 in the second chamber 210b may serve as a binder cracking enclosure when a liquid metal or a liquid salt is used as the liquid 218. In such embodiments, the liquid 218 in the second chamber 210b may be heated such that the heated liquid 218 causes volatilized binder components present in the gaseous effluent to break down to a lower molecular weight species and expand in volume, which may create carbon residue. In such embodiments, not as many volatilized binder components may be collected in the second chamber 210b. In some instances, none of the volatilized binder components may be collected in the second chamber 210b.

Referring back to FIG. 2A, an exemplary process for pressure control and catalyst temperature control with reference to the furnace system 200 is described below. In some embodiments, the controller 116 may control the exemplary process for pressure control and catalyst temperature control as follows. As shown in FIG. 2A, the furnace system 200 may include one or more pressure gauges P0, P1, P2, and P3 for monitoring and/or controlling the pressure throughout the furnace system 200. The furnace system 200 may further include one or more thermocouples TC1, TC2, and TC3 for monitoring and/or controlling the temperature throughout the furnace system 200. The furnace system 200 may also include a mass flow controller 1 (MFC1), which may adjustably control the inlet gas flow into the furnace chamber 102, and MFC2, which may adjustably control the amount of oxidizing gas introduced into the furnace system 200. It will be understood that although four pressure gauges and thermocouples, and two mass flow controllers are depicted in given locations, any suitable number and arrangement of pressure gauges, thermocouples, and mass flow controllers may be included in the furnace system 200.

With respect to pressure control, pressure may be controlled so as to not over-pressurize the furnace chamber 102 so as to not compromise the components connected downstream of the furnace chamber 102. Initially, a gas inlet pressure may be set at P0 either manually or by controller 116. In some embodiments, the gas inlet pressure at P0 may be set in a range of 0-10 PSI. For example, the gas inlet pressure at P0 may be set in a range of 0-3 PSI when the furnace chamber 102 comprises a ceramic tube furnace chamber. As another example, the gas inlet pressure at P0 may be set in a range of 0-10 PSI when the furnace chamber 102 comprises a metal furnace chamber. The liquid bubbler 202 of isolation system 104 may prevent or mitigate pressure build up within the furnace system 200 during a sintering process as long as the liquid 218 contained within the liquid bubbler 202 does not collect too many binder components. In some instances, when there are too many binder components contained in the liquid 218, the liquid may become viscous and/or may form a gel-like substance. This may clog the various conduits associated with the liquid bubbler 202, e.g., the furnace exhaust conduit 103, the connecting conduit 204, and/or the outlet conduit 206. In some embodiments, the pressures at P1, P2, and P3 may be monitored, e.g., manually or by the controller 116, and processing performed within the furnace system 200 may be stopped if the pressure at one or more of P1, P2, and P3 exceeds or falls below one or more predetermined thresholds. In some embodiments, the pressures at P1 and P2 may be maintained as approximately equal. In the context of the current disclosure, about a 0.5 PSI pressure difference in the pressure at P1 and P2 may be considered as approximately equal. There may be a pressure drop at P3 such that the pressure at P3 is lower that the pressure at P1 and P2. For example, the pressure at P1 and P2 may be 2-3 PSI and the pressure at P3 may be 0-2 PSI. As another example, the pressure at P1 and P2 may be 1-3 PSI and the pressure at P3 may be 0-1 PSI. In some instances the predetermined pressure threshold for the pressure at P1 and P2 may be 3 PSI. In such instances, the furnace chamber 102 may comprise a ceramic furnace chamber. In some instances the predetermined pressure threshold for the pressure at P1 and P2 may be 10 PSI. In such instances, the furnace chamber 102 may comprise a metal furnace chamber. In some embodiments, an alarm may be initiated if the pressure at one or more of P0, P1, P2, and P3 exceeds or falls below one or more predetermined thresholds.

With respect to catalyst temperature control, the furnace system 200 may be configured to try to achieve a substantially constant temperature at TC2. That is, the temperature of the catalyst contained in the catalyst enclosure 111a should be maintained at a constant temperature range. In some embodiments, the temperature at TC2 may be maintained within a range of 285-600 degrees Celsius. In some embodiments, the temperature at TC2 may depend on the catalyst contained in the catalyst enclosure 111a. The catalyst heater 111b may control an adjustable setpoint at TC1 based on the monitored temperature feedback from TC2. In some embodiments, the adjustable setpoint at TC1 may be within a range of 225-425 degrees Celsius. If TC2 meets or exceeds the setpoint (i.e., if the catalyst becomes overheated) the following steps may be performed: (1) the catalyst heater 111b may be turned off; (2) the oxidizing gas flow from the oxidizing gas source 106 through MFC2 may be increased; and/or (3) the inlet gas flow through MFC1 may be decreased. The increased oxidizing gas flow may cool the catalyst such that the catalyst stays below a maximum temperature. In some embodiments, if the CO detector 112 (or other detector(s)) detects CO, or detects an amount of CO that meets or exceeds a threshold value, then MFC1, MFC2, and/or power to the one or more heating elements 122 may be shut off. In some embodiments, an alarm may be initiated if the CO detector 112 detects CO or detects an amount of CO that meets or exceeds a threshold value. In some embodiments, a heater for the furnace exhaust conduit 103 may be controlled based on a temperature measured at TC3. In some embodiments, the temperature at TC1, TC2, and TC3 may be monitored by the controller 116 or manually, and processing performed within the furnace system 200 may be stopped if the temperature at one or more of TC1, TC2, and TC3 exceeds or falls below one or more predetermined thresholds. In some embodiments, an alarm may be initiated if the temperature at one or more of TC1, TC2, and TC3 exceeds or falls below one or more predetermined thresholds.

FIG. 3 is a block diagram of a furnace system 300 according to one embodiment. Similar components shown in FIG. 3 may operate in a substantially similar manner as the corresponding components described in reference to FIGS. 1, 2A, and 2B. As shown in FIG. 3, the isolation system 104 may include a check valve 302 (also referred to as a one-way valve). In this embodiment, the oxidizing gas source 106 may be fluidly connected via MFC2 to a conduit 306 extending between the isolation system 104 and the catalytic converter system 110. In some embodiments, the oxidizing gas source 106 may direct oxidizing gas towards the catalytic converter system 110 using a vacuum pump and/or the air injector 109, as described in reference to FIG. 1.

The check valve 302 may be configured to isolate the furnace chamber 102 from the oxidizing gas source 106 (e.g., a blower or compressed air). The check valve 302 may be configured to maintain a pressure difference across the check valve 302 and to prevent back diffusion of oxidizing gas into the furnace chamber 102. In some embodiments, the check valve may provide a pressure drop of about ⅓ PSI to about 10 PSI. In some embodiments, the furnace system 300 may comprise an atmospheric furnace. In such embodiments, low pressures, e.g., pressure up to 3 PSI, may be used.

Both the furnace exhaust conduit 103 and the conduit 306 may be heated in order to prevent or reduce condensation of high molecular weight species in the volatilized binder components contained within the gaseous effluent from furnace chamber 102. MFC1 may be configured to adjustably control the gas inlet such that a sufficient quantity of non-reactive gas is present in the gaseous effluent. In some embodiments, a sufficient quantity of non-reactive gas may refer to a sufficient proportion of non-reactive gas present in the gaseous effluent that is able to bring the gaseous effluent below a lower explosive limit (LEL). The mixture of the non-reactive gas, the volatilized binder effluent, and the oxidizing gas do not form an explosive or self igniting mixture before entering the catalytic converter system 110. In some embodiments, the conduits, e.g., the furnace exhaust conduit 103 and the conduit 306, may be sized appropriately so that pressure buildup is reduced or minimized. During a thermal debinding process for a part 126 in the furnace chamber 102, most of the gaseous flow within the furnace system 300 may depend on the inert gas introduced through the gas inlet conduit 115 via MFC1. Accordingly, there may not be much fluctuation in the total flow rate of gas in the furnace system 300 during the thermal debinding process.

An exemplary process for pressure control and catalyst temperature control with reference to the furnace system 300 is described below. In some embodiments, the controller 116 may control the exemplary process for pressure control and catalyst temperature control as follows. As shown in FIG. 3, the furnace system 300 may include one or more pressure gauges P0, P1, P2, P3, and P5 for monitoring and/or controlling the pressure throughout the furnace system 300. The furnace system 300 may further include one or more thermocouples TC1, TC2, TC3, and TC4 for monitoring and/or controlling the temperature throughout the furnace system 300. The furnace system 300 may also include MFC1, which may adjustably control the inlet gas flow in to the furnace chamber 102, and MFC2, which may adjustably control the amount of oxidizing gas introduced into the furnace system 300. It will be understood that although five pressure gauges, four thermocouples, and two mass flow controllers are depicted in given locations, any suitable number and arrangement of pressure gauges, thermocouples, and mass flow controllers may be included in the furnace system 300.

With respect to pressure control, pressure may be controlled so as to not over-pressurize the furnace chamber 102 so as to not compromise the components connected downstream of the furnace chamber 102. Initially, a gas inlet pressure may be set at P0 either manually or by controller 116. In some embodiments, the gas inlet pressure at P0 may be set in a range of 0-10 PSI. For example, the gas inlet pressure at P0 may be set in a range of 0-3 PSI when the furnace chamber 102 comprises a ceramic tube furnace chamber. As another example, the gas inlet pressure at P0 may be set in a range of 0-10 PSI when the furnace chamber 102 comprises a metal furnace chamber. The pressure at P1 and P2 may be maintained as approximately equal. In the context of the current disclosure, about a 0.5 PSI pressure difference in the pressure at P1 and P2 may be considered as approximately equal. The pressure at P3 may be less than at P2 due to leak pressure of the check valve 302. The pressure control within furnace system 300 may be primarily controlled via MFC2 and MFC1 in some embodiments. The conduits may be sized appropriately so that there is no significant pressure buildup as oxidizing gas from MFC2 is mixed with effluent. If the pressure at P1, P2, or P3 is over a predetermined safety threshold, then the gas flow through MFC2 and/or MFC1 may be decreased. In some embodiments, the flow of gas through MFC2 may be decreased first and then the flow through MFC1 may be decreased. In some embodiments, the pressures at P0, P1, P2, P3, and P5 may be monitored by the controller 116 or manually, and processing performed within the furnace system 300 may be stopped or gas flow through MFC2 and/or MFC1 may be reduced or stopped if the pressure at one or more of P0, P1, P2, P3, and P5 exceeds or falls below one or more predetermined thresholds. In some embodiments, an alarm may be initiated if the pressure at one or more of P0, P1, P2, P3, and P5 exceeds or falls below one or more predetermined thresholds.

With respect to catalyst temperature control, the furnace system 300 may be configured to try to achieve a substantially constant temperature at TC2. That is, the temperature of the catalyst contained in the catalyst enclosure 111a may be maintained at a substantially constant temperature range. In some embodiments, the temperature at TC2 may be maintained within a range of 285-600 degrees Celsius. In some embodiments, the temperature at TC2 may depend on the catalyst contained in the catalyst enclosure 111a. The catalyst heater 111b may be configured to control the adjustable setpoint at TC1 based on the monitored temperature feedback from TC2. In some embodiments, the adjustable setpoint at TC1 may be within a range of 225-425 degrees Celsius. If the temperature at TC2 meets or exceeds the setpoint (i.e., if the catalyst becomes overheated) the following steps may be performed: (1) the catalyst heater 111b may be turned off; (2) the oxidizing gas flow from the oxidizing gas source 106 through MFC2 may be increased; and/or (3) the inlet gas flow through MFC1 may be decreased. In some embodiments, if the CO detector 112 detects CO, or detects an amount of CO that meets or exceeds a threshold value, then an alarm may be initiated. In some embodiments, upon CO detection, MFC1 and/or power to the one or more heating elements 122 may be shut off while MFC2 remains open to provide backpressure on the check valve 302 and the furnace chamber 102. In some embodiments, one or more heaters for the furnace exhaust conduit 103 and/or conduit 306 may be controlled based on temperatures measured at TC3 and/or TC4. In some embodiments, the temperatures at TC1, TC2, TC3, and TC4 may be monitored by the controller 116 or manually, and processing performed within the furnace system 300 may be stopped if the temperature at one or more of TC1, TC2, TC3, and TC4 exceeds or falls below one or more predetermined thresholds. In some embodiments, an alarm may be initiated if the temperature at one or more of TC1, TC2, TC3, and TC4 exceeds or falls below one or more predetermined thresholds.

FIG. 4 is a block diagram of a furnace system 400 according to one embodiment. Similar components shown in FIG. 4 may operate in a substantially similar manner as the corresponding components described in reference to FIGS. 1, 2A-2B, and 3. As shown in FIG. 4, the isolation system 104 may include a check valve 302 and a venturi pump 402. In this embodiment, the oxidizing gas source 106 may be fluidly connected via MFC2 to the venturi pump 402. The oxidizing gas source 106 may also be fluidly connected via MFC3 to a conduit 406b between the venturi pump 402 and the catalytic converter system 110. In some embodiments, the oxidizing gas source 106 may direct oxidizing gas towards the catalytic converter system 110 using a vacuum pump and/or the air injector 109, as described in reference to FIG. 1.

As described with reference to FIG. 3, the check valve 302 may be configured to isolate the furnace chamber 102 from the oxidizing gas source 106 (e.g., a blower or compressed air). The check valve 302 may be configured to maintain a pressure difference across the check valve 302 and to prevent back diffusion of oxidizing gas into the furnace chamber 102. In some embodiments, the check valve 302 may provide a pressure drop of about ⅓ PSI to about 10 PSI. In some embodiments, the furnace system 400 may comprise an atmospheric furnace. In such embodiments, low pressures, e.g., pressure up to 3 PSI, may be used.

One or more of the furnace exhaust conduit 103, a conduit 406a between the check valve 302 and the venturi pump 402, and conduit 406b may be heated in order to prevent condensation of high molecular weight species in the volatilized binder components present in the gaseous effluent. MFC1 may be configured to adjustably control the gas inlet such that a sufficient quantity of non-reactive gas is present in the gaseous effluent. In some embodiments, a sufficient quantity of non-reactive gas may indicate a proportion of the non-reactive gas present in the gaseous effluent to bring the gaseous effluent below the explosive limit (LEL). The mixture of the non-reactive gas, the volatilized binder effluent, and the oxidizing gas do not form an explosive or self igniting mixture before entering the catalytic converter system 110.

The venturi pump 402 may be located at the point of the oxidizing gas inlet and may be configured to utilize the oxidizing gas provided by the oxidizing gas source 106 to draw gas and pull the gaseous effluent from the check valve 302. As such, the venturi pump 402 may prevent back pressure on the check valve 302 and the furnace chamber 102. As shown in FIG. 4, separate MFC2 and MFC3 may provide separate oxidizing gas flows to the venturi pump 402 and the conduit 406b, respectively. In some embodiments, the conduits may be sized appropriately such that pressure does not build up upstream of the oxidizing gas source 106. In such embodiments, the venturi pump may not be needed.

An exemplary process for pressure control and catalyst temperature control with reference to the furnace system 400 is described below. In some embodiments, the controller 116 may control the exemplary process for pressure control and catalyst temperature control as follows. As shown in FIG. 4, the furnace system 400 may include one or more pressure gauges P0, P1, P2, P3, P4, and P5 for monitoring and/or controlling the pressure throughout the furnace system 400. The furnace system 400 may further include one or more thermocouples TC1, TC2, TC3, TC4, and TC5 for monitoring and/or controlling the temperature throughout the furnace system 400. The furnace system 400 may also include MFC1, a venturi pump MFC2, and a venturi pump bypass MFC3 to control the flow of various gases within the furnace system 400. It will be understood that although six pressure gauges, five thermocouples, and three mass flow controllers are depicted in given locations, any suitable number and arrangement of pressure gauges, thermocouples, and mass flow controllers may be included in the furnace system 400.

With respect to pressure control, pressure may be controlled so as to not over-pressurize the furnace chamber 102 so as to not compromise the components connected downstream of the furnace chamber 102. Initially, a gas inlet pressure may be set at P0 either manually or by the controller 116. In some embodiments, the gas inlet pressure at P0 may be set in a range of 0-10 PSI. For example, the gas inlet pressure at P0 may be set in a range of 0-3 PSI when the furnace chamber 102 comprises a ceramic tube furnace chamber. As another example, the gas inlet pressure at P0 may be set in a range of 0-10 PSI when the furnace chamber 102 comprises a metal furnace chamber. The pressure at P1 and P2 should be almost equal. In the context of the current disclosure, about a 0.5 PSI pressure difference in the pressure at P1 and P2 may be considered as almost equal. P3 should be less than P2 by the leak pressure of the check valve 302. The venturi pump MFC2 and the venturi pump bypass MFC3 may be utilized to control the back pressure on the venturi pump 402. For example, draw of the effluent gas through the venturi pump 402 may be controlled via the venturi pump MFC2 and/or venturi pump bypass MFC3, which in turn may control the backpressure on the venturi pump 402. A pressure drop across the venturi pump 402 may be monitored at P4. In some embodiments, flow through MFC2 may be increased and/or the flow through MFC3 may be decreased. In some embodiments, the flow through MFC2 may be increased and/or the flow through MFC3 may be decreased if the pressure drop across the venturi pump 402 is insufficient and falls below a predetermined threshold. In some embodiments, the pressure measured at P3 may be slightly above atmospheric pressure, e.g., about 30 Hg. In such embodiments, the venturi pump 402 may be configured to generate vacuums at about 29 Hg. The furnace chamber 102 may be a vacuum furnace or an atmosphere furnace. In embodiments in which the furnace chamber 102 is an atmosphere furnace, the atmosphere furnace may potentially use more gas compared to a similar sized vacuum furnace. Accordingly, more dilution gas may be used within the catalytic converter in the atmosphere furnace than with a vacuum furnace as more volume exchanges may be generated at vacuum than at atmospheric pressure. In some embodiments, the pressures at P0, P1, P2, P3, P4, and P5 may be monitored by the controller 116 or manually, and processing performed within the furnace system 400 may be stopped if the pressure at one or more of P0, P1, P2, P3, P4, and P5 exceeds or falls below one or more predetermined thresholds. In some embodiments, an alarm may be initiated if the pressure at one or more of P0, P1, P2, P3, P4, and P5 exceeds or falls below one or more predetermined thresholds.

With respect to catalyst temperature control, the furnace system 400 may be configured to try to achieve a substantially constant temperature at TC2. That is, the temperature of the catalyst contained in the catalyst enclosure 111a may be maintained at a substantially constant temperature range. In some embodiments, the temperature at TC2 may be maintained within a range of 285-600 degrees Celsius. In some embodiments, the temperature at TC2 may depend on the catalyst contained in the catalyst enclosure 111a. The catalyst heater 111b may control the adjustable setpoint at TC1 based on the monitored temperature feedback from TC2. In some embodiments, the adjustable setpoint at TC1 may be within a range of 225-425 degrees Celsius. If TC2 is equal to or above the adjustable setpoint (i.e., if the catalyst gets overheated) the follow steps may be performed: (1) the catalyst heater 111b may be turned off; (2) the oxidizing gas flow from the oxidizing gas source 106 through MFC2 and/or MFC3 may be increased; and/or (3) the inlet gas flow through MFC1 may be decreased. In some embodiments, if the CO detector 112 detects CO, or detects an amount of CO that meets or exceeds a threshold value, then MFC1, MFC2, and power to the one or more heating elements 122 may be shut off while MFC3 remains open such that backpressure may be provided on the venturi pump 402, the check valve 302, and the furnace chamber 102. In some embodiments, an alarm may be initiated if CO detector 112 detects CO or detects an amount of CO that meets or exceeds a threshold value. In some embodiments, one or more heaters for the furnace exhaust conduit 103 and conduits 406a-b may be controlled based on temperatures measured at TC3, TC4, and/or TC5. In some embodiments, the temperature at TC1, TC2, TC3, TC4, and TC5 may be monitored by the controller 116 or manually, and processing performed within the furnace system 400 may be stopped if the temperature at one or more of TC1, TC2, TC3, TC4, and TC5 exceeds or falls below one or more predetermined thresholds. In some embodiments, an alarm may be initiated if the temperature at one or more of TC1, TC2, TC3, TC4, and TC5 exceeds or falls below one or more predetermined thresholds.

FIG. 5 is a block diagram of a furnace system 500 according to one embodiment. Similar components shown in FIG. 5 may operate in a substantially similar manner as the corresponding components described in reference to FIGS. 1, 2A-2B, 3, and 4. As shown in FIG. 5, the furnace system 500 may include a binder cracking system 501 and the isolation system 104 may include a check valve 302 and a venturi pump 402. The binder cracking system 501 may be positioned downstream from the check valve 302 and may include a binder cracking enclosure 502, a binder cracking heater 504, a steam source 505, a flame arrestor 508, a valve 510, and MFC4. The binder cracking enclosure 502 may be fluidly connected to the steam source 505 via MFC4. The binder cracking enclosure 502 may also be fluidly connected to the oxidizing gas source 106 via the valve 510. In some embodiments, the oxidizing gas source 106 may direct oxidizing gas towards the catalytic converter system 110 using a vacuum pump and/or the air injector 109, as described in reference to FIG. 1. In some embodiments, one or more of the furnace exhaust conduit 103, a conduit 506a between the check valve 302, and the binder cracking system 501 may be heated in order to prevent or reduce condensation of high molecular weight species in the volatilized binder components that may be present in the gaseous effluent.

The binder cracking enclosure 502 may be a heated enclosure substantially free of oxygen for decomposing high molecular weight binder components into lower molecular weight binder components. In the context of the current disclosure, the lower molecular weight binder components may typically be gases at room temperature and so are non-condensable. In some embodiments, the binder cracking enclosure 502 may be sized such that the high molecular weight binder components may stay within the binder cracking enclosure 502 a sufficient amount of time in order to decompose into lower molecular weight binder components. In some embodiments, the binder cracking enclosure 502 may comprise a catalyst. In such embodiments, the catalyst may lower the temperature at which the high molecular weight binder components decompose into lower molecular weight binder components. In some embodiments, the binder cracking enclosure 502 may be heated by the binder cracking heater 504. In some embodiments, the binder cracking heater 504 may comprise an electronic heating component. In some embodiments, the steam source 505 and MFC4 may be used while the binder cracking enclosure 502 is processing volatilized binder components. In some embodiments, the binder component decomposition may generate some unsatisfied chemical bonds. Such unsatisfied chemical bonds may result in carbon (C) atoms. In such embodiments, the steam source 505 may be configured to provide steam, i.e., H20 to the binder cracking enclosure 502 such that the steam may react with the carbon to form a combination of CO and CH4 and/or a combination of CO and H2. Accordingly, the steam provided by the steam source 505 may prevent a carbon deposit within the furnace system 500, e.g., the binder cracking enclosure 502. In some embodiments, the valve 510 may be configured to provide oxidizing gas to the binder cracking enclosure 502 to periodically remove carbon buildup from the binder cracking enclosure 502. In such embodiments, the oxidizing gas may be provided in between processes, such as sintering, within the furnace system 500. In some embodiments, the binder cracking enclosure 502 may not need the oxidizing gas depending on the compositions of the volatilized binder components and the inlet gas provided via the gas inlet conduit 115 to the furnace chamber 102. For example, if the inlet gas contains hydrogen, oxidizing gas may not be needed, as the hydrogen may react with any carbon atoms generated within the binder cracking enclosure 502 due to unsatisfied chemical bonds.

The flame arrestor 508 may be configured to prevent the propagation of a flame originating at the binder cracking heater 504 towards the catalytic converter system 110. Specifically, the flame arrestor 508 may prevent any flames from propagating due to the heater 504 igniting the gaseous effluent. In some embodiments, the furnace system 500 may include various flame arrestors close to and on either side of any point of potential ignition for any of the embodiments described herein. Further, although flame arrestor 508 is discussed in conjunction with furnace system 500, it is contemplated that one or more flame arrestors 508 may be incorporated into any furnace system described herein.

An exemplary process for pressure control and catalyst temperature control with reference to the furnace system 500 is described below. In some embodiments, the controller 116 may control the exemplary process for pressure control and catalyst temperature control as follows. As shown in FIG. 5, the furnace system 500 may include one or more pressure gauges P0, P1, P2, P3, P4, P5, and P6 for monitoring and/or controlling the pressure throughout the furnace system 500. The furnace system 500 may further include one or more thermocouples TC1, TC2, TC3, TC4, and TC5 for monitoring and/or controlling the temperature throughout the furnace system 500. The furnace system 500 may also include various mass flow controllers MFC1, MFC2, MFC3, and MFC4 to control the flow of various gases within the furnace system 500. It will be understood that although seven pressure gauges, five thermocouples, and four mass flow controllers are depicted in given locations, any suitable number and arrangement of pressure gauges, thermocouples, and mass flow controllers may be included in the furnace system 500.

With respect to pressure control, pressure may be controlled so as to not over-pressurize the furnace chamber 102 so as to not compromise the components connected downstream of the furnace chamber 102. Initially, a gas inlet pressure may be set at P0 either manually or by the controller 116. In some embodiments, the gas inlet pressure at P0 may be set in a range of 0-10 PSI. For example, the gas inlet pressure at P0 may be set in a range of 0-3 PSI when the furnace chamber 102 comprises a ceramic tube furnace chamber. As another example, the gas inlet pressure at P0 may be set in a range of 0-10 PSI when the furnace chamber 102 comprises a metal furnace chamber. The pressure at P2 and the pressure at P1 may be maintained as approximately equal. In some embodiments, the pressure at P1 and P2 may be maintained as approximately equal. In the context of the current disclosure, about a 0.5 PSI pressure difference in the pressure at P1 and P2 may be considered as approximately equal. P3 may be less than P2 by the leak pressure of the check valve 302. In some embodiments, the leak pressure of the check valve 302 may be about 0.3 PSI or larger. There may be a back pressure caused by the binder cracking enclosure 502 as the pressure at P4 may increase depending on the amount of gas molecules generated within the binder cracking enclosure 502. That is, the pressure within the binder cracking enclosure 502 may increase due to the decomposition of the high molecular weight binder components. As such, the venturi pump 402 may provide relief for the pressure built up at P4. The venturi pump 402 may relieve pressure by generating a vacuum on the gaseous effluent inlet side of the venturi pump 402 through the use of a flowing gas from the oxidizing gas source 106. In some embodiments, the pressure at P5 may be monitored and maintained at about atmospheric pressure. Monitoring may be regular, intermittent, or continuous. By monitoring the pressure at P5 and maintaining it at roughly atmospheric pressure, gas may properly flow through the furnace system 500. When the pressure at P5 is at roughly atmospheric pressure, this may indicate that gas is properly flowing. A monitored difference in pressure between P4 and P5 across the flame arrestor 508 should be small. In the context of the current disclosure, about a 0.5 PSI pressure differential in the pressure at P4 and P5 may be considered small. A relatively large difference in pressure between P4 and P5 may indicate a clog within the flame arrestor 508. In some embodiments, the clog may be caused by condensed binder components and/or sooting, which may deposit carbon.

MFC2 and MFC3 may be manipulated to alter furnace system 500. In some embodiments, MFC2 may be used to draw more gaseous effluent through the venturi pump 402, thereby increasing the flow within the furnace system 500 and decreasing the pressure at P5. In some embodiments, decreasing the flow using MFC3 may cause less back pressure on the venturi pump 402, thereby decreasing the pressure at P5. In some embodiments, the pressures at P0, P1, P2, P3, P4, P5, and P6 may be monitored by the controller 116 or manually, and processing performed within the furnace system 500 may be stopped if the pressure at one or more of P0, P1, P2, P3, P4, P5, and P6 exceeds or falls below one or more predetermined thresholds. In some embodiments, an alarm may be initiated if the pressure at one or more of P0, P1, P2, P3, P4, P5, and P6 exceeds or falls below one or more predetermined thresholds.

With respect to catalyst temperature control, the furnace system 500 may be configured to try to maintain the temperature at TC2 at a substantially constant temperature. That is, the temperature of the catalyst contained in the catalyst enclosure 111a may be maintained at a substantially constant temperature range. In some embodiments, the temperature at TC2 may be maintained within a range of 285-600 degrees Celsius. In some embodiments, the temperature at TC2 may depend on the catalyst contained in the catalyst enclosure 111a. The catalyst heater 111b may control the adjustable setpoint at TC1 based on the monitored temperature feedback from TC2. In some embodiments, the adjustable setpoint at TC1 may be within a range of 225-425 degrees Celsius. If the temperature detected at TC2 meets or exceeds the setpoint (i.e., if the catalyst gets overheated) the following steps may be performed: (1) the catalyst heater 111b may be turned off; (2) the oxidizing gas flow from the oxidizing gas source 106 through MFC2 or MFC3 may be increased; and/or (3) the inlet gas flow through MFC1 may be decreased. In some embodiments, if the CO detector 112 detects CO, or detects an amount of CO that meets or exceeds a threshold value, then MFC1, MFC2, MFC4, the binder cracking heater 504, and the power to the one or more heating elements 122 may be shut off while MFC3 remains open such that backpressure is provided on the venturi pump 402. In some embodiments, an alarm may be initiated. The back pressure provided on the venturi pump 402, in turn, may provide back pressure to the check valve 302 configured to isolate the furnace chamber 102 from oxidizing gas. In some embodiments, one or more heaters for the furnace exhaust conduit 103 and conduit 506a may be controlled based on a temperature measured at TC3. In some embodiments, the temperature at TC1, TC2, TC3, TC4, and TC5 may be monitored by the controller 116 or manually, and processing performed within the furnace system 500 may be stopped if the temperature at one or more of TC1, TC2, TC3, TC4, and TC5 exceeds or falls below one or more predetermined thresholds. In some embodiments, an alarm may be initiated if the temperature at any one of TC1, TC2, TC3, TC4, and TC5 exceeds or falls below one or more predetermined thresholds.

FIG. 6 is a block diagram of a furnace system 600 according to one embodiment. Similar components shown in FIG. 6 may operate in a substantially similar manner as the corresponding components described in reference to FIGS. 1, 2A-2B, 3, 4, and 5. As shown in FIG. 6, the furnace system 600 may include a binder trap system 601 and the isolation system may include a check valve 302. The binder trap system 601 may itself include a binder trap 602 and a binder trap cooling device 604 according to some embodiments. The binder trap 602 may be used to condense or to coalesce volatilized binder components present in the gaseous effluent, removing at least a portion of the volatilized binder components from the gaseous effluent before the gaseous effluent is directed to the catalytic converter system 110. This may reduce the load exerted on the catalytic converter system 110, which may increase the lifespan of catalytic converter system 110, and/or may reduce the capacity of catalytic converter system 110 required to create an office-safe furnace system 600. In some embodiments, the binder trap system 601 may comprise a binder trap bypass conduit fluidly connected to the furnace exhaust conduit 103 and conduit 603. In such embodiments, gaseous effluent from the furnace chamber 102 may be pumped via one or more furnace exhaust conduits through the binder trap system 601 or the binder trap system bypass conduit. In some embodiments, a valve on the binder trap system bypass conduit may be closed, and the gaseous effluent may be pumped from the furnace chamber 102 through the binder trap system 601 during a thermal debinding process. In some embodiments, one or more valves positioned upstream and downstream of the binder trap system 601 may be closed, the valve on the binder trap system 601 may be open, and the gaseous effluent may be pumped from the furnace chamber 102 through the binder trap system bypass conduit during a main sintering (e.g., densification) process.

Binder trap 602 may be a cooled enclosure that traps condensable or coalescable binder components (i.e., those with a higher boiling point). In some embodiments, the binder trap 602 may include a large interior surface area such that the gaseous effluent flowing through the binder trap 602 impinges on multiple interior surfaces in order for the volatilized binder components to cool down and condense and/or coalesce out of a gas phase. In some embodiments, the large interior area comprises a metal insert with a high surface area, e.g., metal mesh wool, metal turnings, metal springs, molecular sieve trap, among others. In some embodiments, the metal insert may be a copper insert. In some embodiments, the condensed and/or coalesced binder components may be collected on a surface area of the metal insert during use. In such embodiments, the metal insert may be detachable, and the metal insert may be detached to collect and remove the binder components from the metal insert. In some instances, the collected binder components may be removed using a solvent. In some embodiments, the metal insert may be reattached after removing the binder components. In some embodiments, the binder trap 602 may be cooled by the binder trap cooling device 604 to facilitate the condensing or coalescing of volatilized binder components. In such embodiments, heating the portion of the system downstream of the binder trap may not be required. In some embodiments, the furnace exhaust conduit 103 may be heated in order to prevent condensation of high molecular weight species in the volatilized binder components present in the gaseous effluent when in the furnace exhaust conduit 103.

In some embodiments, the binder trap 602 may including a cooled surface, e.g., a cooled rod. In some embodiments, the chamber may be a cylindrical chamber and the rod may be a coaxial rod removably inserted into the chamber. In some embodiments, the binder trap cooling device 604 may be configured to cool the coaxial rod and/or the cylindrical chamber. In some embodiments, the coaxial rod comprise a tube containing liquid nitrogen to cool the coaxial rod. The cylindrical chamber may comprise an inlet on a first end of the cylindrical chamber and an outlet on an opposing second end of the cylindrical chamber. Accordingly, the gaseous effluent directed into the inlet of the cylindrical chamber may flow along the length of the coaxial rod within the cylindrical chamber towards the outlet of the cylindrical chamber. The volatilized binder components present in the gaseous effluent may condense and/or coalesce when the volatilized binder components contacts a surface of the coaxial rod and/or the cylindrical chamber. Accordingly, the condensed and/or coalesced binder components may be collected on one or more surfaces of the coaxial rod and/or the cylindrical chamber. In some embodiments, the coaxial rod and/or the cylindrical chamber may be detached and the collected binder components may be removed. In some instances, the collected binder components may be removed using a solvent. In some embodiments, the coaxial rod and/or the cylindrical chamber may be reattached after the collected binder components have been removed. For example, in some embodiments, the rod may be a tube, e.g., an elongated tube with approximately a 1-inch diameter, containing liquid nitrogen or another suitable coolant. In other embodiments, a cooled molecular sieve trap may be used to condense and/or coalesce binder components. Once binder components have been collected, the molecular sieve trap may be thrown out or regenerated by heating under vacuum. In still other embodiments, a cooling trap may be formed by producing one or more tortuous cooled flow paths. For example, a cooled chamber containing copper mesh may be used to condense and/or coalesce binder components. Such an embodiment may operate similarly to a molecular sieve.

An exemplary process for pressure control and catalyst temperature control with reference to the furnace system 600 is described below. In some embodiments, the controller 116 may control the exemplary process for pressure control and catalyst temperature control as follows. As shown in FIG. 6, the furnace system 600 may include one or more pressure gauges P0, P1, P2, P3, P4, P5, and P6 for monitoring and/or controlling the pressure throughout the furnace system 600. The furnace system 600 may also include one or more thermocouples TC1, TC2, TC3, and TC4 for monitoring and/or controlling the temperature throughout the furnace system 600. The furnace system 600 may further include various mass flow controllers MFC1 and MFC2 to control the flow of various gases within the furnace system 600. In some embodiments, the oxidizing gas source 106 may direct oxidizing gas towards the catalytic converter system 110 using a vacuum pump and/or the air injector 109, as described in reference to FIG. 1. It will be understood that although seven pressure gauges, four thermocouples, and two mass flow controllers are depicted in given locations, any suitable number and arrangement of pressure gauges, thermocouples, and mass flow controllers may be included in the furnace system 600.

With respect to pressure control, pressure may be controlled so as to not over-pressurize the furnace chamber 102 so as to not compromise the components connected downstream of the furnace chamber 102. Initially, a gas inlet pressure may be set at P0 either manually or by controller 116. In some embodiments, the gas inlet pressure at P0 may be set in a range of 0-10 PSI. For example, the gas inlet pressure at P0 may be set in a range of 0-3 PSI when the furnace chamber 102 comprises a ceramic tube furnace chamber. As another example, the gas inlet pressure at P0 may be set in a range of 0-10 PSI when the furnace chamber 102 comprises a metal furnace chamber. The pressure at P2 and P1 may be almost equal. In the context of the current disclosure, about a 0.5 PSI pressure difference in the pressure at P1 and P2 may be considered as almost equal. P3 may be less than P2 by the leak pressure of the check valve 302. The pressure control within furnace system 600 may be primarily controlled via MFC2 and MFC1. The conduits may be sized appropriately so that there is no significant pressure buildup as oxidizing gas from MFC2 is mixed with effluent. If the pressure at P2, P3 or P4 is over a predetermined safety threshold, then the flows through MFC2 and/or MFC1 may be decreased. In some embodiments, the flow through MFC2 may be decreased first and then the flow through MFC1 may be decreased. In some embodiments, the pressures at P0, P1, P2, P3, P4, P5, and P6 may be monitored by the controller 116 or manually, and processing performed within the furnace system 600 may be stopped if the pressure at one or more of P0, P1, P2, P3, P4, P5, and P6 exceeds or falls below one or more predetermined thresholds. In some embodiments, an alarm may be initiated if the pressure at one or more of P0, P1, P2, P3, P4, P5, and P6 exceeds or falls below one or more predetermined thresholds.

With respect to catalyst temperature control, the furnace system 600 may be configured to try to achieve a substantially constant temperature at TC2. That is, the temperature of the catalyst contained in the catalyst enclosure 111a may be maintained at a substantially constant temperature range. In some embodiments, the temperature at TC2 may be maintained within a range of 285-600 degrees Celsius. In some embodiments, the temperature at TC2 may depend on the catalyst contained in the catalyst enclosure 111a. The catalyst heater 111b may effectively control the adjustable setpoint at TC1 based on the monitored temperature from TC2. In some embodiments, the adjustable setpoint at TC1 may be within a range of 225-425 degrees Celsius. If a temperature measured by TC2 meets or exceeds the setpoint (i.e., if the catalyst gets overheated) the following steps may be performed: (1) the catalyst heater 111b may be turned off; (2) the oxidizing gas flow from the oxidizing gas source 106 through MFC2 may be increased; and/or (3) the inlet gas flow through MFC1 may be decreased. In some embodiments, if the CO detector 112 detects CO, or detects an amount of CO that meets or exceeds a threshold value, then MFC land power to the one or more heating elements 122 may be shut off while MFC2 and/or MFC3 may remain open such that back pressure is provided on the check valve 302 and the furnace chamber 102. In some embodiments, an alarm may be initiated if CO detector 112 detects CO or detects an amount of CO that meets or exceeds a threshold value.

The binder trap 602 may be cooled during a sintering process within the furnace system 600. The binder trap cooling device 604 may be configured to cool the binder trap 602 based on the temperature at TC4. In some embodiments, the binder trap cooling device 604 may utilize fluid cooling (e.g., water and/or air cooling), one or more fans, a combination of a thermoelectric cooler and one or more fans, or a heat pipe, among others, to control the temperature of the binder trap 602. In some embodiments, one or more heaters for the furnace exhaust conduit 103 may be controlled based on a temperature measured at TC3. In some embodiments, the temperature at TC1, TC2, TC3, and TC4 may be monitored by the controller 116 or manually, and processing performed within the furnace system 600 may be stopped if the temperature at one or more of TC1, TC2, TC3, and TC4 exceeds or falls below one or more predetermined thresholds. In some embodiments, an alarm may be initiated if the temperature at one or more of TC1, TC2, TC3, and TC4 exceeds or falls below one or more predetermined thresholds.

FIG. 7 is a block diagram of a furnace system 700 according to one embodiment. Similar components shown in FIG. 7 may operate in a substantially similar manner as the corresponding components described in reference to FIGS. 1, 2A-2B, 3, 4, 5, and 6. As shown in FIG. 7, the isolation system 104 may include a proportional valve 702. The furnace system 700 may include the binder trap system 601 as described above with respect to FIG. 6. Although the binder trap system 601 is depicted in FIG. 7, it is also contemplated that furnace system 700 may not include binder trap system 601 and may only include proportional valve 702.

The proportional valve 702 may function to isolate the furnace chamber 102 from the oxidizing gas source 106 (e.g., a blower or compressed air). In some embodiments, the proportional valve 702 may comprise a proportional butterfly valve and/or a proportional solenoid valve. The furnace system 700 may include a pressure gauge P2 disposed between the furnace chamber 102 and the proportional valve 702. In some embodiments, the controller 116 may be communicatively connected to the pressure gauge P2 and the proportional valve 702. As such, the controller 116 may be configured to adjust a position of the proportional valve 702 to maintain a desired pressure drop across the proportional valve 702. The furnace exhaust conduit 103 may be heated in order to prevent or reduce condensation of high molecular weight species in the volatilized binder components present in the gaseous effluent. MFC1 may adjustably control the gas inlet such that a sufficient quantity of non-reactive gas is present in the gaseous effluent. In some embodiments, a sufficient quantity of non-reactive gas may indicate a proportion of non-reactive gas present in the gaseous effluent great enough to bring the gaseous effluent below a lower explosive limit (LEL). The mixture of the non-reactive gas, the volatilized binder effluent, and the oxidizing gas may not form an explosive or self igniting mixture before entering the catalytic converter system 110.

An exemplary process for pressure control and catalyst temperature control with reference to the furnace system 700 is described below. In some embodiments, the controller 116 may control the exemplary process for pressure control and catalyst temperature control as follows. As shown in FIG. 7, the furnace system 700 may include one or more pressure gauges P0, P1, P2, P3, and P4 for monitoring and/or controlling the pressure throughout the furnace system 700. The furnace system 700 may also include one or more thermocouples TC1, TC2, TC3 and TC4 for monitoring and/or controlling the temperature throughout the furnace system 700. The furnace system 700 may further include various mass flow controllers MFC1 and MFC2 to control the flow of various gases within the furnace system 700. In some embodiments, the oxidizing gas source 106 may direct oxidizing gas towards the catalytic converter system 110 using a vacuum pump and/or the air injector 109, as described in reference to FIG. 1. It will be understood that although five pressure gauges, four thermocouples, and two mass flow controllers are depicted in given locations, any suitable number and arrangement of pressure gauges, thermocouples, and mass flow controllers may be included in the furnace system 700.

With respect to pressure control, pressure may be controlled so as to not over-pressurize the furnace chamber 102 so as to not compromise the components connected downstream of the furnace chamber 102. Initially, gas inlet pressure may be set at P0. In some embodiments, the gas inlet pressure at P0 may be set in a range of 0-10 PSI. For example, the gas inlet pressure at P0 may be set in a range of 0-3 PSI when the furnace chamber 102 comprises a ceramic tube furnace chamber. As another example, the gas inlet pressure at P0 may be set in a range of 0-10 PSI when the furnace chamber 102 comprises a metal furnace chamber. The pressure at P2 may be monitored, and the pressure at P2 and P1 should be maintained to be almost equal. In the context of the current disclosure, about a 0.5 PSI pressure difference in the pressure at P1 and P2 may be considered as almost equal. The proportional valve 702 may control the difference in pressure between P3 and P4. A pressure difference may be set so that the back flow of gas is decreased or minimized. In some embodiments, the pressure difference between P3 and P4 may be set to about a 3 PSI difference, where the pressure at P3 is higher than that the pressure at P4. In some embodiments, the pressures at P0, P1, P2, P3, and P4 may be monitored by the controller 116 or manually, and processing performed within the furnace system 700 may be stopped if the pressure at one or more of P0, P1, P2, P3, and P4 exceeds or falls below one or more predetermined thresholds. In some embodiments, an alarm may be initiated if the pressure at one or more of P0, P1, P2, P3, and P4 exceeds or falls below one or more predetermined thresholds.

With respect to catalyst temperature control, the furnace system 700 may be configured to try to maintain the temperature at TC2 at a substantially constant temperature. That is, the temperature of the catalyst contained in the catalyst enclosure 111a may be maintained at a substantially constant temperature range. In some embodiments, the temperature at TC2 may be maintained within a range of 285-600 degrees Celsius. In some embodiments, the temperature at TC2 may depend on the catalyst contained in the catalyst enclosure 111a. The catalyst heater 111b may control the adjustable setpoint at TC1 based on the monitored temperature feedback from TC2. In some embodiments, the adjustable setpoint at TC1 may be within a range of 225-425 degrees Celsius. If the temperature at TC2 meets and/or exceeds the setpoint (i.e., if the catalyst gets overheated) the following steps may be performed: (1) the catalyst heater 111b may be turned off; (2) the oxidizing gas flow from the oxidizing gas source 106 through MFC2 may be increased; and (3) the inlet gas flow through MFC1 may be decreased. The CO detector 112 detects CO from flowing out of the catalytic converter system 110. In some embodiments, if the CO detector 112 detects CO, or detects an amount of CO that meets or exceeds a threshold value, then MFC1, MFC2, and power to the one or more heating elements 122 may be are shut off and/or an alarm may be initiated. In some embodiments, one or more heaters for the furnace exhaust conduit 103 may be controlled based on a temperature measured at TC3. In some embodiments, the temperature at TC1, TC2, TC3, and TC4 may be monitored by the controller 116 or manually, and processing performed within the furnace system 700 may be stopped if the temperature at one or more of TC1, TC2, TC3, and TC4 exceeds or falls below one or more predetermined thresholds. In some embodiments, an alarm may be initiated if the temperature at one or more of TC1, TC2, TC3, and TC4 exceeds or falls below one or more predetermined thresholds.

FIG. 8 is a block diagram of a furnace system 800 according to one embodiment. Similar components shown in FIG. 8 may operate in a substantially similar manner as the corresponding components described in reference to FIGS. 1, 2A-2B, 3, 4, 5, 6, and 7. As shown in FIG. 8, the isolation system 104 may include a pump 802. The furnace system 800 may also include the binder trap system 601, which may function as described above with reference to FIG. 6. Although the binder trap system 601 is depicted in FIG. 8, it is also contemplated that furnace system 800 may not include binder trap system 601 and may only include pump 802.

The pump 802 may function to isolate the furnace chamber 102 from the oxidizing gas source 106 (e.g., a blower or compressed air). In some embodiments, the pump 802 may be a low speed pump, e.g., a variable low speed pump. In such embodiments, the low speed pump may draw a small amount such that the pump 802 may keep up with the flow of the gaseous effluent within the furnace chamber 800 and may not generate a vacuum. For example, the flow through the pump 802 may be equal to the flow through MFC 1. In some embodiments, the pump 802 may be a positive displacement pump, a lobe pump, a diaphragm pump, a peristaltic pump, and/or a piston pump. In some embodiments, the pump 802 may be a variable speed low speed pump. In such embodiments, the pump 802 may be controlled based on a pressure measurement at P3. The pump 802 may maintain a pressure difference across the pump 802 and may prevent back diffusion of oxidizing gas into the furnace chamber 102. In some embodiments, the furnace system 800 may include a conduit 804 fluidly connecting the pump 802 and the catalytic converter system 110. In some embodiments, the pump 802 may prevent back diffusion of binder components into the catalytic converter system 110. The furnace exhaust conduit 103 may be heated in order to prevent condensation of high molecular weight species in the volatilized binder components present in the gaseous effluent. MFC1 may adjustably control the gas inlet such that a sufficient quantity of non-reactive gas is present in the gaseous effluent. In some embodiments, a sufficient quantity of non-reactive gas may indicate a proportion of the non-reactive gas present in the gaseous effluent that is large enough to bring the gaseous effluent below a lower explosive limit (LEL). The mixture of the non-reactive gas, the volatilized binder effluent, and the oxidizing gas may not form an explosive or self igniting mixture before entering the catalytic converter system 110.

An exemplary process for pressure control and catalyst temperature control with reference to the furnace system 800 is described below. In some embodiments, the controller 116 may control the exemplary process for pressure control and catalyst temperature control as follows. As shown in FIG. 8, the furnace system 800 may include one or more pressure gauges P0, P1, P2, P3, and P4 for monitoring and/or controlling the pressure throughout the furnace system 800. The furnace system 800 may also include one or more thermocouples TC1, TC2, TC3, and TC4 for monitoring and/or controlling the temperature throughout the furnace system 800. The furnace system 800 may further include various mass flow controllers MFC1 and MFC2 to control the flow of various gases within the furnace system 800. It will be understood that although five pressure gauges, four thermocouples, and two mass flow controllers are depicted in given locations, any suitable number and arrangement of pressure gauges, thermocouples, and mass flow controllers may be included in the furnace system 800. In some embodiments, the oxidizing gas source 106 may direct oxidizing gas towards the catalytic converter system 110 using the vacuum pump 107 and/or the air injector 109, as described in reference to FIG. 1.

With respect to pressure control, pressure may be controlled so as to not over-pressurize the furnace chamber 102 so as to not compromise the components connected downstream of the furnace chamber 102. Initially, gas inlet pressure may be set at P0 either manually or by controller 116. In some embodiments, the gas inlet pressure at P0 may be set in a range of 0-10 PSI. For example, the gas inlet pressure at P0 may be set in a range of 0-3 PSI when the furnace chamber 102 comprises a ceramic tube furnace chamber. As another example, the gas inlet pressure at P0 may be set in a range of 0-10 PSI when the furnace chamber 102 comprises a metal furnace chamber. The pressures at P2 and P3 may be monitored, and the pressure at P2 may be maintained as about the same pressure as the pressure at P1. In the context of the current disclosure, about a 0.5 PSI pressure difference in the pressure at P1 and P2 may be considered as about the same pressure. The pump 802 may maintain a substantially constant pressure range across P3 and P4. In some embodiments, the pump 802 may be a variable low speed pump. In such embodiments, the pump 802 may be controlled based on at least the measured pressure at P3. In some embodiments, the pressures at P0, P1, P2, P3, and P4 may be monitored by the controller 116 or manually, and processing performed within the furnace system 800 may be stopped if the pressure at one or more of P0, P1, P2, P3, and P4 exceeds or falls below one or more predetermined thresholds. In some embodiments, an alarm may be initiated if the pressure at one or more of P0, P1, P2, P3, and P4 exceeds or falls below one or more predetermined thresholds.

With respect to catalyst temperature control, the furnace system 800 may be configured to try to maintain the temperature at TC2 at a substantially constant temperature. That is, the temperature of the catalyst contained in the catalyst enclosure 111a may be maintained at a substantially constant temperature range. In some embodiments, the temperature at TC2 may be maintained within a range of 285-600 degrees Celsius. In some embodiments, the temperature at TC2 may depend on the catalyst contained in the catalyst enclosure 111a. The catalyst heater 111b controls the adjustable setpoint at TC1 based on the monitored temperature feedback from TC2. In some embodiments, the adjustable setpoint at TC1 may be within a range of 225-425 degrees Celsius. If TC2 meets or exceeds the setpoint (i.e., if the catalyst gets overheated) the following steps may be performed: (1) the catalyst heater 111b may be turned off; (2) the oxidizing gas flow from the oxidizing gas source 106 through MFC2 may be increased; and (3) the inlet gas flow through MFC1 may be decreased. In some embodiments, the speed of pump 802 may slow down to match the decreased flow of the inlet gas flow through MFC1. Eventually the inlet gas flow through MFC1 may be stopped, thereby isolating the furnace chamber 102 from the oxidizing gas source 106. In some embodiments, if the CO detector 112 detects CO, or detects an amount of CO that meets or exceeds a threshold value, then MFC1, MFC2, and power to the one or more heating elements 122 may be shut off. In some embodiments, the temperature at TC1, TC2, TC3, and TC4 may be monitored by the controller 116 or manually, and processing performed within the furnace system 800 may be stopped if the temperature at one or more of TC1, TC2, TC3, and TC4 exceeds or falls below one or more predetermined thresholds. In some embodiments, an alarm may be initiated if the temperature at one or more of TC1, TC2, TC3, and TC4 exceeds or falls below one or more predetermined thresholds.

FIGS. 9A-B are block diagrams of variations of a furnace system 900 according to exemplary embodiments. As shown in FIG. 9A, the isolation system 104 may include an extended exhaust conduit 902a. In some embodiments, the extended exhaust conduit 902a may be an extension of the furnace exhaust conduit 103. The extended exhaust conduit 902a isolates the furnace chamber 102 from the oxidizing gas source 106 (e.g., a blower or compressor). As shown in FIG. 9A, the extended exhaust conduit 902a may be a conduit of sufficient length and tortuosity such that back diffusion of oxidizing gas against a flow of gaseous effluent exiting the furnace chamber 102 is reduced or minimized. Extended exhaust conduit 902a may have, e.g., serpentine, zig-zag, corkscrew, or other tortuous shapes having regular or irregular undulations.

As shown in FIG. 9B, the extended exhaust conduit 902b may be a conduit of sufficient length and dimension with minimal tortuosity or linear shape, according to some embodiments. In such embodiments, the extended exhaust conduit 902b may be an extension of the furnace exhaust conduit 103. The extended exhaust conduit 902b may be of sufficient dimension (e.g., length and cross section) such that the back diffusion of oxidizing gas against the flow of gaseous effluent exiting the furnace chamber 102 may be reduced or minimized. For example, the extended exhaust conduit 902b may reduce the back diffusion of oxidizing gas against a flow of gaseous effluent exiting the furnace chamber 102 such that the oxidizing gas concentration in the furnace chamber 102 may be less than a predetermined threshold, e.g., 1 parts per billion (ppb) or 1 parts per million (ppm). The predetermined threshold for the oxidizing concentration may depend on a material of the part 126 being processed in the furnace chamber 102. For example, the predetermined threshold may be about 1 ppb when the part 126 is composed of titanium, which may be slightly lower than the predetermined threshold when the part 126 is composed of steel. In such embodiments, a gas flow may be 0.001 liters per minute to several standard liters per minute (slm). In some embodiments, the gas flow may depend on a size of the furnace chamber 102. For example, the gas flow in the furnace chamber 102 of an industrial furnace may be about 20-50 slm. Exemplary embodiments of the extended exhaust conduit 902b with sufficient dimensions (e.g., length and cross section) for reduced back diffusion are described in further detail below.

The extended exhaust conduit 902b may have dimensions (e.g., length and cross section) designed to facilitate gas flow at a given rate and to provide a Peclet number sufficiently high in magnitude, with the flow of appropriate direction, for limiting concentration of a certain gas, e.g., oxidizing gas, to a predetermined amount, e.g., less than 1 ppb or 1 ppm, within the furnace chamber 102. In some embodiments, the Peclet number may be of magnitude greater than one of 10, 20, 40, 100, and 1000. That is, for a given flow of effluent gas, the dimensions of the extended exhaust conduit 902b may be selected so as to provide a Peclet number sufficiently high in magnitude, with the flow of appropriate direction, to maintain the furnace chamber 102 at less than or equal to 1 ppb or 1 ppm.

As a non-limiting first example, when nitrogen is used as a process gas in the furnace chamber 102 and the catalytic converter system 110 operates at 500 degrees Celsius, the extended exhaust conduit 902b may comprise a length of 50 mm and an inside diameter of 1.7 mm to facilitate a process gas flow of about 0.0017 slm and reduce or minimize the back diffusion of oxidizing gas against a flow of gaseous effluent such that the oxidizing gas concentration in the furnace chamber 102 is about 1 ppb. That is, the extended exhaust conduit 902b may be configured to reduce or minimize the back diffusion of oxidizing gas to 1 ppb when the process gas flow is about 0.0017 slm. In some embodiments, the furnace chamber 102 fluidly connected to the extended exhaust conduit 902b configured to maintain a predetermined oxidizing gas concentration, e.g., about 1 ppb, may include an oxidizing gas concentration larger than the predetermined oxidizing gas concentration, e.g., about 1 ppm. This may be due to leaks within the furnace system 900 and/or unwanted process gas within the furnace chamber 102. Accordingly, the furnace chamber 102 may under perform compared to the isolation system 104, i.e., the extended exhaust conduit 902b. That is, the large oxidizing gas concentration in the furnace chamber 102 may be contributed more to such leaks and/or unwanted process gas compared to the reduced back diffusion of oxidizing gas from the isolation system 104. In some embodiments, the back diffusion of oxidizing gas used in the catalytic converter system 110 may be maintained at a level that may be orders of magnitude below other sources of oxidizing gas, such as leaks, virtual leaks, and unwanted process gas. For example, the back diffusion of the oxidizing gas used in the catalytic converter system 110 may be maintained at about 1 ppb where the oxidizing gas concentration in the furnace chamber 102 may be about 10 ppm (or 10,000 ppb). In this example, the back diffusion of the oxidizing gas used in the catalytic converter system 110 may be about 4 orders of magnitude below other sources of oxidizing gas for the furnace chamber 102. It is understood that one order of magnitude indicates a factor of 10.

An exemplary Matlab script providing exemplary calculations for determining the dimensions of the extended exhaust conduit 902b is provided below with related description following the Matlab script. As shown below, several comments are embedded in the Matlab script to provide context and clarity.

% Example calculation for back-diffusion prevention in a tube (e.g., extended exhaust conduit 902b)
%1D model, L>>dia (as shown in FIGS. 9B-9C
dia=(0.125-0.03*2)*25.4/1000;% [m] internal diameter of the tube
L=0.05;% [m] length of the tube
% C0=200e3;% [ppm] concentration of impurity species in ‘dirty’ region: e.g., O2 in atmosphere
C0=781e3; % [ppm] concentration of impurity species in ‘dirty’ region: e.g., N2 in atmosphere
C1=1e-3;% [ppm] target concentration of impurity species in ‘clean’ chamber
Tgas=700;% [K] temperature of the gas at which to evaluate the diffusivity and fluid properties
% Operate at atmospheric pressure
rho=0.69528; %[kg/m{circumflex over ( )}3] density of the gas at the prescribed temperature
mew=4.3492e-5; % [Pa*s] kinematic viscosity of the gas at the prescribed temperature
% Calculations follow
Pe=−1*log(C1/C0);% [-] required Peclet number to achieve concentrations listed above
A=dia{circumflex over ( )}2*pi/4; % [m{circumflex over ( )}2] cross-sectional area of the tube
% Calculate the diffusivity of the two species of interest, e.g., O2 and N2
kb=1.380649e-23;% [J/K] Botlzmann constant
Av=6.022140858e23; % [g/mol] Avagadro's number
% Assume pressure differential between chamber (e.g., furnace chamber 102) and ambient is
small, and impact on diffusivity % and density is also small. This assumption is checked later.
ma=40/Av/1000; %[kg] atomic mass of species A: argon
mb=28/Av/1000; %[kg] atomic mass of species B: N2
% mb=32/Av/1000; %[kg] atomic mass of species B: O2
da=1.94e-10; %[m] diameter of species A: argon
db=1.5e-10; %[m] diameter of species B: N2
% db=1.46e-10; %[m] diameter of species B: O2
P=14.696/0.000145038; % [Pa] estimate of absolute gas pressure (1 atm) in the chamber (e.g., furnace chamber 102) and in the approximation throughout the tube (e.g., extended exhaust conduit 902b) (see comment above assuming now pressure drop)
D=⅔*sqrt(kb{circumflex over ( )}3/pi{circumflex over ( )}3)*sqrt(1/(2*ma)+1/(2*mb))*4*Tgas{circumflex over ( )} (3/2)/(P*(da+db){circumflex over ( )}2); %[-] Binary diffusion coefficient of the two species
u=Pe*D/L; %[m/s] % required mean flow velocity in the tube
Q=u*A; % [m{circumflex over ( )}3/s] % required volumetric flow rate in the tube, at Tgas
Re=rho*u*dia/mew; % [-] Reynolds number, for checking laminar assumption <2300
delP=128*L/pi*mew*Q/dia{circumflex over ( )}4*0.000145038;% [psi] pressure drop in circular tube from viscous flow
% If pressure delta is not small as compared to absolute pressure, re-evaluate properties

For the calculations provided in the Matlab script, the furnace chamber 102 may maintain a specified impurity concentration, e.g., an atmosphere substantially free of oxygen, against regular atmosphere using the extended exhaust conduit 902b. Oxidizing gas may be an important gas to prevent from flowing back into the furnace chamber 102. In some embodiments, the extended exhaust conduit 902b may be configured to prevent back diffusion of nitrogen, which may have a slightly higher diffusion coefficient in a clean gas compared to oxidizing gas, and/or water vapor, i.e., gaseous H20. In the context of the current disclosure, the diffusion coefficient (D) may indicate a proportionality coefficient between the flux of species and the gradient of species. The diffusion coefficient may have a unit of (length)2/time. For example, a higher diffusion coefficient for flux (J), where J=−D·dc/dz, indicates a higher flux (J) for a same gradient (dc/dz). For the calculations above, the furnace chamber 102 may use nitrogen as a processing gas, and the extended exhaust conduit 902b may be configured to prevent oxidizing gas back diffusion.

As described with reference to the non-limiting first example, the extended exhaust conduit 902b may have a length of approximately 50 mm and an inner diameter of approximately 1.7 mm to facilitate a nitrogen processing gas mass flow of approximately 0.0017 slm. The extended exhaust conduit 902b may be configured to maintain an oxidizing gas concentration of 1 ppb in the furnace chamber 102. In some embodiments, the atmospheric oxidizing gas concentration may be 200,000 ppm, and the binary diffusion coefficient between the nitrogen processing gas and the oxidizing gas may be estimated to be 8.76e-5 m2/s at a mean gas temperature of 700K and 1 atmospheric pressure. In some embodiments, the binary diffusion coefficient between the nitrogen processing gas and the oxidizing gas may be derived using the Chapman-Enskog theory, as explained in pages 123-124 of “The Properties of Gases and Liquids,” the entirety of which is incorporated by reference into this application. See REID, R. C., PRAUSNITZ, J. M., & POLING, B. E. (1987). The properties of gases and liquids. New York, McGraw-Hill. In some embodiments, the magnitude of the Peclet number and the direction of gas flow needed to maintain oxidizing gas concentration of 1 ppb in the furnace chamber 102 may be approximately 19.11.

Given the above dimensions of the extended exhaust conduit 902b, the mean gas velocity in the extended exhaust conduit 902b may be 34 mm/s. In some embodiments, the mean gas velocity may be converted to a volume flow rate based on a cross-sectional area of the extended exhaust conduit 902b. The volume flow rate may then be converted to a mass flow rate of approximately 0.0017 slm, where density temperature dependency (e.g., PV=nRT) of the flowing gas (e.g., the nitrogen processing gas) may be considered in this conversion to the mass flow rate. In some embodiments, the pressure drop across the extended exhaust conduit 902b may be negligibly small.

For the purpose of the calculation with respect to the Matlab script, the following assumptions may apply: (1) an optimal gas mixing in the furnace chamber 102; (2) the nitrogen gas directed into the furnace chamber 102 is clean, which indicates that there are no additional sources of impurity species other than the oxidizing gas, thereby allowing an observation of the efficiency of the extended exhaust conduit 902b in reducing or minimizing back diffusion of oxidizing gas; (3) the furnace system 900 is isothermal (i.e., uniform temperature throughout the entire furnace system 900) and in a steady state (i.e., properties measured at each and any point in the furnace system 900 may not vary in time); (4) tracks one contaminant species, i.e., the oxidizing gas; and (5) the length of the extended exhaust conduit 902b is large with respect to its diameter.

In some embodiments, the extended exhaust conduit 902b may scale in gas consumption for more stringent purity requirements (i.e., lower oxidizing gas concentration requirements). For example, the mass flow rate of the nitrogen gas may be increased from 0.0017 slm to 0.0019 slm (about an 11% increase in the amount of gas) in order to reduce an oxidizing gas concentration of 1 ppb to 0.1 ppb. Accordingly, a reduction in the oxidizing gas concentration of about an order of magnitude may be achieved by flowing about 11% more nitrogen gas.

It is understood that the calculations included in the Matlab script refer to the non-limiting first example only, and variations of the calculations included in the Matlab script may be performed in alternative embodiments. It is also understood that the various simplifying assumptions with reference to the calculations included in the Matlab script have been made solely for the purpose of explanation and clarity. As such, it is understood that variations of the calculations included in the Matlab script may be provided with reference to alternative embodiments of the furnace system.

Another method of calculation for extended exhaust conduit 902b dimensions is explained in further detail as follows with reference to FIGS. 9C-9F. As shown in FIG. 9C, the furnace chamber 102 may operate at an atmospheric pressure. The furnace chamber 102, which may include a heated reservoir, may receive an uncontaminated processing gas (hereinafter referred to as clean processing gas), e.g., nitrogen, through the gas inlet 115, and gaseous effluent may be directed out of the furnace chamber 102 through the extended exhaust conduit 902b and towards the catalytic converter system 110. The clean processing gas may be flowed through the gas inlet 115 into the furnace chamber 102 at a first rate of mass flow, where the clean processing gas has a first concentration of a species of molecules comprising the first rate of mass flow. The gaseous effluent may flow out of the furnace chamber 102 at a second rate of mass flow, where the gaseous effluent has a second concentration of the species of molecules comprising the second rate of mass flow. The material present in the furnace chamber 102 may be in a well-mixed state. That is, a measurement of material exiting the furnace chamber 102 may be an appropriate approximation of the actual composition of the material present in the furnace chamber 102, assuming the samples are taken at approximately the same time. In some embodiments, the clean processing gas and the gaseous effluent may not be isothermal. In some embodiments, the clean processing gas and the gaseous effluent may be isothermal. In some embodiments, the clean processing gas and the gaseous effluent may not maintain a same temperature in the furnace system 900. For example, the clean processing gas may be at a temperature between approximately 20 and approximately 50 degrees Celsius and the gaseous effluent may be at a temperature between approximately 300 and approximately 1,400 degrees Celsius. In some embodiments, an air injector 109 (also referred to as an oxygen injector, which may introduce air or oxygen gas into the extended exhaust conduit 902b) may be coupled to the extended exhaust conduit 902b downstream of the furnace chamber 102. In some embodiments, the air injector 109 may be positioned upstream of the catalytic converter system 110.

The extended exhaust conduit 902b may be configured to prevent back diffusion of oxidizing gas towards the furnace chamber 102. The furnace chamber 102 may need to be maintained at an atmosphere substantially free of oxygen. In some embodiments, an atmosphere substantially free of oxygen may be considered as an atmosphere including an oxidizing gas concentration of approximately 10 ppm or less.

For the purpose of this method of calculation, the following assumptions may apply: (1) a continuum transport (i.e., not a transition transport or a molecular transport); (2) model as isothermal (i.e., uniform temperature throughout the furnace system 900) and at steady state (i.e., the furnace system 900 is in a steady state)); (3) model as a one dimensional transport, where L>>d (i.e., changes along the length of the extended exhaust conduit 902b may be of more significance than that of the inner diameter); (4) an sufficient gas mixing in the furnace chamber 102; and (5) tracks one contaminant species, e.g., the oxidizing gas. For the purpose of this method of calculation, a temperature difference may help. For example, transport may be encouraged from a relatively hot chamber to a relatively colder chamber (e.g., a chamber or part of a chamber containing impurities), where migration may occur from hot to cold (also referred to as thermophoresis).

As shown in FIG. 9C, c1 indicates a concentration of a contaminant species in the furnace chamber 102, c0 indicates a concentration of the contaminant species at the distal end of the extended exhaust conduit 902b (i.e., the end of the extended exhaust conduit 902b distal to the furnace chamber 102), d indicates an inside diameter of the extended exhaust conduit 902b, L indicates a length of the extended exhaust conduit 902b, and u indicates a mean velocity of the gaseous effluent gas flow in the extended exhaust conduit 902b. In some embodiments, the concentration of the contaminant species in the extended exhaust conduit 902b may be based on the amount of back diffusion of the contaminant species. In some embodiments, the concentration of the contaminant species in the extended exhaust conduit 902b may be further based on the concentration of the contaminant species in the gaseous effluent. In some embodiments, the contaminant species may be the oxidizing gas. In some embodiments, the mean velocity u may encompass the inner diameter d and a prescribed volumetric rate of gas flow per time. In some embodiments, d may be negligibly small compared to L. Given the above noted assumptions, the following equation may be obtained based on the relationship between c1, c0, d, and u:

∂ c ∂ t + u ∂ c ∂ z = D ∂ 2 c ∂ z 2 ( 1 )

where t indicates time, c indicates a concentration profile of the contaminant species, D indicates a diffusivity of the contaminant species, and z indicates a position along the extended exhaust conduit 902b. As there is no time dependency due to the assumption that this calculation is considering a steady state,

∂ c ∂ t

equals 0. Accordingly, the equation (1) may become:

u ∂ c ∂ z = D ∂ 2 c ∂ z 2 ( 2 )

In some embodiments, an ordinary differential equation of equation (2) with scaled, or normalized, variables may be derived as follows:

Pe d c ^ d z ^ = d 2 c ^ d z ^ 2 ( 3 )

where the length z may be scaled with the total length of the extended exhaust conduit 902b as

z ^ = z L ,

the concentration of the contaminant species throughout the furnace system 900 may be scaled with the concentration of the contaminant species at the distal end of the extended exhaust conduit 902b as

c ^ = c c 0 , and Pe = uL D .

In some embodiments, ĉ and {circumflex over (z)} are transformations to a dimensionless space. That is, dimensionless equation (3) may be derived from equation (2), which is in a dimensional form. In some embodiments, a first boundary constraint may be provided as ĉ=1 at {circumflex over (z)}=0 and a second boundary constraint may be provided as ĉ=0 at {circumflex over (z)}=1. In some embodiments, {circumflex over (z)} indicates a normalized position along the extended exhaust conduit 902b, and ĉ indicates a normalized concentration profile of the contaminant species.

In some embodiments, the following equation may be derived from equation (3):

c ( z ) = c 0 ( e Pe - e z l · Pe ) + c 1 ( e z l · Pe - 1 ) ( e Pe - 1 ) ( 4 ) - 1

In some embodiments, equation (4)-1, which is in a dimensional form, may be normalized by dividing equation (4)-1 with c0, thereby obtaining dimensionless equation as follows:

c ^ = e Pe - e z ^ Pe + c 1 c 0 ( e z ^ Pe - 1 ) e Pe - 1 ( 4 ) - 2

where ĉ is plotted as shown in FIG. 9D according to some embodiments. As shown in FIG. 9D, the ĉ, i.e., normalized concentration profiles, may be plotted as a function of a normalized position ({circumflex over (z)}) and Peclet number (Pe) 922, 924, 926, 928, and 930. As shown in FIG. 9D, {circumflex over (z)}=0 indicates a position furthest away from the furnace chamber 102 on the extended exhaust conduit 902b (the distal end of the extended exhaust conduit 902b), and {circumflex over (z)}=1 indicates a position adjacent to the furnace chamber 102 on the extended exhaust conduit 902b (the proximal end of the extended exhaust conduit 902b). This indicates that the gas flow within the extended exhaust conduit 902b flows from z=L towards z=0 (FIG. 9C). Accordingly, a mean velocity (u) and the Peclet number may be less than zero. The concentration of the contaminant species may be highest when {circumflex over (z)} is approximately 0, and the concentration of the contaminant species may be approximately 0 when {circumflex over (z)} is approximately 1. As shown in FIG. 9D, the concentration profile of the contaminant species may be largest toward smaller values of the position {circumflex over (z)}. Further, the concentration species may become higher as {circumflex over (z)} becomes smaller along the extended exhaust conduit. In contrast, the concentration profile of the contaminant species may become lower as {circumflex over (z)} gets higher. Further, FIG. 9D shows that an extended exhaust conduit 902b providing a lower (e.g., more negative) Pe number may better prevent back diffusion of the contaminant species towards the furnace chamber 102.

In some embodiments, a flux (J) (i.e., the rate (per time) at which the contaminant species pass through an area) is derived based on equation (4)-2 as follows:

J = - D dc dz = - D Pe L e Pe - 1 ( - c 0 e z L · Pe + c 1 e z L · Pe ) ( 5 ) - 1 J = - D Pe L · c 0 e Pe - 1 ( - e z L · Pe + c 1 c 0 e z L · Pe ) where Pe = u _ · L D ( 5 ) - 2 J = - u _ · c 0 e Pe - 1 ( - 1 + c 1 c 0 ) e z L · Pe ( 5 ) - 3 J = u _ · c 0 e Pe - 1 ( 1 - c 1 c 0 ) e z L · Pe where flux may be referred to in units of ( amount of species ) / m 2 · s ( 5 ) - 4

In some embodiments, a normalized flux (Ĵ) may be derived as follows:

J ^ = J ( Dc 0 L ) = - Pe e z ^ Pe e Pe - 1 ( c 1 c 0 - 1 ) ( 6 )

FIG. 9E illustrates an exemplary embodiment of the normalized flux (Ĵ) as a function of the Peclet number, where the magnitude of the Peclet number is small.

Referring back to FIG. 9C, a steady-state value is now calculated. As described above, it may be assumed that clean processing gas may be directed into the furnace chamber 102. It may be further assumed that: (1) the concentration values are dimensional; (2) Pe may be positive or negative, where a negative Pe indicates a gas flow away from the furnace chamber 102 and a positive Pe indicates a gas flow towards the furnace chamber 102; (3) a ratio of concentration profiles may be utilized to determine ppm; and (4) the atmospheric oxidizing gas concentration may be approximately 200,000 ppm by volume.

In some embodiments, the rate of change in contaminant species concentration profile may be provided by the following equation:


{Rate of change of species in the chamber}={(Species passing into the furnace chamber 102)−(Species passing out of the furnace chamber 102)}  (7)

In some embodiments, the rate of change of species in the chamber may be set as zero. That is, the concentration of the contaminant species within the furnace chamber 102 may be considered at a steady state. Further, the concentration of contaminant species flowing from the furnace chamber 102 to the exhaust conduit 902b may balance the concentration of the back diffused contaminant species present in the extended exhaust conduit 902b In such embodiments, equation (7) may be provided as follows:


0={flux in}−{flux out}  (8)-1

Equation (8)-1 may be rearranged such that the flux (J) derived above in equation (5) or (6) multiplied by the area (i.e., the cross sectional area of the extended exhaust conduit 902b as defined by inner diameter d) may equal a concentration profile of the contaminant species multiplied by a velocity of gas flow and further multiplied by the area, as shown in the following equation:

0 = { Flux * Area } - { ( Concentration in chamber ) * Velocity * Area } ( 8 ) - 2 = { A u _ · c 0 e Pe - 1 ( c 1 c 0 - 1 ) e z L · Pe } - { u _ · A · c 1 } ( 8 ) - 3

In some embodiments, equation (8)-3 may be rearranged as follows:

c 0 ( e Pe - 1 ) ( c 1 c 0 - 1 ) e Pe = c 1 ( 9 ) - 1 c 0 ( c 1 c 0 - 1 ) = c 1 ( e Pe - 1 ) e Pe ( 9 ) - 2 c 0 c 1 - c 0 = c 1 ( e Pe - 1 ) e Pe ( 9 ) - 3 c 1 ( 1 - ( e Pe - 1 ) e Pe ) = c 0 ( 9 ) - 4

Accordingly, the concentration within the furnace chamber 102 (c1), the concentration at the distal end of the extended exhaust conduit 902b (c0), and the Peclet number (Pe) may be shown to relate based on equation (8) as follows

c 1 = c 0 ( 1 - ( e Pe - 1 ) e Pe ) ( 10 )

where equation (10) is a rearrangement of equation (9)-4. As shown in equation (10), the concentration of the contaminant species (c1) may be provided in terms of the c0, and the Pe. In some embodiments,

Pe = uL D .

The ratio of species

c 1 c 0

may be plotted as shown in FIG. 9F according to some embodiments. Accordingly, the concentration of the contaminant species (c1) may be provided in terms of the c0, extended exhaust conduit 902b (e.g., length (L) and inside diameter (d)), and the diffusivity of the contaminant species (D), as shown in the following equation:

c 1 = c 0 1 - e uL D - 1 e uL D ( 11 )

Air is comprised of about 20.9% oxygen by volume, which is about 209,000 ppm/vol. Accordingly, to achieve a concentration of 10 ppb/vol within the furnace chamber 102, the ratio of

c 1 c 0

may be 4.7×10−8. Accordingly, a target quotient of contaminant species within the furnace chamber 102 as compared to the distal end of the extended exhaust conduit 902b may be estimated as 1×10−9 and the magnitude of Pe may be derived as 20 based on equations (10) and (11).

Referring back to FIG. 9C, the concentration of the contaminant species (c1) may be further derived based on an exit volume flow rate of the gaseous effluent (Qout). As a first step, an inlet volume flow rate of the clean processing gas may be determined. In some embodiments, the inlet volume flow rate may be set with an MFC. In a second step, an exit volume flow rate of the gaseous effluent (Qout) may be derived based on the inlet volume flow rate of the clean processing gas and a change in temperature between the clean processing gas and the gaseous effluent. In some embodiments, the second step may be computed as Qout=Tout/Tin*Qin, where Qin indicates the inlet flow rate, Tout indicates a temperature of the gaseous effluent, and Tin indicates a temperature of the clean processing gas. In a third step, the mean velocity (u) may be derived based on the exit volume flow rate and the area (A) of the extended exhaust conduit 902b. In such embodiments, u may be the equivalent of Qout/A. In a fourth step, a reasonable diffusivity (D) of the contaminant species may be obtained, as explained in “The Properties of Gases and Liquids” at pages 123-124. In some embodiments, the diffusivity (D) of the contaminant species may increase with temperature. The obtained diffusivity of the contaminant species may be a diffusivity value corresponding to a relatively high temperature above room temperature. In some embodiments, the diffusivity value corresponding to the relatively high temperature may be selected because the contaminant species may be more mobile at higher temperatures, which may increase a possibility of the contaminant species contaminating the furnace chamber 102 (i.e., increase the possibility of back diffusion of the contaminant species). In some embodiments, the diffusivity (D) of the contaminant species may be adjusted using the Champman-Enskog result (T{circumflex over ( )}3/2) or an empirical correlation (T{circumflex over ( )}1.75) based on the following equation:

D 1 D 2 = ( T 1 T 2 ) x ( 12 )

where x indicates a predetermined exponent, and 1 or 2 (e.g., D1 and T1 or D2 and T2) may each correspond to one of the reference and/or adjusted states in absolute temperature. Table 1 below provides non-limiting examples of the diffusivity (D) of oxygen when the clean processing gas is air, Ar, and N2, where the temperature indicates the temperature at which the diffusivity may be measured or computed

TABLE 1 Pair Temp, K D, cm∧2/s Air-O2 273 0.176  Ar-O2 300 0.454 N2-O2 293.2 0.22

In a fifth step, the concentration of the contaminant species (c1) may be determined using equation (11) based on the extended exhaust conduit 902b dimensions (e.g., length L and inside diameter d), the derived mean velocity (u), and the determined diffusivity (D) of the contaminant species.

As another non-limiting example, when nitrogen is used as a process gas in the furnace chamber 102 and the catalytic converter system 110 operates at 500 degrees Celsius, the extended exhaust conduit 902b may comprise a length of 20 cm and an inside diameter of about 6 mm to facilitate a gaseous effluent gas flow of 1 slm and reduce or minimize the back diffusion of oxidizing gas against the flow of gaseous effluent such that the gas concentration in the furnace chamber 102 due to back diffusion is below 1 ppm or below 1 ppb. That is, the extended exhaust conduit 902b may be configured to reduce or minimize the back diffusion of oxidizing gas to below 1 ppm or below 1 ppb when the gaseous effluent is flowing through the extended exhaust conduit 902b at a relatively high gas flow of 1 slm. In some embodiments, the extended exhaust conduit 902b may comprise a relatively large inside diameter for practical reasons, such as avoidance of clogging, e.g., caused by binder components. In such embodiments, the extended exhaust conduit 902b may be lengthened in accordance to the larger inside diameter. For example, the length of the extended exhaust conduit 902b may be increased by approximately the square of the increase in the inside diameter of the extended exhaust conduit 902b (hereinafter referred to as “square law scaling relationship”). In some embodiments, a similar isolation performance, i.e., prevention of oxidizing gas back diffusion, may be obtained as long as the square law scaling relationship is observed. In some embodiments, the square law scaling relationship may apply to a range of particle flow (pf) parameters spanning laminar flow and/or turbulent flow, as opposed to molecular or transition flow within the furnace system 900. In some embodiments, the square law scaling relationship may apply in vacuum pressures within the furnace system 900.

It is understood that the examples provided above are non-limiting, and the dimensions for the extended exhaust conduit 902b may vary depending on the furnace system 900, e.g., for any gaseous effluent gas flow and furnace chamber 102 impurity requirement, such that the extended exhaust conduit 902b achieves a Peclet number sufficiently high in magnitude, with the fib of appropriate direction, for the gaseous effluent gas flow to reduce or minimize back diffusion of oxidizing gas.

As shown in FIGS. 9A-B, the extended exhaust conduit 902a-b is fluidly connected to a conduit 906, which may be a separate conduit or a continuation of extended exhaust conduit 902a-b via a valve V1. One or and both of extended exhaust conduit 902a-b and conduit 906 may be heated in order to prevent condensation of high molecular weight species in the volatilized binder components present in the gaseous effluent. MFC1 may adjustably control the gas inlet such that a sufficient quantity of non-reactive gas is present in the gaseous effluent. In some embodiments, a sufficient quantity of non-reactive gas may indicate a proportion of the non-reactive gas present in the gaseous effluent large enough to bring the gaseous effluent below a lower explosive limit (LEL). The mixture of the non-reactive gas, the volatilized binder effluent, and the oxidizing gas do not form an explosive or self igniting mixture before entering the catalytic converter system 110. In some embodiments, the furnace system 900 may further include a binder system 601 disposed between the furnace chamber 102 and MFC2.

An exemplary process for pressure control and catalyst temperature control with reference to the furnace system 900 shown in FIGS. 9A-9B is described below. In some embodiments, the controller 116 may control the exemplary process for pressure control and catalyst temperature control as follows. As shown in FIGS. 9A-9B, the furnace system 900 may include one or more pressure gauges P0, P1, P2, and P3 for monitoring and/or controlling the pressure throughout the furnace system 900. The furnace system 900 may further include one or more thermocouples TC1, TC2, and TC3 for monitoring and/or controlling the temperature throughout the furnace system 900. The furnace system 900 may also include various mass flow controllers MFC1 and MFC2 to control the flow of various gases within the furnace system 900. It will be understood that although four pressure gauges, three thermocouples, and two mass flow controllers are depicted in given locations, any suitable number and arrangement of pressure gauges, thermocouples, and mass flow controllers may be included in the furnace system 900.

With respect to pressure control, pressure may be controlled so as to not over-pressurize the furnace chamber 102 so as to not compromise the components connected downstream of the furnace chamber 102. Initially, gas inlet pressure may be set at P0. In some embodiments, the gas inlet pressure at P0 may be set in a range of 0-10 PSI. For example, the gas inlet pressure at P0 may be set in a range of 0-3 PSI when the furnace chamber 102 comprises a ceramic tube furnace chamber. As another example, the gas inlet pressure at P0 may be set in a range of 0-10 PSI when the furnace chamber 102 comprises a metal furnace chamber. The pressures at P2 and P3 may be monitored, and the monitored pressures at P2 and P3 may be maintained as about the same pressure as the pressure at P0. In the context of the current disclosure, a pressure difference of about 0.5 PSI may be considered as about the same pressure. The control of pressure for the furnace system 900 may be focused on the initial pressure setting at P0 and the flow of oxidizing gas from the oxidizing gas source 106 via MFC2. That is, the pressure control within furnace system 900 may be primarily controlled via MFC2 and the initial pressure setting at P0. In some embodiments, the pressures at P0, P1, P2, and P3 may be monitored by the controller 116 or manually, and processing performed within the furnace system 900 may be stopped if the pressure at one or more of P0, P1, P2, and P3 exceeds or falls below one or more predetermined thresholds. In some embodiments, an alarm may be initiated if the pressure at one or more of P0, P1, P2, and P3 exceeds or falls below one or more predetermined thresholds.

With respect to catalyst temperature control, the furnace system 900 may be configured to try to maintain the temperature at TC2 at a substantially constant temperature. That is, the temperature of the catalyst contained in the catalyst enclosure 111a may be maintained at a substantially constant temperature range. In some embodiments, the temperature at TC2 may be maintained within a range of 285-600 degrees Celsius. In some embodiments, the temperature at TC2 may depend on the catalyst contained in the catalyst enclosure 111a. The catalyst heater 111b may effectively control the adjustable setpoint at TC1 based on the monitored temperature from TC2. In some embodiments, the adjustable setpoint at TC1 may be within a range of 225-425 degrees Celsius. If TC2 meets or exceeds the setpoint (i.e., if the catalyst gets overheated) the following steps may be performed: (1) the catalyst heater 111b may be turned off; (2) the oxidizing gas flow from the oxidizing gas source 106 through MFC2 may be increased; (3) the inlet gas flow through MFC1 may be decreased; and/or (4) valve V1 may be closed. The CO detector 112 detects CO from flowing out of the catalytic converter system 110. In some embodiments, if the CO detector 112 detects CO, or detects an amount of CO that meets or exceeds a threshold value, then MFC1, MFC2, and power to the one or more heating elements 122 may be shut off and/or an alarm may be triggered. In some embodiments, one or more heaters for the extended exhaust conduit 902a-b and/or conduit 906 may be controlled based on a temperature measured by TC3. In some embodiments, the furnace system 900 may include multiple TCs configured to monitor and/or control the one or more heaters for the extended exhaust conduit 902a-b and the conduit 906. In some embodiments, the temperature at TC1, TC2, and TC3 may be monitored by the controller 116 or manually, and processing performed within the furnace system 900 may be stopped if the temperature at one or more of TC1, TC2, and TC3 exceeds or falls below one or more predetermined thresholds. In some embodiments, an alarm may be initiated if the temperature at one or more of TC1, TC2, and TC3 exceeds or falls below one or more predetermined thresholds.

FIG. 10 is a block diagram of a furnace system 1000 according to one embodiment. Similar components shown in FIG. 10 may operate in a substantially similar manner as the corresponding components described in reference to FIGS. 1, 2A-2B, 3, 4, 5, 6, 7, 8, and 9. As shown in FIG. 10, the isolation system 104 may include a porous plug 1002 and a plug heater 1004. The porous plug 1002 may isolate the furnace chamber 102 from the oxidizing gas source 106 (e.g., a blower or compressed air). In some embodiments, the porous plug 1002 may be a micro porous plug. The porous plug 1002 may function to maintain a pressure difference across the porous plug 1002, and the small pores of porous plug 1002 may prevent back diffusion of oxidizing gas into the furnace chamber 102. In some embodiments, the size of the pores in the porous plug 1002 may be designed such that the pores are significantly larger than the mean free path of gas molecules, e.g., oxidizing gas. Such pores, of sizes significantly larger than the mean free path (mfp) of gas molecules, may allow the gas molecules to move around relative to each other to interact with each other. That is, when the mfp of gas molecules is relatively larger than the pore size, the gas molecules may interact with the walls of the pores and not each other. Accordingly, the forward flow of the gaseous effluent may not effectively prevent back diffusion of oxidizing gas. Instead, prevention of back diffusion of oxidizing gas into the furnace chamber 102 may depend on a pressure difference between the furnace chamber 102 and the catalytic converter system 110. In some embodiments, the furnace exhaust conduit 103 may be a conduit of sufficient length and tortuosity such that back diffusion of oxidizing gas against a flow of gaseous effluent exiting the furnace chamber 102 is reduced or minimized. For example, a sufficient tortuosity of the furnace exhaust conduit 103 may increase the velocity of the gaseous effluent such that a ratio of convective transport to diffusive transport is increased.

In some embodiments, the porous plug 1002 may be configured to facilitate the gaseous effluent flow and provide a Peclet number sufficiently high in magnitude, with the flow of appropriate direction, for limiting concentration of a certain gas, e.g., oxidizing gas, to a predetermined amount in an upstream direction, e.g., less than 1 ppb or 1 ppm, as described above with reference to the extended exhaust conduit 902b and related figures. In some embodiments, the porous plug 1002 may be considered as an approximate equivalent of the extended exhaust conduit 902b at least to the extent that any passive isolation arrangement for any give gas flow may be considered to have an effective Peclet number. For example, the porous plug 1002, e.g., a porous graphite plug, may include a plurality of parallel conduits, each of which comprise a certain dimension, e.g., length and inside diameter. Each of the plurality of parallel conduits may provide a Peclet number, as described above with reference to the extended exhaust conduit 902b. In some instances, each length of the multiple parallel conduits through porous plug 1002 may be summed to obtain a total length, and each inside diameter may be summed to obtain a total inside diameter. The total length and the total inside diameter may be the equivalent of the length and the inside diameter of the extended exhaust conduit 902b of FIG. 9B configured to provide a certain Peclet number. Accordingly, the porous plug 1002 may provide an equivalent Peclet number, thereby reducing or minimizing the back diffusion of oxidizing gas at a similar rate as the equivalent extended exhaust conduit 902b. As such, the exemplary calculations and considerations described above with reference to the extended exhaust conduit 902b of FIG. 9B may apply to the porous plug 1002. In some embodiments, the porous plug 1002 may be configured to constrain the gaseous effluent flow such that the gas flow velocity is elevated, thereby reducing or minimizing the back diffusion of oxidizing gas. For example, the porous plug 1002 may include pores larger than about 1 micron, which may be sufficient to facilitate molecular flow of the gaseous effluent at atmospheric pressure.

As shown in FIG. 10, the furnace system 1000 may include the furnace exhaust conduit 103 fluidly connecting the furnace chamber 102 and the porous plug 1002, a conduit 1006a fluidly connected to a conduit 1006b via a valve V1 where the conduits 1006a-b fluidly connect the porous plug 1002 to the catalytic converter system 100. The valve V1 may be left open during a sintering processing in the furnace system 1000. In some embodiments, the furnace system 1000 may include a plug heater 1004 configured to heat the porous plug 1002. The furnace exhaust conduit 103, conduits 1006a-b and/or the porous plug 1002 may be heated in order to prevent condensation of high molecular weight species in the volatilized binder components present in the gaseous effluent. MFC1 may adjustably control the gas inlet such that a sufficient quantity of non-reactive gas is present in the gaseous effluent. In some embodiments, a sufficient quantity of non-reactive gas may indicate a proportion of the non-reactive gas present in the gaseous effluent large enough to bring the gaseous effluent below a lower explosive limit (LEL). The mixture of the non-reactive gas, the volatilized binder effluent, and the oxidizing gas may not form an explosive or self igniting mixture before entering the catalytic converter system 110. In some embodiments, the furnace system 1000 may include a binder trap system (not shown in FIG. 10) disposed between the furnace chamber 102 and the porous plug 1002. The binder trap system may be used to condense or to coalesce volatilized binder components present in the gaseous effluent removing at least a portion of the volatilized binder components from the gaseous effluent before the gaseous effluent is directed to the catalytic converter system 110.

An exemplary process for pressure control and catalyst temperature control with reference to the furnace system 1000 is described below. In some embodiments, the controller 116 may control the exemplary process for pressure control and catalyst temperature control as follows. As shown in FIG. 10, the furnace system 1000 may include one or more pressure gauges P0, P1, P2, and P3 for monitoring and/or controlling the pressure throughout the furnace system 1000. The furnace system 1000 may further include one or more thermocouples TC1, TC2, TC3, and TC4 for monitoring and/or controlling the temperature throughout the furnace system 1000. The furnace system 1000 may also include various mass flow controllers MFC1 and MFC2 to control the flow of various gases within the furnace system 1000. It will be understood that although four pressure gauges, four thermocouples, and two mass flow controllers are depicted in given locations, any suitable number and arrangement of pressure gauges, thermocouples, and mass flow controllers may be included in the furnace system 1000. In some embodiments, an oxidizing gas source 106 may direct oxidizing gas towards the catalytic converter system 110 using a vacuum pump and/or the air injector 109, as described in reference to FIG. 1.

With respect to pressure control, pressure may be controlled so as to not over-pressurize the furnace chamber 102 so as to not compromise the components connected downstream of the furnace chamber 102. Initially, gas inlet pressure may be set at P0 either manually or by the controller 116. In some embodiments, the gas inlet pressure at P0 may be set in a range of 0-10 PSI. For example, the gas inlet pressure at P0 may be set in a range of 0-3 PSI when the furnace chamber 102 comprises a ceramic tube furnace chamber. As another example, the gas inlet pressure at P0 may be set in a range of 0-10 PSI when the furnace chamber 102 comprises a metal furnace chamber. The pressures at P2 and P3 may be monitored, and the pressures at P1 and P2 may be maintained at about the same pressure. In the context of the current disclosure, about a 0.5 PSI pressure difference in the pressure at P1 and P2 may be considered as about the same pressure. The pressure at P3 may be relatively lower than P1 and P2 due to a pressure drop across the porous plug 1002 and the introduction of oxidizing gas from the oxidizing gas source 106 via MFC2 into conduit 1006b. The control of pressure for the furnace system 1000 may be focused on the initial pressure setting at P1 and the flow of oxidizing gas from the oxidizing gas source 106 via MFC2. Accordingly, in the event of overpressure within the furnace system 1000, the inlet gas conduit 115 may be closed. In some embodiments, the overpressure may be caused by clogged binder components in the porous plug 1002. In such embodiments, providing additional heat to the porous plug 1002 via the plug heater 1004 may dislodge clogged binder components, permitting inlet gas conduit 115 to be re-opened and permitting continued operation of furnace system 1000. In some embodiments, the pressures at P0, P1, P2, and P3 may be monitored by the controller 116 or manually, and processing performed within the furnace system 1000 may be stopped if the pressure at one or more of P0, P1, P2, and P3 exceeds or falls below one or more predetermined thresholds. In some embodiments, an alarm may be initiated if the pressure at one or more of P0, P1, P2, and P3 exceeds or falls below one or more predetermined thresholds.

With respect to catalyst temperature control, the furnace system 800 may be configured to try to maintain the temperature at TC2 at a substantially constant temperature. That is, the temperature of the catalyst contained in the catalyst enclosure 111a may be maintained at a substantially constant temperature range. In some embodiments, the temperature at TC2 may be maintained within a range of 285-600 degrees Celsius. In some embodiments, the temperature at TC2 may depend on the catalyst contained in the catalyst enclosure 111a. The catalyst heater 111b may control the adjustable setpoint at TC1 based on the monitored temperature feedback from TC2. In some embodiments, the adjustable setpoint at TC1 may be within a range of 225-425 degrees Celsius. If TC2 meets or exceeds the setpoint (i.e., if the catalyst gets overheated) the following steps may be performed: (1) the catalyst heater 111b may be turned off; (2) the oxidizing gas flow from the oxidizing gas source 106 through MFC2 may be increased; (3) the inlet gas flow through MFC1 may be decreased; and/or (4) valve V1 may be closed. The CO detector 112 may detect CO flowing out of the catalytic converter system 110. In some embodiments, an alarm may be initiated if CO detector 112 detects CO or detects an amount of CO that meets or exceeds a threshold value. MFC1, MFC2, and power to the one or more heating elements 122 may be shut off upon CO detection. In some embodiments, the temperature at TC1, TC2, TC3, and TC4 may be monitored by the controller 116 or manually, and processing performed within the furnace system 1000 may be stopped if the temperature at one or more of TC1, TC2, TC3, and TC4 exceeds or falls below one or more predetermined thresholds. In some embodiments, an alarm may be initiated if the temperature at one or more of TC1, TC2, TC3, and TC4 exceeds or falls below one or more predetermined thresholds.

FIG. 11 depicts a block diagram of a furnace system 1100 according to one embodiment. Similar components shown in FIG. 11 may operate in a substantially similar manner as the corresponding components described in reference to FIGS. 1, 2A-2B, 3, 4, 5, 6, 7, 8, 9, and 10. As shown in FIG. 11, the furnace system 1100 is an embodiment of the furnace system 100 comprising a binder trap system 601, as described above with reference to FIG. 6. The isolation system 104 included in the furnace system 1100 comprises a vacuum pump 1107, as described with reference to FIG. 1. As shown in FIG. 11, the furnace system 1100 comprises a demister 1108, as described with reference to FIG. 1. In some embodiments, the furnace system 1100 further comprises a binder trap system bypass conduit 1105. In some embodiments, the vacuum pump 1107 may pump the gaseous effluent from the furnace chamber 102 via one or more furnace exhaust conduits through the binder trap system 601 or the binder trap system bypass conduit 1105. In some embodiments, a valve 101 on the binder trap system bypass conduit 1105 may be closed, and the gaseous effluent may be pumped from the furnace chamber 102 through the binder trap system 601 during a thermal debinding process of the part 126. In such embodiments, the gaseous effluent may include volatilized binder components, which may be passed through the binder trap system 601 and directed to the catalytic converter system 110. In some embodiments, one or more valves positioned upstream and/or downstream of the binder trap system 601 may be closed, valve 101 may be open, and the gaseous effluent may be pumped from the furnace chamber 102 through the binder trap system bypass conduit 1105 during a main sintering (e.g., densification) process of the part 126. In such embodiments, the gaseous effluent may bypass the binder trap system 601 and may be directed to the catalytic converter system 110. As described above, the gaseous effluent may be directed to bypass or pass through the binder trap system 601 depending on the type of processing for the part 126. For example, the gaseous effluent may be directed to pass through the binder trap system 601 during a thermal debinding process when volatized binder component is being generated and the catalytic converter system 110 is being used to remove the volatized binder component from the effluent. As another example, the gaseous effluent may be directed to bypass the binder trap system 601 during a main sintering process (e.g., densification) when less or no volatized binder component is being produced.

As shown in FIG. 11, the furnace system 1100 may include one or more pressure regulated gas sources, which may each include a process gas supply, a pressure regulator, and one or more pressure gauges and/or valves, e.g., P3, P4, and V3. Valve V3 may be a gas cylinder isolation valve V3 (a second gas cylinder isolation valve V4 is not shown in FIG. 11). The furnace system 1100 may also include a chamber isolation valve V7, an annulus valve V8 (also referred to as valve 101 with reference to FIG. 1), main vacuum valve V9, a vacuum vent valve V11, and an inlet isolation valve V100.

The furnace system 1100 may further include a control thermocouple TC1, a retort thermocouple TC4 for monitoring the load in the furnace chamber 102, a vacuum line heater thermocouple TC8, a binder trap thermocouple TC10; a vacuum pump overtemp thermocouple TC12; a catalyst temperature thermocouple TC13; and a catalyst exhaust thermocouple TC14. In some embodiments, the furnace system 1100 may further include a furnace chamber 102 over temperature thermocouple (not shown in FIG. 11, but potentially included). It will be understood that any suitable number and arrangement of thermocouples and valves be included in the furnace system 1100.

The furnace system 1100 may also include a chamber pressure/vacuum sensor P2, a gas high pressure/vacuum sensor P3 (a second a gas high pressure/vacuum sensor P5 is not shown in FIG. 11 but may be included), a gas low pressure/vacuum sensor P4 (a second gas low pressure/vacuum sensor P6 is not shown in FIG. 11), pump fore line pressure/vacuum sensor P7, and a furnace chamber positive pressure sensor P9. It will be understood that any suitable number and arrangement of pressure/vacuum sensors (also referred to as pressure gauges) be included in the furnace system 1100.

The furnace system 1100 may also include a heater H2 to heat the furnace exhaust conduit 103 and/or the binder trap 602, and a catalyst heater H3 (also referred to as catalyst heater 111b in FIG. 1) configured to the heat the catalytic converter system 110. In some embodiments, the binder trap cooler 604 may include a thermoelectric cooler (TEC), e.g., a peltier cooling device, or a TEC fan.

Described below is an exemplary procedure with reference to the furnace system 1100 according to one embodiment. In some embodiments, the exemplary procedure described below may be applied to a vacuum furnace system where the pressure may be substantially below atmospheric pressure. For example, the pressure may be below 10 Torr, where 1 atmospheric pressure is 760 Torr. While the procedure explained below is described with reference to a sintering process performed in the furnace system 1100, this is not required and the furnace system 1100 may be utilized for various types of processing in alternative embodiments.

In the context of the current disclosure, the following terms are used to described the catalyst temperature monitored and controlled by TC14: (1) T0 is a temperature below which the setpoint of the catalyst heater H3 is about equal to T10 (T10 will be described in further detail below with respect to the terms with reference to TC13); (2) T1 is a temperature at which the setpoint of the catalyst heater H3 is lowered at TC13; (3) T2 is a minimum temperature at which catalyst oxidizes volatilized binder components; (4) T3 is a temperature at which the setpoint of the catalyst heater H3 at TC13 is about equal to T11 (H3 power may be under closed loop control between T1 and T3; T11 will be described in further detail below with respect to the terms with reference to TC13); (5) T4 is a temperature at which a ramp rate of a furnace program (falling temperature) will resume/continue; (6) T5 is a temperature at which a ramp rate of the furnace program (rising temperature) will pause; (7) T6 is a temperature at which V7 will close due to rising temperature; and (8) T7 is a maximum safe operating temperature of the catalyst. The furnace program may be configured to abort if the temperature at TC14 exceeds T7. In some embodiments, T0 may be about 225 degrees Celsius; T1 may be about 270 degrees Celsius; T2 may be about 280 degrees Celsius; T3 may be about 315 degrees Celsius; T4 may be about 365 degrees Celsius; T5 may be about 475 degrees Celsius; T6 may be about 525 degrees Celsius; and T7 may be about 575 degrees Celsius. The temperatures listed above are approximate temperatures, and it is understood that the temperature values may vary depending on a type of catalyst and/or binder used in the furnace system 1100, among other factors, in alternative embodiments.

In the context of the current disclosure, the following terms are used to describe the catalyst heater temperature monitored and controlled by TC13: (1) T8 is a maximum temperature at which a processing within the furnace system 1100 is configured to abort if a monitored temperature at TC13 exceeds T8; (2) T10 is a maximum setpoint of the catalyst heater H3 at TC13; and (3) T11 is a minimum setpoint of the catalyst heater H3 at TC13. In some embodiments, the catalyst heater H3 setpoint may be varied between temperature T1 and T3 above at TC14. In some embodiments, T8 may be 600 degrees Celsius; T10 may be 400 degrees Celsius; and T11 may be 275 degrees Celsius. The temperatures listed above are approximate temperatures, and it is understood that the temperature values may vary depending on a type of catalyst and/or binder used in the furnace system 1100, among other factors, in alternative embodiments.

In some embodiments, the relative values of the temperatures listed above may be as follows: T0<T1<T2<T3<T4<T5<T6<T7, where T8 is similar to, but not equal to, T7, and T11<T10. That is, the setpoint of the catalyst heater H3 is low when the temperature at TC14 is high and the setpoint of catalyst heater H3 is high when the temperature at TC14 is low.

In the context of the current disclosure, the following terms are used to described a furnace pressure at P2: (1) PV1 is a pressure at which the ramp rate of the furnace program will resume (e.g., PV1 indicates falling pressure within the furnace chamber 102); and (2) PV2 is a pressure at which the ramp rate of the furnace program will pause (e.g., PV1 indicates rising pressure within the furnace chamber 102), where PV1<PV2. In some embodiments, the furnace pressure at P2 may be at a baseline pressure of 1-2 Torr. In such embodiments, PV2 may be around 5-6 Torr, and PV1 may be around 3-4 Torr. In some embodiments, the furnace pressure at P2 may be lower, e.g., 0.1-1 Torr. In such embodiments, PV2 may be around 4-5 Torr and PV1 may be around 2-3 Torr. The pressures listed above are approximate pressures, and it is understood that the pressure values may vary in alternative embodiments.

Referring back to FIG. 11, an exemplary procedure with reference to a sintering process in the furnace system 1100 is described in detail below. In some embodiments, the exemplary procedure may be a control method performed by the controller 116.

At the beginning of the sintering process, the furnace chamber 102 may be loaded with a part 126 for a sintering process and closed. As noted above, the sintering process in the context of the current disclosure may include at least one of a thermal debinding process and a main sintering process (e.g., densification). Subsequently, V3 may be closed and MFC 113 may be set to zero flow. The vacuum pump 107 may be turned on and may remain operational for the duration of the procedure. After the vacuum pump 107 is started: (1) V7 and V9 may be opened, and (2) V8 may be closed. In some embodiments, V7 may be fluidly connected via internal conduits to the retort 124. The heater H2 may be turned on to heat the furnace conduit 103. The binder trap cooler 604, e.g., the TEC and/or the TEC fan, may be turned on. The binder trap cooler 604 may be configured to cool the binder trap 602 to facilitate the condensing or coalescing of volatilized binder components present in the gaseous effluent. In some aspect, operation of the binder trap cooler 604 may allow the binder trap 602 to collect sufficient volatilized binder components. Otherwise, if not enough binder component is collected, the non-collected volatilized binder components may clog the vacuum pump 107 or may flow through the vacuum pump 107 and into the catalytic converter system 110. Volatilized binder components in the catalytic converter system 110 may cause the enclosed catalyst to overheat. Non-collected volatilized binder components may also condense in the vacuum line between the binder trap 602 and the vacuum pump 107 and cause a clog.

The catalyst heater H3 and the air injector 109 may be turned on. In some embodiments, the vacuum pump 107 may include a ballast to provide an air injection from the oxidizing gas source 106. The oxidizing gas provided by the vacuum pump 107 and/or the air injector 109 may be used to partially or completely combust volatilized binder components present in the gaseous effluent. In some embodiments, the gaseous effluent flowing out of the vacuum pump 107 exhaust and towards the catalytic converter system 110 may include pump oil. The demister 108 may be positioned adjacent to the vacuum pump 107 exhaust and may be configured to remove and drain the pump oil back to the vacuum pump 107. Without the demister 108, the pump oil present in the gaseous effluent may enter the catalytic converter system 110, which may clog the catalytic converter system 110 and cause the enclosed catalyst to overheat. Further, the continuous loss of the pump oil may cause the vacuum pump 107 to run dry.

The furnace chamber 102 may be pumped down until the pressure at P2 reaches a desired level. The desired level may vary depending on a type of pump used in the furnace system 1100 and amount of insulation implemented. In some embodiments, the desired level may be 1e−5 Torr. In some embodiments, the desired level may be less than 50 mTorr. In some embodiments, the desired level may be less than 1 Torr. The controller 116 may next initiate a system check before the furnace system 1100 begins to heat up. As a pre-heat system check, an automated leak check may be performed on the furnace system 1100, including the binder trap 602. The automated leak check may be performed by measuring the pressure at P2 and P7. As another pre-heat system check, TC8 may be used to monitor the temperature of the furnace exhaust conduit 103, which is heated by heater H2. The sintering process may not continue if the temperature at TC8 is below a predetermined minimum temperature threshold. In some embodiments, the predetermined minimum temperature threshold may be about 150 degrees Celsius. H2 may function to prevent condensation of high molecular weight species in the binder components present in the gaseous effluent binder from condensing before desired and clogging the furnace exhaust conduit 103. As another pre-heat system check, TC10 may be used to monitor the temperature of the binder trap 602. The sintering process may not continue if the temperature at TC10 is above a predetermined maximum temperature threshold. In some embodiments, the predetermined minimum temperature threshold may be about 15 degrees Celsius. In some embodiments, the temperature of the binder trap 602 may be cooled to 10 degrees Celsius. As yet another pre-heat system check, TC13 may be used to monitor the temperature of the catalyst enclosure 111a. The sintering process may not continue if the temperature at TC13 is not at a proper temperature, e.g., about 225-400 degrees Celsius.

After the pre-heat system, heating may be initiated for the furnace system 1100. Once heating is started, V7 and V9 may remain open. V3 may be opened, and the WC 113 may set the desired flow valve for the gas inlet conduit 115. Power may be applied to the heating elements, e.g., heating elements 122 in the furnace chamber 102. During heating, TC1 and TC4 may be used to monitor and to control the ramp rate. Accordingly, the temperature within the furnace chamber 102 may be controlled such that it ramps at a desired rate. In some embodiments, the desired rate may be 1-5 degrees per minute (deg/min).

Once the temperature monitored by TC1 and/or TC4 indicates that the temperature of within the furnace chamber 102 is approaching a debinding temperature, the temperature ramp rate may be slowed by the controller 116. In the context of the current disclosure, a debinding temperature is a temperature in which a thermal debinding process is performed. For example, a debinding temperature of 370 degrees Celsius may degrade binder components included in the part 126. In some embodiments, the debinding temperature may depend on the type of binder components included in the part. For example, the debinding temperature of 370 degrees Celsius may be for a polypropylene binder. In some embodiments, the debinding temperature may be between 350-400 degrees Celsius. In some embodiments, the debinding temperature may be between 250-400 degrees Celsius. In some embodiments, the debinding temperature may depend on a temperature ramp rate of the furnace chamber 102. For example, the debinding temperature may be lower for a slower temperature ramp rate. Slower ramp rates may start to produce volatilized binder at lower temperatures.

Once the temperature within the furnace chamber 102 exceeds the debinding temperature, the part 126 may begin to release volatilized binder components within the furnace chamber 102. As the thermal debinding process begins, the furnace chamber temperature continues to ramp at a slowed rate. For example, the ramp rate may be slowed from 3 deg/min to 0.5 deg/min. Further, the binder trap 602 may begin to collect volatilized binder components that are condensable and/or coalescable. In some embodiments, the binder trap 602 may collect about 20-60%, e.g., about 40%, of the total binder components included in the part. The CO detector 112 may be used to continuously or intermittently monitor furnace system 1100 exhaust for the presence of CO. The controller 116 may be configured to abort the sintering process if the CO level detected by the CO detector 112 surpasses a predetermined threshold.

During the sintering process, the temperature of the catalyst enclosure 111a may be continuously or intermittently monitored and controlled by using the TC14. The monitoring and control may be designed to prevent catastrophic results in the catalytic converter system 110 in the event a non-debound part is left in the furnace chamber 102. In the context of the current disclosure, a non-debound part refers to a part that has not been solvent debound or incompletely solvent debound prior to the thermal debinding performed in the furnace system 1100. Such non-debound parts may contain a lot of primary binder, e.g., wax, that vaporize at a relatively low temperature and may then be consumed by the catalytic convertor.

A substantially constant temperature may be maintained at TC14 during the sintering process. In some embodiments, the catalyst heater H3 may heat the catalyst enclosure 111a. TC13 may be used to measure the temperature of the catalyst heater H3, and the setpoint of the catalyst heater H3 may vary between T10 and T11. As the gaseous effluent flows through the furnace system 1100 and into the catalyst enclosure 111a, the catalyst reaction may generate heat. Accordingly, once the catalyst reaction begins, the setpoint of the catalyst heater H3 may be lowered. That is, the catalyst heater H3 may not need to provide the same amount of heat to the catalyst enclosure 111a due to heat generated by the catalyst reaction.

If the temperature of the catalyst enclosure 111a measured at TC14 exceeds T3, the catalyst heater H3 may be turned off.

If the temperature of the catalyst enclosure 111a measured at TC14 exceeds T5, the furnace chamber temperature ramp may be paused. This will decrease the amount of gaseous effluent generated in the furnace chamber 102. Accordingly, the amount of catalyst reaction may decrease, which may lower the temperature at TC14. Once the temperature at TC14 becomes lower than T4, the furnace chamber temperature ramp may be resumed.

If the temperature measured at TC14 exceeds T6, then V7 may be closed. The closure of V7 may block off the flow of gaseous effluent to the catalyst enclosure 111a. Accordingly, the temperature at TC14 may start to decrease shortly thereafter. The furnace chamber temperature ramp may remain paused. In order to recover from the furnace system 1100 condition in which the temperature measured at TC14 exceeds T6, the following procedures may subsequently be performed. When the temperature at TC14 falls below T4, the V7 may be opened for a short period of time (set time) and then closed again. In some embodiments, the short period of time may be less than 1 minute, e.g., 10-30 seconds. The flow of gaseous effluent directed towards the catalyst enclosure 111a during the short period of time may cause the temperature at TC14 to rise again. For example, the temperature at TC14 may rise to exceed T5. As V7 is closed, the temperature at TC14 may again fall below T4, at which time the V7 may be opened. The opening and closing of V7 may be continued for increasingly longer opening times until the temperature at TC14 does not reheat over T5. At this point, V7 may be kept open and the sintering process may be continued.

If the temperature at TC14 exceeds T7, the sintering process may be aborted. If the temperature at TC13 exceeds T8, the sintering process may be aborted.

The binder components included in the part 126 may be completely volatilized when the furnace temperature is sufficiently high, e.g., about 500 degrees Celsius. In some embodiments, the sufficiently high furnace temperature may vary depending on the binder components. Once the controller 116 determines that the binder components have been volatilized, the temperature ramp rate for the furnace chamber 102 may be further increased. In some embodiments, the controller 116 may determine that the binder components have been volatilized when the measured temperature at TC14 is lower than T3. In some instances, this may indicate that there is no gaseous effluent going through the catalytic converter system 110, thereby cooling the temperature at TC14 to lower than T3, although, in practice, there may be residual binder that exits furnace chamber 102 as furnace chamber is heated a bit more. In some embodiments, there may be an increase in the catalyst enclosure 111a temperature at TC 13 and pressure in the furnace chamber 102 once the temperature ramp rate for the furnace chamber is 102 is further increased. This may be due to residual binder components remaining in the parts or the fact that some binder components may have deposited in relatively colder portions of the furnace chamber 102. The further increase in the temperature ramp rate may volatize the remaining binder components, thereby causing an increase in the catalyst enclosure 111a temperature at TC 13 and pressure in the furnace chamber 102.

Once the binder components in the part 126 have been volatilized, the furnace system 1100 may switch to a main sintering process (e.g., densification) mode. In some embodiments, the temperature of the furnace chamber 102 may be initially increased to about 500-600 degrees Celsius, e.g., about 550 degrees Celsius. In the main sintering (e.g., densification) process mode, V7 and V9 may be closed in order to seal the binder trap 602. This may be because the binder trap 602 may no longer be needed once all of the binder has been removed from the part 126, and thus no additional volatilized binder component may be present in the gaseous effluent.

With the binder trap 602 sealed, V8 may be opened, which may open up the isolation system bypass conduit 105. The isolation system bypass conduit 105 may be connected to the inside of the furnace chamber 102 in a region between the insulation and the furnace chamber wall. Accordingly, gaseous effluent remaining in the furnace chamber 102 may bypass the binder trap 602 and may be directed to the catalytic converter system 110.

The temperature for the furnace chamber 102 may be increased and gas may be provided via the gas inlet conduit 115.

At higher temperatures (around 650 degrees Celsius), the furnace system 1100 may begin to produce CO. In some embodiments, the CO may be generated due to the reduction of metal oxides to metal by residual carbon in the part 126. Any CO generated from the furnace chamber is passed through the catalyst enclosure 111a to ensure that the gaseous effluent is safe.

If the catalyst enclosure 111a cools sufficiently such that the temperature at TC13 is lower than T1, the catalyst heater H3 may be turned back on.

Once the main sintering (e.g., densification) process is complete, the heating elements 122 may be turned off. In some embodiments, the controller 116 may determine that the main sintering process is complete based on a predetermined time duration at a measured main sintering process temperature in the furnace chamber 102. In some embodiments, the controller 116 may determine that the main sintering process is complete based on various temperature measurements throughout the furnace system 1100. The furnace chamber 102 may cool to an intermediate temperature of about 1000 degrees Celsius. The furnace chamber 102 may then be backfilled by closing V8 and being filled with inert gas through the gas inlet conduit 115 until P9 reads a predetermined fill pressure, e.g., about 930 Torr, or about 760 atm. In some embodiments, the predetermined fill pressure may depend on the furnace chamber 102 material. For example, the predetermined fill pressure may be higher for a furnace chamber 102 made of stronger materials.

The furnace chamber 102 may continue to cool under pressure. Inert gas may be periodically added via the gas inlet conduit 115 to maintain the pressure as the gas cools.

Eventually, the furnace chamber temperature as measured by TC4 may reach a safe opening temperature of less than 200 degrees Celsius. In some embodiments, the furnace chamber 102 may contain significant CO at this point in the process. In such embodiments, the furnace chamber 102 may be pumped down by closing V3, MFC 113, and V100. V8 may be opened, and at least a portion of the gas containing CO may be pumped out and directed to the catalytic converter system 110, where the CO may be converted to CO2.

The furnace chamber 102 may be left at vacuum pressure until a user decides to open it. In some embodiments, an alarm or other indicator may signal to the user that the furnace chamber is safe for opening. Once the user decides to open the furnace chamber 102, the furnace chamber may be backfilled to atmospheric pressure with room air through V11. Finally, the air pump 108, the vacuum pump 107, and the catalyst heater H3 may be turned off. The user may then open the door to examine the sintered part.

In some embodiments, further processes may be performed to prevent the catalyst in the catalytic converter system 110 from overheating. For example, catalyst overheating may be prevented or mitigated by monitoring furnace chamber pressure at P2. If the pressure at P2 rises above PV2, the furnace chamber heating rate may pause. When the pressure at P2 falls below PV1, the furnace chamber heating rate may resume. In some instances, this may indicate a slowed generation rate of volatilized binder components. Accordingly, when the pressure at P2 falls below PV1, this may indicate that there is less gaseous effluent for the catalytic converter system 110 to react.

As another example, catalyst overheating may be prevented or mitigated based on air injection via the air injector 109. The air injector 109 inject additional air to the catalytic converter system 110 if the catalyst temperature exceeds a predetermined threshold. The additional air flowing through the catalyst may remove excess heat and cool the catalytic converter system 110. The additional air injection must be measured appropriately, as the additional air injection may reduce the residence time of gaseous effluent in the catalytic converter system 110. Unless properly monitored, reduced residence time may prevent volatilized binder components present in the gaseous effluent from complete combustion.

As yet another example, catalyst overheating may be prevented or mitigated based on inert gas flow. This may not be particularly applicable to vacuum furnaces, but may be applicable to atmosphere furnaces. Gas inlet flow through the gas inlet conduit 115 may be stopped or decreased when the temperature at TC14 exceeds T5. By decreasing the inlet flow, the outlet flow may also be decreased. The flow may resume to the previous rate when the temperature at TC14 falls below T4.

In an aspect, the controller 116 may automatically control the furnace systems described herein based on pre-set schedules and/or on user input. In some embodiments, the control of the furnace systems described herein may also be manual and performed by a user. In some embodiments, the furnace systems described herein also include a manual override and/or emergency stop such that a user may configure and/or stop a process performed within the furnace system.

The furnace chamber 102 in any of the embodiments described herein may include the one or more heating elements 122 and one or more temperature measurement devices, such as a thermocouple. The furnace system in any of the embodiments described herein may include one or more oxygen getters configured to prevent back diffusion of oxidizing gas and/or various other types of gas.

FIG. 12A illustrates an exemplary system 1200 for forming a printed object, of which the furnace systems described herein may be a part of. System 1200 may include a three-dimensional (3D) printer, for example, a metal 3D printing subsystem 1202, and one or more treatment site(s), for example, a debinding subsystem 1204 and a furnace subsystem 1206 for treating the green part after printing. In some embodiments, the furnace subsystem 1206 may be the furnace system in any of the embodiments described herein. Metal 3D printing subsystem 1202 may be used to form an object from a build material, for example, by depositing successive layers of the build material onto a build plate. The build material may include metal powder and at least one binder material. In some embodiments, the build material may include a primary binder material (e.g., a wax) and a secondary binder material (e.g., a polymer).

Debinding subsystem 1204 may be configured to treat the printed object by performing a first debinding process, in which the primary binder material may be removed. In some embodiments, the first debinding process may be a chemical debinding process, as will be described in further detail with reference to FIG. 12C. In such embodiments, the primary binder material may dissolve in a debinding fluid while the secondary binder material remains, holding the metal particles in place in their printed form.

In other embodiments, the first debinding process may comprise a thermal debinding process. In such embodiments, the primary binder material may have a vaporization temperature lower than that of the secondary binder material. The debinding subsystem 1204 may be configured to heat the deposited build material to a temperature at or above the vaporization temperature of the primary binder material and below the vaporization temperature of the secondary binder material such that the primary binder material is removed from the printed part. In alternative embodiments, the furnace subsystem 1206 rather than a separate heating debinding subsystem 1204 may be configured to perform the first debinding process. For example, the furnace subsystem 1206 may be configured to heat the deposited build material to a temperature at or above the vaporization temperature of the primary binder material and below the vaporization temperature of the secondary binder material such that the primary binder material is removed from the deposited build material.

Furnace subsystem 1206 may be configured to treat the printed object by performing a secondary debinding process (or also a primary debinding process, as in the alternative embodiment described above), in which the secondary binder material and/or any remaining primary binder material may be removed from the printed part. In some embodiments, the secondary debinding process may comprise a thermal debinding process, in which the furnace subsystem 1206 may be configured to heat the part to a temperature at or above the vaporization temperature of the secondary binder material to remove the secondary binder material. The furnace subsystem 1206 may then heat the part to a temperature just below the melting point of the metal powder to sinter the metal powder and to densify the metal powder into a solid metal part.

As shown in FIG. 12A, system 1200 may also include a user interface 1210, which may be operatively coupled to one or more components, for example, to metal 3D printing subsystem 1202, debinding subsystem 1204, and furnace subsystem 1206, etc. In some embodiments, user interface 1210 may be a remote device (e.g., a computer, a tablet, a smartphone, a laptop, etc.) or an interface incorporated into system 1200, e.g., on one or more of the components. User interface 1210 may be wired or wirelessly connected to one or more of metal 3D printing subsystem 1202, debinding subsystem 1204, and/or furnace subsystem 1206. System 1200 may also include a control subsystem 1216, which may be included in user interface 1210, or may be a separate element.

Metal 3D printing subsystem 1202, debinding subsystem 1204, furnace subsystem 1206, user interface 1210, and/or control subsystem 1216 may each be connected to the other components of system 1200 directly or via a network 1212. Network 1212 may include the Internet and may provide communication through one or more computers, servers, and/or handheld mobile devices, including the various components of system 1200. For example, network 1212 may provide a data transfer connection between the various components, permitting transfer of data including, e.g., part geometries, printing material, one or more support and/or support interface details, printing instructions, binder materials, heating and/or sintering times and temperatures, etc., for one or more parts or one or more parts to be printed.

Moreover, network 1212 may be connected to a cloud-based application 1214, which may also provide a data transfer connection between the various components and cloud-based application 1214 in order to provide a data transfer connection, as discussed above. Cloud-based application 1214 may be accessed by a user in a web browser, and may include various instructions, applications, algorithms, methods of operation, preferences, historical data, etc., for forming the part or object to be printed based on the various user-input details. Alternatively or additionally, the various instructions, applications, algorithms, methods of operation, preferences, historical data, etc., may be stored locally on a local server (not shown) or in a storage and/or processing device within or operably coupled to one or more of metal 3D printing subsystem 1202, debinding subsystem 1204, sintering furnace subsystem 1206, user interface 1210, and/or control subsystem 1216. In this aspect, metal 3D printing subsystem 1202, debinding subsystem 1204, furnace subsystem 1206, user interface 1210, and/or control subsystem 1216 may be disconnected from the Internet and/or other networks, which may increase security protections for the components of system 1200. In either aspect, an additional controller (not shown) may be associated with one or more of metal 3D printing subsystem 1202, debinding subsystem 1204, and furnace subsystem 1206, etc., and may be configured to receive instructions to form the printed object and to instruct one or more components of system 1200 to form the printed object.

FIG. 12B is a block diagram of a metal 3D printing subsystem 1202 according to one embodiment. The metal 3D printing subsystem 1202 may extrude build material 1224 to form a three-dimensional part. As described above, the build material may include a mixture of metal powder and binder material. For example, the build material may include any combination of metal powder, plastics, wax, ceramics, polymers, among others. In some embodiments, the build material 1224 may come in the form of a rod comprising a predetermined composition of metal powder and one or more binder components (e.g., a primary and a secondary binder).

Metal 3D printing subsystem 1202 may include an extrusion assembly 1226 comprising an extrusion head 1232. Metal 3D printing subsystem 1202 may include an actuation assembly 1228 configured to propel the build material 1224 into the extrusion head 1232. For example, the actuation assembly 1228 may be configured to propel the build material 1224 in a rod form into the extrusion head 1232. In some embodiments, the build material 1224 may be continuously provided from the feeder assembly 1222 to the actuation assembly 1228, which in turn propels the build material 1224 into the extrusion head 1232. In some embodiments, the actuation assembly 1228 may employ a linear actuation to continuously grip and/or push the build material 1224 from the feeder assembly 1222 towards the extrusion head 1232.

In some embodiments, the metal 3D printing subsystem 1202 includes a heater 1234 configured to generate heat 1236 such that the build material 1224 propelled into the extrusion head 1232 may be heated to a workable state. In some embodiments, the heated build material 1224 may be extruded through one or more nozzle 1233 to extrude workable build material 1242 onto a build plate 1240. It is understood that the heater 1234 is an exemplary device for generating heat 1236, and that heat 1236 may be generated in any suitable way, e.g., via friction of the build material 1224 interacting with the extrusion assembly 1226, in alternative embodiments.

In some embodiments, the metal 3D printing subsystem 1202 comprises a controller 1238. The controller 1238 may be configured to position the one or more nozzles 1233 along an extrusion path relative to the build plate 1240 such that the workable build material is deposited on the build plate 1240 to fabricate a three dimensional printed object 1230. The controller 1238 may be configured to manage operation of the metal 3D printing subsystem 1202 to fabricate the printed object 1230 according to a three-dimensional model. In some embodiments, the controller 1238 may be remote or local to the metallic printing subsystem 1202. The controller 1238 may be a centralized or distributed system. In some embodiments, the controller 1238 may be configured to control a feeder assembly 1222 to dispense the build material 1224. In some embodiments, the controller 1238 may be configured to control the extrusion assembly 1226, e.g., the actuation assembly 1228, the heater 1234, the extrusion head 1232, and/or the one or more nozzle 1233. In some embodiments the controller 1238 may be included in the control subsystem 1216.

FIG. 12C depicts a block diagram of a debinder subsystem 1204 for debinding a printed object 1230 according to one embodiment. The debinder subsystem 1204 may include a process chamber 1250, into which the printed object 1230 may be inserted for a first debinding process. In some embodiments, the first debinding process may be a chemical debinding process. In such embodiments, the debinder subsystem 1204 may include a storage chamber 1256 to store a volume of debinding fluid, e.g., a solvent, for use in the first debinding process. The storage chamber 1256 may comprise a port which may be used to fill, refill, and/or drain the storage chamber 1256 with the debinding fluid. In some embodiments, the storage chamber 1256 may be removably attached to the debinder subsystem 1204. In such embodiments, the storage chamber 1256 may be removed and replaced with a replacement storage chamber (not shown in FIG. 1C) to replenish the debinding fluid in the debinding subsystem 1204. In some embodiments, the storage chamber 1256 may be removed, refilled with debinding fluid, and reattached to the debinding subsystem 1204.

The debinding fluid contained in the storage chamber 1256 may be directed to the process chamber 1250 containing the inserted printed object 1230. In some embodiments, the build material that the printed object 1230 is formed of may include a primary binder material and a secondary binder material. In some embodiments, the printed object 1230 in the process chamber 1250 may be submerged in the debinding fluid for a predetermined period of time. In such embodiments, the primary binder material may dissolve in the debinding fluid while the secondary binder material stays intact.

In some embodiments, the debinding fluid containing the dissolved primary binder material (hereinafter referred to as “used debinding fluid”) may be directed to a distill chamber 1252. For example, after the first debinding process, the process chamber 1250 may be drained of the used debinding fluid, and the used debinding fluid may be directed to the distill chamber 1252. In some embodiments, the distill chamber 1252 may be configured to distill the used debinding fluid. In some embodiments, the debinding subsystem 1204 may further include a waste chamber 1254 fluidly coupled to the distill chamber 1252. In such embodiments, the waste chamber may collect waste accumulated in the distill chamber 1252 as a result of the distillation. In some embodiments, the waste chamber 1254 may be removably attached to the debinding subsystem 1204 such that the waste chamber 1254 may be removed and replaced after a number of distillation cycles. In some embodiments, the debinding subsystem 1204 may include a condenser 1258 configured to condense vaporized used debinding fluid from the distill chamber 1252 and return the debinding fluid back to the storage chamber 1256.

FIG. 13A illustrates another exemplary system 1300 for forming a printed object, of which the furnace systems described herein may be included. System 1300 may include a printer, for example, a binder jet fabrication subsystem 1302, and a treatment site(s), for example, a de-powdering subsystem 1304 and a furnace subsystem 1306. In some embodiments, the furnace subsystem 1306 may be the furnace system in any of the embodiments described herein. Binder jet fabrication subsystem 1302 may be used to form an object from a build material, for example, by delivering successive layers of build material and binder material to a build plate. As shown in FIG. 13A, a build box subsystem 1308 may be movable and may be selectively positioned in one or more of binder jet fabrication subsystem 1302, de-powdering subsystem 1304, and furnace subsystem 1306. For example, build box subsystem 1308 may be coupled or couplable to a movable assembly. Alternatively, a conveyor (not shown) may help transport the object between portions of system 1300.

The build material may be a bulk metallic powder delivered and spread in successive layers. The binder material may be, for example, a polymeric liquid that may be deposited onto and may be absorbed into layers of the build material. One or more of binder jet fabrication subsystem 1302, de-powdering subsystem 1304, and furnace subsystem 1306 may include a shaping station to shape the printed object and a debinding station to treat the printed object to remove a binder material from the build material. Furnace subsystem 1306 may heat and/or sinter the build material of the printed object. System 1300 may also include a user interface 1310, which may be operatively coupled to one or more components, for example, to binder jet fabrication subsystem 1302, de-powdering subsystem 1304, and furnace subsystem 1306, etc. In some embodiments, user interface 1310 may be a remote device (e.g., a computer, a tablet, a smartphone, a laptop, etc.). User interface 1310 may be wired or wirelessly connected to one or more of binder jet fabrication subsystem 1302, de-powdering subsystem 1304, and furnace subsystem 1306. System 1300 may also include a control subsystem 1316, which may be included in user interface 1310, or may be a separate element.

Binder jet fabrication subsystem 1302, de-powdering subsystem 1304, furnace subsystem 1306, user interface 1310, and/or control subsystem 1316 may each be connected to the other components of system 1300 directly or via a network 1312. Network 1312 may include the Internet and may provide communication through one or more computers, servers, and/or handheld mobile devices, including the various components of system 1300. For example, network 1312 may provide a data transfer connection between the various components, permitting transfer of data including, e.g., geometries, the printing material, one or more support and/or support interface details, binder materials, heating and/or sintering times and temperatures, etc., for one or more parts or one or more parts to be printed.

Moreover, network 1312 may be connected to a cloud-based application 1314, which may also provide a data transfer connection between the various components and cloud-based application 1314 in order to provide a data transfer connection, as discussed above. Cloud-based application 1314 may be accessed by a user in a web browser, and may include various instructions, applications, algorithms, methods of operation, preferences, historical data, etc., for forming the part or object to be printed based on the various user-input details. Alternatively or additionally, the various instructions, applications, algorithms, methods of operation, preferences, historical data, etc., may be stored locally on a local server (not shown) or in a storage and/or processing device within or operably coupled to one or more of binder jet fabrication subsystem 1302, de-powdering subsystem 1304, furnace subsystem 1306, user interface 1310, and/or control subsystem 1316. In this aspect, binder jet fabrication subsystem 1302, de-powdering subsystem 1304, furnace subsystem 1306, user interface 1310, and/or control subsystem 1316 may be disconnected from the Internet and/or other networks, which may increase security protections for the components of system 1300. In either aspect, an additional controller (not shown) may be associated with one or more of binder jet fabrication subsystem 1302, de-powdering subsystem 1304, and furnace subsystem 1306, etc., and may be configured to receive instructions to form the printed object and to instruct one or more components of system 1300 to form the printed object.

FIG. 13B illustrates an exemplary binder jet fabrication subsystem 1302 operating in conjunction with build box subsystem 1308. Binder jet fabrication subsystem 1302 may include a powder supply 1320, a spreader 1322 (e.g., a roller) configured to be movable across powder bed 1324 of build box subsystem 1308, a print head 1326 movable across powder bed 1324, and a controller 1328 in electrical communication (e.g., wireless, wired, Bluetooth, etc.) with print head 1326. Powder bed 1324 may comprise powder particles, for example, micro-particles of a metal, micro-particles of two or more metals, or a composite of one or more metals and other materials.

Spreader 1322 may be movable across powder bed 1324 to spread a layer of powder, from powder supply 1320, across powder bed 1324. Print head 1326 may comprise a discharge orifice 1330 and, in certain implementations, may be actuated to dispense a binder material 1332 (e.g., through delivery of an electric current to a piezoelectric element in mechanical communication with binder material 1332) through discharge orifice 1330 to the layer of powder spread across powder bed 1324. In some embodiments, the binder material 1332 may be one or more fluids configured to bind together powder particles.

In operation, controller 1328 may actuate print head 1326 to deliver binder material 1332 from print head 1326 to each layer of the powder in a pre-determined two-dimensional pattern, as print head 1326 moves across powder bed 1324. In embodiments, the movement of print head 1326, and the actuation of print head 1326 to deliver binder material 1332, may be coordinated with movement of spreader 1322 across print bed 1324. For example, spreader 1322 may spread a layer of the powder across print bed 1324, and print head 1326 may deliver the binder in a pre-determined, two-dimensional pattern, to the layer of the powder spread across print bed 1324, to form a layer of one or more three-dimensional objects 1334. These steps may be repeated (e.g., with the pre-determined two-dimensional pattern for each respective layer) in sequence to form subsequent layers until, ultimately, the one or more three-dimensional objects 1334 are formed in powder bed 1324.

Although the example embodiment depicted in FIG. 13B depicts a single object 1334 being printed, it should be understood that the powder print bed 1324 may include more than one object 1334 in embodiments in which more than one object 1334 is printed at once. Further, the powder print bed 1324 may be delineated into two or more layers, stacked vertically, with one or more objects disposed within each layer.

An example binder jet fabrication subsystem 1302 may comprise a powder supply actuator mechanism 1336 that elevates powder supply 1320 as spreader 1322 layers the powder across print bed 1324. Similarly, build box subsystem 1308 may comprise a build box actuator mechanism 1338 that lowers powder bed 1324 incrementally as each layer of powder is distributed across powder bed 1324.

In another example embodiment, layers of powder may be applied to powder print bed 1324 by a hopper followed by a compaction roller. The hopper may move across powder print bed 1324, depositing powder along the way. The compaction roller may be configured to follow the hopper, spreading the deposited powder to form a layer of powder.

For example, FIG. 13C illustrates another binder jet fabrication subsystem 1302′ operating in conjunction with a build box subsystem 1308′. In this aspect, binder jet fabrication subsystem 1302′ may include a powder supply 1320′ in a metering apparatus, for example, a hopper 1321. Binder jet subsystem 1302′ may also include one or more spreaders 1322′ (e.g., one or more rollers) configured to be movable across powder bed 1324′ of build box subsystem 1308′, a print head 1326′ movable across powder bed 1324′, and a controller 1328′ in electrical communication (e.g., wireless, wired, Bluetooth, etc.) with one or more of hopper 1321, spreaders 1322′, and print head 1326′. Powder bed 1324′ may comprise powder particles, for example, micro-particles of a metal, micro-particles of two or more metals, or a composite of one or more metals and other materials.

Hopper 1321 may be any suitable metering apparatus configured to meter and/or deliver powder from powder supply 1320′ onto a top surface 1323 of powder bed 1324′. Hopper 1321 may be movable across powder bed 1324′ to deliver powder from powder supply 1320′ onto top surface 1323. The delivered powder may form a pile 1325 of powder on top surface 1323.

The one or more spreaders 1322′ may be movable across powder bed 1324′ downstream of hopper 1321 to spread powder, e.g., from pile 1325, across powder bed 1324. The one or more spreaders 1322′ may also compact the powder on top surface 1323. In either aspect, the one or more spreaders 1322′ may form a layer 1327 of powder. The aforementioned powder delivery and spreading steps may be successively performed in order to form a plurality of layers 1329 of powder. Additionally, although two spreaders 1322′ are shown in FIG. 13C, binder jet fabrication subsystem 1302′ may include one, three, four, etc. spreaders 1322′.

Print head 1326′ may comprise one or more discharge orifices 1330′ and, in certain implementations, may be actuated to dispense a binder material 1332′ (e.g., through delivery of an electric current to a piezoelectric element in mechanical communication with binder material 1332′) through discharge orifice 1330′ to the layer of powder spread across powder bed 1324′. In some embodiments, the binder material 1332′ may be one or more fluids configured to bind together powder particles.

In operation, controller 1328′ may actuate print head 1326′ to deliver binder material 1332′ from print head 1326′ to each layer 1327 of the powder in a pre-determined two-dimensional pattern, as print head 1326′ moves across powder bed 1324′. As shown in FIG. 13C, controller 1328′ may be in communication with hopper 1321 and/or the one or more spreaders 1322′ as well, for example, to actuate the movement of hopper 1321 and the one or more spreaders 1322′ across powder bed 1324′. Additionally, controller 1328′ may control the metering and/or delivery of powder by hopper 1321 from powder supply 1320 to top surface 1323 of powder bed 1324′. In embodiments, the movement of print head 1326′, and the actuation of print head 1326′ to deliver binder material 1332′, may be coordinated with movement of hopper 1321 and the one or more spreaders 1322′ across print bed 1324′. For example, hopper 1321 may deliver powder to print bed 1324, and spreader 1322′ may spread a layer of the powder across print bed 1324. Then, print head 1326 may deliver the binder in a pre-determined, two-dimensional pattern, to the layer of the powder spread across print bed 1324′, to form a layer of one or more three-dimensional objects 1334′. These steps may be repeated (e.g., with the pre-determined two-dimensional pattern for each respective layer) in sequence to form subsequent layers until, ultimately, the one or more three-dimensional objects 1334′ are formed in powder bed 1324′.

Although the example embodiment depicted in FIG. 13C depicts a single object 1334′ being printed, it should be understood that the powder print bed 1324′ may include more than one object 1334′ in embodiments in which more than one object 1334′ is printed at once. Further, the powder print bed 1324′ may be delineated into two or more layers 1327, stacked vertically, with one or more objects disposed within each layer.

As in FIG. 13B, build box subsystem 1308′ may comprise a build box actuator mechanism 1338′ that lowers powder bed 1324′ incrementally as each layer 1327 of powder is distributed across powder bed 1324′. Accordingly, hopper 1321, the one or more spreaders 1322′, and print head 1326′ may traverse build box subsystem 1308′ at a pre-determined height, and build box actuator mechanism 1338′ may lower powder bed 1324 to form object 1334′.

Although not shown, binder jet fabrication subsystems 1302, 1302′ may include a coupling interface that may facilitate the coupling and/or uncoupling of the build box subsystems 1308, 1308′ with the binder jet fabrication subsystems 1302, 1302′, respectively. The coupling interface may comprise one or more of (i) a mechanical aspect that provides for physical engagement, and/or (ii) an electrical aspect that supports electrical communication between the build box subsystem 1308, 1308′ to the binder jet fabrication subsystem 1302, 1302′.

As shown in FIG. 14, a device 1400 used for performing the various embodiments of the present disclosure (e.g., the controller 116, the controller subsystem 1216, the controller subsystem 1316, the various furnace systems, system 1200, and system 1300 disclosed herein, and/or any other computer system or user terminal for performing the various embodiments of the present disclosure) may include a central processing unit (CPU) 1420. CPU 1420 may be any type of processor device including, for example, any type of special purpose or general-purpose microprocessor device. As will be appreciated by persons skilled in the relevant art, CPU 1420 also may be a single processor in a multi-core/multiprocessor system, such system operating alone, or in a cluster of computing devices operating in a cluster or a server farm. CPU 1420 may be connected to a data communication infrastructure 1410, for example, a bus, message queue, network, or multi-core message-passing scheme.

A device 1400 (e.g., the controller 116, the controller subsystem 1216, the controller subsystem 1316, the various furnace systems, system 1200, and system 1300 disclosed herein, and/or any other computer system or user terminal for performing the various embodiments of the present disclosure) may also include a main memory 1440, for example, random access memory (RAM), and may also include a secondary memory 1430. Secondary memory 1430, e.g., a read-only memory (ROM), may be, for example, a hard disk drive or a removable storage drive. Such a removable storage drive may comprise, for example, a floppy disk drive, a magnetic tape drive, an optical disk drive, a flash memory, or the like. The removable storage drive in this example may read from and/or write to a removable storage unit in a well-known manner. The removable storage unit may comprise a floppy disk, magnetic tape, optical disk, etc., which is read by and written to by the removable storage drive. As will be appreciated by persons skilled in the relevant art, such a removable storage unit generally includes a computer usable storage medium having stored therein computer software and/or data.

In alternative implementations, secondary memory 1430 may include other similar means for allowing computer programs or other instructions to be loaded into device 1400. Examples of such means may include a program cartridge and cartridge interface (such as that found in video game devices), a removable memory chip (such as an EPROM, or PROM) and associated socket, and other removable storage units and interfaces, which allow software and data to be transferred from a removable storage unit to device 1400.

A device 1400 may also include a communications interface (“COM”) 1460. Communications interface 1460 may allow software and data to be transferred between device 1400 and external devices. Communications interface 1460 may include a modem, a network interface (such as an Ethernet card), a communications port, a PCMCIA slot and card, or the like. Software and data transferred via communications interface 1460 may be in the form of signals, which may be electronic, electromagnetic, optical, or other signals capable of being received by communications interface 1460. These signals may be provided to communications interface 1460 via a communications path of device 1400, which may be implemented using, for example, wire or cable, fiber optics, a phone line, a cellular phone link, an RF link, a wireless connection (e.g., Bluetooth connection, wireless local are network (WLAN) connection, and cellular network connection) or other communications channels.

The hardware elements, operating systems, and programming languages of such equipment are conventional in nature, and it is presumed that those skilled in the art are adequately familiar therewith. A device 1400 also may include input and output ports 1450 to connect with input and output devices such as keyboards, mice, touchscreens, monitors, displays, etc. Of course, the various server functions may be implemented in a distributed fashion on a number of similar platforms, to distribute the processing load. Alternatively, the servers may be implemented by appropriate programming of one computer hardware platform.

The systems, apparatuses, devices, and methods disclosed herein are described in detail by way of examples and with reference to the figures. The examples discussed herein are examples only and are provided to assist in the explanation of the apparatuses, devices, systems, and methods described herein. None of the features or components shown in the drawings or discussed below should be taken as mandatory for any specific implementation of any of these the apparatuses, devices, systems, or methods unless specifically designated as mandatory. For ease of reading and clarity, certain components, modules, or methods may be described solely in connection with a specific figure. In this disclosure, any identification of specific techniques, arrangements, etc., are either related to a specific example presented or are merely a general description of such a technique, arrangement, etc. Identifications of specific details or examples are not intended to be, and should not be, construed as mandatory or limiting unless specifically designated as such. Any failure to specifically describe a combination or sub-combination of components should not be understood as an indication that any combination or sub-combination is not possible. It will be appreciated that modifications to disclosed and described examples, arrangements, configurations, components, elements, apparatuses, devices, systems, methods, etc., can be made and may be desired for a specific application. Also, for any methods described, regardless of whether the method is described in conjunction with a flow diagram, it should be understood that unless otherwise specified or required by context, any explicit or implicit ordering of steps performed in the execution of a method does not imply that those steps must be performed in the order presented but instead may be performed in a different order or in parallel.

Throughout this disclosure, references to components or modules generally refer to items that logically can be grouped together to perform a function or group of related functions. Like reference numerals are generally intended to refer to the same or similar components. Components and modules can be implemented in software, hardware, or a combination of software and hardware. The term “software” is used expansively to include not only executable code, for example machine-executable or machine-interpretable instructions, but also data structures, data stores and computing instructions stored in any suitable electronic format, including firmware, and embedded software.

It is intended that the specification and examples be considered as exemplary only, with a true scope and spirit of the disclosure being indicated by the following claims.

Claims

1. A furnace system, comprising:

a furnace chamber defining an interior region, wherein the furnace chamber is configured to maintain an atmosphere substantially free of oxygen within the interior region;
an outlet fluidly coupled to the furnace chamber for removal of an exhaust gas from the furnace chamber;
a conduit fluidly coupled to the outlet;
an oxygen injector fluidly coupled to the conduit, wherein the oxidizing injector is positioned downstream of the furnace chamber and is configured to introduce an oxidizing gas into the exhaust gas;
an isolation system fluidly coupled to the conduit between the furnace chamber and the oxygen injector, wherein the isolation system is configured to prevent a backflow of the oxidizing gas into the furnace chamber; and
a catalyst enclosure comprising an oxidizing catalyst, wherein the catalyst enclosure is configured to receive a mixture of the exhaust gas and the oxidizing gas.

2. The furnace system of claim 1, wherein the isolation system comprises a pump configured to direct the exhaust gas through the isolation system and towards the catalyst enclosure, wherein the pump is at least one of a vacuum pump, a lobe pump, a diaphragm pump, a piston pump, or a venturi pump.

3. The furnace system of claim 2, further comprising:

a demister positioned between the vacuum pump and the catalyst enclosure, wherein the demister is configured to remove at least a portion of fluid present in the exhaust gas directed towards the catalyst enclosure, and wherein the demister is fluidly connected to the vacuum pump such that the removed fluid is drained back to the vacuum pump.

4. The furnace system of claim 1, wherein the isolation system comprises a check valve configured to prevent the backflow of the oxidizing gas into the furnace chamber.

5. The furnace system of claim 1, wherein the isolation system comprises a proportional valve configured to prevent the backflow of the oxidizing gas into the furnace chamber, wherein the proportional valve is at least one of a proportional butterfly valve or a proportional solenoid valve.

6. The furnace system of claim 1, wherein the isolation system comprises a porous plug configured to prevent the backflow of the oxidizing gas into the furnace chamber.

7. The furnace system of claim 1, further comprising a heater operably coupled to the conduit, and wherein the conduit is configured to be adjustably heated.

8. The furnace system of claim 7, wherein the isolation system comprises a liquid bubbler configured to prevent the backflow of the oxidizing gas into the furnace chamber and to collect at least a portion of a component present in the exhaust gas.

9. The furnace system of claim 8, wherein the liquid bubbler comprises a connecting conduit with a first end and a second end, a first chamber fluidly connected to the conduit and the first end of the connecting conduit, and a second chamber fluidly connected to an outlet conduit and the second end of the connecting conduit,

wherein the first end of the connecting conduit is located within the first chamber, and the second end of the connecting conduit is located within the second chamber, and the second chamber is at least partially filled with a liquid such that a top surface of the liquid is above the second end of the connecting conduit, and
wherein the liquid bubbler is configured to sequentially receive the exhaust gas through the first chamber, the connecting conduit, the second chamber, and the outlet conduit.

10. A furnace system, comprising:

a furnace chamber defining an interior region, wherein the furnace chamber is configured to maintain an atmosphere substantially free of oxygen within the interior region;
an outlet fluidly coupled to the furnace chamber for removal of an exhaust gas from the furnace chamber;
a binder trap system fluidly coupled to the outlet;
an isolation system fluidly coupled to the binder trap system, wherein the isolation system is positioned downstream of the binder trap system and is configured to prevent a backflow of an oxidizing gas into the furnace chamber;
a catalyst enclosure comprising an oxidizing catalyst, wherein the catalyst enclosure is positioned downstream of the isolation system and is configured to receive a mixture of the exhaust gas and the oxidizing gas; and
an oxygen injector fluidly coupled to at least one of the isolation system or the catalyst enclosure, wherein the oxidizing injector is positioned downstream of the furnace chamber and is configured to introduce the oxidizing gas into the exhaust gas.

11. The furnace system of claim 10, wherein the isolation system comprises at least one of a check valve, a proportional valve, a pump, or a porous plug.

12. The furnace system of claim 10, wherein the binder trap system comprises a binder trap cooler configured to adjust a temperature of the binder trap.

13. The furnace system of claim 10, further comprising:

a binder trap system bypass conduit fluidly coupled to the outlet downstream of the binder trap system and to the isolation system upstream of the binder trap system, wherein the binder trap system bypass conduit is configured to direct the exhaust gas to bypass the binder trap system.

14. The furnace system of claim 13, wherein the bypass conduit includes at least one valve configured to optionally open the bypass conduit to allow the exhaust gas to bypass the binder trap system or to close the bypass conduit to allow the exhaust gas to flow through the binder trap system.

15. A furnace system, comprising:

a furnace chamber defining an interior region, wherein the furnace chamber is configured to maintain an atmosphere substantially free of oxygen within the interior region;
an outlet fluidly coupled to the furnace chamber for removal of an exhaust gas from the furnace chamber;
an isolation system fluidly coupled to the outlet, wherein the isolation system is configured to prevent a backflow of an oxidizing gas into the furnace chamber;
a binder cracking system fluidly coupled to the isolation system, wherein the binder cracking system is positioned downstream of the isolation system;
a catalyst enclosure comprising an oxidizing catalyst, wherein the catalyst enclosure is positioned downstream of the isolation system and is configured to receive a mixture of the exhaust gas and the oxidizing gas; and
an oxygen injector fluidly coupled to at least one of the isolation system or the catalyst enclosure, wherein the oxidizing injector is positioned downstream of the furnace chamber and is configured to introduce the oxidizing gas into the exhaust gas.

16. The furnace system of claim 15, wherein isolation system comprises a check valve configured to prevent a backflow of the oxidizing gas into the furnace chamber.

17. The furnace system of claim 15, wherein the binder cracking system comprises an enclosure substantially free of oxygen and a heater configured to heat the enclosure.

18. The furnace system of claim 17, wherein the enclosure contains a catalyst configured to react with at least the portion of a component of the exhaust gas.

19. The furnace system of claim 17, wherein the binder cracking system further comprises a steam source and a flame arrestor positioned downstream of the enclosure.

20. The furnace system of claim 17, wherein the isolation system further comprises a venturi pump positioned downstream of the binder cracking system and is configured to prevent a backflow of the oxidizing gas into the furnace chamber.

Patent History
Publication number: 20200376547
Type: Application
Filed: May 27, 2020
Publication Date: Dec 3, 2020
Applicant: Desktop Metal, Inc. (Burlington, MA)
Inventors: Aaron SILIDKER (Guilford, CT), Richard Remo FONTANA (Cape Elizabeth, ME), Brian KERNAN (Andover, MA), Mark SOWERBUTTS (Townsend, MA), Tomek BRZEZINSKI (Lynnfield, MA), Ricardo FULOP (Lexington, MA), Leon FAY (Lexington, MA), Daniel R. JEPEAL (Andover, MA), Nathan WOODARD (Medford, MA)
Application Number: 16/884,576
Classifications
International Classification: B22F 3/00 (20060101); B22F 1/00 (20060101); B22F 3/10 (20060101);