NOVEL VELOCITY CONTROL DEVICE FOR A BURNER USING BIMETALLIC MATERIALS FOR PREHEATED FUEL AND OXIDIZER

Abstract

Methods and systems for controlling jet velocity of a preheated gas are described herein. Through the use of a temperature-sensitive bimetallic valve, the flow of a gas can be redirected to maintain jet velocity based on temperature. The temperature-sensitive bimetallic valve can redirect flow of the gas based on the position of a bimetallic strip. The bimetallic strip and a connected blocking device can change position based on the temperature of the gas. The position of the bimetallic strip and the blocking device control the size of the port that the gas is delivered to the burner through. Thus, preheated gas and standard temperature gas can be delivered at appropriate velocities based on the needs of the user.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

Embodiments described herein generally relates to control of jet velocity of a fuel gas or oxidizing gas. Specifically, embodiments described herein relate to maintaining proper jet velocity for gases delivered to a burner at non-standard temperatures.

2. Description of the Related Art

Many industrial operations employ furnaces within which fuel and oxidant are combusted, so that the heat of combustion can heat material that is in the furnace. Examples include furnaces that heat solid material to melt it, such as smelting furnaces, and furnaces that heat objects such as steel slabs to raise the material's temperature (short of melting it) to facilitate shaping or other treatment of the material or object. The required high temperature is generally obtained by combustion of a hydrocarbon fuel such as natural gas. The combustion produces gaseous combustion products, also known as flue gas. Even in metal heating equipment that achieves a relatively high efficiency of heat transfer from the combustion to the solid materials to be melted, the flue gases released generally reach temperatures in excess of 1300 degrees Celsius (° C.), and thus represent a considerable waste of energy that is generated in the high temperature operations, unless that heat energy can be at least partially recovered from the combustion products.

One mechanism to recover this lost energy is to preheat one or more of the combustion reactants (fuel or oxidant) using the flue gases. The combustion reactants can be heated to a critical temperature, thus increasing the heat delivered to the furnace during the combustion process. However, problems arise from the preheating of the combustion reactants. As the combustion reactants are heated, the gases expand leading to an increase in jet velocity. Jet velocity is the velocity with which the gases escape the burner. Increased jet velocity leads to shorter residence time before the combustion reaction which can reduce flame luminosity. A larger jet velocity can resolve this problem, but this solution is not applicable to both low temperature and high temperature combustion reactants.

Thus, there is a need in the art for automated control of jet velocity.

SUMMARY OF THE INVENTION

The invention described herein generally relates to systems and methods for controlling jet velocity. In one embodiment, a system for controlling jet velocity, can include a source of oxidizing gas; a source of fuel gas; at least one temperature-sensitive bimetallic valve in connection with one of the source of oxidizing gas or the source of fuel gas, the valve comprising a bimetallic strip, a blocking device and a flow control structure and configured to receive an oxidizing gas or a fuel gas, wherein the oxidizing gas or the fuel gas is at a first temperature; change the temperature of at least the bimetallic strip from a second temperature to the first temperature; change position of the bimetallic strip, as measured from the flow control structure, in response to the change in temperature from the second temperature to the first temperature; and change the velocity of the oxidizing gas or the fuel gas through the valve based on the position of the bimetallic strip; and a burner configured to receive an oxidizing gas or a fuel gas from the at least one temperature-sensitive bimetallic valve, wherein the oxidizing gas or the fuel gas is at the first temperature; combine and combust the fuel gas with the oxidizing gas to create a jet; and deliver the jet to a target material.

In another embodiment, a method for controlling of gas velocity can include flowing an oxidizing gas or a fuel gas into a temperature-sensitive bimetallic valve at a first temperature, the temperature-sensitive bimetallic valve comprising a bimetallic strip, a blocking device and a flow control structure; transferring heat from the oxidizing gas or the fuel gas to the bimetallic strip, wherein the bimetallic strip changes from a second temperature to the first temperature; changing the position of the bimetallic strip, as measured from the flow control structure, in response to the change in temperature from the second temperature to the first temperature; and delivering the oxidizing gas or the fuel gas from the temperature-sensitive bimetallic valve to a burner at a second velocity, wherein the second velocity of the oxidizing gas or fuel gas changes dependant on the position of the bimetallic strip.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above recited features of the present invention can be understood in detail, a more particular description of the invention, briefly summarized above, may be had by reference to embodiments, some of which are illustrated in the appended drawings.

It is to be noted, however, that the appended drawings illustrate only typical embodiments of this invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments.

FIG. 1A-1C is a schematic view of a burner including a temperature-sensitive bimetallic valve described herein.

FIGS. 2A-2H are representations of the temperature-sensitive bimetallic valve, according to one or more embodiments.

FIG. 3 is a flow diagram of a method for automated control of gas flow, according to one embodiment.

To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures. It is contemplated that elements disclosed in one embodiment may be beneficially utilized on other embodiments without specific recitation.

DETAILED DESCRIPTION

Methods and systems for controlling jet velocity are described herein. Significant energy is lost during the combustion process, specifically through heat that escapes to the atmosphere in flue gases. For example, in an oxy-fuel fired glass furnace, where all the fuel is combusted with pure oxygen, and for which the temperature of the flue gas at the furnace exhaust is of the order of 1350° C., typically 30% to 40% of the energy released by the combustion of the fuel is lost in the flue gas.

The methods and systems described herein propose heating the combustion reactants to recover a portion of the heat lost in the flue gases, which can then be redelivered to the furnace to reduce the reactant energy input required for the overall process. To maintain jet velocity in the heated combustion reactants, a temperature-sensitive bimetallic valve can be positioned between the gas source and the burner. The temperature-sensitive bimetallic valve can control the velocity of the combustion reactants to the burner, thus allowing for an optimal jet velocity and residence time for both preheated and cooled gases, based on the temperature of the gas delivered to the valve. The embodiments of the invention disclosed herein are more clearly described with reference to the figures below.

FIGS. 1A-1C are schematic diagrams of a jet velocity control device 100 according to one or more embodiments. FIG. 1A depicts the jet velocity control device 100 receiving a heated fuel gas and a standard temperature oxidizing gas, according to one embodiment. The jet velocity control device 100 can include a burner 104 in connection with one or more temperature sensitive bimetallic valves, shown here as two temperature-sensitive bimetallic valves 110a and 110b. The temperature-sensitive bimetallic valve 110a can receive either a heated or standard temperature oxidizing gas through an oxidizing gas line 106. In this embodiment, the oxidizing gas is standard temperature, depicted here as a small arrow, flowing to the temperature-sensitive bimetallic valve 110a. The temperature-sensitive bimetallic valve 110b can receive either a heated or standard temperature fuel gas through a fuel gas line 108. In this embodiment, the fuel gas is heated, depicted here as a large arrow, flowing to the temperature-sensitive bimetallic valve 110b.

The temperature-sensitive bimetallic valves 110a and 110b can be used to control the jet velocity of the jet 102 produced by the burner 104. In this embodiment, a first temperature-sensitive bimetallic valve 110a is in fluid connection with the burner 104 through a first oxidizing gas pipe 112 and a second oxidizing gas pipe 114. A second temperature-sensitive bimetallic valve 110b is in fluid connection with the burner 104 through a first fuel gas pipe 116 and a second fuel gas pipe 118. The fuel gas and the oxidizing gas can be heated prior to flowing into the temperature-sensitive bimetallic valve 110a and 110b. The gases, either the fuel gas or the oxidizing gas, will equilibrate temperature with the temperature-sensitive bimetallic valves 110a and 110b, thus increasing the temperature of the valve from a second temperature to the first temperature in the presence of the heated gases. The increase in temperature causes the temperature-sensitive bimetallic valves 110a and 110b to change in port size upon over a gradient of temperatures. When the temperature-sensitive bimetallic valves 110a and 110b change in port size, the gas is delivered the velocity of either the fuel gas or the oxidizing gas is adjusted appropriate to the gas temperature.

The burner 104 can receive a fuel gas and an oxidizing gas as redirected through the temperature-sensitive bimetallic valves 110a and 110b. In this embodiment, the oxidizing gas is delivered through the temperature-sensitive bimetallic valve 110a to the first oxidizing gas pipe 112 and the fuel gas is delivered through the temperature-sensitive bimetallic valve 110b to the second fuel gas pipe 118. The temperature-sensitive bimetallic valves 110a and 110b have a first state and a second state. The temperature-sensitive bimetallic valve 110a is depicted in the first state based on receiving a cold oxidizing gas. The cold oxidizing gas does not have significant thermal energy to transfer to the temperature-sensitive bimetallic valve 110a, thus the temperature-sensitive bimetallic valve 110a remains in the first state. The first state of the temperature-sensitive bimetallic valve 110a prevents flow of the oxidizing gas through the second oxidizing gas pipe 114 while allowing flow through the first oxidizing gas pipe 112. The temperature-sensitive bimetallic valve 110b is depicted in the second state based on receiving a heated fuel gas. The heated fuel gas heats the temperature-sensitive bimetallic valve 110a as it flows in from the fuel gas line 108, thus the temperature-sensitive bimetallic valve 110a bends based on the bimetallic effect. The second state of the temperature-sensitive bimetallic valve 110b prevents flow of the oxidizing gas through the first fuel gas pipe 114 while allowing flow through the second fuel gas pipe 112.

FIG. 1B depicts the jet velocity control device 100 receiving a standard temperature fuel gas and a heated oxidizing gas, according to one embodiment. In this embodiment, the temperature-sensitive bimetallic valve 110a receives a heated oxidizing gas through the oxidizing gas line 106, while the temperature-sensitive bimetallic valve 110b receives a standard temperature fuel gas through a fuel gas line 108. Thus, the temperature-sensitive bimetallic valve 110a is in the second state and flows the heated oxidizing gas to the burner 104 through the second oxidizing gas pipe 114. The temperature-sensitive bimetallic valve 110b is in the first state and flows the standard temperature fuel gas through the first fuel gas pipe 116 to the burner 104. As shown here between FIGS. 1A and 1B, the state of the valve 110a and 110b is maintained only as long as the temperature of the gas delivered is maintained. Therefore, a gas may initially be delivered at a standard temperature and then be switched to a heated gas or vice versa.

FIG. 1C depicts the jet velocity control device 100 receiving a heated fuel gas and a heated oxidizing gas, according to one embodiment. In this embodiment, the temperature-sensitive bimetallic valve 110a receives a heated oxidizing gas through the oxidizing gas line 106, while the temperature-sensitive bimetallic valve 110b simultaneously receives a heated fuel gas through a fuel gas line 108. Thus, in this embodiment, the temperature-sensitive bimetallic valves 110a and 110b are both in the second state. The temperature-sensitive bimetallic valves 110a and 110b flow the heated oxidizing gas through the second oxidizing gas pipe 114 and the heated fuel gas through the second fuel gas pipe 118 to the burner 104. In the embodiments depicted above, the valve will change state based on temperature to maintain constant jet velocity. Stated another way, the standard temperature gas flowing through the first fuel gas pipe 116, as shown in FIG. 1B, is flowing to the burner 104 at approximately the same velocity as the heated fuel gas through the second fuel gas pipe 114, as shown in FIG. 1A.

Though shown here as permutations of a dual pipe embodiment, various designs may be employed to control velocity of gases delivered to the burner 104. In one embodiment, the oxidizing gas pipes 112 and 114 and the fuel gas pipes 116 and 118 may be a pipe-in-pipe design where a portion of the pipe is closed off for the standard temperature gas and the portion of the pipe is opened for heated gases. In general, the designs for both the valves and the pipes are only limited by the desire to maintain the same flame shape and size when flowing either heated or standard temperature gases at the same flow rate.

In one or more embodiments, the pipe used for the heated gases can be larger than the pipe used for the standard temperature gases. As the heated gases are delivered at a higher temperature, they are also at a higher pressure. The higher pressure can increase the velocity of the gas which reaches the burner, thus increasing the jet velocity. By effectively increasing the volume based on temperature, the jet velocity can be maintained between heated and standard temperature gases.

The fuel gas and the oxidizing gas can be any known fuel or oxidizer. In one embodiment, the fuel gas is natural gas and the oxidizing gas is oxygen. The fuel gas or the oxidizing gas may be heated. In order that the burners may use the heated oxidizing gas, such as preheated oxygen, with the fuel gas without serious safety problems, the difficulties in handling the preheated oxidizing gas should be considered. Therefore, the parts of the burners used in the apparatus and process of the invention in contact with the preheated oxidizing gas can be made of material compatible with preheated oxygen or other oxidant. These compatible materials can be refractory oxides such as silica, alumina, alumina-zirconia-silica, zirconia and the like. Alternatively, certain metallic alloys that do not combust in preheated oxygen use may be used. Coating metallic materials with ceramic materials on the surface exposed to the preheated oxidizing gas can also be employed for the construction of the burner. Components used in the temperature-sensitive bimetallic valves 110a and 110b or the burner 104 may be coated with Alconel.

A flue gas can be thermally connected with the fuel gas, the oxidizing gas or downstream contacts to either container which are prior to the burner 104. When using natural gas as the fuel gas and oxygen (O₂) as the oxidizing gas, temperatures can be maintained below 450° C. and 550° C. respectively. As the flue gas can reach temperatures of 1350° C. or higher, the heat transfer from the flue gas can be delivered through a secondary device (not shown) to better maintain heat transfer to the fuel gas and the oxidizing gas.

There are various means by which the flow of the gases can be adjusted by the temperature-sensitive bimetallic valves 110a and 110b as the temperature changes. In one embodiment, the fuel gas or the oxidizing gas is flowed through a pipe wherein the outlet of the pipe expands as the tube heats up, based on blocking devices connected to bimetallic layers formed at the outlet. In another embodiment, the flow of the gases is redirected based on a pipe-in-pipe design, where a portion of the pipe is either blocked or open based on reaching a threshold temperature. This design would allow higher flow through the overall pipe when the threshold temperature is reached, thus allowing for a reduced jet velocity. In another embodiment, the flow of the gases is increased based on an “overlaying-leaf” design which increases in size as temperature increases. One skilled in the art will appreciate that numerous permutations of controlling velocity of a gas using a bimetallic strip as disclosed in the invention described herein.

Embodiments described herein relate to relevant portions of a typical burner useable with one or more embodiments of the invention. There can be other components that are not explicitly named which may be included or excluded based on the choice of design and other parameters. The components described herein may differ in shape, size or positioning from those used in practice. Further, the embodiments described herein are for exemplary purposes and should not be read as limiting of the scope of the invention described herein, unless explicitly limited herein.

FIGS. 2A and 2B depict a side view of a temperature-sensitive bimetallic valve 200 according to one embodiment. The temperature-sensitive bimetallic valve 200 described herein can be used to maintain velocity of a gas as temperature of the gas changes. The gas described herein can be a fuel gas, an oxidizing gas or another gas. The gas can be preheated as previously described, such as by recovering lost heat from a flue gas as described above. The gas, whether preheated or not, can then be flowed through an aperture 202 of the valve 200. The aperture 202 can connect the temperature-sensitive bimetallic valve 200 to the oxidizing gas pipe or the fuel gas pipe.

The aperture 202 can be formed in the valve chamber 204 of the temperature-sensitive bimetallic valve 200. The valve chamber 204 can be fluidly sealed providing for the controlled velocity of the gases, which flow through the aperture 202. The valve chamber 204 can be composed of a material which is resistant to at least the expected levels of heat from and the chemistry of the gases delivered. In one embodiment, the valve 200 is composed of ceramics or metals coated with a ceramic. Though the valve chamber 204 is shown as a cylindrical structure, this is not intended to be limiting of possible embodiments of the invention. For example, the valve chamber 204 can be square, rectangular, cylindrical, circular, or combinations of those shapes.

The temperature-sensitive bimetallic valve 200 can include one or more bimetallic strips 206 in connection with the valve chamber 204, shown here as bimetallic strips 206a, 206b, 206c and 206d. The bimetallic strips 206a, 206b, 206c and 206d can be affixed at one end in connection with the valve chamber 204. The bimetallic strips 206a, 206b, 206c and 206d can be affixed by one or more connection devices, shown here as connection devices 207a, 207b and 207c. The connection devices 207a, 207b and 207c can include various connections to the valve chamber 204, such as a spot welding point, a rivet, a clamp or other devices as used in the art. The connection devices 207a, 207b and 207c can be thermally conductive.

The bimetallic strips 206a, 206b, 206c and 206d can be composed of two or more layers of a metal, which can be a pure metal or a metal alloy. These layers may be of any thickness and in any order, based on the desired movement from the bimetallic strips 206a, 206b, 206c and 206d. The layers may further be distinct from one another or may blend into one another. The first metal can expand during temperature changes at a rate which is higher than the second metal. The layers of metal can include a first metal which has a coefficient of thermal expansion which is at least 1.1 times greater than the second metal. In one embodiment, the first metal can be selected from the group consisting of iron, palladium, platinum or combinations thereof. In another embodiment, the second metal can be selected from the group consisting of copper, cobalt, nickel or combinations thereof.

Without intending to be bound by theory, the thermal expansion of a metal is generally believed to be a function of the amount of the metal present and the thermal expansion coefficient of the metal. When the first metal is placed in connection with a second metal and the metals have significantly different coefficients of expansion, the expansion of one metal will necessarily be greater than the expansion of another metal. This differential expansion creates tension against the slower expanding metal, thus creating a bend in the direction of the slower expanding metal.

The bimetallic strips 206a, 206b, 206c and 206d can be connected with one or more blocking devices 208, shown here as blocking devices 208a, 208b, 208c and 208d. The blocking devices 208a, 208b, 208c and 208d can form a partial barrier to flow through the end of the valve 200. The blocking devices can be composed of a material that is not sensitive to high temperatures or to the specific chemistries used in the valve. In one embodiment, the blocking devices 206a, 206b, 206c and 206d are resistant to oxidizing gases, such as oxygen. In another embodiment, the blocking devices 208a, 208b, 208c and 208d are resistant to oxidizing gases, such as oxygen. For example, the blocking devices 208a, 208b, 208c and 208d can be composed of an austenitic nickel-chromium-based alloy such as Inconel. Shown in FIG. 2A, when the bimetallic strips 206a, 206b, 206c and 206d are at an ambient temperature, the blocking devices 208a, 208b, 208c and 208d can be positioned to form a port 203a. In this embodiment, the bimetallic strips 206a, 206b, 206c and 206d are designed to be straight at ambient temperatures. When employing a gas at standard temperature, port 203a restricts flow creating a specific jet velocity for the cool gas. The size and shape of this port can be any size and shape based on the desires of the user, shown here in a circular shape.

FIG. 2B depicts the temperature-sensitive bimetallic valve 200 upon heating, according to one embodiment. As the bimetallic strips 206a, 206b, 206c and 206d heat due to exposure to a preheated gas, the strips will bend based on the composition and formation of the layers and the temperature of the gas. In general, the bimetallic strips 206a, 206b, 206c and 206d will bend in the direction of the metal with the lower thermal expansion coefficient. As the bimetallic strips 206a, 206b, 206c and 206d bend, the blocking devices 208a, 208b, 208c and 208d will separate from one another, thus separating the port 203a. Heat can be transferred to the bimetallic strips 206a, 206b, 206c and 206d through the valve chamber 204, based on the composition of the valve chamber, through the connection devices 207a, 207b and 207c or other means of transmitting heat to the bimetallic strips 206a, 206b, 206c and 206d.

The bent bimetallic strips 206a, 206b, 206c and 206d cause the blocking devices 208a, 208b, 208c and 208d to separate from one another, thus exposing an port 203b. The port 203b is larger than port 203a, which allows the gas to flow at a constant velocity. By increasing the volume of the area, the velocity can be maintained between the cool gas and the more energetic preheated gas. With consideration of the temperatures, the automated process described above allows for safe transition between preheated and cold gas processes.

FIGS. 2C and 2D depict a side view of a temperature-sensitive bimetallic valve 200, according to another embodiment. In this embodiment, the temperature-sensitive bimetallic valve 200 can include an aperture 212, a valve chamber 214, a flow control structure 215, one or more bimetallic strips 216a, 216b, 216c and 216d, and one or more blocking devices 218a, 218b, 218c and 218d. The bimetallic strips 206a, 206b, 206c and 206d can be formed internal to the valve chamber 214 allowing for direct transmission of heat from the gas flow.

FIG. 2C depicts a low temperature embodiment of the temperature-sensitive bimetallic valve 200. When the gas flow is delivered through the aperture 212 at an ambient temperature, such as room temperature, the bimetallic strips 216a, 216b, 216c and 216d are positioned in a relaxed state. In this embodiment, the bimetallic strips 216a, 216b, 216c and 216d are mounted to the internal wall of the valve chamber 214 and connected with the blocking devices 218a, 218b, 218c and 218d. In this embodiment, the blocking devices 218a, 218b, 218c and 218d can overlay one another to form a port 213a between the blocking devices 218a, 218b, 218c and 218d and the flow control device 215, to reduce the flow through the valve 200.

FIG. 2D depicts a high temperature embodiment of the temperature-sensitive bimetallic valve 200 described above. As the temperature of the gas delivered through the aperture 212 is increased above a standard temperature, the bimetallic strips 216a, 216b, 216c and 216d expand and flex. As the bimetallic strips 216a, 216b, 216c and 216d flex, the blocking devices 218a, 218b, 218c and 218d, connected with the bimetallic strips 216a, 216b, 216c and 216d will reposition. As the bimetallic strips 216a, 216b, 216c and 216d change position over a wide range of temperatures, the movement of the bimetallic strips 216a, 216b, 216c and 216d and the attached blocking devices 218a, 218b, 218c and 218d is only limited by the walls of the valve chamber 214 and the maximum temperature of the gas delivered. In this embodiment, the blocking devices 218a, 218b, 218c and 218d continue to overlay one another to form a complete port 213b in conjunction with blocking device 215. The blocking devices 218a, 218b, 218c and 218d may be composed of any material capable of preventing flow of a gas while surviving both the temperature and the chemistry of the gas. The blocking devices 218a, 218b, 218c and 218d may be of a non-uniform composition. Further, the blocking devices 218a, 218b, 218c and 218d may differ in composition from one another.

The number and shape of the bimetallic strips 216a, 216b, 216c and 216d and the blocking devices 218a, 218b, 218c and 218d are depicted here for exemplary purposes only. Further embodiments of this invention may include more of fewer bimetallic strips 216a, 216b, 216c and 216d and the blocking devices 218a, 218b, 218c and 218d as well as different shapes, based on the needs and desires of the user.

FIGS. 2E and 2F depict a side view of a temperature-sensitive bimetallic valve 200 employing a coil-style bimetallic strip, according to another embodiment. In this embodiment, the temperature-sensitive bimetallic valve 200 can include an aperture 222, a valve chamber 224, a flow control structure 225, a bimetallic strip 226, a mounting device 227, a blocking device 228 and a motion control structure 229. The bimetallic strip 226 is formed in a coil to allow for greater motion in response to temperature. Increased motion of the bimetallic strip 226 can position the blocking device 228 to block one of the one or more ports 223a and 223b.

FIG. 2E depicts the apparatus described above at an ambient temperature. The aperture 222 can deliver gas from the gas container into the valve chamber 224. The gas can be delivered at an ambient temperature. The bimetallic strip 226 is positioned centrally around a mounting device 227 and in fluid connection with the gas. The blocking device 228 is positioned in conjunction with the flow control device 225 to block port 223b and redirect flow of the gas through port 223a. The bimetallic strip 226 delivers force to the blocking device 228 by using the motion control structure 229. The motion control structure 229 is depicted here as a rounded bar extending from the wall of the valve chamber 224.

FIG. 2F depicts the apparatus described above when exposed to a preheated gas. As the preheated gas is delivered to the valve chamber 224 through the aperture 222, the temperature of the bimetallic strip 226 increases. The increased temperature causes the bimetallic strip 226 to flex due to thermal expansion and subsequently apply force to the blocking structure 228. In this embodiment, the force from the bimetallic strip 226 is redirected in a second direction using the motion control structure 229. As force is applied, blocking structure 228 moves into a second position, which acts in conjunction with the flow control structure 225 to block port 223a and redirect the gas through port 223b. In this embodiment, the port 223b is larger than port 223a, thus maintaining the jet velocity between the cooler gas delivered through port 223a and the preheated gas delivered through port 223b.

In one or more of the embodiments described above, the temperature may be directly delivered to the bimetallic strip 226 or indirectly. In one embodiment, the heat from the preheated gas is delivered through a conductive material to the mounting device 227. The mounting device 227 can then transfer heat to the bimetallic strip 226. The mounting device 227 can be formed of any material appropriate to the temperatures and chemistries of the gas flowed through the valve 200. The mounting device 227 may also be a conductive material, such as a metal. For example, the mounting device 227 may comprise copper or a copper alloy.

FIGS. 2G and 2H depict a side view of a temperature-sensitive bimetallic valve 200 employing a bimetallic strip blocking structure, according to another embodiment. In this embodiment, the temperature-sensitive bimetallic valve 200 can include an aperture 232, a valve chamber 234, a flow control structure 235, a bimetallic strip 236, and a support structure 238. The bimetallic strip 226 is formed in a curved shape to attenuate flow through the valve chamber 234 when the valve 200 receives a cold gas.

FIG. 2G depicts the apparatus described above at an ambient temperature. In this embodiment, the bimetallic strip 236 is mounted on the flow control structure 236. As shown, the bimetallic strip redirects flow of gas from the aperture 232 to the port 233. This embodiment does not require an independent blocking structure, thus the shape of the bimetallic strip 236 is designed to inhibit gas flow through the valve chamber 234. The standard temperature gas is delivered through the aperture 232 and into the valve chamber 234 where it is directed through the port 233 as formed between the bimetallic strip 236 and wall of the valve chamber 234.

FIG. 2H depicts the apparatus described above when exposed to a preheated gas. As preheated gas is delivered to the valve 200, the bimetallic strip 236 flexes, based on the mechanism described above. As the bimetallic strip 236 flexes, the port 233 grows larger, as formed between the walls of the valve chamber 234 and the bimetallic strip 236. Since the bimetallic strip 236 is fixed to the flow control structure 235, the bimetallic strip 236 flexes on one side only, thus bending the bimetallic strip 236 into position with support structure 238. The larger port 233 can maintain gas velocity for the preheated gas at a similar velocity to the cold gas.

Though the embodiments above focus primarily on gradual effects of a bimetallic strip, one or more of the embodiments above can incorporate a design which requires a specific level of force to transition from one state to another. Stated another way, the bimetallic strip can be employed in a way that creates a transition temperature for redirecting gas flow. Further, one or more sources of force, such as springs, may be employed for more complex operations incorporating the bimetallic strip designs described above.

FIG. 3 is a flow diagram of a method 300 for automated control of gas velocity, according to one embodiment. In embodiments described herein, an oxidizing gas or a fuel gas can be heated prior to flowing to a burner. Positioned between the gas container and the burner is a temperature-sensitive bimetallic valve. Initially, the temperature-sensitive bimetallic valve, in a first state, allows the gas to flow at a velocity which is standard for a gas delivered at a standard temperature, such as room temperature. As the preheated gas flows through the valve, the bimetallic layer heats up. The expansion effect, based on the bimetallic layer composition, causes either gradual or dramatic shifts in the position of the blocking device. These shifts in the blocking device maintain a constant velocity of the gas at an equal flow rate between the heated gas and the standard temperature gas.

The method 300 begins at step 302 by flowing an oxidizing gas or a fuel gas into a temperature-sensitive bimetallic valve at a first temperature, the temperature-sensitive bimetallic valve comprising a bimetallic strip, a blocking device and a flow control structure. In one or more embodiment, the fuel gas can be heated by using a flue gas. As described above, thermal energy is wasted from the furnace in the form of heat in the flue gas. One mechanism to recover this lost heat, is to heat the oxidizing gas and/or the fuel gas prior to delivering to the burner. In one or more embodiments, either the oxidizing gas or the fuel gas is heated, while the other gas is maintained at standard temperature. After one or more of the gases are heated, the gases are then flowed to the temperature-sensitive bimetallic valve. In standard embodiments, the gas will enter at one velocity and exit at a predetermined velocity based on port size. The velocity of entry and the velocity of exit may be equal based on the size of the port and the initial flow velocity from the gas container. Preheated gases will enter the temperature-sensitive bimetallic valve at a faster velocity than comparatively colder gas, given other conditions such as flow rate remain constant between the preheated gas and cold gas.

At step 304, the oxidizing gas and the fuel gas can transfer heat with the bimetallic strip in the temperature-sensitive bimetallic valve. As the gases flow into the temperature-sensitive bimetallic valve, the components which are in thermal contact with the gas equilibrate based on the starting temperature of the gas and the starting temperature of the components of the temperature-sensitive bimetallic valve. The temperature-sensitive bimetallic valve is expected to start at a second temperature, which can be an ambient temperature, such as room temperature. However, this can be altered by preheating the valve to assure quick transition from one state to another. The oxidizing gas and the fuel gas will be delivered at a first temperature which is the temperature each was heated to in the previous step. When the fuel gas is natural gas, the first temperature should be less than or equal to about 450° C. When the oxidizing gas is oxygen (O₂), the first temperature should be less than or equal to about 550° C. As the gases are delivered to the temperature-sensitive bimetallic valve, the components of the temperature-sensitive bimetallic valve including the bimetallic strip will change from the second temperature to the first temperature.

At step 306, the position of the bimetallic strip can change as measured form the flow control structure, in response to the change in temperature from the second temperature to the first temperature. As the bimetallic strip changes from the second temperature to the first temperature, the bimetallic strip can flex and bend in proportion to the change in temperature and the composition of the bimetallic strip. Based on the change in the bimetallic strip, the size of the port for the temperature-sensitive bimetallic valve can change. In further embodiments, the temperature change can be used to redirect the gas to a second port. The goal of either the size or the port change is maintain the velocity of the gas between the standard temperature gas and the heated gas as they exit the temperature-sensitive bimetallic valve. Using the bimetallic strip, the gas can be flowed into a second port or into a larger port to maintain the final velocity of the gas.

At step 308, the oxidizing gas or the fuel gas can be delivered from the temperature-sensitive bimetallic valve to the burner at a second velocity. In this embodiment, the temperature of the gas affects the position of the bimetallic strip in the temperature-sensitive bimetallic valve. By changing the bimetallic strip position in the temperature-sensitive bimetallic valve, the port size is increased by one or more of the above described means, which increases the volume and changes the velocity of the gas. The change in velocity of the gas creates a second velocity which is approximately equal between the standard temperature gas and the heated gas. In one or more embodiments, the temperature-sensitive bimetallic valve gradually shifts between two states, with the second state providing a larger port for the preheated gas to flow through after changing from the standard temperature gas to the preheated gas. It is important to note that, although the second velocity can be different from the first velocity, this is not required.

The transfer of heat to the bimetallic strip does not need to be a direct transfer. In one or more embodiments, an insulated heat pipe could sample and “transmit” heat from the area where process flow temperature is seen, to a bimetallic strip positioned proximate, but thermally isolated from, the gas, such that the bimetallic strip is not directly subject to the heat or chemistry of the gas. The bimetallic strip flexes based on the temperature change to either open a second port or decrease the effective size of the first port.

CONCLUSION

Embodiments described herein relate to automated control of the velocity of a gas based on temperature. Recovery of lost thermal energy is becoming more important as fuel costs rise. One important point of lost thermal energy in standard furnaces is through flue gas. One means to recapture this lost thermal energy is through heating of the combustion gases, one or more of the fuel gas or the oxidizing gas, prior to combustion. As gases heat up, they expand which changes the pressure and the subsequent velocity of the gas flow. This change can affect the proper mixture of the gases and subsequent burn in the furnace.

Embodiments described herein teach the method and apparatus for controlling jet velocity using a temperature-sensitive bimetallic valve. By redirecting the flow based on a temperature gradient, proper jet velocity at the burner can be maintained using high temperatures or standard temperature gases without the inherent dangers of manual manipulation of a valve.

While the foregoing is directed to embodiments of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.

Claims

1. A system for controlling jet velocity of a gas, comprising:

a source of oxidizing gas;

a source of fuel gas;

at least one temperature-sensitive bimetallic valve in connection with one of the source of oxidizing gas or the source of fuel gas, the valve comprising a bimetallic strip, a blocking device and a flow control structure and configured to: receive an oxidizing gas or a fuel gas, wherein the oxidizing gas or the fuel gas is at a first temperature; change the temperature of at least the bimetallic strip from a second temperature to the first temperature; change position of the bimetallic strip, as measured from the flow control structure, in response to the change in temperature from the second temperature to the first temperature; and change the velocity of the oxidizing gas or the fuel gas through the valve based on the position of the bimetallic strip; and

a burner configured to: receive an oxidizing gas or a fuel gas from the at least one temperature-sensitive bimetallic valve, wherein the oxidizing gas or the fuel gas is at the first temperature; combine and combust the fuel gas with the oxidizing gas to create a flame; and direct the flame to a target material.

2. The system of claim 1, wherein the temperature-sensitive bimetallic valve is configured to deliver the oxidizing gas or the fuel gas to the burner with an approximately constant velocity.

3. The system of claim 1, wherein the temperature-sensitive bimetallic structure further comprises the blocking device configured to:

change position with the bimetallic strip; and

change the velocity of the oxidizing gas and/or the fuel gas based on the position of the bimetallic strip in conjunction with the flow control structure.

4. The system of claim 1, wherein the bimetallic strip is configured to act as the blocking device.

5. The system of claim 1, wherein the temperature-sensitive bimetallic valve is configured to receive the fuel gas, the fuel gas is natural gas and the first temperature is less than or equal to 450 degrees Celsius.

6. The system of claim 1, wherein the temperature-sensitive bimetallic valve is configured to receive the oxidizing gas, the oxidizing gas is oxygen (O2) and the first temperature is less than or equal to 550 degrees Celsius.

7. The system of claim 1, wherein the source of oxidizing gas or the source of fuel gas is configured to receive and transmit heat from a flue gas.

8. The system of claim 1, wherein the burner comprises a first oxidizing gas pipe and a first fuel gas pipe which are configured to deliver an oxidizing gas or a fuel gas to the burner.

9. The system of claim 8, wherein the temperature-sensitive bimetallic valve is configured to change the velocity of the oxidizing gas or the fuel gas through the valve by redirecting at least a portion of the oxidizing gas or the fuel gas through one or more second oxidizing gas pipes or one or more second fuel gas pipe.

10. The system of claim 8, wherein the temperature-sensitive bimetallic valve is configured to change the velocity of the oxidizing gas or the fuel gas through the valve by increasing the volume of the first oxidizing gas pipe or the first fuel gas pipe.

11. The system of claim 1, wherein the bimetallic strip comprises a first metal and a second metal and wherein the first metal is selected from the group consisting of iron, palladium, platinum or combinations thereof.

12. The system of claim 1, wherein the bimetallic strip comprises a first metal and a second metal and wherein the second metal is selected from the group consisting of copper, cobalt, nickel or combinations thereof.

13. The system of claim 1, further comprising a protective cover configured to:

isolate the bimetallic strip from the oxidizing gas or the fuel gas; and

transmit heat to the bimetallic strip.

14. A method for controlling gas velocity in a furnace comprising:

flowing an oxidizing gas or a fuel gas into a temperature-sensitive bimetallic valve at a first temperature, the temperature-sensitive bimetallic valve comprising a bimetallic strip, a blocking device and a flow control structure;

transferring heat from the oxidizing gas or the fuel gas to the bimetallic strip, wherein the bimetallic strip changes from a second temperature to the first temperature;

changing the position of the bimetallic strip, as measured from the flow control structure, in response to the change in temperature from the second temperature to the first temperature; and

delivering the oxidizing gas or the fuel gas from the temperature-sensitive bimetallic valve to a burner at a second velocity, wherein the second velocity of the oxidizing gas or fuel gas changes dependant on the position of the bimetallic strip.

15. The method of claim 14, wherein the oxidizing gas or the fuel gas are heated to a temperature below a critical temperature of the gas.

16. The method of claim 14, wherein the oxidizing gas or the fuel gas indirectly exchanges heat with the bimetallic strip.

17. The method of claim 14, wherein the oxidizing gas and/or the fuel gas is preheated using a flue gas.

18. The method of claim 14, wherein the second velocity is less than the first velocity.

19. The method of claim 14, wherein the oxidizing gas or the fuel gas is heated to the first temperature by a flue gas prior to flowing into the temperature-sensitive bimetallic valve.

20. The method of claim 14, wherein the oxidizing gas or the fuel gas is delivered from the temperature-sensitive bimetallic valve to the burner through one or more first pipes.

21. The method of claim 20, wherein the oxidizing gas or the fuel gas is delivered at the second velocity by changing the available volume of the one or more first pipes.

22. The method of claim 20, wherein the oxidizing gas or the fuel gas is delivered at the second velocity by using the one or more first pipes in conjunction with one or more second pipes.

23. The method of claim 14, wherein the fuel gas is natural gas and the first temperature is less than or equal to 450 degrees Celsius.

24. The method of claim 14, wherein the oxidizing gas is oxygen (O2) and the first temperature is less than or equal to 550 degrees Celsius.