Production of Synthetic Gas From Organic Waste

Abstract

A pyrolysis device has a pyrolyzer (retort) and a thermal oxidizer, each with its own burner, but coupled so that the burner of the pyrolyzer can be down-regulated as heat from the thermal oxidizer is used to hear the pyrolyzer. One or more automatic controllers preferably adjust a burn rate of the extrinsic gas by the first burner as a function of a rate at which heat is transferred from the thermal oxidizer to the pyrolyzer. In preferred embodiments, the burn rate of the extrinsic gas can be adjusted to ≦50%, ≦30% or even lower relative to a base rate that would be required to pyrolyze the waste without the heat thermal oxidizer.

Description

PRIORITY CLAIM

This application claims priority to provisional application Ser. No. 60/810382 filed Jun. 1, 2006.

FIELD OF THE INVENTION

The field of the invention is pyrolysis.

BACKGROUND

Pyrolysis of wastes often produces combustible gases (i.e., synthetic or syn gases) that can be burned in a thermal oxidizer to produce heat, and ultimately to generate electricity. US619214 to Walker et al. (September '03) and U.S. Pat. No. 7,044,069 to Cole et al. May 2006) teach that some of the heat produced by oxidation of the syn gas can also be used for other purposes, including heating of the reaction chamber of the pyrolytic converter (also referred to herein as the pyrolyzer), and drying of the waste prior to pyrolysis.

Various other improvements are described in patents and applications of the same family, including US700551 (February '06), U.S. Pat. No. 6,988,453 (January 2006), US2005/0039651 (February 2005), U.S. Pat. No. 7,191,714 (March 2007), and US 11/286552 (filed Nov. 22, 2005). These and all other extrinsic materials referenced herein are incorporated by reference in their entirety. Where a definition or use of a term in an incorporated reference is inconsistent or contrary to the definition of that term provided herein, the definition of that term provided herein applies and the definition of that term in the reference does not apply.

Significantly, both Walker '213 and Cole '069 patents contemplate that all of the heat used to pyrolyze the waste comes from the thermal oxidizer. There is no separate burner to provide heat directly to the pyrolyzer. The Walker '213 design splits the thermal oxidizer into two sections, each with its own burners. The burners of the first section are used to heat up the pyrolyzer upon cold start, and then to assist in burning the syn gas once pyrolysis is underway. The Cole '069 design shunts the combustion gasses from the thermal oxidizer into the outer chambers of dual pyrolyzers. Both designs turn out to be problematic because of difficulties in implementation.

What is needed are systems and methods in which the pyrolyzer has its own burner(s), which can be controlled independently of the thermal oxidizer, but which can be down-regulated as heat from the thermal oxidizer is used to hear the pyrolyzer.

SUMMARY OF THE INVENTION

The present invention provides systems, methods and devices in which a pyrolyzer has its own burner(s), which can be controlled independently of the thermal oxidizer, but which can be down-regulated as heat from the thermal oxidizer is used to hear the pyrolyzer.

In preferred embodiments of the apparatus, a device for pyrolytically treating a waste comprises a pyrolyzer and a thermal oxidizer, a first burner that primarily heats the pyrolyzer to produce a synthetic gas from the waste, a second burner that primarily assists in combusting the synthetic gas in the thermal oxidizer; and a heat transfer component that carries heat from the thermal oxidizer to the pyrolyzer. The first and second burners can advantageously receive a supply of extrinsic gas, such as from a natural gas line.

One or more automatic controllers preferably adjust a burn rate of the extrinsic gas by the first burner as a function of a rate at which heat is transferred from the thermal oxidizer to the pyrolyzer. In preferred embodiments, the burn rate of the extrinsic gas can be adjusted to ≦50%, ≦30% or even lower relative to a base rate that would be required to pyrolyze the waste without the heat thermal oxidizer.

It is also contemplated that a line can carry a portion of the un-combusted or partially combusted syn gas to be burned along with the extrinsic gas at the first burner, which process can also be under the control of an automatic controller.

Various objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of preferred embodiments of the invention, along with the accompanying drawings in which like numerals represent like components.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a perspective view of a prior art pyrolysis system including a retort and a thermal oxidizer.

FIG. 2 is a perspective view of a novel pyrolysis system in which combustion gas from the thermal oxidizer is used to assist in heating the pyrolyzer.

FIG. 3 is a perspective view of a novel pyrolysis system in which syn gas is being fed to the burner of the pyrolyzer.

FIG. 4 is a perspective view of a novel two level pyrolysis system in which combustion gas from the thermal oxidizer is used to assist in heating the pyrolyzer.

DETAILED DESCRIPTION

In FIG. 1, a prior art pyrolytic device 100 includes an inner chamber 112 and an outer chamber 113. A rotating drive 114 carries waste 111 through the inner chamber 112, where the waste is subjected to heat to produce a combustible synthetic (“syn”) gas 116 and pyrolyzed solids 119. The pyrolyzing heat is provided by a burner 120, which burns natural or other extrinsic gas 117 and releases the exhaust into outer chamber 113. Syn gas 116 generated by the process travels to the thermal oxidizer (“after burner”) 120, where it is combined with air, and combusted along with additional extrinsic gas 127. Combusted gas exhaust from the thermal oxidizer 120 is sent to the boiler of a power plant 130 to produce steam and ultimately, electricity. Details are provided in the patents and applications incorporated herein by reference.

In FIG. 2, a novel pyrolytic device 200 includes all the listed components discussed above for device 100. In addition, device 200 includes line 142 that carries combusted or semi-combusted gasses from the thermal oxidizer 120 to the outer chamber 113 of the pyrolyzer 110, where they provide heat to pyrolyze the waste 111. Exhaust from the pyrolyzer 110 can be used to dry waste 111 before it is fed into the pyrolyzer, utilized in operating the power plant, or utilized for any other purpose. Although not preferred, the exhaust could also be vented. Lines carrying the exhaust are not shown.

Once syn gas is being produced in good quantity, and depending upon selected operating parameters, the heat provided via line 142 can provide a majority or even all of the heat needed to pyrolyze the waste 111. In especially preferred embodiments, the balance of heat provided by combusting the extrinsic gas and the heat being provided via line 142 is automatically controlled by controller 150. For example, if the natural gas or other extrinsic gas is being procured at very low cost, or if energy production is being maximized, the amount of heat being siphoned off via line 142 could be low or even zero. On the other hand, if the extrinsic gas is relatively expensive, or if energy production is not being maximized, or perhaps more heat is being generated that can be effectively used in the power plant, relatively more heat could be siphoned off via line 142. It is contemplated that the controller could automatically adjust a burn rate of the extrinsic gas to below 50% of a base rate that would be required to pyrolyze the waste without the heat thermal oxidizer. That percentage could be cut further to below 30%, below 25%, below 20% and even down to zero for a period of time.

It is also contemplated that the controller could automatically adjusts relative amounts of the extrinsic and syn gasses as a function of a characteristic of the syn gas being produced. Suitable characteristics upon which to base the adjustments include quantity of syn gas, and relative amounts of combustible and non-combustible constituents of the syn gas.

Given this disclosure, development and appreciation of contemplated electronic and other controls are well within the skill of those in the art, including for example Johnson Controls™.

In FIG. 3, device 300 is similar to device 200 except that here some of the syn gas is ported to the burner 116 of the pyrolyzer 110 via line 144. At present is a less preferred embodiment, and would generally make sense where the syn gas being ported has not yet been fully combusted.

In FIG. 4, device 400 is again similar to device 200. One major difference is that here the pyrolyzer 110 and thermal oxidizer 120 are vertically disposed relative to one another rather than horizontally disposed. Among other things, this configuration can provide much greater efficiency in terms of land usage. In this particular instance, heat (in the form of hot combusted or semi-combusted gasses) are ported from the thermal oxidizer 120 to the pyrolyzer 110 via line 146.

It should be appreciated that in each of FIGS. 2-4, burner 116 is used primarily to heat the pyrolyzer 110, to produce a synthetic gas from the waste 111. Similarly, in each of FIGS. 2-4, the second burner 126 primarily assists in combusting the synthetic gas in the thermal oxidizer 120. As used herein, the term “primarily” refers to functions during normal steady-state operation, as opposed for example to start-up or shutdown procedures. In contrast, the primary function of burner 66 in U.S. Pat. No. 6,619,214 is to provide heat to the thermal oxidizer 26, not to heat the pyrolytic converter 24.

It should also be apparent to those skilled in the art that many more modifications besides those already described are possible without departing from the inventive concepts herein. Moreover, in interpreting the disclosure, all terms should be interpreted in the broadest possible manner consistent with the context. In particular, the terms “comprises” and “comprising” should be interpreted as referring to elements, components, or steps in a non-exclusive manner, indicating that the referenced elements, components, or steps could be present, or utilized, or combined with other elements, components, or steps that are not expressly referenced. Where the specification claims refers to at least one of something selected from the group consisting of A, B, C . . . and N, the text should be interpreted as requiring only one element from the group, not A plus N, or B plus N, etc.

Claims

1. A device for pyrolytically treating a waste, comprising:

a pyrolyzer and a thermal oxidizer;

a first burner that primarily heats the pyrolyzer to produce a synthetic gas from the waste;

a second burner that primarily assists in combusting the synthetic gas in the thermal oxidizer; and

a heat transfer component that carries heat from the thermal oxidizer to the pyrolyzer.

2. The device of claim 1, wherein the first burner receives a supply of extrinsic gas.

3. The device of claim 2, further comprising a controller that automatically adjusts a burn rate of the extrinsic gas by the first burner as a function of a rate at which heat is transferred from the thermal oxidizer to the pyrolyzer.

4. The device of claim 2, further comprising a controller that automatically adjusts a burn rate of the extrinsic gas to below 50% of a base rate that would be required to pyrolyze the waste without the heat thermal oxidizer.

5. The device of claim 2, further comprising a controller that automatically adjusts a burn rate of the extrinsic gas to below 30% of a base rate that would be required to pyrolyze the waste without the heat thermal oxidizer.

6. The device of claim 2, further comprising a controller that automatically adjusts relative amounts of the extrinsic and syn gasses combusted by the first burner as a function of a characteristic of the syn gas.

7. The device of claim 1, further comprising a line that carries a portion of the syn gas to the first burner.