Piggybacked Pyrolyzer and Thermal Oxidizer

Abstract

A pyrolysis waste treatment system having a pyrolyzer and a thermal oxidizer that are aligned in a partially or completely piggybacked fashion, and heat from the exhaust gas of the thermal oxidizer is shunted back to the pyrolyzer to help sustain pyrolysis. Such conduits can have any suitable configuration, including for example where the conduit extends from sides (as opposed to the ends) of each of the pyrolyzer and the thermal oxidizer. Contemplated pyrolyzers and the thermal oxidizers can have any suitable dimensions, but are preferably at least 5 meters long, and have a cross sectional area of at least 10 m2. In most contemplated embodiments, the thermal oxidizer has a length within 20% of the length of the pyrolyzer.

Description

This application is a continuation-in-part of U.S. application Ser. No. 11/757,189, filed Jun. 1, 2007, which claims the benefit of U.S. Provisional App. No. 60/810,382, filed Jun. 1, 2006.

FIELD OF THE INVENTION

The field of the invention is furnaces, and especially furnaces involved with liberating gas from solid fuel. (Class 110/229).

BACKGROUND

Pyrolysis employs high temperatures in a relatively oxygen free environment to remove volatiles from solid fuels, as well as gases that can be released at high temperature from breaking down a feedstock. Depending on the feedstock, the volatiles can then be burned to produce usable energy.

It is known to pyrolyze innumerable different types of fuels, including trash, old tires, and other municipal wastes. As discussed in commonly-assigned U.S. patent application Ser. No. 10/517,023 to Walker, which is a national phase entry of PCT/US02/20362, filed Jun. 26, 2002, and U.S. Pat. No. 6,619,214 to Walker (September 2003), a typical waste treatment system utilizing pyrolysis includes: (a) an input structure for introducing waste; (b) a pyrolytic converter for breaking down a feedstock and generating waste gases; and (c) a thermal oxidizer that burns the waste gases (also referred to herein as “syngas” or “syn gases”). In preferred embodiments a portion of the heated gases can be transported back into an outer chamber of the pyrolyzer to help sustain continued pyrolysis of the feedstock.

It is known to dispose the pyrolyzer and thermal oxidizer in end-to-end configurations (see e.g., U.S. Pat. No. 5,586,855 to Eshleman (December 1996); U.S. Pat. No. 5,653,183 to Hansen et al. (August 1997); U.S. Pat. No. 6,758,150 to Ballantine et al. (July 2004)), and in side-by-side configurations (see e.g., U.S. Pat. No. 6,701,855 to Barba (March 2004); U.S. Pat. No. 6,745,707 to Suzuki et al. (June 2004)).

One advantage of the side-by-side configuration is that one can readily transfer heat from the thermal oxidizer to the pyrolyzer. Barba '855, for example, teaches combusting the syn gases in a thermal oxidizer, and then transferring a portion of the exhaust gas from the oxidizer back into the pyrolyzer.

It is also known to dispose the pyrolyzer and thermal oxidizer in a piggyback configuration, where the pyrolyzer is disposed below the thermal oxidizer. The piggybacking can take within a common housing (see e.g., U.S. Pat. No. 4,084,521 to Herbold et al. (April 1978), U.S. Pat. No. 5,411,714 to Wu et al. (May 1995)), or without a common housing (see e.g., U.S. Pat. No. 4,802,424 to McGinnis et al. (February 1989))

Interestingly, however, no one seems to have appreciated that it can be advantageous to transfer heat from the thermal oxidizer to the pyrolyzer with a piggyback configuration. In two piggyback configurations using a common housing, Herbold '521 and Wu '714, syngas produced in an inner chamber of the pyrolyzer is shunted back to an outer chamber of the pyrolyzer for burning. But that is not the same as burning the syngas in a thermal oxidizer, and then transferring the heat back to the pyrolyzer, for example by shunting the exhaust gas from the thermal oxidizer to the pyrolyzer. In a piggyback configuration without a common housing, McGinnis '424, there is no teaching at all of diverting anything back from the thermal oxidizer to the pyrolyzer.

Walker, Eshleman, Hansen, Ballantine, Barba, Suzuki, Herbold, Wu, and McGinnis, and all other extrinsic materials discussed 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.

Thus, there is still a need for systems, methods and apparatus that decrease the space requirements for a waste treatment system having a pyrolyzer and a thermal oxidizer, while still retaining efficient heat transfer.

SUMMARY OF THE INVENTION

The present invention provides apparatus, systems and methods in which a pyrolyzer and a thermal oxidizer of a waste treatment system are aligned in a partially or completely piggybacked fashion, and heat from the exhaust gas of the thermal oxidizer is shunted back to the pyrolyzer. Such configurations can advantageously decrease the floor space needed in a waste treatment facility, while still providing excellent energy efficiency.

As used herein, the terms “piggyback”, “piggybacking” and the like should be interpreted broadly as applied to a pyrolyzer and the thermal oxidizer combination, to include all situations where a vertical line would pass through portions of both the pyrolyzer and the thermal oxidizer. Thus, all configurations where the thermal oxidizer or the pyrolyzer lies directly over the other are considered piggybacked, as are configurations where the alignment is more askew, but one of the pyrolyzer and the thermal oxidizer is still at least partially over the other. In preferred embodiments, one of the pyrolyzer and the thermal oxidizer is elevated relative to one another by at least 2 meters (m). In preferred embodiments the pyrolyzer is also distanced from the thermal oxidizer by less than 2 meters, and a saddle is disposed between the pyrolyzer and the thermal oxidizer to prevent heat transfer.

Preferred pyrolyzers have an inner chamber that carries a waste stream, an outer chamber that provides heat to the inner chamber to sustain pyrolysis, and an outlet for release of syngas produced during pyrolysis.

Preferred thermal oxidizers burn at least a portion of the syn gases in a hot flame from a natural gas burner, thereby producing hot exhaust gases. Thermal oxidizers also preferably have a conduit that transports a portion of the hot exhaust gases back to the outer chamber of the pyrolyzer, which conducts heat to a waste stream in the inner chamber of the pyrolyzer to help sustain pyrolysis. Such conduits can have any suitable configuration, including for example where the conduit extends from sides (as opposed to the ends) of each of the pyrolyzer and the thermal oxidizer.

The pyrolyzer and the thermal oxidizer can have any suitable dimensions, but preferably the pyrolyzer and the thermal oxidizer are at least 5 meters long, and have a cross sectional area of at least 10 m². In most contemplated embodiments, the thermal oxidizer has a length within 20% of the length of the pyrolyzer.

Various objects, features, aspects and advantages of the inventive subject matter will become more apparent from the following detailed description of preferred embodiments, 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 pyrolyzer and a thermal oxidizer in a piggyback configuration.

FIG. 2A comprises a vertical end view of the piggyback configuration of FIG. 1.

FIG. 2B comprises a vertical end view of an alternative piggyback configuration of a pyrolyzer and a thermal oxidizer.

DETAILED DESCRIPTION

FIGS. 1 and 2A generally depict a waste treatment system 100 having a pyrolyzer 110 and a thermal oxidizer 140 in a preferred piggyback configuration.

Pyrolyzer 110 generally includes an outer housing 112, an inner housing 114, a heated outer chamber 112A between the inner and outer housings, and an inner reaction chamber 114A in which pyrolysis occurs. Conveyor mechanism 120 is disposed within, and passes through inner housing 114. Preferably, conveyor mechanism 120 is a screw type conveyor that transports waste input as shown by arrow 118, through inner reaction chamber 114A as pyrolysis occurs.

Waste input 118 can accept any suitable type of waste, including for example, municipal waste, and especially including dried waste from sewage, municipal garbage, plastic scraps, scrap wood, oil impregnated rags and refuse oils, scrap metal, and old tires and other articles of rubber. Waste processed in the pyrolyzer exits the inner reaction chamber 114A as char, shown by arrow 124, via char outlet conduit 122. Processing of the waste also produces syn gases (pyrolysis waste gases), which exits the inner reaction chamber 114A via conduit 126, as shown by arrow 128, and then travels to the thermal oxidizer 140.

Thermal oxidizer 140 generally includes an input of syngas from conduit 126, a burner 142, an exhaust gas return conduit 144, and an exhaust gas outlet 148. The composition of the syngas can vary greatly as a function of the waste being pyrolyzed, with syngas from pyrolysis of municipal waste, for example, typically including hydrogen, carbon monoxide, methane, and lower molecular weight hydrocarbons, as well as nitrogen and carbon dioxide. A hot flame from a natural gas burner 142 is preferably used to initiate combustion of the syn gases 128, thereby producing hot exhaust gases 145.

Exhaust gas return conduit 144 shunts a portion of hot exhaust gases 145 back to outer chamber 112A of pyrolyzer 110. Outer chamber 112A of pyrolyzer 110 conducts heat to a stream of waste in inner reaction chamber 114A of pyrolyzer 110 to help sustain pyrolysis. Exhaust gas return conduit 144 can have any suitable configuration, including for example where the conduit extends from sides (as opposed to the ends) of each of the pyrolyzer 110 and the thermal oxidizer 140. Any portion of hot exhaust gases 145 not shunted to pyrolyzer 110 are carried out of thermal oxidizer 140 by exhaust gas conduit 148.

Pyrolyzer 110 and thermal oxidizer 140 can have any suitable dimensions, but preferably pyrolyzer 110 and thermal oxidizer 140 are at least 3, 5, 6, or 7 meters long, and have a cross sectional area of at least 8, 9, 10, or 12 m². In most contemplated embodiments, the thermal oxidizer has a length within 20%, 15%, or more preferably 10% of the length of the pyrolyzer. Also, as shown in FIG. 2A, pyrolyzer 110 is distanced from thermal oxidizer 140 by less than 2, 1.5, 1 or even 0.5 meters, as shown by distance 132.

As shown in FIGS. 1 and 2A, pyrolyzer 110 and thermal oxidizer 140 have a piggyback configuration. It is contemplated that the piggyback configuration includes all situations where vertical line 170 (see FIG. 2A) passes through portions of both pyrolyzer 110 and thermal oxidizer 140. Thus, all configurations where thermal oxidizer 140 or pyrolyzer 110 lies directly over the other are considered piggybacked. Pyrolyzer 110 and thermal oxidizer 140 each have a bottom 116 and 146 respectively, and in preferred embodiments, the bottom of one is elevated at least 2, 3, 4, or even 5 meters relative to the bottom of the other. FIG. 2B generally depicts an alternative piggyback configuration that is slightly askew, but one where the thermal oxidizer 240 is only partially disposed over the pyrolyzer 210 such that a vertical line 270 exists that passes through portions of both the pyrolyzer 210 and the thermal oxidizer 240.

FIGS. 1 and 2A also depict saddles 130A that support pyrolyzer 110 and saddles 130B disposed between pyrolyzer 110 and thermal oxidizer 140. The saddle 130A, 130B allow expansion and contraction of the chambers as temperature changes, particularly along its length, without causing the chambers to buckle such as by bending, warping, or crumpling. Ceramic saddles are particularly desirably under the pyrolyzer 110 because they have a relatively low coefficient of thermal conductivity, and would tend to inhibit the flow of heat out of the pyrolyzer 110.

It should 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. The inventive subject matter, therefore, is not to be restricted except in the spirit of the appended claims. Moreover, in interpreting both the specification and the claims, 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 can 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 waste, comprising:

a pyrolyzer having an inner chamber that carries a waste stream, an outer chamber that provides heat to the inner chamber to sustain pyrolysis, and a outlet for release of syngas produced during pyrolysis;

a thermal oxidizer that produces hot exhaust gases from oxidation of at least some of the syngas;

a conduit that passes at least some of the exhaust gases to the outer chamber of the pyrolyzer; and

wherein the pyrolyzer and the thermal oxidizer each have a bottom and the bottom of one is at least elevated 2 meters relative to the bottom of the other.

2. The device of claim 1, further comprising the pyrolyzer and thermal oxidizer disposed such that a vertical line exists that passes through at least some portion of the pyrolyzer and at least some portion of the thermal oxidizer.

4. The device of claim 1, wherein each of the pyrolyzer and thermal oxidizer are at least 5 meters long.

5. The device of claim 1, wherein the thermal oxidizer has a length within 20% of a length of the pyrolyzer.

6. The device of claim 1, wherein the pyrolyzer is distanced from the thermal oxidizer by less than 2 meters.

7. The device of claim 1, wherein the conduit extends from sides of each of the pyrolyzer and the thermal oxidizer.

8. The device of claim 1, further comprising a saddle disposed between the pyrolyzer and the thermal oxidizer.