EXHAUST GAS TRANSFER

This application claims priority to U.S. Application No. 13/081,749 filed April 7, 2011. U.S. Application No. 13/081,749 filed April 7, 2011 is a continuation-in-part of U.S. Application No. 11/862378, filed September 27, 2007, which is a continuation-in-part of U.S. Application No. 11/757189, filed June 1, 2007, which claims the benefit of U.S. Provisional App. No. 60/810382, filed June 1, 2006.

Field of the Invention

[0001] The field of the invention is waste treatment systems. More particularly, the invention concerns waste treatment systems whereby the waste is processed by an apparatus comprising a pyrolyzer and a thermal oxidizer.

Background

[0002] 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.

[0003] 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, No. 10/517023 to Walker, which is a national phase entry of PCT/US02/20362, filed Jun. 26, 2002, and U.S. Pat. No. 6619214 to Walker (Sept. 2003), a typical waste treatment system utilizing pyrolysis includes: (a) an input structure for introducing waste; (b) a pyro lytic 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.

[0004] It is known to dispose the pyrolyzer and thermal oxidizer in end-to-end configurations (see e.g., U.S. Pat. No. 5586855 to Eshleman (Dec. 1996); U.S. Pat. No. 5653183 to Hansen et al. (Aug. 1997); U.S. Pat. No. 6758150 to Ballantine et al. (Jul. 2004)), and in side-by-side configurations (see e.g., U.S. Patent No. 6701855 to Barba (Mar. 2004); U.S. Patent No.

6745707 to Suzuki et al. (Jun 2004)).

[0005] 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.

[0006] 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. 4084521 to Herbold et al. (Apr. 1978), U.S. Pat. No. 5411714 to Wu et al. (May 1995), U.S. Pat. No. 5826520 to Mainord (Oct. 1998)), or without a common housing (see e.g., U.S. Pat. No. 4802424 to McGinnis et al. (Feb. 1989)).

[0007] Interestingly, however, no one seems to have appreciated that it can be advantageous to transfer the hot exhaust gases produced by the thermal oxidizer to the pyrolyzer in a piggyback configuration, such that the pyrolyzer and thermal oxidizer are contained within a common housing or are not contained within a common housing.

[0008] Still further it is known to condition the syngas produced during pyrolysis of municipal waste for use by burners for heating the pyrolyzer. For example, Herbold '521 and Wu '714 teach cooling the syngas and passing it through a condenser, and then using the syngas as a fuel source for a burner that heats the pyrolyzer. But that is much different from burning the syngas in a thermal oxidizer, and then transferring the hot exhaust gas back to the pyrolyzer for sustaining pyrolysis. In a side-by- side configuration within a common housing, such as that disclosed in Barba '855, teaches transferring a portion of the hot exhaust gas from the thermal oxidizer back to the pyrolyzer, but the syngas is not conditioned before use, nor is the hot exhaust gases conditioned before being vented to the atmosphere.

[0009] Walker, Eshleman, Hansen, Ballantine, Barba, Suzuki, Herbold, Wu, Mainford, 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.

[0010] Thus, there is still a need for systems, methods and apparatus that: (1) decrease the space requirements for a waste treatment system having a pyrolyzer and a thermal oxidizer; (2) improve the heat transfer from the thermal oxidizer to the pyrolyzer; and (3) decrease the reliance of the system on external fuels (e.g. natural gas).

Summary of the Invention

[0011] The present invention provides apparatus, systems and methods in which a continuous waste processing device for pyro lyrically treating municipal waste, comprises: (1) a pyrolyzer comprising an inner and outer chamber, wherein the inner chamber further comprises a syngas outlet; (2) a thermal oxidizer comprising an elongated combustion chamber; (3) an exhaust gas transfer duct fluidly coupled to the combustion chamber of the thermal oxidizer and the outer chamber of the pyrolyzer; and (4) a particulate separator for removing particulates from the syngas. In preferred embodiments the pyrolyzer and the thermal oxidizer are aligned in a partially or completely piggybacked fashion, wherein the hot exhaust gases from the thermal oxidizer are shunted back to the outer chamber of the pyrolyzer for sustaining pyrolysis. Such configurations can advantageously decrease the floor space needed in a waste treatment facility, while providing energy efficiency.

[0012] 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. [0013] In an alternative embodiment, a side -by-side configuration is contemplated that has an exhaust gas transfer duct fluidly coupled to top sides of the thermal oxidizer and the pyrolyzer. This configuration is preferred with larger configurations due to the weight of the components.

[0014] 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 an exhaust gas transfer duct 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 reaction chamber of the pyrolyzer to sustain pyrolysis. Such exhaust gas transfer ducts can have any suitable configuration, including for example where the conduit extends from sides and/or the ends of each of the pyrolyzer and the thermal oxidizer. It is also contemplated that the elongated combustion chamber of the thermal oxidizer and the exhaust gas transfer duct are sized and dimensioned to allow at least a one to twenty second residence time, but most preferably a three second residence time to ensure substantially complete combustion of the syngas. In addition, the thermal oxidizer and the exhaust gas transfer duct are sized and dimensioned to operate at an efficiency of at least 10-20 therms (thm) per ton of municipal waste, and more preferably at 15 therms per ton of municipal waste. By optimizing the thermal oxidizer and the exhaust gas transfer duct improves the heat transfer from the thermal oxidizer to the pyrolyzer; and decrease the systems reliance on external fuels.

[0015] It is further contemplated that the syngas entering the thermal oxidizer is mixed with fossil fuel such that the syngas being combusted in the thermal oxidizer comprises less than 25% fossil fuel.

[0016] 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 1 m ² , 5 m ² , and/or 10 m ² . In contemplated embodiments, the thermal oxidizer has a length within 20% of the length of the pyrolyzer and the cross sectional area of the pyrolyzer, thermal oxidizer and the exhaust gas transfer duct are substantially the same.

[0017] 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

[0018] Figure 1 is a perspective view of a pyrolyzer and a thermal oxidizer in a piggyback configuration.

[0019] Figure 2 A comprises an end view of the piggyback configuration of Figure 1.

[0020] Figure 2B comprises a vertical end view of an alternative piggyback configuration of a pyrolyzer and a thermal oxidizer.

[0021] Figure 3 A is a perspective view of a pyrolyzer and a thermal oxidizer in a piggyback configuration having a preferred exhaust gas transfer duct.

[0022] Figure 3B is a top view of the piggyback configuration of Figure 3 having a preferred exhaust gas duct and a particulate separator.

[0023] Figure 4 is an elevational view of a continuous waste processing system having a pyrolyzer and thermal oxidizer.

Detailed Description

[0024] In the following description, reference is made to the accompanying drawings that form a part hereof, and in which is shown, by way of illustration, specific embodiments in which the invention may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention and it is to be understood that other embodiments may be utilized without departing from the scope of the present invention. The following description is, therefore, not to be taken in a limited sense.

[0025] Figures 1 and 2A generally depict a waste treatment system 100 having a pyrolyzer 110 and a thermal oxidizer 140 in a piggyback configuration.

[0026] 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 pyro lysis 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.

[0027] It is also contemplated that the rate of movement of waste material through the inner reaction chamber 114A can be varied. For example, the waste material might move at a slower rate when it first enters the chamber and move at a faster rate after it has been heated and as is moved towards the exit of the inner chamber 114A. It is contemplated that the conveyor mechanism 120 could consist of a screw conveyor section (not shown) and a paddle section (not shown) in which the pitch of the paddles or the screw threads could vary to change the rate of movement through the inner reaction chamber.

[0028] 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.

[0029] Processing of the waste also produces syn gases (pyrolysis waste gases) such that the syngas exits the inner reaction chamber 114A via syngas outlet 127. The syngas outlet is fluidly coupled to syngas conduit 126 (arrow 128 shows the flow of the syngas) which feeds the syngas to the thermal oxidizer 140.

[0030] Thermal oxidizer 140 generally includes an input of syngas from syngas conduit 126, a burner 142, an exhaust gas transfer duct 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 that are shunted to the outer chamber 112A of the pyrolyzer 110. It is contemplated that a portion of the hot exhaust gases are transferred to a waste-heat boiler or other components of the system via exhaust gas outlet 148. It is further contemplated that thermal oxidizer 140 can comprise a first and second subchamber that is divided by a baffle means for controlling the flow of gases between the chambers. [0031] 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, 7, 8, 9, 10, 12, 14, 16 ...20 meters long, and have a cross sectional area of at least 6, 8, 9, 10, 12, 14, and 16 m ² . In most preferred embodiments, the thermal oxidizer has a length within 20%, 15%, or more preferably 10% of the length of the pyrolyzer. As shown in Figure 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. It is

contemplated that the pyrolyzer, thermal oxidizer, and exhaust gas transfer duct are constructed from a castable refractory material capable of withstanding temperatures in excess of 3200 degrees Fahrenheit.

[0032] As shown in Figures 1 and 2 A, pyrolyzer 110 and thermal oxidizer 140 have a piggyback configuration. It is contemplated that the piggyback configuration includes all situations where a 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. Figure 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. It is also contemplated that the thermal oxidizer can be positioned above and/or below the pyrolyzer in such a manner that a vertical line does not pass through portions of the thermal oxidizer and the pyrolyzer. It is further contemplated that the thermal oxidizer and the pyrolyzer can be in a side- by-side or end-to-end configuration. A side-by-side configuration is contemplated that has an exhaust gas transfer duct fluidly coupled to top sides of the thermal oxidizer and the pyrolyzer. The side-by-side configuration is preferred with larger configurations due to the weight of the individual components.

[0033] Figures 3A, 3B and 4 depict an alternative continuous waste processing system 300 having, among other things, pyrolyzer 310 and thermal oxidizer 340 in a piggyback

configuration, syngas conduit 326, exhaust gas transfer duct 344, and a particulate separator 350. Processing of the waste produces syngases that exit the inner reaction chamber (not shown) of pyrolyzer 310 via a syngas outlet (not shown), which feeds into the syngas conduit 326. The syngas conduit 326 is fluidly coupled to particulate separator 350. The particulate separator 350 is also fluidly coupled to thermal oxidizer 340.

[0034] Preferred particulate separator 350 is a multiclone separator that utilizes cyclonic separation to remove particulates from the syngas without the need to cool the syngas before being combusted in the thermal oxidizer. It is contemplated that the multiclone separator consists of 2, 3 , 4, 5 , 6, 7, 8...15...40...N cyclone separators arranged into one unit. The syngas enters the particulate separator 350 and is spun inside the separator before exiting. This spinning action forces any solid particles in the syngas to the wall of the separator and gravity allows the particulates to settle to the bottom where they can be collected. It is also contemplated that other suitable particulate separators can be utilized, such as an electrostatic precipitator and other particle separators known in the art. Once the syngas leaves the particulate separator 350 it enters the thermal oxidizer 340 and a burner (not shown) is preferably used to initiate

combustion of the syngases thereby producing hot exhaust gases. It is contemplated that the syngas entering the thermal oxidizer is mixed with fossil fuel such that the syngas being combusted in the thermal oxidizer comprises less 50%, 40%, 30%>, 20%>, 10%> fossil fuel. By optimizing the thermal oxidizer and the exhaust gas transfer duct improves the heat transfer from the thermal oxidizer to the pyrolyzer; and thereby decreases the percentage of external fuel needed by the system. In preferred embodiment the percentage of fossil fuel is less then 25%.

[0035] Preferred thermal oxidizer 340 is sized and dimensioned such that it comprises an elongated combustion chamber 343 having an exhaust gas transfer 344 duct extending therefrom, which is fluidly coupled to the outer chamber of the pyrolyzer 310. Exhaust gas transfer duct 344 diverts the hot exhaust gases produced in the thermal oxidizer back to outer chamber of pyrolyzer 310 to sustain pyrolysis. Preferred exhaust gas transfer duct 344 extends from a side of the elongated combustion chamber 343 of the thermal oxidizer and the outer chamber of the pyrolyzer 310, but it is contemplated that the exhaust gas transfer duct 344 can extend from the ends of the thermal oxidizer 340 and the pyrolyzer 310. Still further, the hot exhaust gas being shunted to the outer chamber of the pyrolyzer can then be diverted from the outer chamber of the pyrolyzer to other downstream devices, such as a boiler. [0036] Pyrolyzer 310, thermal oxidizer 340 and the exhaust gas transfer duct 344 are sized and dimensioned to have a cross sectional area of at least lm ² , 2m ² , 3m ² , 4m ² , 5m ² , 6m ² , 7m ² , 8m ² , 40m2, but any suitable cross sectional area is contemplated for the desired performance of the system. In most preferred embodiments, pyrolyzer 310, thermal oxidizer 340 and the exhaust gas transfer duct 344 are sized and dimensioned to have cross sectional areas that are substantially the same. As such, it is contemplated that the elongated combustion chamber 343 of the thermal oxidizer and the exhaust gas transfer duct 344 are an extension of the outer housing 312 of the pyrolyzer 310. Still further, it is contemplated that the elongated combustion chamber 343 of the thermal oxidizer and the exhaust gas transfer duct 344 are sized and dimensioned to allow at least a 1-20 second residence time, but most preferably a 3 second residence time to ensure substantially complete combustion of the syngas. By optimizing the dimensions of the thermal oxidizer and the exhaust gas transfer duct the energy efficiency of the system is greatly increased. In most preferred embodiments the thermal oxidizer 340 and the exhaust gas transfer duct 344 are sized and dimensioned to operate at an efficiency of at least 10-20 therms (thm) per ton of municipal waste, and more preferably at 15 therms per ton of municipal waste.

[0037] Figures 1, 2A, 3A, 3B and 4 depict saddles (130A and 330A, respectively) that support pyrolyzer (110 and 310 respectively) and saddles (130B and 330, respectively) disposed between pyrolyzer (110 and 310, respectively) and thermal oxidizer (140 and 340 respectively). It is contemplated that the saddles allow expansion and contraction of the thermal oxidizer and pyrolyzer 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 because they have a relatively low coefficient of thermal conductivity, and would tend to inhibit the flow of heat out of thermal oxidizer and pyrolyzer.

[0038] 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.