Abstract:
A pyrolyzer has a heated inner housing that includes first and second conveyors. Preferred conveyors have independent or at least potentially independent flows of material to be pyrolyzed. All suitable conveyors are contemplated, including especially screw conveyors, or combination of screw and paddle conveyors. Both first and second conveyors can be disposed within a common lumen, with a partial divider between them. An alternative divider is also contemplated that more or less divides the inner housing into two lumens. Thus, the lumens can be entirely distinct, or can have cross-flow of gases and/or material being pyrolyzed. Heat transfer fins can be advantageously attached, extend from, or be otherwise coupled to the inner housing to assist in transfer of heat into the lumen(s) of the inner housing.

Description:
[0001]     This application is a continuation-in-part of U.S. Ser. No. 10/517,023 filed Oct. 24, 2005, which is a national phase filing of PCT/US02/20362 filed Jun. 26, 2002. 
     
    
     FIELD OF THE INVENTION  
       [0002]     The field of the invention is pyrolysis (US 110/229, Int Cl. F23G 5/12).  
       BACKGROUND  
       [0003]     Pyrolysis employs high temperatures in a relatively oxygen free environment to remove volatiles, 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.  
         [0004]     It is known to pyrolyze trash, old tires, and other municipal wastes. A typical waste treatment system utilizing pyrolysis includes an input structure for introducing the waste; a chamber or retort from which air can be restricted, and some sort of conveyor mechanism for moving the waste through the system. A dual housing is commonly used, in which the conveyor mechanism conveys the waste through the inner housing, heated gas (exhaust) is introduced into the space between the housings, and heat is conducted to the waste through the walls of the inner housing.  
         [0005]     U.S. Pat. No. 5,178,077 to Norris et al. (January 1993) teaches use of dual parallel screws for removing volatiles from soil. Norris, however, contemplates temperatures of only 800° C., and therefore fails to teach the use of dual conveyors in the context of pyrolysis. Indeed, the temperatures of Norris are sufficiently low that there is no need for inner and outer housings, and apparatus or methods for efficiently transferring heat into an inner housing.  
         [0006]     U.S. Pat. No. 6,758,150 to Ballantine et al. (July 2004) teaches use of dual screws to transport waste in a pyrolyzer operation, but the screws are not operated in parallel. One of the screws is outside the pyrolyzer. U.S. Pat. No. 4,759,300 to Hansen et al. (July 1988) teaches a dual screw for conveying waste. In that case, both screw conveyors are disposed within the pyrolyzer, but the screws are still not operated in parallel. The output of one screw conveyor provides partially pyrolyzed material input to the other screw. U.S. Pat. No. 7,182,028 to White (February 2007) also teaches dual conveyers (although not a screw conveyor) disposed within a pyrolyzer, but there again the output of one conveyor provides partially pyrolyzed material input to the other conveyor.  
         [0007]     Norris, Ballantine, Hansen, White, 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  
         [0008]     Thus, there is still a need for a pyrolyzer with dual processing shafts, and for more efficient transfer of heat through the wall of the inner housing.  
       SUMMARY OF THE INVENTION  
       [0009]     The present invention provides apparatus, systems and methods in a pyrolyzer has a heated inner housing that includes first and second conveyors.  
         [0010]     Preferred conveyors have independent or at least potentially independent flows of material to be pyrolyzed. All suitable conveyors are contemplated, including especially screw conveyors, or combination of screw and paddle conveyors.  
         [0011]     Both first and second conveyors can be disposed within a common lumen, with a partial divider between them. Such a divider can be continuous with the inner housing such that the inner housing and divider comprise a generally inverted heart shape. A particular advantage of that design is that the divider can be sufficiently large to provide substantial structural support to the pyrolyzer.  
         [0012]     An alternative divider is also contemplated that more or less divides the inner housing into two lumens. Thus, the lumens can be entirely distinct, or can have cross-flow of gases and/or material being pyrolyzed.  
         [0013]     Heat transfer fins can be advantageously attached, extend from, or be otherwise coupled to the inner housing to assist in transfer of heat into the lumen(s) of the inner housing. Both internally and externally projecting fins are contemplated. Fins  222 ,  224  can have any suitable number, dimensions, and orientations, including especially a number of six to ten, a thickness of 2 to 4 cm, a height of 5 to 10 cm, and a length of 10 cm to several meters. Fins are preferably parallel to one another, and parallel to the long axis of the inner housing  220 , but alternative fins  222 ,  224  could have any other suitable orientation, and for example could be co-linear or non-linear. Fins  222 ,  224  can be separated by any suitable distance, which would typically be between 20 cm and 1 meter. Unless a contrary meaning is apparent from the context, all ranges described here are inclusive of their endpoints.  
         [0014]     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  
       [0015]      FIGS. 1A and 1B , when considered together, comprise a side-elevational view of one form of the apparatus of the invention.  
         [0016]      FIG. 1C  is an enlarged, side-elevational view of the feed means of the invention.  
         [0017]      FIGS. 2A and 2B , when considered together, comprise an enlarged, side elevational view of the thermo converter and thermo oxidizer components of the apparatus partly broken away to show internal construction.  
         [0018]      FIG. 3  is an enlarged, cross-sectional view taken along the lines  3 - 3  of  FIG. 2A .  
         [0019]      FIG. 4  is an enlarged, cross-sectional view taken along lines  4 - 4  of  FIG. 2A .  
         [0020]      FIG. 5  is a greatly enlarged, cross-sectional view taken along lines  5 - 5  of  FIG. 2A .  
         [0021]      FIG. 5A  is a greatly enlarged, cross-sectional view taken along lines  5   5 A of  FIG. 2A   
         [0022]      FIG. 6  is a cross-sectional view taken along lines  6 - 6  of  FIG. 2A .  
         [0023]      FIG. 7  is a cross-sectional view taken along lines  7 - 7  of  FIG. 2B .  
         [0024]      FIG. 8  is a cross-sectional view taken along lines  8 - 8  of  FIG. 2B .  
         [0025]      FIG. 9  is a cross-sectional view taken along lines  9 - 9  of  FIG. 2B .  
         [0026]      FIG. 10  is an enlarged, cross-sectional view taken along lines  10 - 10  of  FIG. 2B .  
         [0027]      FIG. 11  is a cross-sectional view taken along lines  11 - 11  of  FIG. 10 .  
         [0028]      FIG. 12  is a generally perspective, exploded view of one form of barrier ring assembly of the thermo oxidizer.  
         [0029]      FIGS. 13A and 13B , when considered together, comprise a top plan view of components shown in  FIGS. 2A and 2B .  
         [0030]      FIG. 14  is an enlarged, fragmentary view of a portion of the thermo oxidizer component showing the barrier ring in a closed position.  
         [0031]      FIG. 15  is a fragmentary view similar to  FIG. 14  but showing the barrier ring in an open position.  FIG. 16  is a block diagram illustrating the operation of the apparatus of the invention.  
         [0032]      FIG. 16  is a block diagram illustrating the operation of the apparatus of the invention.  
         [0033]      FIG. 17  is a vertical cross-section of a pyrolyzer that includes first and second conveyors, and heat transfer fins.  
         [0034]      FIG. 18  is a vertical cross-section of an alternative pyrolyzer that includes first and second conveyors, heat transfer fins, and dual lumens. 
     
    
     DETAILED DESCRIPTION  
       [0035]     Referring to the drawings and particularly to  FIGS. 1A and 1B , one form of the apparatus of the invention is there shown. The apparatus here comprises seven major cooperating subsystems, namely a dryer  20 , a feed means  22 , a thermal chemical reactor or pyrolytic converter  24 , a two-stage, thermal oxidizer  26 , a steam generator  28 , and a steam turbine  30  that is driven by the steam converted by the steam generator.  
         [0036]     In the operation of the apparatus of the invention, the waste material to be treated is first introduced into the dryer subsystem  20  via an inlet  32 . After drying in a manner presently to be described, the dried waste material is controllably fed into the thermal reactor  24  by the novel feed means  22  which uniquely includes both a solid feed means and a liquid feed means. The solid feed means for feeding solid waste material to the converter comprises a gravity fed, bottom surge feed hopper  33  of the, general construction shown in  FIG. 1C . As will be described more fully hereinafter, the liquid waste materials can be introduced into the pyrolytic converter simultaneously with the introduction of solid materials via the liquid feed means that is generally designated in  FIG. 1C  by the numeral  35 . This novel liquid feed means includes an atomizer means for at least partially atomizing the liquid waste.  
         [0037]     As illustrated in  FIGS. 2A , and  5 , the novel thermal reactor or pyrolytic converter subsystem  24  of the present form of the invention is of a unique configuration that comprises a hollow housing  34  having first and second ends  34   a  and  34   b.  Disposed within housing  34  is a reaction chamber  36  that is defined by an elongated hollow structure  38  that in cross section has a novel three dome, generally triangular configuration ( FIG. 5 ). Structure  38  is preferably constructed from a castable refractory material capable of withstanding temperatures in excess of 3200 degrees Fahrenheit. As shown in  FIG. 5 , chamber  36  includes first and second longitudinally extending, semicircular shaped, subchambers  36   a  and  36   b.  Extending longitudinally of chamber  36   a  is a first conveyor means, or conveyor mechanism  40 . Extending longitudinally of chamber  36   b  is a similarly configured second conveyor means or conveyor mechanism  42 . These conveyor mechanisms  40  and  42  are of a novel construction with each comprising a first helical screw section  43  for conveying less pyrolyzed and, therefore, more dense waste and a second paddle like section  45  for conveying the more pyrolyzed, less dense waste (see  FIGS. 5 and 5 A). The twin conveyor mechanisms are mounted within the reactor using conventional bearings  41  and are controllably rotated by conventional drive means  41  a of the chamber shown in  FIG. 6 .  
         [0038]     The upper portion  36   c  of reaction chamber  36  functions to permit generated gases within the chamber to expand and, in a manner presently to be described, to be transported from the reaction chamber via a chamber outlet  44  ( FIG. 2A ). As illustrated in  FIGS. 2A and 5 , the inner surfaces  34   c  of the hollow housing  34  within which the reactor chamber is mounted, are covered by a ceramic fiber insulation  46  that is connected to the inner walls of the housing by suitable fasteners. As will presently to be described, the area between the inner surfaces  34   c  of the housing and the ceramic reaction chamber  38 , is initially controllably heated by the first stage of the thermal oxidizer  26 .  
         [0039]     Turning particularly to  FIGS. 2B , and  13 B the thermal oxidizer  26 , of the present form of the invention, includes a hollow housing  47  having an inner wall  47   a.  Disposed between the inner and outer wall is a ceramic fiber insulation  49 . Within housing  47  is a first stage defined by a first subchamber  50  and a second stage defined by a second subchamber  52 . Dividing subchambers  50  and  52  is a novel baffle means for controlling the flow of gases between the chambers. This baffle means here comprises a novel barrier ring assembly  56  that comprises a pair of fixedly mounted semicircular segments  57  ( FIGS. 10, 12 ,  13 B, and  15 ) and a pivotally mounted assembly  58 . Assembly  58  is made up of a pair of semicircular segments  59  that are affixed to a ceramic baffle plate  60  (see  FIGS. 10, 12 ,  13 B, and  15 ). As illustrated in  FIGS. 12, 13B  and  15 , the baffle ring assembly  56  is movable between the first and second positions illustrated by the solid and phantom lines in  FIG. 13B . Thermal oxidizer  26  is also is also capable of withstanding temperatures in excess of 3000 degrees Fahrenheit.  
         [0040]     Thermal oxidizer  26  further includes a first stage heater means for controllably heating subchamber  50  and second stage heater means for controllably heating subchamber  52 . In the present form of the invention, the first stage heater means comprises a first burner assembly  62  that includes a generally cylindrically shaped housing  64  ( FIG. 7 ) that is connected to the first end  26   a  of thermal oxidizer  26  in the manner best seen in  FIG. 2B . Housing  64  carries four circumferentially spaced gas burners  66  that are of conventional construction and function to initially heat subchamber  50  at time of startup. Similarly, the second stage heater means here comprises a second burner assembly  70  that is mounted in housing  47  intermediate subchambers  50  and  52  in the manner shown in  FIG. 2B . As best seen in  FIG. 9 , second burner assembly  70  comprises four circumferentially spaced gas burners  72  that are also of conventional construction and function to initially heat second subchamber  52  at the time of startup. Burners  66  and  72  are of a conventional construction and are commercially available from sources such as Eclipse Combustion, Inc. of Rockford, Ill., U.S.A.  
         [0041]     First subchamber  50  has an outlet port  74  that is in communication with a port  76  formed in reactor  24  via a conduit  78  ( FIGS. 1A and 1B ). In a manner presently to be described, reaction chamber  36 , which preferably operates at less than five percent (5%) oxygen is initially heated in a flame-free manner by heated gases transferred from subchambers  50  and  52  of the thermal oxidizer to the area between the inner surfaces  34   c  of the housing  34  and the ceramic reaction chamber  38 .  
         [0042]     Second subchamber  52  of the thermal oxidizer has an outlet port  82  that communicates with an inlet port  84  of the steam generator subsystem  28  via a conduit  86 . Steam generator subsystem  28 , which includes a high pressure steam tank  28   a  and a lower mud drum  28   b,  is of a conventional design and is readily commercially available from various sources as, for example, Babcock Wilcox of Mississippi. Drum  28   b  is provided with a plurality of cleanout assemblies  85  for periodically removing sludge and the like from the drum. As shown in  FIG. 1B , drum  28   b  is interconnected with tank  28   a  by a plurality of spaced-apart, connector tubes  89  and is also connected with a water supply here provided in the form of make-up water tank  88 . The water contained within tank  88  is pumped to drum  28   b  via conduit  87  by a conventional pumping system  90  ( FIG. 1B ) and is converted to high-pressure steam within the connector tubes  89  which are impinged upon by the heated gases transferred from the thermal oxidizer  26  to the steam generator via conduit  86 .  
         [0043]     In system operation, the high pressure steam contained within tank  28   a  is transferred to steam turbine  30  via a conduit  94 . Steam turbine  30 , which is of conventional construction and is also readily commercially available from sources such as De Mag La-Vale, generates electricity that may be used to power the various electrically driven components of the apparatus, such as the pumping system  90 . The steam exhausted from steam turbine  30  is carried to a conventional condenser  96  via a conduit  98 . The water formed in condenser  96  is then transferred to a cooling tower  100 , which is also of conventional construction, via a conduit  102 . The water that has been cooled within the cooling tower  100  is returned to condenser  96  via a conduit  104  and is then transferred to tank  88  via a conduit  106  ( FIG. 1B ).  
         [0044]     As shown in  FIGS. 1A and 1B , a portion of the waste gases flowing through steam generator  28  is first cooled with dilution air and is then transferred to the dryer subsystem  20  via a diverter valve  110  and a conduit  112 . These hot waste gases at a temperature of about 550 degrees Fahrenheit are used to efficiently dry the waste contained within the dryer  20 . From dryer  20  the gases are returned to the thermal oxidizer via an overhead conduit  114  ( FIG. 1B ). The portion of the gases from the steam generator that are not diverted to the dryer are transferred to a condensed scrubber apparatus  118  which effectively removes harmful contaminants from the exhaust gases so that the gases can be safely discharged to atmosphere via a conventional blower unit  119 . Scrubber apparatus  118  is commercially available from various sources such as C. W. Cole Fabricators, Inc. of Long Beach, Calif. Similarly, blower unit  119  is readily available from sources such as New York Blowers Co. of Willow Brook, Ill.  
         [0045]     In operating the apparatus of the invention, the baffle assembly  56  of the thermo oxidizer  26  is moved into a closed position wherein chamber  50  is substantially sealed relative to chamber  52 . This done, burners  72  of burner assembly  70  are ignited to controllably heat chamber  52  to a temperature sufficient to cause the water contained within tubes  89  of the steam generator apparatus  28  to be converted into high-pressure steam. When tank  28  of the steam generating system is filled with pressurized steam, the steam can be conveyed to the turbine generator  30  via conduit  94 . With the generator  30  in operation, sufficient electricity can be generated to operate the various electrical components of the apparatus including the pumping system  90  which is used to pump water to the make-up tank  88 .  
         [0046]     Once sufficient power is being generated by generator  30  to operate the electrical system, burners  66  of burner assembly  62  can be ignited in order to controllably heat chamber  50 . When the gases within chamber  50  reach a temperature sufficient to pyrolyze the waste material that is contained within dryer  20 , the material can be transferred to the feed means by transfer means shown here as a conventional waste conveyor  120 . As previously mentioned, the material within dryer  20  is dried by the excess gases flowing from the thermal oxidizer through the steam generator and into conduit  112  via diverter valve  110 . Once the gases within chamber  50  have reached the pyrolyzing temperature, they are transferred to the reactor chamber via conduit  78 , to heat the reactor chamber to a pyrolyzing temperature. When this has been achieved, baffle assembly  56  can be moved into the open position shown in  FIG. 2B  and the feeding of the dried waste can begin.  
         [0047]     As the waste material, being transferred to the hopper by waste conveyor  120 , starts to flow into the hopper  33 , the upper butterfly valve  122  of the hopper system is moved into the open position shown in  FIG. 1C  of the drawings and the lower butterfly valve  124  is moved into a closed position blocking any transfer of waste material from the hopper into the auger portion  126  of the feed assembly. Once intermediate chamber  128  of the feed assembly is filled with the waste to be pyrolyzed, a vacuum is drawn within chamber  128  by a vacuum pump “V” that is interconnected with chamber  128  by a conduit  123  ( FIG. 1C ). After chamber  128  has been suitably evacuated, butterfly  124  is moved into an open position permitting the waste contained within chamber  128  to flow into the auger conveyor means of the feed assembly without jeopardizing the integrity of the vacuum within the reactor chamber. As is indicated by the arrow  129  in  FIG. 1C , the dried waste material entering the chamber  130  that contains the conveyor screw  133  is controllably fed into the reactor chamber via hollow shaft  132  and inlet  134  of the reactor chamber ( FIG. 2A ).  
         [0048]     The waste material entering the, reactor chamber will fall downwardly in the direction of the arrow  135  of  FIG. 2A  in a direction toward the screw conveyors  43 . As illustrated in  FIG. 5 , the waste material flowing into chamber  36  will impinge upon the elongated, angular shaped distribution member  136  that is disposed within chamber  36  (see also  FIG. 2A ). As the waste being introduced into the reactor impinges on diverter member  136 , the waste will be directed toward the two twin conveyors  40  and  42  in the direction of the arrows of  FIG. 5 . It is to be understood that with the construction just described, waste materials can be controllably metered into the reactor chamber  36  and evenly distributed between the two screw conveyors  40  and  42 .  
         [0049]     The waste material introduced into chamber  36  in the manner just described will be carried forwardly of the reactor by the conveyor mechanisms  40  and  42  and, as it travels forwardly of the reactor will be undergo pyrolyziation due to the elevated temperature of the reactor chamber. By the time the waste material reaches the end of the screw conveyor, sections  43 , it will have been substantially reduced to carbon form which is of a lesser density that will permit it to be transferred through the remaining length of the reactor chamber by the novel paddle conveyors  45  that are of a construction best seen in  FIG. 5A .  
         [0050]     Turning once again to  FIG. 1C , it is to be noted that the apparatus of the invention further includes a fluid waste tank  140  that is adapted to store fluid waste as, for example, waste oil. Because of the novel construction of the feed means of the invention, the waste fluid can be disposed of simultaneously with the disposal of the solid waste. When it is desired to dispose of the fluid waste contained within tank  140 , a conventional pumping means  142 , which is shown here as a conventional, progressive, cavity, positive displacement pump  142 , is used to transfer the fluid from vessel  140  to the atomizing means of the apparatus. This novel atomizing means here comprises the assembly generally designated in  FIG. 1C  by the numeral  144 . In the present form of the invention, the atomizing means comprises a chicksan rotating joint  145  that permits the introduction of various carrier gases such as steam into the hollow shaft  146  of the feed means. The atomizing means further includes a steam inlet  148  through which steam at least 400 degrees Fahrenheit from steam generator  28  can be controllably introduced in the direction shown by the arrow  149  of  FIG. 1C . Steam entering steam inlet  148  will create a venturi effect within a Y-fitting  150  that defines a venturi mixing chamber that is interconnected within a conduit  146  via the chicksan joint  145 . The venturi effect created within fitting  150  will draw the fluid into the venturi chamber where it will be atomized in a manner well understood by those skilled in the art. The atomized fluid will then flow into the previously identified chamber  130  via hollow shaft  146 . As the atomized fluid enters chamber  130 , it will intermix with the waste material contained therein and will travel with the waste material into the reactor in the manner earlier described. It is, of course, apparent that the intermixture of the dried waste material and the atomized fluid will be readily pyrolyzed within the reactor as the material is carried forwardly of the reactor by the conveyor means of the invention.  
         [0051]     It is to be understood that the novel conveyor means of the invention that is mounted within the reactor chamber in the manner best seen in  FIG. 6  is relatively light weight. In the prior art wherein the conveyor systems were made up of elongated, helically shaped, screw-type conveyors, the conveyor was of a substantial weight and, when only supported at each end experienced undesirable sagging proximate its center. With the novel construction of the present invention, wherein a large part of each of the screw conveyors comprise the much lighter weight paddle wheel-type construction, the overall weight of the conveyors is substantially reduced when compared to the prior art, single-piece helical screwtype conveyors. Additionally, since conveyors of the present invention are disposed in a side-by-side relationship, the overall length of the reactor can be substantially reduced from that which would be required if only a single helical type screw conveyor were to be used. In summary, because of the novel design of the conveyor systems of the present invention, undesirable sagging of the conveyors is prevented and, as a result of the twin conveyor design, the length of the reactor can be significantly reduced.  
         [0052]     When the waste material reaches the second end  34   b  of the reactor, the pyrolyzed waste will be introduced via extensions  156   a  into a pair of side-by-side outlet conduits generally designated in  FIG. 4  by the numeral  156  where the pyrolyzed waste products can be recovered. Extensions  156   a  are in communication with the chambers that house the conveyor means so that the waste carried by the conveyor means will be introduced into outlet conduits  156  in the manner indicated by the arrow  160  of  FIG. 2A .  
         [0053]     As previously mentioned, the heated gases produced by the pyrolytic reactor will be transferred to the thermal oxidizer  26  via outlet  44  and conduit  44   a.  A portion of the heated gases produced by the pyrolysis of the waste material will be returned from the thermal oxidizer to the reactor to sustain the pyrolysis and a portion will be transferred via conduit  86  to the steam generator subsystem  28  via conduit  86 . These later heated gases will function to heat the water contained within tubes  89  to convert it to high pressure steam which, in turn, will be used to drive turbine  30 . It is important to note that to maintain the desired transfer of the heated gases, the baffle assembly  56  is strategically operated so as to continuously create a slight positive pressure within first stage  50 . This positive pressure will urge a portion of the heated gases to be return to the reactor via conduit  78  to sustain the pyrolysis of the waste. To accomplish this strategic balance, the pressure differential between chambers  50  and  52  is continuously monitored by a differential pressure gauge and the position of the baffle assembly is precisely regulated by a baffle operating means shown in the drawings as comprising a control mechanism  163 .  
         [0054]     As best seen in  FIGS. 10, 11 , and  12 , the unique baffle assembly of the present invention comprises a generally circular-shaped ceramic plate  60  to which a pair of semicircular barrier rings  59  are affixed in the manner illustrated in  FIG. 12 . The baffle assembly, which comprises plate  60  and the semicircular rings affixed to either side of the plate is mounted for pivotal movement within the thermal oxidizer about an axis  159  that is defined by a pair of spaced-apart pivot pins  161 . Pivot pins  161  are mounted within the wall of the thermal oxidizer housing in the manner shown in  FIG. 12  so that the baffle assembly can be pivoted about axis  159  by the control mechanism  163  from a first closed position to a second open position. As best seen in  FIG. 10 , the control mechanism here comprises a drive motor  165  having a drive shaft  165   a  that drives a toothed gear  167  that is drivably connected to upper pivot pin  161 . As is schematically shown in  FIG. 14 , the differential pressure gauge  169  is in communication with both of the chambers  50  and  52  so that the pressure within the chambers can be continuously monitored. The differential pressure gauge is readily commercially available from several sources. However a gauge sold under the name and style MAGNEHELIC by Dwyer Instruments, Inc. of Anaheim, Calif. has proven satisfactory for the present purpose. In a manner well understood by those skilled in the art, gauge  169  is operably associated with drive motor  165  to appropriately operate the motor to open and close the baffle assembly in a manner to continuously maintain the desired pressure differential between chambers  50  and  52 . As previously mentioned, when the pressure differential is properly controlled, the heated gases within chamber  50  will controllably flow into the thermal converter  24  to maintain the pyrolysis of the waste. Accordingly, during normal operation, no heat need be added to the system by the gas fired burners  66  and only a pilot flame need be maintained.  
         [0055]     By way of summary, during the operational cycle, as illustrated in  FIG. 16 , the municipal waste to be treated is deposited in an incoming pit  170 . From there the waste is transferred by means of a feed system  172  to a conventional shredder  174  which shreds the waste prior to its introduction into the previously identified dryer  20 . From the dryer, the dried waste is introduced into the thermal converter  24  via the previously discussed feed means  22 . Heated gases generated in the thermal converter are transferred to the thermal oxidizer  26  in the manner previously discussed. As shown in  FIG. 16 , a portion of the heated gases contained within the thermal oxidizer is returned to the thermal converter via conduit  78 . Another portion of the heated gases within the thermal oxidizer is transferred to the waste-heat boiler which forms a part of the previously identified steam generator  28 . As depicted in  FIG. 16 , the heat from the waste-heat boiler is transferred to the blender-dryer by conduit  112  to accelerate the drying process. In turn, the excess gases from the blender-dryer are returned to the thermal oxidizer via conduit  114 . A portion of the excess heated gases within the waste-heat boiler  176  are transferred to the wet scrubber and, in the manner previously described, fluids from the wet scrubber are transferred to the water treatment system  178  via a conduit  180 . Similarly, gaseous emissions from the wet scrubber are transferred to an admissions monitoring system  182  to ensure that harmful emissions are not emitted into the atmosphere. As indicated by the arrow  184 , solid recyclable byproducts are recovered from the thermal converter  24  for appropriate recycling.  
         [0056]      FIG. 17  generally depicts a pyrolyzer  200  having an outer housing  210 , an inner housing  220 , a heated space  230  between the inner and outer housings, first and second conveyor mechanisms  240 ,  242 , which preferably carry waste streams independently of one another, and a chamber outlet  250  for transporting pyrolysis exhaust gases out of the inner housing.  
         [0057]     The inner housing  220  has both inner and outer heat conduction fins  222 ,  224 , respectively. The fins  222 ,  224  can be mounted on the inner housing  220  in any suitable manner, including for example, casting or welding. Fins  222 ,  224  can have any suitable number, dimensions, and orientations, including especially a number of six to ten, a thickness of 2 to 4 cm, a height of 5 to 10 cm, and a length of 10 cm to several meters. Fins are preferably parallel to one another, and parallel to the long axis of the inner housing  220 , but alternative fins  222 ,  224  could have any other suitable orientation, and for example could be co-linear or non-linear. Fins  222 ,  224  can be separated by any suitable distance, which would typically be between 20 cm and 1 m.  
         [0058]     The pyrolyzer  300  of  FIG. 18  is similar to that of  FIG. 17  except that there is divider  310  that more or less completely separates the first and second conveyor mechanisms conveyor mechanisms  240 ,  242 . The divider  310  thus cooperates with the inner wall of inner housing  220  to define first and second lumens  312 ,  314 . The divider  310  can be of any suitable material and dimensions, but typically would be of the same material and thickness as the wall of inner housing  220 .  
         [0059]     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 may 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.