Abstract:
A pyrolysis chamber for the extraction of combustible gasses from biomass waste such as wood chips has a gravity fed chamber, where fuel passes, in succession, through a pre-heating zone, an oxidation and reduction zone, a gas outlet zone and a solids offloading zone. The pre-heating zone has plasma torches which direct an air plasma into the chamber, thereby pre-heating the fuel to a temperature of 1200-1500° C., after which the fuel enters the oxidation and reduction zone, where it is exposed to a steam plasma of 1500° C. which travels through plasma torches to an annular ring distributor surrounding the chamber and having apertures directing the steam plasma into the chamber, thereby providing enhanced generation of combustible gasses of CO and H 2 . The combustible gasses are removed in the gas outlet zone, which has a half annular ring collector removing combustible gasses out of the chamber and half annular ring distributor injecting an air plasma into the chamber for gasification of the ash residual carbon. A solids offloading part has a rotating grate for the removal of ash and slag for delivery to a water trough.

Description:
FIELD OF THE INVENTION 
       [0001]    The current invention is drawn to the field of Pyrolysis chambers and processes. More specifically, the invention relates to a top-loading Pyrolysis chamber for organic fuel such as wood chips, the chamber having a plurality of air plasma torches for pre-heating, steam plasma torches coupled to an enclosed annular ring distributor for uniform steam plasma application during oxidation and reduction, air plasma torches coupled to an enclosed half annular ring distributor for introduction of air plasma into outlet zone for removing ash and slag and a half annular ring collector for collection and offloading of combustible gasses. 
       BACKGROUND OF THE INVENTION 
       [0002]    Pyrolysis is commonly defined as the thermal decomposition of an organic fuel in an environment of less-than-stoichiometric oxygen, and devices utilizing this process are known as partial oxidation reactors. Devices utilizing organic combustion include coal-based gasification projects, which use direct and incomplete combustion of feed material to generate the necessary reaction heat. One class of prior art device heats the organic feed material only to the point of leaving a carbon-ash composite solid (known as char) as a reactor product/waste. Another class of prior art device utilizes this residual char material as an external combustion fuel to generate the required process reaction heat. In one such device, the char is burned outside the pyrolysis reactor to generate the required heat, and the resulting hot char recycled to heat the incoming feed fuel. Another prior art device uses pure oxygen or oxygen-enriched air to increase the temperature in the reactor, since standard air combustion will provide a maximum reactor temperature of only 1000-1100° C. Oxygen-enrichment can also be used to reduce the formation of undesired NOx gasses from atmospheric N 2  (nitrogen) present in the chamber. 
         [0003]    The combustion of organic material such as wood chips generates ash as a waste product. As the reaction temperature increases to 1100-1500° C., for certain compositions, the ash will melt into a viscous material known as slag. Additionally, metals which may be present in the ash will also melt into the slag when the respective metal melting point temperature is reached, which starts for many metals at temperatures above 1500° C. 
         [0004]    In the Pyrolysis process, the ratio by volume of waste (ash and slag) to incoming fuel is 2-4% (representing a 25× to 50× reduction in fuel volume), depending upon the amount of noncombustible materials in the mixed wastes. By contrast, an efficiently-operated conventional incinerator produces a solid residue of 10% or more of the volume of refuse burned. 
         [0005]    Prior art low temperature wood waste gasification operates in the range of 800-900° C. and yields 70-140 m 3  per ton, recovering no more than 8-12% of potential heat contained in the fuel. The pryrolysis apparatus and method operates at maximum efficiency for fuel generation and waste volume reduction at increased temperatures, and as described above, these elevated temperatures may be reached using oxygen enhanced combustion air, but the use of oxygen represents an additional operational expense. It is therefore desired to provide an improved pyrolysis chamber with increased internal operating temperature and resultant efficiency without the use of oxygen enriched air. 
       OBJECTS OF THE INVENTION 
       [0006]    A first object of the invention is a Pyrolysis chamber having a top-loading hopper where fuel is introduced and gravity fed into to a pre-heating zone which includes a plurality of air plasma torches directly coupling an air plasma into the chamber thereby pre-heating the fuel, after which the pre-heated fuel is gravity fed into an oxidation and reduction zone where a plurality of steam plasma torches couple high temperature steam plasma into an annular ring distributor having many apertures which uniformly couple the steam plasma into the pre-heated fuel of the oxidation and reduction zone, where the oxidizing fuel is spent and releases combustible gasses, particularly H 2  and CO, and these combustible gasses are separated from the spent fuel in a gas outlet zone having a half annular ring collector with many apertures for collection and offload of the combustible gases for subsequent utilization. Opposite the half annular ring collector is a half annular ring distributor which is fed by an air plasma torch coupling an air plasma into the gas outlet zone of the enclosure. Below the gas outlet zone is a solids offloading zone having a rotating grate with apertures for collecting the waste solids and transferring them into a water trough which also provides a water seal for the pyrolysis chamber. The water trough may also provide means for the removal and disposition of ash and slag waste. 
         [0007]    A second object of the invention is a process for pyrolysis in a chamber, the process having: 
         [0008]    a first step of loading fuel into a pre-heating zone, the pre-heating zone heated by a plurality of air plasma torches coupling an air plasma into the chamber and thereby forming pre-heated fuel; 
         [0009]    a second step of exposing the pre-heated fuel to an oxidation and reduction zone where a steam plasma torch generates a steam plasma which is delivered to an annular ring distributor with apertures coupled to the chamber, the annular ring distributor and apertures surrounding the pre-heated fuel and coupling the steam plasma to the pre-heated fuel, thereby releasing combustible gasses and solid waste products of ash and slag; 
         [0010]    a third step of introducing an air plasma from an air plasma torch into the oxidized and reduced fuel (char and ash), where the air plasma is delivered to a half annular ring distributor with apertures coupled to the chamber, the half annular ring distributor and apertures delivering air plasma to the oxidized and reduced fuel, thereby gasifying the char and forming ash residue ; 
         [0011]    a fourth step of removing the combustible gasses using a half annular ring collector for collection and offload of the combustible gases, the combustible gases moving through a plurality of apertures into the half annular ring collector and carried out of the chamber; 
         [0012]    a fifth step of removing ash and slag waste products by exposing the oxidized and reduced fuel to a rotating grate which has apertures larger than an ash or slag grain size, the ash and slag passing through the rotating grate and transferred to the a trough. 
       SUMMARY OF THE INVENTION 
       [0013]    A Pyrolysis chamber has, in succession, a fuel loading zone, a fuel pre-heating zone, a steam plasma oxidizing and reduction zone, a gas outlet zone including a combustible gas outlet, and a solids offloading zone for removing ash and slag. The fuel pre-heating zone has a plurality of air plasma torches which couple a 1200-1500° C. air plasma into the chamber and heat the fuel to a pre-heat temperature of approximately 1200-1500° C., after which the pre-heated fuel is exposed to a steam plasma of approximately 1500° C. which is generated by a plurality of steam plasma torches which first couple the steam plasma into an annular ring distributor within the walls of the chamber, the annular ring distributor containing a plurality of apertures into an oxidation and reduction zone of the chamber, whereby the steam plasma and pre-heated fuel oxidize and reduce to generate combustible gasses and waste solids. The combustible gasses and solid waste are thereafter directed towards a gas outlet zone which is formed by the half annular ring distributor and the half annular ring collector. The half annular ring distributor is pressurized by a plurality of air plasma torches coupling an air plasma into the half annular ring distributor within the chamber walls, the half annular ring distributor having a plurality of apertures conducting the air plasma into the gas outlet zone. The half annular ring collector contains a plurality of apertures coupled to the chamber for drawing the combustible gasses out of the chamber and to external equipment such as a steam turbine or internal or external combustion engine for energy extraction. Below the gas outlet zone is a solids offloading zone with a rotating grate for removal of slag and ash, the rotating grate having apertures for solids removal and in contact with a water trough for aggregation of solids and slag removal. 
         [0014]    In another embodiment of the invention, a process for pyrolysis in a chamber has a first step of loading fuel into a pre-heating zone, the pre-heating zone heated by a plurality of air plasma torches coupling air plasma into the chamber and thereby forming pre-heated fuel; 
         [0015]    a second step of exposing pre-heated fuel to a steam plasma generated by a steam plasma torch coupling the steam plasma into an annular ring distributor in the chamber and surrounding the pre-heated fuel, coupling the steam plasma in the annular ring distributor to the pre-heated fuel using a plurality of apertures, thereby oxidizing and reducing the pre-heated fuel and generating combustible gasses and waste products of ash and slag; a third step of gasification of the ash residual carbon by injecting an air plasma into the oxidized and reduced fuel with a half annular ring distributor having a plurality of apertures directing the air plasma into the outlet zone; 
         [0016]    a fourth step of removing the combustible gasses by means of a half annular ring collector having a plurality of apertures coupling the chamber with the half annular ring collector and directing the combustible gases to the combustible gas outlet for energy extraction; 
         [0017]    a fifth step of removing ash and slag waste products by exposing the oxidized and reduced fuel to a rotating grate having apertures for removing ash and slag solids which have a grain size smaller than the apertures of the rotating grate, ash and slag solids which pass through the rotating grate thereafter coupled to a waste accumulation reservoir. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0018]      FIG. 1  shows the cross section diagram of a plasma pyrolysis chamber. 
           [0019]      FIG. 2  shows the cross section view through section A-A of  FIG. 1 . 
           [0020]      FIG. 3  shows the cross section view through section B-B of  FIG. 1 . 
           [0021]      FIG. 4  shows a cross section view of the walls of a pyrolysis chamber. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0022]    The present invention describes an apparatus and method for pyrolytic waste recovery which can extract energy in the form of combustible gases from a wide variety of heterogeneous organic materials including municipal refuse, biomass, agriculture wastes, wood and forest product processing wastes, hazardous wastes, petroleum coke, coal or oil shale, individually or as mixtures. Depending on the nature of the input fuel, the resultant combustible gas is suitable use as a fuel for electric power generation, for conversion to synthetic hydrocarbons, hydrogen, or other valuable chemicals. In one embodiment of the invention, the combustible gas includes H 2  and CO and a steam plasma is injected in the oxidation and reduction zone which generates these gasses, the steam plasma containing sufficient energy to compensate for the endothermic heat required to generate these combustible gasses. In another embodiment of the invention, the fuel is wood chips or other biomass fuel. The instant process operates with a volume reduction on the order of 20× of input fuel volume and a weight reduction on the order of 10× in fuel with respect to the waste ash and slag. 
         [0023]    In one prior art system described in U.S. Pat. No. 7,452,392, oxygen is removed from a combustible gas stream by oxidizing a portion of the fuel with less than the stoichiometric amount of oxygen, typically as close to 50% as possible. Steam is also added to the combusted gases in deliberately controlled quantity. This process reaction, known as gaseous partial oxidation, is quick, complete (in terms of oxygen removal extent), and generates significant heat as it is highly exothermic. 
         [0024]    Many different fuels may be used in the present device, including those listed in the table below: 
         [0000]    
       
         
               
               
               
               
             
               
               
               
               
             
           
               
                   
                   
               
               
                   
                 Material 
                 Type 
                 BTU/lb 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 Cardboard/Kraft 
                 Paper 
                 6233 
               
               
                   
                 Paper/Newsprint 
               
               
                   
                 High Grade Paper/Magazines/ 
                 Paper 
                 5446 
               
               
                   
                 Phone Books Other Mixed &amp; 
                 Paper 
                 5481 
               
               
                   
                 Waste Paper 
               
               
                   
                 CRV/PET 
                 Plastic 
                 13200 
               
               
                   
                 HDPE, LDPE, PP 
                 Plastic 
                 13800 
               
               
                   
                 PVC 
                 Plastic 
                 8000 
               
               
                   
                 Polystyrene (PS) 
                 Plastic 
                 17700 
               
               
                   
                 Rubber/Tires (w/o metal) 
                 Plastic 
                 8443 
               
               
                   
                 Other Plastic 
                 Plastic 
                 12000 
               
               
                   
                 Yard Waste 
                 Organics 
                 4500 
               
               
                   
                 Food Waste, Dead Animals 
                 Organics 
                 3265 
               
               
                   
                 Wood Waste 
                 Organics 
                 6933 
               
               
                   
                 Textile 
                 Organics 
                 6595 
               
               
                   
                 Leather 
                 Organics 
                 8433 
               
               
                   
                 Misc. Organics 
                 Organics 
                 6600 
               
               
                   
                 Disposable Diapers 
                 Other 
                 4500 
               
               
                   
                 Asphalt 
                 Other 
                 14000 
               
               
                   
                 Glass 
                 Glass 
                 0 
               
               
                   
                 Aluminum, Ferrous Metal, 
                 Metals 
                 0 
               
               
                   
                 Other metals Concrete, Clay, 
                 Inerts 
                 0 
               
               
                   
                 Brick, Rock, Sand, 
               
               
                   
                 Soil, Ash, Other Inerts Paint 
                 HazWaste 
                 200 
               
               
                   
                 Motor Oil HazWaste 
                 HazWaste 
                 19000 
               
               
                   
                 Lead Acid Batteries 
                 HazWaste 
                 0 
               
               
                   
                 Other Household Waste 
                 HazWaste 
                 3000 
               
               
                   
                 Municipal Solid Waste (MSW) 
                 Waste 
                 4560 
               
               
                   
                   
               
             
          
         
       
     
         [0025]      FIG. 1  shows a plasma pyrolysis chamber  100 . Feed fuel  102  is placed above a controllable feed valve  104 , which periodically opens and introduces new fuel  102  from a hopper above feed valve  104  through throat  108  and into the pryolysis chamber  109 , which has a fuel pre-heating zone  140  heated by air plasma torches  110  and  112 , an oxidation and reduction zone  142  where steam plasma is introduced using steam plasma torch  126 , and gas outlet zone  143  where air plasma torch  134  introduces air plasma through half annular ring distributor  135 . Combustible gas  137  formed in the oxidation and reduction zone  142  and also from the gasification of the char is removed using half annular ring collector  136  in gas outlet zone  143  to outlet port  139 , and slag and ash are removed from the pyrolysis chamber in solids offloading zone  144 . 
         [0026]    The preheat zone  140  provides for introduced fuel  122  to be heated to approximately 1200-1500° C. through the rapid introduction of air plasma at a temperature of 2000-4000° C. through air plasma torches  110  and  112 , where air  114 ,  118  is forced through the plasma torches  110  and  112 , respectively, which air plasma  116 ,  120 , respectively, exits directly into the chamber pre-heated fuel  122 , is gravity packed with a fuel/air volume ratio preferably on the order of 1:1 and a fuel density range of 180-800 kg/m 3 , with 400 kg/m 3  being a typical density. The pre-heated fuel  122  is then subjected to a steam plasma which is generated by steam  124  injected into plasma torch  126 , and the resultant steam plasma which is at a temperature of approximately 1500 degrees C. is then directed through an annular ring distributor  128  formed in chamber  109 , then through a plurality of apertures  202  (shown in  FIG. 2 ) directing the steam plasma downward into the chamber and into the oxidation and reduction zone  142  in region  130  of chamber  109 , where the following basic reactions take place: 
         [0000]      C+CO2→2CO   (Eq 1)
 
         [0000]      C+H 2 O→CO+H 2 −31.2Kcal/mole of C   (Eq 2)
 
         [0000]      CO+H 2 O→CO 2 +H 2    (Eq 3)
 
         [0000]    Equation 1 is known as Bouduart reaction, equation 2 is known as the water gas shift reaction, and equation 3 is known as the hydrogen shift equation. Equations 1 and 2 are endothermal, and the use of a steam plasma  128  at 1500° C. or more in this stage introduces sufficient external energy to offset the endothermic heat loss during combustible gas (CO and H 2 ) generation. The combustible gasses  123  and  125  migrate to the gas outlet zone  143 , via the apertures  304  (described later for  FIG. 3 ), where they enter into the half annular ring collector  136  directing the combustible gases  137  to an outlet port  139  directed to an energy extraction device such as a gas turbine. Air  132  enters air plasma torch  134  and exiting air plasma is coupled to a half annular ring distributor  135 , coupling air plasma into the chamber volume  138  via apertures  302  (shown in  FIG. 3 ), the air plasma acting on the oxidized and reduced fuel  127  and the gasified ash residual carbon. When the pyrolysis process is carefully regulated through the metered introduction of steam plasma and air plasma into the reaction chamber, minimal reaction of nitrogen (present in the air plasma as it is derived from atmospheric air) occurs, and the generation of combustible gasses CO and H 2  results in decrease of the nitrogen as a percentage of volume of the gas  137  which exits the outlet port  139 . The oxidized and reduced fuel char  138  is thereby reduced to ash, and at temperatures above 1500° C. the ash vitrifies into slag, and the ash and slag pass through a rotating grate  150  which is above a water bath  158  in trough  162 , which isolates air outside chamber  109  from the inner volume of the pyrolytic chamber  109 , and also provides a collection region for ash and slag  154  which passes through the apertures of grate  150 , into the trough  162 , and eventually is removed by ash and slag conduit  160 . 
         [0027]      FIG. 2  shows section A-A of  FIG. 1  including steam plasma annular ring distributor  128 , and also shows the steam plasma directed from steam plasma torches  126  through the annular ring distributor  128 , through the plurality of apertures  202  into fuel  130  which is oxidizing and reducing to generate combustible gas.  FIG. 3  shows section B-B of  FIG. 1  through the inlet air plasma half annular ring distributor  135  and also the half annular ring collector  136  accumulating the combustible gas  137 , which leads to gas outlet port  139 . 
         [0028]      FIG. 4  may be viewed in combination with  FIGS. 1 ,  2 , and  3 , and shows one embodiment for construction of the walls of chamber  109  of  FIG. 1 , including the steam plasma annular ring distributor  128  for region  180 , air plasma half annular ring distributor  135  for region  182 , and half annular ring collector  136  of region  184  (shown for reference as rotated for the opposite side of region  182 ). In the example embodiment shown in  FIG. 4 , firebrick  400  may be used to form the structure of the enclosure  109 , with refractory brick  404  applied to the combustion-facing surfaces and also inside the air or steam plasma channels feeding the annular ring distributor  128  for  FIG. 1  detail  180 , half annular ring distributor  135  shown in  FIG. 1  detail  182 , or half annular ring collector  136  shown in  FIG. 1  detail  184 . The apertures  202 ,  302 ,  304  for annular ring distributor  128 , half annular ring distributor  135 , and half annular ring collector  304 , respectively, are shown in  FIG. 4  oriented downward into the pyrolysis chamber to minimize blockage of the port apertures  202 ,  302 , and  204  from char, ash, and slag in the pyrolysis chamber. Additionally, in one embodiment of the invention, any of the annular rings  128 ,  135 , and  136  may be formed with expansion joints in the refractory brick lining, such that thermal expansion and contraction is absorbed by these joints. The pre-heating torches produce an air plasma which is directly introduced into the chamber through a passageway. A material such as thermostable steel may be used as an exterior surface  402  of the chamber  109 . Inner surfaces which are combustion facing or plasma facing may be provided with furnace linings of aluminum oxide, magnesite (magnesium carbonate), silicon carbide, or dolomite as is known in the prior art to increase the useful life of the underlying surfaces protected by these furnace linings. 
         [0029]    The high speed pyrolysis of the current system has several advantages over a prior art pyrolysis system, including a greater conversion fraction of the incoming waste to combustible gas. Thermal or normal pyrolysis promotes liquefaction giving only 45-50% conversion to pyrolysis gases, while rapid pyrolysis of the present invention has gas yields of greater than 65%. 
         [0030]    Many methods for extraction of energy from the combustible gasses  137  using the gas outlet port  139  are possible. With the efficiency of gas turbine-combined cycle systems approaching 60%, the present method of waste-to-energy conversion provides an effective alternative to standard waste incinerators. Under favorable conditions, the incinerator-steam generator systems achieve 15-20% efficiency in the conversion of the potential energy contained in the waste to usable electric energy. In one example system, 1 Kg of incoming waste generates 14-15 MJ of chemical energy at the combustible gas outlet port, and 2-3 MJ of electrical energy is consumed in the generation of the various plasmas which feed the chamber. 
         [0031]    The specific gravity of slag will be on the order of 2.0-2.5 which will allow it to adequately gravity feed through the apertures of the grate. The solid vitrified waste products produced in accordance with the present invention when the oxidation and reduction temperatures are sufficiently high may be used in a variety of applications. The vitrified slag waste may be crushed and incorporated into asphalt for use in roads and the like. Alternatively, the vitrified slag may be utilized to replace cinder in cinder or building blocks, thereby minimizing absorption of water within the block. Further, the vitrified slag may be solidified to a final form which exhibits substantial volume reduction over prior art vitrification products. The solidified form is suitable for disposal without health risks or risks to the environment. 
         [0032]    Pre-heating plasma torches ( 110 , 112 ), steam plasma torch ( 126 ) and air plasma torch ( 134 ) gasifying the ash residual carbon can be realized using any prior art long arc torch configuration, and operative on 4-12 KV with an arc length greater than 0.3 m. Although specific numbers of plasma torches are shown for clarity, any number of torches may be used in each respective pre-heat zone (torch  110 ,  112 ), oxidation and reduction zone (torch  126 ), and gas outlet zone (torch  134 ). Many different prior art embodiments of the plasma torch can be utilized in the present invention. In one embodiment, each torch is a long arc forming plasma torch of the type described in U.S. Pat. No. 3,818,174 for a single phase excitation, or as described in U.S. Pat. No 7411,353 by Routberg et al. for polyphase excitation. Long arc column plasma torches have become well known in the art as having the capability of sustaining stabilized plasma arcs on the order of one meter in length. In contrast, conventional short arc plasma torches generally sustain arcs of less than 0.2 meter and typical non-plasma electric arc devices have no stabilizing character and produce relatively short arcs. The apparatus and method of the invention recognize and utilize features of the long arc torch which makes its stabilized, electrically conducting gas column especially suited for use with gasification of coal as a source of radiant heat and particularly when used in multiple and arranged as described with the “long arc” being at least 0.3 meter in length. 
         [0033]    One advantage of long plasma arc torches such as those described above is the conversion of electrical energy to heat with an efficiency of approximately 90% as compared with an efficiency of 30-50% for conventional short arc torches. Further, it is recognized that the capability of the long arc torch in combination with the annular ring distribution is that the torches are now placed outside of the furnace wall and away from the intense furnace heat produced during gasification. This advantage reduces the wear on the torch and increases the thermal efficiency of the process. Also, the invention recognizes that the long arc torch requires significantly less current than a conventional torch thereby reducing the cost of electrical conductors and reducing the complexity of the electrical power connections. 
         [0034]    Chamber  109  including annular ring plasma distributors  128  and  135  and half annular ring collector  136  may be formed using any material which provides resistance to surface degradation from exposure to the high temperature plasma and pyrolysis process. Suitable materials include brick with a refractory brick (fire brick) lining with a typical maximum temperature of 1650° C., or steel treated with an insulating material. In another embodiment, a chamber for 100 kg/hr wood waste has an inside dimension of 0.6 m and a preheat zone, oxidation and reduction zone, gas outlet zone, and solids offloading zone with 1.9 m overall vertical extent, with the chamber constructed of heatproof steel with the high temperature areas insulated with aluminum oxide. 
         [0035]    Many different embodiments of the present invention are possible, and those shown are for clarity in understanding the invention, and do not limit the invention, which is understood as set forth in the claims below.