Abstract:
An appliance is provided having a waste receptor module and an energy generation module for converting household waste into energy. The receptor module has a rotary drum with an opening for receiving the household waste and a steam reforming means for converting the waste into synthesis gas. A swing arm is attached adjacent to the opening in the rotary drum and a sealing door is mounted on the swing arm for sealing the opening when the waste receptor module is in operation. An outer door is used to cover the sealing door. The steam reforming means includes a tube mounted within the rotary drum for receiving the volatilized organic waste and an internal heater for heating the organic waste to temperatures to convert the waste into the synthesis gas. The energy generation module has an inlet in fluid communication with the waste receptor module for receiving the synthesis gas and a fuel cell for converting the synthesis gas into electrical energy.

Description:
FIELD OF THE INVENTION 
     This application claims the benefit of U.S. Provisional Application No. 60/732,053 filed Nov. 2, 2005, incorporated by reference. 
    
    
     The invention relates to an appliance for the destruction of residential and building waste to form hydrogen-rich syngas to power a fuel cell for the generation of electric power, steam and heat or cooling for use in residences and buildings as well as hydrogen fuel for vehicles. 
     BACKGROUND OF THE INVENTION 
     Across the nation, and indeed the world, the energy content of this household waste is enormous; for example, for each person in the U.S. this municipal solid waste can be converted to produce roughly 6 kWh of electricity per person per day. This is really very significant, when one considers that the average person in the U.S. consumes about 7 kWh per person per day. 
     There have not been any new appliances for single family or small multiple family residents to convert their household waste into useful recyclables and/or energy. The closest appliance has been the garbage compactor. Typical suppliers of such appliances include G.E., DeLonghi, Kenmore, Sears, Honeywell, Beoan, KitchenAid, Whirlpool, and others. Compactors have not been successful since garbage pickup costs are not reduced significantly by reducing the volume of the garbage. The cost of pickup of one can is the same regardless of the volume of the residential garbage in the can. Also, there are many operational problems: special and hard-to-locate compactor bags, consumable carbon filters that have to be replaced in order to avoid serious odor problems, frequent jammed rams from bottles, cans, and bulky waste not placed in the center of the load that can jam the drawer, leaking bags from punctures from sharps within the garbage spilling out disgustingly odiferous bio-hazardous liquids, and the necessity to use the compactor regularly and to remove the bags to avoid rotting garbage left in the unit, and the like. Further, the compactor does not produce energy or heat; instead it consumes energy. 
     There is a need for a household appliance that can eliminate a major portion of household waste and convert the waste into useful recyclables and/or energy. 
     SUMMARY OF THE INVENTION 
     The present invention offers a new approach in which a substantial amount of residential waste can be eliminated in a small, compact appliance that has appearance of a washer/dryer stack found in households. 
     The appliance of the present invention comprises a waste receptor module having a rotary drum having an opening for receiving household wastes, and steam reforming means for converting at least a substantial amount of the household waste into synthesis gas and an energy generation module having an inlet that is connected to said waste receptor module for receiving the synthesis gas and a fuel cell for converting the synthesis gas into at least electrical energy. The appliance of the present invention has vent, electrical, gas, sewer, and water connections. The appliance cures the problems of garbage compactors by greatly reducing the mass of the garbage, producing sterilized recyclable glass and metals, eliminating garbage requiring landfills, and using the organic chemical fraction of the waste to produce electricity, steam and heat. 
     The waste receptor module carries out endothermic reactions of steam reforming and is heated with waste heat and electrical power. Alternatively, this module can be heated by a natural gas burner. The module includes a rotary drum, into which are placed bags of waste that can consist of normal garbage as well as toilet solid waste. Glass and metal are not melted in this drum and are recovered as completely sterilized at the end of the process cycle. 
     Household waste contained in common paper or plastic bags is thrown into the waste receptor module through a sealed door like a dryer. The door is closed and the “on” button is pushed, beginning the processing of the waste. The automatic cycle is about 90 minutes. All of the organic waste is converted to synthesis gas (hereafter called “syngas”). The sterilized glass and metal remaining in the drum are cooled and retrieved for curbside recycling pickup. 
     The waste inside the drum is tumbled slowly while it is heated from the hot cartridge heater/steam reformer (SR) in the center of the drum. This SR central cylinder is heated internally by induction heat or with natural gas by means of a matrix heater. The vapors from this heated waste are pulled through the outer perforated portions of the SR cartridge to a hotter interior, in which the vapor temperature is raised to about 900-1050° C. (1650-1900° F.) and reacted with the steam from the waste and the re-circulated syngas. The hot syngas leaving the SR cartridge is cooled by two tandem heat exchangers to 50-90° C. (120-190° F.) and is pulled through a gas cleaning bed and condenser from which the liquid water is dropped out and sent to drain or to non-potable landscape watering. 
     The energy generation module receives the syngas produced by the waste receptor module and a fuel cell within the energy generation module converts the syngas into electricity, steam and heat. Specifically, cleaned gas from waste conversion module is pulled into the suction side of a blower out of which is discharged the syngas under pressure to feed the anode side of the fuel cell. The anode side of the fuel cell converts the syngas to hot CO 2  and steam at about 650° C. (1200° F.), while producing electricity from the H 2  and CO in the syngas. A fraction of this hot CO 2  and steam passes into the SR cartridge for recycling through the drum of the waste conversion module and the balance of this fraction passes through a heat exchanger to recover heat at high temperature useful for producing domestic hot water. The cathode side of the fuel cell is fed a high volume of hot air that is heated in the heat exchanger from the hot syngas and passes into the fuel cell cathode where the oxygen is electrochemically reduced on the catalytically active fuel cell elements. Leaving the hot cathode is as high volume of hot nitrogen at around 400° C. (750° F.) which is available for raising steam, space heating or cooling, or other applications. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIGS. 1A and 1B  are conceptual drawings of two possible arrangements of the two modules of the residential household waste-to-energy appliance; 
         FIGS. 2A and 2B  shows the details of the rotary drum and its sealing and locking drum door on a swing arm; 
         FIG. 3  shows a preferred embodiment of a rotary drum that is heated by induction coils, typically supplied by InductoHeat of New Jersey and others; and the process configuration downstream of the rotary drum where the syngas is used for production of electricity, steam and heat; 
         FIG. 4  shows a preferred embodiment of a rotary drum that is heated by natural gas matrix heater cartridge and the process configuration downstream of the rotary drum where the syngas is used for production of electricity, steam and heat; and 
         FIG. 5  shows the details of this natural gas matrix heater cartridge, typically supplied by the Hauck Burner Corp., Baekert, Gmbh, and others. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       FIG. 1A  shows an isometric view of the residential appliance in a stacked arrangement Waste Receptor Module a module on the top of module  4 , which includes a waste processing system that steam reforms the waste into valuable syngas. Energy generation module uses the syngas to feed a fuel cell located therein for the production of electricity, steam and heat and optionally hydrogen and method also contains heat exchangers, blowers, valves, piping and controls that are described in reference to  FIGS. 3 and 4 . 
       FIG. 1B  shows an isometric view of another embodiment of the residential appliance of the present invention in a side-by-side, arrangement with the waste receptor module on the right. 
     Referring to  FIGS. 1A and 1B , waste receptor module  4  consists of an assembly that includes a rotary drum for processing of the waste fitted with a sealing drum door  6  with a locking mechanism, pivot and swing arm  8  to permit the opening and closing of this drum door. There is also an outer door  9  that is closed to cover up the locking drum door handle that turns when the drum rotates as the processing of the waste is underway. The energy generation module  2  uses this syngas that feeds a fuel cell  60  located therein for the production of electricity, steam and heat and optionally hydrogen. Module  2  also contains heat exchangers, blowers, valves, piping and controls. The two modules are connected together by a pipe  47  that feeds the syngas produced from the waste receptor module  4  to the energy generation module  2 . Pipe  50  returns unreacted syngas, steam, and carbon dioxide from the energy generation module  2  to the waste receptor module  4 . 
     Referring to  FIG. 2A , the locking and sealing drum door  6  mounted on swing arm  8  fits the main receptacle receiving the waste that consists of a rotary drum  14  that is well insulated on the inside. Referring to  FIG. 2B  there is shown a cross-section through drum  14  that is pivoted by rotary shaft  16 . The inner wall of the drum  14  consists of a heavy wall alloy  18  as well as a central cylinder of even thicker alloy wall  20  to contain the highest temperature heat. This drum  14  rotates around a rotary shaft and seal  16  that excludes air and allows gases to pass through and is described in more detail in  FIGS. 3 and 4 . The drum door  6  has to rotate and seal at the same time, so that it is designed with a door handle  22  to operate the door locking mechanism  24  that consists of an array of bars which pivot and slide away from the drum top edge lip. When the handle  22  is rotated, these bars pivot off of a ramp releasing pressure on the drum and its seal so that it can be opened. There are pressure sensors that insure that drum  14  is closed, locked and pressure sealed before it is rotated and any heat is applied. Since handle  22  rotates through swing arm  8 , it needs to be protected by an outer closing door  9  for safety reasons. The outer layer of rotating drum  14  is very well insulated by layers of insulation,  13  and  15 , to insure good energy efficiency. The inner enclosure of module,  2 , is also well insulated with conversion layer  26  to avoid burns from users of the appliance and to further achieve high energy efficiency. The outer wall also contains induction coils  30  for heating conductive susceptors  18  and  20 . 
       FIG. 3  shows one of the preferred embodiments of the present invention that uses a steam reforming means that includes an internal heater, which in this embodiment is in the form of induction coils  30  for heating the rotary drum  14  in which is placed the waste  44  and tube  32 . This rotary drum heats the waste  44  to about 450-600° C. (840-1100° F.) and starts the steam reforming reactions. The waste volatiles and initially formed syngas are produced in a volume  42  inside rotary drum  14 . When the steam reforming reactions within this drum volume  42  form syngas, these gases pass through the heated perforated central cylindrical tube  32  that is heated by the fixed induction heaters  30  around the outside of the enclosure. Within this central cylindrical tube  32  the syngas is heated to about 900-1050° C. (1650-1900° F.) and reacted with the steam and CO 2  to form very hot syngas exiting this central cylindrical tube  32  is syngas stream  47  at 800-950° C. (1470-1750° F.). Within perforated cylindrical tube  32  is a removable filter cartridge  34  which captures any entrained particulate matter to avoid carrying this fine material downstream in the process lines  47 , through which the syngas so produced exits the rotary drum system that is rotated by motor system  45 . A rotary process piping seal  36  is used to inject steam and carbon dioxide through pipe  46  and the synthesis gas so produced exits through pipe  47 . 
     This very hot syngas  47  enters heat recuperator exchanger  52  that cools this syngas to 600-800° C. (1100-1450° F.) in pipe  58  with the cooler stream  56  at 550-750° C. (1020-1380° F.) containing CO 2  and steam. Air  84  is blown via blower  72  through heat exchanger  70  to supply heated air  71  to serve the cathode of the fuel cell. The cathode exhaust gas  74  comes from fuel cell  60 . The fuel cell anode exhaust stream  56  can contain a small fraction of unconverted syngas, which can be recirculated back to the steam reformer drum volume  42  shown in cross-section for utilization. Part of this 800-950° C. (1470-1750° F.) exchanger exit stream  54  also is recirculated as stream  50  back into the cartridge steam reformer  32  to make more syngas. The gas  54  leaving heat exchanger  52  will be about 800-950° C. (1470-1750° F.) and can be used to drive a Brayton cycle turbine to make more electricity and use its exhaust to raise steam for sale, or stream  54  can be used for other useful purposes. One such purpose is to feed a commercial pressure swing absorber such as those manufactured and sold by Air Products, Quest Air, and others, for producing pressurized fuel-quality hydrogen for local storage and used to fuel vehicles. 
     The very warm syngas  58  leaves heat exchanger  52  at about 650-750° C. (1200-1380° F.) and enters heat exchanger  70 , which can also be a second set of coils in exchanger  52 . Cool outside air  84  is fed into this exchanger  70  by blower  72  to be heated to 570-670° C. (1050-1150° F.) as exit stream  71 , which in-turn is the hot air feeding the fuel cell  60 . The air stream is electrochemically reduced in the cathode to exit as nitrogen gas  74  at about 600-700° C. (1100-1300° F.) and is fed to exchanger  76  and exiting as  77  at about 130° C. (270° F.) to be used for other purposes, such as generating domestic hot water. 
     The cooled syngas  67  at about 150-200° C. (300-400° F.) passes into packed bed absorber  66  to clean the syngas of impurities containing chlorine and sulfur and other potential poisons to the fuel cell. A condensate stream  68  leaves this absorber  66  to go to sewer drain. The clean, cool syngas  64  is pulled from the absorber  66  at about 130° C. (270° F.) by blower  62  and feeds the exchanger  76  which raises the syngas temperature to 600-700° C. (1100-1300° F.) for feeding the anode side  78  of the fuel cell  60 . Natural gas, propane, or other fuel source can be used in line  79  to start up fuel cell  60  and the system via mixing valve  80 . 
     Another preferred embodiment of the present invention is shown in  FIG. 4 , which involves heating volume  42  of the rotary drum  14  through combustion of natural gas. This embodiment has two disadvantages because it uses expensive natural gas and it involves the evolution of carbon dioxide. As shown in  FIG. 4 , drum  14  shown in isometric has internal volume  42 . It has a manually operated means of handle  22  to lock the autoclave-type sealing door  6  that rotates with the drum. The waste  44  enters the rotary drum that is rotated by means of a motor drive system  45 . Inside and co-centric to the rotary drum there is a stationary heated cartridge cylinder  100  through which the waste volatiles pass that is heated by an internal heater, which in this embodiment, is in the form of a matrix heater,  112  shown in  FIG. 5  fed by a outside combustible gas fuel stream  46  venting to the outside through pipe  49 . This rotary drum volume  42  heats the waste to about 700-900° C. (1300-1650° F.) and starts the steam reforming reactions. The waste volatiles and initially formed syngas produced inside this rotary drum are pulled into the inside of this cartridge wherein the organics are heated to about 900-1050° C. (1650-1900° F.) and reacted with the steam and CO 2  to form very hot syngas exiting this central cartridge as syngas stream  47  at 800-950° C. (1470-1750° F.) 
     This very hot syngas  47  enters heat recuperator exchanger  52  that cools this syngas to 650-750° C. (1200-1380° F.) in pipe  58  with the cooler stream  56  at 570-670° C. (1050-1150° F.) containing CO 2  and steam. The cathode exhaust gas  74  comes from fuel cell  60 . The fuel cell anode exhaust stream  56  can contain a small fraction of unconverted syngas, which can be recirculated back to the steam reformer drum volume  42  for utilization. Part of this 700-900° C. (1300-1650°) exchanger exit stream  54  also is recirculated as stream  50  back into the cartridge steam reformer  100  to make more syngas. The gas  54  leaving heat exchanger  52  will be about 700-900° C. (1300-1650°) and can be used to drive a Brayton cycle turbine to make more electricity and use its exhaust to raise steam for sale, or stream  54  can be used for other useful purposes. One such purpose is to feed a commercial pressure swing absorber, such as those manufactured and sold by Air Products, Quest Air, and others for producing pressurized fuel-quality hydrogen for local storage and used to fuel vehicles. 
     The very warm syngas  58  leaves heat exchanger  52  at about 650-750° C. (1200-1380° F.) and enters heat exchanger  70 , which can also be a second set of coils in exchanger  52 . Cool outside air  84  is fed into this exchanger  70  by blower  72  to be heated to 570-670° C. (1050-1150° F.) as exit stream  71 , which in turn is the hot air  71  feeding the fuel cell  60 . The air stream is electrochemically reduced in the cathode to exit as nitrogen gas  74  at about 570-700° C. (1050-1300° F.) and is fed to exchanger  76  and exiting as  77  at about 130° C. (270° F.) to be used for other purposes, such as generating domestic hot water. 
     The cool syngas  67  at 80° C. passes into packed bed absorber  66  to clean the syngas of impurities containing chlorine and sulfur and other potential poisons to fuel cell  60 . A condensate stream  68  leaves absorber  66  to go to sewer drain. The clean, cool syngas  64  is pulled from the absorber  66  at about 130° C. (270° F.) by blower  62  and feeds via  82  the exchanger  76  which raises the syngas temperature to 600-700° C. (1100-1300° F.) for feeding the anode side  78  of fuel cell  60 . Natural gas, propane, or other fuel source can be used in line  79  to start up fuel cell  60  and the system via mixing valve  80 . 
     The details of the steam reforming cartridge  100  are shown in  FIG. 5 . The cartridge is inside the end of the rotary drum wall  102  and remains fixed while the drum rotates and remains sealed by rotary seal  120 . The hot waste volatiles and partially formed syngas are pulled in through ports  104 . This gas is heated while it travels along the outer annulus  105  of the cartridge and turns around at the end of the annulus  106  to travel along the hotter inner annulus  107  and exiting at port  118 . The annulus tube assembly is kept centered by a plug insulator  108  at the right end of the annulus tube. The center of the cartridge inside tube  110  is heated by burning a combustible gas  114  in the matrix heater  112  that radiates heat out to the surrounding annuli  105  and  107 . The combustion products of this matrix gas burning leave at port  116 . Alternately this central heater could also be supplying heat by electrical resistance heaters, induction heaters, or other means of generating heat. 
     EXAMPLE 
     The first step in the reduction to practice of the appliance of the subject invention was to conduct experimental, small-scale pilot tests to reveal the identity and nature of the syngas produced. Accordingly, just completed was a gas test using the Bear Creek Pilot plant where solid waste was steam/CO 2  reformed to make syngas. The syngas composition is shown in Table 1 below. 
     
       
         
               
               
               
               
             
               
               
               
             
               
               
               
               
             
           
               
                 TABLE 1 
               
               
                   
               
             
             
               
                 H 2   
                 Hydrogen 
                 62.71 
                 Vol % 
               
             
          
           
               
                 CO 
                 Carbon Monoxide 
                 18.57  
               
               
                 CO 2   
                 Carbon Dioxide 
                 10.67  
               
               
                 CH 4   
                 Methane 
                 7.58 
               
               
                 C 2 H 6   
                 Ethane 
                 0.48 
               
               
                 C 3  TO C 6   
                 Propane through hexane 
                 &lt;0.01  
               
             
          
           
               
                 C 6 H 6   
                 Benzene 
                 &lt;17 
                 ppm 
               
               
                 COS 
                 Carbonyl Sulfide 
                 4 
                 ppm 
               
               
                 CS 2   
                 Carbon Disulfide 
                 0.05 
                 ppm 
               
               
                 H 2 S 
                 Hydrogen Sulfide 
                 &lt;5 
                 ppm 
               
               
                 C 10 H 8   
                 Naphthalene 
                 2.6 
                 ppb 
               
               
                 C 10 H 7 CH 3   
                 2-Methylnaphthalene 
                 ~0.6 
                 ppb 
               
               
                 C 12 H 8   
                 Acenaphthalene 
                 ~0.4 
                 ppb 
               
               
                 C 12 H 8 O 
                 Dibenzofuran 
                 0.36 
                 ppb 
               
               
                 PCDF + PCDD 
                 Polychlorinated-dibenzo- 
                 0.0041 
                 ppt TEQ 
               
               
                   
                 furans + Dioxins 
               
               
                   
               
             
          
         
       
     
     What has been found was that the syngas was very rich in hydrogen and carbon monoxide—most suitable for a variety of high temperature fuel cells (such as molten carbonate, solid oxide, and similar fuel cells.). And the minor contaminants, such as carbonyl sulfide, hydrogen sulfide, carbon disulfide, hydrogen chloride, and polychlorinated organics were identified and a removal system specified. 
     The pilot process configuration used to conduct these tests was published, see reference (1) below, and was used as the basis for improvements shown in  FIG. 3 . The standard, common-knowledge process train was configured for cleaning the syngas: Standard chilled caustic scrubber, demister mat, carbon bed and HEPA filter, after which the product syngas was subjected to a very exhaustive chemical analyses. Three parallel gas-sampling trains were used: Gas-Chromatography, GC-MS for volatile hydrocarbons, semi-volatile hydrocarbons, chlorine-containing and sulfur-containing compounds. 
     The standard scrubber widely used in industry for gas clean-up removed hydrogen sulfide and hydrogen chloride, but not carbonyl sulfide, carbon disulfide, or polychlorinated organics. It was found that these compounds penetrated right through this syngas standard clean-up process train and that these compounds would be poisons to a molten carbonate or solid oxide high temperature fuel cell by the mechanism of chlorine or sulfur poisoning. So this important information was used to design the syngas clean-up system that would handle all these contaminants. 
     Volatile heavy metals can also poison the fuel cell and the collected solids in the scrubber were analyzed for such heavy metals and they were mostly removed. Highly volatile heavy metals, such as mercury or heavy metal chlorides or fluorides would be removed in the future clean-up system. 
     The scrubbed syngas was next fed to a room temperature demister mat, onto which a steadily increasing deposit of fine soot-like particles occurred. The pressure drop across this demister during the run was determined and found it to show a steady, linear increase in pressure drop as the deposit layer built up on the upstream face. These deposits were not analyzed. The downstream side of this demister filter remained clean and white throughout the entire run. Deposits appear to be soot with a slight odor of naphthalene. 
     The syngas leaving the demister was next fed into a granular activated carbon bed, which was designed to capture the volatile organics and volatile heavy metals that reached this point. The carbon bed was found to remove a great amount of these minor constituents and quickly became saturated throughout its entire length and broke through about 2 hours into the 3 hour solid waste feed period. The carbon load is believed to be mostly benzene and low molecular weight volatile chloro-organics. 
     The final step in the syngas cleanup was the HEPA filter, which worked very well during the whole run, not showing any build up in pressure from entrained fines or humidity; however, there was a substantial amount of volatile heavier hydrocarbons and sulfur- and chlorine-containing hydrocarbons that got through: benzene&lt;16 ppm, naphthalene=2.6 ppb, methylnaphthalene=0.6 ppb, acenaphthalene=0.4 ppb, and non-chlorinated dibenzofuran=0.36 ppb, polychlorinated dibenzodioxin and dibenzofuran TEQ=0.0041 ppt, COS=4 ppm, and CS 2 =0.05 ppm. H 2 S was below level of detection so the chilled scrubber did well on H 2 S, as well as HCl. 
     The very small, but still detectible polychlorinated dibenzodioxin and dibenzofurans were probably formed at the cooler end of the process train, since they are not formed during the steam reforming process. Their formation was probably before the quenching portions of the scrubber. Thus, the industry-standard scrubber approach alone is not sufficient for making syngas of high enough quality for fuel cells but the new syngas clean-up system does this. 
     The pilot tests showed that very high hydrogen content syngas can be produced using the steam/CO 2  reforming chemistry with a typical feed-stream of household waste. 
     Reference: (1) T. R. Galloway, F. H. Schwartz and J. Waidl, “Hydrogen from Steam/CO 2  Reforming of Waste,” Nat&#39;l Hydrogen Assoc., Annual Hydrogen Conference 2006, Long Beach, Calif. Mar. 12-16, 2006.