CLAIMS
I claim:
1. A commercial appliance comprising:
(a) a Waste Receptor Module containing a rotary drum into which household waste is placed where it is converted into syngas and
(b) an Energy Generation Module that receives the syngas produced in the module above and that contains the syngas-fed fuel cell, supplying electricity, steam, and heat for domestic hot water as well as lower grade heat for space heating and cooling.
2. The method of 1 where the raw waste is steam/CCh reformed in the temperature range from 93 to 48O 0 C (200 to 900 0 F) in a rotary drum heated by a central cartridge operating around 590 to 1150 0 C (1100 to 2100 0 F), through which is passed the syngas so produced for a second stage of further steam/C0 2 reforming with additional steam and carbon dioxide at from 480 to 1090 0 C (900 to 2000 0 F) for the production of very clean syngas very rich in hydrogen from 45 to 70% by volume.
3. The system of claim 1 where the spent waste in the 370 to 48O 0 C (700-900 0 F) drum consists of un-melted glass and metal that is recyclable.
4. The system of claim 1 where the hot syngas from the cartridge is cooled by heat exchanging the hot CO 2 and steam from the fuel cell to heat domestic hot water.
5. The system of claim 1 where the hot syngas from the cartridge is further cooled by heat exchanging with and heating a stream of room air so it can supply the cathode side of the fuel cell.
6. The system of claim 1 where the unit can be used for residences and households for processing their waste to generate electricity.
7. The system of claim 1 where the electricity and heat can be used to separate and purify the hydrogen in the syngas to produce hydrogen fuel for vehicles.
8. The system of claim 1 where the high volume of nitrogen leaving the fuel cell is used to provide steam and space heating and cooling for buildings.
9. The system of claim 1 where the cool syngas is cleaned by special beds and the water is condensed for non-potable uses or discharged to sewer.
10. The system of claim 1 where toilet solid waste can be included in the waste feed.
11. The system of claim 3 where the recyclable glass and metal can be picked up by regular curbside recycling.
12. The system of claim 2 where the steam/CO 2 reforming uses steam and CO 2 from the heated waste as well as hydrogen, CO, steam and CO 2 from the recycled syngas in amounts that are super-stoichiometric by the combination of steam and CO 2 to react the waste to a very high degree of completion and form syngas consisting of H 2 and CO at high levels of purity.
13. The system of claim 2 where CO 2 can be augmented or replaced by other greenhouse gases, such as CH 4 .
14. The system of claim 2 where the steam reforming further uses the CO 2 out of the fuel cell anode for reaction with the residual high-carbon pyrochar to convert to CO.
15. The system of claim 2 where the fuel cell anode exhaust can be used to feed a commercial pressure swing absorber for producing pressurized fuel-quality hydrogen for local storage and used to fuel vehicles.
16. The system of claim 2 where the natural gas and the syngas and waste volatiles are passed through concentric pipes around which the rotary drum pivots to simplify the need for rotational seals.
17. The system of claims 4 and 5 where these two heat exchangers can be combined into a single, multiple pass heat exchanger producing several hot gas streams for different uses as well as steam to be used in the SR cartridge or used in buildings.
18. The central cartridge of claim 2 can contain a porous foam ceramic cylindrical filter cartridge for further cleaning the syngas of any entrained particulate matter.
19. The central cartridge of claim 2 can be heated by electrical resistance heat.
20. The central cartridge of claim 2 can be heated by induction heat.
21. The central cartridge of claim 2 can be heated by burning a combustible gas in a matrix heater or other means. |
APPLIANCE FOR CONVERTING HOUSEHOLD WASTE INTO ENERGY
FIELD OF THE INVENTION
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 appliances 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, etc. Further, the compactor does not produce energy or heat; instead it consumes energy.
SUMMARY OF THE INVENTION
The present invention comprises a new approach where residential waste can be handled in a small, compact appliance that looks like the washer/dryer stack that includes a waste receptor module and an energy generation module. 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 is 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 1050 0 C (1900 0 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 70 0 C .(16O 0 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 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 (75O 0 F) which is available for raising steam, space heating or cooling, or other applications.
BRIEF DESCRIPTION OF THE DRAWINGS
Figures IA and IB are conceptual drawings of two possible arrangements of the two modules of the residential household waste-to-energy appliance;
Figure 2A and 2B shows the details of the rotary drum and its sealing and locking drum door on a swing arm; Figure 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;
Figure 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;
Figure 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
Figure IA 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 generator 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 Figures 3 and 4.
Figure IB 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 Figure IA and IB, 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 generator 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 generator module 2. Pipe 50 returns unreacted syngas, steam, and carbon dioxide from the energy generator module 2 to the waste receptor module 4.
Referring to Figure 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 Figure 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 Figure 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.
Figure 3 shows one of the preferred embodiments of the present invention that uses induction coils 30 for heating the drum 14 in which is placed the waste 44. This rotary drum heats the waste 44 to about 480 0 C (900 0 F) and starts the steam reforming reactions. The waste volatiles and initially formed syngas are produced inside a rotary drum volume 42. When the steam reforming reactions within this drum 14 form syngas, these gases pass through a perforated heated 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 1100 0 C (2010 0 F) and reacted with the steam and CO 2 to form very hot syngas exiting this central cartridge 32 as syngas stream 47 at 900 0 C (1650 0 F). Within perforated cylinder 32 as 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. The rotary process piping seal 36 has steam and carbon dioxide injected through piping 46 and the syngas so produced exits through pipe 47.
This very hot syngas 47 enters heat recuperator exchanger 52 that cools this syngas to 700 0 C (1290 0 F) in pipe 58 with the cooler stream 56 at 650 0 C (1200 0 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 850°C (1560 0 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 850°C (1560 0 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 700 0 C (129O 0 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 620 0 C
(115O 0 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 650 0 C (1200 0 F) and is fed to exchanger 76 and exiting as 77 at about 130 0 C (270 0 F) to be used for other purposes, such as generating domestic hot water.
The cool syngas 67 at 80 0 C (18O 0 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 0 C (270 0 F) by blower 62 and feeds the exchanger 76 which raises the syngas temperature to 650 0 C (1200 0 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.
Anther preferred embodiment of the present invention is shown in Figure 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 Figure 4, drum 14 shown in isometric has internal volume 42. It has a manually operated by means of handle 22, 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 a matrix heater 110, 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 900 0 C (1650°) 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 HOO 0 C (2010 0 F) and reacted with the steam and CO 2 to form very hot syngas exiting this central cartridge as syngas stream 47 at 900 0 C (1650°).
This very hot syngas 47 enters heat recuperator exchanger 52 that cools this syngas to 700 0 C (129O 0 F) in pipe 58 with the cooler stream 56 at 65O 0 C (1200 0 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 85O 0 C (1560 0 F) 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 850 0 C (1560 0 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 700 0 C (1290 0 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 620 0 C (115O 0 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 65O 0 C (1200°F) and is fed to exchanger 76 and exiting as 77 at about 13O 0 C (27O 0 F) to be used for other purposes, such as generating domestic hot water.
The cool syngas 67 at 8O 0 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 sorber 66 at about 13O 0 C (27O 0 F) by blower 62 and feeds via 82 the exchanger 76 which raises the syngas temperature to 650 0 C (1200 0 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 Figure 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 is 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 is to conduct experimental, small-scale pilot tests to reveal the identify 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
MEDWASTE STEAM/CO 2 GAS TEST RESULTS
H 2 Hydrogen 62.71 vol%
CO Carbon Monoxide 18.57
Polychlorinated dibenzofurans + dioxins 0.0041 ppt TEQ
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, etc.). 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 we analyzed the collected solids in the scrubber 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 was analyzed across this demister during the run 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 <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/Cθ 2 Reforming of Waste," Nat'l Hydrogen Assoc, Annual Hydrogen Conference 2006, Long Beach, Calif. Mar. 12-16, 2006.
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