Catalytic Biogas Combined Heat and Power Generator

Abstract

An apparatus and method to desulfurize a biogas containing sulfur. Since biogas is produced by an anaerobic digester from human, animal, kitchen and agriculture's wastes, Itis a short term recycled product from the photosynthesis of CO.sub.2, and has a net zero carbon emission. The sulfur compounds in the biogas can be removed by the following steps: (1) converting all sulfur compounds into H.sub.2S by the hydrogen produced from the biogas over Pt group metal catalysts; (2) adsorbing the H.sub.2S at high temperature by the regenerable Pt group metal catalyst and adsorbents. The desulfurized biogas is further converted by an ATR/CPO reformer or a steam generating reformer to produce various reformates.

Claims

1-20. (canceled)

21. An apparatus to produce a reformate containing a given H.sub.2/CH.sub.4 ratio from one or more of a biogas or hydrocarbon gas, comprising: (A) a gas storage tank configured to hold the biogas or hydrocarbon gas; (B) a catalytic H.sub.2 reformer selected from one or more of a flex-fuel catalytic ATR, a catalytic steam generating reformer or a CPO reformer to produce a reformate gas containing the given H.sub.2/CH.sub.4 ratio from the biogas or hydrocarbon gas over a Pt metal group catalyst; (C) a reformate storage tank and/or a manifold configured to store the reformate; and (D) an automatic control system including one or more devices selected from a programmable logic controller, a microprocessor, a valve, a flow controller, a thermocouple, a sensor and a pump, wherein the automatic control system is configured to provide an inlet fuel mixture to the catalytic H.sub.2 reformer, the inlet fuel mixture having at least one of 1) an O.sub.2/CH.sub.4 ratio, 2) a H.sub.2O/CH.sub.4 ratio, and 3) a (H.sub.2O+CO.sub.2)/CH.sub.4 ratio.

22. The apparatus of claim 21, comprising an optional water electrolysis device for producing H.sub.2 and O.sub.2 from water.

23. The apparatus of claim 21, wherein the Pt metal group catalyst contains at least one or more metals selected from the group consisting of a Platinum, a Palladium, a Rhodium, an Iridium and a Ruthenium metal supported on an Al.sub.2O.sub.3 powder at 0.01 to 10.0% metal content.

24. The apparatus of claim 23, wherein the Al.sub.2O.sub.3 powder contains a high temperature oxide stabilizer to provide a stabilized Al.sub.2O.sub.3, and wherein the high temperature oxide stabilizer includes one or more oxides selected from the group consisting of lanthanum, cerium, praseodymium, rhenium, zinc, tin, calcium, potassium, zirconium, an yttrium, barium, strontium, neodymium and magnesium.

25. The apparatus of claim 24, wherein the Pt metal group catalyst supported on the stabilized Al.sub.2O.sub.3 includes one or more oxides selected from the group consisting of Zn, Ni, Ce, Ce/Zr, Fe, Co, Mo, Cu, Cu/Zn, zeolite, Mn, La, Ba, Sr, Al and Si as a H.sub.2S adsorbent.

26. The apparatus of claim 23, wherein the Pt metal group catalyst is further coated on the surface of a high temperature inert carrier at 0.1 to 2500 g/ft.sup.3, and the inert carrier is selected from the group consisting of a ceramic monolith, a metallic monolith, a pellet, a wire mesh, a screen, a foam, a plate, a gauze, a silicon carbide, a static mixer and a heat exchanger.

27. The apparatus of claim 21, wherein the inlet fuel mixture contains pure oxygen, water, and one or more fuels selected from the group consisting of a natural gas, a hydrocarbon and a bio-fuel for the purpose of increasing the % (hydrogen and CO) concentration in the reformate.

28. The apparatus of claim 21, comprising a downstream IC engine/gas turbine, wherein the produced reformate from the catalytic H.sub.2 reformer, with a given H.sub.2/CH.sub.4 ratio, is used as the fuel to perform hydrogen assisted combustion by the downstream IC engine/gas turbine producing an exhaust gas.

29. The apparatus of claim 28, wherein the engine/gas turbine is connected to an electric generator to produce power as a distributed power station.

30. The apparatus of claim 29, wherein the heat in the exhaust gas is recovered as hot air and/or hot water, so that the apparatus becomes a distributed combined heat and power generator.

31. The apparatus of claim 28, wherein the biogas or hydrocarbon gas is a vaporized gas of one or more fuels selected from the group consisting of a bio-fuel, a natural gas, a LPG, a CNG, a bio-ethanol, a methanol, a gasoline, a diesel, and a bio-diesel, and wherein the produced reformate is used as the sole fuel or part of the fuel mixture for the engine/gas turbine to perform hydrogen assisted combustion.

32. The apparatus of claim 28, wherein the catalytic steam generating reformer is operably connected to at least one of the gas turbine and IC steam engine and is configured to produce high pressure steam to at least one of the gas turbine and IC steam engine, and wherein the inlet fuel mixture of the steam generating reformer operates at an O.sub.2/CH.sub.4 ratio greater than 1.0, and a H.sub.2O/CH.sub.4 ratio greater than 3.0, and at a temperature below 1000° C., and a pressure between 5 to 50 atmospheres.

33. The apparatus of claim 28, wherein the CPO reformer is configured to adjust a reformate H.sub.2/CH.sub.4 ratio as a fuel for at least one of the gas turbine and IC steam engine, and wherein the O.sub.2/CH.sub.4 ratio of the inlet fuel mixture is less than 0.80, and a (CO.sub.2+H.sub.2O)/CH.sub.4 ratio is less than 5.0.

34. The apparatus of claim 21, wherein the O.sub.2/CH.sub.4 ratio of the inlet reformer's fuel mixture is used to control a reaction path, and wherein the produced reformate is used as the fuel for one of a reformate IC engine, a gas turbine, a steam turbine and a fuel cell device to generate electricity.

Description

BRIEF DESCRIPTION OF THE DRAWING

[0038] FIG. 1: Flow Chart for a Catalytic Biogas Combined Heat and Power Generator.

[0039] FIG. 2: Flow Chart for a Regenerable Desulfurization System (identified by #8).

[0040] FIG. 3: Automatic Control Hardware Devices Consisting of One computer, One Programmable Logic Controller (PLC) and Several Input/output Interface Modules.

[0041] FIG. 4: A Control Curve for Reactants' Flow Rates as a Function of Reformate Pressure in the Storage Vessels.

DETAILED DESCRIPTION OF THE INVENTION

Description of the Preferred Embodiments

[0042] Because of the global warming and the abnormal worldwide weather pattern in recent years, it is wise to combine the renewable energy resources such as biogas, solar, wind and geothermal energies to cut down the carbon emission and to provide heat and electricity from biogas for daily living.

[0043] For this invention, a Catalytic Biogas Combined Heat and Power (CHP) Generator and method of operating this CHP generator comprises:

[0044] (1). one biogas storage tank at 1 to 100 atmospheres;

[0045] (2). one regenerable desulfurization system comprising:

[0046] a) one CPO sulfur converter for converting all sulfur compounds in the biogas over the supported Pt group metal catalyst into H.sub.2S at a temperature between 200° to 800° C., wherein the O.sub.2/C ratio of the inlet fuel mixture is between 0.05 to 0.25, and the % (H.sub.2+Steam) in the gas mixture is between 0% to 20%, and

[0047] b) one high temperature regenerable adsorbent bed at a temperature between 300° to 900° C., wherein the supported Pt group metal catalyst containing one or more oxides selected from the group of Ni, Cu, Fe, Co, Mo, Zn, Cu/Zn, Ce, Ce/Zr, Al, Mn and the mixture thereof are used to react/adsorb the H.sub.2S on the catalyst,

[0048] c) one engine exhaust gas with <2% excess O.sub.2 or a hot gas containing <5% O.sub.2 and <2% CH.sub.4 for catalyst regeneration, wherein the reacted/adsorbed sulfur on said supported Pt metal group catalyst is converted into odorless SO.sub.2 at a temperature between 300° to 900° C.;

[0049] (3). one or more catalytic biogas reformers for producing various type of reformate gas over the Pt group metal catalysts by controlling the O.sub.2/CH.sub.4 ratio of the reformer's inlet fuel mixture selected from:

[0050] a) one flex-fuel catalytic ATR reformer to produce H.sub.2 reformate as a fuel for the IC engine/gas turbine, fuel cell electric generator or H.sub.2 storage, wherein the reformer's inlet fuel mixture contains O.sub.2/CH.sub.4<0.80 and (H.sub.2O+CO.sub.2)/CH.sub.4<10.0;

[0051] b) one steam generating reformer to produce high pressure steam for a steam turbine/steam engine, wherein the inlet fuel mixture of the generator is operated at O.sub.2/CH.sub.4 ratio >1.0, H.sub.2O/CH.sub.4 ratio >3.0 and at a temperature below 1000° C. and a pressure between 5 to 50 atmospheres, and

[0052] c) one CPO reformer to adjust the reformate's H.sub.2/CH.sub.4 ratio as a fuel for the reformate engine/gas turbine, wherein the O.sub.2/C ratio of the biogas inlet fuel mixture is <0.80, and the (CO.sub.2+H.sub.2O)/CH.sub.4 is <5.0,

[0053] (4). one or more power devices selected from the group of reformate engine, gas/steam turbine, steam engine, IC engine and fuel cell device for utilizing the proper reformate produced from the reformers described in (3) to produce power, wherein they are used to drive one or more electric generators to generate electricity;

[0054] (5). several heat exchangers for recovering heat from the reformate and/or from the engine/gas turbine's exhaust gas, wherein the produced hot air and/or hot water from the heat exchangers are available for local residents and/or for general applications;

[0055] (6). one electrolyzer for dissociating DI water to produce H.sub.2 and O.sub.2, wherein the generator's self-generated electricity, and/or the electricity generated from a solar panel, a wind turbine, or an electric grid are used for the electrolysis of water;

[0056] (7). several storage tanks for storing the reformate, H.sub.2 and O.sub.2 gases at 1 to 100 atmospheres, wherein each stored gas is used for general application; and

[0057] (8). an automatic control system consisting of a control computer/micro processor, valves, flow controllers, thermocouples, sensors, pumps and control software, wherein the controlling system is used to deliver the specific inlet fuel mixture to each reformers at the specific O.sub.2/CH.sub.4, H.sub.2O/CH.sub.4, (H.sub.2O+CO.sub.2)/CH.sub.4 ratios, and also to control the reactions at the specific temperature and pressure.

[0058] Producing Hydrogen from Hydrocarbons and Bio-Fuels:

[0059] In the 1980s, U.S. Pat. No. 4,522,894 first introduced the monolithic Pt/Pd/Al.sub.2O.sub.3 catalyst to produce H.sub.2 and CO by the catalytic partial oxidation reactions of the sulfur containing commercial diesel fuel, and also to provide heat for the following Ni/Al.sub.2O.sub.3 or Pt/Rh/Al.sub.2O.sub.3 pellet catalyst to produce more H.sub.2 and CO by catalytic steam reforming (SR) reactions. Because of its extremely rapid reaction rate and an excellent selectivity, the O.sub.2 in the reformer's inlet fuel mixture can be converted completely in less than 36 milliseconds (space velocity >100,000/hr @STP), and it is also found that the reacted diesel oil was mostly converted selectively into the main H.sub.2 and CO products, but not the unwanted full combustion products of H.sub.2O and CO.sub.2. Therefore, it was concluded that the monolithic Pt/Pd/Al.sub.2O.sub.3 catalyst is an excellent partial oxidation catalyst. Later, in the 2000s, further additional developments worldwide had found that the unsupported or the supported monolithic or pellet Pt group metal catalysts were all excellent partial oxidation catalysts for producing H.sub.2 and CO from fuels such as natural gas, LPG, vaporized hydrocarbons and bio-fuels.

[0060] According to U.S. Pat. Nos. 4,522,894 and 9,440,851, the Pt group metal catalysts could be prepared by impregnating one or more of Pt group metal solutions at a given concentration into an Al.sub.2O.sub.3 power, and obtain a catalyzed washcoat powder at 0.01 to 10.0% metal content. The Al.sub.2O.sub.3 power has surface area between 50 to 600 m2/g, and also contains high temperature oxide stabilizer such as one or more oxides selected from the group of lanthanum, cerium, praseodymium, rhenium, zinc, tin, calcium, potassium, zirconium, yttrium, barium, strontium, neodymium, magnesium and the mixture thereof. Furthermore, one or more oxide powders, which are selected from the group of Ni, Cu, Fe, Co, Mo, Zn, Cu/Zn, Ce, Ce/Zr, Al, Mn and the mixture thereof, can be added and mixed with the above catalyzed Pt group washcoat powder as the H.sub.2S adsorbents, and these H.sub.2S adsorbents are either unsupported oxides or oxides supported on the above stabilized Al.sub.2O.sub.3. Then, the combined washcoat powders are coated on the surface of an high temperature inert carrier such as the ceramic monolithic support to obtain the total Pt group metal loading between 0.1 to 2500 g/ft3.

[0061] The inert monolith support was a ceramic carrier which contains 10 to 1200 CPI. The other suitable inert catalyst support can be a ceramic monolith, metallic monolith, pellet, wire mesh, screen, foam, plate, silicon carbide, static mixer etc. For the mobile devices/equipments, monolithic catalyst supports are preferred. But the monolith, pellet, gauze, wire mesh, screen, foam, plate, static mixer, heat exchanger or other shapes of catalyst's supports can satisfactory be used for stationary devices/equipments.

[0062] To be used as the catalyzed washcoat support, the inert materials must be capable of sustaining a temperature between 500° C. to 1200° C. in a rich or lean atmosphere without losing its surface area, strength and shape. For example, The inert ceramic substrate can be made of alumina, alumina-silica, alumina-silica-titania, mullite, cordierite, zirconia, zirconia-ceria, zirconia spinel, zirconia-mullite or silicon carbide, and the metallic substrate can be made of Fecralloy, Kanthal, stainless steel and other high temperature alloys.

[0063] Biogas ATR Reformer:

[0064] Due to the fact that the biogas contains large amount of CO.sub.2, and CO.sub.2 has high heat capacity, CO.sub.2 can be used to replace water in the inlet fuel mixture for controlling the reformer's temperature below 1200° C. In other words, the composition of the inlet reformer's biogas fuel mixture should be modified, and the H.sub.2O/CH.sub.4 ratio in the inlet fuel mixture can be decreased, and the CO.sub.2/CH.sub.4 ratio can be increased from those described in U.S. Pat. No. 9,440,851. For this Biogas CHP Generator, the O.sub.2/CH.sub.4 of the inlet reformer fuel mixture should be maintained <0.80, and the (H.sub.2O+CO.sub.2)/CH.sub.4 ratio between <10.0. In general, the reformer's temperature should be controlled below 1200° C. to maintain high methane conversion activity, and also to extend catalysts' service life without thermal deactivation and coke formation.

[0065] Additionally, the preferred operating condition without coke formation for this biogas CHP generator is to perform the reforming reactions, and to generate electricity under a steady (stationary) condition. Therefore, the reactants' flow rates. the inlet O.sub.2/CH.sub.4 ratio, the inlet (CO.sub.2+H.sub.2O)/CH.sub.4 ratio and the reactor temperature are mostly controlled under a given steady state operating condition, and avoid any sudden abrupt change of each reactant's flow rate.

[0066] According to U.S. Pat. No. 9,440,851, all hydrocarbons which can be vaporized such as natural gas, LPG, CNG, biogas, bio-ethanol, methanol, gasoline, diesel, bio-diesel and other hydrocarbons, can be converted in this reformer to produce H.sub.2 and CO reformate by the Pt group metal catalysts under a given temperature and pressure. Therefore, in emergency or any special occasions, any one of the above fuels and/or their fuel mixture can be used as fuel for this apparatus. In other words, in addition to biogas, this Biogas CHP Generator is a multiple fuel CHP generator.

[0067] Reformate IC Engine/Gas Turbine:

[0068] According to U.S. Pat. Nos. 4,522,894 and 9,440,851, if the O.sub.2/C ratio of the inlet reformer's fuel mixture is below 0.50 at a space velocity >100,000/hr (@STP), all O.sub.2 in the mixture will completely be converted by the Pt group metal catalysts to become part of the reformed gas, while the conversion of the hydrocarbon fuel will be less than 100%. Therefore, the % biogas conversion can be controlled by adjusting the O.sub.2/CH.sub.4 ratio of the inlet fuel mixture between 0.05 to 0.50. In other words, the % methane remaining in the reformed gas can be controlled by adjusting the O.sub.2/CH.sub.4 ratio and, thus, can produce various H.sub.2/CH.sub.4 ratios of the Hythane gas (i.e. methane and H.sub.2 mixture) for the downstream IC engine/gas turbine. As mentioned previously in U.S. Pat. No. 7,721,682, herein incorporated by reference, the Hythane gas mixture can improve the engine's thermal efficiency and can reduce the NOx pollution.

[0069] Catalytic High Pressure Steam Generating Reformer:

[0070] According to reaction (4), bio-methane can be combusted completely into CO.sub.2 and H.sub.2O, and the total reaction heat produced by the reaction can then be used completely to vaporize water and to generate high pressure reformate containing high % steam. This reformate stream is then used via pressure difference to drive a steam turbine, a turbocharger or a steam engine, which in turn will drive an electric generator to generate electricity (U.S. Pat. No. 8,397,509). Therefore, this catalytic reformer can be used to replace a traditional power plant's shell and tube boiler for high pressure steam generation. In addition, complete catalytic combustion of bio-methane with excess oxygen at a temperature below 1000° C. will not produce CH.sub.4 and NOx pollutants, and the total reaction heat is used completely for steam generation. In other words, there are no waste heat loss through the flue gas, and the system's thermal efficiency is improved.

[0071] Flow Control Curves:

[0072] One or more flow control curves can be used to define each reformer's reactant flow rate and the total reformer's output flow capacity as a function of pressure in the reformate's storage vessels. In other words, a given flow control curve is used to regulate each reactant's flow rate, to define the O.sub.2/CH.sub.4 and (CO.sub.2+H.sub.2O)/CH.sub.4 ratios of the inlet fuel mixture, to define the dry reformate composition, to decide the reformer's start-up and shutdown, to regulate the reformer's operating temperature and pressure, and to determine the total reformer's reformate flow output. Briefly, according to the location on a given control curve, every single point on a given control curve can supply a group of pre-calibrated set points for all flow meters/controllers, the operating temperature and pressure, and these set points are down loaded from the control computer and/or the microprocessors to the programmable Logic Controller (PLC) for the purpose of controlling each reactant's flow rate, and the reformer's temperature and pressure; Once each reactant's flow rate is fixed according to the pre-calibrated set point, the O.sub.2/CH.sub.4 and the (H.sub.2O+CO.sub.2)/CH.sub.4 ratios of the inlet fuel mixture are fixed, and the total flow rate of the inlet fuel mixture is fixed. Subsequently, after complete conversion of the inlet CH.sub.4 and O.sub.2 by the Pt group metal catalysts in the biogas reformer at a given reaction temperature and pressure, the total reformate flow output produced and the dry gas composition are determined.

[0073] In addition, if several multiple points on the same control curve are pre-calibrated at the same the O.sub.2/CH.sub.4 and the (H.sub.2O+CO.sub.2)/CH.sub.4 ratios, but at different flow rates, these points are capable of producing a series of different reformate flow outputs with the same dry gas composition. Furthermore, multiple pre-calibrated control curves for other fuels are used to provide different reformer's inlet fuel mixtures and, thus, would produce by the same reformer the dry reformate from various hydrocarbon fuels and/or bio-fuels with different gas composition. In other words, by selecting the proper control curve, this reformer can operate effectively and efficiently with all potential fuels, and the biogas CHP generator can be a multiple fuel CHP generator. Therefore, it can be very useful in an emergency situation when biogas is not available or in short supply.

[0074] Catalytic De-Sulfurization Process:

[0075] If the biogas contains high % sulfur compounds and/or other various containments, one low temperature pre-desulfurizer at a temperature between −25° to 50° C. can be installed between the biogas storage tank and the CPO sulfur converter. The regenerable supported Pt group metal catalysts is preferred to be used in this pre-desulfurizer, and it comprises: (1). one or more regenerable Pt group metal catalysts, which comprise one or more metals of Pt, Pd, Rh, Ir, Ru, Os and mixture thereof, are supported on the stabilized Al.sub.2O.sub.3, and (2). one or more oxides selected from the group consisting of Zn, Ni, Ce, Ce/Zr, Fe, Co, Mo, Cu, Cu/Zn, zeolite, Mn, La, Ba, Sr, Al, Si and mixture thereof, wherein these oxides can be unsupported or supported on the stabilized Al.sub.2O.sub.3.

[0076] As described previously in U.S. Pat. No. 4,522,894, all organic sulfur compounds can be converted into H.sub.2S by the hydrogen produced inside the ATR reformer, and the produced H.sub.2S can be adsorbed and removed from the reformate by the downstream ZnO bed at a temperature between 300° to 400° C. However, under the influence of high % water/steam, the capacity of adsorbing H.sub.2S by ZnO will be decreased rapidly from 10-20 gS/100 g to 0.1 gS/100 g, and lost its efficiency to remove H.sub.2S from the stream (Farrauto, R. et al., Annu. Rev. Mater. Res. 2003, Vol. 33, Page 1-27). Therefore, in order to improve the H.sub.2S adsorption capacity, the O.sub.2/CH.sub.4 ratio of the inlet fuel mixture to the CPO sulfur converter in this regenerable desulfurization system is controlled at a value between 0.05 to 0.25, and the % (H.sub.2+Steam) between 0 to 20%.

[0077] At a value of the O.sub.2/CH.sub.4 ratio between 0.05 and 0.25, enough amount of O.sub.2 is provided to convert all the sulfur compounds in the inlet fuel mixture into H.sub.2S by the hydrogen produced from the CPO reactions of biogas. Then, the produced H.sub.2S is removed effectively in the following adsorption bed at a temperature between 200° to 800° C. It is known that sulfur compounds can be adsorbed strongly on the oxide surface of Ni, Cu, Fe, Co, Mo, Zn, Cu/Zn, Ce, Ce/Zr, Al, Mn and the mixture thereof, and that the Pt group metal catalyst can convert the adsorbed/reacted sulfur into SO.sub.2. Therefore, as discussed previously, this high temperature regenerable adsorbent bed comprises one or more regenerable supported Pt group metal catalysts, which also contains one or more oxides as H.sub.2S adsorbents. However, the catalyst must be kept below 900° C. to avoid thermal deactivation of the Pt group catalyst and the H.sub.2S adsorbents.

[0078] Subsequently, the de-sulfurized biogas is then used by one or more CPO, ATR and steam generating reformers to produce various reformate composition according to the demand of the desired applications, as shown in FIG. 1.

[0079] The adsorbed/reacted sulfur on the catalyst's washcoat (i.e. oxide) can be regenerated by passing either an exhaust gas with <2% excess O.sub.2, or a hot gas containing <5% O.sub.2 and <2% CH.sub.4 over the Pt group metal catalysts, and can be released as SO.sub.2 at a temperature between 300° to 900° C. If the engine's exhaust gas is below 300° C., it is necessary to inject both air/O.sub.2 and CH.sub.4 simultaneously, and uses the CPO reaction heat to maintain the temperature during the regeneration. However, most of the time, the engine's exhaust gas temperature is high enough to do the regeneration and, in this case, only O.sub.2/air is required to be injected into the exhaust gas.

[0080] During regeneration, the adsorbed/reacted sulfur will be converted into SO.sub.2, which can either be vented into atmosphere, or be removed/absorbed by the traditional lime/limestone, water, or caustic soda wash techniques.

[0081] Due to the fact that every adsorbent has its own unique adsorbing capacity (i.e. limitation) for removing a specific contaminant compound, a combination of several different adsorbents operated at different temperatures is frequently required to remove completely the contaminants from a given fuel mixture, and the adsorbents are most likely required to be changed when a new fuel with different sulfur compounds is admitted into the inlet fuel mixture. However, if all organic sulfur compounds in the inlet fuel mixture are converted catalytically into H.sub.2S, the removal of all sulfur compounds becomes a simpler task of removing H.sub.2S from the reformate stream. Furthermore, since the supported Pt group catalysts used here can be regenerated for continuous application, this new sulfur removal technology becomes very convenient, and the catalyst/adsorbent can have a longer service life without being replaced and/or being land filled. Therefore, it has advantages over the current biogas non-regenerable H.sub.2S removal techniques described previously.

[0082] To avoid deactivation of the electrodes for the fuel cell electric generators, such as PEMFC and SOFC, the sulfur level of the purified biogas must be maintained below 10 ppbv, while it is satisfactory to maintain below 25 ppmv for an IC engine/gas turbines. In other words, the degree of desulfurization of the biogas will depend on the intended application.

[0083] To insure the sulfur content of the purified biogas is constantly maintained below 10 ppbv, a polishing desulfurizer bed, which is controlled at a temperature between −25° to 600° C., can be installed between the high temperature regenerable adsorbent bed and the ATR/CPO reformer. This polishing desulfurizer bed comprises: (1). one or more regenerable Pt group metal catalysts supported on the stabilized Al.sub.2O.sub.3, and (2). one or more oxides selected from the group consisting of Zn, Ni, Ce, Ce/Zr, Fe, Co, Mo, Cu, Cu/Zn, zeolite, Mn, La, Ba, Sr, Al, Si and mixture thereof. The main purpose of this polishing desulfurizer is to clean up the residual sulfur compounds before the reformers with oxide adsorbents at a lower space velocity (i.e. larger adsorbent reactor volume).

[0084] Other fuels, such as natural gas, LPG, bio-ethanol, methanol, gasoline, diesel, bio-diesel, and other vaporized organic compounds, can utilize this sulfur removal methods and this Catalytic Biogas CHP Generator to remove all sulfur compounds from the fuel mixture. In other words, if the O.sub.2/C ratio in the inlet fuel mixture of this CPO reformer is controlled at a value between 0.05 to 0.25 (i.e. C is the fuel carbon, does not include C in CO.sub.2), and the % (H.sub.2+H.sub.2O) is between 0% to 20%, all organic sulfur compounds in any fuels mentioned previously will be converted into H.sub.2S by the H.sub.2 produced by the CPO reaction, and the H.sub.2S can be removed by the subsequent high temperature regenerable adsorbent bed and, if necessary, by the additional polishing desulfurizer bed.

[0085] Exemplary Embodiments Described

[0086] FIG. 1 is the flow chart for the Catalytic Biogas CHP Generator of this invention. As shown in FIG. 1. the biogas which is generated by an anaerobic digester can be stored in tank #10, and the excess water, H.sub.2S and other contaminants in the biogas will first be treated in the desulfurization system #8. As shown in FIG. 2, the desulfurization system #8 comprises: (a). one low temperature pre-desulfurizer (#19); (b). one CPO sulfur converter (#20); (c). two parallel high temperature H.sub.2S adsorbent beds (#21A &21B); (d). one polishing desulfurizer (#21C). Here, the low temperature pre-sulfurizer (#19) is used to partially remove the H.sub.2S, moisture and other contaminants from the biogas; CPO converter #20 is used to convert all remaining sulfur compounds into H.sub.2S; the two parallel high temperature adsorbent bed #21A/21B are used to remove the H.sub.2S from the biogas down to about 25 ppm level for the IC reformate engines, and the polishing desulfurizer (#21C) is used to remove the H.sub.2S in the reformate from about 25 ppm down to 10 ppbv level for the fuel cell devices. Briefly, the CPO sulfur converter #20 and the adsorbent bed #21A and #21B are the main units for removing the sulfur compounds from the biogas in this desulfurization system #8. But the pre-desulfurizer #19 and the polishing desulfurizer #21C are optional units, which are used only when the system requires additional treatments to either remove extra containments from the biogas, or to meet the more demanding sulfur requirement of the downstream fuel cell devices.

[0087] As shown in FIG. 2, the dry desulfurized biogas from the desulfurization system #8 is compressed and is stored in tank #24A at a pressure between 1 to 100 atmospheres. It can then be injected directly with additional amount of water and air/O.sub.2 into the following CPO reformer (#22) to provide a fuel mixture at a given O.sub.2/CH.sub.4 and H.sub.2O/CH.sub.4 ratio. This CPO reformer #22 in the system can adjust the H.sub.2/CH.sub.4 ratio to provide a given Hythane gas for the downstream reformate engine #6. In addition, the desulfurized biogas can be injected with additional amount of air/O.sub.2 and water at a specified O.sub.2/CH.sub.4 and H.sub.2O/CH.sub.4 ratio to the following ATR or steam generating reformer (#9), and the reformers will produce the reformate according the fuel mixture's O.sub.2/CH.sub.4 ratio for the downstream power generating devices, such as IC engine, gas turbine, steam turbine/engine, fuel cell electric generators et. al.

[0088] Also, shown in FIG. 2, the exhaust gas from the reformate engine #6 can be used to the regenerate the Pt group metal catalysts which are used in the pre-desulfurizer #19, the high temperature H.sub.2S adsorbent bed #21A and #21B, and the polishing desulfurizer #210 at a temperature between 300° and 900° C. In this case, the exhaust gas with air injection to <2% O.sub.2 is required to convert the adsorbed/reacted sulfur on the catalyst adsorbents into SO.sub.2. However, if the temperature of the exhaust gas is not high enough, it is necessary to inject both biogas and air to obtain <5% CH.sub.4 and <2% O.sub.2 concentration, and to produce reaction heats over the Pt group metal catalyst for maintaining the regeneration temperature. Furthermore, any hot gas containing <5% CH.sub.4 and <2% O.sub.2 can also be used to replace the exhaust gas for the catalyst regeneration.

[0089] As shown in FIG. 1, in addition to provide electricity to the CHP generator's PLC controller unit #3, the excess electricity from reformate engine and electric generator #6 can be combined with wind power/solar power #1, and/or the electricity from the general distribution grid #2 to perform electrolysis of DI water in vessel #5. The H.sub.2 and O.sub.2 so produced can be stored separately in tanks #4 and #7 respectively. The H.sub.2 in tank #4 can be used to assist the lean fuel combustion at high compression ratio inside the reformate engine's cylinder, which can improve its thermal efficiency; The O.sub.2 in tank #7 can be used to replace air as the reformer's oxidant in the ATR reformer's inlet fuel mixture, which can improve the % (H.sub.2+CO) concentration in the reformate to be close to that produced by a steam reformer, and can make the separation of H.sub.2 from other gases easier.

[0090] When the reformer is first started, the biogas and the O.sub.h fuel mixture must reach a minimum temperature (i.e. light-off temperature) between 200 to 350° C. to initiate and to accelerate the catalytic partial oxidation reactions of bio-methane. Therefore, the biogas fuel mixture must be preheated by one of the following three methods: (1). utilize the exhaust gas from engine #6; (2). utilize the H.sub.2 and O.sub.2 gases in tanks #4 and #7 to generate the oxidation reaction heat by passing them through the Pt group catalyst bed, and (3). utilize an igniter to ignite the biogas and air/O.sub.2 flame. Because H.sub.2 and O.sub.2 can react with each other to produce the reaction heat over the Pt group metal catalyst at the room temperature, using the produced reformate or the engine's exhaust gas is an excellent method to preheat the reformer. After the CPO reaction is initialized, the CPO reaction of bio-methane can generate enough reaction heat to keep the catalyst itself above its minimum reaction temperature (i.e. light-off temperature), and the reactions can be performed in an adiabatic condition.

[0091] After the ATR and water gas shift reformer #9, the reformate can pass through heat exchanger #11, and the cooled dry gas is stored in tank #14. The IC engine/gas turbine #15 can then use the stored reformate to drive an electric generator #16 to generate electricity. Finally, the exhaust gas from #15 can passed through #17 heat exchanger to generate hot water or hot air to provide heat for local residents. However, if a steam generating reformer is used to replace the ATR reformer in #9, the high pressure reformate containing high % steam can be used to drive a steam turbine/engine, and an electric generator to generate electricity. After the heat exchanger #11, the condensed water can be recycle back to #9 for reuse according to U.S. Pat. No. 8,397,509, and hot water and hot air are also generated from heat exchanger #11.

[0092] FIG. 3 is the brain of the control system, and it is shown as FIG. 3A in FIG. 1. Here, a programmable logic controller (PLC) can communicate with a PC laptop computer via a RS-232 or an Ethernet cable, and the PLC can communicate with the input/output modules which connect directly to the automatic controlled devices. A control software is stored in the PC. As a group of the pre-calibrated set points is down loaded from the PC to the CPU inside the PLC, the CPU will then transmit the control signals to the respective control channels of the output module and, then, to the flow controllers to perform the actual flow rate and/or temperature control. In other words, when a given output module receives the set points, it will give the set point signals to each controlling device such as flow controllers, solenoid valves, oxygen sensor/regulator, temperature PID loops, and other instrument and devices, and the controlling devices would control flow rate and temperature according to the set points received. Similarly, each device can transmits its current status and any update information from the input modules to the PC computer via the reverse signal transmission loops.

[0093] FIG. 4 is an actual control curve, which indicates the % reformate flow output as a function of the pressure in the storage vessel. Briefly, every point on a given control curve includes a group of pre-calibrated set points for each flow controller and for the operating temperature and pressure. Therefore, each point will provide the fuel mixture with a given pre-calibrated O.sub.2/CH.sub.4 and (H.sub.2O+CO.sub.2)/CH.sub.4 ratios, the pre-calibrated reactants' flow rate and the total reformate flow output flow. In other words, a given group of set points will be down loaded from the control PC to the PLC, these pre-calibrated flow set points will be transmitted individually to each flow controller and the flow controller in the system will adjust each reactant's flow rate. By combining and mixing each reactant's flow rate together at the reformer's inlet, a fuel mixture with the specified pre-calibrated O.sub.2/CH.sub.4 and (H.sub.2O+CO.sub.2)/CH.sub.4 ratios can be obtained. If every point in the same control curve is pre-calibrated to give the fuel mixture with the same O.sub.2/CH.sub.4 and (H.sub.2O+CO.sub.2)/CH.sub.4 ratios, but with different flow rates, every point on the same control curve will provide the same reformate composition but with different flow output. Similarly, different pre-calibrated control curve can provide a biogas fuel mixture with different O.sub.2/CH.sub.4 and (H.sub.2O+CO.sub.2)/CH.sub.4 ratios and, thus, different reformate composition and flow output.

[0094] For other hydrocarbons and bio-fuels, similar pre-calibrated control curve can provide a fuel mixture with a given O.sub.2/CH.sub.4 and (H.sub.2O+CO.sub.2)/CH.sub.4 ratio and, thus, a given reformate composition and flow output can be obtained.

[0095] For a small system, the combination of a PC and a PLC can be replaced with a powerful microprocessor, or by a PC which is equipped with the necessary input/output modules to accomplish the same control strategy.