JP2009230927A - Fuel cell system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve a thermal efficiency of a fuel cell system formed by combining a reformer and a fuel cell. <P>SOLUTION: This fuel cell system is equipped with: an internal heating type reformer 2 to generate a hydrogen-rich reformed gas from a mixture of steam and fuel gas; a fuel cell 7 to generate power using the reformed gas obtained in the reformer 2 as fuel; and a cooling water system 9 to cool the fuel cell 7. The fuel cell 7 is formed to be operated in a temperature range evaporating a part of the cooling water circulating in the cooling water system 9, a steam separator 30 to separate steam from the cooling water is provided in the cooling water system 9, and a steam supply system 35 to mix the steam separated in the steam separator 30 with a raw material gas and supply it to the reformer 2 is provided. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an internal heating type reformer that generates a hydrogen-rich reformed gas from a mixture of water vapor and fuel gas, a fuel cell that generates electricity using the reformed gas obtained by the reformer, and a fuel cell. The present invention relates to a fuel cell system provided with a cooling water system for cooling the fuel.

  A fuel cell system including a reformer that generates hydrogen-rich reformed gas from a mixture of water vapor and fuel gas, and a fuel cell that generates electricity using the hydrogen-rich reformed gas generated by the reformer as fuel is known. Yes. There are various types of fuel cells. Among them, a polymer electrolyte fuel cell (PEFC) is considered promising.

  Patent Document 1 discloses a reformer that generates a hydrogen-rich reformed gas. This reformer reforms steam in the presence of a reforming catalyst into a steam generating means for combusting fuel to generate steam, and a raw material-steam mixture obtained by mixing the steam generated by the steam generating means and the source gas. An internal heating type reformer that generates a hydrogen-rich reformed gas is provided. In addition, city gas, natural gas, methane gas, etc. are used as source gas.

  There are two types of reformers: an external heating type and an internal heating type. The external heating type is a system in which the wall of the reformer is heated from the outside with combustion gas generated by a combustion device such as a burner, and heat necessary for the reforming reaction is supplied into the reformer through the wall. In the internal heating type, a partial oxidation reaction layer filled with an oxidation catalyst is provided on the raw material supply side of the reformer, air is supplied to oxidize part of the raw material gas, and the oxidation heat is required for the reforming reaction. It is a method used as heat. Therefore, when an internal heating type reformer is employed, a combustion apparatus using a burner or the like is used only for the steam generating means for supplying steam to the reformer.

  In the case of a fuel cell system that generates electricity using a general stationary polymer electrolyte fuel cell with an operating temperature of about 70 ° C., the current technology achieves a power generation efficiency of 33% (HHV) and a thermal efficiency of 45% (HHV). is doing. However, this thermal efficiency is achieved by recovering the exhaust heat of the fuel cell from its cooling water. However, recovering the exhaust heat at a low temperature of about 70 ° C. of the fuel cell is limited to a system in combination with a hot water supply facility. ing.

  FIG. 4 is a process flow diagram showing an example of a fuel cell system that combines a conventional reformer, a solid polymer fuel cell, and hot water supply equipment. The reformer 1 in this example includes an external heating type reformer 2, a steam generating means 3, a mixer 4 composed of an ejector, a shift converter 5 and a CO reducer (PROX) 6.

  A solid polymer fuel cell 7 shown in FIG. 4 is a general stationary polymer electrolyte fuel cell having an operating temperature of about 70 ° C., and is rich in hydrogen reforming supplied from the reformer 1. Gas and air are reacted to generate electric power, and the electric power is supplied to the home power supply system via the inverter 8. In order to cool the fuel cell 7 and recover the exhaust heat, the cooling water of the cooling water system 9 flows inside the fuel cell 7.

  The cooling water system 9 includes a cooling water tank 10, a circulation pipe 11 and a pump 12, and a hot water storage tank 13 is provided in the middle of the circulation pipe 11. When the pump 12 is operated, the cooling water in the cooling water tank 10 is supplied to the fuel cell 7 through the circulation pipe 11, and the cooling water heated by exchanging heat in the fuel cell 7 is recovered in the hot water storage tank 13 and is stored in the cooling water tank 10. Return.

  On the other hand, since the anode exhaust gas discharged from the anode of the fuel cell 7 contains about 20% of hydrogen, it is supplied to the reformer 1 via the pipe 14 and used as a heat source. Specifically, the anode exhaust gas (and the air from the pipe 16) is supplied to the burner 15 that heats the steam generating means 3 and the external heating type reformer 2 constituting the reformer 1 respectively.

  Water such as pure water is supplied to the water vapor generating means 3 through a pump 17 and a pipe 18. In the water vapor generating means 3, water is heated by the combustion of the burner 15 to generate water vapor, and the water vapor is supplied to the mixer 4. The mixer 4 sucks the raw material gas flowing from the pipe 19 by the suction force of the supplied water vapor, and the raw material-water vapor mixture to be generated is supplied to the reformer 2. The raw material gas is supplied to the mixer 4 through the pipe 19 after the sulfur component is removed by the desulfurizer 20.

  In the reformer 2, the raw material gas is steam reformed in the presence of the reforming catalyst to generate a hydrogen-rich reformed gas. The generated reformed gas is supplied to a CO reducer 6 after CO (carbon monoxide) is removed by a shift converter 5 equipped with a shift catalyst, and after remaining CO is slightly reduced to ppm order. It is supplied to the fuel cell 7.

  FIG. 5 is a process flow diagram showing another example of a fuel cell system in which a conventional reformer, a solid polymer fuel cell, and a hot water supply facility are combined. The only difference between this example and the example of FIG. 4 is that the reformer constituting the reformer 1 is the internal heating type reformer 2, and the rest of the configuration is the same. Accordingly, the same parts are denoted by the same reference numerals, and redundant description is omitted.

  As described above, the internal heating type reformer 2 is provided with a partial oxidation reaction layer filled with an oxidation catalyst on the raw material supply side of the reformer, and supplies air to oxidize a part of the raw material gas. Since the oxidation heat is used as heat necessary for the reforming reaction, the burner 15 that burns the anode exhaust gas heats only the steam generation means 3. On the other hand, the oxidizing air of the reformer 2 is supplied from the pipe 21.

JP 2004-155650 A

  In the conventional fuel cell system in which the reformer 1 as shown in FIG. 4 or FIG. 5, the fuel cell 7, and the hot water supply facility such as the hot water storage tank 13 are combined, in order to take advantage of the effectiveness of the system, There is a problem that a fuel cell power generation pattern (or power generation operation pattern) that conforms to or follows demand fluctuations must be adopted.

  Specifically, taking a 1KW class fuel cell system for home power generation that is currently undergoing a large-scale demonstration test in Japan as an example, the hot water for a day consumed by a standard household is stored in a hot water tank. Since the heating time required for raising the temperature to the predetermined temperature may be about half a day, the operating rate of the fuel cell system adapted to the heating time must be lowered. Furthermore, the operating rate of the fuel cell system is further lowered in the summer when there is little demand for hot water, and such a low operating rate is one of the obstacles to the spread of stationary fuel cell systems. .

  Furthermore, in the conventional fuel cell system, since water vapor is generated from the anode exhaust gas of the fuel cell, the anode exhaust gas cannot be used as a heat source for other heat load equipment. Accordingly, an object of the present invention is to solve such problems in the conventional fuel cell system, and to provide a new fuel cell system therefor.

  The fuel cell system of the present invention that solves the above problems includes an internally heated reformer that generates hydrogen-rich reformed gas from a mixture of water vapor and fuel gas, and reformed gas obtained by the reformer. The fuel cell system includes a fuel cell that generates power as fuel and a cooling water system that cools the fuel cell. The fuel cell is configured to operate in a temperature range in which a part of the cooling water circulating in the cooling water system can be evaporated, and a steam separator that separates the water vapor generated by evaporation in the cooling water system from the cooling water And a steam supply system for mixing the steam separated by the steam separator with a raw material gas and supplying the mixture to the reformer (Claim 1).

  In the fuel cell system, the anode exhaust gas of the fuel cell can be supplied to a heat load facility (claim 2).

  The heat load equipment is a gas heat pump type air conditioning equipment, and the anode exhaust gas can be configured to be supplied as a fuel for a hydrogen engine constituting the gas heat pump type air conditioning equipment.

  The heat load facility is an absorption gas cooling / heating facility, and the anode exhaust gas can be configured to be supplied as fuel for regenerator heating of the absorption gas cooling / heating facility.

  The heat load facility is a biomass ethanol production facility, and the anode exhaust gas can be configured to be supplied as a fuel for heating the biomass ethanol production facility (Claim 5).

  In the fuel cell system provided with the biomass ethanol production facility, a water vapor supply system for supplying the water vapor separated by the steam separator as a heat source of the biomass ethanol production facility can be provided.

  In the fuel cell system provided with the biomass ethanol production facility, at least a part of the ethanol generated in the biomass ethanol production facility can be supplied to the reformer as a raw material gas.

  According to the fuel cell system of the present invention, the temperature range in which the fuel cell can evaporate a part of the cooling water circulating in the cooling water system, for example, a medium temperature of 100 ° C. or higher, preferably 150 ° C. or higher, A steam supply system is provided that is configured to operate in a high temperature range and mixes the steam separated by the steam separator provided in the cooling water system of the fuel cell with the raw material gas and supplies it to the reformer. It has been.

  If comprised in this way, since water vapor | steam can be supplied to a reformer using the exhaust heat of a fuel cell, the fuel consumption for water vapor | steam generation | occurrence | production becomes substantially unnecessary. Furthermore, since the anode exhaust gas of the fuel cell does not have to be consumed for generating steam, it can be used as a heat source for other heat load equipment. Therefore, it becomes possible to construct a fuel cell system having high thermal efficiency. Furthermore, since the steam separator in the cooling water system has a kind of buffer function, the steam supply by the steam supply system is not greatly affected by temperature fluctuations in the cooling water system. Therefore, it is possible to independently control the amount of steam supplied to the reformer without being affected by changes in power demand.

  If the fuel cell system is configured to supply the anode exhaust gas of the fuel cell to a heat load facility as described in claim 2, it is possible to construct a fuel cell system having high thermal efficiency.

  According to a third aspect of the present invention, when the heat load facility is a gas heat pump type air conditioner, the fuel of the hydrogen engine constituting the gas heat pump type air conditioner can be covered with the anode exhaust gas.

  As described in claim 4, when the heat load facility is an absorption gas cooling / heating facility, fuel for regenerator heating of the absorption gas cooling / heating facility can be covered by the anode exhaust gas.

  As described in claim 5, when the heat load facility is a biomass ethanol production facility, fuel for heating the biomass ethanol production facility can be covered with the anode exhaust gas.

  In the fuel cell system provided with the biomass ethanol production facility, a water vapor supply system for supplying the water vapor separated by the steam separator as a heat source of the biomass ethanol production facility may be provided as described in claim 6. it can. With this configuration, the thermal efficiency of the fuel cell system can be further improved.

  The fuel cell system provided with the biomass ethanol production facility may be configured to supply at least a part of the ethanol generated in the biomass ethanol production facility as a raw material gas for the reformer as described in claim 7. it can. If comprised in this way, since the raw material gas of a reformer can be supplied from biomass ethanol manufacturing equipment, the energy consumption of a fuel cell system can be reduced further.

  Next, the best mode for carrying out the present invention will be described with reference to the drawings. FIG. 1 is a process flow diagram showing an example of a fuel cell system of the present invention. In the embodiment of FIG. 1, the same parts as those in the conventional example of FIG.

  In the present embodiment, an internal heat type reformer 2 similar to the example of FIG. 5 is used as the reformer 2 constituting the reformer 1. However, the fuel cell 7 uses a medium temperature solid polymer fuel cell (PEFC) whose operating temperature range is about 150 ° C. The cooling water system 9 for cooling the fuel cell 7 is not provided with the cooling water tank 10 as in the example of FIG. 5, but is provided with a steam separator 30 instead.

  The circulation pipe 11 returning from the fuel cell 7 to the vapor separator 30 is provided with a three-way regulating valve 31 driven by a control signal from the temperature regulator 34 or the pressure regulator 34a. The connection part B of the three-way regulating valve 31 communicates with the inlet side of a hot water tank 13 as a hot water supply facility similar to the example of FIG. 5 through a pipe 32, and the outlet side of the hot water tank 13 is connected with a steam separator through a pipe 33. 30.

  As described above, in this embodiment, the cooling water flowing out from the fuel cell 7 flows into the steam separator 30, where water vapor is generated and heat is recovered, and at least a part of the cooling water flowing out from the fuel cell 7 is recovered. Heat is recovered by supplying the hot water tank 13 as a heat source. The hot water tank 13 (and the three-way adjustment valve 31) can be omitted as necessary.

  When the system is configured to perform heat recovery by the hot water tank 13 as described above, the three-way regulating valve 31 can be controlled so that water vapor generation in the steam separator 30 is reliably performed. For example, when the temperature of the cooling water flowing out from the fuel cell 7 becomes low, the temperature or pressure of the steam separator 30 decreases, so that the hot water storage tank 13 is controlled by a control signal from the temperature regulator 34 or the pressure regulator 34a. The three-way regulating valve 31 can be controlled so as to reduce the flow rate of the cooling water that circulates.

  The steam separated by the steam separator 30 is supplied to the mixer 4 constituting the reformer 1 through the steam supply system 35. The steam supply system 35 includes a pipe 36 that communicates between the upper part of the steam separator 30 and the steam supply unit of the mixer 4, a steam control valve 37 provided in the pipe 36, and a flow rate control unit that controls the steam control valve 37. 38 is provided. A pipe 30b provided with a pump 30a is connected to supply the steam separator 30 with water such as pure water as necessary. The flow rate control unit 38 outputs a control signal to the steam control valve 37. For example, the flow rate control unit 38 outputs a control signal to the steam control valve 37 so that a steam amount corresponding to the load of the fuel cell 7 is supplied to the reformer 2. Can do.

  In the present embodiment, the anode exhaust gas of the fuel cell 7 is supplied as a heat source (or a fuel source) to a gas heat pump type heating / cooling facility 40 as a heat load facility. Specifically, the anode exhaust gas of the fuel cell 7 is supplied as fuel to the hydrogen engine 41 constituting the cooling / heating facility 40 through the pipe 46. A gas heat pump type air conditioner 40 includes a hydrogen engine 41 that rotates using hydrogen as a fuel, a compressor 42 that is driven by the hydrogen engine 41, an evaporator 43 that evaporates the working medium compressed by the compressor, an expansion valve 44 for the working medium, and A condenser 45 and the like are provided.

  Next, the operation of the fuel cell system of FIG. 1 will be described. The raw material gas supplied from the pipe 19 and the water vapor supplied from the pipe 36 are mixed in the mixer 4, and the raw material-water vapor mixture flowing out from the outlet of the mixer 4 is supplied to the reformer 2. Part of the raw material gas supplied to the reformer 2 is combusted by the action of the oxidation catalyst, and the temperature inside the reformer 2 is raised to the reforming reaction temperature (for example, about 700 ° C.). Most of the remaining raw material gas reacts with steam by the action of the reforming catalyst and is steam reformed to produce hydrogen-rich reformed gas.

  Since the generated reformed gas contains CO, after the CO is removed by the shift converter 5 filled with the shift catalyst, the CO remaining in the reformed gas is further reduced to the PPm order by the CO reducer 6. The ammonia derived from the raw material gas is removed by the ammonia remover 6 a and then supplied to the fuel cell 7.

  The fuel cell 7 generates electric power by reacting hydrogen contained in the supplied reformed gas with oxygen in the air supplied separately, and the electric power is converted into alternating current by the inverter 8 to be used in a power receiving system in the home. Supplied. On the other hand, the fuel cell 7 is cooled by the cooling water sent from the steam separator 30 through the circulation pipe 11, and the cooling water heated by the internal heat exchange and flowing out of the fuel cell 7 is supplied to the three-way circulation pipe 11. It returns to the steam separator 30 through the regulating valve 31, and a part is separated from the three-way regulating valve 31, passes through the hot water storage tank 13, and then returns to the steam separator 30.

  The steam separated by the steam separator 30 is supplied to the mixer 4 of the reformer 1 by the steam supply system 35. At that time, the opening degree of the steam control valve 38 is adjusted by the control signal from the flow rate adjusting unit 37 provided in the steam supply system 35, and the steam supply amount to the mixer 4 is controlled. On the other hand, the anode exhaust gas discharged from the fuel cell 7 contains about 20% of unreacted hydrogen. By supplying the gas to the gas heat pump type air conditioning equipment 40 from the pipe 46, the unreacted hydrogen is recovered as a heat source. The

  FIG. 2 is a process flow diagram showing another example of the fuel cell system of the present invention. 2 is different from the example of FIG. 1 in that the anode exhaust gas discharged from the fuel cell 7 is supplied to the absorption gas cooling and heating equipment 50, and the other configuration is the same. Therefore, the same parts as those in FIG.

  In this embodiment, the anode exhaust gas of the fuel cell 7 is supplied as a heat source (or fuel) of the absorption gas cooling / heating facility 50 as a heat load facility. Specifically, the anode exhaust gas of the fuel cell 7 is supplied by a pipe 46 as a heating fuel for the regenerator 51 that constitutes the absorption gas cooling and heating equipment 50. With this configuration, the anode exhaust gas discharged from the fuel cell 7 is supplied from the pipe 46 to the absorption gas cooling / heating facility 50, and unreacted hydrogen is recovered as a heat source.

  The absorption gas cooling and heating equipment 50 in this embodiment includes a regenerator 51, a condenser 52 that condenses water vapor generated by the regenerator 51, an evaporator 53 that evaporates water condensed by the condenser 52, an absorber 54, and An indoor unit 56 that performs cooling and heating with a working medium circulating to the cooling tower 55 and the condenser 52 is provided.

  FIG. 3 is a process flow diagram showing still another example of the fuel cell system of the present invention. The characteristic part of this embodiment is that anode exhaust gas discharged from the fuel cell 7 is supplied to a biomass ethanol production facility 60 as a heat load facility, and at least a part of ethanol generated by the biomass ethanol production facility 60 is modified. It is to supply to the gasifier 2 as a raw material gas, and to supply a part of the exhaust heat of the fuel cell 7 converted to water vapor as a heat source of the biomass ethanol production facility 60, and the other configuration is the same as the example of FIG. Is done. Therefore, the same parts as those in FIG.

  The biomass ethanol production facility 60 includes a pulverizing and drying device 61, a saccharifying device 62, a fermentation device 63, a distillation device 64, and a dehydrating device 65 that pulverize and dry wood chips or the like as biomass raw materials. In this embodiment, the anode exhaust gas of the fuel cell 7 is supplied as a heat source (or fuel) of the biomass ethanol production facility 60 as a heat load facility.

  Specifically, the anode exhaust gas of the fuel cell 7 is supplied as a heat source for the distillation operation of the distillation apparatus 64 constituting the biomass ethanol production facility 60 through the pipe 46. When wood is used as the biomass raw material, the saccharification device 62 needs to have a temperature of about 300 ° C. Therefore, as the heat source, the anode exhaust gas may be supplied to the heating burner of the saccharification device 62 as shown by the dotted line. it can.

  A heat exchanger for controlling each of the pulverization and drying device 61 (for example, 105 ° C.), the saccharification device 62 (for example, 90 ° C.), and the fermentation device 63 (for example, 60 ° C.) constituting the biomass ethanol production facility 60 to a predetermined temperature. Is provided. Therefore, in the present embodiment, the steam separated by the steam separator 30 is supplied to the mixer 4 of the reformer 1 by the steam supply system 35, and the pulverizing and drying device 61, the saccharification device 62, and the fermentation of the biomass ethanol production facility 60 are supplied. A part of the water vapor is supplied to each heat exchanger of the apparatus 63 by another water vapor supply system 66.

  The steam supply system 66 includes a pipe 67 that connects the upper part of the steam separator 30 and the above-described devices of the biomass ethanol production facility 60, a steam control valve 68 provided in the pipe 67, and a flow rate control unit 69 that controls the steam control valve 68. Have The operations of the steam control valve 68 and the flow rate control unit 69 are the same as the operations of the steam control valve 38 and the flow rate control unit 37 in the water vapor supply system 35.

  In the present embodiment, as described above, the anode exhaust gas discharged from the fuel cell 7 is supplied from the pipe 46 to the biomass ethanol production facility 60 and the heat recovery is performed. Further, the exhaust heat of the fuel cell 7 is converted into water vapor and supplied as a heat source of the biomass ethanol production facility 60, whereby heat recovery of the exhaust heat of the fuel cell 7 is performed.

  On the other hand, since at least a part of the ethanol generated in the biomass ethanol production facility 60 is supplied as a raw material gas to the reformer 2 via the pipe 67a and the mixer 4, the raw material gas is supplied to the reformer 2 from the other. Or the amount of the raw material gas supplied to the reformer 2 from the other can be reduced.

  The fuel cell system of the present invention can be used as a fuel cell system for home use that recovers exhaust heat of the fuel cell and uses the anode exhaust gas as a heat source of the heat load facility.

The process flow figure showing one example of the fuel cell system of the present invention. The process flow figure which shows the other example of the fuel cell system of this invention. The process flow figure which shows the further another example of the fuel cell system of this invention.

The process flow figure which shows one example of the conventional fuel cell system. The process flow figure which shows the other example of the conventional fuel cell system.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Reformer 2 Reformer 3 Steam generation means 4 Mixer 5 Shift converter 6 CO reducer 7 Fuel cell 8 Inverter 9 Cooling water system 10 Cooling water tank

DESCRIPTION OF SYMBOLS 11 Circulation piping 12 Pump 13 Hot water storage tank 14 Piping 15 Burner 16 Piping 17 Pump 18, 19 Piping 20 Desulfurization device 21 Piping

30 Steam Separator 30a Pump 30b Piping 31 Three-way Adjusting Valve 32, 33 Piping 34 Temperature Regulator 34a Pressure Adjusting Unit 35 Steam Supply System 36 Piping 37 Steam Control Valve 38 Flow Control Unit

40 Gas Heat Pump Type Heating and Cooling Equipment 41 Hydrogen Engine 42 Compressor 43 Evaporator 44 Expansion Valve 45 Condenser 46 Piping

50 Absorption-type gas cooling and heating equipment 51 Regenerator 52 Condenser 53 Evaporator 54 Absorber 55 Cooling tower 56 Indoor unit

60 Biomass ethanol production equipment 61 Grinding and drying device 62 Saccharification device 63 Fermentation device 64 Distillation device 65 Dehydration device 66 Steam supply system 67 Piping 67a Piping 68 Steam control valve 69 Flow control unit

Claims (7)

An internally heated reformer 2 that generates hydrogen-rich reformed gas from a mixture of water vapor and fuel gas, a fuel cell 7 that generates electricity using the reformed gas obtained in the reformer 2 as fuel, and the fuel In the fuel cell system including the cooling water system 9 for cooling the battery 7,
The fuel cell 7 is configured to be operated in a temperature range in which a part of the cooling water circulating in the cooling water system 9 can be evaporated, and the steam separation for separating the water vapor generated by the evaporation in the cooling water system 9 from the cooling water. The fuel cell system is provided with a steam supply system 35 for supplying the reformer 2 with the steam separated by the steam separator 30 by mixing with the raw material gas. .   2. The fuel cell system according to claim 1, wherein the anode exhaust gas of the fuel cell 7 is supplied to a heat load facility.   3. The heat load equipment according to claim 2, wherein the heat load equipment is a gas heat pump type air conditioning equipment 40, and the anode exhaust gas is supplied as fuel of a hydrogen engine 41 constituting the gas heat pump type air conditioning equipment 40. A fuel cell system.   3. The heat load facility according to claim 2, wherein the heat load facility is an absorption gas cooling / heating facility 50, and the anode exhaust gas is supplied as a heating fuel for the regenerator 51 of the absorption gas cooling / heating facility 50. Fuel cell system.   3. The fuel cell system according to claim 2, wherein the heat load facility is a biomass ethanol production facility 60, and the anode exhaust gas is supplied as a heating fuel for the biomass ethanol production facility 60.   6. The fuel cell system according to claim 5, further comprising a water vapor supply system 66 for supplying the water vapor separated by the vapor separator 30 as a heat source of the biomass ethanol production facility 60.   7. The fuel cell system according to claim 5, wherein at least a part of ethanol produced by the biomass ethanol production facility 60 is supplied to the reformer 2 as a raw material gas.

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