JP2007141772A - Fuel cell system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a fuel cell system in which hydrogen concentration in a reformed gas supplied from a reactor to a fuel cell is high and hydrogen utilization rate of the fuel cell is improved. <P>SOLUTION: The fuel cell system 10 is provided with a reactor 26 which produces hydrogen-contained reformed gas from a hydrocarbon material supplied by a reforming reaction including steam reforming reaction, a fuel cell 12 which generates power by being supplied to an anode electrode 16 with hydrogen-contained gas produced in the reactor 26, a gas separator 44 which selectively separates hydrogen and steam from an anode off-gas exhausted from the anode electrode 16 of the fuel cell 12 and obtains separation gas, and a separation gas supply line 50 which supplies the separation gas separated by the separator 44 to the reactor 26, and a scavenging pump 52. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a fuel cell system in which hydrogen-containing reformed gas generated by reforming hydrocarbons is supplied to a fuel cell to generate power.

There is known a fuel cell system that generates a reformed gas containing hydrogen from a hydrocarbon raw material by a reforming reaction and supplies the reformed gas as a power generation fuel to a polymer electrolyte fuel cell (PEFC) (for example, Patent Document 1). In the fuel cell system described in this document, the cathode offgas of PEFC is returned to the steam inlet of the reformer, and the steam in the cathode offgas is used for the steam reforming reaction. Further, the fuel cell system described in this document also discloses a configuration in which anode off-gas is supplied as fuel to a combustor for heating a reforming section that performs a reforming reaction.
JP 2002-289245 A

  However, in the conventional techniques as described above, since hydrogen contained in the anode off gas is combusted by exhaust or a combustor, there is room for improvement from the viewpoint of effective utilization of hydrogen obtained by the reforming reaction.

  In view of the above facts, an object of the present invention is to obtain a fuel cell system in which the hydrogen concentration in the reformed gas supplied from the reactor to the fuel cell is high and the hydrogen utilization rate of the fuel cell is improved. .

  In order to achieve the above object, a fuel cell system according to claim 1 is a reaction for generating a reformed gas containing hydrogen from a hydrocarbon raw material supplied by a reforming reaction including a steam reforming reaction. Hydrogen and water vapor are selectively separated from the reactor, the fuel cell in which the reformed gas generated in the reactor is supplied to the anode electrode to generate power, and the anode off-gas discharged from the anode electrode of the fuel cell. A gas separator for obtaining a separation gas, and a separation gas supply means for supplying the separation gas separated by the gas separator to the reactor.

  In the fuel cell system according to claim 1, the fuel cell in which the reformed gas generated by reforming the hydrocarbon raw material in the reactor is supplied to the anode electrode is configured to generate power while consuming the reformed gas, The gas not consumed by the power generation is discharged as anode off gas. The anode off gas is separated by the gas separator into a separation gas mainly composed of hydrogen and water vapor that has not been consumed in the fuel cell, and the remaining gas.

  Then, the separation gas is supplied to the reactor by the separation gas supply means. The water vapor in the separation gas is used for the steam reforming reaction, and the hydrogen in the separation gas is reintroduced into the fuel cell via the reactor (while increasing the hydrogen concentration as a component in the reformed gas).

  Thus, in the fuel cell system according to claim 1, the hydrogen concentration of the reformed gas supplied from the reactor to the fuel cell is increased, and the hydrogen utilization rate of the fuel cell is improved. And by providing a gas separator, in order to selectively supply to the reactor water vapor, which is a component that contributes to promoting the reforming reaction in the anode off-gas, and hydrogen, which is a component that directly contributes to power generation in the fuel cell. Effective use of gas in the entire system (improvement of material balance) is achieved.

  A fuel cell system according to a second aspect of the present invention is the fuel cell system according to the first aspect, wherein the fuel cell has a proton-conducting electrolyte, and water is generated on the cathode electrode side during power generation. It is set as the structure.

  In the fuel cell system according to claim 2, in the fuel cell, hydrogen in the reformed gas supplied to the anode electrode is protonated with power generation, and the proton (hydrogen ion) moves to the cathode electrode to generate oxygen. And water (water vapor) is generated at the cathode electrode. Therefore, the water vapor in the anode off-gas, that is, the separation gas, is mainly water vapor contained in the reformed gas, and is supplied to the reactor to perform an auxiliary function of increasing the water vapor concentration in the reactor. As described above, the present fuel cell system also increases the hydrogen concentration of the reformed gas supplied from the reactor to the fuel cell, even in the configuration including the fuel cell in which water is generated on the cathode electrode side as the power is generated. Promote quality reactions.

  A fuel cell system according to a third aspect of the present invention is the fuel cell system according to the second aspect, further comprising a cathode offgas supply means for supplying the cathode offgas discharged from the cathode electrode to the reactor. .

  In the fuel cell system according to claim 3, cathode offgas containing water (steam) generated during power generation is supplied to the reactor, and steam in the cathode offgas is mainly used for steam reforming reaction in the reactor. Is done. On the other hand, the water vapor in the separated gas separated from the anode off-gas is supplementarily supplied to the reactor to increase the water vapor concentration in the reactor and promote the steam reforming reaction. That is, it becomes possible to maintain the steam reforming reaction with the steam generated in the system and to promote the steam reforming reaction to increase the amount of hydrogen generation.

  A fuel cell system according to a fourth aspect of the present invention is the fuel cell system according to any one of the first to third aspects, wherein the heat generated by burning the fuel is supplied to the reactor. The apparatus further includes a heating unit, and a fuel supply unit configured to supply the residual gas obtained by separating the separation gas from the anode off-gas by the gas separator as fuel to the heating unit.

  In the fuel cell system according to claim 4, in a reactor that is supplied with combustion heat from a heating unit, a steam reforming reaction (including a reaction) in which a hydrocarbon raw material reacts with steam is performed, and other than hydrogen and hydrogen The reformed gas containing the combustible components (carbon monoxide, methane, unreformed hydrocarbon, etc.) is generated. The reformed gas is supplied to the anode electrode of the fuel cell, and power generation by the fuel cell is performed. The anode off gas is separated by a gas separator into a separation gas mainly containing hydrogen as a combustible component and a residual gas mainly containing a combustible component other than hydrogen.

  Here, since the residual gas containing combustible gas other than hydrogen is supplied to the heating unit as fuel, the residual gas is effectively used, and the overall efficiency of the fuel cell system is improved. In addition, since the use of hydrogen as a fuel in the heating unit is suppressed, the hydrogen utilization rate in the fuel cell can be improved.

  A fuel cell system according to a fifth aspect of the present invention is the fuel cell system according to any one of the first to fourth aspects, wherein the detector outputs a signal corresponding to the state of the reactor, and the detection And a control device for controlling the supply amount of the separation gas to the fuel inlet of the fuel cell by the separation gas supply means based on the detection result of the vessel.

  In the fuel cell system according to claim 5, for example, the state of the reactor such as the amount of hydrogen produced by the reactor and the temperature of the reactor is detected by the detector, and based on the detection result, the control device Since the supply amount to the reactor is controlled, it is possible to improve the overall efficiency even in the fuel cell system in which the operating state easily changes.

  The fuel cell system according to a sixth aspect of the present invention is the fuel cell system according to any one of the first to fifth aspects, wherein the separation gas supply means is an outlet of the separation gas in the gas separator. The separation gas is supplied to the separation gas inlet of the reactor by a gas pump provided in a separation gas supply line that connects the separation gas inlet of the reactor.

  In the fuel cell system according to the sixth aspect, the separation gas separated from the anode off-gas is reliably supplied to the separation gas inlet of the reactor by the operation of the gas pump. Further, in the configuration in which the supply amount of the separation gas by the gas pump is controlled, the control is easy.

  A fuel cell system according to a seventh aspect of the present invention is the fuel cell system according to any one of the first to fifth aspects, wherein the separation gas supply means supplies the raw material or cathode off gas to the reactor. The separation gas is supplied to the reactor by an ejector provided in the reforming reaction gas supply line.

  In the fuel cell system according to the seventh aspect, since the separated gas separated from the anode off-gas by the operation of the ejector joins the reforming reaction gas supply line, no power is required and the structure is simple.

  A fuel cell system according to an eighth aspect of the present invention is the fuel cell system according to any one of the first to seventh aspects, wherein the gas separator includes a porous body separation membrane.

  In the fuel cell system according to claim 8, since the gas separator includes a porous body separation membrane composed of a porous body such as polyimide or ceramic, the selectivity of hydrogen and water vapor is high. For this reason, hydrogen and water vapor in the anode off-gas can be effectively separated and returned to the reactor (separated gas inlet, reformed reaction gas supply line, etc.).

  As described above, the fuel cell system according to the present invention has an excellent effect that the hydrogen concentration of the reformed gas supplied from the reactor to the fuel cell is increased and the hydrogen utilization rate of the fuel cell is improved.

  A fuel cell system 10 according to a first embodiment of the present invention will be described with reference to FIG. FIG. 1 shows a system configuration diagram (process flow sheet) of the fuel cell system 10. As shown in this figure, the fuel cell system 10 includes a fuel cell 12 that generates power by consuming hydrogen, and a reformer (modified) for generating hydrogen-containing reformed gas to be supplied to the fuel cell 12. 14) as main components.

  In this embodiment, the fuel cell 12 is a proton-conducting fuel cell that operates on the same principle as a polymer electrolyte fuel cell (PEFC), a phosphoric acid fuel cell (PAFC), or the like. Specifically, as schematically shown in FIG. 2, the fuel cell 12 sandwiches an electrolyte 20 having proton conductivity between an anode electrode (fuel electrode) 16 and a cathode electrode (air electrode) 18. It consists of Further, the fuel cell 12 includes an anode channel 22 for introducing reformed gas (hydrogen) into the anode electrode 16 and a cathode channel 24 for introducing cathode air containing oxygen into the cathode electrode. I have.

  In the fuel cell 12, in the anode electrode 16, hydrogen in the reformed gas supplied from the fuel inlet 22 </ b> A of the anode flow channel 22 releases electrons to be protonated, and the protons (hydrogen ions) are passed through the electrolyte 20. Via, it moves from the anode electrode 16 to the cathode electrode. On the other hand, in the cathode electrode 18, protons reached via the electrolyte 20, electrons reached from the anode electrode 16 via an external load (not shown), and cathode air introduced from the air inlet 24 </ b> A of the cathode channel 24. The water reacts with oxygen to produce water.

  Therefore, in the fuel cell 12, water is generated on the cathode electrode 18 side with power generation, and this water is discharged out of the fuel cell 12 from the offgas outlet 24 </ b> B of the cathode channel 24 as water vapor that is part of the cathode offgas. It is like that. The fuel cell 12 is configured to be operated in an intermediate temperature range of about 300 ° C. to 700 ° C., for example.

  The reformer 14 includes a reactor 26 as a reforming unit that generates a hydrogen-containing reformed gas to be supplied to the anode electrode 16 of the fuel cell 12, and heat for the reactor 26 to perform a reforming reaction. The heating part 28 for supplying is comprised as a main component. The reactor 26 has a built-in reforming catalyst (not shown), and contains hydrogen gas by catalytically reacting the supplied hydrocarbon gas (gasoline, methanol, natural gas, etc.) and the reforming gas (steam). A reformed gas is generated (reforming reaction is performed).

The reforming reaction in the reactor 26 includes each reaction including the steam reforming reaction represented by the formula (1) as represented by the following formulas (1) to (4). Thus, the reformed gas obtained in the reforming process, the hydrogen (H _2), carbon monoxide (CO), methane (CH _4), cracked hydrocarbons and unreacted feed hydrocarbon (C _x H _y) or the like Combustible gas and carbon dioxide (CO ₂ ), water (H ₂ O), and other non-flammable gases.

_{C n H m + nH 2 O} → nCO + (n + m / 2) H 2 ... (1)
_{C n H m + n / 2O} 2 → nCO + m / 2H 2 ... (2)
CO + H ₂ O⇔CO ₂ + H ₂ (3)
CO + 3H ₂ ＣＨ CH ₄ + H ₂ O (4)
The main steam reforming reaction of the formula (1) in the reforming reaction is an endothermic reaction, and the reactor 26 supplies the reformed gas to the fuel cell 12 operated at an intermediate temperature or a high temperature as described above. In order to do so, it is operated at a temperature higher than a predetermined temperature. The heating unit 28 is configured to supply heat for maintaining the reforming reaction and operating temperature in the reactor 26. The heating unit 28 includes an oxidation catalyst and is provided adjacent to the reactor 26. The heating unit 28 is configured to bring the supplied fuel into contact with the oxidation catalyst together with oxygen to cause catalytic combustion.

  The reformer 14 supplies combustion heat obtained by catalytic combustion of fuel in the heating unit 28 to the reactor 26 via the partition wall 30. For this reason, the structure which can provide heat quantity directly to the reactor 26, without converting calorie | heat amount into temperature like the structure which heats the reactor 26 via heating media (fluid), such as combustion gas, and Has been. The combustion exhaust gas from the heating unit 28 is discharged from the exhaust gas outlet 28B.

  The fuel cell system 10 includes a raw material pump 32 for supplying a hydrocarbon raw material to the reactor 26, and a discharge portion of the raw material pump 32 is connected to a raw material inlet 26 </ b> A of the reactor 26 via a raw material supply line 34. It is connected. The hydrocarbon raw material is supplied to the reactor 26 in a gas phase or atomized state by a vaporizing means (not shown) such as an evaporator or an injection, for example.

  The reformed gas outlet 26B of the reactor 26 is connected to the upstream end of the reformed gas supply line 36 whose downstream end is connected to the fuel inlet 22A of the anode flow path 22. Thus, the reformed gas generated in the reactor 26 is supplied to the anode electrode 16 of the fuel cell 12. The intermediate portion of the reformed gas supply line 36 is a high-temperature gas side flow path of a heat exchanger 38 for cooling the reformed gas (the high-temperature gas side flow path of the heat exchanger 38 is arranged in series. ing).

  The fuel cell system 10 also includes a cathode air pump 40 for supplying cathode air to the cathode electrode 18, and the discharge portion of the cathode air pump 40 has an air inlet of the cathode channel 24 at the downstream end. The upstream end of the cathode air supply line 41 connected to 24A is connected.

  Further, the upstream end of the water vapor supply line 42 is connected to the off-gas outlet 24 </ b> B of the cathode channel 24, and the downstream end of the water vapor supply line 42 joins the raw material supply line 34. Thus, the cathode off gas containing the water vapor generated at the cathode electrode 18 is used for the water vapor reforming reaction in the reactor 26. Further, the water vapor supply line 42 has an intermediate portion serving as a low temperature gas side flow path of the heat exchanger 38, and the cathode off gas passes through the high temperature side gas flow path (reformed gas supply line 36) of the heat exchanger 38. The reformed gas that circulates is cooled.

  On the other hand, the upstream end of the anode offgas line 44 is connected to the offgas outlet 22B of the anode flow path 22, and the anode offgas inlet 46A of the anode offgas separator 46 is connected to the downstream end of the anode offgas line 44. . The anode off-gas separator 46 has a built-in separation membrane 48 for separating the components of the anode off-gas. In this embodiment, the separation membrane 48 is a porous membrane made of a porous body such as polyimide carbide or ceramic, and has high hydrogen selectivity and water vapor selectivity. In particular, if a polyimide carbonized film obtained by carbonizing a polyimide film with high film thickness controllability is used as the separation film 48, high hydrogen and water vapor permeability can be obtained while maintaining high hydrogen selectivity and water vapor selectivity. it can.

  The separation gas outlet 46B (on the separation side) separated from the anode offgas inlet 46A by the separation membrane 48 in the anode offgas separator 46 has a downstream end downstream of the heat exchanger 38 in the steam supply line 42 (raw material supply line). 34 is connected to the upstream end of the separation gas supply line 50 that joins to the side 34). A scavenging pump 51 as a gas pump is disposed in an intermediate portion of the separation gas supply line 50. The scavenging pump 51 operates to pump and join the gas on the anode off-gas separator 46 side to the steam supply line 42 (raw material supply line 34).

  The anode off-gas separator 46 is a gas in the anode off-gas due to a pressure difference between the separation gas outlet 46B side (low pressure side) and the anode off gas inlet 46A side (high pressure side) with respect to the separation membrane 48 generated by the operation of the scavenging pump 51. Hydrogen and water vapor, which are highly permeable components, are selectively separated. Accordingly, the scavenging pump 51 constitutes a gas separator in the present invention together with the anode off-gas separator 46 and constitutes a separation gas supply means together with the separation gas supply line 50.

  The upstream end of a fuel gas supply line 52 as a fuel gas supply means (supply path) is connected to the residual gas outlet 46C (on the mainstream side) directly communicating with the anode offgas inlet 46A in the anode offgas separator 46. The downstream end of the fuel gas supply line 52 is connected to the fuel inlet 28 </ b> A of the heating unit 28.

  As described above, in the fuel cell system 10, by the operation of the scavenging pump 51, the separation gas mainly composed of hydrogen and water vapor separated from the anode off gas by the anode off gas separator 46 is supplied to the raw material inlet 26A of the reactor 26. In addition, the residual gas after the separation gas is separated from the anode off gas is supplied to the heating unit 28 as fuel.

In the fuel cell system 10 in which the reformed gas generated by the above reforming reaction is supplied to the fuel cell 12, the main components of the residual gas are carbon monoxide (CO), hydrocarbon (HC), methane (CH ₄ ), Carbon dioxide (CO ₂ ). Therefore, in the heating unit 28, carbon monoxide, hydrocarbons, and methane, which are combustible components in the residual gas, are consumed as fuel. An exhaust gas line 53 for discharging combustion exhaust gas to the outside of the system is connected to the exhaust gas outlet 28B of the heating unit 28.

  Furthermore, the fuel cell system 10 includes a cooling air pump 54 for supplying cooling air to the fuel cell 12, and the discharge portion of the cooling air pump 54 has a downstream end of a refrigerant flow (not shown) of the fuel cell 12. It is connected to the upstream end of the cooling air line 56 connected to the inlet 12A of the passage.

  The refrigerant flow path outlet 12 </ b> B is connected to the upstream end of the combustion support gas supply line 58. The combustion support gas supply line 58 is joined to the fuel gas supply line 52, and supplies a cooling off gas containing oxygen as a combustion support gas to the heating unit 28. The combustion support gas supply line 58 may be connected to the heating unit 28 so as to supply the cooling off gas to the heating unit 28 independently of the fuel gas supply line 52. An exhaust branch line 58 </ b> A is connected between the combustion support gas supply lines 58.

  Next, the operation of the first embodiment will be described.

  In the fuel cell system 10 configured as described above, the hydrocarbon raw material and water vapor (cathode off-gas) are introduced from the raw material supply line 34 into the reactor 26 of the reformer 14 by the operation of the raw material pump 32 and the cathode air pump 40. In the reactor 26, the reforming reactions represented by the equations (1) to (4) including the steam reforming reaction are performed, and a reformed gas containing hydrogen at a high concentration is generated.

  The reformed gas generated in the reactor 26 is cooled by heat exchange with the cathode off-gas in the heat exchanger 38, and from the fuel inlet 22 </ b> A of the anode channel 22 to the anode electrode 16 at a temperature close to the operating temperature of the fuel cell 12. To be supplied. In the fuel cell 12, hydrogen in the reformed gas supplied to the anode electrode 16 is protonated, and this proton moves to the cathode electrode 18 through the electrolyte 20 and is introduced into the cathode electrode 18. Reacts with oxygen. As the protons move, electrons flow from the anode electrode 16 toward the cathode electrode through the external conductor, and power generation is performed.

  With this power generation, the fuel cell 12 consumes hydrogen in the reformed gas supplied to the anode electrode 16 and oxygen in the cathode air supplied to the cathode electrode 18 according to the power generation amount (load power consumption). The cathode electrode 18 generates water (water vapor). This gas containing water vapor is pushed out from the cathode electrode 18 to the water vapor supply line 42 as the cathode off gas, and after the reformed gas is heated by the heat exchanger 38, it is introduced into the reactor 26 via the raw material supply line 34. .

  On the other hand, the gas after the hydrogen in the reformed gas is consumed in accordance with the amount of power generated as a result of power generation is discharged from the offgas outlet 22B of the anode channel 22 as an anode off and introduced into the anode offgas separator 46. . In this anode off-gas separator 46, the scavenging pump 51 is operated, so that the separation side is at a low pressure relative to the main stream side. Due to this pressure difference, mainly unused hydrogen contained in the anode off-gas, reforming Water vapor contained in the gas passes through the separation membrane 48 and is separated.

  The separation gas mainly composed of hydrogen and water vapor is sucked into the scavenging pump 51 and discharged from the separation gas outlet 46B of the anode off-gas separator 46, and is pumped to the scavenging pump 51 to join the water vapor supply line 42. Then, together with the cathode off-gas, it joins the raw material supply line 34 and is supplied to the reactor 26 from the raw material inlet 26A. Therefore, the hydrocarbon raw material, the water vapor in the cathode off-gas, and the water vapor and hydrogen in the separation gas are introduced into the reactor 26, and the reforming reaction (especially the water vapor reforming of the formula (1)) is performed in an environment with a high water vapor concentration. A reformed gas (a gas supplied to the anode electrode 16 of the fuel cell 12) having a high hydrogen concentration can be obtained by mixing hydrogen that is not used in the fuel cell 12 and the hydrogen is mixed in the fuel cell 12.

  On the other hand, the residual gas after separation of hydrogen and water vapor (at least a part thereof) from the anode off-gas is supplied to the reformer 14 together with the cooling off-gas after cooling the fuel cell 12 via the fuel gas supply line 52. It is supplied to the heating unit 28. In the heating unit 28, catalytic combustion occurs using the combustible component in the residual gas as fuel and oxygen in the cooling off gas as combustion support gas. The heat generated by this catalytic combustion is supplied to the reactor 26 through the partition wall 30. With this heat, the reactor 26 maintains the reforming reaction, which is an endothermic reaction, and maintains the operating temperature (reformed gas temperature) at a temperature close to the operating temperature of the fuel cell 12.

  As described above, in the fuel cell system 10, hydrogen in the reformed gas that has not been consumed (utilized) in the fuel cell 12 and water vapor contained in the reformed gas are separated from the anode offgas by the anode offgas separator 46. Since the steam concentration in the reactor 26 that supplies the reactor 26 and performs the steam reforming reaction, which is the main reaction among the reforming reactions, is increased, the steam reforming reaction is promoted and a reformed gas with a high hydrogen concentration is produced. can get. That is, the reforming efficiency in the reactor 26 of the reformer 14 is improved. Moreover, since hydrogen in the separation gas is added to the reformed gas and supplied to the fuel cell 12, a gas having a higher hydrogen concentration is supplied to the fuel cell 12, and this hydrogen was not used for power generation. Since the fraction is circulated to the reactor 26, the hydrogen utilization rate is improved.

  Further, in the fuel cell system 10, since the cathode off gas containing water generated at the cathode electrode 18 with power generation is supplied to the reactor 26, the steam reforming reaction is maintained without supplying steam from outside the system. Can do. In such a configuration in which the reforming reaction is maintained with the generated water in the system, the steam contained in the anode off-gas (reformed gas) is supplementarily provided for the steam reforming reaction as described above, thereby providing a reactor. It has been realized that the reforming efficiency is improved by increasing the water vapor concentration in 26.

  Further, in the fuel cell system 10, the residual gas after mainly hydrogen and water vapor are separated from the anode off-gas by the anode off-gas separator 46 is used as fuel in the heating unit 28 of the reformer 14. Further, the combustible gas in the residual gas and the heat quantity of the residual gas are effectively used, and the overall efficiency of the fuel cell system 10 is improved.

  That is, in the present fuel cell system 10, by providing the anode off-gas separator 46, components (steam and hydrogen) that contribute to reforming or improving the hydrogen concentration in the anode off-gas and combustion heat generation in the heating unit 28 are generated. It was realized that components that contributed (carbon monoxide, hydrocarbons, methane, etc.) were separated and each component was used efficiently. That is, effective gas utilization (improvement of material balance) of the entire system is achieved. In particular, in the fuel cell system 10, since the porous body separation membrane is used as the separation membrane 48, the anode off-gas separator 46 has high hydrogen and water vapor selectivity, which contributes to improvement of the hydrogen utilization rate.

  Thus, in the fuel cell system 10 according to the first embodiment, the hydrogen concentration of the reformed gas supplied from the reactor 26 to the fuel cell 12 is increased, and the hydrogen utilization rate of the fuel cell 12 is improved. Further, by supplying a separation gas from the relatively high temperature anode off-gas to the reactor 26, it is possible to effectively use the amount of heat of the separation gas.

  Further, since the scavenging pump 51 is used in the fuel cell system 10 to drive the separation gas, the low-pressure separation gas can be reliably joined to the relatively high-pressure steam supply line 42 with a simple structure.

  Furthermore, in the fuel cell system 10, since the water vapor in the separation gas is supplied to the reactor 26 as described above, the water vapor concentration in the reactor 26 is increased. In other words, the S / C ratio (carbonization) in the reactor 26 is increased. Since the amount of water vapor relative to the amount of carbon in the hydrogen gas is increased, carbon deposition on the reforming catalyst is suppressed.

  Here, in FIG. 3, the horizontal axis represents the S / C ratio, and the vertical axis represents the O / C ratio (the amount of oxygen for performing the partial oxidation reaction of the formula (2) with respect to the amount of carbon in the hydrocarbon gas). The carbon deposition limit line for each temperature is shown. From this figure, it can be seen that the higher the S / C ratio, the easier it is to move to the non-deposited side of carbon with respect to the carbon deposition limit line. For example, when the reforming temperature is 400 ° C., if the reaction point shifts from the point A in FIG. 3 to the point B across the carbon deposition limit line by supplying the separation gas, carbon deposition is prevented.

  In the first embodiment, the cathode off gas is supplied to the reactor 26 to maintain the steam reforming reaction. However, the present invention is not limited to this, and for example, water from a water tank is evaporated. It is also possible to supply the reactor 26 with water vapor obtained by evaporation in a reactor. Also in this configuration, since the water vapor concentration can be increased by supplying the separation gas to the reactor 26, the capacity of the water tank can be reduced and the capacity of the evaporator can be reduced. Furthermore, in this configuration, hydrogen gas can be more effectively separated by supplying water vapor generated in the evaporator to the separation gas side of the gas separator.

  Next, another embodiment of the present invention will be described. Note that parts and portions that are basically the same as those in the first embodiment or the previous configuration are denoted by the same reference numerals as those in the first embodiment or the previous configuration, and description thereof is omitted.

(Second Embodiment)
FIG. 4 shows a system configuration diagram (process flow sheet) of a fuel cell system 60 according to the second embodiment of the present invention. As shown in this figure, the fuel cell system 60 is different from the fuel cell system 10 according to the first embodiment in that an ejector (jet pump) 62 is provided instead of the scavenging pump 51.

  The ejector 62 is disposed at the junction of the water vapor supply line 42 as the reaction gas supply line and the separation gas supply line 50, and the low pressure separation is caused by the negative pressure generated along with the flow of the cathode off gas in the water vapor supply line 42. The gas is introduced from the separation gas supply line 50 into the water vapor supply line 42. Further, due to the separation gas suction action of the ejector 62, the separation gas outlet 46B side (separation side) with respect to the separation membrane 48 in the anode off gas separator 46 is set to a relatively low pressure relative to the anode off gas inlet 46A side (main flow side), A separation gas is separated from the anode off gas.

  That is, like the scavenging pump 51, the ejector 62 constitutes a gas separator in the present invention together with the anode off-gas separator 46, and constitutes a separation gas supply means together with the separation gas supply line 50.

  Other configurations of the fuel cell system 60 are the same as the corresponding configurations of the fuel cell system 10. Therefore, the fuel cell system 60 according to the second embodiment can obtain the same effect by the same operation as that of the first embodiment.

  In the fuel cell system 60, since the ejector 62 is used to drive the separation gas, the low-pressure separation gas is reliably joined to the relatively high-pressure reformed gas supply line 36 with a simple structure that does not require power. be able to.

  In the configuration in which the separation gas supply line 50 is joined to the raw material supply line 34 independently of the water vapor supply line 42, an ejector 62 is provided at the junction of the separation gas supply line 50 in the raw material supply line 34 as a reaction gas supply line. It may be arranged.

(Third embodiment)
FIG. 5 shows a system configuration diagram (process flow sheet) of a fuel cell system 70 according to the third embodiment of the present invention. As shown in this figure, the fuel cell system 70 is different from the first embodiment in that it includes a gas separation amount controller 72 as a control device for controlling the scavenging pump 51.

  The gas separation amount controller 72 is electrically connected to the scavenging pump 51 and is also electrically connected to a temperature sensor 74 as a detector that outputs a signal corresponding to the temperature of the reactor 26. When the gas separation amount controller 72 determines that the temperature of the reactor 26 is equal to or lower than a predetermined first threshold based on the output signal of the temperature sensor 74, the gas separation amount controller 72 reduces the rotation speed (discharge amount) of the scavenging pump 51. When the temperature of the reactor 26 is determined to be equal to or higher than the second threshold value higher than the first threshold value based on the output signal of the temperature sensor 74, the rotational speed (discharge amount) of the scavenging pump 51 is increased. Has been. Other configurations of the fuel cell system 70 are the same as the corresponding configurations of the fuel cell system 10.

  In the fuel cell system 70 described above, when the temperature of the reactor 26 is equal to or lower than the first threshold value, the gas separation amount controller 72 reduces the rotation speed of the scavenging pump 51, so that the hydrogen and water vapor in the anode off-gas are reduced. The amount of separation by the separation membrane 48 (the amount of supply to the reactor 26) is reduced, and the residual gas containing the reduced amount of hydrogen is supplied to the heating unit 28 of the reformer 14. Therefore, the calorific value of the residual gas increases and the temperature of the reactor 26 rises. This promotes the reforming reaction at 20 in the reaction. When the temperature of the reactor 26 becomes equal to or higher than the second threshold value, the gas separation amount controller 72 increases the number of rotations of the scavenging pump 51, thereby increasing (returning) the supply amount of hydrogen and steam to the reactor 26. .

  As described above, in the fuel cell system 70 according to the third embodiment, the same effect as that of the first embodiment can be obtained, and the hydrogen and water vapor in the anode off-gas to the reactor 26 can be obtained. Since the supply amount is controlled, it is possible to effectively use an appropriate anode off gas according to the operation state of the entire fuel cell system 70. That is, the efficiency of the fuel cell system 70 as a whole is improved. The fuel cell system 70 is applied to an application in which the operating state (battery load) and the operating environment (outside temperature, etc.) are likely to change, and can perform efficient operation. Further, since the supply amount of hydrogen and water vapor in the anode off-gas to the reactor 26 is controlled by the rotation speed of the scavenging pump 51, the control is easy.

  In the third embodiment, an example of control in which the number of rotations of the scavenging pump 51 is switched to two stages has been described. However, the present invention is not limited to this, and for example, the number of rotations of the scavenging pump 51 can be increased in multiple stages. You may make it perform the control changed continuously (continuously).

(Fourth embodiment)
FIG. 6 shows a system configuration diagram (process flow sheet) of a fuel cell system 80 according to the fourth embodiment of the present invention. As shown in this figure, the fuel cell system 80 is different from the second embodiment in that a control valve 84 whose valve opening degree is controlled by a gas separation amount controller 82 is provided in the separation gas supply line 50. Different.

  The gas separation amount controller 82 is electrically connected to the control valve 84 and is electrically connected to a gas sensor 86 as a detector that outputs a signal corresponding to the hydrogen concentration in the reformed gas discharged from the reactor 26. It is connected. The gas sensor 86 is disposed upstream of the heat exchanger 38 in the reformed gas supply line 36.

  When the gas separation amount controller 82 determines that the hydrogen concentration of the reformed gas is equal to or less than a predetermined first threshold based on the output signal of the gas sensor 86, the gas separation amount controller 82 decreases the valve opening of the control valve 84, and the gas sensor 86. When the hydrogen concentration of the reformed gas is determined to be equal to or higher than the second threshold value higher than the first threshold value based on the output signal, the valve opening degree of the control valve 84 is increased. Other configurations of the fuel cell system 80 are the same as the corresponding configurations of the fuel cell system 60. The control valve 84 constitutes the separation gas supply means in the present invention, and also constitutes the control device in the present invention together with the gas separation amount controller 82.

  In the fuel cell system 80 described above, when the hydrogen concentration of the reformed gas is less than or equal to the first threshold value, the gas separation amount controller 82 reduces the valve opening of the control valve 84 so that the hydrogen in the anode off gas and The amount of water vapor separated by the separation membrane 48 (the amount supplied to the reactor 26) is reduced, and the residual gas containing the reduced amount of hydrogen is supplied to the heating unit 28 of the reformer 14. Therefore, the calorific value of the residual gas, that is, the amount of heat supplied from the heating unit 28 to the reactor 26 is increased, the reforming reaction is promoted, and the hydrogen concentration of the reformed gas is increased. When the hydrogen concentration of the reformed gas becomes equal to or higher than the second threshold value, the gas separation amount controller 72 increases the valve opening of the control valve 84, thereby increasing the supply amount of hydrogen and steam to the reactor 26 (recovery). To do).

  Thus, in the fuel cell system 80 according to the fourth embodiment, a similar effect can be obtained by the same operation as in the first and second embodiments, and a reactor for hydrogen and water vapor in the anode off-gas Since the amount supplied to the fuel cell system 26 is controlled, an appropriate anode off-gas can be effectively used according to the operation state of the fuel cell system 80 as a whole. That is, the efficiency of the fuel cell system 80 as a whole is improved. This fuel cell system 80 is applied to an application in which the operating state (battery load) and the operating environment (outside temperature, etc.) are likely to change, and can perform efficient operation. Further, in the configuration having the ejector 62 that does not use power, a configuration for controlling the supply amount of hydrogen and water vapor in the anode off-gas to the reactor 26 was realized.

  In the fourth embodiment, an example of control in which the valve opening of the control valve 84 is switched in two stages has been described. However, the present invention is not limited to this, and for example, the valve opening of the control valve 84 is increased. You may make it perform the control changed to a step or a continuous (stepless).

  In the fourth embodiment, an output signal of the temperature sensor 74 may be used as a control parameter of the gas separation amount controller 82 instead of the output signal of the gas sensor 86. Similarly, in the third embodiment, the output signal of the gas sensor 86 may be used as the control parameter of the gas separation amount controller 72 instead of the output signal of the temperature sensor 74.

1 is a system configuration diagram showing a schematic overall configuration of a fuel cell system according to a first embodiment of the present invention. It is a mimetic diagram of a fuel cell which constitutes a fuel cell system concerning an embodiment of the present invention. It is a diagram which shows the carbon deposition limit line of the reforming reaction in the reactor which comprises the fuel cell system which concerns on embodiment of this invention. It is a system block diagram which shows the schematic whole structure of the fuel cell system which concerns on the 2nd Embodiment of this invention. It is a system block diagram which shows the schematic whole structure of the fuel cell system which concerns on the 3rd Embodiment of this invention. It is a system block diagram which shows the schematic whole structure of the fuel cell system which concerns on the 4th Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Fuel cell system 12 Fuel cell 16 Anode electrode 18 Cathode electrode 20 Electrolyte 26 Reactor 28 Heating part 42 Steam supply line (reactive gas supply line)
46 Anode off-gas separator (gas separator)
48 Separation membrane (porous separation membrane)
50 Separation gas supply line (separation gas supply means)
51 Scavenging pump (gas pump, separation gas supply means, gas separator)
52 Fuel gas supply line (fuel supply means)
60, 70, 80 Fuel cell system 62 Ejector (Separation gas supply means, gas separator)
72 ・ 82 Gas separation amount controller (control device)
74 Temperature sensor (detector)
84 Control valve (separation gas supply means, control device)
86 Gas sensor (detector)

Claims (8)

A reactor for generating a reformed gas containing hydrogen from a hydrocarbon feed supplied by a reforming reaction including a steam reforming reaction;
A fuel cell in which the reformed gas generated in the reactor is supplied to the anode electrode to generate power; and
A gas separator for selectively separating hydrogen and water vapor from the anode off-gas discharged from the anode electrode of the fuel cell to obtain a separation gas;
Separation gas supply means for supplying the separation gas separated by the gas separator to the reactor;
A fuel cell system comprising:   The fuel cell system according to claim 1, wherein the fuel cell includes a proton-conducting electrolyte, and water is generated on the cathode electrode side with power generation.   The fuel cell system according to claim 2, further comprising cathode offgas supply means for supplying cathode offgas discharged from the cathode electrode to the reactor. A heating unit for supplying heat generated by burning fuel to the reactor;
Fuel supply means for supplying the residual gas obtained by separating the separated gas from the anode off-gas by the gas separator as fuel to the heating unit;
The fuel cell system according to any one of claims 1 to 3, further comprising: A detector that outputs a signal according to the state of the reactor;
A control device for controlling the supply amount of the separation gas to the fuel inlet of the fuel cell by the separation gas supply means based on the detection result of the detector;
The fuel cell system according to any one of claims 1 to 4, further comprising:   The separation gas supply means supplies the separation gas to the separation gas of the reactor by a gas pump provided in a separation gas supply line that connects the separation gas outlet of the gas separator and the separation gas inlet of the reactor. The fuel cell system according to any one of claims 1 to 5, wherein the fuel cell system is supplied to an inlet.   The separation gas supply means supplies the separation gas to the reactor by an ejector provided in a reforming reaction gas supply line for supplying the raw material or cathode off-gas to the reactor. The fuel cell system according to claim 1.   The fuel cell system according to any one of claims 1 to 7, wherein the gas separator includes a porous body separation membrane.