JP4961769B2 - Fuel cell system - Google Patents

Description

  The present invention relates to a fuel cell system in which a hydrogen-containing gas generated by reforming a reforming raw material such as hydrocarbon is supplied to a fuel cell to generate electric power.

In a fuel reformer that obtains hydrogen-rich gas from hydrocarbons containing sulfur compounds by steam reforming, when the catalytic activity of the reforming catalyst is reduced due to sulfur poisoning, the reforming section containing the reforming catalyst is heated. A technique is known in which the catalytic activity of the reforming catalyst is recovered by heating at a section and supplying an inert gas or water vapor gas to the reforming section for a predetermined time (see, for example, Patent Document 1). Such a recovery operation of the catalyst activity is performed in a time zone other than the startup operation, the stop operation, and the normal operation operation of the fuel reformer.
JP 2000-351606 specification

  However, in the conventional technology as described above, when recovering the catalytic activity, energy such as fuel, electric power, and heat for heating the reforming unit with respect to the heating unit, that is, operation of the reforming unit (hydrogen rich gas) In order to generate a large amount of energy loss, it is necessary to supply energy that does not contribute directly. In particular, when steam gas is used to recover the catalyst activity, energy equivalent to latent heat for converting water into steam is further required, so that the problem of energy loss becomes significant and is improved from the viewpoint of energy efficiency. There is room for.

  An object of the present invention is to obtain a fuel cell system capable of efficiently recovering the catalytic activity of a reforming catalyst in consideration of the above facts.

In order to achieve the above object, a fuel cell system according to a first aspect of the present invention includes a reforming unit that generates a hydrogen-containing gas from a reforming raw material containing a sulfur component using a reforming catalyst, and the hydrogen-containing gas to generate electricity by consuming hydrogen is discharged and the fuel cell to produce water at the cathode electrode side with the power-generating, from the after stop of the supply of reforming material and the cathode electrode to the reforming section After performing the gas storage step of increasing the pressure of the supply line for supplying the cathode off gas to the reforming unit, the cathode off gas is supplied to the reforming unit for a predetermined time, thereby increasing the activity of the reforming catalyst. And a catalyst regeneration means for performing a regeneration process for recovery.

  In the fuel cell system according to the first aspect, the hydrogen-containing gas generated by the reforming unit reforming the reforming raw material (reformed fuel) is consumed by the fuel cell (anode electrode) to generate electric power. With this power generation, water is generated on the cathode electrode side of the fuel cell, and this water is discharged from the cathode electrode as water vapor. By the way, in a reforming section that reforms a reforming raw material containing a sulfur component to generate a hydrogen-containing gas, the reforming catalyst is poisoned by the sulfur component in the raw material during operation.

  When performing the regeneration process for recovering the catalytic activity of the reforming catalyst whose activity has been reduced by sulfur poisoning, the catalyst regeneration means supplies the cathode offgas from the fuel cell to the reforming section. Since this cathode off gas contains water vapor and has a temperature corresponding to the operating temperature of the fuel cell as described above, in the reforming section to which this cathode off gas is supplied, sulfur components on the reforming catalyst are removed and the catalytic activity is reduced. Can be recovered. That is, by using a high-temperature cathode off-gas containing water vapor generated in a fuel cell, the energy for generating water vapor is unnecessary, and the amount of heat (energy) necessary for the regeneration process is suppressed from the outside ( Including the case of not introducing it).

  Thus, in the fuel cell system according to claim 1, the catalytic activity of the reforming catalyst can be efficiently recovered. Note that oxygen contained in the cathode off-gas is introduced into the reforming unit together with water vapor and contributes to sulfur removal on the reforming catalyst (promotes sulfur removal).

Further, in the present fuel cell system, the regeneration process is based on the knowledge that the sulfur removal effect for recovering the activity of the reforming catalyst described above depends on the supply time rather than the supply amount of the supplied steam (and oxygen). When performing the above, the catalyst regeneration means supplies the cathode off gas to the reforming section over a predetermined time. Thereby, for example, compared with the case where the same amount of water vapor (and oxygen) is supplied to the reforming section in a short time, the sulfur component on the reforming catalyst can be effectively removed, and the catalytic activity is excellent. It will be recovered.

Further, in this fuel cell system, the catalyst regeneration means in the regeneration step increases the pressure of the supply line to the cathode offgas reforming section before starting the supply of the cathode offgas to the reforming section. Store off-gas. After that, by supplying the cathode offgas stored in the supply line to the reforming unit, the cathode offgas can be supplied to the reforming unit for a predetermined time as described above. That is, when the regeneration process is performed, the generation of hydrogen-containing gas is stopped with the stop of fuel supply to the reforming section, and the generation of water (steam) on the cathode electrode side is also stopped with the stoppage of power generation in the fuel cell. Because it stops, the time from the start of the regeneration process to the stop of water generation on the cathode electrode side is short (only the time lag of the gas flow), but the water (steam) generated in this short time is converted to pressure Thus, the cathode off gas containing water vapor can be supplied to the reforming section over a predetermined time.

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 catalyst regeneration means includes a gas storage section that is provided in the supply line and stores the cathode off gas.

In the fuel cell system according to the second aspect , since the cathode offgas can be stored in the gas storage part, it is possible to reliably store the cathode offgas to be supplied to the reforming part over a predetermined time. Note that the gas storage unit may store, for example, the cathode offgas as the pressure of the supply line in the reforming catalyst activity recovery process increases, or may store the cathode offgas during operation of the fuel cell.

A fuel cell system according to a third aspect of the present invention is the fuel cell system according to the first or second aspect , wherein the catalyst regeneration means reduces the cathode offgas to a predetermined time by reducing the supply flow rate of the cathode offgas. A throttling means is provided for supplying the reforming section.

In the fuel cell system according to the third aspect , the cathode offgas is gradually supplied to the reforming section while reducing the supply flow rate of the cathode offgas. This prevents the cathode off gas from being supplied to the reforming section in a short time. In particular, the cathode off gas converted into pressure and stored in a short time after the start of regeneration in the configuration of claim 3 or claim 4 is supplied effectively over a predetermined time (distributed in the time axis direction). Can do.

The 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 reforming unit consumes the hydrogen-containing gas in the fuel cell. A heating unit is provided for supplying heat obtained by burning the anode off gas discharged from the anode electrode to the reforming catalyst.

In the fuel cell system according to claim 4, when performing the activity recovery process of the reforming catalyst, the anode off-gas of the fuel cell (a gas excluding hydrogen consumed in the fuel cell among the hydrogen-containing gas obtained in the reforming unit) ) Is supplied to the heating unit and burned, and heat for performing (maintaining) the regeneration step is supplied to the reforming unit. As a result, in addition to the heat of the cathode off gas, combustion heat from the heating unit is supplied to the reforming unit, so that energy introduced from the outside for heating the reforming unit is further suppressed.

  As described above, the fuel cell system according to the present invention has an excellent effect that the catalytic activity of the reforming catalyst can be efficiently recovered.

  A fuel cell system 10 according to a first embodiment of the present invention will be described with reference to FIGS. 1 to 3. FIG. 1 shows a system configuration diagram (process flow sheet) of the fuel cell system 10. As shown in these drawings, the fuel cell system 10 includes a fuel cell 12 that generates power by consuming hydrogen, and a reformer (a reformer for generating hydrogen-containing reformed gas to be supplied to the fuel cell 12). Reformer) 14 as main components.

  In this embodiment, the fuel cell 12 is a proton-conducting fuel cell that operates on the same principle as, for example, a polymer electrolyte fuel cell (PEFC) or a phosphoric acid fuel cell (PAFC). 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 The fuel cell 12 also 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. ing.

  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.

  As shown in FIG. 1, the reformer 14 includes a reformer (reactor) 25 that generates a hydrogen-containing reformed gas to be supplied to the anode electrode 16 of the fuel cell 12, and a reformer 25 is modified. A heating unit 26 for supplying heat for performing a quality reaction is configured as a main component. The reforming unit 25 incorporates a reforming catalyst 28 and contains hydrogen gas by catalyzing a hydrocarbon gas (gasoline, methanol, natural gas, etc.) to be supplied with a reforming gas (steam). A reformed gas is generated (reforming reaction is performed).

The reforming reaction in the reforming unit 25 includes each reaction including the steam reforming reaction represented by the formula (1) as represented by the following formulas (1) to (4). Therefore, the reformed gas obtained in the reforming process includes hydrogen (H ₂ ), carbon monoxide (CO), methane (CH ₄ ), cracked hydrocarbons, unreacted raw material hydrocarbons (C _x H _y ), etc. 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 ＣＨCH ₄ + H ₂ O (4)
The main steam reforming reaction of the formula (1) in the reforming reaction is an endothermic reaction, and the reforming unit 25 supplies the reformed gas to the fuel cell 12 operated at an intermediate temperature or a high temperature as described above. In order to supply, it is operated at a temperature higher than a predetermined temperature. The heating unit 26 is configured to supply heat for maintaining the reforming reaction and the operating temperature in the reforming unit 25. The heating unit 26 includes an oxidation catalyst (not shown) and is provided adjacent to the reforming unit 25. The heating unit 26 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 26 to the reforming unit 25 through the partition wall 30. For this reason, heat quantity can be directly given to reforming part 25, without changing calorie | heat amount into temperature like the structure which heats reforming part 25 via heating media (fluid), such as combustion gas. It is configured.

  The fuel cell system 10 includes a raw material pump 32 for supplying a hydrocarbon raw material to the reforming unit 25, and a discharge unit of the raw material pump 32 is connected to a raw material inlet of the reforming unit 25 via a raw material supply line 34. 25A. The hydrocarbon raw material slightly contains a sulfur component (sulfur compound) that does not contribute to the above reforming reaction. The hydrocarbon raw material is supplied to the reforming unit 25 in a gas phase or atomized state by a vaporizing means (not shown) such as an evaporator or an injection.

  The reformed gas outlet 25 </ b> B of the reforming unit 25 is connected to the upstream end of the reformed gas supply line 36 whose downstream end is connected to the fuel inlet 22 </ b> A of the anode flow path 22. As a result, the reformed gas generated in the reforming unit 25 is supplied to the anode electrode 16 of the fuel cell 12. On the other hand, the upstream end of the anode offgas line 38 is connected to the offgas outlet 22 </ b> B of the anode flow path 22, and the downstream end of the anode offgas line 38 is connected to the fuel inlet 26 </ b> A of the heating unit 26.

As described above, in the fuel cell system 10, the hydrogen in the reformed gas generated in the reforming unit 25 is consumed in the fuel cell 12, and the remaining components other than the consumed hydrogen are introduced into the heating unit 26 as anode offgas. The combustible components (hydrogen (H ₂ ), carbon monoxide (CO), hydrocarbon (HC), methane (CH ₄ ), carbon dioxide (CO ₂ )) are consumed as fuel in the heating unit 26. It has become. An exhaust gas line 39 for discharging combustion exhaust gas to the outside of the system is connected to the exhaust gas outlet 26B of the heating unit 26.

  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 42 connected to 24A is connected. Further, the upstream end of the steam supply line 44 is connected to the off-gas outlet 24 </ b> B of the cathode channel 24, and the downstream end of the steam supply line 44 is connected to the steam inlet 25 </ b> C of the reforming unit 25. Thereby, the cathode off gas containing the water vapor generated at the cathode electrode 18 and the oxygen not consumed at the cathode electrode 18 is used for the steam reforming reaction in the reforming unit 25.

  Furthermore, the fuel cell system 10 includes a cooling air pump 45 for supplying cooling air to the fuel cell 12, and the discharge portion of the cooling air pump 45 has a refrigerant flow (not shown) of the fuel cell 12 at the downstream end. It is connected to the upstream end of a cooling air line 46 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 48. The combustion support gas supply line 48 is connected to a combustion support gas inlet 26 </ b> C in the heating unit 26, and supplies a cooling off gas containing oxygen as a combustion support gas to the heating unit 26. Thus, the heating unit 26 is configured to cause catalytic combustion by bringing the anode off gas from the anode off gas line 38 and the cooling off gas from the combustion support gas supply line 48 into contact with the built-in oxidation catalyst.

  The fuel cell system 10 includes a regulating valve V1 and an on-off valve V2 that are provided in the water vapor supply line 44 and constitute the catalyst regeneration means in the present invention. The regulating valve V1 is arranged on the downstream side in the cathode off-gas flow direction with respect to the on-off valve V2 that can open and close the water vapor supply line 44, and the valve opening degree can be adjusted. This regulating valve V1 functions as a pressure increasing means for increasing the pressure of the steam supply line 44 in the fully closed state, and functions as a throttle means for reducing the supply flow rate of the cathode off gas to the reforming unit 25 in the partially opened state.

  A chamber 50 serving as a gas reservoir is provided between the regulating valve V1 and the on-off valve V2 in the water vapor supply line 44. In this embodiment, the chamber 50 is provided in series with the water vapor supply line 44. The chamber 50 has a heat insulating structure in which a heat insulating portion (not shown) is provided on the inner periphery or outer periphery.

  Each of the regulating valve V1 and the on-off valve V2 described above is controlled to be opened / closed or controlled by a catalyst regeneration controller 52 as a control device. Further, the fuel cell system 10 includes an on-off valve V3 that is provided in the cooling air line 46 and can open and close the cooling air line 46. The opening / closing of the on-off valve V3 is controlled by the catalyst regeneration controller 52.

  Based on a signal from a main controller (not shown) that controls the overall operation of the fuel cell system 10, the catalyst regeneration controller 52 has conditions for performing a regeneration process for recovering the catalytic activity of the reforming catalyst 28 of the reforming unit 25. If it is determined that the regeneration process is established, the operations of the raw material pump 32, the cathode air pump 40, the cooling air pump 45, the regulating valve V1, and the on-off valves V2 and V3 are controlled to perform carbonization. Cathode off gas is supplied to the reforming section 25 where the supply of hydrogen gas is stopped. The condition for starting the regeneration process is a condition corresponding to that the sulfur poisoning of the reforming catalyst 28 has progressed to a certain degree or is estimated to have progressed. For example, after the previous regeneration process of the fuel cell system 10 That the cumulative operation time in the fuel cell 12 and the accumulated power generation amount of the fuel cell 12 (the reforming amount of the reforming device 14) exceed a predetermined threshold, the hydrogen concentration in the reformed gas generated by the reforming unit 25 reaches the predetermined threshold. It is possible to employ one or more of below, that the temperature of the reforming catalyst 28 exceeds a predetermined threshold, and the like.

  Further, the catalyst regeneration controller 52 is configured to store the cathode off-gas at a predetermined pressure in the steam supply line 44 (mainly the chamber 50) in the regeneration process. The capacity of the chamber 50 is such that when the cathode off gas stored at the above-mentioned predetermined pressure is supplied to the reforming unit 25 while reducing the valve opening of the regulating valve V1, the cathode off-gas is supplied to the reforming unit 25 for a predetermined time. It is set as possible capacity. Specific control of catalyst regeneration by the catalyst regeneration controller 52 will be described later together with the operation of this embodiment.

  In this embodiment, the water vapor supply line 44, the regulating valve V1, the on-off valve V2, the chamber 50, and the catalyst regeneration controller 52 correspond to the catalyst regeneration means in the present invention. Note that the water vapor supply line 44 and the cooling air line 46 are also used during normal operation of the fuel cell system 10 (during power generation by the fuel cell 12), and therefore the regulating valve V1, the on-off valve V2, the cooling provided in these lines. The on-off valve V3 of the working air line 46 is fully opened during normal operation.

  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 to the reforming unit 25 of the reformer 14 by the operation of the raw material pump 32 and the cathode air pump 40. . In the reforming unit 25, reforming reactions represented by the equations (1) to (4) including a steam reforming reaction are performed, and a reformed gas containing hydrogen at a high concentration is generated.

  The reformed gas generated in the reforming unit 25 is supplied to the anode electrode 16 from the fuel inlet 22A of the anode channel 22. 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 via the electrolyte and is introduced into the cathode electrode 18. React with. 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 at the operating temperature). The gas containing water vapor is pushed out from the cathode electrode 18 to the water vapor supply line 44 as a cathode off gas, and is introduced into the reforming unit 25 through the water vapor inlet 25C. At this time, the chamber 50 is filled with the cathode off-gas while being replaced.

  On the other hand, the gas after the hydrogen in the reformed gas is consumed according to the amount of power generated along with the power generation is discharged from the anode electrode 16 as the anode off, and this anode off gas passes through the anode off gas line 38, It is supplied to the heating unit 26 of the reformer 14. The heating unit 26 is supplied with a cooling off gas after cooling the fuel cell 12 from the combustion support gas supply line 48. In the heating unit 26, catalytic combustion occurs with combustible components in the anode off-gas as fuel and oxygen in the cooling off-gas as combustion support gas. The heat generated by the catalytic combustion is supplied to the reforming unit 25 through the partition wall unit 30. With this heat, the reforming unit 25 maintains the reforming reaction, which is an endothermic reaction, and maintains the operating temperature (reformed gas temperature) at a temperature necessary for the reforming reaction.

  The main controller controls the entire fuel cell system 10 so that an amount of hydrogen corresponding to the amount of power generated by the fuel cell 12 is generated by the reformer 14 and the above operation is maintained.

  Along with the operation of the fuel cell system 10 as described above, the reforming catalyst 28 of the reforming unit 25 constituting the reforming device 14 is poisoned by the sulfur component contained in the hydrocarbon raw material, and the catalytic activity decreases. . For this reason, in the fuel cell system 10, a regeneration process is performed to recover the catalytic activity of the reforming catalyst 28 in a predetermined case. Hereinafter, the operation of this regeneration step will be described with reference to the flowchart shown in FIG.

  In step S10, the catalyst regeneration controller 52 of the fuel cell system 10 determines whether or not a condition for performing (starting) the regeneration process is satisfied (at catalyst regeneration timing) based on a signal from the main controller. If it is determined that the condition for performing the regeneration process is not satisfied, the process returns to step S10 and is repeated until this condition is satisfied.

  On the other hand, when the conditions for performing the regeneration process are satisfied, the catalyst regeneration controller 52 proceeds to step S12 and stops the material pump 32. Thereby, the supply of hydrocarbon gas to the reforming unit 25 is stopped. Next, the catalyst regeneration controller 52 proceeds to step S14 and fully closes the adjustment valve V1. Steps S12 and S14 may be executed simultaneously. As a result, the supply of the cathode off-gas (steam) to the reforming unit 25 is also stopped, and the reforming reaction is performed in the reforming unit 25 by the amount of the reforming raw material, steam, and the like remaining. On the other hand, since the operation of the cathode air pump 40 is continued, the water vapor in the cathode flow path 24 is pushed out to the water vapor supply line 44. Thereby, the pressure in the water vapor supply line 44 and the chamber 50 increases.

  The catalyst regeneration controller 52 proceeds to step S16, and determines whether or not the elapsed time from the fully closing of the regulating valve V1 has exceeded a predetermined time. If the predetermined time has not elapsed since the regulating valve V1 is fully closed, the process returns to step S16 and is repeated until the predetermined time elapses. When a predetermined time has elapsed since the regulating valve V1 is fully closed, the process proceeds to step S18, and the on-off valve V2 is fully closed. Further, the cathode air pump 40 is stopped. In this state, the cathode off-gas (gas containing water vapor and oxygen) having a temperature equivalent to the operating temperature of the fuel cell 12 is almost at a predetermined pressure in the chamber 50 between the regulating valve V1 and the on-off valve V2 in the water vapor supply line 44. Are stored. In step S16, the closing timing of the on-off valve V2 may be controlled based on, for example, whether or not the pressure in the chamber 50 has reached a predetermined pressure, instead of the elapsed time from the closing of the regulating valve V1.

  Then, the catalyst regeneration controller 52 proceeds to step S20 and partially opens the adjustment valve V1. As a result, the cathode off gas stored in the steam supply line 44 and the chamber 50 is gradually supplied to the reforming unit 25 while the supply flow rate is reduced by the regulating valve V1. The sulfur component on the reforming catalyst 28 is removed by supplying the cathode off gas. Further, the supply of the cathode off gas causes the gas in the reforming unit 25 to be discharged, and a gas flow is generated in the reformed gas supply line 36, the anode flow path 22, and the anode off gas line 38, and the anode flow path 22 and the anode off gas. The anode off gas staying in the line 38 is supplied to the reforming catalyst 28.

  As a result, the endotherm associated with the reforming reaction is stopped in the reforming unit 25, whereas the combustible component in the anode off-gas supplied in the heating unit 26 is converted into an oxidation catalyst together with oxygen from the combustion support gas supply line 48. Burns in contact. The heat accompanying this combustion is supplied to the reforming catalyst 28 of the reforming section 25 via the partition wall section 30, and is used for removing sulfur components, that is, for recovering the catalytic activity.

  Next, in step S22, the catalyst regeneration controller 52 finishes the combustion of the anode off gas in the heating unit 26 based on information from the main controller (for example, the anode off gas component (gas sensor output) and the temperature distribution of the heating unit 26). Determine whether or not. If it is determined that the combustion in the heating unit 26 has not ended, the process returns to step S22 and is repeated until the end of combustion. On the other hand, if it is determined that the combustion in the heating unit 26 has ended, the process proceeds to step S24, and the on-off valve V3 is fully closed. Further, the cooling air pump 45 is stopped. As a result, the supply of low-temperature air that lowers the temperature of the reforming unit 25 (reforming catalyst 28) by sensible heat cooling is stopped.

  Further, the catalyst regeneration controller 52 proceeds to step S26, and determines whether or not the elapsed time from the partial opening of the regulating valve V1, that is, the start of supply of the cathode off gas to the reforming unit 25, has reached a predetermined time. If the predetermined time has not elapsed since the start of the cathode offgas supply, the process returns to step S26 and is repeated until the predetermined time elapses. When a predetermined time has elapsed from the start of the cathode offgas supply, that is, when the catalyst regeneration end condition is satisfied, the process proceeds to step S28, where the regulating valve V1, the on-off valves V2, V3 are fully opened, and the control is terminated. Thereby, the fuel cell system 10 returns to the control state by the main controller, and restarts the operation for generating power by the fuel cell 12. The predetermined time for supplying the cathode off gas to the reforming unit 25 may be, for example, a preset time or may be calculated from an operation time between catalyst regenerations.

  Here, in the fuel cell system 10, the cathode offgas of the fuel cell 12 is supplied to the reforming unit 25 to regenerate the reforming catalyst 28, that is, to recover the catalyst activity. The regeneration of the catalyst 28 can be performed. Specifically, the cathode offgas contains water vapor and oxygen necessary for the regeneration of the reforming catalyst 28, and the cathode offgas itself has a temperature (heat) corresponding to the operating temperature of the fuel cell 12, for example. , Evaporating water (supplying latent heat) to generate water vapor and supplying it to the reforming catalyst 28, and directly contributing to the operation of the fuel cell 12 and the hydrogen generation in the reformer 14 to the heating unit 26. Compared with the configuration in which the reforming catalyst 28 is heated by supplying unperformed fuel, energy for generating steam and energy for heating the reforming catalyst 28 are unnecessary, and the efficiency of the entire system is high.

  Moreover, in the fuel cell system 10, the anode off gas (combustible gas) staying in the anode flow path 22 and the anode off gas line 38 of the fuel cell 12 is burned in the heating unit 26, so that it does not depend on external energy supply. Further, heat necessary for catalyst regeneration can be further applied to the reforming catalyst 28 of the reforming unit 25. Thereby, the sulfur component on the reforming catalyst 28 can be more effectively removed. Immediately after stopping the raw material pump 32 (reforming raw material supply) for catalyst regeneration, the endothermic reaction on the reforming side decreases, while the heat balance on the heating side is generated. There is no state. By this imbalance, it is possible to raise the temperature of the reforming catalyst 28 in a relatively short time.

  Thus, in the fuel cell system 10 according to the first embodiment of the present invention, the catalytic activity of the reforming catalyst 28 can be efficiently recovered.

  Further, in the fuel cell system 10, the cathode off gas is supplied to the reforming unit 25 for catalyst regeneration. In other words, both the water vapor contributing to (promoting) catalyst regeneration and low-concentration oxygen are reformed. Therefore, sufficient recovery of the catalyst activity can be realized in a very short regeneration step. In the fuel cell system 10 to which the combustion heat of the anode off gas is supplied as described above, the catalyst regeneration time with respect to the operation time is several tenths to hundreds in order to satisfy the three conditions of water vapor, low concentration oxygen, and temperature. It can be a tenth. For this reason, in the fuel cell system 10, the catalytic activity of the reforming catalyst 28 could be recovered by the catalyst regeneration step for the predetermined time described above.

  In the fuel cell system 10, the pressure of the water vapor supply line 44 is increased by closing the regulating valve V1 before starting the catalyst regeneration step, and the cathode off-gas is stored in a short time after the fuel supply is stopped. It was realized that the supply to the reforming unit 25 was continued. That is, a limited amount of cathode off-gas supplyable time was converted to pressure, stored, and supplied for a predetermined time while being throttled by the regulating valve V1. In addition, since the water vapor supply line 44 is provided with the chamber 50, it has been realized that a sufficient amount of cathode off-gas can be stored in the regeneration process.

  Next, a second embodiment of the present invention will be described. Note that parts and portions that are basically the same as those of the first embodiment are denoted by the same reference numerals as those of the first embodiment, and description thereof is omitted. FIG. 4 shows a fuel cell system 60 according to the second embodiment of the present invention in a system flow diagram corresponding to FIG. As shown in this figure, the fuel cell system 60 differs from the fuel cell system 10 in that an accumulator 62 is provided instead of the chamber 50.

  The accumulator 62 is connected to the downstream end of the branch line 64 branched from the portion between the regulating valve V1 and the on-off valve V2 in the water vapor supply line 44. Similarly to the chamber 50, the capacity of the accumulator 62 is determined so that the catalyst regeneration process for a predetermined time can be performed in a state where the cathode off-gas having a predetermined pressure is stored. The branch line 64 is provided with an on-off valve V4 that can be opened and closed by the catalyst regeneration controller 52. The on-off valve V4 is fully closed during normal operation of the fuel cell system 10.

  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 the fuel cell system 10 according to the first embodiment. Further, in the fuel cell system 60 including the accumulator 62 and the on-off valve V4, when the fuel cell system 10 is started up, the accumulator 62 is smoothly started up without being filled with the cathode off gas, and the accumulator is operated during the operation of the fuel cell 12. The cathode off gas can be stored in 62.

  For example, when there is a request to reduce the amount of power generation of the fuel cell 12 and the reformed gas generation amount of the reformer 14 is reduced, the cathode off gas becomes excessive with respect to the required reforming amount. The on / off valve V4 is opened while the pressure is reduced, and the cathode offgas can be stored in the accumulator 62 while reducing the amount of cathode offgas supplied to the reforming unit 25. Further, for example, the cathode off gas can be stored in the accumulator 62 while reducing the power generation amount of the fuel cell 12 immediately before performing the regeneration step for recovering the catalytic activity of the reforming catalyst 28. That is, the fuel cell system 60 can also convert the cathode fugus into the pressure of the water vapor supply line 44 and the accumulator 62 and hold it before starting the catalyst regeneration step, which is sufficient for the recovery of the catalytic activity of the reforming catalyst 28. Time catalytic reforming steps can be performed.

1 is a system flow 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 flowchart which shows the control flow for catalyst reproduction | regeneration of the fuel cell system which concerns on embodiment of this invention. It is a system flow figure showing a schematic whole structure of a fuel cell system concerning a 2nd embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Fuel cell system 12 Fuel cell 16 Anode electrode 18 Cathode electrode 25 Reforming part 26 Heating part 28 Reforming catalyst 42 Cathode air supply line (supply line)
50 chamber (gas reservoir)
52 Catalyst regeneration controller (catalyst regeneration means)
60 Fuel cell system 62 Accumulator (gas reservoir)
V1 regulating valve (catalyst regeneration means, throttle means)
V2 to V4 open / close valve (catalyst regeneration means)

Claims (4)

A reforming unit that generates a hydrogen-containing gas from a reforming raw material containing a sulfur component using a reforming catalyst;
A fuel cell that consumes hydrogen in the hydrogen-containing gas to generate power, and generates water on the cathode electrode side with the power generation;
After stopping the supply of the reforming raw material to the reforming section and after performing a gas storage step of increasing the pressure of a supply line for supplying the cathode off-gas discharged from the cathode electrode to the reforming section, the cathode A catalyst regeneration means for performing a regeneration step for recovering the activity of the reforming catalyst by supplying off-gas to the reforming unit over a predetermined time ;
A fuel cell system comprising: The fuel cell system according to claim 1, wherein the catalyst regeneration unit includes a gas storage unit that is provided in the supply line and stores the cathode off gas . 3. The fuel cell system according to claim 1 , wherein the catalyst regeneration unit includes a throttle unit that throttles a supply flow rate of the cathode off gas to supply the cathode off gas to the reforming unit over a predetermined time . The reforming section is provided with a heating section for supplying the reforming catalyst with heat obtained by burning anode off-gas discharged from an anode electrode that consumes the hydrogen-containing gas in the fuel cell. The fuel cell system according to any one of claims 1 to 3 .

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