JP4784047B2 - Fuel cell system - Google Patents

Description

  The present invention provides a fuel cell including a reforming unit that generates reformed gas containing hydrogen by reforming the supplied fuel and reformed water with a reforming catalyst filled therein and leads the reformed gas to the fuel cell. More particularly, the present invention relates to a fuel cell system having a function of regenerating a shift catalyst poisoned during operation.

  The fuel cell system includes a reforming unit that generates and derives a reformed gas containing hydrogen by reforming the supplied fuel with a reforming catalyst filled therein, and the reforming unit derived from the reforming unit. A device having a carbon monoxide shift reaction part that reduces and derives the carbon monoxide concentration in the reformed gas by a shift catalyst filled therein is known.

  As the fuel supplied to the reforming section, city gas mainly composed of natural gas, LPG, naphtha, kerosene, etc. are used. City gas or LPG contains several ppm of sulfur compounds as odorants, Kerosene contains several tens of ppm of sulfur compounds as impurities. The fuel supply means of the fuel cell system is provided with a desulfurizer for removing sulfur compounds in the fuel in order to prevent the sulfur compounds from poisoning catalysts such as reforming catalysts and shift catalysts. However, since the desulfurizer cannot completely remove the sulfur compound, the sulfur compound continues to slightly flow into the catalyst. As a result, the catalyst was gradually poisoned by the sulfur compound, eventually failing to satisfy the necessary catalytic function, and labor for replacing the reforming catalyst and the reforming unit was generated. Further, like the reforming unit, the shift catalyst is poisoned with sulfur in the carbon monoxide shift reaction unit, and it takes time to replace the shift catalyst and the carbon monoxide shift reaction unit.

  There is a fuel reformer described in Patent Document 1 as a means for recovering the catalyst performance to solve this problem. In this fuel reformer, as disclosed in Patent Document 1, a recovery gas supply unit 4 that supplies an inert gas or water vapor gas to the reforming unit 1 is provided. While supplying an inert gas or water vapor gas to the reforming unit 1 and heating the reforming unit 1 with the heating jig 2 (for example, about 500 to 800 ° C.), the catalytic activity of the reforming catalyst is recovered. .

  Further, there is a reforming catalyst device described in Patent Document 2. In this reforming catalyst device, as shown in FIG. 1 of Patent Document 2, fuel and air are supplied to the reforming catalyst layer 2 and the temperature of the reforming catalyst is 500 ° C. or higher and 800 ° C. or lower. The performance of the reforming catalyst is restored. Fuel and air are supplied to the reforming catalyst layer 2 by the fuel introduction means 4 and the air introduction means 5, respectively.

  Furthermore, there is a method for producing a reforming catalyst described in Patent Document 3. Patent Document 3 describes a method of regenerating a catalyst by adjusting a supply ratio of fuel, air, and steam, or increasing a catalyst temperature.

Further, there is a shift catalyst body deterioration determination device and a hydrogen generation device described in Patent Document 4. In this apparatus, the temperature of the shift portion of the reformer for reforming LPG (there are Cu—Zn catalyst, Fe—Cr catalyst, noble metal catalyst, etc. as the catalyst) is raised during catalyst deterioration. That is, the reactivity on the catalyst is improved by controlling the temperature of the catalyst. This temperature control is performed by a cooling fan and an electric heater.
Japanese Unexamined Patent Publication No. 2000-351606 (pages 3, 4 and 1) JP 2002-282710 A (pages 3, 4 and 1) Japanese translation of PCT publication No. 2003-503186 (page 4-10, FIGS. 1 and 2) JP 2003-217636 A (page 5-12, FIG. 1-13)

  In the fuel reforming apparatus described in Patent Document 1 described above, since the recovery gas supply unit 4 is provided, there is a problem that the apparatus becomes complicated and expensive. Further, in the reforming catalyst device described in Patent Document 2, it is unclear what causes the reforming catalyst to deteriorate. Further, when air is blown into the reforming catalyst, a heat spot is generated and the catalyst may be deteriorated. Further, since the air introduction means 5 is provided, there is a problem that the apparatus becomes complicated and expensive. Moreover, in patent document 3, it is not fully disclosed about the method of solving the catalyst poisoned with sulfur. Moreover, in the apparatus described in Patent Document 4, the temperature of the catalyst is controlled within a predetermined temperature range, but there is a problem that the controllability is poor, and in Patent Document 4, sulfur poisoning has occurred. There is no description of how to solve the catalyst.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a fuel cell system capable of regenerating a sulfur-poisoned shift catalyst with a simple configuration and good controllability.

In order to solve the above problems, the structural feature of the invention according to claim 1 is that a reformed gas containing hydrogen is generated by reforming the supplied fuel with a reforming catalyst filled therein. A fuel cell comprising a reforming section for deriving and a carbon monoxide shift reaction section for deriving by reducing the carbon monoxide concentration in the reformed gas derived from the reforming section with a shift catalyst filled therein The system further includes a heat exchange means provided in the carbon monoxide shift reaction section for exchanging heat with the reformed gas, and using the reformed gas generated in the reforming section with a sulfur-poisoned shift catalyst. Therefore, by adjusting the temperature of the shift catalyst to the catalyst regeneration temperature by heat exchange means, the sulfur-poisoned shift catalyst is at least raised to the catalyst regeneration temperature at which sulfur can be removed from the shift catalyst and sulfur compounds. Warm It is.

  Further, the structural feature of the invention according to claim 2 is that, in claim 1, the catalyst regeneration temperature is higher than the normal operation temperature.

Further, the structural feature of the invention according to claim 3 is that in claim 1 or claim 2 , the heat exchange means introduces a reformed gas and an oxidant gas derived from the carbon monoxide shift reaction section. The combustion gas is supplied from a combustor combusted by a built-in combustion catalyst, and heat is exchanged between the combustion gas and the reformed gas.

The structural feature of the invention according to claim 4 is that in claim 3 , the shift catalyst is heated to the catalyst regeneration temperature by adjusting the amount of the oxidant gas input.

A structural feature of the invention according to claim 5 is that in any one of claims 1 to 3 , further comprising reforming water supply means for supplying reforming water to the reforming section. The quality water supply means is to raise the temperature of the shift catalyst to the catalyst regeneration temperature by supplying a larger amount of reforming water than the supply amount during normal operation when the shift catalyst is regenerated.

In the invention according to claim 1 configured as described above, when the fuel cell system is started, the sulfur-poisoned shift catalyst is regenerated using the reformed gas generated in the reforming section. The shift catalyst thus heated is at least heated to a catalyst regeneration temperature at which sulfur can be removed from the shift catalyst and sulfur compounds. As a result, the chemical reaction opposite to the poisoning of the shift catalyst, which is an exothermic reaction, is promoted by utilizing the reaction equilibrium, so that the substance combined with the adsorbed catalyst or the adsorbed substance can be easily separated (removed) from the catalyst. can do. Therefore, by regenerating the shift catalyst without providing another device, the complexity and cost of the device can be suppressed.
Furthermore, a heat exchanging means provided in the carbon monoxide shift reaction section for exchanging heat with the reformed gas is further provided. By adjusting the temperature of the shift catalyst to the catalyst regeneration temperature by the heat exchanging means, the normal operation is performed. Sometimes, by regenerating the catalyst using heat exchange means that lowers the reformed gas at a high temperature to the shift reaction temperature, it is not necessary to use electric energy to operate the fan and the electric heater. The catalyst can be efficiently regenerated.

  In the invention according to claim 2 configured as described above, in the fuel cell system according to claim 1, since the catalyst regeneration temperature is higher than the normal operation temperature, the catalyst can be reliably regenerated.

In the invention according to Claim 3 configured as described above, in the fuel cell system according to Claim 1 or Claim 2 , the heat exchange means includes a reformed gas and an oxidant gas derived from the carbon monoxide shift reaction section. Because the combustion gas is supplied from the combustor that burns with the built-in combustion catalyst and heat is exchanged between the combustion gas and the reformed gas, the reformed gas that cannot be supplied to the fuel cell at startup Is used to raise the temperature of the reformed gas which is still low and raise the temperature of the shift catalyst. Therefore, the catalyst can be regenerated by efficiently using the energy input to the fuel cell system with a simple configuration.

In the invention according to claim 4 configured as described above, in the fuel cell system according to claim 3 , the temperature of the shift catalyst is controlled by adjusting the amount of combustion gas heat by adjusting the input amount of the oxidant gas. Adjust to regeneration temperature. Therefore, the catalyst temperature can be adjusted with good controllability.

In the invention according to Claim 5 configured as described above, in the fuel cell system according to any one of Claims 1 to 3 , the reforming water supply means for supplying the reforming water to the reforming unit is further provided. This reforming water supply means raises the shift catalyst to the catalyst regeneration temperature by supplying a larger amount of reforming water than the amount supplied during normal operation when regenerating the shift catalyst. Can be raised to the catalyst regeneration temperature more quickly.

1) First Embodiment Hereinafter, a first embodiment of a fuel cell system according to the present invention will be described. FIG. 1 is a schematic diagram showing an outline of this fuel cell system. As shown in FIG. 1, this fuel cell system includes a fuel cell 10 and a steam reforming reformer 20 that generates hydrogen gas necessary for the fuel cell 10. The fuel cell 10 includes a fuel electrode 11 and an air electrode 12, and generates power using the reformed gas supplied to the fuel electrode 11 and the air (cathode air) supplied to the air electrode 12.

  The reformer 20 includes a reforming unit 21 that reforms fuel and a carbon monoxide shift reaction unit (hereinafter referred to as a CO shift unit) that removes carbon monoxide contained in the reformed gas derived from the reforming unit 21. ) 23 and a carbon monoxide selective oxidation unit (hereinafter referred to as a CO selective oxidation unit) 24 that further removes carbon monoxide contained in the reformed gas derived from the CO shift unit 23. Examples of the fuel include natural gas, LPG, kerosene, gasoline, methanol, and the like. In the present embodiment, description will be made on natural gas.

  The reforming unit 21 includes a reaction chamber 21b that is formed in a bottomed cylindrical shape and is disposed so as to open downward, and is filled with a catalyst (reforming catalyst) 21a. The reforming unit 21 is provided with a combustion unit 22. The combustion unit 22 includes a heating chamber 22a that is provided in close contact with the reaction chamber 21b and heats the reaction chamber 21b, and a burner 22b that supplies high-temperature combustion gas to the heating chamber 22a.

  A fuel supply pipe 41 connected to a fuel supply source Sf (for example, a city gas pipe) is connected to the reaction chamber 21b, and fuel is supplied from the fuel supply source Sf. The fuel supply pipe 41 is provided with a first fuel valve 42, a fuel pump 43, a desulfurizer 44, a second fuel valve 45, and a heat exchange unit 46 in order from the upstream. The first and second fuel valves 42 and 45 open and close the fuel supply pipe 41 according to commands from the control device 30. The fuel pump 43 sucks the fuel supplied from the fuel supply source Sf and discharges it to the reaction chamber 21 b of the reforming unit 21, and adjusts the fuel supply amount according to a command from the control device 30. The desulfurizer 44 removes a sulfur content (for example, a sulfur compound) in the fuel. The heat exchange unit 46 supplies the preheated fuel to the reaction chamber 21b of the reforming unit 21 by exchanging heat with the high temperature reformed gas supplied from the reforming unit 21 to the CO shift unit 23. It is. Thereby, the sulfur content is removed from the fuel, and the fuel is preheated and supplied to the reaction chamber 21b.

  Further, a steam supply pipe 52 connected to the evaporator 55 is connected between the second fuel valve 45 of the fuel supply pipe 41 and the heat exchanging section 46, and the steam supplied from the evaporator 55 is mixed with the fuel. To the reaction chamber 21b of the reforming section 21. A water supply pipe 51 connected to a water tank Sw that is a reforming water supply source is connected to the evaporator 55. The water supply pipe 51 is provided with a water pump 53 and a water valve 54 in order from the upstream. The water pump 53 sucks the reformed water supplied from the water tank Sw and discharges it to the evaporator 55, and adjusts the reformed water supply amount according to a command from the control device 30. The water valve 54 opens and closes the water supply pipe 51 according to a command from the control device 30. The water supply pipe 51 is wound around the outer periphery of the heating chamber 22a, and the running water in the water supply pipe 51 is preheated by the high heat of the heating chamber 22a. The evaporator 55 is provided with an exhaust pipe 81 having one end connected to the heating chamber 22a and the other end opened to the outside. The evaporator 55 passes the preheated reformed water supplied to the exhaust pipe 81 through the exhaust pipe 81. Heating is performed by combustion gas (exhaust gas) discharged from the flowing heating chamber 22a to the outside and supplied to the reaction chamber 21b. As a result, the reformed water is preheated and supplied to the evaporator 55, and is supplied to the reaction chamber 21b as water vapor. Note that, in the first embodiment, the evaporation section 56 is constituted by the water supply pipe 51 and the portion wound around the heating chamber 22 a and the evaporator 55. The evaporator 55 is provided with a temperature sensor 55a for detecting the internal temperature.

  The reaction chamber 21b is heated by the combustion gas of the burner 22b as will be described later, and the fuel and water vapor supplied into the reaction chamber 21b are converted into a reforming catalyst 21a (for example, Ru, The hydrogen gas and the carbon monoxide gas are generated by reaction and reforming by a Ni-based catalyst (so-called steam reforming reaction). At the same time, in the reaction chamber 21b, the so-called carbon monoxide shift in which carbon monoxide generated by the steam reforming reaction is converted into hydrogen gas and carbon dioxide by reacting with steam as shown in the following chemical formula 2. A reaction is occurring. The generated gas (so-called reformed gas) is cooled through the heat exchange unit 46 and led to the CO shift unit 23. A temperature sensor 21a1 for detecting the temperature of the reforming catalyst 21a is provided in the reaction chamber 21b.

(Chemical formula 1)
_{CH 4 + H 2 O → 3H} 2 + CO-Q1
(Chemical formula 2)
CO + H ₂ O → H ₂ + CO ₂ + Q2

  The steam reforming reaction is an endothermic reaction, and as is clear from the above chemical formula 1, when the reaction proceeds to the right side, the amount of heat Q1 is absorbed, and conversely, when the reaction proceeds to the left side, the amount of heat Q1 is generated. Further, the carbon monoxide shift reaction is an exothermic reaction, and as is clear from the chemical formula 2, when the reaction proceeds to the right side, the amount of heat Q2 is generated, and conversely, when the reaction proceeds to the left side, the amount of heat Q2 is absorbed.

  In the CO shift unit 23, the carbon monoxide contained in the supplied reformed gas is caused by the shift catalyst 23a (for example, Pt-based catalyst) filled in the CO shift unit 23, as shown in Chemical Formula 2 above. A so-called carbon monoxide shift reaction that reacts with water vapor and transforms into hydrogen gas and carbon dioxide gas occurs. As a result, the reformed gas is derived with the carbon monoxide concentration reduced by the carbon monoxide shift reaction described above. A temperature sensor 23a1 for detecting the temperature of the shift catalyst 23a is provided in the CO shift unit 23. The CO shift unit 23 has a folded structure, and the reformed gas is introduced from the center of the lower part and led out from the side surface of the folded lower part at the upper part.

  The reformed gas having a reduced carbon monoxide concentration derived from the CO shift unit 23 is supplied to the CO selective oxidation unit 24. On the other hand, the CO selective oxidation unit 24 is connected to an oxidation air supply pipe 61 connected to an air supply source Sa, and air, which is an oxidant gas, is supplied from the air supply source Sa (for example, the atmosphere). . The oxidation air supply pipe 61 is provided with a filter 62, an air pump 63, and a first air valve 64 in order from the upstream. The filter 62 filters air. The air pump 63 sucks in air supplied from the air supply source Sa and discharges it to the CO selective oxidation unit 24, and adjusts the air supply amount in accordance with a command from the control device 30. The first air valve 64 opens and closes the oxidizing air supply pipe 61 according to a command from the control device 30, and adjusts the flow rate when it is open. As a result, a predetermined amount of air is supplied to the CO selective oxidation unit 24.

  The carbon monoxide remaining in the reformed gas supplied to the CO selective oxidation unit 24 is converted into the catalyst 24a (for example, Ru-based or Pt-based) filled in the CO selective oxidation unit 24 as shown in the following chemical formula 3. The catalyst) reacts with the oxygen in the air supplied as described above to become carbon dioxide. As a result, the reformed gas is derived by further reducing the carbon monoxide concentration by oxidation reaction (10 ppm or less), and is supplied to the fuel electrode 11 of the fuel cell 10. Note that hydrogen in the reformed gas is also oxidized into water.

(Chemical formula 3)
CO + 1 / 2O ₂ → CO ₂ + Q3
This reaction is an exothermic reaction, and as is clear from the chemical formula 3 above, the amount of heat Q3 is generated when the reaction proceeds to the right side, and conversely, the amount of heat Q3 is absorbed when the reaction proceeds to the left side.

  A CO selective oxidation unit 24 is connected to the inlet of the fuel electrode 11 of the fuel cell 10 via a reformed gas supply pipe 71 so that the reformed gas is supplied to the fuel electrode 11. A burner 22b is connected to the outlet of the fuel electrode 11 through an off-gas supply pipe 72, and anode off-gas discharged from the fuel cell 10 (reformed gas containing hydrogen that has not been used in the fuel electrode 11). The burner 22b is supplied. The bypass pipe 73 bypasses the fuel cell 10 and directly connects the reformed gas supply pipe 71 and the offgas supply pipe 72. The reformed gas supply pipe 71 is provided with a first reformed gas valve 74 between the branch point of the bypass pipe 73 and the fuel cell 10. The off gas supply pipe 72 is provided with a first off gas valve 75 between the junction with the bypass pipe 73 and the fuel cell 10. A second reformed gas valve 76 is provided in the bypass pipe 73. The first and second reformed gas valves 74 and 76 and the first off gas valve 75 open and close the respective pipes and are controlled by the control device 30.

  The leading end of a cathode air supply pipe 67 branched from the oxidizing air supply pipe 61 is connected to the inlet of the air electrode 12 of the fuel cell 10 upstream of the air pump 63. Air, which is an oxidant gas, is supplied. The cathode air supply pipe 67 is provided with a cathode air pump 68 and a cathode air valve 69 in order from the upstream. The cathode air pump 68 sucks air supplied from the air supply source Sa and discharges it to the air electrode 12 of the fuel cell, and adjusts the cathode air supply amount in accordance with a command from the control device 30. The cathode air valve 69 opens and closes the cathode air supply pipe 67 according to a command from the control device 30. Further, one end of an exhaust pipe 82 whose other end is opened to the outside is connected to the outlet of the air electrode 12 of the fuel cell 10.

  Further, a combustion fuel supply pipe 47 branched from the fuel supply pipe 41 is connected to the burner 22b upstream of the fuel pump 43 so that combustion fuel is supplied. The combustion fuel supply pipe 47 is provided with a combustion fuel pump 48. The combustion fuel pump 48 sucks the fuel supplied from the fuel supply source Sf and discharges it to the burner 22b. The fuel supply amount for combustion is adjusted according to the above. Further, a combustion air supply pipe 65 branched from the oxidizing air supply pipe 61 is connected to the burner 22b upstream of the air pump 63, and combustion air for burning combustion fuel, reformed gas or off-gas. Is to be supplied. The combustion air supply pipe 65 is provided with a combustion air pump 66. The combustion air pump 66 sucks air supplied from the air supply source Sa and discharges it to the burner 22b. The combustion air supply amount is adjusted according to the above. When the burner 22b is ignited by a command from the control device 30, the combustion fuel, reformed gas or anode off-gas supplied to the burner 22b is combusted to generate a high-temperature combustion gas, and this combustion gas enters the heating chamber 22a. The reforming catalyst 21a is heated by heating the reaction chamber 21b. The combustion gas that has passed through the heating chamber 22a is exhausted to the outside through the exhaust pipe 81 and the evaporator 55 as exhaust gas.

  A reformed gas condenser 77, an anode offgas condenser 78, and a cathode offgas condenser 79 are provided in the middle of the reformed gas supply pipe 71, offgas supply pipe 72, and exhaust pipe 82, respectively. The reformed gas condenser 77 condenses water vapor in the reformed gas supplied to the fuel electrode 11 of the fuel cell 10 flowing in the reformed gas supply pipe 71. The anode offgas condenser 78 condenses water vapor in the anode offgas discharged from the fuel electrode 11 of the fuel cell 10 flowing in the offgas supply pipe 72. The cathode offgas condenser 79 condenses the water vapor in the cathode offgas discharged from the air electrode 12 of the fuel cell 10 flowing in the discharge pipe 82. Each of the condensers 77 to 79 is provided with a refrigerant pipe through which a low-temperature liquid in a hot water tank (not shown) or a liquid cooled by a radiator and a cooling fan is supplied, and each gas is exchanged by heat exchange with the liquid. The water vapor inside is condensed.

  These condensers 77, 78, and 79 communicate with a pure water device 85 through a pipe 84, and condensed water condensed in each condenser 77, 78, and 79 is led out to the pure water device 85 and collected. It has become so. The deionizer 85 converts the condensed water supplied from each of the condensers 77, 78, 79, that is, recovered water into pure water by using a built-in ion exchange resin, and the purified water is led to the water tank Sw. To do. Note that a pipe for introducing makeup water (tap water) supplied from a tap water supply source (for example, a water pipe) is connected to the water purifier 85, and the amount of water stored in the water purifier 85 is below the lower limit water level. And tap water is supplied.

  The fuel cell system includes a combustor 86. The combustor 86 is a reformed gas derived from the CO shift unit 23 (more specifically, a reformed off-gas derived from the CO selective oxidation unit 24 and supplied without passing through the fuel cell 10) and an oxidant gas. Air is introduced and burned by a built-in combustion catalyst (for example, palladium-based catalyst, platinum-based catalyst, platinum-palladium-based catalyst), and the combustion gas is supplied to the heat exchanger 87 (which is a heat exchange means). ing. The heat exchanger 87 includes first and second heat exchangers 87a and 87b provided at the lower part and the upper part of the CO shift unit 23, respectively. The first heat exchanger 87a exchanges heat between the reformed gas introduced into the CO shift unit 23 and the combustion gas, and the second heat exchanger 87b passes through the folded portion of the CO shift unit 23. Heat is exchanged between the reformed gas and the combustion gas. The first and second heat exchangers 87a and 87b can also lower the temperature of the reformed gas, which is high during normal operation, to the shift reaction temperature.

  A combustion off-gas supply pipe 88 branched from the off-gas supply pipe 72 downstream of the condenser 78 is connected to the introduction port of the combustor 86, and the reformed off-gas from the CO selective oxidation unit 24 or the fuel cell 10. The anode off gas from is supplied. A combustor air supply pipe 89 branched from the oxidizing air supply pipe 61 between the air pump 63 and the first air valve 64 is joined to the combustion offgas supply pipe 88, and an oxidant gas from the air supply source Sa. Is mixed with the reformed off gas or anode off gas and supplied to the combustor 86. Further, a combustion gas supply pipe 90 that joins the off-gas supply pipe 72 upstream of the burner 22b via the first and second heat exchangers 87a and 87b is connected to the outlet of the combustor 86, and combustion is performed. Gas is supplied to the burner 22b through the first and second heat exchangers 87a and 87b. The combustion gas bypass pipe 91 bypasses the first and second heat exchangers 87a and 87b and directly connects the combustion gas supply pipe 90 and the off gas supply pipe 72.

  The off gas supply pipe 72 is provided with a second off gas valve 92 between a branch point with the combustion off gas supply pipe 88 and a junction with the combustion gas supply pipe 90 and the combustion gas bypass pipe 91. The combustion off gas supply pipe 88 is provided with a third off gas valve 93 between the branch point of the off gas supply pipe 72 and the combustor 86. The combustion gas supply pipe 90 is provided with a first combustion gas valve 94 between the combustor 86 and the first heat exchanger 87a, and between the second heat exchanger 87b and the off-gas supply pipe 72. A second combustion gas valve 95 is provided. The combustion gas bypass pipe 91 is provided with a third combustion gas valve 96. The combustor air supply pipe 89 is provided with a second air valve 97. These valves 92 to 96 open and close the respective pipes and are controlled by the control device 30. Similar to the first air valve 64, the second air valve 97 opens and closes the combustor air supply pipe 89 according to a command from the control device 30, and adjusts the flow rate when the combustor air supply pipe 89 is open. As a result, a predetermined amount of air (oxidant gas) is supplied to the combustor 86.

  The fuel cell system also includes a control device 30, which includes the temperature sensors 21 a 1, 23 a 1, 55 a, the pumps 43, 48, 53, 63, 66, 68, the valves 42, 45, 54, 64, 69, 74, 75, 76, 92 to 97, and the burner 22b are connected (see FIG. 2). The control device 30 includes a microcomputer (not shown), and the microcomputer includes an input / output interface, a CPU, a RAM, and a ROM (all not shown) connected through a bus. The CPU executes a program corresponding to the flowchart of FIG. 3 to regenerate the shift catalyst 23a poisoned during the operation of the fuel cell system using the reformed gas generated in the reforming unit 21, The sulfur-poisoned shift catalyst 23a is heated to a catalyst regeneration temperature that can remove sulfur from the shift catalyst 23a and the sulfur compound, and that is higher than the normal operating temperature range and lower than the heat resistance temperature of the shift catalyst. You are in control. The RAM temporarily stores variables necessary for executing the program, and the ROM stores the program.

  Next, activation of the above-described fuel cell system will be described with reference to FIGS. When a start switch (not shown) is turned on at time t0, control device 30 executes the program shown in FIG. 3 and controls the fuel cell system as shown in FIG. In step 102, the control device 30 closes the first reformed gas valve 74, the first offgas valve 75, the third offgas valve 93, the second combustion gas valve 95, and the third combustion gas valve 96, The second off-gas valve 92 is opened to connect the CO selective oxidation unit 24 to the burner 22b, the first fuel valve 42 is opened, the second fuel valve 45 is closed, and the combustion fuel pump 48 and the combustion air pump 66 are driven. Combustion fuel and combustion air are supplied to the burner 22b to ignite the burner 22b. Thereby, the fuel for combustion is combusted, and the reforming catalyst 21a and the evaporator 55 in the reforming unit 21 are heated by the combustion gas.

  The control device 30 detects the temperature of the evaporator 55 by the temperature sensor 55a, and when the detected temperature is equal to or higher than the first predetermined temperature Th1 (time t1), the water valve 54 is opened and the water pump 53 is driven. The water in the water tank Sw is supplied to the reforming unit 21 through the evaporator 55 by a predetermined flow rate (predetermined supply amount: normal operation flow rate, for example, a flow rate at which S / C is 3) (steps 104 and 106).

  The control device 30 starts counting the timer from the time (time t1) when the temperature of the evaporator 55 becomes equal to or higher than the predetermined temperature Th1. If the timer is equal to or longer than the first predetermined time T1 (for example, 1 minute) (time t2), the second fuel valve 45 is opened to drive the fuel pump 43, and the fuel from the fuel supply source Sf is supplied at a predetermined flow rate (predetermined supply amount: normal The operating flow rate, for example, a flow rate at which S / C becomes 3) is supplied to the reforming unit 21, and the first air valve 64 is opened to drive the air pump 63, and the air from the air supply source Sa is supplied at a predetermined flow rate (predetermined flow rate). (Supply amount: normal operation flow rate) is supplied to the CO selective oxidation unit 24 (steps 108 and 110). Thereby, in the reforming part 21, the steam reforming reaction and the carbon monoxide shift reaction described above occur and the reformed gas is generated. The reformed gas derived from the reforming unit 21 is derived from the CO selective oxidizing unit 24 with the carbon monoxide gas reduced by the CO shift unit 23 and the CO selective oxidizing unit 24 and supplied to the burner 22b of the combustion unit 22. And burned.

  The control device 30 starts counting of the timer from time t2, and when the timer becomes equal to or longer than a second predetermined time T2 (eg, 3 minutes) (time t3), the second offgas valve 92 is closed and the third offgas valve 93, and The first and second combustion gas valves 94 and 95 are opened, and the CO selective oxidation unit 24 is connected to the combustor 86 via the reformed gas supply pipe 71 and the bypass pipe 73 without passing through the fuel cell 10, and CO selective oxidation is performed. The reformed off-gas from the unit 24 is supplied to the combustor 86, and the second air valve 97 is opened to supply air from the air supply source Sa to the combustor 86 at a predetermined flow rate (steps 112 and 114). As a result, the reformed off-gas is combusted in the combustor 86, and the combustion gas is supplied to the burner 22b through the first and second heat exchangers 87a and 87b, and unburned combustible gas remains. It is burned by the burner 22b.

  In the first heat exchanger 87a, the reformed gas introduced into the CO shift unit 23, which is still at a low temperature at the time of startup, is heat-exchanged with the combustion gas, and the temperature is raised. The reformed gas thus introduced is introduced and the shift catalyst 23a is heated to the catalyst regeneration temperature (described later). In the second heat exchanger 87b as well, the reformed gas passing through the CO shift portion 23 that is still at a low temperature at the time of start-up is heat-exchanged with the combustion gas, and the temperature is raised. The reformed gas whose temperature has been raised is introduced, and the shift catalyst 23a after the turn-up portion is heated to a catalyst regeneration temperature (described later).

  The temperature control of the CO shift unit 23 is performed by adjusting the input amount (supply amount) of air to the combustor 86. When the fuel supply amount is 1, the input amount is 1.1 at the start of input (at the start of CO shift unit warm-up) and 0 at the end of input (at the completion of CO shift unit warm-up). . From the start to the end of charging, the supply amount is variable, and the range is 0.7 to 1.1. In any case, the maximum supply amount is set in consideration of the heat resistance temperature (300 ° C. to 500 ° C.) of the shift catalyst. In practice, the temperature of the CO shift unit 23, that is, the shift catalyst 23 a is 300 ° C. to 350 ° C. It is set to be ℃.

  Thus, during the generation of the reformed gas, the control device 30 detects the temperature of the catalyst 23a of the CO shift unit 23 by the temperature sensor 23a1, and if this detected temperature is equal to or higher than the second predetermined temperature Th2 (time). t4), the second air valve 97 is gradually closed over a third predetermined time T3 to stop the supply of air to the combustor 86 (steps 116, 118, 120). As a result, the amount of heat of the combustion gas supplied to the first and second heat exchangers 87a and 87b gradually decreases, that is, the temperature of the reformed gas is not increased by the combustion gas.

  The control device 30 starts counting the timer from time t4, and when the timer reaches a third predetermined time T3 (for example, 30 minutes) or more (time t5), the first reformed gas valve 74, the first offgas valve 75, and the first The 2 off gas valve 92 is opened, the 3rd off gas valve 93, the 1st-3rd combustion gas valves 94-96, and the 2nd reformed gas valve 76 are closed, and the CO selective oxidation part 24 is made into the inlet of the fuel electrode 11 of the fuel cell 10. And the outlet of the fuel electrode 11 is connected to the burner 22b (steps 120 and 122).

  In step 124, the control device 30 starts a steady operation (an operation mode in which the fuel cell 10 generates power). At this time, the fuel pump 43, the water pump 53, and the air pump 63 are continuously driven to supply fuel, water (water vapor), and air to the reformer 20. Specifically, the reforming water supply flow rate is substantially constant from time t1, and the fuel supply flow rate is substantially constant from time t2. Medium supply amount) of reforming water and fuel are continuously supplied at a predetermined ratio (for example, S / C (steam carbon ratio) = 3). The supply flow rate of the oxidizing air to the CO selective oxidation unit 24 is basically constant from time t2, but the temperature at the inlet of the CO selective oxidation unit 24 is controlled between 80 ° C. and 200 ° C. The supply flow rate is adjusted as follows. Further, the combustion fuel pump 48 and the combustion air pump 66 are driven so that the combustion fuel and the combustion air are supplied to the burner 22b so as to have a predetermined flow rate (predetermined supply amount: steady operation flow rate) in consideration of the supply amount of the anode off gas. Supply. When the stop switch is pressed, the fuel cell system stops.

  When such a fuel cell system in which the normal operation is repeatedly started and stopped is used for a long time, the shift catalyst 23a is poisoned by the sulfur compound during the normal operation. This is due to the following reason. As the fuel supplied to the reforming unit 21, city gas mainly composed of natural gas, LPG, naphtha, kerosene, etc. are used. City gas or LPG contains several ppm of sulfur compounds as odorants. Kerosene contains several tens of ppm of sulfur compounds as impurities. The fuel supply pipe 41 that supplies fuel to the reforming unit 21 is provided with a desulfurizer 44 that removes sulfur compounds in the fuel in order to prevent the reforming catalyst 21a and the shift catalyst 23a from being poisoned by sulfur compounds. ing. However, since the desulfurizer 44 cannot completely remove the sulfur compound, the sulfur compound continues to slightly flow into the shift catalyst 23a. As a result, the shift catalyst 23a is gradually poisoned by the sulfur compound. In addition, the shift catalyst 23a of the CO shift unit 23 downstream of the reforming unit 21 is poisoned by the sulfur compound removed when the poisoned reforming catalyst 21a is regenerated.

Specifically, when the shift catalyst 23a is a Pt (platinum) system, the reforming catalyst 21a is poisoned by a sulfur compound by a chemical reaction as shown in the following chemical formula 4.
(Chemical formula 4)
Pt + 2H ₂ S → PtS ₂ + 2H ₂ −Q1
As is apparent from the above-mentioned chemical formula 4, when the reaction proceeds to the right side, the amount of heat Q1 is absorbed, and conversely, when the reaction proceeds to the left side, the amount of heat Q1 is generated.

  However, as described above, at the time of start-up, specifically, for a predetermined time with time t4, the temperature of the shift catalyst 23a becomes the catalyst regeneration temperature (specifically, 400 ° C. or more). Thereby, the shift catalyst 23a is regenerated. The catalyst regeneration temperature is higher than the steady operation temperature range (150 ° C. to 350 ° C.) and lower than the heat resistant temperature of the catalyst (about 500 ° C.), and is a temperature (temperature) at which sulfur can be removed from the shift catalyst 23a and the sulfur compound. Range). Further, the catalyst regeneration temperature is set to a temperature necessary for the reaction to proceed on the left side in the above chemical formula 4. Therefore, in the shift catalyst 23a, the reaction proceeding to the left side as apparent from the above chemical formula 4 occurs, so that the poisoned catalyst and hydrogen in the reformed gas react to generate sulfide and Pt (platinum). Thus, sulfur is removed from the poisoned catalyst and the catalyst is regenerated.

  As can be understood from the above description, in the first embodiment, the reformed gas generated in the reforming unit 21 is converted to the sulfur-poisoned shift catalyst 23a when the fuel cell system is started. In order to regenerate, the sulfur-poisoned shift catalyst 23a is at least heated to a catalyst regeneration temperature at which sulfur can be removed from the shift catalyst 23a and a sulfur compound. Accordingly, the chemical reaction opposite to the poisoning of the shift catalyst 23a, which is an exothermic reaction, is promoted using the reaction equilibrium, so that the substance combined with or adsorbed to the shift catalyst 23a can be easily separated from the catalyst. (Can be removed). Therefore, by regenerating the shift catalyst without providing another device, the complexity and cost of the device can be suppressed.

  Further, since the catalyst regeneration temperature is higher than the normal operation temperature (steady operation temperature range), the shift catalyst 23a can be reliably regenerated.

  The CO shift unit 23 further includes first and second heat exchangers 87a and 87b that exchange heat with the reformed gas, and the first and second heat exchangers 87a and 87b shift the shift catalyst 23a. Is adjusted to the catalyst regeneration temperature. Accordingly, the electric energy for operating the fan and the electric heater is obtained by regenerating the catalyst using the first and second heat exchangers 87a and 87b that reduce the high temperature reformed gas to the shift reaction temperature during normal operation. Since it is not necessary to use the catalyst, the entire fuel cell system can regenerate the catalyst efficiently.

  The first and second heat exchangers 87a and 87b supply the combustion gas from the combustor 86 that introduces the reformed gas and the oxidant gas derived from the CO shift unit 23 and burns with the built-in combustion catalyst. Since the heat exchange is performed between the combustion gas and the reformed gas, the reformed gas that is still at a low temperature is heated by using the reformed gas that cannot be supplied to the fuel cell 10 at the time of start-up, and the shift catalyst 23a. Raise the temperature. Therefore, the catalyst can be regenerated by efficiently using the energy input to the fuel cell system with a simple configuration.

  Further, the temperature of the shift catalyst 23a is adjusted to the catalyst regeneration temperature by adjusting the input amount of the oxidant gas to adjust the heat amount of the combustion gas. Therefore, the catalyst temperature can be adjusted with good controllability.

  In the above-described embodiment, the air input to the combustor 86 is started when the predetermined time T2 has elapsed from the fuel (reformation 13A) start time, but the fuel start time (time t2). ) May be started at the same time.

2) Second Embodiment Hereinafter, a second embodiment of the fuel cell system according to the present invention will be described with reference to FIGS. Compared to the first embodiment described above, the following two points are different. In the second embodiment, the reforming catalyst 21a is heated to the catalyst regeneration temperature by controlling the water pump 53 and supplying a larger amount of reforming water than the amount supplied during normal operation. . The combustion of the combustor 86 is started simultaneously with the start of fuel supply.

  The control device 30 executes the program according to the flowchart shown in FIG. 5, but basically executes the same processing as the program shown in FIG. 3 described above. Hereinafter, parts different from the program shown in FIG. 3 will be described. In step 106, the control device 30 opens the water valve 54 and starts supplying reformed water, and starts counting the timer from the time (time t11) when the temperature of the evaporator 55 becomes equal to or higher than the predetermined temperature Th1. . If the timer is equal to or longer than a fourth predetermined time T4 (for example, 30 minutes) (time t12), the processes of steps 110 and 114 described above are performed simultaneously to supply fuel to the reforming unit 21 at a predetermined flow rate and at the same time air is predetermined. Only the flow rate (predetermined supply amount: normal operation flow rate) is supplied to the CO selective oxidation unit 24 (steps 202 and 204).

  At this time, the control device 30 executes the program in parallel according to the flowchart shown in FIG. That is, the control device 30 opens the water valve 54 in step 106 and starts supplying reforming water, and then, the control device 30 increases the amount that is larger than the supply amount during normal operation for a sixth predetermined time T6 (for example, 20 minutes). Supplying quality water. (Steps 302 to 306). For example, the reforming water is supplied so that the second regeneration operation flow rate is S / C (steam / carbon ratio) = 15 with respect to the fuel of the normal operation flow rate. Thus, when only a large amount of reformed water is introduced into the reforming section 21 heated to a predetermined temperature, a large amount of steam is generated and this steam functions as a heat medium. Therefore, the heat conduction of the reforming catalyst 21a. As a result, the heat supplied from the combustion unit 22 and the heat received by the heat medium from the heat vessel of the reformer that has been locally heated easily propagate in the catalyst. Therefore, the temperature of the reforming unit 21 is raised from the steady operation temperature range. As a result, the reformed gas heated to a high temperature in a short time is supplied to the CO shift unit 23. Furthermore, since the high temperature due to the large amount of reforming water generated in the reforming unit 21 described above also occurs in the CO shift unit 23, the CO shift unit 23 is heated from the steady operation temperature range. The second regeneration operation flow rate is set so that the temperature of the CO shift unit 23 becomes the catalyst regeneration temperature (specifically, 300 to 350 ° C.).

  Further, the catalyst regeneration temperature is set to a temperature necessary for the reaction to proceed on the left side in the above chemical formula 4. Therefore, in the shift catalyst 23a, the reaction proceeding to the left side as apparent from the above chemical formula 4 occurs, so that the poisoned catalyst and hydrogen in the reformed gas react to generate sulfide and Pt (platinum). Thus, sulfur is removed from the poisoned catalyst and the catalyst is regenerated.

  Further, the control device 30 starts counting the timer from time t13, and when the timer becomes equal to or longer than a fifth predetermined time T5 (for example, 3 minutes) (time t15), the first reformed gas valve 74 and the first off-gas valve 75. In addition, the second off gas valve 92 is opened, the third off gas valve 93, the first to third combustion gas valves 94 to 96, and the second reformed gas valve 76 are closed, and the CO selective oxidation unit 24 is connected to the fuel electrode 11 of the fuel cell 10. In addition to being connected to the inlet, the outlet of the fuel electrode 11 is connected to the burner 22b (steps 206 and 122).

  As can be understood from the above description, in the second embodiment, the shift catalyst 23a poisoned during the normal operation of the fuel cell system is used by using the reformed gas generated in the reforming unit 21. At the time of regeneration, the combustion unit 22 combusts in the same manner as during normal operation, and controls the water pump 53 to supply a larger amount of reforming water than the amount supplied during normal operation, thereby regenerating the shift catalyst 23a. Raise to temperature. As a result, the chemical reaction opposite to the poisoning of the reforming catalyst, which is an exothermic reaction, is promoted by utilizing the reaction equilibrium, so that the substance combined with the reforming catalyst or the adsorbed substance can be easily separated from the catalyst. (Can be removed). Therefore, by regenerating the reforming catalyst without providing another device in the conventional fuel cell system, the complexity and cost of the device can be suppressed.

  In the above-described embodiments, the present invention is applied to the fuel cell system including the steam reforming reformer 20, but can be applied to the fuel cell system including the autothermal reforming device. It is. In the steam reforming method, heat necessary for the steam reforming reaction, which is an endothermic reaction, is supplied from the outside (for example, a combustion section such as a burner). On the other hand, in the autothermal system, fuel is supplied to the reforming section. In addition, an oxidant gas (air) is supplied together with reforming water, and the fuel is subjected to an oxidative reaction that is an exothermic reaction with the oxidant gas, and heat generated at that time is used for the steam reforming reaction. Therefore, it is not necessary to adjust the amount of combustion in the combustion section to supply the heat necessary for the steam reforming reaction during normal operation, but the ratio of fuel, reforming water and oxidant gas supply to the reforming section It is necessary to adjust.

  In the case of this autothermal method, the reforming water supply means raises the reforming catalyst to the catalyst regeneration temperature by supplying a larger amount of reforming water than the supply amount during normal operation when the catalyst is regenerated. It is preferable to do.

  In each of the above-described embodiments, the case where the regeneration process is performed when the fuel cell system is activated has been described. However, the regeneration process may be performed periodically while the fuel cell system is operating.

  Moreover, in each embodiment mentioned above, although comprised so that the combustor 86 and the heat exchanger 87 might be provided separately, you may make it make the heat exchanger 87 and the combustor 86 integral. Specifically, as shown in FIG. 8, the combustor 86, the second heat exchanger 87b, the combustion gas supply pipe 91, and the third combustion gas valve 96 are deleted from the fuel cell system of the first embodiment. The first heat exchanger 87a is configured to incorporate a combustion catalyst similar to the combustor 86. A combustion offgas supply pipe 88 branched from the offgas supply pipe 72 downstream of the condenser 78 is connected to the introduction port of the first heat exchanger 87a, and the reformed offgas or fuel from the CO selective oxidation unit 24 is connected. The anode off gas from the battery 10 is supplied. Further, the combustor air supply pipe 89 is joined to the combustion off gas supply pipe 88 so that the air, which is the oxidant gas, is mixed with the reformed off gas or the anode off gas and supplied to the first heat exchanger 87a. It has become. A combustion gas supply pipe 90 that joins the off-gas supply pipe 72 upstream of the burner 22b is connected to the outlet of the first heat exchanger 87a so that the combustion gas is supplied to the burner 22b. . Thereby, since it burns in the heat exchanger 87 (1st heat exchanger 87a), combustion heat can be used efficiently. When combustion is used as a combustion catalyst, a sufficient effect can be obtained with combustion heat within a range not exceeding the heat resistance of the catalyst.

1 is a schematic diagram showing an outline of a first embodiment of a fuel cell system according to the present invention. It is a block diagram which shows the fuel cell system shown in FIG. It is a flowchart of the control program performed with the control apparatus shown in FIG. It is a time chart which shows operation | movement of 1st Embodiment of the fuel cell system by this invention. It is a flowchart of the control program performed with the control apparatus shown in FIG. It is a flowchart of the control program performed with the control apparatus shown in FIG. It is a time chart which shows operation | movement of 2nd Embodiment of the fuel cell system by this invention. It is a schematic diagram which shows the outline | summary of other embodiment of the fuel cell system by this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Fuel cell, 11 ... Fuel electrode, 12 ... Air electrode, 20 ... Reformer, 21 ... Reforming part, 21a ... Reforming catalyst, 21a1 ... Temperature sensor, 21b ... Reaction chamber, 22 ... Combustion part, 22b ... Burner, 23 ... CO shift unit, 23a ... catalyst, 24 ... CO selective oxidation unit, 24a ... catalyst, 24a1 ... temperature sensor, 30 ... control device, 41 ... fuel supply pipe, 42 ... first fuel valve, 43 ... fuel pump 44 ... Desulfurizer, 45 ... Second fuel valve, 46 ... Heat exchange section, 47 ... Fuel supply pipe for combustion, 48 ... Fuel pump for combustion, 51 ... Water supply pipe, 52 ... Water vapor supply pipe, 53 ... Water pump, 54 ... Water valve, 55 ... Evaporator, 55a ... Temperature sensor, 61 ... Oxidation air supply pipe, 62 ... Filter, 63 ... Air pump, 64 ... First air valve, 65 ... Combustion air supply pipe, 66 ... Combustion Air pump, 67 ... Cathau Air supply pipe, 68 ... Cathode air pump, 69 ... Cathode air valve, 71 ... Reformed gas supply pipe, 72 ... Off-gas supply pipe, 73 ... Bypass pipe, 74 ... First reformed gas valve, 75 ... First Off gas valve, 76 ... second reformed gas valve, 77, 78, 79 ... condenser, 81, 82 ... exhaust pipe, 84 ... recovered water outlet pipe, 86 ... combustor, 87 ... heat exchanger, 87a, 87b ... first 1 and 2nd heat exchanger, 88 ... Combustion off gas supply pipe, 89 ... Combustor air supply pipe, 90 ... Combustion gas supply pipe, 91 ... Combustion gas bypass pipe, 92 ... Second off gas valve, 93 ... Third off Gas valves, 94 to 96, first to third combustion gas valves, 97, second air valve, Sa, air supply source, Sf, fuel supply source, Sw, reformed water supply source.

Claims (5)

A reforming unit that generates and derives a reformed gas containing hydrogen by reforming the supplied fuel with a reforming catalyst filled therein, and one of the reformed gases derived from the reforming unit In a fuel cell system including a carbon monoxide shift reaction unit that reduces and derives a carbon oxide concentration by a shift catalyst filled therein,
Heat exchange means provided in the carbon monoxide shift reaction section for exchanging heat with the reformed gas;
In order to regenerate the shift catalyst poisoned with sulfur using the reformed gas generated in the reforming section, the temperature of the shift catalyst is adjusted to the catalyst regeneration temperature by the heat exchange means, so that sulfur A fuel cell system, wherein the poisoned shift catalyst is heated to at least a catalyst regeneration temperature capable of removing sulfur from the shift catalyst and a sulfur compound.   2. The fuel cell system according to claim 1, wherein the catalyst regeneration temperature is higher than a normal operation temperature. 3. The heat exchange means according to claim 1 , wherein the heat exchange means introduces a reformed gas and an oxidant gas derived from the carbon monoxide shift reaction section and burns the combustion gas from a combustor combusted by a built-in combustion catalyst. Is supplied, and heat exchange is performed between the combustion gas and the reformed gas. 4. The fuel cell system according to claim 3 , wherein the shift catalyst is heated to a catalyst regeneration temperature by adjusting an input amount of the oxidant gas. The reforming water supply means according to any one of claims 1 to 3 , further comprising a reforming water supply means for supplying the reforming water to the reforming section, wherein the reforming water supply means is used when regenerating the shift catalyst. A fuel cell system, wherein the shift catalyst is heated to a catalyst regeneration temperature by supplying a larger amount of reforming water than the amount supplied during normal operation.

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