JP4087842B2 - Fuel cell system - Google Patents

Description

  The present invention relates to a fuel cell system including a fuel cell, a reformer that generates fuel gas to be supplied to the fuel cell, a hot water storage tank for storing hot water, and a hot water circulation circuit for circulating the hot water. .

  The fuel cell system includes a fuel cell, a reformer that generates fuel gas to be supplied to the fuel cell, a hot water storage tank for storing hot water, a hot water circulation circuit for circulating hot water, and a fuel cell. And a first heat exchanger for exchanging heat between the hot water and the fuel cell heat medium, and a hot water circulation circuit It is well known that the temperature of the circulating hot water is raised by recovering at least one of exhaust heat of off-gas discharged from the fuel cell and exhaust heat generated in the reformer.

  As one type of such a fuel cell system, one disclosed in Patent Document 1 “Fuel Cell Power Generation System” is known. As shown in FIG. 1 of Patent Document 1, the fuel cell power generation system 10 includes a heat exchange medium circulation path 50 (hot water circulation circuit) through which a heat exchange medium 54 (water or hot water; hot water) circulates. . In the heat exchange medium circulation path 50, the heat exchange medium 54 stored in the hot water tank 52 is transferred from the hot water tank 52 to the anode offgas heat exchanger 42, the cathode offgas heat exchanger 44, the combustion exhaust gas heat exchanger 45, and the cooling water heat exchange. The circulation path is such that after passing through the vessel 46 (first heat exchanger) in this order, it returns to the hot water storage tank 52 again. The anode offgas heat exchanger 42 recovers the heat of the anode offgas discharged from the anode by the heat exchange medium 54, and the cathode offgas heat exchanger 44 converts the heat of the cathode offgas discharged from the cathode to the heat exchange medium 54. The combustion exhaust gas heat exchanger 45 recovers the heat of the combustion exhaust gas by the heat exchange medium 54, and the cooling water heat exchanger 46 includes the fuel cell 40, the initial off-gas heat exchanger 58, and the initial off-gas. The heat exchange medium 54 recovers the heat of the cooling water (fuel cell heat medium) flowing through the cooling water circulation path 43 (fuel cell heat medium circulation circuit) passing through the combustor 57. During steady operation, the fuel cell power generation system 10 controls the flow rate of the heat exchange medium 54 (hot water) so as to maintain the temperature of the fuel cell 40, that is, the coolant flowing through the fuel cell 40, within a specified temperature range. .

Further, as another type, one disclosed in Patent Document 2 “Solid Polymer Fuel Cell Power Generation Device” is known. As shown in FIGS. 1 to 3 of Patent Document 2, the polymer electrolyte fuel cell power generator GS1 includes a heat exchanger 32 of an exhaust system 31, a heat exchanger 46 of an exhaust system 45, and a fuel cell 6. After the heat exchanger 71 of the gas discharged from the air electrode k, a heat exchanger HEX is further installed, and water in the hot water storage tank 50 is passed through the heat exchanger HEX by the pump P, and the heat exchangers 71, 32, A line L1 (hot water circulation circuit) is provided that circulates and sends hot water A (hot water), which is sent to 46 and heat-exchanged to recover exhaust heat, directly to the water tank 21 so that heat can be exchanged. A line L2 for sending the hot water A to the hot water storage tank 50 when the hot water A does not need to be sent to the water tank 21 via the line L1 is also provided. Cooling water (fuel cell heat medium) circulating through the cooling unit 6 c of the fuel cell 6 by the pump 48 flows into the water tank 21 via the water pipe 73 (fuel cell heat medium circulation circuit). As a result, the water in the water tank 21 and the hot water A exchange heat.
JP 2003-257457 A (page 4-7, FIG. 1) JP 2002-216819 A (page 2-6, Fig. 1-3)

  In the fuel cell power generation system described in Patent Document 1 described above, the heat exchange medium 54 (hot water storage water) is maintained so that the cooling water flowing through the fuel cell 40, that is, the temperature of the fuel cell 40 is maintained in a specified temperature range during steady operation. The anode offgas heat exchanger 42, the cathode offgas heat exchanger 44, the flue gas heat exchanger 45, and the cooling water heat exchanger 46 are connected in series to the heat exchange medium circulation path 50. Is arranged. Therefore, the heat exchange medium 54 (hot water storage) passes through the anode offgas heat exchanger 42, the cathode offgas heat exchanger 44, and the combustion exhaust gas heat exchanger 45 at the same flow rate as that flow rate. In each of these heat exchangers 42, 44, 45, the anode offgas, cathode offgas, sensible heat of combustion exhaust gas, and latent heat of the exhaust gas may be sufficiently recovered at the flow rate. When the ratio to the amount of heat recovered from the cathode off-gas and combustion exhaust gas is low, for example, in the case of power generation at a low load or when the influence of heat radiation is great in winter, there are cases where it cannot be recovered. As a result, there is a problem that the heat recovery efficiency may be lowered as a whole system. The polymer electrolyte fuel cell power generator described in Patent Document 2 described above has the same problem as the fuel cell power generation system described in Patent Document 1 as described above.

  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 operating while maintaining high heat recovery efficiency from the start to stop of power generation of the system. .

In order to solve the above problems, the structural feature of the invention according to claim 1 is that it is heated by a fuel cell, a reformer that generates fuel gas to be supplied to the fuel cell, and heat generated by the fuel cell. A hot water storage tank for storing hot water, a hot water circulation circuit including the hot water tank for circulating the hot water, a fuel cell heat medium circulation circuit for circulating a fuel cell heat medium for exchanging heat with the fuel cell, and hot water storage In a fuel cell system comprising a first heat exchanger that exchanges heat between water and a fuel cell heat medium, exhaust heat recovery that is provided independently of a hot water circulation circuit and in which an exhaust heat recovery heat medium circulates An exhaust heat recovery means provided in the heat medium circulation circuit, the exhaust heat recovery heat medium circulation circuit, and recovering the exhaust heat of the combustion gas or reformed gas generated in the reformer to the exhaust heat recovery heat medium; A second heat exchanger for exchanging heat between the water and the exhaust heat recovery heat medium; Further comprising, hot water circulation circuit includes a flow passage provided flow path and provided with a first heat exchanger and the second heat exchanger is provided in parallel, the flow path and the second heat provided first heat exchanger It is further provided with a flow rate adjusting means for adjusting each flow rate of the flow path provided with the exchanger .

Further, the structural feature of the invention according to claim 2 is that in claim 1, the exhaust heat recovery means converts the water vapor in the reformed gas supplied from the reformer to the fuel cell to the heat of the exhaust heat recovery heat medium. It includes a reforming gas condenser that condenses by exchange and recovers the exhaust heat of the reformed gas to an exhaust heat recovery heat medium .

Further, the structural feature of the invention according to claim 3 is that in claim 1 or claim 2 , the flow path provided with the first heat exchanger and the flow path provided with the second heat exchanger are used simultaneously. is there.

In the invention according to claim 1 configured as described above, in the hot water circulation circuit, the flow path provided with the first heat exchanger and the flow path provided with the second heat exchanger are provided in parallel. Thus, during steady operation of the system, the hot water stored in the flow path provided with the first heat exchanger recovers the exhaust heat generated by the power generation of the fuel cell. On the other hand, the hot water circulating through the flow path provided with the second heat exchanger recovers the exhaust heat of the combustion gas or reformed gas generated in the reformer via the exhaust heat recovery heat medium. As a result, the exhaust heat generated by the power generation of the fuel cell and the exhaust heat of the combustion gas or reformed gas generated in the reformer can be recovered independently in parallel rather than in series. Therefore, it becomes possible to recover heat at the most efficient hot water flow rate. Therefore, when the ratio of the amount of heat recovered from the fuel cell to the amount of heat recovered from the anode off-gas, cathode off-gas, and combustion exhaust gas is low, for example, in the case of power generation at a low load or when the influence of heat dissipation in the winter is large, Since heat can be sufficiently recovered from each of these gases, it is possible to provide a fuel cell system that can be operated while maintaining high heat recovery efficiency from the start to the stop of power generation of the system.
Further, in addition to the above effects, there are the following effects. The exhaust heat recovery heat medium circulation circuit circulates an exhaust heat recovery heat medium that recovers exhaust heat of combustion gas or reformed gas generated in the reformer, and is provided independently of the hot water circulation circuit. At the same time, heat exchange is performed between the stored hot water and the exhaust heat recovery heat medium via the second heat exchanger. That is, the hot water is combustion exhaust gas, the fuel gas not to the (reformed gas) and direct heat exchange, so that the indirect heat exchange via the second heat exchanger. Therefore, when the hot water tank is a sealed type in which tap water is directly replenished, high pressure tap water pressure is applied to the hot water tank and hot water circulation circuit, but the exhaust heat recovery heat medium circulation circuit is independent of the hot water circulation circuit. Therefore, the exhaust heat recovery means der Ru combustion exhaust gas, direct water pressure in the heat exchanger for heat exchange with the fuel gas (reformed gas) is not applied is arranged in the exhaust heat withdrawing heat medium circulation circuit on Therefore, the waste heat recovery means does not need to have an excessive pressure-resistant structure, so that it is possible to provide a fuel cell system that can replenish hot water from a high-pressure water source without increasing the cost and increasing the size.
Furthermore, in addition to the above-described effects, the apparatus further includes flow rate adjusting means for adjusting the flow rates of the flow path provided with the first heat exchanger and the flow path provided with the second heat exchanger. The flow rate of the hot water stored in the flow path provided with the heat exchanger and the flow path provided with the second heat exchanger can be adjusted with certainty, and the optimum heat recovery efficiency and recovered hot water temperature can be realized.

In the invention according to claim 2 configured as described above, in the invention according to claim 1, the water vapor in the reformed gas supplied from the reformer to the fuel cell is exchanged with the exhaust heat recovery heat medium. Since the reformed gas condenser for condensing and recovering the exhaust heat of the reformed gas in the exhaust heat recovery heat medium is provided in the exhaust heat recovery heat medium circulation circuit, the reformed gas condenser is provided. The flow rate of the exhaust heat recovery heat medium flowing through the exhaust heat recovery heat medium circulation circuit can be adjusted independently of the flow path provided with the first heat exchanger, and consequently the exhaust heat provided with the reforming gas condenser. The temperature of the heat medium flowing in the recovered heat medium circulation circuit can also be adjusted independently. Therefore, the humidity of the reformed gas (anode gas) from the reformer to the fuel cell can be adjusted.

In the invention according to claim 3 configured as described above, in claim 1 or claim 2 , the flow path and the second heat exchanger provided with the first heat exchanger provided in parallel with each other in the hot water circulation circuit The flow path provided with is used simultaneously. Accordingly, the hot water can be circulated at an appropriate flow rate in both flow paths, so that the heat of the fuel cell heat medium and each exhaust heat can be recovered efficiently and independently.

1) Reference Embodiment will be described below by reference in the form of a fuel cell system according to the present invention. FIG. 1 is a schematic diagram showing an outline of this fuel cell system. The fuel cell system includes a fuel cell 10 and a reformer 20 that generates a reformed gas (fuel gas) containing hydrogen gas necessary for the fuel cell 10.

  The fuel cell 10 includes a fuel electrode 11, an air electrode 12 that is an oxidant electrode, and an electrolyte 13 interposed between the electrodes 11 and 12, and supplies the reformed gas supplied to the fuel electrode 11 and the air electrode 12. Electric power is generated using air (cathode air), which is the oxidant gas. A supply pipe 61 that supplies air and a discharge pipe 62 that discharges cathode off-gas are connected to the air electrode 12 of the fuel cell 10. Air is humidified in the middle of the supply pipe 61 and the discharge pipe 62. A humidifier 14 is provided. The humidifier 14 is of a water vapor exchange type and dehumidifies water vapor in the gas discharged from the discharge pipe 62, that is, from the air electrode 12, and supplies the water vapor into the supply pipe 61, that is, air supplied to the air electrode 12. And humidify. Note that air-enriched gas may be supplied instead of air.

The reformer 20 steam-reforms the fuel and supplies a hydrogen-rich reformed gas to the fuel cell 10, and includes a burner 21, a reforming unit 22, a carbon monoxide shift reaction unit (hereinafter referred to as a CO shift unit). 23) and a carbon monoxide selective oxidation reaction part (hereinafter referred to as CO selective oxidation part) 24. Examples of the fuel include natural gas, LPG, kerosene, gasoline, methanol, and the like. In this embodiment , the description will be made with natural gas.

  The burner 21 is supplied with combustion fuel and combustion air from the outside during start-up, or supplied with reformed gas and combustion air that have a high carbon monoxide concentration and is not supplied to the fuel cell 10, or during steady operation. Anode off-gas (reformed gas supplied to the fuel cell and discharged without being used) is supplied from the fuel electrode 11, and the supplied gas is combusted and the combustion gas is led to the reforming unit 22. . This combustion gas heats the reforming section 22 (so that it becomes the activation temperature range of the catalyst of the reforming section 22), and then the water vapor contained in the combustion gas is condensed through the combustion gas condenser 34. And exhausted to the outside. The combustion fuel and the combustion air are supplied to the burner 21 by a combustion fuel pump P1 and a combustion air pump P2 which are combustion fuel supply means and combustion air supply means, respectively. Both pumps P1, P2 are controlled by a control device 90 to control the flow rate (delivery amount).

  The reforming unit 22 reforms a mixed gas obtained by mixing the fuel supplied from the outside with the water vapor (reformed water) from the evaporator 25 by using a catalyst charged in the reforming unit 22 to generate hydrogen gas and carbon monoxide. Gas is generated (so-called steam reforming reaction). At the same time, carbon monoxide and steam generated by the steam reforming reaction are converted into hydrogen gas and carbon dioxide (so-called carbon monoxide shift reaction). These generated gases (so-called reformed gas) are led to the CO shift unit 23. The fuel is supplied to the reforming unit 22 by a fuel pump P3 which is a fuel supply means. This pump P3 is controlled by the control device 90, and its flow rate (delivery amount) is controlled.

  The CO shift unit 23 is converted into hydrogen gas and carbon dioxide gas by reacting carbon monoxide and water vapor contained in the reformed gas with a catalyst filled therein. Thus, the reformed gas is led to the CO selective oxidation unit 24 with the carbon monoxide concentration reduced.

  The CO selective oxidation unit 24 generates carbon dioxide by reacting carbon monoxide remaining in the reformed gas and CO oxidation air (air) further supplied from the outside with a catalyst filled therein. is doing. Thereby, the reformed gas is led to the fuel electrode 11 of the fuel cell 10 with the carbon monoxide concentration further reduced (10 ppm or less). The CO oxidation air (air) is supplied to the CO selective oxidation unit 24 by a CO oxidation air pump P4 which is a CO oxidation air supply means. The pump P4 is controlled by the control device 90, and its flow rate (delivery amount) is controlled.

  The evaporator 25 is disposed in the middle of the reforming water supply pipe 68 having one end disposed in the water reservoir 50 and the other end connected to the reforming unit 22. A reforming water pump 53 is provided in the reforming water supply pipe 68. The pump 53 is controlled by a control device 90 and pumps recovered water used as reforming water in the water reservoir 50 to the evaporator 25. The evaporator 25 is heated by, for example, the combustion gas discharged from the burner 21, the heat of the reforming unit 22, the CO shift unit 23, and the like, thereby steaming the reformed water fed under pressure.

  A condenser 30 is provided in the middle of a pipe 64 that connects the CO selective oxidation unit 24 of the reformer 20 and the fuel electrode 11 of the fuel cell 10. The condenser 30 is an integral structure in which a reformed gas condenser 31, an anode off gas condenser 32, a cathode off gas condenser 33, and a combustion gas condenser 34 are integrally connected. The reformed gas condenser 31 condenses water vapor in the reformed gas supplied to the fuel electrode 11 of the fuel cell 10 flowing in the pipe 64. The anode off-gas condenser 32 is provided in the middle of a pipe 65 that communicates the fuel electrode 11 of the fuel cell 10 and the burner 21 of the reformer 20, and the fuel electrode 11 of the fuel cell 10 that flows in the pipe 65. Water vapor in the anode off-gas discharged from is condensed. The cathode offgas condenser 33 is provided downstream of the humidifier 14 in the discharge pipe 62, and condenses the water vapor in the cathode offgas discharged from the air electrode 12 of the fuel cell 10 flowing in the discharge pipe 62. The combustion gas condenser 34 is provided downstream of the burner 21 and collects latent heat obtained by condensing water vapor together with sensible heat of the combustion exhaust gas.

  The pipe 64 is provided with a seventh temperature sensor 64a in the vicinity of the inlet of the fuel electrode 11 of the fuel cell 10, and the seventh temperature sensor 64a is an inlet of the fuel electrode 11 of the reformed gas fuel cell 10. The temperature T7 is detected, and the detection result is output to the control device 90.

  The above-described condensers 31 to 34 communicate with the deionizer 40 via the pipe 66 so that the condensed water condensed in each of the condensers 31 to 34 is led out to the deionizer 40 and collected. It has become. The deionizer 40 converts the condensed water supplied from the condenser 30, that is, the recovered water into pure water using a built-in ion exchange resin, and leads the purified water to the water reservoir 50. The water reservoir 50 temporarily stores the recovered water derived from the pure water device 40 as reformed water. Further, a pipe for introducing makeup water (tap water) supplied from a tap water supply source (for example, a water pipe) is connected to the deionizer 40, and the amount of water stored in the deionizer 40 is below the lower limit water level. And tap water is supplied.

  The fuel cell system generates heat between the fuel cell 10 and a hot water tank 71 that stores hot water heated by heat generated in the fuel cell 10, a hot water circulation circuit 80 that includes the hot water tank 71 and circulates the hot water, and the fuel cell 10. FC cooling water circulation circuit 73 that is a fuel cell heat medium circulation circuit in which FC cooling water that is a fuel cell heat medium to be exchanged circulates, and a first heat exchanger that performs heat exchange between the hot water and FC cooling water 74 is provided. Further, “FC” in this specification and the accompanying drawings is described as an abbreviation of “fuel cell”.

  The hot water storage tank 71 is provided with one columnar container, in which hot water is stored in a layered manner, that is, the temperature of the upper part is the highest and lower as it goes to the lower part, and the temperature of the lower part is the lowest. It has become so. Water (low-temperature water) such as tap water is replenished to the lower part of the columnar container of the hot water tank 71, and hot hot water stored in the hot water tank 71 is led out from the upper part of the columnar container of the hot water tank 71. ing. Further, the hot water tank 71 is of a sealed type, and is of a type in which the pressure of tap water is directly applied to the inside, and consequently to the hot water circulation circuit 80.

  The hot water storage circuit 80 is provided with a flow path 72 provided with exhaust heat recovery means (condenser 30) and a bypass path 75, which is a flow path provided with a first heat exchanger 74, in parallel. One end and the other end of the flow path 72 are connected to the lower part and the upper part of the hot water tank 71. On the flow path 72, in order from one end to the other end, a fourth temperature sensor 72a, a hot water circulation first pump P5 as a hot water circulation means, a radiator 76, an anode off-gas condenser 32, a combustion gas condenser 34, A cathode offgas condenser 33, a reformed gas condenser 31, a third temperature sensor 72b, and a first valve 77 are provided.

  The fourth and third temperature sensors 72a and 72b detect the outlet temperature T4 of the hot water storage tank 71 and the outlet temperature T3 of the reformed gas condenser 31, respectively, and output the detection results to the control device 90. It is. The hot water circulation first pump P5 sucks hot water in the lower part of the hot water tank 71, causes the flow path 72 to flow through it, and discharges it to the upper part of the hot water tank 71. Amount) is controlled.

The radiator 76 is a cooling means for cooling the fluid (hot water storage water), and is controlled to be turned on / off by a command from the control device 90. The radiator 76 cools the fluid in the on state and does not cool it in the off state. The cooling capacity of the radiator 76 is a graph or an arithmetic expression showing a correlation of the required cooling capacity of the fuel cell system with respect to the power generation output of the fuel cell 10 at the maximum temperature T _max of hot water stored in a second map described later. This is the required cooling capacity H1 of the fuel cell system corresponding to the minimum power generation output E1 of the fuel cell 10 when the hot water tank 71 is full of hot water. In addition, since the maximum temperature _Tmax of the stored hot water is defined by the maximum heat generation temperature (for example, 60 to 70 ° C.) of the fuel cell 10, the stored hot water temperature does not exceed that.

The anode off-gas condenser 32, the combustion gas condenser 34, the cathode off-gas condenser 33, and the reformed gas condenser 31 are sensible heat of hot water stored in the anode off-gas, combustion gas, cathode off-gas, and reformed gas. At the same time, each latent heat obtained by condensing water vapor is recovered to raise the temperature. That is, the anode offgas condenser 32 and the cathode offgas condenser 33 recover the exhaust heat of the offgas discharged from the fuel cell 10 into the hot water storage, that is, the offgas exhaust heat recovery apparatus. Further, the combustion gas condenser 34 and the reformed gas condenser 31 recover the exhaust heat generated in the reformer 20 into the hot water storage, that is, the reformer exhaust heat recovery apparatus. In the present embodiment , the exhaust heat recovery means is composed of the above-described off-gas exhaust heat recovery device and reformer exhaust heat recovery device. The exhaust heat recovery means may be configured from either an off-gas exhaust heat recovery device or a reformer exhaust heat recovery device.

  In addition, arrangement | positioning of each condenser 31-34 is not restricted to the order mentioned above, Moreover, each condenser 31-34 is not restricted to the case where it arrange | positions in series with one piping, The flow path 72 is branched into two or more. You may make it arrange | position in parallel on each branch path. Further, it is preferable that at least the reformed gas condenser 31 is disposed on the flow path 72. Furthermore, it is preferable to provide at least one of an off-gas exhaust heat recovery device and a reformer exhaust heat recovery device in the flow path 72. Thereby, the hot water circulating in the flow path 72 can recover the temperature of at least one of the exhaust heat of the off-gas discharged from the fuel cell 10 and the exhaust heat generated in the reformer 20 and raise the temperature.

  The first valve 77 is an open / close valve that is provided in the flow path 72 between the bypass path 75 and the inlet of the hot water storage tank 71 and opens and closes the flow path 72 and is controlled to open and close according to a command from the control device 90. The first valve 77 is closed until the fuel cell 10 reaches a predetermined temperature during start-up operation, and is basically open after that.

  Further, in the bypass passage 75, the hot water circulation second pump P6 and the first heat which are hot water circulation means are sequentially arranged from a branch point near the outlet side of the hot water tank 71 to a junction point near the inlet side of the hot water tank 71. An exchanger 74 is provided. The hot water circulation second pump P6 sucks hot water in the lower part of the hot water tank 71, causes the bypass passage 75 to pass through, and discharges it to the upper part of the hot water tank 71. Amount) is controlled.

  Each flow rate of the flow path 72 and the bypass path 75 can be adjusted by the flow rate control of the hot water circulation first pump P5 and the hot water circulation second pump P6 described above. That is, the hot water circulation first pump P5 and the hot water circulation second pump P6 are flow rate adjusting means.

  An FC cooling water circulation pump P7, which is an FC cooling water circulation means, is disposed on the FC cooling water circulation circuit 73. The FC cooling water circulation pump P7 is controlled by the control device 90 to control its flow rate (delivery amount). It has come to be. Further, on the FC cooling water circulation circuit 73, first and second temperature sensors 73a and 73b are disposed, and the first and second temperature sensors 73a and 73b are respectively provided at the inlet of the fuel cell 10 for FC cooling water. The temperature and the outlet temperature are detected, and the detection results are output to the control device 90. Further, a first heat exchanger 74 is disposed on the FC cooling water circulation circuit 73.

  Further, the fuel cell system includes an inverter (power converter) 45. The inverter 45 converts the power generation output of the fuel cell 10 into AC power and supplies it to a power usage place 47 that is a user destination via a power transmission line 46. A load device (not shown), which is an electric appliance such as an electric lamp, iron, TV, washing machine, electric kotatsu, electric carpet, air conditioner, refrigerator, etc., is installed in the power usage place 47, and the AC supplied from the inverter 45 Electric power is supplied to the load device as needed. A power supply system power supply 48 is also connected to the power transmission line 46 connecting the inverter 45 and the power use place 47 (system connection), and the total power consumption of the load device exceeds the power generation output of the fuel cell 10. In such a case, the insufficient power is received from the system power supply 16 and compensated. The wattmeter 47 a is user load power detection means for detecting user load power (user power consumption), detects the total power consumption of all the load devices used in the power usage location 47, and transmits it to the control device 90. It is supposed to be.

  The inverter 45 steps down or boosts the power generation output, and the direct-current power is supplied to the pumps P1 to P5 and 53, which are constituent members of the fuel cell system, the valves (not shown), the ignition device of the burner 21, and the like. Parts are supplied to so-called auxiliary machines.

  Moreover, each temperature sensor 73a, 73b, 72a, 72b, 64a mentioned above, each pump P1-P7, 53, the 1st valve | bulb 77, and the wattmeter 47a are connected to the control apparatus 90 (refer FIG. 2). The control device 90 has a microcomputer (not shown), and the microcomputer includes an input / output interface, a CPU, a RAM, and a ROM (all not shown) connected via a bus. The CPU generally controls the operation of the fuel cell system. In particular, the CPU executes a program corresponding to the flowchart of FIG. 5 or FIG. 7 and FIG. 8 to each temperature sensor 73a, 73b, 72a, 72b, 64a. The power generation output of the fuel cell 10 is controlled based on one of the temperatures detected by the power meter 47 and the user load power detected by the wattmeter 47a. The RAM temporarily stores variables necessary for executing the program, and the ROM stores the program.

  Further, a storage device 91 is connected to the control device 90, and this storage device 91 stores the first map or the arithmetic expression shown in FIG. The first map or the arithmetic expression is obtained by calculating the hot water tank outlet temperature T4 detected by the fourth temperature sensor 72a serving as the hot water tank outlet temperature detecting means, the hot water tank outlet temperature T4, and the power generation output limit value EL of the fuel cell 10. This shows the correlation. As is apparent from the first map or the calculation formula, the hot water tank outlet temperature T4 and the power generation output limit value EL of the fuel cell 10 are in an inversely proportional relationship.

This first map or calculation formula is the second map or calculation formula showing the correlation of the required cooling capacity of the fuel cell system with the power generation output of the fuel cell 10 for each temperature of the hot water, the cooling capacity of the radiator 76, Based on the above, it can be created by deriving the power generation output of the fuel cell 10 corresponding to the cooling capacity of the radiator 76 at each temperature of the hot water storage. First, the second map or calculation formula is created as follows. As shown in FIG. 4, the required cooling capacity of the fuel cell system with respect to the FC power generation output is calculated or measured while the temperature of the hot water circulating in the flow path 72 is kept constant. When this is changed within a predetermined temperature range, for example, the FC power generation is performed at temperatures T _{max-1 to} T _{max-4 that} are lower than the maximum temperature T _max and T _{max of the} hot water tank 71 by a predetermined temperature. A graph (function) of the required cooling capacity of the fuel cell system with respect to the output is calculated or measured, respectively. In this way, the second map or arithmetic expression can be created. On the other hand, as described above, the cooling capacity of the radiator 76 is expressed by a graph or an arithmetic expression showing the correlation of the required cooling capacity of the fuel cell system with respect to the power generation output of the fuel cell 10 at the maximum temperature T _max of the hot water. It is defined as the required cooling capacity H1 of the fuel cell system corresponding to the minimum power generation output E1 of the fuel cell 10 when the tank 71 is full of hot water.

Therefore, the fuel cell 10 corresponding to the cooling capacity E1 of the radiator 76 in the graph or the calculation formula showing the correlation of the required cooling capacity of the fuel cell system with the power generation output of the fuel cell 10 for each temperature of the hot water calculated previously. Is generated as the FC power generation output limit value EL. Specifically, for example, when the temperature of the hot water (that is, the outlet temperature T4 of the hot water tank) is T _max , as described above, the FC power generation output limit value EL is E1 and T _{max −1.} The FC power generation output limit value EL is E2, the FC power generation output limit value EL is E3 when _Tmax-2 , and the FC power generation output limit value EL is E4 when _Tmax-3. In the case of _Tmax-4 , the FC power generation output limit value EL is _Emax . The predetermined temperature range is the range from the maximum temperature T _max of the hot water tank to the temperature at which the FC power generation output limit value EL becomes the maximum power generation output E _max of the fuel cell 10 (T _max-4 in this embodiment ). is there.

  Since the capability of the radiator 76 varies depending on the outside air temperature (radiator cooling medium temperature), further efficiency can be achieved by having / calculating the maps of FIGS. 3 and 4 according to each outside air temperature. When determining the capability of the radiator 76, it is performed under the severest conditions of the outdoor temperature in summer.

  Next, control for optimizing the heat recovery efficiency in the fuel cell system described above will be described. First, the flow rate of the hot water circulating second pump P6 is controlled so that the FC cooling water FC inlet temperature T1 (or the FC cooling water FC outlet temperature T2) becomes the optimum operating temperature of the fuel cell. Further, the flow rate of the FC cooling water circulation pump P7 is controlled so that the temperature difference ΔT between the FC cooling water FC inlet temperature T1 and the FC cooling water FC outlet temperature T2 becomes the target temperature difference ΔT * (for example, 3 to 5 ° C.). Yes. The target temperature difference ΔT * is set so that the water vapor in the reformed gas channel or the air channel of the fuel cell 10 can be maintained under the optimum humidification condition. The flow rate of the first hot water circulating pump P5 is controlled so that the fuel cell inlet temperature T7 of the reformed gas becomes the target temperature T7 * (for example, 55 to 65 ° C.). The target temperature T7 * is set so as to be an optimum humidification condition in which no flooding occurs, and is set so as to be a temperature at which fungal growth can be suppressed in the collected hot water storage water. Further, the flow rate of the hot water circulating first pump P5 is controlled so that the anode off gas (AOG) condenser outlet temperature T3 of the condensed refrigerant becomes the target temperature T3 * (for example, 55 to 65 ° C.). The target temperature T3 * is set so as to be an optimum humidification condition in which no flooding occurs, and is set to a temperature at which fungal growth can be suppressed in the collected hot water storage water.

  Thereby, during the steady operation of the system, the hot water flowing through the bypass 75 at an appropriate flow rate recovers the exhaust heat generated by the power generation of the fuel cell most efficiently. On the other hand, the hot water that circulates in the flow path 72 at an appropriate flow rate that is independent of the hot water flowing through the bypass passage 75 at an appropriate flow rate and that is not limited by the flow rate is discharged from the fuel cell. The most efficient recovery of waste heat and waste heat generated in the reformer. Then, both hot water storage water merges and flows into the hot water storage tank 71.

1a) First Control Example Hereinafter, a first control example of the above-described fuel cell system will be described with reference to FIGS. 5 and 6. The control device 90 executes the program shown in FIG. 5 every predetermined short time when a start switch (not shown) is turned on to start the fuel cell system to complete the start-up operation and become a steady operation capable of generating power. In step 102, the controller 90 detects the hot water storage hot water tank outlet temperature (hot water storage tank outlet temperature) T4 by the fourth temperature sensor 72a. In step 104, the hot water tank outlet temperature T4 detected in step 102, and the first map or arithmetic expression showing the correlation between the hot water tank outlet temperature T4 and the power generation output limit value EL of the fuel cell 10 are obtained. Based on this, a power generation output limit value EL is derived (first power generation output limit value deriving means).

  In steps 106 to 114, the control device 90 controls the power generation output of the fuel cell 10 based on the power generation output limit value EL derived by the first power generation output limit value deriving unit (first power generation control unit). Specifically, in step 106, the user load power is detected by the wattmeter 47a (user load power detection means). In step 108, the power generation output EU of the fuel cell corresponding to the user load power detected in step 106 is derived based on a map or arithmetic expression indicating the correlation between the user load power and the power generation output (power generation output deriving means). . In step 110, it is determined whether or not the power generation output limit value EL derived in step 104 is greater than or equal to the power generation output EU derived in step 108 (determination means). If it is determined in step 112 that the power generation output limit value EL is greater than or equal to the power generation output EU, the power generation output of the fuel cell 10 is controlled to follow the user load power (following control means). If it is determined in step 114 that the power generation output limit value EL is less than the power generation output EU, control is performed to limit the power generation output of the fuel cell 10 to the power generation output limit value EL (limit control means). . In both the follow-up control and the limit control described above, the fuel supply amount, the reforming water supply amount, the combustion fuel supply amount, the combustion are set so as to obtain the power generation output of the fuel cell 10 in consideration of the combustion efficiency and the like. The air supply amount for CO and the air supply amount for CO oxidation are derived, and the fuel pump P3, the reforming water pump 53, the combustion fuel pump P1, the combustion air pump P2, and the CO oxidation air supply amount are derived so as to obtain these derived supply amounts. The flow rate of the pump P4 is controlled by the control device 90.

  According to such control, when the hot water tank outlet temperature T4 changes as shown in the upper part of FIG. 6, the power generation output limit value EL is set to the hot water tank outlet as shown in the middle part of FIG. It changes opposite to temperature T4. On the other hand, when the power generation output EU based on the user load changes as shown in the middle part of FIG. 6, the power generation output limit value EL is less than the power generation output EU at times t11 to t12 and t13 to t14. The power generation output limit value EL is limited to the power generation output limit value EL, and the power generation output limit value EL is equal to or greater than the power generation output EU in other time zones, so that follow-up control is performed to follow the user load power without limiting the power generation output ( Lower part of FIG. 6).

  Therefore, according to the first control example, the first power generation output limit value deriving unit is configured to detect the hot water tank outlet temperature T4 detected by the fourth temperature sensor 72a, the hot water tank outlet temperature T4, and the power generation output of the fuel cell 10. The power generation output limit value EL is derived based on the first map or the arithmetic expression indicating the correlation with the limit value EL, and the first power generation control means derives the power generation output limit derived by the first power generation output limit value deriving means. Based on the value EL, the power generation output of the fuel cell 10 is controlled. As a result, during the power generation of the fuel cell 10, the hot water stored in the fuel cell 10 and the reformer 20 generated by the power generation is recovered and the hot water is heated. In this case, since the power generation output of the fuel cell 10 is limited according to the hot water tank outlet temperature T4, the heat generation from the fuel cell 10 is suppressed as much as possible to maintain the balance between the power generation output and the use of exhaust heat, and the heat surplus It is possible to efficiently operate the fuel cell system while avoiding the state as much as possible.

  Further, in the first power generation control means, in step 108, the power generation output EU of the fuel cell corresponding to the user load power detected in step 106 is derived, and in step 110, the power generation output limit derived in step 104 is derived. It is determined whether or not the value EL is greater than or equal to the power generation output EU derived in step 108. If it is determined in step 112 that the power generation output limit value EL is greater than or equal to the power generation output EU, Then, the power generation output of the fuel cell 10 is controlled to follow the user load power. If it is determined in step 114 that the power generation output limit value EL is less than the power generation output EU in step 110, the fuel cell 10 The power generation output is controlled to be limited to the power generation output limit value. As a result, the fuel cell system can be stably and simply operated based on the power generation output EU of the fuel cell and the power generation output limit value EL corresponding to the user load power detected by the user load power detection means.

  In addition, the first map or the arithmetic expression is the second map or the arithmetic expression indicating the correlation of the required cooling capacity of the fuel cell system with the power generation output of the fuel cell for each temperature of the hot water, and the exhaust heat of the reformer 20. The cooling capacity of the radiator 76 at each temperature of the stored hot water based on the cooling capacity of the radiator 76 that is provided in the second heat medium circulation circuit 75 that circulates the recovered second heat medium and cools the second heat medium It is created by deriving the power generation output of the fuel cell corresponding to. Therefore, since the power generation output limit value EL is derived based on the hot water tank outlet temperature T4 and the cooling capacity of the radiator 76, the power generation output of the fuel cell is determined in consideration of the cooling capacity of the radiator 76. The operation of the fuel cell system can be efficiently carried out while maintaining a better balance of exhaust heat utilization and avoiding the excess heat state as much as possible.

In addition, the cooling capacity of the radiator 76 is determined based on the second map or the calculation formula showing the correlation between the required cooling capacity of the fuel cell system and the power generation output of the fuel cell at the maximum temperature T _max of the hot water. Since the required cooling capacity of the fuel cell system corresponding to the minimum power generation output of the fuel cell at the time of full water can be used, the radiator 76 with a low cooling capacity can be used. Therefore, the radiator 76 can be made compact, and thus the fuel cell system Overall compactness can be achieved.

1b) Second Control Example Hereinafter, a second control example of the fuel cell system described above will be described with reference to FIGS. When the start switch (not shown) is turned on to start the fuel cell system, the control device 90 completes the start-up operation and becomes a steady operation capable of generating electric power. The program is executed every predetermined time TMa. In step 202, the controller 90 detects the temperature (fuel gas FC inlet temperature) T7 of the fuel gas flowing into the fuel electrode inlet of the fuel cell 10 by the seventh temperature sensor 64a. Instead of the fuel gas FC inlet temperature T7, a temperature correlated with the fuel gas temperature T7, for example, the outlet temperature of the hot water reforming gas condenser 31 (the outlet temperature of the hot water reforming gas condenser) T3 is set. You may make it detect with the 3rd temperature sensor 72b. Then, the subsequent processing may be executed using the detected value.

  In step 204, the fuel gas FC inlet temperature T7 detected in step 202 is compared with a predetermined temperature Ta, and the power generation output limit value EL of the fuel cell 10 is derived based on the comparison result (second). Power generation output limit value deriving means). Specifically, the control device 90 executes a subroutine shown in FIG. That is, when the temperature T7 detected in step 202 is higher than the predetermined temperature Ta, the control device 90 subtracts the predetermined power amount ΔE from the previous power generation output limit value EL to obtain the current power generation output limit value EL−Δ. If calculated (steps 302 and 304) and the same as the predetermined temperature Ta, the previous power generation output limit value EL is calculated as the current power generation output limit value EL (steps 302 and 306) and is smaller than the predetermined temperature Ta. In this case, the power generation output limit value EL + Δ is calculated by adding a predetermined amount ΔE to the previous power generation output limit value EL (steps 302 and 308). Then, the program is advanced to step 310, the subroutine processing is terminated, and the program proceeds to step 206 and subsequent steps. In step 302, the fuel gas FC inlet temperature T7 detected in step 202 is compared with the predetermined temperature Ta, but the fuel gas FC inlet temperature T7 is compared with a predetermined temperature range (dead zone). Also good.

  Since the predetermined temperature Ta is regulated to a temperature at which the fuel electrode 11 of the fuel cell 10 does not flood, the fuel cell system can be stably operated by reliably preventing the power generation reduction and stoppage of the fuel cell by flooding.

  In steps 206 to 214, the control device 90 controls the power generation output of the fuel cell 10 based on the power generation output limit value EL derived by the second power generation output limit value deriving means (second power generation control means). Specifically, in step 206, the user load power is detected by the wattmeter 47a (user load power detection means). In step 208, the power generation output EU of the fuel cell corresponding to the user load power detected in step 206 is derived based on a map or arithmetic expression indicating the correlation between the user load power and the power generation output (power generation output deriving means). . In step 210, it is determined whether or not the power generation output limit value EL derived in step 204 is greater than or equal to the power generation output EU derived in step 208 (determination means). If it is determined in step 212 that the power generation output limit value EL is equal to or greater than the power generation output EU, the power generation output of the fuel cell 10 is controlled to follow the user load power (following control means). If it is determined in step 214 that the power generation output limit value EL is less than the power generation output EU, control is performed to limit the power generation output of the fuel cell 10 to the power generation output limit value EL (limit control means). .

  Then, the controller 90 waits for the predetermined time TMa to elapse in step 216 while performing follow-up control or limit control, and then proceeds to step 218 to end the program. As a result, after the control determined in step 212 or 214 is executed for a predetermined time TMa, the processing after step 202 is executed again.

  According to such control, when the hot water tank outlet temperature T4 rises as shown in the upper part of FIG. 9 due to the thermal energy accompanying the power generation of the fuel cell 10 as requested by the user, the condensed refrigerant is cooled in the second heat exchanger 76. The condensed refrigerant temperature increases. Along with this, the reformed gas FC inlet temperature T7 also starts to rise (time t21). It is assumed that the reformed gas FC inlet temperature T7 up to time t21 is maintained at a predetermined temperature Ta. Further, it is assumed that the power generation output of the fuel cell 10 is not limited until time t21 and that power generation is possible up to the maximum power generation output.

  When the reformed gas FC inlet temperature T7 becomes higher than the predetermined temperature Ta at time t21, until the reformed gas FC inlet temperature T7 becomes equal to or lower than the predetermined temperature Ta as shown in the middle part of FIG. 9 (time t25). The power generation output limit value EL gradually decreases (steps 202, 204, 302, 304, 310, 206 to 218). At the same time, the power generation output limit value EL and the power generation output EU of the fuel cell corresponding to the user load power are compared to determine whether to perform follow-up control or limit control, and the control is executed. Since the follow-up control is also executed within a range where the power generation output limit value EL gradually decreases, the power generation output (power generation output maximum value) of the fuel cell 10 is suppressed in any case, and the heat generation from the fuel cell 10 is suppressed. If the load on the radiator 76 is reduced and the cooling capacity is sufficient, the condensed refrigerant can be cooled, and the reformed gas FC inlet temperature T7 can be reduced.

  As a result, the reformed gas FC inlet temperature T7 reaches the predetermined temperature Ta at t25. When the power generation output EU based on the user load changes as shown in the middle part of FIG. 9 at time t21 to t25, the power generation output limit value EL is less than the power generation output EU at time t21 to t22 and time t23 to t24. Since the power generation output is limited to the power generation output limit value EL, and the power generation output limit value EL is not less than the power generation output EU in other time zones, the follow-up control follows the user load power without being limited by the power generation output. Is performed (the lower part of FIG. 9).

  When the reformed gas FC inlet temperature T7 becomes lower than the predetermined temperature Ta at time t29, for example, when hot water is used, the reformed gas FC inlet temperature T7 is again set to the predetermined temperature as shown in the middle part of FIG. The power generation output limit value EL gradually increases until reaching Ta or higher (time t31) (steps 202, 204, 302, 308, 310, 206 to 218). At the same time, the power generation output limit value EL and the power generation output EU of the fuel cell corresponding to the user load power are compared to determine whether to perform follow-up control or limit control, and the control is executed. Since the follow-up control is also executed within a range where the power generation output limit value EL gradually increases, in any case, the power generation output (power generation output maximum value) of the fuel cell 10 is increased, and the heat generation from the fuel cell 10 is increased. Then, the temperature of the condensed refrigerant can be raised, and thus the reformed gas FC inlet temperature T7 can be raised.

  As a result, the reformed gas FC inlet temperature T7 reaches the predetermined temperature Ta at t31. When the power generation output EU based on the user load changes as shown in the middle part of FIG. 9 at times t29 to t31, the power generation output limit value EL is less than the power generation output EU at times t29 to t30. Since the power generation output limit value EL is not less than the power generation output EU in other time zones, the follow-up control is performed to follow the user load power without limiting the power generation output (see FIG. 9 bottom).

  Therefore, according to the second control example, the second power generation output limit value deriving means is predetermined with the temperature of the fuel gas fuel cell inlet temperature T7 detected by the seventh temperature sensor 64a or the temperature correlated with the temperature of the fuel gas. The temperature Ta is compared, a power generation output limit value of the fuel cell is derived based on the comparison result, and the second power generation control means is based on the power generation output limit value EL derived by the second power generation output limit value deriving means. The power generation output of the fuel cell 10 is controlled. As a result, during the power generation of the fuel cell 10, the hot water stored in the fuel cell 10 and the reformer 20 generated by the power generation is recovered and the hot water is heated. In this case, the power generation output of the fuel cell 10 is limited in accordance with the fuel gas fuel cell inlet temperature T7 or the temperature T3 that correlates with the temperature of the fuel gas, so that the heat generation from the fuel cell 10 is suppressed as much as possible. The fuel cell system can be efficiently operated while maintaining the balance between the power generation output and the use of exhaust heat and avoiding the excessive heat state as much as possible.

  Further, the second power generation output limit value deriving means, when the fuel gas fuel cell inlet temperature T7 detected by the seventh temperature sensor 64a is higher than the predetermined temperature Ta, is a predetermined amount ΔE from the previous power generation output limit value EL. The current power generation output limit value EL−ΔE is calculated by subtraction, and when the temperature is lower than the predetermined temperature Ta, the current power generation output limit value EL + ΔE is calculated by adding a predetermined amount ΔE from the previous power generation output limit value EL. . As a result, the power generation output limit value EL can be calculated easily and accurately based on the fuel gas fuel cell inlet temperature T7 or the temperature correlated with the temperature of the fuel gas.

  In the second power generation control means, in step 208, the power generation output of the fuel cell corresponding to the user load power detected in step 206 is derived, and in step 210, the power generation output limit value derived in step 204. It is determined whether or not EL is equal to or greater than the power generation output EU derived in step 208. In step 212, if it is determined in step 210 that the power generation output limit value EL is equal to or greater than the power generation output EU. Then, the power generation output of the fuel cell 10 is controlled to follow the user load power. If it is determined in step 214 that the power generation output limit value EL is less than the power generation output EU in step 210, the fuel cell 10 The power generation output is controlled to be limited to the power generation output limit value EL. As a result, the fuel cell system can be stably and simply operated based on the power generation output EU of the fuel cell and the power generation output limit value EL corresponding to the user load power detected by the user load power detection means.

  Each process by the fuel gas fuel cell inlet temperature detection means, the second power generation output limit value derivation means, and the second power generation control means is repeatedly executed every predetermined time TMa set in consideration of the responsiveness of the fuel gas. Thus, the control process can be executed at an appropriate time. In addition, the control process can be executed more precisely.

As is clear from the above description, in this reference embodiment , the hot water circulation circuit 80 includes the flow path 72 provided with the exhaust heat recovery means (condenser 30) and the flow path provided with the first heat exchanger 74. By providing the bypass path 75 in parallel, the exhaust heat generated by the power generation of the fuel cell 10 is recovered in the FC cooling water during normal operation of the system, and the hot water stored in the bypass path 75 is circulated. Then, it is recovered via the first heat exchanger 74, and as a result, the stored hot water is heated (heated up). The exhaust heat of the off-gas discharged from the fuel cell 10 and the exhaust heat generated in the reformer 20 are recovered directly into the hot water storage via the condensers 32 and 33 and the condensers 31 and 34. As a result, the hot water storage is performed. Is heated (heated up). Thus, the exhaust heat generated by the power generation of the fuel cell 10, the exhaust heat of the off-gas discharged from the fuel cell 10, and / or the exhaust heat generated in the reformer 20 may be recovered in series. However, since heat can be recovered independently in parallel, it is possible to recover heat at the most efficient hot water flow rate. Therefore, when the ratio of the amount of heat recovered from the fuel cell to the amount of heat recovered from the anode off-gas, cathode off-gas, and combustion exhaust gas is low, for example, in the case of power generation at a low load or when the influence of heat dissipation is large in winter, Since heat can be sufficiently recovered from each of these gases, it is possible to provide a fuel cell system that can be operated while maintaining high heat recovery efficiency from the start to the stop of power generation of the system.

  Further, off-gas exhaust heat recovery devices (condensers 32 and 33) that recover the exhaust heat of the off-gas discharged from the fuel cell 10 into the hot water storage, and reforming that recovers the exhaust heat generated by the reformer 20 into the hot water storage water. Since at least one of the condenser exhaust heat recovery units (condensers 31 and 34) is provided in the flow path 72, the hot water stored in the flow path 72 is discharged from the fuel cell 10, and the exhaust gas is discharged from the fuel cell 10 and the reformer. At least one of the exhaust heat generated at 20 can be reliably recovered.

  Further, since the flow rate adjusting means (the first hot water circulation first pump P5 and the second hot water circulation second pump P6) for adjusting the respective flow rates of the bypass passage 75 and the flow passage 72 is further provided, the hot water flowing through the bypass passage 75 and the flow passage 72 is provided. The flow rate of water can be adjusted with certainty, and optimal heat recovery efficiency and recovered hot water temperature can be realized.

2) Embodiment will now be described embodiments of a fuel cell system according to the present invention. FIG. 10 is a schematic diagram showing an outline of the periphery of the hot water circulating circuit 80, the FC cooling water circulating circuit 73, and the condensed refrigerant circulating circuit 75 in the fuel cell system according to the embodiment . In the reference embodiment described above, each of the condensers 31 to 34 is provided on the flow path 72, and the exhaust heat of the offgas discharged from the fuel cell 10 and the exhaust heat generated in the reformer 20 are Although it is made to collect | recover to direct hot water through 33 and the condensers 31 and 34, as shown in FIG. 10, you may make it collect | recover indirectly to hot water. In addition, the same code | symbol is attached | subjected about the structural member same as a reference form, and the description is abbreviate | omitted.

In the present embodiment , the exhaust heat recovery means is a condensation that is an exhaust heat recovery heat medium that recovers at least one of exhaust heat of off-gas exhausted from the fuel cell 10 and exhaust heat generated in the reformer 20. Condensed refrigerant circulation circuit 78, which is an exhaust heat recovery heat medium circulation circuit through which refrigerant (condenser heat medium) circulates, and second heat exchanger 79 in which heat is exchanged between the hot water and condensed refrigerant. ing. Thereby, at least one of the exhaust heat of the off-gas discharged from the fuel cell 10 and the exhaust heat generated in the reformer 20 is recovered by the condensed refrigerant through the condenser 30, and the second heat exchanger 79 is The hot water is then recovered (hot) as a result.

  A second heat exchanger 79 is disposed on the condensed refrigerant circulation circuit 78. In addition, on the condensing refrigerant circulation circuit 78, in order from the outlet of the second heat exchanger 79, the condensing refrigerant circulation pump P8, the radiator 76, the anode offgas condenser 32, the combustion gas condenser 34, and the cathode offgas condensation. 33, a reformed gas condenser 31, and a fifth temperature sensor 78a are provided. The condensing refrigerant circulation pump P8 is condensing refrigerant circulation means, and is controlled by the control device 90 to control the flow rate (delivery amount). The fifth temperature sensor 78 a detects the outlet temperature T5 of the reforming gas condenser 31 of the condensed refrigerant and outputs the detection result to the control device 90. The anode off-gas condenser 32, the combustion gas condenser 34, the cathode off-gas condenser 33, the reformed gas condenser 31, and the radiator 76 are omitted from the flow path 72, and the condensed refrigerant circulation circuit 78 is removed. Has been relocated.

  Next, control for optimizing the heat recovery efficiency in the fuel cell system described above will be described. First, the flow rate of the hot water circulating second pump P6 is controlled so that the FC cooling water FC inlet temperature T1 (or the FC cooling water FC outlet temperature T2) becomes the optimum operating temperature of the fuel cell. Further, the flow rate of the FC cooling water circulation pump P7 is controlled so that the temperature difference ΔT between the FC cooling water FC inlet temperature T1 and the FC cooling water FC outlet temperature T2 becomes the target temperature difference ΔT * (for example, 3 to 5 ° C.). Yes. The target temperature difference ΔT * is set so that the water vapor in the reformed gas channel or the air channel of the fuel cell 10 can be maintained under the optimum humidification condition. The flow rate of the condensed refrigerant circulation pump P8 is controlled so that the anode off-gas (AOG) condenser outlet temperature T5 of the condensed refrigerant becomes the target temperature T5 * (for example, 55 to 60 ° C.). The higher the outlet temperature T5 of the condensed refrigerant for the reformed gas, the better the efficiency of collecting and recovering the amount of condensed water in the second heat exchange 79. Therefore, it is desirable to set the target temperature T5 * higher. On the other hand, when the reformed gas condenser outlet temperature T5 of the condensed refrigerant increases, the temperature of the reformed gas that exchanges heat with the condensed refrigerant in the reformed gas condenser 31, that is, the temperature of the reformed gas FC inlet temperature T7 increases. Thus, the fuel electrode 11 of the fuel cell 10 is flooded. Therefore, the target temperature T5 * is set to a temperature at which the recovery efficiency of the condensed recovery heat amount is as good as possible within the range where no flooding occurs.

  Thereby, during the steady operation of the system, the hot water flowing through the bypass 75 at an appropriate flow rate recovers the exhaust heat generated by the power generation of the fuel cell most efficiently. On the other hand, in the second heat exchanger 79, hot water that circulates in the flow path 72 at an appropriate flow rate that is independent of the hot water flowing through the bypass passage 75 at an appropriate flow rate and that is not restricted by the flow rate. The exhaust gas exhaust heat discharged from the fuel cell 10 and the exhaust heat generated in the reformer 20 are recovered most efficiently. Then, both hot water storage water merges and flows into the hot water storage tank 71.

In this embodiment, the control of the first and second control examples described above is also performed. In the second control example, instead of the fuel gas FC inlet temperature T7, the temperature correlated with the fuel gas temperature T7, for example, the outlet temperature of the condensed refrigerant reformed gas condenser 31 (condensed refrigerant reformed gas condenser outlet). The temperature T5 may be detected by the fifth temperature sensor 78a.

According to the present embodiment, in addition to the operation and effect of the reference embodiment , the operation and effect can be obtained as follows. The condensed refrigerant circulation circuit 78 circulates condensed refrigerant that collects at least one of exhaust heat of off-gas discharged from the fuel cell 10 and exhaust heat generated in the reformer 20. Are provided independently, and heat exchange is performed between the hot water and the condensed heat medium via the second heat exchanger 79. That is, the stored hot water does not directly exchange heat with the anode off-gas, cathode off-gas, combustion exhaust gas, and fuel gas (reformed gas), but indirectly exchanges heat through the second heat exchanger 79. Become. Therefore, when the hot water tank 71 is a sealed type in which tap water is directly replenished, a high pressure tap water pressure is applied to the hot water tank 71 and the hot water circulation circuit 80, but the condensing refrigerant circulation circuit 78 is independent of the hot water circulation circuit 80. Therefore, the heat exchanger (condenser 30) for exchanging heat with the anode off-gas, cathode off-gas, combustion exhaust gas, and fuel gas (reformed gas) disposed on the condensing refrigerant circulation circuit 78 is directly supplied with water. Since no water pressure is applied, the heat exchanger does not need to have an excessive pressure-resistant structure, so that it is possible to provide a fuel cell system capable of replenishing hot water from a high-pressure water source without increasing the cost and increasing the size. .

  Further, a condenser 30 is provided on the condensing refrigerant circulation circuit 78 for recovering the amount of heat from the high-temperature and steam-containing gas flowing through the reformer and the fuel cell, and condensing the gas. Since it is the condensed refrigerant | coolant which distribute | circulates 30, it can heat up a condensed heat medium reliably with a simple structure, without enlarging by utilizing the conventional structure effectively.

In the above-described embodiment , the radiator 76 may be arranged in the hot water circulating circuit 80 or the FC cooling water circulating circuit 73, and at least any of the condensed refrigerant circulating circuit 78, the hot water circulating circuit 80, and the FC cooling water circulating circuit 73. It may be arranged in one. According to this, when the temperature of the hot water reaches the temperature required by the fuel cell, or when the hot water reaches the temperature required by the condensed refrigerant that recovered the exhaust heat of the reformer 20, the hot water stores the exhaust heat. In order to prevent the temperature from rising further, the temperature of the stored hot water or / and the FC cooling water and the condensing heat medium can be efficiently cooled by the radiator 76 serving as a cooling means.

Further, in the reference and embodiment described above, the flow rate adjusting means is constituted by the two hot water circulating first pumps P5 and the second hot water circulating second pump P6 which are the two hot water circulating means, but as shown in FIG. You may make it comprise with one stored hot water circulation means and one set (one) flow rate ratio adjustment means. Specifically, what is necessary is just to comprise from the hot water storage 3rd pump P9, the 2nd and 3rd valve | bulb 81,82. The third hot water circulation pump P9 is provided in the flow path 72 between the bypass 75 and the outlet of the hot water tank 71, and is controlled by the control device 90 to control the flow rate (delivery amount). Yes. The second valve 81 is an open / close valve that is provided in the flow path 72 on the condenser 30 (second heat exchanger 79) side from the branch point with the bypass path 75 and that can open and close the flow path 72 and adjust the opening degree. The opening / closing is controlled and the opening degree is adjusted by a command from the control device 90. The third valve 82 is an open / close valve that is provided in the bypass passage 75 and that opens and closes the bypass passage 75 and that can be adjusted in opening degree. According to this, by controlling the total flow rate of the hot water by the hot water circulation third pump P9 and controlling the flow rate ratio of the flow path 72 and the bypass path 75 by the respective opening degrees of the second and third valves 81 and 82. Each flow rate of the flow path 72 and the bypass path 75 can be adjusted. In place of the second and third valves 81 and 82, other types of flow ratio adjusting means, for example, a flow ratio adjuster may be provided at a branch point.

In the reference and embodiment described above, the pump for sending gas out of the pumps can be replaced with a blower.

It is a schematic diagram showing an outline of a reference form 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 1st map which shows correlation with hot water tank exit temperature and FC electric power generation output limit value. It is a 2nd map which shows the correlation of the required cooling capacity of the said fuel cell system with respect to the electric power generation output of the fuel cell for every temperature of stored hot water. It is a flowchart of the control program of the 1st control example performed with the control apparatus shown in FIG. It is a time chart which shows operation | movement of the 1st control example of the fuel cell system by this invention. It is a flowchart of the control program of the 2nd control example performed with the control apparatus shown in FIG. It is a flowchart of the subroutine of the control program of the 2nd control example performed with the control apparatus shown in FIG. It is a time chart which shows operation | movement of the 2nd control example of the fuel cell system by this invention. It is a schematic diagram showing an outline of an embodiment of a fuel cell system according to the present invention. It is a schematic diagram which shows the modification of the flow volume adjustment means 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 ... Burner, 22 ... Reformer, 23 ... Carbon monoxide shift reaction part (CO shift part), 24 ... Carbon monoxide Selective oxidation reaction section (CO selective oxidation section), 25 ... evaporator, 30 ... condenser, 31 ... reformer gas condenser, 32 ... anode off-gas condenser, 33 ... cathode off-gas condenser, 34 ... combustion gas Condenser, 40 ... pure water device, 45 ... inverter, 46 ... power transmission line, 47 ... power usage place, 47a ... power meter, 48 ... system power supply, 47 ... power line, 50 ... water reservoir, 53 ... reformed water Pump, 61-66 ... Piping, 68 ... Reformed water supply pipe, 71 ... Hot water storage tank, 72 ... Flow path, 73 ... FC cooling water circulation circuit, 74 ... First heat exchanger, 75 ... Bypass passage, 76 ... Radiator, 77 ... 1st valve, 78 ... Condensed refrigerant circulation circuit, 79 ... 2 heat exchangers, 80 ... hot water circulation circuit, 81, 82 ... second and third valves, P1 to P9, 53 ... pumps, 73a, 73b, 72b, 72a, 78a, 64a ... first to fifth, seventh Temperature sensor, 90 ... control device.

Claims (3)

A fuel cell, and a reformer that generates fuel gas to be supplied to the fuel cell;
A hot water storage tank for storing hot water heated by heat generated in the fuel cell;
A hot water circulation circuit including the hot water tank and circulating the hot water;
A fuel cell heat medium circulation circuit in which a fuel cell heat medium that exchanges heat with the fuel cell circulates;
A first heat exchanger for exchanging heat between the hot water and the fuel cell heat medium;
In a fuel cell system comprising:
An exhaust heat recovery heat medium circulation circuit that is provided independently of the hot water circulation circuit and in which the exhaust heat recovery heat medium circulates;
An exhaust heat recovery means provided in the exhaust heat recovery heat medium circulation circuit for recovering the exhaust heat of the combustion gas or reformed gas generated in the reformer to the exhaust heat recovery heat medium;
A second heat exchanger that exchanges heat between the hot water and the exhaust heat recovery heat medium,
The reserved hot water circulation circuit includes a flow path having a flow path and the second heat exchanger provided with the first heat exchanger is found connected in parallel,
The fuel cell system further comprising flow rate adjusting means for adjusting the flow rates of the flow path provided with the first heat exchanger and the flow path provided with the second heat exchanger, respectively . 2. The exhaust heat recovery means according to claim 1, wherein the exhaust heat recovery means condenses the water vapor in the reformed gas supplied from the reformer to the fuel cell by heat exchange with the exhaust heat recovery heat medium to exhaust the reformed gas. A fuel cell system comprising a reformed gas condenser for recovering heat to the exhaust heat recovery heat medium .   3. The fuel cell system according to claim 1, wherein the flow path provided with the first heat exchanger and the flow path provided with the second heat exchanger are used simultaneously.

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