JP2008277198A - Fuel cell cogeneration system - Google Patents

Abstract

A fuel cell cogeneration apparatus is provided that optimizes the amount of water contained in an anode gas in accordance with the operating state of a fuel cell and prevents a decrease in power generation efficiency.
A condenser (anode gas heat exchanger 84) disposed in an anode gas supply path (first anode gas supply path 62a) and a fuel cell heat exchanger 100 that recovers exhaust heat generated in a fuel cell 12. And a heat exchanger (anode offgas heat exchanger 80, cathode offgas heat exchanger 82) disposed in at least one of the anode offgas discharge path 64 and the cathode offgas discharge path 78, and the cooling water is used as fuel cell heat. After being supplied from the exchanger to the heat exchanger via the first cooling water supply path 110, it is supplied to the condenser via the second cooling water supply path 114, that is, to the condenser, the anode off-gas in the heat exchanger. And supply cooling water heat-exchanged with cathode off-gas.
[Selection] Figure 1

Description

  The present invention relates to a fuel cell cogeneration apparatus, and more specifically, a fuel cell cogeneration apparatus that optimizes the amount of water contained in the anode gas in accordance with the operating state of the fuel cell and prevents a decrease in power generation efficiency. About.

  In recent years, there has been proposed a fuel cell cogeneration apparatus that recovers exhaust heat by supplying cooling water to the fuel cell and exchanging heat with exhaust heat generated in the fuel cell. The apparatus generally uses a polymer electrolyte fuel cell. In order to generate electricity with a polymer electrolyte fuel cell, it is necessary to contain moisture in the polymer electrolyte membrane. Therefore, moisture is supplied to the fuel cell by humidifying the anode gas (hydrogen gas) or cathode gas (reaction air). Is done.

  On the other hand, the anode gas described above is produced by reacting a fuel gas (for example, city gas) and water vapor with a reforming catalyst, and therefore contains a large amount of moisture. When such anode gas is directly supplied to the fuel cell, moisture is condensed inside the fuel cell, the gas flow path is blocked, and gas diffusion is hindered, resulting in a decrease in power generation efficiency of the fuel cell. There is.

Thus, for example, in the technique described in Patent Document 1, a condenser is disposed in the anode gas supply path for supplying the anode gas to the fuel cell, and the moisture contained in the anode gas is condensed and removed. The fuel cell is configured to prevent excessive moisture from being supplied.
JP 2006-302779 A (paragraph 0024, FIG. 1, etc.)

  However, the amount of water required in the fuel cell varies depending on the operating state. Specifically, the temperature of the fuel cell gradually rises from the start of power generation to the rated operation state, but the required amount of water increases in proportion to the temperature rise of the fuel cell. In the technique described in Patent Document 1 described above, the change in the required amount of water with respect to the operating state of the fuel cell is not taken into account, and depending on the operating state, the moisture of the anode gas is excessively removed by the condenser, There is a possibility that the amount of water supplied to the fuel cell is insufficient and the power generation efficiency is lowered.

  Accordingly, an object of the present invention is to provide a fuel cell cogeneration apparatus that solves the above-described problems, optimizes the amount of water contained in the anode gas according to the operating state of the fuel cell, and prevents a decrease in power generation efficiency. There is to do.

  In order to solve the above-mentioned object, in claim 1, a fuel cell, an anode gas supply path connected to the fuel cell for supplying an anode gas, and an anode gas supply path disposed in the anode gas supply path A condenser that condenses and removes moisture contained in the gas, exhaust heat recovery means that recovers the exhaust heat by supplying cooling water to the fuel cell and exchanging heat with the exhaust heat generated in the fuel cell, A fuel cell cogeneration apparatus comprising: an anode offgas discharge path for discharging an anode offgas generated by a fuel cell; and a cathode offgas discharge path for discharging a cathode offgas generated by the fuel cell; A heat exchanger disposed in at least one of the cathode offgas discharge paths, and the exhaust heat recovery means and the heat exchanger are connected. A first cooling water supply path for supplying the heat exchanged cooling water from the exhaust heat recovery means to the heat exchanger; and connecting the heat exchanger and the condenser to supply the first cooling water. And a second cooling water supply path for supplying the cooling water supplied to the heat exchanger via the path to the condenser.

  The combustion burner connected to the anode offgas discharge passage and combusts the discharged anode offgas to heat the reforming catalyst, and the combustion generated by the combustion connected to the combustion burner. Combustion exhaust gas discharge path for exhausting exhaust gas, a second heat exchanger disposed in the combustion exhaust gas discharge path, the condenser and the second heat exchanger connected to each other, and the second cooling water supply path A third cooling water supply passage for supplying the cooling water supplied to the condenser via the second heat exchanger to the second heat exchanger, and connecting the second heat exchanger and the exhaust heat recovery means. And a fourth cooling water supply path for supplying the cooling water supplied to the second heat exchanger via the third cooling water supply path to the exhaust heat recovery means.

  In the fuel cell cogeneration apparatus according to claim 1, the condenser disposed in the anode gas supply path and the cooling water are supplied to the fuel cell so as to exchange heat with the exhaust heat generated in the fuel cell. It is disposed in the exhaust heat recovery means to be recovered and at least one of the anode off-gas exhaust path and the cathode off-gas exhaust path (in other words, the exhaust path for exhausting the gas generated by the fuel cell (anode off-gas or cathode off-gas)) The cooling water that is heat-exchanged in the exhaust heat recovery means is supplied from the exhaust heat recovery means to the heat exchanger via the first cooling water supply path, and then the second cooling is performed. It is configured so as to be supplied to the condenser through the water supply path, that is, the condenser is supplied with the cooling water of the exhaust heat recovery means heat-exchanged with the anode off-gas or the cathode off-gas in the heat exchanger. Since the condenser is configured, the condenser condenses and removes moisture contained in the anode gas at a temperature corresponding to the temperature change of the fuel cell, and thus the moisture content of the anode gas is reduced to the operating state of the fuel cell (specifically, The temperature can be optimized according to the temperature of the fuel cell), and a reduction in power generation efficiency can be prevented.

  Specifically, the amount of water required in the fuel cell changes according to the operating state, and more specifically, increases in proportion to the temperature of the fuel cell that gradually increases from the start of power generation to the rated operating state. As described above, since the cooling water of the exhaust heat recovery means exchanged with the anode off-gas and cathode off-gas discharged from the fuel cell is supplied to the condenser, the temperature of the condenser is the temperature of the fuel cell. As the temperature rises, the dew point of the anode gas in the condenser rises, so that the moisture content of the anode gas to be removed can be gradually reduced. The amount of water to be generated can be gradually increased as compared with the start of power generation. As a result, the amount of moisture contained in the anode gas can be optimized according to the operating state of the fuel cell (specifically, the anode gas containing a large amount of moisture is supplied to the fuel cell and the moisture is condensed inside the fuel cell). Thus, the gas flow passage is not blocked, and the anode gas is excessively removed to prevent the amount of water supplied to the fuel cell from being deficient), thereby preventing a decrease in power generation efficiency. In other words, the fuel cell can always perform efficient power generation. Further, the temperature of the cooling water of the exhaust heat recovery means is increased by exchanging heat with the anode off gas or the cathode off gas, so that the exhaust heat of the fuel cell can be efficiently recovered.

  In the fuel cell cogeneration apparatus according to claim 2, the second heat exchanger is disposed in the combustion exhaust gas discharge path for discharging the combustion exhaust gas generated by the combustion in the combustion burner and is supplied to the condenser. Since the cooling water is supplied to the second heat exchanger via the third cooling water supply path and then supplied to the exhaust heat recovery means via the fourth cooling water supply path, the above-described effect In addition, the temperature of the cooling water of the exhaust heat recovery means is increased by the heat exchange with the combustion exhaust gas, so that not only the exhaust heat of the fuel cell but also the exhaust heat of the combustion burner can be recovered. Driving efficiency can be improved.

  DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of a fuel cell cogeneration apparatus according to the present invention will be described below with reference to the accompanying drawings.

  FIG. 1 is a schematic diagram showing the configuration of a fuel cell cogeneration apparatus according to an embodiment of the present invention.

  In FIG. 1, the code | symbol 10 shows a fuel cell cogeneration apparatus. The fuel cell cogeneration apparatus 10 is a stationary apparatus installed in a home, a factory, or the like, and includes a fuel cell (stack) 12 and an anode gas supply system 14 that supplies anode gas (reformed gas) to the fuel cell 12. A cathode gas supply system 16 that supplies cathode gas (reactive air) to the fuel cell 12, a power control system 20 that controls the power generated in the fuel cell 12, and exhaust heat that recovers exhaust heat generated in the fuel cell 12. A recovery system 22 is provided.

  The fuel cell 12 includes an electrolyte membrane (solid polymer membrane), an anode electrode (fuel electrode) and a cathode electrode (air electrode) that sandwich the membrane, and a separator (all not shown) disposed outside each electrode. And a known solid polymer fuel cell formed by stacking a plurality of single cells (cells) composed of

  The anode gas supply system 14 reforms a fuel gas (for example, a city gas containing methane as a main component) to generate an anode gas containing hydrogen to be supplied to the anode electrode of the fuel cell 12. Is provided. The reformer 24 is connected to a fuel gas pipe 24a into which fuel gas or the like flows and a fuel gas pipe 24a, and is filled with a reforming catalyst 24b that reacts the fuel gas with water vapor to reform the anode gas. A reforming pipe 24c, an anode gas pipe 24d that is connected to the reforming pipe 24c and discharges the anode gas generated by the reforming catalyst 24b; And a combustion exhaust pipe 24f that is connected to the combustion burner 24e and circulates the combustion exhaust gas generated by the combustion.

  The fuel gas pipe 24a of the reformer 24 includes a first fuel gas supply path 26a for supplying fuel gas from a fuel gas supply source (not shown) and water for reforming (not shown). A reforming water supply path 30 that is supplied as “reforming water” is connected.

  In the first fuel gas supply path 26a, a desulfurizer 32 that removes an odorant of the fuel gas, such as an organic sulfur compound, and a first fuel gas that has passed through the desulfurizer 32 are pumped to the reformer 24. A fuel gas pump 34 and a first on-off valve (electromagnetic valve) 36 that opens and closes the first fuel gas supply path 26 a are provided on the downstream side of the first fuel gas pump 34. The reforming water supply path 30 includes a water supply pump 40 that pumps the reforming water to the reformer 24 and a second on-off valve (electromagnetic) that opens and closes the reforming water supply path 30 on the downstream side of the water pump 40. Valve) 42 is arranged. In this specification, “upstream” and “downstream” mean upstream and downstream in the flow direction of gas or liquid (fluid) flowing therethrough.

  A combustion air supply path 44 for supplying combustion air (hereinafter referred to as “combustion air”) or the like is connected to the combustion burner 24e. The combustion air supply path 44 is provided with a combustion air pump 46 that pumps air as combustion air to the combustion burner 24e, and a mixer (ejector) 50 that mixes fuel gas with the combustion air.

  The mixer 50 is connected to the first fuel gas supply path 26a via the second fuel gas supply path 26b. As shown in FIG. 1, the second fuel gas supply path 26b is branched from between the desulfurizer 32 and the first fuel gas pump 34 of the first fuel gas supply path 26a, and the fuel gas is ejected in the middle of the ejector 50. A second fuel gas pump 52 that pumps the fuel gas and a third on-off valve (solenoid valve) 54 that opens and closes the second fuel gas supply path 26 b are installed on the downstream side of the second fuel gas pump 52.

  The combustion exhaust gas pipe 24f includes a discharge port 24f1 for discharging combustion exhaust gas, and a combustion exhaust gas discharge path 60 is connected to the discharge port 24f1. Therefore, the combustion exhaust gas discharge path 60 is connected to the combustion burner 24e via the combustion exhaust gas pipe 24f and discharges (exhausts) the combustion exhaust gas generated by the combustion.

  The anode gas supply system 14 further includes a first anode gas supply path 62 a that connects the fuel cell 12 and the reformer 24, and an anode off-gas discharge path 64. More specifically, the first anode gas supply path 62a has an upstream end connected to the anode gas pipe 24d of the reformer 24, and a downstream end connected to an anode gas supply port (not shown) of the fuel cell 12. ). The anode off gas discharge path 64 has an upstream end connected to an anode off gas discharge port (not shown) of the fuel cell 12 and a downstream end connected to a combustion burner 24 e of the reformer 24. Accordingly, the first anode gas supply path 62a supplies the anode gas generated by the reformer 24 to the fuel cell 12, and the anode offgas discharge path 64 discharges the anode offgas generated by the fuel cell 12. The discharged anode off gas is supplied to the combustion burner 24e as a combustion fuel.

  A three-way valve (electromagnetic valve) 66 is disposed in the first anode gas supply path 62a. The first anode gas supply path 62 a is connected to the second anode gas supply path 62 b via the three-way valve 66, and the downstream end of the second anode gas supply path 62 b is connected to the anode offgas discharge path 64. The The three-way valve 66 supplies the anode gas discharged from the reformer 24 to the fuel cell 12 when not energized. When the amount of the anode gas required in the fuel cell 12 decreases, the three-way valve 66 is energized to pass the anode gas to the second. The anode gas supply passage 62b is set to be supplied to the anode offgas discharge passage 64.

  A fourth on-off valve (electromagnetic valve) 70 that opens and closes the anode off-gas discharge path 64 is disposed upstream of the connection position of the second anode gas supply path 62 b in the anode off-gas discharge path 64. Note that the first to fourth on-off valves 36, 42, 54, 70 are all electromagnetic valves, and in order to prevent fuel gas and the like from flowing out when the fuel cell 12 is not in operation, the fuel cell It is assumed that all valves are closed at the end of the operation. In other words, the first to fourth on-off valves 36, 42, 54, 70 are all normally / close type solenoid valves (closed when not energized and opened when energized (when energized)). Solenoid valve).

  The cathode gas supply system 16 includes a cathode gas supply path 72 that supplies cathode gas to the cathode electrode (cathode gas supply port (not shown)) of the fuel cell 12. In the cathode gas supply path 72, a cathode gas pump 74 that sucks air and pumps the air as a cathode gas to the fuel cell 12, and a cathode gas discharged from the fuel cell 12 on the downstream side of the cathode gas pump 74 (hereinafter referred to as “cathode”). A humidifier 76 for humidifying by “off gas” or the like is installed.

  The cathode gas supply system 16 further has one end connected to a cathode offgas discharge port (not shown) of the fuel cell 12 and the other end opened to the atmosphere so that the cathode offgas generated by the fuel cell 12 is externally exposed. A cathode off-gas discharge path 78 for discharging is provided. The humidifier 76 described above is disposed in the middle of the cathode off gas discharge path 78.

  As shown in FIG. 1, heat exchangers 80, 82, 84, and 86 are respectively provided in the anode offgas discharge path 64, the cathode offgas discharge path 78, the first anode gas supply path 62 a, and the combustion exhaust gas discharge path 60. Be placed. Specifically, an anode offgas heat exchanger (first heat exchanger) 80 is disposed between the connection position of the second anode gas supply path 62b and the combustion burner 24e in the anode offgas discharge path 64. A cathode offgas heat exchanger (first heat exchanger) 82 is disposed downstream of the humidifier 76 in the cathode offgas discharge path 78. An anode gas heat exchanger (condenser) 84 is disposed between the three-way valve 66 and the fuel cell 12 in the first anode gas supply path 62a, and combustion exhaust gas heat is supplied to the combustion exhaust gas discharge path 60. An exchanger (second heat exchanger) 86 is arranged.

  The heat exchangers 80, 82, 84, 86 are supplied with cooling water (described later) of the exhaust heat recovery system 22 and exchange heat with the anode off gas or the like. Of the four heat exchangers 80, 82, 84, and 86, the anode off-gas heat exchanger 80, the cathode off-gas heat exchanger 82, and the anode gas heat exchanger 84 are each an anode off-gas that has been heat-exchanged with cooling water. And a gas-liquid separator (not shown) for condensing the cathode off gas and the anode gas and separating them into a gas component and a liquid component (condensed water). The gas-liquid separator is connected to discharge paths 80a, 82a, 84a for discharging condensed water obtained by the separation. That is, the anode offgas heat exchanger 80, the cathode offgas heat exchanger 82, and the anode gas heat exchanger 84 function as a condenser that condenses and removes moisture contained in the anode offgas, the cathode offgas, or the anode gas. The discharge passages 80a, 82a, 84a are connected to a humidifier 76, and the condensed water is used as water for humidifying the cathode gas.

  The power control system 20 converts an electronic control unit (Electronic Control Unit; hereinafter referred to as “ECU”) 90 including a microcomputer and the power (DC current) generated by the fuel cell 12 into an AC current having a predetermined frequency. And an inverter 94 that outputs to an electric load (AC power supply device) 92 and the like, and is connected to an output terminal 96 that outputs power generated in the fuel cell 12. The ECU 90 is connected to auxiliary devices such as the first fuel gas pump 34 and the on-off valves 36, 42, 54, and 70 via signal lines (not shown) and controls their operations.

  The exhaust heat recovery system 22 includes a fuel cell heat exchanger (exhaust heat recovery means) 100 that recovers exhaust heat by supplying cooling water to the fuel cell 12 and exchanging heat with exhaust heat generated in the fuel cell 12. The fuel cell heat exchanger 100 includes a primary cooling water recirculation path 102 for recirculating the primary cooling water to the fuel cell 12 and a secondary cooling water flow path for circulating the secondary cooling water heat-exchanged with the primary cooling water. 104 is connected.

  One end of the primary coolant circulation path 102 is connected to a coolant inlet (not shown) of the fuel cell 12 and the other end is connected to a coolant outlet (not shown) of the fuel cell 12. The The cooling water introduction port and the cooling water discharge port are communicated with each other via a cooling pipe (not shown) disposed inside the fuel cell 12. A primary cooling water pump 106 that pumps the cooling water to the fuel cell 12 is disposed in the middle of the primary cooling water return path 102. Accordingly, the primary cooling water is pumped to the primary cooling water pump 106, whereby the fuel cell 12, the primary cooling water recirculation path 102, the fuel cell heat exchanger 100, the primary cooling water recirculation path 102, the primary cooling water The cooling water pump 106 is circulated in this order.

  In the secondary cooling water flow path 104, a hot water storage tank (hot water storage tank) that stores secondary cooling water (hot water; hereinafter simply referred to as “cooling water”) exchanged with the primary cooling water in the fuel cell heat exchanger 100. 108 is arranged. The cooling water stored in the hot water storage tank 108 is supplied to the heat exchangers 80, 82, 84, 86 through the secondary cooling water flow path 104.

  More specifically, the secondary cooling water flow path 104 connects the fuel cell heat exchanger 100 and the anode offgas heat exchanger 80 (more precisely, the fuel cell heat exchanger 100 and the anode offgas heat exchanger 80 are connected to a hot water tank. 108, the first cooling water supply passage 110 for supplying the cooling water subjected to heat exchange from the fuel cell heat exchanger 100 to the anode offgas heat exchanger 80, the anode offgas heat exchanger 80, and the cathode offgas. A connection channel (first cooling water supply channel) 112 that connects (connects) the heat exchanger 82 to supply the cooling water supplied to the anode off-gas heat exchanger 80 to the cathode off-gas heat exchanger 82, and the cathode off-gas The heat exchanger 82 and the anode gas heat exchanger (condenser) 84 are connected to be supplied to the cathode offgas heat exchanger 82 via the first cooling water supply passage 110 and the connection passage 112. It is the a second cooling water supply passage 114 for supplying cooling water to the anode gas heat exchanger 84.

  The secondary cooling water flow path 104 further connects the anode gas heat exchanger 84 and the combustion exhaust gas heat exchanger 86 and supplies the cooling water supplied to the anode gas heat exchanger 84 via the second cooling water supply path 114. A third cooling water supply path 116 that supplies the combustion exhaust gas heat exchanger 86, a combustion exhaust gas heat exchanger 86 and the fuel cell heat exchanger 100 are connected, and the combustion exhaust gas heat passes through the third cooling water supply path 116. A fourth cooling water supply path 120 that supplies the cooling water supplied to the exchanger 86 to the fuel cell heat exchanger 100 is provided.

  A cooling water pump 122 that pumps the cooling water toward the anode offgas heat exchanger 80 or the like is disposed in the first cooling water supply path 110. Therefore, the cooling water heat-exchanged in the fuel cell heat exchanger 100 is pumped to the cooling water pump 122, so that the first cooling water supply passage 110, the anode off-gas heat exchanger, as indicated by arrows in FIG. 80, connection flow path 112, cathode offgas heat exchanger 82, second cooling water supply path 114, anode gas heat exchanger 84, third cooling water supply path 116, flue gas heat exchanger 86, fourth cooling The water supply path 120, the fuel cell heat exchanger 100, the first cooling water supply path 110, the hot water storage tank 108, and the cooling water pump 122 are supplied (circulated) in this order.

  The hot water storage tank 108 is supplied with a water supply channel 124 for supplying (supplementing) water from a water source (not shown) when the amount of hot water stored in the hot water storage tank 108 decreases, and cooling water (hot water) stored in the hot water storage tank 108. A hot water supply channel 130 that supplies hot water using equipment (for example, a hot water shower) 126 is connected.

  Next, the operation of the fuel cell cogeneration apparatus 10 configured as described above will be outlined.

  First, when a start instruction for the fuel cell cogeneration apparatus 10 is issued (more specifically, when a start switch (not shown) is turned on by an operator), an anode gas is generated in the reformer 24. Specifically, the combustion air pump 46 and the second fuel gas pump 52 are operated, and the third on-off valve 54 is opened. As a result, the combustion air is sucked by the combustion air pump 46, dust is removed by an air filter (not shown), and then supplied to the mixer 50 via the combustion air supply path 44. Further, fuel gas supplied from a fuel gas supply source (not shown) is supplied to the desulfurizer 32 through the first fuel gas supply path 26a to remove the odorant, and then the second fuel gas. It is supplied to the mixer 50 via the supply path 26b, the second fuel gas pump 52, and the third on-off valve 54.

  When the combustion air and the fuel gas are supplied, the mixer 50 mixes the fuel gas with the combustion air to generate a premixed gas, which is discharged toward the combustion burner 24e of the reformer 24. The combustion burner 24e ignites (ignites) the supplied premixed gas with an ignition electrode (not shown), and combusts it. A combustion exhaust gas having a relatively high temperature is generated by the combustion.

  The combustion exhaust gas is circulated in the combustion exhaust pipe 24f as indicated by an arrow in FIG. Since the flue gas pipe 24f has a shape that covers the outer wall 24c1 of the reforming pipe 24c, the flue gas in the flue gas pipe 24f rises the reforming pipe 24c and the reforming catalyst 24b filled therein. Let warm. Thereafter, the combustion exhaust gas is discharged (exhaust) into the atmosphere via the exhaust port 24f1 of the combustion exhaust gas pipe 24f, the combustion exhaust gas passage 60, and the combustion exhaust gas heat exchanger 86.

  When the reforming catalyst 24b is heated to a temperature capable of reforming (for example, about 700 [° C.]), the first, second, and fourth on-off valves 36, 42, and 70 are then opened and the first The fuel gas pump 34 and the water pump 40 are driven. Thus, the fuel gas and the reforming water are supplied to the reforming pipe 24c of the reformer 24, and the reforming operation is started. Specifically, in the reforming catalyst 24b of the reforming tube 24c, the reforming water is heated and evaporated by the combustion exhaust gas of the combustion burner 24e to become steam. The steam is mixed with the fuel gas and then supplied to the reforming catalyst 24b heated to a reformable temperature, where a steam reforming reaction takes place, that is, anode gas is generated from the mixed fuel gas and steam. Is done.

  The anode gas generated by the reforming catalyst 24b of the reforming tube 24c is supplied to the anode of the fuel cell 12 via the anode gas tube 24d, the first anode gas supply path 62a, the three-way valve 66, and the anode gas heat exchanger 84. Supplied to the pole.

  Next, the cathode gas pump 74 is operated. Thus, the cathode gas is allowed to flow into the humidifier 76 via the cathode gas supply path 72 after dust is removed by an air cleaner (not shown). The cathode gas is supplied to the cathode electrode of the fuel cell 12 after being humidified to a desired humidity by receiving the moisture contained in the cathode off gas by the humidifier 76.

  In the fuel cell 12, the anode gas supplied to the anode electrode is electrochemically reacted with the cathode gas supplied to the cathode electrode to perform a power generation operation. The electric power (direct current) generated in the fuel cell 12 by the electrochemical reaction is taken out from the output terminal 96, a part of which is used as a power source for auxiliary equipment such as the ECU 90 and the first fuel gas pump 34, and the remaining part. Is supplied to the electric load 92 via the inverter 94.

  Cathode off-gas generated in the fuel cell 12 is supplied to the humidifier 76 via the cathode off-gas discharge path 78, humidifies the cathode gas flowing through the cathode gas supply path 72, and then flows into the atmosphere via the cathode off-gas heat exchanger 82. It is exhausted (exhausted). Thus, since the cathode off gas contains a large amount of moisture (generated water) generated by power generation, the cathode off gas is exhausted after passing through the humidifier 76 to humidify the cathode gas.

  The anode off-gas generated in the fuel cell 12, more precisely the anode off-gas discharged without being used in the power generation operation of the fuel cell 12, is the anode off-gas discharge path 64, the fourth on-off valve 70, the anode off-gas heat exchanger. Through 80, the fuel is supplied to the combustion burner 24e of the reformer 24 as fuel for combustion.

  When the power generation operation is started in the fuel cell 12 and the anode off gas is supplied to the combustion burner 24e, the third on-off valve 54 is closed and the second fuel gas pump 52 is stopped. As described above, when the fuel cell 12 is in a power generation operation, the anode off-gas is supplied to the combustion burner 24e as a fuel for combustion. Therefore, the fuel gas is supplied to the combustion burner 24e through the fourth on-off valve 92. It is shut off (stopped) by closing the valve.

  When the power generation operation is started in the fuel cell 12, the temperature of the fuel cell 12 gradually rises, so that it is cooled by the exhaust heat recovery system 22, in other words, the exhaust heat generated in the fuel cell 12 is converted into the exhaust heat recovery system. 22 is collected. Specifically, the primary cooling water pump 106 and the cooling water pump 122 are operated. The primary cooling water discharged from the primary cooling water pump 106 passes through the inside of the fuel cell 12 that has become high temperature and cools the fuel cell 12. The primary cooling water that has been heated by cooling the fuel cell 12 is supplied to the fuel cell heat exchanger 100 where heat is exchanged with the cooling water (heat exchange). The heat of the next cooling water is transmitted to the cooling water, and the cooling water is heated to become hot water. The primary cooling water that has passed through the fuel cell heat exchanger 100 is sucked into the primary cooling water pump 106 and supplied again to the fuel cell 12.

  The cooling water exchanged in the fuel cell heat exchanger 100 is supplied to the anode off-gas heat exchanger 80 and the like by the cooling water pump 122 as described above. More specifically, the cooling water heated and raised in the fuel cell heat exchanger 100 is temporarily stored in the hot water storage tank 108, and then the anode off-gas heat exchanger 80 via the first cooling water supply path 110. To be supplied. The cooling water is heat-exchanged with the anode off-gas in the anode off-gas heat exchanger 80, specifically, the heat of the anode off-gas is transmitted and the temperature is raised. The anode off gas contains a large amount of moisture (produced water) generated by power generation, but the anode off gas heat exchanger 80 exchanges heat with cooling water and introduces it into the gas-liquid separator, so that the moisture is condensed. Removed. Therefore, misfiring can be prevented in the combustion burner 24e to which the anode off gas is supplied.

  Thereafter, the cooling water is supplied to the cathode offgas heat exchanger 82 via the connection channel 112, and heat is exchanged with the cathode offgas, more specifically, the heat of the cathode offgas is transmitted to raise the temperature. On the other hand, the moisture of the cathode offgas is already removed in the humidifier 76, but the cathode offgas heat exchanger 82 also exchanges heat with cooling water and introduces it into the gas-liquid separator, thereby further removing moisture.

  In this way, the cooling water is heated in the anode offgas heat exchanger 80 and the cathode offgas heat exchanger 82 by heat exchange with the anode offgas and cathode offgas discharged from the fuel cell 12, in other words, the fuel The temperature is raised to substantially the same as the temperature of the battery 12 or slightly lower than the temperature of the fuel cell 12.

  Next, the cooling water is supplied to the anode gas heat exchanger 84 via the second cooling water supply path 114. The cooling water is heat-exchanged with the anode gas in the anode gas heat exchanger 84. To be exact, the heat of the anode gas is transmitted and the temperature is raised. Since this anode gas is produced by a steam reforming reaction, it contains a large amount of moisture. However, the anode gas heat exchanger 84 exchanges heat with cooling water and introduces it into the gas-liquid separator, so that the moisture is condensed. Removed. Therefore, it is possible to prevent excessive supply of moisture to the fuel cell 12.

  In addition, the amount of water necessary for the fuel cell 12 increases as the temperature of the fuel cell increases, but in the anode gas heat exchanger 84, the amount of water to be removed changes as the temperature increases. That is, the temperature of the fuel cell 12 gradually increases from the start of power generation to the rated operation state, and accordingly, the temperature of the cooling water supplied to the anode gas heat exchanger 84 also increases. As a result, the temperature of the anode gas heat exchanger 84 also rises, and the dew point of the anode gas in the anode gas heat exchanger 84 also rises, thereby reducing the amount of water that can be removed. In other words, the fuel cell 12 The amount of water in the anode gas supplied to is increased.

  Thereafter, the cooling water is supplied to the combustion exhaust gas heat exchanger 86 through the third cooling water supply path 116 to exchange heat with the combustion exhaust gas, specifically, the heat of the combustion exhaust gas is transmitted and the temperature is raised. Next, the cooling water is supplied to the fuel cell heat exchanger 100 via the fourth cooling water supply passage 120, and is heated up by exchanging heat with the primary cooling water as described above. Thus, the cooling water is supplied in the order of the anode offgas heat exchanger 80, the cathode offgas heat exchanger 82, the anode gas heat exchanger 84, the combustion exhaust gas heat exchanger 86, and the fuel cell heat exchanger 100, and gradually rises. Since it is heated, exhaust heat from the fuel cell 12 and the combustion burner 24e can be efficiently recovered.

  As described above, in the embodiment of the present invention, the fuel cell 12, the anode gas supply path (the first anode gas supply path 62a) connected to the fuel cell and supplying the anode gas, and the anode gas A condenser (anode gas heat exchanger 84) disposed in a supply path for condensing and removing moisture contained in the anode gas; and cooling water (secondary cooling water) is supplied to the fuel cell to supply the fuel cell. Exhaust heat recovery means (fuel cell heat exchanger 100) that recovers the exhaust heat by exchanging heat with the exhaust heat generated in the above, an anode offgas discharge path 64 that discharges the anode offgas generated in the fuel cell, and the fuel In the fuel cell cogeneration apparatus 10 including the cathode offgas discharge path 78 for discharging the cathode offgas generated in the battery, the anode offgas discharge path A heat exchanger (anode offgas heat exchanger 80, cathode offgas heat exchanger 82) disposed in at least one of the cathode offgas discharge paths, and the exhaust heat recovery means and the heat exchanger are connected to A first cooling water supply channel 110 (connection channel 112) for supplying the heat exchanged cooling water from the exhaust heat recovery means to the heat exchanger, the heat exchanger and the condenser are connected, and the first And a second cooling water supply path 114 for supplying the cooling water supplied to the heat exchanger to the condenser via one cooling water supply path.

  In this way, the condenser (anode gas heat exchanger 84) is configured to supply the cooling water heat-exchanged with the anode off-gas and the cathode off-gas in the heat exchanger, so that the condenser is the temperature of the fuel cell 12. The moisture contained in the anode gas is condensed and removed at a temperature corresponding to the change, so that the moisture content of the anode gas is optimized according to the operating state of the fuel cell 12 (specifically, the temperature of the fuel cell). It is possible to prevent a decrease in power generation efficiency.

  Specifically, the amount of water required in the fuel cell 12 changes according to the operating state, and more specifically increases in proportion to the temperature of the fuel cell 12 that gradually increases from the start of power generation to the rated operating state. However, since the cooling water exchanged with the anode off-gas and cathode off-gas discharged from the fuel cell 12 is supplied to the condenser as described above, the temperature of the condenser increases as the temperature of the fuel cell 12 increases. As a result, the dew point of the anode gas in the condenser rises, so that the moisture content of the anode gas to be removed can be gradually reduced. The amount of water to be generated can be gradually increased as compared with the start of power generation. As a result, the amount of water contained in the anode gas can be optimized according to the operating state of the fuel cell 12 (specifically, the anode gas containing a large amount of water is supplied to the fuel cell 12 and the inside of the fuel cell 12). It is possible to prevent the moisture from condensing and blocking the gas flow path, and further preventing the moisture in the anode gas from being excessively removed and the amount of water supplied to the fuel cell 12 from being insufficient). The reduction can be prevented, in other words, the fuel cell 12 can always perform efficient power generation. Furthermore, since the cooling water of the fuel cell heat exchanger 100 is heat-exchanged with the anode off-gas or the cathode off-gas and its temperature rises, the exhaust heat of the fuel cell 12 can be efficiently recovered.

  Further, the combustion burner 24e is connected to the anode offgas discharge path and burns the discharged anode offgas to heat the reforming catalyst 24b, and the combustion exhaust gas generated by the combustion is connected to the combustion burner and discharged. Combustion exhaust gas discharge path 60, a second heat exchanger (combustion exhaust gas heat exchanger 86) disposed in the combustion exhaust gas discharge path, the condenser and the second heat exchanger are connected to connect the second heat exchanger. A third cooling water supply path 116 for supplying the cooling water supplied to the condenser via the cooling water supply path to the second heat exchanger, the second heat exchanger and the exhaust heat. A fourth cooling water supply path 120 for connecting the recovery means and supplying the cooling water supplied to the second heat exchanger via the third cooling water supply path to the exhaust heat recovery means; It was configured to provide. As a result, the temperature of the cooling water is exchanged with the combustion exhaust gas and its temperature rises, so that not only the exhaust heat of the fuel cell 12 but also the exhaust heat of the combustion burner 24e can be recovered, improving the operating efficiency of the entire apparatus. Can be made.

  In the above embodiment, the heat exchanger (the anode offgas heat exchanger 80 and the cathode offgas heat exchanger 82) is arranged in both the anode offgas discharge path 64 and the cathode offgas discharge path 78. The point is that the cooling water may be configured to exchange heat with the gas discharged from the fuel cell (anode off-gas and cathode off-gas). The heat exchanger is disposed in at least one of the above.

  Further, although the temperature at which the reforming catalyst 24b can be reformed is specifically shown, those numerical values are illustrative and are not limited.

  Moreover, although it comprised so that city gas could be used as fuel gas, it is not restricted to it, LP gas etc. may be sufficient.

It is the schematic which shows the structure of the fuel cell cogeneration apparatus which concerns on the Example of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 Fuel cell cogeneration apparatus, 12 Fuel cell, 24b Reforming catalyst, 24e Combustion burner, 60 Combustion exhaust gas discharge path, 62a First anode gas supply path (anode gas supply path), 64 Anode off gas discharge path, 78 Cathode off gas Exhaust path, 80 Anode off-gas heat exchanger (heat exchanger), 82 Cathode off-gas heat exchanger (heat exchanger), 84 Anode gas heat exchanger (condenser), 86 Combustion exhaust gas heat exchanger (second heat exchange) ), 100 fuel cell heat exchanger (exhaust heat recovery means), 110 first cooling water supply path, 112 connection flow path (first cooling water supply path), 114 second cooling water supply path, 116 second 3 cooling water supply path, 120 4th cooling water supply path

Claims (2)

  A fuel cell; an anode gas supply path connected to the fuel cell for supplying anode gas; a condenser disposed in the anode gas supply path for condensing and removing moisture contained in the anode gas; and the fuel Exhaust heat recovery means for recovering the exhaust heat by supplying cooling water to the battery and exchanging heat with the exhaust heat generated in the fuel cell; an anode off-gas exhaust path for discharging the anode off-gas generated in the fuel cell; In a fuel cell cogeneration apparatus comprising a cathode offgas discharge path for discharging a cathode offgas generated in the fuel cell, heat exchange disposed in at least one of the anode offgas discharge path and the cathode offgas discharge path And the exhaust heat recovery means and the heat exchanger connected to the heat exchanged cooling water from the exhaust heat recovery means The cooling water supplied to the heat exchanger via the first cooling water supply path by connecting the heat exchanger and the condenser to the first cooling water supply path to be supplied to the heat exchanger And a second cooling water supply passage for supplying the fuel to the condenser.   A combustion burner that is connected to the anode offgas discharge path and burns the discharged anode offgas to heat the reforming catalyst, and a combustion exhaust gas discharge path that is connected to the combustion burner and discharges combustion exhaust gas generated by the combustion. And a second heat exchanger disposed in the combustion exhaust gas discharge path, and the condenser and the second heat exchanger are connected to be supplied to the condenser through the second cooling water supply path. A third cooling water supply path for supplying the cooled cooling water to the second heat exchanger, and the third cooling water supply path by connecting the second heat exchanger and the exhaust heat recovery means. 2. A fuel cell cogeneration system according to claim 1, further comprising: a fourth cooling water supply path that supplies the cooling water supplied to the second heat exchanger via the first heat recovery means. apparatus.

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