JP2008300251A - Fuel cell cogeneration device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel cell cogeneration device in which a reformer is made to have an optimum state, reduction or the like of reforming efficiency is prevented, and driving efficiency as the whole device is improved even in the case a power generating state of a fuel cell changes. <P>SOLUTION: In an anode off gas supplying passage 40 to supply the anode off gas discharged from the fuel cell 12 by connecting the fuel cell 12 to the reformer 34 to the reformer 34 as a fuel for heating a reforming catalyst, a flow rate of the anode off gas supplied to the reformer 34 is adjusted by a flow rate adjusting valve 82, and the reforming catalyst is retained at a prescribed temperature. Moreover, out of the anode off gas connected to a branch route 84 branched from the anode off gas supplying passage 40 and discharged from the fuel cell 12, this is equipped with a burner 90 in which the anode off gas exceeding in an amount necessary for retaining the reforming catalyst at the prescribed temperature is combusted, and a heat exchanger 92 is equipped which is connected to the burner 90 and in which heat generated by combustion in the burner 90 is recollected. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a fuel cell cogeneration apparatus, and more specifically, to a fuel cell cogeneration apparatus configured to supply anode offgas discharged from a fuel cell to a reformer as fuel for heating a reforming catalyst. .

Conventionally, a fuel cell cogeneration apparatus provided with a reformer that reacts fuel and water vapor with a reforming catalyst to reform anode gas, and a fuel cell that generates electricity by reacting the reformed anode gas with reaction air. Various proposals have been made. Since the reaction (steam reforming reaction) with the above reforming catalyst is an endothermic reaction, the reforming catalyst needs to be continuously heated. Therefore, for example, the technique described in Patent Document 1 is configured to heat the reforming catalyst by supplying the anode off-gas discharged from the fuel cell to the combustion burner of the reformer and burning it. ing.
Japanese Patent Laid-Open No. 2001-189162 (paragraphs 0019, 0023, FIGS. 1 and 2, etc.)

  However, since the flow rate of the anode off gas increases or decreases depending on the power generation state of the fuel cell, when the reforming catalyst is heated by burning the anode off gas as in the technique described in Patent Document 1, the reforming efficiency is improved. There is a risk of lowering. In other words, when the amount of power generated by the fuel cell increases and a large amount of anode gas is used, the amount of anode off-gas discharged from the fuel cell and supplied to the combustion burner decreases. The required amount of heat is insufficient, the reforming reaction becomes difficult to proceed, and the reforming efficiency decreases. On the other hand, when the amount of power generated by the fuel cell decreases, the amount of anode off-gas increases, so the amount of heat in the reformer also increases excessively, thus causing problems such as an increase in carbon monoxide concentration in the anode gas and a decrease in reforming efficiency Occurs.

  Therefore, the object of the present invention is to solve the above-mentioned problems, and even when the power generation state of the fuel cell changes, the reformer is brought into an optimum operating state, preventing a reduction in reforming efficiency, etc. An object of the present invention is to provide a fuel cell cogeneration apparatus that improves the overall operation efficiency.

  In order to solve the above-mentioned object, according to claim 1, a reformer for reacting a fuel with a reforming catalyst to reform the anode gas, and reacting the reformed anode gas with reaction air. A fuel cell for generating power, and an anode offgas supply for connecting the fuel cell and the reformer and supplying an anode offgas discharged from the fuel cell to the reformer as a fuel for heating the reforming catalyst A temperature at which the reforming catalyst is maintained at a predetermined temperature by adjusting a flow rate of the anode off gas supplied to the reformer and inserted in the anode off gas supply path. Holding means and a branch path branched from the anode off gas supply path, the reforming catalyst is held at the predetermined temperature in the anode off gas discharged from the fuel cell. A combustion means for combusting the anode off-gas than is required for that is connected to the combustion unit, and configured to include a heat recovery means for recovering the heat generated by combustion in the combustion unit.

  According to claim 2, the heat recovery means includes a heat exchanger, and the heat exchanger causes a flow path of primary cooling water for cooling the fuel cell by heat exchange, and the heat exchange. It was configured to be connected to at least one of the channels through which the secondary cooling water for cooling the heated primary cooling water by heat exchange.

  In the fuel cell cogeneration apparatus according to claim 1, the anode off-gas discharged from the fuel cell is supplied to the reformer as a fuel for heating the reforming catalyst by connecting the fuel cell and the reformer. In the anode off gas supply path, the flow rate of the anode off gas supplied to the reformer is adjusted to maintain the reforming catalyst at a predetermined temperature. Even if the increase / decrease is increased, it becomes possible to bring the reforming catalyst to a predetermined temperature, specifically, a temperature suitable for the reforming reaction. A decrease in efficiency can be prevented.

  Further, the anode offgas connected to the branch path branched from the anode offgas supply path and exceeding the amount necessary for maintaining the reforming catalyst at a predetermined temperature out of the anode offgas discharged from the fuel cell (i.e., reforming). Combustion means for burning anode off gas unnecessary for maintaining the catalyst at a predetermined temperature, in other words, surplus anode off gas), and heat recovery for recovering heat generated by combustion in the combustion means. The surplus anode off gas unnecessary for heating the reforming catalyst can be burned and recovered as heat, and as a result, the operation efficiency of the entire fuel cell cogeneration system can be improved. Can do.

  In the fuel cell cogeneration apparatus according to claim 2, the heat recovery means includes a heat exchanger, and the heat exchanger circulates a primary cooling water for cooling the fuel cell by heat exchange; Since the primary cooling water whose temperature has been raised by heat exchange is configured to be connected to at least one of the flow paths through which the secondary cooling water that is cooled by heat exchange is circulated, The temperature of the primary cooling water raised by cooling by heat exchange is further raised by the heat recovered by the heat recovery means, or raised by cooling the primary cooling water by heat exchange. It is also possible to further raise the temperature of the secondary cooling water with the heat recovered by the heat recovery means, so that the heat obtained by burning the surplus anode off gas can be efficiently recovered (utilized).

  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 a first 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 or a factory. The fuel cell cogeneration apparatus 10 includes a fuel cell (stack) 12 that generates electricity by reacting an anode gas with a cathode gas (reaction air), and a fuel cell 12. A cathode gas supply system 14 that supplies the cathode gas, an anode gas supply system 16 that supplies the anode gas to the fuel cell 12, a power control system 20 that controls the power generated in the fuel cell 12, and an exhaust generated in the fuel cell 12 An exhaust heat recovery system 22 that recovers heat 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 cathode gas supply system 14 includes a cathode gas supply path 24 that is connected to a cathode gas supply port (not shown) of the fuel cell 12 and supplies the cathode gas. The cathode gas supply path 24 is humidified by a cathode gas pump 26 that sucks air and pumps it as a cathode gas to the fuel cell 12, and the cathode gas is humidified by a cathode off gas discharged from the fuel cell 12 on the downstream side of the cathode gas pump 26. A humidifier 30 is installed. In this specification, “upstream” and “downstream” mean upstream and downstream in the flow direction of gas or liquid (fluid) flowing therethrough.

  Further, one end of the cathode gas supply system 14 is connected to a cathode offgas discharge port (not shown) of the fuel cell 12, while the other end is opened to the atmosphere, so that the cathode offgas generated by the fuel cell 12 is made outside. A cathode off-gas discharge path 32 for discharging is provided. The humidifier 30 described above is disposed in the middle of the cathode offgas discharge path 32.

  The anode gas supply system 16 reforms a reforming fuel (fuel, for example, city gas mainly composed of methane) with a reforming catalyst (not shown) to reform the anode gas containing hydrogen. A reformer 34, a reformer 34, and the fuel cell 12 (specifically, an anode gas supply port (not shown) of the fuel cell 12) is connected to supply the reformed anode gas to the fuel cell 12. 1 anode gas supply path 36a, a fuel cell 12 (specifically, an anode off-gas exhaust port of the fuel cell 12 (not shown)) and a reformer 34 (more precisely, a combustion burner of the reformer 34 described later). An anode off-gas supply path 40 is provided for supplying the anode off-gas connected and discharged from the fuel cell 12 to the reformer 34 as fuel for heating the reforming catalyst.

  The reformer 34 includes a reforming fuel supply path 42 for supplying reforming fuel from a reforming fuel supply source (not shown), and water for reforming (not shown). A reforming water supply path 44 that is supplied as “reforming water” is connected. A desulfurizer 46 that removes an odorant of reforming fuel, such as an organic sulfur compound, is disposed in the reforming fuel supply path 42, while reforming water is modified in the reforming water supply path 44. A water supply pump 50 that pumps to the mass device 34 is disposed.

  A reformer outlet temperature sensor 52 is attached to a portion (reformer outlet) near the reforming catalyst of the reformer 34 where the reformed anode gas is discharged. A signal corresponding to the temperature TA at the reformer outlet is output.

  The reformer 34 also includes a combustion burner 34a that heats the reforming catalyst and the like by burning a fuel for heating (for example, city gas). A combustion air supply path 54 for supplying combustion air (hereinafter referred to as “combustion air”) or the like is connected to the combustion burner 34a. The combustion air supply path 54 is provided with a combustion air pump 56 that pumps air as combustion air, and a heating fuel supply path 60 that supplies heating fuel to the combustion air is provided downstream of the combustion air pump 56. Connected. The reformer 34 is further connected with a combustion exhaust gas discharge path 62 for discharging (exhausting) the combustion exhaust gas generated by the combustion in the combustion burner 34a to the outside.

  A first on-off valve (shutoff valve) 64 for opening and closing the first anode gas supply path 36a is interposed in the first anode gas supply path 36a, and a first anode gas supply path is provided downstream thereof. A second anode gas supply path 36b for connecting 36a and the anode off gas supply path 40 is connected. A second on-off valve (solenoid valve) 66 for opening and closing the second anode gas supply path 36b is inserted in the second anode gas supply path 36b. The second on-off valve 66 is closed when not energized. When the amount of anode gas required in the fuel cell 12 decreases, the second on-off valve 66 is energized to supply the anode gas through the second anode gas supply path 36b. It is set to supply to the path 40.

  In the first anode gas supply path 36a, a first heat exchanger 70 and a first gas-liquid separator 72 are disposed downstream of the connection position of the second anode gas supply path 36b. The first heat exchanger 70 is connected to a cooling water supply path 70a that supplies cooling water for cooling the anode gas. The first gas-liquid separator 72 is configured to separate the anode gas cooled in the first heat exchanger 70 into a gas component and a liquid component (condensed water). The first gas-liquid separator 72 includes a discharge path 72a that discharges condensed water obtained by separation, and a third path that opens and closes the discharge path 72a according to the amount of condensed water. An on-off valve (electromagnetic valve) 72b is installed.

  The anode off gas supply path 40 is provided with a fourth on-off valve 74 that opens and closes the anode off gas supply path 40. Both the fourth on-off valve 74 and the first on-off valve 64 described above are electromagnetic valves, and the operation of the fuel cell 12 is terminated in order to prevent the anode gas or the like from flowing out when the fuel cell 12 is not in operation. It is assumed that sometimes everything is closed.

  A second heat exchanger 76 and a second gas-liquid separator 80 are arranged on the downstream side of the fourth on-off valve 74 in the anode off-gas supply path 40 via the connection position of the second anode gas supply path 36b. Is done. The second heat exchanger 76 is connected to a cooling water supply path 76a that supplies cooling water for cooling the anode off gas. The second gas-liquid separator 80 separates the anode off gas cooled in the second heat exchanger 76 into a gas component and a liquid component, and discharges the condensed water obtained through the discharge path 80a. A fifth on-off valve (electromagnetic valve) 80b that opens and closes the discharge path 80a according to the amount of condensed water is installed in the discharge path 80a. The discharge passages 72a and 80a of the first and second gas-liquid separators 72 and 80 are both connected to the humidifier 30 and the condensed water is used as the humidifying water for the cathode gas.

  A flow rate adjusting valve (temperature holding means) 82 for adjusting the flow rate of the anode off gas is inserted downstream of the second gas-liquid separator 80 in the anode off gas supply path 40. Therefore, the anode off gas from which moisture has been removed in the second gas-liquid separator 80 is supplied to the combustion burner 34a as a fuel for heating the reforming catalyst via the flow rate adjustment valve 82.

  A branch path 84 is provided in the middle of the anode off-gas supply path 40 (specifically, between the second gas-liquid separator 80 and the flow rate adjustment valve 82). The branch path 84 is an excess anode off-gas described in detail later. Will be distributed. A relief valve (relief valve) that opens when the pressure by the surplus anode off gas (in other words, the flow rate of surplus anode off gas) is equal to or higher than a predetermined value and closes when the pressure is less than the predetermined value. 86 is inserted. The predetermined value is set to a value that opens when the flow regulating valve 82 is driven in the closing direction and the anode off-gas in the anode off-gas supply path 40 is supplied as surplus anode off-gas.

  A combustor (combustion means) 90 for combusting surplus anode off gas is connected to the downstream side of the relief valve 86 in the branch path 84, and is generated by combustion in the combustor 90 on the downstream side of the combustor 90. A third heat exchanger (heat recovery means) 92 for recovering the heat of the combustion exhaust gas is connected.

  The power control system 20 converts an electronic control unit (Electronic Control Unit; hereinafter referred to as “ECU”) 94 composed of a micro computer and the like and electric power (DC current) generated by the fuel cell 12 into AC current having a predetermined frequency. And an inverter 100 that outputs to an electric load (AC power supply device) 96 and the like, and is connected to an output terminal 102 that outputs electric power generated in the fuel cell 12. The ECU 94 receives signals from the reformer outlet temperature sensor 52 and the like via a signal line (not shown) and the like, and operates auxiliary equipment such as the flow rate adjustment valve 82 based on the input sensor signal. This will be described later.

  The exhaust heat recovery system 22 includes a primary cooling water flow path (flow path) 104 through which primary cooling water for cooling the fuel cell 12 by heat exchange and a fourth heat exchanger 106 in the primary cooling water flow path 104. And a secondary cooling water flow path for circulating secondary cooling water for cooling the primary cooling water heated by heat exchange with the fuel cell 12 by heat exchange in the fourth heat exchanger 106. (Flow path) 110 is provided.

  One end of the primary cooling water flow path 104 is connected to a cooling water inlet (not shown) of the fuel cell 12, and the other end is connected to a cooling water discharge port (not shown) of the fuel cell 12. In the primary cooling water flow path 104, the third heat exchanger 92, the fourth heat exchanger 106, and the primary cooling water that pressure-feeds the primary cooling water to the fuel cell 12 in order from the cooling water discharge port side of the fuel cell 12. A cooling water pump 112 is arranged. In this way, the third heat exchanger 92 disposed in the branch path 84 is connected to the primary cooling water flow path 104. Thus, the primary cooling water is pumped to the primary cooling water pump 112, whereby the fuel cell 12, the third heat exchanger 92, the fourth heat exchanger 106, and the primary cooling water pump 112 are sequentially used. Circulated.

  In addition to the fourth heat exchanger 106, the secondary cooling water channel 110 includes secondary cooling water (more precisely, the secondary cooling water that has been heated by cooling the primary cooling water through heat exchange). A hot water storage tank 114 in which hot water is stored and a secondary cooling water pump 116 that sucks the secondary cooling water in the hot water storage tank 114 and circulates in the secondary cooling water flow path 110 are arranged. Therefore, the secondary cooling water is circulated in the order of the fourth heat exchanger 106, the hot water tank 114, and the secondary cooling water pump 116 by being pumped to the secondary cooling water pump 116.

  In the hot water storage tank 114, when the amount of hot water stored in the hot water storage tank 114 decreases, a water supply channel 120 that supplies (supplements) water from a water source (not shown), and secondary cooling water (hot water) stored in the hot water storage tank 114. ) Is supplied to a hot water use device (for example, a hot water shower) 122, and the like.

  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 12 is given (more specifically, when a start switch (not shown) is turned on by an operator), an anode gas is generated in the reformer 34. Specifically, the combustion air pump 56 is operated, and the combustion air is circulated toward the combustion burner 34 a via the combustion air supply path 54. The combustion air is supplied with heating fuel via the heating fuel supply passage 60 to generate a premixed gas, which is supplied to the combustion burner 34a. The combustion burner 34a ignites (ignites) the supplied premixed gas by an ignition electrode (not shown) and burns it, and a combustion exhaust gas having a relatively high temperature is generated by the combustion. The combustion exhaust gas is heated to raise the temperature of the reforming catalyst and the like, and then exhausted to the atmosphere through the combustion exhaust gas passage 62.

  When the reforming catalyst is heated to a temperature capable of reforming (for example, about 700 ° C.), the first and fourth on-off valves 64 and 74 and the flow rate adjusting valve 82 are opened and the water supply pump 50 is driven. . As a result, the reforming water is supplied to the reforming catalyst of the reformer 34 via the reforming water supply path 44. Further, the reforming fuel is supplied to the reforming catalyst through the reforming fuel supply path 42 and the desulfurizer 46, and the reforming operation is started. Specifically, the reforming water is heated by the combustion exhaust gas from the combustion burner 34a and evaporated to become steam. After the steam is mixed with the reforming fuel, it is supplied to the reforming catalyst heated to a reformable temperature, where a steam reforming reaction occurs, that is, the mixed reforming fuel and steam are converted into the anode gas. To improve.

  After the removal of carbon monoxide and the like in the reformer 34, the anode gas is supplied through the first anode gas supply path 36 a and the first on-off valve 64 to the first heat exchanger 70 and the first gas / liquid. The water is supplied to the separator 72 and the water is appropriately removed, and then supplied to the anode electrode of the fuel cell 12.

  Next, the cathode gas pump 26 is operated. Thereby, the cathode gas is allowed to flow into the humidifier 30 through the cathode gas supply path 24 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 being supplied with moisture and the like contained in the cathode off gas by the humidifier 30.

  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 generated in the fuel cell 12 by the electrochemical reaction is taken out from the output terminal 102, a part of which is used as a power source for auxiliary equipment such as the ECU 94 and the water pump 50, and the rest is electrically connected via the inverter 100. The load 96 is supplied.

  Cathode off-gas generated and discharged by the fuel cell 12 is supplied to the humidifier 30 via the cathode off-gas discharge path 32, humidifies the cathode gas flowing through the cathode gas supply path 24, and is then exhausted to the atmosphere.

  The anode off-gas generated and discharged by the fuel cell 12, more precisely the anode off-gas discharged without being used in the power generation operation of the fuel cell 12, passes through the anode off-gas supply path 40 and the fourth on-off valve 74. After being supplied to the second heat exchanger 76 and the second gas-liquid separator 80 and appropriately removing water, it is supplied (refluxed) to the combustion burner 34a of the reformer 34 via the flow rate adjustment valve 82. The When the power generation operation is started in the fuel cell 12 and the anode off gas is supplied to the combustion burner 34a, an on-off valve (not shown) installed in the heating fuel supply passage 60 is closed, and the heating fuel supply passage 60 is closed. The supply of the fuel for heating to the combustion burner 34a via is interrupted (stopped).

  At this time, the relief valve 86 is closed because the flow rate adjusting valve 82 is not driven in the closing direction, and the pressure of the supplied anode off-gas is less than a predetermined value. On the other hand, when the flow regulating valve 82 is driven in the closing direction as will be described later, the pressure of the anode off-gas (excess anode off-gas) supplied to the relief valve 86 exceeds a predetermined value, so that the valve is opened. It is supplied to the combustor 90 and burned there. The combustion exhaust gas generated by the combustion in the combustor 90 passes through the third heat exchanger 92 and is then exhausted to the outside.

  Further, since the temperature of the fuel cell 12 gradually increases due to the power generation operation, the fuel cell 12 is cooled by the exhaust heat recovery system 22 (in other words, the exhaust heat generated in the fuel cell 12 is recovered by the exhaust heat recovery system 22). . Specifically, the primary cooling water pump 112 and the secondary cooling water pump 116 are operated. Thereby, the primary cooling water discharged from the primary cooling water pump 112 passes through the inside of the fuel cell 12 which has become high temperature, and is cooled by heat exchange.

  The primary cooling water whose temperature has been raised by cooling the fuel cell 12 is supplied to the third heat exchanger 92 where heat is exchanged with the combustion exhaust gas (heat exchange) to further raise the temperature. . That is, when the surplus anode off gas is burned in the combustor 90, the combustion exhaust gas flows through the third heat exchanger 92, so that the heat of the combustion exhaust gas is transmitted to the primary cooling water, and the primary cooling water further The temperature is raised.

  Next, the primary cooling water is supplied to the fourth heat exchanger 106, where the heat of the primary cooling water is transmitted to the secondary cooling water, so that the secondary cooling water is heated to become hot water. The primary cooling water whose temperature has decreased due to the heat exchange in the fourth heat exchanger 106 is drawn into the primary cooling water pump 112 and supplied again to the fuel cell 12. The secondary cooling water exchanged in the fourth heat exchanger 106 is temporarily stored in the hot water storage tank 114 and then supplied again to the fourth heat exchanger 106 by the secondary cooling water pump 116.

  Next, of the operation of the fuel cell cogeneration apparatus 10 according to the first embodiment, the control of the operation of the flow rate adjustment valve 82 by the ECU 94 will be described with reference to FIG.

  FIG. 2 is a flowchart showing the operation of the ECU 94 of the cogeneration apparatus 10.

  2 will be described below. First, the outlet temperature TA of the reformer 34 detected through the reformer outlet temperature sensor 52 in S10 is read. Next, in S12, it is determined whether or not the detected outlet temperature TA is equal to or higher than a first predetermined outlet temperature TAref1. The first predetermined outlet temperature TAref1 means an upper limit value of the outlet temperature when the reforming catalyst is in a state where the reforming reaction can be sufficiently performed (optimum operation state), and is set to 660 ° C., for example. .

  When the result in S12 is negative, the processing of S14 and S16 described later is skipped, while when the result is affirmative, that is, the outlet temperature TA of the reformer 34 is excessively increased, and the reforming catalyst has a predetermined temperature ( When it is determined that the temperature exceeds the appropriate temperature range in the optimum operating state (for example, 700 to 750 ° C.), the process proceeds to S14.

  In S14, the flow rate adjustment valve 82 is driven so as to keep the reforming catalyst at a predetermined temperature. Specifically, the flow rate adjustment valve 82 is driven in the closing direction so that only the amount necessary for maintaining the reforming catalyst at a predetermined temperature passes among the anode off gas, and is supplied to the combustion burner 34a. Reduce the anode off-gas flow rate. As a result, the amount of heat in the combustion burner 34a also decreases, and the temperature of the reforming catalyst gradually decreases until reaching a predetermined temperature. In this way, the flow rate adjustment valve 82 is driven so as to adjust the flow rate of the anode off gas supplied to the reformer 34 and maintain the reforming catalyst at a predetermined temperature.

  The decrease amount of the anode off gas by the flow rate adjusting valve 82 is specifically determined by searching a preset map (not shown) based on the detected outlet temperature TA or the like. The amount of decrease is between 0.5 to 10% of the total amount of anode off gas, for example, 0.5% when the outlet temperature TA slightly exceeds the first predetermined outlet temperature TAref1, and the first predetermined outlet temperature TAref1. Is set so as to be 10%.

  When the flow regulating valve 82 is driven in the closing direction in S14, the anode off-gas exceeding the amount necessary for maintaining the reforming catalyst at a predetermined temperature, that is, the surplus anode off-gas in the anode off-gas passes through the branch path 84. To the relief valve 86. As a result, the relief valve 86 is opened when the pressure of the surplus anode off gas exceeds a predetermined value, and thus surplus anode off gas is supplied to the combustor 90.

  When the surplus anode off gas is supplied to the combustor 90, the process proceeds to S16, and the combustor 90 is driven. Specifically, the supplied surplus anode off gas is combusted in the combustor 90. The flue gas generated by the combustion in the combustor 90 is supplied to the third heat exchanger 92, where the temperature of the primary cooling water in the primary cooling water channel 104 is raised as described above. Thus, the third heat exchanger 92 recovers heat generated by the combustion in the combustor 90.

  Next, in S18, it is determined whether or not the outlet temperature TA is equal to or lower than a second predetermined outlet temperature TAref2. The second predetermined outlet temperature TAref2 is set to a lower limit value (for example, 600 ° C.) of the outlet temperature when the reforming catalyst is in a state where the reforming reaction can be sufficiently performed.

  When the result in S18 is negative, the subsequent processing is skipped and the process is terminated, while when the result is positive, that is, the outlet temperature TA of the reformer 34 is excessively lowered, and the reforming catalyst falls below a predetermined temperature. When it is determined that the flow rate is determined, the process proceeds to S20, and the flow rate adjustment valve 82 is driven (opened) in the fully open direction. Thus, when the flow rate adjustment valve 82 is driven in the closing direction in the processing of S14 or the like, the flow rate of the anode off gas supplied to the combustion burner 34a is increased to increase the amount of heat, and the temperature of the reforming catalyst is increased. be able to.

  Next, in S22, the operation of the fuel cell 12 is controlled so that the reforming catalyst is maintained at a predetermined temperature. Specifically, the flow rate of anode off-gas discharged from the fuel cell 12 by reducing the power generation amount (load) of the fuel cell 12 (in other words, reducing the amount of anode gas used in the fuel cell 12). Thus increasing the flow rate of the anode off-gas supplied to the combustion burner 34a. As a result, the amount of heat in the combustion burner 34a also increases, so that the temperature of the reforming catalyst gradually increases until reaching a predetermined temperature. As described above, the operation of the fuel cell 12 is controlled such that when the outlet temperature TA is equal to or lower than the second predetermined outlet temperature TAref2, the power generation amount is adjusted and the reforming catalyst is held at the predetermined temperature.

  Note that the amount of power generation reduced in the fuel cell 12 is determined by searching a preset map (not shown) based on the detected outlet temperature TA and the like, similarly to the amount of decrease in the anode off gas described above. Is done. The power generation amount to be reduced is between 0.5 to 10% of the total power generation amount, for example, 0.5% when the outlet temperature TA is slightly lower than the second predetermined outlet temperature TAref2, and the second predetermined outlet temperature. When it is relatively below TAref2, it is set to 10%.

  As described above, in the fuel cell cogeneration apparatus according to the first embodiment of the present invention, the fuel cell 12 and the reformer 34 are connected, and the anode off-gas discharged from the fuel cell 12 is heated with the reforming catalyst. In the anode off-gas supply path 40 that is supplied to the reformer 34 as fuel for the purpose, the flow rate of the anode off-gas supplied to the reformer 34 is adjusted by the flow rate adjustment valve 82 to keep the reforming catalyst at a predetermined temperature. Thus, when the power generation state of the fuel cell 12 changes, the anode offgas flow rate increases or decreases, and the temperature of the reforming catalyst changes (specifically, the outlet temperature TA of the reformer 34 is the first temperature). Even when the predetermined outlet temperature TAref1 or higher), the reforming catalyst can be set to a predetermined temperature, specifically, a temperature suitable for the reforming reaction. Driving condition To be, it is possible to prevent a decrease in reforming efficiency. In addition, since the reforming catalyst is held at a predetermined temperature by adjusting the flow rate of the anode off gas, the flow rate of the anode gas supplied to the fuel cell 12 can be made constant, so that the fuel cell 12 can generate power stably. The action can be performed.

  Further, the anode off gas (connected to the branch path 84 branched from the anode off gas supply path 40) exceeds the amount necessary for maintaining the reforming catalyst at a predetermined temperature out of the anode off gas discharged from the fuel cell 12. That is, an anode off gas unnecessary for maintaining the reforming catalyst at a predetermined temperature (in other words, surplus anode off gas) is combusted, and is connected to the combustor 90 and generated by combustion in the combustor 90. Since the third heat exchanger 92 for recovering heat is provided, surplus anode off gas unnecessary for heating the reforming catalyst can be burned and recovered as heat, resulting in fuel cell cogeneration. The operation efficiency of the entire apparatus can be improved by about 3% to 10%.

  In addition, since the third heat exchanger 92 is configured to be connected to the primary cooling water flow path 104 that distributes the primary cooling water that cools the fuel cell 12 by heat exchange, the fuel cell 12 is exchanged by heat exchange. The primary cooling water that has been heated by cooling can be further heated by the heat of the combustion exhaust gas recovered by the third heat exchanger 92, and thus the heat obtained by burning the surplus anode off-gas. Can be efficiently recovered (utilized).

  The fuel cell 12 generates power when the load due to the electric load 96 fluctuates, when the fuel cell 12 is not in a steady state such as when the fuel cell 12 is started, or when the anode gas composition or the amount of anode gas fluctuates due to deterioration of the reforming catalyst. Although the operation is controlled so as to decrease the amount, even in such a case, the surplus anode off gas can be combusted in the combustor 90 and recovered as heat, so that the operating efficiency of the entire fuel cell cogeneration apparatus is reduced. Can be minimized.

  Next, a fuel cell cogeneration apparatus according to a second embodiment of the present invention will be described.

  FIG. 3 is a schematic view similar to FIG. 1 showing the configuration of the fuel cell cogeneration apparatus according to the second embodiment.

  The following description focuses on the differences from the first embodiment. In the second embodiment, the third heat exchanger 92 is connected to the secondary cooling water flow path 110 as shown in FIG. The That is, the secondary cooling water heated by cooling the primary cooling water by heat exchange in the fourth heat exchanger 106 is transferred to the third heat exchanger 92 via the secondary cooling water channel 110. Then, heat is exchanged with the combustion exhaust gas of the combustor 90 and the temperature is further raised.

  As described above, in the fuel cell cogeneration apparatus according to the second embodiment of the present invention, the secondary cooling water can be further heated with the heat recovered by the third heat exchanger 92, and therefore the surplus The heat obtained by burning the anode off gas can be efficiently recovered (utilized).

  The remaining configuration and effects are not different from those of the first embodiment.

  Next, a fuel cell cogeneration apparatus according to a third embodiment of the present invention will be described.

  The following description focuses on the differences from the first embodiment. In the third embodiment, the reformer outlet temperature sensor 52 is removed, and as shown by an imaginary line in FIG. A reformer inlet temperature sensor 130 is attached to a portion (reformer inlet) where reforming fuel and reforming water are supplied near the reforming catalyst of the mass device 34. The reformer inlet temperature sensor 130 outputs a signal corresponding to the reformer inlet temperature TB to the ECU 94.

  FIG. 4 is a flowchart similar to FIG. 2 showing the operation of the ECU 94 of the cogeneration apparatus 10 according to the third embodiment.

  First, the inlet temperature TB of the reformer 34 detected through the reformer inlet temperature sensor 130 in S10a is read. Next, in S12a, it is determined whether or not the detected inlet temperature TB is equal to or higher than a first predetermined inlet temperature TBref1. The first predetermined inlet temperature TBref1 is set to an upper limit value of the inlet temperature when the reforming catalyst can sufficiently perform the reforming reaction (optimal operation state), for example, 500 ° C.

  When the result in S12a is affirmative, that is, when it is determined that the inlet temperature TB of the reformer 34 is excessively increased and the reforming catalyst exceeds the predetermined temperature, the process proceeds to S14 and S16, and the above-described process is performed. Execute the process. Thereby, the temperature of the reforming catalyst can be lowered to a predetermined temperature, and the heat obtained by burning the surplus anode off gas in the combustor 90 can be recovered in the third heat exchanger 92. it can.

  When the process of S16 is completed, or when the result in S12a is negative, the process proceeds to S18a, and it is determined whether or not the inlet temperature TB is equal to or lower than a second predetermined inlet temperature TBref2. The second predetermined inlet temperature TBref2 is set to a lower limit value (for example, 400 ° C.) of the inlet temperature when the reforming catalyst can sufficiently perform the reforming reaction.

  When the result in S18a is negative, the subsequent processing is skipped and the process is terminated, while when the result is affirmative, that is, it is determined that the inlet temperature TB is excessively decreased and the reforming catalyst is below the predetermined temperature. If YES, the process proceeds to S20 and S22, and the same process as in the first embodiment is executed. Accordingly, the flow rate of the anode off gas supplied to the combustion burner 34a can be increased, and the amount of heat in the combustion burner 34a can be increased, so that the temperature of the reforming catalyst can be increased to a predetermined temperature.

  The remaining configuration and effects are not different from those of the previous embodiments.

  Next, a fuel cell cogeneration apparatus according to a fourth embodiment of the present invention will be described.

  Hereinafter, a description will be given focusing on the differences from the first embodiment. In the fourth embodiment, the reformer outlet temperature sensor 52 is removed, and as shown by the imaginary line in FIG. A flame temperature sensor 140 is disposed in the vicinity of the flame of the burner 34a. The flame temperature sensor 140 measures the temperature of the flame using, for example, the thermoelectromotive force of a thermocouple made of platinum and platinum rhodium, and the thermocouple is disposed in the vicinity of the flame of the combustion burner 34a. The flame temperature sensor 140 outputs a signal corresponding to the flame temperature TC of the combustion burner 34a to the ECU 94.

  FIG. 5 is a flowchart similar to FIG. 2 showing the operation of the ECU 94 of the cogeneration apparatus 10 according to the fourth embodiment.

  First, the flame temperature TC of the combustion burner 34a detected via the flame temperature sensor 140 in S10b is read. Next, in S12b, it is determined whether or not the detected flame temperature TC is equal to or higher than a first predetermined flame temperature TCref1. The first predetermined flame temperature TCref1 means an upper limit value of the flame temperature when the reforming catalyst can sufficiently perform the reforming reaction, and is set to 750 ° C., for example.

  When the result in S12b is affirmative, that is, when it is determined that the flame temperature TC is excessively increased and the reforming catalyst exceeds the predetermined temperature, the process proceeds to S14 and S16, and the above-described processing is executed. Thereby, the temperature of the reforming catalyst can be lowered to a predetermined temperature, and the heat obtained by burning the surplus anode off gas in the combustor 90 can be recovered in the third heat exchanger 92. it can.

  When the process of S16 is completed, or when negative in S12b, the process proceeds to S18b, and it is determined whether or not the flame temperature TC is equal to or lower than a second predetermined flame temperature TCref2. The second predetermined flame temperature TCref2 is set to a lower limit value (for example, 660 ° C.) of the flame temperature when the reforming catalyst is in a state in which the reforming reaction can be sufficiently performed.

  When the result in S18b is negative, the subsequent processing is skipped and the process is terminated. When the result is affirmative, that is, it is determined that the flame temperature TC is excessively lowered and the reforming catalyst is below the predetermined temperature. If YES, the process proceeds to S20 and S22, and the same process as in the first embodiment is executed. As a result, the flow rate of the anode off gas supplied to the combustion burner 34a can be increased, and the amount of heat in the combustion burner 34a can be increased, so that the temperature of the reforming catalyst can be raised to a predetermined temperature.

  The remaining configuration and effects are not different from those of the previous embodiments.

  Next, a fuel cell cogeneration apparatus according to a fifth embodiment of the invention will be described.

  The following description focuses on the differences from the first embodiment. In the fifth embodiment, the reformer outlet temperature sensor 52 is removed, and as indicated by an imaginary line in FIG. 1, the hydrogen concentration of the anode gas supplied to the fuel cell 12 is detected between the reformer 34 and the first on-off valve 64, and a signal corresponding to the concentration is sent to the ECU 94. The output first hydrogen concentration sensor 150 is connected.

  FIG. 6 is a flowchart similar to FIG. 2 showing the operation of the ECU 94 of the cogeneration apparatus 10 according to the fifth embodiment.

  First, the hydrogen concentration CA of the anode gas detected through the first hydrogen concentration sensor 150 is read in S10c, and then the process proceeds to S12c to determine whether or not the hydrogen concentration CA of the anode gas is equal to or higher than the first predetermined hydrogen concentration CAref1. . The first predetermined hydrogen concentration CAref1 is set to an upper limit value of the hydrogen concentration of the anode gas when the reforming catalyst is in a state where the reforming reaction can be sufficiently performed, for example, 75%.

  When the determination in S12c is affirmative, that is, when the hydrogen concentration CA of the anode gas is excessively increased and it is determined that the reforming catalyst exceeds the predetermined temperature, the process proceeds to S14 and S16, and the same as in the first embodiment. Execute the process. Thereby, the temperature of the reforming catalyst can be lowered to a predetermined temperature, and the heat obtained by burning the surplus anode off gas in the combustor 90 can be recovered in the third heat exchanger 92. it can.

  When the process of S16 is completed, or when the result of S12c is negative, the process proceeds to S18c to determine whether or not the hydrogen concentration CA is equal to or lower than the second predetermined hydrogen concentration CAref2. The second predetermined hydrogen concentration CAref2 is set to a lower limit value (for example, 60%) of the hydrogen concentration of the anode gas when the reforming catalyst can sufficiently perform the reforming reaction.

  When the result in S18c is negative, the subsequent processing is skipped and the process is terminated. When the result is positive, that is, the hydrogen concentration CA of the anode gas is excessively decreased, and the reforming catalyst is below the predetermined temperature. When it is determined that the process proceeds to S20 and S22, the above-described processing is executed. Accordingly, the flow rate of the anode off gas supplied to the combustion burner 34a can be increased, and the amount of heat in the combustion burner 34a can be increased, so that the temperature of the reforming catalyst can be increased to a predetermined temperature.

  The remaining configuration and effects are not different from those of the previous embodiments.

  Next, a fuel cell cogeneration apparatus according to the sixth embodiment of the invention will be described.

  Hereinafter, a description will be given focusing on differences from the first embodiment. In the sixth embodiment, the reformer outlet temperature sensor 52 is removed, and as shown by an imaginary line in FIG. According to the hydrogen concentration CB of the anode off-gas discharged from the fuel cell 12, the off-gas supply path 40 (precisely, near the anode off-gas outlet of the fuel cell 12 and upstream of the fourth on-off valve 74). A second hydrogen concentration sensor 160 that outputs the obtained signal to the ECU 94 is connected.

  FIG. 7 is a flowchart similar to FIG. 2 showing the operation of the ECU 94 of the cogeneration apparatus 10 according to the sixth embodiment.

  First, the hydrogen concentration CB of the anode gas detected through the second hydrogen concentration sensor 160 in S10d is read. Next, in S12d, it is determined whether or not the detected hydrogen concentration CB of the anode gas is equal to or higher than the first predetermined hydrogen concentration CBref1. The first predetermined hydrogen concentration CBref1 is set to an upper limit value (for example, 35%) of the hydrogen concentration of the anode off gas when the reforming catalyst can sufficiently perform the reforming reaction.

  When the determination in S12d is affirmative, that is, when the hydrogen concentration CB of the anode off gas is excessively increased and the temperature of the reformer 34 is determined to exceed the predetermined temperature, the process proceeds to S14 and S16, and the above-described processing is performed. Do. Thereby, the temperature of the reforming catalyst can be lowered to a predetermined temperature, and the heat obtained by burning the surplus anode off gas in the combustor 90 can be recovered in the third heat exchanger 92. it can.

  When the process of S16 is completed or when negative in S12d, the process proceeds to S18d, and it is determined whether or not the hydrogen concentration CB read in S10d is equal to or lower than the second predetermined hydrogen concentration CBref2. The second predetermined hydrogen concentration CBref2 is set to a lower limit value (for example, 17%) of the hydrogen concentration of the anode off-gas when the reforming catalyst can sufficiently perform the reforming reaction.

  When the result in S18d is negative, the subsequent processing is skipped, while when the result is affirmative, that is, when it is determined that the hydrogen concentration CB of the anode off-gas is lowered and the temperature of the reforming catalyst is low, the process proceeds to S20 and S22. Perform the processing described above. As a result, the flow rate of the anode off gas supplied to the combustion burner 34a can be increased, and the amount of heat in the combustion burner 34a can be increased, so that the temperature of the reforming catalyst can be raised to a predetermined temperature.

  The remaining configuration and effects are not different from those of the previous embodiments.

  As described above, in the first to sixth embodiments of the present invention, the reformer 34 for reacting fuel (reforming fuel) with the reforming catalyst to reform the anode gas, and the reforming A fuel cell 12 that generates electricity by reacting the anode gas with reaction air (cathode gas), and connecting the fuel cell and the reformer to heat the reforming catalyst with anode off-gas discharged from the fuel cell In the fuel cell cogeneration apparatus 10 provided with an anode offgas supply path 40 that supplies the reformer as fuel to perform, the anode offgas supplied to the reformer is inserted into the anode offgas supply path Temperature holding means (flow rate adjusting valve 82, ECU 94, S14) for adjusting the flow rate and holding the reforming catalyst at a predetermined temperature, and a branch path 8 branched from the anode off-gas supply path Combusting means (combustor) for combusting anode off-gas (excess anode off-gas) exceeding the amount necessary for maintaining the reforming catalyst at the predetermined temperature among anode off-gas discharged from the fuel cell 90. The ECU 94. S16) and a heat recovery means (third heat exchanger 92) connected to the combustion means and recovering heat generated by combustion in the combustion means.

  In addition, the heat recovery means includes a heat exchanger (third heat exchanger 92), and the heat exchanger causes a flow path (primary water) through which primary cooling water for cooling the fuel cell by heat exchange flows. The cooling water flow path 104) and at least one of the flow paths (secondary cooling water flow path 110) for circulating the secondary cooling water that cools the primary cooling water heated by the heat exchange by heat exchange. It was configured as follows.

  In the first to sixth embodiments described above, the first predetermined outlet temperature TAref1, the first predetermined inlet temperature TBref1, the temperature at which the reforming catalyst can be reformed are specifically shown. Is illustrative and not limiting.

  In the fourth embodiment, the flame temperature sensor 140 is configured to measure the flame temperature TC of the combustion burner 34a, but may be configured to measure the radiant heat temperature of the flame instead of the flame temperature TC. .

  Further, although the city gas is used as the reforming fuel or the heating fuel, the present invention is not limited to this, and LP gas or the like may be used.

It is the schematic which shows the structure of the fuel cell cogeneration apparatus which concerns on 1st Example of this invention. It is a flowchart which shows operation | movement of ECU of the cogeneration apparatus shown in FIG. FIG. 3 is a schematic view similar to FIG. 1 showing a configuration of a fuel cell cogeneration apparatus according to a second embodiment of the present invention. It is the same flow chart as FIG. 2 which shows operation | movement of ECU of the cogeneration apparatus which concerns on 3rd Example of this invention. It is a flowchart similar to FIG. 2 which shows operation | movement of ECU of the cogeneration apparatus which concerns on 4th Example of this invention. It is a flowchart similar to FIG. 2 which shows operation | movement of ECU of the cogeneration apparatus which concerns on 5th Example of this invention. It is a flowchart similar to FIG. 2 which shows operation | movement of ECU of the cogeneration apparatus which concerns on 6th Example of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 Fuel cell cogeneration apparatus, 12 Fuel cell, 34 Reformer, 40 Anode off-gas supply path, 82 Flow control valve (temperature holding means) 84 Branch path, 90 Combustor (combustion means), 92 3rd heat exchanger (Heat recovery means), 94 ECU, 104 Primary cooling water flow path (flow path), 110 Secondary cooling water flow path (flow path)

Claims (2)

  A reformer that reacts fuel with a reforming catalyst to reform the anode gas, a fuel cell that generates electricity by reacting the reformed anode gas with reaction air, and the fuel cell and the reformer are connected. In the fuel cell cogeneration apparatus, the anode offgas supply path for supplying the anode offgas discharged from the fuel cell to the reformer as fuel for heating the reforming catalyst. And a temperature holding means for adjusting the flow rate of the anode off gas supplied to the reformer to hold the reforming catalyst at a predetermined temperature, and a branch path branched from the anode off gas supply path Of the anode offgas discharged from the fuel cell, the anode offgas exceeding the amount necessary to maintain the reforming catalyst at the predetermined temperature is burned. A combustion unit that is connected to the combustion unit, the fuel cell cogeneration system, characterized in that it comprises a heat recovery means for recovering the heat generated by combustion in the combustion unit.   The heat recovery means includes a heat exchanger, and the heat exchanger circulates a primary cooling water that cools the fuel cell by heat exchange, and primary cooling that is heated by the heat exchange. 2. The fuel cell cogeneration apparatus according to claim 1, wherein the fuel cell cogeneration apparatus is connected to at least one of flow paths for circulating secondary cooling water for cooling water by heat exchange.

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