JP2010153147A - Exhaust-heat recovery device, and fuel cell system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To attain high efficiency of heat collection in an exhaust-heat recovery device and a fuel cell system while aiming at reduced costs and space-saving upon recovering exhaust-heat generated in a device (system) as stored hot water. <P>SOLUTION: The exhaust-heat recovery device includes a stored hot and water circulation line 32 communicated with a stored hot water container 31 and circulating the stored hot water, a first thermal medium circulation line 33 for circulating a first thermal medium which collects exhaust-heat of a reformer 20, a first heat exchanger 35 wherein the stored hot water and the first thermal medium are heat-exchanged, a second heat exchanger 36 located on the stored hot water circulation line 32 and at a downstream side of the stored hot water against the first heat exchanger 35 and arranged between the first heat exchanger 35 and the stored hot water container 31 and heat-exchanging between the stored hot water and the second thermal medium, and a flow rate adjusting means 40 for adjusting a flow rate of the first thermal medium by controlling a first thermal medium circulation means 33a so that inlet temperature of the first heat exchanger 35 of the first thermal medium for circulating the first thermal medium circulation line 33 is set up to be target temperature. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an exhaust heat recovery apparatus and a fuel cell system.

  As one type of the exhaust heat recovery device and the fuel cell system, the one shown in Patent Document 1 is known. As shown in FIG. 1 of Patent Document 1, an exhaust heat recovery device and a fuel cell system are provided with a hot water storage tank 20 capable of storing hot water and a hot water storage line that is connected to the hot water storage tank 20 and circulates hot water. Heat generation heat that circulates the common medium 26, the heat recovery forward path 128a, the heat recovery return path 128b, the second hot water path 43, and the first hot water path 42) and the heat medium (which recovers the generated heat) that exchanges heat with the fuel cell 114 A heat exchanger 118 for exchanging heat between the medium circulation path 124, the hot water circulating in the hot water circulation line and the heat medium circulating in the power generation heat medium circulation path 124, and the heat medium provided in the power generation heat medium circulation path 124. The heat medium pump 127 to be circulated, the path 130 having one end connected to the outlet 122c of the heat medium three-way valve 122 and the other end connected to the fuel cell 114, and one end connected to the outlet 122b of the heat medium three-way valve 122 Has passed 130, a heat medium radiator 120 provided in the middle of the path 129, a heat medium cooling fan 119 provided adjacent to the heat medium radiator 120, and a power generation heat medium circulation path 124. And a heat medium temperature sensor 117 provided on the downstream side of the fuel cell 114.

In this exhaust heat recovery device and the fuel cell system, if the heat medium temperature detected by the heat medium temperature sensor 117 becomes too high, the generated heat is not recovered sufficiently. Do. The inlet 122a and outlet 122b of the heat medium three-way valve 122 are communicated with each other, and the heat medium cooling fan 119 is operated at the same time. When the inlet 122 a and the outlet 122 b of the heat medium three-way valve 122 communicate with each other, the heat medium flows into the path 129. The heat medium flowing into the path 129 passes through the heat medium radiator 120 and radiates heat by the air blown from the heat medium cooling fan 119. When the heat medium temperature detected by the heat medium temperature sensor 117 is lowered, the inlet 122a and the outlet 122c of the heat medium three-way valve 122 are communicated again. By repeating the switching of the heat medium three-way valve 122 as described above, the temperature of the heat medium is maintained within a predetermined range.
JP 2007-57173 A

  In the exhaust heat recovery apparatus and the fuel cell system described in Patent Document 1 described above, the heat exchanger inlet temperature of the heat medium is detected by the heat medium temperature sensor 117, the three-way valve 122 is switched by the sensor detection value, and the flow path is changed. The route is switched to the route 129 or the route 130. When the sensor detection value is higher than the determination threshold, the heat medium cooling fan 119 is used to lower the temperature of the heat medium. When the sensor detection value is lower than the determination threshold, the flow path 130 is not passed through the flow path 129 cooled by the heat medium cooling fan 119, but the flow path 130 is passed. In this way, the temperature at the inlet of the heat exchanger is controlled to achieve high efficiency in heat recovery. However, there is a problem in that heat is generated due to cooling using the heat medium cooling fan 119, and high efficiency of heat recovery cannot be achieved sufficiently. In addition, since a cooling (heat radiation) flow path is provided separately, there is a problem in that extra cost and space are required to configure the flow path.

  The present invention has been made to solve the above-described problems. In the exhaust heat recovery apparatus and the fuel cell system, when recovering the exhaust heat generated in the apparatus (system) into the hot water, low cost and space saving. It aims at achieving further high efficiency of heat recovery, aiming at improvement.

  In order to solve the above problems, the structural features of the invention of the exhaust heat recovery apparatus according to claim 1 are a hot water storage tank capable of storing hot water, a hot water circulation line connected to the hot water tank and circulating the hot water. The first heat medium circulation line through which the first heat medium recovered from the exhaust heat of the power generator circulates, the hot water circulating through the hot water circulation line, and the first heat medium circulating through the first heat medium circulation line are heat exchanged. First heat exchanger, first heat medium circulating means provided on the first heat medium circulation line for circulating the first heat medium, and first heat of the first heat medium flowing through the first heat medium circulation line And a flow rate adjusting means for adjusting the flow rate of the first heat medium by controlling the first heat medium circulating means so that the inlet temperature of the exchanger becomes a target temperature.

  The exhaust heat recovery apparatus according to claim 2 is characterized in that the flow rate adjusting means is an inlet of the first heat exchanger of the first heat medium flowing through the first heat medium circulation line. The flow rate of the first heat medium is adjusted by controlling the first heat medium circulation means by performing feedback control from the target temperature of the temperature and the actually measured temperature of the inlet temperature of the first heat exchanger of the first heat medium. That is.

  Further, in the configuration of the invention of the exhaust heat recovery apparatus according to claim 3, in claim 1 or 2, the flow rate adjusting means is information on the temperature of the hot water flowing into the first heat exchanger from the hot water tank. Also, the flow rate of the first heat medium is adjusted by controlling the first heat medium circulation means.

  According to a fourth aspect of the present invention, there is provided an exhaust heat recovery apparatus comprising a fuel cell that uses a reformed gas reformed by a reformer as an anode gas. The exhaust heat of the reformer is recovered, and the flow rate adjusting means takes into account information relating to the power generation load of the fuel cell that uses the reformed gas reformed by the reformer as the anode gas. The flow rate of the first heat medium is adjusted by controlling the circulation means.

  The exhaust heat recovery apparatus according to claim 5 is characterized in that the flow rate adjusting means is the inlet of the first heat exchanger of the first heat medium flowing through the first heat medium circulation line. A PID control unit that calculates the control amount of the first heat medium circulating means by PID control from the target temperature of the temperature and the actually measured temperature of the inlet temperature of the first heat exchanger of the first heat medium, and is used for PID control A first gain schedule unit that schedules at least one of a proportional gain, an integral gain, and a differential gain according to information on the power generation load of the fuel cell; and at least one of a proportional gain, an integral gain, and a differential gain used for PID control And a second gain schedule unit that schedules one of the hot water from the hot water storage tank into the first heat exchanger according to information related to the temperature of the hot water.

  Further, in the configuration of the invention of the exhaust heat recovery apparatus according to claim 6, in claim 4, when the flow rate adjusting means considers information on the power generation load of the fuel cell, the power generation load of the fuel cell fluctuates. In consideration of the first delay time set in advance corresponding to the dead time when the influence appears as a change in the inlet temperature of the first heat exchanger of the first heat medium, When considering the information about the temperature of the hot water flowing into the heat exchanger, when the temperature of the hot water changes, the effect appears as a change in the inlet temperature of the first heat exchanger of the first heat medium. The flow rate of the first heat medium is adjusted by controlling the first heat medium circulating means in consideration of the preset second delay time corresponding to the time.

  According to a seventh aspect of the present invention, there is provided a feature of the exhaust heat recovery apparatus according to the fifth aspect, wherein the flow rate adjusting means inputs information on the power generation load of the fuel cell and the power generation load of the fuel cell fluctuates. A first delay processing unit that executes a delay process based on a preset first delay time, the effect of which corresponds to a dead time that appears as a change in the inlet temperature of the first heat exchanger of the first heat medium; When the information regarding the temperature of the hot water flowing into the first heat exchanger from the hot water tank is input, and the temperature of the hot water varies, the effect is the fluctuation of the inlet temperature of the first heat exchanger of the first heat medium. And a second delay processing unit that executes a delay process based on a preset second delay time corresponding to the dead time that appears as

  According to an eighth aspect of the present invention, there is provided a structural feature of the exhaust heat recovery apparatus according to any one of the fourth to seventh aspects, wherein the exhaust heat recovery apparatus is supplied from the reforming section of the reformer to the fuel electrode of the fuel cell. From the third heat exchanger for exchanging heat between the anode gas and the first heat medium, from the fourth heat exchanger for exchanging heat between the anode off gas supplied from the fuel electrode to the burner of the reformer and the first heat medium, from the burner The exhaust heat of the reformer and / or the exhaust heat of the fuel cell is converted into the first heat medium by at least one of the fifth heat exchangers that exchange heat between the exhaust gas discharged and the first heat medium. It is to collect.

  A structural feature of the fuel cell system according to claim 9 is that the exhaust heat recovery device according to any one of claims 1 to 8 is provided.

  In the invention of the exhaust heat recovery apparatus according to claim 1 configured as described above, the inlet temperature of the first heat exchanger of the first heat medium flowing through the first heat medium circulation line is the target temperature. The flow rate of the first heat medium is adjusted by controlling the first heat medium circulation means so that That is, the temperature of the first heat medium flowing into the first heat exchanger can be set to the target temperature only by adjusting the flow rate of the first heat medium by controlling the first heat medium circulation means. Therefore, the temperature of the first heat medium can be set as the target temperature without providing a separate cooling (heat radiation) flow path as in the prior art, so that the heat recovered in the first heat medium can be cooled (heat radiation) as in the prior art. ) Can be recovered in the hot water storage in the first heat exchanger without radiating heat in the first flow path, that is, high efficiency of heat recovery can be achieved without lowering the heat recovery efficiency. At the same time, it is not necessary to separately provide a cooling (heat radiation) flow path, so that low cost and space saving can be achieved.

  In the invention of the exhaust heat recovery apparatus according to claim 2 configured as described above, in claim 1, the flow rate adjusting means is the first heat exchanger of the first heat medium flowing through the first heat medium circulation line. The flow rate of the first heat medium is adjusted by controlling the first heat medium circulation means by performing feedback control from the target temperature of the inlet temperature and the actually measured temperature of the inlet temperature of the first heat exchanger of the first heat medium. To do. Thus, with a simple configuration, the temperature of the first heat medium flowing into the first heat exchanger can be set as the target temperature only by adjusting the flow rate of the first heat medium by controlling the first heat medium circulation means. it can.

  In the invention of the exhaust heat recovery apparatus according to claim 3 configured as described above, in claim 1 or claim 2, the flow rate adjusting means relates to the temperature of the hot water flowing into the first heat exchanger from the hot water tank. In consideration of the information, the flow rate of the first heat medium is adjusted by controlling the first heat medium circulation means. Thereby, when the temperature of the hot water flowing into the first heat exchanger from the hot water tank fluctuates, the temperature of the first heat medium after the heat exchange in the first heat exchanger fluctuates with the fluctuation. In addition, taking into account information related to the temperature of the hot water flowing into the first heat exchanger from the hot water tank, the flow rate of the first heat medium is adjusted by controlling the first heat medium circulation means and flows into the first heat exchanger. The temperature of the 1st heat medium to perform can be made into target temperature.

  In the invention of the exhaust heat recovery apparatus according to claim 4 configured as described above, the power generation apparatus includes a fuel cell using the reformed gas reformed by the reformer as an anode gas, and the first heat medium Recovers the exhaust heat of the reformer, and the flow rate adjusting means takes into account the information regarding the power generation load of the fuel cell that uses the reformed gas reformed by the reformer as the anode gas. The flow rate of the first heat medium is adjusted by controlling the medium circulation means. Thereby, when the power generation load of the fuel cell fluctuates, the amount of exhaust heat recovered from the reformer varies with the variation, so even if the temperature of the first heat medium that recovered the exhaust heat fluctuates, Considering information on the power generation load of the fuel cell, the first heat medium circulating means is controlled to adjust the flow rate of the first heat medium, and the temperature of the first heat medium flowing into the first heat exchanger is set as the target temperature. be able to.

  In the invention of the exhaust heat recovery apparatus according to claim 5 configured as described above, in claim 4, the PID control unit is the first heat exchanger of the first heat medium flowing through the first heat medium circulation line. Based on the target temperature of the inlet temperature and the actually measured temperature of the inlet temperature of the first heat exchanger of the first heat medium, the control amount of the first heat medium circulating means is calculated by PID control, and the first gain schedule unit Schedule at least one of proportional gain, integral gain and differential gain used for control according to information on fuel cell power generation load, and second gain schedule unit uses proportional gain, integral gain and differential gain used for PID control Is scheduled according to information about the temperature of the hot water flowing into the first heat exchanger from the hot water tank. Thereby, each gain of the PID control executed by the PID control unit is scheduled by information regarding the power generation load of the fuel cell and / or information regarding the temperature of the hot water flowing into the first heat exchanger from the hot water tank. Therefore, when the power generation load of the fuel cell fluctuates, the amount of exhaust heat recovered from the reformer fluctuates with the fluctuation, so even if the temperature of the first heat medium that recovered the exhaust heat also fluctuates, the fuel In consideration of the information about the power generation load of the battery, the first heat medium circulating means is controlled to adjust the flow rate of the first heat medium, and the temperature of the first heat medium flowing into the first heat exchanger is set as the target temperature. Can do. Further, when the temperature of the hot water flowing into the first heat exchanger from the hot water tank changes, even if the temperature of the first heat medium after the heat exchange in the first heat exchanger also changes with the change, The first heat medium circulating means is controlled in consideration of the information about the temperature of the hot water flowing into the first heat exchanger from the hot water tank to adjust the flow rate of the first heat medium and flows into the first heat exchanger. The temperature of one heat medium can be set as the target temperature.

  In the invention of the exhaust heat recovery apparatus according to claim 6 configured as described above, in claim 4, when the flow rate adjusting means considers information on the power generation load of the fuel cell, the power generation load of the fuel cell is In consideration of the first delay time set in advance, which corresponds to the dead time at which the influence of the fluctuation appears as the fluctuation of the inlet temperature of the first heat exchanger of the first heat medium, When considering the information about the temperature of the hot water flowing into one heat exchanger, when the temperature of the hot water changes, the effect appears as the fluctuation of the inlet temperature of the first heat exchanger of the first heat medium. The flow rate of the first heat medium is adjusted by controlling the first heat medium circulating means in consideration of the second delay time set in advance corresponding to the dead time. Thereby, when the power generation load of the fuel cell fluctuates, the first heat medium circulation can be performed at an appropriate timing even if a dead time occurs in which the effect appears as a fluctuation in the inlet temperature of the first heat exchanger of the first heat medium. The temperature of the first heat medium flowing into the first heat exchanger can be set as the target temperature by controlling the means to adjust the flow rate of the first heat medium. Further, when the temperature of the hot water flowing into the first heat exchanger from the hot water tank fluctuates, even if a dead time occurs in which the effect appears as a fluctuation in the inlet temperature of the first heat exchanger of the first heat medium, It is possible to control the first heat medium circulating means at an appropriate timing to adjust the flow rate of the first heat medium and to set the temperature of the first heat medium flowing into the first heat exchanger as the target temperature.

  In the invention of the exhaust heat recovery apparatus according to claim 7 configured as described above, in claim 5, the first delay processing unit inputs information on the power generation load of the fuel cell, and the power generation load of the fuel cell fluctuates. A delay process is executed based on a preset first delay time corresponding to a dead time in which the influence appears as a fluctuation in the inlet temperature of the first heat exchanger of the first heat medium. The delay processing unit inputs information on the temperature of the hot water flowing into the first heat exchanger from the hot water tank, and when the temperature of the hot water changes, the influence of the first heat exchanger of the first heat medium is affected. Delay processing is executed based on a second delay time set in advance, which corresponds to a dead time that appears as a change in inlet temperature. Thereby, when the power generation load of the fuel cell fluctuates, the first heat medium circulation can be performed at an appropriate timing even if a dead time occurs in which the effect appears as a fluctuation in the inlet temperature of the first heat exchanger of the first heat medium. The temperature of the first heat medium flowing into the first heat exchanger can be set as the target temperature by controlling the means to adjust the flow rate of the first heat medium. Further, when the temperature of the hot water flowing into the first heat exchanger from the hot water tank fluctuates, even if a dead time occurs in which the effect appears as a fluctuation in the inlet temperature of the first heat exchanger of the first heat medium, It is possible to control the first heat medium circulating means at an appropriate timing to adjust the flow rate of the first heat medium and to set the temperature of the first heat medium flowing into the first heat exchanger as the target temperature.

  In the invention of the exhaust heat recovery apparatus according to claim 8 configured as described above, the exhaust heat recovery apparatus according to any one of claims 1 to 7 is supplied to the fuel electrode of the fuel cell from the reforming section of the reformer. A third heat exchanger for exchanging heat between the anode gas and the first heat medium, a fourth heat exchanger for exchanging heat between the anode off gas supplied from the fuel electrode to the burner of the reformer and the first heat medium, and a burner The exhaust heat of the reformer and / or the exhaust heat of the fuel cell is converted into the first heat medium by at least one of the fifth heat exchangers that exchange heat between the combustion exhaust gas discharged from the first heat medium. To recover. Thereby, the exhaust heat of the reformer and / or the exhaust heat of the fuel cell can be reliably recovered in the first heat medium.

  In the invention of the fuel cell system according to claim 9 configured as described above, the exhaust heat recovery apparatus according to any one of claims 1 to 8 is provided. As a result, a fuel cell system having the operational effects of the first to eighth aspects of the invention can be provided.

  Hereinafter, an embodiment of a fuel cell system including an exhaust heat recovery apparatus according to the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing the configuration of the fuel cell system. This fuel cell system includes a fuel cell 10, a reformer 20, an exhaust heat recovery device 30, and a control device 40.

  The fuel cell 10 is supplied with a fuel (for example, reformed gas containing hydrogen) and an oxidant gas (for example, air containing oxygen), generates electric power through a chemical reaction between hydrogen and oxygen, and outputs a DC voltage (for example, 40 V). It is. In the present embodiment, the fuel cell 10 will be described by taking a polymer electrolyte type as an example. The fuel cell 10 supplies the generated power to the external power load 13. For example, the maximum output power of the fuel cell 10 is 1000 W, and the minimum output power is 300 W.

  The reformer 20 steam-reforms the raw material (reforming fuel) and supplies hydrogen-rich reformed gas to the fuel cell 10, and includes a burner (combustion unit) 21 and a reforming unit 22. It is configured. Examples of raw materials include natural gas, LPG, kerosene, gasoline, and methanol. In the present embodiment, the raw material is natural gas.

  The burner 21 is supplied with combustion fuel and combustion air from the outside during start-up operation, or anode off-gas (reformed gas that is supplied to the fuel cell and discharged without being used) from the fuel electrode of the fuel cell 10 during steady operation. Are supplied, each supplied combustible gas is burned with combustion air, and the reforming unit 22 is heated with the combustion gas.

  The reforming unit 22 reforms a mixed gas obtained by mixing the raw material supplied from the outside with water vapor (reformed water) from the evaporator by using a catalyst charged in the reforming unit 22 to generate hydrogen gas and carbon monoxide gas. (So-called steam reforming reaction). At the same time, carbon monoxide and steam generated by the steam reforming reaction are converted into hydrogen gas and carbon dioxide (so-called carbon monoxide shift reaction). These generated gases (so-called reformed gas) are led to the fuel electrode of the fuel cell 10.

  The reforming unit 22 is also provided with a CO shift unit and a CO purification unit (not shown). The CO shift unit is converted into hydrogen gas and carbon dioxide gas by reacting carbon monoxide and water vapor contained in the reformed gas from the reforming unit 22 with a catalyst filled therein. As a result, the reformed gas is led to the CO purification unit with a reduced carbon monoxide concentration. The CO purification unit generates carbon dioxide by reacting carbon monoxide remaining in the reformed gas with CO purification air further supplied from the outside using a catalyst filled therein. As a result, the reformed gas is led to the fuel electrode of the fuel cell 10 with the carbon monoxide concentration further reduced (10 ppm or less).

  The exhaust heat recovery device 30 includes a hot water tank 31, a hot water circulation line 32, a hot water circulation pump 32b, a condensing refrigerant circulation line (first heat medium circulation line) 33, and a condensing refrigerant circulation pump (first heat medium circulation means) 33a. , Fuel cell heat medium circulation line (second heat medium circulation line) 34, fuel cell heat medium circulation pump (second heat medium circulation means) 34a, first heat exchanger 35, second heat exchanger 36, and condenser 37.

  The hot water storage tank 31 is a tank capable of storing hot water. The hot water storage tank 31 is provided with one columnar container, in which hot water is stored in a layered manner, that is, the temperature of the upper part is the highest and lower as it goes to the lower part, and the temperature of the lower part is the lowest. It has become so. Water (low-temperature water) such as tap water is supplied to the lower part of the columnar container of the hot water tank 31 through the introduction pipe 31a. Hot hot water stored in the hot water tank 31 is led out from the upper part of the columnar container of the hot water tank 31 through the outlet pipe 31b.

  The stored hot water circulation line 32 is a line (pipe system) that communicates with the hot water storage tank 31 and circulates the stored hot water. One end of the hot water circulation line 32 is connected to the lower part of the hot water tank 31, and the other end is connected to the upper part of the hot water tank 31. A temperature sensor 32a, a hot water circulating pump 32b as hot water circulating means, and a first heat exchanger 35 are arranged on the hot water circulating line 32 in order from one end to the other end. The temperature sensor 32 a detects the temperature of the hot water flowing from the hot water storage tank 31 into the first heat exchanger 35 (the hot water first heat exchanger inlet temperature) and sends it to the control device 40. The temperature sensor 32 a is provided between the hot water tank 31 and the first heat exchanger 35, and is preferably provided in the main body housing H. The hot water circulating pump 32b sucks hot water in the lower part of the hot water tank 31, passes the hot water circulating line 32 in the direction of the arrow in the figure, and sends it to the upper part of the hot water tank 31, and is controlled by the control device 40. The discharge amount (delivery amount) is controlled.

  The condensing refrigerant circulation line (first heat medium circulation line) 33 is a line (piping system) through which the condensing refrigerant (first heat medium) recovered from the exhaust heat of the reformer 20 circulates. As the condensing refrigerant, an antifreeze such as an aqueous propylene glycol solution or water is used. On the condensing refrigerant circulation line 33, the first heat exchanger 35, the condensing refrigerant circulation pump 33a, the first condenser 37a, and the second heat exchanger 35 are sequentially arranged from the upstream to the downstream starting from the first heat exchanger 35. A condenser 37b, a third condenser 37c, and a temperature sensor 33b are provided.

  The condensation refrigerant circulation pump (first heat medium circulation means) 33a is a pump that is provided on the condensation refrigerant circulation line 33 and circulates the condensation refrigerant. The condensing refrigerant circulation pump 33a circulates the condensing refrigerant in the direction indicated by the arrow in the condensing refrigerant circulation line 33. The condensing refrigerant circulation pump 33a is controlled by the control device 40 to control its discharge amount (delivery amount). ing. The temperature sensor 33b detects the inlet temperature of the first heat exchanger 35 for condensing refrigerant (condensing refrigerant first heat exchanger inlet temperature), and transmits the detection result to the control device 40. ing.

  The first condenser (anode off-gas condenser) 37a is configured such that the condensation refrigerant is supplied and the anode off-gas discharged from the fuel electrode of the fuel cell 10 is supplied, and heat is exchanged between the condensation refrigerant and the anode off-gas. Has been. The first condenser 37a is a condenser (fourth heat exchanger) that condenses water vapor in the anode off gas by heat exchange between the condensing refrigerant and the anode off gas. The first condenser 37a collects the exhaust heat of the anode off gas of the fuel cell 10 into a condensing refrigerant.

  The second condenser (combustion exhaust gas condenser) 37b is configured such that the condensation refrigerant is supplied and the combustion exhaust gas discharged from the burner 21 is supplied, and the condensation refrigerant and the combustion exhaust gas exchange heat. The second condenser 37b is a condenser (fifth heat exchanger) that condenses water vapor in the combustion exhaust gas by heat exchange between the condensing refrigerant and the combustion exhaust gas. The second condenser 37b collects the exhaust heat of the combustion exhaust gas from the reformer 20 into a condensing refrigerant.

  The third condenser (anode gas condenser) 37c is supplied with a condensing refrigerant and is supplied with an anode gas (reformed gas) supplied from the reformer 20 to the fuel electrode of the fuel cell 10, and the condensing refrigerant. The anode gas is configured to exchange heat. The third condenser 37c is a condenser (third heat exchanger) that condenses water vapor in the anode gas by heat exchange between the condensing refrigerant and the anode gas. The second condenser 37b recovers the exhaust heat of the anode gas of the reformer 20 into a condensing refrigerant.

  In the present embodiment, the condensing refrigerant circulating in the condensing refrigerant circulation line 33 exchanges heat in the order of anode gas, combustion exhaust gas, and anode off gas. The order in which the condensers are arranged may be different from the order in the present embodiment. In addition, a fourth condenser (cathode off-gas condenser) may be provided. The fourth condenser is a condenser that condenses water vapor in the cathode off-gas discharged from the air electrode of the fuel cell 10 by heat exchange with the condensing refrigerant. The fourth condenser recovers the exhaust heat of the cathode off gas of the fuel cell 10 into a condensing refrigerant.

  The fuel cell heat medium circulation line (second heat medium circulation line) 34 is a line (piping system) through which a fuel cell heat medium (second heat medium) that exchanges heat with the fuel cell 10 circulates. The hot water circulation line 32, the condensing refrigerant circulation line 33, and the fuel cell heat medium circulation line 34 are provided independently of each other. On the fuel cell heat medium circulation line 34, the fuel cell 10, the second heat exchanger 36, and the fuel cell heat medium circulation pump 34 a are arranged in order from upstream to downstream starting from the fuel cell 10. Yes.

  The fuel cell heat medium circulation pump (second heat medium circulation means) 34a is a pump provided on the fuel cell heat medium circulation line 34 to circulate the fuel cell heat medium. The fuel cell heat medium circulation pump 34a circulates the fuel cell heat medium in the direction indicated by the arrow in the fuel cell heat medium circulation line 34, and is controlled by the control device 40 to control its discharge amount (delivery amount). It is like that.

  The first heat exchanger 35 is configured such that heat can be exchanged between the hot water circulation line 32 and the condensing refrigerant circulation line 33, and circulates through the hot water circulating through the hot water circulation line 32 and the condensing refrigerant circulation line 33. The heat exchanger exchanges heat with the condensing refrigerant.

  The second heat exchanger 36 is provided on the hot water circulation line 32, downstream of the hot water with respect to the first heat exchanger 35, and between the first heat exchanger 35 and the hot water tank 31. . The second heat exchanger 36 is configured such that heat can be exchanged between the hot water circulating line 32 and the fuel cell heat medium circulating line 34, and the hot water circulating through the hot water circulating line 32 and the fuel cell heat medium circulating line 34 are connected to each other. The heat exchanger exchanges heat with the circulating second heat medium.

  According to the exhaust heat recovery apparatus 30 configured as described above, the exhaust heat (heat energy) generated by the power generation of the fuel cell 10 is recovered in the fuel cell heat medium and stored in the hot water via the second heat exchanger 36. As a result, the hot water is heated (heated up). Further, the exhaust heat of the anode gas supplied to the fuel cell 10 is also recovered to the fuel cell heat medium via the third condenser 37c, and is recovered to the hot water storage via the second heat exchanger 36. As a result, Heat the stored hot water (heat up).

  The exhaust heat of the anode off-gas discharged from the fuel cell 10 is recovered by the condensing refrigerant via the first condenser 37a, and recovered by the hot water via the first heat exchanger 35. As a result, the hot water is Heat (heat up). Further, the exhaust heat of the combustion exhaust gas from the burner 21 is also recovered into the condensing refrigerant via the second condenser 37b, and is recovered into the hot water storage via the first heat exchanger 35. As a result, the hot water is heated. (Raise the temperature).

  The exhaust heat exhausted from the fuel cell 10 includes not only exhaust heat of the anode off-gas exhausted from the fuel cell 10 but also exhaust heat generated by power generation of the fuel cell 10. The exhaust heat generated in the reformer 20 includes exhaust heat of the anode gas, exhaust heat of the combustion exhaust gas from the burner 25, and exhaust heat exchanged with the reformer 20 (exhaust heat of the reformer itself). It is.

  The fuel cell system further includes an inverter 11. The inverter 11 receives a DC voltage output from the fuel cell 10, converts the DC voltage into a predetermined AC voltage, and outputs the AC voltage to a power line 14 connected to the AC system power supply 12 and the external power load 13; A second function of inputting an AC voltage from the system power supply 12 through the power supply line 14, converting the AC voltage into a predetermined DC voltage, and outputting the same to the auxiliary machine.

  The system power supply (or commercial power supply) 12 supplies power to the external power load 13 via the power supply line 14 connected to the system power supply 12. The fuel cell 10 is connected to a power supply line 14 via an inverter 11. The external power load 13 is a load driven by an AC power supply, and is an electrical appliance such as a dryer, a refrigerator, or a television.

  The auxiliary machine includes a motor-driven pump and an electromagnetic valve for supplying reforming fuel, water, and air to the reformer 20, a motor-driven pump for supplying air to the fuel cell 10, and the fuel cell 10. An electromagnetic valve for supplying reformed gas and air (oxygen), and each pump 32b, 33a, 34a of the exhaust heat recovery device 30 are configured.

  The inverter 11 includes a power sensor 11a. The power sensor 11 a detects the voltage of power from the inverter 11 to the power supply line 14 or from the power supply line 14 to the inverter 11. The detection result of the power sensor 11a is input to the control device 40. The power sensor 11a includes a current sensor and a voltage sensor, and detects power based on the current and voltage detected by both sensors. Note that the current sensor and the voltage sensor detect the R phase and the S phase of the system power supply 12 that are single-phase three-wires one by one. The current sensor and the voltage sensor each have two sensors for the R phase and the S phase. The power from the inverter 11 to the power supply line 14 or from the power supply line 14 to the inverter 11 can be obtained by adding the product of the R-phase current and voltage and the product of the S-phase current and voltage.

  The power line 14 is provided with a power sensor 14a. The power sensor 14 a detects power input / output and power amount with respect to the system power supply 12, and the detection result is input to the control device 40. The power sensor 14a has the same configuration as the current sensor 11a.

  Further, the fuel cell system includes a control device 40. The control device 40 is connected to the temperature sensors 32a, 33b, the power sensors 11a, 14a, and the pumps 32b, 33a, 34a described above (see FIG. 1). The control device 40 includes a microcomputer (not shown), and the microcomputer includes an input / output interface, a CPU, a RAM, and a ROM (all not shown) connected through a bus. The CPU executes a program corresponding to the flowchart of FIG. 8 to operate the fuel cell system. The RAM temporarily stores variables necessary for executing the program, and the ROM stores the program.

  In the state in which the fuel cell 10 is capable of generating power, the control device 40 generates an external power load based on the output power from the inverter 11 detected by the voltage sensor 11a and the power input to and output from the system power source 12 detected by the voltage sensor 14a. The power consumption consumed in 13 is calculated. For example, the sum of the output power from the inverter 11 and the power input to and output from the system power supply 12 is calculated as the power consumption. The control device 40 controls the supply amount of the raw material, water, etc. supplied to the reformer 20 so that the generated power of the fuel cell 10 becomes the input power consumption. When the power consumption exceeds the maximum generated power of the fuel cell 10, the fuel cell 10 is operated with the maximum generated power. The power to be generated by the fuel cell 10 with respect to the power consumption (power that can be generated) is defined as a power generation load (power generation load power).

  The fuel cell 10 described above (a generator that generates DC power), a reformer 20, and an inverter 11 (a converter that converts DC power supplied from the generator into AC power and outputs it) are included. A power generator is provided. The power generator of the present embodiment is a so-called fuel cell power generator. This power generator supplies power to the power load 13. In addition to the fuel cell power generation device, the power generation device may include a prime mover such as a diesel engine, a gas engine, a gas turbine, or a micro gas turbine, and a generator driven by the prime mover. The hot water storage tank 31 stores hot water from which the exhaust heat of the power generator is recovered.

  The fuel cell system adjusts the temperature of the condensing refrigerant circulation line 33 by feedback control (PID control) using the control system shown in FIG. FIG. 2 shows a control device 40, a condensing refrigerant circulation pump 33a, a driver circuit 33a1 of an electric motor (not shown) of the condensing refrigerant circulation pump 33a, a condensing refrigerant circulation line 33, and a temperature sensor 33b. . The PID control unit 43 of the control device 40 is a controller that calculates a control signal, and outputs the control signal (duty ratio duty [%] in the present embodiment) to the condensing refrigerant circulation pump 33a that is an actuator. The condensing refrigerant circulation pump 33a converts the duty ratio duty, which is a control signal, into a flow rate of the condensing refrigerant circulation line 33, which is an operation amount (flow rate per unit time: mL / min). The condensing refrigerant circulation line 33 is a control target. The temperature sensor 33b observes the inlet temperature of the first heat exchanger 35 for the condensing refrigerant in the condensing refrigerant circulation line 33. The detection value of the temperature sensor 33 b (actually measured temperature of the inlet temperature of the first heat exchanger 35 for the condensing refrigerant) is output to the PID control unit 43.

As illustrated in FIGS. 2 and 3, the control device 40 includes a first delay processing unit 41, a second delay processing unit 42, and a PID control unit 43.
The first delay processing unit 41 inputs information related to the power generation load of the fuel cell 10, and when the power generation load of the fuel cell 10 fluctuates, the effect is the first heat exchanger 35 of the refrigerant for condensation (first heat medium). The delay process is executed based on a first delay time set in advance, which corresponds to a dead time that appears as a fluctuation in the inlet temperature. That is, the first delay processing unit 41 calculates the fluctuation amount of the power generation load from the information regarding the power generation load of the fuel cell 10 and calculates the first delay time according to the fluctuation amount. At this time, a map or an arithmetic expression indicating the correlation between the fluctuation amount and the delay time may be used. In the present embodiment, the first delay time is set to several hundred seconds, for example.

  The first delay processing unit 41 inputs information related to the power generation load of the fuel cell 10, delays the input information by a first delay time, and outputs the delayed information to the first gain scheduling unit 43c.

  The reason why the dead time occurs will be described with reference to FIG. 4 and FIG. (1) The power generation load fluctuates (decreases) from 1000 W to 300 W. In FIG. 5, the fluctuation (decrease) in the power generation load starts at time t1. (2) The flow rate of the raw material charged into the reforming unit 22 changes (decreases) with the fluctuation of the power generation load. (3) The flow rate of the anode off gas that passes through the reforming unit 22 and the fuel cell 10 and flows out of the fuel cell 10 changes (decreases). (4) In the first condenser 37a, the amount of heat that can be given from the anode off gas to the condensing refrigerant changes (decreases). That is, the amount of heat exchange changes (decreases). (5) In the condensing refrigerant circulation line 33 and downstream of the first heat exchanger 35, the temperature of the condensing refrigerant changes (decreases), and the first heat exchanger inlet temperature of the condensing refrigerant also changes (decreases). To do. In FIG. 5, at the time t2, the first heat exchanger inlet temperature of the condensing refrigerant starts to decrease.

  Thus, from the start of fluctuation of the power generation load (time t1) until the influence of the fluctuation appears as fluctuation of the inlet temperature of the first heat exchanger 35 for the refrigerant for condensation (time t2), the reforming unit 22 The time required for the reformed gas to reach the fuel cell 10, the time required for the anode off-gas from the fuel cell 10 to reach the first condenser 37a, and the refrigerant for condensation from the first condenser 37a perform the first heat exchange. The total time required to reach the container 37a is required. A time lag (dead time) will occur accordingly.

  The second delay processing unit 42 receives information on the temperature of the hot water flowing into the first heat exchanger 35 from the hot water tank 31 and the influence of the refrigerant when the temperature of the hot water changes fluctuates (first The delay process is executed based on a preset second delay time corresponding to a dead time that appears as a change in the inlet temperature of the first heat exchanger 35 of the heat medium. That is, the second delay processing unit 42 calculates the amount of fluctuation in the temperature of the hot water from the information related to the temperature of the hot water flowing into the first heat exchanger 35 from the hot water tank 31, and the second delay processing unit 42 2 delay time is calculated. At this time, a map or an arithmetic expression indicating the correlation between the fluctuation amount and the delay time may be used. In the present embodiment, the second delay time is set to several hundred seconds, for example.

  The second delay processing unit 42 inputs information related to the temperature of the hot water flowing into the first heat exchanger 35 from the hot water storage tank 31, delays the input information by a second delay time, and a second gain schedule unit. Output to 43d.

  The reason why the dead time occurs will be described with reference to FIGS. (1) For example, when hot water (high-temperature (for example, 60 ° C.) hot-water storage water) is derived from the outlet 31b of the hot water tank 31 in order to fill the bath, the low temperature (for example, 20 ° C.) from the inlet 31a of the hot water tank 31 ) Tap water. (2) The replenished tap water flows from the hot water tank 31 through the hot water circulation line 32 and flows into the first heat exchanger 35 by driving of the hot water circulation pump 32b. In this way, when the low temperature hot water starts to flow from the hot water storage tank 31 into the main body housing H and then the first heat exchanger 35 and the temperature of the hot water starts to decrease (fluctuate) (time t11 in FIG. 7), 1 The inlet temperature of the heat exchanger 35 starts to decrease. (3) In the first heat exchanger 35, the amount of heat that can be given from the hot water to the condensing refrigerant changes (decreases). That is, the amount of heat exchange changes (decreases). (4) In the condensing refrigerant circulation line 33 and downstream of the first heat exchanger 35, the temperature of the condensing refrigerant changes (decreases), and the first heat exchanger inlet temperature of the condensing refrigerant also changes (decreases). To do. In FIG. 7, at the time t12, the first heat exchanger inlet temperature of the condensing refrigerant starts to decrease.

  Thus, from the start of the temperature change of the hot water (time t11) until the influence of the change appears as a change in the inlet temperature of the first heat exchanger 35 for the condensing refrigerant (time t12), the hot water storage tank 31. The total time of the time required for the hot-water storage water from reaching the first heat exchanger 35 and the time required for the refrigerant for condensation from the first condenser 37a to reach the first heat exchanger 37a is required. A time lag (dead time) will occur accordingly.

  The PID control unit 43 sets the target temperature of the inlet temperature of the first heat exchanger 35 of the condensing refrigerant (first heat medium) flowing through the condensing refrigerant circulation line 33 and the first temperature of the condensing refrigerant (first heat medium). 1 From the actually measured temperature of the inlet temperature of the heat exchanger 35, the discharge amount (rotation speed of the motor), which is the control signal value of the condensing refrigerant circulation pump 33a, is calculated by PID control.

  The PID control unit 43 includes a subtractor 43a, a PID controller 43b, a first gain schedule unit 43c, a second gain schedule unit 43d, and a multiplier / divider 43e.

  The subtractor 43a inputs the actually measured temperature of the inlet temperature of the first heat exchanger 35 for the refrigerant for condensation acquired from the temperature sensor 33b, and is stored in advance in a storage device (not shown) of the control device 40. The target temperature of the inlet temperature of the first heat exchanger 35 for the condensing refrigerant flowing through the condensing refrigerant circulation line 33 is input. The subtractor 43a calculates the deviation e by subtracting the read actual temperature from the read target temperature, and outputs it to the PID controller 43b.

  The PID controller 43b includes a target temperature of the inlet temperature of the first heat exchanger 35 for the condensing refrigerant flowing through the condensing refrigerant circulation line 33, and an actually measured temperature of the inlet temperature of the first heat exchanger 35 for the condensing refrigerant. Then, the control signal value of the condensing refrigerant circulation pump 32b is calculated by PID control. The PID controller 43b receives the deviation e calculated by the subtractor 43a, and calculates a control signal value that is the rotational speed (pump discharge amount (flow rate)) of the condensing refrigerant circulation pump 32b based on the deviation e. . In this case, if the condensing refrigerant circulation pump 32b is PWM-controlled, the control signal value is a duty ratio (duty) of PWM control.

  The PID controller 43b performs PID control (speed type). The PID controller 43b has a proportional actuator that outputs an output value proportional to the deviation e, an integral actuator that outputs an output value proportional to the time integral of the deviation e, and an output value proportional to the time change rate of the deviation e. Differentiating actuators (not shown) for outputting are provided. The PID controller 43b calculates a value obtained by adding the output values of the proportional operation unit, the integration operation unit, and the differentiation operation unit as the feedback control signal value duty of the condensing refrigerant circulation pump 32b. In this way, the PID controller 43b has a target temperature for the inlet temperature of the first heat exchanger 35 for the condensing refrigerant flowing through the condensing refrigerant circulation line 33 and an inlet temperature for the first heat exchanger 35 for the condensing refrigerant. The feedback control signal value duty is calculated based on the actually measured temperature.

  The PID control performed by the PID controller 43b is not only one that exhibits all the functions of the proportional operation unit, the integration operation unit, and the differentiation operation unit, but also the PI control that exhibits only the functions of the proportional operation unit and the integration operation unit. It also includes P control that exhibits only the function of the proportional actuator. Both P control and PI control calculate the feedback control signal value.

  In the present embodiment, a case where PI control is performed by the PID controller 43b will be described. In this case, the duty ratio duty is calculated by the following formula 1. The calculation result is output to the multiplier / divider 43e.

  Here, Kp is a proportional gain, e is the above-described difference, and Ti is an integration time. The integral gain is Kp / Ti.

  When PID control is performed by the PID controller 43b, the duty ratio duty is calculated by the following formula 2. The calculation result is output to the multiplier / divider 43e.

  Here, Kp is a proportional gain, e is the above-described difference, Ti is an integration time, and Td is a differentiation time. The integral gain is Kp / Ti, and the differential gain is Kp · Td.

  The first gain schedule unit 43 c schedules at least one of a proportional gain, an integral gain, and a differential gain used for the PID control based on information related to the power generation load of the fuel cell 10. That is, the first gain schedule unit 43c inputs information regarding the power generation load of the fuel cell 10 processed and output by the first delay process 41. The first gain schedule unit 43c calculates a coefficient K1 corresponding to the value input from the first delay process 41 using a map and an arithmetic expression indicating the correlation between the power generation load and the coefficient K1, and then a multiplier / divider 43e. Output to.

  The map showing the correlation between the power generation load and the coefficient K1 is such that the coefficient K1 decreases as the power generation load increases, as shown in the first gain schedule unit 43c of FIG. The coefficient K1 has an upper limit value and a lower limit value.

  The second gain schedule unit 43d schedules at least one of a proportional gain, an integral gain, and a differential gain used for the PID control according to information on the temperature of the hot water flowing into the first heat exchanger 35 from the hot water tank 31. To do. That is, the second gain schedule unit 43d inputs information regarding the temperature of the hot water flowing into the first heat exchanger 35 from the hot water tank 31 processed and output by the second delay process 42. The second gain schedule unit 43d uses a map indicating the correlation between the hot water first heat exchanger inlet temperature and the coefficient K2, a coefficient K2 corresponding to the value input from the second delay process 42 using an arithmetic expression. Calculate and output to the multiplier / divider 43e.

  As shown in the second gain schedule unit 43d of FIG. 3, the map showing the correlation between the hot water first heat exchanger inlet temperature and the coefficient K2 increases as the hot water first heat exchanger inlet temperature increases. The coefficient K2 is reduced. The coefficient K2 has an upper limit value and a lower limit value.

  The multiplier / divider 43e receives the duty calculated by the PID controller 43b, the coefficient K1 calculated by the first gain schedule unit 43c, and the coefficient K2 calculated by the second gain schedule unit 43d. The multiplier / divider 43e multiplies the duty, divides by the coefficient K1 (multiplies the reciprocal of the coefficient K1), divides by the coefficient K2 (multiplies the reciprocal of the coefficient K2), and calculates the duty after the schedule. It outputs to the driver circuit 33a1 of the electric motor (illustration omitted) of the condensing refrigerant circulation pump 33a.

  Thus, the duty after the schedule is expressed by the following formula 3.

  As can be understood from Equation 3, in the present embodiment, the coefficients K1 and K2 are constants for scheduling the proportional gain Kp. That is, the proportional gain Kp is scheduled as Kp × (1 / K1) × (1 / K2). The above formulas 1 and 3 represent the PID control in a position form.

In this embodiment, only the proportional gain Kp is scheduled. However, the integral gain Ki can be scheduled, and the differential gain Kd can also be scheduled.
When the integral gain Ki is scheduled, the duty after the schedule is expressed by the following equation (4).

  Here, the coefficients K1 'and K2' are constants for scheduling the integral gain Ki. That is, the integral gain Ki is scheduled as Ki × K1 ′ × K2 ′. The above formula 4 represents the PID control in a position form.

  When the differential gain Kd is scheduled, the duty after the schedule is shown by the following formula 5.

  Here, the coefficients K1 "and K2" are constants for scheduling the differential gain Kd. That is, the differential gain Kd is scheduled as Kd × (1 / K1 ″) × (1 / K2 ″). The above formula 5 represents the PID control in a position form.

  Next, the operation of the above-described fuel cell system will be described with reference to the flowchart of FIG. The control device 40 executes a program corresponding to the above flowchart every predetermined time when a main power supply (not shown) is in an on state. In step 102, the control device 40 acquires (receives) the measured temperature (temp_r) of the inlet temperature of the first heat exchanger 35 for the refrigerant for condensation acquired from the temperature sensor 33 b, and also stores the storage device ( A target temperature (temp_t) of the inlet temperature of the first heat exchanger 35 of the condensing refrigerant circulating in the condensing refrigerant circulation line 33, which is stored in advance (not shown), is acquired (received).

  Similarly to the processing of the PID controller 43b described above, the control device 40 determines the target temperature (temp_t) of the inlet temperature of the first heat exchanger 35 for the condensing refrigerant circulating in the condensing refrigerant circulation line 33 in step 104. The control signal value (duty_pre) of the condensing refrigerant circulation pump 32b is calculated by PID control from the measured temperature (temp_r) of the inlet temperature of the first heat exchanger 35 for condensing refrigerant. duty_pre is synonymous with the duty on the left side of Equation 1 above. The duty_pre is calculated by the following equation (6).

(Equation 6)
duty_pre = ctrl_pi (temp_t, temp_r)

  In parallel with the processing of steps 102 and 104, the control device 40 acquires (receives) the power generation load (inv) of the fuel cell 10 in step 106, and corresponds to a dead time corresponding to the fluctuation of the power generation load. 1 (Delay_inv) is acquired (received). Subsequently, in Step 108, the control device 40 calculates a schedule coefficient (K1) from the power generation load (inv) and the first delay time (Delay_inv). K1 is obtained by the following equation (7).

(Equation 7)
K1 = calc_K1 (inv, Delay_inv)

  Further, in parallel with the processing of Steps 102 and 104, the control device 40 obtains the temperature of hot water stored in the first heat exchanger 35 from the hot water storage tank 31 (referred to as tank hot water temperature, tank) in Step 110 ( And receiving (receiving) a second delay time (Delay_tank) corresponding to the dead time corresponding to the fluctuation of the tank hot water temperature. Subsequently, in Step 112, the control device 40 calculates a schedule coefficient (K2) from the tank hot water temperature (tank) and the second delay time (Delay_tank). K2 is obtained by the following equation (8).

(Equation 8)
K2 = calc_K2 (tank, Delay_tank)

  Then, similarly to the processing of the multiplier / divider 43e described above, the control device 40 calculates the duty (duty_gs) after the constant schedule in Step 114. This duty is obtained by the following equation (9).

(Equation 9)
duty_gs = ctrl_gs (duty_pre, K1, K2)

  Further, in step 116, the control device 40 acquires (receives) the maximum value (Max_duty) and the minimum value (Min_duty) of the output duty. In step 118, the control device 40 performs guard processing for the duty (duty_gs) after the constant schedule calculated in step 114. When the duty_gs is equal to or greater than the maximum value (Max_duty), the Max_duty is set to duty_gs. When the duty_gs is equal to or smaller than the minimum value (Min_duty), the Min_duty is set to duty_gs. Then, the processed duty is set to duty_out.

  In step 120, the control device 40 transmits a control signal value (duty_out) to the driver circuit 33a1 that drives the condensing refrigerant circulation pump 33a. In addition, the code | symbol in the right parenthesis of the said Formula 6 to Formula 9 represents the argument. For example, in the above equation 6, temp_t and temp_r.

  Further, operations and effects of the present embodiment will be described with reference to FIGS. 9 and 10. FIG. 9 shows a case where a fluctuation (1000 W to 300 W) occurs in the power generation load of the fuel cell 10. In this case, the proportional gain Kp is scheduled by the coefficient K1 calculated by the first delay processing unit 41 and the first gain scheduling unit 43c, and the duty is calculated by the PID controller 43b. The condensation refrigerant circulation pump 33a is driven with the duty. The result is shown in FIG.

  As is apparent from FIG. 9, when the power generation load of the fuel cell 10 varies, the inlet temperature of the first heat exchanger of the condensing refrigerant is suppressed to variation within a range of about ± 1 ° C. with respect to the target temperature. Can be confirmed. That is, it can be confirmed that the fluctuation is suppressed to be small compared to the fluctuation of the first heat exchanger inlet temperature of the condensing refrigerant by only PID control in which the gain schedule of PID control is not performed. In this case, as shown in FIG. 5, the first heat exchanger inlet temperature of the condensing refrigerant fluctuates in a range of ± about 1 ° C. with respect to the target temperature.

  FIG. 10 shows a case where a change (for example, 45 ° C. to 20 ° C.) occurs in the temperature of the hot water introduced from the hot water tank 31 to the first heat exchanger 35. In this case, the proportional gain Kp is scheduled by the coefficient K2 calculated by the second delay processing unit 42 and the second gain scheduling unit 43d, and the duty is calculated by the PID controller 43b. The condensation refrigerant circulation pump 33a is driven with the duty. The result is shown in FIG.

  As apparent from FIG. 10, when the temperature of the hot water stored in the first heat exchanger 35 from the hot water tank 31 varies, the inlet temperature of the first heat exchanger of the condensing refrigerant is about ± 2 with respect to the target temperature. It can be confirmed that the fluctuation is suppressed in the range of ° C. That is, it can be confirmed that the fluctuation is suppressed to be small compared to the fluctuation of the first heat exchanger inlet temperature of the condensing refrigerant by only PID control in which the gain schedule of PID control is not performed. In this case, as shown in FIG. 5, the first heat exchanger inlet temperature of the condensing refrigerant fluctuates in the range of + 1 ° C. to −6 ° C. with respect to the target temperature.

  As is apparent from the above description, in the present embodiment, the flow rate adjusting means (control device 40) is a first heat medium (for condensation) that circulates through the first heat medium circulation line (condensation refrigerant circulation line 33). The flow rate of the first heat medium is adjusted by controlling the first heat medium circulation means (condensing refrigerant circulation pump 33a) so that the inlet temperature of the first heat exchanger 35 of the refrigerant becomes the target temperature. That is, the temperature of the first heat medium flowing into the first heat exchanger can be set to the target temperature only by adjusting the flow rate of the first heat medium by controlling the first heat medium circulation means. Therefore, the temperature of the first heat medium can be set as the target temperature without providing a separate cooling (heat radiation) flow path as in the prior art, so that the heat recovered in the first heat medium can be cooled (heat radiation) as in the prior art. ) Can be recovered in the hot water storage in the first heat exchanger without radiating heat in the first flow path, that is, high efficiency of heat recovery can be achieved without lowering the heat recovery efficiency. At the same time, it is not necessary to separately provide a cooling (heat radiation) flow path, so that low cost and space saving can be achieved.

  Further, the flow rate adjusting means (the control device 40) sets the target of the inlet temperature of the first heat exchanger 35 of the first heat medium (condensation refrigerant) flowing through the first heat medium circulation line (condensation refrigerant circulation line 33). By controlling the first heat medium circulation means (condensing refrigerant circulation pump 33a) by performing feedback control from the temperature and the measured temperature of the inlet temperature of the first heat exchanger of the first heat medium, the first heat medium Adjust the flow rate. Thus, with a simple configuration, the temperature of the first heat medium flowing into the first heat exchanger can be set as the target temperature only by adjusting the flow rate of the first heat medium by controlling the first heat medium circulation means. it can.

  The flow rate adjusting means (control device 40) also takes into account at least one of information on the power generation load of the fuel cell 10 and information on the temperature of the hot water flowing into the first heat exchanger 35 from the hot water tank 31. The flow rate of the first heat medium (condensation refrigerant) is adjusted by controlling the first heat medium circulation means (condensation refrigerant circulation pump 33a). Thereby, when the power generation load of the fuel cell 10 fluctuates, the amount of exhaust heat recovered from the reformer 20 fluctuates with the variation, so the temperature of the first heat medium that recovered the exhaust heat fluctuates. In consideration of the information regarding the power generation load of the fuel cell 10, the first heat medium circulation means (condensing refrigerant circulation pump 33a) is controlled to adjust the flow rate of the first heat medium and flow into the first heat exchanger 35. The temperature of the 1st heat medium to perform can be made into target temperature. Further, when the temperature of the hot water flowing into the first heat exchanger 35 from the hot water tank 31 changes, the temperature of the first heat medium after the heat exchange in the first heat exchanger 35 fluctuates with the change. Even in this case, the first heat medium is controlled by controlling the first heat medium circulation means (condensing refrigerant circulation pump 33a) in consideration of the information about the temperature of the hot water flowing into the first heat exchanger 35 from the hot water tank 31. And the temperature of the first heat medium flowing into the first heat exchanger 35 can be set as the target temperature.

  In addition, the PID control unit 43b has a target temperature of the inlet temperature of the first heat exchanger 35 of the first heat medium (condensation refrigerant circulation line 33) flowing through the first heat medium circulation line (condensation refrigerant circulation line 33), From the measured temperature of the inlet temperature of the first heat exchanger 35 for one heat medium (condensation refrigerant), the control amount of the first heat medium circulation means (condensation refrigerant circulation pump 33a) is calculated by PID control, and the first The gain schedule unit 43c schedules at least one of proportional gain, integral gain, and differential gain used for PID control based on information related to the power generation load of the fuel cell, and the second gain schedule unit 43d uses it for PID control. At least one of proportional gain, integral gain, and differential gain is scheduled based on information on the temperature of the hot water flowing into the first heat exchanger 35 from the hot water tank 31. To Le. Thereby, each gain of the PID control executed by the PID control unit 43b is scheduled by information on the power generation load of the fuel cell 10 and / or information on the temperature of the hot water flowing into the first heat exchanger 35 from the hot water tank 31. Is done. Therefore, when the power generation load of the fuel cell 10 fluctuates, the amount of exhaust heat recovered from the reformer 20 fluctuates with the variation, so the temperature of the first heat medium that recovered the exhaust heat also fluctuates. In consideration of the information regarding the power generation load of the fuel cell 10, the first heat medium circulation means (condensing refrigerant circulation pump 33a) is controlled to adjust the flow rate of the first heat medium (condensing refrigerant) to perform the first heat exchange. The temperature of the first heat medium flowing into the vessel 35 can be set as the target temperature. In addition, when the temperature of the hot water flowing into the first heat exchanger 35 from the hot water tank 31 fluctuates, the first heat medium (condensation refrigerant) after heat exchange in the first heat exchanger 35 is accompanied by the fluctuation. ), The first heat medium circulation means (condensing refrigerant circulation pump 33a) is controlled in consideration of the information about the temperature of the hot water flowing into the first heat exchanger 35 from the hot water tank 31. The flow rate of the first heat medium (condensing refrigerant) is adjusted, and the temperature of the first heat medium flowing into the first heat exchanger 35 can be set as the target temperature.

  Further, when considering the information regarding the power generation load of the fuel cell 10, the flow rate adjusting means (the control device 40) is affected by the first heat medium (condensing refrigerant) when the power generation load of the fuel cell 10 fluctuates. The hot water storage that flows into the first heat exchanger 35 from the hot water storage tank 31 is also taken into account in consideration of a preset first delay time corresponding to a dead time that appears as a change in the inlet temperature of the first heat exchanger 35. When considering the information on the temperature of the water, when the temperature of the stored hot water fluctuates, the dead time appears as the fluctuation of the inlet temperature of the first heat exchanger 35 of the first heat medium (condensing refrigerant). The first heat medium (condensing refrigerant) of the first heat medium (condensation refrigerant) is controlled by controlling the first heat medium circulation means (condensation refrigerant circulation pump 33a) in consideration of the preset second delay time. Adjust the flow rate. Thereby, when the power generation load of the fuel cell 10 fluctuates, even if a dead time occurs in which the influence appears as a fluctuation of the inlet temperature of the first heat exchanger 35 of the first heat medium (condensing refrigerant), it is appropriate. The first heat medium (condensation refrigerant circulation pump 33a) is controlled at the timing to adjust the flow rate of the first heat medium (condensation refrigerant) and flow into the first heat exchanger 35 (condensation refrigerant). The temperature of the refrigerant can be set as the target temperature. Further, when the temperature of the hot water flowing into the first heat exchanger 35 from the hot water tank 31 fluctuates, the effect is the fluctuation of the inlet temperature of the first heat exchanger 35 of the first heat medium (condensing refrigerant). Even if a dead time appears, the first heat medium circulating means (condensing refrigerant circulation pump 33a) is controlled at an appropriate timing to adjust the flow rate of the first heat medium (condensing refrigerant), and the first heat exchanger 35 The temperature of the first heat medium (condensation refrigerant) flowing into the refrigerant can be set as the target temperature.

  Further, the first delay processing unit 41 inputs information related to the power generation load of the fuel cell 10, and when the power generation load of the fuel cell 10 fluctuates, the effect is the first heat exchange of the first heat medium (condensing refrigerant). A delay process is executed based on a preset first delay time corresponding to a dead time that appears as a change in the inlet temperature of the vessel 35, and the second delay processing unit 42 performs first heat exchange from the hot water tank 31. The information regarding the temperature of the hot water flowing into the storage device 35 is input, and when the temperature of the hot water is changed, the effect is the change in the inlet temperature of the first heat exchanger 35 of the first heat medium (condensing refrigerant). Delay processing is executed based on a preset second delay time corresponding to the dead time that appears. Thereby, when the power generation load of the fuel cell 10 fluctuates, even if a dead time occurs in which the influence appears as a fluctuation of the inlet temperature of the first heat exchanger 35 of the first heat medium (condensing refrigerant), it is appropriate. The first heat medium (condensation refrigerant circulation pump 33a) is controlled at the timing to adjust the flow rate of the first heat medium (condensation refrigerant) and flow into the first heat exchanger 35 (condensation refrigerant). The temperature of the refrigerant can be set as the target temperature. Further, when the temperature of the hot water flowing into the first heat exchanger 35 from the hot water tank 31 fluctuates, the effect is the fluctuation of the inlet temperature of the first heat exchanger 35 of the first heat medium (condensing refrigerant). Even if a dead time appears, the first heat medium circulating means (condensing refrigerant circulation pump 33a) is controlled at an appropriate timing to adjust the flow rate of the first heat medium (condensing refrigerant), and the first heat exchanger 35 The temperature of the first heat medium (condensation refrigerant) flowing into the refrigerant can be set as the target temperature.

  A third heat exchanger (third condenser 37c) in which the anode gas supplied from the reforming unit 22 of the reformer 20 to the fuel electrode of the fuel cell 10 and the first heat medium exchange heat, and from the fuel electrode. A fourth heat exchanger (first condenser 37a) in which the anode off-gas supplied to the burner 21 of the reformer 20 and the first heat medium exchange heat, combustion exhaust gas discharged from the burner 21, and the first heat medium. The exhaust heat of the reformer 20 and / or the exhaust heat of the fuel cell 10 is recovered to the first heat medium by at least one of the fifth heat exchangers (second condenser 37b) that exchange heat with . Thereby, the exhaust heat of the reformer 20 and / or the exhaust heat of the fuel cell 10 can be reliably recovered in the first heat medium.

  The present invention can also be applied to an exhaust heat recovery device other than a fuel cell system, for example, a cogeneration system such as a gas engine cogeneration system. In this case, heat is recovered from exhaust heat (exhaust gas or cooling water) of the gas engine. Further, the fuel cell is not limited to the polymer electrolyte type, but can be applied to a solid oxide form, a phosphoric acid form, a molten carbonate form, a solid oxide form, and the like. In this case, the solid oxide form has a reformer but no second heat medium. The present invention can also be applied to such a system.

It is a figure which shows the structure of one Embodiment of the fuel cell system to which the waste heat recovery apparatus by this invention is applied. It is a figure which shows the control system of the fuel cell system shown in FIG. It is a block diagram which shows the PID control part shown in FIG. It is a figure (system block diagram) for demonstrating the reason for the dead time when the power generation load of the fuel cell fluctuates. It is a figure for explaining the reason why dead time occurs when the power generation load of the fuel cell fluctuates (a time chart of the power generation load and the refrigerant first heat exchanger inlet temperature for condensing). It is a figure (system block diagram) for demonstrating the reason for the dead time when the stored hot water temperature which flows into a 1st heat exchanger from a hot water tank changes. The figure for demonstrating the reason for the dead time when the temperature of the stored hot water flowing into the first heat exchanger from the hot water tank fluctuates (the stored water first heat exchanger inlet temperature, the refrigerant first heat exchanger inlet for condensation) Temperature time chart). It is a flowchart of the control program performed with the control apparatus shown in FIG. It is a figure (time chart of power generation load and refrigerant | coolant 1st heat exchanger inlet temperature for a condensation) for demonstrating the effect | action and effect by this Embodiment when the power generation load of a fuel cell fluctuates. The figure for demonstrating the effect | action and effect by this Embodiment in case the temperature of the hot water which flows in into a 1st heat exchanger from a hot water tank fluctuates (The hot water 1st heat exchanger inlet temperature, the refrigerant | coolant 1st heat | fever for condensation) It is a time chart of exchanger inlet temperature.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Fuel cell, 11 ... Inverter, 11a ... Electric power sensor, 12 ... System power supply, 13 ... Electric power load, 14 ... Power supply line, 14a ... Electric power sensor, 20 ... Reformer, 21 ... Burner, 22 ... Reformer, 31 ... Hot water storage tank, 32 ... Hot water circulation line, 32a ... Temperature sensor, 32b ... Hot water circulation pump, 33 ... Condensation refrigerant circulation line (first heat medium circulation line), 33a ... Condensation refrigerant circulation pump (first heat medium) Circulating means), 33b ... temperature sensor, 34 ... fuel cell heat medium circulation line (second heat medium circulation line), 34a ... fuel cell heat medium circulation pump (second heat medium circulation means), 35 ... first heat exchanger. , 36 ... second heat exchanger, 37a ... first condenser (fourth heat exchanger), 37b ... second condenser (fifth heat exchanger), 37c ... third condenser (third heat exchanger) 40 ... Control device (flow rate adjusting means) 1 ... first delay processing unit, 42 ... second delay processing unit, 43 ... PID controller, 43c ... first gain scheduling unit, 43d ... second gain scheduling unit.

Claims (9)

A hot water storage tank capable of storing hot water,
A hot water circulation line communicating with the hot water tank and circulating the hot water;
A first heat medium circulation line through which the first heat medium recovered from the exhaust heat of the power generation device circulates;
A first heat exchanger for exchanging heat between the hot water circulating through the hot water circulation line and the first heat medium circulating through the first heat medium circulation line;
First heat medium circulation means provided on the first heat medium circulation line for circulating the first heat medium;
The flow rate of the first heat medium is controlled by controlling the first heat medium circulation means so that the inlet temperature of the first heat exchanger of the first heat medium flowing through the first heat medium circulation line becomes a target temperature. A flow rate adjusting means for adjusting
An exhaust heat recovery apparatus comprising:   2. The flow rate adjusting means according to claim 1, wherein the flow rate adjusting means includes the target temperature of the inlet temperature of the first heat exchanger of the first heat medium flowing through the first heat medium circulation line, and the first temperature of the first heat medium. An exhaust heat recovery apparatus that adjusts the flow rate of the first heat medium by controlling the first heat medium circulating means by performing feedback control from the measured temperature of the inlet temperature of the heat exchanger.   3. The flow rate adjusting unit according to claim 1, wherein the flow rate adjusting unit controls the first heat medium circulating unit in consideration of information on the temperature of the hot water flowing into the first heat exchanger from the hot water storage tank. Thus, the exhaust heat recovery apparatus is characterized in that the flow rate of the first heat medium is adjusted. The power generation device according to claim 3,
A fuel cell that uses the reformed gas reformed by the reformer as the anode gas,
The first heat medium recovers exhaust heat of the reformer;
The flow rate adjusting means controls the first heat medium circulating means by taking into account information relating to a power generation load of a fuel cell that uses the reformed gas reformed by the reformer as an anode gas. 1. An exhaust heat recovery apparatus that adjusts the flow rate of a heat medium. The flow rate adjusting means according to claim 4,
From the target temperature of the inlet temperature of the first heat exchanger of the first heat medium flowing through the first heat medium circulation line and the actually measured temperature of the inlet temperature of the first heat exchanger of the first heat medium. A PID control unit that calculates a control amount of the first heat medium circulating means by PID control;
A first gain scheduling unit that schedules at least one of a proportional gain, an integral gain, and a differential gain used for the PID control according to information on the power generation load of the fuel cell;
A second gain scheduling unit that schedules at least one of a proportional gain, an integral gain, and a differential gain used for the PID control according to information on the temperature of the hot water flowing into the first heat exchanger from the hot water tank; And an exhaust heat recovery apparatus.   5. The flow rate adjusting means according to claim 4, wherein when the information regarding the power generation load of the fuel cell is taken into account, the influence of the first heat of the first heat medium is affected when the power generation load of the fuel cell fluctuates. Considering a preset first delay time corresponding to a dead time that appears as a change in the inlet temperature of the exchanger, it relates to the temperature of the hot water flowing into the first heat exchanger from the hot water tank. When considering the information, when the temperature of the stored hot water fluctuates, it is set in advance corresponding to a dead time in which the effect appears as a fluctuation of the inlet temperature of the first heat exchanger of the first heat medium. The exhaust heat recovery apparatus is characterized in that the flow rate of the first heat medium is adjusted by controlling the first heat medium circulation means in consideration of the second delay time. The flow rate adjusting means according to claim 5,
Information related to the power generation load of the fuel cell is input, and when the power generation load of the fuel cell fluctuates, the effect corresponds to a dead time that appears as a fluctuation in the inlet temperature of the first heat exchanger of the first heat medium. A first delay processing unit for executing a delay process based on a preset first delay time;
Information on the temperature of the hot water flowing into the first heat exchanger from the hot water tank is input, and when the temperature of the hot water changes, the influence of the first heat exchanger of the first heat medium is affected. An exhaust heat recovery apparatus, further comprising: a second delay processing unit that executes a delay process based on a second delay time set in advance, which corresponds to a dead time that appears as a change in inlet temperature. .   The third heat exchange according to any one of claims 4 to 7, wherein the anode gas supplied from the reforming unit of the reformer to the fuel electrode of the fuel cell and the first heat medium exchange heat. A fourth heat exchanger for exchanging heat between the anode off-gas supplied from the fuel electrode to the burner of the reformer and the first heat medium, a combustion exhaust gas discharged from the burner, and the first heat medium The exhaust heat of the reformer and / or the exhaust heat of the fuel cell is recovered into the first heat medium by at least one of the fifth heat exchangers that exchange heat with the first heat medium. Heat recovery device. A fuel cell system comprising the exhaust heat recovery device according to any one of claims 1 to 8.

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