JP4615888B2 - Fuel cell cogeneration system - Google Patents

Description

  The present invention relates to a fuel cell cogeneration system, and more particularly to a fuel cell cogeneration system that warms up a fuel cell.

The fuel cell is provided with a cooling system to remove heat generated by the electrochemical reaction and maintain the fuel cell at a temperature state optimal for the electrochemical reaction. The fuel cell cogeneration system supplies hot water by effectively using heat recovered from the cooling system. On the other hand, since the fuel cell cannot perform the power generation operation unless the temperature is suitable for the electrochemical reaction, it is necessary to warm up the fuel cell when the fuel cell cogeneration system is started. Therefore, in a conventional fuel cell cogeneration system, cooling water is heated using a heater during warm-up, and the cooling system is applied to warm-up the fuel cell (see, for example, Patent Document 1).
JP-A-2-230665 (page 5, FIG. 1)

  However, in the conventional fuel cell cogeneration system, since a heater is mainly used for warming up the fuel cell, it takes time to warm up, and energy consumption by the heater causes a decrease in energy efficiency of the fuel cell cogeneration system. There was a problem.

  This invention is made | formed in view of such a situation, and it aims at providing the fuel cell cogeneration system which improves the energy efficiency of a fuel cell cogeneration system.

  In order to solve the above problems, a fuel cell cogeneration system according to the present invention includes a fuel cell, a cooling water circulation path for circulating cooling water for maintaining the fuel cell at a predetermined temperature, and the cooling water circulation path. A cooling water circulating means for circulating the cooling water, a heat exchanger disposed in the cooling water circulation path, a hot water circulation path for circulating hot water for heat exchange with the cooling water in the heat exchanger, and the hot water storage A hot water storage tank of a stacked boiling system disposed in a water circulation path, a first circulation direction in which the hot water is circulated from the upper part of the hot water tank, and a second circulation in which water is taken from the bottom of the hot water tank. Hot water circulation direction switching means for switching between directions, hot water circulation means for circulating hot water in the hot water circulation path, and the temperature of the cooling water at a predetermined cooling water temperature detection position. And a hot water temperature detecting means for detecting the temperature of the hot water at a predetermined hot water temperature detecting position, and the hot water temperature detecting means detects when the fuel cell is warmed up. When the detected temperature difference between the detected hot water detection temperature and the detected cooling water temperature detected by the cooling water temperature detecting means is equal to or smaller than the first set temperature difference, the hot water circulates in the second circulation direction. When the detected temperature difference is larger than the first set temperature difference, the stored hot water circulation direction switching means circulates the stored hot water so that the stored hot water circulates in the first circulation direction. ). With such a configuration, the hot water stored in the hot water storage tank can be used for warming up the fuel cell according to a predetermined temperature condition, so that the efficiency of the fuel cell cogeneration system can be improved. .

  The hot water circulation direction switching means circulates the hot water in the first circulation direction for a predetermined time from the start of warming up, and when the detected temperature difference is less than or equal to the first set temperature difference, The circulation direction of the hot water is switched to the second circulation direction (Claim 2). This configuration eliminates the effects of hot water temperature in the hot water circulation path and the decrease in hot water temperature due to piping in the hot water circulation path, so fuel cell cogeneration using hot water stored in the hot water tank Efficient warm-up of the system is possible.

  The predetermined coolant temperature detection position is on the coolant circulation path between the coolant outlet of the fuel cell and the coolant inlet of the heat exchanger (Claim 3).

  The predetermined hot water temperature detection position is on the hot water circulation path between the upper connection portion of the hot water storage tank and the heat exchanger in the first circulation direction or in the vicinity of the upper connection portion in the hot water storage tank. (Claim 4).

  The predetermined time is at least one of a distance of the hot water circulation path between the hot water tank upper connection part and the hot water temperature detection means, a heat capacity of piping of the hot water circulation path, and a flow rate of the hot water. It can be set or changed according to (Claim 5). With such a configuration, the optimum setting can be realized even when the installation conditions of the fuel cell cogeneration system are changed or modified, so that the degree of freedom of installation of the fuel cell cogeneration system is improved.

  The fuel cell cogeneration system further includes a cooling water heater disposed in the cooling water circulation path, and the cooling water heater operates when the detected temperature difference is equal to or less than the first set temperature difference. (Claim 6). With such a configuration, the energy consumption of the cooling water heater can be saved, so that the efficiency of the fuel cell cogeneration system can be improved.

  The fuel cell cogeneration system includes a cooling water heat exchanger bypass path disposed in the cooling water circulation path so that the cooling water circulates without passing through the heat exchanger, and a circulation path of the cooling water. And a cooling water circulation path switching means for switching between a first cooling water circulation path passing through the cooling water heat exchanger and a second cooling water circulation path passing through the cooling water heat exchanger bypass path, Circulates through the second cooling water circulation path, and when the detected temperature difference is larger than the first set temperature difference, the cooling water circulation path switching means turns the cooling water circulation path into the first cooling water circulation path. (Claim 7). Alternatively, the hot water storage heat exchanger bypass path disposed in the hot water circulation path so that the hot water circulates without passing through the heat exchanger, and the hot water circulation path are connected to the heat exchanger. There is further provided hot water circulation path switching means for switching between a first hot water circulation path that passes through and a second hot water circulation path that passes through the hot water heat exchanger bypass path, and the hot water is the second hot water circulation path. When the detected temperature difference is larger than the first set temperature difference, the hot water circulation path switching means switches the hot water circulation path to the first hot water circulation path (Claim 11). With such a configuration, when the detected temperature difference is small, it is possible to prevent heat exchange between the hot water stored in the hot water storage tank and the cooling water, thereby improving the efficiency of the fuel cell cogeneration system. Is possible.

  After the cooling water circulation path switching means switches the cooling water circulation path to the first cooling water circulation path, the cooling water heater operates when the detected temperature difference is equal to or smaller than a second set temperature difference. (Claim 8). Alternatively, after the hot water circulation path switching means switches the hot water circulation path to the first hot water circulation path, the cooling water heater is used when the detected temperature difference is equal to or smaller than a second set temperature difference. (Claim 12). With such a configuration, according to the detected temperature difference, the cooling water can be heated by the combined use of the heat exchange with the hot water and the cooling water heater, thereby shortening the warm-up time. It becomes possible.

  After the cooling water circulation path switching means switches the circulation path of the cooling water to the first cooling water circulation path, the third preset temperature difference smaller than the first preset temperature difference and the second preset temperature difference. When the detected temperature difference is large, the detected temperature difference is detected and calculated again (claim 9). Alternatively, after the hot water circulation path switching means switches the hot water circulation path to the first hot water circulation path, the third preset temperature is smaller than the first preset temperature difference and the second preset temperature difference. When the detected temperature difference is larger than the difference, the detected temperature difference is detected and calculated again (claim 13). With such a configuration, as the detected temperature difference becomes smaller, the cooling water heater is operated to become equal to or smaller than the second set temperature difference, and then the heat exchange between the cooling water and the stored hot water becomes equal to or smaller than the third set temperature difference. Therefore, the heat exchange between the hot water and the cooling water can be continued as much as possible while avoiding a prolonged warm-up time as much as possible.

  After the cooling water circulation path switching means switches the cooling water circulation path to the first cooling water circulation path, the cooling water circulation path switching means is provided when the detected temperature difference is equal to or smaller than the third set temperature difference. The circulating path of the cooling water is switched to the second circulating path of the cooling water, and the hot water circulating direction switching means switches the circulating direction of the hot water to the second circulating direction (Claim 10). Alternatively, after the hot water circulation path switching means switches the hot water circulation path to the first hot water circulation path, the hot water circulation path switching is performed when the detected temperature difference is equal to or smaller than the third set temperature difference. The means switches the hot water circulation path to the second hot water circulation path, and the hot water circulation direction switching means switches the hot water circulation direction to the second circulation direction (Claim 14). With such a configuration, since the heat exchange between the cooling water and the hot water is continued until the detected temperature difference becomes equal to or smaller than the third set temperature difference, the efficiency of the fuel cell cogeneration system can be improved.

  A combustion apparatus that combusts surplus anode gas discharged from the fuel cell; and a combustion apparatus exhaust gas heat exchanger disposed in the hot water circulation path, wherein the combustion apparatus exhaust gas heat exchanger includes: Heat exchange is performed between the exhaust gas of the combustion device and the hot water storage (claim 15). With such a configuration, the surplus anode gas discharged from the fuel cell is used for heat storage in the hot water storage, so that the efficiency of the fuel cell cogeneration system can be improved.

  Only after the hot water circulation direction switching means switches the circulation direction of the hot water to the second circulation direction, the combustion apparatus exhaust gas heat exchanger exchanges heat between the exhaust gas and the hot water. (Claim 16). With such a configuration, when the hot water circulation direction is the first circulation direction, hot water stored at a temperature higher than the hot water stored at the top of the hot water tank can be prevented from flowing into the bottom of the hot water tank. Damage to the structure can be prevented.

  The combustion device is a combustion part of a reformer attached to the fuel cell (claim 17). With such a configuration, the surplus anode gas discharged from the fuel cell is used for reforming the anode gas in addition to the heat storage in the hot water storage, thereby further improving the efficiency of the fuel cell cogeneration system. It becomes possible.

  As described above, the present invention has an effect of improving the energy efficiency of the fuel cell cogeneration system.

  The best mode for carrying out the present invention will be described below with reference to the drawings.

(Embodiment 1)
FIG. 1 is a schematic diagram showing a schematic configuration of a fuel cell cogeneration system according to Embodiment 1 of the present invention.

  As shown in FIG. 1, the fuel cell cogeneration system according to Embodiment 1 of the present invention includes a fuel cell 11, a cooling water circulation pump 12 (cooling water circulation means), a cooling water heater 13, and a heat exchanger 14. The cooling water circulation path 15, the cooling water temperature detection means 16, the cooling water heat exchanger bypass path 17, the three-way valve 18 (cooling water circulation path switching means), the hot water storage tank 21, the hot water storage water circulation path 23, and the hot water circulation. It has a pump 22 (hot water circulating means), hot water circulating direction switching means comprising a switching path 23a ', 23b' and three-way valves 26a, 26b, hot water temperature detecting means 24, and a control device 29. ing.

  The hot water circulation path 23 is formed so that the hot water circulates through the hot water storage tank 21 and the heat exchanger 14, and the hot water circulating pump 22 that circulates the hot water in the middle thereof and the hot water water that detects the temperature of the hot water. A temperature detecting means 24 and three-way valves 26a and 26b are arranged.

  The hot water storage tank 21 is a stacked boiling system that stores hot hot water in the upper part and stores relatively low temperature hot water in the lower part. The hot water is disposed so as to circulate through the upper connection portion 21 a and the bottom connection portion 21 b of the hot water storage tank 21.

  The three-way valve 26 a is disposed between the bottom connection portion 21 b of the hot water storage tank 21 and the hot water storage inlet 14 a of the heat exchanger 14. The port a1 of the three-way valve 26a is connected to the hot water circulation path 23 on the bottom connection portion 21b side, the port a2 is connected to the hot water circulation path 23 on the heat exchanger 14 side, and the port a3 is connected to the switching path 23a ′. ing.

  The three-way valve 26 b is disposed between the upper connection portion 21 a of the hot water storage tank 21 and the hot water outlet 14 b of the heat exchanger 14. The port b1 of the three-way valve 26b is connected to the hot water circulation path 23 on the upper connection portion 21b side, the port b2 is connected to the hot water circulation path 23 on the heat exchanger 14 side, and the port a3 is connected to the switching path 23b ′. ing.

  The switching path 23a 'is disposed so as to connect the port a3 of the three-way valve 26a and the hot water circulation path 23 between the three-way valve 26b and the upper connection portion 21a.

  The switching path 23b 'is disposed so as to connect the port b3 of the three-way valve 26b and the hot water circulation path 23 between the three-way valve 26a and the bottom connection part 21b.

  Thereby, it becomes possible to switch the circulating direction of the hot water by switching the port connection of the three-way valves 26a, 26b.

  The hot water storage temperature detection means 24 is provided in the vicinity of the upper connection portion 21a in the hot water storage tank 21 or from the upper connection portion 21a when the hot water is circulated from the upper connection portion 21a (first circulation direction A). It is disposed in a hot water circulation path 23 up to the hot water inlet 14a. Here, it is disposed in a hot water circulation path 23 between the port a2 of the three-way valve 26a and the hot water inlet 14a of the heat exchanger 14.

  The hot water circulating pump 22 is disposed at a position where the hot water can be circulated even when the circulation direction is switched by the switching paths 23a 'and 23b'. Here, it is disposed between the port a2 of the three-way valve 26a and the stored hot water temperature detecting means 24.

  The cooling water circulation path 15 is formed so that the cooling water circulates through the fuel cell 11 and the heat exchanger 14, and a cooling water circulation pump 12 that circulates the cooling water in the middle thereof, and a cooling water heater that heats the cooling water. 13, a cooling water temperature detecting means 16 for detecting the temperature of the cooling water, and a three-way valve 18 are arranged.

  The cooling water heater 13 is disposed between the cooling water outlet 14 d of the heat exchanger 14 and the cooling water inlet 11 a of the fuel cell 11. As the cooling water heater 13, a general heater such as an electric heater can be used.

  The cooling water temperature detection means 16 is disposed between the cooling water outlet 11 b of the fuel cell 11 and the cooling water inlet 14 c of the heat exchanger 14.

  Here, a thermocouple can be used for the cooling water temperature detection means 16 and the hot water storage temperature detection means 24, for example. Moreover, the method of detecting the temperature of the fluid in piping by measuring the temperature of piping which comprises the cooling water circulation path 15 and the hot water storage water circulation path 23 may be used.

  The three-way valve 18 is disposed between the cooling water temperature detection means 16 and the cooling water inlet 14 c of the heat exchanger 14. The port c1 of the three-way valve 18 is connected to the cooling water circulation path 15 on the cooling water temperature detecting means 16 side, the port c2 is connected to the cooling water circulation path 15 on the cooling water inlet 14c side of the heat exchanger 14, and the port c3 is The cooling water heat exchanger bypass path 17 is connected.

  The cooling water heat exchanger bypass path 17 is disposed so as to connect the port a3 of the three-way valve 18 and the cooling water circulation path 15 between the cooling water outlet 14d of the heat exchanger 14 and the cooling water heater 13. . Thereby, by switching the port connection of the three-way valve 18, the circulation path of the cooling water is changed to the circulation path via the heat exchanger 14 (first cooling water circulation path C) and the circulation path via the cooling water heat exchanger bypass path 17 ( It is possible to switch to the second cooling water circulation path D).

  Further, the control device 29 detects the elapsed time t after the start of warm-up of the fuel cell 11 or the detected hot water temperature detected by the cooling water temperature detecting means 16 and the detected hot water temperature detected by the hot water temperature detecting means 24. Based on the detected temperature difference ΔT with respect to the temperature T1, the three-way valves 26a, 26b, the cooling water heater 13 or the three-way valve 18 are controlled.

  The operation of the fuel cell cogeneration system according to Embodiment 1 configured as described above will be described.

  FIG. 2 is a flowchart showing the operation of the fuel cell cogeneration system when the fuel cell 11 according to Embodiment 1 of the present invention is warmed up. The operation shown in this flowchart is performed when the fuel cell cogeneration system is controlled by the control device 29. Here, the time when the fuel cell 11 is warmed up refers to a period from the start of the fuel cell 11 until the fuel cell starts power generation. The start of the fuel cell 11 means the time when the fuel cell 11 shifts from the operation standby state to the temperature rising state. For example, when the operation switch of the fuel cell cogeneration system that is stopped is turned on.

  In FIG. 2, after the start of warming-up of the fuel cell 11 in step S <b> 1, in step S <b> 2, hot water is circulated from the upper connection portion 21 a of the hot water tank 21 by the hot water circulation pump 22 (first circulation direction A). That is, in FIG. 1, it is the arrow A side in the figure. The three-way valve 26a is switched so that the port a3 and the port a2 are connected, and the hot water is supplied from the upper connection part 21a of the hot water tank 21 via the switching path 23a ′ to the hot water circulating pump 22 and the heat exchanger 14. It flows to go through. The three-way valve 26b is switched so that the port b2 and the port b3 are connected, and the hot water flows through the switching path 23b 'so as to circulate to the bottom connection part 21b of the hot water tank 21. In the hot water storage tank 21, which is a stacked boiling system, hot water of a high temperature is distributed from the bottom to the upper part. By circulating the hot water from the upper part of the hot water tank 21, this hot water is used. The cooling water can be heated. Further, by returning from the bottom connection portion 21 b of the hot water storage tank 21, the hot water stored in the heat exchanger 14 does not come into contact with the hot hot water in the hot water storage tank 21. Can prevent damage.

  In step S3, the three-way valve 18 is switched so that the port c1 and the port c3 are connected, and the cooling water does not pass through the heat exchanger 14 but passes through the cooling water heat exchanger bypass path 17. Circulate (second cooling water circulation path D).

  In step S4, it is determined whether or not the elapsed time t after the start of warm-up has passed the predetermined time t1, and if the predetermined time t1 has not passed, the states of steps S2 and S3 are maintained. The This is because it takes time for the hot water stored in the upper connection portion 21a of the hot water storage tank 21 to reach the position of the hot water temperature detecting means 24 after the warming up of the fuel cell 11 is started. The predetermined time t1 is for accurately detecting the temperature of the hot water in the hot water storage tank 21 by circulating the hot water in the first circulation direction A.

  Here, the predetermined time t1 depends on setting conditions such as the distance between the upper connecting portion 21a of the hot water tank 21 and the hot water temperature detecting means 24, the heat capacity of the piping of the hot water circulation path 23, the flow rate of the hot water, and the like. It is set in consideration of the time until the hot water stored in the upper connection portion 21a of the hot water storage tank 21 sufficiently reaches the position of the hot water temperature detecting means 24. The setting conditions such as the distance between the upper connecting portion 21a of the hot water storage tank 21 and the hot water temperature detecting means 24, the heat capacity of the piping of the hot water circulation path 23, the flow rate of the hot water, and the like are specific to the installation of the fuel cell cogeneration system. It depends on the conditions. Therefore, it is preferable that the predetermined time t1 can be set or changed according to these specific installation conditions. For example, a predetermined time t1 corresponding to these specific installation conditions, or a circuit (not shown) that calculates and processes the predetermined time t1 based on these specific installation conditions is stored in the control device 29 in advance. The setting of t1 can be realized. Thereby, it becomes possible to set or change the predetermined time t1 more accurately after the fuel cell cogeneration system is installed. That is, the degree of freedom of installation of the fuel cell cogeneration system can be improved.

  After elapse of the predetermined time t1, in step S5, the stored hot water temperature detection means 24 detects the stored hot water temperature T1, and in step S6, the cooling water temperature detection means 16 detects the cooling water detection temperature T2, and in step S7. , A detected temperature difference ΔT between the hot water detection temperature T1 and the cooling water detection temperature T2 is calculated, and the detected temperature difference ΔT is compared with the first set temperature difference X in step S8.

  When the detected temperature difference ΔT is equal to or smaller than the first set temperature difference X, the cooling water heater 13 is activated in step S16. In step S18, the hot water circulating direction is switched from the bottom connecting portion 21b of the hot water tank 21 (second circulating direction B). That is, in FIG. 1, it is the arrow B side in the figure. The three-way valve 26a is switched so that the port a1 and the port a2 are connected, and the hot water is routed from the bottom connection portion 21b of the hot water tank 21 via the path 23b, via the hot water circulation pump 22 and the heat exchanger 14. To flow. The three-way valve 26b switches so that the port b2 and the port b1 are connected, and flows so as to circulate to the upper connection part 21a of the hot water storage tank 21 via the path 23a. Thereby, heating of the cooling water by the cooling water heater 13 is started, and the cooling water is not heated by heat exchange with the hot water storage.

  When the detected temperature difference ΔT is larger than the first set temperature difference X, in step S9, the three-way valve 18 is switched so that the port c1 and the port c2 are connected, and the cooling water is supplied from the heat exchanger 14. (First cooling water circulation path C). As a result, the temperature difference between the hot water and the cooling water can be utilized to raise the temperature of the cooling water in the heat exchanger 14 and thus the temperature of the fuel cell 11 can be raised.

  In step S10, the detected temperature difference ΔT is compared with the second set temperature difference Y.

  If the detected temperature difference ΔT is larger than the second set temperature difference Y, the process proceeds to step S11 as it is. As a result, the temperature of the cooling water can be raised in the heat exchanger 14, so that the fuel cell 11 can be efficiently warmed up without using the cooling water heater 13.

  When the detected temperature difference ΔT is equal to or smaller than the second set temperature difference Y, the cooling water heater 13 is activated in step S15, and the process proceeds to step S11. As a result, the heating in the heat exchanger 14 and the heating by the cooling water heater 13 can be used in combination to raise the temperature of the cooling water and thus the temperature of the fuel cell 11.

  Here, the time and energy efficiency required for warming up the fuel cell 11 can be appropriately adjusted by setting the second set temperature difference Y. That is, when it is desired to save the energy consumption of the cooling water heater 13, the second set temperature difference Y is set small, the range of the detected temperature difference ΔT where the cooling water heater 13 stops is expanded, and the fuel cell 11 When it is desired to shorten the warm-up time, the second set temperature difference Y can be set large, and the range of the detected temperature difference ΔT at which the cooling water heater 13 operates can be expanded.

  Next, in step S11, the detected temperature difference ΔT is compared with the third set temperature difference Z.

  When the detected temperature difference ΔT is equal to or smaller than the third set temperature difference Z, in step S17, the three-way valve 18 is switched so that the port c1 and the port c3 are connected, and the path of the cooling water is the second cooling water circulation. It becomes the path | route D and progresses to step S18. Thereby, the temperature increase of the cooling water by heat exchange with the hot water storage is completed.

  When the detected temperature difference ΔT is larger than the third set temperature difference Z, the stored hot water detection temperature T1 is detected again (step S12), the cooling water detection temperature T2 is detected (step S13), and the detected temperature difference. ΔT is calculated (step S14), and steps S10 to S11 are repeated.

  The third set temperature difference Z is set smaller than the second set temperature difference Y. As a result, before the detected temperature difference ΔT is reduced to the third set temperature difference Z, the cooling water heater 12 is operated in step S15. The third set temperature difference Z is set to be equal to or less than the first set temperature difference X. If the third set temperature difference Z is larger than the first set temperature difference X, after the heat exchange is started in step S9, a situation in which the heat exchange stops immediately in step S17 occurs. is there.

  Further, the first set temperature difference X, the second set temperature difference Y, and the third set temperature difference Z are the distances between the cooling water temperature detecting means 16 and the stored hot water temperature detecting means 24 and the heat exchanger 14, respectively. The temperature is set in consideration of the corresponding heat radiation and the temperature of heat loss in the heat exchanger 14 (about several degrees Celsius).

  Further, in step S18, after the hot water circulation direction is switched to the second circulation direction B, a combustion apparatus (not shown) that performs combustion treatment of excess anode gas (referred to as excess anode gas) discharged from the fuel cell 11. ) And a combustion apparatus exhaust gas heat exchanger (not shown) that performs heat recovery by exchanging heat between the exhaust gas of the combustion apparatus and the stored hot water, thereby heating the stored hot water. be able to. That is, by configuring the hot water circulation path 23 so as to pass through the combustion apparatus exhaust gas heat exchanger, the heated hot water is returned to the hot water storage tank 21 from the upper connection portion 21a, and the stacked boiling is performed. Can be. As a result, surplus anode gas is utilized for heat storage in the hot water storage, and the energy efficiency of the fuel cell cogeneration system is improved. Here, the anode gas refers to a gas supplied to the anode side of the fuel cell 11, and generally hydrogen or a gas containing a large amount of hydrogen is used.

  In addition, it is good to comprise so that heat exchange with the exhaust gas of a combustion apparatus and hot water may be performed in a combustion apparatus exhaust gas heat exchanger only after the circulation direction of hot water storage is switched to the 2nd circulation direction B. For example, it can be realized by branching the hot water circulation path 23 via a switching valve (not shown) so that the hot water is circulated in the combustion apparatus exhaust gas heat exchanger. Alternatively, it can be realized by configuring the exhaust gas of the combustion device to flow through the combustion device exhaust gas heat exchanger only after the hot water circulation direction is switched to the second circulation direction B. Thereby, when the circulation direction of the hot water is the first circulation direction A, it is possible to avoid the hot water having a temperature higher than the hot water in the vicinity of the hot water tank upper connection portion 21a from flowing into the hot water tank bottom connection portion 21b. Damage to the laminated structure of the hot water storage tank 21 can be prevented.

  Further, this combustion apparatus may be a combustion section (not shown) of a reformer. The reformer is a device generally attached to the fuel cell 11 when a hydrocarbon-based fuel other than hydrogen is used for the anode gas of the fuel cell 11, and burns the anode gas supplied to the fuel cell 11. The steam is reformed by heat. As a result, surplus anode gas is used for reforming the anode gas in addition to heat storage in the hot water storage, and the energy efficiency of the fuel cell cogeneration system is improved.

  Further, when the fuel cell 11 generates power, the cooling water circulates in the first cooling water circulation path C, and the hot water is circulated in the second circulation direction B. At this time, the cooling water is heated by the fuel cell 11, passes through the cooling water passage 15, and is cooled by the hot water storage by the heat exchanger 14. Then, the hot water is heated in the heat exchanger 14 and returned to the hot water storage tank 21 from the upper connection portion 21a, and the laminated boiling is performed.

  By the way, the hot water circulation direction switching means can also be implemented by the following modifications.

(Modification 1)
FIG. 3 shows the configuration of the hot water circulation path 23 according to the first modification of the first embodiment.

  As shown in FIG. 3, the first modification is a modification of the hot water circulation direction switching means of the first embodiment. That is, the switching valve 25 is disposed in the hot water circulation path 23, and the hot water storage pump connected to the hot water circulation pump suction side attachment path 22 a connected to the suction side of the hot water circulation pump 22 and the discharge side of the hot water circulation pump 22 is connected to the switching valve 25. A water circulation pump discharge side mounting path 22b is connected.

  The switching valve 25 can switch and connect the hot water circulation pump suction side path 22a and the hot water circulation pump discharge side path 22b to the hot water circulation path 23, thereby switching the hot water circulation direction in the reverse direction. It is configured as follows.

  The operation of the hot water circulation direction switching means configured as described above will be described.

  In FIG. 3, the first circulation direction A is the arrow A side in the figure, that is, the switching valve 25 connects the hot water circulating circuit 23 side of the heat exchanger 14 and the hot water circulating pump suction side path 22a, and hot water circulating. It is configured by connecting the hot water storage tank 21 side of the path 23 and the hot water circulating pump discharge side path 22b.

  The second circulation direction B is the arrow B side in the figure, that is, the switching valve 25 connects the heat exchanger 14 side of the hot water circulation path 23 and the hot water circulation pump discharge side path 22b to store the hot water in the hot water circulation path 23. It is configured by connecting the tank 21 side and the hot water circulating pump suction side path 22a. The operation of the switching valve 25 is controlled by the control device 29.

  The hot water circulating pump 22 may be a pump that can reverse the discharge direction of the pump. For example, the pump includes a switching valve 25, a hot water circulation pump suction side passage 22a, and a hot water circulation pump discharge side passage 22b. In this case, the operation of the switching valve 25 is replaced with a switching operation of the discharge direction of the hot water circulating pump 22.

(Modification 2)
FIG. 4 shows the hot water circulation path 23 according to the second modification of the first embodiment.

  As shown in FIG. 4, the modification 2 is a modification of the hot water circulation direction switching means of the first embodiment. That is, the configuration of the switching paths 23a ′ and 23b ′ is the same as that of the first embodiment, the switching path 23a ′ is connected to the hot water circulation path 23 at the position of the three-way valve 26a, and the switching path 23b at the position of the three-way valve 26b. 'Is connected to the hot water circulation path 23.

  Between the hot water outlet 14b of the heat exchanger 14 of the hot water circulation path 23 and the upper connection portion 21a of the hot water storage tank 21, the portion of the path 23a between the connection points of the replacement paths 23a 'and 23b' An on-off valve 28a is provided.

  Between the bottom connection part 21b of the hot water storage tank 21 and the hot water storage water inlet 14a of the heat exchanger 14 in the hot water circulation path 23, a part of the path 23b between the connection points of the exchange paths 23a 'and 23b' is opened and closed. A valve 27b is provided.

  An open / close valve 27a is disposed in the switching path 23a '.

  An open / close valve 28b is disposed in the switching path 23b '.

  The operation of the hot water circulation direction switching means configured as described above will be described.

  In FIG. 4, the circulation in the first circulation direction A is performed on the arrow A side in the drawing, that is, the hot water is transferred from the upper connection part 21 a of the hot water tank 21 via the switching path 23 a ′, The on-off valve 27a is opened so as to pass through the vessel 14, and the on-off valve 27b is closed, and the on-off valve 28b is opened so as to circulate to the bottom connection portion 21b of the hot water storage tank 21 via the switching path 23b ′. The on-off valve 28a is closed.

  Further, the circulation in the second circulation direction B is performed on the arrow B side in the drawing, that is, the hot water passes through the hot water tank 22 and the heat exchanger 14 via the path 23b from the bottom connection portion 21b of the hot water tank 21. Thus, the on-off valve 27b is opened, the on-off valve 27a is closed, and the on-off valve 28a is opened so as to circulate to the upper connection part 21a of the hot water storage tank 21 via the path 23a, and the on-off valve 28b is closed. Formed. These operations are controlled by the control device 29.

(Embodiment 2)
FIG. 1 is a schematic diagram showing a schematic configuration of a fuel cell cogeneration system according to Embodiment 2 of the present invention.

  The second embodiment is a fuel cell cogeneration system provided with a hot water storage heat exchanger bypass path 19 as an alternative to the cooling water heat exchanger bypass path 17 of the first embodiment. Therefore, only the parts different from the first embodiment will be described.

  The three-way valve 20 (hot water circulation path switching means) is disposed between the hot water temperature detecting means 24 and the hot water inlet 14 a of the heat exchanger 14. The port c1 of the three-way valve 20 is connected to the hot water circulating path 23 on the hot water temperature detecting means 24 side, the port c2 is connected to the hot water circulating path 23 on the hot water inlet 14a side of the heat exchanger 14, and the port c3 is connected to the port c3. The hot water storage water heat exchanger bypass path 19 is connected.

  Here, the hot water storage heat exchanger bypass path 19 connects the port a3 of the three-way valve 20 and the hot water circulation path 24 in the vicinity of the hot water outlet 14b of the heat exchanger 14 with the port a3 of the three-way valve 20 here. The stored hot water circulation path 24 is connected between the stored hot water outlet 14b and the stored hot water circulation direction switching means (specifically, the three-way valve 26b). Thereby, by switching the port connection of the three-way valve 20, the hot water circulation path is changed to the circulation path via the heat exchanger 14 (first hot water circulation path E) and the hot water storage heat exchanger bypass path 19 ( It is possible to switch to the second hot water storage water circulation path F).

  The operation of the fuel cell cogeneration system according to Embodiment 2 configured as described above will be described.

  FIG. 6 is a flowchart showing the operation of the fuel cell cogeneration system when the fuel cell 11 according to Embodiment 2 of the present invention is warmed up. In FIG. 6, the “cooling water circulation path switching means” in FIG. 2 is replaced with “hot water circulation path switching means”. In the following, parts different from FIG. 2 will be described.

  First, in step S2, the three-way valve 20 is switched so that the port c1 and the port c3 are connected, and the stored hot water does not pass through the heat exchanger 14 but passes through the stored hot water heat exchanger bypass path 19. It circulates (2nd hot water storage water circulation path F). Thus, immediately after the start of warm-up, the stored hot water bypasses the heat exchanger 14 until it is determined in step S8 that the detected temperature difference ΔT is greater than the first set temperature difference X.

  When the detected temperature difference ΔT is larger than the first set temperature difference X, in step S9, the three-way valve 20 is switched so that the port c1 and the port c2 are connected, and the stored hot water is used as the heat exchanger 14. (First cooling water circulation path E). As a result, the temperature difference between the hot water and the cooling water can be utilized to raise the temperature of the cooling water in the heat exchanger 14 and thus the temperature of the fuel cell 11 can be raised.

  Further, in step S17, when the detected temperature difference ΔT is equal to or smaller than the third set temperature difference Z, the three-way valve 20 is switched so that the port c1 and the port c3 are connected, and the path of the stored hot water is the second. It becomes hot water storage water circulation path F, and proceeds to step S18. Thereby, the temperature increase of the cooling water by heat exchange with the hot water storage is completed.

  When the fuel cell 11 generates power, the hot water circulates in the second circulating direction B through the first hot water circulation path E. At this time, the cooling water is heated by the fuel cell 11, passes through the cooling water passage 15, and is cooled by the hot water storage by the heat exchanger 14. Then, the hot water is heated in the heat exchanger 14 and returned to the hot water storage tank 21 from the upper connection portion 21a, and the laminated boiling is performed.

  The fuel cell cogeneration system according to the present invention is useful as a fuel cell cogeneration system with high energy efficiency.

It is a schematic diagram which shows schematic structure of the fuel cell cogeneration system which concerns on Embodiment 1 of this invention. 4 is a flowchart showing the operation of the fuel cell cogeneration system when the fuel cell according to Embodiment 1 of the present invention is warmed up. FIG. 7 is a schematic diagram showing a hot water circulation path according to a first modification of the first embodiment. FIG. 10 is a schematic diagram showing a hot water circulation path according to a second modification of the first embodiment. It is a schematic diagram which shows schematic structure of the fuel cell cogeneration system which concerns on Embodiment 2 of this invention. It is a flowchart which shows operation | movement of the fuel cell cogeneration system at the time of warming up of the fuel cell which concerns on Embodiment 2 of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Fuel cell 11a Cooling water inlet 11b Cooling water outlet 12 Cooling water circulation pump 13 Cooling water heater 14 Heat exchanger 14a Hot water inlet 14b Hot water outlet 14c Cooling water inlet 14d Cooling water outlet 15 Cooling water circulation path 16 Cooling water temperature detection means 17 Cooling water heat exchanger bypass path 18, 20 Three-way valve 19 Hot water storage heat exchanger bypass path c1, c2, c3 Port 21 Hot water storage tank 21a Upper connection part 21b Bottom connection part 22 Hot water circulation pump 22a Hot water circulation pump suction side installation path 22b Hot water storage water circulation pump discharge side mounting path 23 Hot water circulation path 23a Path 23a 'switching path 23b path 23b' switching path 24 Hot water temperature detection means 25 Switching valve 26a Three-way valve a1, a2, a3 Port 26b Three-way valve b1, b2, b3 Port 27a Open / close valve 27b Closed valve 28a Open / close valve 28b Open / close valve 29 Control device A (hot water) first circulation direction B (hot water) second circulation direction C first cooling water circulation path D second cooling water circulation path E first Hot water circulation path F Second hot water circulation path t Elapsed time t1 Predetermined time T1 Hot water detection temperature T2 Cooling water detection temperature ΔT Detection temperature difference X First set temperature difference Y Second set temperature difference Z Third setting Temperature difference

Claims (17)

A fuel cell;
A coolant circulation path through which coolant for maintaining the fuel cell at a predetermined temperature circulates;
Cooling water circulation means for circulating cooling water in the cooling water circulation path;
A heat exchanger disposed in the cooling water circulation path;
A hot water circulation path through which hot water for heat exchange with the cooling water circulates in the heat exchanger;
A hot water storage tank of a stacked boiling type disposed in the hot water circulation path;
Hot water circulation direction switching means for switching the circulation direction of the hot water between a first circulation direction for taking water from the upper part of the hot water storage tank and a second circulation direction for taking water from the bottom part of the hot water storage tank;
Hot water circulation means for circulating hot water in the hot water circulation path;
Cooling water temperature detection means for detecting the temperature of the cooling water at a predetermined cooling water temperature detection position;
Hot water storage temperature detecting means for detecting the temperature of the hot water stored at a predetermined hot water temperature detection position;
When the fuel cell is warmed up, the detected temperature difference between the hot water detection temperature detected by the hot water temperature detection means and the cooling water detection temperature detected by the cooling water temperature detection means is equal to or less than a first set temperature difference. In this case, the stored hot water circulates in the second circulation direction, and when the detected temperature difference is larger than the first set temperature difference, the stored hot water circulates in the first circulation direction. A fuel cell cogeneration system in which the hot water circulation direction switching means circulates the hot water.   The hot water circulation direction switching means circulates the hot water in the first circulation direction for a predetermined time from the start of warming up, and when the detected temperature difference is less than or equal to the first set temperature difference, The fuel cell cogeneration system according to claim 1, wherein the circulating direction of the hot water is switched to the second circulation direction.   2. The fuel cell cogeneration system according to claim 1, wherein the predetermined coolant temperature detection position is on the coolant circulation path between the coolant outlet of the fuel cell and the coolant inlet of the heat exchanger.   The predetermined hot water temperature detection position is on the hot water circulation path between the upper connection portion of the hot water storage tank and the heat exchanger in the first circulation direction or in the vicinity of the upper connection portion in the hot water storage tank. The fuel cell cogeneration system according to claim 1.   The predetermined time is at least one of a distance of the hot water circulation path between the hot water tank upper connection part and the hot water temperature detection means, a heat capacity of piping of the hot water circulation path, and a flow rate of the hot water. The fuel cell cogeneration system according to claim 2, wherein the fuel cell cogeneration system is configured to be set or changed in accordance with the above. A cooling water heater disposed in the cooling water circulation path;
The fuel cell cogeneration system according to claim 1, wherein the cooling water heater is operated when the detected temperature difference is equal to or less than the first set temperature difference. A cooling water heat exchanger bypass path disposed in the cooling water circulation path so that the cooling water circulates without passing through the heat exchanger;
A cooling water circulation path switching means for switching the cooling water circulation path to a first cooling water circulation path via the heat exchanger and a second cooling water circulation path via the cooling water heat exchanger bypass path; Prepared,
The cooling water circulates through the second cooling water circulation path, and when the detected temperature difference is larger than the first set temperature difference, the cooling water circulation path switching means moves the cooling water circulation path through the first cooling water. The fuel cell cogeneration system according to claim 6, wherein the fuel cell cogeneration system is switched to a water circulation path.   After the cooling water circulation path switching means switches the cooling water circulation path to the first cooling water circulation path, the cooling water heater operates when the detected temperature difference is equal to or smaller than a second set temperature difference. The fuel cell cogeneration system according to claim 7.   After the cooling water circulation path switching means switches the circulation path of the cooling water to the first cooling water circulation path, the third preset temperature difference smaller than the first preset temperature difference and the second preset temperature difference. The fuel cell cogeneration system according to claim 7, wherein the detected temperature difference is detected and calculated again when the detected temperature difference is large.   After the cooling water circulation path switching means switches the cooling water circulation path to the first cooling water circulation path, the cooling water circulation path switching means is provided when the detected temperature difference is equal to or smaller than the third set temperature difference. 10. The fuel cell core according to claim 9, wherein the cooling water circulation path is switched to the second cooling water circulation path, and the hot water circulation direction switching means switches the circulation direction of the hot water to the second circulation direction. Generation system. A hot water storage heat exchanger bypass path disposed in the hot water circulation path so that the hot water circulates without passing through the heat exchanger;
A hot water circulation path switching means for switching the hot water circulation path between the first hot water circulation path via the heat exchanger and the second hot water circulation path via the hot water heat exchanger bypass path; Prepared,
The stored hot water circulates in the second stored hot water circulation path, and when the detected temperature difference is larger than the first set temperature difference, the stored hot water circulation path switching means sets the stored hot water circulation path to the first stored hot water. The fuel cell cogeneration system according to claim 6, wherein the fuel cell cogeneration system is switched to a water circulation path.   After the hot water circulation path switching means switches the hot water circulation path to the first hot water circulation path, the cooling water heater operates when the detected temperature difference is equal to or smaller than a second set temperature difference. The fuel cell cogeneration system according to claim 11.   After the hot water circulation path switching means switches the hot water circulation path to the first hot water circulation path, the third preset temperature difference is smaller than the first preset temperature difference and the second preset temperature difference. The fuel cell cogeneration system according to claim 11, wherein the detected temperature difference is detected and calculated again when the detected temperature difference is large.   After the hot water circulation path switching means switches the hot water circulation path to the first hot water circulation path, when the detected temperature difference is not more than the third set temperature difference, the hot water circulation path switching means 14. The fuel cell core according to claim 13, wherein the hot water circulation path is switched to the second hot water circulation path and the hot water circulation direction switching means switches the hot water circulation direction to the second circulation direction. Generation system. A combustion apparatus for performing combustion treatment of surplus anode gas discharged from the fuel cell;
A combustion apparatus exhaust gas heat exchanger disposed in the hot water circulation path,
The fuel cell cogeneration system according to claim 1, wherein the combustion apparatus exhaust gas heat exchanger performs heat exchange between the exhaust gas of the combustion apparatus and the hot water storage.   Only after the hot water circulation direction switching means switches the circulation direction of the hot water to the second circulation direction, the combustion device exhaust gas heat exchanger performs heat exchange between the exhaust gas and the hot water. The fuel cell cogeneration system according to claim 15.   The fuel cell cogeneration system according to claim 15, wherein the combustion device is a combustion part of a reformer attached to the fuel cell.

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