JP5375119B2 - Cogeneration system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cogeneration system capable of surely preventing occurrence of a situation of excessive heat exchange heating in a preheating operation in starting an exhaust heat source applying a heat medium for heating as a heat source, while keeping high heat exchange efficiency in an exhaust heat recovering operation from the exhaust heat source such as a fuel cell to the heat medium for heating. <P>SOLUTION: The warm water circulated in a heating circulation circuit 4 and the cooling water of the fuel cell 2 circulated in an exhaust heat recovering circulation circuit 3 are made to exchange heat by a heat exchanger 5. A first thermomotive valve 47b is opened and a second thermomotive valve 45b is closed in an exhaust heat utilization heating operation by recovering exhaust heat from the cooling water, to heat the return warm water of low temperature in a return flow channel 47 by heat exchange based on countercurrent. The first thermomotive valve is closed, and the second thermomotive valve is opened in a start preheating operation of the fuel cell 2 to allow the water of high temperature from a high-temperature going passage 45 to flow to the heat exchanger with parallel flow, thus the excessive heat exchange heating to the cooling water can be suppressed. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention heats a heating heat medium by exchanging heat with exhaust heat generated by, for example, operation (power generation) of an exhaust heat source such as a fuel cell, and serves as a preheating heat source when the exhaust heat source such as a fuel cell is activated. The present invention relates to a cogeneration system that uses a heating heat medium, and in particular, to a technique that can reliably avoid an excessive increase in preheating temperature at the time of activation of a waste heat source such as a fuel cell with a simple configuration.

  2. Description of the Related Art Conventionally, a cogeneration system is known in which a heating medium is heated by heat exchange with exhaust heat generated by the operation of a fuel cell (see, for example, Patent Document 1). For this, jacket cooling is performed by flowing the return side heating heat medium whose temperature is lowered by heat radiation at the heating terminal and the jacket cooling water of the fuel cell so as to face the exhaust heat recovery heat exchanger. It is disclosed that the return side heating heat medium is heat exchange heated by exhaust heat of water.

  As another cogeneration system, there is known a system in which water in a hot water storage tank is heated by heat exchange with exhaust heat generated by the operation of a fuel cell and used for hot water supply (for example, patents). Reference 2). In this type, when the fuel cell is started, hot water in the hot water storage tank is reheated and burned and heated by a burner, and the heat energy of the heated high temperature water is absorbed by heat exchange to give the fuel cell side higher thermal energy. It is disclosed to do so.

Japanese Patent Laid-Open No. 2004-361028 JP 2002-42840 A

  By the way, in the case of heat exchange heating of a heating heat medium by exhaust heat recovery from an exhaust heat source such as a fuel cell, when the exhaust heat source such as a fuel cell is started, the exhaust heat source such as a fuel cell or the like is conversely used with the heating heat medium as a heat source. It is conceivable to preheat. In this case, in the heating heat exchanger, for example, the jacket cooling water which is the heat medium on the exhaust heat source side and the heating heat medium are mutually heat-exchanged to heat the heat medium on the exhaust heat source side with the heating heat medium. Become. At this time, in order to increase the heat exchange efficiency, the heating medium on the heat source side is desirably a higher temperature, and if the heating medium having a low temperature and a high temperature can be supplied, the heating medium having a high temperature can be used. The heating medium is supplied to the heating heat exchanger.

  However, when a high-temperature heating medium is used as a preheating heat source at the start of an exhaust heat source such as a fuel cell, excessively high temperature heat is generated with respect to the exhaust heat source such as a fuel cell depending on the operating condition on the heating side. There is a risk that the medium will be supplied, and in such a case, there is a risk of adversely affecting the durability of the functional component on the exhaust heat source side such as a fuel cell, for example, a pump.

  For example, as shown in FIG. 4, in the case of a normal exhaust heat utilization heating operation in which the heating medium is heat-exchanged and heated by exhaust heat from the fuel cell 2 as an exhaust heat source, the thermal valve 401 is opened. A low-temperature heating medium (see the dashed arrow) returned through the return flow path 402 after releasing heat from the heating terminal (not shown) flows from the inlet 404 of the heating heat exchanger 403 to the inside, while being connected to the fuel cell 2. The fuel cell side heat medium circulated in (1) is flowed into the heat exchanger 403 so as to be opposed to the heating heat medium. By the liquid-liquid heat exchange in the heat exchanger 403, the reaction heat generated by the operation (power generation) of the fuel cell 2 is recovered to the heating heat medium in the return flow path 402 via the fuel cell side heat medium. Will be. On the other hand, when the fuel cell 2 is started, the thermal valve 401 is closed, and instead, the thermal valve 405 is opened, and a high-temperature (for example, 80 ° C.) heating medium heated by combustion by a heat source device not shown is used. It switches so that it may flow in the heat exchanger 403 from the said inlet 404. FIG. Thereby, the fuel cell side heat medium cooled by the high temperature heating medium is heat exchange heated, and the fuel cell 2 is preheated by the fuel cell side heat medium. That is, in any case, the heat medium on the heat source side in the heat exchanger 403 and the heat medium on the heat exchange-heated side are caused to flow in opposite directions to increase the heat exchange efficiency. The If the fuel cell 2 is a polymer electrolyte fuel cell, it is necessary to preheat the fuel cell side heat medium heated to about 40 to 50 ° C. during circulation and to preheat it.

  However, in the preheating at the time of the above startup, if the heating terminal is in the operation stop state on the heating side, there is no heat dissipation of the heating medium, and if the combustion heating by the heat source machine is continued, the heat exchanger 403 has an excessive heat source. Therefore, it is necessary to add control measures such as intermittent combustion of the heat source machine, changing or adjusting the set temperature of combustion heating of the heat source machine, or lowering the heat medium temperature by mixed water. It will occur. In this case, particularly in the case of measures for stopping combustion or changing the combustion amount, there is a possibility that a heating medium having a high temperature of 80 ° C. or higher is circulated and supplied to the heat exchanger 403 due to factors such as overshoot. Further, as an example in which such a high-temperature heating medium having a temperature of 80 ° C. or higher is supplied to the heat exchanger 403, a high-temperature heating medium (for example, 80 ° C.) is supplied to the high-temperature heating terminal. This may also occur when the preheating operation at the start-up time of the fuel cell 2 overlaps when the heating operation is in progress and the heat radiation amount (heating load amount) at the heating terminal is relatively small. On the other hand, when considering structural measures other than taking complicated countermeasure control as described above, maintain high heat exchange efficiency in normal exhaust heat recovery operation so as not to impair heat exchange efficiency. Will be required. Such a situation is not limited to the case where the exhaust heat source is a fuel cell, but may also occur in other exhaust heat sources such as a gas engine.

  The present invention has been made in view of such circumstances, and an object thereof is to maintain high heat exchange efficiency in an exhaust heat recovery operation from an exhaust heat source such as a fuel cell to a heating medium. Another object of the present invention is to provide a cogeneration system that can surely avoid the occurrence of an excessive heat exchange heating in the preheating operation at the time of activation of an exhaust heat source such as a fuel cell using a heating heat medium as a heat source.

In order to achieve the above object, in the present invention, an exhaust heat recovery circuit that circulates a heat medium carrying exhaust heat from an exhaust heat source, and a heating heat medium circulated and supplied to a heating terminal as a heat radiation heat source A cogeneration system comprising: a heating circulation circuit; and a heating heat exchanger for exchanging heat between the exhaust heat source side heat medium flowing in the exhaust heat recovery circulation circuit and the heating heat medium flowing in the heating circulation circuit The following specific items were prepared for the target. That is, it is provided with a flow direction switching mechanism for switching the flow direction of the exhaust heat source side heat medium and the heating heat medium in the heating heat exchanger between a parallel flow and a counter flow, and the flow direction. In the start-up preheating operation at the start of the exhaust heat source that heat-exchanges and heats the exhaust heat source side heat medium using the heating heat medium as a heat source, the switching mechanism is switched to parallel flow, while the exhaust heat from the exhaust heat source side heat medium recovered by the waste heat utilization heating operation the heating heat medium heating the heat exchanger is configured to be switched controlled counterflow.

In the case of this specific matter , during the heating operation using exhaust heat, the heating heat medium recovers the exhaust heat efficiently and heats it based on the heat exchange by the counter flow in the heating heat exchanger. In the start-up preheating operation of the heat source, heat is exchanged in a state in which excessive heat exchange heating from the heating medium to the exhaust heat source side heat medium is suppressed based on heat exchange by parallel flow in the heating heat exchanger. Will get. As a result, while maintaining high heat exchange efficiency in the exhaust heat recovery operation from the exhaust heat source to the heating medium, excessive heat exchange heating is performed in the preheating operation when starting the exhaust heat source using the heating medium as the heat source. Therefore, it is possible to avoid occurrence of a situation that adversely affects the durability of various components on the exhaust heat source side. In addition, such an operation can be obtained by simple switching control without adding complicated control.

In addition, as the flow direction switching mechanism in the present invention, configured to switch to another and parallel flow and counter-flow by reversing the flow direction of the heating heat medium to the heat exchanger for the heating in each other. By doing in this way, supply of the heating heat medium to the heating heat exchanger and switching of the flow direction thereof can be easily realized.

In addition, in the present invention, as the heating circulation circuit, as a circulation flow path for the heating heat medium, a forward flow path for supplying the heating medium to the heating terminal, and a heating heat medium after the heat radiation at the heating terminal And a return flow path that returns from the heating terminal, and as the exhaust heat recovery circuit, the exhaust heat source side heat medium is moved from one end side to the other end side with respect to one internal flow path in the heating heat exchanger. connected to the heating heat exchanger back to the exhaust heat source after flow, and the flow direction switching mechanism specifically constructed as follows. That is, as the flow direction switching mechanism, the heating medium returned from the return flow path by bypassing the return flow path from the upstream branch point of the return flow path of the heating circulation circuit to the downstream junction point is heated. A return bypass passage that flows from the other end side to the one end side with respect to the other internal passage in the exchanger, a first on-off valve that opens and closes the return bypass passage, and a branch from the forward passage of the heating circulation circuit The branch forward flow path for flowing the heating medium supplied by the forward flow path from one end side to the other end side with respect to the other internal flow path of the heating heat exchanger, and switching the opening and closing of the branch forward flow path to the was configured with a second on-off valve (claim 1). By doing in this way, switching of the flow direction of the heating medium with respect to the heating heat exchanger can be realized concretely and easily.

The 1st on-off valve of this invention can be interposed in the return bypass flow path downstream from the one end side of the heat exchanger for heating (Claim 2 ). In this way, opening and closing of the return bypass flow path can be realized with certainty, and opening and closing of the branch forward flow path can be easily and reliably realized by simply interposing the second open / close valve in the branch forward flow path. Will be able to. For this reason, switching of the flow direction can be easily realized.

In the above case, as the switching control by the flow direction switching mechanism, in the startup preheating operation, the first on-off valve is switched to the closed state and the second on-off valve is switched to the open state, while the exhaust heat utilization heating operation is performed. opened the first on-off valve in the second on-off valve such that each switching control in the closed state, so that which can be realized by simple control (claim 3).

Furthermore, an auxiliary heat source device that heats the heating heat medium is provided as a heating circulation circuit, and the heating heat medium heated to a high temperature by the heating by the auxiliary heat source device is circulated and supplied to the high-temperature heating terminal as the circulation channel. A high-temperature forward flow path, and a low-temperature forward flow path that circulates a low-temperature heating medium to the low-temperature heating terminal, and the branch forward flow path is branched from the high-temperature forward flow path. (Claim 4 ). In this way, the exhaust heat source side heat medium in the start-up preheating operation can be quickly heat-exchanged with the heating medium heated to end the preheating, while the high-temperature heating is used as the heat source. Even if the heating medium is supplied, excessive heat exchange heating to the exhaust heat source side heat medium is suppressed, and the durability of various components on the exhaust heat source side is not adversely affected. In addition, since the branch outgoing flow path is branched from the high temperature outgoing flow path, the heating operation is performed on the heat exchanger for heating through the branch outgoing flow path regardless of the heating operation state on the heating circulation circuit side. It is possible to supply a heating medium having a more stably controlled temperature rather than a heating medium having a temperature that is influenced by the situation.

In the case of a configuration for supplying a high-temperature heating medium as described above, the exhaust heat recovery circuit is configured to include a storage tank interposed in a circulation channel through which the exhaust heat source side heat medium is circulated, In the reheating operation for forcibly heating the inside of the storage tank as the flow direction switching mechanism, the first on-off valve is switched to the closed state and the second on-off valve is switched to the open state, and heated by the auxiliary heat source machine. A high-temperature heating medium can be passed through the heating heat exchanger (claim 5 ). When such a reheating operation is executed, the heat source side heat medium is heat-exchanged and heated by a high-temperature heating medium, and the heat source side heat medium is circulated and supplied to the storage tank so that the inside of the storage tank is forcibly regenerated. It will be heated. Thereby, for example, even if the heat medium in the storage tank is not used for a long time, Legionella bacteria and the like can be inactivated.

A fuel cell can be used as an exhaust heat source in the above cogeneration system (Claim 6 ), and the fuel cell can be a solid polymer fuel cell (Claim 7 ). When a fuel cell is used, it is possible to generate power at a lower temperature, and preheating at start-up can be completed early.

As described above, according to the cogeneration system according to any one of claims 1 to 7 , in the case of heating operation using exhaust heat, heating is performed from an exhaust heat source such as a fuel cell based on heat exchange by a counter flow. While maintaining high heat exchange efficiency in the exhaust heat recovery operation to the heat medium, it is ensured that the exhaust heat source will experience excessive heat exchange heating based on the heat exchange by parallel flow during the startup preheating operation Therefore, it is possible to reliably avoid the occurrence of a situation that adversely affects the durability on the exhaust heat source side. Moreover, such an effect can be obtained by simple switching control without adding complicated control.

In addition, specific on the as possible out easily be realized switching supply and its flow direction of the heating heat medium, the switching of the flow direction of the heating heat medium for heating heat exchanger for heating heat exchanger Can be realized easily and easily.

Then, according to claim 2, branch just as well it is possible to reliably perform opening and closing of the return bypass passage according to claim 1, the second on-off valve interposed in the branch forward passage forward The flow channel can be opened and closed easily and reliably, and as a result, the flow direction can be easily switched. In addition, according to the third aspect , the switching of the flow direction by the flow direction switching mechanism can be realized by a simple control of switching the opening / closing of the first on-off valve or the second on-off valve.

Furthermore, according to the fourth aspect , the exhaust heat source side heat medium in the start preheating operation can be quickly heat-exchanged by the heating medium heated to finish preheating, while the high temperature heating is used as the heat source. Even if the heating medium is supplied, excessive heat exchange heating to the exhaust heat source side heat medium is suppressed and the durability of various components on the exhaust heat source side is not adversely affected. In addition, since the branch outgoing flow path is branched from the high temperature outgoing flow path, the heating operation is performed on the heat exchanger for heating through the branch outgoing flow path regardless of the heating operation state on the heating circulation circuit side. It becomes possible to supply a heating medium having a more stably controlled temperature, rather than a heating medium having a temperature that is affected by the situation.

On the other hand, according to the fifth aspect , the reheating operation can be executed, and the inside of the storage tank can be forcibly reheated by the execution of the reheating operation. Even if the heat medium is not used, Legionella bacteria and the like can be inactivated.

According to claim 6 , a cogeneration system can be constructed using a fuel cell as an exhaust heat source, and according to claim 7 , an optimum cogeneration system is constructed using a polymer electrolyte fuel cell as the fuel cell. can do.

It is a mimetic diagram showing a 1st embodiment of the present invention. It is a schematic diagram which shows 2nd Embodiment. It is a schematic diagram which shows 3rd Embodiment. It is a partial view of the assumed cogeneration system contrasted with this invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

<First Embodiment>
FIG. 1 shows a cogeneration system according to a first embodiment of the present invention, wherein reference numeral 2 denotes a fuel cell as an exhaust heat source, 3 denotes an exhaust heat recovery circuit for recovering exhaust heat from the fuel cell 2 and storing hot water, 4 A heating circulation circuit 5 for realizing a hot water circulation heating function using hot water as a heating heat medium is a heating heat exchanger for exchanging heat between the exhaust heat recovery circulation circuit 3 and the heating circulation circuit 4. . This uses the exhaust heat recovered from the fuel cell 2 for heat exchange heating of the warm water for heating in the heating circuit 4, while the warm water for heating is used as a heat source for preheating the fuel cell 2 when the fuel cell 2 is started up. System.

  The fuel cell 2 is composed of, for example, a polymer electrolyte fuel cell (PEFC), and recovers exhaust heat generated by generating power by heat exchange with cooling water to generate hot water. Then, the operation of the circulation pump 21 provided on the fuel cell 2 side circulates the cooling water that has become hot water to the exhaust heat recovery circuit 3. This cooling water is a fuel cell-side heat medium, and tap water supplied to and stored in a storage tank 31 described later is used as the cooling water.

  The exhaust heat recovery / circulation circuit 3 includes, as a basic component, a circulation channel 32 that circulates cooling water as a fuel cell side heat medium between the storage tank 31 and the fuel cell 2. Then, the water (tap water) supplied / stored in the storage tank 31 is used as the cooling water, and the water is made into hot water by the exhaust heat recovery from the fuel cell 2 and stored in the storage tank 31 to recover the water. The exhaust heat is stored. A water supply flow path 33 from an external water supply source is connected to the bottom of the storage tank 31, and a discharge flow path 34 for use in hot water supply or the like is connected to the top. The circulation flow path 32 includes a heat medium forward flow path 36 that goes from the fuel cell 2 through the heating heat exchanger 5 and the hot water storage switching valve 35 to the top of the storage tank 31, and a circulation pump 21 from the bottom of the storage tank 31. And a non-tank circulation passage 38 that branches from the hot water storage switching valve 35 and communicates with the heat medium return passage 37 without passing through the storage tank 31. Yes. Then, if the storage tank 31 side of the hot water storage switching valve 35 is communicated and the non-tank circulation flow path 38 side is shut off (tank communication state), the cooling water flows between the fuel cell 2 and the storage tank 31. If the storage tank 31 side of the hot water switching valve 35 is shut off and the non-tank circulation flow path 38 side is connected (tank cutoff state), the fuel is not passed through the storage tank 31. Cooling water is circulated between the battery 2 and the heating heat exchanger 5 (non-tank circulation).

  Here, the heating heat exchanger 5 is a liquid-liquid heat exchanger that performs liquid-liquid heat exchange between the cooling water flowing in one internal flow path and the warm water for heating flowing in the other internal flow path. It is configured as. And the heat-medium going flow path 36 is the other end from the one end (left end of FIG. 1) 51 side with respect to the one internal flow path in the heat exchanger 5 for the cooling water which flows through this heat-medium going flow path 36. (The right end of the figure) It is connected to the heating heat exchanger 5 so as to flow toward the 52 side. In FIG. 1 or other drawings, the heating heat exchanger 5 is illustrated so as to extend in the left-right direction of the drawing, but is not limited thereto, and may be disposed so as to extend in the vertical direction. The one end and the other end are the upper end or the lower end. Hereinafter, the “left end” or “right end” is displayed along the illustrated one.

  The heating circulation circuit 4 passes through the auxiliary heat source 41 for backup that heats and heats the circulating hot water using combustion heat, and the heating heat exchanger 5, and is connected to a low-temperature heating terminal or a high-temperature heating terminal that is not shown in the drawing. A circulation channel 42 for circulating hot water between the two is provided. The circulation flow path 42 sends low temperature water returned to the expansion tank 43 and stored to the auxiliary heat source unit 41 by the operation of the circulation pump 44 for heating, and the high temperature water heated by combustion here is sent to the high temperature flow path 45. To a high-temperature heating terminal (for example, a bathroom dryer) outside the figure. Further, by the operation of the circulation pump 44, the low-temperature water in the expansion tank 43 is supplied to a low-temperature heating terminal (for example, a floor heater) (not shown) via the low-temperature forward flow path 46, and the high-temperature heating described above. The low-temperature water, which has become low temperature due to heat radiation from all the heating terminals such as terminals and low-temperature heating terminals, is circulated in such a manner as to return to the expansion tank 43 through the return flow path 47.

  The return flow path 47 branches to the return bypass flow path 47a before returning to the expansion tank 43 and passes through the heating heat exchanger 5, or without passing through the heating heat exchanger 5. It returns to the expansion tank 43 as it is. That is, a return bypass channel 47a is attached to the return channel 47, and the return bypass channel 47a bypasses the return channel 47 between the upstream branch point d1 and the downstream junction point d2, and is in the middle. Are formed so as to pass through the heat exchanger 5 for heating. Specifically, the return bypass flow path 47a causes the return hot water diverted from the branch point d1 at the upstream position to flow from the right end 53 to the other internal flow path in the heating heat exchanger 5 and from the right end 53 to the left end 54. The return warm water flowing out from the left end 54 after flowing into the flow path is joined to the return flow path 47 at the downstream junction point d2. In addition, a first thermal valve 47b as a first on-off valve is interposed downstream of the return bypass passage 47a and between the left end 54 of the heating heat exchanger 5 and the junction d2. .

  Further, a high temperature branch forward flow path 45a branched from a branch point d3 in the middle of the high temperature forward flow path 45 is connected to the left end 54 of the heating heat exchanger 5, and the high temperature branch forward flow path 45a has a second opening and closing. A second thermal valve 45b as a valve is interposed. The flow direction of the hot water for heating flowing through the other internal flow path of the heat exchanger 5 for heating is determined by the high temperature branch forward flow path 45a, the second thermal valve 45b, the return bypass flow path 47a, and the first thermal valve 47b. A flow direction switching mechanism 10 for reversing each other is configured.

  The above cogeneration system is controlled by a controller (control means) not shown. As the operation control, when the fuel cell 2 is in the power generation operation (power generation) and when there is a heating operation request, the exhaust heat of the fuel cell 2 is recovered and heating hot water is used as the normal operation control. Waste heat utilization heating operation control used for heat exchange heating of the fuel cell, and startup preheating operation control for preheating the fuel cell 2 using the warm water for heating as a heat source when the power generation operation of the fuel cell 2 is started from the stop state. And storage tank reheating operation control that reheats (boils) the inside of the storage tank 31 as a countermeasure against Legionella in the absence of a long period of time.

  In the exhaust heat utilization heating operation control, the hot water storage switching valve 35 is switched to the tank shutoff state and the circulation pump 21 is operated with the heat medium circulation passage 32 being non-tank circulation, while the first thermal valve 47b is opened. The second thermal valve 45b is converted into a closed state. As a result, the cooling water whose temperature has risen in the fuel cell 2 flows from the left end 51 to the right end 52 with respect to the heating heat exchanger 5 (refer to the dashed line arrow in FIG. 1), while the low temperature return returned from the return flow path 47. The warm water returns to the bypass passage 47a and flows from the right end 53 to the left end 54 with respect to the heating heat exchanger 5 (see the broken arrow in the figure). For this reason, in the heating heat exchanger 5, the liquid-liquid heat exchange is performed while the cooling water and the return warm water flow in opposite directions, and the return warm water is used for the liquid-liquid heat exchange by the opposite flow. Based on this, heat is exchanged efficiently. If the temperature of the cooling water discharged from the right end 52 of the heating heat exchanger 5 has not dropped to a predetermined temperature even after the return hot water has been subjected to heat exchange heating, the hot water storage switching valve 35 is connected to the tank. Alternatively, it is desirable to switch to an intermediate switching state that communicates with the storage tank 31 and at the same time communicates with the non-tank circulation flow path 38 and can be diverted to both, and exchanges heat with the stored hot water in the storage tank 31 or mixes it with a predetermined temperature ( For example, the temperature may be lowered to 45 ° C. or lower and then returned to the fuel cell 2.

  In the startup preheating operation control, the hot water storage switching valve 35 is switched to the tank shut-off state and the circulation pump 21 is operated with the heat medium circulation passage 32 being non-tank circulation, while the first thermal valve 47b is closed. The second thermal valves 45b are each converted to an open state. As a result, the cooling water cooled to a low temperature during the operation stop flows from the left end 51 to the right end 52 with respect to the heating heat exchanger 5 (see the one-dot chain line arrow in FIG. 1), while the high temperature from the high temperature branch forward flow path 45a. After water flows from the left end 54 to the right end 53 with respect to the heating heat exchanger 5, it returns to the expansion tank 43 through the upstream portion of the return bypass flow path 47a and the return flow path 47 (the solid line in the figure). See arrow). For this reason, in the heat exchanger 5 for heating, liquid-liquid heat exchange is performed while the cooling water and the high-temperature water flow in parallel with each other, and the cooling water is heat-exchanged and heated by the high-temperature water. However, excessive heating based on liquid-liquid heat exchange by parallel flow is avoided. For example, while the circulating flow rate of the cooling water in the heat medium circulation channel 32 is 30 ° C. at 1 L / min, the circulating flow rate of the high-temperature water from the high temperature branch flow channel 45 a is 10 L / min and usually 80 ° C. However, consider the case where the flow is slightly overflowing at 85 ° C. In this case, the temperature of the cooling water after heat exchange heating is 80 ° C. [(85 × 10 + 30 × 1) / ( 10 + 1) = 80], and in the case of a counter flow, the cooling water is excessively heated compared to the fact that the cooling water is heated to a temperature close to the heat source side temperature (85 ° C.). It becomes possible to avoid heat exchange heating. Thereby, the durability of the functional components on the fuel cell 2 side such as the circulation pump 21 can be favorably maintained without adversely affecting the durability.

  In the reheating operation control, the hot water storage switching valve 35 is switched to the tank communication state and the circulation pump 21 is operated in a state where the heat medium circulation passage 32 is circulated between the tanks. The thermal valve 47b is converted into a closed state, and the second thermal valve 45b is converted into an open state. Thereby, the cooling water heated by the high-temperature water in the heating heat exchanger 5 is supplied to the storage tank 31, and the inside of the storage tank 31 is boiled up to a temperature (for example, 60 ° C. or more) that can inactivate Legionella bacteria. Can do.

  In short, by providing the flow direction switching mechanism 10, the heat exchange in the heating heat exchanger 5 can be switched between the heat exchange by the counter flow and the heat exchange by the parallel flow. Thus, in the start-up preheating operation of the fuel cell 2 using the warm water for heating as the heat source while maintaining high heat exchange efficiency in the exhaust heat utilization heating operation in which the warm water for heating is heat exchange heated by the exhaust heat of the fuel cell 2. It is possible to reliably avoid the occurrence of a situation of excessive heat exchange heating.

Second Embodiment
FIG. 2 shows a cogeneration system according to the second embodiment of the present invention. The second embodiment corresponds to a more specific configuration of the first embodiment. That is, in the second embodiment, in addition to the configuration of the first embodiment, the hot water supply circuit 6 that heats the premixed water that is mixed with the hot water stored in the storage tank 31 and temperature-controlled, and heated, And a bath reheating circuit 7 that performs liquid-liquid heat exchange heating using high-temperature water heated by the auxiliary heat source device 41, and a latent heat recovery function is added as the hot water supply heat source device 61 of the auxiliary heat source device 41 and the hot water supply circuit 6. A high-efficiency type is used. In addition, the same code | symbol as 1st Embodiment is attached | subjected to the thing of the same structure as 1st Embodiment, the detailed description which overlapped is abbreviate | omitted, and a different point is demonstrated.

  The hot water supply circuit 6 includes a hot water supply heat source device 61, a premixed water supply passage 62 for supplying the premixed water supply to the hot water supply heat source device 61, and a hot water supply flow for supplying hot water heat-exchanged by the hot water supply heat source device 61. Road 63 is provided. The hot water supply heat source device 61 includes a primary heat exchanger 65 that mainly heats by sensible heat accompanying combustion of the combustion burner 64, and a secondary heat exchanger 66 that recovers latent heat from the combustion exhaust gas and preheats the premixed water supply. The flow path 62 is configured so that the premixed feed water is first preheated by passing it through the secondary heat exchanger 66 and then passed through the primary heat exchanger 65. Further, in the middle of the hot water supply flow path 63, a mixed water supply flow path 67 branched from the water supply flow path 33 of the exhaust heat recovery circulation circuit 3 is joined, and mixed water is used for the hot water from the primary heat exchanger 65. The water supply from the water supply channel 67 is mixed to adjust the temperature to the set hot water supply temperature. Further, a pouring circuit 8 branched from the hot water supply passage 63 located downstream of the confluence of the mixed water supply water passage 67 is connected to the bath reheating circuit 7, and the hot water supply passage 63 passes through the pouring circuit 8. Hot water can be poured into the bathtub 71.

  The bath reheating circuit 7 is configured such that a bath heater 72 as a liquid-liquid heat exchange type heating unit is interposed in a reheating circulation channel 75 including a bath return channel 73 and a bath flow channel 74. The bath water taken out from the bathtub 71 through the bath return flow path 73 by the operation of the recirculation circulation pump 76 is sent to the bath heater 72, and is branched and supplied from the high temperature forward flow path 45 of the heating circulation circuit 4 in the bath heater 72. The hot water is reheated by liquid-liquid heat exchange using high-temperature water as a heat source, and the bath water after reheating is sent to the bathtub 71 through the forward flow path 74.

  The auxiliary heat source device 41 of the heating circulation circuit 4 is similar to the hot water supply heat source device 61, the primary heat exchanger 48 that mainly heats by the sensible heat accompanying the combustion of the combustion burner 41a, and the secondary heat source 48 that collects and preheats the latent heat from the combustion exhaust gas. And a secondary heat exchanger 49. Then, the return warm water returned by the return flow path 47 is first preheated through the secondary heat exchanger 49 and then returned to the expansion tank 43, and the hot water taken out from the expansion tank 43 is heated through the primary heat exchanger 48. The high-temperature water thus supplied is supplied to the high-temperature forward flow path 45.

  Further, reference numeral 91 in FIG. 2 is a high-temperature heating terminal, and 92 is a low-temperature heating terminal, both of which return to the return flow path 47 as return hot water after heat radiation. The exhaust heat recovery circulation circuit 3 branches from the heat medium flow path 36 at a position in front of the heating heat exchanger 5, and the heat medium flow path at an intermediate position between the hot water switching valve 35 and the storage tank 31. 36 is connected to a heat medium bypass flow path 39, and the heat medium bypass flow path 39 opens the electromagnetic valve 39 a interposed in the middle, thereby cooling the cooling water from the fuel cell 2 to the heat exchanger for heating. 5 and the heat medium bypass passage 39 can be shunted.

  Also in the second embodiment, the same operation control as in the first embodiment, that is, the exhaust heat utilization heating operation control, the startup preheating operation control, and the storage tank reheating operation control are not shown in the figure (controller). The operation is controlled by. And by providing the same operation effect as what was explained by a 1st embodiment, ie, flow direction change mechanism 10, heat exchange in heating heat exchanger 5 is based on heat exchange by counterflow, and parallel flow. It becomes possible to switch to heat exchange, and thereby, while maintaining high heat exchange efficiency in the exhaust heat utilization heating operation in which the hot water for heating is heat exchange heated by the exhaust heat of the fuel cell 2, the hot water for heating is maintained. In the start-up preheating operation of the fuel cell 2 using as a heat source, it is possible to reliably avoid the occurrence of a situation in which excessive heat exchange heating occurs. As operation control other than the operation control described in the first embodiment, hot water storage operation control to the storage tank 31, that is, cooling water from the fuel cell 2 is circulated between the storage tank 31 and the fuel cell 2 is discharged. When performing operation control for storing heat as hot water in the storage tank 31 by heat recovery, the cooling water from the fuel cell 2 is divided into both the heating heat exchanger 5 and the heat medium bypass passage 39. At the same time, both the first thermal valve 47b and the second thermal valve 45b (the first thermal valve 47b and the second thermal valve 46b in the third embodiment described later) on the heating circulation circuit 4 side are closed. Switch to the state. By doing in this way, it can avoid that the exhaust heat which the cooling water of the fuel cell 2 has is radiated to the heating circulation circuit 4 side via the heating heat exchanger 5, and the heating circulation circuit 4 can be avoided. The hot water storage operation by exhaust heat recovery can be efficiently performed by preventing the heat radiation loss to the side.

<Third Embodiment>
FIG. 3 shows a cogeneration system according to the third embodiment of the present invention. The third embodiment includes a flow direction switching mechanism 10a according to a modification of the flow direction switching mechanism 10 in the first embodiment. The other configurations of the third embodiment are the same as those of the first embodiment, and the same configurations as those of the first embodiment are denoted by the same reference numerals as those of the first embodiment, and detailed description thereof is omitted and different. Add a description of the points.

  The flow direction switching mechanism 10a is a low temperature branched from a branch point d4 in the middle of the low temperature forward flow path 46 instead of the high temperature branch forward flow path 45a and the second thermal valve 45b in the flow direction switching mechanism 10 of the first embodiment. The branch forward flow path 46a is connected to the left end 54 of the heating heat exchanger 5, and the low temperature branch forward flow path 46a is provided with a second thermal valve 46b as a second on-off valve. The low temperature branch forward flow path 46a, the second thermal valve 46b, the return bypass flow path 47a, and the first thermal valve 47b constitute a flow direction switching mechanism 10a for warm water for heating. That is, in the heat exchanger 5 for heating, the object to be flowed in parallel with the cooling water from the fuel cell 2 is not the high-temperature water in the first embodiment but the low-temperature water in the third embodiment.

  In the case of the third embodiment, the exhaust heat utilization heating operation control is performed in the same manner as described in the first embodiment, and the return hot water is heated with high heat exchange efficiency based on the liquid-liquid heat exchange by the counter flow. be able to. Further, in the start preheating operation control, the hot water storage switching valve 35 is switched to the tank shutoff state and the circulation pump 21 is operated with the heat medium circulation passage 32 being non-tank circulation, while the first thermal valve 47b is closed. The second thermal valve 46b is converted into an open state. As a result, the cooling water cooled to the low temperature state during the operation stop flows from the left end 51 to the right end 52 with respect to the heating heat exchanger 5 (see the arrow of the one-dot chain line in FIG. 3), and expands through the low temperature branch forward flow path 46a. The low-temperature water supplied from the tank 43 flows from the left end 54 to the right end 53 with respect to the heating heat exchanger 5 and then returns again to the expansion tank 43 through the upstream side of the return bypass passage 47a and the return passage 47. (See the solid arrow in the figure). Also in this case, since the low temperature water from the expansion tank 43 is about 50 ° C., for example, the lower limit temperature (for example, 35 ° C.) of the preheating required when starting the fuel cell 2 by heat exchange heating of the cooling water using this low temperature water The above heat can be applied to the fuel cell 2.

  Therefore, if it is not necessary to perform reheating operation control for the storage tank 31 using high temperature water, low temperature water can be used as a heat source for heat exchange heating of the cooling water by the parallel flow in the heating heat exchanger 5. .

<Other embodiments>
The present invention is not limited to the first to third embodiments described above, but includes other various embodiments. That is, the heating heat exchanger 5 used in each of the above embodiments may be a liquid-liquid heat exchanger, and is not limited to the illustrated example. Further, the cogeneration system can be configured by replacing the fuel cell 2 in each of the above embodiments with another exhaust heat source. For example, a gas engine can be used as an exhaust heat source, and in this case, cooling water of the gas engine can be used as an exhaust heat source side heat medium.

  In addition to warm water, oil, antifreeze, or the like can be used as the heating medium in the above embodiments. Further, if the configuration for storing hot water for drinking water in the storage tank 31 is omitted, the above-described oil, antifreeze or the like is used in addition to the cooling water as the heat medium on the fuel cell side where the exhaust heat of the fuel cell 2 is carried. Can do.

  Furthermore, in each said embodiment, although the flow direction switching mechanisms 10 and 10a for switching the flow direction of the warm water for heating with respect to the heat exchanger 5 for a heating were shown, not only this but the flow direction of the warm water for heating is predetermined. Instead of changing the flow direction in one direction, a flow direction switching mechanism for switching the flow direction of the cooling water, which is the heat medium on the fuel cell side, to the heating heat exchanger 5 is switched between forward and reverse. May be.

  INDUSTRIAL APPLICABILITY The present invention can be used as a household or industrial combined heat and power supply system, and in particular, can obtain both power generation by the fuel cell 2 and the like and heating by the heating circulation circuit 4. Is available.

2 Fuel cell (exhaust heat source)
3 Heat recovery circuit 4 Heating circuit 5 Heating heat exchanger 10, 10a Flow direction switching mechanism 31 Reservoir tank 42 Heating hot water circulation channel 45 High temperature forward channel 46 Low temperature forward channel 47 Return channel 45a High temperature Branch / outward flow path 45b Second thermal valve (second on-off valve)
46a Low temperature branch outgoing flow path 46b Second thermal valve (second on-off valve)
47a Return bypass passage 47b First thermal valve (first on-off valve)
d1 Upstream branch point d2 Downstream junction

Claims (7)

An exhaust heat recovery circuit that circulates a heat medium carrying exhaust heat from an exhaust heat source, a heating circuit that circulates and supplies the heating medium as a heat dissipation heat source to the heating terminal, and the exhaust heat recovery circuit A cogeneration system comprising a heating heat exchanger for exchanging heat between an exhaust heat source side heating medium flowing through the heating medium and a heating heating medium flowing through the heating circulation circuit,
A flow direction switching mechanism for switching the flow direction of the exhaust heat source side heat medium and the heating heat medium in the heating heat exchanger to a parallel flow and a counter flow;
The flow direction switching mechanism is controlled to be switched to parallel flow in the startup preheating operation at the time of startup of the exhaust heat source that heats and heats the exhaust heat source side heat medium using the heating heat medium as a heat source. In the exhaust heat utilization heating operation for heat exchange heating of the heating medium by exhaust heat recovery of, it is configured to be controlled to switch to the counter flow, and
The flow direction switching mechanism is configured to mutually switch between a parallel flow and a counter flow by reversing the flow directions of the heating medium with respect to the heating heat exchanger.
The heating circulation circuit includes, as a heating heat medium circulation flow path, a forward flow path for supplying the heating heat medium to the heating terminal, and a return flow for returning the heating heat medium after heat radiation at the heating terminal from the heating terminal. Road and
The exhaust heat recovery circulation circuit includes a heating heat exchanger such that the exhaust heat source side heat medium flows from one end side to the other end side with respect to one internal flow path in the heating heat exchanger and then returns to the exhaust heat source. Connected,
The flow direction switching mechanism bypasses the return flow path from the upstream branch point of the return flow path of the heating circulation circuit to the downstream merge point, and exchanges the heating heat medium returned by the return flow path for heating. A return bypass flow channel that flows from the other end side to the one end side relative to the other internal flow channel in the chamber, a first on-off valve that switches the return bypass flow channel, and a forward flow channel of the heating circulation circuit. A branch forward flow path for flowing the heating medium supplied by the forward flow path from one end side to the other end side with respect to the other internal flow path of the heating heat exchanger, and opening / closing switching of the branch forward flow path that is configured and a second on-off valve,
Co over generator system, characterized in that. The cogeneration system according to claim 1 ,
The first on-off valve is a cogeneration system that is interposed in a return bypass flow path downstream of one end side of the heating heat exchanger. The cogeneration system according to claim 1 or 2 ,
The flow direction switching mechanism switches the first on-off valve to the closed state and the second on-off valve to the open state in the startup preheating operation, and opens the first on-off valve in the exhaust heat utilization heating operation. And a cogeneration system configured to control each of the second on-off valves to be closed. A cogeneration system according to any one of claims 1 to 3,
The heating circulation circuit includes an auxiliary heat source device that heats the heating heat medium, and circulates and supplies the heating heat medium heated to the high temperature by the heating by the auxiliary heat source device to the high temperature heating terminal as the circulation channel. A high-temperature flow path and a low-temperature flow path that circulates a low-temperature heating medium to the low-temperature heating terminal,
A cogeneration system in which the branch outgoing channel is branched from the high temperature outgoing channel. The cogeneration system according to claim 4 ,
The exhaust heat recovery circuit includes a storage tank interposed in a circulation channel through which the exhaust heat source side heat medium is circulated,
In the reheating operation for forcibly heating the inside of the storage tank, the flow direction switching mechanism is controlled by switching the first on-off valve to the closed state and the second on-off valve to the open state, and is heated by the auxiliary heat source unit. A cogeneration system configured to flow a high-temperature heating medium through a heating heat exchanger. The cogeneration system according to any one of claims 1 to 5 ,
A cogeneration system in which the exhaust heat source is a fuel cell. The cogeneration system according to claim 6 ,
The fuel cell is a solid polymer fuel cell, a cogeneration system.

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