JP2010071091A - Composite power generation system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enhance thermal energy utilization efficiency of the whole composite power generation system by efficiently distributing to power generation and heat demand destination the exhaust heat supplied to a binary power generation device from a fuel cell power generation device. <P>SOLUTION: In a composite power generation system which generates power by transmitting discharge heat of a fuel cell power generating device to a binary power generation device 11 by combining a phosphate type fuel cell power generating device 1 and a binary power generation device 11, the binary power generation device keeps a heat exchanger 18 between an outlet in a turbine 12 and a condenser 17 at a rear stage to utilize heat recovered from working fluid through the heat exchanger in the heat demand destination by a water heater or the like, and includes two outlets having different steam pressure and a flow rate adjusting valve 19 connected thereto as a means for adjusting turbine outlet pressure. When the heat demand supplying heat to the heat demand destination through the heat exchanger 18 is small, the turbine outlet pressure is set lower to enhance power generating output. When the heat demand is large, the turbine outlet pressure is set higher to lower the power generating output. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  This invention combines a phosphoric acid fuel cell power generator with a binary power generator that uses a low-boiling point medium such as pentane, isopentane, hexane, and ammonia as a working fluid, and inputs the exhaust heat of the fuel cell power generator to the binary power generator. The present invention relates to a combined power generation system that drives a turbine.

  The phosphoric acid fuel cell mentioned above is being put to practical use as an on-site type cogeneration system.

  As is well known, in a phosphoric acid fuel cell, a raw fuel such as city gas or LP gas is reformed into a hydrogen-rich fuel gas by a reformer, and the fuel gas and air are converted into a fuel electrode of the fuel cell body. , Electricity is generated by supplying each to the air electrode. The operating temperature of this phosphoric acid fuel cell is around 200 ° C., and hot water at around 90 ° C. (hereinafter referred to as “hot water”) as heat output by exhaust heat recovery of the fuel cell power generator and hot water at around 50 ° C. (Hereinafter referred to as “low temperature water”), the “high temperature water” obtained by exhaust heat recovery of the fuel cell power generation device is used for heating, hot water supply, cooling using an absorption refrigerator, and the like. Moreover, the cogeneration system utilized for hot water supply has already been put into practical use for “low temperature water” (for example, see Non-Patent Document 1).

  By the way, the heat demand used for heating and cooling varies greatly depending on the season. In addition, depending on the customer, the amount of heat required is small, and the amount of heat supplied from the fuel cell power generator may always exceed the heat demand and become excessive. Such an imbalance between heat demand and heat supply reduces the energy utilization efficiency of the fuel cell power generation device and leads to a loss of economic efficiency as a cogeneration system.

  On the other hand, since electricity is energy that is highly usable compared to heat, the energy efficiency and economic efficiency of the fuel cell power generator can be further improved by generating power using the exhaust heat of the fuel cell power generator. In this respect, binary power generation using a low-boiling point medium such as hydrocarbon or ammonia as a working fluid can generate power by driving a turbine with a working fluid vaporized using a low-temperature heat source. A combined power generation technique that performs binary power generation using exhaust heat as a heat source has been proposed (see, for example, Patent Document 1 and Patent Document 2).

  Next, FIG. 4 shows a flow sheet of a phosphoric acid fuel cell cogeneration system that is currently in practical use. In FIG. 4, 1 is a phosphoric acid fuel cell power generator, 2 is a fuel reformer, 2a is a burner, 3 is a fuel cell stack, 3a, 3b, and 3c are a fuel electrode, an air electrode, and a water-cooled cooling plate, respectively. is there. The structure and function of the fuel reformer 2 and the fuel cell stack are well known, and detailed description thereof is omitted here.

  In the illustrated cogeneration system, the heat exchanger 4 is provided in the cooling water circulation circuit of the cooling plate 3c and passes through the cooling plate 3c in order to recover and use the exhaust heat of the fuel cell power generation device 1 Water heated by heat exchange with the high-temperature cooling waste water A is supplied to the heat demand destination (heat utilization equipment) from the secondary side pipe 4a of the heat exchanger 4, and heating, hot water supply, or an absorption refrigerator is used. It is used for air conditioning.

  The air electrode exhaust gas B that has passed through the air electrode of the fuel cell stack 3 and the combustion exhaust gas C of the burner 2a of the fuel reformer 2 are guided to a water recovery device (gas-liquid separator) 5 for gas-liquid separation. The exhaust gas is discharged out of the system, and the water collected here is a heat exchanger 8 inserted into the cooling water circulation circuit of the fuel cell stack cooling plate 3c through the flow rate adjusting valve 7, and a heat exchanger 9 for heat recovery. The low-temperature water that is sent to the heat exchanger 9 and heat-exchanged by the heat exchanger 9 is supplied to the heat demand destination from the secondary side pipe 9a and used for heat. In the figure, reference numeral 6 denotes a heat radiator attached to the water recovery unit 5, and 10 denotes a heat exchanger attached to the burner 2a of the fuel reformer 2 to preheat combustion air and burner fuel.

In the fuel cell cogeneration system described above, the cooling drainage A that has passed through the cooling plate 3c of the fuel cell stack 3 passes through the heat exchangers 4, 8, and 9, assuming that the power generation output of the phosphoric acid fuel cell power generation device 1 is 100 kW. Heat amounts of 40 kW and 90 kW are transferred to the secondary sides of the heat exchangers 4 and 9, respectively, and "high temperature water" and "low temperature water" recovered by the heat exchanger are supplied to the heat demand destination and used. Further, after removing moisture from the air electrode exhaust gas B and the combustion exhaust gas C by the water recovery device 5, exhaust heat 82 kW is released to the outside (atmosphere side) through the radiator 6. In the operation state in which the heat demand is reduced and the heat recovery amount from the heat exchangers 4 and 9 is almost zero, the retained heat amount 90 kW of the cooling waste water A is discharged out of the system through the radiator 6 in order to perform heat treatment. The maximum amount of heat radiation is 172 kW (82 kW + 90 kW).
Product catalog "Fuel cell power generation system", [online], March 2004, Fuji Electric Systems Co., Ltd. [Search June 13, 2008], Internet <URL: HYPERLINK "http://www.fesys.co .jp / sougou / seihin / p27 / pdf / K106b.pdf "www.fesys.co.jp/sougou/seihin/p27/pdf/K106b.pdf> Japanese Utility Model Publication No. 5-12603 (FIG. 2) JP 2005-133702 A

  Although Patent Document 1 and Patent Document 2 disclose the basic configuration of a combined power generation system that performs binary power generation using the exhaust heat of the fuel cell, the waste heat of the system is recovered and used for hot water supply or the like. There is no disclosure about generation, and all the thermal energy that was not converted into electric power by the binary power generator that generates electricity using the exhaust heat of the fuel cell power generator as the heat source is released from the condenser of the binary power generator to the outside of the system. Yes.

  On the other hand, a combined power generation system is configured by combining the binary power generation device disclosed in Patent Documents 1 and 2 with the cogeneration system of the fuel cell power generation device described in FIG. 4, and a part of the exhaust heat of the fuel cell power generation device is recovered. In the case of generating electricity by supplying the remainder of the exhaust heat to the binary power generation device while consuming it at the heat demand destination, the power generation output of the binary power generation device is reduced, and the heat energy that has not been converted into electric power by the binary power generation device Is discharged out of the system as it is from the condenser, so the utilization efficiency of the heat energy is lowered, and the merit of the combined power generation system cannot be fully utilized as it is.

  In this respect, all the exhaust heat of the fuel cell power generator is supplied to the binary power generator to generate power, and the heat energy that has not been converted into electric power by the binary power generator is not thrown out of the system, for example, from a condenser If the cogeneration system is assembled so that it can be recovered and supplied to the heat demand destination, it can be easily estimated that the combined heat energy utilization efficiency of the combined power generation system will be further improved.

  However, in order to specify a phosphoric acid fuel cell power generation device and supply the exhaust heat to the binary power generation device to generate power, the following considerations are necessary in terms of the supply processing of exhaust heat from the fuel cell. . That is, the exhaust heat from the phosphoric acid fuel cell power generator includes cooling drainage that cools the fuel cell stack to the operating temperature, exhaust gas from the air electrode accompanying the electrode reaction at the air electrode, and fuel reformer burner. There are combustion exhaust gases, and the cooling waste water, the air electrode exhaust gas, and the combustion exhaust gas have different temperatures and heat amounts.

  This will be supplementarily explained based on specific numerical values. The battery heat is the largest amount of heat in the exhaust heat of the phosphoric acid fuel cell. The cooling water that has passed through the cooling plate of the fuel cell stack has a temperature of about 150 ° C., and this cooling wastewater has a larger heat capacity than other exhaust gases, so the working fluid (low boiling point medium) of the binary power generator is evaporated. It is suitable for the heat source of the evaporator. When a phosphoric acid fuel cell with a power generation output of 100 kW is used as a test model, the amount of heat held in the cooling wastewater that cools the fuel cell stack is about 90 kW, and this heat amount (90 kW) is used as a heat source for the evaporator of the binary power generator In order to convert the working fluid (isopentane) into steam as a heat source for the engine, it is necessary to preheat the working fluid with the preheater provided at the front stage of the evaporator, and the preheating of the working fluid is required for preheating the working fluid. The necessary amount of heat is obtained from the air electrode exhaust gas of the phosphoric acid fuel cell power generator or the combustion exhaust gas of the fuel reformer burner.

  In this case, the combustion exhaust gas temperature of the fuel reformer burner is a high temperature of about 200 ° C. but it is a gas, so the heat capacity is small, and when the temperature of this combustion exhaust gas changes from 200 ° C. to 100 ° C. It is about 23 kW. Therefore, this combustion exhaust gas alone does not have enough heat for preheating the working fluid. It is possible to increase the amount of heat given to the preheater by increasing the temperature change of the exhaust gas. However, since the heat transfer coefficient of gas is lower than that of liquid, the heat transfer area of the preheater must be increased. The equipment becomes larger and the equipment cost increases.

  Moreover, the air electrode exhaust gas that has passed through the air electrode of the phosphoric acid fuel cell is a mixed gas of about 150 ° C. in which unreacted oxygen is contained in nitrogen and water vapor, and the temperature of this exhaust gas is lowered to a temperature of 100 ° C. Since the change in the amount of heat is about 23 kW, similarly to the burner combustion exhaust gas of the reformer described above, the air electrode exhaust gas alone cannot secure the amount of heat necessary for preheating the working fluid. Under these conditions, in order to increase the power generation output of the entire system by combining the fuel cell power generation device with the binary power generation device, the exhaust heat from the fuel cell power generation device (cooling drainage, air electrode exhaust gas, combustion exhaust gas retained heat) ) Must be combined appropriately and supplied to the working fluid evaporator and preheater.

  On the other hand, all the exhaust heat of the fuel cell power generation device is input to the binary power generation device to generate power, and the heat that has not been converted into electric power by the binary power generation device is recovered from, for example, a condenser and used for hot water supply at a heat demand destination. In this case, the power generation amount of the binary power generation device increases, but the temperature and heat amount of the working fluid discharged from the turbine in the process of power generation decreases, so the cogeneration system of the fuel cell power generation device alone (Non-Patent Document 1) The amount of heat that can be used for hot water supply, air conditioning, etc. is reduced compared to (see). In addition, if the current demand remains unchanged, it will not be possible to sufficiently respond to the increase or decrease in heat demand. In particular, if the heat demand of heat-use equipment decreases, the amount of heat released outside the system will increase. There is a problem that energy utilization efficiency is lowered.

  The present invention has been made in view of the above points, and is directed to a combined power generation system in which a binary power generation device is combined with a phosphoric acid fuel cell power generation device. A first object of the invention is a binary power generation device rather than a fuel cell power generation device. Efficiently distributes the waste heat energy input to power generation and heat demand for heat generation as cogeneration so that overall heat energy utilization efficiency of the entire system can be improved, and the second purpose is phosphoric acid Efficiently preheats the working fluid by appropriately distributing and supplying the cooling drainage of the fuel cell, the exhaust gas from the cathode, and the combustion exhaust gas from the reformer burner to the evaporator and preheater of the binary power generator. It is to provide a combined power generation system that can evaporate.

In order to achieve the above object, according to the present invention, in a combined power generation system that combines a phosphoric acid fuel cell power generator and a binary power generator, and inputs the exhaust heat of the fuel cell power generator into the binary power generator to generate power. ,
(1) The binary power generation device is provided with a heat exchanger between the turbine outlet and the subsequent condenser, and the heat recovered from the working fluid of the binary power generation device is supplied to the heat demand destination via the heat exchanger. (Claim 1).
(2) In the combined power generation system of (1), when the binary power generation device includes a control unit that adjusts the outlet pressure of the turbine, and the heat demand for supplying heat to the heat demand destination via the heat exchanger is small, When the turbine outlet pressure is set low to increase the power generation output of the binary power generator, and the heat demand is high, the turbine outlet pressure is set high to control the operation so as to reduce the power generation output (Claim 2).
(3) In the combined power generation system according to (2), the turbine of the binary power generator is provided with two working fluid outlets having different outlet pressures, and a flow rate adjusting valve is connected to the working fluid outlet to connect the outlet pressure of the turbine. The control means is configured (claim 3).
(4) In the combined power generation system according to (1) to (3), the binary power generation apparatus is configured as a three-fluid heat exchanger to preheat the working fluid, and evaporates the working fluid preheated by the preheater. The combustion exhaust gas that has passed through the fuel reformer burner of the phosphoric acid fuel cell power generator and the air electrode exhaust gas that has passed through the air electrode of the fuel cell stack are sent to the working fluid and heated. The working fluid is preheated by passing it through the preheater of the binary power generator to be replaced, and the cooling water that has passed through the water cooling plate of the fuel cell stack of the phosphoric acid fuel cell power generator is passed to the evaporator of the binary power generator. The working fluid is evaporated to flow (Claim 4).
(5) In the combined power generation system according to the above (1) to (3), the binary power generation device includes first and second preheaters connected in parallel and first and second preheaters for preheating the working fluid. An evaporator for evaporating the preheated working fluid, and the flue gas that has passed through the fuel reformer burner of the phosphoric acid fuel cell power generator is used as the first preheater and the air electrode of the fuel cell stack The air electrode exhaust gas that has passed through the second preheater is sent to the working fluid so as to face the working fluid so as to exchange heat, and the working fluid is preheated to cool the water cooling of the fuel cell stack of the phosphoric acid fuel cell power generator. The cooling water that has passed through the plate is caused to flow through the evaporator of the binary power generation apparatus so that the working fluid is evaporated (Claim 5).

The combined power generation system configured as described above can achieve the following effects.
(1) The binary power generator is provided with a heat exchanger between the turbine outlet and the subsequent condenser, and the heat recovered from the working fluid of the binary power generator is supplied to the heat demand destination via the heat exchanger. By using heat, the overall heat energy utilization efficiency of the entire power generation system can be improved.
(2) Further, the binary power generator is provided with a control means for adjusting the outlet pressure of the turbine so that the amount of condensation of the working fluid can be controlled between the heat exchanger for heat recovery and the condenser. When there is little demand for heat recovered from the heat exchanger and used for hot water supply etc., the turbine outlet pressure is set low to increase the pressure difference between the turbine inlet / outlet and generate higher power than the binary power generator. Output is obtained. In addition, when the heat demand recovered from the heat exchanger and used for hot water supply or the like increases, the power generation output of the binary power generator decreases by setting the turbine outlet pressure high, but the pressure output from the turbine Since a high working fluid is condensed in a heat exchanger for heat recovery, the amount of heat recovered from the heat exchanger is increased, and the overall utilization efficiency of heat energy is improved.
(3) On the other hand, with regard to the exhaust heat input from the phosphoric acid fuel cell power generator to the binary power generator, the binary exhaust power is generated from the combustion exhaust gas that has passed through the fuel reformer burner and the air exhaust gas that has passed through the air electrode of the battery stack. The working fluid is preheated through the device preheater, and the cooling water that has passed through the water-cooled cooling plate of the fuel cell stack is passed through the binary power generator evaporator to evaporate the working fluid. By configuring the preheater with a three-fluid heat exchanger that exchanges heat by sending combustion exhaust gas and air electrode exhaust gas to the working fluid opposite to each other, the amount of heat required for preheating the working fluid is efficiently combined with the heat retained by each exhaust gas. Can be supplied well.
(4) Further, the preheater of the binary power generator is configured by two preheaters connected in parallel, and the combustion exhaust gas that has passed through the fuel reformer burner of the phosphoric acid fuel cell power generator and the air of the battery stack Even if the temperature of the combustion exhaust gas and that of the air electrode exhaust gas are different by passing the air electrode exhaust gas that has passed through the poles through different preheaters to preheat the working fluid, it is necessary to preheat the working fluid by combining the retained heat of each exhaust gas Can be supplied efficiently.

  DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of a combined power generation system according to the present invention will be described below based on the examples shown in FIGS. 1 is a flow chart of the binary power generation apparatus of the first embodiment combined with the phosphoric acid fuel cell power generation apparatus, FIG. 2 is a flow sheet of the phosphoric acid fuel cell power generation apparatus combined with the binary power generation apparatus, and FIG. It is a flow sheet of the binary power generator of the 2nd example corresponding to Drawing 1, and the same numerals are given to the member corresponding to Drawing 4 in each figure.

  The system configuration of the first embodiment will be described with reference to FIGS. The numerical values shown in the description below are a model model of a combined power generation system that combines a phosphoric acid fuel cell power generation device with a power generation output of 100 kW and a binary power generation device that uses exhaust heat from the fuel cell power generation device as a heat source. The numerical values of exhaust heat, calorific value of the working fluid, temperature, and pressure are calculated.

  First, the binary power generation apparatus 11 shown in FIG. 1 uses isopentane as a low boiling point medium as a working fluid, the working fluid as a turbine 12, an evaporator 14, a preheater 15, a working fluid pressurizing pump 16, a condenser 17, and heat recovery. The turbine cycle (Rankine cycle) is constituted by circulating and feeding to the heat exchanger 18 and the heat recovery unit 20. In addition, 13 is a generator, 16a is a drive motor for the pump 16, and 19 is a flow rate adjusting valve used for turbine outlet pressure control means described later.

  In this binary power generator 11, the flow rate of the working fluid circulating in the turbine cycle is 0.32 kg / sec. After the pressure is increased to 1100 kPa by the pump 16, the pressure is sent to the evaporator 14 via the preheater 15. The vapor of the working fluid evaporated in the evaporator 14 drives the turbine 12 to obtain a power generation output from the generator 13. The steam of the working fluid that has exited from the turbine 12 exchanges heat with the working fluid that is directed to the preheater 15 by the heat recovery device 20 to recover a part of the heat energy, and then passes through the heat exchanger 18 and the condenser 17. Flowed, condensed, liquefied and returned to the pump 16 again. In the heat exchanger 18, water is supplied from the outside to the secondary pipe 18 a, and hot water heated by heat exchange with the working fluid is supplied to a heat demand destination for heat utilization.

  Here, the evaporator 14 is supplied with the high-temperature cooling waste water A that has passed through the water-cooled cooling plate in the fuel cell stack 3 of the phosphoric acid fuel cell power generator 1 to evaporate the working fluid that has passed through the preheater 15. . The preheater 15 is preheated by flowing the cathode exhaust gas B exhausted from the phosphoric acid fuel cell power generator 1 and the burner combustion exhaust gas C of the fuel reformer 2 to preheat the working fluid. In the example, a plate stack type three-fluid heat exchanger having the following configuration is adopted as the preheater 15.

  That is, the preheater 15 incorporates heat exchange blocks 15a and 15b configured by laminating a flow path plate in which two thin steel plates are joined in a shell (outer shell case), and the air electrode exhaust gas B and the combustion are respectively built into the shell. The exhaust gas C is passed through to exchange heat with the working fluid. As a result, the working fluid is heated from 67 ° C. to 115 ° C. by receiving a total of 46 kW of heat from each of the air electrode exhaust gas B and the combustion exhaust gas C by 23 kW.

  In the evaporator 14, the working fluid exchanges heat with the cooling water A at 150 ° C. that has passed through the cooling plate of the fuel cell stack 3, and the working fluid that receives 90 kW of heat from the cooling water A is 125 ° C. vapor. And sent to the turbine 12.

  On the other hand, the turbine 12 is a small-capacity radial turbine, and the turbine 12 includes a final stage exhaust port (outlet pressure: 150 kPa) and a bleed port 12a (outlet pressure: 250 kPa) at the intermediate pressure stage of the turbine. Has two outlets. Further, a flow rate adjusting valve (three-way valve) 19 is connected between the two turbine outlets. With this configuration, the outlet pressure of the turbine 12 can be varied by changing the flow rate of the working fluid passing through each outlet of the turbine 12. I try to control it. The flow rate adjusting valve 19 may be one that performs ON / OFF switching control or that continuously adjusts the flow rate ratio.

  Next, a flow sheet of the phosphoric acid fuel cell 1 constituting the combined power generation system in combination with the binary power generation device 11 having the above-described configuration is shown in FIG. The phosphoric acid fuel cell power generator 1 is basically the same as the configuration described in FIG. 4, and the high-temperature cooling waste water A that has passed through the cooling plate 3 c of the fuel cell stack 3 is transferred to the evaporator 14 shown in FIG. 1. Circulating water is used to evaporate the working fluid. On the other hand, the air electrode exhaust gas B that has passed through the air electrode 3b and the burner combustion exhaust gas C of the fuel reformer 2 are supplied to the preheater 15 in FIG. 1 to preheat the working fluid.

  Further, the air electrode exhaust gas B and the combustion exhaust gas C containing water vapor that has passed through the preheater 15 of the binary power generator 11 are sent to the water recovery device (gas-liquid separator) 5 in the same manner as the fuel cell power generator of FIG. After being cooled by direct contact heat exchange with water to separate and remove moisture, it is discharged outside the system (atmosphere side) as exhaust.

  With the above configuration, when the flow rate adjustment valve 19 closes the extraction port 12a of the turbine 12 and sets the turbine outlet pressure to 150 kPa, the power generation output of the generator 13 is 10 kW. On the other hand, when the flow regulating valve 19 fully opens the bleed port 12a of the turbine 12 (fully closes the exhaust port) and sets the outlet pressure of the turbine to 250 kPa, the heat drop between the inlet and the outlet of the turbine 12 decreases. Thus, the power generation output of the generator 13 is 7.3 kW. Accordingly, since the power generation output of the phosphoric acid fuel cell is 100 kW, the power generation output of the combined power generation system including the power generation output (10 kW or 7.3 kW) of the binary power generation device 11 is the phosphoric acid fuel cell power generation device. The power generation output is increased by 7 to 10% as compared with the case of the above alone.

  The steam temperature of the working fluid that has passed through the turbine 12 is about 95 ° C., and a part of the heat energy is consumed by heat exchange with the working fluid toward the preheater 15 in the heat recovery unit 20 (see FIG. 1). After that, the working fluid is sent to the heat exchanger 18 at the subsequent stage, and the heat recovered by the heat exchanger 18 is supplied to the heat demand destination.

  Here, when the outlet pressure of the turbine 12 is set to 250 kPa in accordance with the increase in heat demand, the working fluid dissipates heat to the water flowing through the secondary side pipe 18a in the process of passing through the heat exchanger 18. Most of the steam condenses (steam has a nature that the condensation temperature at which it liquefies increases as the pressure increases). As a result, the heat exchanger 18 can recover heat of up to about 100 kW. Further, since the working fluid is condensed in the heat exchanger 18, the amount of heat that is radiated outside the system in the latter-stage condenser 17 is reduced to about 29 kW at the minimum. In this operation state, by increasing the outlet pressure of the turbine 12 from 150 kPa to 250 kPa, the power generation output of the binary power generator 11 decreases from 10 kW to 7.3 kW as described above.

  On the other hand, when the heat demand decreases and the flow rate adjusting valve 19 closes the extraction port 12a of the turbine 12 and sets the turbine outlet pressure to 150 kPa in accordance with this, the working fluid is condensed in the condenser 6 in this case. Therefore, the maximum amount of heat released to the outside of the system is 126 kW, but the power generation output of the binary power generator 11 increases from 7.3 kW to 10 kW.

  As described above, the heat exchanger 18 is provided in the binary power generator 11 that uses the exhaust heat from the phosphoric acid fuel cell power generator 1 as a heat source, and the heat recovered through the heat exchanger 18 is received at the heat demand destination. By constructing a cogeneration system to be used for hot water supply etc. and adjusting the outlet pressure of the turbine 12 according to fluctuations in the heat demand, while maintaining high thermal energy utilization efficiency in the entire combined power generation system, The output can be increased.

  Next, FIG. 3 shows a flow sheet of the binary power generation apparatus of the second embodiment in which the preheater of the binary power generation apparatus 11 is changed as an embodiment different from the first embodiment. That is, in the first embodiment, the preheater 15 is constituted by a three-fluid heat exchanger. In this embodiment, two shell and tube preheaters 15-1 and 15-2 are used as preheaters. Connected in parallel, the preheater 15-1 passes through the cathode exhaust gas B of the fuel cell stack 3, and the other preheater 15-2 passes through the burner combustion exhaust gas C of the fuel reformer 2 to preheat the working fluid. Other configurations are the same as those in FIG. This embodiment is applied when, for example, the gas temperatures of the air electrode exhaust gas B and the combustion exhaust gas C are different, and the working fluids that have passed through the preheaters 15-1 and 15-2 are merged and sent to the evaporator 14.

Flow sheet of binary power generation apparatus of first embodiment in fuel cell power generation system of the present invention Flow sheet of a phosphoric acid fuel cell power generator combined with the binary power generator of FIG. Flow sheet of the binary power generator of the second embodiment corresponding to FIG. Flow sheet of a conventional fuel cell cogeneration system

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Fuel cell power generation device 2 Fuel reformer 2a Burner 3 Fuel cell stack 3b Air electrode 3c Cooling plate 5 Water recovery device 6 Radiator 10 Heat exchanger 11 Binary power generation device 12 Turbine 12a Extraction port 13 Generator 14 Evaporator 15, 15-1, 15-2 Preheater 16 Pump 17 Condenser 19 Flow rate adjusting valve A Cooling drain B Air electrode exhaust gas C Burner combustion exhaust gas

Claims (5)

In a combined power generation system that combines a phosphoric acid fuel cell power generator and a binary power generator, and inputs the exhaust heat of the fuel cell power generator into the binary power generator to generate power,
The binary power generator is provided with a heat exchanger between the turbine outlet and the condenser, and heat recovered from the working fluid of the binary power generator is supplied to the heat demand destination via the heat exchanger. A featured combined power generation system.   The combined power generation system according to claim 1, wherein the binary power generation device includes a control unit that adjusts the outlet pressure of the turbine, and when there is little heat demand to supply heat to the heat demand destination via the heat exchanger, A combined power generation system characterized in that the outlet pressure is set low to increase the power generation output of the binary power generator, and that operation control is performed so as to reduce the power generation output by setting the turbine outlet pressure high when heat demand is high. 3. The combined power generation system according to claim 2, wherein two working fluid outlets having different outlet pressures are provided in a turbine of the binary power generator, and a flow rate adjusting valve is connected to the working fluid outlet to constitute an outlet pressure control means of the turbine. Combined power generation system characterized by that.   The combined power generation system according to any one of claims 1 to 3, wherein the binary power generation device includes a preheater configured as a three-fluid heat exchanger to preheat the working fluid, and the working fluid preheated by the preheater. A vaporizer that evaporates, and the combustion exhaust gas that has passed through the fuel reformer burner of the phosphoric acid fuel cell power generator and the air electrode exhaust gas that has passed through the air electrode of the fuel cell stack are sent oppositely to the working fluid. The working fluid is preheated by flowing through the preheater of the binary power generator so as to exchange heat, and the cooling water that has passed through the water-cooled cooling plate of the fuel cell stack of the phosphoric acid fuel cell power generator is supplied to the evaporator of the binary power generator. A combined power generation system characterized by evaporating a working fluid through a flow.   4. The combined power generation system according to claim 1, wherein the binary power generation device includes first and second preheaters connected in parallel and first and second preheaters for preheating the working fluid. 5. And an evaporator for evaporating the preheated working fluid, and the combustion exhaust gas that has passed through the fuel reformer burner of the phosphoric acid fuel cell power generator is used as the first preheater and the air electrode of the fuel cell stack. The air electrode exhaust gas that has passed through the second preheater is sent to the second preheater so as to be opposed to the working fluid and exchanged heat to preheat the working fluid, and the water cooling of the fuel cell stack of the phosphoric acid fuel cell power generator A combined power generation system, characterized in that the working fluid is evaporated by flowing cooling water that has passed through a cooling plate to an evaporator of a binary power generation device.

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