JP2012221723A - Fuel cell system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel cell system which permits exhaust heat circulation water in an exhaust heat circulation circuit associated with a hot water type exhaust heat recovery system to be stably circulated without inclusion of air, and capable of generating electric power stably by using an exhaust heat circulation circuit which is easy to control and satisfies durability performance.SOLUTION: The fuel cell system includes a fuel cell 1 which supplies electric power and heat; a circulation passage 2 in which a heat medium for absorbing the heat of the fuel cell 1 circulates; a heat storage unit 4 which stores the heat of the heat medium; a pump 71, disposed in the circulation passage 2, which circulates the heat medium; and a controller 50 which at least controls the pump 71. The controller 50, when the fuel cell 1 is producing electric power, controls the pump 71 so as to change the operation amount of the pump 71 in two steps, one for a high operation amount and one for a low operation amount greater than zero.

Description

  The present invention relates to an exhaust heat recovery system that stores heat as hot water in a hot water storage tank that has left exhaust heat in a cogeneration system such as a fuel cell cogeneration system.

  As a conventional hot water storage type exhaust heat recovery system, there has been a fuel cell cogeneration system (see, for example, Patent Document 1). FIG. 4 shows a conventional fuel cell cogeneration system described in Patent Document 1. In FIG.

  In FIG. 5, the fuel cell 101 discharges surplus heat by passing it to the heat recovery water by the heat exchanger 102. This heat recovery water is conveyed from the lower part of the hot water storage tank 104 through the heat recovery pipe A105 and the heat recovery pipe B106 by the circulation pump 103. The heat recovery water heated by surplus heat of the fuel cell 101 in the heat exchanger 102 is detected by the heat exchange temperature sensor 108, and when the temperature is higher than the temperature of the upper part of the hot water storage tank 104, the heat recovery pipe C107 stores the hot water storage. It is conveyed to the upper part of the tank 104. When the temperature of the heat recovery water heated here is lower than the temperature of the upper part of the hot water storage tank 104, the changeover valve 109 conveys the heat recovery water to the junction of the heat recovery pipe A105 through the bypass circuit 110 and circulates in the circuit.

JP-A-11-223385

  However, in the conventional configuration, when the excessive heat generated in the fuel cell 101 is small, in order to send hot hot water to the hot water storage tank 104, it is transferred to the heat recovery water by the heat exchanger 102, and the hot water storage tank by the circulation pump 103. The flow rate of the heat recovery water sent to 104 needs to be extremely small.

  In this case, since the circulation flow rate of the circulation pump 103 becomes small, air engagement is derived inside the circulation pump 103, and there is a problem that the circulation pump 103 is damaged due to cavitation and defective circulation occurs.

  In addition, when installed in an apartment house or the like, it is sufficiently assumed that the heat recovery pipe becomes longer due to the installation of a hot water tank and a fuel cell.

  In this case, the heat radiation amount of the heat recovery pipe is increased, and there is a problem that sufficient heat storage cannot be performed in the hot water storage tank.

  The present invention solves the above-described conventional problems, and an object thereof is to improve the durability performance of the exhaust heat recovery circulation pump and to improve the installation margin.

In order to solve the conventional problems, a hot water storage type exhaust heat recovery system includes a fuel cell that supplies electric power and heat, a circulation path through which a heat medium that absorbs heat from the fuel cell circulates, and heat of the heat medium. A heat accumulator that stores heat, a circulation pump that is arranged in the circulation path and circulates the heat medium, and a controller that controls at least the circulation pump. The controller performs power generation by the fuel cell. In this case, the fuel cell system controls the pump so that the operation amount of the pump is intermittently changed into at least two steps of a high operation amount and a low operation amount greater than zero.

  With this configuration, the air pump of the circulation pump can be prevented.

  According to the hot water storage type exhaust heat recovery system of the present invention, it is possible to prevent the air pumping of the circulation pump used for the heat recovery water between the fuel cell unit and the hot water storage unit of the heat recovery pipe by simple control, and durability performance In addition, by increasing the amount of high-temperature recovered water sent to the hot water storage tank through the heat recovery pipe, it is possible to extend the heat recovery pipe by reducing the heat radiation amount of the heat recovery pipe.

1 is a configuration diagram showing a fuel cell system according to Embodiment 1 of the present invention. Time chart showing control of circulating pumps according to first and second embodiments of the present invention Time chart showing control of circulating pump of embodiment 3 of the present invention Configuration diagram showing a conventional fuel cell system

According to a first aspect of the present invention, there is provided a fuel cell that generates power by supplying hydrogen and air, a cooling water circulation circuit that circulates cooling water that cools the fuel cell that generates heat when the fuel cell generates power, and a cooling water circulation circuit. A cooling water tank that stores the cooling water, a cooling water circulation pump that circulates the cooling water in the cooling water circulation circuit, a hot water storage tank, and a heat recovery water circulation circuit that returns the heat recovery water flowing out of the hot water storage tank to the hot water storage tank. A cooling water heat exchanger for exchanging heat between the cooling water in the cooling water circulation circuit and the heat recovery water in the heat recovery water circulation circuit;
A circulation pump that circulates heat recovery water between the hot water tank and the cooling water heat exchanger,
A fuel cell system for controlling the pump so as to intermittently change the operation amount of the circulation pump into at least two stages of a high operation amount and a low operation amount greater than zero when recovering the exhaust heat of the fuel cell; It is.

According to a second aspect of the invention, there is provided a fuel cell that generates power by supplying hydrogen and air, a cooling water circulation circuit that circulates cooling water that cools the fuel cell that generates heat during power generation of the fuel cell, and a cooling water circulation circuit. A cooling water tank that stores the cooling water, a cooling water circulation pump that circulates the cooling water in the cooling water circulation circuit, a hot water storage tank, and a heat recovery water circulation circuit that returns the heat recovery water flowing out of the hot water storage tank to the hot water storage tank. A cooling water heat exchanger for exchanging heat between the cooling water in the cooling water circulation circuit and the heat recovery water in the heat recovery water circulation circuit;
A circulation pump that circulates heat recovery water between the hot water tank and the cooling water heat exchanger,
When recovering the exhaust heat of the fuel cell, the operation amount of the circulation pump is intermittently changed to at least two stages of a high operation amount and a minimum operation amount when the fuel cell is generating power. A fuel cell system for controlling a pump.

According to a third aspect of the invention, there is provided a fuel cell that generates power by supplying hydrogen and air, a cooling water circulation circuit that circulates cooling water that cools the fuel cell that generates heat during power generation of the fuel cell, and a cooling water circulation circuit. A cooling water tank that stores the cooling water, a cooling water circulation pump that circulates the cooling water in the cooling water circulation circuit, a hot water storage tank, and a heat recovery water circulation circuit that returns the heat recovery water flowing out of the hot water storage tank to the hot water storage tank. A cooling water heat exchanger for exchanging heat between the cooling water in the cooling water circulation circuit and the heat recovery water in the heat recovery water circulation circuit;
A circulation pump that circulates heat recovery water between the hot water tank and the cooling water heat exchanger,
A fuel cell that controls the pump so as to intermittently change the operation amount of the circulating pump by setting the operation amount to be divided into a plurality of operation amounts when recovering the exhaust heat of the fuel cell; System.

(Embodiment 1)
FIG. 1 shows the configuration of a fuel cell system including a heat recovery circuit that controls the operation amount of the circulation pump 71 according to the first embodiment of the present invention. FIG. 2 shows the operation amount of the circulation pump. It is a time chart of the heat recovery circuit to be controlled.

  Hereinafter, specific configuration examples and operation examples of the fuel cell heat recovery circuit according to the embodiment of the present invention will be described with reference to the drawings based on the configuration examples of the fuel cell system.

  FIG. 1 is a block diagram showing a configuration example of a fuel cell system according to an embodiment of the present invention. As shown in FIG. 1, a fuel cell system 100 is a fuel cell that generates hydrogen by generating a reforming reaction between a fuel cell 1 that generates and generates heat using fuel gas (hydrogen gas) and methane in the combustion gas. A machine 10 is provided.

  In the fuel cell 1, the fuel gas supplied to the anode (not shown) of the fuel cell 1 and the oxidizing gas (for example, air) supplied to the cathode (not shown) of the fuel cell 1 are electrochemical. In response to heat (exothermic reaction), power and heat are generated. The electric power generated by the fuel cell 1 can be used in various electric devices, for example. Further, the heat generated by the fuel cell 1 can be used for various purposes, for example, at home heating or hot water supply.

  The internal structure of the fuel cell 1 is known. Therefore, the detailed description is abbreviate | omitted. In the power generation of the fuel cell 1, since the above-described electrochemical reaction (exothermic reaction) proceeds, the operating temperature during power generation of the fuel cell 1 is maintained at a temperature suitable for the reaction (for example, about 70 ° C. to 80 ° C.). In general, a mechanism for keeping the temperature of the fuel cell 1 constant is generally employed.

  First, the fuel cell cooling circuit will be described.

  As shown in FIG. 1, the fuel cell cooling circuit corresponds to a cooling water circulation circuit 2 that circulates cooling water for cooling the fuel cell 1 during power generation of the fuel cell 1 (corresponding to a “circulation path” in claim 1). ), A cooling water tank 4 provided with an excess heater 3 provided in the cooling water circulation circuit 2 and storing cooling water, a cooling water circulation pump 6 for circulating the cooling water in the cooling water circulation circuit 2, and the cooling water circulation circuit The cooling water heat exchanger 5 that absorbs the waste heat 2 and stores the heat in the hot water storage tank 20 and the temperature detector 7 provided at the cooling water outlet of the fuel cell 1 are provided. In FIG. 1, the flow direction of the cooling water is indicated by a solid arrow. The cooling water circulation circuit 2 includes a cooling water circulation circuit a21 that connects the cooling water tank 4 and the cooling water heat exchanger 5, a cooling water circulation circuit b22 that connects the cooling water heat exchanger 5 and the fuel cell 1, a fuel cell 1 and a cooling water circulation pump. 6, a cooling water circulation circuit c <b> 23 that connects 6, and a cooling water circulation circuit d <b> 24 that connects the cooling water circulation pump 6 and the cooling water tank 4.

  Next, a reformed water supply circuit for supplying reaction water for the reforming reaction to the fuel processor 10 for supplying fuel gas (hydrogen gas) using city gas or the like to the fuel cell 1 will be described.

The reforming water supply circuit includes a water supply circuit 12 branched from the cooling water circulation circuit d24 of the cooling water circulation circuit 2, a supply pump 11 for supplying reaction water to the fuel processor, and water for reaction to the fuel processor 10. The first fuel processing valve 15a for turning on and off, the condensed water circuit 14 branched from the supply pump 11, the second fuel processing valve 15b, the water supply tank (condensed water tank) 16, and the cooling water supply pump 13 And a cooling water supply circuit 17b. In FIG. 1, the flow direction of the cooling water is indicated by dotted arrows. The water supply circuit 12 branches from a cooling water circulation circuit c23 that connects the fuel cell 1 and the cooling water circulation pump 6, and connects the water supply circuit 12 that connects the supply pump 11, the supply pump 11, and the first fuel processing valve 15a. b32, a water supply circuit c33 connecting the first fuel processing valve 15a and the fuel processor 10, a water supply circuit d34 branching from the water supply circuit b32 and connecting the second fuel processing valve 15b, and a second fuel A water supply circuit e35 that connects the processing valve 15b and a water supply tank (condensate water tank) 16 is configured. The water supply tank 16 is connected to a drainage path for draining when it overflows, and an overflow valve 16b is disposed in the drainage path.

  The cooling water supply circuit 17b includes a cooling water supply circuit c17c, a cooling water supply circuit d17d, and a cooling water supply circuit e17e. A cooling water tank valve 4b is arranged in the cooling water circulation circuit e17e.

  Further, a controller 50 that controls the components of the fuel cell system including the circulation pump 71 is disposed.

  Next, the fuel cell power generation process will be described in the order of water flow, circulating water filling operation of the circulation circuit (hereinafter referred to as initial water filling) fuel treatment, and fuel cell power generation.

  Initial filling is performed to fill the circulation circuit of the fuel cell system with water.

  First, the circuit of the first switching means 61 provided in the first bypass circuit 60 is set to “open”. Accordingly, the makeup water in the hot water tank 20 passes through the hot water circulation circuit 41, the circulation pump 71 (corresponding to the “pump” in the claims), the makeup water circuit 51a, the first bypass circuit 60, and the cooling water supply circuit. It is guided to the cooling water tank 4 through c17c, the cooling water supply circuit d17d, the ion exchange resin 18, and the cooling water supply circuit e17e. These series of operations are performed by the supply pressure of the water supply applied to the hot water tank 20.

  When the water level in the cooling water tank 4 rises, the cooling water tank level switch 8 detects that the water level is full and “closes” the circuit of one switching means 61.

  Simultaneously with the initial water filling, water is supplied to the water supply tank (condensate water tank) 16. A water tank (condensed water) is supplied via a replenishment water circuit a51 and a replenishment water circuit b52 branched from the hot water circulation circuit 41, the circulation pump 71 and the hot water circulation circuit b42 with the water tank valve 72 opened. Tank) 16 is replenished. When the water level in the water supply tank (condensate water tank) 16 rises, the water supply tank level switch 17 detects full water, stops the circulation pump 71, and closes the water supply tank valve 72.

  The operation is performed regardless of whether the circulation pump 71 is in operation.

  When filling of the cooling water in the cooling water circulation circuit 2 is completed, fuel gas (hydrogen gas) is supplied from the fuel processor 10 to the fuel cell 1 and reacts with the oxidizing gas (for example, air) to start power generation. . Then, electric power and heat are generated by this power generation. This electric power is consumed by the electrical equipment, and the generated heat is heat-exchanged by the cooling water heat exchanger 5 from the hot water storage tank 20 by the hot water circulating through the exhaust heat circulation circuit 40 by the circulation pump 71 and stored in the hot water storage tank 20. .

  The makeup water circulation circuit comprises a hot water storage circuit 41 that connects the hot water tank 20 and the circulation pump 71, a makeup water circulation circuit a42 that connects the circulation pump 71 and the cooling water heat exchanger 5, the cooling water heat exchanger 5 and the hot water tank 20. The makeup water circulation circuit c43 is connected.

Further, when surplus electricity is generated during power generation in the fuel cell system, the surplus power is converted into heat by a heater and stored in the hot water tank 20. Specifically, surplus power is converted into hot water by the surplus heater 3 provided in the cooling water tank 4. Hot water in the cooling water tank is sent to the cooling water heat exchanger 5 by the cooling water circulation pump 6, and heat is exchanged from the hot water storage tank 20 by the hot water circulating through the exhaust heat circulation circuit 40 by the circulation pump 71 to store heat in the hot water storage tank 20. Is done.

  Next, the operation control of the circulation pump 71 when the power generation amount is changed, the heat exchange is performed in the cooling water heat exchanger 5 and the heat stored in the hot water tank 20 is changed will be described with reference to FIG.

  FIG. 2 is a time chart with the horizontal axis as the operation time. The upper diagram in FIG. 1 shows the relationship between the amount of generated heat (heat generation amount) and the operation time, and the lower diagram shows the relationship between the operation amount (circulation amount) of the circulation pump 71 and the operation time.

  In this case, when the amount of generated heat exhausted (power generation) of the fuel cell 1 is maximum with the maximum power generation amount, the operation amount (circulation amount) of the circulation pump 71 is set to the maximum (high operation amount) by the cooling water heat exchanger 5. Then, heat is exchanged from the hot water storage tank 20 by the hot water circulating through the exhaust heat circulation circuit 40 by the circulation pump 71 and is stored in the hot water storage tank 20.

  Next, when the power generation amount of the fuel cell 1 decreases and the power generation exhaust heat amount (power generation amount) falls below a preset threshold value, the operation amount (circulation amount) of the circulation pump 71 is controlled at the maximum heat generation amount. The cooling water heat exchanger 5 exchanges heat from the hot water storage tank 20 with the hot water circulating through the exhaust heat circulation circuit 40 by the cooling water heat exchanger 5 and stores the heat in the hot water storage tank 20 with a low operation amount smaller than the amount (circulation amount). . At this time, the pump circulation may be stopped by setting the pump operation amount (circulation amount) to zero. Thereafter, the above operation is repeated according to the amount of heat generated by the fuel cell.

  As described above, the controller 50 controls the pump operation amount (circulation amount) based on a certain threshold value according to the hot water storage type exhaust heat recovery system used in the fuel cell system and the like configured. Therefore, by providing a large difference in the pump operation amount (circulation amount), the air bite generated inside the pump with a low operation amount can be discharged at a high operation amount (circulation amount).

(Embodiment 2)
Next, a second embodiment of the present invention will be described with reference to FIG.
The description of the order of the power generation process of the fuel cell, water flow, circulating water filling operation of the circulation circuit, fuel processing, and power generation of the fuel cell is the same as (Embodiment 1), and is therefore omitted.

  The present embodiment is characterized in that the low operation amount described in the first embodiment is set to the minimum operation amount of the circulation pump 71.

  That is, when the generated power exhaust heat amount (power generation amount) of the fuel cell 1 is the maximum with the maximum power generation amount, the operation amount (circulation amount) of the circulation pump 71 is set to the maximum (high operation amount) by the cooling water heat exchanger 5. Heat is exchanged from the hot water storage tank 20 by the hot water circulating through the exhaust heat circulation circuit 40 by the circulation pump 71 and is stored in the hot water storage tank 20.

  Next, when the power generation amount of the fuel cell 1 decreases and the power generation exhaust heat amount (power generation amount) falls below a preset threshold value, the operation amount (circulation amount) of the circulation pump 71 is controlled at the maximum heat generation amount. Heat is exchanged by hot water stored in the exhaust heat circulation circuit 40 from the hot water tank 20 by the circulation pump 71 by the cooling water heat exchanger 5 with the minimum operation amount of the circulation pump being a low operation amount smaller than the amount (circulation amount). Then, heat is stored in the hot water tank 20. At this time, the pump circulation may be stopped by setting the pump operation amount (circulation amount) to zero. Thereafter, the above operation is repeated according to the amount of heat generated by the fuel cell.

  As described above, according to the hot water storage type exhaust heat recovery system used for the fuel cell system and the like configured, since it is controlled based on a certain threshold value, there is a large difference in the pump operation amount (circulation amount). By providing, the air bite generated in the pump with a low operation amount can be discharged at a high operation amount.

(Embodiment 3)
Next, a third embodiment of the present invention will be described with reference to FIG.

  The description of the order of the power generation process of the fuel cell, water flow, circulating water filling operation of the circulation circuit, fuel processing, and power generation of the fuel cell is the same as (Embodiment 1), and is therefore omitted.

  The present embodiment is characterized in that the pump circulation amount is controlled by dividing it into a plurality of operation amounts from the maximum to the minimum of the power generation exhaust heat amount.

  That is, when the generated power exhaust heat amount (power generation amount) of the fuel cell 1 is the maximum with the maximum power generation amount, the operation amount (circulation amount) of the circulation pump 71 is set to the maximum (high operation amount) by the cooling water heat exchanger 5. Heat is exchanged from the hot water storage tank 20 by the hot water circulating through the exhaust heat circulation circuit 40 by the circulation pump 71 and is stored in the hot water storage tank 20.

  Next, when the power generation amount of the fuel cell 1 decreases and the power generation exhaust heat amount (power generation amount) falls below a preset threshold value, the operation amount (circulation amount) of the circulation pump 71 is controlled at the maximum heat generation amount. Heat is exchanged by hot water stored in the exhaust heat circulation circuit 40 from the hot water tank 20 by the circulation pump 71 by the cooling water heat exchanger 5 with the minimum operation amount of the circulation pump being a low operation amount smaller than the amount (circulation amount). Then, heat is stored in the hot water tank 20.

  Specifically, as shown in FIG. 3, when the power generation exhaust heat amount (power generation amount) falls below the first threshold value, the circulation pump operation amount (circulation amount) is reduced to the first operation amount.

  Thereafter, as the second threshold value decreases to the fifth threshold value, the circulation pump operation amount (circulation amount) also decreases correspondingly from the second operation amount to the fifth operation amount. When the power generation exhaust heat amount (power generation amount) becomes the minimum and falls below the sixth threshold value, the circulation pump operation amount (circulation amount) is controlled with a low operation amount. At this time, the pump circulation may be stopped by setting the pump operation amount (circulation amount) to zero. Thereafter, the above operation is repeated according to the amount of heat generated by the fuel cell.

  As described above, according to the hot water storage type exhaust heat recovery system used in the fuel cell system configured as described above, the pump operation amount (circulation amount) is controlled based on a plurality of threshold values, so that stable exhaust The amount of heat can be stored in the hot water tank 20.

  In addition, by providing a large difference in the pump operation amount (circulation amount) compared to the case where the pump operation amount (circulation amount) is controlled linearly, the air bit generated inside the pump can be discharged at a high operation amount with a low operation amount. it can.

  As described above, the hot water storage type exhaust heat recovery system according to the fuel cell cooling device according to the present invention can eliminate the air pumping of the circulation pump, and can easily control the circulation pump without air biting and has a durable exhaust heat. A circulation circuit can be realized. As a result, it is possible to provide a hot water storage type exhaust heat recovery system related to a fuel cell system that can secure a sufficient heat exchange performance that satisfies the initial setting performance and can perform stable power generation.

1 Fuel cell 2 Cooling water circulation circuit (circulation path)
3 Excess heater 4 Cooling water tank (heat accumulator)
4b Cooling water tank valve 5 Cooling water heat exchanger 6 Cooling water circulation pump 7 Temperature detector 8 Cooling water tank level switch 10 Fuel processor 11 Supply pump 12 Supply water circuit 13 Supply pump 14 Condensate water circuit 15a First fuel processing valve 15b Second fuel processing valve 16 Water supply tank (condensate tank)
16b Overflow valve 17 Water supply tank level switch 17c Cooling water supply circuit c
17d Cooling water supply circuit d
17e Cooling water supply circuit e
18 Ion exchange resin 20 Hot water storage tank 21 Cooling water circulation circuit a
22 Cooling water circulation circuit b
23 Cooling water circulation circuit c
24 Cooling water circulation circuit d
32 Water supply circuit b
33 Water supply circuit c
34 Water supply circuit d
35 Water supply circuit e
40 Waste heat circulation circuit 41 Hot water storage circuit 42 Hot water storage circuit b
43 makeup water circulation circuit c
50 controller 51 makeup water circuit a
52 makeup water circuit b
60 First bypass circuit 71 Circulation pump (pump)
72 Water tank valve

Claims (3)

A fuel cell for supplying power and heat;
A circulation path through which a heat medium that absorbs heat of the fuel cell circulates;
A regenerator for storing heat of the heat medium;
A pump disposed in the circulation path and circulating the heat medium;
A controller for controlling at least the pump;
Have
The controller controls the pump so that the operation amount of the pump is intermittently changed into at least two steps of a high operation amount and a low operation amount greater than zero when the fuel cell is generating power. ,
Fuel cell system. The low operation amount is a minimum operation amount when the fuel cell is generating power.
The fuel cell system according to claim 1. The high operation amount is set to be divided into operation amounts of a plurality of sizes.
The fuel cell system according to claim 1 or 2.