JP2002025590A - Fuel cell power generating device and its control method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel cell power generating device and its control method in which improvement is aimed in utilization of a waste heat using equipment by increasing the exhaust-heat recovery temperature of the fuel cell, and a cell cooling water having a predetermined temperature can be supplied to the fuel cell without unreasonable increase of the equipment capacity of a system which cools the cell cooling water. SOLUTION: The fuel cell power generating device is composed of a system piping 50 for circulating the cooling water after cooling a cell to a hot water tank 12 as a waste heat use equipment, a 1st flow rate control valve 22, a cell cooling water cooler 7 equipped downstream the control valve, a 2nd flow rate control valve 25, a by-pass line 24, a thermometer 20 equipped for supplying the cell cooling water of the predetermined temperature to a cooling plate of the fuel cell, and a control equipment 62 which adjusts the opening of the 1st flow rate control valve 22 and the 2nd flow rate control valve 25 based on the difference of the output of the thermometer and the predetermined temperature.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention includes a waste heat utilization facility for recovering heat of cooling water received from a fuel cell in order to effectively supply waste heat of a fuel cell to an external heat utilization facility. The present invention relates to a fuel cell power generator and a control method thereof.

[0002]

2. Description of the Related Art There are various types of fuel cells to be incorporated in a fuel cell power generator, depending on the type of electrolyte, the type of reforming material, and the like. As a fuel cell of a relatively low temperature of about 80 ° C., a solid polymer electrolyte fuel cell is well known.

[0003] As in the case of the phosphoric acid fuel cell, the solid polymer electrolyte fuel cell converts hydrogen in the fuel gas obtained by steam reforming a raw fuel such as methane gas and oxygen in the air into fuel. To the fuel and cathode of the battery,
It generates electricity based on the electrochemical reaction, and even in a fuel cell power generator incorporating a solid polymer electrolyte fuel cell, heat generated during power generation is supplied by supplying cooling water to keep the temperature of the fuel cell body constant. In addition, the generated heat is recovered and effectively used by waste heat utilization equipment such as a waste heat utilization water heater.

In reforming raw fuel into fuel gas, a method of adding steam to raw fuel to promote reforming by a catalyst in a fuel reformer has been adopted. It is necessary to constantly replenish the required amount of steam, and it is necessary to constantly replenish the water supply device with the corresponding amount of water. The water used must be high-purity water, and ion-exchanged water from which impurities have been removed by an ion-exchange type water treatment apparatus is generally used.

On the other hand, in the electrochemical reaction of the fuel cell, water generated by power generation is generated, and in the fuel reformer, the water generated by combustion is accompanied by combustion for heating the catalyst to perform a steam reforming reaction, which is an endothermic reaction, constantly. However, these generated waters have less impurities than ordinary tap water, and if these generated waters are used as raw water, the load on the water treatment equipment can be reduced. In addition, a method of collecting these generated waters is employed.

FIG. 2 is a basic system diagram of a conventional solid polymer electrolyte fuel cell power generator equipped with this type of waste heat utilization equipment, mainly focusing on a waste heat recovery system and a generated water recovery system. .

In FIG. 2, a fuel cell 1 schematically shown
Is provided with a cooling plate 4 having a cooling pipe or a cooling groove every time a plurality of unit cells having a fuel electrode 2 and an air electrode 3 are stacked,
It is configured by stacking.

[0008] As a cooling water for the fuel cell, a pure water tank 5 is used.
The pure water stored in the battery cooling water circulation pump 6 is used.
Accordingly, the fuel is supplied to the fuel cell through the cell cooling water circulation system pipe 40. The cooling water discharged from the fuel cell is cooled by a battery cooling water cooler 7 provided in a battery cooling water circulation system pipe 40, a bypass line 8 bypassing the battery cooling water cooler 7, and a three-way control for adjusting the flow rate ratio between the two. The valve 9 keeps cooling to a predetermined temperature, for example, 75 ° C. This adjustment control is performed by adjusting the opening of the three-way control valve 9 based on the difference between the output value of the thermometer 20 provided in the pure water tank 5 and a predetermined temperature set value.

On the other hand, the battery cooling water cooler 7 is supplied with the recovered water in the fuel cell power generator to cool the battery cooling water. The recovered water in the recovered water tank 10 is supplied to the battery cooling water cooler 7 by the recovered water pump 11, then taken out of the fuel cell power generator package, and supplied to the hot water storage tank 12 as waste heat utilization equipment. Here, the waste heat of the fuel cell is supplied and used for hot water supply or the like.

If the temperature of the hot water in the hot water storage tank 12 is sufficiently high and the waste heat from the fuel cell cannot be discarded here, it is cooled by a recovered water cooler 13 and a recovered water cooling fan 14 located downstream thereof. . Thereafter, the recovered water is supplied to the exhaust gas cooler 15, and the exhaust gas from the air electrode of the fuel cell and the combustion exhaust gas from the fuel reformer (not shown) are brought into direct contact with the recovered water to cool these exhaust gases. Collect the generated water. 31 is an exhaust air outlet pipe, and 131 is a recovered water cooler outlet pipe.

At the outlet of the battery cooling water circulating pump 6, there is provided a branch line 16 of pure water which becomes steam for reforming.
From there, reforming water is constantly supplied to a fuel reformer (not shown). Therefore, it is necessary to constantly replenish the water, but this is replenished from the recovered water via the water treatment device 17.
Supplied from

Since the operating temperature of the solid polymer electrolyte fuel cell is about 80 ° C., the fuel cell outlet temperature of the cooling water is also about 80 ° C. in order to maintain this temperature. On the other hand, in order to collect the exhaust gas and reduce the amount of external make-up water as much as possible, the temperature of the collected water discharged from the collected water cooler 13 is set to 45 ° C.
Since it is necessary to lower the temperature to below, as a result, the inlet temperature of the hot water storage tank becomes about 50 ° C.

[0013]

However, the solid polymer electrolyte fuel cell power generator equipped with the above-mentioned conventional waste heat utilization equipment has the following problems.

In general, it is desirable that the waste heat recovery temperature be as high as possible from the viewpoint of utilization efficiency and usability of the waste heat utilization equipment. For example, the temperature of hot water in a hot water storage tank for hot water supply is 60 to 80 ° C. It is desirable that In the conventional fuel cell power generator, the temperature of the recovered water circulated to the hot water storage tank is about 50 ° C. as described above, and has a drawback that it is considerably lower than the desired temperature. The temperature of the circulating recovered water can be raised to about 70 ° C. only for cooling the battery cooling water to a predetermined temperature, for example, 75 ° C., but in that case, as a result, the battery cooling water is It becomes necessary to increase the capacity of the equipment of the cooling system. That is, in the case of the system shown in FIG. 2, it is necessary to increase the capacity of the battery cooling water cooler 7 and / or the recovered water cooler 13 to an extent unsuitable for the size of the fuel cell power generator. Yes, or otherwise, the return temperature to the exhaust gas cooler 15 will be high, and the amount of produced water recovered will be insufficient, and replenishment water will enter from outside. There is a problem that the life of the processing device 17 is shortened.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to increase the waste heat recovery temperature of a fuel cell to improve the utility value of waste heat utilization equipment, and Provided is a fuel cell power generation apparatus having a waste heat utilization facility capable of supplying battery cooling water at a predetermined temperature to a fuel cell without inappropriately increasing the capacity of a system for cooling the battery cooling water, and a control method therefor. It is in.

[0016]

In order to solve the above-mentioned problems, the present invention provides a fuel cell for removing generated heat by cooling water flowing through a cooling plate, and a cooling water discharged from the cooling plate. In a fuel cell power generator for supplying heat to waste heat utilization equipment, a battery cooling water circulation pipe for circulating cooling water to a cooling plate, and cooling water after battery cooling are separated from a first branch point of the battery cooling water circulation pipe. After flowing and passing through the waste heat utilization equipment, the waste heat utilization equipment circulation pipe returning to the first junction of the battery cooling water circulation pipe, and the downstream of the first junction of the battery cooling water circulation pipe A cooling water cooler provided, and a cooling water diverted from a second branch point between the first junction and the battery cooling water cooler and returned to a second junction downstream of the battery cooling water cooler. A bypass line and the first junction or the first junction And the first flow control valve provided in the waste heat utilization equipment circulation system piping, and the second flow rate provided in the second branch point or the second junction point A control valve, or one of a second flow rate control valve provided in a battery cooling water circulation system pipe between a second branch point and a second junction, and a thermometer for measuring a temperature of cooling water supplied to the cooling plate. A control device that adjusts an opening of the first flow control valve and an opening of the second flow control valve based on a difference between an output value of the thermometer and a predetermined temperature set value. (The invention of claim 1).

According to the above configuration, as described later in detail,
It is possible to supply battery cooling water at approximately 80 ° C to the waste heat utilization equipment without increasing the capacity of the system equipment that cools the battery cooling water, thereby improving the use value of the waste heat utilization equipment. be able to.

The application of the first aspect of the present invention is not limited to the system shown in FIG. For example, the waste heat utilization equipment is not limited to hot water supply, but may be a heating device.Also, instead of the recovered water, the cooling water for cooling the battery cooling water flowing to the battery cooling water cooler 7 may be: Using ordinary cooling water or a different refrigerant, the refrigerant can be supplied to the second waste heat utilization facility to separately recover heat.

Further, the application of the present invention is not limited to a solid polymer electrolyte fuel cell power generator. For example, the present invention can be applied to a case where the waste heat recovery at a normal operating temperature of about 170 ° C. and the waste heat recovery at a relatively low temperature are used in combination in a phosphoric acid fuel cell power generator.

As an embodiment of the first aspect of the present invention in which the first aspect of the present invention is combined with a part of the system shown in FIG. 2, the inventions of the second to fifth aspects are preferable. That is,
In the fuel cell power generator according to claim 1, the waste heat utilization equipment is a hot water tank for supplying hot water (the invention of claim 2). This makes it possible to supply hot water of 60 ° C. or higher.

Also, as in the invention of claim 3, claim 1
3. The fuel cell power generator according to 2, wherein a pure water tank is provided in the battery cooling water circulation pipe, and cooling water flows from the pure water tank to the cooling plate. Furthermore, as in the invention of claim 4, in the fuel cell power generator according to any one of claims 1 to 3, the cooling refrigerant of the battery cooling water flowing to the battery cooling water cooler is a fuel cell power generator. A refrigerant outlet pipe and a refrigerant inlet pipe for circulating the recovered water as the cooling refrigerant, a recovered water cooler and a recovered water tank provided between the two pipes, And a water treatment device provided between the water treatment device and the water tank. As described above, a system that is rational and has high thermal efficiency can be achieved as a whole of the cogeneration fuel cell power generation system.

Also, as in the invention of claim 5, claim 3
Or in the fuel cell power generator according to 4, wherein the thermometer measures the temperature of the cooling water in the pure water tank, so that the temperature in the pure water tank can be maintained even when there is disturbance such as a change in the temperature of the recovered water. Temperature change does not fluctuate so much,
Stable control of the control valve becomes possible.

Further, as a control method of the power generation device, the method of claim 6 is preferable. That is, in the control method of the fuel cell power generator according to any one of claims 1 to 5, when supplying cooling water at a predetermined temperature to the cooling plate,
The adjustment of the opening of the first flow control valve takes precedence over the adjustment of the opening of the second flow control valve, and the second flow control valve is fixed to a state in which the entire amount of the cooling water flows to the bypass line. If the temperature of the cooling water exceeds a predetermined set temperature in a state where the flow rate control valve of the first method is adjusted so that the entire amount of the cooling water flows to the waste heat utilization facility, the second cooling water is cooled.
The opening adjustment of the flow control valve is started. The specific contents and operation of this method will be described later in detail.

[0024]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a system diagram showing an embodiment according to the present invention. Members having the same functions as those in FIG. The difference between FIG. 1 and FIG.
1 and the cooling water after battery cooling is diverted from the first branch point (point C) of the battery cooling water circulation system piping 40 to utilize waste heat. After flowing through the hot water storage tank 12 as a facility, waste heat is returned to a first flow control valve (three-way control valve) 22 provided at a first junction (point D) of the battery cooling water circulation system piping 40. The point is that the equipment circulation system piping 50 is provided, and the following configuration is further provided.

That is, the battery cooling water cooler 7 provided downstream of the first junction (point D) of the battery cooling water circulation system pipe 40, the first junction (point D) and the battery cooling water cooler 7 And a second flow control valve (three-way control valve) 25 provided at a second junction (point H) downstream of the battery cooling water cooler 7 from a second branch point (point E). Bypass line 2 that returns to
4, a thermometer 20 provided in the pure water tank 5, an opening of the first flow control valve 22 and a second flow control valve based on a difference between an output value of the thermometer and a predetermined temperature set value. And a control unit 62 for adjusting the opening degree of the control unit 25.

The positions where the flow rate control valves are provided are as follows:
The present invention is not limited to the above, and may not be a three-way control valve depending on the position. For example, instead of the first flow control valve 22 shown in FIG. 1, a three-way control valve is provided at the first branch point (point C in FIG. 1) of the battery cooling water circulation system piping, or the waste heat utilization equipment circulation system piping 50 At point A or point B
By providing a directional flow control valve, the same function is obtained. Further, instead of the second flow control valve 25 shown in FIG. 1, a second branch point (E in FIG. 1) of the battery cooling water circulation system piping is used.
A three-way control valve is provided at point (2) or at the second branch point (point E).
The same function can be obtained by providing a two-way flow control valve at point F or point G of the battery cooling water circulating system pipe between the second junction (point H).

In the above configuration, a predetermined temperature, for example, 75 ° C.
When the cell cooling water is supplied to the cooling plate of the fuel cell, each flow control valve is controlled as in the invention of claim 6.
That is, the opening adjustment of the first flow control valve (three-way control valve) 22 takes precedence over the opening adjustment of the second flow control valve (three-way control valve) 25, and first, the second flow control valve 25 is bypassed. The cooling water temperature is set to a predetermined value in a state in which the first flow rate control valve 22 is adjusted to a state in which the entire amount of cooling water flows to the waste heat utilization facility by fixing the entire amount of the cooling water to the line. When the temperature exceeds 75 ° C., the opening adjustment of the second flow control valve is started to cool the cooling water. Such control is referred to as split control.

The above-described split control will be described in detail below with respect to specific contents showing numerical examples and operations.

An example of control for keeping the temperature of the pure water tank at 75 ° C. will be described below. First, at the time of startup when the fuel cell is not generating power, the temperature of the battery cooling water is raised to about 60 ° C. by an electric heater in the pure water tank 5 (not shown).
The battery cooling water circulation pump 6 is driven. At this time, since the temperature of the water in the pure water tank is still sufficiently low, there is no need to cool the water, and the first flow control valve 22 and the second flow control valve 25 are not required.
In both cases, the opening degree is such that the entire amount flows through the battery cooling water circulation system piping 40 and the bypass line 24. Here, this state is called an opening degree of 0%.

Then, with the start of power generation by the fuel cell, the cooling water entering the fuel cell at 60 ° C. becomes 60 ° C. + α,
Heat the pure water tank gradually. In this case, the control device 62 (for example, a PID control device) sets the set temperature (75 ° C.)
And the difference between the temperature of the pure water tank and the temperature of the pure water tank are calculated so that the difference is zero, that is, the temperature of the pure water tank is 75 ° C.
Only the opening of the first flow control valve 22 is controlled.

Eventually, even if the output of the fuel cell becomes large or the temperature of the outside hot water storage tank becomes high, the first flow rate control valve 22 becomes fully open to the hot water storage tank 12 side. Only when the temperature of the water tank can no longer be maintained at 75 ° C. (when the temperature becomes 75 ° C. or higher), the second flow control valve 25 is opened, and the cooling of the battery cooling water is performed by the battery cooling water cooler 7. Start.

In this case, it is assumed that the first flow rate control valve 22 has such an opening degree as to flow to the hot water storage tank side and the second flow rate control valve 25 has such an opening degree as to entirely flow through the bypass line. Call it%. When the first flow rate control valve and the second flow rate control valve both have an opening that flows to the opposite side to the battery cooling water circulation system piping and the bypass line, the opening is referred to as 100% here.

The opening is 0%, the opening is 50% and the opening is 10
As is clear from the description of 0%, the first flow control valve and the second flow control valve are not both simultaneously adjusted to the intermediate opening degree, and either of the first and second flow control valves is not fully opened or fully closed. In this state, the opening of the other valve is controlled. Such a control method is called split control.

In the system diagram of FIG. 1, when the water temperature in the pure water tank 5 is 75 ° C., an example of the temperature at other main points is as follows.

Fuel cell outlet temperature: 80 ° C Water temperature in hot water tank: 60 ° C Temperature at point A of waste heat utilization equipment circulation system piping: 80 ° C Temperature at point B of waste heat utilization equipment circulation system piping: 65 ° C Refrigerant outlet pipe temperature: 50 ° C. Refrigerant inlet pipe temperature: 35 ° C. Recovered water cooler outlet pipe temperature: 45 ° C. According to the above, hot water of about 80 ° C. can be supplied to hot water storage tank 12 and battery cooling water is supplied. The temperature of the recovered water as a cooling medium at the outlet of the recovered water cooler can be 45 ° C. or lower. Therefore, the waste heat recovery temperature of the fuel cell can be increased, and the predetermined temperature 7 can be maintained without inappropriately increasing the capacity of the system for cooling the battery cooling water.
5 ° C. cell cooling water can be supplied to the fuel cell.

Further, since the temperature of the recovered water can be kept sufficiently low, the generated water can be recovered and the water can be self-sustained. Driving becomes possible.

[0038]

As described above, according to the present invention, the heat generated by the cooling water flowing through the cooling plate is removed from the fuel cell, and the heat of the cooling water discharged from the cooling plate is transferred to the waste heat utilization equipment. In the fuel cell power supply to be supplied, a battery cooling water circulation pipe for circulating cooling water to the cooling plate, and cooling water after battery cooling is diverted from a first branch point of the battery cooling water circulation pipe to provide a waste heat utilization facility. A waste heat utilization equipment circulation pipe that returns to a first junction of the battery cooling water circulation pipe after flowing, and a battery cooling water cooler provided downstream of the first junction of the battery cooling water circulation pipe A bypass line for diverting cooling water from a second branch point between the first junction and the battery cooling water cooler and returning to a second junction downstream of the battery cooling water cooler; A first flow control provided at a branch point or the first junction; A valve or a first flow control valve provided in the waste heat utilization equipment circulation system piping, and a second flow control valve provided in the second branch point or the second junction, or a second branch point Any one of the second flow control valves provided in the battery cooling water circulation system pipe between the first and second junctions,
A thermometer for measuring the temperature of cooling water supplied to the cooling plate,
A control device that adjusts an opening of the first flow control valve and an opening of the second flow control valve based on a difference between an output value of the thermometer and a predetermined temperature set value. As a result, the waste heat recovery temperature of the fuel cell is raised to improve the utility value of the waste heat utilization equipment, and the battery cooling water at a predetermined temperature is maintained without inappropriately increasing the capacity of the system for cooling the battery cooling water. Fuel cell power generation apparatus having a waste heat utilization facility capable of supplying the fuel cell to the fuel cell, and a control method therefor.

[Brief description of the drawings]

FIG. 1 is a system diagram showing an embodiment of a fuel cell power generator according to the present invention.

FIG. 2 is a system diagram showing an example of a conventional fuel cell power generator.

[Explanation of symbols]

1: fuel cell, 5: pure water tank, 7: battery cooling water cooler, 10: recovered water tank, 12: hot water storage tank, 13: recovered water cooler, 17: water treatment device, 20: thermometer, 24: Bypass line, 22: first flow control valve, 25: second flow control valve, 40: battery cooling water circulation system piping, 50: waste heat utilization equipment circulation system piping, 62: control device, 71: refrigerant outlet piping, 72: refrigerant inlet pipe.

Claims (6)

[Claims] 1. A fuel cell, wherein heat generated by cooling water flowing through a cooling plate is removed, and a fuel cell power generator for supplying heat of cooling water discharged from the cooling plate to a waste heat utilization facility, A battery cooling water circulating pipe for circulating cooling water to the battery cooling water circulating pipe;
A waste heat utilization facility circulating pipe that recirculates to a first junction of the battery cooling water circulation pipe after diverting from the branch point and flowing through the waste heat utilization facility; and the first junction of the battery cooling water circulation pipe A battery cooling water cooler provided further downstream than the battery cooling water cooler; and a second branch downstream of the battery cooling water cooler that divides cooling water from a second branch point between the first junction and the battery cooling water cooler.
A bypass line that returns to the junction, a first flow control valve provided at the first branch point or the first junction, or a first flow control valve provided at the waste heat utilization equipment circulating system piping A second flow control valve provided at the second branch point or the second junction, or a second flow control valve provided in a battery cooling water circulation system pipe between the second branch point and the second junction. One of the valves, a thermometer for measuring the temperature of cooling water supplied to the cooling plate, and an opening degree of the first flow control valve based on a difference between an output value of the thermometer and a predetermined temperature set value. A control device for adjusting the opening degree of the second flow control valve. 2. The fuel cell power generator according to claim 1, wherein the waste heat utilization equipment is a hot water tank for supplying hot water. 3. The fuel cell power generator according to claim 1, wherein a pure water tank is provided in the battery cooling water circulation pipe, and cooling water flows from the pure water tank to the cooling plate. Characteristic fuel cell power generator. 4. The fuel cell power generator according to claim 1, wherein a cooling refrigerant for the battery cooling water flowing to the battery cooling water cooler is recovered water in the fuel cell power generator. A refrigerant outlet pipe and a refrigerant inlet pipe for circulating recovered water as a cooling refrigerant, a recovered water cooler and a recovered water tank provided between the two pipes, and between the refrigerant inlet pipe and the pure water tank. A fuel cell power generator, comprising: a water treatment device provided. 5. The fuel cell power generator according to claim 3, wherein the thermometer measures a temperature of a cooling water in a pure water tank. 6. The control method for a fuel cell power generator according to claim 1, wherein when the cooling water at a predetermined temperature is supplied to the cooling plate, the opening of the first flow control valve is adjusted. Takes precedence over the opening degree adjustment of the second flow control valve, performs the second flow control valve in a state where the entire amount of the cooling water flows to the bypass line, and sets the first flow control valve to the waste heat utilization equipment. If the temperature of the cooling water exceeds a predetermined set temperature while adjusting the state in which the entire amount of the cooling water flows,
A method for controlling a fuel cell power generator, characterized by starting adjustment of an opening degree of a second flow control valve in order to cool cooling water.