JPH05190190A - Fuel cell type power generation system - Google Patents

Abstract

PURPOSE:To reduce dimension of the plant equipment and permit the disposal of a variety of waste heat utilization by installing a steam generator on the downstream side of the water phase outlet of a gas/water separator and generating steam by heating the water in a secondary steam generation system, and feeding the steam to a waste heat utilizing device. CONSTITUTION:The cooling water 2b separated by a gas/water separator 2 is introduced into a heat exchanger 5 for adjusting temperature through the primary side of a steam generator 4 by a battery cooling water circulation pump 3, and the cooling water which is temperature-adjusted is returned to a battery cooling device 1c through an electric heater 6 for the battery cooling water, and a battery cooling water system is constituted. In the steam generator 4, the water in the secondary steam generation system is heated by the battery cooling water which flows on the primary side, and steam 4a is generated, and supplied into a waste heat utilizing device 13 through a steam feeding pipe 11 and a pressure adjusting valve 12. The condensed water after the utilization by the device 13 is returned to the generator 4 through a condensate returning pipe 15 by a condensate circulation pump 14. Accordingly, a variety of waste heat utilization is enabled.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel cell power generation system, and more particularly to a steam and hot water supply system utilizing waste heat.

[0002]

2. Description of the Related Art A fuel cell power generation system converts chemical energy contained in a fuel such as city gas or propane gas into electric energy and is an apparatus for producing hydrogen from a fuel cell main body and fuel such as city gas or propane gas. , A converter for converting a direct current output generated by the fuel cell main body into an alternating current, a heat exchanger for maintaining the temperature of the working gas at a temperature suitable for the operation of the fuel cell main body and hydrogen generation, and the like. The fuel cell main body directly converts the binding energy between hydrogen gas generated by the hydrogen generator and oxygen in the air into electric energy, but at the same time, heat is also generated.

As described above, the fuel cell power generation system is evaluated as a clean power generation system having high power generation efficiency, low emission of air pollutants, and low noise due to power generation by chemical reaction.

By the way, in order to efficiently carry out the electrochemical reaction of the fuel cell body, the temperature of the fuel cell body must be maintained at a constant temperature level, and the fuel cell body is cooled to an appropriate temperature by cooling water or the like. This cooling water system consists of a steam separator, a pump,
Exhaust heat, which is composed of a heat exchanger and the like, is used for various purposes. This exhaust heat is generally taken out as hot water, but in recent years, there has been a strong demand for taking out steam in order to expand the range of uses of the exhaust heat.

FIG. 4 is a characteristic diagram showing the relationship between the general power generation load and the total thermal efficiency of a fuel cell power generation system. As can be seen from this characteristic diagram, the power generation efficiency for the power generation load is 4
Although it is 0%, the total efficiency is 80% or more when all of the low temperature exhaust heat recovery component at the hot water level and the high temperature exhaust heat recovery component at the steam level are used. As described above, the present fuel cell power generation system can effectively use not only power generation but also exhaust heat outside the system. It is highly useful as a drive source for turbines. Conventionally, as a fuel cell power generation system incorporating such an exhaust heat utilization system, there is a configuration as shown in FIG.

As shown in FIG. 2, a fuel cell body 2 having a fuel electrode 21a, an air electrode 21b and a cell cooler 21c.
The reaction heat generated in 1 is taken out by exchanging heat with the battery cooling water in the battery cooler 21c, and the battery cooling water becomes a gas-liquid two-phase flow and is guided to the high temperature exhaust heat recovery heat exchanger 22, Further, it is introduced into the steam separator 23. This steam separator 23
Then, the battery cooling water system in which the vapor 23a of the gas-liquid two-phase flow is liquefied to form the cooling water 23b, which is guided to the cooler 21c by the battery cooling water circulation pump 24 through the exhaust heat recovery heat exchanger 25 and the battery cooling water electric heater Is composed of.

In the fuel cell power generation system having such a structure, the high temperature exhaust heat recovery heat exchanger 22 is replaced by the steam separator 2.
Since it is installed before 3, the high temperature exhaust heat can be taken out indirectly. However, the battery cooling water that has exited the battery cooler 21c is in a gas-liquid two-phase flow, and the gas-liquid mixing ratio of the battery cooling water changes due to changes in the amount of power generated by the battery due to fluctuations in the power generation load, etc. There is a problem that the amount of heat recovery fluctuates, and it is difficult to take out and utilize stable high temperature exhaust heat.

On the other hand, as a fuel cell power generation system different from the above, there is a system as shown in FIG. 3 in which excess steam is directly taken out from a steam separator. That is, as shown in FIG. 3, the reaction heat generated in the fuel cell main body 31 including the fuel electrode 31a, the air electrode 31b, and the cooler 31c is taken out by exchanging heat with the cell cooling water in the cooler 31c, and then the cell is cooled. The cooling water becomes a gas-liquid two-phase flow and is introduced into the steam-water separator 32. In this gas-water separator 32, the vapor-liquid two-phase flow steam 32a is liquefied into cooling water 32b, and this cooling water is passed through a heat exchanger 34 for recovering exhaust heat and a battery cooling water electric heater 35 by a battery cooling water circulation pump 33. A battery cooling water system for returning to the cooler 31c is configured. In addition, the excess steam in the steam separator 32 is introduced into the exhaust heat utilization device 37 through the steam supply pipe 36, and a part of the liquefied cooling water is condensed by the circulation pump 38 through the condensed water return pipe 39. 32 is returned to the downstream side, and the exhaust heat utilization device 3
Another part of the cooling water liquefied in 7 is introduced into the water treatment device 40, and the cooling water treated here is returned to the downstream side of the steam separator 32.

In the fuel cell power generation system having such a structure, since the surplus steam is directly introduced into the exhaust heat recovery device 37 from the steam separator 32, there is an advantage that the steam having a high temperature level can be taken out. However, since the battery cooling water system and the exhaust heat utilization device 37 are the same piping system, the exhaust heat utilization device 37 needs to be provided with leak prevention measures and water pollution measures.
There is a problem that the quality of the material is increased and the capacity of the water treatment device 40 is increased, which also increases the plant equipment and the cost.

[0010]

As described above, the conventional fuel cell power generation system has a structure capable of recovering high-temperature exhaust heat. There was a problem that it would lead to size increase and cost increase due to increased capacity.

Further, in order to take out the high temperature exhaust heat from the battery cooling water system, not only the high temperature steam is always required but it may be taken out as the high temperature water. In the conventional system, the high temperature steam and the high temperature water are taken out at the same time. It is difficult to cope with the diversification of utilization of exhaust heat. It is an object of the present invention to provide a fuel cell power generation system that can reduce the size of plant equipment and make it inexpensive to cope with diversification of utilization of exhaust heat.

[0012]

A fuel cell body having a fuel electrode, an air electrode and a cooler, and two-phase flow cooling water heated by reaction heat of the fuel cell body is separated into a gas phase and a water phase. In the fuel cell power generation system, the fuel cell cooling water system is composed of a gas phase separator that does, and a cell cooling water circulation pump that circulates the cooling water separated by the steam separator through the cooler of the fuel cell body, A steam generator for heating the water of the secondary steam generation system separated from the fuel cell cooling water system by the excess heat of the cell cooling water system to generate steam is provided on the downstream side of the water phase outlet of the steam separator. The steam generated from this steam generator is supplied to the exhaust heat utilization device.

[0013]

In the fuel cell power generation system having such a configuration, the water in the secondary steam generation system of the steam generator is separated from the cell cooling water system by the cell cooling water flowing out from the steam separator. By heating to generate steam, the steam can be supplied to the exhaust heat utilization apparatus, so that the plant equipment can be downsized as compared with the conventional one, and it is economically advantageous.

Further, by connecting a hot water supply system to the downstream side of the steam generator and taking out excess saturated water other than the amount of steam, high temperature water can be supplied to the exhaust heat utilization device that requires hot water. It is possible to cope with diversification of utilization of waste heat.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram of a fuel cell power generation system according to the present invention. In FIG. 1, reference numeral 1 denotes a fuel cell main body including a fuel electrode 1a, an air electrode 1b and a cooler 1c. The reaction heat generated in the fuel cell main body 1 is exchanged with the cell cooling water in the cell cooler 1c. The two-phase flow battery cooling water, which has been taken out in the above step, is introduced into the steam separator 2 and steam 2a.
And cooling water 2b. The cooling water 2b separated by the steam / water separator 2 is supplied to the steam generator 4 provided downstream of the water phase outlet of the steam / water separator 2 by the battery cooling water circulation pump 3.
A battery which is introduced into the temperature adjusting heat exchanger 5 through the primary side (high temperature side) of the battery and returns cooling water whose temperature is adjusted by the temperature adjusting heat exchanger 5 to the battery cooler 1c through the battery cooling water electric heater 6. It constitutes the cooling water system. In this case, an inlet control valve 8 is provided in the pipe line 7 connecting the steam separator 2 and the steam generator 4. Further, a bypass piping line 9 which bypasses the inlet control valve 8 and the steam generator 4 and flows the cooling water 2b from the gas phase separator 2 to the battery cooling water circulation pump 3 side is provided. A control valve 10 is provided.

Here, the steam generator 4 heats the water in the secondary steam generating system by the battery cooling water flowing to the primary side to generate steam. The steam 4a generated by the steam generator 4 is used.
Is supplied to the first exhaust heat utilization device 13 through the steam supply pipe 11 and the pressure regulating valve 12. And this first
The condensed water that has been used in the waste heat utilization device 13 is returned to the steam generator 4 by the condensed water circulation pump 14 through the condensed water return pipe 15.

The condensed water of the steam generator 4 is supplied to the second exhaust heat utilization device 17 through the hot water supply pipe 16 and at the same time, the steam generation blow line 1 is supplied to the water treatment device 18.
The water supplied through 9 and treated by the water treatment device 18 is introduced into the battery cooling water system.

In the figure, 19 is a pressure detector for detecting the steam pressure in the steam generator 4, and 20 is the opening of the pressure regulating valve 12 so as to keep the pressure of the steam generator 4 at a predetermined value. It is a pressure controller. Next, the operation of the fuel cell power generation system configured as described above will be described.

Now, when the fuel cell main body 1 is operated without exhaust heat recovery, the control valve 10 of the bypass piping line 9 is open and the inlet control valve 8 is closed. In such a state, in order to generate the steam from the steam generator 4 and perform the exhaust heat recovery operation, the control valve 10 of the bypass piping line 9 is closed and the inlet control valve 8 is opened. The battery cooling water flowing out from the separator 2 flows through the battery cooling water system through the primary side of the steam generator 4. Then,
The water in the secondary steam generation system of the steam generator 4 is heated by the excess heat of the battery cooling water system to generate steam, and this steam is supplied to the first exhaust heat utilization device 13 via the pressure adjustment valve 12,
The condensed water after using the exhaust heat is returned to the steam generator 4 by the condensed water circulation pump 14. In this case, the opening degree of the pressure adjusting valve 12 is controlled by the pressure controller 20, and the steam pressure in the steam generator 4 is kept constant.

The condensed water in the steam generator 4 is supplied as warm water to the second exhaust heat utilization device 17 through the hot water supply pipe 16, and a part of the condensed water in the steam generator 4 is fed to the water treatment device. The water introduced and treated here is supplied to the battery cooling water system.

As described above, in this embodiment, the steam generator 4 is provided on the downstream side of the steam separator 2, and the water in the secondary steam generation system of the steam generator 4 is heated by the excess heat of the battery cooling water system. Since the steam is generated by the steam generator, the steam can be supplied to the first exhaust heat utilization device 13 in a state of being separated from the battery cooling water system, and the condensed water of the steam generator 4 can be supplied to the second exhaust heat utilization device 17 as hot water. As it can be supplied simultaneously, it is possible to cope with diversification of exhaust heat.

Further, in the battery cooling water circulation pump 3, when the pressure loss of the battery cooling water system due to, for example, piping is large, there is a possibility that cavitation may occur when the pressure falls below the saturated vapor pressure of water, which causes noise and vibrations in the pump. It causes the deterioration of performance. However, by installing the steam generator 4 in front of the cooling water circulation pump 3 as described above,
Since the cell cooling water that has become high temperature due to the reaction heat of the fuel cell body 1 is cooled (undercooled), the pump can be effectively used.
The SH (net suction head) can be increased, and it works effectively for the pump. In this case, the pressure drop due to the pressure loss of the battery cooling water system in the steam generator 4 is minute as compared with the undercool amount.

Therefore, since steam can be indirectly taken out from the battery cooling water system, the steam generator 4 having a large pressure loss corresponding to the undercool of the battery cooling water cooled by the steam generator 4 can be installed. The capacity of the vessel 4 can be reduced, and the power of the cooling water circulation pump 3 can be reduced, which can reduce the size of plant equipment and reduce the cost.

Further, an inlet control valve 8 provided on the inlet side of the steam generator 4 and a piping line 9 bypassing these
Since the bypass control valve 10 is provided in the above, by opening the inlet control valve 8 at the time of heat-up of the battery cooling water system at the time of plant startup, the temperature rise on the secondary side of the steam generator 4 can be accelerated. On the other hand, when increasing or decreasing the load on the exhaust heat utilization device during plant operation, controlling the inlet control valve 8 and the bypass control valve 10 causes the operation of the exhaust heat utilization device to fluctuate or start up. Even when the plant is stopped, it is possible to operate the plant stably without affecting the power generation characteristics. In the above embodiment, the steam generator 4
Although it is shown as an image diagram of a kettle type boiler, the same exhaust heat recovery can be performed by a steam generator of another form.

In the above embodiment, the condensed water of the steam generator 4 is directly supplied to the second exhaust heat utilization device 17 as hot water, but the secondary system pressure of the steam generator 4 is saturated with the generated steam. There is a case where the temperature is as high as the vapor pressure and the hot water is pressurized. In such a case, it is possible to deal with this by providing a pressure reducing valve in the middle of the hot water supply piping line 16.

Furthermore, the steam generator 4 may deteriorate the performance of the steam generator due to the accumulation of scale, rust, etc. inside the steam generator 4 during operation. The water may blow out one by one. In such a case, the blown water is not simply discharged to the outside, but may be injected into the water treatment device 18 to be treated with water and then returned to the battery cooling water system. Good.

[0028]

As described above, according to the present invention, the surplus heat of the battery cooling water system is indirectly taken out as steam having a high heat utilization value in a form separated from the battery cooling water system. It is possible to provide a fuel cell power generation system capable of achieving downsizing and cost reduction, and being able to cope with load fluctuations of exhaust heat utilization devices and diversification of exhaust heat utilization.

[Brief description of drawings]

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

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

FIG. 3 is a configuration diagram showing another example of a conventional fuel cell power generation system.

FIG. 4 is a characteristic diagram showing the relationship between the power generation load and the total thermal efficiency of the fuel cell power generation system.

[Explanation of symbols]

1 ... Fuel cell main body, 1a ... Fuel electrode, 1b ... Air electrode, 1c
... Cooler, 2 ... Steam separator, 3 ... Battery cooling water circulation pump, 4 ... Steam generator, 5 ... Heat exchanger for temperature adjustment, 6 ... Battery cooling water electric heater, 13 ... First exhaust heat utilization device , 17
... second exhaust heat utilization device, 18 ... water treatment device

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Hiroshi Sakamoto, Inventor Hiroshi Sakamoto 3-2-95 Chiyosaki, Nishi-ku, Osaka City, Osaka Prefecture Fuel Cell Project Department, Osaka Gas Co., Ltd. (72) Eiichi Sugiyama, Suehiro, Tsurumi-ku, Yokohama-shi, Kanagawa 2-4, Machi Within the Keihin office of Toshiba Corporation

Claims (1)

[Claims] 1. A fuel cell main body having a fuel electrode, an air electrode and a cooler, and a gas phase separation for separating cooling water heated by reaction heat of the fuel cell main body into a two-phase flow into a gas phase and an aqueous phase. And a fuel cell cooling water system configured by a cell cooling water circulation pump that circulates the cooling water separated by the water and water separator through the cooler of the fuel cell body, wherein the steam separation A steam generator for heating the water of the secondary steam generation system separated from the fuel cell cooling water system by the excess heat of the cell cooling water system to generate steam is provided on the downstream side of the water phase outlet of the steam generator. A fuel cell power generation system characterized in that steam generated from the exhaust gas is supplied to an exhaust heat utilization device.