JPH02230665A - Fuel cell power generating system - Google Patents

Abstract

PURPOSE:To enable the common use of a heat source for a steam generation line and fuel cell preheating and to facilitate the temperature decrease in operation stop by installing an electric heater in a heat circulation line and connecting a branch circulation line having a cooler in a cooling water circulation line. CONSTITUTION:When a system is started, stored water is circulated with a pump 23, and heated with a heater 22, and at the same time, a three-way valve 13 is switched to the B side, and a pump 12 in a cooling water circulation line 10 is driven and water 8 is circulated as a heating medium through a fuel cell 1 and a branch circulation line 30. At this time, a cooler 32 is stopped and a temperature control valve 33 is controlled to preheat to a specified temperature. When power generation is started, the heater 22 and the pump 23 are stopped, and the valve 15 is switched to the C side. When the system is stopped, the valve 15 is switched to the B side, a valve 32B of the cooler 32 is opened and temperature of the circulation line 30 is controlled with the valve 33 so as to decrease at a specified rate. The common use of the heat source for steam generation line and fuel cell preheating is made possible without any adverse effect on output of the cell 1, and decrease in temperature in operation stop is made easy.

Description

[Detailed Description of the Invention] [Field of Industrial Application] This invention relates to the structure of a reforming steam generation system and a fuel cell cooling system of a water-cooled fuel cell power generation device, and in particular to temperature control characteristics during starting and stopping thereof. Regarding the improvement of [Prior Art] The fuel cell power generation system 1 is a reformer that generates hydrogen-rich gas by steam reforming using natural gas, methanol, etc. as a raw material. It consists of a fuel cell that uses the hydrogen produced by this reformer as fuel and air as an oxidizer to generate electricity, and an orthogonal conversion device that converts the DC output of the fuel cell into AC. When starting power generation in this fuel cell power generation device, a mixed gas of raw material gas and steam is first introduced into the reformer to perform a reforming reaction.
For this purpose, it is necessary to have equipment that generates water vapor (approximately 160'C saturated steam) as equipment. In addition, in order to generate electricity, the temperature of the battery body must be raised to approximately 130°C, which requires an electric heater or the like to be installed in the battery cooling water system to raise the temperature. For this reason, some are known to have two pieces of equipment for startup, such as a boiler for steam generation and a heater for raising battery temperature. In addition, when stopping the operation of the fuel cell, the cooling water, which has reached a high temperature of, for example, 160°C or higher due to the heat generated by the fuel cell, is cooled to bring the fuel cell temperature to a temperature suitable for storage, for example, 80°C or lower. However, the reality is that many systems rely on natural cooling.

(Problem to be solved by the invention) In order to avoid complicating the configuration of a conventional bag storage system that is equipped with a heat source for steam generation and a heat source for battery preheating, an electric heater is installed in the battery cooling water system as a dual-use type for both heat sources. At the start of power generation, the cooling water is heated to approximately 130°C to preheat the fuel cell, and the heated cooling water is used as a steam generation source, and during power generation operation, the cooling water supplied to the fuel cell is minimized. Attempts have also been made to maintain the fuel cell at its operating temperature by controlling the flow rate on and off, but
Although the battery temperature can be maintained at a certain operating temperature, there is a considerable temperature difference in the vertical direction of the stacked fuel cell, resulting in a difference in output characteristics between each vehicle cell, which causes a decrease in output characteristics and deterioration of the electrode catalyst layer. There is a problem that this is promoted, and improvement is required.

On the other hand, if power generation operation is stopped by performing purge with inert gas while the fuel cell is at a high operating temperature when power generation operation is stopped, a delay in reaction gas purge may cause sintering phenomenon in some single cells. There is a problem in that the effective reaction area of the electrode catalyst decreases, which accelerates the decrease in output characteristics, and there is a need to improve this problem. An object of the present invention is to provide a steam generation system for a water-cooled fuel cell that can share a heat source for the steam generation system and for preheating the fuel cell without adversely affecting the output characteristics of the fuel cell, and that can easily lower the temperature when the operation is stopped. and to obtain a cooling system.

[Effect]

In the above means, when starting the fuel cell, a heating circulation system having an electric heater heats the water stored in the steam converter to a predetermined temperature to generate steam, and supplies the heated steam to the steam reformer system to produce raw fuel. At the same time, the contained water is used as a heating medium to circulate to the fuel cell through a branch TL & science system having a temperature control valve and a cooling water m* system to heat the fuel cell to its starting temperature, During power generation, the cooling water whose temperature has risen due to the heat generated by the fuel cell is circulated through the cooling water circulation system to the steam separator, where it is used as a heat medium for steam generation.At the same time, the stored water, which has lost its heat of vaporization and cooled down, is used to power the fuel cell. When the power generation operation is stopped, the cooling water cooled by the cooler arranged in the branch circulation system is circulated to the fuel cell to cool the fuel cell at a predetermined rate of rise. The generation of reforming steam and the startup of the fuel cell are achieved through the combination of three circulating systems connected to each other, an electric heater and a cooler. driving. AM control in three states, including stop, can be performed stably, and deterioration in fuel cell performance can be avoided. [Example] This invention will be explained below based on an example. Fig. 1 is a piping system diagram of the main parts showing an embodiment of the present invention, and Fig. 2 is a connection diagram of the main parts of the electrical system, mainly showing the water system section consisting of the cooling water circulation system and the steam generation system. It is something. In FIG. 1, 1 is a water-cooled fuel cell, 2 is a steam reformer system including a steam reformer 2A, and 3 is a steam separator containing contained water 8 and high-temperature steam 9. is supplied from a condenser or the like (not shown) via a valve 6, and its liquid level is maintained at a predetermined level by a level controller 6A. Further, 10 is a cooling water circulation system that circulates the stored water 8 as a heating medium or a cooling medium to the cooler of the fuel cell 1,
Piping 11 connected to the bottom branch circulation system of the steam separator 3,
It is configured as a circulation passage including a circulation bomb 12, a flow control valve 13, a fuel cell outlet side pipe 14, a three-way valve 15, and a pipe 16 connected to the upper part of the steam separator 3.

2l is a heating circulation system for stored water 8, which includes an electric heater 22,
11-ring pump 23 and piping 21A, 218 that forms a circulation passage between these and the steam separator. Compiled with 21C. 30 is a branch circulation system including a cooler 32 and a temperature control valve 33, one of which pipes 31A is connected to one port B of a three-way valve.
is switchably connected to the cooling water circulation system 10 through the pipe 31C, and the other end is connected to the upper part of the water M portion Ma3 through the pipe 31C, and one port B of the three-way temperature control valve 33 is connected to the pipe 31 [ 1 to the suction side of the circulation bomb 12, the cooling water circulation system 10 receives water vapor.
A W1 ring passage is formed that bypasses ll3.

As mentioned above! ．． :． In the configured example bag storage, when starting the device, the stored water 8 of the steam separator 3 is circulated by the pump 23 and heated by the electric heater 22, and the three-way valve 15 is switched to the A-B side to complete the cooling water circulation system. 10 pumps 12 are driven, and stored water 8 is circulated as a heating medium through the fuel cell 1 and the branch circulation system 3o. At this time, the valve 32B of the cooler 32 is closed to stop its cooling function. As the temperature of the stored water 8 increases, the temperature of the cooling plate of the fuel cell 1 increases as shown by a curve 101 in FIG. By controlling the ratio of the amount of water that is divided into 3111 and 3111, the average temperature of the battery can be preheated to, for example, about 130° C. before the start of power generation.

On the other hand, the temperature of the water vapor contained in Hn3 is shown by curve 10 in Figure 3.
As shown in 2, for example, the temperature controller 6A is used up to 130°C.
, the pressure regulator 5A and the pressure regulator 5
In other words, by controlling the heat of vaporization, the generated amount of saturated steam 9 is maintained at, for example, 160°C by controlling the opening of will be held. Then, when power generation is started based on the production of reformed gas, the fuel cell 1
The temperature of the cooling plate rises as shown by curve 101 due to self-heating, and the starting operation of the water system is completed. Therefore, the current to the electric heater 22 is cut off, the circulating saturated steam 23 is stopped, and the three-way valve 15 is switched to the A-C side. By circulating Wl through the cooling water circulation system 10, it is possible to generate the saturated steam necessary for reforming using the generated heat of the fuel cell 1 as a heat source, and the contained water whose temperature has decreased due to the heat of vaporization being taken away is used as cooling water for the fuel cell. The fuel cell 1 is cooled by being circulated to the fuel cell 1, and power generation operation is performed while maintaining a predetermined operating temperature. When stopping the power generation operation, after cutting off the reactant gas supplied to the fuel cell, switch the three-way valve from A to B, and open the cooling water on-off valve 32B of the cooler 32 to open the branch circulation system 30. As the temperature of the circulating water decreases, the temperature control valve 33 controls the temperature of the cooling water at the inlet of the fuel cell to decrease at a prescribed temperature drop rate, so that the temperature of the cooling plate of the battery and the temperature of the water in the steam separator are maintained at the same level. As shown by curves 111 and 112 in FIG. 4, when the battery inlet temperature drops to about 70° C. to 80° C., the valve 32B is closed to complete the operation of stopping the cooling water system.

As shown in FIG. 2, the on/off control of the electric heater 22 is performed by closing the electromagnetic switches 45 and 46 at the time of starting, and controlling the two electric heaters 22A, 22A,
22B to start the water system, and when the amount of reformed gas reaches the specified value, the DC switch 43 is closed to start the orthogonal conversion station 41, and the 1t magnetic switch 45.
46 is opened, and the electromagnetic switches 47 and 48 are closed instead to generate heat from one electric heater 22A, and when the amount of reformed gas further increases, the electromagnetic switch 49 is closed to cause the other electric heater 22B to generate heat. . The specified amount of gas has been introduced into the fuel cell, and the gas. When the start-up of the water system is completed, the electromagnetic switches 47, 48, and 49 are turned off, the interconnection switch 44 is closed, and power transmission to the power grid is started. However, if the fuel cell generator is equipped with a storage battery for starting, this can be used as the power source for the electric heater. [Effects of the Invention] As mentioned above, the present invention provides a heating circulation system having an electric heater in the steam separator, and a branch circulation system that can be switched and connected to the cooling water circulation system connecting the steam separator and the fuel cell. The branch circulation system was configured with a temperature control valve and a cooler. As a result, the electric heater is used as a heat source for both steam generation and fuel cell preheating, and the temperature control valve in the branch circulation system controls the starting temperature of the fuel cell, making it possible to start the water system. The power generated by the fuel cell during operation can be used to heat the electric heater, which eliminates the need for a steam generation boiler and its piping in conventional equipment, simplifying the equipment configuration, and reducing the heating medium flow rate.・It eliminates the widening of fuel cell temperature differences and the performance degradation caused by this, which was a problem with the conventional off-control method, and therefore simplifies the system so that the device can be started efficiently without adversely affecting the fuel cell performance. It is possible to provide a water-cooled fuel cell power generation device. In addition, when stopping power generation operation, the cooling water temperature can be controlled and cooled using the cooler and temperature control valve installed in the branch circulation system, so it is possible to stop the fuel cell while cooling it at a desired rate of temperature reduction. This eliminates the deterioration of the electrode catalyst and the resulting decline in performance, which was a problem with the conventional method of stopping the fuel cell at its operating temperature, and has the advantage of contributing to extending the life of the fuel cell.

[Brief explanation of the drawing]

1 and 2 are piping system diagrams showing the main parts of an embodiment of the device of the present invention and a connection diagram of its electrical system, FIG. 3 is a temperature characteristic diagram at startup of the embodiment device, and FIG. 4 is a It is a temperature characteristic diagram when the example device is stopped. 1: water-cooled fuel cell, 2: steam reformer system, 2^: steam reformer, 3: steam separator, 5: pressure regulating valve, 8: stored water, 9: saturated steam, 10: cooling water circulation system , 15: Three-way valve, 21: Heating circulation system, 22. 22A, 22B = electric heater, 30: branch circulation system, 32: cooler, 33: temperature control valve, 12, 23 8 circulation bomb, 4l: orthogonal conversion device, 45, 46. 47, 48, 49 8 it magnetic opening/closing 43: Switch, 44: Interconnection switch. 1 Yamaguchi Takeshi, -1.7+1, Hana 2 times

Claims (1)

[Claims] 1) A water-cooled fuel cell is connected to this via a cooling water circulation system, and during power generation operation, the stored water is heated to a predetermined temperature by the waste heat of the fuel cell, and high-temperature steam is sent to the raw fuel steam reformer system. and a steam separator for supplying steam, including an electric heater that generates heat when starting the fuel cell,
a heating circulation system for heating the stored water to a temperature suitable for starting the fuel cell; a branch circulation system having a cooler and a temperature control valve switchably connected to the cooling water circulation system; and a branch circulation system provided in the branch circulation system. 1. A fuel cell power generation device comprising: a cooler for cooling cooling water at an arbitrary temperature decreasing rate when the fuel cell is stopped.