JPH02260370A - Fuel cell power generating system - Google Patents

Abstract

PURPOSE:To prevent small void rate two phase flow to operate steady power generation at optional output by varying cooling water pressure within a fuel cell with a variable pressure loss unit. CONSTITUTION:A pressure control valve 12 serving as a variable pressure loss unit is installed on the way of a pipeline 8 (exhaust water pipeline), and a pressure detector 13 is installed between the pressure control valve 12 and a cooling unit 2. Water from the cooling unit 2 flows through the pipeline 8 and its pressure is reduced with the pressure control valve 12, and it returns to a steam separator 7. The pressure control valve 12 is controlled so that pressure (inlet pressure of the pressure control valve 12) in the pipeline 8 is kept in a set value according to fuel cell output detected with a fuel cell output power detector. Continuous operation within a small void rate two phase flow output range can be prevented for steady operation.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a fuel cell power generation device in which a fuel cell is cooled by a water-cooled cooler.

(Prior Art) In general, a fuel cell has a small capacity as a single cell, so a cell stack in which a plurality of single cells are stacked is housed in a container. Furthermore, since fuel cells generate heat during power generation, they must be cooled by some means, and for this reason air coolers or water coolers have often been used.

FIG. 3 is an example of a fuel cell power generation device in which a fuel cell is cooled by a conventionally used water cooler. Makeup water from a make-up water pipe 3 is supplied to the inlet side of a water cooler (hereinafter simply referred to as a cooler) 2 built into the fuel cell 1 via a pipe 4, a pump 5, and a pipe 6 in sequence. This constitutes the water supply piping system. The outlet side of the cooler 2 is connected to a steam separator 7 via a pipe 8.
The lower pipe 11 is connected to the connecting part of the pipes 3 and 4,
These constitute the drainage piping system.

An electric heater 9 is installed in the steam/water separator 7, and a cooler 2
This is to heat the water when the enthalpy held by the water in the pipe 8 on the outlet side of the pipe 8 cannot cover the steam taken out from the upper plumber 0.

In such a configuration, water supplied from the pipes 3 and 4 is pressurized by the pump 5 and sent to the cooler 2 via the pipe 6.
The hot water heat-exchanged here is sent to the steam-water separator 7 via piping 8.

Here it is separated into steam and water. This separated steam is
It is introduced into a reformer (not shown) from the upper pipe 10 and used for steam reforming. Further, the water separated by the steam-water separator 7 passes through the lower pipe 11 and is mixed with water from the make-up water pipe 3. After this, the water is supplied to the pump 5 through the pipe 4, and then the water is returned to the pipe by the pump 5. 6 and is supplied to the cooler 2.

Since the steam-water separator 7 is placed at a high place, and the pump 5 and the fuel cell 1 are placed at a low place, the water head pressure causes the piping 11 to
, 4.6 and pump 5 have supercooled water.

For this reason, even if the fuel cell 1 generates heat during power generation, the heat is removed by the cooler 2, and the temperature can be maintained within a predetermined operating temperature range.

(Problem to be Solved by the Invention) Now, in the configuration shown in FIG. 3, if the fuel cell 1 is made to have a low output, the water will be warmed by the cooler 2, but since the amount of heat input is small, the water will not flow even in the piping 8. It becomes a supercooled state or a saturated state, and is heated by the electric heater 9 in accordance with the steam taken out from the pipe 10. Furthermore, as the output of the fuel cell 1 increases, the amount of heat generated by the fuel cell 1 also increases, the amount of heat exchanged in the cooler 2 also increases, and the enthalpy of water in the cooler 2 and the pipe 8 becomes The enthalpy of the saturated water becomes higher than that of the saturated water, and a part of the water becomes steam and returns to the steam-water separator 7.

When the output of the fuel cell 1 is low, the water in the cooler 2 and the pipe 8 is in a supercooled state, and when the output of the fuel cell 1 is high, a part of the water is in a two-phase flow state of steam, but when the output of the fuel cell 1 is In an intermediate state between low output and high output, a two-phase flow with a very small amount of steam, that is, a two-phase flow with a small void ratio, may occur.

However, in the cooling piping inside the cell stack disposed inside the fuel cell 1, there is a part of the piping that has a downward flow, but in the fuel cell 1 using multiple cell stacks, there are multiple downflow piping. Because it is a parallel configuration, the above-mentioned low-void two-phase flow can cause phenomena such as clogging of cooling water in some cell stacks due to rising steam, uneven flow, intermittent flow of cooling water, pipe vibration, etc., resulting in poor flow. The cell stack may overheat, which may adversely affect the lifespan of the fuel cell 1.

For this reason, stable power generation cannot be achieved in the case of a two-phase flow with a small void ratio.

An object of the present invention is to provide a fuel cell power generation device that can prevent two-phase flow with a small void ratio and can generate stable power at any output.

[Structure of the Invention] (Means for Solving the Problem) In order to achieve the above object, the present invention includes a water cooler for cooling the fuel cell with cooling water, and a water supply that supplies water to the water cooler. In a fuel cell power generation device equipped with a piping system and a drainage piping system for discharging water from a water cooler, the drainage piping system of the water cooler is provided with a variable pressure loss adjustment device that adjusts pressure loss according to the fuel cell output. In addition, at low output when the amount of heat generated by the fuel cell is small, the pressure loss is increased by the variable pressure loss device to increase the pressure of the cooling water inside the fuel cell, and the cooling water is kept in a liquid state. At high output when the battery generates a large amount of heat, the pressure loss of the variable pressure loss device is reduced to lower the pressure of the cooling water inside the fuel cell, and the cooling water is brought into a two-phase flow state of a mixture of liquid and gas. It is something to do.

(Function) According to the present invention, since the pressure loss of the drain piping system on the outlet side of the cooler can be adjusted by the variable pressure loss device, by changing the pressure of the cooling water inside the fuel cell, the cooling water inside the fuel cell can be adjusted. The supercooled water, which is a single-phase flow, becomes a stable two-phase flow with a relatively large void ratio, and stable power generation can be performed at any power generation output.

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings. FIG. 1 is a cooling water system diagram showing an embodiment of the fuel cell power generation device of the present invention. This is because, in the conventional example shown in FIG. 3, a pressure regulating valve 12, for example, is disposed as a variable pressure loss device in the middle of the piping 8 (drainage piping system), and the pressure regulating valve 12 is further disposed between the pressure regulating valve 12 and the cooler 2. The only difference is that a pressure detector 13 is provided in the pipe 8.

In such a configuration, the water in the lower pipe 11 of the steam-water separator 7 and the make-up water pipe 3 join together, and supercooled water is supplied to the pump 5 via the pipe 4. Then, the water is pressurized by the pump 5, and the supercooled water is supplied to the cooler 2 in the fuel cell 1 through the pipe 6. The water in the cooler 2 passes through a pipe 8 and is supplied to the steam-water separator 7, but when the water passes through the cooler 2, it is heated from outside and its temperature rises.

The water flowing out of the cooler 2 passes through a pipe and a pressure regulating valve 12, is depressurized by the pressure regulating valve 12, and is returned to the steam-water separator 7. The pressure regulating valve 12 controls the pressure in the pipe 8 (the inlet pressure of the pressure regulating valve 12) to maintain a preset pressure according to the fuel cell output detected by a fuel cell output power detection device (not shown). be done. Specifically, the pressure regulating valve 12 is controlled so that the pressure of the pressure detector 13 becomes the pressure regulating valve inlet pressure Kerr fuel cell output curve diagram shown in FIG.

Now, when the fuel cell output is 0, the front pressure of the pressure regulating valve 12 (detected pressure of the pressure detector 13) is at point A, and as the fuel cell output increases, the inlet pressure is increased, and the cooler 2
This prevents the degree of supercooling from decreasing due to a rise in the temperature of the cooling water due to heat input. In the example shown in Fig. 2, the unstable range of small void ratio when the pressure control valve 12 is fully opened is the fuel cell output range between G and H, so the output increase is by increasing the pressure when the output reaches the 0 point. When the 0 point is reached, the pressure control valve 12 is fully opened and the pressure becomes the D point, resulting in a two-phase flow with a high void ratio.
The pressure control valve 12 is operated with fully open until point E, which is 0% output. When decreasing the fuel cell output, the pressure regulating valve 12 is fully opened until point F. When decreasing the fuel cell output from point F, the pressure regulating valve 12 is closed to point B, and then the pressure regulating valve 12 is fully opened to point H and point G. is passed through as supercooled water.

By doing so, continuous operation in a two-phase flow output range with a small void ratio can be prevented, and stable operation is therefore possible.

In the above embodiment, the pressure regulating valve 12 was used as the variable pressure loss device, but it is also possible to use a fixed pressure loss device such as an orifice or a manual valve in combination with a shield that bypasses the fixed pressure loss device. Good too. Furthermore, although the pressure in front of the pressure regulating valve 12 is based on the fuel cell output power, elements other than the output power, such as the output voltage and the amount of hydrogen consumed by the fuel cell, may be used. Furthermore, precise control is possible by detecting the fuel cell cooling water outlet pressure and temperature and using the degree of subcooling as a load factor.

[Effects of the Invention] According to the present invention described above, it is possible to provide a fuel cell power generation device that can prevent two-phase flow with a small void ratio and can stably generate power at any output.

[Brief explanation of drawings]

Fig. 1 is a cooling system diagram showing one embodiment of the fuel cell power generation device according to the present invention, and Fig. 2 is a pressure control valve inlet pressure car fuel cell output curve diagram for explaining the operation of the pressure control valve shown in Fig. 1. , FIG. 3 is a cooling system diagram of a conventional fuel cell power generation device. 1... Fuel cell, 2... Cooler, 3... Make-up water piping, 4.6.8... Piping, 5... Pump, 7...
Steam/water separator, 9... Electric heater, 10... Upper piping, 11... Lower piping, 12... Pressure control valve, 13.
...Pressure detector. Applicant's Representative Patent Attorney Takehiko Suzue

Claims (1)

[Scope of Claims] A fuel comprising a water cooler for cooling a fuel cell with cooling water, a water supply piping system for supplying water to the water cooler, and a drainage piping system for discharging water from the water cooler. In the battery power generation device, a variable pressure loss adjustment device is added to the drainage piping system of the water cooler to adjust the pressure loss according to the output of the fuel cell, and the variable pressure loss is adjusted at low output when the amount of heat generated by the fuel cell is small. The device increases the pressure loss to increase the pressure of the cooling water inside the fuel cell and keeps the cooling water in a liquid state, and also reduces the pressure loss of the variable pressure loss device at high output when the fuel cell generates a large amount of heat. A fuel cell power generation device characterized in that the cooling water pressure inside the fuel cell is reduced by reducing the size of the fuel cell, and the cooling water is brought into a two-phase flow state of a mixture of liquid and gas.