JPH0227789B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a fuel cell body comprising a matrix layer holding an electrolyte and a fuel electrode and an air electrode arranged oppositely on both sides thereof, and a fuel gas line and an air line connected to each electrode. The present invention relates to an improvement in a supply gas pressure control method for a fuel cell configured to feed fuel gas and air through the fuel cell.

As is well known, the main body of this type of fuel cell consists of a porous matrix layer holding an electrolyte between two electrodes, an anode and a cathode, which are spaced apart from each other. There is. This matrix layer is made of a porous material and has a structure in which the electrolyte is held in the micropores. Regarding the operation of such a matrix fuel cell, pressure control of the fuel gas (for example, hydrogen) and the oxidant (for example, air) supplied to the cell is an extremely important issue. For example, if fuel gas passes through the matrix layer that holds the electrolyte and reaches the spaced-apart counter electrode, it not only deteriorates the electrical characteristics of the fuel cell, but also causes the fuel gas and air to mix, resulting in an explosion. This includes the possibility of causing an explosion. Conversely, when air passes through the matrix layer and reaches the opposite electrode, there is a similar risk. On the other hand, although the matrix layer that holds the electrolyte has its own certain bubble pressure that suppresses the migration of the reactant gas from one electrode side to the other, In addition, the matrix layer has a weak mechanical strength and is brittle, so if the pressure difference between the fuel gas pressure and the air pressure on both sides of the matrix layer exceeds the allowable limit, The risk of the above-mentioned mixing of fuel gas and air passing through the matrix layer from one side to the other, and damage to the matrix layer.
This causes a decrease in lifespan. Moreover, the allowable range of this pressure difference in the cell body is extremely small, about several tens of millimeters of water column. Therefore, in the gas supply system of the fuel cell, the pressure difference between the fuel gas pressure and the air pressure that is sent to the fuel cell through the fuel gas line and air line is extremely small. The pressure of the supplied gas must be controlled with extremely high accuracy on the order of 1/1000 of the gas pressure at the cell inlet to prevent excessive pressure differences from occurring. In this case, it is also desirable to ensure that the fuel gas and air do not mix directly with each other even when pressure fluctuations occur due to an unexpected situation in the gas supply system.

By the way, a conventional gas pressure control system for a gas supply system of a fuel cell is configured as shown in FIG. That is, in FIG. 1, 10 is a battery main body, which includes a fuel electrode 11, an air electrode 12, a matrix layer 13, a fuel chamber 14, and an air chamber 15.
It consists of Fuel gas and air are fed into the fuel chamber 14 and the air chamber 15 through a fuel gas line 20 and an air line 30, respectively. Further, pressure regulating means such as flow rate and pressure regulators 21, 31, various control valves 22, 23, and 32, 33 are inserted and connected to each line 20, 30, respectively. In addition, vent 2 in the diagram
4 and 34 communicate with a condenser, and vents 25 and 35 communicate with, for example, a fuel gas reformer.
The fuel gas passes through a reformer (not shown), and the air is blown from the atmosphere in a pressurized state by a blower or the like. In the gas pressure control system for the gas supply system described above, a differential pressure transmitter 40 as differential pressure detection means is connected between the fuel gas line 20 and the air line 30, and the output signal of the differential pressure transmitter 40 is connected to the fuel gas line 20 and the air line 30. The control valves 23 and 3 inserted into the pressure regulators 21 and 31 and the branch lines from the respective lines 20 and 30 are controlled by feedback control or arithmetic processing based on the above.
3, etc., to perform pressure control. and fuel gas line 20 and air line 3
0, the pressure is controlled so that the pressure difference between the fuel gas pressure and the air pressure on the inlet side of the battery main body 10 falls within an allowable value range. Note that 41, 42, and 43 in the figure are a fuel gas line 20 and an air line 3, respectively, for maintenance, inspection, and zero point adjustment of the differential pressure transmitter 40.
This is a manual stop valve inserted between the line 2 and both lines, and the zero point adjustment of the differential pressure transmitter 40 is performed by closing the stop valves 41 and 42 and opening line 2.
This is done with the pressure balanced on the battery main body side at 0.0 and 30. Also, stop valves 41 and 42 are always open.
43 is held in the closed state.

However, in the conventional pressure control systems, it is extremely dangerous to inspect the differential pressure transmitter 40 and adjust the zero point while the battery is in operation, and it has not been possible to do so. The reason is that when the stop valve 43 is opened,
This is because there is a possibility that the fuel gas and air will directly mix with each other, leading to an explosion accident. Further, in the above system, there is a similar danger if maintenance personnel accidentally open the stop valve 43 during operation, and this is a serious drawback in terms of safety in the pressure control system. Furthermore, in the above system, control is performed by detecting only the relative pressure difference between fuel gas pressure and air pressure, so each line is required to control the supply gas pressure required for fuel cell operation. A separate control system must be installed for each. For this reason, the control operations of the two control systems interfere with each other, causing a hunting phenomenon, making it extremely difficult to perform the required high-precision pressure control.

This invention was made in consideration of the above points, and its purpose is to eliminate the drawbacks of the conventional method, eliminate the fear of direct mixing of fuel gas and air, and simultaneously control and supply the differential pressure between fuel gas and air. It is an object of the present invention to provide a supply gas pressure control method that is highly reliable in terms of safety and control accuracy, such as being able to perform pressure control.

This purpose is to supply fuel and air to each electrode of the battery body, which consists of a fuel electrode and an air electrode as opposite electrodes with a matrix layer holding an electrolyte in between, through a fuel gas line and an air line each equipped with a pressure regulator. , an inert gas line equipped with a pressure regulator is provided separately from the fuel gas line and the air line, and inert gas is supplied into the container housing the fuel cell main body through the inert gas line. A supply gas pressure control device for a fuel cell comprising: a control valve provided in a branch line of the fuel gas line and the air line, and between the inert gas line and the fuel gas line and the air line; control valves provided respectively, and differential pressure detection means provided respectively between the inert gas line and the fuel gas line and air line, and based on the differential pressure signal obtained by the differential pressure detection means. This is achieved by controlling the control valve and pressure regulator so that the fuel gas pressure and air pressure in the battery body, and the differential pressure between the fuel gas pressure and air pressure, respectively, fall within set values and allowable ranges. be done.

The present invention will be described in detail below based on illustrated embodiments.

In FIG. 2, according to the present invention, an inert gas line 50 using nitrogen gas, for example, is newly provided separately from the fuel gas line 20 and the air line 30. This inert gas line 50 is connected on one side to a nitrogen gas pressure source and also connected to the pressure vessel 16 housing the battery body 10 to maintain an inert gas atmosphere inside the pressure vessel. Further, a pressure regulator 51 is inserted on the pressure source side, and bypass pipes 54 and 55 are connected to the fuel gas line 20 and the air line 30 and have control valves 52 and 53 inserted therein, respectively. ing. 56 is a vent leading to the exhaust gas system. In such a gas supply system, the gas pressure in the inert gas line 50 is first maintained at a predetermined pressure via the pressure regulator 51 in accordance with the setting value given to the pressure setting device 57. This pressure is determined based on the reactant gas supply gas pressure required for operation of the fuel cell. Also, between the inert gas line 50 and the fuel gas line 20, and between the inert gas line 50 and the air line 3
differential pressure transmitters 60 and 7 each equipped with a pressure sensor and an arithmetic device;
0 is connected, and its output signal is transmitted to the pressure regulator 21 and control valve 23 for the differential pressure transmitter 60.
52, and a control circuit is configured to be applied to the pressure regulator 31 and control valves 33, 53 for the differential pressure transmitter 70. In addition, manual stop valves 61, 62, 71, 72 are inserted as shown in the figure.
and 58 are operated when performing maintenance, inspection, and zero point adjustment of the differential pressure transmitters 60, 70, and normally the stop valves 61, 71, 58 are open, and the stop valve 6 is closed.
2,72 are held closed.

In the above configuration, if the cell inlet pressure of the fuel gas line is now higher than the inlet pressure of the inert gas line 50, the differential pressure transmitter 60 gives a control signal to the pressure regulator and causes the control valve 23 to open. The pressure is controlled so that the pressure difference between the fuel gas line and the inert gas line at the cell inlet is within a predetermined range. Conversely, when the gas pressure in the fuel gas line becomes lower than the gas pressure in the inert gas line, the differential pressure transmitter 60 gives a command to the pressure regulator 21 to increase the pressure, and on the other hand, the control valve 52 As a result, nitrogen gas is supplied to the fuel gas line 20 to increase the pressure in the fuel gas line, and the relative pressure difference between the fuel gas and nitrogen gas is increased to a predetermined preset value. Stay within range. On the other hand, similar pressure control is performed between the air line 30 and the inert gas line 50, so that the relative pressure difference between the fuel gas pressure and the air pressure is within an acceptable range. The zero point adjustment of the differential pressure transmitter 60 is performed by closing the stop valves 61 and 58 and opening the stop valve 62 to balance the pressure between the fuel gas line 20 and the inert gas line 50 in the downstream region. On the other hand, zero point adjustment by the differential pressure transmitter 70 is performed by closing the stop valves 58 and 71 and opening the stop valve 72. In either case, the fuel gas and air are always mixed together with the inert gas line 50, so there is no fear that the fuel gas and air will mix directly with each other. In addition, the supply pressure of fuel gas and air supplied to the battery can be controlled by setting the setting value given to the pressure setting device 57 in the inert gas line 50 in accordance with a predetermined gas pressure necessary for battery operation.
Based on this set value, the differential pressure control described above is performed at the same time. In other words, the differential pressure control system between fuel gas and air and the supply gas pressure control system, which were previously separate, can be controlled simultaneously by the same control system, making it possible to control the pressure with higher precision. becomes.

As described above, according to the pressure control method of the present invention, the differential pressure between the fuel gas line and the air line is controlled via the inert gas line, which eliminates the drawbacks of conventional methods. This makes it possible to reliably prevent direct mixing of fuel and air.
In addition, since an inert gas line is interposed between the fuel gas line and the air line, there is no direct mixing of fuel gas and air due to valve operation errors, etc., and highly reliable pressure control is possible. becomes.

In addition to the effect that there is no direct mixing of fuel gas and air as described above and highly reliable pressure control, this invention also has the advantage that the fuel gas line is adjusted based on the gas pressure of the inert gas line. Controls are provided between the inert gas line and the fuel gas line or air line when the pressure of the fuel gas line or air line is low. An inert gas controlled by a valve is supplied to the fuel gas line or air line to properly control the pressure, so that the response of the pressure regulator installed in the fuel gas line or air line is Even when the speed is slow, it is possible to control the supply gas pressure of the fuel cell with extremely high accuracy, and sufficient reliability can be obtained even when the fuel cell is operated at high pressure. In other words, if the pressure of the inert gas line is set to a predetermined pressure in advance, the differential pressure between the fuel gas pressure supplied to the battery body and the air pressure will be
At the same time, the differential pressure is controlled to be within the permissible range determined from the viewpoint of mechanical protection of the matrix layer and bubble pressure maintenance of the matrix layer, and at the same time, the pressure is controlled based on the gas pressure set in the inert gas line. Pressure control can be performed to match the supply pressure of fuel gas and air at the cell inlet side to a set value. In this way, more reliable fuel cell operation can be achieved.

[Brief explanation of drawings]

FIGS. 1 and 2 are system diagrams of a conventional fuel cell supply gas pressure control system and an embodiment of the present invention, respectively. 10: fuel cell main body, 20: fuel gas line,
30: Air line, 50: Inert gas line, 2
1, 31, 51: pressure regulator, 57: pressure setting device, 60, 70: differential pressure transmitter as differential pressure detection means, 23, 33, 52, 53: control valve,
58, 61, 62, 71, 72: Manual stop valve.

Claims (1)

[Claims] 1. Fuel and air are supplied to each electrode of the battery body, which is made up of a fuel electrode and an air electrode as opposite electrodes with a matrix layer holding an electrolyte in between, through a fuel gas line and an air line each equipped with a pressure regulator, and the fuel A fuel cell including an inert gas line equipped with a pressure regulator, separate from the gas line and the air line, and supplying inert gas into a container housing the fuel cell main body through the inert gas line. The supply gas pressure control device includes a control valve provided in a branch line of the fuel gas line and the air line, and a control valve provided between the inert gas line and the fuel gas line and the air line. a control valve, and differential pressure detection means provided between the inert gas line and the fuel gas line and the air line, respectively. The fuel is characterized in that the control valve and the pressure regulator are controlled so that the fuel gas pressure and air pressure of the main body and the differential pressure between the fuel gas pressure and air pressure are respectively within set values and allowable ranges. Battery supply gas pressure control device.