JPH081808B2 - Fuel cell plant - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a fuel cell plant, and more particularly to a fuel cell plant provided with a gas releasing device for pressure adjustment on a gas supply side or a gas discharge side of a fuel cell. .

[Conventional technology]

This type of fuel cell plant that has been generally adopted in the past has been designed to prevent gas differential pressure between the fuel electrode gas system and the air electrode gas system in order to avoid mixing of different gases due to gas leakage in the cell. The gas system is usually equipped with a gas releasing device for pressure adjustment.

Various types of gas releasing devices can be considered, but most commonly, a gas releasing valve is often used as described in JP-A-60-198064.

That is, in the fuel electrode gas system and the air electrode gas system,
A gas release valve that controls the gas pressure by releasing the gas in these systems to the outside of the system is installed, and this gas release valve is used when the gas pressure difference between the two polar gas systems exceeds a certain value. It is opened so that the gas pressure difference between the two polar gas systems is suppressed.

[Problems to be Solved by the Invention]

In this case, generally, the capacity of the gas release valve used for this pressure adjustment is the maximum gas differential pressure between the bipolar gas systems, that is, the gas differential valve that requires driving of the gas release valve, within the predetermined time. It is determined by the volume of gas to be passed through the release valve. Therefore, when a gas differential pressure is generated between the fuel electrode gas system and the air electrode gas system, and if the temporal change in the generated differential pressure (differential pressure increase rate) is large, opening and closing the release valve will allow sufficient gas differential pressure. However, if the generated differential pressure changes little with time, on the contrary, when the gas release valve is closed, the gas release valve has a finite closing time, so a large amount of gas is released. In other words, the gas pressure on the system side that attempts to reduce the gas pressure becomes too low, the gas differential pressure between the two electrode systems exceeds the allowable value, and the electrolyte layer in the battery may eventually break down and different gases may mix. was there.

An object of the present invention is that the gas differential pressure generated between the fuel electrode gas system and the fuel electrode gas system has a large temporal change and is small, that is, it occurs in all operating steps when operating the fuel cell. It is an object of the present invention to provide a fuel cell plant in which abnormal pressure is not mixed by sufficiently absorbing the pressure difference regardless of the time-dependent pressure difference.

[Means for solving the problem]

In order to achieve the above-mentioned object, the present invention chemically reacts a fuel gas supplied at a substantially constant pressure via a fuel electrode gas system with air supplied at a substantially constant pressure via an air electrode gas system to generate electric power. A fuel cell body, a differential pressure detector for detecting a gas differential pressure between the fuel electrode gas system and the air electrode gas system, and a fuel electrode gas system and an air electrode gas system. The gas pressure difference between the gas discharge unit for discharging the fuel gas in the gas system or the air in the air electrode gas system to the outside and the gas pressure difference between the both electrode gas systems detected by the pressure difference detection unit is equal to or more than a predetermined value. At this time, in a fuel cell plant including a control unit that operates the gas release unit to reduce the gas differential pressure, a plurality of gas release valves having the same capacity and a small capacity are used as the gas release unit. Polar gas system and the air electrode The same number is provided for each of the gas pressure systems, and a plurality of differential pressure increase rate calculating means for calculating the increase rate of the gas differential pressure by receiving the signal from the differential pressure detecting section, and a plurality of them when activating the gas release valve are provided. Among the gas release valves provided, gas release valve control means for operating a number of gas release valves in proportion to the rate of increase are provided in the control unit.

[Action]

According to the above configuration, the gas release valves, the number of which is proportional to the increase rate of the differential pressure between the fuel electrode gas system and the air electrode gas system, operate to release the fuel gas or air. For example, when the rate of increase is small, one gas release valve operates, so that the amount of fuel gas or air released can be kept small, and it is possible to prevent the system gas pressure from dropping too low.

Further, in the above configuration, since the gas discharge valves provided in the fuel electrode gas system and the air electrode gas system have the same capacity and a small capacity, there is no large variation in the operating speed of the valves, and the gas differential pressure is eliminated. The time can be controlled with high accuracy, the operating speed of the valve can be improved, and a state without gas differential pressure can be quickly realized.

〔Example〕

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

The figure shows the system of the main part of the fuel cell plant, 1 is the space of the battery container, 2 is the gas space of the air electrode, 3
Indicates the gas space of the fuel electrode. In the steady state,
Nitrogen flows into the gas system of the battery container from the inlet side via the flow rate adjusting valve 4, and the outlet side is connected to the reformer combustion unit 6 via the differential pressure adjusting valve 5 between the battery container and the air electrode. In the gas system of the air electrode, air flows into the gas space 2 of the air electrode through the flow rate control valve 7 on the inlet side, consumes oxygen necessary for generating an electric current, and then is discharged to the downstream side to a heat exchanger or the like. Flows into the reformer combustion section 6 via the pressure loss 8 due to. on the other hand,
In the gas system of the fuel electrode, the reformer process side (not shown)
After the reformed gas generated in 1 flows into the gas space 3 of the fuel electrode through the flow rate control valve 9 and hydrogen required for power generation is consumed,
It flows into the reformer combustion section 6 via a pressure difference control valve 10 installed on the downstream side of the fuel electrode and a pressure loss 11 due to a heat exchanger or the like.

The differential pressure between the gas system of the air electrode and the gas system of the fuel electrode in normal operation is suppressed by the differential pressure control valve 10, but when a gas differential pressure that cannot be controlled by the differential pressure control valve 10 occurs. The differential pressure absorption is performed by activating the gas release device 12 of the gas system on the high gas pressure side to release the gas.

The gas discharge device 12 is formed of discharge valve groups 12a to 12f in which a plurality of small capacity valves are connected in parallel to form a valve having a required capacity. The discharge valve groups 12a to 12f are controlled by the control device 22.
In this case, the gas pressure increase rate of the gas system is incorporated as a drive element of the discharge valve group in the control signal of the control device 22 in particular. The number of open release valves in the release valve group is set in proportion to the rate of increase in gas pressure. That is, when a predetermined gas differential pressure is generated, the release valve group 12a, 12b, 12c provided on the air electrode downstream side (air discharge side) and the fuel electrode downstream side (fuel gas discharge side) are provided. Among the discharge valve groups 12d, 12e, 12f that are present, a required number of discharge valves of the gas system on the high pressure side are activated to suppress the gas differential pressure.

That is, the gas differential pressure signal detected by the detection device 20 is input to the differential calculator 21 to calculate the gas differential pressure increase rate, and the calculation result is input to the control device 22 together with the differential pressure detection value from the detection device 20. To be done. When the measured value of the gas differential pressure exceeds a certain level and the rate of increase in the gas differential pressure at that time, that is, the rate of change of the differential pressure, the control device 22 causes the opening operation when the value is less than the first set level. The number of discharge valves is 1,
When the level is equal to or higher than the first set level and lower than the second set level, the number of release valves to be opened is set to 2, and when the level is equal to or higher than the second set level, the number of release valves to be opened is set to 3. By adopting such an operation method, it is possible to exert the differential pressure suppressing function with respect to the differential pressure fluctuation speed in a wide range of the fuel cell plant.

In this embodiment, the space 1 of the cell container, the gas space of the air electrode and the gas space 3 of the fuel electrode constitute a part of the fuel cell body. Further, the detection device 20 corresponds to a differential pressure detection part, the gas release device 12 corresponds to a gas release part, the differential calculator 21 corresponds to a differential pressure increase rate calculation means, and the control device 21 corresponds to a gas release valve control means. The differential calculator 21 and the control device 21 are provided in the control unit.

In the above description, the case where the number of discharge valves is three in the discharge valve group has been described, but the number of discharge valves is not limited to this number, and the larger the number, the more advantageous in terms of performance. However, in terms of conservativeness and economy, 2-5
The position is practical.

〔The invention's effect〕

As described above, according to the present invention, when the increase rate of the gas differential pressure between the fuel electrode gas system and the air electrode gas system is small, for example, only one of the plurality of gas release valves is provided. Since it operates, it is possible to avoid a situation where the fuel gas or air in the system is released more than necessary. Also, since the diameters of the gas release valves provided in the fuel electrode gas system and the air electrode gas system are all the same, there is no large variation in the operating speed of the valves, and the time until the gas differential pressure is eliminated must be controlled with high accuracy. In addition, since the gas release valve is a small-capacity valve, the operating speed of the valve is fast, and a state without gas differential pressure can be quickly realized. As a result, mixing of fuel gas and air can be completely prevented, and a highly reliable fuel cell plant can be obtained.

[Brief description of drawings]

FIG. 1 is a schematic view of the essential parts of a fuel cell plant of the present invention. 1 ... Battery container space, 2 ... Air electrode gas space, 3 ...
… Gas space of fuel electrode, 5,10 …… Differential pressure control valve, 6 …… Reformer combustion part, 12 …… Gas release device, 20 …… Detection device, 21
...... Differentiation calculator, 22 …… Control device.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-60-198064 (JP, A) JP-A-60-7065 (JP, A) Practical application Sho-57-84012 (JP, U)

Claims (1)

[Claims] 1. A fuel cell main body for obtaining electric power by chemically reacting a fuel gas supplied at a substantially constant pressure via a fuel electrode gas system with air supplied at a substantially constant pressure via an air electrode gas system. A differential pressure detection unit that detects a gas differential pressure between the fuel electrode gas system and the air electrode gas system, and a fuel gas in the fuel electrode gas system that is provided in the fuel electrode gas system and the air electrode gas system. Alternatively, when the gas pressure difference between the gas discharge unit for discharging the air in the air electrode gas system to the outside and the bipolar gas system detected by the differential pressure detection unit becomes a predetermined value or more, the gas discharge unit In the fuel cell plant comprising: a control unit for activating the gas pressure difference to reduce the gas differential pressure, a plurality of gas discharge valves having the same capacity and a small capacity are provided as the gas discharge unit and the air electrode gas system and the air as the gas discharge unit. The same number for each polar gas system A differential pressure increase rate calculation means for calculating the increase rate of the gas differential pressure by taking in a signal from the differential pressure detection section, and a plurality of gas discharges provided when the gas release valve is operated. A fuel cell plant comprising: a gas release valve control unit that operates a number of gas release valves of the valves that are proportional to the rate of increase.