JPH01286260A - Protecting device for fuel cell - Google Patents

Abstract

PURPOSE:To perform the stable long-term power generation operation by providing multi-stage comparators in a judging circuit and performing the control in response to the leaked combustible gas concentration. CONSTITUTION:When fuel gas 9 is leaked in a cell, the light combustible gas is floated in a frame 2 and collected from the frame 2 into a collecting chamber 21 protruded upward. When the combustible gas concentration in the collecting chamber 21 is increased, the level of the concentration actual signal 6A of a detector 6 is increased. The signal 6A is compared with set values of the corresponding first-stage comparator 22, second-stage comparator 23, and highest-level comparator 24 by a judging circuit 20, control signals 22C-24C are issued when they are higher than the set values. The signal 22C opens a solenoid valve 27B and releases the mixed gas 31 from a releasing mechanism section 27, the signal 23C releases the gas 31 from a releasing mechanism section 28. The signal 24C controls and operates an abnormality control circuit 25 and issues an alarm 25A and stops the operation. The situation is coped with in stages, the operation is not stopped when the level of the signal 6A is lowered at the low stage, thereby the stable long-term operation can be performed.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is directed to controlling the concentration of combustible gas leaked into the casing of a fuel cell in which a fuel cell stack is housed together with an inert gas at a predetermined pressure in the casing. It relates to a protective device that suppresses the concentration below.

[Conventional technology]

FIG. 2 is a schematic cross-sectional view of a fuel cell showing a conventional device.
A fuel cell stack 21 (hereinafter referred to as a stack), which is formed by stacking a large number of single cells and applying a predetermined surface pressure to the stacked surfaces, is supported in the casing 2, and the mutually opposing sides thereof are provided with a plurality of blocks, for example. The divided supply/discharge manifolds 6A and 3B of the fuel gas 9 are airtightly attached, and are drawn out of the housing 2 by the supply side collection pipe 4A and the discharge side output pipe 4B. A supply/discharge manifold and a supply/discharge collection pipe for reaction air as an oxidizing agent (not shown) are airtightly connected to the two sides and drawn out to the outside of the housing 2.In addition, the housing 2 is equipped with an inert gas such as nitrogen. (Nz) 10 supply pipes 5A are provided, and N2 at a predetermined pressure is supplied into the housing from the supply pipes 5A that open near the bottom of the housing 2. Also, 5B has an opening at the top of the housing 2. It is a nitrogen exhaust pipe with a
A variable throttle valve 7 is provided to allow a small amount of inert gas to be discharged from the housing in response to changes in the respective gas pressures, and to control the mutual pressure of the fuel gas, reaction air, and inert gas. The balance is maintained and power generation operation is performed.

By the way, power generation operation is carried out by maintaining the operating temperature of the fuel cell with the differential pressure of the fuel gas and reaction air suppressed below a predetermined level. It has many joints, such as the joint between the stack 1 and the manifold, and the joint between the manifold and the collecting pipe, and there is a possibility that fuel gas or reaction air may leak into the casing 2 from the sealing surfaces of these joints. Therefore, inert gas 1 inside the housing
0 gas pressure to the gas pressure of fuel gas and reaction air 10
0 to 300 mmAq al& By keeping it always high, the fuel gas or reaction air is configured to prevent leakage into the housing 2.

However, in preparation for an unexpected gas leak, an inert gas exhaust pipe 5BKVi and a combustible gas concentration detection sensor 6 are provided to detect hydrogen (H2) leaking into the housing 2.

Since the specific gravity of methane (CH4), -carbon oxide (CO), etc. is lighter than that of nitrogen as an inert gas, the formation of a leakage ol flammable gas reservoir 11 in the upper part of the housing 2 is utilized. Exhaust W5B with an inlet near the gas reservoir 11
A detection sensor 6 detects the concentration of combustible gas discharged together with nonflammable gas through a control circuit 8 that issues an alarm when the output signal level exceeds a predetermined level. Some devices are known that are equipped with a protection device to stop them.

[The problem that the invention aims to solve]

If there is a sudden increase or decrease in electrical load or an emergency stop during the above-described power generation operation of the fuel cell, the gas pressure will change based on the timing difference between the amount of fuel or reaction air consumed by the fuel cell and the amount of supply. In particular, when the load suddenly decreases or there is an emergency stop, the gas pressure increases due to the sudden decrease in the amount of gas consumed, and this increased gas pressure transiently approaches or exceeds the inert gas pressure, causing leakage of fuel gas and reaction air. A sudden increase may occur. The occurrence of such a situation is i
"Increases the amount of combustible gas retained in the flammable gas reservoir, increases the oxygen concentration in the inert gas, and
Increases the risk of gas explosion due to gas mixture. However, with the conventional method of flowing a small amount of inert gas, it takes a long time to exhaust the leaked flammable gas, which increases the frequency of emergency stop of the fuel cell's power generation operation and increases the length of the fuel cell. There is a problem that hourly power generation operation is inhibited.

The purpose of this invention is to quickly discharge flammable gas that has leaked into the housing according to the amount of leakage, and to maintain long-term power generation operation by issuing an emergency stop signal only when a dangerous level of leakage occurs. The goal is to stabilize it.

[Means to resolve the problem]

According to the present invention, the above problems can be solved.

The contents of the fuel cell, including a fuel cell stack and a reaction gas passage for supplying and discharging fuel gas and oxidizing gas to and from the fuel cell stack, respectively, are housed in a casing having a supply and discharge passage for inert gas at a predetermined pressure. A collection chamber for leaking combustible gas formed in a convex manner above the housing, a detector for the concentration of the combustible gas provided in the collection chamber, and an actual value of the concentration detected by the detector. It consists of a judgment circuit that compares the signal with set value signals of multiple stages and issues a control signal for each concentration stage, and a control valve for the flow rate of released gas connected to the collection chamber, and is controlled by the control signal to generate a concentration stage 1s. ! [It shall be equipped with a discharge mechanism section that discharges a corresponding flow rate of flammable gas together with an inert gas, and an abnormality control circuit that receives a control signal at the highest concentration stage and issues a signal instructing an emergency stop.]

[Effect]

In the above means, since the flammable gas collection chamber is protruded above the housing and the flammable gas concentration detector is provided,
Collecting and detecting the concentration of flammable gas leaking into the housing is accelerated. In addition, a judgment circuit is provided to compare the actual concentration value signal detected by the detector with the set value signals of multiple stages and output a control signal for each concentration stage. ! - By controlling the gas concentration according to the detected gas concentration, for example, if a small amount of combustible gas leaks, the first stage control signal allows the gas to be released at a small flow rate, without affecting the inert gas pressure. If the amount of leakage is larger, the concentration of flammable gas in the collection chamber increases, so the amount of gas released is increased by the next-stage one-trick control signal, and the release of combustible gas is accelerated.

When the amount of leakage becomes larger and the concentration of combustible gas in the fruit picking room reaches the dangerous range, a control signal of the highest level A is output, and an emergency stop command signal for bud alarm signal 2 power generation operation is output from the abnormality control circuit. Since the system is protected, and an emergency stop signal is output only when a dangerous leakage point is reached, protection can be achieved with minimal impact on long-term power generation operation.

〔Example〕

The present invention will be explained below based on examples.

FIG. 1 is a block diagram showing a device according to an embodiment of the present invention, and the same reference numerals are used for parts common to the conventional device for detailed explanation. 52 omitted. In the figure, the upper part of the housing 2 has a tubular collection chamber 2 whose lower end is opened on the lid plate 2A.
1 is provided protrudingly, and in the fruit-thinning chamber 21, there is a first-stage release mechanism section 27 consisting of a series body of a fixed diaphragm D27A and a solenoid valve 27B;
For example, a discharge mechanism section 26 composed of a next-stage discharge mechanism section 28 such as an electric control valve is provided, and each discharge side is formed to communicate with an exhaust pipe 29 . For example, a hydrogen gas concentration sensor 6 as a detector for combustible gas concentration is located in the fruit picking chamber 2.
1, and its output signal, the actual concentration value signal 6A, is outputted to the judgment circuit 20.

The judgment circuit 20 has a plurality of comparators such as a first stage comparator 222, a second stage comparator 23, and a highest level comparator 24, and the actual concentration value signal 6A is input to each comparator, and the setter 22
A, 23A, 24A concentration level setting signal 228.23
The electromagnetic valve 27 of the first stage discharge mechanism section 27 is compared with the first stage comparator output control signal 22C.
B is controlled to open and close, and the output control signal 23 of the next stage comparator 26
C controls the ejection flow of the next stage ejection mechanism section 28 so as to gradually increase the number of copies. The highest level comparator 24
The output control signal 24C is input to the abnormal flflJ control circuit 25, and the actual value signal 6A is set to the highest level 11II2.
When the level of 4S is exceeded, an honor signal 25A and an emergency stop command signal 25B for power generation operation are output.

During power generation operation of the embodiment device configured as described above, the fuel cell stack 1. Manifold 3A.

When fuel gas 9 leaks from inside the fuel cell, which consists of pipes 3B, 4A, 4B, etc., hydrogen and hydrocarbons, which are lighter than nitrogen 10 as an inert gas, leak.

- Combustible gas such as carbon oxide floats inside the housing 2 and collects in the collection chamber 21 protruding above the unit 2, and the combustible gas in the mixed gas 31 of inert gas and combustible gas As the concentration increases, for example, the level of the actual concentration signal 6A output from the hydrogen concentration detector 6 increases, so the determination circuit 20 compares it with a set value and outputs a control signal.

The setting values for multiple concentration stages are preferably below the explosion limit (lower limit) of combustible gas; for example, the first stage setting value 22S is 5QQPPm, the second stage setting value 23S is 1.000PPm, and the highest level setting (If 24 S
As 3000PPmO! Sea urchin can be selected to be less than 1/10 of the explosive limit.

Assuming that the concentration levels of the comparators 22, 23, and 24 of the judgment circuit 20 are set in multiple stages as described above, when the hydrogen concentration in the fruit thinning chamber 21 reaches 500 PP m VC, the first stage comparator 22 When the control signal 22C is output, the electromagnetic valve 27B of the first-stage discharge mechanism section 27 opens, and the mixed gas 31 whose discharge gas flow rate has been throttled by the fixed throttle 27A is discharged.

If the hydrogen concentration in the mixed gas in the collection chamber 21 decreases due to this first-stage release, there is no danger of explosion due to leakage of flammable gas, so power generation operation can be continued while repeating the release intermittently. The pressure drop in the inert gas 10 due to the gas discharge is compensated by the supplementary inert gas from the supply pipe 5A.

If the hydrogen gas concentration in the fruit-picking chamber 21 rises further, the control signal 23C is output from the next-stage rice cooker 23 when the hydrogen gas concentration reaches 11,000 PP, and the electric valve 2
8 gradually opens, and the first stage and next stage release mechanism parts 27.2
Mixed gas 31 is released from both sides of 8. The reason why the discharge mechanism section 28 in the next stage is configured as an electric valve to gradually increase the amount of released gas is that by rapidly increasing the amount of released gas, the inert gas pressure inside the housing decreases, and the fuel gas system.

This is to avoid causing an increase in leakage of fuel gas 9 due to a reduction in the differential pressure with respect to the gas pressure of the reaction-containing air, and the rate of increase in the amount of released gas is equal to the rate of increase in the supply of inert gas 10. determined based on. If the hydrogen gas concentration in the collection chamber 21 decreases by controlling the amount of released gas in two stages as described above, it is determined that power generation operation is possible again, and operation is continued.

The hydrogen gas concentration in the collection chamber 21 further increases to 300QPPm.
, the control signal 2 is output from the highest level comparator 24.
4S is output, the abnormality control circuit 25 operates, and the honor signal 25 is output.
A. By outputting the emergency stop command signal 25B, etc., operations necessary for an emergency stop can be performed, such as supplying or stopping fuel gas to the fuel cell, or purging with an inert gas such as fuel gas. At the same time, the detector 6 detects a decrease in the concentration of the ol combustible gas, and the valves 28, 27B, in turn, stop the gas discharge from the discharge mechanism section 26, thereby completing the maintenance operation of the fuel cell.

〔Effect of the invention〕

As described above, this invention provides a collection chamber for leaking flammable gas that protrudes above a housing that stores the contents of a fuel cell together with an inert gas at a predetermined pressure, and a detector for detecting the concentration of combustible gas.
A determination unit that compares the output actual value signal with set values for multiple concentration levels and outputs control signals respectively controls the release mechanism unit and the abnormality control circuit in which the amount of released gas varies in stages corresponding to the concentration level. It was configured as follows. As a result, the light flammable gas leaking from the fuel cell contents floats up in the heavy inert gas and increases the concentration of combustible gas in the collection chamber, and the detector and judgment unit that detects this increases the concentration level. Since the amount of gas released from the release mechanism is controlled in stages accordingly, it is possible to control the amount of released gas depending on the scale of the fuel gas leak.
In the case of small-scale gas leaks, the concentration of flammable gas within the housing can be suppressed to a non-hazardous level, allowing stable power generation operation to continue. In addition, the abnormality control circuit outputs an alarm and an emergency stop command signal only when a gas leak occurs on a scale that cannot reduce the combustible gas concentration in the collection chamber with the amount of gas released from the release mechanism, so the fuel cell is in a dangerous state. It is possible to provide a protection device for a fuel cell, which can avoid the danger and grasp dangerous conditions more accurately than conventional devices, so that long-term power generation operation is not hindered by frequent emergency stops of power generation operation. can.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a device according to an embodiment of the present invention, and FIG. 2 is a schematic sectional view of a fuel cell showing a conventional device. 1... fuel cell stack (stack), 2... casing,
6A, 3B... Manifold (fuel gas side), 4A
.

Claims (1)

[Claims] 1) The contents of the fuel cell, including a fuel cell stack and a reactive gas passage for supplying and discharging fuel gas and oxidizing gas to and from the fuel cell stack, respectively, are placed in a housing having a passage for supplying and discharging inert gas at a predetermined pressure. In the stored product, there is a collection chamber for leaking combustible gas formed in a convex manner above the housing, a detector for detecting the concentration of combustible gas provided in this collection chamber, and a detection concentration of the gas by the detector. It consists of a judgment circuit that compares the actual value signal with set value signals of multiple stages and issues a control signal for each concentration stage, and a control valve for controlling the flow rate of released gas connected to the collection chamber, and the concentration is controlled by the control signal. It is characterized by being equipped with a discharge mechanism section that releases flammable gas at a flow rate corresponding to the stage together with an inert gas, and an abnormality control circuit that receives a control signal for the highest concentration stage and issues a signal instructing an emergency stop. Fuel cell protection device.