JPS6196675A - Abnormal differential pressure preventing apparatus for fuel cell - Google Patents

Abstract

PURPOSE:To effectively increase a surge function and to reduce the size of an abnormal differential pressure preventing apparatus for a fuel cell by providing a series combination of a volume chamber with the surge function and a liquid seal device between a fuel gas supply line and the atmosphere surrounding the body of the fuel cell. CONSTITUTION:In a normal operation, a liquid seal is effected between the atmospheric pressure and a fuel gas pressure as both the pressures are balanced while the water surface in a pipe 22 pressed down by the fuel gas pressure to a level of the height nearly equal to a water depth H. On a sudden increase in a fuel gas chamber pressure, the increment compresses the gas in a volume chamber 15a, which absorbs and relieves the increment. At the same time, the water surface level is lowered and a surge function is increased. On an additional sudden and large increase in the fuel gas chamber pressure, a part of the fuel gas is blown into the water through the open end of the pipe 22 to be discharged into the atmosphere. When a negative pressure is produced in the fuel gas chamber, the water overflown from the pipe 22 remains in the bottom of the volume chamber 15a and therefore there is no danger that the water is sucked into the fuel gas chamber.

Description

[Detailed description of the invention] [Technical field to which the invention pertains]

This invention provides an abnormal pressure difference in a fuel cell in which a fuel electrode, an electrolyte chamber (including a circulating electrolyte chamber, a fixed electrolyte matrix, etc.), and an air electrode are sandwiched between a fuel gas chamber and an air chamber. Regarding prevention devices.

[Prior art and its problems]

Fuel cell electrodes are generally made thin, and the bubble resistance of the matrix layer that holds the electrolyte is relatively low, so if the differential pressure between the fuel gas chamber and the air chamber exceeds the permissible limit, the electrode , the strength of the matrix layer is threatened, and there is a risk of explosion due to mixture of fuel gas and air due to destruction or poor sealing. For this reason, it is required to prevent a pressure difference exceeding a certain level from being applied between the fuel gas chamber and the air chamber, and as a countermeasure, the pressure in the fuel gas chamber and the air chamber must be adjusted to the fuel gas and air supply, respectively. Conventionally, a method has been adopted in which control is performed using a pressure regulating valve installed in the line. This pressure control system will be explained with reference to FIG. 4. In the figure, reference numeral 1 indicates a fuel cell main body, and as is well known, the fuel cell main body 1 has a fuel gas chamber 2. Fuel electrode 3.
The electrolyte chamber 4° consists of an air electrode 5 and an air chamber 6. Here, a fuel gas supply line 7 is piped between the fuel gas chamber 2 and a gas reformer (not shown), and fuel gas is supplied through a fuel gas supply valve 8. Further, a pressure regulating valve 9 as a pressure regulating means is provided on the outlet side of the fuel gas chamber 2, and a pressure detector 10 on the inlet side is provided.
The internal pressure of the fuel gas chamber is controlled to be maintained within a predetermined range based on the output of the fuel gas chamber. On the other hand, air is supplied to the air chamber 6 through an air supply line 11 and an air supply valve 12 . Similarly to the fuel gas supply line, the air supply line 11 is also provided with a pressure regulating valve 13, and is controlled based on the output of the pressure detector 14 so that the indoor pressure of the air chamber 6 is within a predetermined range. In this manner, the fuel cell is controlled so that almost no differential pressure is generated between the fuel gas chamber 2 and the air chamber 6 during the steady operation state of the fuel cell. In addition to the illustrated absolute pressure control method, a differential pressure control method is also known in which the pressure difference in each chamber is controlled by detecting the pressure difference between the fuel gas chamber 2 and the air chamber 6. However, with the conventional pressure control method, the following operational problems remain. In other words, when the consumption of fuel gas and air inside the fuel cell stops instantaneously, such as when the load of the fuel cell is cut off, especially in a fuel cell that uses an air-cooling method, the amount of fuel gas and air supplied to the cell may be reduced. Because of the difference in the consumption rate within the battery, the increase in volume on the fuel gas side is greater than on the air side, which causes a larger pressure increase on the fuel gas chamber side than on the air chamber side. Occurs rapidly. When such a sudden pressure change occurs, the pressure in the fuel gas chamber 2 cannot be reduced in a quick response due to the unavoidable control delay of the pressure control system described above, and the pressure in the fuel gas chamber 2 and the air It is unavoidable that an excessive pressure differential will occur between the chamber and the chamber. On the other hand, as a protective measure against this problem, a liquid sealing device and a surge tank of a predetermined volume are installed in parallel on the inlet or outlet side of the fuel gas chamber to prevent the fuel cell from being exposed to danger even during load shedding. An abnormal differential pressure prevention device has already been proposed by the same applicant as the present invention. (Unexamined Japanese Patent Publication No. 5
8-1641 Such an abnormal pressure differential prevention device includes a liquid seal device 15 connected in parallel to the fuel gas supply line 7 on the fuel gas chamber 2 side and a surge tank 1 of a predetermined volume in FIG.
It consists of 6. Among these, the liquid sealing device 15 is connected to a water supply and drainage channel 17, 18, and a pipe 19 open to the atmosphere as a sealing liquid, and has water 2 inside.
A pipe 22 connected to the fuel gas supply line 8 is configured to open to a depth H below the water surface in the tank 21 in which the fuel gas 0 is accommodated. The head pressure corresponding to the underwater depth H is set slightly higher than the predetermined pressure of the fuel gas system.The function of this liquid seal device is well known, and in a steady state, the sealed water in the tank 20 is The fuel gas is isolated and sealed from the atmosphere, and when the pressure on the fuel gas chamber side increases abnormally, the water level in the pipe 22 is pushed down and the gas is released into the water, passing through the pipe 19 and causing excessive pressure. On the other hand, the surge tank 16 acts as a pressure relief valve to quickly release the pressure to the atmosphere. On the other hand, the surge tank 16 absorbs and alleviates the transient pressure increase when the pressure on the fuel gas side increases suddenly. The volume is selected to be a volume value that absorbs and alleviates the pressure increase that occurs transiently based on the inertia of the operation of the liquid sealing device 15 at the time of the expected maximum pressure increase, including when the load is cut off. By the way, the above-mentioned conventional abnormal pressure differential prevention device works effectively to prevent abnormal pressure differential from occurring due to pressure increase on the fuel cell main body side, but on the other hand, for example, when starting the operation of the fuel cell, it is difficult to supply fuel gas or air. In the process of cooling the fuel cell body under such conditions, if the pressure in the fuel gas chamber and air chamber decreases below the atmospheric pressure of the surrounding atmosphere as the temperature decreases, water as a sealing liquid may pipe 22
This has the drawback that the fuel gas may be sucked into the fuel gas supply line 7 through the fuel gas. Furthermore, since each independent surge tank and liquid seal device are placed side by side, there is also the drawback that the installation space for the entire device is large.

[Purpose of the invention]

This invention has been made in view of the above points.
The object of the present invention is to provide an abnormal differential pressure prevention device for a fuel cell that eliminates the drawbacks of conventional devices, increases the effectiveness of the surge function, and makes the device more compact.

[Key points of the invention]

In order to achieve the above object, the present invention has been developed to reduce the surge potential between the gas supply line and the ambient atmosphere surrounding the fuel cell main body. By installing a volume chamber and a liquid seal device in series, the surge function of the volume chamber can be made effective, including the volume change caused by the change in liquid level in the gas path in the liquid seal device during pressure fluctuations. In addition to expanding the capacity, even if the internal pressure on the fuel cell main body side becomes negative with respect to the surrounding atmosphere, the seal liquid is released from the liquid sealing device using the internal space of the volume chamber. The seal liquid is temporarily stored to prevent the seal liquid from being sucked into the gas supply line. [Embodiments of the Invention] Figures 1, 2, and 3 show different embodiments of the present invention. This shows an example circuit diagram, and in each figure, the same parts as in Fig. 4 are given the same symbols.First, Fig. 1 shows a fuel cell main body installed in an ambient atmosphere at atmospheric pressure. This is an example in which there is a volume chamber 1 in the fuel gas supply in 7 on the inlet side of the fuel gas chamber 2.
A liquid sealing device 15, which is assembled and configured integrally with 5a, is connected and installed. In this device, a volume chamber 15a is partitioned into the upper half of the tank 23, and a liquid seal chamber 24 containing water 20 as a sealing liquid is partitioned into the lower half, and a pipe 22 drawn out from the bottom of the volume chamber 15a serves as the liquid seal chamber. It is piped so as to open to the underwater depth H within 24. Further, the indoor space of the volume chamber 15a is connected to the fuel gas supply line 7 via a pipe 25, and a pipe 19 drawn out from the upper part of the liquid seal chamber 24 is open to the atmosphere. With this configuration, during steady operation of the fuel cell, as shown in the figure, the water surface is pushed down in the vibrator 22 to a level close to the underwater depth H by the fuel gas pressure, and the pressure is balanced and a liquid seal is created between it and the atmosphere side. Is going. If the pressure in the fuel gas chamber suddenly increases from this state for some reason, the pressure increase change will be applied to the volume chamber 15all.
The Ig gas is compressed and absorbed and relaxed. At that time, the water level in the pipe 22 will decrease, so the volume chamber 1 will decrease by that amount.
The effective volume for 5a is increased to extend its surge capability. Further, when the pressure in the fuel gas chamber suddenly increases as in the case of load interruption, the water level in the pipe 22 in the liquid sealing device is further lowered and the liquid sealing function is temporarily lost. As a result, a portion of the fuel gas is discharged into the water from the open end of the pipe 22 and is discharged to the atmosphere through the exhaust pipe 19. This makes it possible to quickly release excessive pressure in the fuel gas chamber and protect the fuel gas body. Conversely, when the pressure in the fuel gas chamber decreases and becomes negative with respect to atmospheric pressure, the water level in the pipe 22 rises transiently, compressing the gas in the volume chamber 15a. From this point on, the indoor pressure in the fuel gas chamber quickly recovers to approach the predetermined pressure. Further, in this case, the water overflowing from the pipe 22 accumulates at the bottom of the volume chamber 15a, and there is no risk of it being sucked into the fuel gas chamber. Although the illustrated embodiment shows an example in which the liquid seal device is installed on the inlet side of the fuel gas chamber, it goes without saying that similar effects can be obtained even if the liquid seal device is installed on the outlet side. Furthermore, by installing a liquid sealing device 15 similar to that on the fuel gas chamber side on the air chamber side in FIG. can be increased. Figure 2 shows a fuel cell main body 1 and an inert gas chamber 2 such as nitrogen gas.
As shown in the figure, the fuel cell main body is housed in an inert gas chamber, and inert gas is supplied into the inert gas chamber 26 through an inert gas supply line 27. At the same time, the indoor pressure is measured by the gas pressure detector 2, and the pressure control system of the pressure regulating valve 29 detects the fuel gas chamber 2.
．． By controlling the pressure to be maintained at a value close to the pressure in the air chamber 6, the pressure difference between the inside and outside of the fuel cell body is kept to a lower value than when the surrounding atmosphere of the fuel cell body is at atmospheric pressure as shown in Figure 1. 8 to increase confidence in sealing performance.
It is possible. For a fuel cell with such a configuration,
In this embodiment, the fuel gas chamber 2. For each air chamber 6, a liquid seal 215 similar to that shown in FIG. 1 is interposed between the gas supply line 7.11 connected to each chamber and the inert gas chamber 26. That is, the volume chambers 15a of the liquid sealing devices 15 of 2 & I are each connected to the gas supply line 7.11 via the piping 25, whereas the pipes 19 drawn out from the liquid sealing chambers of each liquid sealing device are Both are connected to an inert gas chamber 26 in communication. With this piping system, the pressure difference applied on both sides of the liquid sealing water in the liquid sealing device 15 becomes small in steady operation, so even if the system pressure of the fuel cell body is set considerably higher than atmospheric pressure. , liquid sealing can be easily performed without increasing the underwater depth H in the figure. This allows the height of the liquid sealing device to be kept low (reduced) to make it compact. With the above configuration, the load can be reduced from steady operation to When the pressure in the fuel gas chamber 2 rises rapidly, such as when the fuel gas chamber 2 is shut off, and the differential pressure between the fuel gas chamber 2 and the inert gas chamber 26 becomes equal to or higher than the liquid seal setting value, the fuel gas flows through the liquid seal device 15 into the inert gas chamber. It flows into the fuel gas chamber 26 and quickly lowers the pressure in the fuel gas chamber, suppressing an increase in the differential pressure between the fuel gas chamber 2 and the air chamber 6.It also acts in the same way against pressure fluctuations on the air chamber 6 side. The gas that has flowed into the inert gas chamber is discharged to the outside of the system through the inert gas supply line 27. Conversely, the pressure in the fuel gas chamber 2 or the air chamber 6 becomes negative with respect to the pressure in the inert gas chamber. in case of,
It operates to restore the pressure based on the pressure in the inert gas chamber 26 by changing the liquid level within the liquid sealing device 15. FIG. 3 shows an embodiment in which the embodiment shown in FIG. 2 is further improved. Fuel gas chamber 2 i11 of fuel cell main body 1 inside! A sealing member 30 is provided at the boundary between I and the air chamber 6 side, and the indoor space of the inert gas chamber is divided into a fuel gas chamber area 26a and an air chamber inclined wall 26b. The inert gas supply line 27 branches on the population side of the inert gas chamber 26 to supply inert gas to each of the regions 26a and 26b, and discharges the inert gas separately from the outlet side to the outside of the system. It is plumbed like this. In this embodiment, for such a fuel cell, the regions 26a and 26b of the inert gas chamber 26 are interconnected via another set of liquid seal devices 150 having the same structure as the liquid seal device 15. This liquid sealing device 150 prevents the generation of differential pressure between each region of the inert gas chamber. With this configuration, when a sudden pressure rise occurs in the fuel gas chamber or air chamber on the fuel cell main body side during operation of the fuel cell, the fuel gas passes through the liquid seal device 15 to the region 26a of the inert gas chamber. The air flows into the region 26b and is discharged separately from the system together with the inert gas, making it possible to prevent the fuel gas and air from directly mixing together. Effects of the Invention As described above, according to the present invention, there is no surge 4I between the gas supply line and the surrounding atmosphere surrounding the fuel cell main body, at least on the fuel gas chamber side of the fuel gas chamber and the air chamber. ! By installing a volume chamber with one function and a liquid sealing device in series, it has a higher surge function compared to conventional devices, and when the pressure on the fuel cell side becomes negative with respect to the surrounding atmosphere. The abnormal pressure differential has a high practical value and has a wide range of applications for fuel cells, such as there is no risk of the sealing liquid of the liquid sealing device being sucked into the battery body, and the volume chamber and liquid sealing device can be integrated into a compact unit. A prevention device can be provided.

[Brief explanation of the drawing]

1, 2, and 3 are configuration circuit diagrams of different embodiments of the present invention, and FIG. 4 is a conventional configuration circuit diagram. In Figure 0, 1: fuel cell main body, 2: fuel gas chamber. , 3: fuel electrode, 4
jt solute chamber, 5: air electrode, 6: air chamber, 7: fuel gas supply line, 9.13: pressure regulating valve, ll: air supply line, 15,150F liquid sealing device, 15a; volume chamber, 26
: inert gas chamber, 26a: fuel gas chamber region, 26b: air chamber region, 27: inert gas supply line, 30: sealing member. Sai1 (2) Saizr! : 4 years old 3 figures

Claims (1)

[Claims] 1) A fuel cell in which a fuel electrode, an electrolyte chamber, and an air electrode are sandwiched between a fuel gas chamber and an air chamber, and a fuel gas chamber is provided in a fuel gas supply line and an air supply line, respectively. , in which a pressure control means for the air chamber is provided, at least for the fuel gas chamber side, a volume chamber having a surge function and a liquid sealing device are provided between the gas supply line and the ambient atmosphere surrounding the fuel cell main body. An abnormal differential pressure prevention device for a fuel cell, characterized in that it is installed in series. 2) In the abnormal pressure differential prevention device as set forth in claim 1, the liquid sealing device is one in which the gas passages communicating with each other at the bottom of the room are sealed with a sealing liquid having a free surface. Features: Abnormal differential pressure prevention device for fuel cells. 3) The abnormal pressure differential prevention device according to claim 1, characterized in that the volume chamber communicates with the gas path of the liquid seal device and is assembled integrally with the upper part of the liquid seal device. Abnormal differential pressure prevention device for fuel cells. 4) In the abnormal pressure differential prevention device according to claim 1, the volume chamber and the liquid sealing device maintain the indoor pressure at a predetermined pressure for each fuel gas and air supply line communicating with the fuel gas chamber and the air chamber. What is claimed is: 1. An abnormal differential pressure prevention device for a fuel cell, characterized in that the device is installed astride between an inert gas chamber and an inert gas chamber that accommodates a fuel cell main body. 5) In the abnormal pressure differential prevention device according to claim 4, the inert gas chamber is partitioned into a fuel gas chamber region and an air chamber region, and between the fuel gas chamber region and the air chamber region. An abnormal differential pressure prevention device for a fuel cell, characterized in that the two are interconnected via a liquid seal device.