JPH04264365A - Reaction gas piping structure for fuel cell - Google Patents

Abstract

PURPOSE:To prevent the residence of condensed water bedewed in piping, check the water immersion accident of a unit cell or the flood fault accident of a reaction gas occurring due to the residence, and stabilize gas pressure by improving the structure of the outlet side piping of an offgas including produced water steam. CONSTITUTION:A drain pot 8 is connected to a low place of discharge system piping, including outlet collecting piping linked to an outlet manifold 3, to collect condensed water, and an discharging means 9 including a level switch and a drain valve is provided to discharge collected water outside without a gas pressure variation. Also a bursting tube and a discharge tube are added to the drain pot 8 and a water level is retained constant with the discharging means to also use the drain pot for a water sealing device to restrain the abnormal rise of gas pressure in the piping.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] This invention relates to phosphoric acid fuel cells,
Structure of reactant gas piping on the outlet side of fuel cells such as alkaline fuel cells, molten carbonate fuel cells, and solid polymer electrolyte fuel cells, especially piping with means for collecting and discharging generated water condensed in the piping. Regarding structure.

0002

[Prior Art] A fuel cell (stack) is constructed as a laminate of multiple layers of unit cells in which a fuel electrode and an oxidizer electrode are arranged with an electrolyte sandwiched between them.
Hydrogen-rich fuel gas is supplied to the fuel electrode maintained at a predetermined operating temperature through a pair of manifolds, and reaction air as an oxidant, for example, is supplied to the oxidizer electrode. Direct power generation is achieved by causing a reaction, and water is generated at one of the electrodes as a result of the electrode reaction. The electrode that generates generated water differs depending on the type of fuel cell; in phosphoric acid fuel cells, the electrode is located on the oxidizer electrode (also called air electrode) side, and in alkaline, molten carbonate, and solid polymer electrolyte fuel cells, it is located on the fuel electrode. Generate on the side. In any case, the produced water passes through the porous electrode base material, is released into the outlet manifold, and is diffused as high-temperature water vapor into the off-air or off-gas (hereinafter also referred to as off-gas) after the reaction. is sent to the exhaust system via an outlet collection pipe connected to the manifold. The off-gas discharge system is generally equipped with a heat exchanger for waste heat utilization and a condenser for recovering produced water. It is used as fuel gas or combustion supporting gas for quality equipment burners. Therefore, the piping of the exhaust system is kept warm in order to prevent water vapor in the off-gas from condensing and staying in the piping and obstructing the flow of the off-gas.

0003

[Problem to be Solved by the Invention] The off-gas temperature of a fuel cell is 100% because the operating temperature differs depending on the type of fuel cell.
It is quite difficult to maintain the pipe temperature at the same level as the off-gas temperature using heat insulating material that wraps the pipes, and when the heat retention effect decreases due to aging, water vapor condenses on the pipe walls and condenses. Condensed water flows down to low points in the piping and accumulates. In particular, the outlet collection pipe may stand up and be connected to the off-gas exhaust system at the top, or it may fall down and be connected to the exhaust system at a lower location. A situation arises in which accumulated condensed water flows into the stack via the connection with the outlet manifold. In the latter case, the connecting part between the collecting pipe and the exhaust system is located at the lowest point of the piping, and condensed water accumulates in this part, which tends to cause off-gas flow problems and abnormal increases in gas pressure. . In particular, a structure is known in which a water seal is provided at the inlet of the discharge system in order to avoid an abnormal rise in gas pressure within the piping, but water that condenses in the piping flows into the water seal and is normally kept at a constant level. The water level in the water seal, which is supposed to maintain the water level, rises, causing the inconvenience that the discharge pressure rises. In particular, if condensed water enters the stack and wets the unit cells,
The electrolyte held between the electrodes dissolves into the porous electrode base material, which obstructs the permeation of the reactant gas, necessitating disassembly and repair to replace the flooded unit battery with a new one. Furthermore, if an abnormal rise in gas pressure occurs within the piping, the differential pressure between the electrodes of the unit cell will increase and the reaction gas will blow through, making disassembly and repair essential in this case as well.

[0004] The purpose of the present invention is to prevent the accumulation of condensed water by improving the structure of the off-gas outlet side piping.
The purpose is to prevent accidents such as flooding of unit batteries and failure of flow of reactant gas caused by this, and to stabilize the gas pressure in the piping.

[0005]

[Means for Solving the Problems] In order to solve the above problems, according to the present invention, a stack consisting of a laminate of unit cells supplies a reactive gas to a fuel electrode and an oxidizer electrode of the unit cells, respectively. In a fuel cell having an inlet manifold, an inlet collection pipe that connects the inlet manifold to a reaction gas supply system, an outlet manifold that discharges reacted gas, and an exit collection pipe that connects the same to the reaction gas discharge system, the outlet collection pipe A drain pot connected to a lower part of the discharge system including the outlet collecting pipe to collect the generated water condensed in the pipe, and a discharge means for discharging the collected water in the drain pot to the outside. It shall be installed at a position lower than the system piping.

[0006] Also, a level switch in which the discharge means operates by detecting a change in the water level in the pot within a predetermined adjustment range;
It shall consist of a drain valve whose opening and closing are controlled by this level switch.

Further, the means for discharging the collected water is set to maintain the water level in the drain pot at a constant level, and the drain pot has a discharge pipe that maintains the space above the liquid level at atmospheric pressure, and a lower end thereof. A pressure relief pipe that opens into the collected water of the drain pot and has an upper end communicating with a discharge system including an outlet collecting pipe, and the drain pot also serves as a water seal to prevent excessive pressure rise of the reaction gas. do.

[0008]

[Function] A drain pot is connected to the lower part of the exhaust system including the outlet collection pipe connected to the outlet manifold where the produced water is released as steam into the reacted reaction gas (off-gas), and the water level of the drain pot is adjusted. By being configured to include a discharge means for collected water, the condensed water condensed in the outlet side piping is collected into the drain pot by gravity, and the water level in the drain pot is maintained within a predetermined adjustment range by the discharge means. This makes it possible to prevent problems related to condensed water and to stably maintain the fuel cell in a normal operating state.

[0009] Furthermore, if the discharge means is composed of a level switch that operates by detecting changes in the water level in the pot within a predetermined range, and a drain valve that is controlled to open and close by this level switch, off-gas can be discharged. Since the water level in the drain pot can be adjusted without affecting the gas pressure inside the battery, the collected water can be released to the outside without affecting the gas pressure inside the battery, thereby providing a function to prevent troubles related to the accumulation of condensed water.

Furthermore, if the drain pot is configured to double as a water seal, troubles related to condensed water and problems related to increase in gas pressure can be solved simultaneously with one device, and by providing a discharge means, the water inside the pot can be solved simultaneously. This provides the ability to keep the operating pressure of the water seal stable by adjusting the water level to a constant level.

[0011]

[Examples] The present invention will be explained below based on examples. FIG. 1 is a partially exploded cross-sectional view showing a simplified reaction gas piping structure of a fuel cell according to an embodiment of the present invention, and FIG. An example of application to a fuel cell is shown. In the figure, 1 is a fuel cell (stack) consisting of a stack of unit cells, and is housed in a pressurized tank 10 containing an inert gas (nitrogen) at the same pressure as the reaction gas. Reference numeral 2 denotes a reaction air inlet manifold divided into a plurality of upper and lower parts, which is drawn out from the bottom of the pressurized tank via an inlet collection pipe 4 connected near the lower end of each manifold, and connected to a reaction air supply system 6. reaction air is supplied as an oxidizing agent. On the other hand, 3 is an outlet manifold for reacted air (off-air), and the reacted off-air containing vapor of produced water generated at the oxidizer electrode of each unit cell is connected near the upper end of the outlet manifold 3. The air is drawn out from the bottom of the pressurized tank via the outlet collection pipe 5 and sent to the off-air exhaust system 7. The drain pot 8 is arranged at a lower position than the outlet collecting pipe 3 and the discharge system 7 and is flange-connected to the lower end of the outlet collecting pipe 5, so that water vapor in the off-air condenses on the pipe walls of the outlet collecting pipe 5 and the discharge system 7. The resulting condensed water flows down by gravity and is collected in the drain pot 8 as collected water 8A.

The collected water discharge means 9 is as shown in FIG.
The level sensor 9B measures the level of collected water in the drain pot 8.
The level switch 9A is turned on at the upper limit level and turned off at the lower limit level, which opens and closes the drain valve 9C, which is an operating valve, and the level of the collected water increases. The collected water is configured to be discharged to the outside until it decreases from the upper limit level to the lower limit level.

In the reactant gas piping structure of the fuel cell configured as described above, the generated water released as high-temperature steam into the off-air in the outlet manifold 3 is heated for a short time due to the slight temperature difference between it and the piping. Dew condenses on the wall, but the condensed water naturally flows down the pipe wall and is collected as collected water 8A in the drain pot 8 connected to a low place, and the condensed water stays in the low place of the pipe and drains off air It is possible to avoid situations that obstruct the distribution of products. Furthermore, since the discharge of collected water by the discharge means 9 does not stop at the lower limit level and release off air, the collection of condensed water and the discharge of collected water can be performed without affecting the gas pressure of the reaction air system. This makes it possible to prevent troubles related to condensed water while avoiding secondary disasters such as blow-through accidents between electrodes due to fluctuations in the differential pressure between electrodes of a unit battery.

FIG. 3 is a simplified side view showing a different embodiment of the present invention, in which the stack 1 is a low-pressure fuel cell in which the reactant gas pressure is close to atmospheric pressure, and the reactant gas rises from an inlet collecting pipe 4. Outlet collective piping 5 that flows into the inlet manifold 2 and also rises from the outlet manifold 3
The drain pot 8 is connected to the lower end of the outlet collecting pipe 5 from below.

[0015] In a fuel cell having a piping structure constructed as described above, a large amount of condensed water flows down the outlet collecting pipe. Therefore, if there is no drain pot, the condensed water will remain at the bottom of the outlet collection pipe 5, and the worst case scenario will likely occur where the overflowing condensed water flows into the outlet manifold 3 and the unit batteries located at the bottom are submerged. However, according to this embodiment, the drain pot collects the condensed water, and the discharge means 9 monitors the liquid level and discharges the collected water.
The worst situation mentioned above can definitely be avoided.

FIG. 4 is a configuration diagram showing another embodiment of the present invention, in which the drain pot 18 is removed from the reaction air system (which may be a fuel gas system) due to a flow obstruction in the off-air exhaust system 7.
An example is shown in which the water seal is configured to also function as a water seal to prevent abnormal pressure rises. That is, the drain pot 18 is equipped with a discharge pipe 18A that maintains its upper space at atmospheric pressure, and a pressure relief pipe 1 is provided in the inlet piping section 7A of the discharge system 7 including the outlet collective piping 5.
8B is connected, and the lower end of the pressure relief pipe opens at a predetermined depth in the collected water. Further, the adjustment width of the collected water discharging means 9 is set to be narrow so as to discharge the inflowing collected water in fine steps so as to maintain the liquid level at a constant position.

Drain pot 18 configured in this way
In this case, a head difference determined depending on the water depth is added to the opening of the pressure relief pipe 18B, and if the pressure of the off-air is a steady pressure, it will be in a water-sealed state, and the off-air will flow through the heat exchanger 7B of the exhaust system 7. The waste heat is utilized in the condenser 7C, and the generated water is recovered in the raw water tank 7D after being separated into steam and water in the condenser 7C.Oxygen-containing off-air is used, for example, as combustion support air for the reformer burner. Also, condensed water in the pipes is collected in a drain pot and released little by little. On the other hand, if some sort of off-air flow failure occurs in the discharge system 7 and the gas pressure in the piping abnormally rises to the extent that it exceeds the above-mentioned head difference, the water in the pressure relief pipe is pushed out by the gas pressure, and the water in the pressure relief pipe 18B is pushed out by the gas pressure. The off-air that floats up as bubbles is discharged to the outside from the discharge pipe 18A, and the drain pot 18 functions as a water seal to suppress abnormal pressure rise. Furthermore, since the level of collected water in the drain pot is maintained at a constant level by the discharge means, the operating pressure of the water seal is stabilized. Therefore, troubles related to condensed water and troubles such as blow-through of reactant gas caused by increase in gas pressure can be solved simultaneously with one device, and there is an advantage that the operation of the fuel cell can be further stabilized.

[0018]

Effects of the Invention As described above, the present invention provides a drain system at a low point in the exhaust system including the outlet collection pipe connected to the outlet manifold on the side where the produced water is released as steam into the reacted reaction gas (off-gas). The pots are connected and a means for discharging collected water is provided to adjust the water level in the drain pot. As a result, it becomes possible to collect the condensed water that has condensed in the outlet pipe into the drain pot by gravity, and to maintain the water level in the drain pot within a predetermined adjustment range using the discharge means. This prevents problems with conventional piping structures that do not have a discharge means, such as flooding of unit batteries with condensed water or blow-through of reactant gas due to piping flow problems, resulting in stable operating conditions and long-term reliability. It is possible to provide high fuel cells.

[0019] Furthermore, if the drain pot is configured with a level switch that operates by detecting changes in the water level within the pot within a predetermined width, and a drain valve that is controlled to open and close by this level switch, off-gas can be released. Since the water collected in the drain pot can be discharged to the outside without any change in gas pressure, it is possible to provide a fuel cell having a simple piping structure that can discharge the collected water without fluctuations in gas pressure.

Furthermore, if the drain pot is configured to double as a water seal, troubles related to condensed water and problems related to increase in gas pressure can be solved simultaneously with one device, and it is possible to solve problems related to condensed water and increases in gas pressure at the same time. It is also possible to avoid changes in operating pressure due to the inflow of condensed water, which has caused problems in the fuel cell, thereby providing an economically advantageous fuel cell with a piping structure that has a variety of trouble-preventing functions.

[Brief explanation of the drawing]

[Fig. 1] A partially fragmented cross-sectional view showing a simplified reaction gas piping structure of a fuel cell according to an embodiment of the present invention.

[Fig. 2] A configuration diagram showing the main parts of the example device

FIG. 3 is a simplified side view of different embodiments of the present invention.

[Fig. 4] A configuration diagram showing another embodiment of the present invention.

[Explanation of symbols]

1 Fuel cell (stack) 2 Inlet manifold 3 Outlet manifold 4 Inlet collection pipe 5 Outlet collection pipe 6 Reaction gas supply system (air side) 7 Off-gas discharge system 8 Drain pot 8A Collected water 9 Collected water discharge means 9A Level switch 9C Drain valve 18 Drain pot (water seal) 18A Discharge pipe 18B Pressure discharge pipe

Claims (3)

[Claims] 1. A stack consisting of a laminate of unit cells includes an inlet manifold for supplying a reaction gas to a fuel electrode and an oxidizer electrode of the unit cells, an inlet manifold connecting the same to a reaction gas supply system, and a reaction gas supply system. In a fuel cell having an outlet manifold for discharging reactant gas and an outlet collecting pipe connecting the outlet manifold to an exhaust system for reactant gas, the fuel cell is connected to a lower part of the exhaust system including the outlet collecting pipe and condensed in the pipe. A fuel cell characterized in that a drain pot for collecting water and a discharge means for discharging the collected water in the drain pot to the outside are provided at a position lower than the inlet pipe of the discharge system including the outlet collecting pipe. Reactant gas piping structure. 2. A claim characterized in that the discharge means comprises a level switch that operates by detecting changes in the water level in the pot within a predetermined adjustment range, and a drain valve that is controlled to open and close by the level switch. 1. Reactant gas piping structure of the fuel cell according to 1. 3. The means for discharging the collected water is set to maintain the water level in the drain pot at a constant level, and the drain pot has a discharge pipe that maintains the space above the liquid level at atmospheric pressure and a lower end thereof. The drain pot is equipped with a pressure relief pipe that opens into the collected water of the drain pot and communicates with the discharge system including the outlet collecting pipe at its upper end, so that the drain pot also serves as a water seal for preventing excessive pressure rise of the reaction gas. A reactant gas piping structure for a fuel cell according to any one of claims 1 and 2, characterized in: