JPS62131474A - Cooling device of alkaline type fuel cell - Google Patents

Abstract

PURPOSE:To effectively cool without losing the balance of electrolyte concentration and generation of leakage current by connecting a cooling tube arranged in an electrolyte chamber to a coolant circulation line. CONSTITUTION:When an electrolyte chamber 4 is filled with electrolyte and reaction gases are supplied to a fuel electrode 2 and an oxidizing agent electrode 3 to operate a fuel cell, heat is generated by polarization of each electrode and liquid resistance of the electrolyte, and the temperature of electrolyte is increased. When a pump 9 in a coolant circulation line 11 is operated to circulate coolant between a cooling tube 7 and the circulation line 11, heat generated in the fuel cell 1 is transferred by the coolant flowing within the tube 7 from the cell and exhausted outside with a heat exchanger 8, and the coolant cooled in the heat exchanger 8 is circulated again to the cell 1. Since a power generating line and a cooling line are separated, the fuel cell is effectively cooled without an adverse are separated, the fuel cell is effectively cooled without an adverse effect on power generation such as break of balance of electrolyte concentration.

Description

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

This invention consists of a fuel electrode, an oxidizer electrode, and a supply path for supplying fuel and oxidizer reaction gas to each electrode on both sides of an electrolyte chamber filled with an electrolyte, which is an alkaline aqueous solution. The present invention relates to a cooling device for an alkaline fuel cell constructed by stacking a large number of cells with separate plates interposed therebetween.

[Prior art and its problems]

A fuel cell generates electricity through an electrochemical reaction between fuel and an oxidizer, and the resulting electricity is used as fuel. Approximately 50% of the activation energy of the oxidant is distributed to the electrode i
, is converted into heat and lost due to the internal resistance of the pond. For this reason, it is necessary to cool the fuel cell main body by removing the generated heat generated during operation of the fuel cell to the outside of the system by some means. By the way, the above-mentioned alkaline fuel cell can be operated at room temperature, and the upper limit of its operating temperature is determined by the boiling point of the alkaline aqueous solution that is the electrolyte. Therefore, by setting the operating temperature of the fuel cell to about 15 to 80'e, it becomes possible to use a plastic material such as polyethylene, which has low heat resistance but is available at low cost, as a constituent material of the fuel cell. However, in such alkaline fuel cells, the difference between the operating temperature and the outside temperature is small, and the plastic material that makes up the cell has poor thermal conductivity, so the cooling effect due to heat dissipation from the fuel cell body is limited. There is a problem in that if the temperature is low and exceeds the allowable operating temperature, the plastic material that makes up the battery will melt, causing irreversible damage. For this reason, conventionally, a fuel gas circulation method has been used as a heat removal method for the generated heat generated during operation of the fuel R+II fuel tank. Alternatively, a method is generally adopted in which the generated heat is forcibly removed by employing an electrolyte circulation method or the like. Among these, the former fuel gas circulation method takes out the water generated on the fuel side by the cell reaction to the outside of the cell together with the fuel gas, separates this water into gas and liquid, and removes it from the system. The fuel gas is cooled by a cooling heat exchanger and then circulated and supplied to the fuel cell side again to cool the fuel cell body. However, fuel gas, which is hydrogen, has low thermal conductivity, and for this reason, in order to obtain the required cooling capacity, a large amount of fuel gas must be circulated through the system. In this case, the power of the fuel gas circulation blower and the heat exchanger for heat removal are large, which not only reduces the overall efficiency of the fuel cell but also causes the problem that the entire fuel cell power generation equipment becomes larger. Furthermore, when a large amount of fuel is circulated and ventilated, a large amount of electrolyte is simultaneously removed from the inside of the cell together with the fuel gas, which disrupts the concentration balance of the electrolyte. On the other hand, the electrolyte circulation method described above cools the electrolyte by circulating the electrolyte between a heat exchanger for heat removal installed outside the battery, and uses the electrolyte as a heat medium to generate heat in the fuel cell. While this method allows efficient cooling, it also prevents electrical conduction between the individual cells that make up the stacked battery using the electrolyte as a medium. Leakage into the electrolyte in order to be used! S! Current flows and battery output decreases,
It has the disadvantage of causing electrolytic corrosion of battery components. In addition, in each of the conventional cooling methods described above, it is possible to increase the cooling capacity to a certain extent by increasing the circulation amount of fuel gas or electrolyte, but there is a limit to the rate of increase. If abnormal heat generation occurs in the fuel cell due to damage to the electrodes of the single cells that make up the N battery, there is a risk that the fuel cell will not be able to deal with this and the temperature will exceed the maximum allowable operating temperature. There is a possibility that this may occur.

[Purpose of the invention]

This invention addresses the above points, and effectively cools the fuel cell body without the fear of imbalance in electrolyte concentration or occurrence of leakage current, which are problems with conventional cooling methods. An object of the present invention is to provide a cooling device for an alkaline fuel cell that can perform cooling.

[Key points of the invention]

In order to achieve the above object, the present invention includes piping a cooling tube within an electrolyte chamber defined between a fuel electrode and an oxidizer electrode, and passing an external heat removal heat exchanger to the cooling tube. A refrigerant circulation line is connected between the cooling tube and the refrigerant, and the refrigerant is circulated through the refrigerant circulation line during operation of the fuel cell, thereby removing the heat generated in the fuel cell body to the outside of the system. The exhaust heat is then removed from the yarn through a heat exchanger. According to such a cooling system, the power generation system and the cooling system of the fuel cell are independent, and the refrigerant that is sent between the cooling tube installed for each vehicle battery and the external refrigerant circulation line is an electrolytic solution. Because they are completely separated, there is no leakage current due to the liquid junction between the cells, which was a problem with the conventional cooling method mentioned above, and an imbalance in the electrolyte concentration caused by the electrolyte being carried away. There is no influence on the power generation system, and it becomes possible to operate the power generation system and the cooling system separately under optimal operating conditions. It is also possible to use pure water as the refrigerant used in the cooling system, but by using a low boiling point refrigerant such as methyl alcohol, it can be used in the event of abnormal heat generation due to fuel cell failure, etc. When the temperature approaches the maximum allowable temperature of the fuel cell, methyl alcohol boils, and its latent heat of vaporization automatically increases the cooling capacity, making it possible to sufficiently cope with abnormal heat generation.

[Practice of the invention N]

FIG. 1 is a system diagram of the entire cooling device according to the embodiment of the present invention, and FIGS. 2 and 3 are sectional views showing the internal structure of the stacked alkaline fuel cell main body and the electrolyte chamber according to the embodiment of FIG. 1, respectively. FIG. 3 is a perspective view showing a cooling tube piping structure. First, in FIG. 1, reference numeral 1 denotes an alkaline fuel cell, which includes a fuel electrode 2, an oxidizer electrode 3, and an electrolyte chamber 4 defined between the fuel electrode 2 and the oxidizer electrode 3. It consists of reaction gas passages 5 and 6 that supply reaction gases of fuel gas and oxidant gas to the fuel electrode and oxidizer electrode, respectively. Here, according to the present invention, a cooling tube made of an alkali-resistant insulating material shown by reference numeral 7 is piped inside the electrolyte chamber 4 of the fuel cell 1 described above, and is connected to the cooling tube 7 and connected to the outside. A water-cooled heat exchanger for heat removal 8. Refrigerant flow pump 9. A refrigerant circulation line 11 equipped with a buffer tank 10 is connected thereto. Next, the cooling tube 7 piped inside the fuel cell main body
The piping structure will be explained with reference to FIGS. 2 and 3. In FIG. 2, each cell includes an outer frame 12 of the electrolyte chamber 4, outer frames 13 and 14 on the fuel electrode side and oxidizer electrode side connected to both sides of the outer frame, and the outer frame 13. The fuel electrodes 2 and the oxidizers 8i3 are attached to the fuel electrodes 2 and 8i3, respectively, and the cells are stacked with separate plates 15 interposed between them to form a stacked alkaline fuel cell. Note that 16 is a j interposed between the separate plate and each t8i.
This is an It board. Here, the refrigerant inlet flow path 17 and outlet flow path 18 penetrating between each of the outer frames 12 to 14 and the separate plate 15 and extending over each unit cell are bored on opposite sides, and the inlet flow path The above-mentioned cooling tube 7 is connected to the electrolyte chamber 4 and spans between the electrolyte chamber 17 and the outlet flow path 18 . Furthermore, as clearly shown in FIG. 3, the cooling tube 7 is piped in a meandering manner throughout the electrolyte chamber 4, and with this piping structure, the cooling tube 7 is connected to the fuel electrode 2 at the same time. It also serves as a spacer to separate the electrode from the oxidizer electrode 3. In addition, in a normal fuel cell, the electrolyte chamber 4
The thickness of the cooling tube 7 is from 3 to 41, and a tube thinner than this thickness is used as the cooling tube 7. In FIG. 3, reference numerals 19 and 20 denote inlet channels for supplying fuel gas and oxidant gas, which are bored in each outer frame and separate plate so as to extend between the cells in parallel with the refrigerant channel; Reference numerals 21 and 22 denote reaction gas outlet channels that are bored on the opposite side of the outer frame, facing the inlet channels 19 and 20. Reference numerals 23 and 24 are an inlet channel and an outlet channel for the electrolyte that are bored on the upper side of the outer frame, and the inlet channel 23 communicates with the bottom of the electrolyte chamber 3 via a relay channel 25. . The electrolyte inlet and outlet channels 23 and 24 described above are used for replenishing and exchanging the electrolyte. When the electrolyte in the electrolyte chamber 4 expands due to temperature rise during fuel cell operation, the electrolyte flows, but in other normal operating conditions, the liquid level of the electrolyte is at the inlet and outlet channels 23.
．． 24, so that the batteries are not connected to each other by the electrolyte via the cough electrolyte flow path. Next, the cooling effect of the fuel cell with the above configuration will be described. That is, when the electrolyte chamber 4 of the fuel cell is filled with electrolyte and the fuel electrode 2 and the oxidizer electrode 3 are supplied with a reactive gas to start the operation of the fuel cell, the polarization of each electrode, Heat is generated by the resistor, etc., and the temperature of the electrolytic solution rises due to the generated heat. On the other hand, in this operating state, the first
By starting the liquid pump 9 of the refrigerant circulation line 11 shown in the figure and circulating the refrigerant between the cooling tubes 7, the generated heat of the fuel cell main body is transferred to the cooling tube piped in the electrolyte chamber 4. After exchanging heat with the refrigerant flowing through the tubes 7 and transferring the heat to the refrigerant side, the refrigerant is carried out of the battery together with the refrigerant, and the heat is exhausted to the outside of the system by the heat exchanger 8. Furthermore, the refrigerant cooled by the heat exchanger 8 is circulated and sent back to the fuel cell 1 so as to be returned to the fuel cell 1. The refrigerant flow rate in this case is set to a flow rate that can remove generated heat generated within a normal load fluctuation range. Although it is possible to use pure water or a low boiling point refrigerant as the refrigerant to flow through the cooling tube, the following advantages can be obtained by particularly employing methyl alcohol. That is, methyl alcohol has a boiling point of about 50 to 80°C, is electrically insulating, and is not corrosive, so it is not suitable for the heat exchanger 8. which constitutes the refrigerant circulation line 11. Metal can be used not only for the liquid pump 9 and the buffer tank 10 but also for the external piping connecting them. Further, even if abnormal heat generation occurs during operation of the fuel cell, if the refrigerant is a low boiling point refrigerant such as methyl alcohol, the methyl alcohol will boil and take away the heat generated by its latent heat of vaporization. Therefore, this greatly increases the cooling capacity, suppressing the temperature rise in the fuel cell body within the maximum allowable temperature without having to specifically control the flow rate to increase the refrigerant flow rate, and melting the plastic materials that make up the cell. This has the advantage that it is possible to prevent the occurrence of damage that is difficult to repair, such as damage caused by damage.

【Effect of the invention】

As described above, according to the present invention, a cooling tube is installed in the electrolyte chamber, and a refrigerant is circulated between the cooling tube and the cooling tube via an external heat removal heat exchanger. By connecting the refrigerant circulation line to configure the fuel cell cooling system, the fuel cell power generation system and cooling system are separated and independent, which has caused problems with conventional fuel gas circulation systems, electrolyte circulation systems, etc. I! The fuel cell can be effectively cooled without affecting power generation due to loss of solution concentration balance. Furthermore, by using a low-boiling-point refrigerant as the refrigerant, even if abnormal heat generation occurs during fuel cell operation, the refrigerant boils and removes the latent heat of vaporization, keeping the battery within the maximum allowable temperature. It is possible to provide a cooling device that exhibits excellent operation management effects for alkaline fuel cells.

[Brief explanation of drawings]

FIG. 1 is a system diagram of the entire cooling device according to an embodiment of the present invention, and FIGS. 2 and 3 are longitudinal sectional views showing the internal structure of the fuel cell in FIG. 1, and piping of cooling tubes in the electrolyte chamber, respectively. In Figure 0, which is a perspective view of the configuration, l: fuel cell, 2: fuel electrode, 3: oxidizer electrode, 4: electrolyte chamber, 5.6: reaction gas supply path, 7: cooling tube, 8:
heat exchanger for heat removal, 9: refrigerant sending pump, 11: refrigerant circulation line, 12: ii electrolyte outdoor frame, 17: refrigerant inlet channel, 18: refrigerant outlet channel. 1 Bay f+ Figure 1

Claims (1)

[Claims] 1) Power generation by using an alkaline aqueous solution as an electrolyte, filling an electrolyte chamber defined between a fuel electrode and an oxidizer electrode, and supplying a reactive gas to each of the electrodes. A cooling device for an alkaline fuel cell that performs the following steps, wherein a cooling tube is installed in the electrolyte chamber, and a refrigerant is passed between the cooling tube and the cooling tube via an external heat removal heat exchanger. A cooling device for an alkaline fuel cell, characterized in that it is configured by connecting a refrigerant circulation line for circulating circulation. 2) A cooling device for an alkaline fuel cell according to claim 1, characterized in that a low boiling point refrigerant having a boiling point of 50 to 80° C. is used as the refrigerant. 3) A cooling device for an alkaline fuel cell according to claim 2, wherein the coolant is methyl alcohol. 4) In the cooling device according to claim 1, the cooling tube is an alkali-resistant insulating tube, and the cooling tube also serves as a spacer between the fuel electrode and the oxidizer electrode to cover the entire area inside the electrolyte chamber. 1. A cooling device for an alkaline fuel cell, characterized by having meandering piping extending over the area.