JPS60124367A - Electrolyte circulation system of fuel cell - Google Patents

Abstract

PURPOSE:To obtain an electrolyte circulation line whose auxiliary power is decreased by making so small the inner diameter of piping which carries electrolyte from a cell main body to a separating unit such as an electrolyte storage tank that gas bubbles mixed in electrolyte can be sent to the separating unit with electrolyte. CONSTITUTION:A cylindrical connecting fitting 10a is screwed in liquidtightness to the outside of a clamping plate 3 arranged at the end of a stack of a cell main body 1 so as to connect to a hole 3a which fits a manifold 4b, through a packing 10c. The end of a piping 10 is mounted in liquidtightness to the connecting fitting 10a with a cap nut 10b through a packing 10d. Electrolyte in each electrolyte chamber 4a which is formed between electrode plates 2b and 2c enters the manifold 4b through a connecting path 4c formed in a frame 2a, then enters the piping 10 through the connecting fitting 10a. The piping 10 has an inner diameter d which meets the following equation and is bent at around the connecting part to the cell main body so that electrolyte is let flow upward so as to easily move bubbles. d<=0.36(logq+0.7), where, q is electrolyte flow rate cc/cm<3>.

Description

Detailed Description of the Invention [1] Technical field to which the invention pertains [1] The present invention relates to a so-called free electrolyte system in which the electrolyte stored in the liquid compartment of the battery body is repeatedly used via an electrolyte circulation system outside the battery body. Regarding a lightning dissolution circulation system for electrolyte-type fuel cell oil, in which a separation device is installed in the circulation system to separate gas mixed in or contained in the electrolyte within the battery body from the electrolyte. Specifically, it is suitable as an electrolyte circulation system of a fuel cell that uses air as an oxidizing gas and an alkaline electrolyte as an electrolyte.

[Prior art and its problems]

The electrolyte circulation system of a free electrolyte type fuel cell as described above originally prevents the electrolyte from reacting with impurities in the gas supplied to the battery, especially solid phase produced when the electrolyte reacts with carbon dioxide gas in the supplied air. An electrode layer provided in order to separate the reaction products from the electrolyte within the system, or to lead the electrolyte whose temperature has risen due to heat generated within the battery body outside the battery body and cool it within the system. The fuel gas or oxidizing gas is diffused into the electrode layer from the gas compartment in the cell, and at the same time the electrolyte permeates from the electrolyte compartment, and the solid-phase electrode, especially into the electrode layer, is The electrochemical reaction proceeds smoothly and power generation occurs under the coexistence of the three phases of the contained catalyst, gas phase reaction gas, and liquid phase electrolyte, but when the electrolyte is If the gas phase is expelled by excessive leaching into the electrode layer and the above-mentioned three-phase coexistence condition is no longer maintained, power generation will not occur normally due to the so-called wetting phenomenon of the electrode layer.

An advantageous means of solving this problem is to maintain the pressure in the gas compartment during operation at least slightly higher than the pressure in the liquid compartment. FIG. 1 schematically shows a conventional electrolyte circulation system designed as described above. In the figure, the fuel cell main body is indicated by 1, and is made up of a plurality of unit cells 2 stacked together and integrated between a pair of clamping plates 3.3 using a fastening means (not shown), and an electrolytic solution is contained inside. An electrolyte compartment 4 is filled with an electrolyte and a gas compartment 5 is defined into which fuel gas or oxidizing gas is introduced. Each unit cell 2 includes a frame 2a, an electrode 2b for fuel gas, and an electrode 2C for oxidizing gas, and the aforementioned side sections 4 and 5 are separated from each other by these plate-shaped electrodes 2b and 2c. It is being Note that it also includes a passage section 4c. As mentioned above, during operation of the cell, the gas pressure is controlled such that the pressure in the gas compartment 5 is higher than the pressure in the electrolyte compartment 4.

On the other hand, the electrolyte circulation system is generally indicated by 6 and includes an electrolyte tank 7 , a pump 8 , and a piping system 9 . The pump 8 urges the electrolyte in the direction of the arrow in the figure, whereby the electrolyte is sent into the battery body 1, and the electrolyte compartment 4 in the body 1 has a lower manifold section 4b and a lower communication passage section 4.
c. After passing through the electrolyte chamber 4a, the upper communication passage 4c, and the upper manifold part 4b in order from below to above, the electrolyte exits the main body 1, enters the electrolyte tank 7, and is pumped again.

Now, in this conventional electrolyte circulation system 6, the electrolyte tank 7
is arranged so that its liquid level 7a is located above the top of the electrolyte compartment 40 within the battery body 1. This is discharged into the space above the liquid level 7a of the electrolyte tank 7 through the porous electrodes 2b and 2e in the battery body 1, through the electrolyte compartment 4 and the gas compartment 5, which has a higher pressure. ,6aah. 1
F1.2゜Okay, one thing.8.The pressure of the electrolyte inside 44 will naturally be even slightly higher than atmospheric pressure, and the pressure within the gas section will have to be increased accordingly as mentioned above. . The pressure of fuel gas often comes from the gas supply source, so there is usually no problem in increasing the gas pressure, but in the case of oxidizing gas, especially when air is used, the pressure can be increased using a blower or compressor. In addition, it becomes necessary to increase the power supply to the battery, increasing the electric power required for the auxiliary power of the fuel cell power generation equipment, which reduces the overall efficiency of the equipment1.Also, as shown in Figure 1, The piping portion 9a that leads the electrolyte from the battery body 1 to the electrolyte tank 7 is
If the shape is not bent as much as possible, there will be problems such as air bubbles accumulating in the middle of the pipe, or air bubbles not being smoothly discharged into the electrolyte tank together with the electrolyte, so please be careful about the shape of this pipe part. Constraints impose restrictions on routes, which is often undesirable.

Therefore, it is conceivable to place the electrolyte tank 7 below the battery main body 1 and separately provide a gas-liquid separator for separating air bubbles from the electrolysis and place it above the battery main body. In addition to requiring extra equipment, there are many opportunities for the electrolyte to come into contact with the atmosphere, which is undesirable in terms of electrolyte management.

[Purpose of the invention]

The objective is to obtain an electrolyte circulation system for batteries.

[Key points of the invention]

According to the present invention, the above object is achieved by connecting the inner diameter of the pipe that leads the electrolyte from the battery body to a separation device such as an electrolyte reservoir so that gas mixed in the electrolyte in the form of bubbles is sent to the separation device together with the electrolyte. This can be easily achieved by forming the film to be sufficiently thin. At this time, the size of the inner diameter of the pipe naturally varies depending on the type of electrolytic solution and the flow rate of the electrolyte solution flowing through the pipe, but it may be selected within the range shown in the example. However, q is cc
The flow rate of the electrolyte is expressed as /lJ. By using a pipe with such an inner diameter d, even if a considerable amount of gas bubbles are mixed in the electrolyte, a part of the pipe can be
Even if the electrolyte is arranged to flow in the J direction 1,
The bubbles are smoothly transported to the separation device along with the electrolyte.

As a result, there is no problem even if the electrolyte tank as described above is used as a separation device and placed below the battery main body, and there is no need to provide an extra separation device. Note that reducing the inner diameter of the piping means that the flow rate of the electrolyte flowing through one piping [2] will naturally decrease, but as can be easily seen, if the flow rate is insufficient in one piping, It is sufficient to use a plurality of pipes having the above-mentioned inner diameters in parallel, and the present invention can be carried out without losing any of the effects obtained by the present invention.

[Embodiments of the invention]

Embodiments of the present invention will be described in detail below with reference to the drawings. FIG. 2 shows an overall system diagram of a fuel cell power generation device using an electrolyte circulation system 7 according to the present invention, in which the electrolyte reservoir 7 as a separation device is arranged below the cell main body 1 as shown in the figure. According to the present invention, the piping 10 that leads the snowmelt from the lightning melting section 4 of the battery body 1 to the snowmelt reservoir 7 has a narrow inner diameter. It is shown separated into an electrolyte compartment 4, a gas compartment 5f on the fuel gas side, and a gas compartment 5a on the oxidizing gas side, which are separated from each other by an electrode 2b on the gas side and an electrode 2C on the oxidizing gas side. ing. The fuel gas F2, for example, hydrogen, is sent from the gas cylinder 11 as its supply source to the aforementioned gas compartment 5f in the battery body 1 through the ejector device 12, and the fuel gas not consumed within the battery is sent from the gas compartment 5f. It exits downward, passes through the air-cooled heat exchanger 13, and returns to the gas compartment 5f of the battery body 1 again by the pump absorption action of the ejector device 12. In other words, the fuel gas piping system is configured as a type of circulation system9, and several times the amount of fuel gas that is consumed by the battery is passed through the battery body 1, and the reaction product water generated within the battery is is removed from the battery body 1 in the form of steam, condensed in a wide heat exchanger 13, and collected in a condensed water reservoir 15 via a condensed water pipe 14.

On the other hand, oxidizing gas, for example air A, is sucked from the atmosphere by the blower 17 via the carbon dioxide remover 16, and the collected water above a certain amount on the air side in the battery body 1 is discharged from this overflow 15a. When the amount of electrolyte in the above-mentioned electrolyte reservoir 7 located below becomes less than a predetermined value, the solenoid valve 18 in the supply water pipe 15b at the bottom is opened to replenish the electrolyte reservoir 7. Condensed water is supplied as water.

The electrolyte reservoir 7 is schematically indicated as a liquid level gauge 7b. C
A liquid level controller is attached, and when the liquid level 7a falls below a predetermined level, the above-mentioned solenoid valve 18 is opened and the condensed water reservoir 1 is
In addition to replenishing make-up water from 5 to maintain the electrolyte amount and therefore the electrolyte concentration constant, a discharge pipe 7d equipped with a valve 7c is connected to the bottom of the drain pipe 7d to drain the electrolyte and residual air. When carbon dioxide reacts within the battery body and a reaction product of the same phase is generated and precipitates at the bottom of the electrolyte reservoir 7 through the pipe 1o, the valve 7c is opened so that the product can be discharged together with the electrolyte. is taken into consideration. The electrolyte in the electrolyte reservoir 7 is energized by the pump 8 and introduced into the bottom of the electrolyte compartment 4 in the battery body 1 through the pipe 9, and the electrolyte flowing in the pipe 10 is introduced into the bottom of the electrolyte compartment 4 in the battery body 1 between the electrodes 2b and 2c. Gai11□ mixed in the liquid
1. The air bubbles in the pipe 10 are located in the rising part, the descending part, the serpentine part,
”, b'j'Hp, it is smoothly transported with the electrolyte to the electrolyte reservoir 7, and is separated from the electrolyte and released into the atmosphere the moment it exits the lower end 1 oa of the pipe 10. In the figure, the lower end 10a of the piping 10 is depicted as being located above the liquid level 7a of the electrolyte reservoir 7, but this is not particularly necessary, and the lower end 10a is positioned so as not to be too deep below the liquid level 7a. Even if it is opened by submerging it in water, there is no particular problem in separating the bubbles.

As can be seen from the above description, according to the present invention, it is not necessary to provide a special separation device for separating bubbles from the electrolyte, and it is sufficient to share the electrolyte reservoir as the separation device. However, unlike before, the electrolyte reservoir 7 is located in the battery body 1.
Since there is no problem even if the electrolyte is placed below the electrolyte section 4 of the battery body 1, the battery can be operated under conditions 1 in which the pressure of the electrolyte in the electrolyte section 4 of the battery body 1 is approximately the same as atmospheric pressure. J: The gas pressure in the gas compartments 5a and 5f only needs to be slightly higher than atmospheric pressure, so the auxiliary power required for the blower 17,
1@tii is possible. Note that the liquid level of the electrolyte reservoir 7 does not necessarily need to be completely open to the atmosphere, and if there is a concern that the electrolyte may react with carbon dioxide in the atmosphere at this liquid level,
hlt, m ゛-force +l small l 6n -1-MIN
194M, fi, force f-61 a +, □ air, × communicated semi-closedly, and a small amount of inert gas is flowed onto the liquid surface (along with the gas separated in the electrolyte reservoir 7) It may be discharged to the atmosphere through the filter.

FIG. 3 is a perspective view showing the specific structure of the unit battery 2 in the battery body 1, which was shown in a simplified manner in FIG. 2, with parts expanded. A symbol is attached. As shown in the figure, the unit cell 2 is constructed by stacking a frame 2a, an electrode 2b on the fuel gas side, an electrode 2c on the oxidizing gas side, and a separation plate 2d that separates the unit cells from each other, and the electrolyte section 4 is inside the frame 2a. Electrolyte chamber portions 4a and 2 formed in
The lower manifold section 4bl is shown as separated holes, and the upper manifold section 4bu is also shown as separated holes. A number 5 thread is formed between the electrodes 2b and 2c of the separating plate 2d to secure this division. A groove 5C is provided in the frame 2a as a communication path to the sections 5f and 5a.

FIG. 4 is a cross-sectional view showing the structure of the connection between the battery body 1 and the piping 10, and shows the upper manifold part 4b in FIG.
The corner portion where the hole 4bu is provided is cut diagonally and shown. Further, this figure shows a state in which a plurality of unit batteries are stacked, and parts common to those in FIGS. 1 and 3 are given the same reference numerals. As shown in the figure, the frame 2a and the separation plate 2d are laminated with a packing sheet 2e interposed therebetween, and the holes 4bu formed therein form a continuous upper manifold portion 4b in the laminated state.

The fasteners arranged at the ends of the laminate have holes 3a provided on the outer surface of the plate 3 in alignment with the upper manifold part described above.
A cylindrical connecting fitting 10a is connected to the packing 10 so as to communicate with the packing 10.
After this connection, the end of the piping 10 is screwed into the fitting 10a through the seal 10d in a liquid-tight manner.
0t)K is installed more liquid-tightly.

Each electrolyte chamber 4al formed between the electrode plates 2b and 2C
! - It is bent so that the vinegar solution flows upward, which is advantageous for the movement of air bubbles, but as can be seen from the above explanation, it is not necessarily necessary to bend it upward in this way. However, in order to be advantageous in removing gas bubbles from the battery body 1, the connecting part between the piping 10 and the battery body 1 is placed at the top of the electrolyte compartment 4 consisting of the electrolyte chamber 4a, the communication passage 4c, and the manifold part 4b. It is desirable to locate the As shown in FIG. 3, in this embodiment, there are two upper manifold parts 4b, so there are two pipes 10.
is connected to the battery body 1.

FIG. 5 is a graph showing the results of experiments conducted by the inventors, with the horizontal axis representing the logarithm of the flow rate q (CC/wR) and the vertical axis representing the inner diameter d (cm2) of the pipe. The hatched portion indicates the range of the inner diameter d of the pipe in which gas bubbles can move downward in the pipe together with the electrolyte in response to the flow rate of the electrolyte. The electrolyte was mainly an aqueous solution of potassium hydroxide, which is commonly used in fuel cells, and the concentration was varied within the range of 2 to 10 yen. However, regardless of the type or concentration of the electrolyte, , the illustrated relational expression holds true.

1↓As for the experimental conditions, a temperature range was selected that included the operating temperature of the fuel cell and its vinegar circulation system.

・[Effects of the Invention] As explained above, according to the present invention, in order to separate the gas mixed into the electrolyte within the battery body,
When installing the A-separator 1 device in the electrolyte circulation system, by selecting the inner diameter of the electrolyte transfer piping from the battery body to the separation device so as to satisfy a predetermined relational expression, the piping can be directed downward. Even when the electrolyte is directed to flow, gases trapped in the electrolyte in the form of air bubbles can be reliably transferred together with the electrolyte, and the separator, especially the electrolyte reservoir, can be The restriction that it must be placed on the main body side can be completely removed.

This eliminates the need to increase the pressure in the electrolyte compartment within the battery body above atmospheric pressure, making it possible to lower the gas pressure in the gas compartment, which would otherwise be located at the bottom of the entire generator set. The goal of this project is to provide the most rational and ideal design for controlling the amount and concentration of the electrolyte solution, without any unnecessary auxiliary motors.

[Brief explanation of the drawing]

Figure 1 is a system diagram schematically showing the main parts of the electrolyte circulation system of a fuel cell according to the prior art, and everything from Figure 2 onwards shows examples of the electrolyte circulation system of the fuel cell according to the present invention. Fig. 2 is an overall system diagram of a fuel cell power generation device using an electrolyte circulation system according to the present invention, Fig. 3 is an exploded perspective view of a unit cell in the battery main body, and Fig. 4 is a diagram of the battery main body and electrolyte circulation system. FIG. 5 is a cross-sectional view showing the connection with the piping, and is a graph summarizing the experimental results showing the range in which gas bubbles can freely move together with the electrolyte. In the figure, 1: fuel cell main body, 4: electrolyte compartment within the battery main body, 5: gas compartment within the battery main body, 6: electrolyte circulation system, 7
： '；2j Bubble separation position and [7 electrolyte reservoir, 1
02 Piping within the electrolyte circulation system, d: inner diameter of the piping 1. Special details person Kawa 1) Yu Division Figure 3 Figure 5

Claims (1)

[Claims] 1) The electrolytic solution held in the liquid compartment of the fuel cell main body is repeatedly circulated through an electrolytic solution circulation system outside the battery main body, and the electrolytic solution inside the battery main body is An electrolyte circulation system for a fuel cell, characterized in that the electrolyte circulation system for a fuel cell is formed to be narrow so that gas mixed or contained in the electrolyte can be guided from the electrolyte to a separator. 2. In the electrolyte circulation system according to claim 1, the separation means is configured as an electrolyte reservoir having a free liquid level, and the electrolyte is supplied through piping from the battery body within the electrolyte reservoir. A fuel cell electrolytic solution 2-active motherboard characterized in that gas in the electrolytic solution flowing into the reservoir is separated and discharged into the space above the liquid surface. 3) Claim 2. The electrolyte circulation system described above is characterized in that the space above the electrolyte surface in the electrolyte reservoir is communicated with or opened to the atmosphere, and the battery body is operated with approximately atmospheric pressure applied to the electrolyte. Fuel cell electrolyte circulation system. 4) In the electrolyte circulation system according to claim 1, the inner diameter d (cm) of the piping satisfies the formula % with respect to the flow rate q (cc/i) of the electrolyte in the piping. An electrolyte circulation system for a fuel cell characterized by being selected as follows.