JPH02826B2 - - Google Patents

Description

[Detailed description of the invention] [Technical field to which the invention pertains] The present invention relates to a so-called free battery system in which an electrolytic solution held in a liquid compartment of a battery main body is repeatedly used in circulation via an electrolytic solution circulation system of an external battery main body. Regarding the electrolyte circulation system of an electrolyte type fuel cell, in which a separation device is provided in the circulation system to separate gas mixed in or contained in the electrolyte within the battery body from the electrolyte, more specifically. Generally, air is used as the oxidizing gas,
This is suitable as an electrolyte circulation system for a fuel cell that uses an alkaline electrolyte as the 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. This is provided to separate the reaction products from the electrolyte within the system, or to temporarily lead the electrolyte, whose temperature has risen due to heat generated within the battery body, out of the battery body and cool it within the system. However, in addition to this, it is usually necessary to provide a separation device within the system to separate gases mixed or contained in the electrolyte within the battery body.

As is well known, the electrode layer that performs cell power generation in a fuel cell is configured as a so-called porous electrode layer that has gas diffusivity, and the electrode layer contains fuel gas or oxidation from the gas compartment within the cell. At the same time as the gas diffuses, the electrolyte permeates from the electrolyte compartment, forming a three-phase structure consisting of the solid-phase electrode, especially the catalyst contained therein, the gas-phase reaction gas, and the liquid-phase electrolyte. Under conditions in which the electrolyte coexists, the electrochemical reaction proceeds smoothly and power generation occurs, but the electrolyte leaks into the electrode layer excessively and drives out the gas phase.
If the above-mentioned three-phase coexistence condition is no longer maintained, the power generation action will not occur normally due to the so-called wetting phenomenon of the electrode layer.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 a plurality of unit cells 2 are stacked together to form a pair of clamping plates 3, 3.
The electrolyte compartment 4 is filled with an electrolyte and the gas compartment 5 is injected with fuel gas or oxidizing gas.
is defined. Each unit cell 2 includes a frame 2a, an electrode 2b for fuel gas, and an electrode 2c for oxidizing gas, and the aforementioned two sections 4 and 5 are separated from each other by these plate-shaped electrodes 2b and 2c. . Note that the gas introduction route to the gas compartment 5 is omitted for the sake of simplification of the diagram. The electrolyte compartment 4 includes an electrolyte chamber part 4a facing the gas compartment 5 via the aforementioned electrodes 2b and 2c, a pair of manifold parts 4b, and a communication passage part 4c communicating between the two. 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 fed into the battery body 1, and the lower manifold section 4b of the electrolyte compartment 4 in the body 1, and the lower communication passage. 4c, the electrolyte chamber 4a, the upper communication passage 4c, and the upper manifold part 4b from below to above, the flow exits the main body 1, enters the electrolyte tank 7, and returns to the pump 8. to go into. In the figure, this circulatory system path is indicated by an arrow.

In this conventional electrolyte circulation system 6, the electrolyte tank 7 is arranged such that its liquid level 7a is located above the top of the electrolyte compartment 4 in the battery body 1. This is a porous electrode 2 inside the battery body 1.
When gas enters the electrolyte chamber 4a and therefore the electrolyte compartment 4 from the gas compartment 5, which has a higher pressure than the electrolyte compartment 4, through b and 2c, the gas is transferred in the form of bubbles to the upper communication passage 4c. , upper manifold section 4
b and the liquid level 7 of the electrolyte tank 7 through the pipe 9.
This is to discharge the gas into the space above a. However, when the electrolyte tank 7 is positioned above the battery body 1 in order to discharge the gas that has entered the electrolyte section 4, the pressure of the electrolyte in the electrolyte section 4 is naturally slightly lower than atmospheric pressure. However, the pressure in the gas section will have to be increased accordingly, as described above. The pressure of fuel gas usually 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, blowers and compressors can It becomes necessary to supply the battery with increased pressure, which increases the amount of electric power required to power the auxiliary equipment of the fuel cell power generation equipment, and the overall efficiency of the equipment decreases accordingly.

In addition, as shown in FIG. 1, if the piping section 9a that leads the electrolyte from the battery body 1 to the electrolyte tank 7 is not bent as much as possible, air bubbles may accumulate in the middle of the piping, or the air bubbles may mix with the electrolyte. At the same time, there arises the problem that the electrolyte cannot be discharged smoothly into the electrolyte tank, which places restrictions on the shape and route of this piping section, resulting in a loss of freedom in designing the layout of the equipment.
Furthermore, arranging the electrolyte tank 7 above the battery main body 1 itself imposes a large restriction on the overall layout design of the equipment, 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 equipment, this increases the number of opportunities for the electrolyte to come into contact with the atmosphere, which is undesirable in terms of electrolyte management.

[Object of the Invention] The present invention solves the problems of the conventional electrolyte circulation system as described above, and provides a fuel cell that requires less auxiliary power and has no restrictions on the arrangement of devices within the electrolyte circulation system. The objective is to obtain an electrolyte circulation system.

[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 it sufficiently thinly. At this time, the size of the inner diameter of the pipe will naturally vary depending on the type of electrolyte and the flow rate of the electrolyte flowing through the pipe, but for example, if an aqueous solution of alkaline electrolyte is used as the electrolyte, The inner diameter of the pipe d is within the specified concentration range necessary for the operation of the fuel cell.
(cm) should be selected within the range of d0.36 (log q + 0.7). However, q is the flow rate of the electrolyte expressed in cc/cm ³ . By using a pipe with such an inner diameter d, even if a considerable amount of gas bubbles are mixed in the electrolyte, or even if a part of the pipe is arranged so that the electrolyte flows downward, The bubbles are smoothly transported to the separation device along with the electrolyte.

This eliminates any problem even if the electrolyte tank as described above is used as a separation device and is placed below the battery main body, and there is no need to provide an extra separation device. It goes without saying that reducing the inner diameter of the piping will reduce the flow rate of the electrolyte that can flow through one piping, but as can be easily seen, if the flow rate is insufficient in one piping, the above It is sufficient to use a plurality of pipes having such an inner diameter 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 according to the present invention, and an electrolyte reservoir 7 serving as a separation device is arranged below the cell main body 1 as shown in the figure. According to the present invention, the pipe 10 that leads the electrolyte from the electrolyte compartment 4 of the battery body 1 to the electrolyte reservoir 7 has a narrow inner diameter. In addition, among the parts of the battery body 1 and the electrolyte circulation system, the same parts as in FIG. 1 are given the same reference numerals. In FIG. 2, the gas piping system that was omitted in FIG. Therefore, the electrolyte compartment 4, the gas compartment 5f on the fuel gas side, and the gas compartment 5a on the oxidizing gas side are shown separated from each other. The fuel gas F, for example hydrogen, is
The fuel gas that is sent from the gas cylinder 11 as a supply source to the aforementioned gas compartment 5f in the battery body 1 through the ejector device 12 and not consumed within the battery exits downward from the gas compartment 5f and is heated by wind cooling. The gas passes through the 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 system, 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 dissipated. It is removed from the battery body 1 in the form of steam, condensed in a heat exchanger 13, and collected in a condensate reservoir 15 via a condensate pipe 14. On the other hand, oxidizing gas, such as air A, is removed by the carbon dioxide remover 1.
6 from the atmosphere by the blower 17 and enters the air side gas compartment 5a in the battery body 1,
Gas that is not consumed within the battery, such as nitrogen, exchanges heat with the flocculated water in the flocculated water reservoir 15, and then is released into the atmosphere. The flocculating water reservoir 15 is provided with an overflow portion 15a, and a certain amount or more of flocculating water is discharged from this overflow portion 15a, and the amount of electrolyte in the electrolyte reservoir 7 disposed below the overflow portion 15a is increased. When it becomes less than a predetermined value, the solenoid valve 18 in the make-up water pipe 15b at the bottom is opened to supply condensed water to the electrolyte reservoir 7 as make-up water.

The electrolytic solution reservoir 7 is attached with a liquid level controller schematically shown as a liquid level gauge 7b, and when the liquid level 7a falls below a predetermined level, the above-mentioned electromagnetic valve 18 is opened and the condensed water reservoir 15 is opened. In addition to replenishing make-up water from
A discharge pipe 7d equipped with a valve 7c is connected to the bottom of the discharge pipe 7d, and the electrolyte and residual carbon dioxide in the air react within the battery body to generate a solid phase reaction product, which is then passed through the pipe 10 to the electrolyte. When a precipitate is formed at the bottom of the reservoir 7, the valve 7c is opened so that the product can be discharged together with the electrolyte. The electrolyte in the electrolyte reservoir 7 is energized by the pump 8, introduced into the bottom of the electrolyte compartment 4 in the battery main body 1 via piping 9, and passed through the electrodes 2b, 2c to the gas compartments 5a, 5f.
Together with the gas bubbles that have entered from the electrolyte compartment 4, the gas bubbles are led out from the top of the electrolyte compartment 4 and passed through the pipe 10, which has a narrow inner diameter as described above, into the air-cooled heat exchanger 13 for cooling the electrolyte. The electrolyte is returned to the electrolyte reservoir 7 through the wind-cooled spiral pipe. At this time, gas bubbles mixed into the electrolyte flowing in the pipe 10 are smoothly transported to the electrolyte reservoir 7 together with the electrolyte even if the pipe 10 has an ascending section, a descending section, or a serpentine section. The moment it leaves the lower end 10a of the pipe 10, it is separated from the electrolyte and released into the atmosphere. In addition, in the figure, piping 1
Although the lower end 10a of 0 is drawn above the liquid level 7a of the electrolyte reservoir 7, it is not necessary to do so, and the lower end 10a can be submerged to the extent that it is not too deep below the liquid level 7a. Opening does not particularly impede bubble separation.

As can be seen from the above description, according to the present invention, there is no need to provide a special separation device for separating bubbles from the electrolyte, and it is sufficient to share the electrolyte reservoir as a separation device. In addition, unlike the conventional case, there is no problem even if the electrolyte reservoir 7 is placed below the battery body 1, so the pressure of the electrolyte in the electrolyte section 4 of the battery body 1 can be maintained at almost the same pressure as atmospheric pressure. The gas pressure in the gas compartments 5a and 5f only needs to be slightly higher than atmospheric pressure, and therefore the auxiliary power required for the blower 17 can be less than that of the conventional blower. Furthermore, the electrolyte reservoir 7 can be placed rather at the bottom of the overall equipment, and the concentration of the electrolyte can be easily stabilized without requiring power to replenish from the condensate reservoir 15. can. Note that the liquid level of the electrolyte reservoir 7 does not necessarily have to be 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, the upper part of the electrolyte reservoir should be closed. It is also possible to communicate semi-closedly with the atmosphere through a filter or the like, flow a small amount of inert gas on the liquid surface, and discharge it together with the gas separated in the electrolyte reservoir 7 through the filter to the atmosphere. .

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.
is an electrolyte chamber portion 4a formed inside the frame 2a;
The lower manifold section 4bl is shown as separate holes, and the upper manifold section 4bu is also shown as separate holes. Note that the communication passage portion 4c is connected to the hole 4 of the frame 2a.
Although it is formed as a hole provided inside the frame 2a connecting the electrolytic opening liquid chamber 4a and bl, 4bu, it is not shown in this figure. Note that the gas compartments 5f, 5a are formed between each electrode 2b, 2c and the separation plate 2d, and a protrusion 5b for securing this compartment is provided at a portion of the separation plate 2d corresponding to each electrode 2b, 2c. It is being Further, 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 configuration of the connecting portion between the battery body 1 and the piping 10, and is a cross-sectional view obtained by cutting diagonally at the corner where the hole 4bu serving as the upper manifold portion 4b in FIG. 3 is provided. It shows. 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, the frame 2a and the separation plate 2d are laminated with a packing sheet 2e interposed therebetween, and the holes 4bu provided therein form a continuous upper manifold portion 4b in the laminated state. A cylindrical connecting fitting 10a is connected to the outer surface of the tightening plate 3 arranged at the end of the stacked body through a packing 10c so as to communicate with the hole 3a provided in alignment with the above-mentioned upper manifold part. The pipe 10 is screwed into this connection fitting 10a in a liquid-tight manner.
The end of the cap nut 10b is inserted through the packing 10d.
It is installed in a liquid-tight manner. electrode plate 2b,
The electrolytic solution in each electrolytic solution chamber section 4a formed between 2c passes through the communication passage section 4c formed as a hollow hole in the frame 2a to the above-mentioned manifold section 4b.
and enters the piping 10 through the connecting fitting 10a. This piping 10 has an inner diameter d that satisfies the above-mentioned formula, and in the illustrated example, it is bent near the connection with the battery body 1 so that the electrolyte flows upward, which is advantageous for the movement of bubbles. As can be seen from the above description, 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, there are two upper manifold parts 4b in this embodiment, so there are two upper manifold parts 4b.
A main pipe 10 is connected to the battery body 1.

Figure 5 is a graph summarizing the results of experiments conducted by the inventors, where the horizontal axis shows the flow rate q (cc/min).
The internal diameter d (cm) of the piping is plotted on the vertical axis, and the range of the internal diameter d of the piping in which gas bubbles can move downward in the piping together with the electrolyte with respect to the flow rate of the electrolyte is shown by the hatched part. It is something that The electrolyte is mainly an aqueous solution of potassium hydroxide, which is commonly used in fuel cells, and its concentration ranges from 2 to 10.
Experiments were conducted with various changes within the specified range, and the relational expression shown holds true regardless of the type and concentration of the electrolyte. As the temperature for the experimental conditions, a temperature range including the operating temperature of the fuel cell and its electrolyte circulation system was selected.

〔Effect of the invention〕

As explained above, according to the present invention, when installing a separator in the electrolyte circulation system to separate gas mixed into the electrolyte within the battery body, the separation device from the battery body to the separator is By selecting the inner diameter of the electrolyte transfer piping to satisfy a predetermined relational expression, even when the piping is oriented to flow the electrolyte downward, it is possible to prevent air bubbles from entering the electrolyte. This makes it possible to reliably transport the gas containing the electrolyte together with the electrolyte, and completely eliminates the conventional restriction that the separation device, particularly the electrolyte reservoir, must be placed above the battery body. This eliminates the need to increase the pressure within the electrolyte compartment within the battery body above atmospheric pressure.
The gas pressure in the gas compartment can be lowered, and the power required for blowers and the like for boosting the gas pressure can be correspondingly reduced, increasing the overall efficiency of the fuel cell power plant. In addition, when using an electrolyte reservoir as a separation device, its installation position should be placed at the bottom of the entire power generation device, contrary to the conventional method, in order to control the amount and concentration of the electrolyte in the most rational manner and to eliminate excess. This can be done without using auxiliary power. Furthermore, even if you do not pay too much attention to the bending shape of the piping or the installation route, there will be no problem in eliminating air bubbles, so there will be no restrictions or unavoidable problems when designing the entire power generation equipment. The present invention makes it possible to create an ideal design.

[Brief explanation of drawings]

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;
Figure 3 is an exploded perspective view of the unit cell inside the battery body, Figure 4 is a cross-sectional view showing the connection between the battery body and the piping of the electrolyte circulation system, and Figure 5 is a diagram showing how gas bubbles are freed together with the electrolyte. It is a graph diagram summarizing experimental results showing a range in which movement can be made. 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: electrolyte reservoir as a bubble separation device, 10 : Piping in the electrolyte circulation system, d: Inner diameter of piping.

Claims (1)

[Scope of Claims] 1. The electrolytic solution held in the liquid compartment of the fuel cell main body is repeatedly circulated via an electrolytic solution circulation system outside the battery main body, and the electrolytic solution inside the battery main body is circulated within the electrolytic solution circulation system. In a device that is equipped with a separation device that separates the gas mixed or contained in the electrolyte from the electrolyte, the separation device is located below the battery main body, and the inner diameter of the pipe that leads the electrolyte from the battery main body to the separation device is 1. 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 in the liquid in the form of bubbles can be guided to a separation device together with the electrolyte. 2. In the electrolyte circulation system according to claim 1, the separation means is configured as an electrolyte reservoir having a free liquid surface, and the electrolyte flowing into the electrolyte reservoir through piping from the battery body within the electrolyte reservoir. 1. An electrolyte circulation system for a fuel cell, characterized in that gas in the liquid is separated and discharged into a space above the liquid surface. 3. In the electrolyte circulation system described in claim 2, the space above the electrolyte surface in the electrolyte reservoir is communicated with or opened to the atmosphere, and the battery body is in a state where the electrolyte is under approximately atmospheric pressure. An electrolyte circulation system of a fuel cell characterized by being operated. 4 In the electrolyte circulation system according to claim 1, the inner diameter d (cm) of the pipe is expressed by the formula d0.36 (log q+0. 7) An electrolyte circulation system for a fuel cell characterized by being selected to satisfy the following. 5. The electrolyte circulation system for a fuel cell according to claim 1, wherein a pipe is connected to the top of the liquid compartment within the battery main body.