JP3803248B2 - Bipolar ion exchange membrane electrolytic cell - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a bipolar ion exchange membrane electrolytic cell, and particularly to a bipolar electrolytic cell having a low electrolysis voltage and high reliability against fluctuations during operation.
[0002]
[Prior art]
Since an ion exchange membrane electrolytic cell used for electrolysis of an aqueous solution represented by electrolysis of saline solution is operated at an extremely large current density, it is a big problem to reduce the electrolysis voltage.
The electrolysis voltage is determined by a number of factors such as the structure of the electrolytic cell and the characteristics of the electrolysis electrode. In particular, the electrode spacing between the anode and the cathode decreases because the electrolysis voltage decreases as the interval decreases. The distance between the electrodes is reduced, and the operation is performed while substantially eliminating the distance between the cation exchange membrane and the electrodes that partition the anode chamber and the cathode chamber.
[0003]
In the electrolysis of saline solution, since the electrolysis voltage can be lowered by operating the cathode chamber at a pressure higher than that of the anode chamber, the cathode chamber pressure is set higher than the anode chamber pressure. The cation exchange membrane is brought into close contact with the anode by the pressure difference between the anode chamber and the cathode chamber.
In such an electrolytic cell, in order to reduce the distance between the anode and the cathode, it is necessary to bring the cathode closer to the cation exchange membrane in close contact with the anode. With a fixedly mounted cathode, it is difficult to set the electrode spacing with high accuracy over the entire electrolytic surface of a large area. Therefore, the cathode is attached to a spring-like member and the cathode is cationized by the urging force of the spring. It has been proposed to reduce the distance between the electrodes by closely contacting the exchange membrane.
[0004]
When the cathode is attached to the spring-like member, it is possible to improve the adhesion with the cation exchange membrane and reduce the electrode interval. However, an abnormality in the supply device of the electrolytic solution to the electrolytic cell, or the electrolytic cell When the pressure in the anode chamber and the pressure in the cathode chamber are reversed due to an operation error or the like, the cation exchange membrane is pressed against the cathode. Since the cathode is attached by a spring-like member, the cathode is pressed to the partition wall side, the cation exchange membrane extends greatly, adversely affects the cation exchange membrane, or the cathode is pressed to the partition wall side. There is a problem in that the shaped member deforms that cannot be recovered, and subsequent normal operation cannot be performed.
[0005]
[Problems to be solved by the invention]
The present invention provides ion exchange even when the electrode held by a spring-like member and the difference in pressure acting on both surfaces of the ion exchange membrane cannot be balanced in a bipolar filter press type ion exchange membrane electrolytic cell. An object of the present invention is to provide an electrolytic cell that does not adversely affect the membrane and the electrode.
[0006]
The problem of the present invention is that, in a bipolar ion exchange membrane electrolytic cell, both ends are fixed to the partition wall of the unit electrolytic cell in a state where the central portion of the electrolyte circulation passage forming member is deformed to the partition wall side, and in the opposite direction to the partition wall Energized, forming an electrolyte circulation passage extending in the vertical direction of the electrode chamber with the partition wall of the electrolytic cell as one surface, and an electrode is attached to the surface opposite to the partition wall of the electrolyte circulation passage forming member, The surface on the partition wall side of the electrolyte circulation passage forming member is provided with an interval holding member that is longer than the interval with the partition wall when the electrolyte circulation passage no longer recovers from deformation by pressing in the partition wall direction. The both sides of the trapezoidal portion provided with the interval holding member have mountain-like portions whose height is lower than the apex of the trapezoidal portion, and when the interval holding member contacts the partition wall, Electrode exchange membrane electrolysis with electrode in contact with electrode It can be solved by.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
In the bipolar ion exchange membrane electrolytic cell of the present invention, since the interval holding member is provided in the electrolytic solution circulation passage forming member having spring properties, the electrolytic solution circulation passage is formed with the partition wall of the electrolytic cell as one surface and the partition wall. Since the position of the electrode from the bottom is adjustable, it is possible to form the electrolyte circulation path with the minimum necessary components, and to hold the electrode and conduct the conductive connection. A bipolar ion exchange membrane electrolytic cell is provided.
[0008]
The present invention will be described below with reference to the drawings.
FIG. 1 is a diagram for explaining a bipolar ion exchange membrane electrolytic cell of the present invention, and FIG. 1 (A) is a diagram in which a part of a cathode is cut away when the unit electrolytic cell is viewed from the cathode chamber side. FIG. 1B is a perspective view of the adjacent unit electrolytic cell in FIG. 1A cut along a cross section indicated by the line AA ′.
The unit cell 1 of the present invention has a cathode chamber 2 on one surface and an anode chamber 3 on the other surface. In each electrode chamber, a dish-shaped cathode chamber partition wall 4 and an anode chamber partition wall 5 are joined together to form a conductive connection, and an electrolytic cell frame 6 serving as a structural member provided around the unit electrolytic cell 1 The surface is also covered with extensions of the cathode chamber partition wall 4 and the anode chamber partition wall 5 to form a cathode side flange surface 7 and an anode side flange surface 8.
[0009]
A spring-like catholyte circulation passage forming member 9 is attached to the cathode chamber partition wall 4 to form a catholyte circulation passage 10 having the cathode chamber partition wall as one surface. The cross section of the catholyte circulation passage forming member 9 taken along a plane perpendicular to the flow direction of the catholyte circulation passage 10 is symmetrical and joined to the cathode chamber partition 4 at both end portions 11 and 12. . Further, by bending the plate-like body to form the mountain-shaped portions 13 and 14, the plate-like body has a spring property, and the central portion 15 is always urged to the opposite side to the cathode chamber partition wall 4. Become. Further, the central portion 15 has a top portion having a plane parallel to the cathode chamber partition wall, and has a trapezoidal portion 16 protruding from the mountain-shaped portions 13 and 14 on both sides, and is parallel to the partition wall of the trapezoidal portion 16. A cathode 17 is joined to the top, and the cathode is biased to the opposite side of the partition. Further, a gap holding member 18 is attached to the cathode partition wall side of the trapezoidal portion, and the catholyte circulation path forming member 5 is held by the gap holding member 18 even when the cathode is pressed. Therefore, no unrecoverable deformation occurs.
Also, a catholyte inflow pipe 19 is provided in the cathode chamber, and the catholyte is supplied from the catholyte inlet 20 to the cathode chamber and undergoes electrolysis.
[0010]
On the other hand, in the anode chamber 3, an anolyte circulation passage 21 for circulating the anolyte is formed with the anode chamber partition wall 5 as one surface, and the anode 22 is held and electrically connected between the anode chamber partition wall 5 and the anode 22. An anolyte circulation path forming member 23 is attached. The anolyte circulation path forming member 23 has both end portions 24 and 25 joined to the anode chamber partition wall 5 and is composed of a portion 26 perpendicular to the anode chamber partition wall 5 and a portion 27 parallel to the anode chamber partition wall 5. The anode 22 is held by the ridge 28.
As a result of making the pressure in the cathode chamber higher than the pressure in the anode chamber during the operation of the electrolytic cell, the cation exchange membrane 29 disposed between the anode chamber and the cathode chamber presses the surface of the anode 22, so that an anolyte circulation passage is formed. The member 23 is preferably attached by the portion 26 perpendicular to the anode chamber partition wall 5 as described above, and it is preferable that deformation does not occur with respect to the pressure from the cathode chamber side.
[0011]
Further, as shown in FIG. 1 (B), by arranging a portion 27 parallel to the anode chamber partition wall 5 at a distance from the anode surface, an ascending passage for the electrolyte can be formed on the back surface of the electrode. Further, the anolyte circulation passage forming member 22 may be provided with at least one anode spacing member 30 therein. By providing the anode spacing member 30, deformation due to pressure applied from the cathode chamber side to the anode chamber side can be reduced.
The bipolar ion exchange membrane electrolytic cell of the present invention is formed by laminating a plurality of the unit electrolytic cells described above, and at both ends, a cathode side end electrolytic cell having only a cathode chamber and an anode side end having only an anode chamber A partial electrolytic cell can be laminated and used.
[0012]
In the present invention, nickel, a nickel alloy, or the like can be used for the cathode chamber partition. The cathode is made of nickel, a nickel alloy porous body, a net, an expanded metal, or a base thereof, and the surface is coated with an electrode catalyst material such as a platinum group metal-containing layer, a Raney nickel-containing layer, or an activated carbon-containing nickel layer. Those formed and reduced in hydrogen overvoltage can be used. Moreover, the same material as the cathode chamber partition can be used for the catholyte circulation passage forming member.
On the other hand, a thin film forming metal such as titanium, tantalum or zirconium or an alloy thereof can be used for the anode chamber partition. As the anode, an anode in which a coating of an electrocatalytic substance containing a platinum group metal or an oxide of a platinum group metal is formed on the surface of a thin film forming metal such as titanium, tantalum or zirconium or an alloy thereof can be used. .
[0013]
In the bipolar ion exchange membrane electrolytic cell of the present invention, the anolyte circulation passage forming member is preferably 50 mm to 150 mm at both ends, and an anode spacing holding member is provided at the center, The distance between both ends can be the same size, and the catholyte circulation passage forming member can be bent using a member having a thickness of 0.1 mm to 0.5 mm to produce a spring-like member. it can.
When the electrolytic cell of the present invention is used for electrolysis of an aqueous solution of an alkali metal halide, for example, electrolysis of saline, saturated saline is supplied to the anode chamber, and water or dilute sodium hydroxide is supplied to the cathode chamber. The aqueous solution is supplied, electrolyzed at a predetermined decomposition rate, and then taken out from the electrolytic cell.
[0014]
FIG. 2 is a diagram for explaining the flow of the electrolytic solution during operation of the bipolar ion exchange membrane electrolytic cell of the present invention, and is a perspective view seen from the cathode chamber and the cathode chamber side with the partition wall of the electrolytic cell unit interposed therebetween. is there.
A catholyte circulation passage 10 is formed between the catholyte partition 4 and the catholyte circulation passage forming member 9 joined to the cathode chamber partition 4 of the electrolytic cell unit. The catholyte rises in the cathode chamber due to the flow of the catholyte flowing into the cathode chamber from the catholyte inlet 20 of the catholyte inlet tube 19 and the upward flow 31 generated by the rise of bubbles generated by electrolysis. The catholyte, which has been subjected to gas-liquid separation of the catholyte and the generated gas and has an increased apparent specific gravity, descends in the catholyte circulation passage 10 as a downward flow 32. Thus, as a result of the catholyte circulating in the cathode chamber, the concentration distribution of the catholyte is reduced in the cathode chamber.
[0015]
Further, in the anode chamber 3, the anolyte circulation passage 21 is formed with the anode chamber partition 5 as one surface by the anolyte circulation path forming member 23 joined to the anode chamber partition 5. Also in the anode chamber, the anolyte rises in the anode chamber by the anolyte flow and the upward flow 33 generated by the upward flow of bubbles generated by the electrolysis, and the anolyte and the generated gas are separated in the upper part of the anode chamber, and apparent The anolyte having an increased specific gravity descends as a downward flow 34 in the anolyte circulation passage 21, and the anolyte is sufficiently circulated in the anode chamber. The concentration distribution of the catholyte is distributed in the circulation cathode chamber. Even when the operation is performed at a large current density, the electrolysis can be efficiently performed.
[0016]
FIG. 3 is a diagram for explaining the operation of the catholyte circulation passage forming member of the electrolytic cell of the present invention.
FIG. 3A is a diagram for explaining the steady operation of the electrolytic cell. The catholyte circulation passage forming member 5 is positively charged by the normal differential pressure A because the pressure in the cathode chamber is higher than the pressure in the anode chamber. The ion exchange membrane 29 is pressed against the anode 22, and the cathode 17 is further urged by the spring-like catholyte circulation path forming member 9 and is brought into close contact with the cation exchange membrane 29.
[0017]
FIG. 3B is a diagram illustrating a case where the pressure in the anode chamber is higher than the pressure in the cathode chamber.
When the pressure in the cathode chamber and the anode chamber is reversed, the cation exchange membrane 29 is pressed from the anode chamber side to the cathode 17 side by the reverse pressure difference B. However, in the bipolar ion exchange membrane electrolytic cell of the present invention, the spring-like catholyte circulation passage forming member 9 has a spacing member 18. As a result, the cathode 17 joined to the trapezoidal portion 16 of the catholyte circulation passage forming member 9 deforms the catholyte circulation passage forming member 9, but is limited by the spacing holding member 18, so that the distance between the cathode and the cathode partition wall is reduced. Will not be shorter than the length of the spacing member 18. Moreover, since the spring-like catholyte circulation passage forming member 5 has the mountain-shaped portions 13 and 14 at positions symmetrical with respect to the center, the peaks of the mountain-shaped portions 13 and 14 are pressed when pressed. Thus, the cathode chamber partition wall is equally approached to the cathode chamber partition wall 4.
Therefore, if the catholyte circulation passage forming member is designed so that the cathode is in contact with the ridges 13 and 14 when the cathode is pressed and held by the spacing member 18, the pressure due to pressing is held at three places. The cathode does not deform, the catholyte circulation passage forming member does not deform irrecoverably, and even if a pressure abnormality occurs, it can be operated without problems if it recovers to steady operation. Can do.
[0018]
【The invention's effect】
According to the bipolar ion exchange membrane electrolytic cell of the present invention, in the electrolytic cell in which the electrolytic solution circulation path is formed by the springy member to hold the electrode and conduct conductive connection, the electrolytic solution made of the springy member Since the interval holding member is provided in the circulation path forming member, the electrolyte circulation path forming member is deformed in an irrecoverable manner even when the pressure is abnormal, and the electrolytic cell is not practically destroyed, and even if a pressure abnormality occurs. A bipolar ion exchange membrane electrolytic cell capable of maintaining the operating performance can be provided.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating a bipolar ion exchange membrane electrolytic cell of the present invention.
FIG. 2 is a diagram for explaining the flow of the electrolytic solution during operation of the bipolar ion exchange membrane electrolytic cell of the present invention, as viewed from the cathode chamber and the cathode chamber with the partition wall of the electrolytic cell unit interposed therebetween. It is a perspective view.
FIG. 3 is a view for explaining the operation of the catholyte circulation passage forming member of the electrolytic cell of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Electrolytic cell unit, 2 ... Cathode chamber, 3 ... Anode chamber, 4 ... Cathode chamber partition, 5 ... Anode chamber partition, 6 ... Electrolyzer frame, 7 ... Cathode side flange surface, 8 ... Anode side flange surface, 9 ... Catholyte circulation passage forming member, 10... Electrolyte circulation passage, 11, 12... End portion, 13, 14 ... Mountain portion, 15 ... Center portion, 16 ... Trapezoid portion, 17 ... Cathode, 18. Members 19, catholyte inflow pipes 20, catholyte inflow ports 21, anolyte circulation passages 22, anodes 23, anolyte circulation passage forming members 24, 25, both ends 26, vertical parts 27 ... Parallel part, 28 ... Projection strip, 29 ... Cation exchange membrane, 30 ... Anode spacing holding member, 31 ... Upflow, 32 ... Downflow, 33 ... Upflow, 34 ... Downflow

Claims (1)

  In a bipolar ion exchange membrane electrolytic cell, both ends are fixed to the partition wall of the unit electrolytic cell with the central part of the electrolyte circulation passage forming member deformed to the partition wall side, and are energized in the direction opposite to the partition wall. An electrolyte circulation passage extending in the vertical direction of the electrode chamber is formed with one partition wall as a surface, and an electrode is attached to the surface of the electrolyte circulation passage forming member opposite to the partition wall, and the electrolyte circulation passage forming member On the surface of the partition wall, there is provided a spacing member that is longer than the spacing with the partition wall when the electrolyte circulation passage does not recover deformation by pressing in the partition direction. On both sides of the trapezoidal portion, there are mountain-shaped portions whose height is lower than the apex of the trapezoidal portion, and when the spacing member contacts the partition wall, the electrode is in contact with the spacing member and the mountain-shaped portion. Bipolar ion exchange membrane electrolysis characterized by retention .

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