JP2010037619A - Ion exchange membrane system electrolytic cell and method of recovering performance of cathode - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ion exchange system electrolytic cell where the renewal of a cathode is remarkably simply practicable and to provide a method of recovering the performance of the cathode. <P>SOLUTION: In the ion exchange membrane system electrolytic cell where an anodic chamber and a cathodic chamber are separated by an ion exchange membrane, the cathode chamber is provided with the cathode formed by laminating a first expand metal and a second expand metal, and the second expand metal nearer to the ion exchange membrane has a notch width, minor axis and major axis which are smaller than half of that of the first expand metal. The method of manufacturing the ion exchange membrane system electrolytic cell is provided. When the cathode is degraded during the electrolysis from the start of the electrolysis with the cathode comprising the first expand metal, the method of recovering the performance of the cathode constituting the ion exchange membrane system electrolytic cell is used by attaching the second expand metal to be in close contact with the first expand metal. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to various ion exchange membrane method electrolytic cells including ion exchange membrane method salt electrolysis, and a method for recovering the performance of a cathode that has deteriorated after being used for electrolysis for a long time.

  By using the ion exchange membrane method electrolytic cell and / or cathode performance recovery method of the present invention, the energy required for electrolysis such as salt electrolysis can be kept low, and the performance recovery of the cathode is extremely simple. Can be implemented.

  The cathode installed in the cathode chamber of an ion exchange membrane electrolytic cell (hereinafter simply referred to as “electrolytic cell”) used for salt electrolysis, water electrolysis and the like undergoes a hydrogen generation reaction during electrolysis. The cathode usually has a shape of a porous plate for smoothly desorbing the generated hydrogen gas for the purpose of reducing the electrolysis voltage, and further, a catalyst for hydrogen generation is provided on the porous plate to lower the hydrogen overvoltage. It is supported.

  When the electrolytic cell is used for a long period of time, the performance of the hydrogen generating catalyst is lowered and the hydrogen overvoltage increases with time, so that the energy required for electrolysis increases. For this reason, in order to save energy in electrolysis, it is necessary to update or reactivate the cathode at regular intervals.

  The cathode can be renewed, for example, by removing the deteriorated cathode from the electrolytic cell and attaching a newly manufactured cathode to the electrolytic cell.

  For example, the electrolytic cell described in Patent Document 1 is a so-called zero-gap electrolytic cell in which a cathode is pressed against an ion exchange membrane by an elastic repulsive force of a spring, and the cathode is held and energized. In such an electrolytic cell that holds the cathode by the elastic repulsive force of the spring, the cathode does not need to be firmly connected to the electrolytic cell, and it is very easy to attach and detach the cathode. Therefore, it is extremely easy to remove the deteriorated cathode from the electrolytic cell and attach the newly manufactured cathode to the electrolytic cell.

  However, many electrolytic cells in which the distance between the ion exchange membrane and the cathode is set to 1 to 3 mm are still used. FIG. 1 is a cross-sectional view of an electrolytic cell in which the distance between the ion exchange membrane and the cathode is set to 1 to 3 mm. The pressure inside the cathode chamber (3) is kept higher than the pressure inside the anode chamber (1), and the ion exchange membrane (2) is pressed and brought into close contact with the anode (5). On the other hand, the length of the cathode rib (6) and the thickness of the cathode side gasket (12) are adjusted so that the distance between the ion exchange membrane (2) and the cathode (7) is 1 to 3 mm.

  If there is a distribution in the distance between the ion exchange membrane (2) and the cathode (7), the electrolytic current is concentrated in a part and the electrolysis performance deteriorates, so it is important to keep the distance uniform. Therefore, the cathode (7) is firmly attached to the cathode rib (6) by welding or the like so that distortion and deformation do not occur. Therefore, since it is difficult to remove the cathode (7) from the cathode rib (6), it is difficult to apply a cathode renewal method in which a deteriorated cathode is removed from the electrolytic cell and a newly manufactured cathode is attached to the electrolytic cell.

  In order to cope with this problem, conventionally, a method for reactivating the cathode without removing the existing cathode having deteriorated performance from the electrolytic cell has been studied. For example, Patent Document 2 states that “an active electrode having an active nickel plating film containing deteriorated sulfur is dissolved in hydrochloric acid and / or sulfuric acid while the active electrode is attached to an electrolytic cell, and then sulfur is added again. There has been proposed a cathode reactivation method whose main purpose is “to apply an active nickel plating film containing”.

  The reactivation method described in Patent Document 2 is applicable to a method for renewing a cathode of an electrolytic cell because it is not necessary to remove a deteriorated cathode. However, since this method uses the cathode chamber of the electrolytic cell as a plating bath to perform active plating on the cathode, an active plating film is applied to the entire inner wall of the cathode chamber in addition to the cathode. For this reason, the amount of catalyst becomes unnecessarily large, and the renewal cost increases. Furthermore, the plating film on the inner wall of the cathode chamber is often inferior in adhesion, and the coating on the inner wall of the cathode chamber peels off during electrolysis, resulting in problems such as contamination of the electrolyte solution and damage to the ion exchange membrane. .

  Patent Document 3 states that, in an electrolysis tank in which electrolysis is performed with an anode and a cathode, another porous cathode having a lower hydrogen overvoltage than that of the cathode is provided on the surface facing the anode side of the porous cathode. An electrolysis cathode characterized in that it is mounted so that it can be easily removed or detached is proposed. The cathode for electrolysis in Patent Document 3 is a first porous cathode firmly fixed to the cathode chamber of the electrolytic cell, and is attached in a state where the second porous cathode can be removed. Since the functional cathode can be easily replaced, the performance of the cathode can be recovered by replacing the second porous cathode.

  However, on the other hand, the electrolytic cell is a complex electrolytic system in which an advanced functional membrane called an ion exchange membrane is installed, and a large amount of gas is generated from the electrode during electrolysis. There are a number of problems with providing another electrode on top of an existing electrode because of its influence. That is, it is known that when two electrodes are overlapped by providing a new electrode on an existing electrode, the flow of the electrolytic solution is hindered, the detachment of the generated gas is worsened, and the electrolytic performance is lowered. It has been.

  At present, the cathode is mainly used in which a hydrogen generation catalyst such as a nickel alloy is supported on a network called expanded metal produced by expanding the cuts regularly formed in a thin plate. . The shape of the expanded metal affects the flowability of the electrolytic solution and the gas detachability and affects the electrolytic performance.

  Expanded metal comes in various shapes depending on the thickness of the plate used for processing, the interval between cuts, and the pulling distance. As shown in FIG. 3, the shape is a short diameter (8) which is the distance between the centers of the meshes in the short direction, a long diameter (9) which is also the distance between the centers of the meshes in the long direction, and a notch formed on the plate. It can be defined by the step width (10) which is the interval and the plate thickness (not shown) of the expanded plate. As the expanded metal used for the electrode, one that has been flattened in advance by rolling or the like is usually used.

  It is known that the finer the expanded metal, the better the liquid flowability and gas detachability, and the shorter diameter (8), the longer diameter (9), the step width (10), and the plate thickness are smaller. It can be said that the liquid flowability and gas detachability are excellent. However, the smaller the step width (10) and the plate thickness, the higher the electric resistance and the lower the mechanical strength. The shape of the expanded metal used for the electrode is usually determined by the above balance.

  On the other hand, in the cathode in which the second porous cathode is removably attached to the first porous cathode proposed by Patent Document 3, the electrical resistance is reduced and the mechanical strength is maintained. It is easily conceived that the flowability of liquid and gas detachability can be compatible with electrical resistance and mechanical strength by making the second porous cathode a fine mesh. The However, an example of a preferable state described in the example of Patent Document 3 is that the minor diameter (8), the major diameter (9), and the step width (10) of the second porous cathode are the same as those of the first porous cathode. The same as the minor axis (8), major axis (9), and step width (10) of the cathode, the thickness of the second porous cathode is 1 mm, and the thickness of the first porous cathode is 1.5 mm. Two minutes.

  However, the shape of the expanded metal is not the same on the entire surface, and there is an error. Therefore, when the expanded metal having the same short diameter (8), long diameter (9), and step width (10) is overlapped, the hole portion (14) of one expanded metal and the expanded metal of the other expanded metal at the experimental level size. Even if the hole (14) can be overlapped and overlapped, on an industrial scale, the hole (14) of one expanded metal and the hole (14) of the other expanded metal are shifted from the same position. A place arises. In that case, it is known that extreme non-uniformity occurs in the flowability of the liquid and the detachability of the gas, and the electrolytic performance deteriorates.

  Patent Document 4 proposes an anode renewal method in which a new anode is superimposed on an existing anode. The gist of Patent Document 4 is, as described in the claims, “When the activity of an insoluble electrode coated with an electrode catalyst is reduced, a new electrode is welded to an existing electrode and reactivated. The new electrode is obtained by flattening the expanded metal by rolling, etc. The short diameter of the expanded metal mesh of the new electrode is smaller than the short diameter of the existing electrode mesh, and the existing electrode mesh step width is two times. It is a method for activating an electrode for electrolysis characterized by being larger than twice.

  In Patent Document 4, page 10, upper right column, line 10 to page 3, lower left column, line 8 “To reactivate without increasing the cell voltage, the new electrode mesh must be finer than the existing electrode mesh. On the other hand, if it is excessively fine, the opening of the new electrode mesh is blocked by the existing electrode mesh due to the overlap with the existing electrode mesh. However, it has been found that if the minor axis of the new electrode mesh is not more than twice the step size of the existing electrode mesh, there will be a part of the gas clogging part. As a result, the electrolyte is not sufficiently supplied to the exchange membrane, and as a result, chlorine and sodium hydroxide are diffused inside the ion exchange membrane facing the gas clogging portion due to long-term electrolysis, and salt is precipitated inside. As a result, the minor axis of the new electrode mesh must be smaller than the minor axis of the existing electrode mesh and greater than twice the step size of the existing electrode mesh. As described in "Patent Document 4", Patent Document 4 discloses that the expanded metal hole portion (14) in direct contact with the anode is blocked by the existing expanded metal mesh portion (13). It can be said that this is a novel anode renewal method that solves the problem of deterioration due to insufficient supply of electrolyte to the ion exchange membrane.

  On the other hand, in Patent Document 4, the second line from the lower left column on page 3 to the fourth line from the upper right column on page 3 “In the above description, the anode has been described. The activation method is the same as that of the cathode. ” However, it is well known in the art that the electrolytic cell has an anode chamber and a cathode chamber separated by an ion exchange membrane, so that the anode and the cathode are in completely different situations.

  For example, in ion exchange membrane salt electrolysis, chlorine gas is generated from the anode in the anode chamber, and the anode chamber is filled with a saline solution saturated with chlorine gas, while hydrogen gas is generated from the cathode in the cathode chamber. However, it is in a state filled with a sodium hydroxide aqueous solution saturated with hydrogen gas. It is a well-known fact in this technical field that chlorine gas in salt water and the state of hydrogen gas (bubble size, bubble rate) in sodium hydroxide aqueous solution are completely different, and the viscosity and specific gravity of salt water and sodium hydroxide aqueous solution are known. Therefore, the flowability of the electrolyte and the gas separation are completely different.

  Furthermore, as described in the Examples of Patent Document 4, in the ion exchange membrane method salt electrolysis, generally, the pressure in the cathode chamber is kept higher than the pressure in the anode chamber, and the ion exchange membrane is pressed against the anode. Put in condition. Therefore, the anode and the ion exchange membrane are in close contact with each other, and the shape of the contact portion between the anode and the ion exchange membrane, for example, the pores are blocked / not blocked, the liquid to the ion exchange membrane is It is thought that the supply state is different and the presence or absence of deterioration is greatly different. On the other hand, as described above, the cathode is separated from the ion exchange membrane by 1 mm to 3 mm, and it is very easily conceived that the relationship between the cathode shape and the supply state of the liquid to the ion exchange membrane is poor.

  In other words, the characteristics required for the anode and the characteristics required for the cathode are completely different, and applying the proposal made for the anode to the cathode can be applied even to those skilled in the art. ,It's not easy.

  As described above, there has been a demand for an electrolytic cell in which the cathode can be easily updated, and there has been a demand for a cathode renewal method in which the cathode can be easily updated even in a type of electrolytic cell in which it is difficult to update the cathode.

JP 2004-2993 A (Claim 1, paragraph number 0017, paragraph number 0018) Japanese Patent Laid-Open No. 1-168885 (Claims) Japanese Utility Model Publication No. 58-24932 (claim of utility model registration, second page (3) column 16th line to second page (3) column 19th line, FIG. 3) JP-A-4-32594 (Claims, page 3, upper right column, line 10 to page 3, lower left column, line 8)

  Provided are an ion exchange membrane electrolytic cell in which renewal of a cathode can be carried out very easily and a method for recovering the performance of the cathode.

  As a result of intensive studies on the cathode performance recovery method, the present inventors have completed an ion exchange membrane electrolytic cell capable of performing the cathode performance recovery very simply.

  That is, the present invention relates to an ion exchange membrane electrolytic cell partitioned into an anode chamber and a cathode chamber by an ion exchange membrane, wherein the cathode chamber is a cathode in which a first expanded metal and a second expanded metal are laminated. And the step width, minor axis and major axis of the second expanded metal adjacent to the ion exchange membrane are less than half of the step width, minor axis and major axis of the other first expanded metal. It is a membrane method electrolytic cell.

  Moreover, this invention is said ion exchange membrane method electrolytic cell whose distance of the cathode side surface of an ion exchange membrane and the ion exchange membrane side surface of a cathode is 1 mm-3 mm.

  Moreover, this invention is a manufacturing method of said ion exchange membrane method electrolytic cell which attaches a 2nd expanded metal closely_contact | adhered to said 1st expanded metal, after attaching a 1st expanded metal to a cathode chamber.

  Also, the present invention starts electrolysis with a cathode made of the first expanded metal, and when the cathode deteriorates during electrolysis, the second expanded metal is attached in close contact with the first expanded metal, This is a method for recovering the performance of the cathode, which constitutes the above ion exchange membrane electrolytic cell.

  Hereinafter, the present invention will be described in detail.

  In the electrolytic cell of the present invention, the structure of a conventional electrolytic cell can be appropriately applied except for the cathode. It is also possible to apply the present invention to a so-called zero gap electrolytic cell in which the cathode is supported by an elastic current collector such as a spring and the cathode is in close contact with the cation exchange membrane. However, since the zero gap electrolytic cell is originally easy to renew the cathode, the effect of the present invention cannot be fully enjoyed.

  That is, the present invention is particularly effective in an electrolytic cell in which the cathode is firmly welded to a rib or the like and the distance between the ion exchange membrane and the cathode is 1 mm or more, but FIG. 1 illustrates a cross-sectional view of the electrolytic cell. . The electrolytic cell is divided into an anode chamber (1) and a cathode chamber (3) by an ion exchange membrane (2), and an anode (5) is attached to the anode chamber (1) by an anode rib (4). A cathode (7) is fixed to the cathode rib (6) in the chamber (3).

  Generally, the pressure inside the cathode chamber (3) is set higher than the pressure inside the anode chamber (1), and the ion exchange membrane (2) is pressed against the anode (5). The anode surface and the cathode surface are both substantially flat, and the anode surface and the cathode surface are substantially parallel to each other. Further, the length of the rib and the thickness of the cathode side gasket (12) are adjusted so that the cathode (7) is placed at a certain distance from the ion exchange membrane (2). When the distance between the cathode (7) and the ion exchange membrane (2) is too large, the voltage becomes high. When the distance is too close, the cathode (7) is partially pressed excessively against the ion exchange membrane (2), and the ion The exchange membrane is damaged. The distance between the cathode (7) and the ion exchange membrane (2) is usually 1 mm to 3 mm, preferably 1 mm to 2 mm.

  As the anode (5) of the electrolytic cell, an expanded metal that has been flattened by rolling or the like is usually used. The expanded metal is usually titanium, and an electrode catalyst is supported on the surface of titanium. The type of the electrode catalyst of the anode (5) and the shape of the expanded metal may be appropriately selected from known techniques and are not limited.

  FIG. 2 is an enlarged view of part a in FIG. In the electrolytic cell of the present invention, it is essential that the cathode (7) is formed by laminating two expanded metals (7a and 7b). Hereinafter, the other side of the second expanded metal (7b) away from the ion exchange membrane is referred to as a first expanded metal (7a), and the side close to the ion exchange membrane is referred to as a second expanded metal (7b).

  It is essential that any expanded metal (7a, 7b) constituting the cathode (7) is made of a material having high conductivity and having corrosion resistance in the electrolytic solution. For example, nickel or a nickel alloy can be preferably used. If the conductivity is poor, the voltage loss due to electrical resistance is high, and thus the effects of the present invention may not be enjoyed. In addition, using a material that is highly conductive but easily corroded, such as iron or copper, will corrode during operation or operation interruption, contaminating the product, contaminating the electrode catalyst, increasing the voltage, etc. The effect of the present invention may not be obtained.

  Next, the shape of the expanded metal (7a, 7b) constituting the cathode (7) will be described in detail with reference to FIG. It is necessary to use the expanded metal (7a, 7b) that has been flattened by rolling or the like. Without flattening, the expanded metal mesh part (13) is raised, so that the detachment property of hydrogen gas generated during electrolysis deteriorates and the voltage rises. The expanded metal (7a, 7b) Problems such as difficulty in stacking occur.

  Expanded metal is obtained by enlarging the cuts provided in the thin plate by engraving the regular cuts on the thin plate and pulling them. The expanded metal has various shapes depending on the thickness of the plate used for processing, the interval between the cuts, and the pulling distance. As shown in FIG. 3, the shape of the mesh is a short diameter (8) that is the distance between the centers in the short direction of the mesh, a long diameter (9) that is also the distance between the centers in the long direction of the mesh, and a cut provided in the plate. Can be defined by a step width (10), which is a step interval, and a plate thickness (not shown) of the expanded plate.

  The shape of the first expanded metal (7a) is not particularly limited, and a conventional shape is preferably applicable. For example, the plate thickness is 1 mm to 2 mm, the major axis is 8 mm to 16 mm, the minor axis is 4 mm to 8 mm, and the step width is 1 mm to 2 mm. Although the electrode catalyst may be supported on the first expanded metal (7a), since the electrode reaction is performed on the second expanded metal (7b), it is not necessary to support the electrode catalyst on the first expanded metal (7a). is there. However, when the electrode catalyst supported is used as the first expanded metal (7a), it is not necessary to forcibly remove the electrode catalyst. In any case, in the cathode (7) in the electrolytic cell of the present invention, the first expanded metal (7a) plays a role of securing the strength of the cathode (7) and lowering the electric resistance. If any of the plate thickness, the long diameter, the short diameter, or the step width is too small, the electric resistance becomes high, or the strength is poor, and the cathode has problems such as distortion and breakage, or both.

  The minor diameter (8), major diameter (9), and step width (10) of the second expanded metal (7b) are the minor diameter (8) and major diameter (9) of the first expanded metal (7a), respectively. And less than half of each step width (10). Any of the short diameter (8), the long diameter (9), and the step width (10) of the second expanded metal (7b) is the short diameter (8), long diameter (9) of the second expanded metal (7b). ) And more than half of each step width (10), the electrolysis voltage becomes high, and the effect of the present invention cannot be obtained.

  Moreover, when the plate | board thickness of a 2nd expanded metal (7b) is smaller than half the plate | board thickness of a 1st expanded metal (7a), an electrolysis voltage becomes lower and it is preferable.

  The step width (10), minor diameter (8), major diameter (9) and minimum thickness of the second expanded metal (7b) are not particularly limited, but when the electrode catalyst is supported as shown below. In view of the handling property, the step width: 0.1 mm or more, the short diameter: 0.5 mm or more, the long diameter: 1 mm or more, and the plate thickness: 0.1 mm or more are suitable.

  It is essential for the second expanded metal (7b) to carry an electrode catalyst. When no electrode catalyst is supported, the electrolysis voltage is high and the effects of the present invention cannot be obtained. There are no particular limitations on the type of electrode catalyst to be supported and the supporting method, but if the supported hydrogen generating catalyst is too thick, the opening of the second expanded metal becomes small and the electrolysis voltage becomes high. Usually, the thickness of the catalyst coating is 50 μm or less, preferably 10 μm or less. In order to keep the overvoltage low even if the catalyst coating is thin, a noble metal catalyst such as platinum or ruthenium may be used.

  The cathode (7) described above is attached to the electrolytic cell. Although the attachment method is not particularly limited, it is usually performed by the following procedure and method.

  First, the first expanded metal (7a) is attached to the cathode chamber (3) of the electrolytic cell. As described above, since the first expanded metal (7a) needs to secure strength, the first expanded metal (7a) is firmly attached to the rib (6) of the cathode chamber by welding or the like. As a mounting method, a conventional method such as spot welding may be applied as appropriate.

  Further, the planar accuracy of the cathode (7) affects the electrolysis performance. That is, when the planar accuracy of the cathode (7) is poor, a distribution occurs in the distance between the anode (5) and the cathode (7), and the electrolysis current is concentrated in a portion close to the distance, thereby increasing the voltage and decreasing the current efficiency. Invite. In order to ensure the planar accuracy of the cathode (7) with the first expanded metal (7a), the planar accuracy is corrected as necessary when the first expanded metal (7a) is attached to the rib (6). Do. The plane accuracy is usually a reference plane +0.5 to −0.5 mm, preferably +0.2 to −0.2 mm.

  Next, the second expanded metal (7b) is attached to the first expanded metal (7a). The method is not particularly limited, but is preferably attached by welding in order to lower the electric resistance, and spot welding is particularly preferable. The second expanded metal (7b) does not need to have high welding strength, and may be attached under mild welding conditions. In order to ensure the planar accuracy of the cathode (7) by uniformly adhering the second expanded metal (7b) to the first expanded metal (7a), the first expanded metal (7a) and the second expanded metal are secured. It is important that the metal (7b) is in close contact with the second expanded metal so that there is no part of the second expanded metal that is partially lifted from the first expanded metal.

  In addition, in the state which attached the 2nd expanded metal (7b) to the 1st expanded metal (7a), it is difficult to carry | support the catalyst for hydrogen generation, and before attachment to the 1st expanded metal (7a) In addition, a desired hydrogen generation catalyst is supported on the second expanded metal (7b). As a supporting method, a conventional catalyst supporting method such as a coating pyrolysis method or an electroplating method may be appropriately applied.

As described above, salt electrolysis and water electrolysis are performed using the electrolytic cell described above, and the conditions may be appropriately selected from conventionally known methods and are not limited at all. In the case of salt electrolysis, the current density is usually 1 to 6 kA / m ² , the temperature is 80 to 90 ° C., the concentration of the brine at the outlet of the anode chamber is 190 to 230 g / l, and the concentration of the sodium hydroxide aqueous solution at the outlet of the cathode chamber is 30 to 30 °. Performed at 35 wt%.

  By using the electrolytic cell of the present invention, there is no significant difference during the normal operation as compared with the prior art. However, the replacement of a deteriorated cathode is very simple compared to a conventional electrolytic cell. That is, it is only necessary to replace the second expanded metal (7b) for renewal of the cathode, and it is not necessary to remove and replace the first expanded metal (7a) that is firmly attached to the electrolytic cell and maintains the strength. Therefore, the cathode renewal work is very simple and there is no fear of damaging the electrolytic cell during the work.

  As described above, the conventional method of laminating two expanded metals to form a cathode has been proposed in, for example, Patent Document 2, but the electrolytic voltage is higher than that of a single expanded metal cathode. There was a problem. On the other hand, although the electrolytic cell provided by the present invention is not necessarily clear as to why a low voltage can be maintained, the inventors presume as follows.

  FIG. 4 is a partially enlarged plan view of the cathode of the present invention viewed from the second expanded metal surface side. The hole (14) of the first expanded metal (7a) is partially blocked by the mesh portion (13) of the second expanded metal (7b).

  As described above, Patent Document 4 proposes an anode in which the short diameter of the expanded metal mesh of the new electrode is smaller than the short diameter of the existing electrode mesh and larger than twice the step size of the existing electrode mesh. Yes. The main purpose of this is to eliminate a portion where the hole portion of the expanded metal in contact with the ion exchange membrane is completely blocked by the mesh portion of the other expanded metal.

  This is because the pressure in the cathode chamber is higher than the pressure in the anode chamber for electrolysis, so that the ion exchange membrane is pressed against the anode and is in contact with the ion exchange membrane (referred to as “new electrode” in Patent Document 4). This is probably because the presence or absence of the portion of the expanded metal of “) that is completely blocked by the other expanded metal greatly affects the electrolysis performance.

  On the other hand, in the cathode of the present invention, the hole of the second expanded metal (corresponding to “expanded metal of new electrode” referred to in Patent Document 4) on the side closer to the ion exchange membrane has the first expanded metal (Patent Document). 4) (corresponding to “existing electrode mesh”), there is a portion completely covered. However, the cathode of the present invention is not pressed against the ion exchange membrane, but the distance between the ion exchange membrane and the cathode (more precisely, the distance between the cathode side surface of the ion exchange membrane and the ion exchange membrane side surface of the cathode) Is set to 1 to 3 mm, so that even if the hole of the second expanded metal is blocked by the mesh portion of the first expanded metal, it has an influence on the supply state of the electrolyte to the membrane and the gas detachability. It is estimated that it is small.

  On the contrary, the cathode of the present invention, each of the short diameter, the long diameter, the step width, and the plate thickness of the second expanded metal are the short diameter, the long diameter, the step width of the first expanded metal cathode, And, since it is smaller than half of each plate thickness, the electrolytic performance improvement effect due to the uniform reaction on the cathode is the electrolysis in which the hole of the second expanded metal is blocked by the mesh portion of the first expanded metal. It is estimated that a low voltage can be enjoyed by using the cathode of the present invention as a result of compensating for the adverse effect on the performance.

  The ion exchange membrane method electrolytic cell of the present invention described in detail above can be applied to cathode renewal of an electrolytic cell that has been used for a long time and has a deteriorated cathode. That is, the cathode performance can be recovered by attaching the second expanded metal (7b) carrying the hydrogen generating catalyst as the first expanded metal (7a), which has been deteriorated after being used for a long time. It is clear that an ion exchange membrane electrolytic cell having a cathode modified in this way is one of the preferred embodiments of the present invention.

  By using the ion exchange membrane method electrolytic cell of the present invention, the performance of a deteriorated cathode can be recovered very simply. Further, by using the cathode performance recovery method of the present invention, the performance recovery of the cathode of the conventional ion exchange membrane electrolytic cell can be performed very simply.

  EXAMPLES Hereinafter, although this invention is demonstrated in detail using an Example, an Example does not limit this invention. In addition, all the expanded metal used what performed the flattening process by roll application.

Example 1
As the first expanded metal (7a), an expanded metal made of Ni having a plate thickness of 1.5 mm, a major axis: 13 mm, a minor axis: 6 mm, and a step width: 1.5 mm is longitudinally 7.5 cm and laterally 4. Cut to 0 cm. At this time, the short diameter direction of the expanded metal was set to be vertical, and the long diameter direction was set to be horizontal.

  The first expanded metal (7a) is firmly attached to the rib (6) of the cathode chamber of a small electrolytic cell having an effective electrolysis area of 30 cm 2 (length: 7.5 cm, width: 4.0 cm) by welding, One expanded metal (7a) was adjusted to be substantially flat.

  Next, as the second expanded metal (7b), an expanded metal made of Ni having a thickness of 0.5 mm, a major axis: 4 mm, a minor axis: 2 mm, and a step width: 0.5 mm, length: 7.5 cm, width: Cut to 4.0 cm. At this time, the short diameter direction of the expanded metal was set to be vertical, and the long diameter direction was set to be horizontal.

  The second expanded metal (7b) was etched with a 10 wt% hydrochloric acid solution at a temperature of 50 ° C. for 15 minutes, then washed with water and dried.

  Subsequently, a platinum content of the dinitrodiammine platinum nitrate solution (manufactured by Tanaka Kikinzoku, platinum concentration: 4.5% by weight, solvent: 8% by weight nitric acid solution), nickel nitrate hexahydrate and water in a molar ratio of 0. 5. A coating solution in which the total concentration of platinum and nickel in the mixed solution was 5 wt% in terms of metal was prepared.

  Next, this coating solution was applied to the entire surface of the second expanded metal using a brush, dried in a hot air dryer at 80 ° C. for 15 minutes, and then a box-type muffle furnace (Advantech Toyo model KM-600, internal volume 27 L). Was pyrolyzed at 500 ° C. for 15 minutes under air flow. This series of operations was repeated 5 times.

  Said 2nd expanded metal (7b) was attached to the 1st expanded metal (7a) by spot welding, and it was set as the cathode (7) of the ion exchange membrane membrane method electrolytic cell.

  Using the DSE (registered trademark) manufactured by Permerek Electrode Co., Ltd. and the Aciplex (registered trademark) manufactured by Asahi Kasei Chemicals Co., Ltd. in combination with the cathode chamber to which the cathode (7) is attached, Assembled. At this time, the gasket thickness was adjusted, and four types of electrolytic cells in which the distance between the ion exchange membrane and the cathode (7) was 0.5 mm, 1.0 mm, 1.5 mm, and 2.0 mm were assembled.

Using the above four types of electrolytic cells, the pressure in the cathode chamber was set higher by 5 kPa than the pressure in the anode chamber, the ion exchange membrane was brought into close contact with the anode surface, the current density was 6 kA / m ² , and the anode chamber outlet brine concentration: 200 A salt electrolysis test was conducted at ˜210 g / l, a sodium hydroxide aqueous solution concentration at the cathode chamber outlet: 31-33 wt%, and a temperature: 90 ° C., and an electrolysis voltage was measured. The electrolytic voltage was measured and recorded at intervals of 1 second over 5 minutes, and the averaged values are shown in Table 1.

  When the distance between the ion exchange membrane and the cathode was 1 to 2 mm, the electrolytic voltage was almost proportional to the distance between the electrodes, the proportionality constant was about 0.04 V / mm, and the voltage was stable.

  The electrolysis voltage when the distance between the ion exchange membrane and the cathode is 0.5 mm is higher than the electrolysis voltage when the distance between the ion exchange membrane and the cathode is 1 mm, and the instantaneous value of the voltage is 3.09. Vibrated in the range of ~ 3.13V.

Example 2
Length: 7.5 cm and width: 4.0 cm were cut out from a cathode which had been deteriorated by operating for 10 years in an actual electrolytic cell (electrolytic area of 3.3 m ² ). In this cathode, a Ni-Fe-C hydrogen generation catalyst was supported by electroplating on a Ni expanded metal having a plate thickness of 1.5 mm, a major axis: 13 mm, a minor axis: 6 mm, and a step width of 1.7 mm. Is.

  The cut out cathode was immersed in 10 wt% hydrochloric acid at 40 ° C. for 30 minutes to dissolve and remove the hydrogen generating catalyst, and used as the first expanded electrode.

  Other than that, the small electrolytic cell was assembled similarly to Example 1, and the salt electrolysis test was implemented.

  The electrolysis voltage was the same as in Example 1 as shown in Table 1.

Comparative Example 1
Salt electrolysis test in the same manner as in Example 1 except that the second expanded metal (7b) was a Ni expanded metal having a plate thickness of 0.8 mm, a major axis: 8 mm, a minor axis: 4 mm, and a step width of 1 mm. The electrolytic voltage was measured. The results are shown in Table 1. In the cathode of the comparative example, the short diameter of the second expanded metal: 4 mm is larger than twice the step width of the first expanded metal: 1.5 mm.

  The cathode used in the comparative example has a short diameter of the second expanded metal of 4 mm and is larger than half of the short diameter of the first expanded metal: 6 mm. Therefore, the electrolysis voltage is compared with Examples 1 and 2 of the present invention. Is high.

  Even when the distance between the ion exchange membrane and the cathode was changed, the average value of the electrolysis voltage was almost the same. When the distance between the ion exchange membrane and the cathode was 0.5 and 1.0 mm, the instantaneous voltage value oscillated in the range of 3.13 to 3.17V and 3.13 to 3.16V, respectively. When the distance between the electrodes was 1.5 mm or more, voltage oscillation disappeared and was stable.

It is sectional drawing explaining an ion exchange membrane method electrolytic cell. It is an enlarged view of the a part of FIG. 1, and is a figure explaining a cathode. It is a figure explaining an expanded metal. It is a figure explaining the cathode of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Anode chamber 2 Ion exchange membrane 3 Cathode chamber 4 Anode rib 5 Anode 6 Cathode rib 7 Cathode 8 Short diameter 9 Long diameter 10 Step width 11 Anode side gasket 12 Cathode side gasket 13 Expanded metal mesh part 14 Expanded metal hole part

Claims (4)

In an ion exchange membrane method electrolytic cell partitioned into an anode chamber and a cathode chamber by an ion exchange membrane, the cathode chamber includes a cathode in which a first expanded metal and a second expanded metal are laminated, and An ion exchange membrane method electrolytic cell in which the step width, minor axis and major axis of the second expanded metal adjacent to the ion exchange membrane are smaller than half of the step width, minor axis and major axis of the other first expanded metal. The ion exchange membrane method electrolytic cell according to claim 1, wherein the distance between the cathode side surface of the ion exchange membrane and the ion exchange membrane side surface of the cathode is 1 mm to 3 mm. The method for producing an ion exchange membrane electrolytic cell according to claim 1 or 2, wherein after the first expanded metal is attached to the cathode chamber, the second expanded metal is attached in close contact with the first expanded metal. Electrolysis is started with a cathode made of the first expanded metal, and when the cathode deteriorates during electrolysis, the second expanded metal is attached in close contact with the first expanded metal, or the claim 1 or claim Item 3. A method for recovering the performance of a cathode, which constitutes the ion exchange membrane method electrolytic cell according to Item 2.

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