KR890002055B1 - Seal for electrolytic cells - Google Patents

Abstract

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Description

Electrolyzer Assembly and Sealing Method

The present invention relates to an electrolytic cell seal and a method for sealing an electrolytic cell.

Cells used to produce alkali metal hydroxides and chlorine by electrolysis using separators and in particular by electrolysis with aqueous solutions of alkali metal chlorides are generally of two types, diaphragm and membrane. have.

In general, permeable membrane cells are sold by Asahi Glass Co., Ltd. under the trademark Flemion, and the trademark Napaon. children. Sheet-like permeable membranes of ion exchange materials such as those sold by Dupond Nemoa Company are used.

Such cells are usually flat plates or filter presses having a monopolar or bipolar structure.

US Pat. Nos. 4,108,742 and 4,4111,779 to Seko and other co-inventors are examples of bipolar system electrolysers.

Examples of other designs are described by Kenny in US Pat. No. 4,137,144 and in the patent citations cited therein.

In a filter press permeable membrane cell, a sheet-like permeable membrane is usually fixed or otherwise compressed between the axes of the frame members.

In addition, a gasket is inserted between one of the frame members and the permeable membrane surface to prevent leakage of the fluid from one cell compartment to another cell compartment or environment by preventing the fluid from leaking by the compression of the frame and the gasket. This is a common embodiment.

This compression is usually done manually or mechanically using a hydraulic pump or other type of pressurizing device to compress the electrode frame and the separating gasket together.

However, it is possible to obtain a membrane which does not damage the permeable membrane and does not leak the fluid as desired.

The gasket material commonly used between the permeable membrane of the electrolyzer and the electrode frame member is made of an elastic material such as rubber or elastomer.

Commercial bipolar permeable membrane electrolyzers generally use ethylene-propylene (EP) or ethylene-propylene-diene (EPD) as the gasket material between the permeable membrane and the electrode frame.

However, the material tends to expand outward when pressure is applied to the frame through the frame member.

As the gasket deforms outward, any separator in contact with the gasket tends to stretch when tensioned under the pressure of the outwardly deforming gasket.

Stretching of separators or permeable membranes underneath gaskets used on adjacent electrode frames can cause the permeable membrane to break or tear when pressure is applied to the frame to make the cells leak-free.

Any tearing or breaking of the permeable membrane can reduce the current efficiency during operation and greatly increase the current usage while decreasing the operating efficiency of the electrolyte in the cell.

If the current efficiency and the operating efficiency of the electrolyte drop too much, it may inefficiently require the operation of the whole cell when replacing a damaged permeable membrane.

Finishing gaskets, flat sheets or O-ring EPD gaskets are usually manufactured and installed in the cell to minimize damage to the permeable membrane.

However, these elastic gaskets always recover in size and shape after the pressure applied to them is released.

Thus, the elastic gasket cannot be precompressed and the permeable membrane must be installed with the gasket between the cell frames before the pressing side.

This increases the likelihood of damage when the permeable membrane is compressed with the elastic gasket.

In view of the above-mentioned problems, it is desirable to provide a method of sealing a cell with such a seal without damaging the electrolytic cell seal and the permeable membrane of the cell.

The present invention is an electrolyzer assembly comprising a first frame, a second frame, a separator sandwiched between a frame separating the cathode and the anode and a precompressed seal sandwiched at least between the first or second frame and the separator.

The seal may be a gasket made of fluorocarbon polymer material.

The invention also relates to a method of sandwiching a seal between at least a first frame or a second frame and the separator (the separator separates the anode and the cathode in a region defined by the first and second frames), the seal, the separator In the electrolytic cell sealing method comprising a method of applying pressure to the first and second frames, the present invention is characterized by using a seal that is precompressed and deformed forever as a seal.

The present invention relates to a method of sandwiching a single sheet member between a first frame and a second frame, a method of sandwiching a seal made of a material that can be deformed forever between at least the first or second frame and the member, and 2 Frames, sheet members and methods of applying pressure to the seals to deform the seals forever, methods of releasing pressure to remove the seat members, replacing the separators with sheet members and leaking of liquids and gases. It relates to the method of applying pressure to the first and second frames, the precompressed seals and the separators to make the seals insensitive.

1 is a cross-sectional view of an electrolyzer assembly showing a precompressed gasket seal sandwiched between an electrode frame and a separator.

2 is another embodiment of the present invention, which is a cross-sectional view of an electrolyzer assembly showing a precompressed gasket seal sandwiched between an electrode comprising a groove and a separator.

Referring to FIG. 1, there is shown a filter pressure electrolyzer assembly having a pair of adjacent filter pressure frames 11 and 12.

In this case, the first frame 11 in the figure is an anode frame and the second frame 12 is a cathode frame.

In a typical case, the anode frame and the cathode frame are one structure.

Here the anode and cathode are attached to opposite sides of each other or to both sides of the structure and are electrically connected through the structure.

This battery assembly is a representative form of a filter pressure type electrolyzer, which is monopolar or bipolar.

Here, the invention regarding the filter press type electrolytic cell is described with reference to a single electrode type.

The separator 13 and the previously crimped seal 14 are sandwiched between the anode and the cathode frame.

The precompressed seal 14 is sandwiched between the separator and one of the frames 11 or 12.

Moreover, although only one precompressed seal 14 is shown, the present invention uses two precompressed seals on both sides of the separator 13.

Precompressed seal means a seal deformed by pressing force or pressure and the seal remains substantially pressurized or deformed forever before its final use.

The term "permanently deformed seal" means that the seal is pressurized to the desired thickness and substantially changes until its final use, ie, between the battery frames 11 and 12 or until further pressurized. That means without pressure at the desired thickness.

The 'pre-compression' feature for the seals of the present invention is a prior art seal, as the compression with the seals results in the compression being required to deform the seals in the absence of separators which may be damaged by the high compression forces. It has an advantage over the sieve.

Referring back to FIG. 1, battery frame 11 12 includes peripheral sides or faces 15 and 16, respectively.

As shown, the seal 14 is sandwiched between the separator 13 and the cathode frame 12.

However, it may be fitted between the separator 13 and the anode frame 11.

The separator 13 is larger in size than the battery frames 11 and 12 and preferably outside the outer periphery of the frames 11 and 12.

On the other hand, the seal 14 is generally confined within the range of the side 15 of the anode frame 11, or the cathode frame 12 is confined within the side 16 as shown in FIG.

In order to explain the side 15 more clearly, the separator 13 looks bent at a thin angle from the name 15.

The separator is in full contact with the side 15.

That is, it contacts the whole area. Seals 14 line the entire sides 15 or 16 of the frames 11 and 12 of the anode or cathode, respectively.

In addition, an overplate (not shown) on the side 15 or 16 can be used to protect the frame structure from corrosive surroundings.

For example, the battery frame 11 includes a plate made of metal, such as titanium, or a plate made of plastic, such as polytetra fluoro ethylene, adjacent to the side 15.

Frames 11 and 12 are of a type used in a general electrolyzer.

For example, the frame member may be a rectangular bar, a C or U channel, a cylindrical tube, an elliptical tube that is I-shaped or H-shaped.

In a preferred state, the cross section of the electrode frame including the frames 11 and 12 is I-shaped.

Frames 11 and 12 can be made of any material that can resist electrolyte and electrolysis and corrosion by the product.

For example, the anode frame in contact with the anodolite contained in the anode zone may be made of metals such as iron, steel, stainless steel, nickel, titanium, or alloys thereof.

The cathode frame in contact with the cathodeite included in the cathode zone may be made of iron steel, stainless steel, nickel, or an alloy thereof.

Similarly, plastic materials such as polypropylene, polybutylene, polytetrafluoroethylene, fluorinated ethylene propylene and chloric acid-based polyesters can be used as anode and cathode frames.

The separator 13 of the present invention is a separator which may or may not be permeated by concentration differences.

Preferably, an inert elastic separator is used which is ion exchangeable and prevents the flow of gases resulting from electrodynamic flow and electrolysis of the electrolyte.

Rather, more cation exchange permeable membranes are used, such as permeable membranes composed of fluorocarbon polymers having a plurality of sulfonic acid chains or carboxylic acid groups or mixtures of sulfonic acid groups and carboxylic acid groups.

The terms "sulfenic acid group" and "carboxylic acid group" are intended to include carboxylic acid salts which are converted from or converted to acids by processes such as sulfonic acid salts or hydrolysis.

An example of a carboxylic acid type cation exchange membrane is the use of a membrane made by Asahi Glass Co., Ltd. under the trademark Flemion.

Another example of a membrane with cation exchange properties is E.I. DuPont Pneumo & Co. is a perfluorosulfonic acid permeable membrane sold under the trademark Nafion.

The seal 14 of the present invention may be a gasket.

Like the frames 11 and 12, the gasket should be made of a material that is corrosion resistant to the electrolyte and the product of electrolysis.

When chlorine and caustic are produced, for example, the gasket 14 must be substantially inert with respect to acid, sea water, chlorine, hydrogen and sub-catalysts present in the cell under normal operating conditions.

The gasket 14 is non-conductive and should be made of a material that has a solid resistance and good sealability after pressure.

The main characteristic of the present invention is that the material of the gasket 14 may be inelastic or substantially permanently deformed.

Gasket 14 is preferably made of fluorocarbon polymer material and more preferably made of polytetrafluoroethylene (PTFE).

W. L. Gore & Associates, Incorporated. Gaskets made of expanded PTFE are used, sold by Elkton and MD under the Gore-Tex brand.

The gasket 14 of FIG. 1 is attached to the side face 16 of the frame member 12 by an adhesive such as cement or epoxy before applying pressure to the cell assembly.

The cement or epoxy used is inert to the material resulting from the electrolysis.

Another embodiment of the invention shows in Figure 2 a permeable membrane 23 sandwiched between an anode frame 21 and a cathode frame 22 having sides 25 and 26, respectively, and a precompressed first gasket 24. Shown.

The material and structure of the membrane, the precompressed first gasket and the electrical frame shown in FIG. 2 are described in FIG. 1 except that the grooves 27 are visible on the side 26 of the frame member 22 in FIG. Same as the old ones.

It is within the technical scope of the present invention that the side surfaces 25 or 26 or both of the battery frames 21 and 22 may include one or a plurality of grooves.

In addition, FIG. 2 shows that the second gasket 28 fits into the groove 27 in a precompressed or uncompressed state.

The second gasket may be the same material as the first gasket or may be a different material.

Although the gasket 14 of FIG. 1 and the gaskets 24 and 28 of FIG. 2 generally have a rectangular cross section, various other suitable shapes can be used to obtain an improved sealing effect.

For example, the gasket may be circular or toroidal in cross section and the groove may be generally rectangular with rounded corners.

The grooves may be generally semicircular or grooves that appear triangular in cross section or any other desirable form.

A well-known adhesive, such as cement or epoxy, may be applied to the gasket 28 and the pre-compressed gasket 24 to attach the pre-compressed gasket 24 to the side 26 of the cathode prime 22 before pressurizing the cell assembly. It can be used for the contact surface 29.

It is also within the technical scope of the present invention that the gaskets 24 and 28 are one piece.

In carrying out the method of the present invention, an uncompressed gasket is well adhered with an adhesive to the side of the cathode frame or anode frame of the filter pressure electrolyzer.

Then, a membrane having the same thickness and elasticity as the permeable membrane used in the electrolytic cell assembly is sandwiched between the anode and the cathode frame and the gasket.

It may preferably be sheet or paper or plastic and more preferably made of kraft paper.

In good ecology, the thickness of the paper film is in the range of 0.125 to 0.25 mm.

A pressure or load is applied to the battery assembly that may be applied to the assembly by any known hydraulic or tightening means.

After pressing the gasket to the desired thickness, the paper sheet is removed between the gasket and the electrode frame member.

At this time, the gasket is precompressed and generally deformed permanently.

That is, the gasket remains in a pressurized form after the pressure is released.

Generally, pressure loads of 10 to 100 percent of the final pressure load required to achieve a desired electrolyzer brine gap or final gasket thickness are used to precompress the gasket.

For example, pressurize a gasket from 2.0 to 0.38 mm using a pressure from 2750 kPa to 17240 kPa.

After removing the paper film from between the gasket and the electrode frame, the paper sheet is replaced with the permeable film.

Then, the permeable membrane and the precompressed gasket between the battery frames are pressurized to create a complete cell assembly that is free of liquid and gas.

Since the gasket is already under pressure, the pressure applied to the permeable membrane resulting from the gasket deformation can be ignored, thereby minimizing damage to the permeable membrane.

The following examples are provided to illustrate the present invention and are not intended to be limiting.

One example illustrates the use of a precompressed gasket in a filler press electrolyzer using a permeable membrane.

Example 1

A pair of dummy flat cell frames, 0.61 x 0.61 m, is used to test gaskets made of high tex material.

Ropes of 12.7 x 4.76 mm thick high-tex material are attached to one flat side of the frame.

The rope is wrapped to seal the end of it.

No gaskets are attached to the other frame.

Two cell frames are installed on a hydraulic press of 0.61 x 0.61 cm.

About 0.25 mm thick kraft paper film is provided between the frames beyond the periphery of the cell frame.

The gasket between the frames is initially pre-compressed to about 1.6 mm thick under pressure of about 1380 kPa.

The battery frame is then opened and the kraft paper is removed.

A Nafion membrane, numbered 324, is installed between the gasket and the battery frame.

Then the framed cell frame is again inputted together.

Hot water from 85 ° C. to 93 ° C. wraps the cell under an internal cell pressure of 34 to 103 kPa.

In order to keep the gasket pressure constant at about 2413 kPa, the pressure of the presser is increased in proportion to the internal pressure.

The test lasts 140 hours.

No infusion is allowed.

The battery then closes and the test begins.

The membrane shall be free from thinning or gasketing around the gasket.

Comparative Example A

A flat pair of 10cmd × 10cm flat cells is used to test the unreinforced gasket of high tex.

A high 9.5mm wide x 3.2mm thick string is attached to one side of the frame.

The string is wrapped to seal the end.

No gasket is attached to the other frame.

The Nafion 324 membrane is installed between the frames.

Two cell frames are pressurized between the platens of the hydraulic press.

Hot water at 90 ° C. surrounds the cell under a pressure of 34 to 207 kPa.

The water pressure increases in proportion to the internal pressure to maintain the gasket pressure at 3447-4137 kPa to stop the leak.

This test lasts 48 hours.

The cell frame is then opened and the gasket and permeable membrane are inspected.

With the pressure applied to the gasket, observe the area of the membrane going out and thinning out.

Example 2

An electrolyzer consisting of four rectangular flat plate cell frames is gasketed as follows.

A gore-tex strap, 6.35 mm in diameter, is attached to the 6.35 mm groove located on the cathode side of the battery frame.

The end is compressed into the groove so that the top of the gotex is flush with the side of the cell frame.

A string of 12.7 mm wide by 4.76 mm thick with a high tex is then attached to the center of the top of the 6.35 mm diameter string and extends around the entire cathode gasket face.

The string is wrapped to seal the end.

No gaskets are placed on the anode side of the cell frame.

A kraft paper film about 0.25 mm thick that extends beyond the cell frame is attached to the anode side of each cell frame by attaching a table.

A closed cell frame with a sheet of paper attached is installed one at a time on the cell skid between the two platens of the hydraulic press.

Both cells are pressurized at 8274 kPa in the hydraulic cylinder (42676 kg in the press), which equals the 3723 kPa applied to the gasket.

The 12.7mm Goo-Tex strap is pressurized into a gasket that is initially 12.7mm wide by 4.76mm thick and 15.9mm wide by 1.6mm thick.

Then the water pressure is released. The cell frame is unfolded to remove the paper film. Then, Nafion membrane, NO.324, is installed between adjacent cell frames. After the membrane is installed, the cell frame is again subjected to a pressure of about 11377 kPa in the hydraulic cylinder. Anodolite and cathode light are surrounded by the cell and power is turned on to energize the electrolyzer. The cell is operated at a temperature of 90 ° C. and an internal pressure range of 34 to 138 kPa.

The hydraulic cylinder pressure of the compressor varies from 11377 to 15169 kPa to prevent gasket leaks. Gasket thickness varies from 1.27 mm to 9 to 0.76 mm. The average gasket pressure is maintained at about 3447 kPa.

During eight months of operation, the cell was shut down five times with cell modifications and permeable membrane replacement. Used gaskets are removed from the cell during each shutdown and visually inspected. A new gasket was installed following the procedure above after each shutdown, although no damage was seen to the gasket or membrane.

Claims (10)

An electrolytic assembly comprising a first frame, a second frame, and a separator sandwiched between the frames to separate the anode and the cathode, wherein at least a pre-compressed and permanently deformed seal is used between the first or second frame and the separator. Electrolyzer assembly, characterized in that. The electrolytic cell assembly of claim 1, wherein the separator is a permeable membrane and the seal is a gasket made of fluorocarbon polymer. 3. The electrolytic cell assembly of claim 2, wherein the fluorocarbon polymer is a highly pore expanded polyterra fluoroethylene material. 4. The electrolytic cell assembly of claim 3, wherein at least one of the frames has a groove in the frame, the groove comprising a gasket. Sandwiching the seal between at least the first frame or the second frame and the separator and the separator separating the anode and the cathode in a confined area defining the first frame and the second frame and separating the seal, separator and the first and second frames. An electrolytic cell sealing method comprising the step of compressing, wherein the electrolytic cell sealing method uses a precompressed, permanently deformed seal as a seal. An electrolytic cell sealing method comprising the steps of: sandwiching a sheet member between at least a first frame and a second frame; and inserting a seal made of a material that can be permanently deformed between at least the first frame or the second frame and the sheet member; Compressing the seal for permanently deforming the first and second frames, the sheet member and the seal, releasing the compressive force to remove the sheet member, replacing with a separator instead of the sheet member, Compressing the first and second frames, the pre-compressed seal and the separator sufficient to prevent leakage of liquids and gases. 7. The electrolytic cell sealing method according to claim 6, wherein the sheet member is made of paper or synthetic resin material. The method of claim 6, wherein the seal is permanently deformed to a thickness such that liquid and gas do not leak. The electrolytic cell sealing method according to claim 6, which is a gasket made of a sealed fluorocarbon polymer. 10. The method of claim 9, wherein the fluorocarbon polymer gasket is a pore expanded polytetrafluoroethylene.

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