KR790001868B1 - Improved electrolytic diaphragm cells - Google Patents

Abstract

A continuous net permits the uniform and min. anode-cathode spacing of the cell. The diaphragm is retained and prevented from adhering to the surface of the anodes in this cell. The electrolysis of aq. alkali metal halide brines can be done with lower elec. energy requirements and reduced operating costs. The net may be of glass fibers, asbestos filaments, plastic materials selected from the group consisting of polyfluoroolefins, polyvinyl chloride, polypropylene, and glass fibers coated with the plastic materials.

Description

Improved diaphragm electrolyzer

1 is a plan view showing an electrode portion of a partially assembled diaphragm tank of the present invention.

2 is a partial perspective view of partially assembled positive and negative electrodes.

3 is a side view of one embodiment of a diaphragm tank of the present invention.

The present invention relates to an electrolytic cell used for brine electrolysis. More specifically, the present invention relates to a diaphragm electrolyzer used for the electrolysis of aqueous alkali metal chloride solutions. Diaphragm-type electrolysers known by the known art use a screen or a net between the diaphragm and the electrode. For example, the British patent teaches the use of a support network between the diaphragm and each cathode, electrically connected to the cathode and holding the diaphragm. If the diaphragm expands rapidly when manipulating the tank, the net will be placed between the diaphragm and the anode.

내지

인치의 개구를 갖는다. 조를 조작하는 동안 염수는 흑연입자를 통해 흘러오른다. 양극은 염수 및 가스의 흐름에 기인하는 부식이 주로 흑연 입자위에 일어나서 흑연 블록의 빈번한 교체를 감소시키도록 설계된다. 흑연블록과 스크린 사이의 공간은 최소 약

인치이다. 조가 알카리 금속 염화물 수용액을 전기분해하려고 동작될 때 흑연 입자는 특히 O₂형성에 의해서 부식된다. 다른 흑연입자들이 보충물로 조로 공급된다. 그러나 흑연 입자의 교체문제 때문에 고도의 일정한 전류 효율을 유지하는 것은 어렵다. 그래서 격막 전해조에 있어서 격막이 보유되고 양극과 격막, 양극과 음극사이에 최소의 일정한 공간이 제공되면서, 양극에 부착되니는 것을 방치하는 것이 필요하다.The previous US patent used a porous sheet or screen between the diaphragm and the anode. The back side of the anode consists of graphite blocks, and the front side adjacent to the screen is made of graphite or carbon particles, and has an element that electrically connects the block and the particles. The screen prevents graphite particles from clogging the porous diaphragm

To

It has an opening of inches. During operation of the bath, brine flows through the graphite particles. The anode is designed so that corrosion due to the flow of brine and gas occurs mainly on the graphite particles, reducing the frequent replacement of the graphite blocks. The space between the graphite block and the screen should be at least about

Inches. Graphite particles are corroded, especially by O ₂ formation, when the bath is operated to electrolyze an aqueous alkali metal chloride solution. Other graphite particles are fed into the bath as a replenishment. However, it is difficult to maintain a high constant current efficiency because of graphite particle replacement problem. Thus, it is necessary to leave the diaphragm held in the diaphragm electrolyzer and be attached to the positive electrode while providing a minimum constant space between the positive electrode and the diaphragm, the positive electrode and the negative electrode.

An object of the present invention is to provide a diaphragm tank having a constant space between the anode and the diaphragm. Another object of the present invention is to provide a diaphragm tank which prevents the diaphragm from being attached to the anode efficiently. Another object of the present invention is to provide a diaphragm tank having a minimum space between the anode and the cathode.

These objects of the present invention are performed in a diaphragm electrolyzer consisting of a bath body, a negative electrode plate having a plurality of attached negative electrodes, a diaphragm deposited on the negative electrode, a positive electrode tube having an attached porous metal positive electrode, and the like. The positive electrode plate and the negative electrode plate are hermetically attached to the main body. Contacting them between the anode and the diaphragm is a continuous mesh that spaces the anode and the diaphragm at regular intervals.

The apparatus shown in FIGS. 1-3 produces a halogen gas, such as chlorine, hydrogen gas, and an alkali metal hydroxide liquid when used for the electrolysis of an aqueous alkali metal halide compound such as sodium chloride. However, it would be possible for a person skilled in the art to make modifications for the use of different starting materials to produce different outputs. Figures 1-3 illustrate the novel diaphragm electrolyzer of the present invention.

The top view in FIG. 1 shows an electrolytic cell 1 having a porous metal head 10 attached to a bipolar plate 12. The coarse body 16 is attached to the positive plate by a gasket 17 and a male screw 15. The negative electrodes 20 attached to the negative electrode plate 18 are covered by the diaphragm 22. The cathodes 20 are partially inserted between the porous metal anodes 10. The continuous mesh 11 is covered by a porous metal anode 10 in contact with the diaphragm 22. The conductor 13 attached to the positive electrode plate 12 introduces a current into the electrolytic cell 1 while removing the current from the bath of the conductor 21 fixed to the negative electrode plate 18. The support racquet 14 is attached to the positive electrode plate 12 and the negative electrode plate 18.

2 shows a perspective view of a portion of a bipolar plate 12 having a porous metal anode 10. The continuous net 11 covers the anodes 10. The cathodes 20 have protective covers 23 inserted between the anodes 10 and located between the diaphragm 22 and the continuous mesh 11. The protective covers 23 are removed prior to the final assembly of the anodes 10 and the cathodes 2.

3 shows the side of the assembled electrolyzer 1 in which the positive electrode plate 12 and the negative electrode plate 18 are positioned vertically. The aqueous alkali metal halogen compound solution to be electrolyzed enters the bath body 16 through the brine inlet 24. Halogen gas is removed through the halogen outlet 26 and hydrogen outlet 28, the corrosive liquid is removed through the outlet 30. The drain pipe 31 allows the contents of the bath to be removed. The protrusion 32 assists in positioning and removal of the positive electrode plate 12 and the negative electrode plate 18. The electrolyzer 1 is supported by an insulator 34 which is supported by a sub-kit 14 attached to the positive electrode plate 12 and the negative electrode plate 18 and which remains on the platform 36. The net 11 serving as a space between the anode 10 and the diaphragm 22 is in the form of a continuous sheet covering all the anodes in the anode portion. While providing space between the anode and the diaphragm, the mesh prevents the diaphragm from adhering to the surface of the anode while the bath is operating. Attachment of the diaphragm to the anode surface results in a decrease in current efficiency. The mesh consists of any suitable nonconductive chlorine-resistant material. Typical examples are glass fibers, asbestos filaments, for example polyfluoroolefins, polyvinyl chloride, plastic materials such as polypropylene and polyvinylidene chloride and glass fibers coated with polyfluoroolefins such as polytetrafluoroethylene There is. The proper thickness of the mesh is such that the anode surface is properly separated from the diaphragm. For example, a mesh of approximately 0.003 inches to 0.125 inches thick may be used, with 0.010 inches to 0.080 inches being preferred. Nets with suitable holes are used to allow the brine to flow between the anode and the diaphragm. The net size of the net used is 0.5 to 20 per linear inch, preferably 4 to 12. The mesh is made of knitwear or of nonwoven.

In covering the anode cross section, one end of the continuous mesh is hung on the first anode surface at one end of the anode portion, over the middle anode as shown in FIG. 1 and on the outer surface of the last anode of the anode portion. Although not necessary, the continuous net is attached to the anode, for example by clamps, strings, wires or adhesives.

It may be desirable to cover the diaphragm for a while while the electrolytic cell is assembled so as not to damage the diaphragm. It may have a protective cover, such as a sheet or net, that is properly removed prior to final assembly of the bath. Continuous net lamps may be used as the protective sheath, and in a suitable embodiment one sheath is used for one part of the diaphragm attached to each cathode. It is necessary to use a mobile retaining device to hold the protective covers in place during assembly of the jaw by inserting the negative electrode between the positive electrodes and also lowering the negative electrode. Any suitable retainer may be used, for example a rod or slat that is longer than the cathodes inserted between the cathodes. The protective cover is suitably attached to the retaining device, for example by braiding or fastening it, or by means of gluing means. Retainers are attached to the pair of supports located vertically across the top or bottom of the cathode. During assembly, the support, retainer and shrouds are removed when the cathode is lowered to the required position. The cathodes come to the lower position to complete the next electrode assembly.

Protective covers are any suitable material, such as polyethylene, polytetrafluoroethylene, polyvinylidenechloride, waxed paper and the like. Protective covers are particularly useful when the diaphragm is a material deposited on a cathode such as asbestos.

The anode portion covered by the continuous mesh consists of a plurality of porous metal anodes attached to the anode plate. Suitable metals for the anode consist of valve metals such as titanium and tantalum or metals such as aluminum, steel and copper coated with valve metals. At least a portion of the valve metal surface is thinly coated with an alloy of platinum group metal, platinum group oxide, platinum group metal or mixture. The term "platinum group" refers to an element of the group consisting of rutile, rhodium, palladium, osmium, iridium and platinum.

Porous metals can take many forms. For example, a plate with holes, or a net or screen. The anode has a flat surface with adequately sized holes to allow fluid to flow through the anode surface.

As a suitable example, the anode consists of two porous parts separated from each other. The space shall be sufficient to enclose the conductive support which supplies the current providing the halogen gas passage. If an anode consisting of one porous plate or sheet is used, space must be made for the flow of the fluid. The anode plate to which the anode is attached is made, in whole or in part, of an electrically conductive material such as steel, copper, aluminum, titanium or a mixture of these materials. If the conductive material is attacked by a solution or gas in a bath, it may be covered with, for example, rubber, a chemically inert plastic such as polytetrafluoroethylene, a fiber reinforced plastic, or a metal such as titanium or tantalum. The anode is attached to the anode plate by screwing, welding or soldering. The cathode consists of a conductive element wrapped by a conductive screen or net. The conductive elements can be in the form of plates or rods with attachments for screens or nets, for example.

Many cathodes are attached to a cathode plate suitably composed of at least a portion of a conductive metal such as copper, steel or a mixture thereof. To prevent corrosion damage, the negative plates are covered with, for example, hard rubber, polytets, plastics such as lafluoroethylene, or fiber reinforced plastics. The negative electrode is attached to the negative electrode plate by soldering or screws, for example.

The diaphragm covering the cathodes consists of an inert material which is fluid permeable and halogen resistant. Suitable diaphragms include asbestos, reinforced asbestos and polymers with microporous or ion exchange properties. Ion exchange resins used as diaphragm materials include fluorocarbons having the general formula:

Where m is 2 to 10, the ratio of M and N is sufficient to provide 600 to 2000 equivalents, and R is selected from

여기서 P는 1에서 3 또는

Where P is 1 to 3 or

Where P is 1 to 3, Y is -F, or a perfluoro alkyl group having 1 to 10 carbon atoms.

A is a fraud chosen from the next group.

SO ₂ H,

CF ₂ SO ₃ , H

CCl ₂ SO ₃ H,

R'SO ₃ H,

PO ₃ H ₂ ,

PO ₂ H ₂ ,

COOH,

R'OH where R 'is an allyl group.

Ion exchange resins in which R is SO ₃ H or OCF ₂ -CF ₂ -SO ₃ H are preferred.

When the ion exchange resin is a polymer, the fluorocarbon moiety is a polyfluoroolefin such as metrafluoro ethylene, hexafluoropropylene, octafluoro butylene and higher homologues.

Suitable diaphragm materials are composite membranes composed of a solid fluorocarbon polymer reinforced by a fabric such as polyfluoro olefin fabric or by a screen of suitable metal. Solid fluorocarbon polymers are prepared by copolymerizing tetrafluoroethylene with sulfonated perfluorovinyl ether, for example FSO ₂ CF ₂ CF ₂ OCF (CF ₄ ) CF ₂ OCF = CF ₂ . The fifluorocarbon polymers are prepared by copolymerizing tetrafluoro ethylene and vinyl ether and then converting the FSO ₂ group to -SO ₃ H or a sulfonate group (eg alkali metal sulfonate) or mixtures thereof. The equivalent weight of the fluorocarbon polymer is about 900 to 1600, with a preferred value being 1100 to 1500. Equivalent is defined as the average molecular weight per sulfonyl group. Suitable diaphragm materials are perfluorocarbon polymer composites produced by DuPont.

The space between the anode and cathode is made up of the thickness of the diaphragm and continuous mesh. This space is about 0.010 to 0.500, preferably about 0.030 to 0.250 inches. Among them, the thickness of the diaphragm is about 0.007 to 0.375, preferably about 0.020 to 0.170 inches. The electrolyzer may be of any shape with a porous metal anode. An electrolytic cell is preferably mounted on an electrode plate where the anode and cathode are located vertically. Particularly preferred is a shell type in which the electrolytic cell body has openings at each end. The body of the jaw may be rectangular, cylindrical, oval, etc., and may be constructed of various materials such as hard rubber, steel, rubber-embedded steel, titanium, asbestos, reinforced plastics, and concrete.

If the shell is steel or concrete, it is protected with rubber, ceramic tile composites, asbestos-reinforced plastics, or materials such as polyhaloolefin plastics such as carbon, silica or polytetrafluoroethylene.

The height of the coarse body can be any comfortable height, for example from 1 to 15 feet, suitably from 4 to 12 feet. The jaw body may have a flange around the opening to facilitate attachment of the electrode plates to the openings at each end. The electrode types are attached to the opening at the end of the body of the jaw by a suitable attachment such as a male screw or rod or clamp. As shown in FIG. 3 showing the assembled jaw, the electrode plate is positioned vertically and provides support means for the jaw body.

The diaphragm tank of the present invention allows a minimum space between the anode and the cathode, so that less electric energy is required and the running cost is reduced. In addition, the use of a continuous mesh between the anode and the diaphragm prevents the diaphragm from retaining and adhering to the anode surface and maintaining high current efficiency in operation. In addition, corrosion of the diaphragm due to the flow of gas or liquid is reduced.

Claims (1)

An electrolytic cell body, a negative electrode plate having a plurality of negative electrodes attached thereto, a diaphragm deposited on the negative electrodes, and a positive electrode plate having a plurality of porous metal positive electrodes attached thereto. A diaphragm tank, wherein a mesh is disposed between the anodes and the diaphragm to separate them at a predetermined distance and to contact the diaphragm.

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