US2742419A - Electrolytic cell base structure - Google Patents

Description

April 17, 1956 J. c. BA KER EI'AL ELECTROLYTIC CELL BASE STRUCTURE Filed March 1, 1952 INVENTORS JOSE C. BAKER ()SCAR BEARD United StatesPatent ELECTROLYTIC CELL BASE STRUCTURE Jose C. Baker and Oscar Beard, Pasadena, Tex., assignors to Diamond Alkali Company, Cleveland, Ohio, a corporafion of Delaware Application March 1, 1952, Serial No. 274,348

3 Claims. (Cl. 204-252) This invention relates to electrolytic cells for the production of chlorine and caustic soda, and more particularly relates to improved forms of anode supporting bases for permeable, diaphragm-type electrolytic cellswherein carbon or similar anodes may be mounted in permanent leakproof and suitably insulated relation to said bases.

Modern trends in the design of diaphragm electrolytic cells for the electrolysis of sodium chloride brine to obtain chlorine and caustic soda are all in the direction of cells designed for increased operating current. In cells which have been in use in industry inthe past, the designed amperage loads have been of the order of a few thousand amperes. In such cells, leakage of brine from the cell, while of significance, has usually been controllable by relatively simple expedients. The design of cells for increased operating current which naturally operates at higher temperatures, however, has presented increasingly important leakage problcms'which have for the most part confounded the art in that, especially as to leakage of brine, serious difficulties have been encountered. Only a minimum amount of leakage onto the floor of a cell room can be tolerated in view of safety to workers and general housekeeping conditions. It is, therefore, a desideratum of considerable importance that leakage be In addition to the disadvantage and possible danger of wet conditions on the floor of the cell room arising from such circumstances, the leaking cells themselves must be taken 01f the line and repaired. Such necessity usually occurs at a time at which, other than for repair of leakage, the useful life of the cell may not have been exhausted. Moreover, as considerable corrosion to the metallic base and other parts may occur, early replace-' ment of cell parts, which ordinarily would have much longer life, is directly referable to brine leakage. Thus, cell maintenance costs mount and ultimate capacity'of the cells is accordingly lower.

An outstanding aspect of the disadvantages which have additionally come to light as a result of operating such cells at high amperages arises from the large surface area of bitumen or other organic material which is exposed to the oxidizing action of dissolved chlorine in the anolyte. As a result of this action, significant quantities of organic degradation products form, which materials contaminate the chlorine, form undesirable quantities of sludge in the bottom of the cell, and contribute materially to early plugging of the diaphragm and thus shortened cell life.

It is an object of the present invention to provide a base for an electrolytic cell of the diaphragm type adapted to hold and support a plurality of anodes in liquid-tight and suitably insulated relation to said base.

- It is a further object of the invention to provide an anode supporting base for an electrolytic cell of the character under discussion which shall be completely leakproof in operation, even at very high amperages, where by the various parts of the cell are protected from corrosion by brine and cell room leakage is minimized.

It is a further object of the invention to provide a base for an electrolytic cell 'whereinan asphalt seal is held in positive sealing relation against the anode blades, which sealing relation improves and becomes tighter'and more positive as temperatures of operation increase.

completely avoided, if possible, in electrolytic cells and that in any case leakage of brine from the cells be minimized as far as possible. v

In cells combining a plurality of alternately situated cathodes and flat base supported carbon anodes, such as those'shown in Stuart Patent No. 1,866,065 or Means Patent No. 2,368,861, various expedients, including sundry combinations of concrete, bitumen, and the like, are resorted to in the bases of the cell to insure the absence of leakage between the carbon anodes of the cell and the base materials. A common method of mounting anodes in the base of a cell is to provide for suitable electrical r connections between a source of potential and the bases of the anodes, cover the base of the cell and the anode shafts where they insert into the base with grout or concrete, and cover the entire base assembly with asphaltic material to insure electrical inactivity ofthe base of the cell and sealing against leakage of brine. It is this very type of structure which has heretofore been used very commonly in the art in low amperage cells.

It has now been found, especially in cells designed for operating at amperages of the order of 10,000 amperes and higher, that this form of construction is no longer of value as an insurance against leakage of brine from the cell. It appears particularly where the carbon anodes are mounted in a suitable metallic base and then the base is covered with concrete or grout around the lower portion of the anodes, and finally coated with asphaltic material over the entire base assembly for the purpose of rendering the same electrolytically inactive, that considerable leakage of brine occurs between the asphaltic material as applied to the base, the anode blades, and the grouting, whereby the brine is enabled to seep through this space andultimately run out of the cell onto the floor.

A further object is to provide a cell in which the anodes are sealed in the base in suitable liquid-tight relation but in which a minimum amount of organic sealant is exposed to the oxidizing action of anolyte.

Further objects and advantages will appear from the detailed description of an embodiment of the present invention and a method of achieving its, objects which appears hereinbelow, and from the drawing illustrating said embodiment, in which,

The figure is a vertical, sectional view through a typical permeable, diaphragm-type electrolytic cell, with nonpertinent portions broken away, showing the invention of the present application.

Referring to the drawing, the cell as illustrated includes carbon anodes 4 and foraminous cathodes 6, provided with permeable diaphragms 8, the cathodes and anodes being mounted in alternate relationship and in accordance with well-known principles operated to provide for the electrolysis of sodium chloride brine, which suitably is situated in the anode-containing chamber of the cell in a known manner. During operation of the cell, flow of liquid occurs through diaphragms 8 and cathodes 6' into cathode chambers 11. The chemistry ofthe electrolysis of brine and the details of operation of the cell, not forming a portion of the present invention and being well-understood by those skilled in the art, need not be further elaborated upon.

The base of the cell includes a metallic pan 10, which functions principally as a support for the remaining in-' strumentalities. Relatively soft conducting metal 14, such as type metal, lead, or similar low melting conducting material, is held in pan 10 and may suitably provide an electrical path for electric current from a source of potential, not shown, to the anode blades 4, which are mounted in said type metal 14 in suitably spaced relation.

Blades 4 are inserted in conducting material 14 to a sufficient depth to provide for considerable mechanical support. Anodes 4 may suitably be assembled in pan by placing the same in desired position and pouring molten metal to a sufiicient depth in the pan to provide for support and provide suitable electric connection between the source of potential and the anodes.

In accordance with the principles of the present invention, the assembly of pan 10, anodes 4, and soft conducting metal 14, when fixed in substantially the relationship shown in the drawing, may be dipped in, painted with, or otherwise suitably impregnated with organic sealant material 18 to a depth over that to which ultimately concrete or grout 16 is to be applied, i. e., suitably one inch or more thereabove. While this material may take any suitable form, it preferably is characterized by relative chemical inertness and by cold flow at relatively elevated temperatures, such as cell operating temperatures, i. e., up to 220 F. In addition to these properties, the sealant material must have the characteristic of adhering to the carbon anodes and to the lead base when applied hot and allowed to cool. For this purpose, bitumens, asphalts, and the like may suitably be employed, and the structure herein is for convenience described in connection with the preferred material, i. e., asphaltic sealant of suitable melting point. Sealant material 18 is shown in the drawing with its actual thickness exaggerated for clarity.

After application, the asphaltic material is permitted to harden somewhat, the base assembly is completed by application of the concrete or grout 16 as shown in the drawing, and upon its setting, the anode assembly is complete and ready for combination with the cathode assembly indicated generally at 20. This includes the foraminous cathodes 6 and the end cathodes 22, and is suitably placed over the anode assembly with individual cathodes and anodes in alternate position, as shown, sealing from leakage between the cathode assembly and the anode assembly being secured by means of gasket 24 or the like.

When the procedure of the present invention is followed, it has been found that leakage around anodes and thus out of the cell onto the floor, or the base itself, is

completely avoided by the method of assembly herein and particularly that no leakage occursbetween the carbon anodes and the asphalt layer. Moreover, while a mere reversal of parts appears to be involved, actually advantage has been taken of a heretofore disadvantageous property of high amperage cells, i. e., higher operating temperature, to obtain, rather than a cell of greater leakage problems, one which in fact has less leakage from anode mountings than any heretofore known.

Thus, it is known that asphaltic materials, though they may have reasonably well-defined softening pointsand in the present usage, a softening point (ball and ring method) between 200 and 350 F. is in general preferred-are subject to cold flow at almost any temperature and especially at the operating temperatures of cells such as those under discussion, such as 190 to 200 F.

At such temperatures the grout or concrete will have undergone considerable expansion. In the cell of this invention, this expansion will take place against the asphaltic layer 18 as applied against each anode blade with the result that the higher the temperature at which the. cell is operated, the greater the expansion of concrete 16 and the tighter the seal against the anodes 4 by asphalt layer 18.

In addition to this advantage, it may be observed that rather than the whole top area of asphalt layer 18 being exposed to anolyte, only the relatively small. area of coated anode protruding from the grout is exposed, whereby the oxidative effects of anolyte thereon are minimized.

It will be appreciated that the provision of positive sealing pressure against anode blades, with provision for but minimum exposure of the organic sealant to anolyte, is in contrast to prior art structures wherein the asphalt layer was the uppermost brine-contacting layer of the base of the cell and could easily separate from contact with the anodes or be extensively oxidized by anolyte, whereby leakage between anodes and asphalt occurred and contamination of chlorine with early diaphragm plugging was experienced. Moreover, the greater the temperature variation to which such prior structures were subjected, the greater the chance of broken seal, while in accordance with the present invention, where the grout or concrete expands under the influence of temperature and against the cold flowing asphalt, wide temperature variations can easily be withstood without loss of seal.

While there has been illustrated and described in detail an embodiment of the invention, the described structure is not intended to be understood as limiting the scope of the invention as it is realized that changes therewithin are possible and it is further intended that each element or instrumentality recited in any of the following claims is to be understood as referring to all equivalent elements or instrumentalities for accomplishing substantially the same results in substantially the same or equivalent manner, it being intended to cover the invention broadly in whatever form its principle may be utilized.

What is claimed is:

1. In an electrolytic cell, a base, a plurality of upwardly extending, rigid blade-like anodes mounted in said base, said anodes being supported in conducting material in said base, organic bituminous sealant coating the lower portions of said anodes and said conducting material, and grouting overlying and covering said organic sealant on said conducting material, said grouting having less depth than the upward extent of said organic sealant on said anodes.

2. In an electrolytic cell, an electrically conductive base having a plurality of upwardly extending carbon anodes mounted therein at spaced intervals and connected to a source of potential, said carbon anodes being coated near their lower ends with an asphaltic coating and grout overlying said coating and extending between said anodes, positively engaging said coating, said coating extending above the level of said grout.

3. An electrolytic cell base structure comprising a support, relatively soft metallic conducting material on said support, a plurality of upwardly extending rigid blade-like anodes supported in said conducting material, an organic bituminous sealant overlying said conductting material and covering the lower portions of said anodes to form a liquid-tight sealant barrier over said conducting material and around the lower portions of said anodes, and grout overlying said sealant to a depth less than the height of the sealant material on said anodes.

References Cited in the tile of this patent UNITED STATES PATENTS 731,453 Hargreaves June 23, 1903 1,982,224 Michel Nov. 27, 1934 2,370,087 Stuart Feb. 20, 1945 2,470,073 Low .a May 10, 1949

Claims (1)

1. IN AN ELECTROLYTIC CELL, A BASE, A PLURALITY OF UPWARDLY EXTENDING, RIGID BLADE-LIKE ANODES MOUNTED IN SAID BASE, SAID ANODES BEING SUPPORTED IN CONDUCTING MATERIAL IN SAID BASE, ORGANIC BITUMINOUS SEALANT COATING THE LOWER PORTIONS OF SAID ANODES AND SAID CONDUCTING MATERIAL, AND GROUTING OVERLYING AND COVERING SAID ORGANIC SEALANT ON SAID CONDUCTING MATERIAL, SAID GROUTING HAVING LESS DEPTH THAN THE UPWARD EXTENT OF SAID ORGANIC SEALANT ON SAID ANODES.

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