US3425929A

US3425929A - Method for stabilizing the position of anodes and anode bus bars in an electrolytic cell

Info

Publication number: US3425929A
Application number: US537949A
Authority: US
Inventors: Alvin T Emery; John E Currey
Original assignee: Hooker Chemical Corp
Current assignee: Occidental Chemical Corp
Priority date: 1966-03-28
Filing date: 1966-03-28
Publication date: 1969-02-04
Anticipated expiration: 1986-02-04
Also published as: ES338521A1; DE1671436A1; GB1119817A; NL130825C; NL6704367A; FR1515646A; BE696208A

Description

A. T. EMERY ET AL 3,425,929 AND METHOD FOR STABILIZING THE POSITION OF ANODES ANODE BUS BARS IN AN ELECTROLYTIC CELL Filed March 28, 1966 v a F United States Patent York Filed Mar. 28, 1966, Ser. No. 537,949 US. Cl. 204-266 Claims Int. Cl. B01k 3/00 This invention relates to a means for securing anodes in electrolytic cells and more particularly to a means for reducing or eliminating movement of the anode blades of electrolytic cells due to thermal expansions and contractions, metal migration and other changes encountered during electrolytic cell operations.

Electrolytic cells, particularly those suited for the electrolysis of aqueous solutions, are often composed of a plurality of alternately positioned anode and cathode configurations, The cathode structure is commonly constructed as an electrically unitized configuration having a plurality of projections known as cathode fingers, which projections may span the cathode structure from one side to the other or may be in a serpentine configuration. Typical illustrations of this cathode construction are given at page 93 in the book, Chlorine, Its Manufacture, Properties and Use, ASC Monograph Series No. 154, edited by James S. Sconce, published by Reinhold Publishing Corporation (1962). The cathode fingers are in spaced relationship to each other having a predetermined distance between each finger. Prior to assembly of the electrolytic cell, anode blades are positioned in the cell bottom in a spaced relationship to each other so that when the cell is assembled, the anode blades are positioned between the cathode fingers.

With increasing sizes and capacities of electrolytic cells, the criticality of alignment of the anode blades with respect to the cathode fingers becomes extremely important. Normally, the distance between anode blade and cathode finger is about one-quarter to one-half inch. As the length of the anode blade is increased, the difficulty of maintaining such distance constant, with the electrodes in alignrment, increases because an end of each anode blade is embedded in a conductive material, which material can subsequently act as a fulcrum about which the projected end of the anode blade is pivoted on the slightest movement of the conductive material. Such movements are greatly magnified with increasing lengths of the anode blade. On misaligning the anode blade so that it is no longer centered between the cathode fingers, reduced electrical efliciencies result. If the blade becomes misaligned to the point where it makes contact with the cathode finger, a

direct short occurs, thereby eliminating the usefulness of i the given anode blade and uselessly expending electrical current.

a It is an object of the present invention to provide a means whereby the anode blades can be securely held in position, anchored to the cell bottom, thereby reducing or eliminating movement in subsequent thermal expansions and contractions. Another object of the present in vention is to provide means for securely anchoring anode blades in a cell bottom while retaining such means in a form by which the anode blades can be subsequently removed from the cell bottom without the destruction thereof. These and other objects will become apparent to those skilled in the art from the description of the invention which follows.

In accordance with the invention, a means for securing an anode in an electrolytic cell is provided comprising a cell bottom having therein a preformed irregularity, a

3,425,929 Patented Feb. 4, 1969 conductive medium to which are attached a plurality of anode blades and a bus bar, said conductive medium having one surface thereof shaped to conform to said cell bottom and the irregularity therein, said irregularity in said cell bottom and conductive medium "being a matching projection and recess wherein said irregularity is positioned transversely to the direction of the bus bar in said conductive medium.

The present anchorage system provides a means for firmly holding the anode blades in position thereby reducing or eliminating even slight shifts of the conductive medium such as those encountered with changes in temperature. Further, when lead or other soft metal is used as the conductive medium, migration of the conductive medium at cell operating temperatures is greatly reduced or eliminated.

The invention will be more clearly described by reference to the drawings in which:

FIG. 1 is a top plan view of a cell bottom illustrating the position of the bus bars and preformed irregularity in the cell bottom;

FIG. 2 is a vertical sectional view of the cell bottom of FIG. 1 along plane 22 having added thereto anode blades embedded in a conductive material; and

FIG. 3 is a vertical sectional view along plane 33 of FIG. 1, further illustrating the irregularity in the cell bottom relative to the positioning of the bus bar.

Cell bottom 10 is a preformed structure of desired size and shape having preformed therein an irregularity 16 on the inside bottom surface thereof, Cell bottom 10 can be constructed of any of numerous materials which are inert or can be rendered inert to the environment within the cell. Suitable materials include various ferrous metals such as steel, ferrous alloys such as stainless steel, nickelsteel, and the like, and ferrous materials coated with inert materials such as after-chlorinated polyvinyl chloride, polyvinylidene chloride, Teflon, ceramics, and other suitable inorganic and organic materials. However, concrete is normally a preferred material of construction because of its relative ease of fabrication, non-conductivity, inertness and relatively low cost. Therefore, the cell bottom referred to herein and in the drawings is of concrete. However, it is to be realized that in referring to the cell bottom as being a concrete structure, other structures of other materials used in the art are also contemplated.

Irregularity 16 can be either a projection or a. recess or a combination of both in the cell bottom. A corresponding matching projection or recess is formed in the conductive medium 20 so that when the two parts are joined, the projection and recess fit securely together. Irregularity 16 is positioned transversely, and preferably substantially perpendicular to the general direction of the bus bar 12 in conductive medium 20. In a highly preferred embodiment, irregularity 16 is positioned at or near a plane passing through the center of the mass of the conductive medium 20, which plane is perpendicular to the general direction of the "bus bar. Alternatively, the position of the irregularity relative to the center of the mass of the conductive medium can be displaced therefrom with somewhat lesser effectiveness, or a plurality of irregularities can be used as by placing the irregularities on either side of the plane passing through the center of the mass, especially as in a position equal distances from both sides of the center of the mass. Thus, a plurality or multitude of irregularities are often used. Further, correspondingly good results are obtained by positioning the irregularities near the geometric center of the conductive medium. In computing the center of the mass of conductive material, the bus bar is not included therein and therefore, the center of the mass is often displaced from the geometric center, depending on the configuration and position of the bus bar.

Irregularity 16 can be either a recess or projection that spans the entire side to side distance of the cell bottom or any part thereof. Further, irregularity 16 can be formed in a shape other than the bar projection specifically illustrated. Thus, circular, triangular and rectangular irregularities can be used.

In forming cell bottom 10, the irregularity 16 is preferably formed in a manner such that the projections and recesses have relatively sharp corner angles. Thus, irregularity 16 has an edge of projection 24 or sidewall which is nearly vertical, having corner angles of near 90 degrees. Thus, sidewall 26 is preferably a fiat wall rather than a curved wall. These corner angles are usually slightly more than 90 degrees, preferably being in the range of 90 to about 120 degrees. Most preferably, the corner angles are in the range of about 90.5 to 100 degrees, the slightly obtuse angle providing ease in subsequent removal of the conductive medium from the cell bottom. In a like manner, the sidewalls 26 of bus bar recess 14 are also preferably nearly vertical, the corner angles thereof preferably being relatively sharp angles having angles of about 90 to 120 degrees and most preferably about 90.5 to 100 degrees.

A plurality of anode blades is generally embedded or otherwise attached to the conductive medium. Depending on the particular cell design, there are about the same number of anode blades as there are cathode fingers, The number, which corresponds to the number of rows of anode blades, can vary widely from about two to 100 or more. In most instances, the number is about to 50.

The position of the anode blades with respect to the direction of the bus bar embedded in the conductive medium can be either parallel or perpendicular thereto. The detrimental effects of the conductive medium movements are most pronounced when the anode blades are perpendicular to the direction of the bus bar. However, independent of the positioning of the anode blades with respect to the bus bar, substantial elimination of detrimental movements of the blades is effected by the present invention.

Conductive medium is preferably of a highly conductive metal such as lead, copper or alloys thereof which have a relatively low melting point so that they can readily be cast about anode blades 18 without decomposing the anodes due to the heat of the molten metal. Lead is the most preferred material. The conductive medium 20 having the anode blades 18 embedded therein along with bus bar 12, is normally cast apart from cell bottom 10. In this manner, the anode blades and conductive medium can be replaced in the cell bottom after the anode blades are decomposed due to the electrolytic process. This preferred capability of being able to remove the conductive medium from the cell bottom without destruction of the cell bottom accentuates the difiiculty in securing the conductive medium firmly in place in a manner resistant to movements due to shock, thermal expansion, and the like. On placing the conductive medium within the cell bottom, a thermoplastic sealant 22 is applied across the exposed surfaces of the conductive medium.

Bus bar 12 is embedded in the conductive medium 20 in a manner such that it is preferably recessed into cell bottom 10. Alternatively, the bus bar need not be included in the recess or the recess can be eliminated and replaced with a projection or other irregularity in a position generally parallel to the direction of the bus bar. In many instances, only a single bus bar is utilized in the cell bottom. Equally good results are also obtained with a single bus bar wherein a crossed projection and/or recess arrangement is provided in the cell bottom corresponding to a matching projection and/or recess in the conductive medium.

The preferred height or depth of the irregularities and the width thereof are factors ascertainable, depending on the particular cell bottom design. Thus, depending on the strength of the conductive medium at the cell operating temperature, coupled with the stresses imposed thereon, the combination of the recess depth and width is preferably that suificient to eliminate deformation of the conductive metal and/or the irregularity in the cell bottom where they are joined in tongue and groove fashion. Preferably, the irregularity projection and/or recess varies from about 10 to about 60 percent of the average depth of the conductive medium. The width of the irregularity can also be varied depending on the number used, the length thereof and the size of the conductive medium. In general, the width may range from about 0.5 to about 20 percent of the width of the conductive medium. The most preferred dimensions can be readily determined empirically by those skilled in the art.

The anode anchorage system of the present invention is suited for use in many diiferent types of electrolytic cells. It is particularly useful in cells which utilize carbon or graphite electrodes as the anode. Such uses include electrolytic cells such as chlor-alkali cells, alkali-metal chlorate cells, hydrochloric acid cells and numerous other similar type electrolytic cells.

As previously noted, the anchorage system of the present invention is particularly suited for use in chloralkali cells such as those producing chlorine, caustic soda and hydrogen. Cells of this type utilize a diaphragm between the anode blades and the cathode fingers thereof. These diaphragms are known to the art as deposited or applied diaphragms. The diaphragm utilized is a fluid permeable type composed of materials such as asbestos and synthetic fibers such as after-chlorinated polyvinyl chloride, polyvinylidene chloride, Teflon, polypropylene, and the like. In addition to chlor-alkali cells which electrolyze alkali-metal [chlorides such as sodium chloride, other alkali-metal chlorides can also be readily electrolyzed in the same cells. Such other alkali-metal chlorides include postassium chloride, lithium chloride, rubidium chloride and cesium chloride.

The importance of the present invention is particularly emphasized in electrolytic cells of high electrical capacity. With large chlor-alkali cells, for instance, such as those of 60,000 amperes and higher current capacities, the length of the anode blades is generally increased substantially over lower capacity electrolytic cells, such as those of 30,000 amperes or less. Small movements of the anode anchorage medium are magnified so as to greatly deflect the projecting ends of the anode blades. The importance of careful alignment and the maintaining of such alignment during cell operation, which is usually at a temperature substantially higher than the original aligning temperature, is of utmost importance for eflicient cell operation.

While there have been described various embodiments of the present invention, the apparatuses described are not intended to be understood as limiting the scope of the invention. It is realized that changes therein are possible and it is further intended that each element recited in any of the following claims is to be understood as referring to all equivalent elements for accomplishing substantially the same results in substantially the same or equivalent manner. It is intended to cover the invention broadly in whatever form its principles may be utilized.

What is claimed is:

1. A method for stabilizing the position of anodes and anode bus bars in an electrolytic !Cll which comprises constructing as a unit assembly the anodes and at least one anode bus bar in an anchorage means comprising a conductive medium having one surface thereof shaped to conform to a preformed irregularity of the bottom of said electrolytic cell, said irregularity of said cell bottom and conductive medium being a matching projection and recess wherein said irregularity is positioned transversely to the direction of the bus bar in said conductive medium, and positioning said unit assembly in said cell bottom.

2. The method of claim 1 wherein the anode blades are positioned parallel with respect to the direction of the bus bar in the conductive medium.

3. The method of claim 1 'Wherein the anode blades are positioned substantially transverse with respect to the direction of the bus bar in the conductive medium.

4. The method of claim 1 wherein the irregularity in said cell bottom is a plurality of projections.

5. The method of claim 1 wherein the irregularity in said cell bottom is a tongue and groove projection and recess passing through the center of gravity of said conductive medium.

6. The method of claim 1 wherein the bus bar is at least partially embedded in said conductive medium, wherein the conductive medium has a projection thereon corresponding to said bus bar and wherein said cell bottom has a recess therein corresponding to said conductive medium projection.

7. The method of claim 6 wherein the cell bottom is constructed of concrete and wherein the irregularity therein is a projection and wherein the conductive medium is of lead having a recess therein corresponding to the projection in said cell bottom.

8. The method of claim 7 wherein the recess is in the concrete cell bottom and wherein the projection is in the conductive medium.

9. The method of claim 1 wherein the sidewalls of said projection and recess are nearly vertical thereby forming a relatively sharp corner having an angle of to 120 degrees with the horizontal.

10. The method of claim 9 wherein said angle is of 90.5 to degrees with the horizontal.

References Cited 0 JOHN H. MACK, Primary Examiner.

D. R. JORDAN, Assistant Examiner.

U.S. Cl. X.R. 204-279, 286

Claims

1. A METHOD FOR STABILIZING THE POSITION OF ANODES AND ANODE BUS BARS IN AN ELECTROLYTIC CELL WHICH COMPRISES CONSTRUCTING AS A UNIT ASSEMBLY THE ANODES AND AT LEAST ONE ANODE BUS BAR IN AN ANCHORAGE MEANS COMPRISING A CONDUCTIVE MEDIUM HAVING ONE SURFACE THEREOF SHAPED TO CONFORM TO A PREFORMED IRREGULARITY OF THE BOTTOM OF SAID ELECTROLYTIC CELL, SAID IRREGULARITY OF SAID CELL BOTTOM AND CONDUCTIVE MEDIUM BEING A MATCHING PROJECTION AND RECESS WHEREIN SAID IRREGULARITY IS POSITIONED TRANSVERSELY TO THE DIRECTION OF THE BUS BAR IN SAID CONDUCTIVE MEDIUM, AND POSITIONING SAID UNIT ASSEMBLY IN SAID CELL BOTTOM.