US2542990A - Electrolytic cell - Google Patents

Description

Feb. 27, 1951 c. CARTER ET AL 2,542,990

ELECTROLYTIC CELL Filed Sept. 9, 1946 2 Sheets-Sheet 1 I nvenlors and Charles Carter y Arthur WIRavenscroft MM/ PW tZltomey-S vllflllllllp C. CARTER ET AL ELECTROLYTIC CELL Feb. 27, 1951 2 Sheets-Sheet 2 7 Filed Sept. 9, 1946 M M i y m. 3 mm F v M\/ 7 M &

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Inventors 3 Z a r A m X C H W r. na Z 06mm Patented Feb. 27, 1951 UNITED STATES TENT OFFICE ELECTROLYTIC CELL Application September 9, 1946, Serial No. 695,623 In Great Britain September 17, 1945 Claims.

This invention relates to improvements in electrolyticcells, and more particularly to cells having a liquid electrode such as mercury.

Various electrolytic cells are known having as one electrode a sheet of mercury flowing on the smooth bottom of a trough-shaped vessel slightly inclined to the horizontal, the second electrode being formed of plates or blocks of solid material, usually graphite or another form of carbon, arranged a short distance above the surface of the liquid electrode, and having their undersurfaces substantially parallel thereto. Such liquid electrode cells may be used, for example, for the electrolysis of brine. In copending application of Carter and Glass Serial No. 695,622, filed September 9, 1946, there is described such a cell having the solid electrode plates or blocks attached to the lid, and having means by which the height of the electrodes relative to the liquid electrode can be adjusted very readily and accurately without interrupting the electrolysis, which comprises screw adjusting means for raisin and lowering the lid adapted to be operated from outside the cell, and sealing means at the join of the lid with the fixed part of the cell allowing relative movement of the one part with respect to the other. In one form of the invention the lid of the cell was provided with a skirt, and the lower trough-shaped part of the cell was provided with a channel adapted to receive the skirt, in which channel was a resilient deformable rubber packing contacting both the skirt and the wall of the channel. In use the rubber packing was covered by the mercury cathode which thus formed aseal.

We have now found that a very convenient electrolytic cell having a flowing liquid electrode allowing accurate adjustment of the inter-electrode distance without dismantling is one comprising a flat base portion without upwardly extending side walls, a cover portion carrying a solid electrode and forming a cap over the base portion on which the liquid electrode flows, and a liquid tight seal between the cover and the base capable of being repeatedly made and broken, and means for adjusting the height of the cover portion relative to the base portion.

According to the present invention therefore an electrolytic cell of the liquid electrode type comprises a flat-topped base, without upwardly extending walls, on which the liquid electrode flows, a solid electrode supported above the base, a cover having a skirt enclosing said base and said solid electrode, a liquid-tight seal adapted to be made and broken between the skirt and the periphery of the base, and means for adjusting the height of the cover relative to the base.

Advantageously the liquid tight seal is formed by a deformable resilient packing contacting the skirt and the periphery of the base below the level of the liquid electrode. Advantageously also the resilient packing is disposed in a groove extending around the peripheral faces of the base. Preferably the packing is formed of an endless inflatable rubber tube capable of being filled with fluid under pressure to create the seal and of being evacuated to break the seal.

In one form of the invention the cell comprises a long fiat steel base plate supported by girder members or otherwise so that its length is slightly inclined to the horizontal. Around the bottom edges of the plate metal keeper strips are bolted, and the adjacent outer edges of the plate and of the metal strips are bevelled so as to form a groove extending right around the sides, or peripheral faces, of the base plate. An endless rubber tube having a projecting fin is disposed in the groove with the fin clamped between the base plate and the keeper strips, and the tube is joined to a connection by which the interior of the tube can be either evacuated or filled with water under pressure. The cover portion of the cell comprises a flat steel plate with a skirt, that is, a downwardly projecting vertical portion extending around the edges, which extends downwards below the level of the base plate. The cover portion thus forms a cap which is a loose fit over the base when the rubber tube is deflated, but which fits sufiiciently closely for the gap between the two to be sealed when the rubber tube is filled with water under pressure through the tube bearing on the inner surface of the skirt and on the bevelled faces of the base plate and metal strip. The cover is lined with non-conducting material resistant to chlorine such as ebonite, and is supported by a number of pillars at the sides of the cell bearing on lugs projecting laterally. The height of the cover can be adjusted by screw adjusting means either located at the lugs, or forming part of each pillar. The anode of the cell is formed of a number of carbon or graphite blocks within the cover and attached thereto by carbon rods which pass through it in a gastight manner and which also provide the means for supplying current to the anodes. The cell is also provided with means for flowing mercury over the base portion, for flowing brine through the space between the mercury and the anode, and for Withdrawing gases generated by the electrolysis.

With such an apparatus the spacing between the anode blocks and the mercury surface, or, what is the equivalent, between the anode blocks and the base plate, can be adjusted within very fine limits by defiating the rubber tube when the cell is emptied and operating the screw adjusting means forming part of the support for the cover. After the adjustment the rubber tube can again be filled with water under pressure, thus making the seal again, and the cell is ready for re-use. The adjustment can thus be made without dismantling the Whole cell 'or separately moving each of the rods supporting the anodes. The anodes can fill the whole of the space above the electrolyte, as described and claimed in the patent of Hirsh and Carter No. 2,503,337 dated April 11, 1950, suitable provision being made for withdrawing gaseous chlorine at intervals along the path of the electrolyte, and the cell can then be used for the electrolysis of brine using a high brine speed as described in copending application of Hirsh and Carter Serial No. 695,804, filed Sept. 9, 19%.

This has not been possible in the types of cell and the rubber tube is filled with water under pressure to form the seal. The cell i then put into operation and is worked until voltage measurements indicate that the inter-electrode gap has become too great for satisfactory use. During the whole of this time mercury will fill the space above therubber tube seal and between the edge of the base plate and the skirt, thus protecting the rubber from the action of the brine and of the chlorine so that it will retain its pliability and resilience. When the inter-electrode gap has become too great for satisfactory use, the electrolysis is stopped, the cell emptied of brine and mercury, and the seal between the skirt of the lid and the base plate is broken by evacuatinglthe rubber tube. The necessary alterations to the screw adjusting means are then made to reduce the gap to its proper value, and the seal is remade by again filling the rubber tube with water. The electrolysis can then be recommenced. By making use of the flexibility of the rubber tube, par.- ticularly if a relatively wide gap is left between the two portions of the cell and if a relatively thick tube is used, it is even possible to make slight adjustments to the inter-electrode gap without breaking the seal, and thus without interrupting the electrolysis.

Various modifications of the invention are possible. Thus the carbon rods supporting the solid electrodes may take the form of tubes which can be used as the gas ofitakes for removing the electrolysis gas from the interelectrode space.

Also, instead of fitting the screw adjusting means viding a, particularly sniooth and gradual movement of the lid as a whole.

Again, the base portion of the cell may consist of a fiat topped block or table of concrete, with a groove of semicircular or triangular section to hold the resilient packing. Again, instead of providing the groove in the base portion it may be provided in the inner surface of the skirt of the lid, the base portion being then provided with a skirt to allow the seal to be made even with the base portion in its highest position. However, it is preferable for the groove to be in the base portion, since movement of the one part with respect to the other does not then increase the quantity of mercury retained in the cell at any time, nor is the head of mercury above the seal increased when the base portion is relatively close to the top of the cell.

It is also possible to omit the groove altogether, the deformable packing being then fastened to a skirt around the base portion, or to the skirt of the cap, for example by means of a fin projecting from the deformable packing.

The upper parts of the carbon rods carrying the solid electrodes may be provided with a cover, for example of copper or brass, as described and claimed in copending application of Ravenscroft, Serial No. 695,624, filed Sept. 9, 1946, to prevent exudation or seepage of electrolyte through pores in the carbon.

In any of the variations of the invention in which a rubber sealing tube is used cold water may be circulated through it continually so as to keep it cool as well as form the seal; the life of the tube can then be extended considerably, even though the cell is operated at a considerably elevated temperature.

The invention is further'illustrated by the accompanying diagrammatic drawings, not to scale, in which like numbers represent like parts.

Figure l is a vertical section of one form of the electrolytic cells of this invention, in which the base portion is a fiat-topped table of concrete, and the sealing means consists of an endless band of sponge rubber.

Figure 2 is a vertical section of another form of our cells in which the base portion is a flat steel'plate and the sealing means consists of an endless inflatable rubber tube.

Figure 3 is a vertical section of another specific embodiment of our cells.

Figure l is a section of the inflatable tube used as sealing means in the cells shown in Figures 2 and 3.

Figure 5 shows the method of attaching the inflatable tube to the base portion in Figures 2 and 3.

Figure 6 is a partial, sectional View showing a side elevation of the cells shown in Figures 2 and 3, and illustrating the manner in which the tube and valve for inflating the inflatable tube are arranged with respect to the remainder of the apparatus.

Figure '7 is a partial view showing a side elevational section of a modified form of the cells of this invention, in which the deformable, resilient packing between the skirt and the plate-like base of the cell is carried in a groove in the skirt.

In the drawings, 5 is a fiat base portion carrying a flowing mercury cathode 2. Above the mercury cathode flows aqueous electrolyte 3. The cells are provided with appropriate means (not shown) for supplying mercury and fresh electhe electrolysis, and for supplying electric current to the electrodes.

Each cell has a cover 4 of steel lined with ebonite or other insulating material resistant to the products of electrolysis, carrying a number of solid carbon anode blocks 5 (one of which is shown) each depending from carbon rods 5 (as in Figures 1 and 2), or from carbon tubes 5a (as in Figure 3), which pass through openings in the cover 4 and through Which current is supplied to the anode by means shown only in Figure 2. In the drawings the joint between the cover 5 and the anode supports 5 or to is sealed by a sealing composition 1 or by a rubber ring la, but any other suitable method of making the joint gastight may be employed. The cover t is provided with a downwardly projecting skirt 3, also lined with ebonite or other suitable material, which extends downwards below the level of the mercury cathode 2. From each side of the cover project a number of horizontal lugs 9 (one on each side being visible in Figures 1 to 3). Each lug is supported by a pillar-bolt l I having a stand ll), collar [2 and locknut [3, which controls the height of the cover 4 relative to the base I.

Referring now more particularly to Figure 1, the concrete base portion l is provided with a peripheral groove Id of semicircular cross-section in which is positioned an endless band A5 of sponge rubber having an impermeable outer skin. The band l5 in the unstretched state is slightly less in total length than the peripheral groove I4 and it is therefore held in the groove by the elasticity of the sponge rubber. The clearance between the inner, ebonite lined face of the skirt 8 and the side of the concrete base I is such that a mercury-tight seal is made between them by the band I5. A space running the full length of the cell between the anode 5 and cover 4 is freely accessible to the anode gases which are led out of the cell by one or more gas outlet tubes 16. In putting such a cell into operation the cover l carrying the anodes 5 is adjusted by means of the pillar bolts I I so that the under surface of the anodes is at the desired distance above the flat top of the base I. The mercury circulation and then the electrolyte circulation are started, and the current is switched on. As electrolysis proceeds the under surface of the anode 5 wears away. In order to maintain the gap between the anode 5 and the mercury layer 2 at its initial value the cover is lowered at intervals by the required amount of rotation of the pillar bolts H. The resilience of the band ensures that the seal will be maintained during the process of adjustment.

Referring now to Figure 2, the anodes 5 are fitted closely against the lining of the cover 4, leaving no longitudinal channel in the cell, ac cessible to electrolyte or anode gases, above the level of the interelectrod space. Thus the electrolyte- 3 is forced to flow along the cell through the interelectrode space. The mercury electrode 2 flows on a flat steel plate I supported on girders I! and provided with a peripheral rubber tube 15a. capable of being filled with Water under pressure to the make the seal between the base plate I and the skirt 8 and of being evacuated to break the seal. The rubber tube is shown in section in Figure 4 and the arrangements for attaching it to the under side of the base plate are shown in,

Figure 5. It will be seen that the tube 15a is triangular in section and is provided with a fin I!) attached to one angle. The tube is in the form of a continuous ring which requires to be stretched by a small amount to enable it to sit in the groove formed by the bevelled edges of the base plate I and the keeper strip 25 (Figure 5). The fin i9 is gripped between the base plate and the keeper strips which are held in position by countersunk bolts 21 passing through holes punched in the iin. A thin rubber ring 222 makes a mercury-tight seal between the head of the bolt and the base plate. The tube E50, has a valve (not shown) which passes through a seating in the keeper strip and carries a connection whereby water pressure or suction may be applied to the tube.

Each anode block 5 in Figure 2 is supported by two carbon rods 6, which pass through holes in the cover 4. The part of the carbon rods which projects out of the cell is covered by a brass cap, screwed on to the rod 5 and pressing a hard washer against the rubber ring la, The brass caps carry the electrical connections for the anode, and are fitted with a grease nipple so that grease or oil under pressure may be forced against the upper surface of the rods 5 to prevent seepage of electrolyte through the rods. Narrow vertical spaces extending across the cell between adjacent anode blocks to permit escape of anode gas from the interelectrode space communicate with independent gas offtakes it, which are fitted with vertical extension tubes (not shown), of a height at least equivalent to the head of brine in the cell below the gas offtake, to convey the anode gass to a common header.

Referring now to Figure 3, the sealing means and base plate are the same as for the cell of Figure 2, and as shown in more detail in Figures 4 and 5. Between the anodes 5 and the cell cover 5 there is provided a layer 23 of material resistant to the anode gases, preferably of a resilient nature such as sponge rubber coated with neoprene, to fill any gap between 5 and 5 which would otherwise be liable to permit longitudinal flow of electrolyte through the cell above the interelectrode space. The anode blocks 5 are supported in the cover by hollow carbon tubes 5a, two for each block, which pass through the cover and the layer of resilient material 23 into the block 5, and terminate at the top I8 of a vertical slot cut in the block 5 and extending across the whole width of the anode to allow escape of gas from the interelectrode space. The tubes 6a are provided with electrical connections (not shown) and with vertical extension tubes (not shown) leading the anode gas from the separate anode blocks to a common header. The cells shown in Figures 2 and 3 are adapted for high speed flow of electrolyte and permit the electrolyte to be introduced into the cells at superatmospheric pressure. They are therefore eminently suitable for the electrolysis of brine by the process described and claimed in copending application of Hirsh and Carter, Serial No. 595,804, filed September 9, 1946. The height above the base plate to which the passages leading oif chlorine, e. g., tubes it in Figure 2 and tubes 5a in Figure 3, must extend will be determined by the head of brineat the cell inlet. This head will, in turn, depend on the size of the interelectrode gap and the linear velocity of the brine. With satisfactory operation under high speed brine conditions, the head of brine corresponds to about inch per foot length of cell. It is convenient to carry all the passages to the sam height, although it will be appreciated that the height of the passages at the end by which the brine leaves will not need to be as great as at the other end.

Figure 6 illustrates the means for inflating the inflatable tube la. Thus, at one point along the bottom periphery of the inflatable tube 15 there is molded as a integral part of the tube a T-piece 24 and this T-piece passes through a hole 25 provided therefor in the keeper strip 20. The free end of the T-piece 24 is attached to a metal tube 26 provided with a valve 21. The opposite end of this metal tub 26 connects to a source of fluid pressure (not shown), such as a water line. By opening the valve 27, water under pressure can be introduced into the inflatable tube I5a after which the valve 21 is closed and the inflated tube retained under pressure so as to keep the cell sealed.

In the modification shown in Figure '7, the resilient packing material I5 is carried in an indentation or groove 23 in the skirt 8.

We claim:

1. An electrolytic cell of the liquid electrode type comprising a base having a flat top on which the liquid electrode flows and dependent peripheral vertical sides, a cover having a dependent vertical skirt enclosing said base, a solid electrode enclosed within the cover carried by the cover above said base, a liquid-tight seal adapted to be made and broken, comprising a deformable, resilient packing in the form of an inflated, endless rubber tube positioned between the dependent skirt and the peripheral vertical sides of the base, and means for adjusting the height of said cover relative to the base.

2. A cell as claimed in claim 1, wherein said inflated, endless rubber tube is positioned in a groove extending around the peripheral vertical sides of the base.

3. A cell as claimed in claim 1, wherein said inflated, endless rubber tube is positioned in a groove on the inner face of said dependent skirt.

4. An electrolytic cell according to claim 1, in which said solid electrode is of such size relative to said cover that no space exists between the top and sides of said electrodes and the inside portions of said cover.

5. An electrolytic cell according to claim 1, in which all of the vertical and horizontal space between said solid electrode and said cover is filled with a resilient composition, whereby longitudinal flow of electrolyte through the cell is restricted entirely to the interelectrode space.

CHAS. CARTER. ARTHUR WESLEY RAVENSCROFT.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 498,707 Crane May 30, 1893 953,744 Gaara Apr. 5, 1910 1,570,467 Ewan Jan. 19, 1926 2,212,588 Csanyi Aug. 27, 1940 2,328,665 Munson Sept. '7, 1943 2,334,354 Richardson Nov. 16, 1943

Claims (1)

1. AN ELECTROLYTIC CELL OF THE LIQUID ELECTRODE TYPE COMPRISING A BASE HAVING A FLAT TOP ON WHICH THE LIQUID ELECTRODE FLOWS AND DEPENDENT PERIPHERAL VERTICAL SIDES, A COVER HAVING A DEPENDENT VERTICAL SKIRT ENCLOSING SAID BASE, A SOLID ELECTRODE ENCLOSED WITHIN THE COVER CARRIED BY THE TO BE MADE AND BROKEN, COMPRISING A DEFORMABLE, RESILIENT PACKING IN THE FORM OF AN INFLATED, ENDLESS RUBBER TUBE POSITIONED BETWEEN THE DEPENDENT SKIRT AND THE PERIPHERAL VERTICAL SIDES OF THE BASE, AND MEANS FOR ADJUSTING THE HEIGHT OF SAID COVER RELATIVE TO THE BASE.

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