US2502888A

US2502888A - Electrolytic cell

Info

Publication number: US2502888A
Application number: US695625A
Authority: US
Inventors: Ravenscroft Arthur Wesley
Original assignee: Imperial Chemical Industries Ltd
Current assignee: Imperial Chemical Industries Ltd
Priority date: 1945-09-17
Filing date: 1946-09-09
Publication date: 1950-04-04
Anticipated expiration: 1967-04-04
Also published as: BE467975A; ES174984A1; NL66218C; CH255094A; GB627967A; DE810275C; FR933694A

Description

April 4, 1950 A. w. RAvENscRoFT ELECTROLYTIC CELL Filed Sept. 9, 1946 w MM mm Z W V mm T/ W W M Patented Apr. 4, 1950 ELECTROLYTIC CELL Arthur Wesley Ravenscroft, Frodsham, England,

assignor to Imperial Chemical Industries Limited, a corporation of Great Britain Application September 9, 1946, Serial No. 695,625 In Great Britain September 17, 1945 8 Claims.

This invention relates to improvements in electrolytic cells, and more particularly to cells having a liquid electrode, for example mercury or an amalgam.

Various electrolytic cells are known having as one electrode a sheet of mercury or amalgam flowing on a flat surface slightly inclned to the horizontal, the second electrode being formed of plates or blocks of solid material arranged a short distance above, and having their undersurface substantially parallel to, the surface of the liquid electrode. Such a cell, for example, is one for the electrolysis of brine in which the cathode is a continuous sheet of mercury flowlng over a slightly inclined plane surface forming the bottom of a trough-shaped vessel, and the anode is formed of a number of plates of graphite immersed in the brine and suspended by graphite rods from one or more lids forming the cover of the cell. In operation the under surfaces of the graphite plates Wear away and the electrical resistance of the cell thus increases. It is very desirable to have means for adusting the height of the electrodes to compensate for this wear; such means should however, be capable of operation without the fear of short-circuiting by lowering the electrodes too far.

According to the present invention, in an electrolytic cell of the liquid electrode type having a trough-shaped base carrying a fiowing liquid electrode, a cover on the base and a solid electrode rigidly supported in the cell by said cover with its undersurface disposed a short distance above the liquid electrode and substantially parallel thereto, there is provided adjustable means for sealing the cover to the base comprising a skirt depending from the cover, a channel on the base adapted to receive the skirt, said channel containing a thermoplastic substance resistant to gases evolved in the electrolysis, and heating means for melting the thermoplastic substance in the channel.

Suitable thermoplastic materials which may be used include normally solid chlorinated naphthalene containing, for example, 45% to 55% of chlorine. It is also possible to use other materials such as a solid chlorinated paraifin Wax, alone, or mixed with chlorinated naphthalene. Mixtures of chlorinated paraffin Wax With minor amounts of chlorinated rubber may also be used. In some cases it may also be possible to use natural or Synthetic hydrocarbon waxes. The heating means may conveniently be a steam-pipe located in the bottom of the channel, or against one side of it, through which steam can be passed when it is required to soften or melt the thermoplastic substance. Preferably the heating means is in good thermal contact with the bottom of the skirt. It may be for instance a steam pipe welded or brazed to the bottom edge of the skirt. Alternatively, the heating means may be a suitably insulated electric Wire through which a current can be passed.

In one form of the invention the lid of the cell is provided with laterally projecting lugs each having a thread which also engages a threaded bolt, While the outer walls of the cell are provided beneath the lugs With a ledge on which the bases of the bolts rest. In the thickness of the Wall of the cell is a channel with its mouth at the top edge of the cell and extending the whole of the way round it. Instead of making the channel in the thickness of the wall a stout strip of metal may be welded in position to the outside or inside Wall of the cell so as to make the necessary channel. At the bottom of this channel a steam pipe lies, the ends of the steam pipe passing through the wall at one end of the cell and connected, one to a supply of steam, and the other to an outlet for waste steam and condensate. The channel contains a normally solid chlorinated naphthalene. The lid of the cell carrying the graphite anode blocks has a skirt which dips into the chlorinated naphthalene in the channel. The cell is also provided in the customary manner with means for fiowing mercury and brine through the cell, means for supplying current to the electrodes, and with means for withdrawing chlorine generated in the process.

In another form of the invention the lid of the cell is provided With lugs which are supported by pillar bolts by means of which the Vertical movement of the lid can be controlled. A peripheral channel on the outside of the Wall of the base is adapted to take the skirt which depends from the edge of the lid. A horizontal pipe brazed to the lower edge of the skirt runs round the cell and is provided with Vertical inlet and outlet connections passing upwards through the lid. The channel contains chlorinated naphthalene, having a chlorine content of 45% to by weight, in sufficient quantity to make a seal between the skirt and the base.

In using the apparatus the chlorinated naphthalene in the channel is first melted by passing steam through the steam pipe, and then the lid is fixed in position so that the anodes are the correct distance from the bottom of the cell and the skirt is dipping into the molten chlorinated naphthalene in the channel. The chlorinated asoasse 'naphthalene is then allowed to set; if desired the setting may be accelerated by passing cold water through the steam pipe. The cell is then ready for use. With continued operation the lower surfaces of the anode blocks become worn and it will be necessary to lower the lid slightly in order to bring them nearer the mercury surface. For this purpose the electrolysis is stopped for a short time, steam is passed through the steam pipe to render the chlorinated naphthalene molten and the lid is then lowered by using the screw adjusting means provided, so as to bring the lower surface of the anodes nearer to the liquid electrode. In some cases where the thermoplastic substance tends to be brittle at ordinary temperatures, as is the case with chlorinated naphthalene containing 50% to 55% chlorine, -it is advantageous to maintain the seal at a temperature relatively close to its setting point, for example between C. and C. below its setting point, while the cell is in use. This can be done by means of the heating means provided to melt the thermoplastic substance.

The depth of the channel is chosen according to the length and slope of the cell, and the distance through which it is intended to lower the cover during the life of a given set of anodes. For example, if the brine inlet end of the cell is :r inches higher than the brine exit end when the cell is set at its normal working slope, and if it is intended to allow y inches of anode wear before fitting a new set of anodes, the depth of molten chlorinated naphthalene required to make a seal will usually be at least +y inches at the exit end and at least y inches at the inlet end. In order to reduce the quantity of sealing material required, the channel and the skirt may be so constructed that the bottom of the channel and the lower edge of the skirt are horizontal when the flat surface carrying the liquid electrode is in its normal Working position, i. e. slightly inclined to the horizontal. Alternatively if the slop-e of the cell can be readily varied, the bottom of the channel, and the lower edge of the shirt may be parallel to the surface carrying the liquid electrode. In such a case the cell is brought into a horizontal position before melting the thermoplastic sealing material and adjusting the height of the cover, and the sealing material is then allowed to solidify before the slope is restored to the normal working value.

This invention can be applied to the normal type of electrolytic cell in which the anodes are immersed in 'the ilowing brine and the chlorine is collected from the gas space above the electrolyte level. It is, however, of especial value as applied to cells for the use of high speed brine as described in copending application Serial No. 695,804 of Hirsh and Carter, filed Sept. 9, 1946, which process normally requires the maintenance of elevated pressures within the cell during its operation; one cell to which the invention may be applied is described in 'copending application Serial No. 695,623 of Carter and Ravenscroft, filed Sept. 9, 1946. By this invention a cell is obtained embodying a seal which will withstand the necessary elevated pressures perfectly satisfactorily, but which can be repeatedly made and broken when desired.

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

Figure 1 is a Vertical section of one form of an 4 electrolytic cell incorporating the novel sealing means of this invention.

Figure 2 is a Vertical section of another form of electrolytic cell according to this invention.

Figures 3 and 4 are partial Vertical sections of other forms of electrolytic cells of this invention showing modifications in heating elements associated with the structures.

Figure 1 is a Vertical section of one form of cell according to this invention which comprises a trough-shaped lower portion or base having a smooth surfaced bottom I on which the liquid electrode fiows, double side walls forming a channel 2 containing a thermoplastic sealing material 3 and having a pipe 8, located at the bottom of .the channel, through which steam or cold water can be passed when the sealing material is to be melted or solidiied. Over the base portion there is a cover 4 of steel lined with ebonite or other chlorine resistant material, having a shirt 1 which projects below the surface of the sealing material '3. The height of the cover relative to the base is adjustable by means of the threaded bolts 6 each engaging with the threaded hole of a lug 5 on either side of the lid and bearing on a corresponding lug on the outer wall of the base. The cover 4 carries the carbon anode blocks 9 which are supported by the carbon rods IO which pass through holes 'in the cover. In the drawing the joint between the cover 4 and the rods ll) is sealed by a 'sealing composition H, but any other suitable method of .rendering the joint gas tight may be employed. The cover is provided with one or more chlorine oiftakes |2. The cell is provided with appropriate means (not shown) for supplying mercury and fresh electrolyte to the cell, for removing amalgam and spent electrolyte and for supplying electric current to the electrodes.

Figure 2 is 'a Vertical section of another form of cell according to this invention in which the trough shaped base portion comprises a smooth bottom surface I, and a channel 2 carried by the Vertical walls co-ntaining a thermoplastic sealing material 3, and is supported by the girders |3 so that its length is slightly inclined to the horizontal. The cover 4 .supports the carbon anode block 9 by means of the carbon rods IO, the dimensions of the block 9 being such that as little space as possible is left between the top of block 9 and the cover 4, and between the sides of the block and the inner wall of the base. The cover 4 is provided with lugs 5 carried by pillar-bolts 5 on either side of the cell which permit adjustment of the Vertical 'position of the vcover relative to the base portion. The cover is also provided with the skirt l the lower edge of which carries a steam pipe 8 brazed to the skirt. Chlorine oiftake pipes (not shown) are provided in the cover at points over the gap between successive anode blocks. The cover and base are suitably made of steel, those parts which are liable to corrosion by the electrolyte being lined with ebonite. The ebonite lining of the skirt 1 is carried to a line below the surface of the sealing material 3 but above the level of the steam pipe 8.

Figure 3 -is a partial, Vertical section of another form of the electrolytic cells of this invention in which the heating element is a steam pipe 8 which .is attached to the outside of the channel 2 by means vof welding 15.

Figure 4 illustrates still another form of construction in accordance 'with this invention, in which the heating element for anelting the thermoplastic sealing material '3 consists of electrical heating wires M, carried upon the inner bottom of the channel 2.

I claim:

1. An electrolytic cell of the liquid electrode type comprising a trough-shaped base carrying a flowing mercury cathode, a cover on the base, means for adjusting the height of the cover relative to the base, a solid electrode rigidly supported in the cell by the cover with its undersurface disposed a short distance above the mercury cathode and substantially parallel thereto, adjustable sealing means for sealing the cover to the base comprising in combination, a channel in said base peripherally enclosing the mercury cathode, a Vertical skirt depending from said cover into said channel, a normally solid thermoplastic substance resistant to gases evolved by operation of the cell in said channel, and a heating element integral with said cell in thermal contact with said thermoplastic substance for melting said thermoplastic substance.

2. A cell as claimed in claim 1, in which the thermoplastic substance is a normally solid chlorinated naphthalene.

3. A cell as claimed in claim 1, in which said heating element is an element co-extensive With the channel and held in good thermal contact with the lower part of one of theV sides of said channel.

4. A cell as claimed in claim 1, in which the heating element is a steam pipe located in the channel.

5. A cell as claimed in claim 1, in which said heating element is an elongated electrical heater carried inside the channel upon the bottom thereof.

6. A cell as claimed in claim 1, in which the heating element is a steam pipe co-extensive with the skirt, carried upon the lower edge of said skirt.

7. An electrolytic cell of the liquid electrode type comprising a trough-shaped base carrying a fiowing mercury cathode, a cover on the base, means for adjusting the height of the cover relative to the base, a solid electrode rigidly supported in the cell by the cover with its undersurface disposed a short distance above the mercury cathode and substantially parallel thereto, adjustable sealing means to seal the cover to the base comprising in combination, a channel in said base peripherally enclosing the mercury cathode, a normally solid chlorinated naphthalene containing from 45-55% chlorine by weight in said channel, a Vertical skirt depending from said cover into said channel, the bottom of said channel and the lower edge of said skirt being parallel and horizontal when the cell is in working position, and a heating element located inside said channel for melting said chlorinated naphthalene.

8. A cell as claimed in claim '7, wherein the base is supported upon means for bringing the cell to a horizontal position to adjust the seal between the cover and the base.

ARTHUR WESLEY RAVENSCROFT.

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

UNITED STATES PATENTS Number Name Date '748,985 Rink Jan. 5, 1904 1,127,936 Snyder Feb. 9, 1915 1363228 Buck Dec. 28, 1920 2,104,678 Sorensen Jan. 4, 1938 2,328,665 Munson Sept. 7, 1943 FOREIGN PATENTS Number Country Date 173,520 Germany July 26, 1906