US3235479A

US3235479A - Electrolytic cell

Info

Publication number: US3235479A
Application number: US89942A
Authority: US
Inventors: Szechtman Joshua
Original assignee: Chlormetals Inc
Current assignee: Chlormetals Inc
Priority date: 1961-02-17
Filing date: 1961-02-17
Publication date: 1966-02-15
Anticipated expiration: 1983-02-15

Description

Feb. 15, 1966 .1. szEcHTMAN 3,235,479

ELECTROLYTIC CELL Filed Feb. 17, 1961 N 'CB es w l\ Q5 f l \O y." w la l m ,r \o fj Q N N. QQ \0` l'u E I\\` s Lrg ia N N M w S\ \o INVEN TOR. Q JOSHUA SZECHTMAN ATTR/VEY 3,235,479 ELECTRULYTIC CELL Joshua tlzechtman, Byrarn, Conn., assigner to Chlormetals lirczrporated, New York, N.Y., a corporation of e aware Filed Feb. 17, 1961, Ser. No. 89,942 i Claims. (Cl. 20d-243) This application is a continuation-in-part of my application Serial No. 699,979, led December 2, 1957, now Patent No. 3,104,213, issued September 17, 1963, and of my application Serial No. 22,160, i'iled April 14, 1960, now abandoned.

This invention is concerned With electrolytic cells of the type employed for the decomposition of salts, such as alkali metal chlorides and alkaline earth meal chlorides, and is more particularly concerned with a cover construction for such cells which is etfective to cooperate with the cell body to insure against the infiltration of air from the ambient atmosphere into the cell.

Electrolytic cells of various types are known for the electrolysis of alkali metal salts and alkaline earth metal salts but one of the problems that has plagued the users of such cells for many years has been the tendency of air to leak into the cell. The oxygen contained in such air tends to accelerate the consumption of the anodes, which are generally formed from graphite, and to have an adverse effect upon the reaction `generally, and this situation is particularly serious in the case of the electrolysis of molten salts, which is necessarily carried out at elevated temperatures.

In some cells in use for the electrolysis of salts, no material effort is made to keep out the air and the presence of the air is considered a necessary, if undesired, consequence of the operation. In other cells, particularly horizontal cells of the type in which the electrolyte is in the form of a water solution, e.g. a sodium chloride brine, a cover is provided in an effort to keep out as much air as possible. However, even with the best of the prior cover structures, some air tends to infiltrate around the edges of the cover and also through the apertures which are provided for reception of the anode stems, which extend upwardly above the cover so that they can be suitably connected to a source of positive electrolytic current. Efforts have been made to reduce the quantity of air which tends to infiltrate into such cells, particularly around the stems of the anodes, but none of the prior proposals has been entirely satisfactory and this problem, which is a major problem in the case of the electrolysis of molten salts, has remained generally unsolved.

lt is, accordingly, an object of the present invention to provide a cell construction which involves a cover which effectively solves the foregoing problems and prevents the inltration of air into the cell even when the cell is operated at elevated temperatures with a molten electrolyte.

It is a further object of the invention to provide a cell cover construction by means of which the cell can be hermetically sealed and positive electrolytic current can be supplied to the anodes without the need for the elonggated anode stem and cooperating cover aperture constructions heretofore employed.

ln accordance with the invention, there is provided an electrolytic cell cover which is formed from a material which will conduct electricity, more specifically graphite,

ited States Patent O ice and the anodes are electrically connected to the cover without passing through it. The anodes may be supported from the cover by means of stems which are connected to the cover by direct attachment to its lower side or the anodes may be directly connected to the cover, the lower surface of the graphite cover may itself serve as the anode. The anode stems are in electrically conducting relationship with the cover and with the anodes so that when electrolytic eurent is fed to the cover, it passes directly through the anode stems to the anodes. The cover, in addition, cooperates with the cell body by means of a hydraulic seal which, in the case of a cell for use in the electrolysis of a molten salt, eg. molten sodium chloride, employs a metal which is liquid at electrolysis temperatures, c g. lead. The cell body is, at the same time, formed with a circumferentially-extending channel containing lead, and the cover is provided with a cooperating circumferentiallyextending flange which is received in the channel and is at least partially immersed in the liquid contained in the channel, the cover and cell body being at all times electrically insulated from each other.

It is a feature of the cover construction of this invention that the infiltration of air into the cell through the cover itself or through the joint between the cover and the Cell body is completely prevented, so that a hermetically-sealed electrolytic cell is provided and it is possible to carry out electrolysis without the adverse effects of the presence of oxygen in the electrolysis chamber, both with respect to the operation of the process itself and with respect to the consumption of the graphite anodes.

Other objects and features of this invention will be apparent from the following detailed description of an illustrative embodiment thereof and from the accompanying drawing wherein,

FIG. 1 is a longitudinal cross-sectional view of an electrolytic cell cover and an associated cell body embodying features of the present invention, as seen generally along the line ll--il of FIG. 2; and

FIG. 2 is a transverse sectional view of the cell shown in FIG. 1, taken generally along the line 2-2 of FIG. l.

Referring to the drawing, the cell body 12 of the cell 10 is suitably formed from metal and is supported upon an insulating support 1.4i, indicated in the drawing as refractory blocks or bricks, but it will be understood that any other convenient insulating base may be employed. As seen in FIG. l, the cell 10 defines a sole surface 15 upon which the liquid cathode 16, e.g. molten lead, is adapted to rest and to ow from left to right. Thus, the elongated cell body 12 is formed with an elongated channel of which the sole 15 is the bottom and which provides the electrolysis chamber 17. The sole 15 may be horizontal or it may slope slightly toward the right. The slope of the sole may vary but a slope of 1 or less is preferred. Since the cell is adapted to operate at elevated temperatures for the electrolysis of molten salts, e.g. temperatures of 810 to 850 C. which are suitable for the electrolysis of molten sodium chloride, any convenient means for heating the cell body and maintaining it at an elevated temperature may be employed. Particularly effective, however, for cells intended for the electrolysis of molten salts is the heating means shown in the drawing wherein the cell body is formed with a plurality of longitudinally-extending conduits 20 which form a closed circuit with a heater 22 and a pump 24. These conduits are suitably filled with molten lead which is maintained at the desired temperature by the heater 22 and is then circulated through the cell body by means of the pump 24. Actually, the electrolysis reaction is exothermic but the heating means is provided in order to bring the cell to operating temperature when operation is begun and to minimize heat loss during operation so that the desired operating temperature is always maintained.

Closing the cell is a cover 30 which extends completely across the cell body 12 and also extends from one end of the cell body to the other. This cover is formed from an electrically-conductive material and, most suitably, it is formed from graphite. As seen in FIGS. 1 and 2, the cell body 12 is formed with a circumferentially-extending channel 34 which extends continuously around the side and end walls of the body 12. Channel 34 is adapted to be lled with a fluid which is liquid at cell-operating temperatures and, most advantageously in the case of a cell adapted to be used for the electrolysis of molten salts, this fluid is lead and the channel 34 communicates by means of suitable conduits 36 with the circuit which includes the conduits 2t), the heater 22 and the pump 24. As seen in FIG. l, the molten lead circuit is suitably provided with a branch 38 through which the molten lead from the circuit may be withdrawn when the cell is out of operation in order to drain the conduits and through which molten lead may be introduced when the cell is being started up, branch 38 suitably being controlled by a valve 40. Depending from cover 30 into the chanel 34 is a circumferential flange 42 which is embedded in the cover 3) and which extends downwardly a sucient distance that its lower end will be immersed in the liquid 46 contained in the channel 34 in order to form a hydraulic seal. The flange 42 is suitably formed from a material which is a non-conductor of electricity c.g. a rigid refractory such as silicon carbide with ceramic bond.

The cover 30 directly supports the anodes 50 and such support is effected by means of anode stems 52. While in my co-pending application Serial No. 699,979 I show a conduit extending vertically through the cover for the removal of chlorine generated in the cell during electrolysis, most advantageously, as shown in FIG. 1, provision is made for withdrawing chlorine from the cell through the anodes and through the cover in the manner described in my co-pending application, Serial No. 22,160, filed April 14, 1960. Thus, as seen in FIGS. 1 and 2, the stems 52 are received in

slots

53 and 54 formed in the cover 30 and in the anode blocks S0, respectively, so that these parts are removably interconnected, or the stems may be removably connected only with the cover or only with the anodes, or all parts may be integrally interconnected. The power connections are indicated diagrammatically at 56 and 57, but it will be understood that any conventional means may be employed to attach the power conductors, and a particularly suitable system is shown in my co-pending application Serial No. 699,979. As described in my co-pending application Serial No. 699,979 and, as seen in FIGS. 1 and 2, a continuous refractory lining 60 is provided along the entire interior walls of the electrolysis chamber 17 of the cell, the lining 60 serving as an electrical insulator and also as a protector of the walls against chemical attack by the chemical contents Within the chamber. Since the cover must be electrically insulated from the body of the cell, because it is a conductor of electrolysis current, an insulating sheet 61 cornpletely overliesvthe top edges of the walls of the cell body 12, being interrupted only by the flange 42. The exterior of the cell is suitably provided with a tight heat-insulating covering 63 which extends across the top and side surfaces of the cover 30 and over the exterior walls of the cell body 12. The weight of the cover upon the cell body together with the insulating sheet 61 is generally sufficient, but if a tighter relationship is desired, a plurality of spaced-apart clamps (not shown) can be used to secure the cover to the cell body. Such clamps must, of course, be insulated from the cell body in order to prevent electrical contact between cover 30 and cell body 12. Furthermore, the exterior insulating cover effects not only heat-insulation but electrical-insulation as well.

Referring again to the anodes, it will be seen that the anode blocks 50, the anode stems or supports 52, and the cover 30 are provided with inter-communicating apertures and channels or passageways through which the evolved gas, which will hereafter be referred to as chlorine, is led from the site of evolution to a point exteriorly of the cell with minimum contact with contaminating surfaces. Thus, as shown in FIGS. 1 and 2, each anode block 50 is formed with an interior chamber 65 and a plurality of apertures or ducts 66 extend downwardly from this chamber to the bottom active face of the anode. The cover 3) is also formed with an interior chamber 67 and this chamber communicates with the chamber 65 in the anodes by means of the bore 68 in each anode stem or support 52. The connections between the stems and the cover and between the stems and the anode blocks are suitably gas tight. The cover 30 is formed with an extension conduit 69 which communicates with the cover chamber 67 and to which may be connected an outlet conduit (not shown) to lead the clorine away from the cell by any convenient means. Suitably the connection with the extension 69 provides electrical insulation between the conduit and the extension and any portion of the chlorine-removal system projecting exteriorly of the cover is suitably insulated electrically. An auxiliary outlet channel 70, which may be stoppered to prevent ingress of air, may be provided in cover 30 to permit venting of the electrolysis chamber above the level of the electrolyte.

The manner in which the electrolyte and the liquid cathode are introduced into and removed from the cell form no part of the present invention and the manner described in my co-pending application Serial No. 699,979 is particularly suitable, especially since it insures against entrance of air or oxygen with the electrolyte and the cathode into the electrolysis chamber. Thus, as seen in FIG. 1, the liquid cathode, e.g. molten lead, and the electrolyte, e.g. molten alkali metal chloride or alkaline earth metal chlorine, are introduced at the left-hand end of the cell body, the molten lead suitably being introduced through a conduit and the electrolyte being introduced through a conduit 82. The conduit 82 extends upwardly into the electrolysis chamber 17 and discharges through a selfregulating float valve, indicated diagrammatically at 84, of the type described in FIG. 5 of my co-pending application Serial No. 699,979. At the right-hand end of the cell body 10, there is provided a transverse wall 88 extending between the side walls of the cell body and engaged by the cover 30 to dene the downstream end of the electrolysis chamber proper and to define an end compartment 89. The cell bottom slopes downwardly in the vicinity of the transverse wall in order to form a well 90 into which the wall can extend to form a liquid seal against passage of the lighter electrolyte into the end compartment as long `as the liquid level of the cathode is maintained.

The end compartment 89 is formed with an outlet opening 92. A tall cyindrical sleeve 94 is provide with apertures 95 and with a nose 96 normally disposed in outlet opening 92, the cathode level being maintained by the apertures 95 through which the alloy formed in the cell is discharged. The upper end of the sleeve 94 extends into a recess in cover 30 and it may be lifted, e.g. by electromagnetic means, to permit emptying of the cathode from the cell, as described in my co-pending application Serial No. 699,979. Suitable electrical insulation (not shown) prevents contact between sleeve 94 and cover 30.

When the cell shown in FIGS. 1 and 2 is placed in operation chlorine evolved in the gaps between the opposed surfaces of the anodes and the cathode, e.g. molten lead, immediately flows into the apertures 66 in the anode blocks and then, by subsequent passage through the anode stems and the cover 30, reaches the outlet conduit 69 and such chlorine can be conducted away without contact with contaminating surfaces and without contact with the liberated metal.

It is possible that a negligible portion of the liberated chlorine will not enter the apertures in the anodes and will escape into the general supply of the electrolyte. This chlorine will accumulate in the electrolysis chamber above the electrolyte. This accumulated chlorine can then be drawn off, either continuously or intermittently, through a separate exit, such as the outlet channel '70 shown in FIG. 1. This chlorine will be contaminated because of contact with surfaces within the cell, but it will not be mixed with the main body of pure chlorine, and if the quantity should warrant, it can be separately purified in any conventional manner.

As described in my co-pending application Serial No. 699,979, the temperatures employed are those suflicient to maintain the cathode and the salt in molten form, the cell suitably being heated and the salt and the cathode, e.g. lead, are suitably placed in molten form prior to introduction into the cell. Current is supplied to effect electrolysis in conventional manner.

There is thus provided a cell cover of integral construction devoid of anode-receiving apertures used in prior art cell covers and provided with means for hermeticallysealed relationship with the cell body.

The salt is fused outside of the cell and can be introduced into the hermetically-sealed cell without the introduction of any air therewith. Thus the salt is "suitably melted in a unit outside of the cell and is introduced into the cell as a liquid, free from air and moisture. The elimination of air and of moisture within the apparatus of this invention prevents anode consumption in the electrolysis chamber and also prevents explosions from chemical combination of hydrogen with chlorine and from chemical combination of oxygen with sodium, all disadvantages in prior art electrolytic cells. The air and water free operation of this apparatus permits the employment of a high current 'density compared to the current densities conventionally employed. Thus this in- Vention relates to a cell which will produce many times f more end-products,re.g. chlorine and alkali metal, compared to the conventional cell of substantially the same physical size.

It will also be understod that various changes and modifications may be made in the embodiments of the invention described and illustrated without departing from the scope of the invention as denedin the appended claims, and it is intended, therefore, that all matter contained in the foregoing description and in the drawing shall be interpreted as illustrative only and not as limitative of the invention.

I claim:

1. In an electrolytic cell of the type suitable for the decomposition of salt in the presence of a cathode and at least one anode, a cell body for containing said salt and said cathode, and a cover overlying said body, said cell body being formed with a circumferentially-extending recess7 a plurality of conduit means for supplying a molten liquid to said recess, pump means for forcing said molten liquid into said conduit means, and said cover being formed with a circumferentially-extending depending ange receivable in said recess whereby to cooperate with the molten liquid in saidrecess to provide a hydraulic seal for the contents of said cell body, said cover cooperating with said cell body to confine said recess land the molten liquid supplied thereto by said supplying means, said cover being constructed ofa material which will conduct electricity and said anode being electrically but 'removably connected to said cover by direct attachment to the underside thereof, said cover being provided with means to receive eletrolytic current directly, whereby said current will pass to the anode by passage directly through the cover itself and thence to the associated anode.

2. An electrolytic cell of the type suitable for the decomposition of a salt in the presence of a cathode and at least one anode and having a cell body with surrounding walls, a cover constructed to extend across and wholly enclose said walls and to cooperate with said walls to provide an air-tight covering for said cell body, and said cover being formed of a material which will conduct electricity and said anode being electrically but removably connected to the underside only of said cover with no portion of said anode extending above said cover, whereby said anode does not extend through said cover but may be removed and replaced without destruction of said cover, said cover being provided with means to receive electrolytic current directly, whereby said current will pass to the anode by passage directly through the cover itself and thence to the associated anode, said cell body being formed with a circumferentially-extending recess, a plurality of conduit means for supplying a molten liquid to said recess, pump means for forcing said molten liquid into said conduit means, and said cover being formed with a circumferentially-extending depending nange receivable in said recess whereby to cooperate with the molten liquid in said recess to provide a hydraulic seal for the contents of said cell body, said cover cooperating with said cell body to confine said recess and the molten liquid supplied thereto by said supplying means.

3. In an electrolytic cell of the type suitable for the decomposition of salt in the presence .of a cathode and at least one anode, a cell body for containing said salt and said cathode, and a cover overlying said body, said cell body being formed with a circumferentially-extending recess, means for supplying a molten liquid to said recess, and said cover being formed with a circumferentially-extending depending flange receivable in said recess whereby to cooperate with the molten liquid in said -recess to provide a hydraulic seal for the contents of said cell body, said cover cooperating with said cell body to confine said recess and the molten liquid supplied thereto by said supplying means, said cover being constructed of a material fwhich vwill conduct electricity and said anode being electrically but removably connected to said cover by direct attachment to the underside thereof, said cover being provided with means to receive electrolytic current directly, whereby said current will pass to the anode by passage directly through the cover itself and thence to the associated anode,l said supplying means comprising a plurality of conduits in said cell body communicating with said recess, heating means for said molten liquid, and pumping means for pumping molten liquid to said-recess.

4. An electrolytic cell of the type suitable for the decomposition of a salt in the presence of a cathode and at least one anode and having a cell body with surrounding walls, a cover constructed to extend across and wholly enclose said walls and to cooperate with said walls to provide an air-tight covering for said cell body, and said cover being formed of a material which will conduct electricity and said anode being electrically but removably connected to the underside only of said cover with no portion of said anode extending above said cover, whereby said anode does not extend through said cover but may be removed and replaced without destruction of said cover, said cover being provided with means to receive current directly, whereby said current will pass to the anode by passage directly through the cover itself and thence to the associated anode, said cell body being formed with a circurnferentially-extending recess, means for supplying a molten liquid to said recess, and said cover being formed with a circumferentially-extending depending tlange receivable in said recess whereby to cooperate with the molten liquid in said recess to provide a hydraulic seal for the contents of said cell body, said cover cooperating with said cell body to conne said recess and the molten liquid supplied thereto by said supplying means, said supplying means comprising a plurality of conduits in said cell body communicating with said recess, heating means for said molten liquid, and pumping means for pumping molten liquid to said recess.

References Cited bythe Examiner UNITED STATES PATENTS 596,458 12/1897 Inglis 204245 862,783 8/1907 Allen 204-220 884,124 4/1908 Blackmore 204-266 1,087,937 2/1914 Ellis 204-266 Shaw 2041-266 Williams 204-266 Hulin 204-243 Richardson 204-250 Ravenscroft 204--250 Carter et al. 204-250 Oliver 2041-250 WINSTON A. DOUGLAS, Primary Examiner.

10 -TOSEPH REBOLD, JOHN R. SPECK, Examiners.

Claims

1. IN AN ELECTROLYTIC CELL OF THE TYPE SUITABLE FOR THE DECOMPOSITION OF SALT IN THE PRESENCE OF A CATHODE AND AT LEAST ONE ANODE, A CELL BODY FOR CONTAINING SAID SALT AND SAID CATHODE, AND A COVER OVERLYING SAID BODY, SAID CELL BODY BEING FORMED WITH A CIRCUMFERENTIALLY-EXTENDING RECESS, A PLURALITY OF CONDIUT MEANS FOR SUPPLYING A MOLTEN LIQUID TO SAID RECESS, PUMP MEANS FOR FORCING SAID MOLTEN LIQUID INTO SAID CONDUIT MEANS, AND SAID COVER BEING FORMED WITH A CIRCUMFERENTIALLY-EXTENDING DEPENDING FLANGE RECEIVABLE IN SAID RECESS WHEREBY TO COOPERATE WITH THE MOLTEN LIQUID IN SAID RECESS TO PROVIDE A HYDRAULIC SEAL FOR THE CONTENTS OF SAID CELL BODY, SAID COVER COOPERATING WITH SAID CELL BODY TO CONFINE SAID RECESS AND THE MOLTEN LIQUID SUPPLIED THERETO BY SAID SUPPLYING MEANS, SAID COVER BEING CONSTRUCTED OF A MATERIAL WHICH WILL CONDUCT ELECTRICITY AND SAID ANODE BEING ELECTRICALLY BUT REMOVABLE CONNECTED TO SAID COVER BY DIRECT ATTACHMENT TO THE UNDERSIDE THEREOF, SAID COVER BEING PROVIDED WITH MEANS TO RECEIVE ELETROLYTIC CURRENT DIRECTLY, WHEREBY SAID CURRENT WILL PASS TO THE ANODE BY PASSAGE DIRECTLY THROUGH THE COVER ITSELF AND THENCE TO THE ASSOCIATED ANODE.