US1855351A - Curtain for electrolytic cells employing fused baths - Google Patents

Description

R. M. HUNTER April 26, 1932.

CURTAIN FOR ELECTROLYTIC CELLS EMPLOYING FUSED BATHS Filed July 14, 1928 3 Sheets-Sheet l RF Y m0 E q m M w a Fw w v J V//////////////Z Ap 1932- R. M. HUNTER 1,855,351

CURTAIN FOR ELECTROLYTIC CELLS EMPLOYING FUSED BATHS Filed July 14, 1928 5 Sheets-Sheet 2 I N VEN TOR.

A TTORNEYS April 26, 1932. R. M. HUNTER 1,855,351

CURTAIN FOR ELECTROLYTIC CELLS EMPLOYING FUSED BATHS Filed Jul y 14, 1928 s Sheets-Sheet 5 I N VEN TOR.

A TTORNEY6.

Patented Apr. 26, 1932 UNITED s'rATEs PATENT OFFICE RALPH m. HUNTER, or MIDLAND, MICHIGAN, ASSIGNOR TO THE now, CHEMICAL com- PANY, or mnmnn, mcnreau, A conrom'mon or MICHIGAN CURTAIN non EIILECTROLYTIC CELLS EMPLOYING FUSED BATES Application ma J'u1y 14, 1928. Serial No. 292,679.

The present invention relates to the art of electrolysis of a fused bath of electrolyte cap able of formin when congealed, an insulating medium. gpecific instances of such electrolytes are-fused caustic alkalies and fused alkali and alkalineearth halides.

In the art of electrolysis of fusedelectrolytes, it is generally necessary or desirable to provide or establish an insulating curtain between the cathode and the anode which will divide the electrolyte into two communicating portions, i. e., the catholyte and the anolyte respectively.- A convenient method heretofore used for establishing such a curtain has comprised the installationin the bath of a plurality of interconnected metal tubes or pipes placed one above another through which a cooling agent has been caused to flow and absorb heat from the bath and cause a substantial coatingof congealed bath to form thereon. By carrying the cooling to a point Where coalescing o f the coating on the adjacent cooling pipes occurs, a continuous curtain having suitable insulating properties and not readily destructible as compared with curtains of structural materials such as ceramics and the like is established." The present invention constitutes an improvement on the above described type of curtain.

It has been customary to install such cooling elements in the form of coils either of worm type or connected with headers, the flow of the cooling fluid-being parallel in adjacent tubes. i v

I have found in the practical use of such cooled pipe coil curtains in the electrolysis of fused baths such as, forin'stance, magnesium chloride, (MgCl that if the cooling agent, such as air, the passed throughthe superim posed pipes inthesame direction, i. e., in parallel flow, thecurtain formed will be of variable thickness, being thickest at the point of entrance of the air and thinnest at thepoint ofexit.

i I have found that this variation 'inthickness constitutes an obstacle or difficulty in the operation of suchcells, particularly of large units, Where the surface of the curtain is extensive and variations iii-thickness may become. pronounced, resulting in unnecessary and obstructive thickness upon the well cooled portions of the coils in order to obtain the minimum necessary thickness of curtain upon the less cooled portions.

I have found that, by connecting the coils to the source of coolingfluid in such a manner that the cooling medium may be passed through them individually and separately in counter flow relation as to adjacent pipes of the system or coil, the cooling action is more evenly distributed and a great improvement in the character of the curtain results. That is, its thickness is more nearly uniform and is more readily controlled, it being possible to obtain the desirable thickness practically over the entire curtain area, thus avoiding further the difficulty which formerly arose from over-thick and under-thick curtains when the cooling was done by parallel flow of the cooling agent in adjacent coils.

I have found further that an economy of cooling fiuid results from such manner of Working which in large cell units becomes of appreciable value.

To the accomplishment of the foregoing and related ends, the invention, then, consists of themethod and means hereinafter fully described and particularly pointed out in the claims, the annexed drawings and the following description setting forth in detail certain means and method for carrying out the invention, such disclosed means and method illustrating, however, but severalof various ways in which the principle of the invention may be used.

In saidannexed drawings Figul is a plan view and Fig. 2 a cross sectionalview of a cell employing a single central anode and equipped with my improved curtain. Fig. 3 is a plan view and Fig. having a plurality of anodes arranged in horseshoe formation and also fitted with my improved curtain. Fig. is a partial cross section view of the curtain to enlarged scale on line VV of Fig. 1. Referring to Figs. 1 and 2 .the electrolyte container 1 which may be a metal pot or kettle preferably set in a heating chamber 2 is provided with electrical connection ,3 of

4 a cross sectional view of a similar-cell polarity to make the pot 1 the cathode. An anode, 4, usually of carbon or graphitized carbon, is suspended from above at the center of the pot dipping into the electrolyte therein, the approximate level of which is indicated by the broken line L. Electrical connection 7 determines the use of l as the anode.

In the type of cell illustrated in Figs. 1 and 2 an inverted trough 8 is used for the purpose of providing a gathering zone or area for light metal cathode product which is trapped thereunder and may be led off or removed in various ways as may be desired. Such a metal trough 8 will also act as cathode if electrically connected to the pot 1.

To form the curtain, I preferably install a plurality of ring shaped coils 9-9, 10-10', 1111', 1212, superimposed one above the other. The number is not essential but will vary with the construction and size of the cell to which the curtain is applied. These coils may be assembled together with clamping ban s or otherwise and will be preferably supported by fingers 13 projected from the lower edge of the inverted trough 8. Cooling fluid, such as air, is caused to How through these pipes by being introducedin separate streams at alternate ends of the superimposed coils, the flow being in opposite directions in adjacent coils. For instance, the fluid may be'introduced at 9 and taken off at 9', introduced at 10 and taken off at 10, introduced at 11 and taken off at 11'. introduced at 12 and taken off at 12. In this way adjacent coils are provided with independent counter current cooling and there is formed a substanwould, therefore,

tially even coating of congealed electrolyte as a result of the so distributed cooling effect. This coating, forming the curtain, is shown more clearly in Fig. 5, which is a partial cross section to increased scale, through the curtain as at V-V in Fig. l, the superimposed coils being shown at 9, 10, 11 and 12, respectively, suspended upon the finger 13 projecting from the collecting trough 8 and having congealed about them the curtain 16 of solidified salt.

Such a curtain, as is well-known, provides a convenient, economical and effective insulating screen separating the anolyte from the catholyte. It also, in the present instance, covers the exposed surface of the collecting trough 8, thereby preventing the formation of cathode product thereon which would not be gathered under Said collecting trough and c lost.

Referring now to Figs. 3 and 4, the cathode pot 17 contains the electrolyte, and 18 to 31 inclusive, are units of a plurality of anodes suspended above in horseshoe formation and dipping into the electrolyte, the level of which is indicated by the broken line L. The cathode shown is provided with an inner ring 34 constituting a secondary cathode and collecting well 36 for cathode product such those explained,

as a light metal. An inverted collecting trough 35 around the rim of the pot serves to collect the light cathode product forming on the inner surface of the pot proper. The secondary cathode ring member 34 is also provided with a collecting trough 41 venting through ports 42 into the central well 36. The inverted collecting trough 35 may be connected by a suitable conduit, not shown, with the inner well 36 made by'the ring member 3a which latter may be provided with a cover 37 and this inner well 3G may thereby be made the central collecting area for the said light metal cathode product, such for instance, as metallic magnesium produced when such a cell is used to .electrolyze fused MgCI In this type of cell, which is more fully described in a co-pending application by L.

E. \Vard and It. M. Hunter, Serial No. 210,-

785, filed August 5, 1927, a neutral zone 38 is provided between the ends of the horseshoe ring of anodes and for this cell I provide two cooled curtains 39 and 40, respectivelylocated within and without the anode ring and covering the surface of the collect ing troughs facing the anolyte.

The curtains are here illustrated as comprised each of four superimposed ring shaped coils in horseshoe form. the inlet and outlet ends of which are taken into and out of the cell through the neutral zone 38 or closely adjacent thereto so that the ends of the inner coil tubes of the curtain 39 will form acontinuation thereof 39a limiting the area of. the neutral zone 38 and dividing said neutral zone from the adjacent anode compartment and anolyte. The tubes comprising the core of the curtain will be cooled by the circulation of separate currents of cooling fluid, such as air, therethrough. it being understood that the circulation will be in opposite directions in adjacent tubes of each curtain. This method of distributing the cooling efiect is the essence of my invention rather than the precise and detailed arrangement of the curtain itself with reference to the other structural members of the assembled cell. The flow of the cooling fluid is indicated by the arrows from which it will be seen that an even distribution of cooling effect throughout the general curtain area is obtained, re-

sulting in the formation thereon of a congealed electrolyte of substantially uniform thickness over the general'area of the curtain, enabling further the formation not only of a satisfactory curtain of more uniform thickness but with the use of less cooling fluid and less congealed bath than would have been the case were this circulation of the cooling fluid in directions parallel in adjacent tubes.

Other modes of applying the principle of my invention may be employed instead of change being made as regards the means and the steps herein disclosed, provided those stated by any of the following claims or their equivalent be employed.

I therefore particularly point out and dis- 5 tinctly claim as my invention 1. In a cooling element for congealing a fused electrolytic cell bath into a solid mass about the said element, the combination of a plurality of single run tubular cooling elements arranged in serial juxtaposition, and means to separately supply a fluid cooling agent to each said run to pass therethrough but once and in counter-direction in ad acent runs to thereby distribute the cooling effeet through the cooling element.

2. A cooling curtain for a fused bath electrolytic cell, comprising a plurality of parallel conduits beneath the surface-level of the bath, and means for flowing separate cooling currents counter-currently in adjacent conduits.

3. In fused bath electrolysis with a cool ing curtain, distributing the cooling effect of a fluid cooling agent throughout, an assembly of a plurality of single adjacent runs of tubular elements employed to congeal a solid mass out of a fused electrolytic cell bath by passing the cooling fluid initially and separately in divided flow through the plurality of runs'in counter-current relation in adjacent runs thereof.

4. In electrolysis with a fused bath and a cooling curtain, uniformizing the temperature abstraction under the level of the surface of the bath by passing separate currents of enclosed cooling-media streams counter-currently in closely ad'acent runs.

Signed this 25th day 0 June, 1928.

RALPH M. HUNTER. 4o

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