US1863385A - Electrolytic apparatus - Google Patents

Description

June 14, 1932.

L. E. WARD ET AL ELECTROLYTIC APPARATUS Filed July 29, 1929 4 Sheets-Sheet 2 N t w INVENTORS ATTORNEY June 14, 1932. L. E. WARD ET AL ELECTROLYTIC APPARATUS Filed July 29, 1929 4 Sheets-Sheet 3 ENVENTORS In;

w ,1- a,w W BY KWIQ ATTORNEY June- 14, 1932.

I ELECTROLYTIC APPARATUS Filed July 29, 1929 4 Sheets-Sheet 4 INVENTORS D6144 ISA/2M4 *4 BY mm mm ATTORNEY L. E. WARD ET'AL ,363,385

Patented June 14, 1932 UNITED STATES PATENT orrlca LOUIS E. WARD AND RALPH M. HUNTER, F MIDLAND, MICHIGAN, ASSIGN OBS TO THE DOW CHEMICAL COHPAN Y, OF MIDLAND, MICHIGAN, A CORPORATION OF MICHIGAN ELECTROLYTIC APPARATUS Application filed July 29,

The present improvements, relating as indicated to electrolytic apparatus, have more particular regard to an electrolytic cell forproducing a fused metal li 'hterthan the fused electrolyte, such, for instance, as a cell for producing metallic magnesium from a molten saline bath containing magnesium chloride.

\Ve have disclosed in a copending patent application, Serial No. 210,785, now Patent 1,851,789, an electrolytic cell of the above character employing a pot of circular form and a plurality of anodes arranged in ring formation between the inner surface of the pot and the outer surface of an inner ring therein, said pot and inner ring acting as cathodes.

Among the desirable ends incident to the design of and the conduct of operations in apparatus of the character herein described may be mentioned the following, the proper provisions for which are essential.

The pot should be of steel orother electrically conducting metal suited also to retain and heat a fused bath of the character employed and to act as cathode. The anodes should be adjustable as to depth of immersion, and are to be made of graphitized carbon or other material suited to the introduction of the electric current and resistant to the anodic products of electrolysis. The path for the current through the bath should be as short and of as low ohmic resistance as permissible, giving due consideration to the requirement for separating anodicand cathodic products. The liberated metal and the gaseous anodic products should be effectively separated and separately disposed of. Proj vision should be made for applying heat for initial fusion of the bath, if desired, and in any event for maintaining fluidity during temporary cessation of electrolysis and for heat or temperature control. The metal libcrated will desirably be segregated in acoherent fluid mass of limited area accessible operations, large and workable manner 1a2s. serial No. 1,937.

for removal from the cell. It will be preferably protected from contact with the air to prevent oxidation. The gaseous anodic products will be drawn off as produced for disposal thereof as convenient or desirable and operation under suction for the removal of gaseous products has been found elfective in preventing escape of the gas into the 0perat-ing room. Minor repairs such as the replacement of refractory parts subject to erosion or breakage will preferably be made without interfering with the continuous operation of the cell and in an easy economical manner requiring a minimum of time for the actual operation. Inasmuch as there will be separated in the bath more or less solid basic material which settles out as a sludge, provision for withdrawal or dredging of same from the bath during operation is essential. A continuous feed of new bath 0011-. stituents in a manner to maintain the desired bath composition and level thereof is desirable. Economies in first cost of apparatus, first cost of buildings, operating costs, including labor, power, fuel and repairs must be provided for. A minimum of heat-radiatlng surface properly insulated is'desirable to conserve fuel and power. In large amperage capacity at low voltage per unit cell is desirable.

The object of the present invention is to provide an electrolytic apparatus better adapted to meet the ends above stated than heretofore available and tion to production on a very large scale, embodying novel features permitting such large scale application in a more economical, simple than has heretofore been possible.- Further objects will appear as the description roceeds.

To the accomplishment of the foregoing and related ends, the invention, then, consists of the meanshereinafter fully described and particularly pointed out in the claims, the

annexed drawings and the following descripor at both ends with tion setting forth in detail certain means for carrying out the invention, such disclosed means illustrating, however, but several of the various ways in which the principle of the invention may be used.

In said annexed drawings Fig. 1 is a vertical transverse section on the line 1-1 of Fig. 2 through an electrolytic cell embodying the features herein claimed. Fi .2isalongitudinal vertical section on the ine 22 of Fig. 1. Fig. 3 is a top plan view of the cell from which the anodes have been removed. Fig. 4 is a part longitudinal cross section on line 4-'4 of Fig. 3 showing the metal collecting well. Fig. 5 is an end elevation and Fig. 6 is a plan of the sleeve-type curtain shown in longitudinal cross section in Fi 1.

Referring now to the drawings The (athode cell pot 3 has a rectangular form in the plan and may be of cast steel or other suitable metal. The bottom of the pot may have a variet of shapes but will preferably have some orm of boat-shaped, V-shape'd or gutter;shaped bottom in which sediment is readily collected by subsidence and from which it may be dredged as .required. A double V-shaped bottom is shown in Fig. 1 but various modifications thereof will be apparent to those skilled in the art. The cell may be provided with a central partition 5 integral with the walls of the pot. The active cathode surfaces 6 of the pot walls and 7 of the partition, if employed, will preferably be parallel, substantially vertical and as close to ether as is feasible. If the double V-shaped ottom shown in Fig. 1 be used, the partition 5 may be integral with the bottom also, as shown, suitable passages or ports 8 being provided to permit the free passage of the electrolyte between the two similar compartments thus formed. The length of the pot 1 will vary with the size or capacity desired, e. g. with the number of and spacing of the anodes employed. The pot will further be provided preferably either at one end one or more opemngs into the bath from above such as shown at 14, hereinafter called dredging wells, adapted to the insertion of a dipper or like tool for scraping sediment from the bottom of the pot and removing it out of the bath. The pot will also be provided at one end or at either end with a metal collecting well shownat 13, such a well connected with the metal traps hereinafter described serving the active cathode surfaces in the cell and being adapted to receive and a gregate into a coherent mass floatin upon t e bath the metal flowing into the well from said traps.

Two rows of vertically disposed round anodes 10 depend in the bath from above in the form of cell illustrated in the drawings. They will be preferably supported by adjustable hangers adapted to permit varying the well 13.

depth of immersion in the bath and entire removal of any individual anode from the bath and its reinsertion therein in a convenient manner.

More than two rows of anodes may be employed, three such rows requiring a three compartment pot, that is, one having two partitions, such an arrangement, although feasible,involving a central row of anodes and the features auxiliary thereto in a less accessible position than is desirable in practice. Increase in capacity may better be attained by increasing the number of anodes in two parallel rows.

We provide inverted trough-shaped traps 11 along the upper limits of the active cathode surface 6 of the pot and like traps 12 along the active surface 7 of partition 5. Such troughs may be entirely or only partly below the bath level, beinv adapted to entrap, retain and forward the metal rising through the bath from the cathode surfaces to a collecting well 13 preferably located at an end of the pot. A cross trap 14a between partition and side walls of the pot connects with 11 and 12 to complete the encircling trap along the active cathode surfaces of the pot, including both side walls, end wall and the partition. A portion of the outer depending side of the trough 14a is removed at its junction with the collecting well 13 enablin the floating metal entrapped in the trougi to issue therefrom into said well. Such troughs or traps may be cast or otherwise fabricated integrally with the cell pot and/or partition therein as illustrated in Figs. 1 and 2 or they may consist of separate members disposed in similar manner relative to the cell pot and electrically connected therewith.

Two dredging wells 14 are shown in the drawings, one at either side of the collecting These are shown with covers in place in Figs. 3 and 2.

The collecting well 13 is shown in part cross section in Fig. 4, the trough side wall 14a therein being dotted to show that it is omitted in that part of the trough adjacent to the collecting well. Such well, like the dredging wells, will be preferably at the margin of one end of the pot and may occupy space between the dredging wells 14.

The bath level will preferably be held at or about that shown in Fig. 1. .The pot will also preferably be set within 'a furnace or equivalent setting 15 adapted to supply initial or control heat to the bath.

A brick superstructure 16 supports a plurality of sleeve-like refractory curtain members 17 preferably one for each anode employed.

Such curtain members, shown in longitudinal cross section in Fig. 1, transverse section in Fig. 2, end elevation in Fig. 5 and plan in Fig. 6, may be of general rectangular form in the plan, comprising a sleeve-like portion done at one or with flanges at one end, or other variation in surface contour, adapted to engage with relatively fixed members of the cell superstructure as supports for the curtain member, enabling the removal and replacement of said member at will Without disturbing other portions of the cell structure. However, other forms thereof adapted to be supported by or suspended from the cell superstructure may be used. The curtain members of whatever form serve to blanket those portions of the pot and trap surfaces from which metal liberated thereon would not directly enter the traps and thereby restrict the cathodic action of such surfaces to a minimum. They further serve to form a flue for the anodic ases and to deliver same into the anodic gas 0 ambers 19.

Not only are the removable and replaceable features of the types of curtain herein disclosed advantageous in permitting maintenance thereof without interruption of the cell operation, but in addition to such advantage the occasional removal of material accumulated in the space without the curtain is simplified, since removing or shifting such members of the curtain as will afi'ord access to the space to be cleaned is easily done.

A further advantage of the sectional type of curtain or of individual curtain members as disclosed herein arises from the fact that a small piece of refractory material such as we are enabled to employ in the manner disclosed may be more safely, quickly and uniformly brought to a desired temperature before insertion in the cell and the liability of breakage due to inequalities of temperature throughout the piece is much reduced as the size decreases.

Cover plates 18 complete the enclosure of the anodlc gas chamber 19 and outlets 20 may be provided therein and will be suitably connected with a duct or ducts under suc-.

tion for removal of the anode gas from the cell. Inlets such as shown at 30 may be provided in the covers through which the raw material containing magnesium chloride may be fed to the bath. Feeding will preferably by accomplished in a fairly continuous manner at rate controlled to maintain the bath at the desired level, and may be discontinued for a short time prior to the dredging operation in order to permit better settling out of solid matter from the bath after which feeding may be resumed. Such feeding may be more points as desired. A heat retaining and joint. sealing material, such as magnesia, may be applied to the covers 18, etc., as indicated at 33.

The metal collected in the traps is. indicated at 31 and that in the well 13 at 32. Electrical connections to the anodes may be by flexible cable or the like and that to the cell pot by means of suitable leads to the riser 24 condition. If

cast integrally with the pot, or by equivalent means.

Covers 21 will advisedly be applied over the dredging wells 14 to assist in retaining heat. A cover 22 will be likewise advisedly applied over the collecting well 13 for a similar purpose and to assist in excluding air from contact with the metal therein as well as to retain more or less effectively in the atmosphere above the metal the hydrogen which usually, in practice, accompanies the liberated metal reaching the well.

In the operation of our improved apparatus the cell pot will be charged with material for the bath, either in fused or solid in the solid condition the furnace heat will be controlled to fuse it and later to control the temperature thereof, electric current will be supplied in convenient manner. Anodic gases will be led away under suction together with air leaking into thecom artments 19 and the metal will automatical y be-caught in the traps 11 and 12 and forwarded to the collecting well 13. The metal may then be removed intermittently or continuously from the collecting wells as desired and dredging operations to remove sludge will be required. The removal of metal and sludge may be done without disturbing the operation of the cell except, as before mentioned, that it is desirable to suspend feeding electrolyte during the dredging operation. case of breakage, erosion or other damage to a curtain member, the anode involved may be lifted out, the proper cover-s18 removed, the damaged part lifted outhy means of a suitable tool and a new partilowered into position whereupon the anodeimay be returned to the bath followed by thereturn of the covers. This may all' liadone without interrupting the working of-the cell. Enough suction will be carried upofijtheducts connected with openings 20 to insure that the anodic gaseous products will not emerge into the room while the covers are removed but rather an excess of air will be drawn in through such openings.

. It will be seen that our invention provides an electrolytic apparatus capable of large scale working, e. g., employing currents in excess of 15,000 amperes per cell unit for which a voltage as low as 6 volts is sufficient. The voltage and amperage may be lowered or raised as desired to adjust the output relative to all charges including power, abor, upkeep and the like, at the most economical point. We find that the rectangular form of structure described has marked advantages over the circular type hereinbefore referred to, per unit floor space and building cost to be secured. We find the straight line arrangement of a plurality of anodes to be more ad-vv vantageous than the ring form arrangement,

enabling a higher capacity.

practiced intermittently as the positioning of the dredging well at the end of a straight boat-shaped sedimentation basin in the pot bottom and simplifies dredging operations. We find that the refractory superstructure of the cell in the rectangular form may be made up almost entirely of straight shapes avoiding the necessity for circular shapes required in the circular type of cell. buch straight forms of refractory shapes are cheaper in first cost, more easily laid and more readily maintained and repaired. We find further that the types of curtain herein disclosed made possible by the straight line arrangement are cheaply produced, easily set and adjusted, readily replaced and more easily maintained than vthe circular type, particu arly the circular curtain that is required along the inner side of a ring of anodes. Various shapes of curtain members may be employed, as hereinbefore stated. We find further that the straight line arrangement of a plurality of anodes permits enlarging thecapa'city of the cell to large size by adding anodes without increasing inactive plan area involving greater idle heat radiating surface, as is the case with the circular type which, if enlarged by increasing the diameter of the ring of anodes to accommodate more anodes, greatly increases the area of the enclosed well Without benefit and with coincident increase in heat loss areas. We find that the type of cell herein disclosed may be handled easily and economically as to'labor, fuel, upkeep and other costs and that a very superior grade of metal may be produced directly therein.

Other modes of applying the principle of our invention may be employed instead of the one explained, change eing made as rev ided the means stated by any of the following claims or the equivalent of such stated means be employed. 7

We therefore particularly point out and distinctly claim as our invention 1. In apparatus of the character described, the combination of a metal cathode pot having at least two substantially vertical and parallel opposed principal cathode surfaces, a. plurality of anodes depending therein between said cathode surfaces, a separate inverted trough-like collecting trap therein so related to the principal cathode surface as to entrap light metal rising from said surface through the bath, a collecting well for the light metal so entrapped, a dredging well and a curtain dipping in the bath between said anode and cathode surfaces.

2. In apparatus of the character described, the combination of a rectangular metal cathode pot having at least two compartments connectionsards the mechanism herein disclosed, pro-- separated by a cathode partition, said pot and partition having substantiall vertically disposed parallel opposed catho e surfaces, a plurality of anodes depending from above between said cathode surfaces, aninverted trough-like metal trap along the upper limits of the saidcathode surfaces adapted to env trap therein metal rising from said surfaces through the bath and a collecting well for said metal.

3. In apparatus of the character described, the combination of a rectangular metal cathode pot having at least two compartments separated by a cathode partition, said pot and partition having substantially vertically disposed parallel opposed cathode surfaces, a plurality of anodes depending from above between said cathode surfaces, an inverted trough-like metal trap along the upper limits of the said cathode surfaces adapted to entrap therein metal rising from said surfaces through the bath, a collectin wellfor said metal, and a curtain dipping 1n the bath between the said anode and cathode surfaces.

4. In apparatus of the character described, the combination of a metal cathode pot divided into two parallel compartments by a cathode partition therebetwcen, said partition and pot walls presenting substantially vertically disposed parallel principal cathode surfaces inopposed relation, a plurality of anodes depending from above between said cathode surfaces and arranged in two substantially straight rows, an inverted trough-like projection along the upper limits of the principal cathode surfaces adapted toentrap light metal rising therefrom through the bath, a collecting well for said lightmetal, adjacent an edge of the pot, and in communication with said trough-like projection, a i

dredging well adjacent an edge of the potadapted to permit insertion of a dredging tool and a curtain dipping in the bath between the anodes and cathodes to interpose resistance to the passage of current between said anodes and said projection.

.5. In apparatus for electrolyzing a. fused salt bath to produce a metal lighter than the electrolyte, the combination of a metallic vessel to contain such bath and forming the cathode, and an inverted metal collecting trough adjacent to the upper part of the active cathode surface of said vessel and electrically connected thereto.

6. In apparatus for electrolyzing a fused salt bath to produce a metal lighter than the electrolyte, the combination of a metallic vessel to contain such bath and forming the cathode, and an inverted trough-like flange along the upper part of the lateral wall of said vessel and adapted to entrap metal rising from the surface thereof.

7. In apparatus for electrolyzing a fusedsalt bath to produce a metal lighter than the electrolyte, the combination of a metallic vessel to contain such bath and formin the cathode, and an inverted trough-like ange along the upper part of the lateral wall of said vessel adapted to entrap metal rising from the surface thereof, and a metal collecting well within said vessel communicating with said metal trap and being adapted to receive and aggregate into a coherent floating mass the metal flowing thereinto from said trap.

8. In apparatus for electrolyzing 'a fused salt bath to produce a metal lighter than the electrolyte, the combination of a metallic vessel to contain such bath having at least two substantially vertical and parallel opposed walls to serve as principal cathode surfaces, and an inverted metal collecting trough adjacent to the upper part of said surfaces and electrically connected to said'vessel.

9. In apparatus for electrolyzing a fusedsalt bath to produce a metal lighterthan the electrolyte, the combination of a metallic vessel to contain such bath having at least two substantially vertical and parallel opposed walls to serve as principal cathode sur-* faces, and an inverted troughlike flange along the upper part of said surfaces adapted to entrap metal rising therefrom.

10. In apparatus for electrolyzing a fused salt bath to produce a metal lighter than the electrolyte, the combination of a metallic vessel to contain such bath having at least two substantially vertical and parallel opposed walls to serve as principal cathode surfaces, an inverted trough-like flange along the upper part of said surfaces adapted to entrap metal rising therefrom, and a metal collecting well within said vessel communicating with said inverted trough and being adapted to receive and aggregate into a coherent floating mass the metal flowing thereinto from said trough.

11. In apparatus for electrolyzing a fused salt bath to produce a metal lighter than the electrolyte, the combination of a-Hmetallic vessel to contain such bath having at least two substantially vertical and parallel opeating with osed walls to serve as principalcathode surbaces, a. plurality of anodes depending in said ath trough-like flange along theupper part-' ofs said surfaces adapted to entrap metal rising therefrom,

a metal collecting well communiwell and a' curtainof refractoryemateria dipping in the bath betweensaid anode and 12. In apparatus for electry afused salt bath, the combination of arectangula'r' metallic vessel to contain such bath dividedlengthwise by a partition into'two parallel compartments,

the side walls and partition thereof presenting substantially vertical parallel opposed cathode surfaces; a'plurality of anodes between said surfaces, an inverted .a'id inverted trough; dredginu depending in said bath between V said side walls and said partition in two parallel rows; an inverted trough-like flange along the upper part of said cathode surfaces adapted to entrap metal rising therefrom; a

metal collecting wellcentrally located at one a

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