US2648631A - Fused salt electrolysis cell - Google Patents

Description

J. V. CARLISLE FUSED SALT ELECTROLYSIS CELL Aug. 11, 1953 4 Sheets-Sheet 1 Filed July 15, 1950 INVENTOR.

JAMES V. CARLISLE BYWW 1953 J. v. CARLISLE 2,643,631

F USED SALT ELECTROLYSIS CELL Filed July 13, 1950 tqSIlGGbS-SIXGGT. 2

FIG. 3

INVENTOR.

JAMES V. CARLISLE Aug. 11; 1953 J. v. CARLISLE v F USED SALT ELECTROLYSIS CELL 4 Sheets-Sheet 5 Filed July 15, 1950 FIG. 5

FIG. 4

FIG. 8

FIG. 6

INVENTOR JAMES v. CARLISLE BY 2 2 Q P 4 Sheets-Sheet 4 J. V. CARLISLE FUSED SALT ELECTROLYSIS CELL FIG 9 Aug. 11, 1953 Filed July 15, 1950 INVENTOR.

JAMES v CARLISLE BYMW FIG.

FIG. IO

f atented Aug. 11, 1 953 FUSE-D SALTIELECTROLYSIS CELL James V. Carlisle, Baton Rouge, La., assignor to Ethyl Corporation, New York,

ration of Delaware N. Y., a =corpo- Application July 13,1950, Serial No. 173, 71

This invention relates to an electrolysis cell for the production of chlorine andsodium b'y the electrolysis of sodium chloride in a molten condition. More particularly, the invention relates to an improved anode assembly and cell bottom for cells of the Downs type.

The Downs type electrolysis cell (U. S. Patent 1,501,756) is characterized by a centrally positioned vertical graphite anode and a surrounding steel cathode of cylindrical shape. These electrodes define a narrow annular space within which the electrolysis occurs. A cylindrical diaphragm of wire screen is positioned within this space, concentric with the anode and cathode, for the purpose of preventing recombination of the sodium and chlorine molecules after their release at the cathode and anode, respectively.

As both the chlorine and sodium produced by electrolysis rise in the electrolyte, it is necessary to have a fairly complicated cover with means for separate collection of these products. Hence, the centrally positioned graphite anodes are normally connected to a source of electrical energy through the bottom of the cell. In the past, it has been the practice to build the cells with the anode actually projecting below the cell bottom. The bottom of the cell has previously been constructed by forming a bottom wall of refractory cement from the anode to the wall of the cell. lhe cement layer rested on a base plate containing a hole through which the anode projected.

While in general operable and satisfactory, the former cells, constructed as above described, are deficient in several respects. The anodes were fastened to a casting which in turn was bolted to a copper bus-bar. The bolting of the anode to a steel connector subjected the graphite to severe stresses. These joint conditions cause such severe stresses on the anode graphite that at times fractures occur, necessitating expensive replacement and rebuilding of the cell. Not only are the anodes subjected to severe mechanical stress, but the cells are prone to develop leaks at the joint between the cell bottom and the anode.

An object of the present invention is to provide a cell with an improved anode assembly. Another object is to provide a cell with improved and more lasting electrical connections to the anode. A further object is to provide an anode assembly which makes possible precise registration and vertical alignment of the anodes inassembly, while minimizing the amount of machining heretofore required. One more object is to Claims. (Cl. 204-243) make possible the use of round graphite electrode stock, thereby'achieving'large economies in the initial cost of materials of construction for the cell.

The invention, broadly speaking is a cell bottom and anode assembly comprising a liquid tight metal base pan and .one or more vertical anodes resting thereon, male and female means on the anode base and the base pan registering the anode in a horizontal plane and additional clamping means, attached to the" base pan, retaining the anode in vertical alignment. The base pan-is adapted to" carry the cell current which is transmitted to the anode through a body of low melting metal surrounding at least 'in part the portion ofthe anode within the vertical confines of the bjase pan. An impermeable membrane of refactory materialseals the metal parts of the assembly from contact with the fused electrolyte of the cell. In preferred forms of the invention, a metal plate rests on the base pan beneath the refractory membrane, and snugly surrounds the anode, except at points where the clamping means are provided. .Such plates insure that a small expansion space can be maintained above the low melting metal surrounding the anode base. 1

Numerous embodiments are possible as will appear hereafter. In the preferred embodiments, the means for providing horizontal registration is permissive of a limited movement of an anode in vertical planes about said registration point.

The invention will be more easily understood from the detailed description given hereafter and the accompanying drawings. Referring to the drawings: 1

Fig. 1 is a sectional elevation view of a Downs type cell incorporating an embodiment of the invention. Figure 2 is a cross sectional plan view of the bottomof the cell of Fig. 1. A cut away portion shows the construction details of the anode retaining means, below the final sealing membrane of refractory cement'which comprises the bottom' of the cell interior and retains the fused electrolyte bath. Figs. 3, 5, 6 and 'l 'are elevation drawings showing details of additional embodiments, particularly ofthe anode at thezone of contact with the retaining means providing vertical alignment.

Figs. 4 and 8 show plan views of anode and retaining means of Figs 3 and 5 respectively, and illustrate the manner in which the anode retainingdevice can'be varied.

' Figs. 9 and 11 are elevation views showing different methods by which the anodes are properly registered in a horizontal plane but limited radial adjustment is still permitted.

Fig. 10 is a plan view showing the disposition of the supporting and registering elements of Fig. 9.

Referring to Figs. 1 and 2, an anode l and a concentric cathode 2 are centrally mounted within the cell interior which is bounded by side wall 3 and a refractory bottom I3. The base pan 4 contains a central recess or socket for receiving the anode shank H, an extended lip or rim 5 which provides the foundation for side wall 3, and a connector block 54 protruding at the bottom. The recess in the pan for anode shank II has an inverted cone bottom, thereby automatically registering in horizontal plan the anode l by means of the spherically cut bearing surface 25. Segmental clamps 6, I, 8 and 9 are fastened b bolts It] to pan 4.

The anode shank H is surrounded by lead metal IE, or other relatively low melting metal, which preferably does not fill the complete depth of the annular space between the anode shank I l and the base pan 6. A small expansion space 23 is left when the lead metal I2 is poured. A thin metal plate 24 laid on the top surface of the pan surrounds the anode and fits fairly snugly, except at points at which it is recessed or notched to provide space for the anode clamps 6, l, 3, 9. A layer of molded refractory covers plate 24 and clamps 6, l, 8 and 9.

In assembly, a small amount of molten metal is introduced into pan 4 and the anode is lowered into place. The anode is easily registered or centered with the anode pan by means of the centering action of the spherical surface of the anode and the inverted conical bottom of the pan 5. The anode is then adjusted if necessary by limited movement in a vertical plane about the bearing end on the pan, to provide precise vertical alignment with respect to the plane of the top of the pan. The metal plate 24 and several clamps are put in place, the clamps being securely fastened down with the attaching bolts. At least one clamp is left unattached to permit molten lead or other low melting metal to be poured in the annular space between the anode shank H and the pan 4. As heretofore described, the quantity of molten metal is insufiicient to completely fill the annular space, a small space being normally left as an expansion zone.

The final clamp is then secured in place and the molten metal allowed to solidify and cool. After solidification of the metal, the cell wall is built and then a layer of refractory cement is poured in the cell and allowed to set, forming a sealing and protective layer 13 between all the metal parts in the anode assembly and the fused electrolyte contained in the operating cell.

Electrical power is supplied to the cell through copper bus bars 22 which are bolted to the connector block I4, the latter forming an integrally cast part of the pan. The cell is supported by structural steel members I5 which support, through insulator blocks It the pan and the rest of the cell structure. The cell wall 3 is surrounded and strengthened by a steel shell i8, which, however, does not make electrical contact with the base pan rim 5. A retaining ring 25 welded to the rim 5 is beneficial in strenghening and aligning the lower portion of the cell wall 3. The cathode 2 is inserted in place as the cell wall 3 is being constructed, and is separated by insulating material ll from electrical contact with the steel outer jacket l8.

The collector dome i9 and diaphragm 29 are inserted into the cell structure as a unit, the diaphragm being carefully positioned so as to be concentric with the anode l and the cathode 2.

It will be apparent from Fig. 1 that the precise vertical disposition of anode I is of great importance in obtaining the desired uniform electrolysis zone comprising the annular space between the anode and cathode. Precise location of anodes in a horizontal plane, and vertical alignment thereof, is especially important in cells using a plurality of anodes. In such cells, the anodes must not only be accurately aligned with respect to the cathodes, but also with respect to each other. The anode assembly of the present invention is ideally suited for such plural electrode cells.

Numerous variations in the anode assembly are possible within the scope of the invention. All embodiments are characterized by coacting registration means on the anode and base pan, respectively, and by supplementary retaining means adjustabl attached to the base pan and securing the anode in assembly. In a preferred embodiment, as already described with reference to Figs. 1 and 2, the registration means are permissive of limited movement in a vertical plane during assembly. Various modifications of the anode assembly, particularly with respect to coaction with the vertical retaining means, are illustrated by Figs. 3, 4, 5, 6, '7 and 8.

Referring to Figure 3, this embodiment shows an anode embodiment which is the most economical design possible with respect to utilization of graphite or carbon for the anode. The anode is of uniform diameter in its entire length, with the exception of a shallow circumferential recess in the form of a skewed V 27. A split ring formed of two segments 28 and 29 encircles the anode 3G and bears on the lower frusto-conic face of circumferential V 27. Fig. 4 gives a plan view of Fig. 3, and shows the disposition of bolts 3| adjustably attaching segments 28 and 29 to the base 32. Segments 28 and 29 can be joined by bolts 33 through upright lips 34 in adjacent relationship on segments 28 and 29. The working faces of the ring segments 28 and 29, in contact with the base casting 32 are accurately machined for ease in adjustment of the assembly.

Additional anode designs are illustrated by Figs. 5, 6, and '7. Referring to Fig. 5, shank section 35 of the anode joins the upper or electrolyzing section 38 by a curved shoulder 31. This design is particularly suitable for anodes of relatively small diameter. The use of a curved shoulder minimizes the likelihood of stress concentration at sharp intersections, which would place an undue stress on the anode stock.

The anode illustrated by Fig. 6 represents the simplest type of construction for the invention. A shank portion 38 joins the electrolyzing section 40 by a shoulder 39 of frusto-conic section cut at about 45 degrees to the axis of the anode. This design is easily manufactured from graphitestock of the same diameter as the shank 38.

The anode represented by Fig. 7 is particularly advantageous for embodiments of the invention when the metal surrounding the anode is solid. In this anode, one or more circumferential grooves M are cut in the shank portion 42. In assembly, as molten metal is poured around the anode and subsequently solidifies, the anode is more firmly anchored in proper alignment in the cell. Such grooves are also of particular benefit g in securing strength and rigidity in the constructioncf acell.

Fig. 8 is a plan View of the simplest type of retaining means for securing and fastening the anodein vertical position. This retainingmeans comprises a one piece ring with a similar cross section to the two piece retaining collar illustrated by Figs. 3 and 4. This form of retaining means is especially suitable for anodes having an enlarged .shank, as illustrated by Figs. '6 and 7. The inner diameter of-such .a retaining device is preferably of greater diameter than the electrolysis section of the anode A5.

The anodes for use in the invention can be varied widely with respect to'the meansifor engaging with the adjustable rings -or segments, as above described. In additiomnumerous variations are possible with respect to the bearing end .of the anode which cooperates with the-base pan to obtain positive and accurate registration in a horizontal plane. As already mentioned, the assembly utilizes male and female means on the anode bearing end and the base pan. The preferred registration means will permit limited movement of an anode in a vertical plane about the bearing point in assembly, although this feature is not absolutely essential. It is necessary, however, for the anode base or bearing end to be accurately registered in the horizontal plane.

Examples of alternate means of providingregistration in a horizontal plane for the anode bearing end are given by Figures 9, 10 and 11. Figures Qand lilare, respectively-sectional elevation-and plan views-of a registration means employing a centering pin integrally cast in the base pan. Figure 11 illustrates registration means which also provides support for the anode.

Referring to Figures 9 and 10, a pin is cast integrally with base 52 and centers anode 53 by engaging with hole 5 3. The anode base face is machined fiat and rests on the machined upper faces of ribs 55. The ribs55 provide an accurate seat for the anode and permit molten metal to flow around this surface in assembly. In this embodiment, vertical alignment is primarily achieved by the accurate machining of the anode base and the supporting ribs 55.

Another suitable registration and support means is shown by Figure 11, which is a sectional elevation view of the joint of an anode and a base pan. Referring to the figure, a portion of the base pan 6-3 is shown, and the base or hearing end 61 of the anode. An approximately spherical protrusion 54 is machined on the base pan, and coincides with a conical recess in the end of the anode, registering thel anode in horizontal position. A slot 62 facilitates passage of molten metal to all parts of the anode shank in assembly.

It will be apparent from the foregoing description that a large number of combinations of specific means are possible for different embodiments of the invention. Thus, any of the several anode bearing and designs heretofore shown may be combined with any of the means which retain the anode and also provide for radial adjustment during assembly. Different combinations will be preferred for different cell sizes or designs. For example, if the anode is a foot or more in diameter, the use of segmental clamps such as shown in Figure 2, are preferred for providing radial adjustment and vertical alignment. On anodes of the species having a shank or bearing end of larger diameter than the electrolysis .end, :a zone apiece ..retai-ning means isssuitable.

The electricalefficiency "of the anode assembly, with respect to maintaining :alow voltage drop, is assured by :the 'use .of a poured .metal joint. surrounding the .anode shank'zand. contacting the base ;.pan. The :metal utilized :for'this purpose should, preferably, bea :relatively low melting 'material, of high -electrical conductivity. A gdesirable characteristic .is that *the .metal should .shrink .on ;the .anode shank in :solidificae tion, thereby grip-ping securely atheranode and providinggood electrical contactat all points. Lead and :tin are suitable elemental imetals. Various low .:melting alloys are also quite .satisfactory, especially those containing appreciable proportions of lead; for example solders and type'metals. 'The preferred-metaliis elemental leader-solder. If an alloy is -used,it1is preferred that it should :not contain appreciable .amounts of metals vof high vapor pressure, :for example, mercury, sodium or bismuth should beavoided.

The operating conditions of: the cell,.the specificproportions vof thebase pan, and vtheimetal used'for .electrical contact between the anode and the base pan maybe such that the ;metal is either solid or fused. during: operation. .Either mode of operation is satisfactory. Ingeneral, however, it will be preferred to operate-with a molten metal surrounding the anode and filling the base pan. Although the electrical-conductivity of amolten metal is lessthan -fora solid metal, the actual voltage drop and consequent power loss in the metal is insignificant-in comparison to the-losses-which normally occur at the junction of two solids. Theoverallpower loss involved in passing current through'the base pan and a molten metal "to'the carbon anode istherefore substantially less than occurs if the metal is .in the solid phase.

Havingfully described the invention and embodiments thereof, what I claim is:

1. In a fused salt electrolysis cellcharacterized by a bottom mounted anode, the improved bottom and anode assembly comprising a liquid-tight metal base pan adapted to carry the cell current, avertical anode of circular cross-section having a relatively short vertical-portion'thereof consisting of af-rusto-conicsection, a longitudinal section of said frusto-conic section forming an acute angle to the vertical, said frusto-conic section being adjacent the upper surface of the base pan, a body of low melting metal, and a plurality of arcuate clamps having internal bearing faces, the said faces being portions of a frusto-conic section substantially corresponding to the frustoconic section of the anode, the pan having a socket receiving the lower end of the anode, said socket being larger in lateral area than the anode, but having integral registration means at the lower part contacting and centering the an-- ode end in a lateral plane, the body of low melting metal partially filling the space in the socket not occupied by the anode, the clamps surmounting and attaching to the pan and retaining the anode in vertical alignment.

2. In a fused salt electrolysis cell characterized by a bottom mounted anode, the improved bottom and anode assembly comprising a liquid-tight metal base pan adapted to carry the cell current, a vertical anode of circular cross section and having a peripheral groove, at least the lower side of said groove being a, frusto-conic section, a longitudinal section thereof forming an acute angle to the vertical, said groove being adjacent the upper surface of the base pan, a body of low melting metal, and a plurality of arcuate clamps having internal bearing faces, the said faces being portions of a frusto-conic section substantially corresponding to the frusto-conic section formed by the lower side of the anode groove, the pan having a socket receiving the lower end of the anode, said socket being larger in lateral area than the anode, but having integral registration means at the lower part contacting and centering the anode end in a lateral plane, the body of low melting metal partially filling the space in the socket not occupied by the anode, the clamps surmounting and attaching to the pan and retaining the anode in vertical alignment.

3. In a fused salt electrolysis cell having a bottom mounted anode, the improved bottom and anode assembly comprising a liquid-tight metal base pan adapted to carry the cell current, a vertical anode of circular cross section and having a peripheral groove, at least the lower side of said groove being a frusto-conic section, a longitudinal section thereof forming an acute angle to the vertical, said groove being adjacent the upper surface of the base pan, a body of low melting metal, and a plurality of arcuate clamps having internal bearing faces, the said faces being portions of a frusto-coni-c section substantially corresponding to the frusto-conic section formed by the lower side of the anode groove, the total are lengths of the clamps approaching the peripheral length of the groove, the pan having a socket therein receiving the lower end of the anode, the socket being larger in lateral area than the anode but having integral registration means at the lower part thereof contacting and centering the anode end in a lateral plane but not in themselves preventing limited movement of the anode in a vertical plane about the anode bottom, the body of low melting metal partially filling the space in the socket not occupied by the anode, the clamps surmounting and being attached to the pan and retaining the anode in vertical alignment.

4. In a fused salt electrolysis cell having a bottom mounted anode, the improved bottom and anode assembly comprising a liquid-tight metal base pan adapted to carry the cell current, and having a socket receiving the lower end of the anode, a vertical anode mounted in the socket of circular cross section and having a peripheral groove, the lower side of said groove being a frusto-conic section, a longitudinal section thereof forming an acute angle to the vertical, said groove being adjacent the upper surface of the base pan, the socket being larger in lateral area than the anode, the socket and anode end having integral male and female registration contacting means centering the anode end in the socket but not in themselves restricting the anode from limited movement in a vertical plane about the centered anode end, a body of low melting metal partially filling the space in the socket not occupied by the anode, a plate upon the pan surface snugly surrounding the anode at the point of projection from the socket except for a plurality of notches, a plurality of arcuate clamps surmounting and adjustably attached to the base pan and clamping the anode in vertical alignment, the clamps corresponding in number and being placed in the notches in said plate, the said arcuate clamps having internal bearing faces, the said faces being portions of a frustoconic section substantially corresponding to the frusto-conic section formed by the lower side of the anode groove, the total are lengths of the clamps approaching the length of the groove, and a sealing membrane of refractory impermeable to fused salt sealing the plate and clamps from contact with the fused salt electrolyte.

5. The apparatus of claim 1 further defined in that the lower end of the anode is in the form of a hemisphere and the integral registration means in the socket in the pan is an inverted conical depression.

JAMES V. CARLISLE.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 510,276 Lyte Dec. 5, 1893 2,213,073 McNitt Aug. 27, 1940 2,370,087 Stuart Feb. 20, 1945 2,592,483 Smith et a1 Apr. 8, 1952 FOREIGN PATENTS Number Country Date 146 Great Britain Apr. 31, 1906 40,354 Germany Aug. 15, 1886

Claims (1)

1. IN A FUSED SALT ELECTROLYSIS CELL CHARACTERIZED BY A BOTTOM MOUNTED ANODE, THE IMPROVED BOTTOM AND ANODE ASSEMBLY COMPRISING A LIQUID-TIGHT METAL BASE PAN ADAPTED TO CARRY THE CELL CURRENT, A VERTICAL ANODE OF CIRCULAR CROSS-SECTION HAVING A RELATIVELY SHORT VERTICAL PORTION THEREOF CONSISTING OF A FRUSTO-CONIC SECTION, A LONGITUDINAL SECTION OF SAID FRUSTO-CONIC SECTION FORMING AN ACUTE ANGLE TO THE VERTICAL, SAID FRUSTO-CONIC SECTION BEING ADJACENT THE UPPER SURFACE OF THE BASE PAN, A BODY OF LOW MELTING METAL, AND A PLURALITY OF ARCUATE CLAMPS HAVING INTERNAL BEARING FACES, THE SAID FACES BEING PORTIONS OF A FRUSTO-CONIC SECTION SUBSTANTIALLY CORRESPONDING TO THE FRUSTOCONIC SECTION OF THE ANODE, THE PAN HAVING A SOCKET RECEIVING THE LOWER END OF THE ANODE, SAID SOCKET BEING LARGER IN LATERAL AREA THAN THE ANODE, BUT HAVING INTEGRAL REGISTRATION MEANS AT THE LOWER PART CONTACTING AND CENTERING THE ANODE END IN A LATERAL PLANE, THE BODY OF LOW MELTING METAL PARTIALLY FILLING THE SPACE IN THE SOCKET NOT OCCUPIED BY THE ANODE, THE CLAMPS SURMOUNTING AND ATTACHING TO THE PAN AND RETAINING THE ANODE IN VERTICAL ALIGNMENT.

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