US2934486A - Anode structure - Google Patents

Description

iled May 3 57 s. E. BERGH ET AL 15: STRUCTURE 3 Sheets-Sheet 1 ENTORS fiver-re E Berg? April 26, 1960 s. E. BERGH TAL 2,934,486

moms STRUCTURE Filed May 31, 1957 3 Sheets-Sheet 2 FIG- 2 INVENTORS Sverr-e E. Ber-ah Thcmas ocqn William H.Vin|n3 ATTORA/ I April 26, 1960 5, BERGH ErAl. 2,934,486

ANODE STRUCTURE Filed May 31, 1957 3 Sheets-Sheet 3 FIG. 3

large quantities in the Downs United States .ANODE STRUCTURE fivepre Bergh,eLewiston, N.'Y., Thomas "OCallaghan, Dublin, Ireland, and William H."Vining, 'Niagara'Falls, N.Y., assignors to E. I. du Pont de Nemonrsand Company, Wilmington, DeL, a corporation of Delaware App cat on M 3: er m-662s8 5 z claims. '(Cl. 204-288) inventionrelates to .jfused saltelectrolytic cells and more particularly to a composite graphite anode "for a cell. employed. to, produce sodium.

Fora number of decades sodium has'been produced in c ll. icfh'h a cyl ndrieal graphite anode surround ed with a cylindrical steel cathode. As the size and production capacity of these cells have increased and themarket for sodium has grown, it has been recognized that there is a need for a rectangular sodium cell. The geometry of the conventional cylindrical cell requiresa relatively large factory areafor a given production capacity, as compared with any conceivable rectangular design. Heretofore .a rectangular s d m c l it fl n y and producti y ompa ab e to conventional cylindrical cells has not been devised.

An object of thepresent invention is a large sized fused salt electrolytic cell having a rectangular composite anode made of a plurality of graphite pieces. Another object ,is .a method for constructing such anode. Still other objects will be apparent from the ensuing description.

Figure l is an'end View, partly in vertical cross section and partly inelevation of an electrolytic cell.

"Figure 2 is a vertical cross section through plane II of Figure 1.

The drawings, illustrating one example of the present invention, show an assembly of four vertical graphite anodes mounted in .a fused salt electrolytic cell. The cell is provided with a steel base plate 1 which is rectangular inshape and has vertical side walls 2 forming a rec- ,tapgular box -like structure, hereinafter referred to as the "anode ibox. Four anodes 3 are set in the .anode box end rest on projections 4 which are fastened to the floor '(base plate *1) of the box. 'irojections 4 are machined to a common level and thus serve to properly align the anodes resting thereon. If desired, they may be omitted, provided the floor of the'box is made sufiiciently level to properly align the anodes.

The bases of the four anodes are held together in a tight bundle by means of two tie rods 5 which are threaded at each end and are provided with nuts 6 and washers 7. Between the two washers 7 at one end of each tie bar there is interposed a strong steel spring 8 which fits in a recess cut in the anode. The tension applied on the two tie rods 5 is such as to hold the anode bases tightly together over a considerable range of temperature variation, from the assembly temperature (usually room temperature) to the maximum operating temperature. As the temperature coeflicient of expansion of steel is greater than that of graphite, the initial compression of the spring applied in assembly must exceed the difference in expansion of the steel and the graphite over the temperature range between assembly temperature and maximum operating temperature, for example, of the order of 100 C., above and below the normal cell operation temperature.

Eight vertical bolts 9, provided with eyes or hooks on their upper ends through which tie rods 5 pass, extend through the bottom of the anode box 2 and are fastened Ratented Apr. 26, 1960 '2 with nuts and washers :tO anchor ,the-;anodes ;a gainst,.-a tendency to float in the electrolyte and tohqldlthem in proper position.

The space around the bases of the anode ,3 and the .anode box is filled with a low melting;rnet al alloylll such as Woods metal, which is liquid at theternperature of cell operation, .and serves to provide good electrical contact between the graphiteanodesand the steel anode box. Bus bars (not shown) fastened to the ,anode box, conduct ,anodic current to the cell. Cylindrieal steel weirs 11 welded to the bottom of the anode box and surrounding bolts ,9;serve to prevent leakage of the fusible alloy. around thebolts. Weirs l1. (which nay -be of rectangular cross section instead of cylindrical) projectinto corresponding holes formed in the bases of the anodes. These holes are sufiicientlylarger than the-weirs so that expansion'of the weirs sand ofthe anode box on heating to operating temperature will not impart mechanical stress on the graphite anode.

Verticalrib l4 attachedtothe floor of the anode box holds the anode assembly'frornlongitudinal displacement in the box. it also divides and equalizes theexpansion of the box on heating, in the two-directions :on either .side of the rib. For this purpose,.the rib 14 ,should be located midway in the anode assembly.

The side walls of the cell .are fastened to the anode box as shown by bolts or byothersuitable means. The reel-1 si all th e a p ei lus rated by edr wias are conventional, consistingof steel shell 12 lined with refractory brick work 13. Preferably (but notessential to the present invention), the shell 12 is -.electrically insulated frombase plate 1.

To install the anodes into the ,anode box, they may first be clamped together by means of tie bolts 51, haying the eyes or books of bolts 9 already engaged with the rods, and the assembly thus clamped together ;r nay be lowered into the anode box after which the nuts are tightened on bolts 9. An alternative methodrequires cutting ports in the ends of the anode box; to permit introduction of the tie rods 5. According to this rriethpd, first the anodes are individually set in place over: the upstanding cylindrical weirs 11. Bolts 9 are then-pu hed up through the weirs into position and tie rods 5 are r s ed nt n ac th th eye th uppe n of bolts 9. The washers 7 .andsprings 8 then are bolted in place ,and tension applied by nuts .6 to hold the anodes firmly together. Then-bolts 9 are fastened withnuts and wash Th .fou p r s on th two end th anod .bo wwh h .s eaccss t t .mdsS h n mus bec qs d with tightly fitting plugs or covers. The assembly is completed by introducing the molten alloy while heating the assembly to a temperature above the melting point of the alloy. The space occupied by the molten alloy 10 then is sealed over by means of a refractory cement 15.

The cell is also provided with a rectangular steel cathode to, having arms 17 projecting through the cell walls. Bus bars (not shown) fastened to cathode arms 17 conduct cathodic current to the cell. Diaphragm 18 of corventional type wire gauze (shown diagrammatically) is inserted between the anodes and the surrounding cathode. The cell is further provided with suitable means for collecting the electrolysis products, which may be of conventional design except being rectangular instead of circular.

The foregoing description is merely illustrative; and many modifications thereof may be made without departure from the scope of the present invention. Broadly considered, the inventive concept is that a plurality of graphite pieces of rectangular cross section are arranged in a row to form a rectangular composite anode and are held together by a tension means (e.g., tie rods 5 with associated springs); and further that anchoring means hold said anodes in proper position.

If desired a single tie rod, or more than two tie rods may be used in place of the two (rods illustrated. T ension springs may be mounted on both ends of each tie rod instead of at one end as illustrated. Also, in place of the tie rods and associated springs, other tension devices may be used for holding the anodes together. For example, springs or equivalent resilient devices may be interposed between an end of the composite anode and the end wall of anode box 2 or its equivalent with means for tightening the spring against the end of the anode. In such case the tie bar may be eliminated and, if de sired, other means such as dowels can be used to locls adjacent graphite pieces together. In any case, in accordance with the present invention, the means for pressing the graphite pieces together will include one or more springs or equivalent resilient elements, which maintain substantially constant pressure over a considerable range of temperature variation. 7

The bolts 9 may be replaced by other anchoring devices, for example, pins or projections from the side walls of the anode box or its equivalent which fit into slots or holes in the graphite pieces.

- If desired, the graphite pieces maybe provided with vertical holes or anode wells, with slots or holes leading from the wells to the space between anode and cathode. Such modification, which provides for electrolyte circulation, will be apparent to one skilled in the art of sodium manufacture, as such anode wells and slots have been used in the conventional cylindrical sodium cells.

The invention is not restricted to the above-described composite anode of four pieces; Any number of pieces may be employed, thus'making it possible to construct an anode of any desired length, for example, anodes of 3 to '10 pieces, each piece having a thickness (in the direction of anode length) of around 8 to 18 inches. In the anode assembly, the cross-sectional dimensions of the individual graphite anodes may be such that the rectangular assembly is either square or oblong. Also, a plurality of such composite electrodes may be installed in a single cell, preferably side by side, with intervening cathodes thus producing a cell of very large capacity, occupying a relatively small factory area.

The design of a rectangular sodium cell so as to preserve the operating principles and good characteristics of the conventional cylindrical sodium cells introduces new problems. Oneisthe efiect of the expansion of the steel parts on heating up to operating temperature. While the expansion of steel is also to some extent a problem in the cylindrical cells, the methods there conventionally used to overcome it are not'applicable to the rectangular design. This problem 'and others are satisfactorily answered in the present invention.

In the foregoing andin the appended claims, the term rectangular is used to mean: having approximately the shape of a quadrilateral, either square or oblong, which has four right angles and opposite sides parallel. By rectangular cell is meant a cell whose anode has a rectangular horizontal cross section in the electrolysis zone.

We claim:

1. A rectangular anode assembly for a fused salt electrolytic cell comprising a plurality of vertical elongated graphite pieces, the bottom ends; thereof resting on a steel base plate and surrounded by a liquid alloy to provide electrical connection therewith, at least one horizontal tie rod passing .through said bottom'ends and provided with spring means adapted to'hold the said graphite pieces in a tight row over a wide range of temperature variations, vertical bolts fastened to said tie rod and extending through said base plate to anchor said bottom ends thereto and vertical weirs secured to said base plate and surrounding said vertical bolts so as to prevent leakage of said liquid alloy.

2. A rectangular anode assembly for a fused salt electrolytic cell comprising a plurality of vertical elongated graphite pieces, the bottom ends thereof resting on a steel base plate and surrounded by a liquid alloy to provide electrical connection therewith, at least one horizontal tie rod passing through said bottom ends and provided with spring means adapted to hold the said graphite pieces in a tight row over a wide range of temperature variations, said base plate being provided with a steel rib fastened thereto and extending laterally across the said anode assembly at right angles to 'said tie rod and extending vertically within said row of graphite pieces, vertical bolts fastened to said tie rod and extending through said base plate to anchor said bottom ends thereto and vertical weirs secured to said base plate and surrounding said vertical bolts so as to prevent leakage of said alloy.

References Cited in the file of this patent UNITED STATES PATENTS 765,001 Gin July 12, 1904 2,194,443 Hardy et al Mar. 19, 1940 2,213,073 McNitt Aug. 27, 1940 2,249,765 Hulse July 22, 1941 2,592,483 Smith et a1 Apr. 8, 1952 FOREIGN PATENTS 1,012,545 France July 11, 1952 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION April 26, 1960 Patent No. 2,934,486

Sverre E. Bergh et a1.

It is hereby certif-iedthat error appears in the printed specification of the above numbered patent requiring correction and that the said Letters Patent should readas corrected below.

Column '1 line 38, after "Figure 1.", insert the following reference as a new paragraph:

Figure 3 is a horizontal cross section through plane 111 of Figure 2 drawn on a somewhat larger scale,

Signed and sealed this 11th day of October 1960.

( SEAL) Attcst: KARL H. AXLINE ROBERT (1. WATSON Commissioner of Patents Attesting Officer

Claims (1)

1. A RECTANGULAR ANODE ASSEMBLY FOR A FUSED SALT ELECTROLYTIC CELL COMPRISING A PLURALITY OF VERTICAL ELONGATED GRAPHITE PIECES, THE BOTTOM ENDS THEREOF RESTING ON A STEEL BASE PLATE AND SURROUNDED BY A LIQUID ALLOY TO PROVIDE ELECTRICAL CONNECTION THEREWITH, AT LEAST ONE HORIZONTAL TIE ROD PASSING THROUGH SAID BOTTOM ENDS AND PROVIDED WITH SPRING MEANS ADAPTED TO HOLD THE SAID GRAPHITE PIECES IN A TIGHT ROW OVER A WODE RANGE OF TEMPERATURE VARIATIONS, VERTICAL BOLTS FASTENED TO SAID TIE ROD AND EXTENDING THROUGH SAID BASE PLATE TO ANCHOR SAID BOTTOM ENDS THERETO AND VERTICAL WEIRS SECURED TO SAID BASE PLATE AND SURROUNDING SAID VERTICAL BOLTS SO AS TO PREVENT LEAKAGE OF SAID LIQUID ALLOY.

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