US3544444A - Fused salt electrolysis cell having anode with tapered well therein - Google Patents

Fused salt electrolysis cell having anode with tapered well therein Download PDF

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Publication number
US3544444A
US3544444A US639863A US3544444DA US3544444A US 3544444 A US3544444 A US 3544444A US 639863 A US639863 A US 639863A US 3544444D A US3544444D A US 3544444DA US 3544444 A US3544444 A US 3544444A
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anode
well
diameter
cell
tapered
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US639863A
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Victor J Reilly
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EIDP Inc
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EI Du Pont de Nemours and Co
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    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25C—PROCESSES FOR THE ELECTROLYTIC PRODUCTION, RECOVERY OR REFINING OF METALS; APPARATUS THEREFOR
    • C25C7/00—Constructional parts, or assemblies thereof, of cells; Servicing or operating of cells
    • C25C7/02—Electrodes; Connections thereof
    • C25C7/025—Electrodes; Connections thereof used in cells for the electrolysis of melts

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  • a fused salt electrolysis cell particularly for the production of metallic sodium, having a vertical anode surrounded by a cathode, which anode is provided with a tapered well in the top thereof extending longitudinally through the center of the anode in the portion thereof opposite the electrolysis zone, which Well, in conjunction with perforations, preferably vertical slots, provided in the anode wall, assures circulation of electrolyte from the well into the electrolysis zone.
  • the anode resistance in the cell is desirably reduced without adversely affecting electrolyte circulation.
  • BACKGROUND OF THE INVENTION Sodium is produced commercially by the electrolysis of a fused electrolyte comprising sodium chloride in cells which are basically similar in design to the Downs cell described in Downs US. Pat. 1,501,756.
  • Such cells employ bottom-mounted vertical graphite anodes each surrounded by a metal cathode, the two electrodes thus defining an annular electrolysis zone.
  • a foraminous diaphragm is inserted in the electrolysis zone to separate the electrolysis products.
  • Chlorine produced at the anode is removed from the upper part of the cell through a gas dome positioned above the anode.
  • Sodium produced at the cathode rises into a collecting manifold from which it is removed through a vertical pipe communicating with the exterior of the cell.
  • a factor affecting the economical operation of Downs type cells is the cell resistance, and it is evident that by keeping the resistance as low as possible the cell voltage drop and power costs will be reduced.
  • the anodes are made as large as possible with respect to the other cell parts.
  • Good electrolyte circulation particularly in the electrolysis zone, is essential for economical performance of the cell.
  • the invention relates to a Downs type cell for the production of alkali metals by the electrolysis of fused alkali metal halide electrolytes, particularly for the production of sodium and chlorine by the electrolysis of a fused electrolyte comprising sodium chloride.
  • Such cells comprising a bottom-mounted vertical anode, generally cylindrical in shape, surrounded by a cathode, which is usually supported by side arms extending through the side Walls of the cell, a foraminous diaphragm positioned between the electrodes, and means for separately removing the electrolysis products from the upper part of the cell.
  • Such cells may contain a single pair of electrodes, i.e., an anodecathode pair, or an assembly of several such pairs, generally four.
  • the invention contemplates the use in such a cell of an anode having a tapered well in the top thereof extending longitudinally through the center of the anode in that portion thereof opposite the electrolysis zone, which well is in open communication with the electrolysis zone through perforations, preferably slots, in the anode wall which permit effective circulation of electrolyte from the well into the electrolysis zone.
  • the taper of the anode well is essentially from its top to its bottom, i.e., towards the end of the anode that is connected with the power source.
  • the well Since the anode customarily rises vertically from the bottom of the cell where contact with the power source is effected, the well will be in the upper portion of the anode and will taper towards its bottom, i.e., the diameter of the well will be greater at the top than at the bottom. It has been found that anodes with such tapered Wells which communicate through perforations in the anode wall with the electrolysis zone to permit the desired circulation of electrolyte exhibit a substantially lower resistance in the cell than do otherwise similar anodes having Wells of the conventional cylindrical design. Furthermore, the tapered design of the anode well does not significantly reduce electrolyte circulation.
  • FIG. 1 is a side view in elevation of an anode having a tapered well therein in accordance with the invention.
  • FIG. 2 is a plan view of the anode of FIG. 1 shown with a surrounding cathode and an annular diaphragm positioned between the anode and the cathode.
  • FIG. 3 is a vertical cross-section of the structure of shown, each extending vertically from the bottom of well 3 and terminating a little short of the top of the anode so as to leave a solid collar which is desirable to impart greater strength but is not essential for the functioning of the anode.
  • Anode 1 is mounted at the bottom of the cell (not shown) so as to form intimate contact with a metal conductive member 8 which is connected with the power source.
  • anode 1 Shown surrounding top portion 2 of anode 1 is a cylindrical metal cathode 6 which is generally supported 'by cathode arms (not shown) extending through the cell walls (not shown) where contact with the power source is made.
  • Diaphragm 7 is usually rigidly fastened to a removable product collector assembly (not shown) from which it is suspended in the position indicated in the drawing. It will be noted that well 3 in the anode is generally opposite the electrolysis zone and is substantially coextensive in vertical length therewith.
  • DESCRIPTION OF PREFERRED EMBODIMENTS 'well 3 in the anode will have adiameter at its top which is about twice its diameter at its bottom, with the diameter at the top being approximately halfthe diameter of the anode.
  • electrolyte communication between well 3 and the electrolysis zone is provided by four slots 4 equally spaced radially about the circumference of the upper portion 2 of the anode.
  • more or fewer than four slots e.g., from 2 to 8 equally spaced about anode portion 2, may be employed, but usually four positioned as indicated with each having a width equal to from about 5 to 20%, preferably 8 to 12%, of the top diameter of the anode well, are generally adequate.
  • tapered Well 3 will be no larger than is necessary to provide, in conjunction with slots 4, eflicient circulation of electrolyte from the well into the electrolysis zone, otherwise, the electrical resistance of the anode in the cell will be undesirably increased.
  • the diameter of the well at its top will be equal to from 30 to 80%, preferably 40 to 60%, of the diameter of the anode.
  • the diameter of the well at its bottom should generally be no greater than 70% of the diameter of the well at its top.
  • the diameter of the well at its bottom will be equal to from 0 to 70% of the diameter at its top; most preferably, it will be equal to from 30 to 60% of the diameter at the top.
  • the general shape of the well may be that of an inverted cone but preferably will be that of an inverted truncated cone, the latter being generally preferred as indicated.
  • the perforations in the anode wall providing communication between the well and the electrolysis zone may be in the form of several holes running transversely through the walls of the anode. Such holes, when employed, should be distributed more or less uniformly over that portion of the anode which together with the cathode defines the electrolysis zone, e.g., that'portion of the anode which is generally coextensive with slots 4 in the drawing. Instead of transverse holes, sloping holes may also be employed. However, the preferred type of perforations are those in the form of vertical slots such as slots 4 in the drawing. The number thereof and their width should be sufficient to insure the desired electrolyte circulation and they should be uniformly spaced about the anode.
  • the sides thereof are preferably straight with the taper thereof being downward as indicated previously.
  • tapered wells with side walls that are somewhat curved, either inwardly or outwardly, can be used, although they are not as advantageous as the preferred straight sided tapered wells.
  • the tapered well should be in the center of the anode and symmetrical with respect to the longitudinal axis of the anode, otherwise distribution of the current flow to the active anode surfaces will not be uniform.
  • Each anode included a tapered well centered in approximately its upper half so as to be opposite and approximately coextensive in length with the electrolysis zone.
  • the top diameter of the wells was one-half the diameter of the anodes, while the bottom diameter of the wells was one-half their top diameter.
  • Each anode was also provided with four vertical circulation slots positioned as shown in the drawing, the width of each slot being about 20% of the diameter of the bottom of the anode well and about 10% of the diameter of the top of the anode well.
  • the cells of each of the above groups were operated to produce sodium and chlorine over periods of time ranging from about 9.5 to 20.8 months and the statistical values for power consumptions (kilowatt-hrs, D.C.) per lbs. of sodium produced (averagelife-to-date) were determined.
  • the average power consumption per 100 lbs. of sodium produced in the Test Group of cells was 423.4 kilowatt hours, Weighted for the age of the cells, whereas the corresponding value for the Reference Group of cells was 426.4 kilowatt hours.
  • the power consumption values reported above correspond to a reduction of about 0.06 volt in favor of the cells of the Test Group, i.e., the cells with tapered anode wells.
  • the lower power consumption in the cells of the Test Group resulted from a reduction of the resistance of the anodes having tapered wells.
  • the difference in power consumption found is significant and distinctly advantageous, since it is worth about 1.5 cents per 100 pounds of sodium with power at 0.5 cent per kilowatt hour.
  • the tapered-well anode has about 50% more cross-sectional area. This is important since power loss in older cells dictates the current load they may carry, as well as the age at which they must be retired. In terms of voltage reduction near the end of the useful life of the cells, the taperedwell has an advantage of about 0.1-0.15 volt. The net effect of the reduced average voltage, and the greater reduction in voltage with older cells, is an increase in current capacity of about 23%. A given investment in electrolytic cells and associated facilities can thereby produce 23% more sodium.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Electrolytic Production Of Metals (AREA)
  • Electrolytic Production Of Non-Metals, Compounds, Apparatuses Therefor (AREA)
US639863A 1967-05-19 1967-05-19 Fused salt electrolysis cell having anode with tapered well therein Expired - Lifetime US3544444A (en)

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US63986367A 1967-05-19 1967-05-19

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US (1) US3544444A (en:Method)
BE (1) BE715316A (en:Method)
DE (1) DE1758358B1 (en:Method)
FR (1) FR1563518A (en:Method)
GB (1) GB1205458A (en:Method)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2015024030A2 (en) 2013-08-16 2015-02-19 Csir Molten salt electrolysis apparatus and process

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2415494A (en) * 1944-12-13 1947-02-11 Artemas F Holden Hollow electrode for salt bath furnaces
US2490730A (en) * 1946-02-12 1949-12-06 Dubilier William Device for electrically treating liquids
US2604441A (en) * 1947-11-04 1952-07-22 Pennsylvania Salt Mfg Co Method of producing inorganic compounds of increased oxidation state

Family Cites Families (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2390548A (en) * 1945-12-11 Method of operating electrolytic
US2194443A (en) * 1937-10-04 1940-03-19 Du Pont Anode for electrolytic cells
US2414831A (en) * 1941-10-15 1947-01-28 Robert J Mcnitt Method and apparatus for the purification of fused salt baths

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2415494A (en) * 1944-12-13 1947-02-11 Artemas F Holden Hollow electrode for salt bath furnaces
US2490730A (en) * 1946-02-12 1949-12-06 Dubilier William Device for electrically treating liquids
US2604441A (en) * 1947-11-04 1952-07-22 Pennsylvania Salt Mfg Co Method of producing inorganic compounds of increased oxidation state

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2015024030A2 (en) 2013-08-16 2015-02-19 Csir Molten salt electrolysis apparatus and process

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DE1758358B1 (de) 1972-02-03
GB1205458A (en) 1970-09-16
FR1563518A (en:Method) 1969-04-11
BE715316A (en:Method) 1968-11-18

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