US2451491A - Enriching the alumina content of recirculated cryolite fusions in aluminum production - Google Patents

Enriching the alumina content of recirculated cryolite fusions in aluminum production Download PDF

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US2451491A
US2451491A US575313A US57531345A US2451491A US 2451491 A US2451491 A US 2451491A US 575313 A US575313 A US 575313A US 57531345 A US57531345 A US 57531345A US 2451491 A US2451491 A US 2451491A
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fusion
alumina
aluminum
cell
furnace
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Arthur F Johnson
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Reynolds Metals Co
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Reynolds Metals 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
    • C25C3/00—Electrolytic production, recovery or refining of metals by electrolysis of melts
    • C25C3/06—Electrolytic production, recovery or refining of metals by electrolysis of melts of aluminium
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25C—PROCESSES FOR THE ELECTROLYTIC PRODUCTION, RECOVERY OR REFINING OF METALS; APPARATUS THEREFOR
    • C25C3/00—Electrolytic production, recovery or refining of metals by electrolysis of melts
    • C25C3/06—Electrolytic production, recovery or refining of metals by electrolysis of melts of aluminium
    • C25C3/08—Cell construction, e.g. bottoms, walls, cathodes

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  • My invention relates to improvements in the production of aluminum, the metal, from ores containing hydrated aluminum oxides, commonly designated bauxites.
  • Such ore-s usually co substantial proportions of combined iron, silicon and titanium, but the presence of substantial amounts of these elements in aluminum produced from such ores seriously impairs the quality of the metal.
  • My invention provides improvements in the direct production of fluoride fusions containing dissolved alumina, the electrolyte of the Hall process, of high purity from ores which may contain substantial proportions of impurities such as combined iron, silicon and titanium and improvements in the combined operation including the electrolytic reduction.
  • My invention thus provides for the production of metalof high quality with improved economy and simplified operation.
  • My invention involves a novel double filtration through carbonaceous material of the fluoride fusion, first following a step in which alumina is dissolved from the aluminiferous material in the fusion in the presence of carbonand second following a step in which aluminum is reacted with the once filtered fusion.
  • the complete process of my invention comprises five steps: (1) solution of alumina in the fluoride fusion in the presence of carbon as in a, smelting operation to which the ore and the fusion are supplied, (2) filtration of the fusion through carbonaceous mate'- rial such as a body of coke, (3)- reaction of the fusion filtered in the second step with aluminum, (4) filtration of the fusion reacted with aluminum through carbonaceous material and (5) electrolytic reduction of the twice filtered fusion.
  • the electrolysis is with special advantage carried out in a series of cells through which the fusion is circulated from the second filtration to the solution or smelting operation in repetitions of this cycle.
  • step 1 the bulk of the silicon and of the iron and titanium are removed, being separated from the fusion as an alloy which is recovered as a by-product. For example, or more of the iron may thus be eliminated from the fusion.
  • step 2 the bulk of the remaining silicon, iron and titanium are removed on the carbonaceous material.
  • step 3 the bulk of the remaining traces of silicon, iron and titanium are reduced and thus rendered insoluble in the fusion, probably to elemental form but perhaps to some extent to carbides. The reduced and insoluble material appears in the fusion in finely dispersed condition, corresponding to the state of dispersion of the impurities remaining prior to this reduction.
  • step 4 the reduced and insoluble material is removed on the carbonaceous material.
  • step 3 The treatment of the fusion with aluminum in step 3 apparently serves a double function in the complete process of my invention; the aluminum is a, pcculiarly effective reducing agent and it also seems to promote the removal of the finely dispersed metal or carbides or both by promoting wetting of the carbonaceous material used as a filter by the fusion carrying the dispersed reduced and insoluble material.
  • a fluoride fusion charged with dissolved alumina of high purity is thus produced directly from the aluminiferous material.
  • this fusion is subjected to electrolytic reduction to produce aluminum metal of correspondingly high quality.
  • alumina is subjected to electrolysis in solution in fused cryolite at a temperature approximating, or perhaps somewhat less than, 1000 C. between carbon electrodes with a voltage drop across each cell of the order of 5-6 volts.
  • other salts, fluorides, and fluorspar in particular are added to the cryolite to lower the melting point of the fusion or to increase the solubility of alumina in the fusion.
  • Additions of sodium fluoride, for example, tend to increase the solubility of alumina in the fusion.
  • the fusion usually includes other fluorides, and the range of concentration of dissolved alumina approximates 1%-6% of the fusion.
  • cryolite In foreign practice, cryolite is sometimes used without added fluorides and the upper limit of the range of alumina concentration in the fusion is higher. Direct current in high amperages being economically available at voltages of about 600-700, it is common practice to operate say such cells in series electrically.
  • the bottom electrode, the cathode may be 75 inches Wide and 148 inches long and the top electrode, the anode, ay be 45 inches wide and 120 inches long,
  • the liquid electrolyte may aggregate 8000 lbs. and the solid electrolyte, in theform of a crust cover ing the liquid electrolyte may aggregate 7000 lbs. (excluding electrolyte carried into the cell lining by electro-o-smosis).
  • the fused metal tapped every three days forexample, may-vary in depth over the'bottom electrode from 'a'minimum of about 1 or 2 inches to a maximum of about 6 inches, the depth of liquid electrolyte over the fused metal being about 9 inches, and the power may approximate 32,000 amperes at about 5.5 volts, the current efficiency being about 85%.
  • the alumina dissolved in the fusion is consumed by the electrolysis, fresh alumina'isaddedfrom time to time.
  • a single iabcrer can usually tend eight cells'for his shift aud t-he operation of each of the cells isa separate operation, in effect a batch operation since alumina is charged and consumed and charged againwhen consumed and so on, althou'ghthe electrolysis is carried out continuously.
  • the Hall process requires a regular supply of fresh alumina of high purity.
  • the recovered solution .after regeneration with added caustic soda or; lime andxsodaaash, is re'-used cyclically in the digestion.
  • the. sodium alu min-ate solution instead of being formed by digestion as in. the Bayer process, is formed by sinteringthe ore with lime or lime and'soda and by extracting.thehiluminate from the sintered-prodnot with water or aqueous caustic soda, the
  • tnolyte of each: cell to thenext in the seriesby a trough, thermally well insulated-and with. appropriateinsulationto separate the successive cell chambers electrically, 1 provide a smelting turn'ace to wl-iich the bauxite or other aluminiferous material is charged together with carbon, as coke for xamplaandtowhich Iitra-nsfer fusion from the last cell of the series, I provide a reaction furnace-in which fusion fromthe smelting furnace is reacted with'aluminum, and I provide a pair of filters charged-with carbonaceous materiaL'on e through -:which the'fusion passes'from' the smelting furnacev to the reaction furnace and another thrcugh which'.
  • the fusion passes "from the reaction furnace and from which I transfer the regenerated fusion to the firstcell of the series.
  • I may provide a pair of thermally well insulated resere "voirs connected to the cell chambers :of the first 'a-nd las-tc'ells of the series and then may transfer fusi'on to an-d from these reservoirs rather than" to andffrom the-fi'rstan-d last'cells,respectively, or such reservoirs may 'lo'e omitted.
  • Two such series of' 60 cells again connected in electrical series wi'llta'ke theplace of the conventional battery of 120 cells.
  • the conductivity of the electrolyte being relatively low, I make the current losses through the stream of electrolyte connecting successive pairs of cells negligible by making these troughs lon with respect to the distance between the electrodes in each cell and by restricting their cross section.
  • passage through the several troughs may be made about inches to inches long and about 6 inches wide and deep enough to provide for a stream of liquid electrolyte about 4 inches deep covered with a crust of frozen electrolyte of about the same depth.
  • the cycle of movement of the electrolyte is also a cycle of variation of alumina content from a maximum entering the first cell to a minimum leaving the last. Since I dissolve the alumina in the fusion before the fusion is supplied to the first cell of the series, I no longer need be concerned with the rate of solution of the alumina in the fusion in the cell and, as a consequence, I can safely charge a fusion containing a high concentration of alumina to the first cell since the alumina is dissolved before the fusion enters the cell. Then, havin thus been able to raise the initial concentration, I can economically carry a higher than normal minimum concentration of alumina in the fusion leaving the last cell of the series to avoid occurrence of the anode effect.
  • the concentration of alumina in the fusion as it moves through the series of cells may vary from about 12%14% to about 2%-2.5% in each cycle. Having selected a minimum concentration, circula- .tion of the electrolyte is maintained at a rate sufficient to maintain this minimum concentration. The maximum concentration is maintained by appropriate addition of aluminiferous ore to the smelting furnace. There, and in the associated reaction furnace and the two filters, the alumina content of the ore is dissolved in the fusion and the impurities, particularly iron, silicon and titanium are removed to produce the electrolyte of high purity charged to the first cell of the series containing alumina in maximum concentration.
  • the purification is further controlled, in accordance with my invention, by controlling the NaF:AlF3 ratio in the fusion as it passes through the smelting furnace, the reaction furnace and the two filters. If this ratio is maintained at a value exceeding 150:100, iron is removed almost quantitatively and titanium removal is satisfactory but the residual combined silicon tends to increase; if this ratio is maintained at a value less than 1501100, silicon is removed almost quantitatively and the purification with respect to iron and titanium is satisfactory. I have found a ratio of about 1451100 to be particularly advantageous. This ratio is easily adjusted by appropriate additions, to the smelting operation for example, of sodium fluoride or aluminum fluoride.
  • the first filtration is, with advantage, carried out in a coke filled tower from which coke saturated with impurities is transferred to the smelting operation, the iron, silicon and titanium separated in the filter thus being recovered as part of the alloy separated as a byproduct in the smelting operation.
  • the quantity of material separated from the fluoride fusion in the second filtration although important withrespect to the quality of the metal produced by subsequent electrolysis of the fusion, is relatively small compared to that separated in the first filtration and the quantity of carbonaceous filtering material to be handled in the second filtration is correspondingly small.
  • Fig. l is a flow diagram illustrating the practice of the process of my invention.
  • Fig. 2 is a vertical section of a smelting furnace
  • Fig. 3 is an elevation normal to the view shown in Fig. 2;
  • Fig. 4 is a vertical section of a reaction furnace
  • Fig. 5 is a vertical section normal to the view shown in Fig. 4;
  • Fig. 6 is an elevation in section of three of a series of cells arranged for practicing my invention.
  • Fig. 7 is a vertical section of one of the cells shown in Fig. 6 normal to the view shown in Fig. 6;
  • Fig. 8 is a vertical section of a transfer ladle
  • Fig. 9 is a top view of the transfer ladle shown in Fig. 8.
  • Fig. 10 is a bottom view of the transfer ladle shown in Fig. 8.
  • Fig. 1 The several rectangles [0 represent four cells of a series of sixty.
  • the cells are in electrical series through the several connections II, the terminal anode being indicated at l2 and the terminal cathode at l3.
  • the several cells are also connected in chemical series by troughs I4.
  • the cells and troughs may be constructed as illustrated in Figs. 6 and '7.
  • a smelting furnace such as is illustrated in Figs. 2 and 3
  • a calcining furnace such as a conventional rotary kiln, is illustrated at 46.
  • a carbonaceous filter for fusion discharged from the smelting furnace is represented at 41.
  • a reaction furnace constructed, for example, as illustrated in Figs.
  • the alumina content of the ore is dissolved in depleted electrolyte, the fluoride fusion, from the last cell of the series, the sixtieth cell in the series illustrated, and th thus regenerated electrolyte is transferred to the first filter 41 after separation from the bulk of the iron, silicon and titanium in the smelting furnace II.
  • the filter 41 the fusion from the smelting furnace I! is filtered through a body of carbonaceous material such as coke, the bulk of the remaining iron, silicon and titanium being removed by the carbonaceous material in this filter,
  • reactionfurnace 48 the reactionfurnace 48.
  • the reaction furnace 48 the 'bulk of the remaining traces of iron, silicon and titanium are reduced and thusrendered insoluble in the fusion by reactionwith aluminum.
  • the aluminum for this reaction is with advantage added to the reaction furnace 48 as scrap aluminum but it may be produced in this furnace by tsubjectinglthe fusion passing through the furnace to electrolysis in the furnace.
  • the thus reduced insoluble material is then separated from the fu- .sionzby the second filtration through carbonaceous material in filter l
  • the twice filtered, regenerated electrolyte is transferred, or permitted :to flow, from the filter 45 to the first cell of the series.
  • the electrolyte is then circulated through the several cells of the series and a portion of its alumina content is electrolytically reduced to aluminum in each cell.
  • the smelting furnace illustrated comprises a steel shell 28 electrically separated into two parts'by insulation between "the annular flanges near the upper end-of the :shell, an insulating refractory lining 21, a fire brick lining 22 in its upper part and a carbon lining'23 in its lower part.
  • An opening 24 is'provided "in the upper end of the furnace through which it 'is charged and through which a carbon (electrode 2 may be inserted into'the charge'within the :furnace.
  • a spout 26 is provided for pouring metal and fusion from the lower part of the furnace.
  • a pair of tuyre 27 open into the furnac'e through trunnions just above the carbon lining.
  • Carbon inserts 28 are provided for elec- L ltrical connection to'the carbon lining in'the lower part of the furnace.
  • alumina isdissolved in the fluoride fusion introduced through opening '2 1- from aluminiferous material in the presence of carbon at a temperature effective to reduce iron compounds present to metallic iron.
  • crystallite or fluoride fusion mixture is with ad-' vantage introduced into the furnace in molten condition although it may be chargedzas a solid,
  • ajbody 30 of molten iron or iron alloy also containing silicon or titanium or both is accumulated and maintained in the lower part of the furnace. If the. ore contains insuficient iron to provide this body,'scrap iron or the. like in the-requisite amount is also charged to the smelting furnace.
  • the :fiuoride fusion is further purified, particularly with respect to silicon and titanium, by contact at high temperature with this molten metal.
  • thexbody of .molten iron or iron alloy in the lower part of the furnace may be stirred, electromagnetically for example.
  • the fluoride fusion can be further purified after .passagethrough the coke before being :poured from the furnace, by againblowingthe coke with air, through. the tuyres 21, to raise the temperature in the upper part of the furnaceto :a :point at which the reduced iron and any associated impurities melt and move downwardly through the coke and thence through the fluoride fusion into th molten metal in the lower part of the furnace.
  • This, cycle of operations is repeated tomaintain the required supply'of fluoride fusion containing dissolved alumina to be poured-from thefurnace as required for electrolysis.
  • the molten metal is poured from the furnace from time to time as it accumulates.
  • the composition of the iron may be such that :it :tends to remain on the coke except at temperatures excessively :high with respect to the fluoridefusion.
  • the iron can be removed from the-coke by melting, by air-blowing, after the bulk of the fluoride fusion has-been poured from the furnace higher temperatures can beused and-appropriate provisions can be made to recover vaporized fluorine and fluorides, for example, as specifically '"described.
  • this heat, or part of it, can with advantage be supplied by inserting the electrode "25 in the upper part of the furnace charge'and by passing an alternating current between this electrode and the carbon lining 23 in thelower part of the furnace.
  • the cokefilledtower constituting the first filter designated 4-? in Fig. 1 may be constructed in the same manner as the smelting furnace illustratedin Figs. 2 and 3, although it may be smaller than the smelting furnace.
  • Thetuyres may be omitted, but an electrode corresponding to that designated 25 and inserts connecting with the carbon lining in the lower part of the vessel corresponding to those designated 28 are with advantage provided to permit the maintenance of temperatures, by heat supplied electrically, above the melting point of fusion passing through the coke.
  • the reaction fur nace illustrated comprises a cylindrical steel shell 50 supported to permit pouring through spout 5! by rotation on trunnions 52, an insulating refractory lining 53, a fire brick intermediate lining 54 and a carbon inner lining 55.
  • a pair of carbon electrodes 56 are inserted through the openings 51 for electrically heating the reaction furnace. These electrodes may be hollow, as indicated, to permit the introduction through them and into the fusion undergoing treatment in the reaction furnace of a reducing gas such as methane.
  • Port 58 is provided for charging fusion and aluminum to the reaction furnace.
  • a pool of molten fluoride fusion is maintained in the furnace chamber and fusion is added to and withdrawn from this pool at intervals.
  • a temperature ranging from about 1060 C. to about 1150" C. is maintained in the furnace chamber by passing an alternating current through the pool of fusion as a resistor between the electrodes 56.
  • corresponding additions of scrap aluminum in amount sufficient to reduce the traces of silicon, iron and titanium remaining in the fusion charged to this furnace are also made.
  • This reaction furnace can be operated on a batch by batch basis although control of the tem perature of the fusion in the furnace is facilitated by operating it as just described.
  • the quantity of material separated from the fluoride fusion in the second carbonaceous filter is small enough to permit the use of very simple apparatus for this step.
  • the fusion may at this point in my process be filtered by passing it through a porous carbon plate as it enters the cell or cells to which it is being supplied.
  • This plate can be arranged in a simple vessel deep enough to provide a head of fusion sufficient to effect the fiow through the plate and well enough insulated to maintain the temperature of the fusion well above its melting point.
  • Such carbon plates can be pre-fabricated in appropriate shapes and can be replaced from time to time as they become charged with the separated reduced and insoluble impurities.
  • Figs. 6 and 7 The cells, or as they are commonly called reduction pots, illustrated are, considered individually, conventional in character except that the steel shells usually arranged between the carbon lining and the surrounding refractory are omitted.
  • the cell struc-- ture may include such conventional steel shells if desired.
  • Each cell comprises a carbon cell chamber 35 supported by but thermally insulated from a concrete foundation 3! by means of a layer of refractories 38 and a pair of carbon anodes 39 suspended by metal supports 40 also serving to connect the anodes to the bus-bar system. These anodes are shown elevated above normal operating position in Figs. 6 and 7 to facilitate illustration of the rest of the cell structure. Petroleum coke is a conventional and satisfactory anode material.
  • in the bases of each of the several cell chambers through extensions 42 serve to connect the cell chambers to the bus-bar system.
  • each of the cells of the series is connected to the next cell by a trough which provides for transfer of the fused electrolyte seriatim from cell to cell through the series.
  • the normal level of the liquid electrolyte in each cell chamber other than the first is slightly lower than that of the preceding chamber.
  • Each cell chamber being connected to the next by a trough 43, the electrolyte thus flows from cell to cell through the series from the first cell to the last cell of the series.
  • Each of these troughs is also supported by but thermally insulated from the concrete foundation 3'! by the refractory layer 38.
  • the trough lining 44 in contact with the electrolyte is formed of carbon to resist the action of the electrolyte, but to break the electrical connection between adjacent cell chambers through the trough lining, the series of separators 45, originally of the same section as the trough, are inserted as spacers in the carbon lining of the trough between each pair of cells.
  • These separators are with advantage fabricated as fused chromite-alumina blocks.
  • the cells illustrated in Figs. 6 and 7 are with advantage arranged so that the maximum electrolyte level is approximately at or somewhat below the level of the floor from which the cells are attended.
  • the cells can be positioned in a foundation supporting them laterally as well as from below; it is thus that the conventional steel shells can be omitted as previously stated to attain ims portant savings in installation costs and in maintenance costs. Breaking out of the electrolyte through the cell walls and over the floor is avoided and thus a serious danger to the operators is eliminated, shut down of cells through the running out of the electrolyte is avoided and the losses of electrolyte involved, directly and through contamination, are avoided. In my experience something more than 40% of the throw outs, that is the shut downs, of individual cells in a series during operation of the series results from such breaking out.
  • the transfer ladle illustrated comprises a steel shell 60, an insulating refractory lining 6
  • An eduction pipe 64 opens into the interior of the ladle through a carbon filter 65.
  • An electrode 66 extends through the cover in registry with an electrode 61 secured in the lower part of the ladle to permit electrical heating of the contents of the ladle, for example, to maintain fusion temperatures.
  • An opening 68 with a tight fitting closure is also provided in the cover 63.
  • a spout 69 is arranged to open into the lower part of the'ladle through the seat member 10 and a plug ll, arranged to close the opening to the spout 69 through the seat member 10, is carried by an operating extension 12 passing through the cover 63,
  • the spout 69 is with advantage of graphitized carbon. Trunnions T3 are provided to facilitate handling of the ladle and particularly the positioning of the spout 69, with an appropriate crane.
  • this transfer ladle In one way of operating this transfer ladle, starting with the ladle empty and the plug II away from the seat 10, the spout 69 is inserted in the material to be transferred, for example in the pouring spout of the smelting furnace illustrated in Figs. 2 and 3, a Vacuum suificient to draw the material into the ladle is applied through connection 64, when the ladle is full the plug H is rammed into the seat 10, the vacuum is released, the spout 69 is then repositioned at the desired point of discharge and the plug 11- is withdrawn from the seat 10. material may also be accelerated by imposing a pressure through connection 64.
  • a thermocouple is conveniently provided at a selected level at the upper part of the ladle to indicate to the operator that the fusion has reached this level when the ladle is being filled.
  • the reaction furnace such as indicated at 48 in Fig. 1 may be omittedand the reaction of the once filtered fusion from the first filter, indicated at 41 in Fig. 1, with aluminum may be carried out in a ladle used for transferring fusion from the first carbonaceous filter to the second carbonaceous filter.
  • this reaction with aluminum can be effected in a transfer ladle such as is illustrated in Figs. 8, 9 and 10 by charging the required quantity of aluminum through the opening 68 after the ladl'e has been filled with fusion, the plug rammed into the seat on the bottom pouring spout and the vacuum has been released.
  • concentration ofalumina in the fusion charged to the first cell of the series may; approximate 12-.%-14% and that of the fusion-dischargedafrom the last cell of the series may approximate 2%.-2.-5%"once the cycle of movement had. been established
  • The-balance of the. fusion mayibe of any conventional composition. 'Ihealumina-content. of thefusion discharged from-.thelast: cell Off/he series is replenished by dissolvin -alumina in the fusion.
  • Th'e fluoride, fusion replenished with respect to alumina, and at: least partially purified is passed through thefirst carbonaceous filter where it is subjected to a further purification with respect particularly to iron, silicon and titanium.
  • This once filtered'fusion is then reacted with aluminum in the reaction furnace andthe bulk of the remaining-traces"of'sili con, iron and titanium are thus reduced-and rendered insoluble in-the fusion.
  • This reduced and insoluble material is then removed in-the second carbonaceous filter where the fusion is subjected to a still further purification.
  • the replenished andpurified fluoride fusion is then charged to'the first cell of the series.
  • Acycle' of electrolyte flow in which the electrolyte is repeatedly replenished with dissolved alumina repeatedly purified by the double filtration coupled with the intermediate reaction with aluminum and in which the purified aluminathus supplied is progressively'electrolyzed to produce aluminum in a series of cellsis thus established.
  • Some aluminiferous 1 materials, rawor' partially processed bauxites, occur in a form or in-a state of subdivision such that the impurities, particularly compounds ofiron and" silicon, become dispersed: in an extraordinaryminute: state of-tsubdivision in caustic liquors used, as vinithe- Bayer. process, to dissolve: their alumina content and thus impose an unusual: burden upon. conven tional practices'in connectionwiththe separation of such dispersed solid impurities prior t'o'precipit'ation of aluminum hydrate from the solution.
  • My process is ofspecial'advant'age inapplication to such raw materials for the'production of aluminum. In its broader. aspect, and particularly in theconnection just noted; my process is.
  • alumina-containing fluoride fusion consistingessentially of the fluoridesnof sodiumandaluminum throughaseriesof cells in each of which it is subjected: to; electrolysis i'esultingwin-.-adiminution* of thealuminacontentof tthe-fusion, dis.-
  • the improvement which comprises circulating an alumina-containing fluoride fusion consisting essentially of the fluorides of sodium and aluminum through a series of cells in each of which it is subjected to electrolysis resulting in a diminution of the alumina content of the fusion, dissolving alumina in the alumina-depleted fluoride fusion discharged from the last cell of the series by bringing said alumina-depleted fusion in the presence of coke into contact with a charge of material consisting essentially of alumina but also including impurities of the group consisting of combined iron, silicon and titanium while maintaining a temperature effective to reduce a part of the iron compounds present to metallic iron in a smelting operation, separating the fluoride fusion with its alumina content thus replenished from the bulk of the metallic iron formed in the smelting operation, then filtering the separated fluoride fusion through a body of coke, reacting the alumina-containing fluoride fusion consisting essentially of the fluorides of sodium and aluminum
  • the improvement which comprises circulating an alumina-containing fluoride fusion consisting essentially of the fluorides of sodium and aluminum through a plurality of cells in which it is subjected to electrolysis resulting in a diminution of 'the alumina content of the fusion, dissolving alumina in the alumina-depleted fluoride fusion discharged from said cells by bringing said alumine-depleted fusion in an alumina-replenishing zone and in the presence of carbon into contact with a charge of material consisting essentially of alumina but also including impurities of the group consisting of combined iron, silicon and titanium while maintaining a temperature effective to reduce a part of the iron compounds to metallic iron, separating in said aluminareplenishing zone the fluoride fusion with its alumina content thus replenished from the bulk of the iron, then filtering the fusion with its alumina content thus replenished through a porous
  • the improvement which comprises circulating an alumina-containing fluoride fusion consisting essentially of the fluorides of sodium and aluminum through a series of cells in each of which it is subjected to electrolysis resulting in a diminution of the alumina content of the fusion, dissolving alumina in the alumina-depleted fluoride fusion discharged from the last cell of the series by bringing said alumina-depleted fusion in an alumina-replenishing zone and in the presence of carbon into contact with a charge of material consisting essentially of alumina but also including impurities of the group consisting of combined iron, silicon and titanium while maintaining a temperature effective to reduce a part of the iron compounds present in metallic iron, separating in said alumina-replenishing zone the fluoride fusion with its alumina content thus replenished from the bulk of the iron, then filtering the separated fluoride fusion through a porous mass of

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US575313A 1945-01-30 1945-01-30 Enriching the alumina content of recirculated cryolite fusions in aluminum production Expired - Lifetime US2451491A (en)

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FR917081D FR917081A (fr) 1945-01-30 1945-11-07 Production d'aluminium
CH252394D CH252394A (fr) 1945-01-30 1946-01-25 Procédé de fabrication d'aluminium.

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2587328A (en) * 1946-02-12 1952-02-26 Reynolds Metals Co Purification of alumina-containing materials
US3259557A (en) * 1962-03-02 1966-07-05 Nat Steel Corp Method of electrodepositing aluminum

Citations (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CH472A (fr) * 1889-01-28 1889-03-28 Louis Reuleaux Fourneau destiné au chauffage préalable des matières à soumettre, soit à la chaleur voltaïque, soit au chauffage électrique combiné à l'électrolyse, pour la production de l'aluminium et d'autres métaux analogues
US400766A (en) * 1889-04-02 Process of reducing aluminium by electrolysis
US1384499A (en) * 1920-05-07 1921-07-12 Samuel A Tucker Method of and apparatus for refining metals
US1464625A (en) * 1920-03-18 1923-08-14 Pacz Aladar Electrolyte for aluminum production and method of preparing same
DE477425C (de) * 1926-01-28 1929-06-06 Aluminium Ind Akt Ges Verfahren zur elektrolytischen Gewinnung von reinem Aluminium aus Rohaluminium, Legierungen und sonstigem Aluminiumgut
DE520851C (de) * 1927-10-25 1931-03-14 Eugen Herzog Gewinnung einer fuer die Elektrolyse geeigneten Tonerde
DE642644C (de) * 1932-09-21 1937-03-11 Fritz Frenzel Verfahren zur Herstellung von Aluminiumoxyd durch Schmelzen von z. B. Bauxit im elektrischen Ofen in Gegenwart von Reduktionsmitteln
GB503578A (en) * 1937-05-14 1939-04-11 Cie De Products Chimiques Et E Electrolytic refining of aluminium
US2162942A (en) * 1935-07-20 1939-06-20 Rohden Charles De Process for the preparation of magnesium by the electrolysis of its fused chloride

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Publication number Priority date Publication date Assignee Title
US400766A (en) * 1889-04-02 Process of reducing aluminium by electrolysis
CH472A (fr) * 1889-01-28 1889-03-28 Louis Reuleaux Fourneau destiné au chauffage préalable des matières à soumettre, soit à la chaleur voltaïque, soit au chauffage électrique combiné à l'électrolyse, pour la production de l'aluminium et d'autres métaux analogues
US1464625A (en) * 1920-03-18 1923-08-14 Pacz Aladar Electrolyte for aluminum production and method of preparing same
US1384499A (en) * 1920-05-07 1921-07-12 Samuel A Tucker Method of and apparatus for refining metals
DE477425C (de) * 1926-01-28 1929-06-06 Aluminium Ind Akt Ges Verfahren zur elektrolytischen Gewinnung von reinem Aluminium aus Rohaluminium, Legierungen und sonstigem Aluminiumgut
DE520851C (de) * 1927-10-25 1931-03-14 Eugen Herzog Gewinnung einer fuer die Elektrolyse geeigneten Tonerde
DE642644C (de) * 1932-09-21 1937-03-11 Fritz Frenzel Verfahren zur Herstellung von Aluminiumoxyd durch Schmelzen von z. B. Bauxit im elektrischen Ofen in Gegenwart von Reduktionsmitteln
US2162942A (en) * 1935-07-20 1939-06-20 Rohden Charles De Process for the preparation of magnesium by the electrolysis of its fused chloride
GB503578A (en) * 1937-05-14 1939-04-11 Cie De Products Chimiques Et E Electrolytic refining of aluminium

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2587328A (en) * 1946-02-12 1952-02-26 Reynolds Metals Co Purification of alumina-containing materials
US3259557A (en) * 1962-03-02 1966-07-05 Nat Steel Corp Method of electrodepositing aluminum

Also Published As

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CH252394A (fr) 1947-12-31
FR917081A (fr) 1946-12-24

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