US2915441A - Baths used in igneous electrolysis - Google Patents

Baths used in igneous electrolysis Download PDF

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Publication number
US2915441A
US2915441A US573139A US57313956A US2915441A US 2915441 A US2915441 A US 2915441A US 573139 A US573139 A US 573139A US 57313956 A US57313956 A US 57313956A US 2915441 A US2915441 A US 2915441A
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Prior art keywords
bath
metal
zirconium
titanium
electrolysis
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Expired - Lifetime
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US573139A
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English (en)
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Pruvot Emile Jean Baptiste
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Pechiney SA
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Pechiney SA
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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
    • 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
    • C25C3/18—Electrolytes
    • 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
    • C25C3/24—Refining
    • 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
    • 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
    • C25C7/005—Constructional parts, or assemblies thereof, of cells; Servicing or operating of cells of cells for the electrolysis of melts

Definitions

  • the present invention is directed to improvements in the composition of and method of use of chlorofluorinated baths employed inii'geneous electrolysis for producing and refining .metalsand :moreparticularly, aluminum, beryllium, titanium and zirconium.
  • a further "and-particular obje'ct'oi the present invention is' an improved method for refiningtitanium and zirconium'scrap'and an improved apparatus' for carrying out this .method.
  • Theel'ectrolyte is, generally composed'of a mixture of chlorides and fluorides containing an appreciable proportion of a halogenated compound: of the metal which it is desired to refine in order. the'avoid the deposition,'at
  • the cathode of alkali or alkaline-earth metals, the salts of which generallycons'titute the major portion of the electrolyte.
  • this alumina is precipitated on the anode increasing thereby the ohmic resistance at the contact of the two layers; it islikewise" deposited all around the electrolysis crucible and forms crusts heavily loaded with alumina, since the alumina content may reach 50%,”thusleading to a contraction in the" crosssection of the crucible'and, hence,”to an increase in the current densityanda further cause for the'increas'e. in the'voltageat the terminals'of'the cell.
  • the present invention which is based on applicants investigations, relates to a process which makes it possible to avoid these drawbacks by causing the disappearance of the oxidized compounds from the electrolysis bath or the correcting bath.
  • This process consists in treating the bath with a compound which is capable of exerting onthe oxidized compounds an energetic fiuorinatin It is action and of transforming them into fluorides. possible to use gaseous hydrofluoric acid; however, good results are obtained by the use of alkaline or alkalineearth bifluorides, as for example NaF.HF, KF.HF, CaF .2l-IF.
  • the fluorinating action of ammonium bifluoride starts at 200 C., a temperature sufficiently high to dehydrate most of the halides of which the bath is constituted.
  • the action of the bifluoride may advantageously be extended up to 600 C.
  • Example 1 In the electrolytic refiing of aluminum by means of a bath containing 60% barium chloride and 40% chiolithe (2AlF 3NaF), the correction of the bath is carried out most often by means of a mixture of salts containing NaCl, BaCl and AlF in suitable proportions, sometimes in equal parts, and sometimes in the proportion ofby way of example25% NaCl, 35% BaCl 40% AlFg. v i
  • the process which is the object of the present invention is not limited to the refining of aluminum, but can also be applied in all cases where the presence of an oxidized compound is undesirable, both in electrolytic production (elaboration) as well as in the refining of metals.
  • this process consists in treatingthe bath with an energetic fluorinating agent, for example, hydrofluoric acid or ammonium bifluoride, which is capable ofv transforming the oxidized compounds into fluorides.
  • an energetic fluorinating agent for example, hydrofluoric acid or ammonium bifluoride
  • a further feature of the present invention consists in excluding from the treatment with the fluorinating agent, those chlorides which are susceptible of being transformed into fluorides undesirable in the electrolysis. These chlorides may be separately dried, if necessary in a vacuum, before being mixed with the substances which are subjected to the fluorinating treatment.
  • Example 2 In the continuous refining of aluminum by means of a bath containing 60% BaCl and 40% chiolithe (2AlF .3NaF), there are periodically made corrective additions containing AIF BaCl and NaCl.
  • the fluorinating treatment by means of NH F.HF transforms a portion of the barium chloride into barium fluoride, the presence of which changes the density, the fusion point and the selectivity of the bath which, as a result of such changes, may be rendered unsuitable for the aluminum refining operation. Accordingly, and following applicants further improvement, the procedure adopted is as follows:
  • the hot aluminum fluoride is poured into an aluminum basin and permitted to cool. 'As soon as it is cold, it is immediately mixed with the two other correcting salts BaCl and NaCl which previously have been carefully dried at 120 C. There is obtained in this manner an addition bath free of oxides.
  • the present invention finds a particularly important application in the electrolytic refining of titanium and zirconium.
  • the metallurgy of titanium as well as of zirconium produces a metal which is frequently contaminated with impurities, as for example, oxygen and nitrogen.
  • impurities as for example, oxygen and nitrogen.
  • an appreciable percentage of the resultant metal sometimes between 40% and 50%, does not possess the necessary ductility and constitutes scrap.
  • the production cost of ductile titanium and zirconium is appreciably increased as a result of this circumstance and it becomes mandatory to treat this scrap. It is afurther object of the present invention to use the improved process disclosed herein in the treatment of such titanium and zirconium scrap.
  • Electrolytic refining processes of metals have been known for a long time:
  • the crude metal is used as an anode which is dissolved little by little by the anions of the electrolyte and is deposited in a pure state onthe cathode.
  • This process is especially used in refining aluminum and beryllium, using as electrolytes molten alkaline vor alkalineeearth halides containing ac'ertain proportion of the halide of the metals which it is desired to refine, so as to maintain in the electrolyte a certain concentration of cation of the metal to be deposited, for example, between 35 and 115 gr. of this metal per kgm. of bath.
  • ductile titanium and Zirconium having a Brinell hardness less than 120, and frequently less than 100, by the electrolytic refining of scrap metal in a bath preferably composed of molten alkali chlorides; the necessary quantity of titanium or zirconium ions is obtained preliminarily by acting with a tetrachloride, TiCL, or ZrCl on titanium or zirconium scrap, which constitutes the anode element of the refining cell.
  • An important feature of the improvedprocess according to the invention consists in eliminating all trace of oxygen in the electrolyte prior to starting the refining operation; indeed, it has been observed that when such elimination is suitably carried out, there is obtained at the beginning of the refining operation metallic titanium the Brinell hardness of which is less than 100. A similar improvement has been found in the case of the zirconium also. i
  • NaCl or NaCl+KCl are mixed in the dry condition, with for example, 10% of NH F.HF.
  • the mixture is heated to between 300 and 400 C. to start the deoxi dizing effect.
  • a small quantity of titanium or zirconium chips of the order of a few percent of the bath is added, in order to reduce the sulphates into sulfides; thereupon, the chlorides are molten at a maximum temperature of 900 C. Under these conditions, the sulfides are destroyed by the residual bifluoride which completes in a thorough manner the deoxidization and de-sulfurization.
  • This operation can be carried out in air but, preferably, is carried out in an argon atmosphere as is also the subsequent electrolysis.
  • the titanium or zirconium tetrachloride is then injected into the interior of abasket containing the scrap of the metal to be refined, and which will subsequently form the anode assembly during the electrolysis.
  • the TiCl or ZrCl is transformed almost completely. into bichlorides.
  • the injection of the tetrachloride can be stopped when the bath contains about 40 grms. of titanium or zirconium per kgm. of electrolyte, but the injection can be contined until there is obtained, for example, 60 to grms. of the metal to be refined per kgm.
  • the electrolytic refining is thereafter carried out in known manner without it being necessary to reinject the tetrachloride.
  • the present invention also comprehends an electrolysis cell which enables the refining of titanium or zirconium to be carried out in a continuous manner using the resistance of the bath to maintain the electrolyte in molten condition without the use of an external heat supply.
  • Figures 1 and 2 show an embodiment of an electrolysis cell in accordance with the invention, wherein Figure 1 shows a vertical sectional view along the line 1-1 of Figure 2, of the electrolysis cell, and
  • Figure 2 is a plan View of the cell partly in section, the section plane being along line 22 of Figure 1.
  • 1 designates the external metallic casing of the cell
  • 2 the heat insulation jacket
  • 3 the interior casing which may be of sheet iron.
  • 5 is a circular iron basket made, for example, of a sufliciently close metallic screen; this basket, filled with titanium or zirconium scrap, is connected at 6 to the positive pole.
  • the cathodes 7 are formed of metallic tubes which are closed at their lower ends; they dip into the molten electrolyte the level of which is represented by the line 8-8. These cathodes are extended upwardly by tubes 9, 9 of a smaller diameter, which makes it possible to remove them when the titanium or zirconium deposit has become too thick; these tubes are connected at their upper ends to the negative pole by the conductor 16.
  • the muds accumulate at the bottom of the cell at 11, and can be periodically removed through a lock chamber 12 closed with a tight cover 13.
  • a cylindrical space or chamber 14 extends above the electrolysis cell; it is lined at its circumference by the basket 5 containing the titanium or zirconium scrap and is traversed by the rods 9 carrying the cathodes.
  • the cylindrical chamber is fixed at its lower end to the electrolysis cell by means of a tight joint 15.
  • Openings 20 enable the introduction, when necessary, of an iron bar to facilitate the descent of metal scrap to be refined into the basket 5, or of a tube for introducing TiCl or ZrCl to form the titanium or zirconium cations before the start of the electrolysis.
  • the quantity of titanium or zirconium scrap contained in the basket permits continuous operation of the electrolysis for a period of to days, but there are provided three scrap feeding lock chambers 21 disposed above the iron ring of the cover of the cylindrical chamber 14, at the side of the openings 20. By'the use of these lock chambers, the scrap metal to be formed falls directly into the basket 5.
  • the cathode which it is desired to remove, is first lifted into the cylindrical chamber in order that it may drain; it is then introduced into its lock chamber 17, and the valve 18 thereof is closed; it cools therein and the lock chamber can then be opened at its upper end for the removal of the cathode coated with titanium or zirconium, and for the replacement of the cathode.
  • the same lock chambers which serve for the transfer of the cathodes can advantageously be used for the introduction of the bath previously treated asset out above.
  • the electrolysis cell in accordance with this invention makes it possible to obtain a continuous refining operation.
  • the compact form of the cell makes it possible to maintain the electrolyte in a liquid state by the heat evolved by the passage of the electric current therethrough.
  • the cell can operate with current strengths of thousands of amperes.
  • the fluorinating agent is a compound selected from the class consisting of gaseous hydrofluoric acid, ammonium bifluon'de, alkali metal bifluorides and alkaline earth metal bifluorides.

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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)
  • Inorganic Compounds Of Heavy Metals (AREA)
US573139A 1955-03-30 1956-03-22 Baths used in igneous electrolysis Expired - Lifetime US2915441A (en)

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FR1044420X 1955-03-30

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US (1) US2915441A (de)
CH (1) CH351757A (de)
DE (1) DE1044420B (de)
FR (2) FR1124194A (de)
GB (1) GB813457A (de)

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3725222A (en) * 1971-10-26 1973-04-03 Aluminum Co Of America Production of aluminum

Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US578633A (en) * 1897-03-09 Process of reducing aluminium
US736020A (en) * 1898-09-27 1903-08-11 Charles W Roepper Apparatus for the electrolysis of fused substances.
US786244A (en) * 1903-09-12 1905-03-28 Henry Spencer Blackmore Process of extracting aluminium or other metals.
US842256A (en) * 1905-07-17 1907-01-29 George O Seward Electrolytic cell.
US2451494A (en) * 1947-01-28 1948-10-19 Reynolds Metals Co Enriching alumina content of cryolite fusions
GB713446A (en) * 1951-06-23 1954-08-11 Peter Spence & Sons Ltd A process for preparing titanium metal
US2731402A (en) * 1952-07-03 1956-01-17 Horizons Titanium Corp Production of metallic titanium
US2755240A (en) * 1953-11-02 1956-07-17 Shawinigan Water And Power Com Electrolysis of titanium tetrachloride to produce titanium

Patent Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US578633A (en) * 1897-03-09 Process of reducing aluminium
US736020A (en) * 1898-09-27 1903-08-11 Charles W Roepper Apparatus for the electrolysis of fused substances.
US786244A (en) * 1903-09-12 1905-03-28 Henry Spencer Blackmore Process of extracting aluminium or other metals.
US842256A (en) * 1905-07-17 1907-01-29 George O Seward Electrolytic cell.
US2451494A (en) * 1947-01-28 1948-10-19 Reynolds Metals Co Enriching alumina content of cryolite fusions
GB713446A (en) * 1951-06-23 1954-08-11 Peter Spence & Sons Ltd A process for preparing titanium metal
US2731402A (en) * 1952-07-03 1956-01-17 Horizons Titanium Corp Production of metallic titanium
US2755240A (en) * 1953-11-02 1956-07-17 Shawinigan Water And Power Com Electrolysis of titanium tetrachloride to produce titanium

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Publication number Publication date
DE1044420B (de) 1958-11-20
FR67974E (fr) 1958-03-26
FR1124194A (fr) 1956-10-05
CH351757A (fr) 1961-01-31
GB813457A (en) 1959-05-13

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