EP0107521A1 - Process for the continuous production of lithium by electrolysis of lithium chloride in a molten salt mixture, and apparatus for carrying out said process - Google Patents

Process for the continuous production of lithium by electrolysis of lithium chloride in a molten salt mixture, and apparatus for carrying out said process Download PDF

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Publication number
EP0107521A1
EP0107521A1 EP83401664A EP83401664A EP0107521A1 EP 0107521 A1 EP0107521 A1 EP 0107521A1 EP 83401664 A EP83401664 A EP 83401664A EP 83401664 A EP83401664 A EP 83401664A EP 0107521 A1 EP0107521 A1 EP 0107521A1
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electrolysis
lithium
mixture
anode
cathode
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EP0107521B1 (en
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Monsieur Jean Grosbois
Monsieur Jean-Yves Dumousseau
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Rhodia Chimie SAS
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Rhone Poulenc Specialites Chimiques
Rhone Poulenc Chimie 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
    • C25C3/02—Electrolytic production, recovery or refining of metals by electrolysis of melts of alkali or alkaline earth metals

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  • the present invention relates to a process for the preparation of lithium by electrolysis of lithium chloride in a mixture of molten salts; it also relates to an apparatus used for the implementation of said method.
  • the electrolysis medium consists of a mixture of molten salts based on lithium chloride and at least one other alkaline and / or alkaline earth chloride which, with lithium chloride, form a melting eutectic mixture at a temperature between approximately 320 and 360 ° C.
  • binary mixture which can be used, mention may be made of lithium chloride and potassium chloride; as ternary mixtures which can be used, mention may be made of mixtures containing, in addition to lithium chloride and potassium chloride, a chloride chosen from sodium, rubidium, strontium, magnesium, calcium and barium chlorides.
  • the mixture of molten salts supplying the electrolyzer should have a composition fairly close to the eutectic composition of the mixture used with an excess of lithium chloride which will be subjected to electrolysis.
  • the amount of lithium chloride in said mixture may vary by about 69 mol% in the mixture of molten salts entering the electrolyser at approximately 56 mol% in the mixture leaving the electrolyser.
  • the lithium chloride may be in an excess of up to 10 mol% relative to the eutectic composition of the mixture of molten lithium chloride-potassium chloride salts.
  • the first characteristic of the process is that it is carried out continuously; that is to say that the electrolysis cell is continuously supplied with a fluid constituted by the mixture of molten salts containing, as the electrolysable material, lithium chloride and that the products are also continuously removed from the electrolyser electrolysis, that is to say chlorine on the one hand and the mixture of metallic lithium and molten salts on the other hand.
  • the lithium is not separated from the mixture of molten salts.
  • This characteristic linked to the natural recirculation which will be discussed later, has the consequence that the molten salts play a protective role with respect to the possible recombination of lithium which floats on the surface of the mixture of salts. melted with chlorine which forms the atmosphere above the surface of the electrolysis medium. It is therefore not necessary to take special precautions to isolate the electrolysis medium from said chlorine atmosphere.
  • Electrolysis is moreover carried out without the use of a diaphragm by the organization of a rapid natural circulation of the electrolysis medium.
  • Said circulation will be said to be natural because it is obtained simply by the entrainment effect on the electrolysis medium of the chlorine bubbles which are released at the anode; it is therefore not necessary, but not impossible to use a means of circulation independent of this natural means.
  • the upper part of the cathode is immersed and preferably has a flared shape.
  • the upward movement of the electrolysis medium linked to the preferably flared shape of the cathode makes it possible to push lithium towards the walls of the cell and thus facilitate its natural elimination by overflow while minimizing recombination with chlorine.
  • refractory material is meant a material which remains inert, at the electrolysis temperature, vis-à-vis products with which said refractory material is in contact, that is to say essentially the mixture of molten salts, the chlorine and lithium.
  • This material must be electrically insulating.
  • the sheathing of the anode will therefore be used with a material such as alumina, quartz, silica, thorine, zirconia or beryllium oxide.
  • the cell described can be used to carry out the electrolysis of lithium chloride in a medium of molten salts or according to the variant of the process of the invention for simultaneously carrying out the electrolysis of lithium chloride and calcium chloride (giving rise to a Li-Ca alloy) if the latter product is present in the mixture.
  • the electrolysis of lithium chloride is carried out in a mixture based on lithium chloride-potassium chloride having a composition close to the eutectic; for an intensity of 45 A with an active cathodic surface of 80 cm 2 and an anodic surface of 40 cm 2 , the interpolar distance being 1.6 cm, we obtain faradic yields of 85 - 90% with a voltage of 6 0.0 volts.
  • an electrolysis is carried out of a mixture based on lithium chloride-potassium chloride, calcium chloride, this mixture having a composition close to that of the eutectic; for an intensity of 40 A, with an active cathodic surface of 1.5 dm2 and an anodic surface of 0.47 dm2 (the distance between the electrodes being 2 cm), the faradaic efficiency is greater than 85%, the voltage at the terminals of the cell is 6.6 V and the Li-Ca alloy obtained contains 76% Li and 24% Ca in mole.
  • the extrapolation of the electrolysis device described above to the industrial stage can be carried out for example as shown in FIGS. 2 and 2a by the use of several anode-cathode couples.
  • Such a cell has a total diameter of approximately 120 cm
  • the graphite anodes (4) have a diameter of the order of 14 cm
  • the cathodes arranged around the anodes are made of steel and have an internal diameter of approximately 20 cm.
  • the upper part of the anode is sheathed with alumina.
  • the cell is supplied with a mixture of lithium chloride-potassium chloride containing an excess of about 10% by mole of lithium chloride, relative to the eutectic, the temperature of the electrolysis is 450 ° C, we work at 12 kA (i.e. 4 x 3 kA) (anode current density 85.2 A / dm2 and cathode current 58.7 A / dm2) and at 7 V. We obtain the production of 2.8 kg / h of lithium dispersed in the mixture of molten salts, which corresponds to a faradic yield of 90%.

Abstract

1. Process for the continuous preparation of lithium or of lithium-calcium alloys by electrolysis, at constant bath level, of lithium chloride or of a mixture of lithium chloride and calcium chloride in a mixture of molten salts, with continuous removal by overflow at the surface of the bath of the lithium or the lithium-calcium alloy formed mixed with molten salts and continuous recovery of an undiluted gaseous chlorine formed, the said process being characterized in that : - the electrolysis is performed with a natural circulation of the electrolysis medium between the anode and the cathode without the use of a diaphragm between these ; - the anode is surrounded by the cathode and sheathed with an electrically insulating refractory material on its part rising above the surface of the electrolysis medium and down to below this surface ; and - the removal of the lithium or the lithium-calcium alloy formed mixed with molten salts is performed in the presence of undiluted gaseous chlorine.

Description

La présente invention concerne un procédé pour la préparation de lithium par électrolyse du chlorure de lithium dans un mélange de sels fondus ; elle concerne également un appareillage utilisé pour la mise en oeuvre dudit procédé.The present invention relates to a process for the preparation of lithium by electrolysis of lithium chloride in a mixture of molten salts; it also relates to an apparatus used for the implementation of said method.

On a déjà décrit, par exemple dans le cadre des procédés de préparation de silane des Brevets US 3.078.218 et 3.163.590, la préparation de lithium par électrolyse du chlorure de lithium contenu dans un mélange de sels fondus à base de chlorure de lithium et d'au moins un chlorure alcalin et/ou alcalino-terreux ; les dits procédés sont caractérisés par la mise en oeuvre d'au moins une des caractéristiques suivantes

  • - on opère en semi-continu, c'est-à-dire que l'on charge la cellule d'électrolyse avec un mélange électrolysable et l'on réalise, sur ce mélange, l'électrolyse de la quantité de chlorure de lithium souhaitable, puis on admet dans le mélange restant une nouvelle charge de chlorure de lithium,
  • - on utilise des dispositifs complexes et délicats pour d'une part séparer, dans l'électrolyseur lui-même, le lithium obtenu d'avec le mélange des sels fondus et d'autre part éviter les réactions de recombinaison du chlore gazeux produit avec le lithium, c'est ainsi par exemple que l'on contrôle très soigneusement l'atmosphère de la cellule au-dessus de la couche de lithium et que l'on utilise un diaphragme dans le bain entre l'anode et la cathode.
We have already described, for example in the context of the processes for preparing silane from US Patents 3,078,218 and 3,163,590, the preparation of lithium by electrolysis of lithium chloride contained in a mixture of molten salts based on lithium chloride. and at least one alkaline and / or alkaline earth chloride; said processes are characterized by the implementation of at least one of the following characteristics
  • - operating semi-continuously, that is to say that the electrolysis cell is charged with an electrolysable mixture and is carried out, on this mixture, the electrolysis of the desired amount of lithium chloride , then a new charge of lithium chloride is admitted into the remaining mixture,
  • - complex and delicate devices are used to firstly separate the lithium obtained from the mixture of molten salts in the electrolyser itself and secondly to avoid recombination reactions of the chlorine gas produced with the lithium, for example, very carefully control the atmosphere of the cell above the lithium layer and use a diaphragm in the bath between the anode and the cathode.

La présente invention vise un procédé simplifié pour la réalisation de cette électrolyse ; ce procédé présente les caractéristiques suivantes :

  • - il est mis en oeuvre en continu,
  • - on ne sépare pas, dans l'électrolyseur, le lithium produit du mélange des sels fondus de sorte que l'on sort dudit électrolyseur un mélange constitué du lithium métallique et du mélange des sels fondus, ce qui simplifie considérablement la conduite de l'électrolyse.
  • - on effectue l'électrolyse sans utilisation d'un diaphragme entre l'anode et la cathode, mais en réalisant dans l'espace compris entre l'anode et la cathode, une circulation naturelle rapide du milieu d'électrolyse.
  • - enfin on protège l'anode contre une attaque éventuelle du lithium surnageant à la surface du milieu d'électrolyse et contre une éventuelle réoxydation directe du lithium sur l'anode en gainant ladite anode jusqu'au dessous de ladite surface avec un matériau réfractaire isolant.
  • - par ailleurs le chlore produit par l'électrolyse est soutiré en continu sans dilution par un gaz inerte ce qui permet son utilisation industrielle immédiate.
The present invention relates to a simplified method for carrying out this electrolysis; this process has the following characteristics:
  • - it is used continuously,
  • - In the electrolyser, the lithium produced from the mixture of molten salts is not separated so that a mixture consisting of metallic lithium and the mixture of molten salts is removed from said electrolyser, which considerably simplifies the operation of the electrolysis.
  • - Electrolysis is carried out without the use of a diaphragm between the anode and the cathode, but by producing in the space between the anode and the cathode, rapid natural circulation of the electrolysis medium.
  • - Finally, the anode is protected against a possible attack by the lithium supernatant on the surface of the electrolysis medium and against a possible direct reoxidation of the lithium on the anode by coating said anode to below said surface with an insulating refractory material .
  • - Furthermore, the chlorine produced by the electrolysis is withdrawn continuously without dilution by an inert gas, which allows its immediate industrial use.

Il va de soi que si, à partir du mélange sortant de l'électrolyseur, on désire récupérer le lithium pur, il conviendra de mettre en oeuvre des techniques connues de séparation de ce métal d'avec le mélange des sels fondus.It goes without saying that if, starting from the mixture leaving the electrolyser, it is desired to recover the pure lithium, it will be necessary to use known techniques for separating this metal from the mixture of molten salts.

Le milieu d'électrolyse est.-constitué d'un mélange de sels fondus à base de chlorure de lithium et d'au moins un autre chlorure alcalin et/ou alcalino-terreux qui, avec le chlorure de lithium, forment un mélange eutectique fondant à une température comprise entre 320 et 360°C environ. Comme mélange binaire utilisable, on peut citer le chlorure de lithium et le chlorure de potassium ; comme mélanges ternaires utilisables, on peut citer les mélanges contenant, en plus du chlorure de lithium et du chlorure de potassium, un chlorure choisi parmi les chlorures de sodium, de rubidium, de strontium, de magnésium, de calcium et de baryum.The electrolysis medium consists of a mixture of molten salts based on lithium chloride and at least one other alkaline and / or alkaline earth chloride which, with lithium chloride, form a melting eutectic mixture at a temperature between approximately 320 and 360 ° C. As binary mixture which can be used, mention may be made of lithium chloride and potassium chloride; as ternary mixtures which can be used, mention may be made of mixtures containing, in addition to lithium chloride and potassium chloride, a chloride chosen from sodium, rubidium, strontium, magnesium, calcium and barium chlorides.

Dans tous les cas, on opérera dans un milieu liquide ; l'électrolyse devant être réalisée à une température comprise entre 400 et 500°C environ et de préférence aux environs de 450°C, il convient que le mélange de sels fondus alimentant l'électrolyseur ait une composition assez voisine de la composition eutectique du mélange utilisé avec un excès en chlorure de lithium qui sera soumis à l'électrolyse. C'est ainsi (par exemple) que si l'on utilise comme milieu d'électrolyse un mélange de chlorure de lithium et de chlorure de potassium, on considère qu'à 450°C environ, la quantité de chlorure de lithium dudit mélange pourra varier d'environ 69 % en mole dans le mélange de sels fondus entrant dans l'électrolyseur à environ 56 % en mole dans le mélange sortant de l'électrolyseur. Dans ce cas, le chlorure de lithium peut être dans un excès allant jusqu'à 10 % en mole par rapport à la composition eutectique du mélange de sels fondus chlorure de lithium-chlorure de potassium.In all cases, we will operate in a liquid medium; the electrolysis having to be carried out at a temperature of between 400 and 500 ° C approximately and preferably around 450 ° C, the mixture of molten salts supplying the electrolyzer should have a composition fairly close to the eutectic composition of the mixture used with an excess of lithium chloride which will be subjected to electrolysis. Thus (for example) that if a mixture of lithium chloride and potassium chloride is used as the electrolysis medium, it is considered that at approximately 450 ° C., the amount of lithium chloride in said mixture may vary by about 69 mol% in the mixture of molten salts entering the electrolyser at approximately 56 mol% in the mixture leaving the electrolyser. In this case, the lithium chloride may be in an excess of up to 10 mol% relative to the eutectic composition of the mixture of molten lithium chloride-potassium chloride salts.

La première caractéristique du procédé est qu'il est mis en oeuvre de façon continue ; c'est dire que la cellule d'électrolyse est alimentée en continu avec un fluide constitué par le mélange de sels fondus contenant, comme matériau électrolysable, du chlorure de lithium et que l'on enlève également de façon continue de l'électrolyseur les produits de l'électrolyse, c'est-à-dire le chlore d'une part et le mélange de lithium métallique et de sels fondus d'autre part.The first characteristic of the process is that it is carried out continuously; that is to say that the electrolysis cell is continuously supplied with a fluid constituted by the mixture of molten salts containing, as the electrolysable material, lithium chloride and that the products are also continuously removed from the electrolyser electrolysis, that is to say chlorine on the one hand and the mixture of metallic lithium and molten salts on the other hand.

Comme autre caractéristique, on a signalé le fait que l'on ne sépare pas le lithium du mélange des sels'fondus. Cette caractéristique, liée à la recirculation naturelle qui sera discutée plus loin, a comme conséquence que le-s@'sels fondus jouent un rôle de protection vis-à-vis de la recombinaison possible du lithium qui surnage à la surface du mélange des sels fondus avec le chlore qui forme l'atmosphère au-dessus de la surface du milieu d'électrolyse. Il n'est donc pas nécessaire de prendre des précautions particulières pour isoler le milieu d'électrolyse de ladite atmosphère de chlore.As another characteristic, it has been pointed out that the lithium is not separated from the mixture of molten salts. This characteristic, linked to the natural recirculation which will be discussed later, has the consequence that the molten salts play a protective role with respect to the possible recombination of lithium which floats on the surface of the mixture of salts. melted with chlorine which forms the atmosphere above the surface of the electrolysis medium. It is therefore not necessary to take special precautions to isolate the electrolysis medium from said chlorine atmosphere.

On effectue de plus l'électrolyse sans utilisation d'un diaphragme grâce à l'organisation d'une circulation naturelle rapide du milieu d'électrolyse. Ladite circulation sera dite naturelle parce qu'elle est obtenue simplement par l'effet d'en- trainement sur le milieu d'électrolyse des bulles de chlore qui se dégagent à l'anode ; il n'est donc pas nécessaire,mais non impossible d'utiliser un moyen de circulation indépendant de ce moyen naturel. Comme le milieu d'électrolyse est entrainé verticalement par le mouvement ascendant des bulles de chlore dans l'espace situé entre l'anode et la cathode, il convient d'organiser une recirculation dudit milieu dans la cellule en faisant en sorte que ledit milieu redescende dans l'espace situé au-delà de la cathode pour pénétrer à nouveau, par des ouvertures convenablement aménagées, dans l'espace situé entre l'anode et la cathode. La vitesse de circulation dudit milieu est élevée puisque si on représente par Vo la vitesse de passage du milieu- d'électrolyse dans l'espace entre anode et cathode en absence de recirculation naturelle, la vitesse V réellement atteinte du fait de cette recirculation sera d'environ 100 fois Vo (elle était en moyenne dans les divers essais effectués de 0,5 à 5 cm/sec).Electrolysis is moreover carried out without the use of a diaphragm by the organization of a rapid natural circulation of the electrolysis medium. Said circulation will be said to be natural because it is obtained simply by the entrainment effect on the electrolysis medium of the chlorine bubbles which are released at the anode; it is therefore not necessary, but not impossible to use a means of circulation independent of this natural means. As the electrolysis medium is driven vertically by the upward movement of chlorine bubbles in the space between the anode and the cathode, it is advisable to organize a recirculation of said medium in the cell by causing said medium to descend in the space located beyond the cathode to re-enter, through suitably arranged openings, in the space located between the anode and the cathode. The speed of circulation of said medium is high since if we represent by Vo the speed of passage of the electrolysis medium in the space between anode and cathode in the absence of natural recirculation, the speed V actually achieved due to this recirculation will be approximately 100 times Vo (it was on average in the various tests carried out from 0.5 to 5 cm / sec).

Pour permettre cette circulation naturelle du milieu d'électrolyse, la partie supérieure de la cathode est immergée et présente de préférence une forme évasée.To allow this natural circulation of the electrolysis medium, the upper part of the cathode is immersed and preferably has a flared shape.

Le mouvement ascensionnel du milieu d'électrolyse lié à la forme de préférence évasée de la cathode permet de repousser le lithium vers les parois de la cellule et de faciliter ainsi son élimination naturelle par surverse en minimisant la recombinaison avec le chlore.The upward movement of the electrolysis medium linked to the preferably flared shape of the cathode makes it possible to push lithium towards the walls of the cell and thus facilitate its natural elimination by overflow while minimizing recombination with chlorine.

Enfin, l'anode doit être protégée contre une attaque éventuelle du lithium surnageant par une gaine en matériau réfractaire isolant qui plonge dans le bain d'électrolyse. Par matériau réfractaire, on entend un matériau qui reste inerte, à la température d'électrolyse, vis-à-yis des produits avec lesquels ledit matériau réfractaire est en contact, c'est-à-dire essentiellement le mélange de sels fondus, le chlore et le lithium. Ce matériau doit être isolant électriquement. On utilisera donc le gainage de l'anode par un matériau tel que l'alumine, le quartz, la silice, la thorine, la zircone ou l'oxyde de béryllium.Finally, the anode must be protected against possible attack by the supernatant lithium by a sheath of insulating refractory material which plunges into the electrolysis bath. By refractory material is meant a material which remains inert, at the electrolysis temperature, vis-à-vis products with which said refractory material is in contact, that is to say essentially the mixture of molten salts, the chlorine and lithium. This material must be electrically insulating. The sheathing of the anode will therefore be used with a material such as alumina, quartz, silica, thorine, zirconia or beryllium oxide.

Selon une variante du procédé de l'invention, il est possible le préparer par celui-ci et de façon similaire des alliages Lithium-calcium contenant au moins 50 % en mole de lithium ; dans :e cas on assure l'électrolyse d'un mélange chlorure de Lithium-chlorure de calcium dans un mélange de sels fondus et dans ies conditions similaires à celles qui ont été exposées ci-dessus.According to a variant of the process of the invention, it is possible to prepare it with it and similarly lithium-calcium alloys containing at least 50 mol% of lithium; in: e case the electrolysis of a lithium chloride-calcium chloride mixture is carried out in a mixture of molten salts and under conditions similar to those which have been set out above.

Le procédé selon l'invention conduit à la réalisation d'une cellule d'électrolyse présentant les caractéristiques techniques décrites ci-après :

  • - la cellule comporte une anode gainée entourée d'une cathode ; la partie supérieure de la cathode immergée dans le bain présente de préférence une forme évasée et des ouvertures sont ménagées à la base de ladite cathode ;
  • - l'alimentation de la cellule est réalisée préférentiellement par une amenée du mélange de sels fondus dans le bas de la cellule,
  • - enfin la cellule est pourvue de dispositifs de sortie, évacuant d'une part le mélange de sels fondus et le lithium métallique et d'autre part le chlore gazeux. Ces dispositifs sont constitués pεr un trop-plein et une évacuation de la phase gazeuse qui surmonte le milieu d'électrolyse.
The method according to the invention leads to the production of an electrolysis cell having the technical characteristics described below:
  • - The cell comprises a sheathed anode surrounded by a cathode; the upper part of the cathode immersed in the bath preferably has a flared shape and openings are formed at the base of said cathode;
  • - the cell is preferably supplied by supplying the mixture of molten salts to the bottom of the cell,
  • - Finally, the cell is provided with outlet devices, evacuating on the one hand the mixture of molten salts and metallic lithium and on the other hand chlorine gas. These devices consist of an overflow and an evacuation of the gas phase which overcomes the electrolysis medium.

On donne ci-après de façon non limitative un exemple de réalisation de l'invention pour une cellule contenant un seul couple anode-cathode ; la cellule d'électrolyse est schématisée, en coupe, sur la figure 1 :

  • - Le corps de la cellule 1 est en acier inoxydable.
  • - La cathode 2, en acier inoxydable également, a une forme cylindrique ; cette cathode est soudée au fond de la cellule et comporte, à sa partie inférieure des ouvertures 3 qui permettent la circulation du milieu d'électrolyse dans l'électrolyseur ; la partie supérieure 4 de la cathode est disposée de façon à rester sous la surface du milieu d'électrolyse (lorsque la cellule est en fonctionnement) et a une forme évasée ;
  • - L'anode 6 est en graphite, de forme cylindrique et disposée à l'intérieur de la cathode ; cette anode est gainée dans sa partie au-dessus du milieu d'électrolyse et jusqu'à une certaine distance au-dessous de la surface dudit milieu (lorsque la cellule est en fonctionnement) par une gaine d'alumine 10.
  • - L'alimentation en mélange de sels fondus est effectuée par un conduit d'amenée 5 qui débouche à la base de la cellule immédiatement au-dessous de l'espace situé entre l'anode et la cathode.
  • - La sortie des gaz (chlore) est réalisée à la partie supérieure de la cellule en 9 ; la sortie du mélange provenant de l'électrolyse est réalisée par le conduit 7 dont le niveau 8 détermine le niveau du milieu d'électrolyse dans la cellule.
  • - pour donner un ordre de grandeur des dimensions d'une cellule de ce type on peut indiquer que la distance entre l'anode et la cathode est de l'ordre de 1 à 5 cm environ et que la hauteur du milieu d'électrolyse (sensiblement la hauteur immergée de l'anode) est de l'ordre de 2 à 10 cm
An exemplary embodiment of the invention is given below, without limitation, for a cell containing a single anode-cathode pair; the electrolysis cell is shown diagrammatically, in section, in FIG. 1:
  • - The body of cell 1 is made of stainless steel.
  • - The cathode 2, also made of stainless steel, has a cylindrical shape; this cathode is welded to the bottom of the cell and comprises, at its lower part, openings 3 which allow the circulation of the electrolysis medium in the electrolyser; the upper part 4 of the cathode is arranged so as to remain below the surface of the electrolysis medium (when the cell is in operation) and has a flared shape;
  • - The anode 6 is made of graphite, of cylindrical shape and placed inside the cathode; this anode is sheathed in its part above the electrolysis medium and up to a certain distance below the surface of said medium (when the cell is in operation) by an alumina sheath 10.
  • - The mixture of molten salts is supplied by a supply pipe 5 which opens at the base of the cell immediately below the space between the anode and the cathode.
  • - The gas outlet (chlorine) is carried out at the top of the cell at 9; the output of the mixture from the electrolysis is produced by the conduit 7, the level 8 of which determines the level of the electrolysis medium in the cell.
  • - to give an order of magnitude for the dimensions of a cell of this type, it can be indicated that the distance between the anode and the cathode is of the order of approximately 1 to 5 cm and that the height of the electrolysis medium ( substantially the submerged height of the anode) is of the order of 2 to 10 cm

La description qui précède permet de constater que le chlore qui se dégage dans l'électrolyse est extrait de l'électrolyseur sans être dilué avec, par exemple, un gaz inerte. Cette caractéristique est importante dans la mesure où ce chlore peut être utilisé tel quel industriellement.The above description shows that the chlorine which is released in the electrolysis is extracted from the electrolyser without being diluted with, for example, an inert gas. This characteristic is important insofar as this chlorine can be used as it is industrially.

La cellule décrite est utilisable pour réaliser l'électrolyse du chlorure de lithium dans un milieu de sels fondus ou selon la variante du procédé de l'invention pour effectuer simultanément l'électrolyse du chlorure de lithium et du chlorure de calcium (donnant naissance à un alliage Li-Ca) si ce dernier produit est présent dans le mélange.The cell described can be used to carry out the electrolysis of lithium chloride in a medium of molten salts or according to the variant of the process of the invention for simultaneously carrying out the electrolysis of lithium chloride and calcium chloride (giving rise to a Li-Ca alloy) if the latter product is present in the mixture.

Selon l'invention, on effectue l'électrolyse du chlorure de lithium dans un mélange à base de chlorure de lithium-chlorure de potassium ayant une composition voisine de l'eutectique ; pour une' intensité de 45 A avec une surface active cathodique de 80 cm2 et une surface anodique de 40 cm2, la distance interpolaire étant de 1,6 cm, on obtient des rendements faradiques de 85 - 90 % avec une tension de 6,0 volts.According to the invention, the electrolysis of lithium chloride is carried out in a mixture based on lithium chloride-potassium chloride having a composition close to the eutectic; for an intensity of 45 A with an active cathodic surface of 80 cm 2 and an anodic surface of 40 cm 2 , the interpolar distance being 1.6 cm, we obtain faradic yields of 85 - 90% with a voltage of 6 0.0 volts.

On voit donc que ce dispositif, relativement simple, permet d'obtenir du lithium à un coût énergétique très satisfaisant (27 kWh/kg Li).It can therefore be seen that this relatively simple device makes it possible to obtain lithium at a very satisfactory energy cost (27 kWh / kg Li).

Dans la variante on effectue l'électrolyse d'un mélange à base de chlorure de lithium-chlorure de potassium, chlorure de calcium, ce mélange ayant une composition voisine de l'eutectique ; pour une intensité de 40 A, avec une surface cathodique active de 1,5 dm2 et une surface anodique de 0,47 dm2 (la distance entre les électrodes étant 2cm), le rendement faradique est supérieur à 85 %, la tension aux bornes de la cellule est de 6,6 V et l'alliage Li-Ca obtenu contient 76 % de Li et 24 % de Ca en mole.In the variant, an electrolysis is carried out of a mixture based on lithium chloride-potassium chloride, calcium chloride, this mixture having a composition close to that of the eutectic; for an intensity of 40 A, with an active cathodic surface of 1.5 dm2 and an anodic surface of 0.47 dm2 (the distance between the electrodes being 2 cm), the faradaic efficiency is greater than 85%, the voltage at the terminals of the cell is 6.6 V and the Li-Ca alloy obtained contains 76% Li and 24% Ca in mole.

L'extrapolation du dispositif d'électrolyse décrit ci-dessus au stade industriel peut être réalisé par exemple comme représenté sur les figures 2 et 2 bis par la mise en oeuvre de plusieurs couples anode-cathode.The extrapolation of the electrolysis device described above to the industrial stage can be carried out for example as shown in FIGS. 2 and 2a by the use of several anode-cathode couples.

Sur cette tigure on note :

  • - en 11 la paroi de l'électrolyseur,
  • - en 12 les cathodes qui sont disposées à l'intérieur de l'électrolyseur ; ces cathodes sont percées 13 à leur base,
  • - en 14 les anodes qui sont gainées sur une certaine hauteur avec de l'alumine,
  • - en 15 l'alimentation en mélange de l'électrolyseur,
  • - en 16 l'évacuation du mélange ayant subi l'électrolyse.
On this figure we note:
  • - at 11 the wall of the electrolyser,
  • - At 12 the cathodes which are arranged inside the electrolyser; these cathodes are pierced 13 at their base,
  • - in 14 the anodes which are sheathed over a certain height with alumina,
  • - in 15 supplying the electrolyzer with a mixture,
  • - In 16 the evacuation of the mixture having undergone electrolysis.

Une telle cellule a un diamètre total d'environ 120 cm, les anodes (4) en graphite ont un diamètre de l'ordre de 14 cm, les cathodes disposées- autour des anodes sont en acier et ont un diamètre intérieur d'environ 20 cm. La partie haute de l'anode est gainée d'alumine.Such a cell has a total diameter of approximately 120 cm, the graphite anodes (4) have a diameter of the order of 14 cm, the cathodes arranged around the anodes are made of steel and have an internal diameter of approximately 20 cm. The upper part of the anode is sheathed with alumina.

La cellule est alimentée à l'aide d'un mélange de chlorure de lithium-chlorure de potassium contenant un excès d'environ 10 % en moles de chlorure de lithium, par rapport à l'eutectique, la température de l'électrolyse est de 450°C, on travaille à 12 kA (soit 4 x 3 kA) (densité de courant anodique 85,2 A/dm2 et cathodique 58,7 A/dm2) et sous 7 V. On obtient avec un débit convenable la production de 2,8 kg/h de lithium dispersé dans le mélange des sels fondus ce qui correspond à un rendement faradique de 90 %.The cell is supplied with a mixture of lithium chloride-potassium chloride containing an excess of about 10% by mole of lithium chloride, relative to the eutectic, the temperature of the electrolysis is 450 ° C, we work at 12 kA (i.e. 4 x 3 kA) (anode current density 85.2 A / dm2 and cathode current 58.7 A / dm2) and at 7 V. We obtain the production of 2.8 kg / h of lithium dispersed in the mixture of molten salts, which corresponds to a faradic yield of 90%.

Claims (4)

1) Procédé pour la préparation continue de lithium par électrolyse du chlorure de lithium dans un mélange de sels fondus caractérisé en ce que : - on effectue l'électrolyse en ccntinu avec une circulation naturelle du milieu d'électrolyse entre les électrodes sans utilisation d'un diaphragme entre l'anode et la cathode, - on récupère en continu d'une part le lithium dans le mélange de sels fondus sans en opérer la séparation et d'autre part le chlore sous forme gazeuse. 1) Process for the continuous preparation of lithium by electrolysis of lithium chloride in a mixture of molten salts characterized in that: electrolysis is carried out in continuous with a natural circulation of the electrolysis medium between the electrodes without the use of a diaphragm between the anode and the cathode, - On the one hand, the lithium is continuously recovered from the mixture of molten salts without separating it, and on the other hand the chlorine in gaseous form. 2) Procédé selon la revendication 1, caractérisé en ce que l'on effectue l'électrolyse d'un mélange de sels fondus constitué d'un mélange de chlorure de lithium et de chlorure de potassium et contenant un excès de chlorure de lithium pouvant aller jusqu'à 10% en mole, par rapport à la composition eutectique et en ce que l'électrolyse est effectuée à une température comprise entre 400 et 500°C et de préférence de 450°C. -2) Method according to claim 1, characterized in that one carries out the electrolysis of a mixture of molten salts consisting of a mixture of lithium chloride and potassium chloride and containing an excess of lithium chloride which may range up to 10 mol%, relative to the eutectic composition and in that the electrolysis is carried out at a temperature between 400 and 500 ° C and preferably 450 ° C. - 3) Cellule d'électrolyse utilisable pour la mise en oeuvre d'un procédé selon les revendications 1 et 2, caractérisé en ce que : - la cellule comporte une anode entourée d'une cathode ; des ouvertures sont ménagées à la base de ladite cathode ; la partie supérieure de la cathode immergée dans le bain est de préférence de forme évasée, - l'alimentation de la cellule est réalisée par amenée du chlorure de lithium dans le mélange de sels fondus à la base de la cellule, - la cellule est pourvue de dispositifs de sortie du mélange obtenu, dispositifs constitués par un trop-plein et une évacuation de la phase gazeuse qui surmonte le milieu d'électrolyse. - l'anode est gainée avec un matériau réfractaire isolant dans la partie où cette anode est en contact avec l'atmosphère surmontant le milieu d'électrolyse et plonge dans ledit milieu. 3) Electrolysis cell usable for the implementation of a process according to claims 1 and 2, characterized in that: - The cell has an anode surrounded by a cathode; openings are provided at the base of said cathode; the upper part of the cathode immersed in the bath is preferably flared in shape, - the cell is supplied with power by bringing lithium chloride into the mixture of molten salts at the base of the cell, - The cell is provided with devices for leaving the mixture obtained, devices consisting of an overflow and an evacuation of the gas phase which overcomes the electrolysis medium. - The anode is sheathed with an insulating refractory material in the part where this anode is in contact with the atmosphere overcoming the electrolysis medium and plunges into said medium. 4) Cellule d'électrolyse selon la revendication 3 caractérisée en ce qu'elle comporte plusieurs couples anode-cathode.4) electrolysis cell according to claim 3 characterized in that it comprises several anode-cathode couples.
EP83401664A 1982-08-31 1983-08-16 Process for the continuous production of lithium by electrolysis of lithium chloride in a molten salt mixture, and apparatus for carrying out said process Expired EP0107521B1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FR8214865A FR2532332B1 (en) 1982-08-31 1982-08-31 PROCESS FOR THE CONTINUOUS PREPARATION OF LITHIUM BY ELECTROLYSIS OF LITHIUM CHLORIDE IN A MIXTURE OF MOLTEN SALTS AND APPARATUS FOR CARRYING OUT SAID PROCESS
FR8214865 1982-08-31

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EP0107521B1 EP0107521B1 (en) 1987-07-01

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Publication number Priority date Publication date Assignee Title
EP0156668B1 (en) * 1984-02-24 1987-11-04 Rhone-Poulenc Chimie Process and apparatus for the continuous manufacture of lithium
US4740279A (en) * 1985-09-14 1988-04-26 Metallgesellschaft Aktiengesellschaft Process and apparatus for producing high-purity lithium metal by fused-salt electrolysis

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2007063585A (en) * 2005-08-30 2007-03-15 Sumitomo Titanium Corp MOLTEN SALT ELECTROLYSIS METHOD, ELECTROLYTIC CELL, AND METHOD FOR PRODUCING Ti BY USING THE SAME

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US2075150A (en) * 1932-11-07 1937-03-30 Justin F Wait Process for the producing of metals and utilization thereof
US3344049A (en) * 1967-09-26 Method of producing lithium
US3962064A (en) * 1973-09-07 1976-06-08 Commissariat A L'energie Atomique Electrolyzer and a method for the production of readily oxydizable metals in a state of high purity

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JPS5443811A (en) * 1977-09-16 1979-04-06 Asahi Glass Co Ltd Production of metallic lithium

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US3344049A (en) * 1967-09-26 Method of producing lithium
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US3962064A (en) * 1973-09-07 1976-06-08 Commissariat A L'energie Atomique Electrolyzer and a method for the production of readily oxydizable metals in a state of high purity

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0156668B1 (en) * 1984-02-24 1987-11-04 Rhone-Poulenc Chimie Process and apparatus for the continuous manufacture of lithium
US4740279A (en) * 1985-09-14 1988-04-26 Metallgesellschaft Aktiengesellschaft Process and apparatus for producing high-purity lithium metal by fused-salt electrolysis

Also Published As

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FR2532332A1 (en) 1984-03-02
FR2532332B1 (en) 1986-04-04
JPS5985880A (en) 1984-05-17
EP0107521B1 (en) 1987-07-01
DE3372295D1 (en) 1987-08-06
CA1202596A (en) 1986-04-01

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