EP0230171A1 - Process and apparatus for the continuous manufacture of lithium by electrolysis of lithium chloride - Google Patents

Process and apparatus for the continuous manufacture of lithium by electrolysis of lithium chloride Download PDF

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Publication number
EP0230171A1
EP0230171A1 EP86402645A EP86402645A EP0230171A1 EP 0230171 A1 EP0230171 A1 EP 0230171A1 EP 86402645 A EP86402645 A EP 86402645A EP 86402645 A EP86402645 A EP 86402645A EP 0230171 A1 EP0230171 A1 EP 0230171A1
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Prior art keywords
electrolysis
lithium
molten salts
medium
cell
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EP86402645A
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German (de)
French (fr)
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EP0230171B1 (en
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Eric Leroux
Philippe Nataf
Serge Jacubert
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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

Definitions

  • the present invention relates to a process and an apparatus for the continuous preparation of lithium by electrolysis of lithium chloride in a mixture of molten salts.
  • the applicant has now found a method avoiding these risks and also making it possible to increase the productivity of the electrolysis cell.
  • the invention is a process for the continuous preparation of lithium by electrolysis of lithium chloride in a mixture of molten salts with a natural circulation of the electrolysis medium between the electrodes, without the use a diaphragm, continuous recovery of lithium in a mixture of molten salts on the one hand, and of chlorine in gaseous form on the other hand, said process being characterized in that the electrolysis medium is maintained at a temperature included between the melting point of the mixture of molten salts with the eutectic composition and 400 ° C, and in that the gas phase constituted by the chlorine formed is maintained at a temperature not exceeding 300 ° C.
  • the electrolysis medium consists of a mixture of molten salts based on lithium chloride and at least one other alkali and / or alkaline earth chloride which, with lithium chloride, form a eutectic mixture melting at a temperature between 320 and 360 ° C approximately.
  • binary mixture which can be used, mention may be made of lithium chloride and potassium; 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 electrolyser 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. It is 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 380 ° C., the amount of lithium chloride in said mixture may vary for entry and exit between 57 and 63 mol% of LiCl in the mixture of molten salts, the concentration at the entry being greater than the concentration at the exit. In this case, the lithium chloride may be in an excess of up to 5 mol% relative to the eutectic composition of the mixture of molten lithium chloride-potassium chloride salts.
  • the temperature of the electrolysis bath is generally situated at approximately 10 to 60 ° C. above the melting point of the eutectic composition of the mixture of molten salts, while being less than 400 ° C.
  • the characteristic of the process namely maintaining a temperature of the electrolysis bath below 400 ° C and a temperature of the gas phase below 300 ° C, aims on the one hand to avoid corrosion of the cell by chlorine by allowing the formation of a peripheral crust of crystallized salts on the internal wall of the electrolyser at the level of the gas-liquid interface, level where the temperature of the gas is the highest and on the other hand improve the productivity of the electrolyser by increasing the intensity of the electrolysis current.
  • the gas phase thus has a temperature gradient extending over a range from 300 ° C. to ambient temperature, when one moves away from the interface with the electrolysis medium towards the upper part of the cell.
  • the electrolysis operation is carried out continuously with continuous introduction of the mixture of molten salts containing, as the electrolyzable material of lithium chloride and continuous removal on the one hand, of the metallic lithium formed and of the mixture of molten salts entrained simultaneously and on the other hand, chlorine gas.
  • the electrolysis operation is carried out without the use of a diaphragm thanks to a rapid natural circulation of the electrolysis medium; said circulation is obtained simply by the ripple effect on the electrolysis medium of the chlorine bubbles which are released at the anode.
  • the electrolysis medium is driven vertically by the upward movement of chlorine bubbles in the space between the anode and the cathode, then descends in the space located beyond the cathode to re-enter the space located between the anode and the cathode.
  • the speed of circulation of said medium is high since if one represents by Vo the speed of supply of the electrolysis medium in the cell in the absence of natural recirculation, the speed V actually achieved due to this recirculation will be approximately 250 times Vo .
  • the cathode is completely immersed in the electrolysis medium.
  • the chlorine produced by the electrolysis is drawn off continuously without dilution by an inert gas.
  • the resulting lithium metal may optionally be decanted from the mixture of molten salts driven simultaneously, for example by the method described in the French patent application under number 2560221.
  • the molten salts after readjustment of their lithium chloride concentration, are then recycled into the electrolysis medium.
  • the present invention also relates to the apparatus making it possible to implement the method described above.
  • Said apparatus comprises an electrolysis cell comprising: . an anode surrounded by a cathode totally immersed in the electrolysis medium; . a device for entering the molten salts at the bottom of the cell; . a device for discharging the chlorine gas formed; . an evacuation device by overflow of the lithium formed and of the molten salts entrained simultaneously; said apparatus being characterized in that the electrolysis cell is provided at its periphery: . a lower cooling system located at any level below the level of the electrolysis bath; .
  • the overflow evacuation device for the lithium formed and the molten salts entrained simultaneously is located at the interface of the electrolysis medium and the gas phase, at a distance from the internal wall of the cell sufficient to allow the formation of a peripheral crust of solidified salts on said wall at the interface of the electrolysis medium and the gas phase while avoiding crystallization of the medium to be evacuated continuously.
  • the anode is preferably made of graphite and of cylindrical shape (bar for example); it can be sheathed (by a material such as alumina, quartz, silica ...), in its part not immersed in the electrolysis medium and to a certain depth below the interface of the electrolysis medium and the gas phase.
  • the cathode is preferably cylindrical in shape; it can be fixed to the wall of the cell by any means which does not obstruct the circulation of the electrolysis medium and also ensures electrical conduction.
  • the evacuation device by overflow of lithium and molten salts entrained simultaneously can be constituted by a chute for example.
  • the lower and upper cooling systems can be constituted by any means making it possible to obtain a temperature respectively below 400 ° C. in the medium electrolysis and less than or equal to 300 ° C in the gas phase; thus can be used on the external wall of the cell of the coils or cooling collars by circulation of atmospheric air or water, for example.
  • the lower cooling system is generally located at the average height of the electrolysis bath.
  • the electrolysis cell includes: . a cylindrical tank (1) made of stainless steel 700 mm in internal diameter, 6 mm thick, with a volume close to 500 l; its useful volume, of which about 2/3 is occupied by molten salts, is 350 l; . a cylindrical cathode (2) 800 mm high and 4 mm thick, made of stainless steel; it is completely embedded in the salt bath; electrical conduction is ensured by 6 tie rods 4 mm thick each, welded to the cathode and to the tank; . an anode (3) which is a graphite rod 300 mm in diameter, 150 cm in height and plunging into the bath to a height of approximately 85 cm, the interpolar space separating the anode from the cathode is 20 mm .
  • the current is supplied via a copper bar fixed in the head of the anode; the return is made by three tabs welded to the middle of the cathode. . a lower cooling collar (4) with circulation of atmospheric air at a flow rate of 100 m3 / h located 40 cm below the level of the bath. . an upper cooling collar (5) with circulation of atmospheric air at a flow rate of 100 m3 / h, collar located at the lower part of the gas phase and at the limit of the level of the interface with the electrolysis medium; . a feed device (6) for the mixture of molten salts opening into the lower part of the tank; . a chlorine evacuation device (7) at the top of the tank; . a chute (8) for discharging lithium mixed with the molten salts, a chute whose position determines the level of the bath in the cell; is located 3 cm from the inner wall of the cell; its width is 5 cm and its depth 6 cm.
  • the electrolysis is carried out with a current of 5000 A, using a mixture of molten salts LiCl-KCl at a temperature of 380 ° C with a flow rate of 300 l / h; the temperature of the gas phase at the interface with the electrolysis medium is 300 ° C.
  • the chlorine bubbles formed at the anode induce in the interpolar space a circulation of molten salts of the order of 80 m3 / h.
  • the liquid leaving the electrolyzer is introduced into a decanter comprising: . a settling area of 0.16 m2 in area; . a device for discharging the light phase constituted by lithium, by overflow; . a device for discharging the heavy phase constituted by the mixture of molten salts, comprising a well and a reservoir.
  • the molten salts are filtered and then recycled with a make-up of 170 mol / h of LiCl, in the electrolyser.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Electrolytic Production Of Metals (AREA)
  • Electrolytic Production Of Non-Metals, Compounds, Apparatuses Therefor (AREA)

Abstract

Procédé de préparation du lithium par électrolyse du chlorure de lithium en milieu sels fondus avec circulation naturelle du milieu d'électrolyse ; le lithium est récupéré en continu dans un mélange de sels fondus ; la température du bain d'électrolyse est inférieure à 400°C ; celle de la phase gazeuse constituée par le chlore ne dépasse pas 300°C. Process for the preparation of lithium by electrolysis of lithium chloride in a molten salt medium with natural circulation of the electrolysis medium; lithium is continuously recovered in a mixture of molten salts; the temperature of the electrolysis bath is less than 400 ° C; that of the gaseous phase constituted by chlorine does not exceed 300 ° C.

Description

La présente invention a pour objet un procédé et un appareillage pour la préparation en continu de lithium par électrolyse du chlorure de lithium dans un mélange de sels fondus.The present invention relates to a process and an apparatus for the continuous preparation of lithium by electrolysis of lithium chloride in a mixture of molten salts.

Il est connu d'après les demandes de brevet français publiées sous le no 2.532.332 et no 2.560.221 de préparer en continu du lithium par électrolyse du chlorure de lithium dans un mélange de sels fondus à une température de 400 à 500°C, sans séparation dans l'électrolyseur du lithium métallique du mélange de sels fondus.It is known from the French patent applications published under the No. 2,532,332 and No. 2,560,221 for the continuous preparation of lithium by electrolysis of lithium chloride in a mixture of molten salts at a temperature of 400 to 500 ° C, without separation in the lithium metal electrolyser of the mixture of molten salts.

Cependant à ces températures, un tel procédé ne permet pas d'éviter la corrosion par le chlore gazeuz de la partie du corps de la cellule située au-dessus du niveau du bain d'électrolyse ; en effet cette partie de la cellule est particulièrement sensible à la corrosion car elle se trouve dans la zone où la température du chlore est la plus élevée.However, at these temperatures, such a method does not prevent corrosion by chlorine gas of the part of the cell body located above the level of the electrolysis bath; in fact, this part of the cell is particularly sensitive to corrosion because it is located in the zone where the chlorine temperature is the highest.

La demanderesse a maintenant trouvé un procédé évitant ces risques et permettant en outre d'augmenter la productivité de la cellule d'électrolyse.The applicant has now found a method avoiding these risks and also making it possible to increase the productivity of the electrolysis cell.

Selon l'invention, il s'agit d'un procédé de préparation en continu de lithium par électrolyse du chlorure de lithium dans un mélange de sels fondus avec une circulation naturelle du milieu d'électrolyse entre les électrodes et ce, sans l'utilisation d'un diaphragme, récupération en continu du lithium dans un mélange de sels fondus d'une part, et du chlore sous forme gazeuse d'autre part, ledit procédé étant caractérisé en ce que le milieu d'électrolyse est maintenu à une température comprise entre le point de fusion du mélange de sels fondus à la composition eutectique et 400°C, et en ce que la phase gazeuse constituée par le chlore formé est maintenue a une température ne dépassant pas 300°C.According to the invention, it is a process for the continuous preparation of lithium by electrolysis of lithium chloride in a mixture of molten salts with a natural circulation of the electrolysis medium between the electrodes, without the use a diaphragm, continuous recovery of lithium in a mixture of molten salts on the one hand, and of chlorine in gaseous form on the other hand, said process being characterized in that the electrolysis medium is maintained at a temperature included between the melting point of the mixture of molten salts with the eutectic composition and 400 ° C, and in that the gas phase constituted by the chlorine formed is maintained at a temperature not exceeding 300 ° C.

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 alkali and / or alkaline earth chloride which, with lithium chloride, form a eutectic mixture melting at a temperature between 320 and 360 ° C approximately. As binary mixture which can be used, mention may be made of lithium chloride and potassium; 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.

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 380°C environ, la quantité de chlorure de lithium dudit mélange pourra varier pour l'entrée et la sortie entre 57 et 63 % en mole de LiCl dans le mélange de sels fondus, la concentration à l'entrée étant supérieure à la concentration à la sortie. Dans ce cas, le chlorure de lithium peut être dans un excès allant jusqu'à 5 % en mole par rapport à la composition eutectique du mélange de sels fondus chlorure de lithium-chlorure de potassium.The mixture of molten salts supplying the electrolyser 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. It is 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 380 ° C., the amount of lithium chloride in said mixture may vary for entry and exit between 57 and 63 mol% of LiCl in the mixture of molten salts, the concentration at the entry being greater than the concentration at the exit. In this case, the lithium chloride may be in an excess of up to 5 mol% relative to the eutectic composition of the mixture of molten lithium chloride-potassium chloride salts.

La température du bain d'électrolyse est généralement située à environ 10 à 60°C au-dessus de la température de fusion de la composition eutectique du mélange de sels fondus, tout en étant inférieure à 400°C.The temperature of the electrolysis bath is generally situated at approximately 10 to 60 ° C. above the melting point of the eutectic composition of the mixture of molten salts, while being less than 400 ° C.

La caractéristique du procédé, à savoir maintien d'une température du bain d'électrolyse inférieure à 400°C et d'une température de la phase gazeuse inférieure à 300°C, a pour but d'une part d'éviter la corrosion de la cellule par le chlore en permettant la formation d'une croûte périphérique de sels cristallisés sur la paroi interne de l'électrolyseur au niveau de l'interface gaz-liquide, niveau où la température du gaz est la plus élevée et d'autre part d'améliorer la productivité de l'électrolyseur en permettant d'augmenter l'intensité du courant d'électrolyse.The characteristic of the process, namely maintaining a temperature of the electrolysis bath below 400 ° C and a temperature of the gas phase below 300 ° C, aims on the one hand to avoid corrosion of the cell by chlorine by allowing the formation of a peripheral crust of crystallized salts on the internal wall of the electrolyser at the level of the gas-liquid interface, level where the temperature of the gas is the highest and on the other hand improve the productivity of the electrolyser by increasing the intensity of the electrolysis current.

La phase gazeuse présente ainsi un gradient de température s'étendant sur une plage allant de 300°C à la température ambiante, lorsque l'on s'éloigne de l'interface avec le milieu d'électrolyse vers la partie supérieure de la cellule.The gas phase thus has a temperature gradient extending over a range from 300 ° C. to ambient temperature, when one moves away from the interface with the electrolysis medium towards the upper part of the cell.

L'opération d'électrolyse s'effectue en continu avec introduction en continu du mélange de sels fondus contenant, comme matériau électrolysable du chlorure de lithium et retrait en continu d'un part, du lithium métallique formé et du mélange de sels fondus entraîné simultanément et d'autre part, du chlore gazeux.The electrolysis operation is carried out continuously with continuous introduction of the mixture of molten salts containing, as the electrolyzable material of lithium chloride and continuous removal on the one hand, of the metallic lithium formed and of the mixture of molten salts entrained simultaneously and on the other hand, chlorine gas.

L'opération d'électrolyse est réalisée sans utilisation d'un diaphragme grâce à une circulation naturelle rapide du milieu d'électrolyse ; ladite circulation est obtenue simplement par l'effet d'entraînement sur le milieu d'électrolyse des bulles de chlore qui se dégagent à l'anode. Le milieu d'électrolyse est entraîne verticalement par le mouvement ascendant des bulles de chlore dans l'espace situé entre l'anode et la cathode, puis redescend dans l'espace situé au-delà de la cathode pour pénétrer à nouveau 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 d'alimentation du milieu d'électrolyse dans la cellule en absence de recirculation naturelle, la vitesse V réellement atteinte du fait de cette recirculation sera d'environ 250 fois Vo.The electrolysis operation is carried out without the use of a diaphragm thanks to a rapid natural circulation of the electrolysis medium; said circulation is obtained simply by the ripple effect on the electrolysis medium of the chlorine bubbles which are released at the anode. The electrolysis medium is driven vertically by the upward movement of chlorine bubbles in the space between the anode and the cathode, then descends in the space located beyond the cathode to re-enter the space located between the anode and the cathode. The speed of circulation of said medium is high since if one represents by Vo the speed of supply of the electrolysis medium in the cell in the absence of natural recirculation, the speed V actually achieved due to this recirculation will be approximately 250 times Vo .

Pour permettre cette circulation naturelle du milieu d'électrolyse, la cathode est complètement immergée dans le milieu d'électrolyse.To allow this natural circulation of the electrolysis medium, the cathode is completely immersed in the electrolysis medium.

Le chlore produit par l'électrolyse est soutiré en continu sans dilution par un gaz inerte.The chlorine produced by the electrolysis is drawn off continuously without dilution by an inert gas.

Après l'opération d'électrolyse, le lithium métallique obtenu peut éventuellement être séparé par décantation du mélange de sels fondus entraîné simultanément, par exemple selon la méthode décrite dans la demande de brevet français sous le no 2.560.221.After the electrolysis operation, the resulting lithium metal may optionally be decanted from the mixture of molten salts driven simultaneously, for example by the method described in the French patent application under number 2560221.

Les sels fondus, après réajustment de leur concentration en chlorure de lithium, sont ensuite recyclés dans le milieu d'électrolyse.The molten salts, after readjustment of their lithium chloride concentration, are then recycled into the electrolysis medium.

La présente invention a également pour objet l'appareillage permettant de mettre en oeuvre le procédé ci-dessus décrit.The present invention also relates to the apparatus making it possible to implement the method described above.

Ledit appareillage comprend une cellule d'électrolyse comportant :
. une anode entourée d'une cathode totalement immergée dans le milieu d'électrolyse ;
. un dispositif d'entrée des sels fondus dans le bas de la cellule ;
. un dispositif d'évacuation du chlore gazeux formé ;
. un dispositif d'évacuation par débordement du lithium formé et des sels fondus entraînés simultanément ;
ledit appareillage étant caractérisé en ce que la cellule d'électrolyse est munie à sa périphérie :
. d'un système inférieur de refroidissement situé à un niveau quelconque en-dessous de niveau du bain d'électrolyse ;
. et d'un système supérieur de refroidissement situé à la partie inférieure de la phase gazeuse constituée par le chlore formé et à la limite du niveau de l'interface avec le milieu d'électrolyse ; et en ce que le dispositif d'évacuation par débordement du lithium formé et des sels fondus entraînés simultanément est situé au niveau de l'interface du milieu d'électrolyse et de la phase gazeuse, à une distance de la paroi interne de la cellule suffisante pour permettre la formation d'une croûte périphérique de sels solidifiés sur ladite paroi au niveau de l'interface du milieu d'électrolyse et de la phase gazeuse tout en évitant la cristallisation du milieu à évacuer en continu.Said apparatus comprises an electrolysis cell comprising:
. an anode surrounded by a cathode totally immersed in the electrolysis medium;
. a device for entering the molten salts at the bottom of the cell;
. a device for discharging the chlorine gas formed;
. an evacuation device by overflow of the lithium formed and of the molten salts entrained simultaneously;
said apparatus being characterized in that the electrolysis cell is provided at its periphery:
. a lower cooling system located at any level below the level of the electrolysis bath;
. and an upper cooling system located at the lower part of the gas phase constituted by the chlorine formed and at the limit of the level of the interface with the electrolysis medium; and in that the overflow evacuation device for the lithium formed and the molten salts entrained simultaneously is located at the interface of the electrolysis medium and the gas phase, at a distance from the internal wall of the cell sufficient to allow the formation of a peripheral crust of solidified salts on said wall at the interface of the electrolysis medium and the gas phase while avoiding crystallization of the medium to be evacuated continuously.

L'anode est de préférence en graphite et de forme cylindrique (barreau par exemple) ; elle peut être gainée (par un matériau tel que alumine, quartz, silice ...), dans sa partie non immergée dans le milieu d'électrolyse et jusqu'à une certaine profondeur en-dessous de l'interface du milieu d'électrolyse et de la phase gazeuse.The anode is preferably made of graphite and of cylindrical shape (bar for example); it can be sheathed (by a material such as alumina, quartz, silica ...), in its part not immersed in the electrolysis medium and to a certain depth below the interface of the electrolysis medium and the gas phase.

La cathode est de préférence de forme cylindrique ; elle peut être fixée à la paroi de la cellule par tout moyen ne faisant pas obstacle à la circulation du milieu d'électrolyse et assurant, en outre, la conduction électrique.The cathode is preferably cylindrical in shape; it can be fixed to the wall of the cell by any means which does not obstruct the circulation of the electrolysis medium and also ensures electrical conduction.

Le dispositif d'évacuation par débordement du lithium et des sels fondus entraînés simultanément peut être constitué par une goulotte par exemple.The evacuation device by overflow of lithium and molten salts entrained simultaneously can be constituted by a chute for example.

Les systèmes de refroidissement inférieur et supérieur peuvent être constitués par tout moyen permettant d'obtenir une température respectivement inférieure à 400°C dans le milieu d'électrolyse et inférieure ou égale à 300°C dans la phase gazeuse ; ainsi peuvent être utilisés sur la paroi externe de la cellule des serpentins ou colliers de refroidissement par circulation d'air atmosphérique ou d'eau, par exemple.The lower and upper cooling systems can be constituted by any means making it possible to obtain a temperature respectively below 400 ° C. in the medium electrolysis and less than or equal to 300 ° C in the gas phase; thus can be used on the external wall of the cell of the coils or cooling collars by circulation of atmospheric air or water, for example.

Le systéme de refroidissement inférieur est généralement situé à la hauteur moyenne du bain d'électrolyse.The lower cooling system is generally located at the average height of the electrolysis bath.

On donne, ci-après, de façon non limitative un exemple de réalisation préféré de l'invention en faisant référence à la figure unique annexée.A preferred embodiment of the invention is given hereinafter, without limitation, with reference to the single appended figure.

La cellule d'électrolyse comprend :
. une cuve cylindrique (1) en acier inoxydable de 700 mm de diamètre intérieur, de 6 mm d'épaisseur, de volume voisin de 500 l ; son volume utile, dont les 2/3 environ sont occupés par les sels fondus, est de 350 l ;
. une cathode cylindrique (2) de 800 mm de haut et de 4 mm d'épaisseur, en acier inoxydable ; elle est entièrement noyée dans le bain de sels ; la conduction électrique est assurée par 6 tirants de 4 mm d'épaisseur chacun, soudés à la cathode et à la cuve ;
. une anode (3) qui est un barreau de graphite de 300 mm de diamètre, de 150 cm de hauteur et plongeant dans le bain sur une hauteur de 85 cm environ , l'espace interpolaire séparant l'anode de la cathode est de 20 mm. L'arrivée du courant se fait par l'intermédiaire d'une barre de cuivre fixée dans la tête de l'anode ; le retour s'effectue par trois pattes soudées au milieu de la cathode.
. un collier de refroidissement inférieur (4) avec circulation d'air atmosphérique à un débit de 100 m³/h situé à 40 cm en-dessous du niveau du bain.
. un collier de refroidissement supérieur (5) avec circulation d'air atmosphérique à un débit de 100 m³/h, collier situé à la partie inférieure de la phase gazeuse et à la limite du niveau de l'interface avec le milieu d'électrolyse ;
. un dispositif d'alimentation (6) du mélange de sels fondus débouchant dans la partie inférieure de la cuve ;
. un dispositif d'évacuation (7) du chlore à la partie supérieure de la cuve ;
. une goulotte (8) d'évacuation du lithium en mélange avec les sels fondus, goulotte dont la position détermine le niveau du bain dans la cellule ; est située à 3 cm de la paroi interne de la cellule ; sa largeur est de 5 cm et sa profondeur de 6 cm.The electrolysis cell includes:
. a cylindrical tank (1) made of stainless steel 700 mm in internal diameter, 6 mm thick, with a volume close to 500 l; its useful volume, of which about 2/3 is occupied by molten salts, is 350 l;
. a cylindrical cathode (2) 800 mm high and 4 mm thick, made of stainless steel; it is completely embedded in the salt bath; electrical conduction is ensured by 6 tie rods 4 mm thick each, welded to the cathode and to the tank;
. an anode (3) which is a graphite rod 300 mm in diameter, 150 cm in height and plunging into the bath to a height of approximately 85 cm, the interpolar space separating the anode from the cathode is 20 mm . The current is supplied via a copper bar fixed in the head of the anode; the return is made by three tabs welded to the middle of the cathode.
. a lower cooling collar (4) with circulation of atmospheric air at a flow rate of 100 m³ / h located 40 cm below the level of the bath.
. an upper cooling collar (5) with circulation of atmospheric air at a flow rate of 100 m³ / h, collar located at the lower part of the gas phase and at the limit of the level of the interface with the electrolysis medium;
. a feed device (6) for the mixture of molten salts opening into the lower part of the tank;
. a chlorine evacuation device (7) at the top of the tank;
. a chute (8) for discharging lithium mixed with the molten salts, a chute whose position determines the level of the bath in the cell; is located 3 cm from the inner wall of the cell; its width is 5 cm and its depth 6 cm.

L'électrolyse est réalisée avec un courant de 5000 A, en utilisant un mélange de sels fondus LiCl-KCl à une température de 380°C avec un débit de 300 l/h; la température de la phase gazeuse à l'interface avec le milieu d'électrolyse est de 300°C.The electrolysis is carried out with a current of 5000 A, using a mixture of molten salts LiCl-KCl at a temperature of 380 ° C with a flow rate of 300 l / h; the temperature of the gas phase at the interface with the electrolysis medium is 300 ° C.

Les bulles de chlore formées à l'anode induisent dans l'espace interpolaire une circulation des sels fondus de l'ordre de 80 m³/h.The chlorine bubbles formed at the anode induce in the interpolar space a circulation of molten salts of the order of 80 m³ / h.

Le bilan de l'opération est le suivant ;
- à l'entrée (6) de l'électrolyseur :
. débit de KCl : 274 kg/h ;
. débit de LiCl : 224 kg/h.
- à la sortie liquide (8) de l'électrolyseur :
. débit de Li : 1,2 kg/h.
- à la sortie gaz (7) de l'électrolyseur :
. débit de Cl₂ : 1,9 Nm³/h.The results of the operation are as follows;
- at the inlet (6) of the electrolyser:
. KCl flow rate: 274 kg / h;
. LiCl flow rate: 224 kg / h.
- at the liquid outlet (8) of the electrolyser:
. Li flow rate: 1.2 kg / h.
- at the gas outlet (7) of the electrolyser:
. Cl₂ flow: 1.9 Nm³ / h.

Dans ces conditions, il est possible de réaliser l'électrolyseur du LiCl avec un rendement faradique de 90 %. Le liquide sortant de l'électrolyeur est introduit dans un décanteur comportant :
. une zone de décantation de 0,16 m² de surface ;
. un dispositif d'évacuation de la phase légère constituée par le lithium, par débordement ;
. un dispositif d'évacuation de la phase lourde constituée par le mélange de sels fondus, comportant un puits et un réservoir.Under these conditions, it is possible to produce the LiCl electrolyser with a faradaic yield of 90%. The liquid leaving the electrolyzer is introduced into a decanter comprising:
. a settling area of 0.16 m² in area;
. a device for discharging the light phase constituted by lithium, by overflow;
. a device for discharging the heavy phase constituted by the mixture of molten salts, comprising a well and a reservoir.

Les sels fondus sont filtrés puis recyclés avec un appoint de 170 moles/h de LiCl, dans l'électrolyseur.The molten salts are filtered and then recycled with a make-up of 170 mol / h of LiCl, in the electrolyser.

Claims (6)

1) Procédé de préparation en continu de lithium par électrolyse du chlorure de lithium dans un mélange de sels fondus avec une circulation naturelle du milieu d'électrolyse entre les électrodes et ce, sans utilisation d'un diaphragme, récupération en continu du lithium dans un mélange de sels fondus d'une part, et du chlore sous forme gazeuse d'autre part, ledit procédé étant caractérisé en ce que le milieu d'électrolyse est maintenu à une température comprise entre le point de fusion du mélange de sels fondus à la composition eutectique et 400°C, et en ce que la phase gazeuse constituée par le chlore formé est maintenue à une température ne dépassant pas 300°C.1) Process for the continuous preparation of lithium by electrolysis of lithium chloride in a mixture of molten salts with a natural circulation of the electrolysis medium between the electrodes, without using a diaphragm, continuous recovery of the lithium in a mixture of molten salts on the one hand, and chlorine in gaseous form on the other hand, said process being characterized in that the electrolysis medium is maintained at a temperature between the melting point of the mixture of molten salts at the eutectic composition and 400 ° C, and in that the gas phase constituted by the chlorine formed is maintained at a temperature not exceeding 300 ° C. 2) Procédé selon la revendication 1 caractérisée en ce que la phase gazeuse présente un gradient de température allant de 300°C à la température ambiante lorsque l'on s'éloigne de son interface avec le milieu d'électrolyse vers sa partie supérieure.2) Method according to claim 1 characterized in that the gas phase has a temperature gradient ranging from 300 ° C to room temperature when one moves away from its interface with the electrolysis medium towards its upper part. 3) Appareillage pour la mise en oeuvre du procéde faisant l'objet de la revendication 1 ou 2, comprenant une cellule d'électrolyse comportant :
. une anode entourée d'une cathode totalement immergée dans le milieu d'électrolyse ;
. un dispositif d'entrée des sels fondus dans le bas de la cellule ;
. un dispositif d'évacuation du chlore gazeux formé ;
. un dispositif d'évacuation par débordement de lithium formé et des sels fondus entraînés simultanément ;
ledit appareillage étant caractérisé en ce que la cellule d'électrolyse est munie à sa périphérie :
. d'un système inférieur de refroidissement situé à un niveau quelconque en-dessous du niveau du bain d'électrolyse ;
. d'un système supérieur de refroidissement situé à la partie inférieure de la phase gazeuse constituée par le chlore formé et à la limite du niveau de l'interface avec le milieu d'électrolyse ;
et en ce que le dispositif d'évacuation par débordement du lithium formé et des sels fondus entraînés simultanément est situé au niveau de l'interface du milieu d'électrolyse et de la phase gazeuse, à une distance de la paroi interne de la cellule suffisante pour permettre la formation d'une croûte périphérique de sels solidifiés sur ladite paroi au niveau de l'interface du milieu d'électrolyse et de la phase gazeuse tout en évitant la cristallisation du milieu à évacuer en continu.3) Apparatus for implementing the process which is the subject of claim 1 or 2, comprising an electrolysis cell comprising:
. an anode surrounded by a cathode totally immersed in the electrolysis medium;
. a device for entering the molten salts at the bottom of the cell;
. a device for discharging the chlorine gas formed;
. an evacuation device by overflow of lithium formed and molten salts entrained simultaneously;
said apparatus being characterized in that the electrolysis cell is provided at its periphery:
. a lower cooling system located at any level below the level of the electrolysis bath;
. an upper cooling system located at the lower part of the gas phase constituted by the chlorine formed and at the limit of the level of the interface with the electrolysis medium;
and in that the overflow evacuation device for the lithium formed and the molten salts entrained simultaneously is located at the interface of the electrolysis medium and the gas phase, at a distance from the internal wall of the cell sufficient to allow the formation of a peripheral crust of solidified salts on said wall at the interface of the electrolysis medium and the gaseous phase while avoiding crystallization of the medium to be evacuated continuously. 4) Appareillage selon la revendication 3 caractérisé en ce que les systèmes de refroidissement inférieur et supérieur sont constitués par tout moyen permettant d'obtenir une température respectivement inférieure à 400°C dans le milieu d'électrolyse et inférieure ou égale à 300°C dans la phase gazeuse.4) Apparatus according to claim 3 characterized in that the lower and upper cooling systems are constituted by any means for obtaining a temperature respectively below 400 ° C in the electrolysis medium and less than or equal to 300 ° C in the gas phase. 5) Appareillage selon la revendication 4 caractérisé en ce que les systèmes de refroidissement sont des serpentins ou des colliers de refroidissement par circulation d'air ou d'eau, situés sur la paroi externe de la cellule.5) Apparatus according to claim 4 characterized in that the cooling systems are coils or cooling collars by air or water circulation, located on the outer wall of the cell. 6) Appareillage selon l'une quelconque des revendications 3 à 5 caractérisé en ce que le dispositif d'évacuation par débordement du lithium formé et des sels fondus entraînés simultanément est constitué par une goulotte.6) Apparatus according to any one of claims 3 to 5 characterized in that the evacuation device by overflow of the lithium formed and the molten salts entrained simultaneously consists of a chute.
EP86402645A 1985-12-13 1986-11-28 Process and apparatus for the continuous manufacture of lithium by electrolysis of lithium chloride Expired - Lifetime EP0230171B1 (en)

Applications Claiming Priority (2)

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FR8518483 1985-12-13
FR8518483A FR2591615B1 (en) 1985-12-13 1985-12-13 PROCESS AND APPARATUS FOR THE CONTINUOUS PREPARATION OF LITHIUM BY ELECTROLYSIS OF LITHIUM CHLORIDE

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EP0230171B1 EP0230171B1 (en) 1990-02-07

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Publication number Priority date Publication date Assignee Title
CN101760759A (en) * 2010-02-11 2010-06-30 中国科学院青海盐湖研究所 Method for preparing metal lithium by electrolyzing molten salt

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Publication number Priority date Publication date Assignee Title
US5660710A (en) * 1996-01-31 1997-08-26 Sivilotti; Olivo Method and apparatus for electrolyzing light metals
US5855757A (en) * 1997-01-21 1999-01-05 Sivilotti; Olivo Method and apparatus for electrolysing light metals
CN110306052B (en) * 2019-06-25 2020-09-15 中南大学 Metallic lithium elementary substance and preparation method and application thereof

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US2755244A (en) * 1952-10-30 1956-07-17 Ethyl Corp Temperature control of electrolytic cells
EP0156668A1 (en) * 1984-02-24 1985-10-02 Rhone-Poulenc Chimie Process and apparatus for the continuous manufacture of lithium

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Publication number Priority date Publication date Assignee Title
US4617098A (en) * 1982-08-31 1986-10-14 Rhone-Poulenc Specialites Chimiques Continuous electrolysis of lithium chloride into lithium metal

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Publication number Priority date Publication date Assignee Title
US2755244A (en) * 1952-10-30 1956-07-17 Ethyl Corp Temperature control of electrolytic cells
EP0156668A1 (en) * 1984-02-24 1985-10-02 Rhone-Poulenc Chimie Process and apparatus for the continuous manufacture of lithium

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN101760759A (en) * 2010-02-11 2010-06-30 中国科学院青海盐湖研究所 Method for preparing metal lithium by electrolyzing molten salt
CN101760759B (en) * 2010-02-11 2011-08-31 中国科学院青海盐湖研究所 Method for preparing metal lithium by electrolyzing molten salt

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EP0230171B1 (en) 1990-02-07
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DE3668916D1 (en) 1990-03-15
FR2591615B1 (en) 1988-02-19
JPS62142797A (en) 1987-06-26

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