EP0082096B1 - Floating cathodic elements made of electro conductive refractory material for the production of aluminium by electrolysis - Google Patents

Floating cathodic elements made of electro conductive refractory material for the production of aluminium by electrolysis Download PDF

Info

Publication number
EP0082096B1
EP0082096B1 EP82420176A EP82420176A EP0082096B1 EP 0082096 B1 EP0082096 B1 EP 0082096B1 EP 82420176 A EP82420176 A EP 82420176A EP 82420176 A EP82420176 A EP 82420176A EP 0082096 B1 EP0082096 B1 EP 0082096B1
Authority
EP
European Patent Office
Prior art keywords
aluminium
cathodic
floating
tank
density
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired
Application number
EP82420176A
Other languages
German (de)
French (fr)
Other versions
EP0082096A1 (en
Inventor
Maurice Keinborg
Philippe Varin
Yves Bertaud
Michel Leroy
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Rio Tinto France SAS
Original Assignee
Aluminium Pechiney SA
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Aluminium Pechiney SA filed Critical Aluminium Pechiney SA
Publication of EP0082096A1 publication Critical patent/EP0082096A1/en
Application granted granted Critical
Publication of EP0082096B1 publication Critical patent/EP0082096B1/en
Expired legal-status Critical Current

Links

Images

Classifications

    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25C—PROCESSES FOR THE ELECTROLYTIC PRODUCTION, RECOVERY OR REFINING OF METALS; APPARATUS THEREFOR
    • C25C3/00—Electrolytic production, recovery or refining of metals by electrolysis of melts
    • C25C3/06—Electrolytic production, recovery or refining of metals by electrolysis of melts of aluminium
    • C25C3/08—Cell construction, e.g. bottoms, walls, cathodes

Definitions

  • the present invention relates to floating cathode elements, in electroconductive refractory, such as titanium diboride, intended for the production of aluminum by electrolysis, according to the Hall-Héroult process.
  • the cathode In Hall-Héroult cells, the cathode is universally made up of juxtaposed carbon blocks, in which metal bars are sealed, themselves connected to conductors ensuring the electrical connection with the next tank in the series. In operation, the cathode is permanently covered with a layer of liquid aluminum about twenty centimeters thick.
  • electroconductive refractories belong to the class formed by borides, carbides and nitrides of metals of groups 4A, 5A and 6A but, until now, research has mainly focused on titanium diborides TiB 2 and zirconium ZrB 2 .
  • titanium boride has a resistivity of 60 ⁇ cm - and zirconium boride of 74 ⁇ cm - 2 and 2.5 times that of liquid aluminum, respectively, but more than 5000 times that of electrolysis bath which is around 450,000 ⁇ cm. They are perfectly wetted by liquid aluminum and sufficiently inert with respect to the molten cryolite.
  • patent FR-A-2 471 425 (ALU-SUISSE) describes cathodic elements made of titanium diboride in the form of grainy or in pieces, poured in bulk on the bottom of the tank, and covered with a thickness of liquid aluminum at least equal to 2 mm.
  • this cathode may include an intermediate carbon support placed on the basic carbon substrate, and supporting the bed of particles of titanium diboride.
  • removable cathode elements comprising an inert intermediate support and active elements in electroconductive refractory, such as TiB 2 , integral but separable from said support, the assembly formed by the inert intermediate support and the active elements having a density greater than the density of liquid aluminum at the temperature of electrolysis.
  • the present invention aims to eliminate these drawbacks. It is based on elements in electrically conductive refractories wettable by liquid aluminum and, in particular, based on titanium diboride, not directly linked to the cathode substrate, guided and having a limited degree of freedom, in the vertical direction, and that floating is maintained at the interface between the electrolysis bath and the aluminum produced, whatever the fluctuations of this interface during the electrolysis process, by making them support by an inert intermediate support of lower density to that of liquid aluminum.
  • these elements are removable so as to be put in place and replaced without interrupting the electrolysis, with possible intermediate passage in a chamber for controlled preheating or cooling, with a controlled atmosphere or not.
  • the present invention relates to these floating cathode elements and the electrolytic cells for the production of aluminum comprising these elements.
  • the active cathode element made of TiB 2 (1) is formed by a flat or slightly convex head and a tail (2) which is positioned in the orifices (3) of an inert intermediate support (4) in graphite.
  • the average density of the cathode assembly thus formed is lower than that of liquid aluminum.
  • the heads of the pads (1) are, in normal operation, in the vicinity of the aluminum sheet-electrolyte interface.
  • the cathode element (1) can rest directly on the orifice (3) or be provided with a boss (5) or fins (6) which provide an interval favoring the flow of the liquid aluminum progressively of its production (fig. 2 and 3).
  • Figures 4 and 5 show another embodiment in which the floating cathode element (7) is anchored to the cathode substrate (8) by studs (9).
  • the head (10) of the anchoring stud cooperates with a recess (11) of the intermediate support (7) to ensure a stop which limits its upward stroke.
  • the active cathode elements (12) consist of sections of split tubes (13) and threaded on a rail (14), leaving between them sufficient free space for the flow of aluminum produced. These tubes can have a circular, square or other section.
  • the mass ratio of graphite / mass of TiB 2 is fixed so that the average density of the assembly is less than the density of the electrolyte so that the floating cathode element is , normally in the upper stop.
  • the stroke of the floating element determined by the position of the stopper and the height of the anchoring stud, must be at least equal to the variations in height of the sheet of liquid aluminum. during electrolysis and racking of metal.
  • the active TiB 2 elements (12) must exceed the interface (15) by at least 10 millimeters.
  • FIG. 6 shows another alternative embodiment in which the floating cathode element consists of a graphite plate (17) coated with thin-coated titanium diboride (18) produced by chemical phase deposition steam or plasma torch projection.
  • the floating plate is retained at the bottom by a dense block (19) of refractory concrete, resistant to the action of liquid aluminum (16) resting on the cathode substrate (9).
  • the dense block (19) is provided with channels (20) to ensure the circulation of aluminum and the passage of current.
  • the floating structure may include guide means such as the rollers (21) which cooperate, for example, with the support legs (22) .
  • These rollers can be made, for example, of TiBz or silicon nitride or silicon and aluminum oxynitride (Sialon).
  • the refractory support (24) is fully embedded in the metal.
  • the perforated support (25), which holds the pads (1) of TiBz has a density lower than the density of the electrolysis bath: it is for example graphite, possibly protected by a thin deposit of a refractory such as titanium diboride or Sialon.
  • the perforated support + TiBz pads assembly If the average density of the perforated support + TiBz pads assembly is lower than that of the bath, the perforated support remains permanently in the top stop. If this average density is between that of the bath and that of the metal, the perforated support follows the variations in level of the metal during the electrolysis.
  • FIG. 9 gives the construction detail of the dense refractory support (24) of FIG. 8 with high (25) and low (26) stops.
  • One of its faces may have a removable wall (27). The establishment or removal of such walls makes it possible to direct and control the circulation of the metal and the bath under the effect of electromagnetic forces.
  • FIGS 10 to 13 show the third implementation variant according to which each TiBz element is associated with a graphite float.
  • the cathode active element made of TiB 2 (30) is encased in a graphite ring (31).
  • An intermediate support (32) made of inert material acts as a high stop for the graphite ring (31). This intermediate support comes to bear on the cathode substrate by feet or supports not shown, which do not call for any particular comment.
  • the TiBz element (33) is a plate fixed by the screw (34) to the graphite float (35).
  • the fixing can be carried out by any other equivalent means.
  • the graphite float (36) has a well (37) closed in its lower part and filled with liquid aluminum.
  • the TiBz elements (38) are supported on the graphite float by fins or ribs (39).
  • the “bowl” shape of the element (40) in FIG. 13 promotes the gathering of the liquid aluminum produced and its flow through the channels (41
  • the ratio: mass of the TiB 2 element / mass of the graphite element must be determined, taking into account the density of both, to obtain a resulting average density, either between 2.3 and 2.2, or less than 2.2 and preferably 2.1, in the usual temperature range of 930 to 960 ° C.
  • density values would have to be adapted if an electrolyte having a somewhat different density were used as a result of a modified composition.
  • the present invention offers numerous advantages which make it possible to transpose to the industrial stage a technique which had hitherto remained experimental. .
  • the TiB 2 studs, individually, and above all, grouped together, can be easily replaced and their floating nature makes them less vulnerable to mechanical operating shocks: in the case of FIG. 8, for example, in the event of a shock to when installing or removing an anode, the floating elements (25) can disappear in the dense concrete block (24) ensuring anchoring.
  • the height of the underlying metal can be maintained at a value sufficient to reduce the horizontal currents and the corresponding electromagnetic disturbances to an acceptable value, and the periodic removal of the metal can be carried out as in a conventional electrolysis cell.
  • the alumina sludge which is likely to form, settles at the bottom of the crucible, under the metal, thus sparing the surface of the floating elements on the metal. This device makes it easy to transform conventional tanks into tanks with TiB 2 elements.
  • the invention makes it possible to envisage a new design of electrolytic cells, in which the entire lining, including the bottom, is made of refractory, non-conductive material, and the cathode current is collected. in the sheet of liquid aluminum by a conductor located at the top of the electrolysis cell.
  • FIGS. 14 and 15 there is shown the diagram of such a tank, with the external metal box (42), the thermally insulating lining (43), the refractory and electrically insulating lining (44), the aluminum sheet.
  • li quide (45); the cathode element (46), object of the invention, is of the type described in FIG. 7, the electrolyte (47) the anodes (48) and the anode current inlets (49) (spider).
  • the cathodic current is collected by an element (50) comprising a vertical collector (51) which is a good electrical conductor, possibly protected from corrosion by an insulating sheath (52) and the end of which is capped by a TiB 2 cap (53). .

Landscapes

  • 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)
  • Ceramic Products (AREA)

Description

La présente invention concerne des éléments cathodiques flottants, en réfractaire électroconducteur, tel que le diborure de titane, destinés à la production d'aluminium par électrolyse, selon le procédé Hall-Héroult.The present invention relates to floating cathode elements, in electroconductive refractory, such as titanium diboride, intended for the production of aluminum by electrolysis, according to the Hall-Héroult process.

Dans les cellules Hall-Héroult, la cathode est constituée universellement par des blocs de carbone juxtaposés, dans lesquels sont scellées des barres métalliques elles-mêmes reliées à des conducteurs assurant la connexion électrique avec la cuve suivante de la série. En fonctionnement, la cathode est recouverte en permanence d'une couche d'aluminium liquide d'une vingtaine de centimètres d'épaisseur.In Hall-Héroult cells, the cathode is universally made up of juxtaposed carbon blocks, in which metal bars are sealed, themselves connected to conductors ensuring the electrical connection with the next tank in the series. In operation, the cathode is permanently covered with a layer of liquid aluminum about twenty centimeters thick.

Dans les cuves modernes, qui fonctionnent sous des intensités atteignant ou dépassant 200.000 Ampères, on doit conserver une distance interpolaire d'au moins 40 millimètres entre les anodes et la surface de la couche d'aluminium liquide pour éviter que les vagues se produisant à l'interface entre le métal produit et la bain d'électrolyse ne réentraînent de l'aluminium ou du métalliques, ou partiellement réduits, vers l'anode où ils se réoxyderaient. Celà provoque une chute de tension supplémentaire importante, dépassant 1,5 volts, c'est-à-dire plus du tiers de la chute de tension totale aux bornes d'une cuve.In modern tanks, which operate at intensities reaching or exceeding 200,000 amperes, an interpolar distance of at least 40 millimeters must be maintained between the anodes and the surface of the layer of liquid aluminum to prevent the waves occurring at the surface. 'interface between the metal produced and the electrolysis bath do not entrain aluminum or metal, or partially reduced, to the anode where they would reoxidize. This causes a significant additional voltage drop, exceeding 1.5 volts, that is to say more than a third of the total voltage drop across a tank.

Parmi les différents procédés que l'on a imaginés pour augmenter la mouillabilité de la cathode par l'aluminium liquide et réduire le réen- traînement de cet aluminium liquide par les mouvements conjugués du métal et du bain d'électrolyse, l'utilisation de composés réfractaires électroconducteurs tient une large place et, en particulier, les borures de titane et de zirconium.Among the various processes that have been devised to increase the wettability of the cathode by liquid aluminum and reduce the re-entrainment of this liquid aluminum by the combined movements of the metal and the electrolysis bath, the use of compounds electroconductive refractories holds a large place and, in particular, the borides of titanium and zirconium.

De façon générale, les réfractaires électroconducteurs appartiennent à la classe formée par les borures, carbures et nitrures des métaux des groupes 4A, 5A et 6A mais, jusqu'à présent, les recherches se sont essentiellement axées sur les diborures de titane TiB2 et de zirconium ZrB2.In general, electroconductive refractories belong to the class formed by borides, carbides and nitrides of metals of groups 4A, 5A and 6A but, until now, research has mainly focused on titanium diborides TiB 2 and zirconium ZrB 2 .

Ces réfractaires électroconducteurs, pris séparément, ou en combinaison, peuvent être mis en oeuvre dans les cuves d'électrolyse du type Hall-Héroult, dans la mesure où ils possèdent simultanément les trois propriétés suivantes:

  • - Résistivité électrique inférieure à 1000 µΩcm et, de préférence, à 100 µΩcm à 950-970°C.
  • - Bonne mouillabilité par l'aluminium liquide.
  • - Inertie chimique et physique vis-à-vis de l'aluminium liquide et du bain d'électrolyse.
These electroconductive refractories, taken separately or in combination, can be used in electrolysis cells of the Hall-Héroult type, insofar as they simultaneously have the following three properties:
  • - Electrical resistivity less than 1000 µΩcm and preferably 100 µΩcm at 950-970 ° C.
  • - Good wettability by liquid aluminum.
  • - Chemical and physical inertia towards liquid aluminum and the electrolysis bath.

A 1 000° C, le borure de titane a une résistivité de 60 µΩcm - et le borure de zirconium de 74 µΩcm - soit respectivement 2 et 2,5 fois celle de l'aluminium liquide, mais plus de 5000 fois inférieure à celle du bain d'électrolyse qui est de l'ordre de 450 000 µΩcm. Ils sont parfaitement mouillés par l'aluminium liquide et suffisamment inertes vis-à-vis de la cryolithe fondue.At 1000 ° C, titanium boride has a resistivity of 60 µΩcm - and zirconium boride of 74 µΩcm - 2 and 2.5 times that of liquid aluminum, respectively, but more than 5000 times that of electrolysis bath which is around 450,000 µΩcm. They are perfectly wetted by liquid aluminum and sufficiently inert with respect to the molten cryolite.

Cependant, le prix très élevé des borures de titane et de zirconium, et la sensibilité de ces produits, à l'état massif, aux chocs thermiques, se sont opposés jusqu'à présent à ce que l'on réalise des blocs cathodiques massifs en ces deux matériaux, et, dans la pratique industrielle, on tend à utiliser soit des recouvrements d'épaisseur réduite obtenus par différents procédés, tels que dépôt en phase vapeur ou diffusion à l'état solide, soit des éléments massifs scellés dans la cathode carbonée et émergeant de la nappe d'aluminium liquide produit, dont on trouve une description complète dans deux articles de la revue allemande »Aluminium« pages 642-648 (Octobre 1980) et 713-718 (Novembere 1980) de K. BILLEHAUG et H. A. OYE, sous le titre »Inert cathodes for aluminium electrolysis in Hall-Heroult cells«.However, the very high price of titanium and zirconium borides, and the sensitivity of these products, in the massive state, to thermal shock, have hitherto opposed the production of massive cathode blocks in these two materials, and, in industrial practice, there is a tendency to use either coverings of reduced thickness obtained by different processes, such as vapor deposition or diffusion in the solid state, or solid elements sealed in the carbon cathode and emerging from the sheet of liquid aluminum produced, a full description of which can be found in two articles in the German review »Aluminum« pages 642-648 (October 1980) and 713-718 (Novembere 1980) by K. BILLEHAUG and HA OYE , under the title "Inert cathodes for aluminum electrolysis in Hall-Heroult cells".

Ces revêtements de faible épaisseur, ou de faibles dimensions, en borure de titane ou de zirconium, résolvent de façon relativement satisfaisante le problème de la conductivité électrique des blocs cathodiques et leur mouillabilité par l'aluminium liquide, mais ils sont malheureusement sujets à une usure relativement rapide par dissolution progressive dans l'aluminium avec lequel ils sont en contact. On estime que la consommation de TiB2 peut atteindre 200 Grammes par tonne d'aluminium produit et le TiB2 coûte plusieurs centaines de francs le kilo à l'heure actuelle. En outre, le remplacement des éléments cathodiques usés implique l'arrêt total et le démontage partiel de la cuve d'électrolyse, ce qui est inacceptable dans la pratique industrielle.These thin coatings, or small dimensions, made of titanium or zirconium boride, solve in a relatively satisfactory manner the problem of the electrical conductivity of the cathode blocks and their wettability by liquid aluminum, but they are unfortunately subject to wear relatively fast by progressive dissolution in the aluminum with which they are in contact. It is estimated that consumption of TiB 2 can reach 200 grams per tonne of aluminum produced and TiB 2 costs several hundred francs per kilo at present. In addition, the replacement of the worn cathode elements involves the total shutdown and partial disassembly of the electrolysis cell, which is unacceptable in industrial practice.

Des éléments cathodiques en borure de titane pour la production d'aluminium par le procédé Hall-Héroult ont été décrits initialement dans les brevets français:

  • FR-A-1 195 505 - 1203015 - 1205857 - 1 227 951 - 1 229 537 - 1 148 068 - 1 149 468 de BRITISH ALUMINIUM COMPANY Ltd et 1 165136 de KAISER ALUMINIUM et, plus récemment, dans les brevets FR-A-2 337 210 d'AL-COA - 2430464 d'ALUSUISSE, US-A-4177 128 de PPG INDUSTRIE - US. 4 093 524 de KAISER ALUMINIUM, mais, il ne semble pas qu'ils aient donné lieu à des réalisations à l'échelle industrielle.
Cathode elements made of titanium boride for the production of aluminum by the Hall-Héroult process were initially described in French patents:
  • FR-A-1 195 505 - 1203015 - 1205857 - 1 227 951 - 1 229 537 - 1 148 068 - 1 149 468 from BRITISH ALUMINUM COMPANY Ltd and 1 165 136 from KAISER ALUMINUM and, more recently, in FR-A patents 2 337 210 from AL-COA - 2430464 from ALUSUISSE, US-A-4177 128 from PPG INDUSTRIE - US. 4,093,524 by KAISER ALUMINUM, but, it does not seem that they have given rise to achievements on an industrial scale.

De même, le brevet FR-A-2 471 425 (ALU-SUISSE) décrit des éléments cathodiques en diborure de titane sous forme de matériau grenu ou en morceaux, déversé en vrac sur le fond de la cuve, et recouverts d'une épaisseur d'aluminium liquide au moins égale à 2 mm.Similarly, patent FR-A-2 471 425 (ALU-SUISSE) describes cathodic elements made of titanium diboride in the form of grainy or in pieces, poured in bulk on the bottom of the tank, and covered with a thickness of liquid aluminum at least equal to 2 mm.

Dans notre demande de brevet français n 81 04059 (FR-A-2 500 488) d'ALUMINIUM PECHINEY, on a décrit et revendiqué notamment, d'une part, un procédé de production d'aluminium selon la technique Hall-Héroult consistant à électrolyser de l'alumine dissoute dans un bain à base de cryolithe fondue, à une température de l'ordre de 930 à 960" C, entre un système cathodique comportant un substrat carboné recouvert en permanence par une couche d'aluminium liquide et un système anodique comportant au moins une anode carbonée, caractérisé en ce que l'on dispose sur le substrat cathodique carboné une pluralité d'éléments en diborure de titane, non liés audit substrat et non liés entre eux, formant sur ledit substrat un lit d'épaisseur régulière, en ce que l'on règle l'épaisseur de la couche d'aluminium liquide à une valeur au plus égale à l'épaisseur du lit d'éléments en diborure de titane et en ce que l'on fixe la distance entre le plan du système anodique et le plan supérieur du lit d'éléments en borure de titane à une valeur comprise entre 30 et 10 millimètres et, d'autre part, une cathode pour la mise en oeuvre de ce procédé, caractérisée en ce qu'elle comporte un substrat carboné recouvert d'une pluralité d'éléments en diborure de titane, non liés au substrat et non liés entre eux, formant sur ledit substrat un lit d'épaisseur régulière.In our French patent application No. 81,04059 (FR-A-2,500,488) to ALUMINUM PECHINEY, we have described and claimed in particular, on the one hand, a process for the production of aluminum according to the Hall-Héroult technique consisting of electrolysing alumina dissolved in a bath based on molten cryolite, at a temperature of the order of 930 to 960 "C, between a cathodic system that comprising a carbonaceous substrate permanently covered by a layer of liquid aluminum and an anode system comprising at least one carbonaceous anode, characterized in that a plurality of titanium diboride elements are placed on the carbonate cathode substrate, not linked to said substrate and not linked to each other, forming on said substrate a bed of regular thickness, in that the thickness of the layer of liquid aluminum is adjusted to a value at most equal to the thickness of the bed d elements in titanium diboride and in that the distance between the plane of the anode system and the upper plane of the bed of elements made of titanium boride is fixed at a value between 30 and 10 millimeters and, on the other hand , a cathode for implementing this method, characterized in that it comprises a carbonaceous substrate covered with a plurality of titanium diboride elements, not bonded to the substrate and not bonded to each other, forming on said substrate a bed of regular thickness.

Selon le brevet principal, cette cathode peut comporter un support carboné intermédiaire placé sur le substrat carboné de base, et supportant le lit de particules en diborure de titane.According to the main patent, this cathode may include an intermediate carbon support placed on the basic carbon substrate, and supporting the bed of particles of titanium diboride.

Enfin, dans le certificat d'addition N° 8 112 909 (FR-A-2 508 496) à ce même brevet également au nom d'ALUMINIUM PECHINEY, on a décrit et revendiqué des éléments cathodiques amovibles comportant un support intermédiaire inerte et des éléments actifs en réfractaire électroconducteur, tel que TiB2, solidaires mais séparables dudit support, l'ensemble formé par le support intermédiaire inerte et les éléments actifs ayant une densité supérieure à la densité de l'aluminium liquide à la température de l'électrolyse.Finally, in the certificate of addition No. 8,112,909 (FR-A-2,508,496) to this same patent also in the name of ALUMINUM PECHINEY, there have been described and claimed removable cathode elements comprising an inert intermediate support and active elements in electroconductive refractory, such as TiB 2 , integral but separable from said support, the assembly formed by the inert intermediate support and the active elements having a density greater than the density of liquid aluminum at the temperature of electrolysis.

Cependant, la mise en oeuvre des éléments cathodiques en réfractaire électroconducteur mouillables par l'aluminium liquide, objet des demandes de brevet n° 81 04059 et de certificat d'addition 81 12909 peut dans certains cas, présenter quelques inconvénients:

  • - l'épaisseur de la couche de métal liquide dans laquelle baigne le lit d'éléments mouillables est faible et peut localement devenir le siège d'intenses courants électriques horizontaux, qui risquent d'induire des forces électromagnétiques tendant à mettre ce métal en mouvement et à entraîner les éléments conducteurs mouillables, modifiant ainsi l'uniformité du lit formé par ces éléments;
  • - en cas d'effet d'anode, il est impossible de mettre l'anode, par abaissement de sa position, au contact de la nappe d'aluminium liquide et de dépolariser ainsi la plan anodique;
  • - pour pouvoir prélever périodiquement le volume de métal produit, il est nécessaire de prévoir dans la cathode un puits ou un chenal formant réservoir qui draine le métal s'écoulant du lit cathodique. L'importance du volume de ce réservoir et divers problèmes d'isolement électrique peuvent compliquer la conception du fond de la cuve et augmenter ce coût;
  • - en cas d'embourbement du fond de la cuve par des boues d'alumine et d'électrolyte non dissous, le lit, qui est de faible épaisseur, va se trouver rapidement masqué par ces boues, et le fonctionnement de la cellule en sera perturbé;
  • - il existe un risque d'endommager, ou même de détruire des éléments du support intermédiaire inerte et des éléments en TiB2 en cas de chute ou de descente incontrôlée d'une anode.
However, the use of cathode elements in electroconductive refractory wettable by liquid aluminum, which is the subject of patent applications No. 81 04059 and of certificate of addition 81 12909 may in certain cases have some drawbacks:
  • the thickness of the layer of liquid metal in which the bed of wettable elements is bathed is small and may locally become the seat of intense horizontal electric currents, which risk inducing electromagnetic forces tending to set this metal in motion and driving the wettable conductive elements, thereby modifying the uniformity of the bed formed by these elements;
  • - in the event of an anode effect, it is impossible to bring the anode, by lowering its position, into contact with the sheet of liquid aluminum and thus depolarize the anode plane;
  • - to be able to periodically sample the volume of metal produced, it is necessary to provide in the cathode a well or a channel forming a reservoir which drains the metal flowing from the cathode bed. The large volume of this tank and various problems of electrical insulation can complicate the design of the bottom of the tank and increase this cost;
  • - in the event of the bottom of the tank being bogged down by undissolved alumina and electrolyte sludge, the bed, which is thin, will quickly be masked by this sludge, and the operation of the cell will be disturbed;
  • - There is a risk of damaging, or even destroying elements of the inert intermediate support and TiB 2 elements in the event of an uncontrolled fall or descent of an anode.

La présente invention a pour but de supprimer ces inconvénients. Elle est basée sur des éléments en réfractaires électroconducteurs mouillables par l'aluminium liquide et, en particulier, à base de diborure de titane, non directement liés au substrat cathodique, guidés et disposant d'un degré de liberté limitée, dans le sens vertical, et que l'on maintient flottants à l'interface entre le bain d'électrolyse et l'aluminium produit, quelles que soient les fluctuations de cette interface pendant le processus d'électrolyse, en les faisant supporter par un support intermédiaire inerte de densité inférieure à celle de l'aluminium liquide.The present invention aims to eliminate these drawbacks. It is based on elements in electrically conductive refractories wettable by liquid aluminum and, in particular, based on titanium diboride, not directly linked to the cathode substrate, guided and having a limited degree of freedom, in the vertical direction, and that floating is maintained at the interface between the electrolysis bath and the aluminum produced, whatever the fluctuations of this interface during the electrolysis process, by making them support by an inert intermediate support of lower density to that of liquid aluminum.

En outre, ces éléments sont amovibles de façon à être mis en place et remplacés sans interrompre l'électrolyse, avec passage intermédiaire éventuel dans une enceinte de préchauffage ou de refroidissement contrôlé, à atmosphère contrôlée ou non.In addition, these elements are removable so as to be put in place and replaced without interrupting the electrolysis, with possible intermediate passage in a chamber for controlled preheating or cooling, with a controlled atmosphere or not.

La présente invention a four objet ces éléments cathodiques flottants et les cuves d'électrolyse pour la production d'aluminium comportant ces éléments.The present invention relates to these floating cathode elements and the electrolytic cells for the production of aluminum comprising these elements.

Dans tout ce qui suit, nous conviendrons de désigner par:

  • - élément cathodique flottant: l'ensemble formé par un support intermédiaire inerte et au moins un élément cathodique actif, amovible, caractérisé en ce que sa densité moyenne est inférieure à la densité de l'aluminium liquide dans les conditions normales d'utilisation des cuves Hall-Héroult;
  • - moyen d'ancrage: une structure de densité supérieure à celle de l'aluminium liquide dans les conditions normales d'utilisation des cuves Hall-Héroult, confectionnée soit en matériau réfractaire ou céramique, soit en métal recouvert d'une couche protectrice, et caractérisé en ce qu'elle comporte au moins une butée ou un dispositif limitant, vers le haut, la course verticale d'un ou plusieurs éléments cathodiques flottants;
  • - moyen de guidage: un système mécanique dont l'objectif est de limiter le débattement latéral d'un ou plusieurs éléments cathodiques flottants, tout en lui laissant une liberté de mouvement dans le sens vertical, cette liberté étant éventuellement limitée par le moyen d'ancrage. Le moyen de guidage et le moyen d'ancrage peuvent être partiellement ou totalement confondus;
  • - interface: l'interface entre la nappe d'aluminium liquide produit par l'électrolyse, et l'électrolyte (cryolithe fondue).
In what follows, we agree to designate by:
  • - floating cathode element: the assembly formed by an inert intermediate support and at least one active, removable cathode element, characterized in that its average density is less than the density of liquid aluminum under normal conditions of use of the tanks Hall-Héroult;
  • - anchoring means: a density structure higher than that of liquid aluminum under normal conditions of use of Hall-Héroult tanks, made either of refractory or ceramic material, or of metal covered with a protective layer, and characterized in that it comprises at least one stop or a device limiting, upwards, the vertical stroke of one or more floating cathode elements;
  • - guidance means: a mechanical system whose objective is to limit the lateral clearance of one or more floating cathode elements, while leaving it freedom of movement in the vertical direction, this freedom being possibly limited by the means of anchoring. The Mistletoe Means dage and the anchoring means may be partially or totally combined;
  • - interface: the interface between the sheet of liquid aluminum produced by electrolysis, and the electrolyte (molten cryolite).

Le diborure de titane ayant une densité très supérieure à celle de l'aluminium liquide à la température (env. 960°C) de l'électrolyse (environ 4,5 contre 2,3 à 2,1-2,2 pour l'électrolyte), son utilisation pour constituer des éléments cathodiques flottants, peut s'effecteur selon l'une des trois variantes suivantes:

  • 1. On dispose les éléments sur un substrat inerte de densité sensiblement inférieure à celle de l'aluminium liquide, et on règle la proportion: masse du substrat inerte/masse de TiB2 de façon que l'ensemble ait une densité inférieure à celle de l'AI liquide (2,3) et supérieure à celle de l'électrolyte (l'expression substrat inerte signigie que ce substrat n'a pas pour fonction principale de servir, en lui-même, de cathode pour le dépôt électrochimique d'aluminium métal).
  • 2. procède, comme dans la première variante, mais en plus, on retient les éléments à l'interface par un ancrage sur le substrat cathodique qui leur laisse un degré de liberté dans le sens vertical.
  • 3. On adjoint aux éléments en TiB2 un flotteur en graphite (densité 1,6 à 2 à 960°C) de façon telle que l'ensemble élément + flotteur ait une densité inférieure à celle de l'électrolyte (comprise entre 2,1 et 2,2 dans l'intervalle 930-960°C). Les ensembles flottent au-dessus de l'interface bain-métal. La conduction électrique vers la cathode est alors assurée par des queues conductrices plongeant dans la nappe de métal.
  • Les figures 1 à 15 illustrent les différents modes de mise en oeuvre de l'invention.
  • La figure 1 représente un élément cathodique flottant muni d'une pluralité d'éléments actifs amovibles en TiB2.
  • Les figures 2 et 3 représentent deux formes possibles d'éléments actifs en TiB2.
  • Les figures 4 et 5 représentent deux éléments cathodiques flottants, munis d'éléments actifs en TiB2 de forme tubulaire fendue, et de moyens d'ancrage sur le substrat.
  • La figure 6 représente un élément cathodique flottant ancré dans un bloc de béton réfractaire dense.
  • La figure 7 représente un moyen de guidage latéral d'un élément cathodique flottant.
  • La figure 8 représente un autre type d'élément cathodique flottant, avec butées hautes et basses intégrées dans le support réfractaire.
  • La figure 9 représente le détail de ces butées.
  • Les figures 10 à 13 représentent diverses variantes de réalisation d'éléments cathodiques flottants individuels, chaque élément actif de TiB2 étant muni de son propre flotteur.
  • Les figures 14 et 15 représentent une application de éléments cathodiques flottants à des cuves d'électrolyse à sortie cathodique par le haut, dans lesquelles le courant est collecté dans la nappe d'aluminium.
Titanium diboride having a density much higher than that of liquid aluminum at the temperature (approx. 960 ° C) of the electrolysis (approximately 4.5 against 2.3 to 2.1-2.2 for the electrolyte), its use to constitute floating cathode elements, can be effector according to one of the following three variants:
  • 1. The elements are placed on an inert substrate with a density substantially lower than that of liquid aluminum, and the proportion: mass of the inert substrate / mass of TiB 2 is adjusted so that the assembly has a density less than that of liquid AI (2,3) and higher than that of the electrolyte (the expression inert substrate means that this substrate does not have the main function of serving, in itself, as a cathode for the electrochemical deposition of aluminum metal).
  • 2. proceeds, as in the first variant, but in addition, the elements are retained at the interface by an anchoring on the cathode substrate which leaves them a degree of freedom in the vertical direction.
  • 3. We add to the TiB 2 elements a graphite float (density 1.6 to 2 at 960 ° C) so that the element + float assembly has a density lower than that of the electrolyte (between 2, 1 and 2.2 in the range 930-960 ° C). The assemblies float above the bath-metal interface. The electrical conduction to the cathode is then ensured by conductive tails plunging into the sheet of metal.
  • Figures 1 to 15 illustrate the different embodiments of the invention.
  • FIG. 1 shows a floating cathode element provided with a plurality of removable active TiB 2 elements.
  • Figures 2 and 3 show two possible forms of active TiB 2 elements.
  • Figures 4 and 5 show two floating cathode elements, provided with active TiB 2 elements of split tubular shape, and anchoring means on the substrate.
  • FIG. 6 represents a floating cathode element anchored in a block of dense refractory concrete.
  • FIG. 7 represents a means for lateral guidance of a floating cathode element.
  • FIG. 8 represents another type of floating cathode element, with high and low stops integrated in the refractory support.
  • Figure 9 shows the detail of these stops.
  • Figures 10 to 13 show various alternative embodiments of individual floating cathode elements, each active element of TiB 2 being provided with its own float.
  • Figures 14 and 15 show an application of floating cathode elements to electrolytic cells with cathode outlet from above, in which the current is collected in the aluminum sheet.

Sur la figure 1, l'élément cathodique actif en TiB2 (1) est formé par une tête plate ou légèrement bombée et une queue (2) qui est positionnée dans les orifices (3) d'un support intermédiaire inerte (4) en graphite. La densité moyenne de l'ensemble cathodique ainsi constitué est inférieure à celle de l'aluminium liquide. Les têtes des plots (1) sont, en fonctionnement normal, au voisinage de l'interface nappe d'aluminium-électrolyte.In FIG. 1, the active cathode element made of TiB 2 (1) is formed by a flat or slightly convex head and a tail (2) which is positioned in the orifices (3) of an inert intermediate support (4) in graphite. The average density of the cathode assembly thus formed is lower than that of liquid aluminum. The heads of the pads (1) are, in normal operation, in the vicinity of the aluminum sheet-electrolyte interface.

L'élément cathodique (1) peut reposer directement sur l'orifice (3) ou être muni de bossage (5) ou d'ailettes (6) qui ménagent un intervalle favorisant l'écoulement de l'aluminium liquide au fur et à mesure de sa production (fig. 2 et 3).The cathode element (1) can rest directly on the orifice (3) or be provided with a boss (5) or fins (6) which provide an interval favoring the flow of the liquid aluminum progressively of its production (fig. 2 and 3).

Les figures 4 et 5 montrent un autre mode de réalisation dans lequel l'élément cathodique flottant (7) est ancré au substrat cathodique (8) par des plots (9). La tête (10) du plot d'ancrage coopère avec un redent (11) du support intermédiaire (7) pour assurer une butée qui limite sa course vers le haut. Les éléments cathodiques actifs (12) sont constitués par des tronçons de tubes fendus (13) et enfilés sur un rail (14), laissant entre eux un espace libre suffisant pour l'écoulement de l'aluminium produit. Ces tubes peuvent avoir une section circulaire, carrée ou autre.Figures 4 and 5 show another embodiment in which the floating cathode element (7) is anchored to the cathode substrate (8) by studs (9). The head (10) of the anchoring stud cooperates with a recess (11) of the intermediate support (7) to ensure a stop which limits its upward stroke. The active cathode elements (12) consist of sections of split tubes (13) and threaded on a rail (14), leaving between them sufficient free space for the flow of aluminum produced. These tubes can have a circular, square or other section.

Dans le cas de la figure 5, on a fixé le rapport masse de graphite/masse de TiB2 de façon telle que la densité moyenne de l'ensemble soit inférieure à la densité de l'électrolyte si bien que l'élément cathodique flottant est, normalement, en butée haute.In the case of FIG. 5, the mass ratio of graphite / mass of TiB 2 is fixed so that the average density of the assembly is less than the density of the electrolyte so that the floating cathode element is , normally in the upper stop.

Dans l'un et l'autre cas, la course de l'élément flottant, déterminée par la position de la butée et la hauteur du plot d'ancrage, doit être au moins égale aux variations de hauteur de la nappe d'aluminiums liquide en cours d'électrolyse et de soutirage du métal.In both cases, the stroke of the floating element, determined by the position of the stopper and the height of the anchoring stud, must be at least equal to the variations in height of the sheet of liquid aluminum. during electrolysis and racking of metal.

De façon générale, les éléments actifs en TiB2 (12) doivent dépasser l'interface (15) d'au moins 10 millimètres.In general, the active TiB 2 elements (12) must exceed the interface (15) by at least 10 millimeters.

En outre, on prend soin d'avoir un plateau conducteur (7) assez épais pour être toujours assuré que sa base baigne dans le métal quelles que soient les variations de hauteur de celui-ci. C'est, en effet, ce plateau et non les plots d'ancrage (9) qui transmettront le courant au substrat cathodique carboné (8) par l'intermédiaire de la nappe (16) de métal produit. Il importe de souligner que, dans tous les cas, ce sont les éléments en TiB2 qui jouent le rôle de cathode et c'est sur eux que s'effectue le dépôt d'aluminium produit par l'électrolyse.In addition, care is taken to have a conductive plate (7) thick enough to be always assured that its base is immersed in the metal whatever the variations in height thereof. It is, in fact, this plate and not the anchoring pads (9) which will transmit the current to the carbonaceous cathode substrate (8) via the sheet (16) of metal produced. It is important to emphasize that, in all cases, it is the TiB 2 elements which play the role of cathode and it is on them that the deposition of aluminum produced by electrolysis takes place.

La figure 6 montre une autre variante de réalisation dans laquelle l'élément cathodique flottant est constitué par un plateau (17) en graphite revêtu de diborure de titane en revêtement mince (18) effectué par dépôt chimique en phase vapeur ou projection au chalumeau à plasma. Le plateau flottant est retenu au fond par un bloc dense (19) en béton réfractaire, résistant à l'action de l'aluminium liquide (16) reposant sur le substrat cathodique (9). De préférence, le bloc dense (19) est muni de canaux (20) pour assurer la circulation de l'aluminium et le passage du courant.FIG. 6 shows another alternative embodiment in which the floating cathode element consists of a graphite plate (17) coated with thin-coated titanium diboride (18) produced by chemical phase deposition steam or plasma torch projection. The floating plate is retained at the bottom by a dense block (19) of refractory concrete, resistant to the action of liquid aluminum (16) resting on the cathode substrate (9). Preferably, the dense block (19) is provided with channels (20) to ensure the circulation of aluminum and the passage of current.

Dans le cas de la figure 1, ou de structures analogues à celle des figures 6 et 8, la structure flottante peut comporter des moyens de guidage tels que le des rouleaux (21) qui coopèrent, par exemple, avec les pieds supports (22). Ces rouleaux peuvent être constitués, par exemple, en TiBz ou nitrure de silicium ou oxynitrure de silicium et d'aluminium (Sialon). Dans le cas de la figure 8, le support réfractaire (24) est intégralement noyé dans le métal. Le support perforé (25), qui maintient les plots (1) de TiBz a une densité inférieure à la densité du bain d'électrolyse: c'est par exemple du graphite, éventuellement protégé par un dépôt mince d'un réfractaire tel que le diborure de titane ou le Sialon.In the case of FIG. 1, or of structures similar to that of FIGS. 6 and 8, the floating structure may include guide means such as the rollers (21) which cooperate, for example, with the support legs (22) . These rollers can be made, for example, of TiBz or silicon nitride or silicon and aluminum oxynitride (Sialon). In the case of Figure 8, the refractory support (24) is fully embedded in the metal. The perforated support (25), which holds the pads (1) of TiBz has a density lower than the density of the electrolysis bath: it is for example graphite, possibly protected by a thin deposit of a refractory such as titanium diboride or Sialon.

L'avantage de cette disposition est que l'ensemble du support perforé + plots TiB2 peut s'effacer intégralement dans le support réfractaire dense en cas de poussée vers le bas (cas d'une anode qui serait trop abaissée). Il faut donc avoir e1 5 ez.The advantage of this arrangement is that the whole of the perforated support + TiB 2 studs can be completely erased in the dense refractory support in the event of pushing down (in the case of an anode which would be too low). It is therefore necessary to have e 1 5 ez.

Si la densité moyenne de l'ensemble support perforé + plots de TiBz est inférieure à celle du bain, le support perforé reste en permanence en butée haute. Si cette densité moyenne est comprise entre celle du bain et celle du métal, le support perforé suit les variations de niveau du métal au cours de l'électrolyse.If the average density of the perforated support + TiBz pads assembly is lower than that of the bath, the perforated support remains permanently in the top stop. If this average density is between that of the bath and that of the metal, the perforated support follows the variations in level of the metal during the electrolysis.

La figure 9 donne le détail de construction du support réfractaire dense (24) de la figure 8 avec des butées hautes (25) et basses (26). L'une de ses faces peut comporter une paroi amovible (27). La mise en place ou le retrait de telles parois permet de diriger et de contrôler la circulation du métal et du bain sous l'effet des forces électromagnétiques.FIG. 9 gives the construction detail of the dense refractory support (24) of FIG. 8 with high (25) and low (26) stops. One of its faces may have a removable wall (27). The establishment or removal of such walls makes it possible to direct and control the circulation of the metal and the bath under the effect of electromagnetic forces.

Les figures 10 à 13 représentent la troisième variante de mise en oeuvre selon laquelle chaque élément en TiBz est associé à un flotteur en graphite. L'élément actif cathodique en TiB2 (30) est enchassé dans une bague en graphite (31). Un support intermédiaire (32) en matériau inerte fait office de butée haute pour la bague en graphite (31). Ce support intermédiaire vienten appui sur le substrat cathodique par des pieds ou supports non représentés, qui n'appellent aucun commentaire particulier.Figures 10 to 13 show the third implementation variant according to which each TiBz element is associated with a graphite float. The cathode active element made of TiB 2 (30) is encased in a graphite ring (31). An intermediate support (32) made of inert material acts as a high stop for the graphite ring (31). This intermediate support comes to bear on the cathode substrate by feet or supports not shown, which do not call for any particular comment.

Sur la figure 11, l'élément en TiBz (33) est une plaque fixée par la vis (34) sur le flotteur (35) en graphite. La fixation peut être effectuée par tout autre moyen équivalent.In FIG. 11, the TiBz element (33) is a plate fixed by the screw (34) to the graphite float (35). The fixing can be carried out by any other equivalent means.

Sur les figures 12 et 13, le flotteur en graphite (36) comporte un puits (37) fermé en sa partie basse et rempli d'aluminium liquide. Les éléments (38) en TiBz s'appuient sur le flotteur en graphite par des ailettes ou nervures (39). La forme en »cuvette« de l'élément (40) sur la figure 13 favorise le rassemblement de l'aluminium liquide produit et son écoulement par les canaux (41In Figures 12 and 13, the graphite float (36) has a well (37) closed in its lower part and filled with liquid aluminum. The TiBz elements (38) are supported on the graphite float by fins or ribs (39). The “bowl” shape of the element (40) in FIG. 13 promotes the gathering of the liquid aluminum produced and its flow through the channels (41

Bien entendu, dans toutes les réalisations décrites, le rapport: masse de l'élément en TiB2/ masse de l'élément de graphite doit être déterminé, compte-tenu de la densité de l'un et de l'autre, pour obtenir une densité moyenne résultante, soit comprise entre 2,3 et 2,2, soit inférieure à 2,2 et, de préférence, à 2,1, dans l'intervalle de température habituel de 930 à 960°C. Ces valeurs de densités seraient à adapter si l'on utilisait un électrolyte ayant une densité quelque peu différente par suite d'une composition modifiée.Of course, in all the embodiments described, the ratio: mass of the TiB 2 element / mass of the graphite element must be determined, taking into account the density of both, to obtain a resulting average density, either between 2.3 and 2.2, or less than 2.2 and preferably 2.1, in the usual temperature range of 930 to 960 ° C. These density values would have to be adapted if an electrolyte having a somewhat different density were used as a result of a modified composition.

Par ailleurs, en vue d'alléger les dessins, le système anodiquè n'a pas été représenté, mais il est bien évident qu'il fait face à la partie supérieure des éléments actifs en TiB2, et qu'il est conforme à l'état actuel de la technique.Furthermore, in order to lighten the drawings, the anodic system has not been shown, but it is obvious that it faces the upper part of the active TiB 2 elements, and that it conforms to the 'state of the art.

Avantages procures par l'inventionAdvantages of the invention

Outre les avantages bien connus procurés par les éléments cathodiques en TiB2 très bons conducteurs électriques et mouillables par l'aluminium liquide, la présente invention offre de nombreux avantages qui permettent de transposer au stade industriel une technique qui était jusqu'à présent, restée expérimentale.In addition to the well-known advantages provided by the cathode elements made of TiB 2, very good electrical conductors and wettable by liquid aluminum, the present invention offers numerous advantages which make it possible to transpose to the industrial stage a technique which had hitherto remained experimental. .

Les plots en TiB2, individuellement, et surtout, groupés en ensembles, peuvent être facilement remplacés et leur caractère flottant les rend moins vulnérables aux chocs mécaniques d'exploitation: dans le cas de la figure 8, par exemple, en cas de choc à la mise en place ou à l'enlèvement d'une anode, les éléments flottants (25) peuvent s'effacer dans le bloc de béton dense (24) assurant l'ancrage. La hauteur du métal sous-jacent peut être maintenue à une valeur suffisante pour réduire les courants horizontaux et les perturbations électromagnétiques correspondantes à une valeur acceptable, et le prélèvement périodique du métal peut être effectué comme dans une cellule d'électroluse classique.The TiB 2 studs, individually, and above all, grouped together, can be easily replaced and their floating nature makes them less vulnerable to mechanical operating shocks: in the case of FIG. 8, for example, in the event of a shock to when installing or removing an anode, the floating elements (25) can disappear in the dense concrete block (24) ensuring anchoring. The height of the underlying metal can be maintained at a value sufficient to reduce the horizontal currents and the corresponding electromagnetic disturbances to an acceptable value, and the periodic removal of the metal can be carried out as in a conventional electrolysis cell.

Les boues d'alumine, qui risquent de se former, décantent au fond du creuset, sous le métal, épargnant ainsi la surface des éléments flottants sur le métal. Ce dispositif permet une transformation aisée des cuves classiques, en cuves à éléments en TiB2.The alumina sludge, which is likely to form, settles at the bottom of the crucible, under the metal, thus sparing the surface of the floating elements on the metal. This device makes it easy to transform conventional tanks into tanks with TiB 2 elements.

Mais, en plus, l'invention permet d'envisager une conception nouvelle de cuves d'électrolyse, dans lesquelles l'ensemble du garnissage, y compris le fond, est réalisé en matériau réfractaire, non-conducteur, et le courant cathodique est collecté dans la nappe d'aluminium liquide par un conducteur situé à la partie supérieure de la cuve d'électrolyse.But, in addition, the invention makes it possible to envisage a new design of electrolytic cells, in which the entire lining, including the bottom, is made of refractory, non-conductive material, and the cathode current is collected. in the sheet of liquid aluminum by a conductor located at the top of the electrolysis cell.

Sur les figures 14 et 15, on a représenté le schéma d'une telle cuve, avec le caisson métallique externe (42), le garnissage thermiquement isolant (43), le garnissage réfractaire et électriquement isolant (44), la nappe d'aluminium liquide (45); l'élément cathodique (46), objet de l'invention, est du type décrit sur la figure 7, l'électrolyte (47) les anodes (48) et les arrivées de courant anodique (49) (croisillon).In FIGS. 14 and 15, there is shown the diagram of such a tank, with the external metal box (42), the thermally insulating lining (43), the refractory and electrically insulating lining (44), the aluminum sheet. li quide (45); the cathode element (46), object of the invention, is of the type described in FIG. 7, the electrolyte (47) the anodes (48) and the anode current inlets (49) (spider).

Le courant cathodique est collecté par un élément (50) comportant un collecteur vertical (51) bon conducteur électrique, éventuellement protégé de la corrosion par un gainage isolant (52) et dont l'extrémité est coiffée par un capuchon (53) en TiB2.The cathodic current is collected by an element (50) comprising a vertical collector (51) which is a good electrical conductor, possibly protected from corrosion by an insulating sheath (52) and the end of which is capped by a TiB 2 cap (53). .

On pourrait craindre que, dans cette disposition, le courant horizontal parcourant la nappe de métal n'y induise des mouvements inacceptables du métal. Mais, en fait, ces mouvements sont fortement atténués par les parois des dispositifs d'ancrage et de guidage des éléments cathodiques. En outre, on constate que les éléments cathodiques flottants agissent comme un véritable diaphragme entre la nappe d'aluminium liquide et les anodes, ce qui exclut toute influence néfaste de ces mouvements de métal sur le rendement Faraday, en s'opposant au transport par convection, vers l'anode, d'espèces métalliques ou partiellement réduites, en particulier d'aluminium et de sodium.It might be feared that, in this arrangement, the horizontal current flowing through the sheet of metal induces therein unacceptable movements of the metal. But, in fact, these movements are greatly attenuated by the walls of the anchoring and guiding devices of the cathode elements. In addition, it can be seen that the floating cathode elements act as a real diaphragm between the sheet of liquid aluminum and the anodes, which excludes any harmful influence of these metal movements on the Faraday yield, by opposing transport by convection. , towards the anode, of metallic or partially reduced species, in particular of aluminum and sodium.

On peut ainsi, dans une disposition telle que celle de la figure 15, gagner une grande partie de la chute de tension dans les blocs cathodiques classiques (environ 400 millivolts), et une partie de la chute de tension (environ 100 mV) dans les conducteurs de liaison de cuve à cuve (54) qui sont sensiblement raccourcis, avec une diminution corrélative de l'investissement correspondant à ces conducteurs.It is thus possible, in an arrangement such as that of FIG. 15, to gain a large part of the voltage drop in conventional cathode blocks (approximately 400 millivolts), and part of the voltage drop (approximately 100 mV) in the tank-to-tank connecting conductors (54) which are substantially shortened, with a corresponding reduction in the investment corresponding to these conductors.

Claims (9)

1. A floating cathodic element intended for the electrolytic production of aluminium by means of the Hall-Héroult process in an electrolysis tank comprising a molten cryolite-base bath between a carbonaceous anode and a cathodic layer of molten aluminium, characterised in that it comprise at least one active cathodic element (1) of titanium diboride, which is supported by an intermediate carrier (4) which is inert respect to the liquid aluminium and the electrolyte, the mean density of the assembly of the active cathodic element (1) and the inert intermediate carrier (4) being lower than the density of the liquid aluminium (16) under the normal conditions of operation of the electrolysis tank.
2. A floating cathodic element according to claim 1 characterised in that its mean density is lower than the density of the liquid aluminium and the density of the molten cryolite-base electrolytic bath, under the normal conditions of use of the electrolysis tank.
3. A floating cathodic element according to claim 1 characterised in that its mean density is between the density of the liquid aluminium and the density of the molten cryolite-base electrolytic bath under the normal conditions of use of the electrolysis tank.
4. A tank for the production of aluminium by the electrolysis of alumina which is dissolved in molten cryolite, in accordance with the Hall-Héroult process, wherein the bottom which supports the layer of liquid aluminium is formed by a cathodic substrate (8) and comprising floating cathodic elements according to any one of claims 1 to 3 characterised in that said floating cathodic elements comprise abutment means (11) which cooperate with abutment means (10) connected to means (9) for anchoring to the cathodic substrate for limiting the amplitude of the movements of the floating cathodic elements in the vertical direction.
5. A tank for the production of aluminium according to claim 4 chartacterised in that it comprises a plurality of active cathodic elements associated with an inert intermediate carrier (4).
6. A tank for the production of aluminium according to claim 4 characterised in that each active cathodic element (1) is individually associated with an inert intermediate carrier (31).
7. A tank for the production of aluminium according to any one of claims 4 to 6 characterised in that the inert intermediate carrier (4) is of graphite.
8. A tank for the production of aluminium according to any one of claims 4 to 7 characterised in that the cathodic current is taken off directly from the layer of liquid aluminium (45) by means of at least one collector (51) disposed in the upper part of the electrolysis tank.
9. A tank for the production of aluminium according to any one of claims 4 to 8 characterised in that the bottom of said tank, in contact with the layer of liquid aluminium (45), comprises a material which is a nonconductor or a poor conductor of electrical current.
EP82420176A 1981-12-11 1982-12-09 Floating cathodic elements made of electro conductive refractory material for the production of aluminium by electrolysis Expired EP0082096B1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FR8123780 1981-12-11
FR8123780A FR2518124A1 (en) 1981-12-11 1981-12-11 FLOATING CATHODIC ELEMENTS BASED ON ELECTROCONDUCTIVE REFRACTORY FOR THE PRODUCTION OF ALUMINUM BY ELECTROLYSIS

Publications (2)

Publication Number Publication Date
EP0082096A1 EP0082096A1 (en) 1983-06-22
EP0082096B1 true EP0082096B1 (en) 1985-08-21

Family

ID=9265204

Family Applications (1)

Application Number Title Priority Date Filing Date
EP82420176A Expired EP0082096B1 (en) 1981-12-11 1982-12-09 Floating cathodic elements made of electro conductive refractory material for the production of aluminium by electrolysis

Country Status (19)

Country Link
US (1) US4532017A (en)
EP (1) EP0082096B1 (en)
JP (1) JPS58107491A (en)
AU (1) AU552985B2 (en)
BR (1) BR8207190A (en)
CA (1) CA1195950A (en)
DE (1) DE3265665D1 (en)
ES (1) ES517933A0 (en)
FR (1) FR2518124A1 (en)
GR (1) GR77281B (en)
HU (1) HU191107B (en)
IN (1) IN158855B (en)
NO (1) NO157508C (en)
NZ (1) NZ202697A (en)
OA (1) OA07274A (en)
PL (1) PL134338B1 (en)
SU (1) SU1205779A3 (en)
YU (1) YU268982A (en)
ZA (1) ZA829064B (en)

Families Citing this family (21)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4526669A (en) * 1982-06-03 1985-07-02 Great Lakes Carbon Corporation Cathodic component for aluminum reduction cell
FR2529580B1 (en) * 1982-06-30 1986-03-21 Pechiney Aluminium ELECTROLYSIS TANK FOR THE PRODUCTION OF ALUMINUM, COMPRISING A FLOATING CONDUCTIVE SCREEN
CH651855A5 (en) * 1982-07-09 1985-10-15 Alusuisse SOLID CATHODE IN A MELTFLOW ELECTROLYSIS CELL.
CH654335A5 (en) * 1983-03-11 1986-02-14 Alusuisse CELL FOR REFINING ALUMINUM.
AU2713684A (en) * 1983-04-26 1984-11-01 Aluminium Company Of America Electrolytic cell
US4622111A (en) * 1983-04-26 1986-11-11 Aluminum Company Of America Apparatus and method for electrolysis and inclined electrodes
US4596637A (en) * 1983-04-26 1986-06-24 Aluminum Company Of America Apparatus and method for electrolysis and float
US4664760A (en) * 1983-04-26 1987-05-12 Aluminum Company Of America Electrolytic cell and method of electrolysis using supported electrodes
US4808304A (en) * 1983-10-19 1989-02-28 Deal Troy M Apparatus for the dewatering of phosphate slimes
US4631121A (en) * 1986-02-06 1986-12-23 Reynolds Metals Company Alumina reduction cell
JPH0628943Y2 (en) * 1988-08-10 1994-08-03 多摩川精機株式会社 Needle swing mechanism in winding machine
US4919782A (en) * 1989-02-21 1990-04-24 Reynolds Metals Company Alumina reduction cell
US5129998A (en) * 1991-05-20 1992-07-14 Reynolds Metals Company Refractory hard metal shapes for aluminum production
US5486278A (en) * 1993-06-02 1996-01-23 Moltech Invent S.A. Treating prebaked carbon components for aluminum production, the treated components thereof, and the components use in an electrolytic cell
US5472578A (en) * 1994-09-16 1995-12-05 Moltech Invent S.A. Aluminium production cell and assembly
US5753382A (en) * 1996-01-10 1998-05-19 Moltech Invent S.A. Carbon bodies resistant to deterioration by oxidizing gases
US6071388A (en) * 1998-05-29 2000-06-06 International Business Machines Corporation Electroplating workpiece fixture having liquid gap spacer
GB2371055A (en) * 2001-01-15 2002-07-17 Innovation And Technology Alum Anode for electrolysis of aluminium
RU2454490C1 (en) * 2010-11-02 2012-06-27 Общество с ограниченной ответственностью "Легкие металлы" Electrolysis unit for aluminium manufacture
DE102011111331A1 (en) * 2011-08-23 2013-02-28 Esk Ceramics Gmbh & Co. Kg Titanium diboride granules as erosion protection for cathodes
AU2014334447A1 (en) * 2013-10-07 2016-05-19 Electro-Kinetic Solutions Inc. Method and apparatus for treating tailings using an AC voltage with a DC offset

Family Cites Families (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3407132A (en) * 1965-06-16 1968-10-22 Minnesota Mining & Mfg Floating anode
GB1169012A (en) * 1965-10-21 1969-10-29 Montedison Spa Furnace and Process for Producing, in Fused Bath, Metals from their Oxides, and Electrolytic Furnaces having Multiple Cells formed by Horizontal Bipolar Carbon Electrodes
NO764014L (en) * 1975-12-31 1977-07-01 Aluminum Co Of America
CH635132A5 (en) * 1978-07-04 1983-03-15 Alusuisse CATHOD FOR A MELTFLOW ELECTROLYSIS OVEN.
US4338177A (en) * 1978-09-22 1982-07-06 Metallurgical, Inc. Electrolytic cell for the production of aluminum
US4177128A (en) * 1978-12-20 1979-12-04 Ppg Industries, Inc. Cathode element for use in aluminum reduction cell
US4349427A (en) * 1980-06-23 1982-09-14 Kaiser Aluminum & Chemical Corporation Aluminum reduction cell electrode
CH648870A5 (en) * 1981-10-23 1985-04-15 Alusuisse CATHOD FOR A MELTFLOW ELECTROLYSIS CELL FOR PRODUCING ALUMINUM.

Also Published As

Publication number Publication date
OA07274A (en) 1984-04-30
GR77281B (en) 1984-09-11
ES8402365A1 (en) 1984-01-16
ES517933A0 (en) 1984-01-16
NO157508C (en) 1988-03-30
NO824167L (en) 1983-06-13
NZ202697A (en) 1986-02-21
SU1205779A3 (en) 1986-01-15
JPS58107491A (en) 1983-06-27
PL239350A1 (en) 1983-06-20
AU9145982A (en) 1983-06-16
AU552985B2 (en) 1986-06-26
BR8207190A (en) 1983-10-11
JPS6127474B2 (en) 1986-06-25
US4532017A (en) 1985-07-30
CA1195950A (en) 1985-10-29
YU268982A (en) 1985-03-20
FR2518124B1 (en) 1984-02-17
ZA829064B (en) 1983-09-28
EP0082096A1 (en) 1983-06-22
IN158855B (en) 1987-02-07
FR2518124A1 (en) 1983-06-17
HU191107B (en) 1987-01-28
DE3265665D1 (en) 1985-09-26
PL134338B1 (en) 1985-08-31
NO157508B (en) 1987-12-21

Similar Documents

Publication Publication Date Title
EP0082096B1 (en) Floating cathodic elements made of electro conductive refractory material for the production of aluminium by electrolysis
US5254232A (en) Apparatus for the electrolytic production of metals
US6866768B2 (en) Electrolytic cell for production of aluminum from alumina
CA2767480C (en) Grooved anode for an electrolysis tank
CA1140494A (en) Cathode for a reduction pot for the electrolysis of a molten charge
US4462886A (en) Cathode for a fused salt electrolytic cell
EP0560814A1 (en) Electrode assemblies and multimonopolar cells for aluminium electrowinning.
CA1164823A (en) Electrode arrangement in a cell for manufacture of aluminum from molten salts
NZ197038A (en) Cathode for the production of aluminium
NO177108B (en) Aluminum Reduction Cell
NL8002072A (en) CATHODE FLOW CONDUCTION ELEMENT FOR USE IN ALUMINUM REDUCTION CELLS.
JPS589991A (en) Electrolytic reduction cell
CA1190892A (en) Electrolysis bath with conductive floating screen for the production of aluminum
FR2471425A1 (en) CATHODIC DEVICE FOR IGNATED ELECTROLYSIS OVEN, ESPECIALLY FOR THE PRODUCTION OF ALUMINUM
FR2542326A1 (en) TANK OF ALUMINUM REFINING BY ELECTROLYSIS
US6800191B2 (en) Electrolytic cell for producing aluminum employing planar anodes
NO332628B1 (en) Aluminum electro recovery cells with oxygen-generating anodes
EP0069681B1 (en) Cell for the electrolytic production of a metal from its halide
FR2552450A1 (en) ALUMINA REDUCTION CELL
CH378543A (en) Cell for the electrolytic production of metals from molten compounds
FR2500488A1 (en) Electrolytic prodn. of aluminium - in high current density cell with titanium di:boride particle cathode bed
FR2505368A1 (en) Aluminium prodn. in Hall-Heroult cell - with high current intensity and reduced energy consumption
CN118715340A (en) Advanced aluminium electrolysis cell
AU7679500A (en) Aluminum electrowinning cell with sidewalls resistant to molten electrolyte

Legal Events

Date Code Title Description
PUAI Public reference made under article 153(3) epc to a published international application that has entered the european phase

Free format text: ORIGINAL CODE: 0009012

AK Designated contracting states

Designated state(s): CH DE GB LI NL SE

17P Request for examination filed

Effective date: 19830711

GRAA (expected) grant

Free format text: ORIGINAL CODE: 0009210

AK Designated contracting states

Designated state(s): CH DE GB LI NL SE

REF Corresponds to:

Ref document number: 3265665

Country of ref document: DE

Date of ref document: 19850926

PLBE No opposition filed within time limit

Free format text: ORIGINAL CODE: 0009261

STAA Information on the status of an ep patent application or granted ep patent

Free format text: STATUS: NO OPPOSITION FILED WITHIN TIME LIMIT

26N No opposition filed
PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: NL

Payment date: 19871231

Year of fee payment: 6

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: GB

Effective date: 19881209

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: SE

Effective date: 19881210

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: LI

Effective date: 19881231

Ref country code: CH

Effective date: 19881231

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: NL

Effective date: 19890701

NLV4 Nl: lapsed or anulled due to non-payment of the annual fee
GBPC Gb: european patent ceased through non-payment of renewal fee
REG Reference to a national code

Ref country code: CH

Ref legal event code: PL

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: DE

Effective date: 19890901

EUG Se: european patent has lapsed

Ref document number: 82420176.8

Effective date: 19891205