EP0136969B1 - Cellule pour le raffinage électrolytique de l'aluminium - Google Patents

Cellule pour le raffinage électrolytique de l'aluminium Download PDF

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Publication number
EP0136969B1
EP0136969B1 EP84810343A EP84810343A EP0136969B1 EP 0136969 B1 EP0136969 B1 EP 0136969B1 EP 84810343 A EP84810343 A EP 84810343A EP 84810343 A EP84810343 A EP 84810343A EP 0136969 B1 EP0136969 B1 EP 0136969B1
Authority
EP
European Patent Office
Prior art keywords
cell
diaphragm plate
aluminium
aluminum
graphite
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
EP84810343A
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German (de)
English (en)
Other versions
EP0136969A1 (fr
Inventor
Sylvestre Viré
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.)
Alcan Holdings Switzerland AG
Original Assignee
Schweizerische Aluminium AG
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 Schweizerische Aluminium AG filed Critical Schweizerische Aluminium AG
Publication of EP0136969A1 publication Critical patent/EP0136969A1/fr
Application granted granted Critical
Publication of EP0136969B1 publication Critical patent/EP0136969B1/fr
Expired legal-status Critical Current

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    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25C—PROCESSES FOR THE ELECTROLYTIC PRODUCTION, RECOVERY OR REFINING OF METALS; APPARATUS THEREFOR
    • C25C3/00—Electrolytic production, recovery or refining of metals by electrolysis of melts
    • C25C3/06—Electrolytic production, recovery or refining of metals by electrolysis of melts of aluminium
    • C25C3/24—Refining

Definitions

  • the invention relates to a thermally insulated cell for the electrolytic cleaning of aluminum.
  • the aluminum is oxidized to trivalent aluminum ions at the anode, these ions migrate through the electrolyte layer to the cathode, where they are reduced again to metallic aluminum.
  • the forehearth of the cell which has a lower temperature than the 700 to 800 ° C. customary for the refining of aluminum, removes the crystallized impurities, in particular intermetallic products of Al, Cu, Fe and Si, which are known as Seiger crystals.
  • the 10 to 15 cm thick electrolyte layer in conventional three-layer electrolysis cells cannot be reduced in size as desired without the risk of mechanical contamination of the refined aluminum layer due to contact with the anodically connected aluminum alloy.
  • diaphragms which are in the form of vessels or can be displaced in the vertical direction have been used, which help to reduce the high energy consumption.
  • EP-A-0 049 600 discloses a cell for the electrolytic cleaning of aluminum, in which the metal to be cleaned flows through the cell, the cell being equipped with a separator grill. This cell can be used to produce relatively pure metal, but not pure aluminum. In addition, Seiger crystals cannot be removed.
  • the inventor has set himself the task of creating a cell for the electrolytic cleaning of aluminum which, in addition to low energy consumption, has high metallurgical efficiency and which can be implemented with low investment costs.
  • the diaphragm plate In order for the lowest possible voltage drop to be ensured via the diaphragm plate, its material must be readily wettable by the electrolyte, and the aluminum ions must be able to migrate from the interior to the surface of the diaphragm with the least possible voltage drop. On the other hand, the diaphragm plate must be absolutely impermeable to the metallic aluminum, i.e. not be wettable.
  • the electrode units used in an industrial setting have a cross-sectional area of 2 x 2 m. If these are used in a vertical or almost vertical position, the open-pore structures can no longer be made so fine that the static pressure does not push the unpurified aluminum through the diaphragm plate.
  • the electrode plates are therefore divided with partition walls made of graphite, preferably with a square or rectangular grid, the side length of which is between 5 and 30 cm. Each of these sub-elements formed by the partition walls has a separate diaphragm plate and a feed of aluminum to be cleaned.
  • each sub-element can also be designed as separate units, the wall to wall joined together and held together by a graphite frame.
  • Such electrode units composed of building blocks have the advantage that individual sub-elements can be replaced.
  • each sub-element has its own porous diaphragm plate and a feed line for the aluminum to be cleaned.
  • Window-shaped recesses can be made in the partition walls or in the joined walls.
  • the molten aluminum does not only circulate in one sub-element, neighboring chambers are in the Metal flow included.
  • the dimensions of the recesses had to be so small that the static pressure on the porous diaphragm plate remains below the critical value discussed above.
  • care must be taken to ensure that the thickness of the diaphragm plate, the material of which is the density of the electrolyte, the clear width of the open-pore channels, the dimensions of the sub-elements and the window-shaped recesses in the partition walls are matched to one another in such a way that this increases cleaning molten aluminum cannot penetrate into the pores of the diaphragm plate.
  • Aluminum oxide, magnesium oxide, oxynitrides of silicon or oxynitrides of aluminum and silicon are preferably used as materials for the open-pore diaphragm plate.
  • the porosity is preferably between 60 and 90%.
  • the ceramic filters for cleaning liquid metal of CH-PS 622 230 can also be used as porous diaphragm plates if they are dimensioned appropriately for the graphite frame. In practice, 3-15 mm thick diaphragm plates are used for the electrolytic cleaning of aluminum.
  • the electrode units are used in thermally insulated cells with a steel tub embedded in a wall, which in turn is lined with magnesite stones or refractory material containing nitride.
  • the electrode units form one or more rows inside the cell. All electrode units are arranged parallel to the terminal anode and the terminal cathode.
  • the interpolar distance between the inside of the anodic diaphragm plate and the outside of the cathodic graphite frame is preferably 10-25 mm.
  • the space surrounding the electrode units is filled with electrolyte material which is molten at the working temperature.
  • the level of the electrolyte in the cell is practically not subject to fluctuations and lies above the uppermost part of the electrode units.
  • the electrolyte preferably consists of a mixture of lithium chloride, potassium chloride and sodium chloride, it having a particularly favorable effect if a smaller amount of alkali metal fluoride is added. All of these electrolyte compositions are known and can be found in the specialist literature.
  • the aluminum to be cleaned is introduced into the cell for electrolytic cleaning via forehearths. These foreheads also serve to separate out the Seiger crystals. They consist of intermetallic compounds of aluminum, iron, silicon, titanium etc. As a rule, the Seiger crystals do not contain copper, as is the case with rotating layer electrolysis. Because the aluminum to be cleaned is separated from the high-purity aluminum by the diaphragm plate, the density of the anodic metal does not have to be controlled or increased. This means that the density of the electrolyte is irrelevant, which makes it easier to select an electrically highly conductive material.
  • the electrical direct current is conducted to the terminal anode via at least one anodic electrode rod, and is conducted bipolarly via the electrode units and the electrolytes through the cell to the terminal cathode, where the electrical direct current is in turn discharged through at least one cathodic electrode rod.
  • the electrolysis with a bipolar cell as in the three-layer process, where the aluminum is dissolved from the contaminated metal, passes through the electrolyte (as a result, the electrolyte material located in the open-pored channels of the diaphragm plate and the electrolytes located between the electrode units) and is deposited on the cathode becomes.
  • the cathodic surface is the back wall of the graphite frame.
  • the separated high-purity aluminum flows from the cathodic graphite frame into a scoop channel, which is arranged in the electrically insulating part of the cell bottom and from where the high-purity aluminum can be drawn off with a suction pipe.
  • the bipolar cell shown in FIG. 1 shows five vertical electrode units 10 with a graphite frame 12, the full-area recess of which is closed in the direction of the terminal graphite cathode 14 with a porous diaphragm plate 16.
  • the vessel-shaped cavity of the electrode units 10 is filled with the aluminum 18 to be cleaned, which is present in molten form at an operating temperature of 700 to 800 ° C.
  • drainage channels 20 are cut out for the pure aluminum.
  • the electrolyte 22 is arranged between the electrode units and above the ultrapure aluminum.
  • the partitions dividing the interior of the electrode unit are omitted.
  • the electrode unit 10 shown in FIG. 3 and intended for vertical use consists of four sub-elements 28 which are held together with a graphite rim 30.
  • Each sub-element 28 has a graphite frame 12 with a full-area opening which is closed by the porous diaphragm plate 16.
  • This diaphragm plate is expediently already used with electrolyte material in the open-pore structure.
  • Each sub-element 28 has its own forehearth 32, which communicates via an opening 34 with the interior of the sub-element.
  • the foreheads provided for separating the Seiger crystals and for introducing aluminum to be cleaned are also offset horizontally to make operation easier.
  • the clear height H of a sub-element may only be so great that the static pressure for the passage of aluminum through the open-pore structure is not reached. In the present case, H measures approximately 30 cm.
  • the electrode units 10 of FIG. 2 are used in two rows in the cell according to FIG. 4.
  • a steel trough 36 is inserted into the wall 24 and is closed by means of a corrosion-resistant, double-walled cover 38 made of steel using a seal 40.
  • the steel trough is lined with magnesite stones 42, which are resistant to both the molten electrolyte and the molten aluminum.
  • a steel base plate 44 supports the entire cell and offers additional insulation thanks to the air chambers 46.
  • the cover 38 of the steel trough 36 is penetrated by an insulating tube 58, which on the one hand allows the level 50 of the electrolyte 22 to be kept above the electrode units 10 by material replenishment and on the other hand evolving gases.
  • a special device 48 is connected during cell operation in order to extract any gases that may arise.
  • a siphon 70 allows the cleaned aluminum to be sucked off the trough 20 once or several times a day.
  • the level 52 of the pure aluminum must always be below the electrode units 10.
  • the electrode unit 10 shown in FIG. 5 corresponds essentially to FIG. 3, but is intended for the horizontal arrangement of a cell.
  • the forehearth 32 and its opening 34 are arranged accordingly.
  • the vertical section through the electrode unit 10 runs through a partition wall 54 made of graphite, which has window-shaped recesses 56 on its underside. This enables the circulation of the aluminum to be cleaned between neighboring sub-elements.
  • the height H of about 25 cm is chosen so that the static pressure of the aluminum to be cleaned is not sufficient to press the aluminum into the pores of the diaphragm 16.
  • the bottommost graphite cathode 14 is equipped with three cathodic electrode rods 62, the uppermost terminal graphite anode 60 with three anodic electrode rods 72.
  • the cell is equipped with an outer steel pan 64, with individual refractory stones acting as spacers 66.
  • the space formed by the steel tubs is covered with a light insulation material 68, such as. B. rock wool, filled.

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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)
  • Secondary Cells (AREA)

Claims (7)

1. Cellule isolée thermiquement pour la purifica- tion électrolytique de l'aluminium, comprenant un bac avec une cuve en acier (36) enrobée dans une maçonnerie (24), qui est revêtue avec une matière (42) stable à haute température et résistante à l'électrolyte et fermée par un couvercle (38), un électrolyte (22) à base de chlorures alcalins, des avant- creusets (32) pour l'addition de l'aluminium à purifier (18) et le dépôt des cristaux de liquation, une conduite d'amenée (58) pour la matière d'électrolyte, qui est également conçue comme carneau à gaz, et un système collecteur et d'écoulement pour l'aluminium extra-pur (20), des unités d'électrodes bipolaires (10), plongées dans l'électrolyte (22), couplées électriquement en série dans l'espace intérieur de la cellule, comportant chacune
- un cadre en graphite (12) en forme de récipient, ouvert sur toute sa surface dans la direction de la cathode en graphite terminale (14),
- des cloisons de séparation (54) en graphite pour le cloisonnement en au moins trois sous-éléments (28),
- une plaque-diaphragme (16) obturant de manière étanche l'ouverture de chaque sous-élément (28) dans le cadre en graphite (12), qui est mouillable par l'électrolyte en fusion (22), mais pas par l'aluminium, et dont la structure à pores ouverts est remplie par la matière d'électrolyte, et
- un avant-creuset séparé (32) pour chaque sous-élément (28), pour l'alimentation en aluminium à purifier (18) et le dépôt de cristaux de liquation, la hauteur (H) du volume pour l'aluminium à purifier (18) formé entre le cadre en graphite (12) et la plaque-diaphragme (16) étant telle que la pression statique pour un volume rempli soit inférieure à la valeur critique pour l'écoulement à travers la plaque-diaphragme poreuse (16).
2. Cellule selon la revendication 1, caractérisée en ce que les sous-éléments (28) ont une configuration d'unités séparées et sont maintenus par une enceinte en graphite (30).
3. Cellule selon la revendication 1 ou 2, caractérisée en ce que les cloisons de séparation (54) servant à la stabilisation mécanique de la plaque-diaphragme (16) ou les parois assemblées des sous-éléments (28) ont des évidements en forme de fenêtres (56).
4. Cellule selon l'une au moins des revendications 1 à 3, caractérisée en ce que la plaque-diaphragme (16) a une porosité de 60-90%.
5. Cellule selon l'une au moins des revendications 1 à 4, caractérisée en ce que la distance inter- polaire (d) entre la face interne de la plaque-diaphragme anodique (16) et le cadre en graphite cathodique (12) est de 10-25 mm.
6. Cellule selon l'une au moins des revendications 1 à 5, caractérisée en ce que les unités d'électrodes (10) sont incorporées verticalement ou presque verticalement l'une à côté de l'autre, avec les plaques-diaphragmes (16) disposées latéralement.
7. Cellule selon l'une au moins des revendications 1 à 5, caractérisée en ce que les unités d'électrodes (10) sont disposées horizontalement ou faiblement inclinées l'une au-dessus de l'autre, avec les plaques-diaphragmes (16) vers le bas.
EP84810343A 1983-07-27 1984-07-13 Cellule pour le raffinage électrolytique de l'aluminium Expired EP0136969B1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
CH4131/83A CH655136A5 (de) 1983-07-27 1983-07-27 Zelle zur elektrolytischen reinigung von aluminium.
CH4131/83 1983-07-27

Publications (2)

Publication Number Publication Date
EP0136969A1 EP0136969A1 (fr) 1985-04-10
EP0136969B1 true EP0136969B1 (fr) 1988-06-01

Family

ID=4270409

Family Applications (1)

Application Number Title Priority Date Filing Date
EP84810343A Expired EP0136969B1 (fr) 1983-07-27 1984-07-13 Cellule pour le raffinage électrolytique de l'aluminium

Country Status (8)

Country Link
US (1) US4601804A (fr)
EP (1) EP0136969B1 (fr)
JP (1) JPS6052588A (fr)
AU (1) AU571246B2 (fr)
CA (1) CA1232867A (fr)
CH (1) CH655136A5 (fr)
DE (1) DE3471696D1 (fr)
NO (1) NO163291C (fr)

Families Citing this family (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB8331769D0 (en) * 1983-11-29 1984-01-04 Alcan Int Ltd Aluminium reduction cells
US20030209426A1 (en) * 2000-12-08 2003-11-13 Slaugenhaupt Michael L. Insulating lid for aluminum production cells
CN107223167B (zh) 2015-02-11 2020-05-15 美铝美国公司 用于提纯铝的系统和方法
EP3547474B1 (fr) 2018-03-27 2022-10-12 NKT HV Cables AB Procédé et robot pour usinage d'isolation dans un joint de câble
WO2023172717A1 (fr) * 2022-03-10 2023-09-14 Reynolds Consumer Products LLC Systèmes et procédés de purification de l'aluminium

Family Cites Families (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
NL56521C (fr) * 1939-12-06
FR893325A (fr) * 1942-04-27 1944-06-06 Perfectionnements aux procédés et dispositifs de décomposition électrolytique de solutions liquéfiées par la chaleur, en particulier en vue de la production, ou duraffinage de l'aluminium
AU506485B2 (en) * 1976-06-09 1980-01-03 National Research Development Corp. Packed, bed electrorefining
US4214955A (en) * 1979-01-02 1980-07-29 Aluminum Company Of America Electrolytic purification of metals
NZ197038A (en) * 1980-05-23 1984-04-27 Alusuisse Cathode for the production of aluminium
ZA816719B (en) * 1980-10-07 1982-09-29 Alcan Int Ltd Electrolytic refining of molten metal
JPS5942079B2 (ja) * 1981-12-01 1984-10-12 三井アルミニウム工業株式会社 アルミニウムの精製方法
US4411747A (en) * 1982-08-30 1983-10-25 Aluminum Company Of America Process of electrolysis and fractional crystallization for aluminum purification

Also Published As

Publication number Publication date
NO843001L (no) 1985-01-28
JPS6052588A (ja) 1985-03-25
EP0136969A1 (fr) 1985-04-10
CA1232867A (fr) 1988-02-16
AU3084384A (en) 1985-01-31
US4601804A (en) 1986-07-22
DE3471696D1 (en) 1988-07-07
NO163291B (no) 1990-01-22
AU571246B2 (en) 1988-04-14
CH655136A5 (de) 1986-03-27
NO163291C (no) 1990-05-02

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