DE1148755B - Cell for fused salt electrolysis and process for the production of aluminum - Google Patents

Description

The invention relates essentially to a cell for the fused metal electrolysis and a Process for the production of aluminum using this cell, its plane and parallel Surfaces are inclined from the vertical, the anode being an electrolytically consumable and has a renewable layer attached to a fixed and non-consumable electrode block borders. According to the invention, the surface of the electrode block to which this layer adjoins forms make a V-shaped angle with the plane of the opposite cathode, plus are guides arranged around the anode from top to bottom and parallel to the surface automatically new material to be supplied, namely continuously to the same extent as the electrolytic depletion of the layer, and that stops are provided to limit the flow of material in the guides.

Preferably both the surface of the renewable layer adjoining the non-consumable stationary electrode block, as well as the opposite free area of this layer Vertical inclined to the same side, with the free surface facing down. So can the renewable Anode layer have a triangular cut surface, with the apex of the triangle after below shows. It is advantageous if this layer consists of several blocks one on top of the other. On the other hand, however, the surfaces of the renewable anode layer, which are attached to the fixed Anode block adjoins, and the opposite free surface of this layer to the perpendicular to different Sides be inclined.

The means of supplying renewable energy Anode layer preferably consist of a guide trough whose axis is parallel to the plane of that Is the electrode to which the renewable anode layer is adjacent. This guide trough is advantageous made of fireproof material and is covered with heat-insulating material. The attacks persist preferably from a protrusion at the bottom of the cell.

The renewable anode layer can be made from pre-burned electrode carbon or from baked Söderberg mass exist. In the latter case, the guide troughs are advantageously lined with sheet metal, to make it easier for the layer to slide down.

According to a further embodiment of the invention, the fixed bipolar, non-consumable Electrode block arranged inclined channels that allow limited flow of at the cathode surface formed liquid metal to the cell for fused salt electrolysis

and method of manufacture

of aluminum

Applicant:

Montecatini, Societä Generale per l'Industria

Mineraria e Chimica and Giuseppe de Varda,

Milan (Italy)

Representative: Dipl.-Ing. Dipl.-Chem. Dr. phil. Dr. techn.

J. Reitstötter, patent attorney,

Munich 15, Haydnstr. 5

Claimed priority:
Italy of January 5, 1957 (No. 163)

Giuseppe de Varda, Milan (Italy),
has been named as the inventor

Allow area against which the renewable anode layer borders, thereby allowing the liquid metal in the space between the cathode surface and the anode layer enters. The one in the gap liquid MetaE serves as a lubricant and thus makes it easier for the supplementary layer to slide down. Simultaneously it also facilitates the passage of electrical current between the stationary electrode block and the layer, so that the local voltage drop is decreased.

The invention also relates to a multi-cell oven consisting of cells of the type described above.

The invention also relates to a method for the electrolytic production of aluminum made of aluminum oxide in fluorine salt melts with consumable anodes in cells or multi-cell ovens of the type described, with the supplied to supplement the renewable anode layer Materials are continuously pushed in by means of a pressure exerted from above, wherein

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at the same time the electrode spacing is automatically kept constant using means which absorb the excess pressure.

One can apply current densities that are the same in all electrode surfaces and over all surfaces are evenly distributed. It can also be worked so that the material to supplement of the renewable anode layer is directed downward under pressure such that the pressure component

are present in the cell (e.g. with molten bath or with liquid metal), and it becomes one thin intermediate layer 29 formed between the anode of carbon to be renewed. Between everyone Electrode pair (which are adjacent to each other) there is an electrolysis gap or an electrode gap 14 for the weld pool. This space communicates on the floor with a lower chamber 12, in which the liquid aluminum 11 collects

along the sliding plane of the anode, which melts from the io and which has tap openings 10. Dead weight of the protruding part of the supplement - Both this lower chamber and the elec-

Zungsmaterials originates, that pressure component in the space between the electrodes (except that of the bi in the same plane predominates which electrodically drove the molten bath formed by the polar carbon electrodes on the submerged part of the active walls) are with an inert material 13, the material originates, and that at the beginning 15 15 coated, which is neither attacked by the molten bath trolyse a preformed anodic layer of nor by the metal and impermeable blocks of pre-baked together and also has an electrically insulating effect and cemented electrode carbon or from preformed and
Baked Söderberg mass introduced into the cell
the process during normal loading 20
drifted, with the cell closed and closed
Furnace, takes place.

For example, the following is a description of some embodiments of the invention.

Reference is made to the drawings:
Fig. 1 shows a vertical section along the line CC of FIGS. 2 and 3 of several adjoining cells of a multi-cell oven with fixed

is resistant to the temperature of the bath.

Above the carbon electrodes there are blocks 19 made of an inert, impermeable material and channels 17 which establish the connection between the individual cells through which the molten bath can circulate (cf. arrows 18). The 25 blocks 19 are provided with a heat-insulating layer 24, which is coated with an inert material 28 at those points at which it comes into contact with the molten bath (e.g. dense electrolytically fused magnesite, which is very common in the bipolar electrodes of the type in which it was sintered at high temperature and / or any other suitable and commercially available 204796 and 205 758 described in, for example, Austrian patents, but according to FIG
the present invention are modified;

Fig. 2 is partly a plan view and partly a section through two cells along the line AA of Fig. 1;

Fig. 3 shows a section along the line BB of Fig. 1;

Fig. 4 relates to a vertical section through several
Adjacent cells from a further outlet 40 The space 20 is connected at the upper end in turn with the guide form of a multi-cell oven with bipolar an upper chamber, from which the geelectrodes according to the invention. exhaust gases formed through the outlets 21.

In Fig. 1 contain the individual cells of a multiple It is convenient if the space 20 from the upper

cell furnace for the electrolysis of aluminum oxide, chamber is separated by movable plates (which are dissolved in molten fluorine-containing salts) and which are dissolved, essentially two inclined bipolar electrolytes consist of porous material, which the electrodes 9 that are close together and themselves
renewing outer anodic layers 1, 2, 3, 4,
5, 6 or 27. The non-consumable
Portions 9 of these electrodes consist of graphite, 5o
while the expandable parts 1, 2, 3, 4, 5 and 6 from
pre-burned electrode carbon or consist of a single piece of 27 baked Söderberg mass.

The bipolar electrodes do not have any kind of design and arrangement that the above There is still a gas cushion outside the furnace of the molten bath mechanical device provided to have sufficiently high temperature to a Abdie To vary the distances between the electrodes. to prevent cooling of the bath surface. The renewable anode assembly 1, 2, 3, 4, 5, 6 The renewable anode is made of carbon-based

or 27 with a density less than 1.6 is caused by so tiger material, which by the electrolytic the weld pool is attacked with a density greater than 2 after processes, but is known per se

Material such as refractory silicon carbide bonded by means of silicon nitride or the like Material).

The space between the electrodes communicates at the upper end with an upwardly extending gas collection space 20 and contains in the lower part the weld pool. The walls of this room are made of inert material 19, 28.

trolysis gases through. In addition, however, free passage paths can also be provided in the plates be.

The plates forming the closure of the cells can be made of magnesia and / or asbestos-containing, for example Material, d. H. Material with very good thermal insulation properties at temperatures of about 1000 ° C. You should preferably

up against the protruding part of the renewable anode layer and possibly against the non-consumable part of the electrode is pressed.

The space between the anode layer and the corresponding non-consumable electrode is filled with one or more liquids, which

(for example pre-burnt electrode carbon or baked Söderberg mass).

The upper chamber is covered by a heat insulating layer 22, in which accordingly three openings are provided for each cell, each of which is covered by an easily movable cover 23 made of a very good heat insulating material

Material can be sealed (ζ. Β. Porous, fireproof material or aluminum oxide). To Removal of these covers leads to the supply lines 26 made of refractory material, which with the inclined guides 25 are in communication, at least in their lower part, which is with the weld pool is in contact, are formed from an inert material.

The arrows 16 show schematically the path of the elec-

If these measures have been repeated for each individual cell, the actual electrolysis can begin.

The alternating current is replaced by direct current 5, so that the active surface of the bipolar Electrodes that face upwards act as cathodes, while the face that faces downwards serves as an anode. The circulation device for the weld pool and the feed device for the

tric current, which is made of graphite ίο aluminum oxide (both not shown in the drawings bipolar, non-consumable and staged) are then put into operation, tionary arranged electrodes through the thin, As the electrolysis progresses,

liquid contact layer 29 in the renewable flows the aluminum generated at the cathode The anode runs, the slowly consumed one from the bottom and collects in the lower chamber, odic surface of the same and in the ent- 15 from which it is withdrawn via the individual lines 10 speaking electrode gap (two becomes.

Cells in front of the gap 14 in Fig. 1), which is connected to both the distribution of the electric current in

the molten weld pool is filled with fluorine-containing electrodes as well as the electrolytic attack compounds, and which are then applied to the active anodic surface at all in the adjacent, non-consumable and stationary 20 points of the active surface of the anode layers arranged bipolar graphite electrode through their equally strong, so that the originally present upward cathodic surface occurs. Renewable anode layer 3, 4, 5, 6 on the side of the The arrows 18 show schematically the flow melt bath is used up very evenly, direction (main circulation) of the electrolysis bath, As a result, the tip 7 should theoretically up to the opposite here in a sense that of the electrical 25 position T go back, but the current from above is shown. pressure exerted sufficient that the entire

The renewable anode shown in Fig. 4 (with order slowly slides downwards and thus that of a triangular cut surface, in which the tip of the tip T is in position 7. When the triangle points downwards from above) initially has an exerted pressure, which the effective weight greater strength, because the inclination of the liquid component parallel to the walls of the guide corresponds to the contact layer between the fixed anode and the part of the anode arrangement that is opposite to the renewable anode layer outside the weld pool, greater than that running . Buoyancy of the part of the submerged in the bath

There are narrow channels 30 in the non-consumable anode layer, so it becomes self-complementary bipolar electrode branches a low percentage 35 and renewable anode layer get the autodes At the cathode, aluminum generated the electrode spacing between the treatment of the liquid intermediate layer. This creates electrode surfaces that form a space between the electrodes keeps the regular downward slide of renewables constant.

Anode layer facilitated and the by- If the renewable anode layer consists of a

passage of the electric current through the anodic 40 number of small carbon blocks from pre-intermediate layer If there is burnt electrode carbon originating from liquid melt, then it is to supplement the ohmic Voltage drop to a negligibly small amount of the consumed electrode carbon is sufficient, Values reduced. This embodiment of the fact that one periodically opens the covers and in The invention is very suitable to melt the inlets 26 into a new, small block 1 from above or to supply solid Söderberg mass. 45 pushes at a time when the The operation of a multi-cell furnace according to the invention- previously this layer 1 occupying small blocks as a result is carried out as follows: of the electrolytic attack, position 2 is

The one filled with metal and molten bath has taken. This measure can be done with a mini oven will work at an operating temperature of about times and without disturbing the 900 to 1000 ° C and at this temperature 50 heat equilibrium of the furnace and the cell as well by using, for example, alternating current without disturbing the uniformity of the electrolysis. Then the renewable process and without fluctuations in the liquid electrode layer introduced into each individual cell by performing mirrors.

layers 1, 2, 3, 4, 5, 6 or 27 in several The new block 1 can easily be accessed via block 2

Pieces or in the form of a single piece of 55 or it can be a suitable binding top through the guide channels 25. Because middle between one and the other block

the anode carbon has a density of about 1.5 and the weld pool has a density of about 2, presses the hydrostatic buoyancy of the bath the individual parts 1, 2, 3, 4, 5 or 6 or the individual layer 27 60 upwards so that the entire layer is against the surface of the non-consumable bipolar electrode presses, the surface of which faces downwards (Fig. 1). By applying pressure from above you can

be applied (ζ. Β Söderberg mass, pitch or tar), so the renewable anode layer is stronger to design.

If, on the other hand, a single block of Söderberg mass is used as the self-renewing anode layer is used, one compensates for the consumption of the anode in a manner analogous to that used for the Use of small blocks from Söderberg mass

push the layer downwards slightly until the tip has been written on by prebaked anodes,

comes into contact with the projection 8, which It is also possible to use the appropriate guide troughs

of the molten Söderberg mass as a support base for the bipolar electrode, however

Serving inert layer is formed. After it is then advantageous to remove the inner walls of the guide

Line the channels with metal sheets in the upper part to just above the level of the melt pool.

The invention therefore provides a solution to the problem of self-adjusting and continuous spacing creating between the electrodes and the renewal of the anodes during an electrolysis with slowly consuming anodes, with which a perfect constant maintenance of the electrode spacing in the cell is achieved, which is neither due to progressive consumption of the Anode is still disturbed by the respective renewal of the anode.

This surprising result is achieved without any control device outside the furnace necessary is. In addition, the non-consumable anode layer (which is the case with every bipolar intermediate electrode forms a single body with the cathode) is kept stationary and unchanged. Of course, the versions described and shown here only serve as an example.

Claims (19)

PATENT CLAIMS: 1. Cell for melt flow electrolysis, in particular for the production of aluminum with two electrodes, the flat and parallel surfaces of which are inclined to the vertical, the anode having an electrolytically consumable and renewable layer which is adjacent to a fixed and non-consumable electrode block, characterized in that, that the surface of the electrode block (9) which this layer (27) adjoins forms a V-shaped angle with the plane of the opposite cathode, and that guides (25) are arranged to the anode from top to bottom and parallel to automatically supply new material to the surface, continuously to the same extent that the layer (27) is electrolytically consumed and stops (8) are provided to limit the flow of material in the guides (25). 2. Cell according to claim 1, characterized in that the surface of the renewable Anodes (27), which is adjacent to the stationary electrode block, and the opposite free surface of this layer are inclined to the vertical on the same side, with the free Face down. 3. Cell according to claim 1, characterized in that the renewable anode layer (27) has a triangular cut surface, with the apex of the triangle pointing downwards. 4. Cell according to claim 3, characterized in that the layer consists of several superimposed Blocks (1, 2, 3, 4, 5, 6). 5. Cell according to claim 1, characterized in that the surface of the renewable Anode layer (27), which is adjacent to the fixed anode block, and the opposite free surface of this layer are inclined to the vertical on different sides. 6. Cell according to one of the preceding claims, characterized in that the guide rails (25) consist of a guide channel for feeding the renewable anode layer, whose axis is parallel to the plane of that electrode to which the renewable anode layer adjoins. 7. Cell according to claim 6, characterized in that the guide channel (25) made of refractory Material consists and is covered with heat insulating material. 8. Cell according to one of the preceding claims, characterized in that the stops (8) consist of a protrusion at the bottom of the cell. 9. Cell according to one of the preceding claims, characterized in that the renewable Anode layer (27) consists of prebaked electrode carbon. 10. Cell according to one of claims 1 to 8, characterized in that the renewable Anode layer (27) consists of baked Söderberg mass. 11. Cell according to claim 10, characterized in that the guide channels (25) with sheet metal is lined. 12. Cell according to one of the preceding claims, characterized in that in the fixed bipolar, non-consumable electrode block (9) inclined channels (30) arranged that are limited flow of liquid metal formed on the cathode surface allow to the Hache against which the renewable anode layer borders, whereby the liquid metal enters the space (29) between the cathode surface and the anode layer. 13. Cell according to one or more of the preceding claims for the production of Aluminum from aluminum oxide in fluorine salt melts, characterized in that the fixed, Permanent electrode or anode block (9) made of graphite and the consumable, renewable anode layer (27) made of electrode carbon or Söderberg mass exists. 14. Multi-cell oven, characterized in that it consists of several cells according to one or more several of claims 1 to 13 exists. 15. Process for the electrolytic production of aluminum from aluminum oxide in fluorine salt melts with consumable anodes in cells according to one or more of Claims 1 to 13 or in multi-cell ovens according to Claim 14, characterized in that the supplied to supplement the renewable anode layer Materials are continuously pushed in by means of a pressure exerted from above while the electrode spacing is automatically kept constant using of means that absorb the excess pressure. 16. The method according spoke 15, characterized in that current densities are used that are the same in all electrode surfaces and evenly distributed over all surfaces are. 17. The method according to claim 15 or 16, characterized in that the material to supplement the renewable anode layer is passed down under pressure in such a way that the Pressure component along the sliding plane of the anode, which is caused by the weight of the protruding Part of the supplementary material originates, that pressure component in the same The level predominates, which is caused by the buoyancy of the weld pool on the submerged part of the Material originates. 18. The method according to claims 15 to 17, characterized in that at the beginning of the Electrolysis a pre-formed anodic layer of small blocks of pre-baked and pre-baked 10 electrode carbon cemented together or made of preformed and baked Söderberg mass into the Cell is introduced. 19. The method according to claim 15, characterized in that the process during normal Operation, with the cell and furnace closed. 1 sheet of drawings