ES2224048T3 - CELL FOR THE MANUFACTURE OF ALUMINUM BY ELECTROLYSIS THAT WORKS WITH METALLIC BASED ANODES. - Google Patents

Abstract

A cell for the electrowinning of aluminium comprises a horizontal carbon cathode bottom (11) having an aluminium-wettable surface coating (25) and a series of plates (21) made of aluminium-wettable reticulated porous material, typically foams, filled with aluminium and placed flat on the aluminium-wettable surface coating (25). During use, a thin bottom layer of aluminium (22) wets the aluminium-wettable surface coating (25) on top of the cathode bottom (11) and a bottom part of the porous aluminium-filled plates (21). A top layer of aluminium (23) is formed above the porous aluminium-filled plates (21). The cell may be operated with metal anodes (10) possibly protected with a cerium oxyfluoride coating when operated above about 910°-930° C.

Description

Aluminum manufacturing cell by electrolysis that works with metal base anodes.

Technical sector belonging to the invention

The invention relates to a cell for Aluminum electrolytic manufacturing from dissolved alumina in a molten electrolyte containing fluoride, without crust, at a temperature below 930ºC, and also to the production of aluminum in that cell.

Background of the invention

For the manufacture of aluminum are used, in Currently, cells for alumina electrolysis dissolved in cryolite with an approximate excess of 10% by weight of floruro aluminum, operating at an approximate temperature of 950ºC, using carbon anodes.

Many patents have been filed and granted concerning materials for the cathode and for the anode, referring to the shape, to the cell designs, operating conditions, etc., and many solutions to specific problems have been proposed. Do not However, no provision has been proposed so far general that meets all practical requirements for the Industrial aluminum production with low pollution.

Most metals for anodes that have been released so far, except anodes covered with a Cerium-based protective coating, they are highly soluble in the electrolyte used contaminating the aluminum produced, and they also have other inconveniences such as a low electrical conductivity, reduced life and high cost.

US Patent Nos. 4,614,569 (Duruz / Derivaz / Debely / Adorian), and 4,966,674 (Bannochie / Sheriff), 4,683,037 and 4,680,094 (both in Duruz's name) describe metal anodes for the electrolytic manufacture of aluminum , equipped with a coating with a protective coating of cerium oxyfluoride, formed in-situ in the cell or previously applied, whose coating is maintained by adding small amounts of cerium to the molten cryolite.

European Patent Application 0 306 100 and the US Patents 5,069,771, 4,960,494 and 4,956,068 (all in name from Nyguen / Lazouni / Doan) announce anodes for the manufacture of aluminum that have an alloy substrate protected with a layer of oxygen barrier that is covered with a layer of copper-nickel for anchoring a coating operating surface of cerium oxyfluoride.

Different improvements have been announced referring to the cathode of the cells for the manufacture of aluminum in the following patents.

WO01 / 42168 (from Nora / Duruz) and WO01 / 42531 (Nguyen / Duruz / de Nora) describe a component that contains carbon from a cell for the manufacture of aluminum by alumina electrolysis dissolved in a molten electrolyte based on cryolite, whose cell component is protected against attack of liquid and / or gaseous components of the electrolyte or products, such as aluminum, manufactured during the operation of the cell by a wettable coating on aluminum applied in the form of emulsion. PCT publications WO96 / 07773 (de Nora) and WO98 / 53120 (Berclaz / de Nora) disclose aluminum manufacturing cells that have a cathode horizontal bottom covered with a wettable coating by aluminum applied in the form of emulsion.

It has also been proposed to stabilize the puddle of cathodic aluminum of aluminum production cells conventional when placing bodies on the bottom cathode.

US Patents 5,472,578 and 5,865,981 (both a name of de Nora) unveil a cell for the manufacture of aluminum containing grilles made by walls located a side by side, vertical or inclined, whose ends bottom or bottom rest on a background of the cell of carbon with ceramic coating, covered by the puddle of cast aluminum Each of the grids has, in general, through vertical openings sized to allow that the molten content of the cell occupies the interior of the through openings.

US Patents 4,600,481 (Sane / Wheeler / Gagescu / Debely / Adorian / Derivaz) and 4,650,552 (de Nora / Gauger /
Fresnel / Adorian / Duruz) describe composite materials wettable by aluminum, for use in contact with molten aluminum in an aluminum manufacturing cell. Composite materials are made from alumina and aluminum, in particular with TiB2. Plates of this material can be used to cover a carbon bottom cathode of a conventional cell for the manufacture of aluminum.

Objectives of the invention

An objective of the invention is to give know a cell for the manufacture of aluminum by electrolysis which incorporates anodes with metal base that can work without excessive contamination of the produced aluminum.

Another objective of the invention is to give know a cell for the electrolytic manufacture of alumino that can achieve high productivity, low pollution of the aluminum produced, and whose components resist corrosion and wear.

Another objective of the invention is to give know an aluminum electrolysis cell comprising anodes of metal base that remain substantially insoluble in the operating conditions of the cell.

A global objective of the invention is to make known a cell for electrolytic manufacturing of aluminum from alumina dissolved in a molten electrolyte that It contains a fluoride, which overcomes the various disadvantages of The above proposals.

Characteristics of the invention.

The present invention discloses a cell for the manufacture of aluminum by electrolysis from alumina dissolved in a molten electrolyte that contains a fluoride. This invention can be implemented in a conventional cell or it can be Apply to newly designed cells.

The cell of the present invention comprises a horizontal carbon bottom cathode that has a coating surface wettable by aluminum and a series of plates made based on a porous material, crosslinked, wettable by the aluminum, typically of spongy materials, filled with aluminum and placed flat on the coating surface wettable by aluminum.

During use, a thin bottom layer of alumino moisturizes the wettable surface coating by the aluminum located on top of the bottom cathode, usually all or substantially all of the surface coating, as well as the bottom part of the plates porous stuffed with aluminum.

The application of a wettable coating of aluminum over the carbon bottom cathode below the plates crosslinked porous wettable by aluminum leads to a singular improvement over previous configurations known.

Certainly, as opposed to the configuration that It is disclosed in US Patent Nos. 4,600,481 and 4,650,552 mentioned above, in which the ceramic elements sponges dampened by aluminum rest directly on the carbon-repellent carbon bottom of the cell, in the cell according to the present invention, the wettable porous plates by the aluminum they rest on a wettable coating by the aluminum which, during use, leads the aluminum to form a layer between the porous plates with aluminum padding and the Wettable coating by aluminum. This aluminum coat covers and substantially moisturizes the entire surface of the coating wettable by aluminum and also moisturizes the bottom part of porous plates with aluminum padding, so that it forms a continuous and substantially improved electrical contact between the bottom cathode and cathode aluminum located above.

During use, an upper layer of alumino, which forms above the porous plates with padding aluminum and that is covered with the electrolyte, provides a active cathode surface on which the aluminum.

In a main embodiment of the invention, the cell comprises a series of metal base anodes located by above and parallel to the surface of the upper aluminum layer. Especially for cell operation at a temperature Approximately 910º-930ºC, each of the anodes can have a anode substrate based on a metal protected with a coating electrochemically active performed on the basis of one or more cerium compounds that is maintained by the presence of species of cerium in the electrolyte, as disclosed in the Patents USA No. 4,614,569, 4,966,674, 4,683,037, 4,680,094, 5,069,771, 4,960,494 and 4,956,068 mentioned above, and that prevents a unacceptable contamination of the alumino produced by the materials of the anode.

Other materials suitable for the anode with a metal base optionally coated with the coating before mentioned based on cerium, include iron-based alloys and nickel that can be heat treated in an oxidizing atmosphere as disclosed in WO00 / 06802, WO00 / 06803 (both in the name of Duruz / de Nora / Crottaz), WO00 / 06804 (Crottaz / Duruz), WO01 / 42535 (Duruz / de Nora), WO01 / 42534 (of Nora / Duruz) and WO01 / 42536 (Duruz / Nguyen / de Nora). Other materials of anode that generate oxygen are those that are disclosed in the WO99 / 36593, WO99 / 36594, WO00 / 06801, WO00 / 06805, WO00 / 40783 (all in the name of de Nora / Duruz), WO00 / 06800 (Duruz / de Nora), WO99 / 36591 and WO99 / 36592 (both in the name of de Nora).

Alternatively, the anodes can be consumable carbon anodes on which CO2 forms during the performance.

The anodes can be separated above the surface of the upper layer of alumino in a reduced anode-cathode distance (ACD) of the order of 20 to 40 mm This reduced ACD value allows cell operation with an increase in the density of the electrolysis current of about 0.6 to 1.2 A / cm2 on the surface of the anodes. Increased current intensity produces enough heat to maintain cell stability while producing simultaneously a greater amount of aluminum.

Usually, the bottom layer of aluminum has a thickness between 0.5 and 10 mm. The top layer of aluminum it can have a thickness between 5 and 100 mm and it can even form a puddle

Preferably, the porous plates filled with alumino have a thickness between 10 and 100 mm.

The plates can be manufactured based on the materials disclosed in US Pat. above. mentioned 4,600,481 and 4,650,552. Preferably, the plates are manufactured based on a crosslinked ceramic material that is inert and resistant to molten aluminum that has an agent on its surface aluminum humectant, in particular a metal oxide that can react with the molten aluminum as described further ahead.

The inert and resistant ceramic material can comprise at least one oxide selected from oxides of aluminum, zirconium, tantalum, titanium, silicon, neobium, magnesium and calcium and mixtures thereof, as simple oxide and / or in an oxide mixed, for example, zinc aluminate (ZnALO4) or titanium (TiALO_ {5}). Other inert and resistant ceramic materials Suitable can be selected from nitrides, carbides, borides and oxy compounds, such as aluminum nitride, ALON, SiALON, boron nitride, silicon nitride, silicon carbide, borides aluminum, alkaline earth metal zirconates and aluminates, as well Like your mixes

Porous plates with aluminum fill have preferably a surface layer containing alumina, aluminum and other metal, such as copper, iron and / or nickel. This layer surface can be manufactured by exposing molten aluminum the surface of the aluminum wettable plates it contains, before use, metal oxides, such as oxides of copper, iron and / or nickel, which can react with aluminum molten. Other usable metal oxides that are suitable for the reaction with molten aluminum are disclosed in the documents WO01 / 42168 (de Nora / Duruz) and WO01 / 42531 (Nguyen / Duruz / de Nora).

Similarly, the surface coating wetted by aluminum over the carbon cathode has preferably a surface layer containing alumina, alumino and other metal, such as copper, iron and / or nickel. This surface layer can be manufactured by exposure to cast aluminum of a surface coating wettable by aluminum, which contains, before use, metal oxides, such as oxides of copper, iron and / or nickel, which can react with aluminum cast, as disclosed in the references above mentioned (WO01 / 42168 and WO01 / 42531). These references indicate that, in order to avoid contact between the infiltrated aluminum in the coating moistened by aluminum and the substrate can be use a sublayer to anchor the coating on the substrate boruro, as for example, as disclosed in the US Patents 5,364,513 and 5,651,874, which is inert and impermeable to cast aluminum, or an aluminum repellent layer.

In one embodiment, the metal structure with coating of each anode has a horizontal extension and is equipped with holes for the guided passage of a circulation of electrolyte to and from the coating electrochemically active. Appropriate anode designs are disclosed in the WO00 / 40781 and WO00 / 40782 (both in the name of de Nora).

The electrolyte can be found at a temperature below 960 ° C, typically from 860 ° C to 930 ° C. He electrolyte can comprise cryolite and, in addition to cryolite, a excess of AlF 3 in an amount of 15 to 30% by weight of the cryolite.

The electrolyte in the coating electrochemically active is preferably substantially saturated with alumina. Substantial saturation with alumina can be achieved using means for the distribution of alumina over a large area of the electrolyte, such as a series of point alumina feeders or a projecting device alumina on the molten electrolyte, as disclosed in WO00 / 06804 (from Nora / Berclaz).

The bottom cathode may comprise a container, for example, centrally located in the cell, to Collect produced aluminum. Also, porous plates with padding aluminum can be arranged so that the top layer of aluminum placed on them runs into the container.

The cell, particularly when it is of type adapted afterwards, it can comprise a lateral edge of solid electrolyte and / or an equally solid electrolyte crust. Do not However, the cell can also work with an electrolyte cast without edge and without crust, that is, in a completely state molten.

The invention also relates to a method for the manufacture of aluminum in a cell as described previously. The method comprises the alumina feed to electrolyte and pass the electrolysis current between the electrochemically active anode coatings and layer upper aluminum to generate gas, in particular oxygen, on anodes and cathodically reduce aluminum.

Another additional aspect of the invention relates to to a cell structure of a cell for manufacturing Aluminum electrolytic from alumina dissolved in a molten electrolyte containing fluoride. The structure includes a horizontal carbon bottom cathode that has a coating surface wettable by aluminum, as well as a series of plates made from a crosslinked porous material wettable by the aluminum, located flat on the surface coating Wettable by aluminum.

In a preferred embodiment, the structure of the cell comprises a series of anode substrates with base metallic, located above the horizontal carbon bottom and parallel to it. Each of the anode substrates is protected by an electrochemically active coating made from one or several cerium compounds. I also know they can use, as mentioned above, others anodes with metal base.

It is also possible to use carbon anodes consumables instead of anodes based on cerium or other metals. During an operation of cells with carbon anodes, it is formed CO 2 on the surface of the anodes instead of O 2.

Brief Description of the Drawings

The present invention will be described in further additionally referring to the drawings following schematics, in which:

- Figure 1 is a cross section of a drained cell according to the invention, with metal base anodes; Y

- Figure 2 is a cross section of another drained cell according to the invention with carbon anodes.

Detailed description

The cell shown in Figure 1 has a cathode horizontal coal bottom (11) whose surface is protected with a surface coating (25) wettable by aluminum. He surface coating (25) wettable by aluminum is covered by a series of plates (21) made from a crosslinked porous material wettable by aluminum, with filler of aluminum. These plates (21) form a cathode surface horizontal (20), with drainage, on which it occurs during use a top layer of aluminum (23). A bottom layer of cast aluminum (22) substantially moistens the entire surface coating (25) wettable by aluminum and a bottom part of the plates (21).

The bottom cathode (11) comprises the middle part of the cell, a channel (30) for collecting the aluminum produced, draining the adjacent surfaces (20) of the wettable cathode by the aluminum. The aluminum collection channel (30) is preferably coated with a refractory boride layer applied as an emulsion, as explained above.

The cell is equipped with metal base anodes (10) on which oxygen is generated during use:

The anodes (10) are electrolyte resistant (5) and to oxygen and other gases generated during use, by example, by protecting it with a coating based on cerium oxyfluoride, as disclosed in the Patents USES. 4,614,569, 4,966,674, 4,683,037, 4,680,094, 5,069,771, 4,960,494 and 4,956,068 mentioned above. So alternatively, the anodes (10) can be made on the basis of others suitable anode materials with metal base, as described indicated above.

The cell has side walls (40) made, for example, in silicon carbide, which are covered with a wedge-shaped side covering (41 '), moistened by aluminum, which extends from the periphery of the bottom cathode (11) reaching above the surface of the molten electrolyte (5) to protect the side walls (40) against the electrolyte cast (5). The coating (41 ') of the side wall can be made of the same material as the plates (21) and may be completely filled with molten aluminum retained in the pores of the material by capillary effect.

To prevent the electrolyte (5) from solidify along the coating (41 ') of the side wall and on the surface of the electrolyte (5), the cell is thermally well insulated. As shown, the cell is equipped with a insulating layer (45) on the electrolyte (5). They make themselves known details of suitable caps in WO01 / 31086 (of Nora / Duruz).

To reduce the dissolution of the anodes (10) in the electrolyte, the cell can be operated with an electrolyte (5) at reduced temperature, typically from 730 ° to 960 ° C, preferably from 860 ° to 930 ° C.

Operation with an electrolyte at reduced temperature reduces the solubility of oxides, including alumina Therefore, it is advantageous to favor the dissolution of the alumina in the electrolyte (5).

The increase in alumina dissolution is you can get by using a power device alumina that performs a projection and distribution of particles of alumina over a large area of the electrolyte surface cast (5). Power supply devices of suitable alumina in more detail in WO00 / 63464 (from Nora / Berclaz). Alternatively, alumina can be supplied by several conventional point feeders distributed with respect to the molten electrolyte (5). Besides, the cell can comprise means (not shown) to favor the electrolyte circulation (5) to and from the interstitium anode-cathode to increase the dissolution of alumina in the electrolyte (5) and to permanently maintain a high concentration of alumina dissolved near surfaces active anodes (10), for example, as disclosed in WO00 / 40781 (de Nora).

When the anodes (10) are protected with a Cerium Oxyfluoride based coating, is maintained preferably a certain amount of cerium in the electrolyte to the maintenance of the coatings.

During the operation of the cells that are have shown in figure 1, the alumina dissolved in the electrolyte undergoes electrolysis to produce oxygen over the anodes (10) and aluminum in the cathodes that is incorporated into the upper layer of aluminum (23) on the surfaces (20) of the cathode provided with sewer system. The aluminum (60) of the top layer (23) drains into the collection channel (30) from where it can be extracted.

Figure 2, in which the same have been used reference numerals to designate the same elements, show a rehabilitated cell that uses conventional consumable anodes of coal (10 ') and that works with a crust (70) and edge area (71) Solid electrolyte covering the side walls (40), the coating (41) and wedges (51).

According to a variant, plates can be used connectable by aluminum larger than shown in Figures 1 and 2, extending each of the major plates on a significant part of the cathode block (11), in particular over the entire length of the cathode block cell (11), preferably also extending over a part of the channel (30), as disclosed in document PCT / IB01 / 00953 (of Nora)

According to another variant, a rehabilitated cell without Aluminum pickup slot can work with a top layer of aluminum that forms a puddle of low cathode aluminum. As a consequence, the distance between electrodes can be reduced also, which leads to the reduction of the cell voltage and to energy savings Also, compared to the cells Conventional deep puddle, more is needed small cast aluminum to run the cell, which substantially reduces the costs incurred by the immobilization of large quantities of aluminum in the factories of manufacture of it.

The manufacture of crosslinked porous material Wettable by aluminum, suitable for use as a plate of cathode for a cell according to the present invention, will be described below in the following examples.

Example 1

A structure was made wettable by aluminum alumina with open pores (10 pores per inch, which is equivalent to about 4 pores per centimeter), when applying a coating on it by two layers applied in emulsion of different compositions.

The first emulsion of the first layer was constituted by 60% by weight of oxidized TiB2 particles, with needle-shaped surface (mesh -325) with an area of TiO2 laminar oxide, 3.3% of a wetting agent of the aluminum in the form of Fe 2 O 3 in particles (mesh -325) and 3.3% by weight of TiO2 powder (-325 mesh) in 33% by weight of Al 2 O 3 colloidal (NYACOL® Al-20, liquid milky with a colloidal particle size of approximately 40 to 60 nanometers) When this emulsion is heat treated, the colloidal alumina reacts with a surface oxide of TiO2 and TiO2 powder forming a mixed oxide matrix of Al 2 O 3 and TiO 2 throughout the coating, so that this matrix contains and binds the TiB2 particles and the Fe 2 O 3 particles.

The second emulsion consisted of 33% in weight of partially oxidized copper particles, 37% by weight of a first quality of colloidal alumina (NYACOL® Al-20) and 30% by weight of a second quality of colloidal alumina (CONDEA® 10/2 Sol, an opalescent liquid, transparent, with an approximate colloidal particle size of 10 to 30 nanometers).

A wettable coating was applied by aluminum on the porous alumina structure by immersion of this structure in the first emulsion, followed by drying for 4 hours at 40 ° C and immersion in the second emulsion followed by drying during 15 hours at 40 ° C. The alumina structure with coating was heat treated for 3 hours in the air at 700 ° C to consolidate the coating.

The resulting structure is wettable by aluminum and is suitable for wetting by aluminum before use or can be wetted in situ when used as a cathode plate for a cell according to the invention.

The porous structure wettable by aluminum it was moistened with alumina when immersed in molten aluminum at 850 ° C. After 20 hours, the wetted porous structure was removed from the molten aluminum and allowed to cool to room temperature.

Examination of the porous structure moistened with aluminum showed that it was completely filled with retained aluminum in the pores due to the wettability of the structure and effect capillary, and cover on the outer surface with aluminum.

The electrical resistivity of the structure with aluminum coating was of the order of the resistivity of the metallic aluminum (2.65 µm \ Omega.cm), while before the humidification the structure had a resistivity of 35 to 45 k \ Omega.cm.

Example 2

An aluminum wettable ceramic body for its use as a cathode plate in a cell according to the invention It was manufactured using a mixture of inert material and resistant to cast aluminum, i.e. alumina and titanium oxide, and material Wettable by aluminum, that is, copper oxide. The structure or ceramic body was prepared by coating a spongy material of polyurethane with a ceramic particle emulsion followed by heat treatment.

The emulsion of ceramic material consisted of a 40 g suspension of Al 2 O 3 in the form of particles with a average particle size from 10 to 20 microns, 2.5 gr of CuO in particles with a particle size smaller than about 45 microns, 2.5 gr of TiO2 in particles with a particle size smaller than about 45 microns in a colloidal alumina carrier consisting of 93 gr of deionized water and 6.6 gr of particulate colloidal alumina with a colloidal particle size of about 10 to 30 nanometers

A polyouretane foam that had 10 to 20 pores per inch (equivalent to approximately 4-8 pores per centimeter) was immersed in the emulsion and air dried at a temperature of 40º to 50ºC for a time of 20 to 30 minutes The immersion was repeated three times.

After immersion, the foam was dried at air at 50 ° C for a time of 4 to 5 hours. The foam contained approximately 0.3 to 0.5 g / cm 3 of the dry emulsion. Drying was followed by heat treatment at approximately a temperature from 850º to 1000ºC in the air for 4 to 5 hours to eliminate the polyurethane foam and consolidate the ceramic material formed to from the emulsion in a self-sustaining foam. This heat treatment was followed by an aluminization treatment by immersion in cast aluminum for 2 hours in aluminum melted at 850 ° C.

Aluminized foam was extracted from aluminum molten, allowed to cool to room temperature and cut perpendicular to a surface.

The aluminized foam test showed that the polyurethane foam was gone. The TiO_2 had reacted with Al 2 O 3 in the ceramic foam to form a matrix of mixed oxide of titanium-aluminum. He CuO present on the surface of the ceramic foam had reacted with molten aluminum to produce a surface layer of Al 2 O 3 moistened with aluminum and a copper alloy and aluminum. The pores of the ceramic spongy material were filled completely cast aluminum.

According to a variant, the treatment stage thermal and aluminization stage are carried out simultaneously as a single stage. In another variant, the oxide of copper of the ceramic structure is partially substituted or completely by iron oxide and / or nickel oxide.

Example 3

A silicon carbide body with pores open (30 pores per inch equivalent to about 12 pores per centimeter) for use as a cathode plate in a cell according to the invention it was made wettable by coating aluminum thereof with a layer applied in the form of emulsion.

The emulsion consisted of 75 grams of particles of iron oxidized superficially (mesh -325), 75 gr of sun Nyacol 830 silica (an aqueous and milky liquid containing 32% in weight of colloidal silicon hydroxide that becomes silica after heat treatment) and 0.35 gr of an aqueous solution containing 15% PVA (polyvinyl alcohol) that was used to Adjust the viscosity of the emulsion.

The structure of open pores was submerged in the emulsion and then dried for 30 minutes at 60 ° C. The impregnated porous structure contained 0.278 g / cm3 of the dry emulsion including 0.214 g / cm3 of iron particles surface oxidized

The resulting structure was wettable by aluminum and suitable for wetting by aluminum before use or in situ when used as a cathode.

The porous structure wettable by aluminum was wetted with aluminum by immersing it in molten aluminum at 850ºC. After 15 hours, the wetted porous structure was removed from the molten aluminum and allowed to cool to room temperature.

Examination of the porous structure moistened by aluminum showed that it was full of aluminum retained in the pores for the wettability of the structure and the capillary effect, and cover on the outer surface with aluminum. The pores had an aluminum filling ratio greater than 90% by volume.

Wetted aluminum materials Examples 1 to 3 can also be used to produce a side wall coating or other cell component exposed to at least one of the following: cast aluminum, molten electrolyte and oxidizing or corrosive gas such as oxygen produced anodically.

Claims (22)

1. Cell for the manufacture of aluminum by electrolysis from alumina dissolved in a molten electrolyte which contains a fluoride, which comprises:

-

a horizontal cathode, carbon protected by a coating surface wettable by aluminum, resisting the bottom cathode Coated with corrosion and wear;

-

a series of plates made from a crosslinked porous material Wettable by aluminum, filled with aluminum and arranged flat on the wettable surface coating by aluminum;

-

a thin layer of aluminum bottom between porous plates filled with aluminum and aluminum wettable surface coating on the top of the carbon bottom cathode, whose thin layer of aluminum moisturizes the surface coating and a bottom part of porous plates with aluminum padding; Y

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a aluminum top layer formed above the porous plates filled with aluminum and covered by electrolyte.

2. Cell according to claim 1, which It comprises a series of anodes with metal base located above of the surface of the upper layer of aluminum and parallel to the same. 3. A cell according to claim 2, wherein each metal-based anode has a substrate based on a metal protected by an electrochemically active coating made based on one or several cerium compounds that is maintained by the presence of cerium in the electrolyte. 4. Cell according to claim 2 or 3, in the that the metal-based anodes comprise an alloy based on iron and nickel 5. Cell, according to any of the claims 1 to 4, wherein the anodes are separated by above the surface of the upper layer of aluminum by a reduced anode-cathode distance of the order of 20 to 40 mm 6. Cell, according to any of the previous claims, wherein the bottom layer of aluminum It has a thickness between 0.5 and 10 mm. 7. Cell, according to any of the previous claims, wherein the upper layer of aluminum It forms a puddle. 8. Cell, according to any of the previous claims, wherein the upper layer of aluminum It has a thickness between 5 and 10 mm. 9. Cell, according to any of the previous claims, wherein the porous plates filled with Aluminum have a thickness of the order of 10 to 100 mm. 10. Cell, according to any of the previous claims, wherein the porous plates filled with aluminum have a surface layer that contains alumina, aluminum and an additional metal, such as copper, iron and / or nickel, being able to produce the surface layer by exposing the plates surface wettable by aluminum to cast aluminum, which contain metal oxides, such as copper, iron oxides and / or nickel, which can react with the cast aluminum 11. Cell, according to any of the previous claims, wherein the surface coating wetted with aluminum over the carbon cathode comprises a layer surface containing alumina, aluminum and other metal, such as copper, iron and / or nickel, being able to produce the surface layer by exposure to molten aluminum of a surface coating aluminum wettable containing oxides before use metallic, such as copper, iron and / or nickel oxides, which They can react with molten aluminum. 12. Cell, according to any of the previous claims, wherein the metal structure endowed of coating of each anode has a horizontal extension and is equipped with holes to guide through them a circulation of electrolyte to and from the coating electrochemically active. 13. Cell, according to any of the previous claims, wherein the electrolyte is at a temperature below 960 ° C. 14. A cell according to claim 13, wherein The electrolyte is at a temperature of 860ºC to 930ºC. 15. Cell, according to any of the previous claims, wherein the electrolyte comprises cryolite and, in addition to the cryolite, an excess of AlF 3 in a amount of 15 to 30% by weight of the cryolite. 16. Cell, according to any of the previous claims, wherein the electrolyte on the electrochemically active coating is substantially saturated alumina. 17. Cell, according to any of the previous claims, comprising means for distributing alumina over a large area of the electrolyte. 18. Cell, according to any of the previous claims, wherein the bottom cathode comprises a container for collecting the aluminum produced. 19. Cell according to claim 18, wherein porous plates filled with aluminum are arranged so that the top layer of aluminum placed on them can drain into the container centrally located in the cell. 20. Cell, according to any of the previous claims, comprising a side edge of solidified electrolyte and / or an electrolyte crust solidified 21. Method for manufacturing aluminum in a cell, according to any of the preceding claims, which comprises the alumina feed to the electrolyte and passes a electrolysis current between anode coatings electrochemically active and the top layer of aluminum for generate gas, in particular oxygen, on the anodes and reduce cathodically aluminum. 22. Cell body for a cell for Aluminum electrolytic manufacturing from dissolved alumina in a molten electrolyte containing fluoride, said said comprising structure a protected horizontal carbon cathode bottom by an aluminum-wettable surface coating, the bottom cathode provided with a coating being resistant to the corrosion and wear, and a series of plates made from crosslinked porous material wettable in an aluminum shape flat on the surface wettable by aluminum, the wettable surface coating being arranged by aluminum and the plates located on it for formation between them a thin layer of aluminum that moistens the surface coating and a bottom part of the porous plates filled with aluminum during use.