RU2586183C1 - Electrolysis cell for producing liquid metals by electrolysis of melts - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to electrolytic cells for production of molten metals, particularly aluminium, by electrolysis of molten salts. Electrolytic cell comprises housing, bottom, cover, installed vertically or inclined low-consumed hollow perforated and/or open porous electrodes connected to a DC source, electrodes are inner channels for transportation of electrolysis products. Electrodes are made in cross-section in form of rectangle, are fixed in cover of electrolysis cell and/or in cavities of housing and bottom, and in bottom of cathode part, and are connected from 1 to 100 parallel rows with in-series connected bipolar electrodes in a number from 2 to 100, at distance between electrodes from 0.5 to 5 cm, and from side surface of electrode to side wall of electrolysis cell from 0.01 to 1 cm each row of equipotential electrodes is connected with metal accumulator located in lower part of electrolytic cell.

EFFECT: higher specific efficiency, reduced specific power consumption and weight of current-carrying bus.

3 cl, 13 dwg, 1 tbl

Description

The invention relates to non-ferrous metallurgy, and in particular to devices for the production of metals by electrolysis of molten electrolyte, in particular aluminum. In addition to aluminum, the resulting metals can be copper, magnesium, lithium, sodium, and lead.

Apparatuses used in industry for the production of aluminum by electrolysis have the following disadvantages: low productivity per unit area occupied by the electrolyzer; high specific energy consumption per unit mass of the obtained metal; emission of environmentally harmful substances into the atmosphere, high labor costs.

The invention is known (RF Patent No. 2101392, C25C 3/06, publ. 01.10.1998), according to which many inert anodes are located vertically inside a variety of tubular cathodes made of electronically conductive material. When direct current is passed through parallel-connected electrodes, liquid aluminum is released and flows down at the cathodes, and gaseous oxygen is released and rises up at the anodes.

The vertical arrangement of the electrodes significantly increases their working area, which allows to increase the productivity of electrolyzers, related to the area occupied by them. However, the described configuration of the electrodes does not provide the most dense arrangement of electrodes in the electrolyzer, which prevents the achievement of a high value of productivity per unit area occupied by it.

The closest in technical essence and the achieved result to the claimed electrolyzer for producing liquid metals by electrolysis of melts is the invention (RF Patent No. 2275443, C25C 3/06, publ. 04/27/2006). The invention relates to an installation for producing metals, in particular aluminum, by electrolysis of molten salts and a method for installing electrolysis baths. A multipolar electrolysis bath includes a housing, a hearth, a lid and cathodes and sparing anodes mounted vertically or obliquely and parallel to each other, connected to a direct current source, while the cathodes or their surface are made of material wetted by the metal. The electrodes are made recesses and internal channels for transporting electrolysis products through them, the upper part of the anodes are fixed in the lid. The anodes and cathodes are made in cross section in the form of a hexagon with sharp or rounded corners, with more than half the area of the side surface of each of the electrodes facing the electrode of the opposite sign, and the same electrodes form chains connected in parallel. The cover is made of independently opening sections, and its lower surface is protected by a non-conductive and resistant to electrolyte and electrolysis products material.

Using the prototype does not allow to achieve high performance values per unit occupied by the electrolyzer area. Using a hexagon as the geometric base of the electrode does not allow the most efficient use of the area occupied by the electrolysis bath, because only 4 of 6 faces can be directed to the electrode of the opposite sign. The disadvantage of parallel connection of the electrodes in the described electrolysis bath is the large mass of current-carrying tires.

The objective of the invention is to create a design of an electrolytic cell having a reduced mass of busbars and allowing to obtain molten metals with high productivity per unit area occupied by it and high energy efficiency. The proposed design can be used to obtain metals (aluminum, magnesium, lead, etc.), the density of which is higher than the density of the melt, which includes the decomposable compound.

The technical result consists in increasing the productivity per unit area, in reducing the specific energy consumption, in reducing the mass of the lead-in busbar.

This object is achieved in that the electrolyzer for producing liquid metals by electrolysis of melts, including a housing, a hearth, a lid, vertically or obliquely installed low-consuming hollow perforated and / or openly porous electrodes connected to a direct current source, while the internal channels for transportation are made in the electrodes according to them electrolysis products, according to the invention, the electrodes are made in the cross section in the form of a rectangle, are fixed in the lid of the electrolyzer and / or in the recesses x the case and the hearth, and in the hearth the cathode part, while the electrodes are connected from 1 to 100 parallel rows with bipolar electrodes connected in series from 2 to 100, with a distance between the electrodes of 0.5 to 5 cm, and from the side surface of the electrode to the side wall of the cell from 0.01 to 1 cm, with each row of equipotential electrodes connected to a metal storage located in the lower part of the cell. The electrodes are equipped with ceramic tubes that are resistant to oxygen. In the lid there is a cavity for accommodating materials, such as alumina, and openings for evacuating gases.

The distance between the electrodes is selected based on the presence or absence of suspensions (suspensions) filling the interelectrode gap and the presence of convection in the electrolyte, and can be from 0.5 to 5 cm (when using melts that do not contain suspensions).

The electrodes may be vertical or inclined. The inclination of the electrodes can be from 1 ° to 45 ° from the vertical, which will provide a more efficient evacuation of electrolysis products into the electrode channels under the influence of pressure gradients and gravity.

In the proposed design of the electrolyzer, electrolysis is carried out between the inclined or vertical low-consumable electrodes facing each other. Electrodes with a developed surface are preferred in order to reduce current density.

Electrolysis products are released at the electrode-electrolyte interface, and then evacuated through channels inside the electrode body. The cathode and anode surfaces have openings (channels) for removal of the corresponding electrolysis products. In this case, the electrolysis products - for example, oxygen on the anode surface and aluminum on the cathode - are removed from the reaction zone through cavities in the structure of the electrodes: oxygen rising up inside the anode cavity and metal, for example aluminum, flowing down inside the cathode cavity, due to the difference in densities aluminum and electrolyte, surface tension forces at the boundary of the surface of the electrodes, and gravity. The internal channels of the cathodes are used to drain metal into the storage ring. Connection to cathode channels of vacuum is allowed. Anode gas is evacuated from the anode cavity through ceramic tubes in the upper part of the anode. Connection to ceramic tubes of vacuum is allowed.

The electrodes are held by fixing them in a sectioned lid of the electrolyzer and / or in special recesses of the housing and the hearth. Thus, it is possible to carry out work on the replacement of electrodes or local repair of electrolysis baths, opening only the desired section. The lower part of the lid is made of a material resistant to the effects of heat, vapors and gases, such as refractory high-alumina concrete.

The rectangular cross-sectional shape of the electrode allows you to direct more than 95% of the side surface area to the electrode of the opposite sign.

The presence of a system of metal storage in the lower part of the cell eliminates the possibility of a short circuit on the metal.

The use of series-parallel connection of the electrodes allows to reduce the mass of the current-carrying busbar in proportion to the number of electrodes in each row. With the number of 20 electrodes, the mass decreases by 20 times.

When installing more than 100 rows and / or more than 100 electrodes in each row, the control of the electrolyzer is difficult due to its large size. The use of such an electrolyzer becomes impractical.

The distance from the electrode to the side wall of the cell, not exceeding 1 cm, is sufficient to reduce the bypass currents in the cell.

The installation of electrodes in the lid of the electrolyzer and / or in the recesses of the casing and the bottom of the electrolysis cell eliminates their movement relative to each other and the casing of the cell and thereby fix the required interelectrode distance.

When the angle of inclination of the electrodes to the vertical is more than 45 °, it is difficult to evacuate the electrolysis products due to gravity and pressure.

The use of ceramic tubes in the electrodes is due to the need to evacuate the gaseous products of electrolysis from the cell.

The rounded corners of the electrodes allow for a more uniform current distribution and the exclusion of a high current density at the corners of the electrodes.

When the distance between the electrodes is less than 0.5 cm, mixing of the electrolysis products is observed, which leads to a decrease in current efficiency. With a distance of more than 5 cm, the magnitude of the voltage drop in the interelectrode gap increases.

The proposed design is illustrated by drawings, where:

in FIG. 1 shows an electrolyzer for producing liquid metals by electrolysis of molten assemblies;

in FIG. 2 is a top view of the relative position of the electrodes in a design with two parallel rows of vertical electrodes and four consecutive electrodes in each row;

in FIG. 3 - connection of electrodes with an evacuation system of electrolysis products in a cross section of an electrolyzer;

in FIG. 4 is a longitudinal section of an electrolyzer;

in FIG. 5 - an internal cavity of the cathodes in a longitudinal section of the electrolyzer;

in FIG. 6 - the internal cavity of the anodes in a longitudinal section of the electrolyzer;

in FIG. 7 - a system for loading materials in a cross section of an electrolyzer;

in FIG. 8 - bipolar electrode from the side of the cathode surface;

in FIG. 9 - bipolar electrode from the side of the anode surface;

in FIG. 10 is a sectional top view of a bipolar electrode

in FIG. 11 is a cross-sectional view of a bipolar electrode with perforated cathode and anode surfaces, with inclined and vertical channels, with rounded corners;

in FIG. 12 is a transverse section of the electrolyzer in operation.

in FIG. 13 is a longitudinal section of a cell body.

In FIG. 1 shows an electrolyzer for producing liquid metals by electrolysis of molten assemblies, consisting of a housing 1, a lid divided into independently opening sections 2, metal storage rings 3. Current is supplied to the electrolyzer by means of a busbar 4. Metal from metal storage rings is transported through tubes 5. In the lid there are openings 6 for loading materials, as well as openings 7 for evacuating gases generated during electrolysis. The bottom surface of the lid is made of refractory material, such as concrete.

In FIG. 2 shows a top view of the relative arrangement of the electrodes in the electrolyzer in a section. In the presented embodiment, the electrolyzer includes 2 parallel connected rows of electrodes. Each row of electrodes includes an end anode 8, an end cathode 9, and two bipolar electrodes 10. Thus, in each row, the electrodes are connected in series. Neighboring electrodes from different rows form an equipotential chain connected to the metal accumulator by a system of transfer channels.

FIG. 3 illustrates the connection of electrodes with an electrolysis product evacuation system. Each cathode is associated with a metal storage ring, and each anode with a hole for evacuating gases. In the lid, divided into independently opening sections, there is a cavity 12 for accommodating materials, such as alumina.

FIG. 4 shows a longitudinal section through an electrolyzer as well as two adjacent equipotential electrodes located in a housing. Each end anode and each bipolar electrode is connected to a hole for evacuating gases in the lid, divided into independently opening sections, by means of a ceramic tube 13.

In FIG. 5 is a longitudinal sectional view of the electrolyzer, showing the internal cavity 14 of the cathode portion of the bipolar electrode. In this cavity, liquid metal is transported to a vertical tube 15, and then to a metal storage ring.

In FIG. 6 is a longitudinal sectional view of the electrolyzer, showing the internal cavity 16 of the anode portion of the bipolar electrode. In this cavity, anode gases are transported to a ceramic tube connecting the electrode to the gas evacuation hole.

In FIG. 7 is a cross-sectional view illustrating a system for loading materials into a cell. A material, such as alumina, fills a cavity for placing materials in the lid of the electrolyzer, entering through openings for loading materials. Then, through the hole 17, the material enters the interelectrode gap.

FIG. 8 illustrates the appearance of the bipolar electrode from the side of the cathode portion. In this embodiment, the bipolar electrode has a perforated cathode surface 18 and rounded corners 19. Holes 20 serve for the entry of liquid metals reduced on the cathode surface of the bipolar electrode into the cavity inside the electrode and further transported to the metal storage ring.

FIG. 9 illustrates the appearance of a bipolar electrode from the anode side. In this embodiment, the bipolar electrode has a perforated anode surface 21. The openings 22 serve for the entry of gases generated on the anode surface of the bipolar electrode into the cavity inside the electrode and then transported to the ceramic tube.

In FIG. 10 is a sectional plan view of a bipolar electrode. Inside the cathode and anode parts of the bipolar electrode there are cavities for transporting electrolysis products, and an opening 23 is located in the lower part of the cathode cavity through which liquid metal flows into the metal storage ring.

In FIG. 11 is a cross-sectional view of a bipolar electrode. In the presented embodiment, the holes in the cathode and anode surfaces are connected to the cavities inside the bipolar electrode by means of inclined transverse channels 24 and 25, respectively. Inside the ceramic tube of the anode part of the bipolar electrode there is a vertical longitudinal channel 26 for transporting anode gases. The vertical tube at the bottom of the cathode has a vertical longitudinal channel 27 for transporting molten metal.

FIG. 12 illustrates a side cross-sectional view of an electrolyzer in operation. Electrolysis is carried out in electrolyte 28 between electrodes of the opposite sign.

In FIG. 13 is a longitudinal sectional view of the cell body, showing recesses 29 for fixing electrodes in the hearth and in the walls of the cell.

For spontaneous evacuation of metal, the inner surface of the channels should be wetted with aluminum.

The operation of the electrolyzer is the electrolytic decomposition of metal oxide in the electrode gap into oxygen ions and metal ions, the transfer of oxygen ions to the anode surface 21 of the bipolar electrode 10 with rounded corners 19, or to the end anode 8, the transfer of metal ions to the cathode surface 18 of the bipolar electrode 10, or to the end cathode 9. Liquid metal is reduced at the boundary of the cathode surface 18 and the cathode layer of electrolyte 28 when electrical work is performed on the electrolyzer after a manual ultrasonic inspection cover 2 disposed in the hole 6 starting materials, heating the cell to a temperature 5-20 ° C above the liquidus temperature of the electrolyte and connecting the tire 4 to the DC power source.

Due to the oxidation of oxygen ions, gaseous oxygen is formed in the anode layer of the electrolyte. After saturation of the anode layer of the electrolyte with oxygen, bubbles form on the anode surface 21. Under the influence of pressure gradients, the bubbles enter the openings 22 of the anode surface 21, after which they pass through the inclined or horizontal channels 25 into the internal cavity 16, from where they are evacuated from the cell through the channel 26 of the ceramic tube 13. Metal ions are reduced, forming a liquid metal in the cathode layer of the electrolyte. Drops of liquid metal under the influence of gravity and pressure gradients penetrate the holes 20 of the cathode surface 18, after which, through inclined or horizontal channels 24, they enter the internal cavity 14, from where they flow through the hole 23 along the vertical channel 27 into the metal storage ring 3. Final evacuation of liquid aluminum from the electrolyzer occurs through the tube 5.

The process of production of liquid metal is accompanied by a continuous supply of electrolyzer with the necessary materials (including oxide of the obtained metal) through the hole 6. The supply of materials is maintained at the required level, filling the space for placing materials 12. Directly into the interelectrode gap, the materials enter through the hole 17.

To ensure stability, the electrodes are fixed in the recesses 29 in the hearth 11 and in the walls of the housing 1.

The technical result, the achievement of which the invention is directed, is presented in table 1.

The specific productivity of the electrolyzer exceeds the specific productivity of the prototype by more than 50%. The busbar mass of the electrolyzer was reduced compared to the prototype (as well as with the electrolyzer with OA 200 kA) by 20 times due to the use of series-parallel connection of the electrodes.

The claimed electrolyzer provides a significant reduction in the specific energy consumption for metal production compared to an electrolyzer with OA 200 kA, due to the reduction of the interelectrode distance when using a suspension as an electrolysis medium.

Claims (3)

1. An electrolyzer for producing liquid metals by electrolysis of melts, comprising a housing, a hearth, a lid, vertically or obliquely mounted hollow perforated and / or openly porous electrodes connected to a direct current source, the electrodes having internal channels for transporting electrolysis products through them , characterized in that the electrodes are made in the cross section in the form of a rectangle, fixed in the lid of the electrolyzer and / or in the recesses of the housing and the hearth, and in the hearth - cat the bottom part, while the electrodes are connected in the form of from 1 to 100 parallel rows with series-connected bipolar electrodes in a row from 2 to 100 with a distance between the electrodes of 0.5 to 5 cm, and from the side surface of the electrode to the side wall of the cell from 0 , 01 to 1 cm, with each row of equipotential electrodes connected to a metal storage located in the lower part of the cell. 2. The electrolyzer according to claim 1, characterized in that the electrodes are equipped with ceramic tubes that are resistant to oxygen. 3. The electrolyzer according to claim 1, characterized in that the lid has a cavity for placing materials in it in the form of alumina and openings for evacuating gases.

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