RU2763059C1 - Production of aluminium with a moving electrolyte in an electrolyser - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: present invention relates to non-ferrous metallurgy, in particular, to a structure of electrolysers for producing aluminium. An electrolyser for producing aluminium containing an electrolysis chamber, a cathode and anodes, an input for supplying an aluminium oxide-saturated molten electrolyte, an outlet for the aluminium oxide-depleted molten electrolyte on the other side of the chamber. The cathode is made in the form of a hearth with an inclination ensuring movement of the electrolyte by gravity along the hearth towards the outlet for the aluminium oxide-depleted electrolyte. A bath is located in the front part relative to the flow of the solution for constant removal of excess aluminium. The electrolyser comprises a closed contour ensuring circulation of the electrolyte with the dissolved aluminium oxide and configured to uniformly saturate the electrolyte with aluminium oxide outside of the electrolysis zone during movement thereof from the outlet to the input of the electrolyser. The anodes are made of a pseudo-alloy of copper and tungsten.

EFFECT: increase in the output of aluminium with lower electricity consumption.

5 cl, 2 dwg

Description

1. Field of technology.

The invention relates to the metallurgy of non-ferrous metals, in particular to the design of electrolysers for the production of aluminum.

2. Prior art.

There are chemical methods for producing aluminum and methods using electrolysis. Chemical methods have a high cost of the produced aluminum and low productivity. The most productive chemical method of obtaining is the magnesium-thermal reduction of aluminum trichloride (number of patent RU0002583214 dated 05/10/16, author Begunov Albert Ivanovich).

Much more productive is the production of aluminum using electrolysis, discovered in 1808 and significantly improved in 1886. by the French engineer Paul Héroux and the American student Charles Hall. The Hall-Heroult method with minor modifications is currently used in industry. Progress in the technology of electrolysis production of aluminum occurs in the following areas:

- completion of the design of the electrolyzer as a whole - invention No. EA 201990207 dated June 28, 2019, by Liu Xinghua;

- revision of the aluminum oxide feed - invention No. RU 0002454490 dated 06/27/12, authors Petr Vasilievich Polyakov, Alexey Mikhailovich Vinogradov, Evgeny Viktorovich Nikitin, Alexander Vladimirovich Krasovitsky;

- refinement of the chemical component of the aluminum chloride electrolysis process - invention No. US 4919771 dated 04.24.90 by Wilkening Siegfried.

From the prior art and in production, it is known to pass a molten metal through a filter to clean it from insoluble particles (not metal inclusions, etc.). Special types of glass cloth with a mesh size of about 1 mm or steel mesh are used as filters. The most effective filtration of melts through grain and sintered porous filters. Grain filters represent a 30-60 mm layer of pieces of grains with a diameter of 5-15 mm. Sintered porous filters have pores up to 0.5 mm in size. Both of these types of filters are capable of capturing very small inclusions, up to 20-30 microns in diameter. It is not known from the current state of the art to use such filters for pre-cleaning the aluminum melt inside an electrolytic cell.

All the found inventions concerning the electrolysis of aluminum, slightly improve the technology, without changing it drastically. All improvements do not change the main disadvantages of electrolysis aluminum production:

- huge power consumption,

- unevenness of the electrolysis process due to the use of unevenly burning carbon anodes,

- uneven supply of aluminum oxide to the electrolysis zone

These disadvantages are greatly reduced by the present invention.

3. Disclosure of the invention.

The essence of the presented invention is: increasing the intensity of the electrolysis process with less electricity consumption by the movement of an electrolyte saturated with aluminum oxide along the bottom of the electrolyzer by gravity and the use of metals or their alloys with high conductivity, refractoriness, corrosion and chemical resistance as anodes.

4. The purpose of the invention is:

- high intensity and uniformity of the reaction of dissociation of aluminum oxide into its constituent chemical elements - aluminum and oxygen under the action of a current that excludes the anode effect (blocking of the anodes with a gas film) and precipitation of aluminum oxide, which disrupts the efficiency of electrolysis,

- maintaining the maximum saturation of the electrolyte with dissolved aluminum oxide between the anodes and the cathode (hearth),

- washing away the evolved oxygen bubbles from the anodes by the flow of electrolyte, reducing the anode effect and the oxidation and destruction of the anodes, increasing the wettability of the anodes with the electrolyte,

- energy saving on high conductivity and low electrical resistance of anodes.

The listed factors allow achieving a higher aluminum yield with less electricity consumption. Also, the technological process of the invention makes it possible to obtain oxygen instead of carbon dioxide.

5. This is achieved by:

- in the electrolysis chamber, circulation of the electrolyte with dissolved alumina in a closed loop is ensured,

- due to the high viscosity of the electrolyte with dissolved aluminum oxide, the supply level of the electrolyte mixture is higher than the level of its outflow, which ensures gravity,

- uniform saturation of the electrolyte with aluminum oxide occurs outside the electrolysis zone using stirring and adjusting additives,

- the electrolyte solution with dissolved aluminum oxide is fed into the electrolysis chamber evenly for the purpose of uniform movement between the anodes and the cathode

- the deposited aluminum flows down by gravity along the bottom of a small slope towards the bath, located in front of the solution flow, excess aluminum is constantly taken out for further processing, ensuring a constant level of aluminum at the bottom,

- the bath for collecting molten aluminum can be used for rough cleaning from insoluble particles (not molten, not metal inclusions, etc.),

- the oxygen released at the anodes, in order to avoid blocking the anodes from the solution and entering into a chemical reaction, is constantly removed upward and into the gas removal and purification system,

- for effective separation and removal of oxygen, streamlined anodes (bubble washout) and vibration of the anodes of the optimal frequency are used, the more oxygen is separated from it, the less it will participate in the reversible oxidation of aluminum,

- the released oxygen can be purified and used in industry, transport or medicine,

- anodes should be made of refractory metal or an alloy with high electrical conductivity, low electrical resistance, corrosion and chemical resistance, presumably - a pseudo-alloy of copper and tungsten.

Separately to the presented invention, it is recommended to organize the production of finished products at factories for the production of aluminum from aluminum oxide. This achieves energy savings for reheating / melting billets (ingots of various shapes). Saved, cheap electricity is most effectively used in the production of finished products with high added value.

Additionally, you should add information confirming the impact of each of

the declared design features to achieve the specified technical result, namely, an increase in the intensity of the electrolysis process with a lower electricity consumption:

- The circulation of the electrolyte reduces the formation of an oxygen cushion in the anode space, which increases the electrical resistance and energy consumption. The uniform consumption of aluminum oxide in the flowing electrolyte reduces the possibility of manifestation of the anode effect known in the process of aluminum electrolysis with a decrease in the content of aluminum oxide in the anode space of less than 1%, which also reduces the efficiency of electrolysis - increases power consumption and requires additional measures to eliminate the anode effect.

- Vibration is used from the prior art to detach bubbles of gases released on the electrodes and to accelerate chemical reactions (for example, V.A. Pozdneev, V.N. Tsurkin "On low-frequency oscillation of bubbles in a vibrating liquid" 09/28/2001)

- The use of anodes made of chemically inactive materials significantly reduces the formation of foam (carbon foam when using carbon anodes). Previously proposed anode materials based on: iron, nickel, manganese, titanium, tantalum, zirconium, chromium, niobium, cobalt, vanadium, alloys based on them, carbides and borides of these metals, as well as using composite materials based on refractory ceramics, have from 1.5 to 50 times higher electrical resistance than anodes based on a composite alloy of copper and tungsten and, therefore, higher electricity consumption during electrolysis. The electrical resistance of carbon anodes is 430-600 times higher than the resistance of a composite alloy of copper and tungsten.

Separately to the presented invention, it is recommended to organize the production of finished products at factories for the production of aluminum from aluminum oxide. This achieves energy savings for reheating / melting billets (ingots of various shapes). Saved, cheap electricity is most effectively used in the production of finished products with high added value. The methods described in the invention can be applied, inter alia, in the production of refined (purified) aluminum. The refining process, in order to reduce the cost of production, can be included in one technological cycle with the primary production of aluminum.

6. Brief description of the drawings.

FIG. 1 shows an electrolytic cell with a moving gravity electrolyte, indicated:

1 - exhaust gases

2 - drainage of depleted electrolyte and place of addition of aluminum oxide

3 - removal of molten aluminum

4 - the direction of movement of the electrolyte with dissolved aluminum oxide

5 - hearth, cathode

6 - electrolyte with dissolved aluminum oxide

7 - supply of electrolyte saturated with aluminum oxide

8 - anodes made of metal or metal alloy

9 - busbar

10 - molten aluminum.

Stirring of the added alumina in the electrolyte occurs when it moves from the outlet to the inlet to the electrolyzer.

The electrolyzer can be made in a symmetrical arrangement with the supply of an electrolyte saturated with aluminum oxide from two opposite sides and the withdrawal of an electrolyte depleted in aluminum oxide in the center.

FIG. 2A shows a cross section of the anode with a schematic flow around the electrolyte.

Figure 2B shows

8 - anode installed in the bath of the electrolyzer on the anode electric bus

9 - electric anode bus

11 - vibrating device.

For simplicity, the drawing does not show elements that are not related to the demonstration of the installation of streamlined anodes.

Claims (5)

1. An electrolyzer for the production of aluminum, containing an electrolysis chamber, a cathode and anodes, characterized in that it contains an inlet for supplying a molten electrolyte saturated with aluminum oxide, an outlet for a molten electrolyte depleted in aluminum oxide from the other side of the chamber, the cathode is made in the form of a hearth with an inclination that provides movement of the electrolyte by gravity along the bottom towards the outlet of the electrolyte depleted in aluminum oxide, a bath located in the front part of the solution flow for the constant removal of excess aluminum, a closed loop that circulates the electrolyte with dissolved aluminum oxide and is made with the possibility of uniform saturation of the electrolyte with aluminum oxide outside the electrolysis zone when its movement from the branch to the inlet to the electrolyzer. 2. An electrolyzer according to claim 1, characterized in that the bath is made with the possibility of rough cleaning of molten aluminum. 3. An electrolyzer according to claim 1, characterized in that the anodes are made of a pseudo-alloy of copper and tungsten. 4. An electrolyzer according to claim 1, characterized in that the anodes have a streamlined cross-section. 5. An electrolyzer according to claim 1, characterized in that the anodes are vibration-capable.

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