RU2296188C2 - Aluminum cell controlling method - Google Patents

Abstract

FIELD: cell control method for producing aluminum by electrolysis of melt.

SUBSTANCE: method comprises steps of controlled adding of predetermined quality Q₀ of alumina into electrolyte; determining value of A factor of added to electrolyte quantity Q of alumina rapidly dissolved in electrolyte; determining quantity ΔQ of added alumina not dissolved rapidly in electrolyte; controlling by means of at least control means and(or) al least by means of one control operation and(or) at least by one intervention to cell depending upon received value of ΔQ in such a way that to keep said value or to vary it till achieving its value smaller than reference value S. According to preferable variant factor A is determined by analysis of at least one result of electric measurement realized in cell.

EFFECT: accurate reliable monitoring in time and possibly in space of alumina quantity dissolved in electrolyte.

18 cl, 4 dwg

Description

Technical field

The invention relates to a method for controlling an electrolyzer for producing aluminum by electrolysis of a solution of alumina in an electrolyte based on molten cryolite, in particular, the Hall-Heroux method.

State of the art

In industry, aluminum is produced by electrolysis of melts, namely, by electrolysis of alumina (i.e., aluminum oxide) located in a melt based on cryolite, called an electrolyte, in particular the well-known Hall-Heroux method. The electrolyte is located in baths called “electrolysis baths” and having a steel casing internally coated with refractory and / or insulation materials and a cathode device located in the bottom of the electrolysis bath. The anodes are partially immersed in an electrolyte melt (also called an electrolytic bath). Typically, the anodes are made of carbon material, but they can also completely or partially consist of a material called “inert”, such as metal or a composite ceramic-metal material (or, in other words, “cermet”). The term "cell" usually refers to a device containing an electrolysis bath and one or more anodes.

The electrolysis current that flows in the electrolyte layer and the liquid aluminum layer between the anodes and the cathode elements causes alumina reduction reactions and also maintains the electrolyte temperature at the level of about 950 ° C due to the effect of Joule heat release. Alumina is regularly supplied to the electrolyzer, compensating for its consumption as a result of electrolytic reactions.

A number of factors affect the performance and current efficiency of the electrolyzer, for example, the strength and distribution of the electrolysis current, the temperature of the electrolyte, the amount of dissolved alumina, the acidity of the electrolyte, etc., which are dependent on each other. For example, the melting temperature of an electrolyte based on cryolite decreases with an excess of aluminum trifluoride (AlF ₃ ) relative to the nominal composition (3NaF · AlF ₃ ). The melting point also depends on the presence of compounds such as CaF ₂ , MgF ₂ or LiF. In modern production, such operating parameters are set to obtain a current output of more than 90%.

Therefore, the operation of the electrolyzer requires precise control of operating parameters, such as temperature, amount of alumina, acidity, etc., in order to maintain their definitely specified values. To solve this problem, many control methods have been developed. Typically, these methods relate either to the regulation of the alumina content in the electrolyte, or to the regulation of its temperature, or to the regulation of its acidity, i.e. excess AlF ₃ .

One of the main factors ensuring the regulation of the operation of the electrolyzer for producing aluminum by electrolysis of alumina dissolved in a molten electrolyte based on cryolite is the maintenance of an appropriate amount of alumina dissolved in the indicated electrolyte, and, therefore, the adaptation of the amount of alumina introduced into the electrolyte to the consumption of alumina in the electrolysis bath.

An excess of alumina creates the risk of contamination of the bottom of the electrolysis bath as a result of precipitation of undissolved alumina, which can form solid precipitates (deposits) that can electrically isolate part of the cathode. This phenomenon contributes to the formation of very strong horizontal electric currents in the metal in the electrolysis bath, which, due to interaction with magnetic fields, mix the metal layer and cause instability of the electrolyte-metal interface.

Conversely, a lack of alumina can cause the so-called “anode effect”, i.e. polarization of the anode with a sharp increase in voltage at the terminals of the electrolyzer and the release of significant amounts of fluorine and fluorocarbon products (CF _x ), the high ability to absorb infrared radiation of which causes a greenhouse effect.

The need to maintain the amount of alumina dissolved in the electrolyte within certain rather limited limits and, therefore, to adapt the supply of alumina to the needs of the electrolyzer prompted specialists to develop automatic methods for feeding and controlling the amount of alumina in electrolysis baths. This need became especially apparent with the use of so-called “acidic” electrolytes (with a high content of AlF ₃ ), allowing to lower the bath’s working temperature by 10-15 ° С (approximately 950 ° С instead of the usual 965 ° С and even lower than 950 ° С) by introducing compounds such as CaF ₂ , MgF ₂ or LiF, and thus obtain a current efficiency of at least 94%. Thus, it is necessary to be able to control the alumina content in very precise and very limited limits (usually from 1 to 3.5%, and preferably from 1.5 to 2.5%, in electrolytic cells containing anodes of carbon material), taking into account lowering the solubility of alumina caused by the new composition of the electrolyte and lowering the temperature of the electrolyte.

It is known to use in industrial methods an indirect estimate of the amounts of alumina depending on the electrical parameter associated with the concentration of alumina in such an electrolyte. This parameter usually represents the change in resistance R at the terminals of the electrolytic cell under voltage U, including the anti-electromotive force E, estimated, for example, at 1.65 volts, with the passage of current I, so that R = (U-E) / I. Typically, methods for controlling alumina content are to alumina feed depending on the value of R and its change over time. Until very recently, this fundamental principle was the subject of a number of patents (see, for example, French application FR 2749858, corresponding to US patent US 6033550). These control methods do not directly take into account the dissolution rate of the introduced alumina in the electrolyte.

This control mode allows you to maintain the alumina content in the electrolyte within narrow limits and thus obtain a current efficiency of about 95% using acidic electrolytes, while significantly reducing the number (or frequency) of anode effects in bathtubs, which are calculated by the number of anode effects per bath day (AE / bath / day) and is called an “anode effect indicator”.

The modern development of technology for producing aluminum by melt electrolysis has, however, necessitated additional requirements for precise control of the amount of alumina dissolved in the electrolyte. On the one hand, an increase in the nominal current strength in electrolyzers using anodes made of carbon material by modifying existing bathtubs or developing bathtubs of a new generation in which currents of 500 kA can be reached or exceeded was accompanied by a relatively significant decrease in the electrolyte volume and a relatively significant increase in the number of alumina doses supplied to the electrolyte. These changes reinforced the phenomena that contribute to the rapid change in the amount of alumina dissolved in the electrolyte. On the other hand, electrolyzers equipped with so-called inert anodes, in which the electrolyte temperature can be lower than 950 ° C and / or the concentration of dissolved alumina can be higher than 3% and even more, are also prone to precipitation of alumina. In this case, control methods based on a simple measurement of resistance are hardly applicable, because resistance varies little with alumina concentration.

All of these developments have increased the importance of accurate and reliable control of the amount of alumina dissolved in the electrolyte. Based on this, the applicant offers economical and industrially applicable methods of solving these problems.

Disclosure of invention

The object of the invention is a method for regulating an electrolyzer designed to produce aluminum by melt electrolysis, i.e. during the passage of current through an electrolyte based on molten cryolite containing dissolved alumina, in particular by the Hall-Heroux method.

The method of regulation according to the invention includes the introduction of alumina in the electrolyte in the electrolysis bath and is characterized in that it contains:

a) the controlled introduction of a certain amount of Q ₀ alumina into the electrolyte;

b) determining the value of indicator A of the amount Q of alumina, which quickly dissolved in the electrolyte;

c) determining the amount ΔQ of alumina that did not quickly dissolve in the electrolyte;

d) regulation with at least one regulation means and / or at least one regulation operation and / or at least one intervention in the cell, depending on the obtained quantity ΔQ in such a way as to maintain it or bring it to more lower than the reference S.

Typically, alumina is administered in the form of doses containing a known amount of Q ₀ and supplied with a period P by an automatic device or dispenser.

Index A is mainly determined by an electrical measurement carried out in the electrolyzer, which is capable of detecting changes in the electrical parameters of the electrolyte caused by the fraction of introduced alumina that has passed into the solution in the electrolyte.

The applicant unexpectedly found that the introduction of alumina causes a voltage change in the time interval of the order of several seconds, which can be associated with the kinetics of dissolution. The applicant also came to the conclusion that it is important to take into account the modes of dissolution of alumina and, in particular, the mode of fast or slow dissolution.

Alumina granules (grains) that are broken down when introduced into the electrolyte (under the influence of high temperature and evaporation of water chemically bound to alumina) are dispersed to the fast dissolution regime, dispersing small particles of alumina, which immediately form a suspension in the electrolyte and therefore quickly dissolve in it, usually within a few seconds, i.e. for a shorter period than period P, which means giving the next dose.

Alumina pellets (grains) usually correspond to the slow dissolution regime, which, when they enter the electrolyte, stick together, turning the surrounding electrolyte into a solid state and forming a solid mass that is denser than electrolyte and aluminum, which precipitates and collects at the bottom of the bath. The alumina captured in this way can subsequently dissolve in the electrolyte only very slowly and gradually over a long time, usually from several hours to several days.

Indicator A can, if necessary, be fully or partially determined by sampling or by using sensors, usually chemical sensors, physical sensors or physico-chemical sensors, such as optical sensors (Raman or other).

The amount Q of alumina that quickly dissolved in the electrolyte can be determined by calibrating (calibrating) this indicator A, usually by modeling and / or statistical measurements carried out in electrolyzers of the same type operating under comparable conditions.

The determination of the quantity ΔQ of alumina, which did not quickly dissolve in the electrolyte, is usually carried out by subtracting the amount of Q from Q ₀ , i.e. ΔQ = Q ₀ -Q. This calculation method can be used if alumina is administered in doses of Q ₀ , the size of which is known. The quantity ΔQ can in some cases be determined by more developed methods, such as integral numerical calculus, which take into account, for example, the thermal effects associated with the introduction of alumina, the location of the measuring or sampling points, or other factors affecting this value.

These modifications of at least one regulation means of the electrolyzer and / or at least one regulation operation can advantageously be combined.

Brief Description of the Drawings

The figure 1 shows a cross section of a traditional electrolytic cell using prebaked anodes of carbon material.

Figure 2 illustrates a method for measuring voltage in an electrolysis bath.

Figure 3 illustrates a method for determining the reduced electrical resistance of the cell.

The figure 4 shows the voltage signals measured on one of the electrolytic cells.

DETAILED DESCRIPTION OF THE INVENTION

As shown in figure 1, the electrolytic cell 1 for producing aluminum by electrolysis according to the Hall-Hero method usually contains an electrolysis bath 20, anodes 7, attached by means of supporting and fixing means 8, 9 to the anode frame 10, and alumina supply means 11. The carrier and fixing means typically comprise at least one rod anode holder 9. The bath 20 includes a steel casing 2, inner lining elements 4, 4a and cathode elements 5, 6. The inner lining elements 4, 4a are typically refractory blocks, which can be heat insulating. The cathode elements 5, 6 include collector cathode rods 6 to which electrical conductors are attached, which serve to transmit electric current.

The lining elements 4, 4a and the cathode elements 5, 6 form a shaft inside the bath, capable of containing an electrolyte 13 and a liquid metal layer 12 during the operation of the electrolyzer, the anodes 7 being partially immersed in the electrolyte 13. The electrolyte contains dissolved alumina, while the electrolytic bath is usually coated with an outer a layer (or crust) of 14 alumina. In some modes of operation, the inner side walls 3 may be coated with a hardened electrolyte layer 15.

Electric current passes through the electrolyte 13 from the anode frame 10 to the supporting and fixing means 8, 9, to the anodes 7 and then to the cathode elements 5, 6. The cathode elements usually contain at least one metal cathode rod 6 (usually steel in the case of traditional electrolysis baths).

The supply of alumina to the electrolyzer is aimed at compensating for its essentially continuous consumption by the electrolyzer, which is mainly associated with the reduction of alumina to aluminum metal. The regulation of alumina supply by introducing alumina into the liquid electrolyte 13 is usually carried out independently. The feeding means 11 typically includes metering punches 19 capable of piercing the alumina crust 14 and introducing a dose of alumina into the hole 19a formed in the alumina crust during such piercing.

The aluminum metal obtained during electrolysis is usually collected at the bottom of the bath, and a fairly clear boundary is established between the liquid metal 12 and the electrolyte 13 based on molten cryolite. The position of this electrolyte-metal boundary changes over time: it rises as liquid metal accumulates at the bottom of the bath and drops when the liquid metal is removed from the bath.

Several electrolyzers are usually placed in a line (series) in rooms, usually called electrolysis shops, and using electrical conductors (buses) create a serial connection between them. More specifically, the cathode rods 6 of one bath, called "current next", are connected to the anodes 7 of the bath, called "next current", usually using connecting conductors 16, 17, 18 and supporting and fixing means 8, 9, 10 for supporting the anodes 7. Conventionally, electrolyzers are arranged to form one or more parallel lines. The electrolysis current thus flows in series from one cell to another.

Most of these elements, at least in terms of their function, can be used in electrolysis baths that use non-consumable anodes, also called “inert”. During production, oxygen is released instead of carbon dioxide, which is usually emitted by anodes from carbon material.

According to the invention, a method for controlling an electrolyzer 1 for producing aluminum by electrolytic reduction of alumina dissolved in a cryolite-based electrolyte 13 is proposed, the electrolyzer 1 including an electrolysis bath 20, at least one anode 7, at least one cathode element 5, 6, wherein said bath 20 has inner side walls 3 and is capable of containing liquid electrolyte 13, and said electrolyzer 1 contains at least one means for regulating said electrolyzer (usually under the adjacent anode frame 10, to which the indicated at least one anode 7 is attached) and is configured to pass an electrolysis current having a force I through the electrolyte, and the aluminum obtained by such reduction may form a layer, called a liquid metal layer 12, on one or several cathode elements 5, 6, including the introduction of alumina into the specified electrolyte and characterized in that it contains:

a) the controlled introduction of a certain amount of Q ₀ alumina into the electrolyte 13;

b) determining the value of indicator A of the amount Q of introduced alumina, which quickly dissolved in the electrolyte 13;

c) determining the amount ΔQ of introduced alumina that did not rapidly dissolve in the electrolyte 13;

d) regulation with at least one regulation means and / or at least one regulation operation and / or at least one intervention in the cell, depending on the obtained quantity ΔQ in such a way as to maintain it or bring it to a lower value than the reference value S.

The amount Q of alumina that quickly dissolves in the electrolyte (fast dissolution mode) corresponds to the fraction of alumina that dissolves during a period with a typical duration of the order of several seconds to several tens of seconds. The amount ΔQ of alumina that did not quickly dissolve in the electrolyte (slow dissolution mode) corresponds to the fraction of alumina that dissolves over a period with a typical duration of the order of several hours to several days. To simplify the control method according to the invention, it is possible to set a single time threshold T between fast and slow modes. According to such a simplified method, the amount of Q corresponds to the fraction of alumina that has dissolved over a period less than or equal to a specific time threshold T, and the amount ΔQ corresponds to the fraction of alumina that has dissolved over a longer period than threshold T. The time threshold T is usually from 100 to 1000 seconds.

The amount of ΔQ can be used as an indicator of the dissolution efficiency of the introduced alumina. This amount can be expressed in relative terms, for example:

ΔQ / Q ₀ or (Q ₀ -Q) / Q ₀ = Q / Q ₀ .

The amount of Q ₀ corresponds to the flow rate, which can be continuous or periodic. This amount can usually be expressed as doses per unit time, with the usual doses being on the order of 1 kg.

According to an advantageous embodiment of the invention, said indicator A is determined based on at least one electrical measurement carried out in the electrolyzer 1, which is capable of detecting changes in the electrical parameters of the electrolyte 13 caused by the fraction of the introduced alumina that has passed into the solution in the electrolyte. In particular, the indicator A can be determined based on the analysis of the voltage U and / or current I, measured (s) in the cell 1, possibly expressed as resistance R.

The voltage U is preferably measured between the collector 17 and the riser 16, mainly in the lower part 16a of this riser (as shown in figure 2), which allows, in particular, to limit the length of the wire 22 and facilitate access to the points 24, 25 voltage measurement.

Analysis of the voltage U and / or current I or, possibly, the resistance R can be carried out by processing the signal. Known signal processing methods can be used, for example, spectral analysis or time analysis (for example, decomposition into waves or wave packets, time-frequency analysis or synchronous analysis of several signals (possibly measured at several places in the cell). The signal can be processed in accordance with the data obtained from other sources, such as alumina input commands, in order to establish a correlation and possibly determine transient functions, which can also be processed by statistical methods. For example, voltage signals during its sharp increase caused by the introduction of doses of alumina can be analyzed by their shape by signal processing and by their number by statistical processing.

Index A can also be determined on the basis of an active electrical measurement, such as measuring the resistance of an electrolyte 13, which, under certain conditions, can be carried out by moving the anodes 7 with respect to the cathode elements 5, 6. For example, indicator A can be obtained based on the above change resistance ΔR _S , which can be determined using the measurement method, including:

- determining at least one first value I1 of said current I and at least one first value U1 of voltage drop U at the terminals of said electrolyzer 1;

- calculation of the first resistance R1 based on at least the indicated values of I1 and U1;

- the movement of the anode frame 10 by a certain distance ΔH from the initial position either up (ΔH in this case is positive) or down (ΔH in this case is negative);

- determining at least one second value I2 of said current I and at least one second value U2 of voltage drop U at the terminals of said electrolyzer 1;

- calculation of the second resistance R2 based on at least the indicated values of I2 and U2;

- calculation of the voltage change ΔR according to the formula ΔR = R2-R1;

- calculation of the indicated reduced change in resistance ΔR _S according to the formula ΔR _S = ΔR / ΔН.

Preferably, this measurement method further includes (at least after determining the values of I1, I2, U1 or U2) moving the anode frame 10 in order to bring it to its original position and return to the original regulation of the cell.

These first and second resistances R1 and R2 can be calculated by the formula R = (UU ₀ ) / I, where U ₀ is a constant value, usually from 1.6 to 2.0 volts. For example, R1 and R2 can be calculated using the formulas R1 = (UU ₀ ) / I1 and R2 = (UU ₀ ) / I2. In one embodiment of the invention, R1 and R2 can be obtained by calculating the average value based on a certain number of voltage values U and current I.

In practice, it turned out to be easier to give a command to move the anode frame 10 for a certain time and measure the resulting shift ΔH of the frame.

As shown in figure 3, the resistance R is usually measured using means 23 for measuring the current passing through the cell I and means 21, 22 for measuring the associated voltage drop U at the terminals of the cell (usually the associated voltage drop between the anode frame and the cathode elements of the cell ) The indicated resistance R is usually calculated by the formula R = (UU ₀ ) / I, where U ₀ is a constant value.

Such measurements of the reduced resistance ΔR _S can be carried out at regular intervals (for example, every 20 minutes) and processed statistically.

Typically, means 21 is a voltmeter, means 22 is a current conductor, for example, an electric cable or wire, and means 23 is an ammeter.

The determination of the specified indicator And by electrical measurement provides the advantage of cost-effectiveness and the possibility of its automation.

The applicant also came to the conclusion that the local nature of the alumina dissolution can be determined by separately measuring the electrical parameters of the electrolyzer, i.e. by performing electrical measurements in at least two different places in the cell. Typically, voltage measurements can be taken between different risers 16 and various cathode rods 6, preferably near the alumina feed points 19a (for example, near metering punches, if such an alumina feed method is used).

Said regulation, regulation operation and intervention in the cell may be short-term, medium-term or long-term actions.

Said control with at least one electrolytic cell control means typically includes at least one change in the amount of Q ₀ , i.e. flow rate when feeding alumina to the cell. For example, the amount of Q ₀ can be adjusted by changing the feed rate (i.e., changing the number of alumina doses administered per unit time) and / or by changing the dose administered (i.e., the amount of alumina contained in each dose). These types of regulation usually have a short-term effect.

The specified regulation may also include at least one change in the position of the anodes 7, for example, by moving the movable anode frame 10 either up or down so as to change the distance between the anodes 7 and the cathode elements 5, 6 or, more precisely, the interpolar the distance (MPR) of the anode / metal when the liquid metal forms a layer 12 below the anodes. Such regulation has a thermal nature and a medium-term effect.

Said at least one regulation operation includes, for example, introducing a certain amount of AlF ₃ into said electrolyte 13. This operation usually has a long-term effect.

The specified at least one intervention may include the rapid movement of the anodes 7 in order to change the conditions at the interface between the anodes and the electrolyte and / or eliminate gas bubbles that may be present below the surface of the anodes.

The reference value of S is usually very small, so that ΔQ tends to zero.

One or more anodes 7 may be carbon material anodes or non-consumable anodes. Non-consumable anodes may contain metallic material, coated material, or cermet (i.e., a ceramic-metal composite).

Test

The test was carried out in a prototype electrolysis bath equipped with anodes of carbon material with a current strength of about 480 kA. This bath was equipped with metering punches capable of punching alumina crust and introducing a certain dose of 1 kg of alumina into the hole formed as a result of such punching.

In the bath, the points 24, 25 for measuring the voltage between several anodes and several cathode rods were fixed, as schematically shown in figure 2.

The voltage was recorded during electrolysis for approximately 1 month. Temporary fluctuations of this voltage were of the order of 10 to 20 mV. Analysis of this signal by numerical processing showed voltage shifts from several mV to several tens of mV, which are associated with the introduction of doses of alumina with the help of metering punches (see Fig. 4, which shows an example of voltage U, measured as a function of time t). These shifts had an amplitude and shape, which are associated, at least in part, with the kinetics of the transition of alumina into solution. The applicant used these shifts as indicators of the amount of alumina that dissolved in the electrolyte.

1 - electrolyzer

2 - casing

3 - inner side wall

4, 4a - elements of the inner lining

5 - cathode element

6 - current collector or cathode rod

7 - anode

8 - anode-carrying means

9 - means carrying and fixing the anode, called rod anode holder

10 - anode frame

11 - alumina feed means

12 - a layer of liquid metal

13 - electrolyte

14 - the outer layer (or crust) of alumina

15 - layer of hardened electrolyte

16 - connecting element (riser)

16a - lower part of the riser

17 - connecting element (collector)

18 - connecting element

19 - metering punch

19a - alumina feed point

20 - electrolysis bath

21, 22 - voltage measuring instruments

23 - a means of measuring current

24, 25 - voltage measurement points

Claims (24)

1. The method of regulation of the electrolyzer (1) to produce aluminum by electrolytic reduction of alumina dissolved in an electrolyte (13) based on cryolite, said electrolyzer (1) containing an electrolysis bath (20), at least one anode (7), at least one cathode element (5, 6), wherein said bathtub (20) has inner side walls (3) and is capable of containing liquid electrolyte (13), and the cell also contains at least one means for regulating the cell and is configured to pass through an electric rolls an electrolysis current having a force I, comprising introducing alumina into said electrolyte and characterized in that it comprises: a) controlled introduction of a certain amount of Q ₀ alumina into the electrolyte; b) determining the value of the indicator A of the amount Q of alumina, which corresponds to the fraction of the introduced alumina dissolving in the electrolyte for a period less than or equal to a certain time threshold T; c) determining the amount ΔQ of alumina, which corresponds to the fraction of introduced alumina dissolving in the electrolyte for a period exceeding the time threshold T; d) regulation with at least one regulation means and / or at least one regulation operation and / or at least one intervention in the cell, depending on the obtained quantity ΔQ in such a way as to maintain it or bring it to more lower than the reference S. 2. The method according to claim 1, characterized in that said time threshold T is from 100 to 1000 s. 3. The method according to any one of claims 1 and 2, characterized in that the indicator A is determined based on at least one electrical measurement carried out in the electrolyzer (1), which is capable of detecting changes in the electrical parameters of the electrolyte (13) caused by the fraction of introduced alumina that has passed into the solution in the electrolyte. 4. The method according to claim 3, characterized in that the indicator A is determined based on an analysis of the voltage U and / or current I, measured in the electrolyzer (1), possibly expressed as resistance R. 5. The method according to claim 4, characterized in that the analysis is carried out by processing the signal. 6. The method according to claim 3, characterized in that the indicator A is determined based on the measurement of the resistance of the electrolyte (13), usually by moving the anodes relative to the specified at least one cathode element (5, 6). 7. The method according to claim 3, characterized in that to determine the local nature of the dissolution of alumina, one or more electrical measurements are carried out in at least two different places in the electrolyzer (1). 8. The method according to claim 1, characterized in that the indicator A is determined, in whole or in part, by sampling or using sensors, such as optical sensors. 9. The method according to claim 1, characterized in that the amount of Q is determined by calibrating indicator A. 10. The method according to claim 9, characterized in that the said calibration is usually carried out using modeling and / or statistical measurements carried out in electrolyzers of the same type operating under comparable conditions. 11. The method according to claim 1, characterized in that the amount ΔQ of alumina that has not dissolved in the electrolyte is determined by subtracting the amount of Q from Q ₀ , i.e. ΔQ = Q ₀ -Q. 12. The method according to claim 1, characterized in that said regulation includes at least one change in the amount of Q ₀ alumina introduced per unit time. 13. The method according to claim 1, characterized in that said regulation includes at least one change in position of said one or more anodes (7) to change the distance between said one or more anodes (7) and said one or more cathode elements (5, 6). 14. The method according to claim 1, characterized in that said at least one control operation comprises introducing a certain amount of AlF ₃ into the electrolyte (13). 15. The method according to claim 1, characterized in that the at least one intervention may include the rapid movement of the specified one or more anodes (7), capable of changing the conditions at the interface between the anodes and the electrolyte and / or eliminating gas bubbles possibly present under surface of the anodes. 16. The method according to claim 1, characterized in that the at least one anode (7) is selected among the anodes of carbon material and non-consumable anodes. 17. The method according to clause 16, wherein said non-consumable anodes are selected among metal anodes, coated anodes and metal-ceramic composite anodes. 18. The method according to claim 3, characterized in that the amount ΔQ of alumina that has not dissolved in the electrolyte is determined by subtracting the amount of Q from Q ₀ , i.e. ΔQ = Q ₀ -Q. 19. The method according to claim 3, characterized in that said regulation includes at least one change in the amount of Q ₀ alumina introduced per unit time. 20. The method according to claim 3, characterized in that said regulation includes at least one change in position of said one or more anodes (7) to change the distance between said one or more anodes (7) and said one or more cathode elements (5, 6). 21. The method according to claim 3, characterized in that said at least one control operation comprises introducing a certain amount of AlF ₃ into said electrolyte (13). 22. The method according to claim 3, characterized in that the at least one intervention may include the rapid movement of the specified one or more anodes (7), capable of changing the conditions at the interface between the anodes and the electrolyte and / or eliminating gas bubbles present beneath the surface of the anodes. 23. The method according to claim 3, characterized in that the at least one anode (7) is selected among the anodes of carbon material and non-consumable anodes. 24. The method according to claim 23, wherein said non-consumable anodes are selected among metal anodes, coated anodes, and anodes from a ceramic-metal composite.

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