SI8610950A8 - Arrangement for connecting electrolysis pots of high current for aluminium production including a supply circuit and an independent circuit for the correction of the magnetic field - Google Patents

Description

ALUMINUM ΡΕΟΗΙΝΕΥ

Device for connecting between high-current electrolytic cells for aluminum production, comprising a power supply line and an independent magnetic field correction line

SUBJECT MATTER OF THE INVENTION

The invention relates to a device for electrical connection between consecutive cells in a series for the production of aluminum by electrolysis of molten cryolite dissolved molten, by Hall-Heroult method and comprising an independent line for correcting undesirable effects of magnetic fields. It is used for arrays of cells spaced transversely to the axis of the array and operates at currents greater than 150,000 A, capable of reaching values from 500 to 600 kA, but this value does not form the limit of the scope of the invention.

TECHNICAL FIELD OF THE INVENTION

In order to fully understand the invention, it is first mentioned that aluminum is produced industrially by electrolysis of the melt in tubs which are electrically sequentially connected, by electrolysis of aluminum in molten cryolite heated to a temperature of the order of 950 to 1000 ° C by means of Joule currents flowing through the cell.

Each cell consists of a parallelepiped metal tub, which is thermally insulated and supports a cathode made from graphite blocks containing molten steel rods, called cathode rods, which serve to discharge current from the cathodes toward the anodes of the next cell. The anode system, also made of graphite, is attached to an anode pole called a support cross or height-adjustable anode frame and electrically connected to the cathode poles of the previous cell.

Between the anode and cathode systems is located an electrolysis tub, i.e. Aluminum solution in molten cryolite at a temperature of 930 to 96O ° C. The aluminum recovered is deposited on the cathode; the layer of liquid aluminum is permanently held at the bottom of the cathode melting tub.

The melting tub is rectangular and the anode frame supporting the anodes is generally parallel to the longer sides of the tub, while the cathode poles are parallel to the shorter sides of the tub, called the cell faces.

- 3 The cells are arranged in rows and placed longitudinally or today most often transversely, depending on whether their large side or small side is parallel to the axis of the array. The cells are electrically linked into groups, with the ends of the group bound to the outputs, positive and negative, the electrical rectifier and control substations. Each cell group comprises a set number of strings tied in series, with the number of strings being preferably paired to reduce the length of the conductors.

Electric current flowing through various conductive elements: anodes, electrolytes, liquid metals, cathodes, bonding conductors produces important magnetic fields. These fields cause Laplace forces in the electrolytic tub and in the liquid metal contained in the melting tub, which are detrimental to the well-functioning of the cell due to deformation of the molten metal surface and the currents that cause them. The implementation of cells and connecting conductors is considered to compensate for the effects of magnetic fields caused by different parts of the cell and connecting conductors.

There are numerous patents that address the arrangement of the cell's connecting lines to the next cell. In particular, patent application FR-A 2 505 368 may be described, describing connecting wires for cells operating at currents below 280 kA. PROBLEM STATEMENT

The practitioner has several embodiments of more or less complete elimination of the vertical component of the magnetic fields in the liquid metal and for symmetrizing and minimizing the circulation of the liquid metal and the liquid content in the melting furnace.

The more or complete nullification of the vertical component of the magnetic field is necessary for the following reasons:

The passage of electrical current through the supply conductors and through the conductive parts of the cell causes magnetic drink, which causes movements in the liquid contents of the tub and the metal and deformation of the boundary surface between the metal and the electrolytic tub. These movements of the metal acting on the contents of the electrolytic tub under the anodes may, when too large, shortly conclude this section of the tub by contacting the liquid metal with the anode. The electrolysis efficiency is greatly reduced and the energy consumption is increasing.

It is known to one skilled in the art that the shape of the interface between the metal and the tub and the fluxes of the liquid metal are closely dependent on the value of the vertical component of the magnetic field and the more or less complete symmetrization of the horizontal components; minimizing the value of the vertical component of the field permits the reduction of the height between the points lying in the metal layer at the highest and the lowest, and permits the reduction of the magnetic forces that (

cause disturbance _{in the fceJ layer>}

The possible asymmetry of the metal fluxes with respect to the large axis of the cell presents the following disadvantages.

1. Since mechanical erosion of the solidus cryolite by metal is directly related to the velocity of the metal currents, the asymmetry of these velocity currents would cause uneven erosion of the talus from two large sides of the cell.

2. The exchange of heat between the metal and the talus of solidified cryolite is directly related to the rates of circulation of the metal: the asymmetry of these circulation rates would result in diverse heat exchanges on two large sides into the cells and would result in a difference in the shape of the talus between one and the other large sides, it would be disadvantageous to use the cell.

The larger the currents in the cells and the larger their dimensions, the more complex the formation of the connecting conductors, as the sensitivity of the metal layer to magnetic fields with the dimensions of the layers increases. In general, a larger or smaller portion of the current coming from the top of the cell is discharged to the next cell after encircling the cell's forehead _/ and extends the current path as much as the cell's dimensions are large.

On the other hand, the influence of the magnetic fields generated in the adjacent array cannot be ignored and any asymmetry in the structure or in the compensation loops must be added to the circuit to compensate for these effects of the adjacent array.

It is found that for flows above 350,000 A, it is not easy to design tubs that are economically comparable to tubs for flows between 250,000 and 300,000 A because the investment savings made due to the tub dimension are completely nullified by the increase in cost due to the circuit of conductors that it is lengthening and its complexity is growing faster _; as the size of the cells increases.

In addition to being able to arrange conductors with complex shapes and large dimensions between cells, they must be spaced apart, which further extends the electrical conductors and increases the surface area of the building to be constructed to protect the cells. One might think of simplifying the circuit by allowing some instability of the metal layer: i.e. should be ruled out because losses in the utilization of electrolysis current (typically between 93 and 97%) would increase operating costs to such an extent that the metal obtained would not be economically competitive.

The problem, then, is how to design the circuit of the link knows between the strong cells for e.g. 500 and 600 kA, subject to the following three conditions:

- minimum construction and installation costs for circuits,

- as little space as possible for groups of cells using these circuits,

- as much magnetic stability as possible, that is, Faraday's maximum efficiency taking into account the effects of the adjacent array.

STATUS OF THE INVENTION

We have previously described devices for compensating for magnetic influences originating from conductors arranged along a group or groups and flowing only a small fraction of the electrolytic current, which are covered by US patents 3,616,317 (ALCAN Applicant) and US 4 169 034 corresponding to FR 2 425 482,

- 7 Applicants ALUMINUM ΡΕΟΗΙΝΕΥ. However, in one and the other case, it is solely to compensate for the influence of the adjacent set, that is, essentially a vertical magnetic field and a constant sign over the entire surface of the cell, which is clearly evident in the description and claims of the aforementioned patents, and the process is applied to groups whose connection guides, from. cells to cells are designed to ensure normal operation if no adjacent string is present _? oz. the correction due to the adjacent string appears only marginally. The maximum current strength in the compensation conductors does not exceed 25% of the total group J current according to US patent 3 616 317 and 17% of the total J current according to US patent 4 196 034.

With respect to the object relating to the compensation circuits, we see that they are designed to produce a compensating magnetic field that maintains a constant sign throughout the cell, with the sign opposite that of a vertical field caused by an adjacent array of cells.

DESCRIPTION OF THE INVENTION

The subject of the invention is a connection device, that is, the arrangement of conductors that allow the well-functioning of electrolytic cells, distributed averages and for currents greater than 150,000 A to 500,000 or. 600,000 A with a current efficiency of between 93 and 97%, all of which greatly reduce the weight of the interconnectors between the cells? we and the distance between them.

It is also a device that allows standardization of circuits and simplification of their construction in order to reduce the cost of their manufacture.

Finally, it is a device that allows the magnetic fields to be compensated for by adjacent arrays at no great additional cost.

The following description will therefore distinguish two types of guides:

- conductors that connect the cell to the cell and can be compared with those of the state of the art and that provide the electrical current required for electrolysis,

- Independent conductors for leveling magnetic fields.

The inner side will be called the side of the electrolysis cell, directed toward the symmetry axis of the set of cells. The outer side will therefore be the second side of the cell.

The right side of the cell is called the small side of the cell, which is positioned to the right of the observer, standing in the axis of the array of cells and looking in the direction of the current flowing through that set of cells.

We will call the left forehead of the cell the second small side of the cell.

When designing a new electrolysis cell for very high currents in excess of 350 kA $, it may be tempting to use the same procedures as for cells intended for 200 to 300 kA currents, which are used today, that is, to design connecting lines from the cell from a cell such that the magnetic fields produced by the entire circuit of each cell are offset by each other such that the resulting magnetic field B should have, on average, throughout the cell the following characteristics:

- mean square value of the vertical component B 10 T,

- horizontal component Β _χ antisymmetric with respect to the transverse axis of the cell (small axis),

- keep the horizontal component B as close as possible on average

J antisymmeters with respect to the longitudinal axis of the cell (large axis).

(Antisymmetry exists when the two considered quantities are of the same value but of the opposite sign).

The present invention is based on two ideas that are completely different from the state of the art and which distinguish two functions, the transport of electrolysis current, which will try to keep as simple and direct as possible, and the alignment of magnetic fields, which will be provided by independent guides.

In order to provide the first function, the

a) first design the cell-to-cell connecting conductors that carry the electrolytic current by selecting a path as close as possible to the direct connection in order to reduce the weight of the immobilized aluminum and the distance between the cells (that is, the total surface occupied by it) type or cell types) without magnifying the magnetic effects too much.

b) Designed as one or. several groups of modules that are essentially identical and will connect each group of cathodic collectors of cells of order n in series with each anode riser of cell of order n + 1 in a series, which is achieved by standardizing the construction and first installing the conductors.

This new design of short-circuited conductors is generally expressed in cells with very high currents in a very unfavorable distribution of magnetic fields, which is very incompatible with the normal operation of electrolytic cells. In fact, the vertical magnetic field induced by conductors running directly from cell to cell is very positive on average above the left half of the cell and very negative on average above the right half of the cell (see Fig. 2). As another idea of the invention, which is to repair it, is used. unfavorable magnetic field distributions, a group of independent balancing conductors that are arranged along the string or strings and each side of the string in question and have the following characteristics:

a) the compensating current circulates in the same sense as the electrolytic current across a series of cells, giving rise to a very negative correction field in the left half of the cell and a very positive field in the right half of the cell.

b) Their implementation is very simplified, since they cover practically only straight sections of aluminum bars (excluding direction changes at the ends of the strings).

c) The energy consumption in them is very low since the voltage drop is small if the sum of the currents flowing through the independent conductors is at most J ₁ and may lie between 5 and 80% and preferably between 20 and 70% of the current flowing through to the group, relatively high, and the voltage drop is largely compensated by the voltage gain that comes from the direct conduct of the connecting leads.

d) The overall weight of conductors that conduct electrolysis currents on the one hand and magnetic field correction currents on the other hand is generally much lower, between 5 and 15% and even up to 25% (for currents near 500 kA), relative to the required weight when using a single magnetic self-compensating circuit. However, such independent conductors are still of interest to smaller cells, for example. current J of order of magnitude below 180 to 280 kA, since the modular and simplified design of circuits, if in this case brings little or no savings in cell-to-cell conductors, still saves on fabrication and installation costs, and on the building surface required, to protect the cells.

e) These independent correction conductors simultaneously allow for the favorable configuration of the magnetic field in each cell and at the same time compensate for the effects of adjacent arrays by the asymmetry of currents flowing through the internal and external correction conductors, without significant additional costs, both in investment and operating costs.

More specifically, the present invention is a device for electrical connection between two consecutive cells in a group intended for the production of aluminum by electrolysis of aluminum dissolved in molten Hall-Heroultovere cryolite at currents equal to at least 150 kA and capable of reaching 500 to 600 kA wherein there is every cell made of a metal, parallelepiped, heat-shielded tub, whose large axis is perpendicular to the axis of the string and whose ends are called foreheads, and such a tub carries a cathode formed of graphite blocks placed side by side and in which metal rods are embedded the ends of which extend into the tub, generally on two long sides, up and down (depending on the direction of flow in the string), each cell comprising, inter alia, an anode system formed by at least one rigid horizontal support supporting at least one or most frequently two horizontal conductive rods, called the anode frame, to which the anode hanging rods are attached, wherein the connecting circuit comprises in particular a circuit for conducting electrolytic current between successive cells, consisting of cathode collectors, which are connected, on the one hand, to cathodic outputs of cells of order n and, on the other, to connecting leads, which are connected via risers to the anode frame of a cell of order n +1 in a series; according to the invention, this coupling device comprises, inter alia, an independent circuit for the correction and alignment of magnetic fields, comprising conductors substantially parallel to the axis of the array and flowing a constant current in the same direction as the electrolysis current, and causing a vertical correction magnetic field in cells which is pointing downwards at the left forehead and pointing upwards at the right forehead, the terms left and right being determined by the observer standing on the axis of a series of cells and looking in the direction of the electrolytic current.

The total current Jg running down the magnetic correction circuit is at most equal to the electrolytic current J ^.

The term 'independent' circuits is intended to emphasize that these circuits run along different paths and perform different functions, which does not exclude that they may be powered by the same DC power source or by two branches of the same source.

The electrolysis current supply circuit contains:

- upstream cathodic outputs of cell n in order to be connected to upstream cathode reservoirs, which are connected by the shortest and direct path to the first section of the risers supplying the anode frame of cell n + 1 in the series by means of conductors, the largest portion of which passes below said cell n ;

- the downstream cathode outputs of a cell of order n are connected to downstream cathode reservoirs, which are directly connected to another section of the respective risers;

- circuits for correction and magnetic field alignment consisting of two groups of magnetic field correction conductors, consisting of independent connecting conductors located on one and the other side of a series of cells parallel to the axis of the array and supplied with the entire current flowing in the same direction as the current Jp which it feeds the string and has the total strength J? at most equal to and generally between 5 and 80% and preferably between 20 and 70% J ₁ .

DESCRIPTION OF THE IMAGES

1 to 9 show an embodiment of the invention: FIG. 1 shows the nomenclature used in the description.

The axis ΧΟΧ is the axis of the string; it also indicates the direction of the current and is the small axis of the type, while the large ΥΟΥ is the large axis. The Oz axis represents the vertical axis of Figs. 2 shows the vertical components of the magnetic field above the cell before and after the proofreading of the invention; 3 is a very schematic representation of the general flow of power and correction conductors of FIG. 4 is a schematic, upwards and downwards view of the connection module, FIG. 5 is a schematic view of the arrangement of correction conductors in a series of cells comprising two parallel arrays A and B; FIG. 6 is an isometric view of the upstream and downstream connectors; module between two consecutive cells of a string. Only power leads are drawn. The cathode outputs are shown schematically, FIG. 7 and 8 schematically show the real arrangement of connecting and proofing conductors in a high power series (e.g. 480 kA, Fig. 7 is simplified by reducing the cell to 9 anodes), since it is simply intended to show the position of the conductors (9) (below the cell) and the position of the field correction guides (17) (22), FIG. 8 also shows a display module between two cells, FIG. 9 shows an embodiment of the invention on a single cell row for 280 kA.

In FIG. 3 is a representation of two consecutive cells in a row limited to the circumference of 1 metal tub.

Cathode outputs such as outputs 2, indicated by thick lines, are coupled to upstream cathode reservoirs, such as reservoirs 3, and downstream cathode outputs such as outputs 4 are coupled to downstream cathode reservoirs, such as cathode reservoirs 5.

On a cell of this kind that is e.g. designed for 480 kA, there is a group of 32 upstream cathode outputs, 32 downstream cathode outputs, and two parallel 32 anode lines supported by bars represented by crosses 6 in the down half of the cell. These cathode bars are attached to the anode frame, which consists of two elements 7A and 7B, which are connected to the equipotential bars 7C.

An electrical connection between the cathode collectors of a cell of order n and the anode frame of a cell of order n + 1 is provided by the risers 8; here are eight.

Each riser 8 is doubled. It comprises branch 8A directly connected to the downstream cathode collector 5 and branch 8B connected to the upstream cathode reservoir 3 with at least one connecting rod 9 extending below the cell, following the shortest path. It should be emphasized that in high-current electrolysis, the term shortest link does not necessarily have to be the same as the straight line, because of the dimensions of the conductor (an aluminum rod that conducts a current of 100 kA generally has a cross-section of the order of 3000 cm and can occupy a value of 6000 cm ² , if it goes into a long circuit flowing from the upstream cathodic outputs of cell n to the anode frame following (n + 1) and containing large curvature radii, also to occupy the space under the cells (metal masses, tub reinforcement ribs, tub supports) , which results in the separation of the large rod into two or more parallel bars and due to the requirement for electrical insulation, since the tension between the conductors and the metal masses can reach a value of some 100 volts, the shortest path being the shortest path that meets the above requirements.

In this case, there are two connecting rods 9 for supplying each nearby conductor 8A, each rod 9 being connected to the twin-top cathode outputs 2 via a collector 3 · Apart from achieving as little conductor weight as possible at a prescribed voltage drop, this mounting has the advantage that is suitable for modular construction.

If one of these modules 14 is selected (Fig. 6), it is found that it consists of an assembly

- four downstream cathode outputs 4 of cell n (schematized not to blur the image),

- the downstream cathode collector 5 and the corresponding riser 8a leading to the anode frame 7 A of cell n + 1,

- a connecting conductor 13, which is connected, on the one hand, to the rods 9 extending below cell n and, on the other, to the other half-cell 8B,

- two elements of the upstream cathode collector (3, 3 ') of the n + 1 cell, each connected to two upstream cathode outputs 2 of the n + 1 cell, shown schematically, and to a bar 9 running below the n + 1 cell,

- any contact clades 12 that serve to temporarily disconnect the cell.

The connecting rods 9 running under the tub 1 do not form part of the module. Their position can actually vary from module to module, so that the magnetic field distribution is adjusted to the most favorable configuration. In addition, it will be found that the modules 14 that are mounted on one half of the cell are generally symmetrical, but not identical to the modules that are located on the other half of the cell (relative to the 0x axis).

Does this arrangement of conductors, as we will describe it, give an image of a magnetic field that is completely unacceptable in the currents under consideration _? link compatible with stable cell operation. As an example, for a cell of 480 kA performed according to this scheme, a maximum B of 120.10 " ⁴ T (120 gauss) can be obtained.

The magnetic field correction and offsetting is limited to the independent leveling line schematically shown in FIG. 3 and 5, where the arrows represent the direction of flow in the arrays of de18 cells and in the balancing circuit. FIG. 2 shows the arrangement of the vertical components of the magnetic field along the large axis of the cell before and after the correction by means of the balancing circuit of the invention: B _y values without correction are such that any normal operation of the cells would be impossible. We emphasize that these are the values at the interface between the electrolysis tub and the metal and in the vertical plane containing the large axis of the cell.

In FIG. 5 shows an example of a row consisting of two parallel arrays A and B and comprising a number of cells that can be arbitrary (e.g., 100 cells). These cells are symbolized by a simple rectangle 11. The parallel axes X1, X1 and X2, X2 are positioned within a distance of 100 meters.

The cell connections are made according to the schemes of FIG. 3, 4 and 6.

According to the invention, they are arranged along the cells on one or the other side of a series of groups of correction independent conductors, which are different from the interconnecting conductors between the cells, this group being located substantially at the level of the liquid aluminum layer and at a small distance from the outer side walls of the cells ( order of magnitude of 0.5 to 2 m, for example) and flows along each conductor or bundle of collected conductors in the same direction as the current in the group.

The first correction guide 16 comprises a first section 17 on the outside of type A and a downstream stream flowing there in the same direction as the current ^ supplying that type A, then a connecting section 18 extending around the front of the row and an empty space between rows A and B, then section 19 on the inside of type B, the current following that section 19 being in the same direction as the current supplying the type.

The second correction guide 21 comprises a first branch 22 extending along the exterior and type A, then a connecting section 23 extending around the gap between types A and B, and a section 24 extending along the interior of this type B, currents on sections 17 and 22 on the one hand, and on 19 and 24 on the other side in the same direction as the current supplying the corresponding string.

The regulation of the entire J ₂ current through the correction conductors 16 and 21 is achieved in such a way that the magnetic field image is restored to ensure normal operation, stability and optimum utilization of all cells of the species. This current is at most equal to the current and is normally between 5% and reaches up to 80% of the total current J p that supplies the actual species, preferably between 20 and 70% of J ₁ .

E.g. in the case of a power supply = 480 kA, the correction current may be limited to between 100 and 150 kA in each branch of the external and internal correction circuits; the value of the current J ₂ equals 2x 135 kA, which is generally close to the optimum value for each type, where the influence of the adjacent string does not have to be taken into account and a correction conductor is installed

1.5 m from the outer wall of the metal tub of the cell. This is only an order of magnitude, and the exact optimum value depends on the position with respect to the tub and the level of the intermediate surface of the tubing of independent proofing conductors.

In the case of several arrays (at least two), one skilled in the art knows that the effect of the adjacent array, that is, the input magnetic field on the array by the adjacent array or adjacent arrays, must be taken into account, and the magnetic effects occurring in each cell from the current that running through it.

The present invention also makes it possible to compensate for the effect of a neighboring string. For this purpose, the current is distributed in each group of external and internal correction conductors 21, 16, arranged in a manner different from that which would provide magnetic equilibrium in the absence of an adjacent ³ string: thus, in two groups A and B, whose axes are spaced 130 m apart, the current J decreases from 135 to 120 kA in the external correction conductor 16 and increases from 135 to 150 kA in the correction conductor 21, leaving the total current J? equals 270 kA, which is 56% of current.

If the distance between the eight arrays is reduced to 65 m, the current is reduced to 105 kA in 16 and increased to 180 kA in 21, with the total current J ₂ increasing only by 15 kA to be 285 kA, which is 60% of the current ^J 1 '

There are resources to bring different sets or types together in one place without having to worry about their global stability, and the resulting reduction in the occupied area has many benefits: reducing investment (land acquisition, building area, to be erected), lengths of conductors and sewers of all kinds, and reduction of routes of movement of operators, raw materials, and finished products, and the like.

Finally, it should be borne in mind that the compensation of the effect of the adjacent string by the asymmetry in the currents along the correction conductors, as just described, can also be achieved or improved by other known approaches, in particular by moving the upstream and downstream connecting rods running below the cell and by varying the flow across these different bars. This latter method can be used as an exclusive method to compensate for the effect of the adjacent string or complementary to the method according to the invention by means of asymmetry of the current strength according to the correction conductors.

EXECUTIVE EXAMPLE

EXAMPLE 1

The invention was used in a small experimental row of electrolysis cells disposed transversely to the axis of the species and at 480 kA. The arrangement of the connecting leads between the cells is in accordance with the arrangement in FIG. 3 and 4, each of the lifting conductors 8 (8A, 8B) transmitting a current of 60 kA.

The upper cathode outputs 2 and the downstream cathode outputs 4 are 32 + 32. On the upper large side, two cathode outputs 2 adjacent to each other are connected to a reservoir 3 which is connected to a bar 9 passing below the cell.

In all, there are 16 rods 9 running below the cell, each transmitting a current of 15 kA. On the upside, each group of two rods 9 adjacent to each other is connected to a connecting line 13 that connects to the half lift line 8A.

On the large lower side, the four cathode outputs 4 are coupled to a downstream cathode collector 5, which thus collects 30 kA and supplies the half riser 8B corresponding to it.

The distance between the bars 9 running below the cell may be modified according to whether they correspond to the cathode outputs located in the middle of the cell or close to the forehead, that is, depending on their distance from the small axis of the cell, so as to improve magnetic field image, while taking the shortest path as defined elsewhere. In general, the distance between the bars 9 lying near the front of the cell is smaller than the distance between the bars 9 lying near the center of the cell. These bars 9 can also be spaced evenly.

In the absence of all correction lines (any normal cell operation is therefore impossible), the values of the magnetic field components are estimated by a very reliable computational procedure:

B (maximum value): 69.10 T Z

B (root mean square): 35.10 T

B ^ (root of root mean square up minus root of root mean square down): 2,6.10 ^-4 T.

(The following measurements were made during the operation of the group and when the internal and external correction leads were each supplied with a current of 135 kA and these lines were spaced approximately 1.5 m

- 23 from the outer wall of the metal tub of the cell and the current through both lines was equal to the electrolytic current supplying the group (hence the total corrective current J ₂ = 270 kA, corresponding to 56% of the current jp:

B (maximum value): 14.1O ^-4 T

With _n

B (root mean square): 5.10 T

Z

B _y (root-mean-square root minus root-mean-square root): 1.10 “ ³ T

Finally, with a bundle of conductors laid parallel to the 0X axis _{with a} simulated adjacent array, the axes of the real and simulated groups are spaced 65 m apart.

In order to compensate for the effects of this adjacent simulated string, the correction line 16 positioned on the side opposite the simulated adjacent string is 105 kA and the correction line 21 positioned on the side facing the simulated adjacent line is 180 kA. therefore, the total corrective current J was ₂ 285 kA (60% of the current jp.

Measurements of the magnetic field components yielded the following results:

B (maximum value): 23.10 * ⁴ TZ

2 |

B (root mean square) 5,3.10 * T

B _y (root of root mean square upside minus root of root mean square face down: 6.9.10 ^-4 T.

- 24 The experimental group, with or without a compensated simulated adjacent set, showed complete stability of the liquid aluminum layer, absence of any asymmetric talus erosion, and Faraday efficiency between 93 and 97%.

Finally, depending on the classic solution without correction lines, the weight savings of the conduit group per 14000 kg of aluminum per cell can be estimated, with the group operating at 480 kA. Added to this is a 350mm saving in wheelbase, a saving of 84m in building length for the entire 240-cell group.

The embodiment according to the invention thus opens the way to a new generation of electrolytic cells with a current strength that can reach and exceed 500 kA with considerable stability and a Faraday at least equal to that of previous generations of 250-300 kA.

EXAMPLE 2

In order to prove that the invention is not limited to high power electrolytic cells of the order of 500 kA, the invention was also applied to cells operating below 280 kA. As explained above, the use of an independent correction line and the concept of cell-to-cell modular conduit also leads to considerable cost savings for operation, installation and occupied surface of the building.

FIG. 9 represents two consecutive half cells in a row operating at 280 kA with 5 modular risers 8, each translating a current of 56 kA from cell n toward the anode frame of cell n + 1 in row.

Each independent correction conductor 17, 27 is fed with 90 kA current when there is no adjacent array, with this current flowing in the same direction as the stream feeding the species and causing electrolysis, so the total correction current is 180 kA, ie 64% stream J,.

The following values were measured during normal operation at 280 kA, with two condensation lines each supplied with 90 kA:

B_ (maximum value): 18.10 T z

B (root-mean-square): 4,6.10 “^ T

Z

By (root of root mean square up minus root of root mean square down): -4

2.10 ⁴ T

Then, a neighboring string was simulated in a known manner at a distance of 65 m from the considered array, and the magnetic interference from that string was compensated by increasing the compensation current in the internal independent conductor 27, lying sideways to the adjacent array, to 90 to 120 kA and reduced current through an external independent conductor lying side-by-side facing away from the adjacent array at 90 to 75 kA (Figure 5). The total corrective current thus reached 195 kA, ie 70% of the current

The following values were measured:

B (maximum value): 22.10

B (root mean square): 4.9.10 Z

By (root of root mean square, minus root of root mean square): 2.10 ^H

The cells thus fed showed very stable performance and Faraday efficiency between 93 and 95%.

For cells with 280 kA, the weight savings of the conductors are insignificant, but the savings are 270 mm with a wheelbase of about 64 m on the length of the building for one full row of 240 cells.

Claims (14)

1. An electrical connection device between two consecutive cells of a species for the production of aluminum by electrolysis of molten crystallized molten crystalline metal, according to the Hall Heroult method, with a current strength of at least 150 kA and a maximum of 500 to 600 kA, each cell consisting of heat shielded parallelepiped metal tubs, of which: the large axis is perpendicular to the axis of the species and its two ends are called foreheads and supports a cathode formed by assembling graphite blocks side by side and embedded metal rods whose ends extend into the tub in. generally on two large sides, up and down (depending on the direction of current in a row), and each cell includes, inter alia, an anode system made with at least one rigid horizontal support supporting at least one and most commonly two conductive horizontal bars called an anode frame to which anode suspension rods are attached, and this connecting circuit specifically comprises an electrolytic conductor circuit of the current flow between two consecutive cells, existing from cathodic reservoirs, bound on the one hand to the cathodic outputs of cells of order n and, on the other, to the connecting conductors, which are connected through the risers to the anode frame of a cell of order n + 1 in a row, characterized by that this coupling device comprises, in addition to the electrolysis current conduction circuit, a separate correction circuit and magnetic field alignment derived from conductors substantially parallel to the axis of the species and flowing in the same direction as the electrolytic current in the cells causes a vertical correction magnetic field pointing down near the left forehead and pointing up near the right forehead. An electrical connection device according to claim 1, characterized in that the total current J ₂ flowing through the magnetic correction circuit is at most equal to the electrolytic current Jp Connection device according to claim 1, characterized in that the current lies between 5 and 80% of the current J ^. Connection device according to claim 1, characterized in that the current Jg lies between 20 and 70% of the current J ^. Connection device according to claim 1, characterized in that they are in the electrolytic current supply circuit - the upper cathode outputs of a cell of order n are connected to the upper cathode reservoirs (3), which are directly connected by means of conductors (9), a large portion of which runs below said cell n, to the first part (half riser) 8A) of the risers (8 ) that supply the anode frame of a cell of order n + 1 of the species; - upstream cathode outputs (4) of cells of order n bound to downstream cathode reservoirs (5) that are directly connected to the second section (half riser 8B) of the risers (8). Connection device according to claim 1, characterized in that they are in the supply circuit - on the large upper side, two adjacent cathode outlets (2) connected by means of a collector (3) which is connected to a rod (9), - 29 running under the cell; - each group of rods (9) lying side by side is connected upstream to a connecting cable (13) which is connected to a half riser (8a); - on the large downward side, four adjacent cathode outputs (3) are connected to the downstream cathode reservoir (5), which itself is connected to another suitable half riser (8B). Connection device according to claims 5 or 6, characterized in that the connecting rods (9) are arranged under the tub at equal distances. Connection device according to claim 5 or 6, characterized in that the distance between the connecting rods (9) is varied depending on their position relative to the small axis of the cell. Connection device according to claims 5 or 6, characterized in that the distance between the connecting rods located on the front sides of the cell is less than the distance between the connecting rods located in the middle of the cell. Connection device according to claim 1, characterized in that the circuit for correction and magnetic field alignment consists of two groups of correction lines (17, 22), which are independent of the supply lines and located on one and the other side of a series of cells, and are powered by the entire current Jg flowing in the same direction as the current Jp supplying the array, with current J? at most equal to the flow. Connection device according to claim 1, characterized in that in the case where the row comprises at least two sets of cells arranged in parallel, the compensating conductor or group of compensating conductors is arranged along the side of the adjacent array and flowing therewith with a current , which is greater than the strength of the current flowing along the compensation conductor located along the side facing away from the adjacent string. Connection device according to claim 1, characterized in that the compensation conductors are located at a short distance from the metal tub of cells and, in essence, at the height of the molten aluminum metal layer. Connection device according to claim 1, characterized in that it is part of an independent supply circuit providing a connection between the cathode outputs (2, 4) of the row cell with the anode frame (7) of the row cell (n + 1) in a series, made in the form of modules (14) substantially identical to each other and each belonging to one lifting line (8). Connecting device according to claim 13, characterized in that each module (14) consists of: - four downstream cathode outputs (4) of cell n, - the downstream cathode collector (5) and the half riser (8A) extending towards the anode frame (7A) of the n + 1 cell, - a connecting line (13), which is connected, on the one hand, to two slippers (9) running below cell n and, on the other, to a half-lifting conductor (8B), - 3Υ two upstream elements of the cathode collector (3, 3 '), each connected to two upstream cathode outputs, face n + 1.