SI7810093A8 - Device for supplying electric current to cells for the electrolysis - Google Patents

Description

FIELD OF THE INVENTION

The invention belongs to the colored area? metallurgy, that is, more precisely, in the field of aluminum production technology for alumina AljO ^ alumina, the main raw material for aluminum production, dissolved in the electrolytic cell in molten hot cryolite AlF ^. A direct current, which flows through the series' of these cells, maintains the electrolyte in a molten hot state, and separates the aluminum metal at the cathode of each cell. The amounts of aluminum extracted are commensurate with the intensity of the current flowing through the electrolytic cells, electrically bonded to the line, which is why very high currents of the order of 350,000 amperes or more are used. The device according to the present invention relates to the improvement of the electrolytic cell current supply, ordered by its length, which increases the effect.

Technical problem

It is known that these cells are almost always rectangular in shape and are electrically bound to the row. 0 halls, cells can otherwise be positioned transversely ”, ie. so that the soul of each cell is perpendicular to the axis of the string, either in length, ie. so that the long side of each cell is parallel to the axis of the string.

Figures 1, 2 and 3 show, respectively, a vertical cross-section, a vertical longitudinal cross-section and a straight-line layout, in heavily schematized form, of electrolysis cells, which form part of a series of cells arranged in length. Typically, to distinguish the forehead of a cell, it is referred to as “upstream and downstream relative to the direction of motion of an electric current through a series of cells.

Each cell consists of a single metal crate (1), lined on the inside by a refractory lining and carbon blocks (2), which form the cathode. The metal rods (3) embedded in the carbon blocks collect the electric atrium emerging from the cells and lead it to the collecting conductor (4), which leads the current through the riser (5) to the next cell, to the conductors (6) that form the crossbar for which is the suspended anode (7). The electrolyte bath is located in (8), and a layer of liquid aluminum is formed on the cathode (2) and (9).

With this arrangement, which is completely classic, the cathodic drains of each cell feed the next downstream cell through its upstream face. It is known, after all, that the cost of the genus of cells decreases relatively significantly with the increase in the dimensions of the cells, and it is common to work with intensities of electrical current, which reach and exceed 100,000 amps.

At such current intensities, the influence of the magnetic field, which is acquired by flowing current into conductors, can no longer be neglected.

Laplace's electromagnetic forces. cause in the electrolysis bath the hydrostatic deformation of the boundary surface between the bath and the metal and the hydrodynamic displacement of the aluminum metal, which cause it to move constantly and encourage its dispersion in the bath, causing the effect to decline. They also cause significant denervation of the layer of liquid aluminum in the bath, which again leads to short circuits with the anodes, uneven wear of the anodes, and oscillatory movements of the liquid aluminum, which can be so large, that the liquid metal is ejected from the cell. Overcoming these phenomena and preventing their effect is the subject of constant preoccupation with manufacturers, and for this purpose a large number of solutions have been proposed so far.

The state of the art

German patent no. 1010 744 of Vereinigte Aluminum Werke AG describes a device for improving the power supply of electrolysis cells, arranged in lengths, into pylons, to supply the said cells with electricity either through its upstream and downstream forehead, or through its upstream forehead and one side but both these circuits (upstream face - downstream face or upstream face - lateral ascent line) are connected by an equipotential conductor, which has the inconvenient side of making it significantly difficult for the conductors, and thus requires accurate determination of their intersection in order to provided a convenient current distribution.

In French patent No 1 14? 879 companies

Compagnie Pechiney, describes a device for reducing uneven surfaces of molten metal in high-amp electrolysis cells, especially in series of long-ordered cells equipped with continuous anodes (anodes called “Soederberg).

This device is based on the analysis of various components of the magnetic field induced by the passage of direct current through electrolysis cells and through connecting wires.

for this purpose, considering the central point O at the bottom of the electrolysis vessel, we define a rectangular coordinate system with three dimensions; the horizontal axis 0x is directed in the direction of the current, parallel to the large sides of the cell, the axis 0y in the same horizontal plane, normal to 0x, therefore parallel to the small sides of the cell, and the axis Oz is vertical, directed upwards, therefore normal to the plane xCy, so -that three-charm Oxyz is a croissant.

Denote by B the value of the magnetic field in a given calculus, and by Bx, By, and Bz the projections of B on the axes Ox, Oy, and Oz. Denote by J the intensity value of the current for electrolysis, and by Jx, Jy, and Jz the projections of J on the axis 0x, 0y, and Oz.

The device, which is the subject of French patent No. 1 143 879 consists of towers, to cancel the magnetic effects at point 0. These effects exist on the spacious part of the cell, but they are relatively small, and their value shows a certain symmetry. with respect to point 0, which provides sufficient stability in the operation of the cell. In order to obtain such a result, it has been proved that at point 0 the following conditions should be created;

By = 0 dBy = 0 dz

Figures 4 and 5 show in vertical longitudinal and

39833 'to the horizontal section of two cells as part of a series of cells arranged in length, operating at 70,000 amperes, and in which the conductors are arranged according to French Pat. 1 143 879, so that the two conditions By O and dBy - 0 are satisfied at point 0.

dz

The outputs of the cathodes, 22 of them (11 for each strand of the cell, these figures were determined considering the current density in the conductors, which is known to one skilled in the art) were divided into two groups of cd 8 and 3 bars. Said first groups of eight bars (3) on the upstream side of the cell are connected to conductors (4) that feed the upstream face of the next cell by means of a riser (5), while two groups of three bars (3 ') on the downstream are mentioned. the side of the cell connected to the conductors (4'J supplying the downstream foreheads of the next cell with the aid of the riser (5 ').

While the arrangement according to Figures 1, 2 and 3 hardly allowed it to exceed the current intensity of 50,000 amperes, the arrangement according to the heights 4 and 5 made it possible to achieve a stable and proper operation with a current effect of between 70,000 amps at a current of 86 and 87%.

However, this arrangement has proved to be impermissible at current intensities of over ICO.000 amperes, and even at lower intensities, such an arrangement leaves the magnetic field in place, which does not allow the current output of about 87% to be exceeded, which the aluminum producers today they consider it insufficient.

Cpis solution to a technical problem

The present invention, which will now be described, relates to an apparatus for improving the electrical power supply of a series of electrolytic cells for the production of aluminum, in length, in which the present invention enables a significant increase in the current efficiency at the same electrolysis intensity. The present invention also enables, with some modifications, the conversion of a series of continuous anode cells into a series of pre-baked anode cells, and a reciprocal increase in the intensity of the electrolysis current, thereby producing aluminum by almost 30%, without the diameter of the cell dimensions, enabling electrical energy utilization of at least 88% due to better compensation for the effect of the induced magnetic fields and the resulting Laplace forces.

The invention consists of towers, to separate the cathode outputs from each Side cell in at least two groups, approximately equal in number of conductors, and to supply the anode crossbar of the next cell independently simultaneously through the upstream face and at least one lateral riser from each side. the wound cell, connected to one midpoint of the crossbar between the upstream head and the downstream head, and the conductors connecting each group of cathode bars to the upstream head at the midpoint of the crossbar by means of lateral risers are so independent that each section is calculated such that the circuit conveys approximately equal parts of the total electrolysis current.

According to one particular embodiment of the invention, the cathode bars on each side cell of order n are divided into two independent groups, having approximately the same number of bars. The upstream group feeds the upstream face of the n + 1 transverse cell, and the downstream group supplies, through one lateral ascending line, on each side of the cell, one connector approximately located in the middle of the anode crossbar.

According to another particular embodiment of the invention, which is particularly suitable for very high intensity arrays, for example 150,000 amps and even more, the cathode bars on each side cell of order n are divided into three independent groups, the upstream group feeding the upstream anode face of the next cell of order n + 1 ”, the central group supplying the first lateral riser on each side of the cell, positioned approximately at the first third of the upstream Side of the anode bar, and the downstream group feeding the second lateral riser, on each side of the cell, approximately the other third (starting from the upstream side) of the anode crossbar.

The figures and examples below provide a better explanation of the invention. In some images, the same functional elements bear the same tag numbers.

Figures 1, 2, 3, 4 and 5 refer to previously known methods and their description has already been given above.

6 and 7 show, in longitudinal vertical and horizontal sections, in heavily schematized form, electrolysis cells arranged in length, the conductors of which are arranged according to the invention.

Figures 8 and 9 show schematically, in longitudinal vertical and horizontal cross-sections, a different arrangement of conductors according to the invention, adjusted for cells that operate at a very high current intensity.

Figures 10, 11 and 12 show the current intensity distribution in the anode and cathode conductors according to the earlier method and the invention. They correspond to the arrangement of conductors shown in Figures 2, 4 and 6. Figures 13, 14, 15, 16, 17 and 18 show the magnetic field strength at different points of the interface between electrolytes - aluminum in a single cell according to earlier solutions (Figures 13, 14, 15) and according to the present invention (Figures 16, 17,

18).

Figures 19 and 20 show in vertical longitudinal section and in a planar arrangement of conductors according to the invention, applied to cells with pre-baked anodes.

On these various shearheads, the connecting conductors are shown schematically to make the drawings more understandable, but their arrangement is not necessarily identical to their actual arrangement. In particular, the cathode outputs are generally located in a single horizontal plane.

In sketches 6 and 7, the cell in the n-position is fed by means of conductors starting from the upstream cell of row n - 1 upstream and the cell of row n is fed by the identically arranged conductors to the next cell in the series n + 1 downstream. . On various conductors, the arrows indicate the conventional direction of current.

Both branches of the anode crossbar of cell n are fed simultaneously through the upstream forehead and through two between points «? A and A '.

The cathode outputs on each side of the cell, 11 in number, are divided into two groups, one group of six on the upstream side (benchmark 3) and one group of five on the downstream side (benchmark 3 ') · six upstream cathode outputs (3) , using the bus (4) and the riser (5), the anode crossbar (6) of cell n - 1 over the upstream face. Five downstream cathode terminals (3 ') supply the A-point via the busbars (4 ¹ ) and the riser (5').

As the cell is symmetrical, the same arrangement is located on the other side of the cell to feed both sides of the anode bars A and A '.

Even if the realization of the invention allows some freedom in the division of the cathodic outputs into the upstream and downstream groups, as well as in the selection of the positions of points A and A 'on the anode bar, it has nevertheless been shown that the best results are obtained when the cathode outputs are divided into practically two equivalent groups, and when points A and A 'are practically at the mid-transverse plane of the anode. Thus, the total length of the conductor group that feeds the upstream face of the anode crossbar is practically equal to the total length of the conductor group, which feeds the intermediate points A and A 'of the anode crossbar, which allows the use of rods of the same cross section in both circuits.

Figures 8 and 9 show, in a vertical longitudinal section and in the plane, two cells from a series of cells arranged in length, the connecting wires of which are also arranged according to the invention. It is a series of cells operating at very high amperage (150,000 amperes) and having cathode outputs comprising 15 bars on each side of the cell, ie. a total of 30, which are divided into three groups on each side.

A group of five upright bars (3) of a cell of row n is connected to the face of the anode crossbar (6) of a cell of row n + 1 by means of a conductor (4) and a vertical riser (5).

A group of five center laces (3 *) of a cell of row n is connected to a point A located on the first j upstream third of the anode crossbar, with the help of conductors (4 ') and a lateral riser (5'). A group of five downstream laces (3) of the cell of row n is connected to the second nodal B cell of row n + 1, which is located on the second third of the anode bar, by means of conductors (4) and a lateral riser (5). As the cell is symmetrical, the same arrangement is located on the other side of the cell to feed the points A 'and B' of the anode bar.

It becomes obvious that, in both Figures 6 and 7 and Figures 8 and 9, the conductors (4) and (5) and (4 ') and (5 ·) iii (4) - (5), (4') - (5 ·) and (4) - (5) have practically the same length, which allows the use of laces of the same cross section.

Figures 10, 11 and 12 show how the current is distributed in anode and cathode conductors, along a series of cells, arranged in length. Figure 10 refers to a series of cells according to an earlier embodiment, according to which the anode crossbar of each cell is fed only through the upstream face, starting from the cathode laces of the preceding cell. Figure JI refers to one series of cells according to patent No. PR. 1 143 879, in which the anode crossbar of each cell is fed through two foreheads, the upstream forehead by eight upstream cathode bars of the preceding cell, and the downstream forehead by the three downstream cathode bars of the previous cell. Figure 12 relates to the subject matter of the present invention: the anode crossbar of each cell is fed from its upstream 6 upstream cathode bars on its inlet side and through one intermediate point, which is substantially located in the middle of the anode crossbar, which is fed from 5 downstream cathode bars of the previous cell .

On the front three drawings, on the abscesses are drawn, in an arbitrary scale the length of the cells and the horizontal projections of their connecting circuits, and on the ordinates, in an arbitrary scale, the current.

The diagrams denoted by letter A refer to anode conductors and those denoted by letter K refer to cathode conductors. Vertical arrows indicate a spot arbitrarily located in the middle of the space separating the downstream face of one cell from the upstream face of the next cell, where the cathodic current of cell n - 1 becomes an anode current of cell n.

As the cells are symmetrical with respect to the longitudinal vertical plane, this is considered by the anode and cathode conductors on one side only, and because there are 11 cathode bars on each side of the cell, the current intensities are expressed in fractions 1/11, where I represents half the total intensity of current J flowing through the series.

It can be stated that the intensity distribution along the anode and cathode conductors has been significantly improved, and in particular that the inverse movement of the anode current (point -3), which occurs in the case of drawings 11, between the downstream face and point M, is in stride (sign - indicates that the anode current moves in the reverse direction relative to the general direction of current in the series).

The advantages of the invention become even more apparent if an image is shown that shows the values of the induced magnetic field at different points in an electrolysis cell in the contact plane between the aluminum electrolytes. Figures 13, 14 and 15 refer to the electrolysis cell according to FR No. 1 143 879 (power through two foreheads), and drawings 16, 17 and 18 refer to the cell according to the invention. In figures 13 and 16, the upper number indicates the component Bx of the magnetic field, and the lower number indicates the component By magnetic field, at 9 points of the anode cell surface: at four angles, at the center four sides, and at the center.

In figures 14 and 17, the number indicates the value of the resultant Bxy (vector sum of Bx and By).

It can be stated that the realization of the invention leads to a very significant decrease in the value of Bxy at both ends of the cell, as well as to a significant decrease in the differences between the magnetic field in the middle and at the ends of the cell.

In Figures 15 and 18, the figures show the values for the vertical fields 8z for the previously known cells (Figure 15) and for the cells according to the present invention (Figure 18) and it can be stated here that the realization of the invention will lead to a significant reduction in the difference between the individual values of this field along the long sides of the cell. Lastly, one of the significant advantages of the invention over the French patent number 1 14? 8 ^ 9 is derived in the significant savings of aluminum rods for making a power supply circuit.

If the circuits from line 5 (earlier: 39933) are compared

r) and from the drawings 7 (according to the invention), it can be seen that the machine circuits according to the invention, (?) + (4) + (5) and (? ') * (4'1 + (5') are the same and minimum length.e, while in earlier mode the current circuit (? ') + · (4') + (5 ') is noticeably longer than circuit (3) + (4) + (5).

In order to disrupt the balance of the previous cell, it is necessary to use a much smaller current (in A / cra) for the circuit (3 ') + (4 ¹ ) + (5.J) than in circuit (3) + (4) * (5), means other than “economical strength. As this weak strength is applied to the longest circuit, this results in a significant increase in the weight of the conductor, which otherwise grows with increasing cell dimensions, while in the arrangement according to the invention, since the current density is d. the same in each circuit, it can be optimally] Δο, that is, the most economical.

For one 90,000 ampere cell, the weight savings of the connecting conductors is 8% in favor of the cells of the invention, that is, about 1,000 kg of aluminum rod per cell. For a cell of 150,000 amps, the saving is about 1,800 kg. Experience has shown that the presence of one or two lateral ascending vcds on each side of the electrolysis cell does not cause any interference with the application of various devices and tools when servicing and holding the cells, such as: picking, alumina feed, leaking aluminum, when devices of the semi-portable type of crane bridge, as described in French patents 1 245 598 (Pechiney), 1 526 766 (Pechiney).

Example

A series of electrolysis cells, arranged in length, with Soederberg anodes, operating at 70,000 amperes, and in which the cells are interconnected according to drawings 4 and 5 (the earlier method) produced 485 kg of aluminum per cell per day, corresponding to the effect in electricity ( the Faraday effect) of 8% which may be considered insufficient.

Without changing the metal crates, continuous Doederberg anodes (?) With pre-baked anodes (10) were made, according to Figures 19 and 20, showing 2x4 anodes, to simplify the drawing, and in reality the correct number is 2 x 10 .

The compounds were made according to Figures 6 and 7, according to the invention, in order to minimize the magnetic field disturbances.

In addition, due to the replacement of the continuous anode with pre-baked anodes, it was possible to increase the current intensity of the thus altered cell series from 70,000 to 90,000 amperes, a 28.6% increase in percentages.

Aluminum production increased to 640 kg per cell per day, corresponding to a Faraday output of 88%.

Despite an increase in current intensity of 28.6%, which would cause a corresponding increase in the magnetic fields if the conductor arrangement were not altered, the operation of this altered series of cells was stable and regular.

According to Torn, the realization of the invention therefore enables both the improvement of the existing cell series, greatly enhancing their Faraday effect, reducing the disturbance due to the magnetic field, and increasing the intensity of the electrolysis while maintaining good effect.

It is also possible for special conductors to be applied to the conductors arranged according to the invention to compensate for the magnetic field induced by the adjacent array.

The invention relates to an apparatus for powering a series of cells by electric current, for the production of aluminum electrolysis of alumina dissolved in molten cryolite, and the cells arranged in length along the axis of the series. Each cell has cathode busbars connected to the cathode outputs on each side of the cell, supplying electrical power to the anode pie connection cells of the next cell in series.

The invention aims to reduce the harmful effects of disturbance due to the induced magnetic field on each cell by the connecting conductors. These disturbances are reflected by the unstable functioning of each cell and poor performance in terms of electricity consumption (Faraday effect).

In the case of one set of cells operating at 90,000 amperes each having 11 output cathode bars on each side, 6 of which are upstream connected to the first bus connecting the upstream face of the next cell, and 5 downstream connecting to the second bus which is connected to the anode cross section of the next cell, passing between the fifth and sixth cathode bars of that cell, symmetrically, on either side of the cell.

The values of the horizontal component of the magnetic field along the circumference of the cell, starting from the upstream right angle, expressed in 10 Tesla (Gaussians) are -12, -5, + 3, -3, + 5 and + 12, values, which are extremely small if compared to the values obtained according to the previous solutions: - 19, + 2, + 27, - 27 - 2, + 19. This gives excellent cell stability and a Faraday performance of 88%, which gives a production of 640 kg of aluminum per 24 hours . The invention can best be used commercially for the aluminum production described above.

Figures 12, 16, 17, 18, 19 and 20 show this best way for commercial use of the invention.

Claims (3)

1) An electric power supply device for electrolysis of melt-ordered cells by their length, for the production of aluminum, by the electrolysis of alumina dissolved in cryolite melt, with the cells arranged lengthwise with respect to the axis of the array, and each cell having cathode buses ( 4, 4 ', 4) connected to the cathode outputs (3, 3', 3), on each side of the cell, to power the anode crossbars (6) of the next cell in a row, characterized in that the output cathode bars (3, 3 ', 3), on each side of the cell, are separated into at least two mutually independent groups (3, 3') with the same number of bars, and the anode crossings (6) of the cell of order n are fed by electrical - 39833 ': at the same time along its upstream forehead, starting from the cathodic lever bars (3) and the busbars (4) of the cell of the order (n - 1) ", and by means of at least one lateral riser (4 ·) on each side of the cell connected to at least one anode (An, An ') anode crossbar between its upstream and downstream forehead, starting from the cathode bars (3 *) of the cell of order (n - 1). 2) power supply unit eJekti ichnor by electrolysis chilli machine, arranged lengthwise relative to the axis of claim 1), characterized in that the output cathode bars on each side of the cell are separated in two independent groups (3, 3 '), of which each group has a substantially equal number of bars, and that the anode crossbars (6) of the cells of order n are electrically supplied simultaneously to the upstream face, starting from the upstream cathode bars (3) of the order of cells (n) - 1), and with the help of one lateral riser (4 ¹ ), from each Side cell, connected to one point of the anode crossbar (An, An ') »located in the middle of the anode crossbar, starting from the group of downstream cathode bars (3 · ) cells of the order (n - 1). 3) An electrical supply device for electrolysis cells arranged longitudinally with respect to the axis of claim 1), characterized in that the output cathode bars (3, 3 ', 3) on each side of the cell are separated by three independent groups, each of which has a substantially equal number of bars, and the anode crossings (6) of the cells of order n being electrically supplied simultaneously through the anode upstream face, starting from the cathodic upstream bars (3) of the row cells (n - 1). then by means of the first lateral riser (4 '), on each side of the cell, connected to one point of the anode bars (An, An'), approximately located on the first upstream third of the anode bars, starting from the group of central cathode bars (3 · ) cells of the order (n - 1) ", and finally with the help of another lateral riser (4 ^H ), on each side of the cell, connected to one point of the anode bars (Bn, Bn '), located approximately on the other upstream third, starting from the downstream gru pe. (3) cathode cells of the cell. of order (n -