DE1161695B - Arrangement of power supply lines to suppress the magnetic effects in the melt-flow electrolysis of aluminum - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

GERMAN

PATENT OFFICE

EDITORIAL

Boarding school Class: C22d

German class: 40 c -3/12

Number:
File number:
Registration date:
Display day:

P 19933 VI a / 40 c
January 3, 1958
January 23, 1964

To suppress the harmful influence of magnetic fields on molten metal on the sole of Electrolysis tanks, such as those used in particular for the extraction of aluminum from alumina by fused-salt electrolysis of fluorides, various methods have been proposed.

The arrangement according to the invention can also be used for those arranged one behind the other in longitudinal rows Cells, with the long sides of the rectangular electrolysis tubs each extending the Represent the long sides of the preceding and following rectangular cells in terms of current passage, as for cells arranged in the transverse direction, in which the long sides of the rectangular cells transversely for the general direction of current passage as well as for any other type or arrangement of Cells.

In the following, the magnetic field and the current density at any point in the melt are defined by their projections on three coordinates with the same origin, which lies in the center of the bottom of the electrolytic cell. The x-axis corresponds to the general sense of the passage of current in the row of cells, the j-axis lies at right angles to it in the same horizontal plane, and the z-axis is the ascending branch, perpendicular to the xj-plane. The reference system 0 - χ - y - ζ is therefore a triad with even sides.

B is the magnetic induction or magnetic flux density at a given point and Bx, By and Bz are the projections of B onto the x, y and z axes.

J is the current density and Jx, Jy and Jz are the corresponding projections on the x, y and z axes, respectively.

In the German patent specification 1 131 418 a process is described, whereby one can give the molten metal in electrolysis cells a relatively good stability and that consists in that one suppresses the magnetic effects in the center of the electrolysis tank by that one of the current leads parallel to the x-axis to the cell and the lateral conductors parallel to the x-axis are arranged in such a way that the transverse component (By) of the field thus achieved is in the center of the tub and its partial derivative will be zero.

Since the devices for returning the current to the generators, which are generally in exist in another row of cells through which the current flows in the opposite direction, in another Buildings or at least so far away that you can see the effect of going through Arrangement of power supply lines

to suppress the magnetic effects

in the melt flow electrolysis of aluminum

Applicant:

Pechiney Compagnie de Produits Chimiques et
Electrometallurgiques, Paris

Representative:

Dr.-Ing. F. Wuesthoff, Dipl.-Ing. G. Pulse and

Dipl.-Chem. Dr. rer. nat. E. Frhr. v. Bad luck man,

Patent attorneys,

Munich 9, Schweigerstr. 2

Named as inventor:

Jean Pierre Givry,

L'Echaillon, Saint-Jean-de-Maurienne, Savoie

(France)

Claimed priority:

France of January 5, 1957 (No. 728 910)

France of October 23, 957 (# 750067) -

the magnetic fields occurring in one row of cells on the cells of the other row can be neglected, the above-mentioned known method gives satisfactory results in that the magnetic effects are completely suppressed. The lateral conductors are arranged symmetrically with respect to the plane χ - 0— ζ.

However, one is often forced to arrange the adjacent rows of cells so close together that the The effect of one row of cells on the other can no longer be neglected.

In addition, despite the complete suppression of the magnetic effects, the fields By and in the center of the cell are canceled out in

the neighborhood of this center and everywhere in the tub still have secondary effects, which in turn, too are suppressed.

In the arrangement according to the invention, the outer conductors are placed on the cell so that the effects of the Magnetic field become zero or at least very weak, and not only in the center 0, but over the entire electrolysis tank. According to a particular embodiment, the input

309 780/200

the flow of the neighboring row of cells is also taken into account. In this case, the current leads of the cell and the furthest from the neighboring row are those that are on the same side as those of the neighboring row, at different vertical distances arranged.

The inventive arrangement of power supplies to suppress the magnetic Effects in the whole area of the tank of electrolysis furnaces for the melt flow electrolysis in plants which the individual tubs are arranged in series under the individual conductors so that the components in the transverse direction of the trough of the magnetic field caused by the current paths in the center of the tub and the change in this component along the vertical through the center of the tub assume the value 0, is characterized in that the conductors lying outside the furnace in pairs symmetrically to a plane parallel and to a plane perpendicular to the general direction of the current, which both go through the center of the tub, are arranged in such a way that the for general direction of current parallel conductors pierce the perpendicular plane in points whose

ίο Coordinates in relation to the center for the conductors (2, 2 ') α and b that supply the current to the anodes, for the conductors (3, 3') c and d that carry the current away from the cathodes, for the conductors (3, 3 ') c and d that carry the current to the two Ends of conductor 2 feeding conductor (4,4 ') e and / satisfy the following equations:

K),

2 (c ² + » ²

* -ir # w-- ⁺ 2- _ f (f * - 3 e ² )
^; (<? ² + / ² ) ' ³

where χ and 1 - λ represent the proportions of the currents fed to the two end faces of the furnace in the total current.

1 is a perspective view of the melt as it lies on the bottom of the tub, the x, y and 2 axes being drawn in;

F i g. Fig. 2 shows a series of cells in a longitudinal arrangement, successively from a stream of the same Intensity, the direction of which is given by the arrow, are flowed through;

F i g. 3 shows the same cells in a transverse arrangement;

F i g. 4 is a section through the well 1 of the cell perpendicular to the sense of current. 2.2 'is the distribution frame for the conductors, which receive the current coming from the previous cell and transfer it via the Distribute anode equipment to the cell. 3, 3 'shows the middle layer of the conductors that come from the cell itself Pick up the coming current and forward it to the next cell.

The coordinates of 2 in the plane y - 0 - ζ are through O ₁ and b _1} those of 2 'through a ₂ and b ₂ , those of 3 through C ₁ and d _x and those of 3' through c ₂ and d ₂ shown.

F i g. 5 is a section along the plane χ - 0 - ζ through two rows of cells through which currents flow in opposite directions. In the left row the current flows away from the observer, in the right row towards him. As can be seen, the arrangement of the conductors of the cells in one row is symmetrical to the position of the conductors in the opposite row.

F i g. 6 shows two cells following one another in the direction of flow in a side view, with the distributor frame 2 is only supplied with electricity from one side.

F i g. 7 shows two cells of the same type, but with the distribution system 2 from both ends Power is supplied. The current coming from the previous cell via conductor 3 is thus divided into two parts, with a conductor 4 parallel to 3 leading to the other end of the distribution system 2. In this Trap set the ladder 3 in F i g. 4 and 6 the middle layer of the conductors 3 and 4 from FIG. 7 together. As previously proposed, these conductors 3 and 4 can be smaller than tracks of conductors Dimensions be formed.

Figs. 8, 9, 10 and 11 show the arrangement of the Conductor in various cases, with the magnetic effects suppressed in the whole area of the electrolysis tank are. Here, however, the influence of the other rows of cells is neglected.

Fig. 12 is a section through the trough and the entirety of the conductors in the y - 0 - z plane, the conductors 3 and 4 being arranged separately.

Figure 13 corresponds to Figure 12, but the conductors are to supply the side distribution system of the following cell here above the cell instead of below arranged.

Figure 14 is a section through the in-plane cell

χ - 0 - z, perpendicular to the section according to FIG. 13.

F i g. 15, 16 and 17 show schematically different possible arrangements for solving the problem presented here Problem.

F i g. 18 shows an arrangement of electrolytic cells,

which are traversed by a current / of constant intensity and are divided into four rows.

19 and 20 show the arrangement of the conductors

taking into account the field created by the passage of current in the adjacent row of cells is generated (in the present case there are two rows of cells).

The magnetic effects are marked

by the magnitude of the rotation vector R of the Laplace forces, which can be calculated using the values for the components Bx, By, Bz and the current densities Jx, Jy, Jz and their partial derivatives.

The mathematical expressions for the projections of the vector R onto the x, y and z axes are as follows:

τ> ε. ^dJx , r> ^dJx , D ^dJx τ ^dBx T ^dBx T ^dBx

Rx = Bx —- = f- j8v — 5 f- 5z - = Jx, - Jy - -, Jz --- j-—

_n dJy dJy d Jy _r d By _T d By _T d By

Ry = Bx - ^ - + By- ~ - + Bz - / - - Jx ^ r - Jy - / - - Jz-- ~. dx dy dz dx dy dz

"DJz" dJz " dJz _r dBz _T dBz _r dBz

Rz = Bx-j h By-, h Bz-, Jx-j- Jy-, Jz-j-.

dx dy dz dx dy dz

In the center of the cell, at point O, the decrease is determined by: through the interaction of the symmetrical 15

Order the current density and its derivatives on the j J _x (O) d Bx (O)

single elements in the table that are not equal to Rx (O) = Bx (O) - ^ - - ■ Jz (O) - ^^

Are zero:

Jx dy dz dJx O O dx dJy O O dy dJz O O

= By (O) ^ά ψ - Jz (O)

' ^K ' dy ^v 'dz

Jx 0 ψ 0 0 Rz (O) = Bz (O) ^ά ψ - Jz (O) "

ax dz dz

Jy 0

²⁵ (0) means the value in point 0.

In any point of the tub, which is determined by its coordinates X, Y, Z , one can

j _z j _z 0 0 ^ ^ ^{Z 3} ° ^ ^e rotational components of the Laplace forces in

d ζ write the following form that applies when the expressions

second order for X, Y or Z neglected The rotational components in the center 0 of the cell can be:

Rx (XYZ) = Rx (O) + ^ - (O) X + 4 ^ - (O) Y + ^ P- (O) Z,

dx dy dz

Ry (X YZ) = Ry (O) + Ά- (0) Z + ^ - (0) Y + - ^ - (0) Z, Rz (XYZ) = Uz (O) + - ^ - (O) Z + - ^ - (0) 7+ - ^ - (O) Z,

where expressions like * £ - (0), ** L (0) etc. Funk- Stromdiditei as well as their derivatives up to such

dx ^{v h} dy ^K ' print second order,

tions of values in the center 0 of the fields and the

For example, the calculation gives the following values for:

dRx dBx dJx , " dl Jx , dBy d Jx ," dl Jx , dBz d Jx , _ dl Jx + ^Bx -TTi- + -rf ¹ —τ— + By -JJ-: + —j— —j— + Bz

dx dx dx dx ^z dx dy dy dx dx dz dxdz

dJx dBx _ dlBx d Jy dBx _T dlBx d Jz dBx _ dlBx

- tv * / -it / iy

dx dx Jx ² Jx dy dy dx dx dz dxdz

J Dy

In the center O -, - (O) decreases, if one makes the above assumptions for the current densities, to:

4 ^ - (0) = -Jz (0) 4 ^ r ~ (°) · Jx Jx Jz

Analogous calculations give the value of the other derivatives for the rotation of the Laplace forces:

dy

- = i = - (0) = - ^ p- (0) "~ (0) - - = p- (0) -F dz ^K dz dx dz dz

* m

(ο

dx

^d

dx

dz

dxdz

dz

dz ²

In summary it can be said that, for example, by projecting onto Ox:
the components of the rotation of the Laplace forces

at any point in functions of nineteen 35 d Bz _{/ ΓΛ} d By

Print fields:

dz

Bx (O), By (O), Bz (O),

dx dz

dlBy dy dz

dBz dx

dy (0),

dBz

dl

c? 2 5z _ (/ 2Aj dxdy dxdz

^d l ** ₍ o) _

dx

dy dz

d2By_

dz *

dx dz

dy dz

~ (0),

^r (0),

dy dz

dlBy

~ dz * "

dy dz

These formulas apply to the bathroom, but then: d Jx d Jy d Jz

dx dy dz ~~

If the rows of cells are quite far apart, the current conductors of the individual rows can be arranged symmetrically with respect to the plane x - 0 - ζ

These nineteen fields are not independent, 55 / " _h _ _h _ _h ___ _r _" y_y_ _/ fv

but actually requires the Ampere theorem

(Rotation of B = Απ J) certain relationships. For the symmetry of the currents in relation to the planes

a metal in which 7—0 — Z and X — 0 —Z suppress fields such as:

Jx (XYZ) = -

Jy (X YZ) =

Bx (O), Bz (O), ^d - ^ (0), ^ (0), 4! -

dy

- (0) Y,

dxdz

dz dl Bx

dy dz

(0) ^d2Bz (0)

Jz (XYZ) = Jz (O) +

dJz

(O) Z,

Finally, the rotational components of the Laplace forces are reduced as follows:

Rx (XYZ) = ^ p- (0) Y.

Ry (XYZ) = Ry (O) +

(0) X + ^ (0) Z.

i? z (Z7Z) ==

(0) Y.

Ry (θ) - ~ f " ⁽⁰⁾ ' ^{By (0)} - ^{Jz {0)} ' ^d -Jz ⁽⁰⁾ ·

Z- ⁽⁰⁾ = Ψχ ~ ⁽⁰⁾

- Jz (O)

(0) - 8 π Jz (0) * £ - (0)

Tx

(0)

dJy Ty

(0)

4 * (O) - 4 ⁷ ^ (0) | -

^ (0) = -Ap. (o) \ A * L (o) - Ap. ₍ o)

α >> dz \ dy dz

The main effects are suppressed by making Ry (0) equal to zero (see German patent specification 1 131 418),

or by By (0) and —χ --- (0) becoming equal to zero.

Secondary effects are considerably reduced and, in particular, the level fluctuations are suppressed in that - ^ - (0) equals - ^ - (0) equals zero By, --j- ~ and

also canceled at point 0

become, i.e. - ^ - (O) = O.
By arranging the conductors so that the fields become, it is possible to suppress practically all disturbing magnetic effects.

To calculate these fields, χ I denotes the current intensity that flows into the distribution device 2 from the side of the preceding cell (FIG. 7), and (1 - α) / that of the device 2 from the opposite side Amperage. In the case of FIG. 6 is «= 1.
The calculation of the fields then results in:

dBy

2KI

= α

d ² By

TkT

2} (a ^z + b ² y Λ _ | _ ^ 2) 2>

d (d ² - 3 c ² )

These three expressions must be zero.

In this way one can calculate the solution to the problem posed.

The following table, which is in no way restrictive, shows the positions of the ladder for various Feed options:

4.41 2.60 1.80 1.31 1

0.5

0.6

0.7

0.8

0.9

τ ° ⁵⁸

0.64 0.71 0.78 0, p

-f- co -1.75 -1.50 -1.32 -1.12 -1
b

Figures 8, 9, 10 and 11 illustrate the cases in which α is 0.6, 0.7, 0.8 and 0.9, respectively.

According to another embodiment, not only two but three different groups are assigned

of parallel conductors in the plane Ox (see Fig. 12), the conductors 3 and 4 being neatly separated.

309 780/200

11 12

The calculation of the field at point zero then results in:

_ 1 4, Ϊ

dz ^ψ) 2KI V 2) (a * + ^ ² ) ^{2 +} 2 (c ² + ί / ² ) ² ' ^{U Λ)} (e ² 4- / ψ

- 3 r ² ^ f (f ² - λ ρ ² }

((W * - I * \ * s \ f ^ x * j ± <λ yvi '_L · (\ \ J VJ ~ J C J

öz ² 2 AT / \ 2 / (a ² + o ² ) ³ 2 (c ² + a ² ) ³ (e ² + τ ² ) ¹

In these equations, a / represents the amount of current produced by the current passing through the other row of cells

which can be neglected in the distributor device 2, 2 'from the side of the field. In practice one is

preceding cell, and (1 - α) /, however, often forced to use the different cell

those that are fed from the next cell are to be arranged in a short distance next to each other,

with the current flowing in the conductors 4, 4 '. Another embodiment of the invention

The values for, a, b, c, d, e and / are chosen in such a way that the arrangement according to the ao takes into account the influence of the fact that the three expressions above become equal to zero. by the other series or the other series of These three relationships result, if one puts them on the current going to electrolysis cells,
the seven unknown parameter applies four When the cell rows close enough degrees of freedom and lead as a result, are to, the proximity of the neighboring rows even greater adaptability than the first off 25 acts neuter in the development of a vertical field Bz leadership form, since they are much more opportunities er, which open according to the relative position of the cells. expressed in their distance η (calculated algebraically

The examples serve to illustrate the invention, along Oy), can be easily calculated (in FIG. 20 η is

whereby the possible solutions presented are self-negative). If one neglects the expressions of the second

understandably by no means the only ones. 30th <- ^, - », 1 · _cu

^{66 3} and third order in in the case of only two

Example 1 (see Figs. 13 and 14) " _l

. Rows, the field Bz becomes equal to + 2 ■ ■; are four

a = y, ie the current strength is evenly distributed

•, j, ·, τ- ,, JTr ₄ .-. 1. / rows exist, the value for Bz ^ -

between the two ends of the distribution frame aa. 35> e ₃ "

j,, .. t_ 1 · t_- .., u j j i_ j for the two outer rows I and 4 and for the

α and b can be chosen arbitrarily, ie the η

The distribution frame can be arranged as desired. middle rows 2 and 3.

This solution is shown in FIGS. 13 and 14. There are six rows of cells and there is flow through them

40 all rows 1 to 6 of the stream /, then the

B e i s ρ i e 1 2 (see Fig. 15) /

The value for Bz for rows 1 and 6 is 1.57 -,

3 for rows 2 and 5 equal 0.83 - and for rows

α and b can be chosen arbitrarily, in advance- .. /

set to be ^{3 and 4} 8 ^Comparative ° ^'67 "·

1 22 <- <2 Assuming the case of eight rows 1 to 8,

' α then Bz for rows 1 and 8 would be

^is 1.52--, for rows 2 and 7 the value is 0.76 -,

_ a ² + b * _ a ² + b * l / ₂ __ b ² so ""

^c " J - == ^ = , e -g- ■ - ■ I / a - - ^ -, _{for re} j _hen 3 _{and 6 the value of} Q ₅₇ _ _{and for}

^z uz "2 " η

3 /

rows 4 and 5 have a value of 0.5 -.

r_ __ ^ß2 _ + ^ ² _._ ^ 55 Fig. 18 shows an arrangement of electrolysis

a ² 4 'cells through which the same current / flows and which

are divided into four rows.
Example 3 (see Figs. 16 and 17) ,

Generally one can set Bz = h, in which the

^Ä = 4 · 'd = O · _6o coefficient h can easily be calculated in any case.

Since Bz can no longer be neglected

α and b can be chosen arbitrarily, in advance - the rotational components R at the center:
set that b> α .

fb ² - α ^{2 65} Ry (O) = O,

These solutions apply if the rows of cells are so r _z (O) = Bz (O) - (O).

have a lot of distance that that in a cell by the dz

Head and fields By, ~~ -r ^ ~ and

- like them for

dz """ d ζ ²
infinitely spaced rows was achieved by the arrangement recommended above.

The calculation shows that there is a solution for every type of power supply:

For χ = 1 one finds, for example, that it is useful to give the conductors the following coordinates, according to h, η and α (half the distance between positive conductors.)

α ²
Left positive conductor a _x = b _x = a - h -,

right positive conductor a ₂ - - Z> ₂ = - a - h -,

left negative conductor C ₁ = -d ₁ = a-h

η '
α ²

right negative conductor C ₂ = d _% = - a - h -.

19 and 20 show the case of two rows of cells with a distance of η = -10α.

It follows from this that the magnetic effect of the entire arrangement is very harmful.

Accordingly, the field Bz produced by the adjacent rows of cells is expediently compensated for by arranging the conductors asymmetrically in the row in question. Care must be taken here, however, that the compensation of the fields Bx, -.- ^x - and -j- is not impaired, as would of course be the case with symmetry of the values, such as the value for α, the distance 2 a between the positive conductors 2, 2 ', the distance η between two rows of cells or the number of these rows can of course be varied as desired within extremely wide limits without exceeding the scope of the invention.

Claims (4)

Patent claims: 1. Arrangement of power supply lines to suppress the magnetic effects in the whole area of the tub of electrolytic furnaces with high amperage for the production of aluminum, in which the individual electrolytic furnaces in series and the individual conductors are arranged so that the component in the transverse direction of the tub by the Current paths caused by the magnetic field in the center of the tub and the change in this component along the vertical through the center assume the value zero, characterized in that the conductors lying outside the furnace are each paired symmetrically to a plane parallel and to a plane perpendicular to the general direction of the current, which both pass through the center of the tub, are arranged in such a way that the conductors parallel to the general direction of current penetrate the plane perpendicular to it at points whose coordinates in relation to the center for the conductors (2, 2 ') α and b, for which the current from the Ka methods discharging conductors (3, 3 ') c and d, for the conductors (4, 4') e feeding the current to the two ends of the conductor (2) and / fulfill the following equations: 2c ² a = 0, l \ (έ ² - « ² ) J ^ rf ² -c ^a T (c ² + i / ² ' -3c ² V ¹ ^) + pf where «and 1 - α are the proportions of the two Reflect the streams supplied to the front of the furnace in the total stream. 2. Arrangement according to claim 1, characterized in that the conductors (3, 3 ') discharging the current from the cathodes and the conductors (4, 4') feeding the current to the two ends of the conductor (2) form a common conductor group ( e = c, f = d) and the arrangement is such that the coordinates of the conductors satisfy the following equations: / Λ (δ ² (c ² + rf ² ) ² 2 3. Arrangement according to claim 1 or 2, characterized in that the anodes supplying current Ladder group is adjustable. 4. Arrangement according to claim 1, wherein the distance between the individual rows of cells is relatively small so that the fields of the current flowing through the individual rows influence each other, characterized in that the conductors are arranged such that the conductors of the furnace on furthest from the adjacent row of ovens away from each other have a greater vertical distance from each other than the ladder leading to the Neighboring row facing side are arranged. Considered publications: French patent specification No. 1 HO 685. Older patents considered: German Patent No. 1 049 108. For this purpose 2 sheets of drawings 309 780/200 1.64 @ Bundesdruckerei Berlin