AU623439B2

AU623439B2 - Potline and busbar arrangement

Info

Publication number: AU623439B2
Application number: AU42621/89A
Authority: AU
Inventors: Hans Georg Tidemann Nebell; Trond Tvedt
Original assignee: Norsk Hydro ASA
Current assignee: Norsk Hydro ASA
Priority date: 1988-11-28
Filing date: 1989-10-05
Publication date: 1992-05-14
Anticipated expiration: 2009-10-05
Also published as: NO166657B; AU4262189A; EP0371653A1; ES2038416T3; CN1043163A; RU1833438C; DE68904406T2; NO885292D0; CN1023413C; BR8905984A; EP0371653B1; NZ230814A; NO166657C; NO885292L; DE68904406D1

Description

V J U

AUSTRALIA

Patents Act 6 2 3 4 3 COMPLETE SPECIFICATION

(ORIGINAL)

Class Int. Class Application Number: Lodged: Complete Specification Lodged: Accepted: Published: Priority SRelated Art: o a 0 0 a a 0O6 Applicant(s): Norsk Hydro A.S Bygdoy alle 0257 Oslo NORWAY o a a o a o Addres for Service is: PHILLIPS ORMONDE FITZPATRICK Patent and Trade Mark Attorneys a 367 Collins Street *0 A Melbourne 3000 AUSTRALIA .Complete Specification for the invention entitled: "POTLINF AND BUSBAR ARRANGEMENT".

Our Ref 149411 POF Code: 1346/1346 The following statement is a full description of this invention, including the best method of performing it known to applicant(s): 600- 1 6006 f The present invention relates to a potline for electrolytic production of aluminium which compensates for unwanted magnetic influence between two or more rows of cells in the-potline.

It is common in aluminium potlines to arrange the electrolytic cells transversely in rows, the distance between the centre line of two adjacent rows being around to 50 metres. The cells are connected in series, one after another, and electric current is conducted from the rear of one cell in a row to the next cell via two or more busbars which pass under the cell and also around or under the short ends of the cell.

A cell in a row is magnetically influenced by the electric current in the neighbouring row(s). Due to .the relatively long distance between the rows, the effect of the magnetic field is essentially vertical and overlaps with the magnetic field being created by the electric current in the cell by itself and the neighbouring cells in the same row. This overlapping magnetic field is j ,20 unwanted because it provides electromagnetic forces which in turn causes harmful streaming in the electrolytic bath and deposited aluminium in the cell and reduces the j stability of the cell.

From the applicants Norwegian Patents Nos. 139829 and 140602, it is known to compensate for the unwanted Svertical magnetic field by conducting more current in an unsymmetric busbar system around or under the short end of the cell which is closer to the neighibouring row or rows.

4 With this known technology it is thus possible to provide a vertical magnetic field which is symmetrical with respect to the longitudinal and transversal axes of the cell. However in large electrolysis cells of more than ,ji 150 kA, there is a disadvantage with the known solutions as long busbars are needed to conduct the current from the rear side of the cell to the next cell in a row, and as the vertical magnetic field has large absolute values at the corners of the cells.

An object of the present invention is to provide a 39 busbar arrangement which is not encumbered with the above MJP Z \n -1Adisadvantages, i.e. which substantially compensates for magnetic influence from the neighbouring row(s) of cells and which has relatively low absolute values for the vertical magnetic field at the corner of the cells. Such a busbar arrangement is essentially cheaper than the known solutions.

According to the present invention there is provided a potline for electrolytic production of aluminium comprising at least two rows of electrolytic cells with the cells arranged transversely in each row, electric current being conducted from a rear side of each cell in a row to the next cell via two or more busbars which pass under the cell and also around or under short ends of the cell, the busbars being arranged in an unsymmetrical fashion relative to a centre line of the row of cells, and "j wherein one or more of the busbars beneath the cell are S disposed at an angle relative to the centre line of the row.

Each cell may be provided with five busbars whereof 2 20 at least one busbar is disposed at each short end of the j cell, one busbar is disposed on the side of the centre it f line of the row which is closer to the neighbouring row, and two busbars are disposed beneath the cell symmetrically with respect to one another on either side of the centre line and stretch outwards from the cathode collecting busbar to the riser on the next cell at an angle to the centre line of the row.

The angle between the inclined busbars and the centre line of the row of cells is preferably between and 450 and suitably is approximately 260.

A preferred embodiment of the present invention will now be described with reference to the accompanying drawings in which: Fig. 1 shows schematically a cross section of two cells in a row of aluminium electrolysis cells; Fig. 2 shows the same two cells from above; and 39 -2 VA. yu i: I ~aaP-nr~sl-~-rllc~----~ Fig. 3 a, b and c/show the isogauss curves determined for the field vectors Bx, By and Bz for the cells shown in Fig. 1.

In Figs. 1 and 2 is shown an example of a busbar arrangement for a 180 kA cell in an aluminium potline. The cell has four risers, Si S4, and five busbars kl k5 which conduct electric current from the cathode collecting busbar P to the risers. Three of the busbars, K2, K3 and K4 are disposed underneath the cell, while two of the busbars kl and k5 are 8 stretching around the short end of the cell. The busbars kl, k2, respectively k4, k5 are symmetrically arranged relative ao °0 one another on each side of the centre line of the row, oo«° whereas the busbars k3 is disposed on the side of the centre line being closer to the neighbouring row. Such an arrangement where a larger part of the electric current is conducted towards one end of a cell being closer to the neighbouring 4000 0 row, is denoted to be asymmetric.

a I However, as opposed to common practice, two of the three 8*a busbars underneath the cell, namely k2 and k4 are disposed with an inclined angle between the cathode collecting busbar P and the risers S1 and S4. Such arrangement has, as previously mentioned, the advantages that the electric current path is shorter and that the absolute values for the vertical magnetic field at the corners of the cells are low.

In Figs. 3a, b and c are shown the determined isogauss curves for the magnetic field vectors Bx, By and Bz for the cell shown in Fig. 1. The horizontal field Bx have little influence on the running of the cell, but the other horizontal field By and especially the vertical field Bz have great 0 pact.

I

4 The curves for Bz shows that the vertical field have absolute values below 10 gauss nearly under the whole anode level.

Further, the maximum values are not above 20 gauss, compared to 130 gauss for a similar cell which does not have any busbars disposed underneath.

The current distribution in the five busbars kl k5 is, in the shown example, optimalized with regard to providing a best possible magnetic field, but normally the inclined 0 busbars are g4':an a cross section which will conduct an 0 essential part, more than 40% of the current being lead from the near side of the cells.

0 00 S ou The busbar arrangement is also optimalized with regard to the number of busbars underneath the cells, their positioning and the angel the two inclined busbars have relative to the centre line X of the row. In the example of Fig. 2 which .o as previously mentioned concerns a cell of 180 kA, the angle o is approximately 260. Theoretic figures show, however, that greater achivements can be obtained when using larger or smaller angles in other cells, or rather cell busbar arrange- Sments, at least angles between 15 and 400.

Besides, it should be mentioned that the invention in no way is limited to the examples shown in the attached drawings and described above. Thus, it may, within the scope of the invention :and depending on the size of the cells, be possible to use more or fewer busbars underneath each cell, and to let more or fewer busbars have a declined disposition between the cathode collecting busbar and the risers.

Claims

1. A potline for electrolytic production of aluminium comprising at least two rows of electrolytic cells with the cells arranged transversely in each row, electric current being conducted from a rear side of each cell in a row to the next cell via two or more busbars which pass under the cell and also around or under short ends of the cell, the busbars being arranged in an unsymmetrical fashion relative to a centre line of the row of cells, and wherein one or more of the busbars beneath the cell are disposed at an angle relative to the centre line of the row.

2. A potline as claimed in Claim 1, wherein each cell I 5',5 is provided with five busbars whereof at least one busbar S is disposed at each short end of the cell, one busbar is disposed on the side of the centre line of the row which is closer to a neighbouring row, and two busbars are disposed symmetrically with respect to one another on 20 either side of the centre line and stretch outwards from a cathode collecting busbar to a riser on the next cell at S said angle relative to the centre line of the row. S*

3. A potline as claimed in either claim 1 or 2, wherein said angle is between 150 and 450. :25

4. A potline as claimed in claim 1 or 2, wherein said angle between each of the inclined busbars and the centre line for the row is approximately 260 A potline for electrolytic production of aluminium substantially as herein described with reference to t. accompanying drawings. S/ DATED:

5 February, 1992. PHILLIPS ORMONDE FITZPATRICK Attorneys for: NORSK HYDRO A.S. 3530u 39 MJi