AU619299B2

AU619299B2 - Arrangement of busbars on large, transversally disposed electrolysis cells

Info

Publication number: AU619299B2
Application number: AU36066/89A
Authority: AU
Inventors: Hans Georg Tidemann Nebell; Fredrik Skatvedt
Original assignee: Norsk Hydro ASA
Current assignee: Norsk Hydro ASA
Priority date: 1988-06-06
Filing date: 1989-06-06
Publication date: 1992-01-23
Anticipated expiration: 2009-06-06
Also published as: RU1813124C; DE68905242D1; EP0345959A1; EP0345959B1; CN1020480C; AU3606689A; ES2039859T3; NZ229292A; DE68905242T2; CN1038846A; NO882485D0; NO164721B; NO882485L; NO164721C; BR8902633A

Description

II I~ AUSTRALIA 9 9 Patents Act CCMPLETE SPECIFICATION

(ORIGINAL)

Class Int. Class Application Number: Lodged: Complete Specification Lodged: Accepted: Published: Priority Related Art: Ar Applicant(s): Norsk Hydro A.S Bygdoy alle 2,, 0257 Oslo NORWAY Address for Service is: PHILLIPS ORFMIDE FITZPATRICK Patent and Trade Mark Attorneys 367 Collins Street Melbourne 3000 AUSTRALIA Complete Specification for the invention entitled: ARRANGEMENT OF BUSBARS ON LARGE, TRANSVERSALLY DISPOSED ELECTROLYSIS CELLS Our Ref 133955 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): 6006 6006 -1 This invention relates to a busbar arrangement for an aluminium potline comprising rows of reduction cells with the cells arranged transversally in each row and which is particularly designed for cells having the current conducted through the bottom.

Commonly the cells in a prior art aluminium potline are arranged in rows as mentioned above. The distance between the rows, or rather the distance from the center line of one row to another is from 30 to 50 metres. The !ji 10 cells are arranged in two or larger, equal number of rows *I in which extra busbars for the return current are avoided. The current in two neighbouring rows flows in opposite directions.

A major problem with large prior art aluminium o o 5 potlines in which is used electric current of up to 300 :i jKA, is that the rows of reduction cells magnetically influence each other. The molten metal forming the cathode at the bottom of each cell, is influenced by electromagnetic forces due to the current being conducted through the metal. To compensate the unwanted, vertical magnetic field vector caused by the dominant neighbouring row, more electric current is normally conducted around or under the short end of the cells facing the n-ighbouring row of cells than the other short ends. This is a well '"25 known method which is already patented. With the known o solution it is thus possible to produce a vertical magnetic field being symmetrical about the longitudinal axis as well as the transverse axis of each cell. However the absolute values of the magnetic field will easily rise ji 30 about 30 Gauss, in some cases more than 100 Gauss.

j. Besides, this known solution requires more busbars &J to be used, with the result that investment costs are increased.

The present invention provides a busbar arrangement for an aluminium potline comprising rows of reduction cells with the cells arranged transversally in each row, each cell having at least one current busbar for each carbon cathode block projecting through the bottom of the 39 cell, and in which about half of the electric current is -laconducted to a cathode collector busbar and the other half to another collector busbar wherein the cathode collector busbars are disposed underneath the cell at each of its long sides, electric current from the collector busbar which is disposed at the largest distance from the next cell in the row, is conducted to said next cell via two busbars being provided at the short ends of the cell, and via two or more pairs of busbars provided underneath the cell, whereof the two busbars at the short ends of the cell have a cross section enabling them to conduct about twice as much current as each of the busbars being provided underneath the cells.

In the above arrangement two busbars may be provided underneath the cell and may be positioned close to the short ends of the cell.

Alternatively, four busbars may be provided underneath the cell and two of those busbars may be disposed at the short ends of the cell, whereas the two other busbars each may be disposed in the middle between the short ends and the transverse axis of the cell.

39 -Ibthe vertical magnetic field to a minimum 1 el. Further, it with the result that the investment costs are increased.

It has been an object with the present invention t provide a good and stabil running of the reduction cells/in an aluminium potline by reducing/lowering the abso te values of the vertical magnetic field to a minimum 1 el. Further, it has been an object with the present inv tion to eliminate i, the magnetic influence from the domina neighbouring row of I cells and to reduce the use of busb s, thereby lowering the investment costs.

H This is according to the in ention achieved by disposing-the cathode collector busbar underneath the cells and by conducting the electric current from said cathode collector busbar which is di osed furthest away from the next cell, through two busb rs each being provided close to the short ends of the ells and in pair through two, four or more busbars bei g provided underneath the cells, whereof each of the two sbars being provided at the short ends of the cells have cross section enabling them to conduct about twice as muc current as each of the busbars underneath the cells, as e efin in claim 1 l -imz -24.dofinos preferrd mbdiments of invntio i The invention will now be further described by means of example and with reference to the drawings in which Fig. 1 shows an example of a reduction cell (vertical section) with the electric current exit through the bottom, and Fig. 2 shows schematically the busbar arrangement for these cells seen from above.

During the electrolysis process electric current is lead Ir 3 from the anode A through the electrolytic bath and the melted metal and further down through the carbon cathode C to the two cathode steel bars I (two cathode bars for each carbon /i block, 23 shown all together). Normally the steel busbars t are projecting out through the sides of the cells, but in this example an electric conductor R, made of copper or steel, is welded on to the middle of each cathode steel busbar I. The current is conducted via the conductors through j the bottom of the cell, further via flexible conductors I to i current collector busbars, Bl, B2.

i The number of cathode carbon blocks being disposed in parali lell in the cells is depending upon the width of the carbon blocks, but in large electrolysis cells the number may be up Ito 26, in this example 23, see Fig. 1.

One of the collector busbars B1 is disposed underneath and straight below the long side of the cathode shell, and is ji, "projecting outwards about 0,5 metres from the short ends of the cell. The other collector busbar is disposed similarily on the other side of the cell.

i i Allthough the collector busbars B1, B2 in the abovementioned example are arranged straight below the long sides of the cells, the invention as defined in the claims is not limited that the collector busbars may be disposed somewhat on the outside of the cathode shells, preferably 0,5 meter from the steel shell.

Part of the electric current collected in the collector busbar B1 is conducted to cell No.2 via two busbars, K1 and K6, which are disposed at each short end of the cells, about at the same hight or a bit underneath the melted metal in the cell, see Fig. 2, Cell No. 2. The rest of the current is -II 4 conducted to the collector busbar B2 via 4 busbars, K2,K3,K4 and K5 underneath the cell and further to the next cell via raiser busbars S1,S2,S3,S4 and The current distribution in the six busbars conducting electric current from the collector busbar B1 is according to the invention primarily dependent upon the size of the cross sections for the busbars K1 to K6. If the rows of cells are S positioned far apart from one another, for instance 50 metres or more, the cross sections for the busbars K1 and K2 ought to be twice the size of the cross section for the busbars K2,K3,K4 and K5. This will give an electric current in the busbars K1 and K6 which is twice the size of current in-the busbars K2 to K5, and the current distribution will give a very favourable magnetic field.

By using mathematical models for calculating the current distribution in all of the busbars of the busbar arrangement and the magnetic field in the metal reserve in the cells, it *9 is possible to decide quite correctly the cross sections giving the most favourable magnetic field.

SS

With the here described method the busbar arrangement provides low maximum absolute values for the vertical magnetic field which is below 10 Gauss under the whole anode. Simultaneously, the cells are completely compensated for the magnetic influence from the dominating neighbouring row and the use of busbars is reduced.

Claims

1. Busbar arrangement for an aluminium potline comprising rows of reduction cells with the cells arranged transversally in each row, each cell having at least one current busbar for each carbon cathode block projecting through the bottom of the cell, and in which about half of the electric current is conducted to a cathode collector busbar and the other half to another collector busbar wherein the cathode collector busbars are disposed underneath the cell at each of its long sides, electric current from the collector busbar which is disposed at the largest distance from the next cell in the row, is conducted to said next cell via two busbars being provided at the short ends of the cell, and via two or more pairs of busbars provided underneath the cell, whereof the two busbars at the short ends of the cell have a cross section enabling them to conduct about twice as much current as each of the busbars being provided underneath the cells.

2. Arrangement according to claim 1, wherein two busbars are provided underneath the cell and are positioned close to the short ends of the cell.

3. Arrangement according to claim 1, wherein four busbars are provided underneath the cell and two of these 5 busbars are disposed at the short ends of the cell, whereas the two other busbars each is disposed in the I middle between the short ends and the transverse axis of I the cell.

4. A busbar arrangement according to claim 1 S 30 substantially described as herein with reference to the accompanying drawings. DATED: 30 October, 1991. PHILLIPS ORMONDE FITZPATRICK Attorneys for: NORSK HYDRO A.S. 39 3170u II