AU2005215562B2

AU2005215562B2 - Current busbar

Info

Publication number: AU2005215562B2
Application number: AU2005215562A
Authority: AU
Inventors: Stig Torvund
Original assignee: Individual
Current assignee: Individual
Priority date: 2004-02-20
Filing date: 2005-02-16
Publication date: 2010-05-27
Anticipated expiration: 2025-02-16
Also published as: AU2005215562A1; NO321709B1; EP1853751A1; CA2586786A1; RU2007121270A; WO2005080641A1; US20090127126A1; NO20040762L; ZA200703577B; IS8641A; RU2394116C2; DE112005003212T5; NO20040762D0

Description

WO 2005/080641 PCT/N02005/000056 171086-EH Current busbar 5 Field of the invention The present invention relates to current bus bars for anodes or cathodes for use in production of aluminium by electrolysis of alumina in an electrolysis bath in an electrolysis cell. 10 Background of the invention Production of primary aluminium takes place by electrolysis of alumina solved in a melted halogenide electrolysis bath, for example an electrolysis bath comprising cryolite. By electrolysis, compositions that are split into ions in the electrolyte are reduced at the cathode and oxidized at the anode, by use of impressed current. Thereby aluminium 15 can be produced at the cathode and oxygen at the anode. The process used for production of aluminium, the Hall-Heroult-process, was developed almost simultaneously and independent by the American Hall and the Frenchman Heroult for more than one hundred years ago. For both the anode and the cathode it is most common to use an electrode body of carbon, with one or more current busbars embedded within the carbon. The function of 20 the current busbars are to deliver current to or from the electrode body, to conduct heat away from the electrolysis bath, and to contribute to the mechanical strength and connection. The current busbars are connected directly or via further means to an outer current circuit. In patent publication WO,02/42525 various embodiments of current busbars for 25 anodes and cathodes are illustrated, with associated description of essential features for current busbars. Despite many years of development a demand still exists for improvement of the electrolysis cell, including the current busbars. Particularly a demand exists for current busbars having large heat conduction away from the electrolysis bath. Further, it would be 30 preferable with current busbars with reduced voltage drop, which inter alia is related to the contact area towards the carbon. Further, it would be beneficial with current busbars that, with regard to the anodes, do not require casting to the carbon via a cast iron lining or -socket formed by liquid cast iron being poured into the gap between adapted holes in the electrode body and inserted anode nipples, which is made possible by the holes in the 35 electrode body having slightly larger diameter than the nipples. Accordingly, a demand exists for avoiding the use of a cast iron lining for fastening the current busbars to the carbon, whereby the current busbars can be improved with respect to mounting and demounting to the carbon. A demand also exists for joining embedded parts or sections of C \RPorbI\DCC\CAB\253 16X_1 DOC-16/42010 -2 current busbars to the further parts of the current busbars, in a simple and releasable way, with good electrical, thermal and mechanical contact. Summary of the invention 5 In accordance with one form of the invention there is provided a current busbar for anode or cathode for use in production of aluminium from alumina in an electrolysis bath in an electrolysis cell, which current busbar comprises one or more ends or sections that during operation shall extend out of an electrode body, and one or more ends or sections that during operation shall be embedded or within the electrode body. The current busbar 10 comprising ends or sections that during operation shall be within the electrode body are formed as one or more in substance horizontally oriented conical bodies with largest horizontal cross section diameter within the electrode body, such that by sliding said bodies axially into one ore more adapted conical holes in the electrode body said bodies will be embedded and kept into the electrode body, and 15 said conical bodies or elements connected thereto are manufactured from steel or steel over a copper core, and are provided with one or more in substance horizontally formed cylindrical or conical grooves with largest horizontal cross section dimension within said grooves, such that by sliding in correspondingly formed copper rails on the external parts of the busbar, said bodies and rails are releasably joined. 20 In accordance with another form of the invention there is provided a current busbar for anode or cathode for use in production of aluminium from alumina in an electrolysis bath in an electrolysis cell, which current busbar comprises one or more ends or sections that during operation shall extend out of an electrode body, and one or more ends or sections that during operation shall be within the electrode body, characterized in that ends 25 or sections that during operation shall be within the electrode body are formed as one or more in substance horizontally oriented conical bodies with largest horizontal cross section diameter within the electrode body, such that by sliding said 35 bodies axially into one or more adapted conical holes in e electrode body said bodies will be embedded and kept into the electrode body. 30 In accordance with yet another form of the invention there is provided a current busbar for anode or cathode for use in production of aluminium from alumina in an C WRPorbilDCC\CAB\2853 168.1 DOC-lMW)4/2010 -3 electrolysis bath in an electrolysis cell, which current busbar comprises one or more ends or sections that during operation shall extend out of an electrode body, and one or more ends or sections that during operation shall be within the electrode body, characterized in that the transfer between steel in parts of the current busbar that are to be within or close to 5 the electrode body and copper in external parts from the electrode body are formed as one or more in substance horizontally formed cylindrical or conical grooves in the steel with largest horizontal cross section dimension within said grooves, and correspondingly formed copper rails on the external parts of the current busbar, such that by sliding in the copper rails into the steel grooves the parts will be releasably joined. 10 Preferably, with in substance horizontally oriented it is meant in substance parallel with the electrolysis bath or horizontal with few degrees deviation, most preferable completely horizontal. Preferably, with conical body it is meant an elongated body having increasing or decreasing cross section dimensions over a substantial part of its length, preferably the full 15 length. The corresponding is true for conical holes. With a cylindrical groove or body it is meant an even cross section over a substantial part of the length, preferably all the length except from optional tapering or grounding off at the ends. Cylindrical does not necessarily mean round cross section, the only requirement is that the cross section is the same along the length. The cross section therefore can be triangular, four-sided, five-sided, round, 20 elliptical, T-formed or take any other form, which also is true for conical bodies, provided that the further distinguishing features are maintained. In one form, it is also important to be aware of that the cylindrical body can extend in vertical direction, such that a part of the cylinder body, along the full or parts of its length, can extend out for example from the electrode body. 25 Preferably, the feature of the largest horizontal cross section dimension of the conical body and cylindrical body to be within respectively the electrode body and the groove when these are joined, hinder that bodies as joined can be separated from each other by pullingin vertical direction, orthogonal to the longitudinal axis of the conical body and cylindrical body. For joining into the electrode body it is not required with cast iron 30 lining, ramming paste, ramming mass or glue, which provides savings both with respect to materials and labour. The conical form ensures good thermal, electrical and mechanical C \NRPonbl\DCCC IAB\2H53 ms DOC-1MW/201 0 -4 contact even after beginning of wearing out the conical bodies. A copper rail within a steel groove will during operation have very good electrical thermal and mechanical contact because the copper has larger thermal expansion than the steel, such that an appropriate tolerance for joining at room temperature, for example 0.15-0.5 mm clearance, will be 5 filled out by expansion of the copper. Thereby a releasable joining is achieved with good electrical, thermal and mechanical contact, which provides savings with respect to labour and possibility for easy replacement of parts of a current busbar. It is preferable if the cross section of the parts that are to be built into the electrode body has form of a circle, triangle or quadrangle under or below a high and narrow 10 rectangle, such that the largest horizontal dimension of the circle, triangle or quadrangle is at least four times larger than the horizontal dimension of the rectangle. This results in simple and solid fastening. The current busbar according to the invention is preferably formed such that different materials in the longitudinal direction of the busbar are welded together by linear 15 friction welding, surfacing friction welding, rotation friction welding, induction welding, laser welding or electron beam welding, because of good electrical, thermal and mechanical contact. The current busbar according to the invention can preferably be manufactured with pure aluminium, aluminium alloy, copper or copper alloy used as construction material in 20 the parts furthest away from the electrode body and in a distance close to or within the electrode body, with a protective lining of steel for parts within or close to the electrode body. Thereby the heat conduction is maximized while the electrical resistance is minimized and the electrolysis cell can be operated at high amperage. The current busbar according to the invention is preferably either an anode hanger 25 or a cathode steel. The current busbars according to the invention is preferably surface treated with wolfram, for increased life. The embodiment of the current busbar with only the distinguishing feature with the copper rails, can include traditional nipples as the ends or sections that during operation are within the electrode body. In one form, with the present invention also an electrode body is provided, 30 distinguished in that it in substance consists of carbon and has adapted grooves for mounting of the current busbars according to the present invention. The conical holes in C \NRPortbI\DCC\CAB\285168_ I DOC-16A4/210 -5 the electrode body are preferably slightly longer than the conical bodies, such that said conical bodies will fit into said conical holes even after some wearing out. In one form, with the present invention also an electrode is provided, distinguished in that it comprises current busbars according to the present invention joined with electrode 5 body according to the present invention. Drawings The invention is further illustrated by drawings, of which: The Figures la and lb illustrate an anode hanger according to the present invention. 10 Figure 2 illustrates another embodiment of an anode hanger according to the present invention. Figure 3 illustrates a third embodiment of an anode hanger according to the present invention. 15 Detailed description First, reference is made to the Figures lA and 1B, which illustrate an anode hanger according to the present invention, viewed orthogonal to the conical body 1, for Figure 1 A, and along the longitudinal axis of the conical body, for Figure 11B, respectively. The conical body is joined with an electrode body 2 by being slided into a conical groove 3 20 with form corresponding to the conical body. As apparent from the figure the largest horizontal cross section dimension for the conical body is within the electrode body, such that the conical body as joined with the electrode body during operation is fastened and kept in place into the electrode body. The conical body is on the upper side fastened into a narrower element, with cross section form as a rectangle with far smaller horizontal 25 dimension than the conical body, such that even though the groove in the electrode body is upwardly open along all or parts of the length of the conical body, said conical body cannot escape from the electrode body during operation. In the illustrated embodiment an inner core of copper 4 is provided in the conical body, the rectangle and an above positioned connecting beam. Outside the copper is a steel lining 5. The upper part of the 30 anode hanger is formed by an aluminium part 6, joined with the copper by friction welding. In the illustrated embodiment of the current busbar, in form of an anode hanger, C \NRPrbl\DC CAB\2S3 1691 DOC-16AW/201 -6 copper and aluminium is used in a large extent, which is preferable with respect to thermal and electrical conductivity. The whole anode hanger could be prepared by steel, but out of consideration to thermal and electrical conductivity preferably copper and optionally aluminium are used extensively. For increased heat conduction cooling ribs can be 5 provided in addition to using increased dimension for the different parts of the anode hanger. Reference is further made to Figure 2 that illustrates another embodiment of an anode hanger according to the invention, more specifically an anode hanger where a copper rail 7 is arranged to be slided into a correspondingly formed groove in a cylindrical 10 steel body 8 that is to be embedded into the electrode body. The copper rail and the groove are formed with tolerances such that the copper rail relatively easy can be slided into the groove in the steel body at room temperature. By heating during operation in the cell copper will expand more than steel such that a good electrical, thermal and mechanical connection between the copper and the steel is achieved. 15 Reference is made to Figure 3 where a further embodiment of an anode hanger according to the invention is illustrated, more specifically a steel nipple 9 with groove for sliding in of a copper rail 7 is illustrated. A number of steel nipples can be passed into the copper rail 7. Regarding the anode hangers illustrated on Figures 2 and 3, the cylindrical steel 20 body 8 and steel nipples 9 could be replaced with respect to a conical body of massive steel or with steel lining around a copper core, with grooves for fastening of the copper rail, with the groove either directly into the conical body or above, for example in a connecting beam. The most preferred embodiment of the invention (not illustrated) comprises both a conical body and fastening to the above part of the anode hanger by use of a copper rail, 25 because said embodiment includes all the advantages of the invention. Example An anode hanger with a conical section embedded into the electrode body illustrates some of the advantages of the invention. The cylinder section has length 1.5 m 30 and consists of a 100 to 140 mm diameter bolt under a small, high rectangle where in total 100 mm vertical rectangle side is embedded into electrode body. The resulting contact area C \NRPorlbIOCC\CAB\2853168 1 DOC-1(w4/2010 -7 2 with the electrode body is about 726 500 mm2. A standard anode hanger with 4 nipples has a contact area of typical 281 000 mm2 . The contact area has thereby increased 2.59 times. By having an adapted cross section area, choice of materials and form of the ends or sections of the current busbar that during operation shall extend out from the electrode 5 body, very preferable properties can be achieved with respect to the demands that are met with the present invention Throughout this specification and the claims which follow, unless the context requires otherwise, the word "comprise", and variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated integer or step or group 10 of integers or steps but not the exclusion of any other integer or step or group of integers or steps. The reference in this specification to any prior publication (or information derived from it), or to any matter which is known, is not, and should not be taken as, an acknowledgement or admission or any form of suggestion that that prior publication (or 15 information derived from it) or known matter forms part of the common general knowledge in the field of endeavour to which this specification relates.

Claims

1. Current busbar for anode or cathode for use in production of aluminium from alumina in an electrolysis bath in an electrolysis cell, which current busbar comprises one 5 or more ends or sections that during operation shall extend out of an electrode body, and one ore more ends or sections that during operation shall be within the electrode body, characterized in that ends or sections that during operation shall be within the electrode body are formed as one or more in substance horizontally oriented conical bodies with largest horizontal 10 cross section diameter within the electrode body, such that by sliding said bodies axially into one ore more adapted conical holes in the electrode body said bodies will be embedded and kept into the electrode body, and said conical bodies or elements connected thereto are manufactured from steel or steel over a copper core, and are provided with one or more in substance horizontally 15 formed cylindrical or conical grooves with largest horizontal cross section dimension within said grooves, such that by sliding in correspondingly formed copper rails on the external parts of the busbar, said bodies and rails are releasably joined.

2. Current busbar according to claim 1, characterized in that the cross section of the 20 parts that are to be within the electrode body have form as a circle, triangle or quadrangle under or over a high and narrow rectangle, such that the largest horizontal dimension of the circle, triangle or quadrangle is at least four times larger than the horizontal dimension of the rectangle. 25

3. Current busbar for anode or cathode for use in production of aluminium from alumina in an electrolysis bath in an electrolysis cell, which current busbar comprises one or more ends or sections that during operation shall extend out of an electrode body, and one or more ends or sections that during operation shall be within the electrode body, characterized in that ends or sections that during operation shall be within the electrode 30 body are formed as one or more in substance horizontally oriented conical bodies with largest horizontal cross section diameter within the electrode body, such that by sliding C \NRPo.bI\DCC\CABUK5316(AI DOC-IAW2O0 -9 said 35 bodies axially into one or more adapted conical holes in e electrode body said bodies will be embedded and kept into the electrode body.

4. Current busbar for anode or cathode for use in production of aluminium from 5 alumina in an electrolysis bath in an electrolysis cell, which current busbar comprises one or more ends or sections that during operation shall extend out of an electrode body, and one or more ends or sections that during operation shall be within the electrode body, characterized in that the transfer between steel in parts of the current busbar that are to be within or close to the electrode body and copper in external parts from the electrode body 10 are formed as one or more in substance horizontally formed cylindrical or conical grooves in the steel with largest horizontal cross section dimension within said grooves, and correspondingly formed copper rails on the external parts of the current busbar, such that by sliding in the copper rails into the steel grooves the parts will be releasably joined. 15

5. Current busbar according to any of the claims I to 4, characterized in that the current busbar is an anode hanger.

6. Current busbar according to any of claims 1 to 4, 15 characterized in that the current busbar is a cathode steel. 20

7. Current busbars according to anyone of claims I to 6, characterized in that pure aluminium, aluminium alloy, copper or copper alloy is used as construction material in the parts furthest away from the electrode body and in a distance close to or within the electrode body, with a protective lining of steel for parts within or close to the electrode 25 body.

8. Electrode body, characterized in that it in substance consists of carbon and is provided with adapted grooves for mounting of current busbars according to anyone of claims 1-7. 30

9. Electrode body according to claim 8, characterized in that the conical grooves in C \W b\DCCCABU85316H_ DOC.16U42010 - 10 the electrode body is slightly longer than the conical bodies, such that said conical bodies will fit into said conical grooves even though they have been slightly worn-out.

10. Electrode, characterized in that it comprises current busbars according to anyone of 5 claims 1-7 joined with electrode body according to claim 8.

11. A current busbar as substantially disclosed herein with reference to th drawings and/or examples. 10

12. An electrode as substantially disclosed herein with reference to the drawings and/or examples.