IMPROVEMENTS IN AND RELATING TO THE SUSPENSION OF ANODE BARS IN THE ELECTROLYTIC PRODUCTION OF ALUMINIUM

Abstract: A suspension arrangement for anode bars (10), (11) in cells for electrolytic production of aluminium, comprises two jacks (7) which are disposed along the center line of the anode bar, between the anode superstructure (9) and the anode bars (10), (11). The anode bar is movable in the vertical direction by means of their jacks which are separately driven, or driven by means of one common motor. To prevent the anode bar from rotating around its longi­ tudinal axis, there is disposed a torsion device between the anode bar and the anode superstructure. Further the anode bar is provided with side supporting means (13, 14) which prevents the anode bar from moving side-ways.

Description: The present invention relates to a suspension device for anode bars in cells for the electrolytic production aluminium. A cell for producing aluminium electrolytically consists of a flat steel shell with a carbon lining on the inside. The carbon lining represents the cathode, while the anode, which is also made of carbon, usually comprising several carbon blocks or elements, are fixedly held by anode hangers. The anode hangers are securely attached to an anode bar, providing a firm mechanical as well as electrical con­ nection with the anode bar. Said carbon blocks are usually referred to as anode carbon bodies. During the electrolytic process the carbon bodies are con­ sumed by the precipitated gases, at their lower ends, and to be able to keep a constant distance to the cathode, the anode bars with the anode carbon bodies have to be simultaneously lowered. The anode bar is provided with vertical regulating means, and when the anode bar has reached the lowermost re­ gulating level, all the anode hangers are removed from the anode bar and temporarily attached to a so-called "crossing bar". The anode bar is then raised to its uppermost posi­ tions, whereafter all the anode hangers are reattached to the anode bar in its new position. In a modern electrolytic cell of up to 250 K ampere, the weight of the anode suspension arrangement may be about 35 tons and the length of the anode bar about 11 meters. Ob­ viously, with such dimensions, the anode suspension arrange­ ment is a large and expensive construction. The vertical regulating means for the anode bar has to be so constructed that the anode bar may be raised or lowered by parallel movement, or tilted to either side in its longi­ tudinal direction to achieve an inclined position. The known types of suspension arrangements may roughly be divided into three different methods. A. Four separate jack devices, of which two at a time are driven by the same motor, are each mounted at one of the end corners of the anode bar. The jack devices are placed on or suspended by separate contruction elements which either stand at the short end of the electrolytic cell or on a self-supported anode superstructure. (If one, instead of two motors are used, it is not possible to tilt the anode bar.) B. Separate jack devices which are each driven by a motor. The jack devices are mounted to standing on the floor along the center line of the electrolytic cell, at the short end of the cell, providing an upward movement of the anode bar. C. One single jack device with a motor is mounted at one of the anode superstructure ends. The jack device controls two mechanisms (one on each side of the anode superstruc­ ture, and each attached to one of the beams of which the anode bar is made) and is so arranged that when the jack is moved upwards or downwards, the anode bar is subject to a sheer vertical movement (i.e. it is not possible to tilt the anode bar). These existing methods have several disadvantages. Method A fulfils all the functional demands, but when the electrolytic cells are very long, the mechanical load on the anode bar is unfavourable which means that the anode bar has to be very heavy if deformation stability is to be held within reasonable limits. Method B is encumbered with the same disadvantage as method A and needs besides to be provided with a sideways support for the anode bar. Method C provides a favourable location of the suspension points between the anode bar and the mechanisms, so that the mechanical dimensioning of the anode bar may be optimized. The method, however lacks the possibility of lifting the anode bar which is commonly used in connection with the terminations (killing) of anode effect. It is an object of the present invention to provide an anode suspension arrangement wherein it is possible to optimize the suspension points for the anode bar and the jack devices as described above for method A, at the same time as enabling tilting the anode bar to take place. This is achieved by means of a suspension device in accordance with this invention wherein at least two jacks are disposed along the longitudinal line of the anode bar, the device including torsion devices to prevent the anode bar from rotating around its longitudinal axis, and side guiding or supporting means to prevent the anode bar from moving side-ways. Preferably the torsion device comprises pivotally connected arms each of which at one end is rotatably attached respectively to each side of the ends of the anode bar and at their second ends are fixedly connected to each of the ends of a torsion shaft which is rotatably mounted on the anode superstructure. The side supporting means may consist of guide shoes on the anode bar mounted to slide along vertical guideways on the anode superstructure. The sides supporting means may alternatively consist of rollers disposed on the anode bar which roll against vertical roller bars on the anode superstructure. The invention will now be described in further detail with reference to the accompanying drawings, in which Fig. 1 is a longitudinal view, partly in section, of an anode bar with an anode suspension arrangement according to the invention, Fig. 2 is a horizontal view of the bar of Fig. 1, and Fig. 3 is a cross-section to a larger scale of the anode bar and the suspension arrangement taken along the line A-A in Fig. 1. The anode bar 1 has a frame construction comprising two parallel beams 10, 11 (see Figure 2) from aluminium, which is disposed above an electrolytic cell (not shown) in its longitundinal direction. The two beams 10, 11 are connected to one another by means of cross bars 12 at the ends of the beams, and depending on the length of the beams 10, 11, at one or more points in the longitudinal direction of the beams. In the example shown in Figs. 1 and 2, the beams 10, 11, are provided with four cross bars 12. The anode carbon bodies are connected to the beams 10, 11 in two parallel rows by means of anode hangers (not shown). As the lower ends of the carbons are consumed during the elec­ trolytic process, the consumed carbon is replaced by lowering the anode bar. The suspension arrangement moves the anode bar in the vertical direction and transfers the forces acting on the anode bar to a self-supporting steel construction, the so-called anode superstructure 9, which is either supported by the cathode shell, or independently of this, on a separate structure. The anode suspension arrangement comprises two jack devices 7, which at their lower ends are rotatably attached to cross shafts 8, extending between the beams 10, 11 and at their upper ends are connected to the anode superstructure 9. The shafts 8 are disposed between the beams 10, 11 and are so spaced that the forces acting on the jack devices are equal, and the forces in the beams are as low as possible. Accordingly, the jack devices 7 are arranged in the place of vertical symmetry of the beams 10, 11. The jack devices 7 are separately driven, and provide a ver­ tical, parallel movement as well as tilting movement of the anode bar. To prevent the anode bar from rotating around its longitudinal axis, the ends of the anode bar are provided with torsional devices 6. Each torsional device consist of two arms 4, 5 which are pivotally linked to one another. The lower ends 2 of these arms are rotatably attached to the respective beams 10, 11, while the upper ends are fixedly attached to the ends of a torsion shaft 3 which is rotatably disposed on the anode superstructure 9. The functioning of the torsional devices is as follows: When the anode bar tends to be twisted around its longitudi­ nal axis, the arms 4 on one side of the bar will push the arms 5 on the same side which again results in a rotation of the torsion shaft 3. This rotation will, however, be prevented by the arms 4, 5 on the other side of the beams, whereby the anode bar is kept in its same horisontal position. When used in connection with large electrolytic cell constructions, the anode bar may be provided with additional torsional devices on other places along the anode bar. Whether it is necessary to use more than two torsional devices is, however a matter of judgement. To be able to withstand the side forces acting on the anode bar, a mechanical guiding or supporting arrangement is disposed between the anode bar and the anode superstructure 9. This may consist of rollers which are rotatably disposed on the anode bar, for example at each corner of this, and which can roll against a roll guide on the anode superstructure 9. Or, it may consist of guide shoes mounted on the anode bar which can slide along vertical guide ways on the anode superstructure 9.

Claims: 1. A suspension device for the anode bars of electrolytic apparatus for the production of aluminium wherein the anode bar may be lowered or lifted in the vertical direction by means of jacks (7) which are disposed between the anode bar and anode superstructure characterized in that at least two jacks (7) are disposed along the longitudinal center line of the anode bar, in that the device includes torsion devices (6) to prevent the anode bar from rotating around its longitudinal axis, and side guiding or supporting means (13, 14) to prevent the anode bar from moving side-ways. 2. A suspension device according to Claim 1, characterized in that the torsion devices (6) comprise pivotally connected arms (4, 5) each of which at one end (2) is rotatably attached respectively to each side of the ends of the anode bar, and their second ends are fixedly connected to each of the ends of a torsion shaft (3) which is rotatably mounted on the anode superstructure (9). 3. A suspension device according to Claim 1 or 2 characterized in that the side supporting means consist of guide shoes (14) disposed on the anode bar (1), and which can slide along vertical guide ways (13) disposed on the anode superstructure (9). 4. A suspension device according to Claim 1 or 2 characterized in that the side supporting means consist of rollers disposed on the anode bar, and which roll against vertical roller guides disposed on the anode superstructure (9).

Inventors: SANDVIK, EYSTEIN
Applicants: NORSK HYDRO A.S.
Application year: 1987
Main classification: C25C3
IPC codes: C25C3