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Cathode systems for electrolytically obtaining aluminum

a cathode and aluminum technology, applied in the field of cathode systems for the electrolytic production of aluminum, can solve the problems of increasing the cost of cathode production, affecting the production efficiency of cathode, and the installation of contact pins and the machining of the recesses on the adjoining parts, so as to achieve the effect of not increasing the variety of production measures

Inactive Publication Date: 2006-07-13
SGL CARBON SE
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

The invention aims to improve the uniformity of material removal from cathode blocks in aluminum production. This is achieved by dividing the conduction of electric currents from the cathode into multiple zones with differing electrical resistances. This can be achieved by using different materials or designs in the cathode system, such as multiple parts in the collector or contact composition with different conductivities. The technical effects include improved stability and efficiency of the aluminum production process and reduced production costs.

Problems solved by technology

However, the installation of these contact pins and the machining of the recesses on the adjoining part incur considerable expense.
While the first possibility is to be rejected for economic reasons, the second possibility results in additional complication of the graphitization step which has to be optimized in each case to the specific cathode shape.
All the measures mentioned thus imply particularly increased costs in the production of the cathodes.

Method used

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  • Cathode systems for electrolytically obtaining aluminum
  • Cathode systems for electrolytically obtaining aluminum
  • Cathode systems for electrolytically obtaining aluminum

Examples

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Effect test

example 1

[0060] Graphite cathodes of conventional construction having a length of 3 300 mm were provided with conventional steel supports as collectors and connected electrically by introduction of ramming pastes having differing resistances. Here, the ratio of the specific resistance of the tamping composition in the region near the edge to that in the central region is 5:1. An electrolysis cell equipped in this way with 20 cathode blocks was operated at a current of 220 kA and 4.4 V for 1 000 days. For comparison, cells were operated using the same cathode system but a uniform tamping composition.

[0061] After the period of operation indicated, the cells were emptied and dismantled, and the cathodes were examined for wear. While in the case of the cathodes having a uniform construction the removal of material in the two edge zones was about 7.5 cm and that in the middle of the cathode was only 2.5 cm, in the case of the configuration according to the invention the removal of material in th...

example 2

[0062] Graphite cathodes of conventional construction having a length of 3 300 mm were provided with conventional steel supports as collectors and connected electrically in a conventional way by introduction of a tamping composition. An electrolysis cell having 20 cathode blocks was operated at a current of 220 kA and 4.4 V for 1 000 days (comparison). According to the invention, the same cathodes were joined to steel supports like those shown as 2 in FIG. 4 whose ends had been milled down to ⅚ of their original thickness to a distance of about 700 mm from the end of the cathode. The transition to the unmachined middle zone had an angle of about 160° as shown in FIG. 7. The milled area was covered with a mica sheet 6 having a thickness of about 0.3 mm, and a steel plate 5 having appropriate dimensions was fastened on top of this at each end of the support with the aid of sleeves of the type shown in FIG. 9 which were insulated with mica sheets.

[0063] The steel supports or collector...

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Abstract

Cathode systems for the electrolytic production of aluminum, which are divided in the direction of their long axis on the side of the power conduction from the cathode into at least two parts having differing electrical resistances in such a way that the electrical resistance from the ends of the collector to the part of the marginal zone of the cathode facing the collector is at least 1.2 times the electrical resistance from the ends of the collector to the part of the middle of the cathode facing the collector, where either the contact composition or the collector is divided into zones of differing resistance, processes for producing them and their use in the electrolytic production of aluminum

Description

FIELD OF THE INVENTION [0001] The invention relates to cathode systems for the electrolytic production of aluminum, in particular ones having an improved operating life. BACKGROUND OF THE INVENTION [0002] In the electrolytic production of metallic aluminum in the Hall-Héroult process, aluminum oxide dissolved in about 20 times its amount of molten cryolite (Na3[AlF6]) as flux is decomposed by means of direct current (at a voltage of from 4 to 5 V and a current of from 80 000 to 500 000 A) at a temperature of about 960° C. in electrolysis cells. The liquid aluminum collects on the bottom of the carbon-lined tank serving as cathode under the melt which largely protects it from reoxidation. The carbon electrodes acting as anode (block or Soderberg anodes) are gradually consumed by the oxygen which is liberated. [0003] Suitable electrolysis cells usually comprise a steel tank which is lined on the inside with a thermally insulating material. The bottom of the electrolysis cells comprise...

Claims

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Application Information

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Patent Type & Authority Applications(United States)
IPC IPC(8): C25C3/16C25C3/08
CPCC25C3/08C25C3/16
Inventor BANEK, MANFRED
Owner SGL CARBON SE
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