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Energy Savings from new Cathode Blocks

SGL Group’s innovations optimize aluminum production

The basic technology for aluminum production was invented 125 years ago and has since been continuously developed further. It is an electrolysis process by which aluminum oxide is converted into aluminum with the aid of electric current. Cathode blocks, on the one hand, provide the feed for electrical energy, and on the other hand, make up the base in the construction of the electrolysis cell. They are replaced after an average service life of five to seven years.

Energy efficiency is of strategic significance to our customers. Energy costs account for approx. 30 % of the total aluminum production costs. The cathode block, as one of the structural components, contributes directly and indirectly to the energy efficiency of the production process. SGL Group is working intensively on value adding solutions: in 2010 we started with the market launch of the three new developments. They testify to the innovative strength of SGL Group even in business areas which serve mature markets.

Cathode block material with dual benefits
Cathode block materials require good electrical properties and long service life. However, these two requirements often counteract each other. SGL Group has been able to combine them in one material successfully. The result: reduced energy consumption and longer running times for the electrolysis cell. The longer cell life reduces both the replacement costs as well as the disposal costs of contaminated components of the electrolysis cell.

Improved contact
Cast iron is used for the electrical connection between the cathode block and the system. There are electrical losses in the transition from the cathode block to the cast iron. The solution developed and recently patented 1) by SGL Group minimizes these losses through the use of Sigraflex® graphite foil. Our customers benefit twofold from this concept: on the one hand, the energy consumption in the electrolysis system is decreased, on the other hand the risk of the cathode being damaged by thermal shock during insertion of the hot cast iron is reduced.

More uniform distribution of the current density
Very strong electric currents pass through the cathode block during the electrolysis process. Usually, the current density distribution through the cathode is hetero-
geneous. SGL Group solves this problem with a patented 2) optimization of the slot for the collector bar. Energy consumption and also service life can be positively affected by the significantly more uniform current density.

1) Patent No. PCT/EP 2006/012310
2) Patent No. WO 2007/118510

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