1997 TMS Annual Meeting: Wednesday Session

CARBON TECHNOLOGY: Session IV: Anode Plant

Session Chairperson: Prof. Yasar Kocaefe, Université du Quebec à Chicoutimi, Chicoutimi, Quebec, Canada G7H2B1

2:00 pm

BUTTS CLEANING AT SLOVALCO IMPLEMENTED BY TECHMO: J. Ifju, F. Zannini, F. Marchetti, M. Fontolan, Techmo Car S.P.A., Via R. Colpi, 15/17 35010 Limena (PD) Italy

The best use of anode carbon and bath materials withdrawn from the smelting process by anode changing involves their recycling. In order to provide optimal composition of recycled carbon and bath, a butt cleaning technology is required with the aim to avoid their contamination by each other. A technology and equipment has been elaborated for implementing above objective. Some optimization was fulfilled in order to meet the requirements of the new aluminium smelter implemented by Hydro Aluminium technology, taking into account very tough requirements to the material quality, as well as fitting a piece of equipment into the technology flowsheet planned.

2:25 pm

DUST CONTROL TECHNOLOGY FOR ANODE BUTT RECYCLING: Nathalie Perreault, Betz Water Management Group, Casier Postal 232, Baie Comeau, Québec, Canada G4Z 2G9; Eric Grondin, Engineering Environment and Water Treatment, Reynolds Metals, 100 route Maritine, Baie Comeau, Québec, Canada G4Z 2H7

There are several dust control problems in the Aluminium industry, amongst them is the process of recycling anode butts. In general, prior to being recycled, the butts are cleaned, taken off the hexapod rods and stored and/or shipped to be processed as new anodes. A particular area of concern for fugitive dust during the anode preparation process is anode butt stripping inside the anode rodding room. This process generates a lot of carbon dust. It has been both a health and safety issue, as well as cleaning burden for operating personnel. This paper presents different alternatives, both mechanical and chemical, for controlling fugitive dust, and a decision process for using chemical treatment. In addition, the theory behind the chemical application and a case history will also be presented.

2:50 pm

EFFICIENT ANODE-COLLAR CAST IRON MICROSTRUCTURE: Michael Barstow, 1152 Southvale Road, Pittsburgh, PA 15237

Cast iron is used to secure the steel stub of an anode rod to a carbon block for aluminum reduction cells. The quality is measured by the millivoltage drop across the stub-carbon interface. The electrical resistivity of cast iron varies with it's microstructure, which changes with temperature. Cast iron cannot be simply specified by analysis since it is section sensitive, and the microstructure is affected by minor elements, time, and rate of cooling. If the metallurgical control is limited, collars will develop variable electrical efficiencies. Recycling cast iron callors also causes a change inthe minor element analysis (S,P) which will change the microstructure / electrical resistivity. A cast iron designed for optimum fluidity with low level minor elements will provide lower electrical resistance than one with buildup of Mn, S. Other melting efficiencies are predicted.

3:15 pm BREAK

3:35 pm

AUTOMATIC STUB STRAIGHTENING SYSTEM: Jòn Hjaltalin Magnusson, ALTECH Ltd., Borgartun 18, 105 Reykjavik, Iceland; William Cannon, Portland Aluminium Ltd., Portland, Victoria 3305, Australia

For improving the economy and environment aluminium smelters have increased the automation of diverse tasks. An automatic system has been developed for the task of straightening anode rod stubs instead of cutting them off the rod yoke and welding new onto the yoke. The stub toe-in problem cannot be eliminated, but significant degree of control can be implemented to eliminate its adverse effects and increase the useful life of the stubs and reduce the considerable cost of reparation and stub material. This paper describes the cause of the stub bending in the electrolitic cells together with the details of the new automatic stub straightening system based on preheating the stubs with induction heating coils prior to straightening in a hydraulic cylinder press. Implementation of this straightening system at Portland Aluminium in Australia is also described, where the system was installed in February 1996. The system is installed "in-line" in the P&F overhead monorail and the bending of the stubs is measured automatically for deciding if the straightening is required or not. It will be shown how this system improves the useful life of the stubs leading to significant operational savings for the smelter.