CELL LINES

The Cell Lines department commonly referred to as “The Potrooms” has a primary function of converting alumina (Al2O3) to aluminium.

The Cell Lines department consists of two broad sub-departments, namely, Cell Lines or Potlines and Cell Repairs. The Cell Repairs outfit is further divided into two sub-sections: Cell Repairs Production and Cell Repair Maintenance.

POTLINES

There are altogether five (5) cell lines (potlines) in Valco. These were built in two phases:
Cell Lines 1-3 were first built between 1965 -1966 and started operations in June 1967.
Cell Lines 4-5 were built between 1972 and 1976.At Valco, a potline consists of hundred (100) reduction cells electrically connected in series and housed in two (2) main rooms of fifty (50) cells each.

The cell design type employed at Valco is a Kaiser P69 design with an end-riser buss configuration; modified pseudo-point feed system and a deeper shell cavity.

The reduction process is controlled with the aid of a Kaiser developed computer-based process automation system referred to as “Celtrol”.

The smelter has a rated plant capacity of 200,000 TPA but currently operating at 30% capacity. Power continues to be the major challenge in operating at full capacity.

CELL REPAIR

CELL REPAIR MAINTENANCE:

This section carries out the offline repair works on the cathode steel shells and the upper super structural members of the cell (pot) on failure.

CELL REPAIR PRODUCTION:

This section has a core function of wrecking, installing and constructing reduction cells when they fail. It also has the capability of repairing the failed cathodes.

Together, they constitute a very vital part of the Cell Lines department since they play the key role of keeping the operating cell count at its optimum level to ensure plant maximum productivity.

REDUCTION CELL:

The electrolytic reduction cell consists basically of an assembly of eighteen (18) pre-baked carbon blocks constituting the positive electrode. The metal pad constitutes the negative electrode (active cathode).

The anode is immersed in an electrolyte (molten cryolitic bath) contained in the “cathode” and direct electric current allowed to flow through the molten bath causing the dissolved alumina (aluminium oxide) in solution to decompose into aluminium depositing on the cathode and oxygen to combine with the carbon anode to form carbon dioxide.

This fundamental chemical process for the production of aluminium is typified as follows:

2 Al2O3           +            3C            →         4 Al ↓          +              3CO2 

Alumina                      Carbon Anode          Molten Aluminium      Gas

The anodes are replaced on a regular schedule and the molten aluminium produced is siphoned into opened top crucibles and transported to the Cast House for further processing.

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