ALUMINA, FROM THE V.S. PERSPECTIVE

Hewgill, D.F and Holywell, G.C.

At Alcan's Kitimat Works we have an annual rated capacity of 268,000 tonnes (300,000 tons) and as such use some 520,000 tonnes of alumina yearly. The Smelter is broken into 3 main areas. The first, and oldest, are Electrochemisk designed Vertical Stud Soderberg Cells. They operate at 106.5 KA, are side fed with a wheel and have no basement. The second and third areas are a Pechiney design, modified by Alcan, to increase the amperage to the 125 to 127 KA range. They are Vertical Stud Soderberg, sidefed with a wheel and have a basement.

All of the off-gases are collected in a primary collection system and after being burned, at the cell, are dry scrubbed using the alumina as the scrubbing medium. There is no secondary fume treatment or roof scrubbing.

The operating philosophy of the plant has been, and is, to blend, as much as possible, incoming raw materials to give consistency. The plant has used, since 1980, ore from several different sources, they include: - QAL - Surinam - Aljam - NKK - Tomakomai - Kwinana - NKK - Shimizu - Gove

This paper will discuss, what the smelter considers as important physical and chemical properties of its alumina supply from the point of view of cell operation, cellroom environment, purity, dry scrubbing and material recovery. The accent will be particularly from Kitimat's point of view, that is; VS, sidefed and dry scrubbed.