Operational and Control Improvements in Reduction Lines at Aluminium Delfzijl

Abstract

Nowadays viability of smelters requires operation of cells at or beyond known performance limits. At Aldel over the last ten years the intensity of electrical energy dissipation and alumina dissolution per cubic centimeter of liquid bath have increased by 50% as production (+40%) and specific energy consumption (‒ 6%) have improved. The cell imbalances resulting from this increased intensity must be sensed quickly and their causes corrected or removed to maintain the cells in their most efficient operating zone. This defines a new control objective for smelting relating to diagnosis of causes of abnormality in strongly interactive multivariate processes. Timely identification of these causes of variation is linked to operational practice improvement and better control decisions in reduction lines.

This paper describes smelter based improvement of operational practices and control decisions using the above objective. Statistical multivariate control surfaces are presented for operating cells and identified abnormal behaviours are discussed.