“On the AlF3 and temperature control of an aluminium electrolysis cell”

Authors: Tormod Drengstig, Dag Ljungquist and Bjarne A. Foss,
Affiliation: NTNU, Department of Engineering Cybernetics, Norsk Hydro and Elkem
Reference: 1998, Vol 19, No 1, pp. 31-59.

Keywords: Modeling, metals industry, temperature control, electromechanical processes, AlF3 control

Abstract: In this paper we propose a control strategy for excess AlF3 and bath temperature of a prebake aluminum electrolysis cell based on analyzes of measured data and studies of a simple dynamic model. Model validation indicates that there are dynamics that the model does not capture, and hence, we use real data of excess AlF3 and bath temperature to estimate AlF3 and energy disturbances respectively. The estimation results show that the energy disturbance is the dominating disturbance. Hence, the proposed control strategy is based on an almost constant AlF3 input close to average consumption and energy manipulations to compensate for the disturbances. This requires the possibility tor the resistance reference to be reduced without decreasing the current efficiency. Compared to present control strategies, this introduces an additional degree of freedom in the controller. The proposed control strategy may imply a significant economic potential through increased and stabilized current efficiency, reduced and stabilized energy consumption, reduced consumption of expensive additives and prolongation of cell life.

PDF PDF (3852 Kb)        DOI: 10.4173/mic.1998.1.3

DOI forward links to this article:
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  title={{On the AlF3 and temperature control of an aluminium electrolysis cell}},
  author={Drengstig, Tormod and Ljungquist, Dag and Foss, Bjarne A.},
  journal={Modeling, Identification and Control},
  publisher={Norwegian Society of Automatic Control}