Two-stage lumped parameter observer for spatial alumina concentration in aluminium reduction cells: Validation on simulator and industrial data

Abstract

The absence of continuous dissolved alumina sensors capable of withstanding the difficult conditions inside an aluminium reduction cell makes the design of an observer necessary for the cell’s supervision. In this paper, a two-stage lumped parameter Extended Kalman Filter observer using the cell voltage and the anode currents is proposed to estimate the dissolved alumina distribution in an aluminium reduction cell. The proposed two-stage lumped parameter observer does not require prior knowledge of the bath’s velocity field but instead relies on continuous correction of estimations using anode currents. The observer convergence is validated in two different ways. In the first case, the observer is tested on a dissolved alumina distribution simulator. This simulator includes dissolved and undissolved alumina distributions, as well as ACD dynamics together with anode current redistribution implicit equations. Secondly, the observer is validated on industrial data, using a procedure based on industrially available measurements of tetrafluoromethane gas to overcome the lack of direct alumina sensing.