US 10,472,725 B2Granted

Method for controlling an alumina feed to electrolytic cells for producing aluminum

AssigneeUnited Company RUSAL Engineering and Technology Centre LLC

InventorsDmitriy Aleksandrovich Simakov, Aleksandr Olegovich Gusev, Kirill Borisovich Bakin

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Abstract

The invention relates to nonferrous metallurgy and may be suitable for controlling the feed of alumina to electrolytic cells for producing aluminum to maintain the alumina concentration in the electrolytic melt equal or close to the saturation value. To maintain the alumina concentration within the set range, reduced voltage U or pseudo-resistance R is measured and recorded at fixed time intervals. Underfeeding or overfeeding phases occur compared to a theoretical alumina feeding rate during electrolysis, wherein the duration of underfeeding phases is based on the alumina concentration in the electrolytic melt, and the duration of overfeeding phases is based on the change of one or more electrolytic cell parameters being recorded: reduced voltage, U, pseudo-resistance, R, rates of reduced voltage, dU/dt, pseudo-resistance, dR/dt, change. Adjustments to the anode-cathode distance to maintain the electrolytic cell energy balance may be performed during any of the feeding phases.

Claims14

Dependent claims

A method for controlling a feed of alumina to an electrolytic cell for producing aluminum by electrolysis of a molten salt melt, the method comprising:

measuring a plurality of resistance values between electrodes of the electrolytic cell;
recording the measured resistance values at fixed time intervals;
evaluating an alumina concentration of the molten salt melt;
feeding the alumina at a set rate in underfeeding phases (V1) and overfeeding phases (V2) compared with a theoretical alumina feeding rate;
alternating the underfeeding phases and the overfeeding phases, wherein a pair of successive underfeeding and overfeeding phases makes a feeding cycle (i), such that the alumina concentration is maintained in a range from 5% below a saturation value to the saturation value,
wherein a duration of the underfeeding phases is selected depending on the alumina concentration in the electrolytic melt, and
wherein a duration of the overfeeding phases is determined by a change of one or more recorded electrolytic cell parameters selected from the group consisting of:
reduced voltage, (U),
pseudo-resistance, (R),
rate of change of reduced voltage, (dU/dt), and
rate of change of pseudo-resistance, (dR/dt);
and
in a second feeding cycle (i+1) following a first feeding cycle (i), based on the duration of the overfeeding phase in the first feeding cycle (i), automatically adjusting one or more parameters selected the group consisting of:
the alumina feed rate in the overfeeding phase (V2) for the second feeding cycle;
the change in reduced voltage (ΔU) necessary to terminate the overfeeding phase in the second cycle;
and
the change in pseudo-resistance (ΔR) necessary to terminate the overfeeding phase in the second cycle.

14 more elements

Dependencies are inferred from the claim text.