An investigation of the effect of the electrolyte composition on the consumption of fired anodes during electrolytic aluminum production

Abstract

The effect of adding CaF2, AlF3, and KF into electrolyte on the consumption of fired anode during aluminum electrolysis is investigated. The CaF2 content varied from 5 to 10 wt % in the electrolyte of the industrial composition. Correspondingly, the concentration of AlF3 and KF varied from 4 to 10 and from 0 to 4.7 wt % in the modified electrolytes. Based on the procedure used, the total consumption of carbon and the amount of carbon transported into the gas phase (m g) and foam (m f) were determined. Electrolysis duration was 12 h, the distance between the poles was 40 mm, the temperature was 960°C, and the current density was 0.85 and 1.2 A/cm2. It is established that adding CaF2 and AlF3 increases the consumption of anode, while adding KF decreases it. For CaF2, ∂m f/∂[CaF2] is larger than ∂m g/∂[CaF2], 15.4 and 6.6 kg/(tAl wt %) CaF2, respectively. For AlF3, ∂m f/∂[AlF3] is also larger than ∂m g/∂[AlF3] and equals 6.8 and 4.2 kg/(tAl wt %) AlF3. For KF, ∂m f/∂[KF] is smaller than ∂m g/∂[KF], being −11.3 and −8.1 kg/(tAl wt %) KF.