Study of the influence of the covering material of the baked anodes of the aluminum electrolyser on the main indicators of electrolysis

Covering the anode array of electrolyzers has a significant impact on the technical, economic and environmental performance of cryolite-alumina melt electrolysis, allows reducing the consumption of electricity, carbon materials and the level of pollutant emissions. The purpose of our research was to study the effect of the characteristics of the covering material on the main indicators of the electrolysis of cryolite-alumina melts (using electrolyzers with baked anodes of the RA-300B type as an example). At the alumi-num plant, an experimental group of 12 electrolyzers was determined for testing, where pure metallurgical alumina was used as a covering material. The backfill scheme of the anode blocks was changed to reduce the amount of impurities coming from the covering material into the electrolyte and, consequently, into the resulting aluminum. According to the studies carried out on the experimental group of electrolyzers, it was found that the chemical composition of the covering material affects the process parameters and quality of raw aluminum. It is shown that the change in the chemical composition of the anode covering material helps to reduce the Fe influx into raw aluminum from this material: the decrease was 0.004% by weight. The experiments revealed that the presence of recycled electrolyte in the covering material causes a change in the electrolyte level in RA-300B electrolyzers. It was concluded that it is necessary to change the amount of recycled electrolyte in the material depending on the specific value of the electrolyte level in the bath as-sociated with the influx of Na (as an element determining the cryolite ratio) with alumina. Thus, it is shown that under current production conditions it is possible to produce primary aluminum with a lower content of the main impurities (Fe and Si).