Consumption of Anode Paste for Aluminum Production

In Russia, most aluminum smelters are equipped with cells with self-baking anodes for which the task of reducing of anode paste consumption is relevant, since the fraction of anode materials in the cost of aluminum varies from 8 to 20%. To solve this problem, it is necessary to determine the need for anode paste. The method for calculating the specific anode paste consumption used at the enterprises of the aluminum industry has a large error. The article discusses the main errors of this technique, shows the stages of calculating the flow rate of the anode paste, assesses the adequacy of the calculations, and gives recommendations for improving the technique. In general, the considered methodology adequately reflects the processes of carbon consumption; however, the final result of the calculations may differ significantly from the real one. The values taken constant to simplify the calculation, in fact, can change during the electrolysis, which leads to a significant change in the final result of the calculations. For example, an increase in the fraction of CO₂ from 0.45 to 0.5 leads to a decrease in the anode paste consumption by 15.3 kg/t Al. At the same time, it is known that, with the onset of the anode effect, the composition of the anode gases changes sharply: the fraction of CO₂ decreases, and the fraction of CO increases. In summer, at high ambient temperatures, both the proportion of vaporized pitch and the proportion of anodes with an increased surface temperature rise. A change in the latter to 0.25 leads to an increase in anode paste consumption by 6.6 kg/t Al. The same applies to oxidation in air. The number of depressurized cells may increase, which will increase the carbon consumption. It is necessary to pay attention to the factors affecting the quality of the anode. Incorrectly selected particle size distribution or worn equipment can significantly degrade the quality of the anode and lead to an increase in carbon consumption. To correctly take into account the peculiarities of the formation of carbon monoxide, it is necessary to make adjustments to the calculation.