Thermodynamic Simulation of the Flux Refining of Primary Aluminum in a Ladle

The processing of primary aluminum with boric acid in a ladle is subjected to thermodynamic analysis. The HSC Chemistry 9.0 (Outotec Technologies) software was used for calculations. The temperature range investigated in the calculations (650–950°C) corresponds to the production conditions of the Kazakhstan Electrolysis Plant. The pressure range is determined using the technological conditions of flux treatment of aluminum in a crane ladle with a working height of 2 m and ranged from 101.33 to 148.99 kPa. The presence of a solid phase and low process kinetics are characterized by the lower limit of the temperature range. The upper limit of temperatures demonstrates the conditions closest to the actual working conditions during electrolysis. The pressure at the metal melt surface is represented by the lower limit in the pressure range, and the pressure at the depth of flux immersion equivalent to 2 m is represented by the upper limit. The depth of the suspension immersion in the calculations is varied in the range 0.5–2 m. The thermodynamic analysis in the investigated range of temperatures and pressures unequivocally indicates that vanadium borides are more stable compared to aluminum borides; therefore, they will predominantly form in this temperature range. The stability order also suggests that vanadium can be easily removed from aluminum melts by adding boron.