Thermodynamic Modeling of Flux Refining of Primary Aluminum in a Bucket

This article provides a thermodynamic analysis of the process of processing primary aluminum with boric acid in a ladle. HSC Chemistry 9.0 software from Outotec Technologies was used for calculations. In the calculations, the temperature range under study corresponded to the production conditions of Kazakhstan Electrolysis Plant JSC within the range of 650–950 °C. The pressure range was taken based on the technological conditions for flux processing of aluminum in a transfer ladle with a working height of 2 m and was in the range of 101.33–148.99 kPa. The presence of the solid phase and low kinetics of the processes are characterized by the lower limit of the specified temperature range. The upper temperature limit is the closest to real operating conditions during electrolysis. The pressure at the metal mirror is represented by the lower limit in the pressure range, the upper limit is the pressure at the immersion depth of the flux equivalent to 2 m. The immersion depth of the sample in the calculations varied in the range of 0.5–2 m. The research was carried out within the framework of grant funding from the Science Committee of the Ministry of Science and Higher Education of the Republic of Kazakhstan under the «Zhas Galym» competition under the project IRN AR19175493 «Development of technology for refining primary aluminum with filters with an active surface». Thermodynamic analysis in the studied range of temperatures and pressures clearly indicates that vanadium boride phases are more stable compared to aluminum borides, and, therefore, they will form preferentially in this temperature range. The order of stability also suggests that vanadium can be easily removed from aluminum melts by adding boron.