Effects of electrolysis parameters on the technical and economic performance indicators of OA-300M baths

This works estimates effects of the key electrolysis parameters (bath ratio, electrolyte temperature and the content of calcium fluoride in the melt) on the technical and economic performance indicators of baths with burned anodes OA-300M at the current strength of 313 kA. During one month, complex measurements of technological parameters (melt temperature, metal and electrolyte levels) and the assessment of their impact on the current output and specific power consumption of 5 electrolysis baths were carried out at the branch of RUSAL Bratsk PJSC in Shelekhov. The target values of parameters for the electrolysis housing were calculated as the arithmetic mean of individual target values of the parameters of the working housing electrolysis baths. The specified bath voltage was maintained at 3.92 V. The complex measurement of parameters was performed every 34 hours. Electrolyte sampling to determine the bath ratio was conducted on every fourth day, in the process of carrying out complex measurements. The main technical and economic indicators of the studied electrolysis baths were the current output of 89.1-99.7%, as well as the specific consumption of technological electricity 11,941-13,361 kWh/t. It was found that only 2 out of 5 electrolysis baths under study were characterized by a stable technological mode and performance; therefore, the values of their main parameters were optimal. During the electrolysis of cryolite-alumina melts using OA-300M electrolysis baths, it became possible to achieve high values of current output (97.1-99.7%), the lowest specific consumption of technological electricity (11,941-12,260 kWh/t) at the bath ratio maintained within 2.21-2.35, the electrolyte temperature in the range of 954-968 °C and the content of CaF₂ in the melt ~ 5%. Since this type of electrolysis bath forms calcium fluoride in the electrolyte from calcium oxide entering the process with the raw material (alumina), it is necessary to control the content of CaO.

aluminium metallurgy, electrolysis of cryolite-alumina melts, electrolyte temperature, bath ratio, metal and electrolyte levels, current output