Mathematical modeling of hydrometallurgical processing of dismounted сarbon pot lining of aluminum reduction cells

The purpose of the paper is using the method of mathematical (physico-chemical) modeling to study hydrometallurgical processing of spent carbon pot lining of dismantled cathodes from aluminum reduction cells; using the method of thermodynamic analysis, which is based on the built model of the influence of caustic soda solution concentration (NaOH - Na₂O_ку) and liquid and solid phases ratio to estimate fluorine extraction to solution. Mathematical modeling of fluorine leaching from spent pot lining samples is carried out on the basis of studying the physicochemical laws of the process using the «Selector» program complex based on the minimization of Gibbs energy and is widely used for metallurgical process study. The object of research is a sample of spent carbon pot lining of the aluminum reduction cell of RUSAL Krasnoyarsk OJSC. According to the X-ray phase analysis the fluorine-containing phases in the sample are cryolite Na₃AlF₆, chiolite Na₅Al₃F₁₄, calcium fluoride CaF₂, sodium fluoride NaF. Besides, Si, Fe, Mg, S, K, Ti are also found in the carbon-containing material under investigation. The behavior of the components of the spent carbon pot lining is evaluated in the process of alkaline processing under the action of the solution with Na₂O_ку concentration of 12.5, 17.5 and 25.0 g/dm³ using the formed mathematical model. According to the model the best indicators of fluorine extraction into the solution (72.9-90.57%) have been achieved at the reagent concentration of 12.5, 17.5 g/dm³ Na₂O_ку and the liquid to solid ratio of 10-12:1. The developed model allows to determine the amount of alkaline solution necessary for fluorine extraction and the optimal ratio of liquid and solid phases. The phase composition of cake and forms in which fluorine remains in solid residue (cake) are also determined.

aluminum production, reduction cell, cathode, spent pot lining, fluorine extraction, leaching