PROCESS FOR RECOVERING ALUMINIUM FROM FOUNDRY SLAG

摘要

The invention relates to a process for recovering aluminium from the fine fraction obtained by crushing and screen separating crusts, slags and ashes resulting from aluminium waste melting furnaces. According to the invention, the process consists in washing first the starting material to remove soluble potassium and sodium salts, followed by the solubilization of aluminium in the solid phase by treatment with a solution of sulphuric acid, in a concentration of 20...75%, at temperatures of 80...150A C, in an open or closed system, up to a final pH value of 1.5...4, for 2...5 h, followed by phase separation by filtration, washing the solid phase with water, at a temperature of 70...80A C and separating the aluminium sulphate from the liquid phase containing aluminium sulphates and iron sulphates, by 2-stage evaporation/crystallization, at temperatures of 90...100A C/40...50A C in the first stage, and 40...45A C/20A C in the second stage.