METHOD OF REPROCESSING SODA-POTASH SOLUTION Russian patent published in 1997 - IPC

FIELD: nonferrous metallurgy. SUBSTANCE: invention focuses on reprocessing soda-potash solution formed in integrated process of nepheline material conversion into alumina and coproducts using caking procedure. Method includes concentrating evaporation of initial soda-potash solution; mixing evaporated solution with recycled double soda-potash salt produced in preceding stage of process; evaporation to density 1.48- 1.50 t/cu.m and producing desired sodium carbonate; adding mother solution obtained after potash separation in the next process stage to mother solution obtained after separation of soda and evaporation of mixture to density 1.640-1.645 t/cu.m accompanied with separation of double soda-potash salt which is then directed to mixing with solution obtained after concentrating evaporation; subsequent isolation of desired potash at temperature 68-35 C from mother solution remaining after separation of double soda-potash salt using mother solution obtained after isolation of soda; and concomitantly producing commercial potassium sulfate. The latter, according to invention, is prepared by crystallization at 30-60 C for 5-20 h from mixed solution obtained when adding mother solution after potash separation and/or mother solution after soda isolation to solution containing sodium sulfate, which has been obtained by treating at 30- 70 C solid sodium sulfate or its mixture with sodium carbonate with initial soda-potash solution and/or water taken in amounts ensuring sodium concentration in mixed solution on the level 95-150 g/l Na₂O. In this case, mother solution after isolating potash and/or mother solution after separating soda is utilized in such amount as to ensure relative molar concentration of potassium in solution after potassium sulfate crystallization on the level 50-60% based on summary potassium and sodium concentration. EFFECT: improved quality of commercial soda, increased yield of commercial potassium sulfate (fertilizer), and achieved possibility of varying yield of products in dependence on varying demand. 4 dwg , 1 tbl