EUTECTIC FREEZE CRYSTALLIZATION - APPLICATION TO PROCESS STREAMS AND WASTE-WATER PURIFICATION

Two case studies are presented using eutectic freeze crystallization ( EFC) as an alternative for evaporative crystallization: a 7.8 ton day( -1) 35 w% aqueous sodium nitrate and a 24 ton day(-1) 12 w% copper sul fate stream. The proposed crystallizer is a cooled disk column crystal lizer (CDCC), using indirect cooling for heat transfer. in single stag e operation, the formed ice crystals are used to pre-cool the feed str eam. A two stage refrigeration unit utilizes the formed ice crystals i n the condensation of refrigerant. Expressed as a thermal equivalent e nergy requirement, EFC requires 1282 kJ kg(-1) NaNO3 and 1037 kJ kg(-1 ) CuSO4 . 5H(2)O. Compared to conventional multi-step evaporation, the energy reductions are 30% for sodium nitrate and 65%, for copper sulf ate. (C) 1998 Elsevier Science S.A. All rights reserved.