IMPROVED PROCESS FOR THE RECORVERY OF SULPHATE OF POTASH (SOP) FORM SULPHATE RICH BITTERN

摘要

The present invention relates to an integrated process for the recovery of sulphate of potash (SOP) from sulphate rich bittern. The process requires only bittern and lime as raw materials. Kainite type mixed salt is obtained by fractional crystallization of the bittern. Kainite is converted into schoenite with simultaneous removal of NaCl in a single step and the filtrate (SEL) is used for production of KCl. The schoenite is reacted with aqueous KCl to yield SOP and the filtrate (KEL) is recycled in the kainite to schoenite conversion step. The production of KCl from SEL is carried out with the aid of DPA. Lime is treated with DPA in water for the production of highly soluble Ca(DPA)2, which in turn treated with SEL to produce insoluble K(DPA) with 95% yield. The isolated K(DPA) is treated with 1:1 HCl to produce KCl and insoluble DPA, which can be recycled for the production of Ca(DPA)2. The aqueous KCl thus obtained is treated with schoenite to prepare SOP, purity 90-92%. The KEL obtained along with SOP is recycled to generate schoenite. Utilisation of all effluent and intermediate streams allow for an overall SOP yield 89% w.r.t. the potash content in the mixed salt.