GB464040A - Improvements in or relating to the manufacture of potassium sulphate - Google Patents

Abstract

Potassium sulphate is obtained from potassium chloride by a cyclic process comprising the following steps: (1) the reaction between potassium chloride and sodium sulphate in an aqueous medium comprising the mother liquor from step (2) to produce a solid phase of glaserite with or without potassium chloride which is separated, the mother liquor being worked up by evaporation to separate sodium chloride, followed or preceded by cooling to separate a mixture of potassium chloride and glaserite which is either returned to the reaction or passed to step (2) and the final mother liquor being added to further quantities to mother liquor from the glaserite-producing stage for further recovery; (2) the treatment of the solid product from step (1), if necessary with the addition of further quantities of potassium chloride, with water, or with an aqueous medium including a portion of the mother liquor from step (3), preferably in the cold or at a moderate temperature, to produce crude potassium sulphate which is separated, the mother liquor being returned to step (1); (3) the treatment of the crude potassium sulphate from step (2) in the hot with a liquor comprising the final mother liquor returned from the end of step (3) together with make-up water equivalent to any mother liquor that may have been diverted for use in step (2), followed by cooling with gentle agitation to separate crystals of potassium sulphate. Preferably, insoluble impurities are removed prior to the cooling in step (3). The heating in step (3) may be done by the introduction of steam, surplus condensed water being removed by diverting a portion of the mother liquor for use in step (2). Specifications 410,830 and 439,287 are referred to.