GB460281A - Improvements in or relating to the production of potassium sulphate - Google Patents

Abstract

Potassium sulphate is obtained from potassium chloride in a cyclic process comprising the following steps: (1) the reaction of potassium chloride with sodium sulphate and glaserite in the presence of water and at a temperature not exceeding 55 DEG C., with the separation of solid potassium sulphate; (2) the addition of sodium sulphate to the mother liquor from step (1) to precipitate glaserite which is separated and returned to step (1); (3) the treatment of the mother liquor from step (2) combined with the end liquor returned from the end of step (3) by evaporation to deposit sodium chloride (which is removed) followed or preceded by cooling to deposit a mixture of potassium chloride and glaserite which is returned to step (1), the end liquor being returned to the beginning of step (3). The process may be modified by adding some or all of the potassium chloride in step (2), solid potassium chloride passing with the glaserite to step (1), or by combining steps (1) and (2) as a single step in which potassium chloride, sodium sulphate and glaserite recycled from step (3) are mixed in a single stage. Some water may be removed by evaporation from the liquor from step (1) prior to the glaserite separation of step (2) and the liquor from step (2), or the combined steps (1) and (2), may be similarly treated before combining it with the end liquor from step (3). The glaserite returned to step (1) may be dissolved in the water to be added to the process. The sodium sulphate may be employed in the hydrated form. The separation of the potassium sulphate is preferably effected at a temperature of about 0 DEG C. The cooling may be effected by utilizing the endothermic effect produced by adding the reacting salts to water. Specification 410,830 is referred to.