Production of glaserite and potassium sulphate from gypsum and sylvinite catalysed by ammonia

Ammonia has the property of markedly depressing the solubilities of certain inorganic salts while hardly affecting the solubilities of others. Because of this property ammonia can be used to promote various crystallization processes and some double decomposition reactions between inorganic salts. This paper examines two examples of the second type of application in which gypsum produced from seawater salt plants and sylvinite KCl . NaCl are reacted in aqueous ammonia resulting in the formation and selective crystallization of glaserite, and secondly the glaserite formed is reacted with sylvinite to produce potassium sulphate. Experimental work is described which follows the progress of the reactions under a wide range of conditions. Some of the results give above 98% overall yield of high purity potassium sulphate. (C) 1997 Elsevier Science S.A.