GB386854A - Process for the decomposition of complex salts composed of double sulphates of potassium and calcium - Google Patents

Abstract

In the production of potassium formate from a potassium sulphate solution and lime by treatment with carbon monoxide or producer gas under pressure at an elevated temperature, say at 175 DEG C., the reaction mixture is further heated under pressure to 230 DEG C. to decompose the complex sulphates of potassium and calcium which are formed thereby to permit the reaction to go to completion. Decomposition of the complex sulphates is facilitated by having sufficient lime present to render the reaction solution alkaline. Alternatively formation of the complex sulphates may be avoided by operating throughout at temperatures above 200 DEG C. under pressure. Polyhalite may be used as the source of potassium sulphate in which case sufficient lime is added to render the magnesium insoluble.ALSO:Complex salts consisting of potassium sulphate and calcium sulphate are decomposed by heating with water or aqueous solutions to decomposition temperature in closed pressure vessels, the potassium sulphate passing into solution. In effecting double decomposition between potassium sulphate and calcium salts, the double sulphates formed may be first isolated and then decomposed; or decomposition may be effected by heating the whole of the reaction mixture; or the reaction be carried out under pressure at such temperatures that formation of the double salts is avoided. The decomposition may be accelerated by using solutions to which an alkaline reaction has been imparted, as by addition of quick lime. When complex salts containing magnesium, such as polyhalite, are treated, lime may be added to render the magnesium insoluble. Examples relate to the production of potassium formate from a mixture of potassium sulphate or polyhalite and lime by the action of carbon-monoxide or producer gas, the heat treatment being effected at 230-250 DEG C.; and to the production of potassium nitrate from potassium sulphate, syngenite, or polyhalite and calcium nitrate, the heat treatment being effected at 250 DEG C.