GB355098A - Method of producing ammonium sulphate - Google Patents

Abstract

In the production of ammonium sulphate from calcium sulphate and ammonium carbonate, calcium sulphate suspended in a circulating ammonium sulphate solution and a solution of ammonium carbonate are continuously supplied to a reaction vessel containing a large bulk of finished reaction products while finished reaction products corresponding to the supply of reaction materials are continuously removed, the reaction thus being performed in the presence of a substantially constant high percentage of precipitated calcium carbonate. In this way the calcium carbonate formed is caused to deposit on the calcium carbonate crystals present in the solution and is obtained in a coarse, easily filterable form. Preferably the process is performed in a series of vessels with stirrers, in the first of which calcium sulphate is suspended in an ammonium sulphate solution, preferably one containing suspended calcium carbonate as obtained in the process. The sludge produced flows into the second vessel, to which is added a slight excess of ammonium carbonate solution (which may be obtained by passing ammonia and carbon dioxide into the solution resulting from the washing of the calcium carbonate in the filter plant) together with sufficient water to keep the concentration of the ammonium sulphate solution substantially constant. The reaction products flow to the succeeding vessels where the reaction is completed. From the last vessel a portion of the products is returned to the first vessel and the remainder passes to a filter plant.