Utilization of waste gypsum in fertilizer production

The results of the study regarding utilization of the waste gypsum formed as a by-product during the production of the magnesium sulphate from dolomite have been presented. The use of this waste have been proposed for the production of granulated multi-component fertilizers containing 25% N; 8% S; 14% CaO and 3.5% MgO. In the process of fertilizer production, the urea which will be bounded with the calcium and magnesium sulphate from the waste in the form of adducts of CaSO4 . 4CO(NH2)2 and MgSO4 . CO(NH2)2 . 3H2O will be the source of nitrogen in the fertilizer. It has been stated on the basis of the laboratory tests that the fertilizer with the assumed composition can be obtained by means of granulation of the raw material pulp, along with the dried and ground product return. The possibility of the production of the fertilizer with good physical properties according to the assumed concept has been confirmed in the pilot scale