A PROCESS FOR THE PRODUCTION OF AN ALKALICONTAINING CALCINED-PHOSPHATE FERTILISER

An alkaline high temperature process for the production of alkali containing highly citrate soluble calcined phosphate fertilizer is disclosed. The process comprises calcining a preheated mixture comprising a crude phosphate, an alkaline decomposing agent, silicic acid and phosphoric acid in a rotary kiln at a temperature of between about 900 DEG and 1300 DEG C. The preheated mixture is prepared by introducing phosphoric acid directly into the kiln and therein contacting it with the hot precursory mixture of the remaining starting material having a temperature of between about 150 DEG to 900 DEG C. The amounts of starting materials are preferably chosen such that in the mixture 1 mole of P2O5 is present per about 1.1 to 1.8 moles of alkali oxide, and about 0.5 moles of SiO2 are present per mole of CaO which is in excess of the amount of CaO which can be bound in the form of calcium alkali phosphate.