Production of low-chloride alkali metal phosphates.

摘要

Potassium phosphate useful as a low-chloride content fertilizer is prepared by reacting phosphoric acid, commercial or technical grade, with fertilizer-grade potassium chloride (Muriate of Potash, 60-63% K2O) at a reaction temperature of about 130 DEG to about 200 DEG C and a mole ratio of phosphorus to potassium of at least about 1.3:1. The vaporization of hydrogen chloride from the reaction mixture is effected by a novel technique combining air followed by steam stripping. The reaction product is used to produce various types as well as grades of fertilizers. The procedure may be used to form sodium phosphate in analogous manner from sodium chloride, which then may be converted to trisodium phosphate or sodium tripolyphosphate. The potassium phosphate may be converted to potassium pyrophosphate by neutralization with potassium hydroxide followed by calcination. <IMAGE>