Phosphate fertilisers prepd. from fluorinated phosphorite or apatite - in a process causing less corrosion and deposition in the appts.

摘要

Phosphate fertilisers are prepd. by phosphoric acid attack on a fluorinated phosphorite or apatite, and reaction of the product with ammonium sulphate giving ammonium phosphate and calcium sulphate. By using a fluorinated phosphorite, or apatite, the extent of the deposit on gas conduits and heat exchangers is reduced, the prod. shows less tendency to agglomerate in granulators and corrosion caused by soluble fluorine derivs. is reduced. The pref. mineral is fluorinated apatite having and F/-SiO2 ratio 1.5-2, and 0.5-1.5% Na2O. The phosphoric acid used pref. contains 27-30% P2O5 and 2-3% free H2SO4. The reaction is effected at 60-70 degrees C.