Process for the production of solid urea-nitric phosphate fertilizer products

Abstract

The present invention relates to the reaction of phosphate rock with nitric acid and urea to produce nitrogen-phosphorus containing slurries, which slurries may be granulated and dried to produce solid N-P fertilizer products with agronomically advantageous low pHs (1.1-4.0). Products with optimum physical and chemical properties were discovered by investigating the characteristics of each individual material as a function of the nitric acid acidulation ratio (mole ratio HNO.sub.3 :CaO) and the mole ratio urea:CaO present in each product. Acidulation ratios ranged from 1.2 to 2.1 while ratios urea:CaO ranged from 1.6 to 4.0. Selected products with optimum physicochemical properties are tabulated below:______________________________________AcidulationRatio Ratio MeltingHNO.sub.3 :CaO, M/M Urea:CaO, M/M Grade Pt, .degree.C.______________________________________1.2 2.2 23.8--11.7--0 137-1391.4 2.4 25.0--11.0--0 1361.6 2.8 25.9--9.9--0 133-1371.8 3.0 26.4--9.2--0 134-1352.0 3.3 27.2--8.7--0 1302.1 3.2 36.6--8.8--0 125-130______________________________________Acidulation P.sub.2 O.sub.5 Solubility, Critical Rela-Ratio % pH of 1% tive HumidityHNO.sub.3 :CaO, M/M Water Citrate solution at 25.degree. C., %______________________________________1.2 69.2 82.1 2.5 59.31.4 81.8 90.0 2.4 60.91.6 88.9 91.9 2.3 60.11.8 96.7 98.9 2.1 59.92.1 99.0 100 2.1 60.02.1 100 100 2.1 59.5______________________________________The products have excellent storage characteristics. The improved properties of these products result partially from the formation of a new compound, Ca(H.sub.2 PO.sub.4)(NO.sub.3).CO(NH.sub.2).sub.2, which was discovered during the course of the investigation that led to the instant invention.

Description