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:______________________________________ Acidulation Ratio Ratio Melting HNO.sub.3 :CaO, M/M Urea:CaO, M/M Grade Pt, .degree.C. ______________________________________ 1.2 2.2 23.8--11.7--0 137-139 1.4 2.4 25.0--11.0--0 136 1.6 2.8 25.9--9.9--0 133-137 1.8 3.0 26.4--9.2--0 134-135 2.0 3.3 27.2--8.7--0 130 2.1 3.2 36.6--8.8--0 125-130 ______________________________________ Acidulation P.sub.2 O.sub.5 Solubility, Critical Rela- Ratio % pH of 1% tive Humidity HNO.sub.3 :CaO, M/M Water Citrate solution at 25.degree. C., % ______________________________________ 1.2 69.2 82.1 2.5 59.3 1.4 81.8 90.0 2.4 60.9 1.6 88.9 91.9 2.3 60.1 1.8 96.7 98.9 2.1 59.9 2.1 99.0 100 2.1 60.0 2.1 100 100 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