Pilot plant development of a fertilizer process in which rock phosphate is acidulated with nitric and phosphoric acids is described. The process, technical feasibility of which was demonstrated through operation of a 4-ton-perday pilot plant, involves acidulating rock with mixed acids [mole ratio (HNOa •+ H3P04)/CaO = 2.1 and Ca0/P205 = 2.0], ammonia ting the resultant solution to pH 3.7 to 4.0, drying, and granulating. Introduction of potassium chloride into the molten product from the dryer is optional to produce an N-P2O5-K2O fertilizer.The proportions of N-P2O5-K2O in the product are variant; compositions prepared include 12-33-0, 19-19-0, 11-22-11, and 15-18-10. A FUNDAMENTAL advantage of the use of nitric acid for decomposing rock phosphate in the manufacture of fertilizers is that the cost of the acid is offset by the value of the nitrogen in the fertilizer product. Furthermore, the requirement for-and the expense of-sulfuric acid, fuel, or electrical energy used for decomposing rock phosphate in other processes is eliminated or decreased, the products are more concentrated than the usual

No abstract