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Abstract

A process for producing high-analysis dicalcium phosphate containing phosphatic fertilizers and by-product calcium nitrate. It comprises reacting phosphate rock with nitric acid, followed by pyrolysis of the resulting acidulate to effect liberation of approximately one-half of the initially consumed nitric acid. Recycling of this liberated nitric acid allows production of available phosphate with approximately one-half the acid equivalents normally consumed during sulfuric acid processing. The calcium nitrate in the resulting pyrolyzate is separated from the phosphatic constituent by dissolution in water followed by filtration. Depending upon the initial HNO.sub.3 :CaO acidulation ratio, the available phosphate content of the resulting solid phosphatic fertilizers is high enough (48% P.sub.2 O.sub.5) to allow their use either for bulk blending with nitrogen and potash salts to produce complete grade fertilizers or for direct application as a phosphate nutrient. The resulting calcium nitrate stream may be processed to produce a variety of solid or fluid nitrogen fertilizer products. No 'throw away' by-products (other than possibly siliceous gangue) are produced.

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