Water injection for control of fines for producing defluorinated phosphate rock granules

Abstract

An improved process is described for preparing defluorinated phosphate rock (DPR) granules from fluorine-containing phosphate rock. In particular, the improvement is useful in conventional processes which comprise the steps of: (a) admixing fluorine-containing phosphate rock, phosphoric acid, sodium carbonate, and water to form a non-granulated feed slurry; (b) forming granules in a granulating zone from said non-granulated feed slurry; (c) drying said granules in a drying zone; (d) classifying said dried granules to form a product fraction, an over-size fraction, and a fines fraction of said granules; (e) crushing said over-size fraction and recycling said crushed over-size fraction, said fines fraction and 0-95% by weight of said product fraction back to step (b); (f) heating the unrecycled product fraction to defluorinate said fluorine-containing phosphate rock contained therein without fusion; (g) recovering said defluorinated phosphate rock granules; the improvement which comprises adding an aqueous solution to said granulation zone in a proportion equivalent to form about 5% to about 30% by volume of said non-granulated feed slurry, said aqueous solution being added only when more than about 20% by weight of dried granules discharged from said drying zone are less than about 20 mesh in size.

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