Defluorinated phosphate rock process using lime

Abstract

An improved process is described for preparing defluorinated phosphate rock from fluorine-containing phosphate rock which contains acid insoluble impurities in excess of about 6 percent by weight. The improvement is particularly useful in the fluidized bed technique for preparing defluorinated phosphate rock wherein fluorine-containing phosphate rock, a sodium compound such as sodium carbonate, phosphoric acid and water are admixed to form granules. The resulting granules are dried and heated in a fluidized bed calciner at a temperature within the range of from about 980.degree. to about 1,350.degree. C to evolve sufficient fluorine to produce defluorinated phosphate rock graules having less than 1 part of fluorine per 100 parts of phosphorus by weight. The resulting defluorinated granules are colled and stored for use as an animal feed which contains at least 18 percent by weight of phosphorus. The improvement of this invention comprises admixing a lime compound with the phosphoric acid, prior to mixing with the other ingredients, to form a lime-acid slurry having a CaO to P.sub.2 O.sub.5 weight ratio in the range from about 0.01:1 to about 0.20:1.

Dependencies are inferred from the claim text.