Tricalcium Phosphate → Calcium bis(metaphosphate)

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Reaction Steps

A fertilizer rich in calcium metaphosphate is produced by reacting phosphorite or other calcium phosphate-bearing mineral, with ammonium bisulphate to produce a precipitate of calcium sulphate and an aqueous solution rich in ammonium mono- and biphosphates. The latter is then heated in a furnace in the presence of further calcium phosphate-bearing mineral, to produce calcium metaphosphate. The calcium sulphate can be converted to calcium carbonate by reaction with ammonium carbonate, to produce ammonium sulphate. The ammonium sulphate can be heated with the furnace gases from the production of calcium metaphosphate, to produce the required ammonium bisulphate for reaction with phosphorite and the required ammonium carbonate for a conversion of the calcium sulphate to calcium carbonate.

Provenance & Evidence