Sulfate Ion → Calcium Sulfate, Hemihydrate

Participants

Reaction Steps

adding sulfuric acid in amounts such that the sulfate content of the sulfuric acid plus the sulfate content of the added phospate rock is equivalent to about 90% to about 100% of the stoichiometric amount of sulfate required to react with the calcium present in the phosphate rock added in part (a) to form calcium sulfate hemihydrate to a second reaction vessel maintained at a reduced pressure of about 3 to about 20 inches of mercury absolute and a temperature of about 66°-113° C. which contains a second slurry comprising calcium sulfate hemihydrate, monocalcium phosphate, sulfuric acid and phosphoric acid, whereby the sulfuric acid reacts with the monocalcium phosphate and the phosphate rock to form calcium sulfate hemihydrate and phosphoric acid, said second slurry being maintained at a soluble sulfate concentration of about 0.7% to +4.5 %, provided that the soluble sulfate content of the second slurry is about +1.0% or greater when the soluble sulfate content of the first slurry is about +0.7;

Provenance & Evidence