Start-up procedure in producing phosphoric acid by the hemihydra

Details Start-up procedure in producing phosphoric acid by the hemihydra Start-up procedure in producing phosphoric acid by the hemihydra

1979-10-05

1981-06-30

Carter, Herbert T.

Chemistry of inorganic compounds

Treating mixture to obtain metal containing compound

Alkaline earth metal

423319, 423320, C01B 2522, C01F 1146

Patent

active

042762707

ABSTRACT:
In a multi-stage, multi-vessel phosphoric acid production system where a first reaction vessel contains a first slurry comprising calcium sulfate hemihydrate, monocalcium phosphate and phosphoric acid and a second reaction vessel contains a second slurry comprising calcium sulfate hemihydrate, sulfuric acid and phosphoric acid, in which the reaction slurry undergoes intra- and inter-vessel circulation, preferably through a draft tube, an improved start-up procedure involves filling the system with heated phosphoric acid having a P.sub.2 O.sub.5 analysis in the range of about 28 to about 38% (e.g. 31%), then feeding phosphate rock to the system, preferably in a separate reaction vessel, while phosphoric acid is recycled from a fourth, filter feed vessel, until the solids content in said slurry is in the range of 25-35% (e.g. about 30%) while the sulfate content in the first vessel is maintained at a negative level (e.g. excess calcium ion) and at a positive level in the second, crystallizer vessel. When the solids content, calcium, and sulfate content are at the proper level (e.g. about 30% solids, -5 to -2% sulfate in the first vessel and +2 to +3% sulfate in the second vessel) the slurry is then transported to a filter and the phosphoric acid is separated from the calcium sulfate hemihydrate.

REFERENCES:
patent: 3416889 (1968-12-01), Caldwell
patent: 3418077 (1968-12-01), Robinson
patent: 3522003 (1970-07-01), Lopker
patent: 3968544 (1961-01-01), Zeitz et al.
patent: 4053563 (1977-10-01), Somerville
patent: 4132760 (1979-01-01), Ore et al.
patent: 4196172 (1980-04-01), Ore et al.

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