PHOSPHORIC ACID.pdf - ACID INDUSTRY Phosphoric Acid 1 Raw...

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Phosphoric Acid
ACID INDUSTRY

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Raw Materials for Phosphoric Acid Production
• Phosphate ores are of two major geological origins: –
• Igneous – found in Kola, South Africa, Brazil, etc.
• Sedimentary – found in Morocco, Algeria, Jordan, U.S.A., etc.
• The phosphate minerals in both types of ore are of the apatite group, of which the most
commonly encountered is the Fluorapatite – CaF
2
.3Ca
3
(PO
4
)
2
• Most phosphate ores have to be concentrated or beneficiated before they can be used.

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Principles of the Di-Hydrate Process
• The tricalcium phosphate in the phosphate rock is converted by reaction with concentrated
sulphuric acid into phosphoric acid and the insoluble salt calcium sulphate.
Ca
3
(PO
4
)
2
+ 3H
2
SO
4
2H
3
PO
4
+ 3CaSO
4
• The insoluble calcium sulphate is then separated from the phosphoric acid, most usually by
filtration.
• The reaction between phosphate rock and sulphuric acid is self-limiting because an insoluble layer
of calcium sulphate forms on the surface of the particles of the rock. This problem is kept to a