Concentration design for dilute nitric acid containing trace hydrofluoric acid
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There is currently a waste acid concentration unit that contains 2.5% hydrofluoric acid, 10% nitric acid, and small amounts of metal ions (mainly waste acid from steel cleaning). What is needed is pure dilute nitric acid (at 7.5% concentration). Considering that nitric acid decomposes easily when heated, how should the process flow be designed? Can a conventional three-effect evaporation system be used for this purpose?
According to the book on nitric acid engineering, the sulfuric acid addition process is used because nitric acid is an azeotrope
Nitric acid is an azeotrope and evaporates together with water
Enameled steel cannot be used, nor can glass.
For triple-effect evaporation, this set of equipment is extremely expensive.
I don’t think so; without metal equipment, the investment should not be very high