Removal of fly:ash and gaseous fluorine cpds. - from waste gas in super:phosphate prodn.

摘要

Fly ash is removed in a wet-scrubbing process in which the waste gas stream is sprayed with aqs. sulphonic or phosphoric acid, depending on which is used in the phosphate extraction plant. At least part of the acid used in the scrubbing is recycled to the phosphate extraction plant. The fluorine cpds are removed afterwards. Fully recoverable H2SiF6 can be produced with a controlled concn. of 18-30% whilst dust is effectively removed Process control, maintenance and plant cleaning are easy. The plant is not subject to excessive corrosion. Deposn. of SiO2 is prevented in the gas ducts and scrubbing plant. Relatively weak acids are used for scrubbing, which would otherwise have no direct application. Efficient removal of fluorine cpds. is achieved despite the high concn. of H2SIF6.