Treating waste gas contg. sulphur and nitrogen oxide(s) - with cerium-contg. oxidising soln. to recover nitric and sulphuric acids

摘要

Treatment of residual gas contg. SO2 and NOx involves a main stage of passing the gas into a gas/liq. contactor in which an oxidising soln. is circulated, esp. in countercurrent, to obtain nitric and sulphuric acids by absorption and oxidn. in the soln., the novelty being that the oxidising soln. is an aq. esp. acidic Ce(IV) contg. soln. circulating in a closed circuit. The oxidising soln. is a sulphuric acid soln. circulated in a circuit which includes an electrochemical cell, at the anode of which the Ce(III), obtained at the contactor outlet, is re-oxidised to Ce(IV). ADVANTAGE - The process allows efficient removal of pollutants from waste gas and produces separate nitric acid and sulphuric acid which are free from catalyst traces and are thus marketable.