AIR POLLUTION CONTROL SYSTEM AND METHOD FOR REMOVING MERCURY IN FLUE GAS

A system for discharge gas treatment which comprises: a denitrificator (13) which removes nitrogen oxides from a discharge gas (12) discharged from a coal fired boiler (11) and sprays hydrogen chloride (23) over the gas to oxidize mercury; an air heater (14) which recovers heat from the gas; a dust collector (15) which removes soot/dust from the gas; a desulfurizer (16) which removes sulfur oxides from the gas from which dust has been removed; a chimney (17) which discharges the desulfurized gas outside; a hydrochloric acid vaporizer (21) which vaporizes concentrated hydrochloric acid to obtain hydrogen chloride (23); and a hydrochloric acid neutralization tank (30) in which dilute hydrochloric acid discharged from the hydrochloric acid vaporizer (21) or the concentrated hydrochloric acid is neutralized with an alkali agent (31). The chloride resulting from the neutralization is supplied to a fuel feeder (33) and mixed with coal as a fuel (70). Thereafter, the mixture is burned as a fuel (F) in the boiler (11) to generate hydrogen chloride in a discharge gas. This hydrogen chloride, together with the hydrogen chloride sprayed by the hydrochloric acid vaporizer (21), is used to remove mercury.