Flue gas desulfurization process

Abstract

A flue gas desulfurization process by which gypsum can be recovered; the amount of water used therein is small, the effluent is treated in a closed system, the equipment used is minimized, and no scaling occurs; and an apparatus therefor are provided, the process including the following first process and second process: the first process comprising a cooling step of cooling and dedusting a SO.sub.2 -containing flue gas and removing acidic gases, an absorption step of contacting the cooled gas with a slurry containing limestone and lime to absorb and remove SO.sub.x and form CaSO.sub.3, a pH-adjusting step of adding H.sub.2 SO.sub.4 to the resulting slurry, an oxidation step of blowing an oxygen-containing gas in the pH-adjusted slurry to form gypsum, a step of concentrating the resulting gypsum slurry, a step of adjusting the concentration of the resulting slurry, a step of centrifugally separating gypsum, and a step of treating the effluent discharged from the cooling step, and the second process comprising, in the first process, further feeding the slurry of the absorption step to the cooling step where unreacted limestone is reacted with SO.sub.2 to form CaSO.sub.3 .