TW366324B - A method for desulfurizing sulfur oxides contained in the exhaust - Google Patents

Abstract

A method for desulfurization which comprises a desulfurization step of absorbing and removing sulfur oxides in an exhaust gas by a solution containing a Mg-based desulfurizing agent, an oxidation step of treating the treatment liquid with a gas containing oxygen, a double decomposition step of adding basic calcium compounds to the solution obtained in the oxidation step to carry out a reaction, a separation step of separating a slurry of a mixture of Mg(OH)2 and gypsum dihydrate obtained in the double decomposition step by a wet classifier, a step of returning a Mg(OH)2 slurry separated in the separation step to the desulfurization step, a step of treating a gypsum dihydrate slurry in the oxidation step to convert accompanying Mg(OH)2 into MgSO4, a sedimentation separation step of separating gypsum dihydrate, and a step of returning a supernatant liquid in the sedimentation separation step to the double decomposition step to treat the supernatant liquid; and a method for desulfurization which comprises adding, to the double decomposition step, basic compounds obtained by calcimining and digesting a dolomite in place of basic calcium compounds to carry out double decomposition, separating the solution subjected to the double decomposition by a wet classifier, returning an amount of a Mg(OH)2 slurry necessary for the desulfurization to a desulfurizing tower, concentrating, separating and taking the remaining Mg(OH)2 slurry from the system, oxidizing a gypsum dihydrate slurry to convert accompanying Mg(OH)2 into MgSO4, sedimenting, separating and taking out gypsum dihydrate as gypsum, and then subjecting the resultant supernatant to the double decomposition treatment together with the oxidized desulfurizing treatment liquid.