Method for applying petrochemical exhausted lye to semidry-method flue gas desulfurization

The invention discloses a method for applying petrochemical exhausted lye to semidry-method flue gas desulfurization, belonging to the technical field of environmental protection. The method disclosed by the invention is characterized in that part or all of exhausted lye subjected to pretreatment replaces industrial water and is applied to a semidry-method desulfurization device for boiler flue gas, and injected to a desulfurizing absorption tower according to a required amount, wherein alkaline compounds such as Na2S, NaOH and/or Na2CO3 and the like of the exhausted lye fully react with SO2 in flue gas, then generated sulfur-containing compounds as heavy components are fed into a circulatory ash system and treated along with circulatory ash, and light components are discharged to a desulfurized ash silo of a power plant; and the desulfurization rate of externally-exhausted flue gas is greatly increased and can reach 70-99%, thereby achieving an effect of stable emission on standard. Meanwhile, the applicatio