There are still some F− and Cl− left in flue gas, after entering the washing slurry in desulfurization column, F− will complex with Al in the slurry, causing masking effect on the dissolution of limestone; Too much Cl− may cause corrosion to the absorber and inhibit the dissolution of limestone, thus in limestone–gypsum wet flue gas desulfurization process, part of the slurry have to be discharged as desulfurization wastewater in order to control the amount of F−, Cl− and other dissolved ions [12].