Characteristics of HCl Release and SO2/NOx Absorption in Desulfurization Wastewater Evaporation Using Hot Flue Gas

Desulfurization wastewater (DW) can be effectively treated via evaporation using hot flue gas with zero DW discharge. In this study, the characteristics of HCl release and SO2/NO2 absorption were investigated during DW evaporation based on an experimental spray drying system. The results indicated that increasing the pH of DW effectively inhibited HCl release by inhibiting the acidification of water and hydrolysis of chloride. At high pH, regardless of changes in operational parameters, the HCl release ratio remained less than 4.0%. Additionally, DW with high pH also absorbed SO2 and NO2 during evaporation, and its SO2 absorption efficiency was greater than its NOx absorption efficiency. The main parameters inhibiting HCl release ratio, i.e., higher pH, higher CI- concentration in DW, and lower flue gas temperatures, also promoted SO2/NO2 absorption. However, by adding excess Ca(OH)(2) to DW, the absorption of the acidic pollutants did not increase the release of HCl during DW evaporation. Under the operational parameters of the reference experiment, the absorption efficiencies of SO2 and NOx were 35.6% and 16.2%, respectively, and the corresponding HCl release ratio was approximately only 1.1%.