Intensifying effects of zinc oxide wet flue gas desulfurization process with citric acid

Abstract

A zinc oxide enhanced by citric acid wet flue gas desulfurization process for the removal of medium-low concentration of SO2 from non-ferrous metal smelting flue gas was proposed. The effects of citric acid concentration, initial SO2 concentration and reaction temperature on desulfurization were investigated. The results showed that while the concentration of zinc oxide was 0.5% and 0.25% citric acid was added, the SO2 removal efficiency increased from 81.2% to 92.3%. The mechanism may be the additional citric acid promote the dissolution of zinc oxide and increased the alkalinity and Zn2+ in solution. Meanwhile, the buffering effect of citric acid for pH in desulfurization solution avoids the continuous decline of pH, which can cause higher concentration of SO2 at the gas-liquid interface and enhance the gas-liquid mass transfer capacity of SO2. Furthermore, the simplex industrial zinc oxide ash generated from lead and zinc smelters had poor desulfurization efficiency, but the desulfurization efficiency was drastically improved when citric acid was added. The additional citric acid greatly promoted the conversion rate of ZnSO3 to ZnSO4, which solved the blocking of desulfurization equipment. The process of zinc oxide enhanced by citric acid wet flue gas desulfurization was more suitable for zinc smelting industry to produce metallic zinc.