Novel Process of Removal of Sulfur Dioxide by Aqueous Ammonia–Fulvic Acid Solution with Ammonia Escape Inhibition

A novel wet flue gas desulfurization process by aqueous ammonia–fulvic acid solution was proposed, in which fulvic acid (FA) could inhibit ammonia escape because carboxylic and phenolic groups in FA would interact with aqueous ammonia to form relatively stable ammonium fulvate. Experiments were conducted to research the effect of operating parameters such as initial pH value on the duration time of high efficiency (DTHE, time of above 95%) and absorption efficiency of SO2 in a bubbling reactor. Results indicate that SO2 absorption efficiency and DTHE increase with increasing initial pH value and that SO2 absorption capacity of aqueous ammonia can be improved by synergic action of FA. Concentration of FA has a slight effect on SO2 absorption efficiency (above 98.3%, pH0 8.5) but an obvious effect on DTHE. FA can successfully inhibit ammonia escape from absorption liquid during desulfurization. When the pH of aqueous ammonia–FA absorption liquid is above 4.1, absorption efficiency can be kept above 99.0% (for pH0 10.0). Increasing inlet SO2 concentration brings about the reduction of absorption efficiency and DTHE. High CO2 concentration is detrimental to DTHE. O2 and ammonium sulfate concentration hardly affect SO2 absorption efficiency and DTHE. Among nine operational parameters, gas flow rate has the biggest influence on overall gas-side volumetric mass transfer coefficient. The ammoniation of FA and mechanism of SO2 absorption in aqueous ammonia–FA solution also were demonstrated by FT-IR.