Influence of operating parameters on performance of SO2 absorption in fulvic acid solution

A novel process of flue gas desulfurization by aqueous fulvic acid (FA) solution with acid-base buffering capacity was developed. Experiments were carried out to investigate the influence of operating parameters such as the FA concentration, pH, temperature, gas flow rate, fly ash, O-2, SO2 inlet concentration, CO2 and NO2 on SO2 absorption efficiency and Duration Time of High Efficiency (DTHE, the time of the SO2 absorption efficiency above 95%) in a lab-scale bubbling reactor. The results show high FA concentration has more absorption capacity for SO2, and the optimum concentration of FA solution is 0.08 g mL(-1), at which point the absorption efficiency is above 98%. The inlet SO2 concentration has little influence on absorption efficiency, but DTHE reduces with increasing inlet SO2 concentration. O-2 has a little effect on absorption efficiency. The SO2 absorption efficiency is not affected by pH change in the range from 5.5 to 3.3, and maintained above 97.4%. Fly ash can improve SO2 absorption efficiency and DTHE. NO2 can accelerate the oxidation of bisulfite to sulfate and promote SO2 absorption. CO2 hardly influences on SO2 absorption efficiency, but the SO2 absorption capacity decreases with the increasing of CO2 partial pressure. Furthermore, the thermal stability and regenerability of FA were also evaluated by TG-DTG and XRD, respectively. The results demonstrate that FA with stable performances is a promising regenerative absorbent for the removal of SO2. (C) 2015 Elsevier B.V. All rights reserved.