Effect of Sulfated CaO on NO Reduction by NH_3 in the Presence of Excess Oxygen

摘要

The effect of sulfated CaO on NO reduction by NH_3 in the presence of excess oxygen was investigated to evaluate the potential of simultaneous SO_2 and NO removal at the temperature range of 700-850℃. The physical and chemical properties of the CaO sulfation products were analyzed to investigate the NO reduction mechanism. Experimental results showed that sulfated CaO had a catalytic effect on NO reduction by NH_3 in the presence of excess O_2 after the sulfation reaction entered the transition control stage. With the increase of CaO sulfation extent in this stage, the activity for NO reduction first increased and then decreased, and the selectivity of NH_3 for NO reduction to N_2 increased. The byproduct (NO_2 and N_2O) formation during NO reduction experiments was negligible. X-ray photoelectron spectroscopy (XPS) analysis showed that neither CaSO_3 nor CaS was detected, indicating that the catalytic activity of NO reduction by NH_3 in the presence of excess O_2 over sulfated CaO was originated from the OaSO_4 product. These results revealed that simultaneous SO_2 and NO_x control by injecting NH_3 into the dry flue gas desulfurization process for NO reduction might be achieved.