Improving SO2 and/or NO removal by activated carbon through comprehensive utilization of inherent pyrite and calcite in coal

Abstract

Utilization of inherent active minerals in coal is an effective strategy for high-performance activated carbon (AC) production, such as calcite and pyrite. In this research, ACs were prepared through blending demineralized Ningxia coal with calcite (CaCO3, 0–8 wt.%) and pyrite (FeS2, 0–3 wt.%). The combined effect of inherent pyrite and calcite in coal on the as-prepared AC’s texture and SO2 and/or NO removal performance was discussed. The results indicated that: (1) The combined effect of calcite and pyrite showed nonlinearly on weight loss and burn-off, and reduced AC’s yield. The impact of calcite on pore structure was more evident than pyrite. Meanwhile, calcite and pyrite enhance the content of CO (C 1 s) and π-π*, and new mineral CaS could be formed through interaction between calcite and pyrite; (2) Calcite and pyrite promote AC's SO2 and NO removal ability evidently. Pyrite and calcite regulate physiochemical texture, and the physical and chemical adsorption of SO2/O2/H2O was enhanced. Meanwhile, iron and calcium ingredients in AC catalyzed desulfurization. CaO could participate in the SO2 removal process. Fe2O3 oxidized SO2 to SO3 and then forms H2SO4 rapidly, meanwhile, a redox cycle of Fe3+ and Fe2+ was established. Enhancement of NO removal was more evident than SO2, which was mainly due to Fe2O3 being helpful to oxidizing NO to NO2, and calcium components could enhance the adsorption of NH3 and NO and finally promote “fast SCR”; (3) During simultaneous desulphurization and denitrification, sulfur capacity was obviously enhanced and NO conversion was declined. The mechanism was proposed as follows: the existence of NH3 could enhance the SO2 adsorption through chemisorption and/or catalytic oxidization; Due to the competitive adsorption of SO2, denitrification declined. This research could guide high-performance AC production by utilizing high-inorganic-calcium/iron/sulfur coal.