Utilization of inherent minerals in coal for high-performance activated carbon production: The mechanism of deSO2 and/or deNOx enhanced by in situ transformed calcium sulfide (CaS)

Abstract

Calcium sulfide (CaS) is transformed from the interaction between inherent pyrite and calcite in coal during activated carbon (AC) preparation by vapor activation, which could impact AC's textural and performance. For elucidating the contribution of in situ transformed CaS on the AC structure and SO2/NO removal, as-obtained AC-XCaS (X is the CaS content) were produced by Taixi coal and calcium sulfide (0–4 wt.%) through steam activation. The textural evolution and denitrification and/or desulfurization were also investigated. The results indicated that: (1) Calcium sulfide declined the burn-off linearly. The graphitization degree of ACs presents first enhancing and then decreasing trend with the CaS content increased. Calcium sulfide promotes the AC's micropore porosity development by catalyzing the corrosion of steam on the carbon surface. The specific surface area including total BET and micropore from 954 m2/g and 894 m2/g (AC) first raised to 1017 m2/g and 962 m2/g (AC-1CaS) and then decreased to 808 m2/g and 768 m2/g (AC-4CaS), respectively. Meanwhile, calcium sulfide improves the AC's amounts of C–O and C=O. (2) Calcium sulfide strengthens AC's removal ability of NO and SO2 evidently. The maximum desulfurization capacity is up to 67.1 mg/g of AC-4CaS, which is higher by 50.8% than 44.5 mg/g of AC. Calcium sulfide enhances AC's surface chemical feature and finally favors the adsorption of SO2/O2/H2O. Meanwhile, calcium sulfide catalyzes the desulfurization reaction. The AC-3CaS's NO conversion is up to 22.7%, which is higher 39.3% than 16.3% of AC. Calcium sulfide favors oxygen dissociation to form intermediate C(O), which could strengthen the adsorption of NH3 and NO. (3) During simultaneous removal of SO2 and NO, calcium sulfide shows that anti-SO2 poisoning ability is promising. The results of this research could complement the reference by utilizing coal with high-inorganic-iron/calcium/sulfur for high-performance AC preparations.