Comprehensive insight into the role of HCl on arsenic capture by CaO during coal combustion: A combined experimental and theoretical study

Abstract

Influence of HCl on As capture capability of CaO during coal combustion was studied in this work. Experimental results have confirmed the dramatic suppression role of HCl on As capture by CaO, and demonstrated the potential contributions of CaO chlorination to the inhibition role of HCl on As capture. Meanwhile, the clogging impact of HCl on CaO was omitted. For comprehensive understanding of inhibition mechanism of HCl, theoretical adsorption behaviors of As2O3(g) and AsCl3(g) on CaO (001) slab and CaCl2 (001) slab were investigated. It was concluded that chlorination of As2O3(g) and CaO both contributed to the inhibition effect of HCl, and the inhibition role of As2O3(g) chlorination was stronger than that of CaO chlorination. Comparing with the excellent activity of Ca and O sites in CaO (001) surface for As2O3(g) adsorption, CaO chlorination abolished the function of surface O, while As2O3 chlorination limited the activity of surface Ca. Moreover, interactions between AsCl3(g) and CaCl2 induced the offsetting effect of HCl on As capture capability of CaO. Correspondingly, the validity of As2O3(g) chlorination during coal combustion was verified. Moreover, it was also clarified that the suppression role of HCl on arsenic capture by CaO was better than that of SO2.