The Effect of Acid Gases on Elemental Hg Removal and Experimental Studies Accompanied by Quantum Chemical Calculations (DFT)

In the oxy-fuel combustion flue gas, a complex atmosphere of acid gases such as SO2, HCl, and NO generally exist at the same time. In this work, the effects of SO2, HCl, and NO on Hg removal of carbon-based material by NH4Br and HNO3 co modification are investigated at the experimental level, and the effects of SO2 and NO on Hg removal are studied at the theoretical level. FTIR analysis shows that the co-modification can effectively introduce Br and N-H into the adsorbent. The introduction of HCl and NO can alleviate the inhibitory effect of SO2, which is due to the facilitated conversion of Hg0 to HgCl2 and HgO. XPS results show that the reason adsorbent co-modification with NH4Br and HNO3 possess sulfur resistance effect is that the modification promotes the generation of C-O* and C-Br functional groups and converts Hg0 into HgO and HgBr2, HgBr2 is further converted into HgSO4.The surface adsorption energy, electrostatic potential distribution, bond length variation, and Mulliken charge population transfers of modified char under different working conditions are calculated by DFT simulations. The results indicate that the order of the magnitude of the interaction between different substrates with Hg0 is C-SO2 < C-SO2-NO < C.

Automated summary

The study investigates the effects of SO2, HCl, and NO on mercury removal from carbon-based materials in oxy-fuel combustion flue gas. Experimental and theoretical analyses suggest that co-modification with NH4Br and HNO3 can enhance mercury removal efficiency, while the introduction of HCl and NO can mitigate the inhibitory effect of SO2.