Mercury adsorption and oxidation over magnetic biochar in oxyfuel combustion atmosphere: Impact of enriched CO2 and H2O

Abstract

The abatement of mercury from oxyfuel combustion flue gas should be paid special attention due to the metal embrittlement and aluminum corrosion for CO2 compression device. The effects of enriched CO2 and H2O in oxyfuel combustion atmosphere on mercury removal over biochar (BC) and magnetic biochar (MBC) was studied. Hg0 was firstly captured by physical adsorption and then oxidized to various mercury compounds. A large amount of organic groups, especially CO group, were formed with the assistance of enriched CO2. As a result, more Hg0 was oxidized over BC and more organic Hg (Hg-OM) was formed on BC and MBC. However, the content of chemisorbed oxygen on MBC was reduced under oxyfuel combustion atmosphere, hence reducing the formation of HgO on MBC compared with air combustion atmosphere. The enriched H2O significantly inhibited the removal of mercury over MBC. Chlorine was demonstrated as the most significant active components for mercury removal, since HgCl2 was the dominant species on MBC. This work clarified the effects of enriched CO2 and H2O on Hg0 adsorption over BC and MBC, which is essential for further improving the adsorption activity.