Mercury capture by a regenerable sorbent under oxycoal combustion conditions: Effect of SO2 and O2 on capture efficiency

The present study evaluates an Au/C sorbent based on the direct reduction of a gold salt on a carbon coated structured cordierite monolith for mercury capture under oxyfiring conditions. Both mercury retention efficiency and mercury retention capacity were tested in a bench scale plant under different conditions. The influence of gas temperature (50-150 °C) and gas composition (CO2, N2, SO2, and O2) on sorbent performance for mercury capture is evaluated and discussed. The amount of mercury captured did not vary significantly with temperature under a CO2 atmosphere. These results were compared with those obtained under N2 atmosphere with no remarkable differences found between them. High retention efficiencies were obtained despite the small amount of gold used. The presence of SO2 and O2 in the flue gas led to mercury oxidation that seemed to be mainly promoted by SO2 under the presence of the Au-sorbent.