Characteristics of the mercury vapor removal from coal combustion flue gas by activated carbon using H2S

Removal of Hg0 vapor from the simulated coal combustion flue gases with a commercial activated carbon was investigated using H2S. This method is based on the reaction of H2S and Hg over the adsorbents. The Hg0 removal experiments were carried out in a conventional flow type packed bed reactor system in the temperature range of 80–150 °C using simulated flue gases having the composition of Hg0 (4.9 ppb), H2S (0–20 ppm), SO2 (0–487 ppm), CO2 (10%), H2O (0–15%), O2 (0–5%), N2 (balance gas). The following results were obtained: in the presence of both H2S and SO2, Hg removal was favored at lower temperatures (80–100 °C). At 150 °C, presence of O2 was indispensable for Hg0 removal from H2S–SO2 flue gas system. It is suggested that the partial oxidation of H2S with O2 to elemental sulfur (H2S+1/2O2=Sad+H2O) and the Clause reaction (SO2+2H2S=3Sad+2H2O) may contribute to the Hg0 removal over activated carbon by the following reaction: Sad+Hg=HgS. The formation of elemental sulfur on the activated carbon was confirmed by a visual observation.