Characteristics of the mercury vapor removal from coal combustion flue gas by activated carbon using H_2S

摘要

Removal of Hg~0 vapor from the simulated coal combustion flue gases with a commercial activated carbon was investigated using H_2S. This method is based on the reaction of H_2S and Hg over the adsorbents. The Hg~0 removal experiments were carried out in a conventional flow type packed bed reactor system in the temperature range of 80-150℃ using simulated flue gases having the composition of Hg~0 (4.9 ppb), H_2S (0-20 ppm), SO_2 (0-487 ppm), CO_2 (10%), H_2O (0-15%), O_2 (0-5%), N_2 (balance gas). The following results were obtained; in the presence of both H_2S and SO_2, Hg removal was favored at lower temperatures (80-100℃). At 150℃, presence of O_2 was indispensable for Hg~0 removal from H_2S-SO_2 flue gas system. It is suggested that the partial oxidation of H_2S with O_2 to elemental sulfur (H_2S + 1/2O_2 = S_(ad) + H_2O) and the Clause reaction (SO_2 + 2H_2S = 3S_(ad) + 2H_2O) may contribute to the Hg~0 removal over activated carbon by the following reaction: S_(ad) + Hg = HgS. The formation of elemental sulfur on the activated carbon was confirmed by a visual observation.