Evaluation of decomposition characteristics of mercury compounds using mass

Understanding the decomposition characteristics of mercury compounds is very important for the development of sorbents for mercury removal from coal derived flue gas and fuel gas. The information concerning to the stability of mercury compound are valuable data necessary for the design of solid sorbents. However, there are not enough data available on mercury compound's stability in the flue or fuel gas conditions. The decomposition behavior of mercury compounds such as HgS, HgO, HgSO₄, HgCl₂ Hg₂Cl ₂ were investigated by TPDD (temperature programmed decomposition and desorption) technique using a mass spectrometer (TPD-Mass method). Especially, the stability and reactivity of mercury chloride (HgCl₂ was mainly examined in coal combustion flue gas and coal derived fuel gas conditions. The mercury compounds were diluted with solids (diluents) such as SiO₂ SiC. Al₂O₃ TiO₂ and activated carbon for TPD-Mass experiments. The following results were obtained: (1) the order of the main peak temperature of mercury evolution from the decomposition of mercury compound in He flow was as follows: HgS(meta-cinnabar) = HgO < HgS (cinnabar) < HgSO₄ (2) HgSO₄ was hydrolyzed by H₂O (3) HgO was reduced by SO₂ in the presence of H₂O and O ₂; (3) Hg₂Cl₂ and Hg₂Cl₂ were decomposed more easily over the SiO₂ than the other mercury compounds; (4) HgCl₂ was most easily decomposed over the SiO ₂ and stabilized over the AC; (5) HgCl₂ gas could be converted to Hg⁰ over quartz wool, Pyrex wool, ceramics (SiO ₂-Al₂O₃) wool, carbon fiber and AC.