Influence of SiO_2 Particles on Mercury Removal Using In-Situ Generated TiO_2 Nanosize Particles Activated by UV Irradiation

摘要

The influence of silica particles on the mercury removal using in-situ generated titaniananosize particles activated by UV irradiation was investigated as a model of fly ash particles incoal combustion environments. Elemental mercury (Hg~0) capture efficiencies were measured as afunction of the ratio TiO_2 / SiO_2. The influence of humidity was also investigated. Both TiO_2 andSiO_2 were independently generated and premixed in order to discuss the importance of the pointof injection of a sorbent precursor in a real combustion system.Mercury removal efficiencies increased with the molar ratio titania/silica, and a shieldingeffect by silica particles was observed when precursors were separately generated. Effectivenumber of active sites on TiO_2 surface area was diminished, decreasing the Hg capture. IdealTiO_2 crystal structure for mercury removal was altered when Si and Ti were premixed, indicatingthat the point of injection of the sorbent is a main factor in the flue gas environment. The increasein water vapor in the flow reactor resulted in a recovery of the faster initial rate for Hg~0 capturedue to the activation of more sites on titania’s surface.