Removal of elemental mercury from flue gas by supported MnO_x/Al_2O_3 catalyst at low temperature

Aiming at the difficulty of Hg0 removal from flue gas with its indissolubility in water,a series of studies on the characteristics of elemental mercury( Hg0) catalytic oxidation removal from simulated flue gas were carried out with a laboratory-scale fixed-bed reactor using the MnOx/Al2O3 catalysts prepared by the wet impregnation method.The effects of precursor,MnO x content,calcination temperature,reaction temperature and flue gas compositions on the removal of Hg0 were also investigated. The characteristics of the catalysts were analyzed using the method of nitrogen adsorption / desorption,scanning electron microscope( SEM),and X-ray diffraction( XRD). The result shows that the catalyst prepared with manganese nitrate exhibits a higher Hg0 removal efficiency than the catalyst prepared with manganese acetate. The main active component of the MnOx/Al2O3 catalyst is MnO2,and the surface morphology and species form of MnOx are the main factors for getting an excellent Hg0 removal efficiency. The mercury removal results indicate that at low MnO x content,the precursor shows great impact on mercury removal,while the difference of Hg0 capture efficiency gradually decreases with the increase of MnO x loading. For the MnOx/Al2O3 catalyst,the optimal reaction temperature and calcination temperature are 150 ℃ and 400 ℃,respectively. The oxygen from the flue gas,which replenishes the lattice oxygen of the catalyst consumed,can promote the catalytic oxidation of Hg0. To some extent,the NO,SO2 and H2O displays inhibitory effects on Hg0removal. The influence of SO2 is the highest,followed by H2O and NO.