Abstract
Forced deactivation examinations using biomass combustion ash and KCl, CaCl2 aerosol have been carried out to clarify deactivation mechanism of the V2O5-WO3/TiO2 type DeNOX catalyst for the exhaust gas from coal and biomass co-fired boilers. Commercial honeycomb-type catalysts were used for their examinations. Characterizations were performed by SEM/EDS and NH3-TPD for both fresh and deactivated catalysts. As a result of wet impregnation examinations by using water slurry of biomass combustion ash, DeNOX performance decrease with increasing ash concentration of slurry. Under the liquid water coexists, alkali metals move to a catalyst from biomass combustion ash and cause the chemical deactivation by poisoning of the active sites. In case of the KCl aerosol exposure examination, K component causes the chemical deactivation with time while diffusing in the catalyst inside. As for the CaCl2 aerosol exposure examination under the SO2 coexistence, CaSO4 is deposited in catalyst surface and promotes physical deactivation by clogging catalyst pore that cause the gas diffusion inhibition. As shortly described here, Alkali metals and alkaline earth metals cause the different deactivation mechanism each. The findings will contribute to develop DeNOX catalyst which can maintain good performance even in exhaust gas from biomass co-firing coal boilers.
