Effect of Fly Ash on Catalytic Removal of Gaseous Dioxins over V_2O_5-WO_3 Catalyst of a Sinter Plant

摘要

A PCDD/F (polychlorinated dibenzo-p-dioxin and dibenzofuran)-containing gas stream generating system was developed to investigate the efficiency and effectiveness of V_2O_5-WO_3 catalyst for PCDD/F destruction. Catalytic decomposition of PCDD/Fs (simulated gas streams) was evaluated with lab-scale pelletized and plate-type catalyst based on V_2O_5-WO_3/TiO_2 at controlled temperature, space velocity, and inlet PCDD/F concentration. Due to the lower porosity of the pelletized catalyst PCDD/F destruction efficiencies reach 72.9-83.2% for different levels of inlet PCDD/F concentrations (1.08-3.04 ng-TEQ/Nm~3) of the gas stream (space velocity: 5000 h~(-1)). As the surface area is increased from 287 m~2/m~3 (plate-type A) to 550 m~2/m~3 (plate-type B), the PCDD/F destruction achieved with plate-type catalyst increases from 76.0% to 85.3% at 320℃(space velocity: 5000 h~(-1)). In addition, the results of pilot-scale experiment (real flue gases of a sinter plant) indicate that relatively lower PCDD/F destruction efficiencies (62.1-65.7%) were achieved with the plate-type B catalyst as the solid-phase PCDD/F and fly ash passed through the reactor (space velocity: 5000 h~(-1)). Overall, the lab-scale and pilot-scale experiments indicate that PCDD/F destructions achieved with pelletized and plate-type catalysts strongly depend on the operating temperature of the catalyst The results also indicate that the presence of fly ash the lowers PCDD/F destruction due to significant PCDD/F formation via de novo synthesis at 320℃.