Pilot Tests on the Catalytic Filtration of Dioxins

Tests were conducted to study the removal efficiencies (REs) of polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) from flue gas during a test program involving a pilot-scale catalytic filter (CF) module and a full-scale municipal solid waste incinerator (MSWI). The REs attained with the CF on a side stream and a conventional activated carbon (AC) injection and baghouse filtration system in the full-scale MSWI are evaluated via simultaneous sampling and analysis of both gas- and particle-phase PCDD/Fs. Flue gas without AC is supplied to the pilot-scale CF module for evaluating its RE capabilities. The REs achieved with the CF at 180 degrees C are 96.80 and 99.50%, respectively, for the gas phase and the particulate contained. The gas-phase PCDD/F RE rises significantly at 200 and 220 degrees C. The air/cloth (A/C) ratio defined as is the gas flow rate (m(3)/min) divided by the filtration area (m(2)) also affects the PCDD/F RE, especially in the gas phase. At 180 degrees C, a RE of gas-phase PCDD/Fs of 95.94% is attained with the CF at 0.8 m/min, yet it decreases at higher A/C ratios (1 and 1.2 m/min). A significantly lower toxic equivalency (TEQ) concentration (0.71 ng I-TEQ/g) was measured in the filter dust of the CF module compared to that collected by the AC adsorption system (4.18 ng I-TEQ/g), apparently because of the destruction of gas-phase PCDD/Fs by the catalyst.