Partitioning and removal of dioxin-like congeners in flue gases treated with activated carbon adsorption

Activated carbon adsorption is commonly used to control dioxin-like congener (PCDD/Fs and PCBs) emissions. Partitioning of PCDD/Fs and PCBs between vapor and solid phases and their removal efficiencies achieved with existing air pollution control devices (APCDs) at a large-scale municipal waste incinerator (MWI) and an industrial waste incinerator (IWI) are evaluated via intensive stack sampling and analysis. Those two facilities investigated are equipped with activated carbon injection (ACI) with bag filter (BF) and fixed activated carbon bed (FACB) as major PCDD/F control devices, respectively. Average PCDD/F and PCB concentrations of stack gas with ACI + BF as APCDs are 0.031 and 0.006 ng-TEQ/N m3, and that achieved with FACB are 1.74 and 0.19 ng-TEQ/N m3 in MWI and IWI, respectively. The results show that FACB could reduce vapor-phase PCDD/Fs and PCBs concentrations in flue gas, while the ACI + BF can effectively adsorb the vapor-phase dioxin-like congener and collect the solid-phase PCDD/Fs and PCBs in the meantime. Additionally, the results of the pilot-scale adsorption system (PAS) experimentation indicate that each gram activated carbon adsorbs 105–115 ng-PCDD/Fs and each surface area (m2) of activated carbon adsorbs 10–25 ng-PCDD/Fs. Based on the results of PAS experimentation, this study confirms that the surface area of mesopore + macropore (20–200 Å) of the activated carbon is a critical factor affecting PCDD/F adsorption capacity.