The influence of fly ash load and particle size on the formation of PCDD,PCDF, PCBz and PCB in a pilot incinerator

A laboratory-scale, fluidized bed reactor fuelled by a synthetic fuel was used to study the influence of fly ash load, particle size, temperature and residence time on the low-temperature formation of chlorinated aromatic compounds. Large fly ash particles were removed from the flue gases by means of a cyclone at the entrance to the cooling section of the reactor. The experimental variables were varied according to an experimental plan of full factorial design. Polychlorinated dibenzo-p-dioxins, dibenzo-furans, polychlorinated benzenes and biphenyls were analysed in the collected flue gas samples. Despite the fact that most of the fly ash load was removed by the cyclone, formation of chlorinated aromatics occurred to the same extent as in earlier experiments, without the cyclone. These results demonstrate the importance of small fly ash particles in the post-combustion formation of chlorinated aromatics.