Experimental Study on Thermal Treatment of Dioxins in Fly Ash from Medical Waste Incinerator

Low temperature thermal treatment of poly chlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDDs/PCDFs) in fly ash from commercial-scale medical waste incinerator (MWI) was studied experimentally using a quartz tubular heating system. Experiments were carried out in nitrogen atmosphere at different temperatures, i.e. 250, 300, 350, and 400°C, for two heating times (45 and 90 min). The concentrations of raw fly ash sample was 110.49 ng/g(8.980 ngTEQ/g). After thermal treatment, the concentrations of PCDDs/PCDFs and destruction efficiencies of PCDDs /PCDFs were found to vary from 0.06 ng/g to 18.84 ng/g and from 82.9% to 99.9% in solid. Maximum removal efficiency occurred at 400°C for the case of 90 min-heating. Tetrato octa-chlorinated congeners were observed in the gas phase emitted from thermal treatment, dominated by OCDD. Experimental results exhibited that at a low temperature, while the destruction of PCDDs/PCDFs takes place in fly ashes, the reaction of PCDDs/PCDFs formation is also present.