Study on Emission Control of Dioxins by Thermal Decomposition

Abstract

In this paper, we present the data regarding the thermal decomposition of PCDD/Fs during the manufacturing process of ceramisite from MSWI fly ash, and the efficiency of bag filter with activated carbon injection technology to reduce the gas emission of PCDD/Fs. The distribution of seventeen 2,3,7,8-chlorinated dioxins and furans in MSWI fly ash, ceramisite product, bag filter ash and emission gases were analyzed, and the international toxic equivalents (I-TEQ as 2,3,7,8-tetraCDD) values were calculated by using international-toxicity equivalency factor (I-TEF). The total I-TEQ value of PCDD/Fs in MSWI fly ash reached up to 904.944 ng/kg. After high temperature calcining, only 1.250 ng I-TEQ/kg of PCDD/Fs is left in the ceramisite product. The concentrations of PCDD/Fs in two kinds of bag filter ashes, with activated carbon injection (AC) and without activated carbon injection (NAC), were 324.723 ng I-TEQ/kg and 217.066 ng I-TEQ/kg, respectively. The distribution patterns of seventeen 2,3,7,8-chlorinated dioxins and furans in MSWI fly ash, ceramisite product and bag filter ashes are alike, which suggested that the secondary formation of PCDD/Fs did not significantly occur during the thermal process of manufacturing ceramisite from MSWI fly ash. When no activated carbon was injected, the gas emission of PCDD/Fs was 0.373 ng I-TEQ/Nm3, but 100 mg/Nm3 of activated carbon injection, the gas emission of PCDD/Fs was declined to 0.081 ng I-TEQ/Nm3, which is lower than the gas emission limit established by the European Union Directive of 0.1 ng I-TEQ/Nm3. Therefor, we can recommend that the manufacturing ceramisite from MSWI fly ash using the developed rotary kiln system is an effective measure to safely dispose the MSWI fly ash on the aspect of dioxin emission control.