| PCDD/Fs formation distribution in gas phase and solid phase of medical waste incineration fly ash under both the flowing nitrogen and static air condition were studied within temperature range of 200-450℃. Under the flowing nitrogen, PCDD/Fs in solid phase increased with temperature increase, which reached the maximum concentration at 350℃, both the TEQ and total concentration increased 46.0% and 26.0% respectively of original concentration, then, which decreased with temperature's rising, reaching the lowest level at 450℃, of which 86.8% and 80.5% respectively in turn removed. Under the static air, the maximum concentration in solid phase occurred at 250℃, both the TEQ and total concentration increased 20.7% and 28.7% respectively of original concentration, then, which decreased with temperature increase, reaching the lowest level at 450℃, of which 99.5% and 99.5% respectively in turn removed. There were small generation of PCDD/Fs in gas phase, which took only 0.11%-2.16% of the total quantity of PCDD/Fs in both gas phase and solid phase. The optimal conditions for thermal treatment in this study were under the static air at temperature of 450℃ in duration of 1 h. The mechanism of destruction played the main role in the thermal treatment, while dechlorination and desorption acted as minor role in this study. |
