[Low-temperature thermal treatment of dioxin in medical waste fly ash under unert atmosphere]

Two kinds of fly ash (AG and BG) from hazardous waste rotary kiln were investigated as the targets of thermal treatment. AG was sampled after fabric filter with activated carbon spray and BG was sampled in pipe before fabric filter. The effects of temperature and time on PCDD/Fs degradation rate in fly ash were investigated in quartz tubular. Under nitrogen atmosphere, low-temperature thermal treatment for dioxin degradation had obvious effect. For sample BG, the degradation rate of dioxin in solid phase was 82.8%-99.9%, and the degradation rate of I-TEQ was 77.3%-99.8%. For sample AG, the degradation rate was 66.8% - 99.8%, and the degradation rate of I-TEQ was 43.5% - 99.6%. Although dioxin in solid phase was reduced, it was generated in gas phase, and among all the different temperatures tested, dioxin was generated at highest amounts at 300 degrees C - 350 degrees C, and among all the toxic congeners, OCDD was detected as the most abundant in this experiment. The best conditions of thermal treatment were: heating time 60 min, temperature 400 degrees C, under nitrogen atmosphere. The results indicate that low-temperature thermal treatment under inert atmosphere has good effect on treating dioxin present in medical fly ash, it can be applied in practical projects in large scales.