医疗废物焚烧飞灰二噁英的热处理研究

Thermal Treatment Behavior of PCDD/Fs on the Fly Ash from Medical Waste Incineration

比较了医疗废物焚烧飞灰在温度200～450℃,流动氮气和静态空气气氛中二噁英气固相行为变化.在流动氮气条件下,固相二噁英随温度升高逐渐增加,350℃下飞灰二噁英浓度升至最高,毒性当量浓度和总浓度分别增加了46.0%和26.0%,随后随着温度升高,二噁英含量逐渐降低,450℃条件下浓度减少至最低,分别减少了86.8%和80.5%.在静态空气下,固相二噁英随温度至250℃条件下,飞灰二噁英浓度升至最高,毒性当量浓度和总浓度分别增加了20.7%和28.7%,随着温度进一步升高,二噁英含量逐渐降低,450℃条件下浓度减至最低,分别减少了99.5%和99.5%.气相只有少量二噁英产生,仅占总产生量的0.11%～2.16%.本实验研究飞灰的最佳热处置条件为:静态空气条件下,450℃处置1 h.本研究中,分解反应在PCDDs与PCDFs的降解过程起到主要作用,而脱氯与脱附仅为次要作用.

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.