基于污泥掺烧的某生活垃圾焚烧厂烟道气、飞灰及炉渣中的二噁英特征

Characteristics of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) in flue gas, fly ash and bottom slag from a municipal solid waste incineration (MSWI) plant based on co-firing of sewage sludge

以我国南方某生活垃圾焚烧厂掺烧10%市政污泥的生活垃圾为研究对象,对前/后口废气、飞灰、炉渣及用于掺烧的污泥中17种二噁英的含量进行了测定,并分析了其指纹分布特征.结合焚烧工况及处理设施,从生成机理角度探讨了二噁英的排放特征、毒性当量浓度主成分特征及主要单体的排放因子线性关系.结果表明:掺烧10%的市政污泥后,废气中二噁英的去除率为99.4%,低于国家排放标准;固体废物中二噁英含量为飞灰>炉渣>污泥.这说明采用高温焚烧和"活性炭喷射+布袋除尘"装置不会影响掺烧10%污泥的达标排放.指纹分布特征表明,前口废气以1,2,3,4,6,7,8-Hp CDF和OCDD为主,后口废气以OCDD和OCDF为主;飞灰、炉渣及污泥中的主要单体为OCDD、1,2,3,4,6,7,8-Hp CDD、OCDF、1,2,3,4,6,7,8-Hp CDF.主成分分析显示,前口废气和飞灰中的二噁英毒性分布特征相似;炉渣和污泥的毒性分布特征相似;后口废气有自身的特征.这说明在相同工况条件下,经同一设施处理的废物中二噁英排放特征相似.排放因子分析表明,2,3,4,7,8-Pe CDF和1,2,3,6,7,8-Hx CDF、1,2,3,6,7,8-Hx CDD和1,2,3,7,8,9-Hx CDD与总毒性排放因子具有较强的线性关系,且呋喃类(PCDFs)强于二噁英类(PCDDs).

Determination and fingerprint analysis of PCDD/Fs of the front/back flue gas,fly ash,bottom slag and sewage sludge sampled from a MSWI plant with co-combustion of sewage sludge at 10% in Southern China were performed. Based on incineration operating conditions and treatment facilities,we explored the emission characteristics,principal component（ PC） characteristics of international toxicity equivalent（ I-TEQ） and linear relationship of emission factor of main congeners from a perspective of formation mechanisms of PCDD/Fs. The results revealed that the removal rate of PCDD/Fs in flue gas was 99.4%,which was lower than the national emission standard. The concentrations of PCDD/Fs in solid wastes were in the order as follows： fly ash bottom slag sewage sludge. These indicated that the application of high temperature combustion and activated carbon injection＋bag filter had no effect on the standardized emission of co-firing sewage sludge at 10%. The fingerprint analysis showed that the main congeners in the front flue gas were 1,2,3,4,6,7,8-Hp CDF,OCDD,and those in the back flue gas were OCDD and OCDF. The major congeners in fly ash,bottom slag and sludge were OCDD,1,2,3,4,6,7,8-Hp CDD,OCDF and 1,2,3,4,6,7,8-Hp CDF. Results of principal component analysis（ PCA） revealed that the similarity of I-TEQ distribution characteristics of PCDD/Fs in the front flue gas and fly ash; the I-TEQ distribution characteristics of PCDD/Fs in ash and sludge were also similar,whileas these were specific in the back flue gas. This indicated that the emission characteristics of PCDD/Fs were similar after treated with the same facility and the same operating condition. Analysis of emission factor showed that 2,3,4,7,8-Pe CDF,1,2,3,6,7,8-Hx CDF,1,2,3,6,7,8-Hx CDD and 1,2,3,7,8,9-Hx CDD significantly correlated with total toxic emission factor. And PCDFs showed more significant linear correlations with the total toxic emission factor in comparison with PCDDs.