Industrial-use VOx-based catalysts usually have a higher active temperature window (>250-300℃),which becomes a“bottleneck”for the practical application of PCDD/Fs catalytic degradation technology.In this work,VO_(x)-FeO_(x)/TiO_(2) catalyst prepared via mechanochemically method was investigated for the catalytic removal of PCDD/Fs.The removal efficiency of 1,2-DCBz,pure PCDD/Fs gas generated in the lab,PCDD/Fs from actual fue gas,long-term were studied,and the degradation mechanism was explored using FTIR and TOFMS.The degradation efficiency of 1,2-DCBz and PCDD/Fs on VO_(x)-FeO_(x)/TiO_(2) were higher than that of VO_(x)/TiO_(2)catalyst,and the optimal FeOx addition ratio was 3 wt.%.The characterization results show that the addition of FeOx can effectively improve the pore structure,surface acidity,and VOx dispersion of the catalyst,thus contributing to increasing the V^(5+)content and surface-active oxygen,which is conducive to the improvement of adsorption and redox performance of the catalyst.Under the actual MSWI (municipal solid waste incineration)fue gas,the PCDD/Fs removal efficiency over VTi-3Fe-MC maintained long-term stability,higher than 85%for 240 min.This result was not significantly reduced compared with the data obtained in the laboratory.According to the analysis results of intermediate products by FTIR and GC-TOFMS,it can be inferred that the epoxidation fracture of benzene ring is the rate-limiting step of dioxin catalytic degradation reaction.This work gives an in-depth view into the PCDD/Fs removal over VO_(x)-FeO_(x)/TiO_(2) catalysts and could provide guidelines for the rational design of reliable catalysts for industrial applications.
Minghui TangLing WangHongxian LiXinlei HuangCuicui DuShengyong Lu
针对上海这一特大城市,构建了Weather Research and Forecasting-Community Multiscale Air Quality(WRF-CMAQ)耦合模型以分析二噁英(polychlorinated dibenzo-p-dioxins and furans,PCDD/Fs)的大气传输过程和呼吸暴露风险.结果表明:模型模拟的PCDD/Fs浓度中有69.88%的模拟值为观测值的0.5~2倍,精度良好.2019年上海大气在冬季的PCDD/Fs污染水平最高,其次是在秋季和春季,最低是在夏季,质量浓度分别为847.08、629.53、588.38和406.96 fg/m^(3),毒性当量TEQ浓度分别为59.29、44.46、40.80和28.08 fg I-TEQ/m^(3).大气PCDD/Fs污染严重的地方为杨浦区、虹口区、黄浦区、静安区、宝山区、金山区、松江区.上海居民对PCDD/Fs的呼吸暴露量表现为幼儿>老年人>成年人的趋势,分别为10.67、8.86和8.47 fg I-TEQ/(kg·d),暴露风险均在可接受水平内.此外,本地排放源对污染的贡献远大于外地排放源,这说明上海大气中的PCDD/Fs污染主要是由本地的工业生产过程和燃烧活动造成的.
The dual bag filter(DBF)system is a new polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans(PCDD/Fs)emission control technology that has more efficient(PCDD/Fs)removal performance,a higher activated carbon utilization rate and less activated carbon consumption compared with the traditional single bag filter system.Moreover,few studies have been relevant to the mechanism of the PCDD/Fs removal process in the DBF system,and the selection of operating conditions of the DBF system lacks an academic basis.This study established a PCDD/Fs removal efficiency model of activated carbon injection combined bag filter(ACI+DBF)system for hazardous waste incineration flue gas and predicted the crucial effect factors.New adsorption coefficients k_(1)=532,145 Nm^(3)/(mol s)and k_(2)=45 Nm^(3)/(mol s),and the relationship expression between the number of available adsorption positions of recycled AC(AAC′)and cycle times(n)are proposed in the model.The results verify that the model error was below 5%.In addition,the PCDD/Fs removal efficiency model predicts that in a certain range,the PCDD/Fs removal efficiency increases with increasing activated carbon injection concentration.The best cycle number of activated carbon was less than 3,and the ratio of circulating activated carbon to fresh activated carbon in second bag filter(SBF)should be controlled at 7–8.
Yanan LiQi LiuMinghui TangFei WangShengyong LuMakwarimba Chengetai PortiaYong Chi
