模拟水泥窑工艺对污染土壤热解吸尾气中六氯苯的去除效果

为了降低HCB(六氯苯)污染土壤热解吸修复的成本,分析了水泥窑处理技术去除污染土壤热解吸尾气中HCB的可行性,主要考察了处理温度、停留时间、φ(O₂)和ρ(HCB)初始值对HCB去除的影响. 结果表明:①随着处理温度的升高和停留时间的延长,HCB的去除率逐渐升高,其中,当处理温度≥800 ℃、停留时间≥2 s时,其去除率高于99.93%. ②当处理温度为900 ℃、停留时间为2 s、ρ(HCB)初始值分别为1.70、17.00和85.00 mg/m3时,水泥窑处理后尾气中ρ(HCB)分别为0.60、0.78和1.50 μg/m3,其与ρ(HCB)初始值并不成正比,说明ρ(HCB)初始值对HCB去除的影响较小；φ(O₂)≥2%时对HCB去除的影响也较小. ③水泥窑处理后,HCB的脱氯降解产物中仅有五氯苯被检出,ρ(五氯苯)最大值为1.20 μg/m3；同时处理过程中伴有少量的二英产生,但ρ(二英)满足GB 30485—2013《水泥窑协同处置固体废物污染控制标准》要求. 结果显示,模拟水泥窑工艺可有效去除污染土壤热解吸尾气中的HCB. 

Removal of Hexachlorobenzene in Thermal Desorption Offgas by Simulated Cement Kiln

To save the cost of thermal desorption for remediating contaminated soils, the feasibility of removing HCB in thermal desorption offgas was investigated by cement kiln in the laboratory under different operating conditions of temperature, initial ρ(HCB), φ(O₂) and gas residence time. The removal rate of HCB increased with increasing temperature and residence time. The removal rate of HCB was over 99.93% when the offgas was treated at ≥800 ℃ with a residence time of ≥2 s. When treated at 900 ℃ for 2 s, ρ(HCB) in the offgas were 0.60,0.78, and 1.50 μg/m3 when the initial ρ(HCB) were 1.70,7.00 and 85.00 mg/m3, respectively, which was not proportional to initial ρ(HCB). This suggests that initial ρ(HCB) slightly affects the removal rate of HCB. φ(O₂) was also found to have little effect on the removal rate of HCB when φ(O₂)≥2%. Pentachlorobenzene was the only dechlorination product of HCB; the highest concentration of pentachlorobenzene was 1.20 μg/m3 after the treatment. The PCDD/Fs concentrations in the offgas after the treatment were lower than the standard for pollution control on co-processing of solid wastes in cement kiln. These results indicate that HCB in thermal desorption offgas can be effectively removed by simulated cement kiln.