State Key Laboratory of Clean Energy Utilization, Institute for Thermal Power Engineering, Zhejiang University, Hangzhou 310027, Zhejiang Province, China.
College of Metrology and Measurement Engineering, China Jiliang University, Hangzhou 310018, Zhejiang Province, China; Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Haidian District, 100085 Beijing, China.
J Hazard Mater. 2022 Aug 15;436:129124. doi: 10.1016/j.jhazmat.2022.129124. Epub 2022 May 11.
Formation and emission of dioxins is a great concern during thermal desorption remediation of organic contaminated soil. The differential formation of dioxins from chlorine organic contaminated soil (COCS) and non-chlorine organic contaminated soil (NCOCS) is still unclear and the control technique for the dioxins generated is an urgent need. In this study, the formation and distribution characteristics of dioxins were investigated in the thermal desorption unit combined with flue gas purification system during COCS and NCOCS treatments. Although organic contaminates were well desorbed, de-novo formation of dioxins was observed for both COCS and NCOCS, as well as synthesis from precursors for NCOCS. The gas-phase dioxin in the flue gas purification system continuously decreased during NCOCS thermal desorption, while the dioxin concentration in the quench tower sharply increased from 0.46 to 2.13 ng/Nm through de-novo synthesis during COCS treatment. Furthermore, the emission of dioxins only slightly reduced (for COCS) or even increased (for NCOCS) at 70% operating load. The catalytic adsorption tower within modified activated carbon and V-Mo-Ti catalyst after bag filter can reduce the emission of dioxins up to 91.4% at the condition of secondary combustion chamber closure, demonstrating that the catalytic adsorption tower can replace the secondary combustion chamber for controlling dioxin emission. More importantly, the highly toxic low-chlorinated polychlorinated dibenzodioxins and polychlorinated dibenzofurans (PCDD/PCDFs) were selectively removed from flue gas by the catalytic adsorption tower. These results reveal the differential formation characteristics of dioxins during COCS and NCOCS thermal treatments and highlight V-Mo-Ti/ modified activated carbon as a promising catalytic adsorption material to control the emission of dioxins from the thermal desorption of organic contaminated soil.
热解吸修复有机污染土壤过程中二恶英的形成与排放备受关注。氯代有机污染土壤（COCS）和非氯代有机污染土壤（NCOCS）中二恶英的差异形成机制尚不清楚，急需控制二恶英的生成技术。本研究结合烟气净化系统，考察了 COCS 和 NCOCS 热解吸过程中二恶英的形成与分布特征。尽管有机污染物得到了很好的脱附，但 COCS 和 NCOCS 均发生了二恶英的新生生成，NCOCS 还发生了前驱物合成。NCOCS 热解吸过程中，烟气净化系统气相中二恶英不断减少，而 COCS 处理过程中，急冷塔中二恶英浓度从 0.46 急剧增加到 2.13ng/Nm3，通过新生合成。此外，在 70%运行负荷下，二恶英的排放仅略有减少（对于 COCS）或甚至增加（对于 NCOCS）。袋式除尘器后的改性活性炭和 V-Mo-Ti 催化剂催化吸附塔可将二恶英排放量降低 91.4%，在二次燃烧室关闭的情况下，表明催化吸附塔可替代二次燃烧室来控制二恶英排放。更重要的是，高效能的低氯代多氯二苯并二恶英和多氯二苯并呋喃（PCDD/PCDFs）可通过催化吸附塔从烟气中选择性去除。这些结果揭示了 COCS 和 NCOCS 热解吸过程中二恶英的差异形成特征，并强调了 V-Mo-Ti/改性活性炭作为一种有前途的催化吸附材料，可用于控制有机污染土壤热解吸中二恶英的排放。
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