Gasification is an effective technology for the thermal disposal of municipal solid waste (MSW) with lower dioxin emission compared to the prevailing incineration process. Nevertheless, the mechanism of dioxin formation in the reducing atmosphere during the gasification process was seldomly explored. Herein, the effects of the atmosphere, temperature, and chlorine source were systematically investigated in terms of dioxin distribution. With CO₂ and H₂O as gasification agents, a reducing reaction atmosphere was formed with abundant H₂ which effectively suppressed the generation of C–Cl, contributing to a substantial decrease of dioxin concentration by ∼80% compared to the incineration process. The formation of dioxin was favored at temperatures below 700 °C with its peak concentration achieved at 500 °C. It was unveiled that inorganic chlorine played a dominant role in the reducing atmosphere, with a lower proportion of C–O–C/O–C═O on residual slag compared to an oxidizing atmosphere. Additionally, the generated H₂ reduced the concentration of dioxins by attacking C–Cl and inhibiting the crucial Deacon reaction for dioxin formation, validated by density functional theory calculation. Eventually, the formation route paradigm and the reaction mechanism of dioxin formation from MSW gasification were revealed, facilitating and rationally guiding the control of dioxin emission.

中文翻译：

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揭示城市生活垃圾在还原气氛中气化二恶英的形成机制

气化是一种有效的城市固体废物 (MSW) 热处置技术，与现行的焚烧工艺相比，二恶英排放量较低。然而，很少有人探讨气化过程中还原气氛中二恶英的形成机理。在此，系统地研究了大气、温度和氯源对二恶英分布的影响。以CO ₂和H ₂ O为气化剂，形成富含H _{2的还原反应气氛}这有效地抑制了 C-Cl 的产生，与焚烧过程相比，二恶英浓度大幅降低了约 80%。二恶英的形成在温度低于 700 °C 时有利于形成，其峰值浓度在 500 °C 时达到。揭示了无机氯在还原气氛中起主要作用，与氧化气氛相比，残留渣中的 C-O-C/O-C=O 比例较低。此外，生成的 H ₂通过攻击 C-Cl 和抑制二恶英形成的关键 Deacon 反应来降低二恶英的浓度，通过密度泛函理论计算得到验证。最终揭示了生活垃圾气化生成二恶英的形成路线范式和反应机理，为二恶英排放控制提供了便利和合理的指导。