School of Iron and Steel, Soochow University, China.
School of Iron and Steel, Soochow University, China.
Waste Manag. 2021 May 1;126:832-842. doi: 10.1016/j.wasman.2021.04.021. Epub 2021 Apr 22.
A systematic investigation was conducted onthe co-pyrolysisof FeOand PVC mixtures in temperatures as high as 1373 K upon the development of PVC recycling technology that mitigates chlorine emission. Central to our investigation, PVC decomposition plays the leading role in the co-pyrolysis of FeOand PVC mixtures following a two-stage pattern bifurcated at a temperature of 673 K. In Stage 1, at temperatures 673 K and lower, FeOis chlorinated by chlorine from PVC, resulting in FeCl. The composition of the final solid residue of Stage 1,conjugated polyene, FeCland FeO/FeO, depends on the initial FeOcontent in the mixture. When the temperature is increased to be higher than 673 K, decomposition of conjugated polyene occurs simultaneously with the stepwise reduction of FeO/FeO: FeO → FeO → FeO → Fe. However, in mixtures containing FeOthat is less than 39.6% of the mass, FeOcan coexist with Fe; therefore, the FeO formation step is skipped. Most FeClescapes from the reaction system as vapor, showing the necessity of removing FeClat the end of Stage 1 to avoid harmful substance emission. The presence of FeOcan significantly suppress gaseous emissions, especially HCl originating from PVC decomposition. There was only 0.6% HCl by mass (2.4% PVC base by mass) released when co-pyrolyzing the PVC + 75% FeOmixture due to the complete consumption of PVC and its decomposition products by FeO. After separating FeCl,which is a valuable chemical feedstock, by water-leaching the solid residue obtained at 673 K, the filtered residue,which is a mixture of FeO/FeOand polyene, was confirmedto be suitable for iron-making. The results clearly show the possibility of developing a PVC recycling technology with mitigated chlorine emissions by manipulating the amount of FeOadded.
针对减轻 PVC 回收技术中氯排放的问题，我们对 FeO 和 PVC 混合物在高达 1373 K 的温度下的共热解进行了系统研究。我们的研究重点是，在两段式热解过程中，当温度达到 673 K 时，PVC 分解起着主导作用，该过程在 673 K 时分叉。在第一阶段，当温度低于 673 K 时，FeO 被 PVC 中的氯氯化，生成 FeCl。第一阶段最终固体残留物的组成，共轭多烯、FeCl 和 FeO/FeO，取决于混合物中初始 FeO 的含量。当温度升高到高于 673 K 时，共轭多烯发生分解，同时 FeO/FeO 逐步还原：FeO→FeO→FeO→Fe。然而，在含有低于 39.6%质量的 FeO 的混合物中，FeO 可以与 Fe 共存；因此，跳过 FeO 形成步骤。大多数 FeCl 以蒸气形式从反应体系中逸出，表明在第一阶段结束时需要去除 FeCl，以避免有害物质排放。FeO 的存在可以显著抑制气态排放，特别是源自 PVC 分解的 HCl。由于 FeO 完全消耗了 PVC 及其分解产物，当共热解 PVC + 75% FeO 混合物时，仅释放了 0.6%的质量 HCl（按质量计 2.4%的 PVC 基准）。通过水浸出在 673 K 下获得的固体残留物，除去了有价值的化学原料 FeCl 后，过滤后的残渣，即 FeO/FeO 和多烯的混合物，被证实适合炼铁。结果清楚地表明，通过控制添加的 FeO 量，有可能开发出一种具有减轻氯排放的 PVC 回收技术。
