Key Laboratory of Industrial Ecology and Environmental Engineering, School of Environmental Science and Technology, Dalian University of Technology, Linggong Road 2, Dalian, 116024, People's Republic of China.
Key Laboratory of Industrial Ecology and Environmental Engineering, School of Environmental Science and Technology, Dalian University of Technology, Linggong Road 2, Dalian, 116024, People's Republic of China.
Chemosphere. 2021 Feb;264(Pt 1):128406. doi: 10.1016/j.chemosphere.2020.128406. Epub 2020 Sep 24.
Thermal behavior of municipal solid waste incineration (MSWI) fly ash is extremely complicated due to the simultaneously occurred reactive processes and the products with different chemical compositions, therefore, the investigation of chemical compounds transition behavior and mechanism during the integrated thermal process is of great significance. In this study, the macro-thermal treatment of fly ash and thermo-gravimetric analysis via non-isothermal methods were carried out and Málek method was firstly introduced to explore the mechanism of multi-step reaction for fly ash. The mineral transition results suggested that the halite, sylvite in the raw fly ash transformed to more complex crystals in treated samples, such as chlorellestadite, polyhalite and enstatite during the thermal process. And the heavy metals leaching concentration decreased with the temperature increased from 300 °C to 1200 °C, and the leaching values were lower than the standard limitation after thermal treatment. In addition, three major steps of fly ash reactions (300-380 °C, 650-750 °C and 890-1130 °C) during the thermal process were observed and expressed by first order reaction for the first step, three-dimensional diffusion for the second step and three dimensions of limiting surface reaction between both phases for the third step, respectively. The kinetic study revealed that the mineral transition process was in well accordance with the simulated reaction mechanism during the thermal treatment. The obtained results are expected to provide the research basis for studying detailed thermal characteristics and reaction mechanism during the thermal treatment of MSWI fly ash.
城市固体废物焚烧 (MSWI) 飞灰的热行为极其复杂，因为同时发生的反应过程和具有不同化学成分的产物，因此，研究化学化合物在综合热过程中的转化行为和机制具有重要意义。在这项研究中，对飞灰进行了宏观热处理和非等温热重分析，并首次引入了 Málek 方法来探索飞灰多步反应的机制。矿物转化结果表明，在热过程中，原始飞灰中的石盐和钾盐转化为更复杂的晶体，如氯磷灰石、复盐和顽辉石。并且，随着温度从 300°C 升高到 1200°C，重金属浸出浓度降低，热处理后浸出值低于标准限值。此外，在热过程中观察到飞灰反应的三个主要步骤（300-380°C、650-750°C 和 890-1130°C），并分别用一级反应、三维扩散和两相之间的三维限制表面反应来表示第一阶段、第二阶段和第三阶段。动力学研究表明，矿物转化过程与热处理过程中的模拟反应机制非常吻合。所得结果有望为研究 MSWI 飞灰热处理过程中的详细热特性和反应机制提供研究基础。
