Liu Cheng, Gu Jinxing, Zhou Song, Qian Binbin, Etschmann Barbara, Liu Jefferson Zhe, Yu Dunxi, Zhang Lian
Department of Chemical & Biological Engineering, Monash University, Clayton Campus, Victoria 3800, Australia.
School of Earth, Atmosphere and Environment, Monash University, Clayton Campus, Victoria 3800, Australia.
J Hazard Mater. 2022 Oct 5;439:129620. doi: 10.1016/j.jhazmat.2022.129620. Epub 2022 Jul 16.
The chlorine evolution mechanism remains unclear during the thermal treatment of CaCl/Ca(OH)Cl-containing solid waste. In this paper, we have conducted both experimental investigation and density functional theory (DFT) calculation to elucidate the mechanism of pyro-hydrolysis of CaCl with and without SiO in the temperature ranges of 400-900 °C. It was determined that pyro-hydrolysis of CaCl alone generated a maximum of 12% HCl by decomposition into Ca(OH)Cl, which is a stable intermediate that can be reverted to CaCl at 800 °C. Upon the addition of SiO at an equimolar ratio to CaCl, the HCl release extent was accelerated to 50% at 900 °C. Both experiments and DFT calculations prove that the added SiO can promote the dissociation of water molecules which provides hydroxyl ions that enable the conversion of CaCl into Ca(OH)Cl at low temperatures. The resulting Ca(OH)Cl can also quickly react with SiO to form Cl-bearing silicates such as CaSiOCl and CaSiOCl with weakened CaCl bond that are relatively easy to cleave into Cl-free CaSiO and HCl from 800 °C.
在含CaCl/Ca(OH)Cl的固体废物热处理过程中，氯的析出机制仍不明确。在本文中，我们进行了实验研究和密度泛函理论（DFT）计算，以阐明在400 - 900°C温度范围内，有无SiO时CaCl的热解机制。结果表明，单独的CaCl热解通过分解为Ca(OH)Cl最多产生12%的HCl，Ca(OH)Cl是一种稳定的中间体，在800°C时可还原为CaCl。当以等摩尔比向CaCl中添加SiO时，在900°C时HCl释放程度加速至50%。实验和DFT计算均证明，添加的SiO可促进水分子的解离，提供羟基离子，使CaCl在低温下转化为Ca(OH)Cl。生成的Ca(OH)Cl也能迅速与SiO反应形成含氯硅酸盐，如CaSiOCl和CaSiOCl，其CaCl键减弱，在800°C时相对容易裂解为无氯的CaSiO和HCl。
