Yang Jing, Ma Liping, Yang Jie, Guo Zhiying, Liu Hongpan, Zhang Wei
Faculty of Environmental Science and Engineering, Kunming University of Science and Technology, Kunming, Yunnan 650093, China.
Faculty of Environmental Science and Engineering, Kunming University of Science and Technology, Kunming, Yunnan 650093, China.
Sci Total Environ. 2019 Nov 1;689:854-864. doi: 10.1016/j.scitotenv.2019.06.506. Epub 2019 Jul 1.
Chemical-looping gasification (CLG) is a novel process for syngas generation from solid fuels that shares the same basic principles as chemical-looping combustion (CLC). This method also uses oxygen carriers (mainly metal oxides and calcium sulfate) to transfer heat and oxygen to the fuel. In this work, we used phosphogypsum (PG) as the oxygen carrier in CLG with lignite fuel. Based on experimental and density functional theory (DFT) theoretical calculation analysis, the Ca and S migration characteristics in PG and the reaction mechanism between lignite fuel molecules and the oxygen carrier PG in CLG were explored. The results show that there is a series of tandem and competitive reactions during this process, and the optimal temperature range of the fuel reactor in the chemical looping gasification of PG oxygen carriers is 1173 K-1223 K. The only gaseous sulfide detected is HS, and the solid sulfide CaS and a small amount of unreacted CaSO are detected at a temperature of 1173 K. DFT calculation shows that the presence of S atoms from SO on the top of the CaSO surface is more favourable than Ca for C, CO, and H oxidation at a temperature of 1173 K. During oxidation, lattice O consumption mainly occurs around the S atoms stepwise from S → S at a temperature of 1173 K. In addition, CO and H oxidation occur more easily than that of C at a temperature of 1173 K. The experimental results and the calculated results show good consistency, providing valuable information regarding the reactivity of the oxygen carrier PG and the C, CO, and H oxidation over the CaSO surface at an atomic level.
化学链气化（CLG）是一种从固体燃料中生成合成气的新工艺，与化学链燃烧（CLC）具有相同的基本原理。该方法还使用氧载体（主要是金属氧化物和硫酸钙）将热量和氧气传递给燃料。在这项工作中，我们将磷石膏（PG）用作CLG中与褐煤燃料反应的氧载体。基于实验和密度泛函理论（DFT）理论计算分析，探索了PG中Ca和S的迁移特性以及CLG中褐煤燃料分子与氧载体PG之间的反应机理。结果表明，在此过程中存在一系列串联和竞争反应，PG氧载体化学链气化中燃料反应器的最佳温度范围为1173 K - 1223 K。检测到的唯一气态硫化物是HS，在1173 K的温度下检测到固体硫化物CaS和少量未反应的CaSO。DFT计算表明，在1173 K的温度下，CaSO表面顶部SO的S原子的存在比Ca更有利于C、CO和H的氧化。在氧化过程中，晶格O的消耗主要在1173 K的温度下从S逐步围绕S原子发生。此外，在1173 K的温度下，CO和H的氧化比C的氧化更容易发生。实验结果与计算结果显示出良好的一致性，为氧载体PG的反应性以及CaSO表面上C、CO和H在原子水平上的氧化提供了有价值的信息。
