Study on the Mechanism of Lead Incorporation into Minerals during High-Temperature Coal Combustion
Study on the Mechanism of Lead Incorporation into Minerals during High-Temperature Coal Combustion
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DOI：
10.1021/acs.energyfuels.3c03350
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发表时间：
2023-11
期刊：
影响因子：
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通讯作者：
Guo-chang Song;Zhong-wei Li;Xing-yu Yang;Qiang Song
中科院分区：
文献类型：
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作者：
Guo-chang Song;Zhong-wei Li;Xing-yu Yang;Qiang Song
探讨煤在高温燃烧过程中Pb的滞留机理，有利于通过燃料调控减少Pb污染物的排放。在此基础上，进行了灰和矿物与PbO/PbCl 2的共热实验。通过微区成分分析，获得了Pb、Na、K、Ca的富集特征。据确定，铅被纳入晶格的铝硅酸盐的钠，钾，钙的类质同象取代。采用密度泛函理论计算了PbO和PbCl 2在KAlSi 3 O 8、NaAlSi 3 O 8和Ca 2Al 2SiO 7（0 0 1）表面的取代反应路径.反应步骤包括PbO/PbCl 2吸附、Na-O/K-O/Ca-O/Pb-O键断裂、原子置换和新键形成。速率控制步骤为Na-O、K-O、Ca-O和Pb-O键的断裂。K取代的PbCl 2中Pb的能垒最低，为34.60 kJ mol-1.态密度分析表明，PbCl 2的吸附降低了Na-O和Ca-O的键强度，使Na和Ca更容易脱离晶格结构，降低了能垒。Pb取代的不同金属的反应能垒顺序为K < Ca < Na。Pb对K的同质同象置换反应最容易发生，因此，煤燃烧产物中的Pb主要富集在K-铝硅酸盐中。研究结果可为了解Pb在燃煤系统中的转化规律，优化配煤、添加矿物等污染物排放控制技术提供理论支持。
Exploring the Pb retention mechanism during high-temperature coal combustion is beneficial for reducing the emission of Pb pollutants through fuel regulation. Herein, coheating experiments of ash and minerals with PbO/PbCl2were carried out. The enrichment characteristics of Pb, Na, K, and Ca were obtained through microarea composition analysis. It was determined that Pb was incorporated into the lattice of aluminosilicates by the isomorphous substitution for Na, K, and Ca. Density functional theory calculations were performed to obtain the substitution reaction paths of PbO and PbCl2on the (0 0 1) surfaces of KAlSi3O8, NaAlSi3O8, and Ca2Al2SiO7. The reaction steps included the adsorption of PbO/PbCl2, breaking of the Na–O/K–O/Ca–O/Pb–O bonds, atomic displacement, and formation of new bonds. The rate-determining steps were breaking of Na–O, K–O, Ca–O, and Pb–O bonds. The energy barrier of Pb in PbCl2substituted with K was the lowest at 34.60 kJ mol–1. Density of states analysis showed that the adsorption of PbCl2could reduce the bonding strength of Na–O and Ca–O, making it easier for Na and Ca to detach from the lattice structure and reduce the energy barrier. The order of the reaction energy barriers of the different metals substituted with Pb was K < Ca < Na. The isomorphic substitution reaction of Pb for K is most likely to occur; thus, Pb in coal combustion products is mostly enriched in K-aluminosilicate. The results can provide theoretical support for understanding the transformation of Pb in coal-fired systems and optimizing emission control technologies such as coal blending and mineral addition.