煤中纳米级矿物的地球化学特征及热转化机制

Minerals in coal that are sub-microscopic can be termed Nano-minerals. Nano-minerals are commonly carriers of the hazardous trace elements in coal, and they are difficult to remove by routine beneficiation, so contribute to environmental pollution. The aim of this project is to understand the relationship between the thermal conversion mechanism of Nano-minerals and formation of fine particles from coal combustion and gasification by combining experiments with molecular simulations. This research project will use core samples from Permo-Carboniferous coal measures with different ash and sulphur contents in Qinshui Coalfield and Hedong Coalfield. These coals will be examined Nano-mineral occurrence and distribution using methods such as FE-SEM/EDS and HR-TEM/SEAD/FFT/EDS, with accessory micro-analysis, solvent extraction, low temperature ashing, XRD, Raman, optical microscope, micro-FTIR and ICP-MS. Their occurrence in the Integrated analysis of these results will be used to confirm the relationships among Nano-minerals types, particles distribution, trace elements and organic matter in feed and combustion products. The innovation of the project is reflected in the following aspects: (1) to reveal the geochemistry and occurrences of nano-minerals and their relationships with organic matter types using micro-in situ analysis; to understand their fate and association with fine particles formation from combustion and gasification through experimentation; and (2) to develop a set of molecular simulation methods for studying the thermal conversion of Nano-minerals in coal, confirmed by the experimentation.

纳米级矿物是煤中矿物的重要存在形态和有害微量元素的载体。在煤炭利用过程中纳米级矿物很难被脱除，造成了环境污染问题。项目旨在研究纳米级矿物的热转化机制及其与燃烧、气化过程中微细颗粒物形成之间的关系。以沁水、河东煤田石炭-二叠系不同灰分、硫含量煤为研究对象，以FE-SEM/EDS和 HR-TEM/SEAD/FFT/EDS等微区分析方法为核心，结合常规实验方法分析煤、显微组分及其不同化学组成中纳米级矿物类型、粒度、微量元素含量及与有机质之间的关系，并采用燃烧、气化模拟实验及分子模拟相结合研究纳米级矿物的热转化机制及其与燃烧、气化过程中微细粒物形成的关系。项目的特色与创新体现在：（1）揭示煤中纳米级矿物地球化学特征、赋存状态及其与有机质之间关系，进而分析其与燃煤、气化过程中微细粒物形成的关系；（2）微区-原位、组成-结构、实验-分子模拟等方法结合，建立一套研究煤中纳米级矿物热转化分子模拟方法。

煤中纳米矿物是有害微量元素的载体，燃煤过程中纳米级矿物很难被脱除，造成了环境污染问题。本项目以太原西山煤田屯兰煤矿2#和8#煤、平朔矿区东露天矿4#煤和不同燃烧工况条件电厂入料煤、飞灰、炉渣为研究对象，开展以下工作：（1）利用X射线荧光光谱（XRF）、电感耦合等离子体发射光谱仪(ICP-OES)、电感耦合等离子体质谱（ICP-MS）对不同煤岩组分煤样及电厂飞灰进行常量和微量元素测试，了解样品微量元素和常量元素的分布特征；（2）利用带能谱仪的场发射扫描电镜（SEM-EDX）和高分辨率透射电镜（HR-TEM-EDX）技术对不同煤岩组分原煤、抽提物和残煤及电厂飞样品的纳米矿物（粒度、形态、组成）进行系统分析，提出了纳米矿物的形成机制；（3）用HR-TEM-EDX 、XRD、FTIR、27Si-XPS和Al MAS-NMR技术，对飞灰样品进行颗粒组成和结构分析，提示燃煤过程纳米矿物转化机制。取得进展：（1）煤中纳米矿物主要是粘土矿物、石膏、锐钛矿，还发现了少量的黄铁矿、磷灰石、重晶石、含稀土的矿物。不同煤岩组分原煤中均发现粘土矿物和锐钛矿，Ca纳米矿物主要存在于镜质组含量高的镜煤和亮煤中；（2）抽提物中纳米颗粒主要是粘土矿物和金属离子纳米颗粒，溶剂抽提能够将有机结合态的元素重新组合形成新的纳米颗粒；屯兰2#沥青质中金属离子纳米颗粒为Ca(Si, Al, Na)-Fe(Ti)-Cl-S型，8#抽提物中金属离子纳米颗粒为Ca-(Fe)-S-(F, Cl)型；（3）飞灰样品中纳米颗粒包括经燃烧转化形成的刚玉、赤铁矿、金红石和莫来石等，还存在原煤燃烧残留的粘土矿物，纳米级赤铁矿与莫来石均富集有害元素Cr；（4）发表期刊论文6篇，授权专利1项。