【作者】 张战军；

【导师】 赫英；

【作者基本信息】 西北大学 ， 地球化学， 2007， 博士

【摘要】 高铝粉煤灰是近年来在我国内蒙古中西部地区发现的一种粉煤灰新类型，其Al₂O₃含量高达50％左右，相当于我国中级品位铝土矿中氧化铝的含量。根据高铝粉煤灰的资源特性结合市场需求，确定了对高铝粉煤灰中Al₂O₃、SiO₂以及Ga₂O₃等有用资源逐级提取，最后将剩余产物生产建材的资源化利用方案。本文运用地质学的研究方法，研究高铝粉煤灰的形成和特性及其后续提取氧化铝过程中的物质演化规律和内在机理，旨在为高铝粉煤灰资源化利用技术路线的制定奠定基础。利用光学和电子显微镜、X-射线衍射、化学分析、ICP-MS分析、²⁹Si魔角旋转核磁共振、TGA-DTA分析等手段，综合运用地球化学、矿物学、煤田地质学、煤燃烧学、物理化学以及冶金化工等多个学科的理论知识，从分析高铝粉煤灰的物质来源和成因入手，对产生高铝粉煤灰的燃煤煤种—内蒙古准格尔煤田晚古生代烟煤进行无机地球化学特征研究，发现高铝粉煤灰来源于煤中赋存的细分散状勃姆石和高岭石矿物，而这些矿物的形成由当时特殊的地质和地球化学条件所决定；对高铝粉煤灰的显微结构、物相组成、化学组成以及部分主微量元素在不同物相或物相组合中的分布规律的研究表明，高铝粉煤灰中不仅富含氧化铝，而且富集微晶莫来石及非晶SiO₂和稀有分散元素Ga等有益组分，是一种十分宝贵的再生矿产资源；根据这些特性确定了高铝粉煤灰逐级提取氧化铝等有用资源的总体技术路线如下：先用高浓度NaOH对高铝粉煤灰进行低温脱硅以进一步提高粉煤灰的Al／Si比，脱硅液用于制备白炭黑，然后再用碱石灰烧结法从脱硅粉煤灰中提取氧化铝。通过系列正交实验，获得了高铝粉煤灰预脱硅和提取氧化铝等关键工艺的物理化学条件和参数，结果表明：1)粉煤灰的最佳脱硅条件为：NaOH的浓度为25％，灰碱质量比为1∶0.5，一反应温度95℃，反应时间4小时。经最佳条件反应之后，SiO₂提取率达41.8％。经该条件处理后高铝粉煤灰中Al₂O₃的含量由48.5％增加到了57.38％，Al／Si质量比由原来的1.28提高到了2.39。2)脱硅高铝粉煤灰的最佳焙烧条件为：钙比为2∶1，钠比0.95∶1，焙烧温度1150℃，保温时间60分钟。熟料中铝酸钠的最佳水溶出条件为：温度70℃、溶出时间10分钟。在上述条件下，在实验室制备出了成分指标达到或者超过了行业标准的白炭黑和氧化铝，其中Al₂O₃的提取率超过90％；对粉煤灰玻璃相与NaOH之间的灰—碱反应动力学以及脱硅粉煤灰—碳酸钠—碳酸钙体系的焙烧机理和反应热力学进行了探讨研究；最后，以整个工艺过程中的主要物质演化为主线，分析了高铝粉煤灰中的Ga及U、Th、Pb、Cr等有毒有害元素在该主线中的迁移规律，为Ga₂O₃与Al₂O₃、SiO₂的逐级提取及这些有毒有害元素在生产过程中对人或环境的潜在危害进行防治提供了科学依据。更多还原

【Abstract】 A new type of fly ash was recently found in the west of Inner Mongolia, of which the Al₂O₃ content （close to 50 wt%） is comparative to the middle content bauxite ores. According to the resource characteristics of this high aluminium fly ash, as well the market demand, the route was established for the extraction of Al₂O₃、SiO₂ and Ga₂O₃ step by step, at the same time, the residue was used for structural material. Geological methods was introduced to study the characteristics and cause of formation of the high aluminium fly ash,as well as the regularity of substance evolvement and its inner mechanism during the extraction of Al₂O₃, which aimed to lay a foundation for the establishment of the route to extract Al₂O₃ from the particular fly ash.In this thesis, series of analysis and test measures were applied, including optical and electron microscope, X-ray diffraction, chemical analyse, ICP-MS analysis, ²⁹Si MAS NMR spectra and TGA-DTA analysis, and Multy-knowledge such as geochemistry, mineralogy, coal science, coal combustion science, phychemistry, metallurgy and inorganic chemistry were introduced. Starting with the research of the substance source and cause of formation of the high aluminium . fly ash, conduct the inorganic geochemistry character investigation on the combustion coal of this fly ash- soft coal in late Paleozoic era from Junger coalfield in Inner Mongolia, then we find that this kind of fly ash mainly originates from the thin boehmite and kaolinite that disperses in the coal, and the formation of such minerals was resulted from the particular geological and geochemical condicition; The research on the phases and chemical composition, microstructure and distribution of some major and trace elements in the high aluminium fly ash indicates that this peculiar fly ash is a kind of valuable regenerative mineral resources, apart from alumina, which is also enriched in mullite crystallite, amorphous SiO₂ and useful substance-Ga. According to such characteristics of the fly ash, the brief technical route of cooperatively extracting Al₂O₃ and other useful substance was determined as follows: Firstly, the fly ash is treated by high concentration of NaOH solution under low temperature to extract amorphous SiO₂ and increase its Al/Si ratio, and the desiliconed solution obtained during this treatment can be used for the preparation of white carbon black. Then the alkali-lime-calcined method is used to extract Al₂O₃ from desiliconed fly ash.The main phychemical conditions in the technical route were optimized by series of orthogonal experiments and necessary complementary experiments, and it shows as follwings: （1） The optimized conditions of desiliconlization: concentration of NaOH , 25%; mass ratio of ash to alkali, 1:0.5; reaction temperature 95°C, and reaction time 4 hours. After reaction under the optimum conditions, the extraction efficiency of SiO₂ amounts to 41.8%, the Al₂O₃ content of the fly ash increases from 48.5% to 57.38% and Al₂O₃/SiO₂ mass ratio increases from 1.28 to 2.39. （2） The optimized conditions of treating the desiliconed fly ash: The optimized condtions for calcining the desiliconed fly ash: Ca ratio, 2:1; Na ration,0.95:1; temperature of calcination, 1150°C, heat preservation time, 60 minutes. And the optimized condtions for the extraction of NaAlO₂: temperature, 70°C; time for dissolution of NaAlO₂, 10 minutes. According to the conditions mentioned above, white carbon black and alumina content with nation quality criterion was obtained in laboratory, and that the extraction rate of Al₂O₃ was more than 90%; On the basis of experiments, we conduct the dynamic investigation on the reaction between NaOH solution and the glass of fly ash, and the thermodynamic investigation on the main calcined reactions of the desiliconlized fly ash-Na₂CO₃-CaCO₃; Finally, taking the main substance evolvement as the clue, we discussed the movement behaviour of Ga and some deleterious elements such as U、Th、Pb and Cr, which would provid the scientific guidance for the cooperative extraction of Al₂O₃、SiO₂ and Ga₂O₃, as well for the elimination of the potential harm to human or the environment resulted from these deleterious elements.更多还原