【作者】 李光辉；

【导师】 姜涛； 邱冠周；

【作者基本信息】 中南大学 ， 矿物加工工程， 2002， 博士

【摘要】 本论文为“国家重大基础研究发展规划（‘973’计划）”项目资助课题。 为了有效利用储量丰富的中低铝硅比铝土矿石，并为拜耳法氧化铝生产工艺提供优质原料，本文采用热重分析、差热分析、红外光谱分析、X-射线粉晶衍射分析和高分辨率固体核磁共振分析技术，系统研究了铝土矿中的常见铝硅矿物的加热相变规律，以及铝土矿石的热化学活化脱硅行为，开发了铝土矿热化学活化脱硅新工艺，获得了以下一些主要结果： 1)铝硅矿物的热行为 叶蜡石：在580℃以下，叶蜡石主要脱去吸附水，其结构和物相基本没有变化。从580℃左右开始失去羟基，八面体阳离子中心Al的配位方式由六配位Al^Ⅵ变为五配位Al^Ⅴ、四配位Al^Ⅳ。随着温度的提高，五配位Al^Ⅴ将向四配位Al^Ⅳ和六配位Al^Ⅵ转化。脱羟基的同时，（Si-O）四面体层中Si-O-Si（Al）的键角增大，原子间的相互连结被削弱。但失去羟基后的脱水叶蜡石仍然保持着类似于叶蜡石的层状骨架结构。 脱水动力学研究表明，叶蜡石的脱水反应遵循随机成核与长大规律，反应表观活化能E=128 362.3 J.mol^-1、表观频率因子A=688 716.6 min^-1。 温度达到1100℃后，脱水叶蜡石层状骨架结构破裂，生成无定形SiO₂。但此时也开始有少量莫来石晶体形成。超过1200℃后，无定形SiO₂将逐渐转化成方石英。 高岭石：420℃～660℃时，高岭石失去羟基转变成偏高岭石，八面体结构中Al由六配位Al^Ⅵ变为五配位Al^Ⅴ和四配位Al^Ⅳ，但更高温下五配位Al^Ⅴ将转变为六配位Al^Ⅵ和四配位Al^Ⅳ。脱羟基作用导致高岭石的氢氧铝八面体结构层发生严重地畸变和破坏。 脱水动力学研究表明，高岭石晶体结构中内、外羟基失去的顺序不同，使反应机制在α=0.7左右时发生转变。当0＜α＜0.7时，脱水反应遵循二维扩散控制规律。反应表观活化能E=159 682.0 J.mol^-1、表观频率因子A=1.007×10¹⁰ min^-1。 980℃以后，偏高岭石分解生成无定形SiO₂，同时由四配位Al^Ⅳ、六配位Al^Ⅵ组成立方结构的γ-Al₂O₃。1100℃左右，无定形SiO₂和γ-Al₂O₃重新结合生成莫来石。1200℃以后，无定形SiO₂将转化为方石英。 伊利石：400℃以下，吸附水和层间水的脱去使伊利石的晶格沿C轴方向产生膨胀。500℃～750℃时，伊利石失去羟基转变成脱水伊利石，Al的配位方式由六配位Al^Ⅵ转变为四配位Al^Ⅳ。但脱水伊利石仍然保持着伊利石的基本层状骨架结构。 在1090℃左右，脱水伊利石的层状骨架结构破裂，转化成非晶态的富SiO₂玻璃相，当温度达到1100℃以后，开始有莫来石生成。 一水硬铝石：在490℃～580℃左右失去晶体结构中的羟基，转变为α-Al₂O₃。α-SiO₂：在热处理过程中的结构和物相基本保持不变。 以上研究表明，热处理过程中铝硅矿物的结构、物相将产生一系列变化。在热作用下，铝硅酸盐矿物发生高温固相反应，层状结构中的硅被活化为具有较高活性的无定形博士学位论文.铝硅矿物的热行为及铝土矿石的热化学活化脱硅5102，这为热化学活化脱硅新工艺的开发提供了理论基础。 同时，综合运用多种测试技术系统研究得到的，有关铝硅酸盐矿物从室温一1200℃下的结构、物相变化规律，也可为硅酸盐、耐火材料等行业领域，以及这些非金属矿物的深加工利用提供理论指导和借鉴。研究结果具有较大的学术价值和实际意义。 2)铝土矿石的热化学活化脱硅 热化学活化过程中，由叶蜡石、高岭石和伊利石生成非晶态物质—无定形5102或富510:玻璃相是实现铝土矿石热化学活化脱硅的基础。温度高于1100℃以后的莫来石生成反应导致无定形5102的减少。 碱浸脱硅中，只有无定形5102才能溶解于NaOH溶液被脱除，而脱水叶蜡石、偏高岭石、脱水伊利石、莫来石以及a一510:均不能与NaOH反应，对脱硅没有贡献。但与无定形510:的溶解同时发生的水合铝硅酸钠（钠硅渣）沉淀反应，使溶液中的NaZsiO3又返回精矿，导致脱硅效果变差。 研究表明，在碱浸过程中，高岭石的钠硅渣沉淀反应最弱，生成的水合铝硅酸钠化学组成类似于沸石NaZo.A12O3，x 5102·nHZO;伊利石的钠硅渣沉淀反应最为剧烈，生成的水合铝硅酸钠组成为N助6A196Si9603s4和0.95N赴O·A1203·3.255102·4.79玩O;叶蜡石的钠硅渣组成为O.95Na2O.A12O3’3.25SiO2·4.79H20。因此，高岭石碱浸脱硅效果最好，而伊利石的脱硅效果最差。 与纯矿物的热化学活化脱硅规律一样，经活化处理，铝土矿中的伊利石、叶蜡石和高岭石将转化成无定形5102，而在1 100℃以上的温度下，将有莫来石生成。在碱浸过程中，活化矿中的无定形5102与NaOH反应生成NaZSIO3进入溶液被脱除，但在无定形5102溶解的同时，伴随有钠硅渣的生成。 对于含硅矿物以伊利石、叶蜡石为主的铝土矿，在热化学活化脱硅过程中生成的钠硅渣主要由N助沫1965196035;和0.95N处。·A12O3·3.255102·4.79玩O两者组成。 对含伊利石12.5%、叶蜡石6.0%、高岭石3.2%，刀S=5.85的河南铝土矿热化学活化脱硅试验结果表明，其适宜的活化温度为1 100℃一1150℃，活化时间为12Omin⁶0min。适宜的浸出?更多还原

【Abstract】 Thermal behaviors of silicon aluminium minerals and desilication technology from bauxite ores by thermochemical activation (TCA) have been investigated by using TG, DTA, IR, XRD and 29Si, 27A1 MAS NMR in this thesis. Following conclusions are achieved:1. Thermal behaviors of silicon aluminium mineralsPyrophyllite: Under thermal treatments, dehydroxylation of pyrophyllite (Al2O3 4SiO2 H2O) takes place at the temperature of about 580℃. The six-coordinate of aluminium in octahedrons is converted into five-coordinate or four-coordinate on dehydroxylation of aluminium ions in oxygen octahedrons containing OH groups. However, the five-coordinate Al shifts into four-coordinate Al and five-coordinate Al again with the temperature increase. The bond angle of Si-O-Si (Al) in the silica tetrahedral sheet rises, and the linkage between atoms weakens. But the obtained dehydrated pyrophyllite has a layered structure similar to the initial pyrophyllite.The kinetic of dehydration reaction investigated by non-isothermal thermogravimetric analysis shows that the dehydroxylation of pyrophyllite agrees with the mechanism of randomnucleation: f(α) = (l-α)-[-ln(l-α)] 3. The value of the apparent activation energy E andapparent pre-exponential Arrhenius factor A of the reaction is attained as 128 362.3 Lmor’and 688 716.6 min’1, respectively. The kinetic equation of dehydration is:da 688716.6At the temperature of about 1100℃, the layered structure of dehydrated pyrophyllite collapses and is transformed into amorphous SiO2, but the reconstruction of amorphous substance above 1100℃ forms mullite (3Al203-2SiO2). As the temperature increases, the mulltization is enhanced, and the recrystallization of the amorphous SiO2 into cristobalite will occur when the temperature exceeds 1200℃.Kaolinite: During dehydroxylation at 420α~660α, the kaolinite (Al2O3-2SiO2-2H2O) is converted into a thermally stable product of meta-kaolinite. The six-coordinate of aluminium in oxygen octahedrons containing of OH groups change into five-coordinate or four-coordinate on dehydroxylation. Breaking of some bonds lead octahedrons in kaolinite to be destroyed and distorted, the increase of defect in crystal lattice results in the meta-kaolinite as X-ray amorphous substance.The kinetic results of dehydration reaction show that the mechanism of dehydroxylation of kaolinite changes when the thermal weight loss is about α=0.7 because the OH groups in interlamellar space associated with the alumina sheets lose more easily than those in the intralamellar space between the silica and alumina sheets. When 0<a<0.7, the thermal dehydroxylation of kaolinite obeys the mechanism of two-dimensional diffusion-controlled:/() =[-ln(l -)]"1 . The apparent activation energy E and apparent pre-exporiential Arrheniusfactor A of the reaction are found to be 159 682.0 J.mol"1 and 1.007X 1010 min"1, respectively. The kinetic equation of dehydration is:da 1.007x10’?dT ftAt the temperature of about 980, the decomposition of the meta-kaolinite produces amorphous Si02 and a pinel-like phase y-AOa, and this procedure is exothermic. The formation of the y-AOa is the result of reconstruction of four-coordinate of Al ions and six-coordinate Al ions. The six-coordinate of oxygen octahedrons without OH groups are formed by the change of five-coordinate Al again.The further increase of the temperature to 1 100 results in the appearance of mullite, which is the recrystallization results amorphous SiC and y-AOs. After thermal treatment above 1200, the amorphous SiC2 is transformed into cristobalite.Elite: On thermal treatment, illite firstly loses its hydroscopic water and interlayer water at the temperature of below 400. The dehydration process causes the expansion of crystal along C-direction. With the increase of the temperature up to 500~750, the OH groups split off from the structural framework of illite. Dehydroxylation reactions occur and illite is transformed into dehydrated illite. The six-coordinate of aluminium in oxygen octahedrons wi更多还原