基于高压水化法溶出高钛铝土矿钛的行为机制

The exploitation and utilization of high-titanium bauxite can greatly ease China's bauxite ore supply crisis and ore dilution trend sharply, and is of great significance to the development of Chinese alumina industry. However, titanium is very harmful impurities to Bayer process, with increasing titanium content of bauxite, will not only decrease digestion rate of alumina, but also cause severe scarring on the surface of digesting equipments and heat exchangers, which will affect the normal production process. For treatment of high silicon bauxite or complex bauxite, high pressure hydrothermal method is superior to reduce Al2O3 and Na2O loss. Therefore, high pressure hydrothermal method is proposed to digest high-titanium bauxite in this work. At present, there are some scientific problems needing to be solved for the method, such as, what is the reaction mechanism of Ti minerals, and how to influence the leaching rate of alumina? what is the law of transformation of titanium minerals, and how about the scarring? Based on these, a lot of experiments will be carried out to study the mineralogy of high-titanium bauxite, the kinetics and thermodynamics of digesting titanium minerals, the phases transformation of titanium minerals, the reasons of causing scab and the structure of scab. And the kinetic process of titanium reactions will be described with three-dimensional graphs by computer. Through this research, optimized process conditions were obtained to improve digesting rate of alumina and reduce scrab formation. The results of this work will provide a sound theoretical basis for the exploitation and utilization of high-titanium bauxite.

高钛铝土矿的开发利用可以大大缓解我国铝土矿供矿危机和矿石急剧贫化的趋势，对我国氧化铝工业发展具有重大意义；而高压水化法用于处理高硅铝土矿以及复杂难处理铝土矿生产氧化铝方面有着降低Al2O3和Na2O损失的优越性。因此本课题针对高钛铝土矿常规拜耳溶出过程氧化铝溶出率低并产生严重的钛结疤从而导致高钛铝土矿难以利用的技术难题，提出高压水化法溶出高钛铝土矿，围绕高压水化溶出条件下，含钛矿物的反应行为是如何影响铝土矿的溶出以及是否会对结疤的生成产生抑制作用等科学问题，进行高钛铝土矿矿物学性质、钛矿物反应的动力学和热力学、钛矿物相变规律、结疤生成速率和组成结构等方面的研究，结合计算机三维图形表征，阐明高压水化条件下钛矿物的反应机理，揭示影响氧化铝溶出的主要因素，深入分析钛的反应行为与结疤生成的关系，为高压水化法溶出高钛铝土矿工艺条件优化提供理论依据。

高钛铝土矿的开发利用可以大大缓解我国铝土矿供矿危机和矿石急剧贫化的趋势，对我国氧化铝工业发展具有重大意义；而高压水化法用于处理高硅铝土矿以及复杂难处理铝土矿生产氧化铝方面有着降低Al2O3和Na2O损失的优越性。本项目以云南文山矿为主要研究对象，对高钛铝土矿的化学组成、物相组成、矿物学性质进行分析，考察了不同高压水化溶出条件对铝土矿中氧化铝溶出率、钛残留率及结疤速率的影响，并对溶出实验中获得的赤泥及结疤的物相进行了分析，同时对高钛铝土矿进行了溶出动力学实验；通过一系列的实验研究获得了高钛铝土矿在高压水化溶出时的其中含钛矿物的溶出反应及结疤反应的机理，并建立了含铝矿物及含钛矿物的反应动力学模型。结果表明：此类矿石为含钛矿物以锐钛矿为主的一水硬铝石型高钛铝土矿；在高压水化法溶出条件下，矿石中含钛矿物以羟基钛酸钙→钙钛矿、羟基钛酸钙→钛水化石榴石为主的过程最终转化为钙钛矿和水化石榴石，在转变过程中一部分含钛矿物在反应器壁上结晶形成结疤，高压水化法溶出并不能解决高钛铝土矿溶出时的结疤问题，但通过综合分析考虑，利用高压水化法溶出高钛铝土矿具有较高的可行性，在优化工艺条件下氧化铝实际溶出率可达87%以上；在高压水化溶出条件下含铝矿物及含钛矿物溶出动力学模型符合未反应核模型，含铝矿物的溶出动力学方程可以表述为：1-2/3X-(1-X)2/3=0.6381(COH-)3.28587r0.58531e-23421/RTt，含钛矿物的溶出动力学方程可以表述为：1- (1-X)1/3=1.1148(COH-)2.1021r0.27555e-33651/RTt。本项目的研究结果为高压水化法溶出高钛铝土矿工艺条件优化提供理论依据。