亚熔盐法氧化铝产品高值化利用与硅酸钠钙分解过程研究

发布时间：2018-06-24 11:41

本文选题：亚熔盐 + 高纯氧化铝　；参考：《中国科学院研究生院(过程工程研究所)》2016年博士论文

【摘要】：本论文在亚熔盐法氧化铝清洁生产技术平台的基础上,以工业冶金级氢氧化铝为原料,通过研究硫酸铝铵的结晶过程及结晶中的杂质行为,对结晶过程进行调控,来制备高纯度的硫酸铝铵,进而制得高纯度的氧化铝产品,以实现工业粗产品的高值化利用。另一方面,针对亚熔盐法处理赤泥工艺过程中硅酸钠钙易分解的问题,研究了硅酸钠钙NaCaHSiO4在铝酸钠溶液中的分解规律,为亚熔盐法处理赤泥的实际工业生产操作提供理论依据和现实指导。论文主要研究内容与研究成果如下：测定了硫酸铝铵结晶诱导期与介稳区,并分析了硫酸铝铵结晶过程的成核与生长机理。根据经典成核理论与介稳区理论分析,得出硫酸铝铵结晶成核过程属于连续成核,且符合三维成核机理。根据表面熵因子理论及模型判定方法,判定硫酸铝铵晶体的生长过程属于连续生长机理。此外,还计算了硫酸铝铵晶体在过饱和溶液中的界面张力、表面熵因子、临界晶核半径与临界自由能的值,以及与溶质在溶液中扩散相关的活化能。以工业冶金级氢氧化铝为原料,通过硫酸铝铵结晶及洗涤进行两步除杂,制备出纯度在99.99%以上的高纯氧化铝,工艺简单,实现了工业粗产品的高值化利用。研究表明结晶工艺参数,包括硫酸铝溶液的初始浓度、过饱和度、温度及结晶方式,对硫酸铝铵晶体中杂质的含量有着显著的影响。通过静置自然冷却结晶的方式可以大幅降低硫酸铝铵晶体中的杂质含量。研究了Na+、K+、Mg2+及Fe3+对硫酸铝铵结晶成核动力学的影响。研究表明,溶液中K+及Fe3+的存在缩短结晶诱导期、减小介稳区宽度,促进成核；溶液中Mg2+的存在延长结晶诱导期、增大介稳区宽度,抑制成核；溶液中Na+的存在对硫酸铝铵结晶成核无明显的促进或抑制作用。根据介稳区理论方法计算了硫酸铝铵的初级成核动力学参数。以高纯硫酸铝铵为原料,通过碳酸铝铵焙烧热解制备出纯度达99.9%、颗粒尺寸小于1μm且尺寸分布均匀的超细高纯氧化铝。主要研究了碳酸铝铵的制备条件对产物中K含量的影响,以及碳酸铝铵的焙烧与氧化铝的洗涤除杂。研究了NaCaHSiO4在铝酸钠溶液中的分解反应过程。当NaCaHSiO4在铝酸钠溶液中发生分解时,NaCaHSiO4转变为方钠石Na8Al6Si6O24(OH)2(H2O)2和加藤石Ca2.93Al1.97(Si0.64O2.56)(OH)9.44,继而降低亚熔盐法处理赤泥工艺中提铝的效率。
[Abstract]:In this paper, on the basis of sub-molten salt process alumina cleaner production technology platform, using industrial metallurgical grade aluminum hydroxide as raw material, the crystallization process and impurity behavior of ammonium aluminum sulfate were studied to regulate the crystallization process. In order to realize the high value utilization of industrial coarse products, the high purity aluminum oxide products were prepared by the preparation of high purity ammonium aluminum sulfate. On the other hand, in view of the problem that sodium and calcium silicate decompose easily in the process of treating red mud by submolten salt process, the decomposition law of sodium silicate calcium NaCaHSiO4 in sodium aluminate solution is studied. It provides theoretical basis and practical guidance for the practical industrial operation of submolten salt treatment of red mud. The main contents and results are as follows: the induction period and metastable region of ammonium aluminum sulfate crystallization were determined, and the nucleation and growth mechanism of ammonium aluminum sulfate crystallization process were analyzed. Based on the analysis of classical nucleation theory and metastable zone theory, it is concluded that the crystallization nucleation process of ammonium aluminum sulfate is continuous nucleation and accords with three-dimensional nucleation mechanism. According to the theory of surface entropy factor and the method of model determination, it is determined that the growth process of ammonium aluminum sulfate crystal belongs to the mechanism of continuous growth. In addition, the interfacial tension, surface entropy factor, critical nucleation radius and critical free energy of ammonium aluminum sulfate crystal in supersaturated solution were calculated, as well as the activation energy related to solute diffusion in the solution. High purity alumina with purity over 99.99% was prepared by crystallization and washing of ammonium aluminum sulfate with industrial metallurgical grade aluminum hydroxide as raw material. The process was simple and the high value utilization of industrial coarse products was realized. The results show that the crystallization process parameters, including initial concentration, supersaturation, temperature and crystallization mode of aluminum sulfate solution, have a significant effect on the content of impurities in ammonium aluminum sulfate crystal. The impurity content in ammonium aluminum sulfate crystal can be greatly reduced by static natural cooling crystallization. The effects of Na ~ (2 +) K _ (2) mg _ (2) and Fe _ (3) on the nucleation kinetics of ammonium aluminum sulfate were studied. The results show that the existence of K and Fe _ 3 in solution shortens the induction period of crystallization, reduces the width of metastable zone and promotes nucleation, while mg _ 2 prolongs the induction period of crystallization, increases the width of metastable zone, and inhibits nucleation. The presence of Na in the solution has no obvious effect on the nucleation of ammonium aluminum sulfate. The kinetic parameters of primary nucleation of ammonium aluminum sulfate were calculated according to the theory of metastable zone. Using high purity ammonium aluminum sulfate as raw material, ultrafine and high purity alumina with purity 99.9, particle size less than 1 渭 m and uniform size distribution was prepared by calcination pyrolysis of ammonium aluminum carbonate. The effects of preparation conditions of ammonium aluminum carbonate on K content in the product, roasting of ammonium aluminum carbonate and washing and impurity removal of aluminum oxide were studied. The decomposition process of NaCaHSiO4 in sodium aluminate solution was studied. When NaCaHSiO4 was decomposed in sodium aluminate solution, NaCaHSiO4 was transformed into sodium aluminite Na8Al6Si6O24 (OH) 2 (H2O) 2 and katenite Ca2.93Al1.97 (Si0.64O2.56) (OH) 9.44.
【学位授予单位】：中国科学院研究生院(过程工程研究所)
【学位级别】：博士
【学位授予年份】：2016
【分类号】：TQ133.1

【参考文献】