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亚熔盐法氧化铝清洁生产技术中产品高值化利用与硅酸钠钙分解过程研究; Research on the Highly-Valued Utilization of Product and the Decomposition Process of Sodium Calcium Hydrogen Silicate in Alumina Cleaner Production Technology by Sub-Molten Salt Process
游韶玮
学位类型博士
导师张懿
2016-07
学位授予单位中国科学院研究生院
学位专业化学工艺
关键词亚熔盐 高纯氧化铝 硫酸铝铵 结晶 硅酸钠钙
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。
其他摘要This study was aimed to produce high–purity ammonium alum and further high–purity alumina to realize the utilization of crude product in a high value way with the metallurgical-grade as the raw material and using the method of ammonium alum crystallization where the impurity behavior was investigated and the crystallization process was adjusted and controlled on the technology platform of alumina cleaner production technology by sub-molten salt process. On the other hand, because sodium calcium hydrogen silicate (NaCaHSiO4) could be easily decomposed in the process of red mud treated by sob-molten salt, the decomposition reaction process of NaCaHSiO4 in sodium aluminate solution was investigated in order to provide a theoretical basis and practical guide for the industrial production operation of the process red mud treated by sob-molten salt. The main contents and results of this research were as follows.The induction time and metastable zone width (MSZW) of ammonium alum crystallization were measured and mechanisms about the nucleation and growth process were analyzed. According to the classical nucleation theory and the theoretical analysis of MSZW, it was concluded that the nucleation process of ammonium alum crystallization was continuous and was of three-dimensional nucleation mechanism. According to the surface entropy factor theory and the method of model determination, it was concluded that the growth process of ammonium alum was continuous growth. In addition, values of parameters, including the interfacial tension of ammonium alum crystals in solution, surface entropy factor, critical radius of nucleus, critical free energy, and the activation energy related with the diffusion of solute in solution, were calculated.High-purity of alumina with the purity of beyond 99.99% was produced with the metallurgical-grade as the raw material and two impurity removal processes of ammonium alum crystallization and washing. The process was simple and realized the utilization of crude product in a high value way. Results showed that crystallization parameters, including the initial concentration of sulfate aluminum, supersaturation, temperature and crystallization method, significantly affected the content of impurities in ammonium alum crystals. The impurities content could be greatly reduced by natural cooling crystallization of ammonium alum under the condition of no stirring.Effects of impurity ions, including Na+, K+, Mg2+ and Fe3+, on the kinetics of ammonium alum crystallization were investigated. Results showed that the presence of K+ and Fe3+ in solution shorten induction times and reduced MSZW, promoting the nucleation; the presence of Mg2+ in solution prolonged the induction times and increased MSZW, inhibiting the nucleation; the presence of Na+ in solution had no significant promoting or inhibiting effect on the nucleation. The kinetic parameters were calculated according to the theory on MSZW. High-purity ammonium alum was as the raw material to produce high-purity alumina with the purity of beyond 99.9% by the thermal decomposition of ammonium aluminum carbonate hydroxide, and the prepared ultrafine high-purity alumina has a size of less than 1μm with uniform particle size distribution. Effects of preparation conditions of ammonium aluminum carbonate hydroxide on the K condition of reaction product, calcination of ammonium aluminum carbonate hydroxide and impurity removal of alumina by washing were investigated.The decomposition reaction process of NaCaHSiO4 in sodium aluminate solution was investigated. When NaCaHSiO4 decomposed in sodium aluminate solution, NaCaHSiO4 transformed to Na8Al6Si6O24(OH)2(H2O)2 (sodalite) and Ca2.93Al1.97(Si0.64O2.56)(OH)9.44 ( katoite), reducing the efficiency of alumina extraction in the process of red mud treated by sub-molten salt. 
语种中文
文献类型学位论文
条目标识符http://ir.ipe.ac.cn/handle/122111/22905
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游韶玮. 亚熔盐法氧化铝清洁生产技术中产品高值化利用与硅酸钠钙分解过程研究, Research on the Highly-Valued Utilization of Product and the Decomposition Process of Sodium Calcium Hydrogen Silicate in Alumina Cleaner Production Technology by Sub-Molten Salt Process[D]. 中国科学院研究生院,2016.
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