【作者】 苟中入；

【导师】 李小斌；

【作者基本信息】 中南大学 ， 有色金属冶金， 2002， 硕士

【摘要】 氧化铝是世界经济中最重要的基础原材料之一。2000年世界氧化铝总产量达到6000万吨，成为仅次于钢铁产量的特大型金属冶炼行业。目前，尽管一些氧化铝生产强化技术正不断涌现，但是烧结法生产氧化铝中分解原液氧化铝浓度低、分解过程能耗高、分解设备产能低等问题并没有得到解决，严重制约了氧化铝生产企业的经济效益。 本文在铝酸钠溶液碳酸化分解的分解机理、工艺特点以及主要物质析出热力学进行全面分析的基础上，对高浓度铝酸钠溶液(Al2O3浓度为130～210g L-1)碳酸化分解中的以下问题进行了系统实验研究： 1) 对实际工艺条件下高浓度碳酸化分解的热力学分析表明，高浓度碳酸化分解中氢氧化铝析出是以处于高过饱和度下的铝酸钠自发分解为主；在碳酸化分解中丝钠铝石(Na2O．Al2O3．2CO2．nH2O)析出反应不唯一，增大HCO3-浓度、降低OH-浓度和反应温度均有利于该物质析出：SiO2的平衡浓度与温度、游离碱浓度和苛性比值等有关，分解前期和末期SiO2平衡浓度下降很快，分解中期较稳定。 2) 铝酸钠过饱和度是高浓度碳酸化分解的主要推动力，过饱和度大小不仅影响溶液的分解速度，并且直接影响氢氧化铝中杂质含量水平。提高分解温度和选择合理的通气制度可以降低铝酸钠溶液的过饱和度，生产结晶良好、Na2O和SiO2杂质含量低的粗颗粒氢氧化铝产品。 3) 晶种对降低高浓度碳酸化分解产物中杂质含量具有明显效果。晶种能降低铝酸钠溶液与氢氧化铝晶体之间的界面能，有利于新析出的晶体在晶种表面生长；同时，晶种表面活性比溶液中析出的新鲜粒子小，吸附能力弱，减少氢氧化铝中Na2O和SiO2含量，有利于获得杂质含量低的高浓度碳酸化分解产品。 4) 在经优化后的作业条件下进行高浓度铝酸钠溶液碳酸化分解，能够生产出Na2O和SiO2含量分别低于0.35％、0.035％，中位径和体积平均径分别高于90Llm、100um的优质氢氧化铝。 (图：38，表：19，参考文献：63)更多还原

【Abstract】 Alumina is one of the most important raw materials in the world economics. Since the alumina industry has developed with high speed from 1980’s in the 20th century, nowadays the total output of alumina annually is up to 4,000,000 tone in our country, only junior to the iron & steel yields in the metallurgical industry.In the present dissertation, the technology of carbonization of sodium aluminate solution with high A12O3 concentration (130~210g.L~1) has been studied systematically based on the analysis of the mechanisms and technique characters. Results of the experiment and analysis are as following:1. The reaction Gibbs free energies (ArGr) of NaAl(OH)4 and the complicated compound Na2O A12O3- 2CO2- nH2O were calculated, and the variation character and influencing factors of equilibrium content of SiO2 in the carbonization process were also investigated.2. The liquor supersaturation, which influences both the precipitation speed and the percentage of impurities in the product, is the main impetus of carbonization of sodium aluminate solution with high A12O3 concentration. Improving carbonization temperature or choosing reasonable gas ventilating system may reduce the liquor supersaturation, and then the coarse grain aluminium trihydroxide with good crystallization and low content of impurities (Na2O, SiO2) can be produced.3. It is also demonstrated that the aluminium trihydroxide seeds can improve remarkably quality of the carbonization product. Seeds can decrease the interface energy between aluminium trihydroxide crystal and liquor, which is beneficial to the crystal growth and reduction of impurities absorption.4. The pickup behaviors of impurities (Na2O, SiO2) in the conditions of different temperatures, seeds charges and gas ventilating systems were analyzed in the process of carbonization. The product with good quality from carbonization of sodium aluminate solution with 130~200g.L"’ A12O3 under the optimized conditions has been obtained.(Figures:38; Tables: 19 ; References:63 )更多还原