【作者】 翟坤明；

【导师】 密建国；

【作者基本信息】 北京化工大学 ， 化学工程与技术， 2011， 硕士

【摘要】 工业上氧化铝的生产方法主要有三种：拜耳法,烧结法以及混联法(既有拜耳法又有烧结法)。在用拜耳法生产氧化铝时,脱硅是一个比较关键的步骤,目前工业生产上常用脱硅剂为氧化钙和氢氧化钙。由于氧化钙和氢氧化钙都是不可再生资源,而且价格较贵,因此,新型脱硅剂的开发与利用就成为一个重要的研究方向。二水硫酸钙是一种具有脱硅能力的新型脱硅剂,本论文对二水硫酸钙在铝酸钠溶液中的脱硅行为进行了实验及动力学研究。系统考察了脱硅反应温度,二氧化硅起始浓度,氢氧化钠溶度,氢氧化铝浓度,二水硫酸钙用量及粒度对脱硅实验的影响。结果发现,脱硅反应温度、二氧化硅起始浓度及二水硫酸钙用量是影响脱硅实验效果的主要因素,在最佳操作条件下,可以移除铝酸钠溶液中95%的二氧化硅。本论文用一个拟二级表面反应动力学模型关联了二水硫酸钙在操作条件下的脱硅实验数据,结果表明,此模型很好地关联了实验条件下的脱硅实验数据。通过该模型得出了二水硫酸钙在不同操作条件下的脱硅动力学参数,同时得到了二水硫酸钙在铝酸钠溶液中脱硅反应活化能为52kJ/mol。二水硫酸钙在铝酸钠溶液中的脱硅反应产物用XRD和SEM进行分析和表征,脱硅产物主要为方蓝石(3Na2O·2CaSO4·3Al2O3·6SiO2)和天青石(3Na2O·CaSO4.5Na2SO4·3A12O3·6SiO2)。二水硫酸钙脱硅后母液中硫酸根离子浓度大约为0.021 g/L。更多还原

【Abstract】 There are three main methods for alumina production industry:Bayer method, sintering method and hybrid method (both Bayer and sintering). Desilication process is a critical step during alumina production with Bayer method. Desilication agents used in current alumina industry are calcium oxide and calcium hydroxide. The research and development of new desilication agent has become an important subject as calcium oxide and calcium hydroxide are non-renewable resources and costly.Calcium sulfate dihydrate (CaSO4·2H2O), as a new desilication agent, has the ability of desilication. The desilication kinetics of synthetic Bayer liquor by use of calcium sulfate dihydrate (CaSO4·2H2O) was studied experimentally and modelled mathematically. Factors affecting desilication reaction, namely temperature, initial silica concentration, the concentration of NaOH and Al(OH)3, the particle size and dosage of CaSO4·2H2O, were investigated systematically. Temperature, initial silica concentration and the dosage of CaSO4·2H2O were found to be the main factors affecting desilication reaction. CaSO4·2H2O was proved to remove up to 95% silica from sodium aluminate solution under the optimum operation conditions. A surface integration kinetic model, assuming that the desilication process follows a pseudo-second-order kinetics, was developed and successfully model the experiment data of desilication process via CaSO4·2H2O at the range of operating conditions investigated. An activation energy of 52 kJ/mol was estimated for the desilication process with CaSO4·2H2O over the temperature of 80-100℃. The desilication reaction products (DSP) were analyzed by XRD and SEM, and found to be mainly Hauyne (3Na2O·2CaSO4-3Al203·6Si02) and Lazurite (3Na2O·CaSO4·0.5Na2SO4·3Al2O3·6SiO2). The final sulfate concentration in the liquor after desilication with CaSO4·2H2O was 0.021 g/L.更多还原