【作者】 兰军；

【导师】 吴贤熙；

【作者基本信息】 贵州大学 ， 化学工艺， 2009， 硕士

【摘要】 本文从铝土矿资源的可持续性发展、加快构建资源节约型社会的角度出发,顺应竞争日趋激励的世界氧化铝工业发展的要求,寻求使用高硫低铝硅比的铝土矿经济地生产氧化铝的方法,提出石灰拜耳法生产氧化铝脱硫研究的课题。本文首先对一元和三元型含水硫铝酸钙的热力学进行了研究。（1）采用迭代最小二乘法计算了一元和三元型含水硫铝酸钙标准Gibbs自由能,分别为G_{3CaO·Al2O3·CaSO4·12H2O}^θ=-8894.5KJ/mol,G_{3CaO·Al2O3·3CaSO4·6H2O}^θ=-9994.5KJ/mol。计算了一元和三元型含水硫铝酸钙生成反应的标准反应Gibbs自由能:ΔG_Ⅰ^θ=-104.96KJ/mol,ΔG_Ⅱ^θ=-95.54KJ/mol,两个反应ΔG^θ（?）0。这说明反应向生成一元和三型含水硫铝酸钙的趋势很大。（2）绘制了生成反应Gibbs自由能对温度T的函数曲线,当298K＜T＜545K时,ΔG₁,ΔG₂均是随着温度的升高先减小后增加,然而ΔG₃（T）先减小然后增加,再降低。（3）绘制了pH-温度T图,随着温度的升高,其pH不断降低。采用二水平多因素实验设计和响应面曲面试验设计,研究了硫铝酸钙合成的条件。以N_T、Al₂O₃、Na₂SO₄、CaO、反应时间、反应温度为考察因素,确定出N_T（P＜0.0001）、Na₂SO₄（P=0.0327）、反应时间（P=0.0229）、反应温度（P=0.0022）为硫铝酸钙合成的显著性影响因素。经过响应面优化后,确定出硫铝酸钙合成的最佳试验条件为:反应时间为65min左右,温度应在75-80℃之间,Na₂SO₄浓度越低越好,总碱度N_T在试验中的最佳范围为50-55g/L。采用正交实验设计,研究了石灰拜耳法溶出氧化铝的脱硫率和氧化铝溶出率。脱硫率影响因素的主次关系为:D＞A＞E＞C。较好工艺条件应为:石灰添加量A为10%、碱液浓度C为210g/L、温度D为245℃、脱硫时间E为70min。氧化铝溶出率影响因素的主次关系为:E＞A＞C＞D。较好工艺条件应为:石灰添加量为10%、碱液浓度为225g/L、温度为245℃、脱硫时间为70min。在最佳条件下,脱硫率为31.27%,氧化铝溶出率为90.80%。更多还原

【Abstract】 This article studied new and economic method to produce alumina in highsulfuric bauxite due to the perspective of the continuable development of bauxite andthe construction of resource-saving society, which complies with increasinglycompetitive alumina industrial development. To exploiting high sulfuric bauxite mine,the paper proposes the topic of desulfurization in the course of producing alumina inthe Lime Bayer Process.The thermodynamics of 3CaO·Al₂O₃·CaSO₄·12H₂O and3CaO·Al₃O₃·3CaSO₄-6H₂O was researched .（1） Using interactive least square methodestimated the Gibbs free energies of the 3CaO·Al₂O₃·CaSO₄·12H₂O and3CaO·Al₂O₃·3CaSO₄·6H₂O,G_{3CaO·Al2O3·CaSO4·12H2O}^θ=-8894.5KJ/mol,G_{3CaO·Al2O3·3CaSO4·6H2O}^θ=-9994.5KJ/mol. The Gibbs free energies of reaction ofdesulfurization with sodium aluminates was computed,ΔG_Ⅰ^θ=-104.96KJ/mol,ΔG_Ⅱ^θ=-95.54KJ/mol. Because ofΔG^θ（?）0, it is possible to generate3CaO·Al₂O3·CaSO₄·12H₂O and 3CaO·Al₂O₃·3CaSO₄·6H₂O. （2） To draw the curve ofvariety of the Gibbs free energies with temperature. When temperature varied from298K to 545K,ΔG₁ andΔG₂ are reduced, then increased andΔG₃（T） are reduced,then increased, eventually reduced. （3） To draw the curve of variety of the PH valuewith temperature, PH value is reduced with increased temperature.The genetic condition of calcium sulfoaluminate was researched with methods ofTwo-level factorial designs and RSM（Response Surface Methods）. Some factors suchas total concentration of alkali、alumina、sodium sulfate、calcium oxide , time,temperature. And total concentration of alkali（P＜0.0001）、sodium sulfate（P=0.0327）,time（P=0.0229）, temperature（P=0.0022）were confirmed on mostly influencing factorsto synthesize calcium sulfoaluminate. The experimental conditions were optimized with RSM. Time is about 65min; temperature is between 75and 80; Lesserconcentration of sodium sulfate the better; total concentration of alkali is between 50g/L and 55g/L.The paper studies mainly the effect of desulfurization and the dissolution rate ofalumina in the course of disposing of high grade bauxite containing sulfur. The resultsshow that factors influence of desulfurization rate D＞A＞E＞C. The optimum conditionof desulfurization rate is:calcium oxide for 10%, leaching-temperature at 245℃,leaching-time in 70min, and alkali concentration for 240 g/L. The results show thatfactors influence of the dissolution rate of alumina E＞A＞C＞D. The optimumcondition of the dissolution rate of alumina is:calcium oxide for 10%,leaching-temperature at 245℃, leaching-time in 70min, and alkali concentration for225 g/L. In the optimum condition, the proportion of desulfurization reaches32.27%, and the yield of Al₂O₃ reaches at least 90.80%.更多还原