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镁铝尖晶石制备新工艺及热力学模型
Alternative TitleA Novel Process of Mg-Al Spinel Production and Its Thermodynamic Modeling
高文成
Subtype博士
Thesis Advisor李志宝
2013-05-01
Degree Grantor中国科学院研究生院
Degree Discipline化学工程
Keyword镁铝尖晶石   相平衡测定   溶液热力学   共沉淀方法
Abstract镁铝尖晶石由于具有优良的耐高温,抗热震和腐蚀等特性,除作为高端耐火材料广泛用于冶金、电化学等行业外,近些年来,在工业催化及化学循环燃烧等领域作为载体成为研究的热点。尽管固固反应法和电熔化法制备镁铝尖晶石已用于工业生产,但仍存在着产品品质不均一,合成温度高等缺点。基于此原因,湿法技术如共沉淀、水热合成、溶胶凝胶方法等受到广泛关注。共沉淀法虽然具有原料廉价易得、合成前躯体方便等优点,但仍存在制备的前躯体纯度低,易于形成胶体系统带来过滤困难和排放大量污水等缺点。论文以解决上述问题为目标,提出了以我国丰富的卤水氯化镁和低品位铝资源为原料,利用共沉淀技术制备镁铝尖晶石的新工艺。其关键工段包括:(1) AlCl3·6H2O的制备;(2) Mg-Al前驱体共沉淀;(3) NH4Cl回收等。论文围绕各工段所涉及的物理化学展开研究,取得如下结果:(1)提出了测定高度分散胶体系统溶度积(KSP)的新方法。依据胶体稳定性DLVO理论,对含镁铝氢氧化物(Mg4Al2(OH)14·3H2O)的高度分散胶体系统,通过加入一定浓度的NaCl后,成功测定了Mg4Al2(OH)14·3H2O在NaCl溶液中的溶解度数据,结合Mg2+和Al(OH)4-等离子活度系数的计算得到了Mg4Al2(OH)14·3H2O溶度积常数表达式,进而确定了Mg4Al2(OH)14·3H2O的基本热力学物性数据:ΔGf0,ΔHf0和ΔSf0分别为-6365.50 kJ·mol-1、-7145.05 kJ·mol-1和1241 J·mol-1·K-1。(2)测定了AlCl3-FeCl2-H2O,NH4Cl-MgCl2-AlCl3-H2O和glycine-KCl-NaCl-H2O等体系的相平衡数据,从而建立了NH4+Al+Mg+Fe(II)+Mg+Ca +K+Na+glycine+Cl+H2O复杂体系的热力学模型,应用MSE模型和Bromley-Zemaitis方程成功计算了体系中各组分的活度系数和浓度分布,总偏差小于5%。(3)利用连续进料连续出料 (MSMPR) 反应结晶器成功制备了镁铝氢氧化物,由于其具备良好的过滤性质,从而得到高浓度的氯化铵过滤液,为利用原料MgCl2-AlCl3产生的共离子效应回收氯化铵提供了可能。本方法实现了水的循环利用,减少了污水排放,并在实验室制备出合格的氯化铵产品。(4)在实验室研究基础上提出了利用MgCl2-AlCl3制备高端镁铝尖晶石的新工艺,并进行了全流程实验验证,制备出的镁铝尖晶石产品符合国际标准(ISO)。
Other AbstractDue to its high refractoriness, excellent thermal shock resistance and high chemical inertness, Mg-Al spinel has been widely applied to make a variety of advanced refractories in the metallurgy and electro-chemical industries. Recently, its application in industrial catalysis and chemical-looping combustion as support has attracted more and more attention. Generally, the oxide mixing method and electrofusion are used to produce Mg-Al spinel. However, there still exists some drawbacks such as inhomogeneity and high-synthesis temperature. For this reason, many wet-synthesis techniques like co-precipitation, hydrothermal and sol-gel have been proposed for the synthesis of Mg-Al spinel. Among these methods, co-precipitation is relatively convenient and cost-effective to synthesize precursors from inorganic salt solutions, however, there are some difficulties need to be overcome with the aim of industry application, such as the prepared precursor was impureness, the highly dispersed colloidal solution was difficult to filter, and a large number of wastewater was discharged. To tackle these problems, a novel process of Mg-Al spinel production was proposed using brine magnesium chloride and low-grade aluminum resources as raw material. The process mainly includes: (1) A new method was proposed to determine the solubility product for highly dispersed colloidal system. According to the DLVO theory, the solubility of Mg4Al2(OH)14·3H2O was successfully measured by adding NaCl to the colloidal Mg4Al2(OH)14·3H2O-H2O system. Combining with the calculation of ion activity coefficients, the KSP expression of Mg4Al2(OH)14·3H2O was obtained. Furthermore, the thermodynamic properties such asΔGf0, ΔHf0 andΔSf0 were determined to be -6365.50 kJ·mol-1, -7145.05 kJ·mol-1 and 1241 J·mol-1·K-1, respectively. (2) The phase equilibria of the AlCl3-FeCl2-H2O, NH4Cl-MgCl2-AlCl3-H2O and glycine-KCl-NaCl-H2O systems were determined and a thermodynamic model for the NH4+Al+Mg+Fe(II)+Mg+Ca+K+Na+glycine+Cl+H2O complex system was thus established. The activity coefficients and distribution of species for the system were calculated with the aid of MSE model and Bromley-Zemaitis equation, and most of the deviations were less than 5%. (3) A mixed-suspension mixed-product removal (MSMPR) reactor was applied to produce Mg4Al2(OH)14·3H2O. Due to its excellent filterability, the concentrated NH4Cl solution was obtained, and the NH4Cl-rich solutions provided an opportunity to recover NH4Cl with the aid of common ion effect by feeding MgCl2-AlCl3. This process realized the objective of water recycling and reduced sewage discharge. The recovery of NH4Cl was successfully tested in laboratory. (4) In light of the experimental results mentioned above, a novel process of Mg-Al spinel production was proposed and verified feasible. The Mg-Al spinel product generated through this process satisfied the requirement of the classifications of the magnesia spinel established by International Organization for Standardization (ISO).
Pages141
Language中文
Document Type学位论文
Identifierhttp://ir.ipe.ac.cn/handle/122111/8291
Collection研究所(批量导入)
Recommended Citation
GB/T 7714
高文成. 镁铝尖晶石制备新工艺及热力学模型[D]. 中国科学院研究生院,2013.
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