【作者】 周宁波；

【导师】 陈白珍；

【作者基本信息】 中南大学 ， 冶金物理化学， 2005， 博士

【摘要】 镁作为一种最轻的结构金属材料在各方面的应用正在逐年增加。生产金属镁的方法主要有热还原法和电解法。热还原法炼镁能耗高，工艺落后，生产条件差；电解法炼镁工艺先进，能耗较低，是一种极具发展前景的炼镁方法。电解法炼镁的关键是需制备合适的原料无水氯化镁。我国青海盐湖蕴藏着丰富的镁资源，为电解炼镁提供了大量优质的原料。为了制备低氧化镁含量适合于电解炼镁的无水氯化镁，本文用盐湖水氯镁石和氨法沉镁过滤后的氯化铵溶液为原料，合成铵光卤石，铵光卤石脱水后用有机溶剂法、氨法、气固反应法制备无水氯化镁。以测得的铵光卤石溶解度数据建立了其低温结晶动力学方程；用热重分析法计算了铵光卤石脱水的动力学参数，并研究了氨合氯化镁和氨合铵光卤石的热分解脱氨过程非等温动力学。 对水氯镁石在脱水过程中可能存在的化学反应进行了热力学计算和动力学分析，得出了温度较低时，水氯镁石不易脱水；温度较高时，在脱水的同时不可避免地发生水解反应。无保护气氛条件下110～200℃时，选择适宜的脱水时间可将MgCl₂·6H₂O转化为MgCl₂·2H₂O而无水解反应发生；若继续脱水必须在保护气氛下进行，否则脱水的同时会水解。 研究了用盐湖水氯镁石溶液和氨法沉镁过滤后的氯化铵溶液制备铵光卤石的工艺，当溶液中MgCl₂和NH₄Cl物质的量比1：1，在pH=6.0、温度85℃、搅拌速度500r·min^-1、加热1h、7℃冷却结晶4h，过滤烘干，铵光卤石一次结晶产率为60％，二次结晶产率高达80％。测定了铵光卤石在水溶液中不同温度下的溶解度，利用10℃、20℃的溶解度和动力学参数建立了铵光卤石结晶动力学方程。动力学方程证明铵光卤石的低温结晶受单核结晶生长控制。 对铵光卤石脱水进行了热分析研究。铵光卤石的脱水是分步进行的，在110～180℃范围内可脱水为低水铵光卤石，超过此温度范围铵光卤石在脱水的同时会水解。实验证明铵光卤石160℃脱水4h可得结晶水为0.5～1的低水铵光卤石。Freeman-carroll法计算的动力学参数表明，铵光卤石在各温度范围内脱水反应均不是基元反应，而是由多个不同级数的基元反应所控制。 研究了低水铵光卤石甲醇法制备无水氯化镁的工艺条件。低水铵光卤石甲醇混合液的滴加速度≤2.1g·min^-1，含氯化铵≥3％的饱和了氨的甲醇溶液中通入氨的流量≥160L·h^-1时，氯化镁甲醇配合物与氨取代反应形成的氨合氯化镁沉淀经过惰性气氛下的离心过滤分离，得不含氢氧化镁的氨合氯化镁。氨合氯化镁在氮气保护下，700℃煅烧15min，得颗粒大而均匀氧化镁的质量分数为0.00087的高纯无水氯化镁。经分析无水氯化镁中其它有害杂质元素的含量低，低水铵光卤石转化为无水氯化镁的产更多还原

【Abstract】 As one of the lightest structural materials, magnesium is applied increasingly in various areas. The two main processes of producing magnesium are thermal reduction and electrolysis. The thermal reduction process is an old one with high energy consumption and severe pollution. By comparison, the electrolysis process shows some advantages such as lower energy consumption and lower pollution. It is a very promising technology. The key to electrolysis process is to obtain the suitable raw material of high-puried anhydrous magnesium chloride. There is a great reserve of magnesium chloride in Salt Lake in Qinghai province of China which can provide high grade raw materials for producing magnesium metal. In this thesis, processes of producing high-puried anhydrous magnesium chloride are studied. Ammonium carnallite is synthesized by using bischofite from Salt Lake and filtrate stock of deposit magnesium. Anhydrous magnesium chloride is prepared by organic solvent, reaction of ammonia and gas-solid reaction of ammonium carnallite. The crystallization kinetic equations at low temperature are established with solubility data of ammonium carnallite. The dehydration kinetic parameters of ammonium carnallite are calculated by thermogravimetric analysis. Kinetics of non-isothermal decomposition is studied for ammoniation magnesium chloride and ammoniation ammonium carnallite to eliminate ammonia.The dehydration of MgCl₂·6H₂O is studied by thermal calculation and kinetic analysis. The results show that dehydration is difficult at lower temperature and hydrolysis will take place when MgCl₂·6H₂O is dehydrating at higher temperature. In flowing air condition, when heating temperature is between 110℃ and 200℃, MgCl₂·6H₂O will be changed to MgCl₂·2H₂O without hydrolysis. It must be carried out in a protected atmosphere if it continues to be dehydrated afterwards. Otherwise, hydrolysis would occur when it is being dehydrated.It is studied that the optimum preparative technology of ammonium carnallite with bischfite from Salt Lake and filtrate stock of deposit magnesium by ammonia. When the molar ratio of MgCl₂ : NH4Cl is 1: 1, pH=6.0, reaction temperature is at 85℃, agitating speed is 500r·min^-1 , heating time is 1h, crystallization at 7℃ is 4h, the crystal ratio of ammonium carnallite after filtration and drying is about 60% at first time. The crystal ratio is over 80% for the second time. Solubility of ammonium carnallite is measured from 10℃ to 100℃. Crystallization kinetic equations are established with kinetic parameters更多还原