氧化镁真空碳热还原反应实验研究

【作者】 李志华；

【导师】 戴永年；

【作者基本信息】 昆明理工大学 ， 有色金属冶金， 2002， 硕士

【摘要】 本文综合评述了我国镁工业的发展概况和金属镁及其化合物的性质、用途、生产方法，作者认为无论是电解法还是硅热还原法都存在严重缺陷，电解法工艺复杂，投资大，生产过程中会产生有毒气体—氯气，其废气、废水、废渣处理的任务重，费用大，生产设备和厂房腐蚀严重，维修费用大。硅热法炼镁存在的问题是：①、它所广泛使用的还原剂为含硅75％的硅铁，价格比较高，这就提高了生产成本。②、皮江法所使用的还原罐是由特殊的合金钢制成，不但价格昂贵，使用寿命也不长。③、由于罐内抽真空、罐外常压加热，还原罐的尺寸小，单罐装料量低，还原罐产能低，热效率不高，而且是间断生产，生产能力和劳动生产力低。 在真空中还原金属镁，可以降低反应的温度，提高反应效率，还原出的金属镁也不易被氧化，把真空冶金技术用于金属镁的制取，利用廉价的碳代替昂贵的硅铁，用自行研制的内热式真空炉代替还原罐，真空炉的规模可以突破罐子容量的限制，提高热效率和单台设备的产能，大大降低生产成本，改善劳动条件。由于所有的冶金过程都在密闭的真空系统中进行，无三废产生，对环境污染小。 经国际联机检索，国内无此相关文章发表，国外也很少，根据其中最具代表性的R．Winand于1990年发表的文章（参考文献[31]）来看，他作到了如何在真空中用碳还原氧化镁产出镁蒸气的问题，而并没有解决如何使还原出来的镁蒸气冷凝成为液态或固态结晶镁所需要的条件及相应冷凝器的外形设计。 本课题对氧化镁真空碳热还原过程进行了理论研究和试验研究。研究认为：氧化镁真空碳热还原可行，与常压碳热还原相比，还原温度可降低300～400℃；真空条件不仅可以提高反应速率，而且对镁蒸气在冷凝过程中与CO或CO₂的逆反应有较大抑制作用；在特制的冷凝器上成功的得到了呈粗纤维状垂直生长在冷凝面上的固态块状冷凝镁，结晶状态较好，所得冷凝物中镁的品位可达94％以上，取样时操作安全；还原过程中真空度随时间的变化具有规律性，由此可以判断还原反应进行的速度与程度；还原温度升高，还原时间延长，还原速率增大；物料经过压块焦结后对加快还原速率，提高还原度均有利。添加少量的氟化物对反应有促进作用。得到了氧化镁真空碳热还原反应的原则流程。更多还原

【Abstract】 The development of the domestic magnesium industry, primary magnesium and properties, applications and preparation methods are overviewed in the thesis. It’s the opinion of the author that there are grave defects in traditional methods, say, moltensalt electrolysis or silicothermic reduction of oxides. The former process is complex and needs vast investment, and emits toxic gases like chlorine gas; treatment of production wastes is overburden costly; erosion of the production equipments and plant buildings is badly, and maintenance cost overwhelming. The flaws in the process of magnesium extraction by silicothermic reduction of oxides are: (1) high cost of major reductant, ferrosilicon (70%); the boosted production cost accordingly; (2) short service life of reduction retort, which is made of high Ni-Cr alloy; (3) vacuum inside the retort heated under the normal pressure, small-size of the retort, low forced filling rate, low production capacity thermal efficiency, batch production, low productivity and production.In the process of magnesium extraction in vacuum, the reduction temperature needed is lowered, reduction efficiency enhanced, crude magnesium oxidization more difficult. Introduction of vacuum technology in magnesium extraction, high Ni-Cr alloy is substituded by cheaper carbon and reduction retort by internal heating vacuum furnace; scale of vacuum furnace is free of the limit of retort cubic capacity; thermal efficiency and production of single equipment are raised, cost decreased and working conditions improved. Since all reactions take place in the closed vacuum furnace, there is no production wastesproduced and less influence upon environment.Through inter-link retrieve, relevant papers are absent domestic; and abroad is scarce. R.Wind, the most epitomized(reference 31), solved only how to produce magnesium vapor through magnesia reduction by carbon, conditions and devise of condenser used to condense the vapor into liquid or solid critical magnesium was not touched upon.The thesis expounds on the magnesia reduction by carbon theoretically and experimentally. It is observed: the process is feasible; reducing temperature can be decreased by 300℃-400℃; vacuum can not only enhance reaction rate, but exhibit the reverse reaction of magnesium vapor by CO or CO2; condensed mangnesium taken the shape of solid, lump can be obtained successfully on the inner surface of the condenser, during the course of crystallization magnesium develops vertically the shape of coarse fibre, and has solid crystalliform; the condasate grade is above 94%; sampling is safety; change of vacuum vs time takes regular pattern, thus, reduction velocity and rate can be deduced, temperature enhanced and reduction elongated, reduction velocity increased; material treated by briquetting and coking is in favor of reaction rate and velocity; a small amount of fluorine compounds added can accelerate the reaction; impractical flowsheet of magnesia reduction by carbon is developed.更多还原