中试实验中氧化钼氢还原过程及其相变、形貌演变规律

发布时间：2018-04-11 22:23

  本文选题：三氧化钼 + 二氧化钼　； 参考：《西安建筑科技大学》2015年硕士论文

【摘要】：钼具有良好的物理性能,在冶金工业、电子工业、机械加工、航空航天等领域广泛被应用。虽然有很多学者已对氢气两段还原制取钼粉的工艺、动力学机理有所研究,但均为小试型实验,与实际生产还存在较大差距。本文基于理论结合工厂实际生产,采用中试型实验对氧化钼氢还原过程的工艺参数及其相变、形貌演变规律进行了详细的研究。本文通过改变还原温度、氢气流量、钼舟尺寸、还原时间及料层厚度等5个影响因素,研究了两段还原(MoO3→MoO2,MoO2→Mo)过程中还原率的变化规律,采用X-衍射分析(XRD)和扫描电子显微镜(SEM)对其过程和还原产物进行了表征分析。主要研究结果如下:(1)还原率均随着还原温度的升高而增大。温度过高,一段易出现“过还原”和结块现象,二段会出现“过烧”现象。两段最佳还原温度分别为540℃和920℃。(2)还原率随着氢气流量的增加而增加。氢气超量时,还原率的变化幅度很小,还原温度对两段反应的还原效率占主导因素。两段最佳氢气流量均为1.0m3/h。(3)其它条件一定时,当料层厚度≤1/2钼舟高度时,钼舟壁相对料层的高度越高,还原效率越低。选择钼舟高度与料层厚度相当的钼舟为宜。(4)相同还原条件且料层厚度与钼舟高度一致,还原率随着料层厚度的增加而减小。料层厚度对一段还原产物的物相有影响,MoO3被还原60min时,上层产物为MoO2,中层、底层物料接触氢气受阻碍,M4O11含量较多;70min时,上层产物出现Mo,中层、底层产物为还原良好的MoO2。(5)MoO3→MoO2是个连续还原过程,Mo4O11为中间相。MoO3→Mo4O11,Mo4O11→MoO2的双重反应同时发生,前者反应速率高于后者。MoO2→Mo无中间相出现,其微观形貌演变符合分裂模型。
[Abstract]:Molybdenum has good physical properties and is widely used in metallurgical industry, electronics industry, mechanical processing, aerospace and other fields.Although many scholars have studied the kinetic mechanism of two-stage reduction of hydrogen to molybdenum powder, it is a small scale experiment, and there is still a big gap with the actual production.In this paper, based on the theory and practical production in the factory, the technological parameters, phase transition and morphology evolution of molybdenum oxide reduction process are studied in detail by pilot experiment.By changing the reduction temperature, hydrogen flow rate, the size of molybdenum boat, the reduction time and the thickness of the material layer, the variation law of the reduction rate during the two-stage reduction process of Moo _ 3 / Moo _ 2 / MoO _ 2 / Moo _ 2 / Moo _ 2 was studied.The process and reduction products were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM).The main results are as follows: (1) the reduction rate increases with the increase of reduction temperature.When the temperature is too high, the phenomenon of "overreduction" and caking will occur easily in the first section, and "overburning" will occur in the second stage.The optimum reduction temperature is 540 鈩，

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