Experimental Study Of Magnesium Vapor Condensation Process Of Refining Magnesium Vacuum Carbon Thermal Method

During the past70years, numerous attempts have been made to produce magnesium by carbothermal reduction method. However, it has not been industrialized practically due to the high temperature required, the difficulties in separating magnesium from CO vapor and the explosion of magnesium powders. The chemical basis of the magnesia carbothermal reduction in vacuum is the carbothermal reduction of the MgO-C system. There are still divergent opinions on the effects of magnesium vapor pressure, condensation temperature, and condensation zone temperature gradient on magnesium vapor. In addition, there is lack of unified interpretation on he behavior of un-coagulable CO was experimentally investigated during the condensation process of carbothermic reduction of magnesia at different condensing zone temperatures. Therefore, in this paper analyzes the mechanism of magnesia carbothermal reduction in vacuum was analyzed on this basis, then mixture vapor condensation behaviors of magnesia and CO were studied in terms of several influence factors, and finally the major challenges in magnesium vapor condensation during the vacuum carbothermic reduction of calcined dolomite.The experiments were conducted using magnesia and carbon as raw materials in the vacuum furnace of self-design with X-ray diffraction and scanning electron microscopy as the main analysis methods.This review intends to assess critically recent findings related to coagulable magnesium vapor nucleation and growth in vacuum, with emphasis on understanding these processes at a fundamental molecular level. The effects of magnesium vapor pressure, condensation temperature, and condensation zone temperature gradient on magnesium vapor nucleation in phase transitions and condensation from atomic collision and coacervation with collision under vacuum conditions were discussed. Magnesium powders and magnesium lump condensates were produced under different conditions and characterized by scanning electron microscopy and energy-dispersive X-ray spectroscopy. The right condensation zone temperature approach to the liquid transition primarily improved the magnesium vapor concentration rate. The gas-solid phase transition was primarily inhibited by setting a small condenser temperature gradient. Under the right condensation temperature and temperature gradients, increasing magnesium vapor partial pressure improved crystallization and reduced oxidation rate.Secondly, the behavior of un-coagulable CO was experimentally investigated during the condensation process of carbothermic reduction of magnesia at condensing zone temperatures ranging from923K to1062K. MgO and Mg2C3were detected in the condensing tower. The main effects of the magnesium condensation under vacuum were the Mg partial pressure and the temperature gradients in the condensing district. The phase, surface morphology, and composition of the condensates obtained were examined by means of scanning electron microscopy and energy-dispersive X-ray spectroscopy, respectively. The reverse reaction products C and MgO were formed following the process of magnesium vapor condensation, preventing two metal clusters from mutually combining. Moreover, the nearer the temperature of the condensation zone approached the liquid transition temperature, the lower the rate of the reverse reaction between CO and magnesium vapor. Decreases in the rate of the reverse reaction of magnesium were possible by controlling the condensation temperature. Compared with the reductive product and purity magnesium distillation product. The distillation product had a lump structure and good crystalline feature, but the reductive product had a filament crystallization and chinky structure due to the crystal growth was blocked by CO.Most of researchers believed that the developments on the condensation of magnesium produced by carbothermic reduction just concentrated on two process routes:the "quench" route and the "solvent" route. But this paper will briefly analyzes the major challenges in magnesium vapor condensation during the vacuum carbothermic reduction of calcined dolomite, on equipment upgrade, heat transfers alter, to achieve condensation control and production collection. Solutions are then proposed using theoretical calculations and experiment results. Comparative analysis of the experiment results shows that the burning and even explosion of condensation products during the vacuum carbothermic reduction of calcined dolomite are mainly due to the burning of crystallized powder magnesium, which results from the self-ignition of alkali metals. Finally, this paper proposes a multistage condensation solution to improve traditional vacuum condensation equipment. And result show that the condensation equipment can effectively mitigate the burning and loss during condensation, also the morphology of the condensation products clearly improved, the grain size increased, and the oxidation rate decreased. The potassium/sodium vapor and the magnesium vapor were separately condensed.