Study On The Direct Oxidation Thermal Decomposition Of Magnesium Chloride Byproduct In The Sponge Titanium Production Process To Prepare Magnesium Oxide

Against the status that in the titanium sponge smelting for Kroll process,there is a large investment and High energy consumption for electrolytic equipments,75%of our titanium sponge production capacity is direct outsourcing TiC14 and magnesium chloride produced by reduction and distillation is cheap sale as scrap.The topic proposes "in-situ pyrolysis-thermal reduction Magnesium" new technology of clean titanium sponge production.Namely the molten magnesium chloride which is produced by reduction and distillation direct prepare high purity magnesium and chlorine by pyrolysis.Magnesium hydroxide by thermal method returns TiC14 reduction and chlorine turns back to the process of boiling chlorinated.To achieve the new magnesium,chlorine cycle in the process of titanium sponge production.This article focuses on the pyrolysis reaction of gaseous magnesium chloride with oxygen.Based on the thermodynamics of the reaction,the design of the reactor,the research of product properties under different reaction conditions and reaction kinetics,this research and experiment respects to mechanism of the pyrolysis reaction.Meanwhile the product MgO is characterized.The conclusions are as follows:(1)The reaction can be occurred when the temperature is between 1200K and 1700K,because △G" is below 0.Enthalpy of pyrolysis reaction decreases with increasing temperature.Phase transition appears at 987K,and the endothermic reaction turns to exothermic reaction.Through the calculation of the saturated vapor pressure,the temperature rises from 1073K to 1673K,saturated vapor pressure changes from 0.20 to 92.64.The gas phase reaction of the gaseous magnesium chloride and oxygen can be occurred below the boiling point of magnesium chloride.(2)The design is a horizontal reactor.Oxygen tube is over the crucible of magnesium chloride and the gaseous magnesium chloride is protected by argon atmosphere.A dilution device is installed in the tail of the reactor.The material of the main reactor chooses quartz,and the crucible chooses corundum crucible.Long tube length is 1600mm,diameter is 60mm and thickness is 3mm.A ventilation nozzle is installed in the long tube.The length of ventilation nozzle is 50mm,the diameter is 10mm and the distance from the outlet end of the long tube is 100mm.The length of casing is 800mm,diameter is 36mm.Flow field distributions and particle distribution inside the device can be calculated by using numerical simulation.(3)In the study of single factor experiment,the effects of different conditions(temperature,duration of ventilation and the amount of oxygen)to the reaction are researched.The optimal reaction condition is at the temperature of 1200℃,at the oxygen flow rate of 50L/h,and at oxygen blown time of 30min.MgO content in the product is 98.27%and the average particle size is 278nm.The comprehensive index is better than the superior product of industrial magnesium(4)The three factors and three levels orthogonal experimental scheme are used to study the influence of the three influencing factors.Sequence on effects of the pyrolysis reaction is temperature＞ duration of ventilation>amount of oxygen.Influnce of reaction temperature on the yield is significant,duration of ventilation and amount of oxygen have some influnces on the yield of magnesia.(5)Fit the relationship between consumption of magnesium chloride and time.The consumption rate of magnesium chloride is obtained.Fit the relationship between rate and temperature.Arrhenius equation of the reaction In k=-12640.771931/T+9.76248 is obtained.Activation energy is Ea=10.51kJ mol-1 and the Pre-exponential factor is A= 17369.65.