盐湖卤水热解氧化镁制备高纯电熔镁砂的研究

发布时间：2018-03-10 23:43

本文选题：水氯镁石　切入点：电熔镁砂　出处：《华东理工大学》2015年硕士论文　论文类型：学位论文

【摘要】：以盐湖卤水热解轻烧氧化镁为原料,经电弧炉高温熔炼制备高纯电熔镁砂,通过优化电熔工艺条件,研究影响电熔镁砂致密性和灼烧减量的因素,旨在提高镁砂的纯度,减少有害杂质的含量,提高钙硅比,探讨Ti02等添加剂对于电熔镁砂熔融结晶机理的影响,对提高镁砂质量和改进制备工艺具有重要的实际意义和理论价值,促进盐湖产业链的延伸。研究了电熔镁砂的致密性和灼烧减量的影响因素,结果表明熔池中心的体积密度大于3.43g/cm3,最高达3.57/cm3；中心试样的显气孔率低于0.95%,最低为0.17%。电熔镁砂熔池内部的灼烧减量最低,外部镁砂因受热不均且不充分,呈欠烧状态。由于纯度和次晶相的产生以及杂质等因素的影响,造成镁砂显微结构的不同,从而影响镁砂的致密性。研究了电熔镁砂纯度和杂质的分布情况,原料卤水氧化镁粉料纯度为97.63%,熔融结晶后熔池中心氧化镁含量最高达99.87%,微量杂质元素中相对含量最高的Ti、Na和K累计值低于0.10%。外层电熔镁砂的晶相中生成3CaO·SiO2,2CaO·SiO2,8CaO·5SiO2等复杂硅酸盐矿物,方镁石外观不规整,相与相之间无法紧密地嵌合。中层试样中含有CaO·SiO2,2CaO·SiO2以及含铁的硅酸盐矿物,杂质峰相对较少。其方镁石晶相颗粒变大,表面有细小的碎片状伴生物。中心试样无次晶相生成,氧化镁的特征峰高且尖锐。熔池内部到外部的试样中的方镁石晶面间距逐渐变大,晶格畸变也由0.0066%逐渐增大到0.0562%。研究了添加剂Ti02对于电熔镁砂熔融结晶机理的影响,当TiO2含量为0.25wt%时,除杂效果达到极限值。电熔镁砂的体积密度随着TiO2的不断加入而增大,添加0.25wt%时体积密度最高达3.57g/cm3,显气孔率最小。TiO2一方面通过固溶反应进入氧化镁晶格加速杂质纯化,另一方面Ti02优先和杂质氧化钙反应。当TiO2的添加量达到0.15wt%时,样品晶相由方镁石和少量次晶相尖晶石(MgAl2O4)构成,添加量超过0.25wt%时伴生Mg2TiO4等其他矿石相。因此,Ti02的添加量不能超过在MgO中的固溶极限,生成其他杂质相会影响电熔镁砂的性能。添加Ti02的电熔镁砂晶粒之间结合紧密,由于Ti4+进入MgO晶格,引起空位和晶格畸变造成缺陷,使得晶体显微形貌发生形变,其结晶颗粒纯度高,尺寸大且透明。
[Abstract]:High purity fused magnesite was prepared by high temperature melting of magnesium oxide from salt lake brine by high temperature melting in electric arc furnace. The factors affecting the densification and burning reduction of fused magnesite were studied by optimizing the process conditions, in order to improve the purity of magnesite. Reducing the content of harmful impurities, increasing the ratio of calcium to silicon, discussing the effect of additives such as Ti02 on the mechanism of melting crystallization of fused magnesia has important practical significance and theoretical value for improving the quality of magnesia and improving the preparation process. The densification of fused magnesite and the influencing factors of burning reduction are studied. The results show that the bulk density of the molten pool center is greater than 3.43 g / cm ~ 3, and the maximum is 3.57% 路cm ~ 3. The apparent porosity of the central sample is lower than 0.95 and the lowest is 0.17. The internal burning loss of the fused magnesite is the lowest, and the external magnesite is unevenly heated and inadequate. The microstructure of magnesite is different due to the influence of factors such as purity, subcrystalline phase and impurity, thus affecting the densification of magnesia. The distribution of purity and impurity of fused magnesia is studied. The purity of magnesium oxide powder of raw material brine is 97.63, the content of magnesium oxide in the center of melting pool reaches 99.87, the accumulative value of Tigna Na and K of the highest relative content of trace impurity elements is lower than 0.10. The complex silicate minerals such as 3CaO 路Sio _ 2 Cao 路Sio _ 2 8CaO 路5SiO _ 2 are formed in the crystal phase of the outer layer of fused magnesia. The appearance of periclase is irregular, and the phase and phase can not be tightly intercalated. There are CaO 路SiO2O2CaO 路SiO2 and ferric-bearing silicate minerals in the middle samples, and the impurity peaks are relatively few. There are fine debris associated organisms on the surface. There is no secondary phase in the central sample, and the characteristic peak of magnesium oxide is high and sharp. The periclase crystal plane spacing in the sample from the inside to the outside of the molten pool increases gradually. The lattice distortion also increased from 0.0066% to 0.0562. The effect of additive Ti02 on the melting crystallization mechanism of fused magnesia was studied. When the content of TiO2 was 0.25 wt%, the impurity removal effect reached the limit value. The volume density of fused magnesia increased with the addition of TiO2. The maximum bulk density of 0.25wt% was 3.57g / cm ~ 3. On the one hand, the apparent porosity was minimum. TIO _ 2 accelerated the purification of impurity into magnesium oxide lattice by solid solution reaction, on the other hand, Ti02 preferential reaction with impurity calcium oxide. When the content of TiO2 reached 0.15wt%, The crystal phase of the sample consists of periclase and a small amount of hypocrystalline spinel MgAl _ 2O _ 4. When the addition amount is more than 0.25 wt%, other mineral phases such as Mg2TiO4 are associated. Therefore, the addition amount of TiO2 can not exceed the solution limit in MgO. The formation of other impurity phases will affect the properties of fused magnesia. The grain of fused magnesia added with Ti02 binds closely. Because Ti4 enters the MgO lattice, it leads to the defects of the vacancies and lattice distortion, resulting in the deformation of the micromorphology of the crystals. Its crystal particle purity is high, the size is big and transparent.
【学位授予单位】：华东理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TQ132.2

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