本文選題：水氯鎂石　切入點(diǎn)：電熔鎂砂　出處：《華東理工大學(xué)》2015年碩士論文　論文類型：學(xué)位論文

【摘要】：以鹽湖鹵水熱解輕燒氧化鎂為原料,經(jīng)電弧爐高溫熔煉制備高純電熔鎂砂,通過優(yōu)化電熔工藝條件,研究影響電熔鎂砂致密性和灼燒減量的因素,旨在提高鎂砂的純度,減少有害雜質(zhì)的含量,提高鈣硅比,探討Ti02等添加劑對于電熔鎂砂熔融結(jié)晶機(jī)理的影響,對提高鎂砂質(zhì)量和改進(jìn)制備工藝具有重要的實(shí)際意義和理論價值,促進(jìn)鹽湖產(chǎn)業(yè)鏈的延伸。研究了電熔鎂砂的致密性和灼燒減量的影響因素,結(jié)果表明熔池中心的體積密度大于3.43g/cm3,最高達(dá)3.57/cm3；中心試樣的顯氣孔率低于0.95%,最低為0.17%。電熔鎂砂熔池內(nèi)部的灼燒減量最低,外部鎂砂因受熱不均且不充分,呈欠燒狀態(tài)。由于純度和次晶相的產(chǎn)生以及雜質(zhì)等因素的影響,造成鎂砂顯微結(jié)構(gòu)的不同,從而影響鎂砂的致密性。研究了電熔鎂砂純度和雜質(zhì)的分布情況,原料鹵水氧化鎂粉料純度為97.63%,熔融結(jié)晶后熔池中心氧化鎂含量最高達(dá)99.87%,微量雜質(zhì)元素中相對含量最高的Ti、Na和K累計值低于0.10%。外層電熔鎂砂的晶相中生成3CaO·SiO2,2CaO·SiO2,8CaO·5SiO2等復(fù)雜硅酸鹽礦物,方鎂石外觀不規(guī)整,相與相之間無法緊密地嵌合。中層試樣中含有CaO·SiO2,2CaO·SiO2以及含鐵的硅酸鹽礦物,雜質(zhì)峰相對較少。其方鎂石晶相顆粒變大,表面有細(xì)小的碎片狀伴生物。中心試樣無次晶相生成,氧化鎂的特征峰高且尖銳。熔池內(nèi)部到外部的試樣中的方鎂石晶面間距逐漸變大,晶格畸變也由0.0066%逐漸增大到0.0562%。研究了添加劑Ti02對于電熔鎂砂熔融結(jié)晶機(jī)理的影響,當(dāng)TiO2含量為0.25wt%時,除雜效果達(dá)到極限值。電熔鎂砂的體積密度隨著TiO2的不斷加入而增大,添加0.25wt%時體積密度最高達(dá)3.57g/cm3,顯氣孔率最小。TiO2一方面通過固溶反應(yīng)進(jìn)入氧化鎂晶格加速雜質(zhì)純化,另一方面Ti02優(yōu)先和雜質(zhì)氧化鈣反應(yīng)。當(dāng)TiO2的添加量達(dá)到0.15wt%時,樣品晶相由方鎂石和少量次晶相尖晶石(MgAl2O4)構(gòu)成,添加量超過0.25wt%時伴生Mg2TiO4等其他礦石相。因此,Ti02的添加量不能超過在MgO中的固溶極限,生成其他雜質(zhì)相會影響電熔鎂砂的性能。添加Ti02的電熔鎂砂晶粒之間結(jié)合緊密,由于Ti4+進(jìn)入MgO晶格,引起空位和晶格畸變造成缺陷,使得晶體顯微形貌發(fā)生形變,其結(jié)晶顆粒純度高,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.
【學(xué)位授予單位】：華東理工大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2015
【分類號】：TQ132.2

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