MgO含量对高钠煤灰熔融特性的影响

为研究MgO含量对高钠煤灰熔融特性的影响，配制了不同MgO含量的高钠合成灰并对灰熔融温度进行了测试。利用FactSage 7.0提供的热力学数据库建立了SiO₂-Al₂O₃-Fe₂O₃-CaO-MgO-Na₂O多元体系，模拟不同MgO含量的高钠合成灰的熔融过程。使用X射线衍射（XRD）和扫描电子显微镜（SEM）对合成灰的矿物质组成及微观形貌进行了研究。结果表明，随着MgO含量的增加，灰熔融温度先降低后升高。当MgO质量分数由0增加到5%时，高温下灰中生成大量低熔点的透辉石，透辉石会与霞石等矿物质形成低温共熔体，导致灰熔融温度降低。进一步增加MgO含量，高温下灰中生成镁黄长石、镁橄榄石和镁硅钙石等高熔点矿物质，使灰熔融温度升高。二元相图和似三元相图的结果表明，全液相温度随MgO含量的变化趋势与灰熔融温度相同。对本研究中的煤种，当MgO质量分数为30%时，可以有效提高灰熔融温度并抑制熔融液渣的生成。

Effect of MgO content on the ash fusibility of high sodium coal

In order to study the effect of MgO content on the ash fusibility of high sodium coal,high sodium synthetic coal ash samples with different MgO content were prepared and the ash fusion temperatures were measured. A multicomponent system including SiO₂-Al₂O₃-Fe₂O₃-CaO-MgO-Na₂O was established by the thermodynamic database FactSage 7.0 to simulate the ash melting process. X-ray diffraction(XRD) and scanning morphology microscope(SEM) were applied to investigate the mineral composition and surface morphology of synthetic coal ash samples. The results show that the ash fusion temperatures dropped first and rose later with the increase of MgO content. When the MgO content increase from 0 to 5%,a large quantity of diopside with low melting point was generated in ash at high temperature. Diopside could form eutectics with minerals such as nepheline,and thus reducing the ash fusion temperatures. When the MgO content was further increased,minerals with high melting point such as akermanite,forsterite and merwinite were generated in ash at high temperature,and thus improving the ash fusion temperatures. The results of binary phase diagram and analogous ternary phase diagram indicated that the variation of liquid temperature was consistent with the ash fusion temperatures with the increase of MgO content. For the coal ash samples in this study,the ash fusion temperatures could be improved efficiently and the formation of molten slag could be suppressed significantly when the MgO content reached to 30%.