关键词: 灰熔融特性, 高钠煤, MgO含量, 矿物变化, 热力学, 相平衡

Abstract: 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%.

Key words: ash fusibility, high sodium coal, MgO content, mineral conversion, thermodynamic, phase equilibria