Mineral transmutation of high alkali Zhundong coal in ash melting process

Mineral transmutation in the melting process was studied by the thermal analysis and X-ray diffraction phase analysis to explore Zhundong coal's slagging mechanism. Experimental results show that the apparent weightlessness (960~1250℃) on TG curves of thermal analysis accord with the existence of anhydrite. The release of SO3 gas in the decomposition of anhydrite leads the weightlessness. High alkali ends with many alkali-contained minerals. There are anhydrite, calcite, quartz, hematite, albite, nepheline, hauyne in the coal ash. Nepheline breaks down to form quartz and react with silicates such as albite etc. to form hauyne with low melting point. Intermediate diopside reacts with silicates and hematite to form gehlenite, akermanite, augite etc. These products will further react with each other in eutectic reaction to produce low melting eutectic of melting point at 1170℃. During the eutectic reaction of hauyne, the jadeite with low melting point at 900℃~1000℃ is generated. There are lots of melting-easy minerals and few refractory minerals in high alkali Zhundong coal's ash and in the ash melting process which lead to the low temperature eutectic reaction in which the melt with low melting point is formed, lower the ash fusion temperature, increase the viscosity of ash and slag. This is the reason why Zhundong coal has a strong slagging tendency. ©, 2015, Zhejiang University. All right reserved.