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Mineral conversion and microstructure change in the melting process of Shenmu coal ash
Author(s) -
Jianguo Yang,
Furong Deng,
Hong Zhao,
Kefa Cen
Publication year - 2007
Publication title -
asia‐pacific journal of chemical engineering
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.348
H-Index - 35
eISSN - 1932-2143
pISSN - 1932-2135
DOI - 10.1002/apj.36
Subject(s) - coal , anorthite , gehlenite , eutectic system , fly ash , materials science , microstructure , thermogravimetry , mineralogy , melting point , metallurgy , chemical engineering , chemistry , composite material , organic chemistry , engineering , phase (matter)
China has rich reserves of Shenmu coal, which has the typical characteristic of low‐melting‐point ash. If used in the pulverized‐coal boiler of a power plant, Shenmu coal would cause serious slagging. In order to solve the slagging problem of Shenmu coal, the melting mechanism of Shenmu coal ash is studied in detail in this paper. One of the Shenmu coals – Wenjialiang coal – was selected for the study. On the basis of thermogravimetry‐differential scanning colorimetry (TG‐DSC) methods, the change of the coal ash's physicochemistry with temperature was studied. The typical temperature points in the melting process were obtained. Ash samples of the different temperature points were prepared in a high‐temperature furnace with parameters similar to those used in the TG‐DSC test, and were then cooled quickly in water. Later, the ash samples were analyzed using X‐ray diffraction (XRD) and scanning electron microscopy‐energy dispersive X‐ray analysis (SEM‐EDX) methods in detail. Wenjialiang coal ash started to melt at 980 °C. The ash was found to melt to a great extent at 1200 °C and formed a multiform microstructure. At 1260 °C, it was found to melt into a dense body with many pores, and formed a piece of vitreous body at 1340 °C. Anorthite and gehlenite are the intermediate products that exist between 980 and 1340 °C. They may be the main cause of the ash having low melting points, so that they could convert into a eutectic at low temperatures. Copyright © 2007 Curtin University of Technology and John Wiley & Sons, Ltd.