Correlation between Fluidity Properties and Local Structures of Three Typical Asian Coal Ashes

Correlations among compositions, microstructures, and fluidity properties of three typical Asian coal ashes and their rapidly quenched slags were systematically investigated using Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), and multinuclear solid-state nuclear magnetic resonance (SS-NMR). The viscosities were measured from 1700 °C to their solidification temperatures. Different fluidity properties were found because of the presence of the various microstructures. The Datong ash and slag, with the highest viscosity in this study, mainly consisted of Q4 and Q3 structures of Si with a high degree of polymerization. The Malinau ash and slag with high iron contents had a Si structure similar to that of the Datong ash; the Q4 and Q3 structures indicated that the divalent Fe ions may principally bond as a framework modifier with Al tetrahedrons rather than Si tetrahedrons. In addition, alkaline-earth ions in the Adaro ash and slag segmented the framework to form primary Q3 and Q2 structures, resulting in the lowest viscosity.