To understand the properties of coking coal and coke during carbonization process, changes in stacking structure of carbon and carbon aromaticity were estimated using the XRD and NMR measurement techniques for the different four kinds of coking coals thermally treated at various temperatures. In the XRD measurement, the comparison of the diffraction patterns of the coal samples with and without decalcification indicated the proposed method could successfully eliminate peaks from ash components in the diffraction patterns. After thermal treatment, the average number of stacking layers in all the samples increased around temperature of 400-500 °C and slightly decreased around 500-700 °C. In addition, the average number of stacking layers of each sample tended to be larger for sample with higher carbon content. In the 13 C-NMR measurement, the carbon aromaticity became larger for higher thermal treatment temperature, and the order of the carbon aromaticity almost corresponded with that of coke contraction ratio.

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