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Scanning electron microscope combined with energy dispersive X-ray analysis (SEM-EDX) was used to identify inorganic species in coal ash and to measure the particle size distribution and element composition. Ashes in raw and acid-treated Nantong coal prepared by low temperature ashing (LTA) and high temperature ashing (HTA) were used as sample. Silicate-rich particles showed agglomerate shape, but aluminate-rich particles showed layer-like shape. Silicate appears to cover the aluminate particle surface. Calcium was found in ash of the raw coal, not in ash from the acid treated coal. It is noted that a small amount of aluminate was removed by the mild acid treatment. It seems that fine particle aluminates disappeared from HTA ash by the acid treatment, while the morphology of LTA ash stayed unchanged regardless of the acid treatment.