The ash deposition phenomenon in the coal gasification process is a severe problem for continuous operation. The ash deposition rate is influenced by the behavior of ash particles on the deposit target. Dropped coal ash particles, which exhibit different behaviors on the deposit surface such as attachment, rebounding, and removal, were observed through the view port of a drop tube furnace (DTF). The different behaviors may be influenced by the state of the ash particles such as the sintering phenomenon, which is a function of the mineral content. To verify the mineral components important in sintering among the ash particles, transformation of the particle shape of synthetic ash reacted at 900 degrees C was analyzed through a scanning electron microscope (SEM). The Fe, Ca, and Mg components were the main factors for sintering and agglomeration. The Fe, Ca, and Mg components sintered with Si and Al were observed in the mineral mapping of deposited coal ash by scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDX) analysis. Sintering characteristics of coal ash were analyzed by the dilatometer technique. Sintering temperature,shrinkage, and sintering activation energy (E-sin) were all found to be related to the Fe, Ca, and Mg contents. (C) 2015 Elsevier B.V. All rights reserved.