Coal chars prepared under different carbonization conditions were gasified with CO_2 to different conversion levels. The gasifification rate was decreased with increasing the conversion. Various physical and chemical properties of the chars were measured to clarify the relation to the situation. The items measured were as followed: the composition of C, H and O; carbon crystal structure; surface area and porosity; chemical form of ash components. Oxygen content for char and Lc determined by XRD were increased with increasing the conversion, whereas R value determined by laser Raman band and surface area were decreased. Char with higer conversion gave XRD lines of rankinite, gehlenite, and anorthite, accompanying the agglomeration of mineral matter. These results indicated that the reasons for the diminishing rate of char with increasing the conversion would be dependent on not only the physical and chemical changes in properties but also the activity loss of indigenous calcium by forming chemical bondings with sillica and alumina.
