Abstract: The effects of ash/K₂CO₃/Fe₂O₃ and their interactions on the ignition temperature and combustion rate of acid-washed anthracite were examined. The coal ashes from combustion of anthracite at different temperatures showed very different properties such as chemical compositions, color and morphology. Reactivities of demineralized anthracite with and without catalysts were measured by thermo-gravimetric analyzer (TG-DTG). The results indicate that ash itself has no catalytic effects on ignition temperature while the combustion rate is improved, especially by the ash prepared at high temperatures. The use of ash with K₂CO₃ (or Fe₂O₃) together as combustion catalysts reveals that the interactions (i.e. sintering reactions) between them have caused the reduction in combustion rate, compared with the cases when K₂CO₃ or Fe₂O₃ was employed individually. Similarly, the synergistic effect between K₂CO₃ and Fe₂O₃ was also observed to lower the combustion rate of demineralized anthracite.