Influence of gas atmosphere and coal particle size on coal pyrolysis behavior in spot heater apparatus was investigated in nitrogen, helium and argon atmosphere, and in the size range of 650-1300μm respectively. The inert gas with small thermal conductivity/specific heat provided fast heating and high final temperature, and coal sample in such an inert atmosphere was decomposed more largely and quickly. It turned out that particle size has influence on heating rate but almost no influence on final temperature of coal particle as long as heating time is long enough. Generally, pyrolysis weight loss of smaller coal particle is larger because of its higher heating rate and less residence time of volatiles in particle.
