Ignition and flame propagation characteristics of 18 kinds of coal and a petroleum coke were investigated through a laser ignition experiment. Flame stability was strongly influenced by amount of volatile matter and pyrolysis rate. Lean limit of flame propagation was strongly influenced by amount of volatile matter. Flame propagation was observed when pyrolized volatile matter was mixed with surrounding air or oxygen, until the concentration of pyrolized volatile matter reached a constant value. Flame propagation velocity was strongly influenced by pyrolysis rate. As the pyrolysis rate increased, the flame propagation velocity increased. The flame propagation velocity of petroleum coke was higher than that of coal with the same volatile content. The flame propagation of petroleum coke was superior to what was expected based on the volatile content, primarily because the high pyrolysis rate caused a shorter ignition delay than what would be expected given the volatile content. A database for the lean limit of flame propagation was used to develop a flame stability model to estimate lean flammability of a large-scale burner. The model could predict the effect of the coal rank, the particle diameter distribution for lean flammability limit. The estimated lean flammability limit of petroleum coke (volatile content 11.5%) was equal to that of lv bituminous coal with volatile content of about 15%. (c) 2009 Elsevier Ltd. All rights reserved.