Prediction of lean flammability limit and flame propagation velocity for oxy-fuel fired pulverized coal combustion

Abstract

Lean flammability limit and flame propagation velocity are fundamental properties for engineering design of combustion systems. We developed a model to predict these properties for oxy-fuel fired pulverized coal combustion systems. We measured relationships between lean flammability limit and flame propagation velocity for various coal properties, particle diameter, composition of combustion supporting gas, and radiant heat loss rate from flame to surroundings. When coal particle diameter was the same, lean flammability limit was in inverse proportion to the maximum flame propagation velocity obtained by varying the coal concentration. The ratio of maximum flame propagation velocity and lean flammability limit was in proportion to the square of the particle diameter. When the temperature of the volatile flame around particles was uniform, the flame propagation velocities of CO 2/O 2 combustion and N 2/O 2 combustion were the same. The proposed model was provided with inputs of flame propagation velocity for oxy-fuel combustion, and lean flammability limit of air-combustion from fundamental experiments and an industrial-scale burner experiment. By using the model, we simulated variations of flame propagation velocity during operation of oxy-fuel fired plants. In the oxy-fuel combustion technology, correct driving control technology became important.