Lean Flammability Limit for Oxy-Fuel Fired Pulverized Coal Combustion Systems

We developed a model based on fundamental experimental data to predict lean flammability limit, L, and flame propagation velocity, Sb, for oxy-fuel combustion conditions. The basic model system consisted of two particles. One side of the two particles burns first, then, the other particle is ignited by the heat of combustion of the one burning particle. This phenomenon was defined as flame propagation. We analyzed at what distance the first burning particle could ignite the next particle (flame propagation distance d, and related to L), and how fast the first burning particle could ignite the next particle (flame propagation time s, and related to Sb) under various conditions. The proposed model was verified with data of both fundamental and pilot- and actual-scale experiments. We also applied the model to develop burner systems for lignite-fired oxy-fuel combustion. Local Sb and L near the ignition points of the burner systems could be analyzed from the concentration and temperature profiles of the general CFD results (k-epsilon method). Flame stability was judged by the calculated Sb and L profiles, and past results of blow-off limits obtained with actual-and pilot-scale experiments. We call this proposed technique flammability analysis. By using combination with the technique and Large Eddy Simulation, we could quickly clarify points for improvement of the burner systems. The calculated results were applied to a DS (R) T-burner designed by Hitachi Power Europe, installed at Schwarze Pumpe pilot plant. (C) 2011 Published by Elsevier Ltd.