Entrained Dust Combustion in Pre-Heated Air

In many practical applications, such as in blast furnaces and boilers, pulverized coal is used as a reducing agent and energy source. This chapter presents the predicted characteristics of naturally entrained coal dust flames in a sudden expansion region. Further, it also investigates the effect of particle size and equivalence ratio on the flame dynamics. Commercially available ANSYS Fluent has been used for the numerical simulations. Discrete phase modelling is used for sub-bituminous coal particles tracking. Variable thermo-physical properties are employed. A skeletal chemical kinetic mechanism for methane consisting of 25 species and 121 reactions are used. A User Defined Function (UDF) is used to include the radiation due to species and soot particles. For a given coal flow rate, mass flow rate of air is varied to maintain the required global equivalence ratio at a constant temperature of 1273 K. Particle size distribution (1–25 and 53–63 µm) and equivalence ratio (0.65–0.95) are varied. Steady-state governing equations are solved till convergence. The flame dynamics is investigated through the contours of temperature, devolatilization zones, velocity vectors, mass fraction distribution of important species soot formation and reduction.