| An existing char flame program is modified to predict coal particle behavior in one-dimensional furnaces. The complete p.c. flame program ties the important elements of coal flames, namely volatile matter generation, its combustion and char combustion. Unlike other flame models, where substitution for VM combustion kinetics and approximations for char combustion kinetics are used, this model incorporates experimentally determined kinetics for VM combustion, extensively verified engineering equations for VM release and an extended char combustion model that includes rates for diffusion, adsorption and desorption of oxidizing and product gases. The model thus constructed is used to predict the variations in the density and size of particles in addition to the temperatures and reaction rate profiles. Results showing the relative role of flame radiation in affecting flame stabilization and ignition parameters are calculated. Results are also calculated to show the effect of inlet variables such as mean particle size and fuel-air ratios on flame radiation properties. Predictions are compared with experimental results from different sources. A specific focus of the modelling is the influence of reaction mode on the flame emissivity, and hence on the ignition time. These results account for wide variations in ignition time found experimentally, that were previously attributed to differences in fuel reactivity. |
