Influence of filtration heat transfer on parameters and conditions for ignition of coal-water fuel particles

The paper describes a theoretical study on the influence of filtration of a mixture of gaseous products of pyrolysis and water vapor on the dynamic of ignition of coal-water fuel particles under conditions of high temperature heating. The developed mathematical model offers simulation of the process of ignition of coal-water fuel droplets under conditions close to the furnace space (characterized by intense radiation-convective heating) in typical boilers. Comparisons of experimental data (found previously) and simulation data on the ignition delay time (tign) demonstrate good compliance. Simulation results show that filtration of water vapor and volatiles is a significant factor (influence up to 40 %) affecting the characteristics and conditions of ignition of coal-water fuel droplets. The higher velocity of the vapor-gas mixture flow through the porous structure of the fuel particle results in a longer ignition delay. The effect of using the “simplified” model of filtration heat transfer on the prognostic estimates of coal-water fuel ignition is analyzed. It is demonstrated that using of rather simple models for filtration heat transfer does not bring any significant errors in calculating the ignition delay time.