Large eddy simulation of two-phase reacting turbulent flow in a pilot-scale pulverized coal combustion furnace with flamelet model

A three-dimensional numerical simulation was performed to investigate the physics and combustion characteristics of a two-phase reacting turbulent flow in a pilot-scale pulverized coal combustion furnace. This included an elementary reaction mechanism using an extended flamelet/progress variable (EFPV) method. The simulation was validated via comparison with an experiment in terms of the gaseous temperature and distribution of the gas mole fraction. The EFPV method predicted the flame structure and combustion characteristics of the pulverized coal. In the main reaction zone where the released gas combustion was dominant, two separate combustion regions were observed, and they were attributed to hydrocarbons and CO combustion. Gas flow characteristics such as mixing of low temperature gas and hot burnt gas were well described in the inner recirculation zone. The CO2 conversion reaction to CO occurred slowly and decreased the gaseous temperature beyond the main reaction zone in the low and zero oxygen environments. The simulation predicted the unburned CO combustion correctly beyond the flame when staged air was injected; however, the combustion rate was overestimated due to the fundamental assumption of the EFPV method, attributable to the limitations of the steady state flamelet approach.