Experimental and numerical studies of pulverized coal devolatilization and oxidation in strained methane/air flames

Abstract

Experimental and numerical investigations of the combustion of a methane/air mixture fed with coal particles are performed. The retained configuration is a laminar 1-D strained flame impinging a wall. The wall surface promotes the formation of a methane/air flame front parallel to the stagnation plane. Coal particles oxidation takes place in the hot region between the flame front and the wall. Laser induced fluorescence PLIF measurements of OH radical and imaging of CH*, C2* spontaneous emission are performed to identify the chemical flame structure. The inlet fresh gas boundary conditions are well characterized in the experiments in terms of gas velocity but also number of coal particles and mean particle diameter. These conditions are used to perform numerical simulations with the 1-D REGATH code developed at EM2C laboratory. The governing equations are fully coupled between gas and particle phase. Detailed chemical kinetics based on USC-Mech II reaction scheme, NOx chemistry and OH*/CH*/C2* sub-mechanisms are considered. The numerical predictions showed good agreement with the experimental data. The analysis of obtained results confirmed that the composition of volatile species of coal has a significant influence on the CH* and C2* concentration in the post-flame region. Finally, the effects of volatile matter composition, strain rate and particle size on the NOx, C2H2 and C6H6 formation are studied.