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

Abstract

To cite this version:Meng Xia, Diego Zabrodiec, Philippe Scouflaire, Benoît Fiorina, Nasser Darabiha. Experimental and numerical studies of pulverized coal devolatilization and oxidation in strained methane/air flames. AbstractExperimental 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 * , C * 2 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, NO x chemistry and OH * /CH * /C * 2 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 C * 2 concentration in the post-flame region. Finally, the effects of volatile matter composition, strain rate and particle size on the NO x , C 2 H 2 and C 6 H 6 formation are studied.

Experimental and numerical investigation of a stagnation pulverised coal flame

“…The coal/CH 4 /O 2 /N 2 stagnation strained flame setup described in [17] is illustrated in Fig. 1 .…”

“…In Flame 2 , O 2 is 28% and is 0.64. The spontaneous emissions of chemiluminescent OH * , CH * and C * 2 are measured by a CCD camera with different spectral band pass filters [17] . These data are used to validate the numerical simulations.…”

“…The validity of this assumption was tested against a reference solution with detailed multi-species diffusivity showing a limited impact, mainly related to the fact that C 6 H 6 released is quickly consumed by the oxidation reactions, limiting the impact of the Le = 1 assumption. They contain additional terms to account for the interphase exchanges with the dispersed solid particles [15,17] :…”

“…Interphase terms include the drag forces F x and F r , defined by Stokes law, the convective and radiative heat fluxes ˙ q , and the chemical heat h s ( T p ) [15,17] . Radiative heat fluxes are modeled as described by Xia et al [17] .…”

“…In this work, the FPV model is further extended to include the char burnout products as an additional fuel stream. The new multi-stream FPV model is tested in the stagnation coal/CH 4 /O 2 /N 2 strain burner, previously studied by Xia et al [17] , for conditions which maximize the char conversion. Due to its well-defined boundary conditions and laminar flow field this setup is well suited for model assessment.…”