Experimental and numerical analysis of non-catalytic partial oxidation and steam reforming of CH4/O2/N2/H2O mixtures including the impact of radiative heat losses

Abstract Partial oxidation and non-catalytic steam reforming of methane is studied by conducting an experimental and numerical analysis of reactions taking place in the post-flame region of a generic laminar atmospheric burner operated at fuel-rich conditions. Laminar planar premixed methane/oxygen/nitrogen (CH 4 /O 2 /N 2 ) flames are stabilized above a porous material with an equivalence ratio ϕ  = 1.8. The oxygen enrichment Ω in the O 2 /N 2 mixture varies from 0.32 to 0.45. Mixtures are also diluted with superheated steam. The water vapor mole fraction X H 2 O u in the unburnt mixtures ranges from 0.11 to 0.28. The temperature of burnt gases is measured along the central axis of the burner with a thermocouple. Gas chromatography measurements along the same axis indicate the production of hydrogen (H 2 ) and carbon monoxide (CO) just downstream the flame front. Measurements also reveal a decrease of the CO concentration as the distance to the flame front increases due to a drop of the temperature in the burnt gases. One-dimensional direct simulations of flames using detailed chemistry mechanisms are conducted under non-adiabatic conditions accounting for conductive heat losses to the burner surface and radiative heat transfer of semi-transparent gases using a statistical narrow-band model for the radiative properties of the main species (H 2 O, CO 2 , CO,…). Predicted temperature profiles and major species mole fractions yield satisfactory match with measurements only if radiative heat losses are taken into account in the simulations. It is shown that self-absorption of thermal radiation from H 2 O and to a lesser extend from CO 2 fully controls the temperature profile in the post-flame region. The endothermic steam methane reforming reaction taking place in this region is strongly penalized by radiative heat loss. It is shown that increasing the steam dilution promotes the H 2 /CO ratio within the burnt gases, while rising the oxygen enrichment benefits to the CO production to the detriment of H 2 . This analysis reveals the important role of radiative heat transfer and self-absorption of steam and to a lesser extent carbon dioxide in the syngas formation such as for example the methane auto-thermal reforming process.