Reforming biomass-derived vapors maximizes the utilization of fuels obtained from biomass gasification and pyrolysis. The gas produced can be added to the feedstock for the synthesis of synthetic fuels and chemicals or directly burned to produce heat and power. Knowledge of the laminar flame speed, activation energy, and temperature exponent enables rapid design and analysis of combustion chambers using one-step global chemical kinetic mechanisms. The objective of this work is to evaluate the effect of unburned mixture temperature on adiabatic laminar flame speed, overall activation energy, and temperature exponent for H2/CO/CO2/N2 mixtures, representative of dry reforming of biomass-derived vapors, with H2/CO ratios from 0.43 to 1.0. The reactant temperature ranged from 300 to 400 K, while the equivalence ratio was kept at 0.9. The flat flame with heat loss method was used for the simultaneous measurement of the adiabatic laminar flame speed and overall activation energy. The temperature exponent was determined by two methods. The first uses the power-law relation between the laminar flame speed and unburned mixture temperature. The second estimate is from the measured activation energy. The results from the measurements were compared with calculations using the chemical kinetic mechanisms FFCM-1, HP-Mech, San Diego and Goswami. Adiabatic laminar flame speed increased more strongly with unburned mixture temperature in H2-rich mixtures. The activation energy showed little sensitivity to the unburned mixture temperature, especially in mixtures with lower H2 concentrations. For a mixture with 15% H2, the temperature exponent determined from the activation energy ranged from 2.0 to 2.2 for unburned mixture temperatures between 325 and 500 K, which is consistent with a first-order effective reaction order with respect to the fuel concentration. The adiabatic laminar flame speeds extrapolated using the power-law relation with the temperature exponents from both methods showed greater accuracy for temperature increases of less than 100 K relative to the reference condition, regardless of the H2 content.
Costa et al. (Wed,) studied this question.