International Journal of Hydrogen Energy, Vol.45, No.3, 1615-1628, 2020
The intrinsic kinetics of methane steam reforming over a nickel-based catalyst in a micro fluidized bed reaction system
Methane steam reforming (MSR) is studied experimentally and numerically. The intrinsic kinetics of the reaction are determined using a micro fluidized bed with a catalyst containing more than 50 wt % NiO/alpha-Al2O3. Intrinsic kinetic models are developed for parallel and serial reaction mechanisms, but the parallel mechanism is found to better match the experimental data. The activation energies for CO and CO2 formation are 81.69 kJ/mol and 59.38 kJ/mol, respectively, and the pre-exponential factors are 316.6 mol/(g h kPa(0.85)) and 0.00263 mol/(g h kPa(3.1)), respectively. As the reaction temperature increases, the rate of CO formation increases and that of CO2 decreases. At 800 degrees C, almost all the CH4 is converted to CO and H-2, and the methane conversion rate (X-CH4), the hydrogen production rate (Y-H2), and the CO selectivity (S-CO) are 92.28%, 3.34, and 0.99, respectively. The effects of the steam-to-carbon ratio (S/C), inlet velocity, and preheating temperature at different reaction temperatures are simulated using the FLUENT software package. As S/C increases, X-CH4 and Y-H2 increase, but S-CO decreases. The higher the reaction temperature, the less S/C promotes X-CH4 and Y-H2. When the reaction temperature is 700 degrees C and the inlet velocity is 0.2 m/s (residence time is 0.5 s), X-CH4 is above 95%, and changes in the inlet velocity strongly influence the formation of CO. With increasing preheating temperature, X-CH4, Y-H2, and S-CO all increase gradually. (C) 2019 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.