Numerical Investigation on the Effects of Gas Induction Velocity on the Performance of a Fluidized Bed Reactor

The present study investigates a numerical model for pinewood gasification for different gas induction velocities in fluidized bed reactors. The study aims to predict the product gas composition for different gas flowrates to assess the reactor performance. A two-dimensional Eulerian-Lagrangian approach is employed via the open-source code MFiX (Multiphase Flow with Interphase eXchanges). The chemical reaction rates are implemented into the code through Fortran sub-routines. The results from the simulation are validated with available experimental data. The impacts of the gas inlet velocity variation on the product gas composition and the gasifier performance are discussed and compared with the literature. A good agreement between the current computational study and the previous experiment is achieved with hydrogen being the highest molar gas yield and methane being the lowest, while both carbon monoxide and carbon dioxide having similar magnitudes. It is also observed that the hydrogen and carbon dioxide yields decrease with increasing the gas inlet velocity, whereas the carbon monoxide and methane gases increase. The overall product gas trends for increasing the gas velocity in this study are similar to that for decreasing the steam to biomass ratio according to previous literature. The carbon conversion efficiency and heating value for the product dry gases are enhanced in the examined range of flowrates due to the increase in the carbon monoxide and methane yields. Besides, the dry gas yield decreases with increasing the gas flow due to the reduction in residence time. In our future study, further improvement in the chemical kinetics employed shall be made to predict the product gas molar composition more accurately for pine wood gasification, because the current model tends to overpredict the carbon dioxide and carbon monoxide yields with underprediction of the hydrogen yield.