Gasification of Biomass in an Updraft Fixed Bed Reactor: Effect of Viscous Models
F. J. Alarcón-Gaete and J. C. Elicer-Cortés
Departamento De Ingeniería Mecánica, Universidad De Chile, Beauchef 851, Santiago, Chile
Abstract: A numerical study to investigate the influence of viscous models in the biomass gasification in an updraft fixed bed reactor is presented. The unsteady simulations were performed using finite volume method of ANSYS Fluent. A two-dimensional axisymmetric transient model was used to simulate the biomass gasification process. The model is based on the Euler-Euler multiphase formulation. The reactive gas-solid flow considers both homogeneous and heterogeneous reactions (drying, pyrolysis, combustion and gasification). Source terms and chemical kinetics are incorporated into the code using user-defined functions programmed in C. Results are validated with experimental data available in the literature for gasification in a continuous reactor. Temperatures and mole fractions of CO, CO2, CH4, Tar, and H2 at the reactor exit are in good agreement with the experimental measurements. Laminar model is agreed with experimental data for net calorific value, however, discrepancies are observed when the mixture model is used. This work provides a methodology for studying gasification in fixed beds using a commercial CFD code which can be used in gasifier design, analysis, and optimization.
Keywords: CFD, euler-euler approach, multiphase flow, fixed bed, updraft gasifiers, biomass fuel.