A comprehensive mathematical model for biomass gasification in a bubbling fluidized bed reactor

A mathematical model of biomass gasification in bubbling fluidized gasifier has been developed. It is a one-dimensional, two-phase (bubble and emulsion), two-zone (bottom dense bed and upper freeboard), steady state model. The model is based on global reaction kinetic, mass and energy balances and is capable of predicting temperature, solid hold ups and gas concentration along the reactor’s major axis. The overall model has sub-models to deal with biomass pyrolysis, gasification, bed hydrodynamics, material classification and property calculation. A sub-model for tar generation and cracking is included in this study. The model is capable of dealing with wide variety of biomasses and fluidizing agents, i.e. air, oxygen, steam or a mix of these gases. Results show that during devolatilization step, gases release and mixing are sensitive and critical parameters. They have a strong influence on the overall performance of a gasifier. A comparison with experimental data from numerous literature works was done, which showed fairly good agreement. The model can be used to study and optimize the operation of bubbling fluidized bed gasifier. However, further validation with diverse data will help to fine-tune the model.