Modelisation numerique de la gazeification de la biomasse dans un reacteur a lit fluidise.

摘要

This document presents the results from biomass gasification experiments in a pilot-scale (1.65 m tall x 7.8 cm diameter) air blown bubbling fluidized bed gasifier (BFBG) and compares them with computer simulations. The two-phase one dimensional model encompasses the hydrodynamics of gas and solids and the reaction kinetics; it can predict the concentration profile along the reactor axis. A CCBM approach was used to model the solid mixing in the bed. The thermodynamics conditions are 800°C at atmospheric pressure and the feeding rate is 20 g/min. The air velocity is 2-3 times higher than minimum velocity (0.1 m/s). Model results are compared with the experimental work of this study and other published results on wood gasification in BFBG. Effects of equivalence ratio (ER) and bed temperature on the syngas HHV, tar concentration, gas yield and syngas concentration are studied. Proximate and ultimate analyses for wood and asphalt shingles have been determined and are used in the mathematical model. The model shows good agreement with experimental results reported by others and is consistent with experimental trends. Some discrepancies between the model and experimental values suggest that some reaction rates used in the model are not adequate. Gas analyses were carried out in order to determine the toxicity of the gas obtained by asphalt shingles gasification. Results show the presence of VOC, benzene, SOx, NO x and possible traces of furanes. Further quantitative analyses are strongly suggested.