Influence of the pyrolysis and heterogeneous char reactions modeling in the simulation of sugarcane bagasse gasification in a bubbling fluidized bed reactor

Abstract

The present work investigates different kinetic models for the pyrolysis and heterogeneous char reactions for numerical simulation of the sugarcane bagasse gasification in a bubbling fluidized bed reactor. A two-dimensional Euler-Euler approach is considered, and the reaction rate correlations are implemented in the open code MFIX (Multiphase Flow with Interphase eXchanges) via Fortran sub-routines. The impact of the considered kinetic models for pyrolysis and heterogeneous char reactions upon the prediction of the composition and temperature of the produced gas is evaluated. Six sets of kinetic correlations describing the reactions involved during the sugarcane bagasse gasification are used to perform the computational simulations. Results for the syngas composition obtained in all simulations are compared to available experimental data from literature. Axial profiles for the volumetric fractions of sugarcane bagasse and char, and gas temperature distribution along the reactor are analyzed. Based on the evaluations of this computational study, it is identified that the multiple components parallel competitive reactions pyrolysis model designated as RAN model is superior in the simulations of sugarcane bagasse gasification due to smaller deviations and better prediction of the char formed in the primary pyrolysis. Furthermore, it is shown that the Boudouard and steam gasification reactions modelling have a smaller impact over the predictive capability of the simulations than the char oxidation reaction. Finally, because the results tend to underpredict the O2 amount in the yielded gas, the present work suggests that an improved kinetic correlation for the sugarcane bagasse char oxidation can enhance the simulation predictive capability.