Effects of Particle Shrinkage and Devolatilization Models on High-Temperature Biomass Pyrolysis and Gasification

Abstract

The effects of two different particle shrinkage and devolatilization models on biomass pyrolysis and gasification behavior in a high-temperature (1400 °C) entrained-flow reactor have been studied employing a three-dimensional Eulerian-Lagrangian computational fluid dynamic model in the framework of open-source codes, OpenFOAM. Both qualitative results (temperature distribution, gas composition, and particle distribution) and quantitative results (pyrolysis time, syngas production, carbon conversion, and particle residence time) are presented and analyzed. Results show that particle shrinkage models significantly affect the simulation results and the constant volume model predicts a faster devolatilization rate, higher H2, CO, and CH4 productions, lower CO2 production, higher carbon conversion, and longer particle residence time than the constant density model. However, the two devolatilization models employed give consistent results on the exit syngas production and carbon conversion, although the constant rate devolatilization model predicts a faster devolatilization rate and a longer particle residence time than the single kinetic rate devolatilization model. In addition, the sensitivity of the kinetic constants for the constant rate devolatilization model is also tested. These trends are the same for both the biomass pyrolysis and gasification applications. Moreover, the predicted results are also compared to the experimental data available in the literature, and the differences resulting from different particle shrinkage and devolatilization models are highlighted. © 2015 American Chemical Society.