Multi-scale simulations of biomass particle pyrolysis using lattice Boltzmann method
Date
2023-12
Authors
Cho, Yongsuk
Major Professor
Advisor
Michael, James
Kong, Song-Charng
Bai, Xianglan
Passalacqua, Alberto
Rossmanith, James
Committee Member
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Abstract
Biomass pyrolysis is a thermochemical conversion process to generate renewable energy products in an oxygen-deficient environment. Due to the limited understanding of fluid-particle interaction in the pyrolysis process, empirical coefficients are frequently utilized in the numerical modeling approach. This dissertation focuses on multiphase interactions, particularly interested in particle-scale biomass evolution. The lattice Boltzmann method (LBM) simulation was carried out at the representative elementary volume (REV) scale. Various novel interface modeling approaches, such as immersed boundary, overset method, and conjugate heat transfer, are incorporated in the current numerical simulation, including a detailed 3D simulation with fixed particle and single particle-resolving fluidization simulation. The present simulations were validated with the analytical solution, benchmark numerical solution, and pyrolysis experiments. The results indicate that several reactor-scale factors influence internal heat transfer, including particle size, inlet gas velocity, reactor temperature, and particle geometry. The sub-particle scale phenomena also have notable effects in predicting biomass evolution. The pyrolytic product efflux delays the overall conversion by decreasing particle drag and reducing heat transfer into the particle. The particle shrinkage slightly decreases conversion time but is vital in increasing particle drag. The evolution of the biomass particle drag coefficient reveals that the changing inner characteristics of the biomass, such as porosity and permeability, also significantly influence the particle’s drag coefficient. In future investigations, the results from the present simulation can be used to develop engineering models for various transport coefficients to simulate pyrolysis reactors more accurately.
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Type
dissertation