Multiscale Coupling Framework for Modeling of Large-Size Biomass Particle Gasification in Fluidized Beds

Abstract

This paper is devoted to addressing a multiscale coupling framework for modeling of large-size biomass particle gasification in fluidized beds, where the large diffusions due to the temperature and concentration gradients in large-size particles strongly affect gasification process. Directly incorporating a single particle model (SPM) into a conventional fluidized-bed model tremendously increases the computational cost. In this paper, we propose a loose coupling framework between the SPM and the discrete element method (DEM)–Eulerian continuum model. The SPM is based on detailed reaction mechanisms and has been validated against experimental results. The rationality of the coupling is based on the observations from the SPM that the temperature is the dominating factor and the surrounding gas velocity is a secondary one to the gasification. For this purpose, we use sand particles as thermal carrier to keep the surrounding temperature statistically stable. We then simulated the gasification of beech wood particles mixed with sand particles in a bubbling fluidized bed. The entrainment and mixing of wood particles with sand particles can be observed and the particle distribution and the composition of gas phase can be obtained. The proposed method provides a potential way to account for the gasification process of large-size biomass particles in fluidized beds.