Multiscale simulation of biomass gasification in fluidized bed reactors

Biomass fluidized bed gasifier (BFBG) is core equipment for producing sustainable syngas, which is one of the alternatives to replace fossil fuels in producing green fuels or chemicals. Multiscale simulations provide powerful tools to reveal the biomass gasification behaviors in fluidized bed reactors, thereby supporting the design, optimization, and scaling-up BFBG. This paper systematically reviews sub-models (molecular-scale, particle-scale, and meso-scale models) and reactor-scale models for the multiscale simulation of the BFBG. First, the advantages and disadvantages of various drying models, pyrolysis kinetics, and char gasification models at the molecular scale are discussed. The particle-scale models (i.e., zero-dimensional, corrected zero-dimensional, interface-based, and two-/three-dimensional models) are analyzed in terms of their accuracy and computational demands. The development of meso-scale models is also addressed. Additionally, machine learning methods used to assist in developing sub-models across different scales are summarized. Then, from the perspective of multiscale coupling between models at various scales, the strengths and limitations of reactor-scale models for multiscale simulation of BFBG are analyzed. Finally, the conclusions of this review and perspectives for future research, which aim to develop fast, reliable, and efficient models for the multiscale simulation of BFBG, are presented.