Issue 10, 2024

Impact of particle-scale models on CFD–DEM simulations of biomass pyrolysis

Abstract

The performance of biomass pyrolysis reactors depends on the interplay between chemical reactions, heat and mass transfer, and multiphase flow. These processes occur over a wide range of scales ranging from molecular to reactor level. Accurate predictions of the reactor behavior necessitate integrating adequate kinetic and particle-scale biomass devolatilization models with reactor-level CFD simulations. Global kinetic schemes and homogeneous particle models neglecting spatial variations are commonly used in CFD simulations. Recent CFD investigations have focused on using a spatially resolved particle description modeled by the mass, species, and energy conservation equations. However, the impact of these particle-scale models on the CFD predictions is unclear. This work investigates the role of particle-scale models of biomass devolatilization in CFD–DEM simulations of biomass pyrolysis in fluidized beds. To this end, spatially resolved and homogeneous particle models using a multistep kinetic scheme (with 24 reactions, 19 solid species, and 20 gas species) are integrated with a CFD–DEM framework. The impact of particle-scale models on three-dimensional CFD–DEM simulations is assessed for low (Bi = 0.26) and high (Bi = 1.6) Biot numbers. The relevant time scales are computed to analyze the coupling among various processes. We show that the particle-scale models primarily affect the transient behavior of species composition and bed hydrodynamics within the fluidized bed and have negligible impact on the product composition and yield at the reactor outlet. The cost of CFD–DEM simulations remained unchanged while using the homogeneous model. In contrast, it increased by 20% using the spatially resolved intraparticle model. This increase in cost is attributed to solving the governing equations of the intraparticle model and storing data for a spatially resolved biomass particle.

Graphical abstract: Impact of particle-scale models on CFD–DEM simulations of biomass pyrolysis

Supplementary files

Article information

Article type
Paper
Submitted
16 Yan 2024
Accepted
08 Mud 2024
First published
10 Mud 2024

React. Chem. Eng., 2024,9, 2552-2568

Impact of particle-scale models on CFD–DEM simulations of biomass pyrolysis

B. K. Kumar and H. Goyal, React. Chem. Eng., 2024, 9, 2552 DOI: 10.1039/D4RE00086B

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