110th Anniversary: Commentary: CFD as a Modeling Tool for Fixed Bed Reactors

Abstract

Computational fluid dynamics (CFD) is a valuable tool in the modeling of fixed bed reactors. In particular, resolved-particle CFD in which a bed of particles is simulated directly, without invoking a porous media representation, is being used to probe reaction systems and understand the complexities of reactions in heterogeneous systems. Some reviews are now available, and the number of publications is growing. In this contribution, a broad perspective is attempted on what are some of the key issues, what problems should be solved for further progress, and what new techniques might be applied. Topics discussed are the numerical generation and meshing and simulation of beds of complex particle shapes, coupling microkinetics with resolved-particle CFD, validation with in situ experimental methods, and some suggestions for the possible role of visualization techniques and machine learning in the interpretation of the large amounts of information generated by CFD.

Structure-Resolved CFD Simulations of Different Catalytic Structures in a Packed Bed

“…On the other hand, the rigid body dynamics simulations allow the random packing generation of complex particle shapes (e.g., ref 23). However, the corresponding particle-resolved CFD simulations of such random packing of complex particle shapes are still limited because of meshing difficulties with respect to the treatment of particle−particle contact points 42 and computational limitations in terms of handling a large number of mesh elements that are required to retain the intricate details of the complex particle shapes. Because of these reasons, the packing of the complex 7-hole cylinder shape was performed manually with random displacement in each particle position (r, z) and orientation (r, θ).…”

Capturing the effects of particle heterogeneity on adsorption in a fixed bed

“…17,18 Computational fluid dynamics (CFD) modeling can be used to mitigate the effect of these parameters on overall bed performance at small scale to enable appropriate translation to industrial scale. However, many CFD models do not explicitly simulate heterogeneities in porous AC beds due to intrinsic local variations in porosity, 19,20 particle size distribution, 21 and particle orientation 22 and therefore CFD models often do not align with laboratory measurements. The "homogenization" of local variations can invalidate insights gleaned from computational 23 and experimental 11,12 studies of fixed bed adsorbents rendering recommendations for improvements to industrial scale systems inadequate.…”

Optimizing catalyst supports at single catalyst pellet and packed bed reactor levels: A comparison study

“…To optimize catalyst supports at reactor level, a multi‐scale model is required to describe the coupled reaction, diffusion, flow, and heat transfer in catalyst pellet and reactor. A particle‐resolved CFD model should be a good tool to do this optimization, since reaction and diffusion in a catalyst pellet can be well included in this model 16 . Some researchers 17‐20 developed the particle‐resolved CFD models where catalyst pellets are treated as solid regions.…”