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Modelling catalytic fixed bed reactors with a small tube-to-particle diameter ratio requires a detailed description of the interactions between fluid flow, intra-particle transport, and the chemical reaction(s) within the catalyst. Particle-resolved computational fluid dynamics (PRCFD) simulations are the most promising approach to predict the behaviour of these reactors accurately, since they take into account the local packed bed structure explicitly. In this work, a conjugated heat and mass transfer model for use in PRCFD simulations is presented in order to couple the fluid flow through the fixed bed with transport and reaction in the porous catalyst, while guaranteeing the no-slip boundary condition at the fluid–solid interface. For this purpose, the solutions of the solid and fluid domain are computed separately and are coupled by calculation and updating the boundary condition at the particle surface. Owing to the consideration of secondary gradients, the developed transfer model is also valid for unstructured calculation meshes containing non-orthogonal cells at the fluid–solid interface. Such meshes are often used to resolve complex geometries, such as a packed bed, in a computationally efficient manner. The coupling approach is validated using cases for which an analytical solution or literature correlations derived from experimental data are available. The simulation results of a short catalytic packed bed with rings catalysing the partial oxidation of n-butane to maleic anhydride exemplify the potential of PRCFD involving reactions to analyse the catalyst performance in great detail. [ABSTRACT FROM AUTHOR]

Single‐particle reactors in lab‐scale are a promising technology to gain an in‐depth understanding of the intricate reaction and transport processes that occur in catalyst particles under operando conditions. It is not described whether the effect of the bounding walls in such narrow flow channels influence the processes at the particle. Therefore, this work applies three‐dimensional (3D) computational fluid dynamics (CFD) simulations to analyze the drag coefficient CD alongside the local and average particle Nusselt number Nup as characteristic local and integral quantities in the range of particle Reynolds numbers 10 ≤ Rep ≤ 103. An equation is derived to correct for the wall effects on CD and Nup and assist the experimenter in the interpretation of measured results. [ABSTRACT FROM AUTHOR]

For slender fixed beds, the void fraction and flow properties are complex topics. Different factors can influence the local bed structure. For statistical analysis, 2800 fixed beds have been generated and the impact of friction factor and reactor‐to‐particle diameter ratio on the distribution has been shown. With particle‐resolved computational fluid dynamics, all local structure effects are taken into account for the flow simulations. Pressure drop measurements and simulations showed that these effects can lead to areas with low flow resistance, leading to overestimated pressure drop by typical correlations up to 85 %. [ABSTRACT FROM AUTHOR]

A methodical procedure for the development of additively manufactured innovative packing structures in laboratory scale is described. Since structural development is an evolutionary process, the focus of this publication is on the methodology of development strategies. Therefore, packing structures based on crystal lattices with flexible dimensioning are created with the visual basic for applications (VBA) tool in Autodesk Inventor®. For the characterization, computational fluid dynamics (CFD) simulations are applied to examine the dry specific pressure drop and the liquid distribution. Calculations of packing‐characteristic values with parameter studies and the above‐mentioned CFD simulations reveal indications of the efficiency of these packings. Selective laser sintering using polyamide 12 (PA 12) as material was applied for additive manufacturing of the packing and the column shell. [ABSTRACT FROM AUTHOR]

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