Colloquium Series WS 2018/2019 by the Department of Chemical and Biological Engineering
A catalytic fixed-bed reactor is a widely used reactor type in the chemical and process industry. It is a tube filled with catalytically active pellets with gaseous reactants flowing through the bed and being converted into products. There exists models for such a reactor on different levels of detail, starting from simple areaction vary throughout the bed. Under extreme conditions, e.g., small tube-to-particle diameter ratios and highly endothermic or exothermic reactions, the assumptions of the simple models collapse. With computational fluid dynamics (CFD) it is possible to resolve transport phenomena, i.e., momentum, heat, and mass transport, as well as surface reactions, with a high resolution. Particle-resolved CFD is the approach to resolve geometrically every pellet inside the bed, see Fig. 1, which leads to a huge amount of information.
Figure 1: Detailed CFD simulation of a fixed-bed reactor (L=500 mm).
Here, an introduction and applications of this approach is given. Afterwards, validation cases are presented and discussed. The synthetically generated bed consisting of different shapes will be compared with experimental data. Heat transfer and heterogeneous catalytic systems are validated with spatially resolved data. The simulation results are in very good agreement with the experiments. However, there are still open questions when surface reactions are included in the model. Still, with this approach it is possible to explore “in silico” different designs, for example different shapes of pellets, which have a strong influence on reactor performance. In a concluding outlook, the transfer of this CFD approach to electrochemical systems is given, see Fig. 2.
Figure 2: Detailed CFD simulation of a porous electrode in a redox-flow battery (0,25×0,25×0,25 mm).
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