CFD-MRI Reactions – A Combined Measurement-Simulation Approach for Reactive Flow Characterization

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Catalytic processes are of tremendous importance: many everyday life products and technologies require the use of a catalyst. They are used for the valorization of raw materials, conversion of pollutants or waste, or for the production of chemicals and final goods. Up to 90% of all processes in the chemical technology sector make use of a catalyst with 80% of them being heterogeneous catalysis. Due to its importance in the value-added chain, every improvement to catalytic processes will have a manifold economic effect. Knowledge of concentration, velocity, and temperature distribution in a chemical reactor are essential for a detailed understanding of the reaction. From such distribution, it is possible to deduce mass and heat transfer, (side) product formation, and process limitations, giving them a major role in reactor design. Conventional techniques to measure distributions are often invasive or only have one-dimensional spatial resolution at best. CFD calculations require exact knowledge of the boundary conditions and geometry. MRI can measure spatially resolved temperature, concentration, local velocities, and many other quantities. The technique, however, suffers from low resolution, high noise, and long measurement times, which is especially true for gas phase applications. The CFD-MRI method, developed in the group of PI Krause, applies numerical post-processing on MRI data to reduce noise and increase the resolution. At comparably low effort, this was already shown for several non-reactive flows in simple geometries. Aim of the CFD-MRI Reactions project is to develop the CFD-MRI method together with the MRI measurements to make it applicable for reactive flows in complex geometries. This will help to unravel reaction mechanisms. We will use three-dimensional MRI measurements of flow and species concentration from a chemical reaction in a fixed-bed flow reactor. Using this data alone, we identifynot only the underlying geometry as well as the reaction kinetics but also obtain images of the velocity and species concentration without noise and at a significantly higher resolution. This gives a detailed characterization of flow and chemical reactions with high spatial resolution. Firstly, we perform MRI measurements of both liquid and gas flow in an open-cell foam. We use CFD-MRI to find the underlying geometry as well as a high resolution image of the original fields at significantly reduced noise. Secondly, we use spectroscopic MRI to measure concentration maps during a heterogeneously catalyzed liquid-phase reaction in the foam. We will use CFD-MRI to obtain kinetic parameters and will increase resolution and reduce noise of the original measurements. During the project we will not only generate methodological insight but will also publish all software open source to allow access to all researchers. The results from this project bring us one step closer to a full characteracterization of heterogeneously catalyzed gas phase reactions.