Abstract
Catalytic structured foam reactors show promising characteristics for process intensification such as low pressure drop, high specific surface area, and remarkable heat transport. Especially for the design of small-scale dynamically operated reactors, the understanding of heat transport is crucial. With computational fluid dynamics (CFD), we can thoroughly investigate the thermal field of the coupled gas/solid under reaction conditions and understand heat transport in structured reactors. In the past, we mimicked the heat production during exothermal reactions with uniformly distributed volumetric heat sources in the solid. Here, we compare thermal fields of such simplifications with full-model calculations using the strongly exothermal CO oxidation as a model reaction. We find that heat flows of the reaction and of artificial heat source calculations match well, and reliable mean temperature increases can be computed. While it cannot compute exact hot-spot magnitude and location, this method helps to determine heat removal mechanisms and estimate thermal stress.
Highlights
Open-cell foams are interconnected cellular materials that combine desirable characteristics for catalyst carriers such as low pressure drop, high surface areas, and excellent radial heat transport.[1,2] When used as catalyst carriers, they allow us to decouple and optimize catalyst coatings and the foam individually.[3]
To study heat flows and temperature fields of open-cell foam catalyst carriers decoupled from actual reactions, we proposed to mimic the exothermicity of the reaction through uniform volumetric heat sources in the solid foam.[36]
The heat source approximation can predict global heat flows quite accurately. This allows for rapid prototyping of the catalyst carriers with efficient heat removal as multiple simulations can be carried out fast
Summary
Open-cell foams are interconnected cellular materials that combine desirable characteristics for catalyst carriers such as low pressure drop, high surface areas, and excellent radial heat transport.[1,2] When used as catalyst carriers, they allow us to decouple and optimize catalyst coatings and the foam individually.[3]. Hot spots are undesired during exothermal reactions as they might harm the catalysts through sintering or cause thermal runaway (e.g., during Fischer−Tropsch synthesis).[5] The outstanding potential of open-cell foams for process intensification has been sChHow[4] ncofomrbtuhsetioCnO, 2anmdethoathneartiopnr,oFceisscshese.r6−−8TrAopsrcehcesnytntshtuesdiys,, showed that open-cell foams embedded in reactors (i.e., structured reactors) are only advantageous over conventional pellet-bed reactors when heat is mainly removed radially via conduction (i.e., to the wall) and not axially via convection (i.e., through the fluid).[9] For the design of efficient and robust structured reactors, it is important to understand the fundamental heat transport mechanisms, namely, conduction, convection, and radiation. The thermal behavior, and the performance of catalytic foams during exothermal (and endothermal) reactions needs more extensive research to design foams perfectly tailored for their usage.[10,11]
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