(585av) Designing Pellet Shapes for the Dynamic Catalytic Methantion in Fixed-Bed Reactors Using Particle-Resolved CFD Simulations

Using renewable energies for energy supply is a highly dynamic process due to the fluctuating nature of solar power and wind power. Consequently, the reliable satisfaction of electricity demand needs special design and operation. The electrical power storage for later use is one of those actions [1]. Among storage concepts, chemical storages are promising in terms of storage capacity and storage time. The power-to-gas concept converts electrical power to a gas fuel. This can be either hydrogen for injection into the natural gas grid or methane by using the methanation reaction of hydrogen and carbon dioxide.

Typically, the exothermic methanation reaction (∆H = −165.0 kJ/mol) is carried out in catalytic fixed-bed reactors characterized by a small tube-to-pellet-diameter ratio (N). This is due to a desired low pressure drop and likewise a good radial heat transfer to guarantee for a smooth temperature profile. These special arrangements of fixed beds are characterized by wall channeling and local interactions of transport phenomena and local kinetics. However, most of the available models in literature are based on plug flow and pseudo-homogeneous kinetics. Recently, we presented an approach which spatially resolves the pellets in the bed and calculates transport in the gas phase and pellet phase including detailed surface kinetics [2-4].

In this paper we investigate the methanation reaction under transient operation in catalytic low N fixed-bed reactors by using the particle-resolved CFD approach. Different pellet shapes are simulated and their effect on pressure drop, heat transfer characteristics, and reaction performance is quantified. Promising pellet shapes will be 3D printed and will be tested in the lab to validate the findings of the virtual design approach. This procedure has the potential to speed up catalytic pellet shape development and strengthen the understanding of dynamic operations of fixed-bed reactors.

References

[1] Delucchi & Jacobson (2011) Energy Policy, 39, 1170-1190

[2] Wehinger et al. (2015) Chemical Engineering Science, 122, 197-209

[3] Wehinger et al. (2015) Chemie Ingenieur Technik, 87(6), 734-745

[4] Wehinger et al. (2016) AIChE Journal, 62(12), 4436-4452