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9. Enhanced Transverse Dispersion in 3D-Printed Logpile Structures: A Comparative Analysis of Stacking Configurations.

Author

Rosseau, Leon R. S., van Aarle, Martijn A. A., van Laer, Egbert, Roghair, Ivo, and van Sint Annaland, Martin

Subjects
COMPUTATIONAL fluid dynamics, PRESSURE drop (Fluid dynamics), REYNOLDS number, CHEMICAL processes, CHEMICAL reactors
Abstract

Three-dimensionally printed logpile structures have demonstrated the tunability of the transverse dispersion behavior, which is relevant in the context of chemical reactor design. The current modeling study aims to further investigate the trade-offs in such structures, extending the range of geometries investigated and addressing the limitations associated with the pseudo-2D nature of previous experiments. The relative transverse dispersion coefficient and pressure drop were determined using computational fluid dynamics simulations in OpenFOAM for structures with different stacking configurations, porosities and scaling of the structures' unit cell along the secondary transverse axis. The latter could not be varied in previous experiments, but the current results demonstrate that this limitation suppresses vortex shedding in structures with high porosity. These vortices significantly enhance the transverse dispersion. By using a staggered stacking configuration on both transverse axes, an earlier onset of this phenomenon could be realized. Importantly, operation in this regime could be achieved without an equivalent increase in pressure drop, offering a favorable operating trade-off. The findings demonstrate that at low Reynolds numbers, the studied structures consistently outperform randomly packed beds of spheres, highlighting their potential for chemical process intensification. [ABSTRACT FROM AUTHOR]

Published
2024
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16. Stability of potassium-promoted hydrotalcites for CO2 capture over numerous repetitive adsorption and desorption cycles

Author

Xin, Kun, Boon, Jurriaan, van Dijk, H.A.J., van Sint Annaland, Martin, Xin, Kun, Boon, Jurriaan, van Dijk, H.A.J., and van Sint Annaland, Martin

Abstract

Hydrotalcite-based adsorbents have demonstrated their potential for CO2 capture, particularly in the sorption-enhanced water-gas shift (SEWGS) process. This study aims to investigate the long-term stability of a potassium-promoted hydrotalcite-based adsorbent (KMG30) over many repetitive cycles under various operating conditions. The stability of the adsorbent, both in terms of its structure and sorption capacity, is examined through multiple consecutive adsorption and desorption cycles. However, it is observed that the capacity for CO2 adsorption decreases when subjected to many repeated cycles of CO2 adsorption followed by N2 flushing, or to many repeated cycles of H2O adsorption followed by N2 flushing. In-depth investigations employing various techniques such as thermogravimetric experiments, XRD, BET, and SEM-EDX analyses were conducted to elucidate the underlying phenomena that can explain this observed behavior. The former can be attributed to aggregation of K2CO3 from the sorbent during the CO2 adsorption and N2 flushing cycles (which can be reversed by re-dispersing the K2CO3 either by exposure to air or by processing the sorbent with cycles of CO2/H2O adsorption followed by N2 flushing), whereas the latter is ascribed to the only partial regeneration of the reactive site (referred to site C in earlier work), most likely associated with K2CO3 modification on MG30. In this case, morphological changes were found to be insignificant. Remarkable stability of KMG30, as known from SEWGS process studies, was confirmed during cycles of CO2 adsorption/steam purge. These findings significantly enhance our understanding of the stability of potassium-promoted hydrotalcite-based adsorbents and provide valuable insights for the design of diverse sorption processes.

Published
2024

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