(35d) Three-Dimensional Computational Fluid Dynamics (CFD) Modeling of Post-Combustion Carbon Capture in Intensified Absorption Columns with Structured Packing.

Solvent based post-combustion carbon capture technologies are known to have a potential for considerably reducing carbon emissions from fossil-fuel-fired power plants. Absorption in such systems is typically achieved through absorption columns with structured packing to reduce gas-side pressure drop [1]. While these systems are among the less costly CO₂ capture technologies, they still impose a considerable energy penalty to power plants [2]. Optimizing the rate of CO₂ mass transfer in solvent-based absorption process is complex as it depends on several factors including CO₂ solubility, solvent reaction kinetics and temperature effects on thermophysical properties of the solvent and the flue gas. The overall heat and mass transfer also depends in large part on the hydrodynamics, which in turn, is affected by the packing geometry. Identification of optimal packing geometries necessitates the understanding of key interactions between three-dimensional flow patterns, reaction kinetics, and heat and mass transfer characteristics within the packing device.

In this project falling under the auspices of the Carbon Capture for Industry Impact (CCSI²) program, we aim at obtaining a fundamental understanding of the underlying, governing transport mechanisms in columns with structured packing and in-situ cooling. Therefore, we perform detailed CFD, multiphase flow simulations, through intensified absorption columns (such as in [2]) for MEA solvent. We leverage in our CFD calculations the reaction kinetics, temperature-and-composition-dependent thermophysical properties of MEA-H₂O-CO₂ system, developed under the Institute for Design of Advanced Energy Systems (IDAES) process engineering computational framework.

We model the two phases as multi-component inhomogeneous reacting mixtures of MEA-H₂O-CO₂ solution and flue gas and numerically solve the species transport for participating species separately within each phase. A six species, two-reaction chemical mechanism [3] is used to model kinetics of the MEA-H₂O-CO₂ system. We systematically quantify the effects of flow patterns, liquid load, interfacial area, and conjugate heat transfer to the intensified packing, on the overall CO₂ mass transfer for different geometrical configurations. The implications of these parameters on CO₂ absorption performance and the application of our analyses towards identifying potentially optimal geometries are discussed.

References:

1. Wilcox, J., 2012. Carbon capture. Springer Science & Business Media.

2. Miramontes, E., Love, L.J., Lai, C., Sun, X. and Tsouris, C., 2020. Additively manufactured packed bed device for process intensification of CO2 absorption and other chemical processes. Chemical Engineering Journal, 388, p.124092.
3. Akula, P., Eslick, J., Bhattacharyya, D. and Miller, D.C., 2021. Model Development, Validation, and Optimization of an MEA-Based Post-Combustion CO2 Capture Process under Part-Load and Variable Capture Operations. Industrial & Engineering Chemistry Research, 60(14), pp.5176-5193.