Advancing Solvent-Based CO2 Capture: Integrated Modeling of Packing and Casing Cavity Section in Rotating Packed Beds

Rotating Packed Beds (RPBs) are poised to replace conventional Packed Bed (PB) towers, advancing solvent-based CO₂ capture through intensified mass transfer processes. Effective modeling is crucial for understanding these intensified phenomena and complex liquid flow patterns during CO₂ absorption in RPB reactors. While the cavity section—located between the packing and the casing—plays a significant role in overall capture efficiency, it is often overlooked in existing models that primarily focus on the packing section. In the cavity section, the liquid flows as droplets and forms a film along the casing wall. This work addresses this gap by integrating two distinct mass transfer methodologies, each adapted to the liquid flow variations in both the packing and cavity sections. The proposed integrated absorption model captures all critical phenomena along the radial dimension, offering a comprehensive simulation of RPB performance. The methodology builds on an existing rate-based, steady-state framework from our previous work, while incorporate a semi-empirical approach to predict mass transfer in the cavity section. A custom model for the packing section uses the shooting method to solve material and energy balance equations, focusing on a monoethanolamine (MEA) solution. The model was validated using up-to-date experimental data for a 30 wt.% MEA solution in a RPB absorber across twenty different tests, considering various conditions such as rotational speed, liquid-to-gas ratio, and lean loading. The predicted outlet gas CO₂ mole fraction aligned closely with experimental results, showing a mean absolute deviation of 4%. Additionally, the simulation enabled detailed analysis of key gas and liquid phenomena along the radial dimension, such as variations in gas phase CO₂ molar flow rate and liquid temperature. Notably, the cavity section enhanced capture efficiency, particularly near the inner casing wall where droplets accumulate to form a film.