3D modeling of isothermal adsorption in structured contactors

Structured contactors, such as honeycomb monoliths and laminates, have gained increased interest as sorbent supports in adsorption separations due to their ability to enable process intensification without the trade-offs of traditional packed beds. While 1D models are commonly used in cycle design, they often lump key 3D features of the adsorption process. An accurate description of these features within the contactor, such as spatial variations in sorbent saturation, can be leveraged during the design stage to enhance contactor performance. This work presents a general 3D model for structured contactors under isothermal conditions, capable of capturing flow phenomena like variable cross-flow within unit cells that lead to unconventional sorbent loading dynamics. To illustrate this capability, a case study comparing flow-through (FTM) and wall-flow (WFM) monoliths as air contactors in a direct air CO 2 capture (DAC) cycle was carried out, examining the impact of air flow rate and wall permeability. The analysis highlights differences in fluid dynamics, mass transfer mechanisms, and the evolution of the concentration and loading level of CO 2 on the sorbent for the two configurations, highlighting the 3D effects not captured by 1D models. Finally, a performance comparison based on sorbent requirements and exergy per unit CO 2 captured was carried out, showing under which conditions WFMs may become competitive with FTMs.