Multi-Scale Dynamic Modeling of Radial Flow Fixed Bed Contactors for CO₂ Capture Using a Functionalized Metal–Organic Framework

For solid sorbent-based postcombustion CO2 capture, the contactor technology plays a crucial role in achieving the desired level of technical and economic performance. In this work, radial flow fixed bed (RFFB) contactor technology is investigated. These beds offer considerably lower pressure drop compared with conventional axial flow fixed bed technology. Furthermore, they offer many possible options for flow configurations that can be exploited during cycle design to achieve the high potential of a sorbent. A functionalized metal–organic framework (MOF) that exhibits a step-like isotherm is studied as the sorbent of choice. The MOF has a high heat of adsorption, and due to the steep isotherm, there can be considerable local temperature change upon adsorption/desorption that can considerably affect its performance. To obtain particle level resolution of the transport variables and resulting performance, a particle scale model is developed and coupled with a model of the bulk-scale leading to a multiscale model of the radial flow bed. A multiscale model of an axial flow bed is also developed for comparing the model results with the experimental breakthrough data for the functionalized metal–organic framework. Co-flow and counter-current flow configurations are modeled. An economic model is developed. Operating conditions are optimized. Considering the utility prices for 2017, it is observed that the optimal counter-current and cocurrent RFFBs have 19 and 22.6% lower equivalent annual operating cost (EAOC), respectively, compared to that for the axial flow beds and 13.1 and 17% lower EAOC, respectively, compared to that for the monoethanolamine (MEA)-based capture. For the 2023 utility price, optimal counter- and cocurrent RFFBs have 40.9 and 44.8% lower EAOC, respectively, compared to the MEA-based capture. It is observed that the cocurrent radial flow bed with the flue gas entering at the outer annulus has the best economic performance for this metal–organic framework compared to the counter-current radial flow beds, axial flow beds, and the MEA-based capture.