Thermal Management in Solid Sorbent CO ₂ Capture through Fluidization: Experimental and CFD Studies

Adsorption-based CO2 capture using solid sorbents is a promising alternative to conventional amine scrubbing. This study presents a combined experimental and computational investigation of the adsorption of CO2 on zeolite 13X under packed and fluidized bed conditions. The adsorbent particles, with an average size of 1.8 mm, were characterized for pore structure, size distribution, and cold-flow experiments conducted to determine minimum fluidization velocity and bubble dynamics. The breakthrough experiments were performed with a simulated flue gas mixture (20 vol % CO2 and 80 vol % N2) at multiple gas flow rates in both reactor configurations, measuring axial temperature, and CO2 concentration profiles. A transient Eulerian-Eulerian two-fluid model was developed in ANSYS Fluent 21.1.1 with extended capabilities to incorporate the adsorption kinetics (Linear Driving Force model) and associated heat effects through User-Defined Functions (UDFs). The combined experimental and numerical results demonstrated that fluidization effectively reduced the peak bed temperature by approximately 8 K, improving heat dissipation and adsorption uniformity. Further, the bed fluidization enhanced heat and mass transfer due to vigorous particle mixing and bubble-induced convection, resulting in bed saturation times up to four times shorter than those observed in packed beds. The CFD model effectively captured the flow regime, temperature evolution phases, and CO2 breakthrough curves. However, the peak temperatures and the shape of breakthrough curves were slightly overestimated due to assumptions of uniform bed porosity and the omission of axial dispersion effects, which are known to influence heat dissipation and mass transfer in real systems.