CFD Investigation of CO2 Capture Process with K2CO3 Sorbents in a Bubbling Fluidized Bed

This study employs a Computational Fluid Dynamics (CFD) approach based on the Two-Fluid Model (TFM) to investigate the CO2 capture characteristics in a bubbling fluidized bed reactor using potassium carbonate (K2CO3) as the sorbent. The simulations are conducted at five superficial gas velocities ranging from 1.5 to 3.5 times the minimum bubbling velocity (umb = 0.26 m/s), with a particle diameter of 0.4 mm, particle density of 2300 kg/m3, and an initial solid volume fraction of 0.55. The gas mixture consists of CO2, H2O, and N2 at a molar ratio of 0.1:0.1:0.8 and a temperature of 343 K. First, the numerical simulation was validated against experimental data reported in the literature, confirming its accuracy in quantitatively describing the adsorption process. Subsequently, the distributions of CO2 concentration and adsorption reaction rate in both the bubble phase and the emulsion phase were analyzed under different superficial gas velocities. The simulation results indicate that CO2 concentration and adsorption reaction rate in both phases decrease along the bed height. Compared to the emulsion phase, the bubble phase exhibits higher CO2 concentration and gas temperature but a lower adsorption reaction rate. As the gas velocity increases, CO2 concentration rises in both the bubble and emulsion phases, accompanied by an increase in the proportion of the bubble phase, and a higher CO2 concentration at the reactor outlet. Further comparison of CO2 concentrations in the bubble and emulsion phases at the upper part of the bed with the outlet concentration reveals that the outlet CO2 primarily originates from the unadsorbed portion within the bubble phase, while the contribution from unadsorbed CO2 in the emulsion phase is almost negligible.