CO₂ Sorption Performance of Composite Polymer/Aminosilica Hollow Fiber Sorbents: An Experimental and Modeling Study

The dynamic CO₂ sorption performance of polymer/silica supported polyethylenimine hollow fiber sorbents (CA-S-PEI), focusing on heat and mass transport effects, is investigated experimentally and computationally during sorption of CO₂ from simulated, dry flue gases. The effect of the nonisothermality on the sorption performance is investigated by varying the module materials of construction. The heat effects are minimized by using a heat conductive module case with a diameter of 0.25 in., and, accordingly, the breakthrough capacities are increased by 30% over a similar module constructed from less conductive components, thereby improving fiber sorbents utilization efficiency. The sorption kinetics in CA-S-PEI hollow fiber sorbents are investigated in terms of flow rates, module packing fraction, module length, and silica particle size. A mathematical model developed previously is successfully utilized to predict various contributions to the overall mass transfer resistance. In fiber sorbents where the amine loading is high, such as those employed here, the sorption process is found to be controlled by intraparticle mass transfer resistances. Unlike fiber sorbents based on physisorbents, the external gas diffusion resistance has minimal effects on the breakthrough capacities, as evidenced with the negligible effects of the module packing fraction on the sorption capacities. Sorption capacities are found to increase with the fiber module length as a result of self-sharpening effects. The increase of particle size increases the mass transfer resistance of the fiber sorbents as illustrated by the more diffuse CO₂ breakthrough fronts in fiber modules containing bigger silica particles. The capacities in fiber sorbents with the largest silica particles exhibit the lowest sorption capacity, as expected