SEPARATION OF CARBON-DIOXIDE BY ASYMMETRIC HOLLOW FIBER MEMBRANE OF CELLULOSE TRIACETATE

Permeation behavior of pure CO2, O2, and N2 and separation characteristics of CO2-air mixtures were examined using hollow fiber modules of asymmetric cellulose triacetate membrane at 30-degrees-C. The ideal separation factor for CO2 relative to N2 ranged from 21 to 24. Permeation behavior for pure CO2 was interpreted in terms of the total immobilization model, i.e., a limiting case of the dual-mode mobility model for glassy polymer, where the diffusion coefficient for Henry's law mode is not assumed to be constant and depends on gas pressure via a modified free-volume model. Based on pure gas permeabilities to CO2, O2, and N2, simulation for the separation of CO2-air mixtures was made using a counter-current plug flow model, and the result fitted the corresponding experimental data fairly well. Membrane plasticization induced by CO2 had negligible effect on permeation to mixture of CO2 and air in the range of CO2 composition up to 50% and upstream total pressure up to 1.5 MPa.