Hydrogen separation using asymmetric cellulose acetate hollow fiber membranes

In this study, integrally asymmetric cellulose acetate-based hollow fiber membranes were investigated for the separation of hydrogen/nitrogen gas mixtures commonly found in ammonia plant purge gas. Permeance of pure gases were tested using a short hollow fiber module (23 cm) and a long hollow fiber module (105 cm) to obtain the intrinsic permselectivity of the membrane and to study the pressure buildup in the fiber lumen. Results from the short module test showed that the permeance of hydrogen and nitrogen are independent of pressure and follows an Arrhenius type of relationship with respect to temperature. Experiments with the long module showed that the pressure drop inside the hollow fiber significantly reduced the permeation of hydrogen. Further theoretical analysis was done to explain this behavior. Permeance of the gases were then calculated by incorporating the pressure drop. At 25°C, the permeance of hydrogen and nitrogen was found to be 59.8 and 0.73 GPU respectively, corresponding to a selectivity of 81.7. (Abstract shortened by UMI.)...