USE OF ASYMMETRIC HOLLOW-FIBER MODULES FOR ELIMINATION OF H2S FROM GAS STREAMS VIA A MEMBRANE ABSORPTION METHOD

Asymmetric hollow fibre membrane modules coupled with a concentrated a lkaline solution were investigated both experimentally and theoretical ly for the removal of H2S from gas streams. Each of the modules used c onsisted of a bundle of hollow fibres having an ultrathin layer at the outer edge of the hollow fibre. The hollow fibres were prepared from polysulfone/N-methyl-2-pyrrolidone/1-propanol and polyethersulfone/N-m ethyl-2-pyrrolidone/ethanol polymer solutions. A gas mixture containin g 16-24 ppm of H2S was fed into the fibre lumen and was in countercurr ent contact with a 10% NaOH solution fed in the shell side of the modu les. The effects of membrane area, gas-phase velocity, feed gas pressu re and membrane properties in terms of membrane resistances on H2S rem oval were examined. Laminar parabolic velocity profile was adopted to characterize the flow of the gas mixture in the hollow fibre lumen. Th e numerically calculated results agreed reasonably well with the exper imental data in most cases. Both the experimental and the simulation r esults indicate that unless the resistance of the membranes approaches to zero, the radial concentration gradient of H2S in the hollow fibre lumen is always negligible for the H2S-NaOH (solution) system employe d in this study. (C) 1998 Published by Elsevier Science Ltd. All right s reserved.