The Fabrication of Thin Films on Hollow Fibre Membrane Contactors for Promoting the Absorption of Carbon Dioxide

THE FABRICATION OF THIN FILMS ON HOLLOW FIBRE MEMBRANE CONTACTORS FOR PROMOTING THE ABSORPTION OF CARBON DIOXIDE
Joel Yong, Sandra Kentish, Frank Caruso

The use of a carbonic anhydrase (CA) enzyme as a reaction promoter may overcome the reduced overall absorption rates exhibited by K₂CO₃ relative to MEA. However, these enzymes tend to denature at higher temperatures and would not be suited for use in circulation within a traditional absorber-stripper process. The immobilization of the enzyme within the gas absorber or onto a membrane contactor can increase enzyme stability and avoid thermal denaturation in the stripper.

It was found in this investigation that the deposition of CA as a thin film on the surface of a flat sheet membrane was able to increase the membrane resistance to wetting by closing up the membrane pores. The scaling up of the immobilisation technique to hollow fiber membranes also yielded similar results, where the CO₂ mass transfer rates were significantly increased.

The hollow fibers were operated at elevated temperatures of 35°C and 50°C to determine the survivability of the CA in the membrane contactor at those temperatures. The immobilized CA was also contacted with toxic gases such as nitric oxide (NO) and sulfur dioxide (SO₂) or their associated nitrate NO₃- and sulfate SO42- ions in solution, as these are components of post-combustion gas streams that can inhibit the activity of the CA. The exposure of the immobilized CA to the dry gases or their associated anions did not significantly affect the activity of the immobilized CA. Dr Joel Yong has recently completed his PhD on this topic