An analysis is presented for purposes of evaluating the feasibility of using a thin alkaline liquid film (dynamic membrane) generated on a spinning disk to separate H2S from CO2 or CO2 from nonreactive gases. The analysis accounts for the hydrodynamics of liquid flow and dissolved gas transport and reaction in the spinning alkaline film.
Simulations show that gas permeation (absorption at one surface; diffusion, convection and reaction; and desorption at the other surface) is achievable with practical disk radii, and that the liquid may be re-circulated without a separate regeneration process. Consequently, the flowing liquid film functions as a membrane, rather than merely as a scrubbing medium that must be stripped for recycling.
In very thin films (approximately 10 μm), there is insufficient time for transferring CO2 to have its transport facilitated via reversible conversion to bicarbonate ion, whereas the transport of H2S, which instantaneously undergoes acid dissociation to bisulfide ion, is not subject to the same limitation. Consequently, both very high fluxes and very high H2S/CO2 permselectivities (≈160) are predicted in very thin films. By contrast, systems designed to separate CO2 from nonreactive gases such as N2 require a CO2 hydration catalyst such as the enzyme carbonic anhydrase to promote selectivity in very thin films.
These observations underline the advantage of being able to tune the film thickness on a spinning disk by controlling the rotation and liquid feed rates.
|Advisor:||Meldon, Jerry H.|
|Commitee:||Borgers, Cristoph, Ryder, Daniel H., Smith, Kenneth A.|
|Department:||Chemical and Biological Engineering|
|School Location:||United States -- Massachusetts|
|Source:||DAI-B 71/03, Dissertation Abstracts International|
|Keywords:||Acid gas, Facilitated transport, Gas separation, Liquid film, Membrane, Spinning disk, Thin films|
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