Characterization of CO2 flux through hollow-fiber membranes using pH modeling

CO2 must be delivered efficiently during large-scale microalgal cultivation. Bubbleless mass-transfer via diffusion through hollow-fiber membranes (HFM) can achieve much higher CO2-transfer efficiency than traditional sparging systems. This study developed and used a model to compute accurate values...

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Bibliographic Details
Published in:Journal of membrane science 2019-12, Vol.592 (C), p.117389, Article 117389
Main Authors: Shesh, Tarun, Eustance, Everett, Lai, Yen-Jung, Rittmann, Bruce E.
Format: Article
Language:English
Subjects:
CO2 delivery
Hollow fiber membrane
Mathematical modelling
Membrane carbonation
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Summary:CO2 must be delivered efficiently during large-scale microalgal cultivation. Bubbleless mass-transfer via diffusion through hollow-fiber membranes (HFM) can achieve much higher CO2-transfer efficiency than traditional sparging systems. This study developed and used a model to compute accurate values for the CO2 flux (JCO2), overall mass-transfer coefficient (KL), and overall volumetric mass-transfer coefficient (KLa) based on the rate of change of pH in batch experiments. A composite HFM comprised of two macroporous polyethylene layers and a nonporous polyurethane layer was tested for CO2 transfer to a sodium carbonate solution using a range of total pressures, inlet CO2 concentrations, and open-end versus closed-end modes of operation. The model accurately computed JCO2 and KLa for pH values above 8. Key trends are that (i) JCO2 and KLa increased with increasing average inlet CO2 partial pressure; (ii) open-end HFMs performed better than closed-end HFMs when the supplied CO2 was less than 100%; and (iii) the available membrane area used for CO2 mass-transfer decreased as the inlet CO2 partial pressure decreased due to depletion of CO2 inside the membrane, especially for closed-end HFMs, since inert gases could not be vented. •A model was used to compute CO2-transfer kinetics from real-time pH measurements.•CO2-delivery kinetics for bubbleless gas-transfer membranes was assessed.•CO2 flux increased approximately linearly with partial pressure in open-end mode.•Relationship of CO2 flux to CO2 partial pressure was non-linear for closed-end mode.•While KL is constant, KLa decreased due to CO2 depletion in closed-end mode.
ISSN:0376-7388
1873-3123
DOI:10.1016/j.memsci.2019.117389