Enhanced Mass Transfer in Microbubble Driven Airlift Bioreactor for Microalgal Culture

Kezhen Ying, Mahmood K. H. Al-Mashhadani, James O. Hanotu, Daniel J. Gilmour, William B. Zimmerman

Department of Chemical and Biological Engineering, University of Sheffield, Sheffield, UK.
Department of Molecular Biology and Biotechnology, University of Sheffield, Sheffield, UK.

DOI: 10.4236/eng.2013.59088                

Abstract

In this study, the effect of microfluidic microbubbles on overall gas-liquid mass transfer (CO₂ dissolution and O₂ removal) was investigated under five different flow rates. The effect of different liquid substrate on CO₂ mass transfer properties was also tested. The results showed that the K_La can be enhanced by either increasing the dosing flowrate or reducing the bubble size; however, increasing the flow rate to achieve a higher K_La would ultimately lower the CO₂ capture efficiency. In order to achieve both higher CO₂ mass transfer rate and capture efficiency, reducing bubble size (e.g. using microbubbles) has been proved more promising than increasing flow rate. Microbubble dosing with 5% CO₂ gas showed improved K_La by 30% - 100% across different flow rates, compared to fine-bubble dosing. In the real algal culture medium, there appears to be two distinct stages in terms of K_La, divided by the pH of 8.4.

Keywords

Microbubbles; K_La; CO₂ Capture; Algal Culture

Conflicts of Interest

The authors declare no conflicts of interest.

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