Submitted to: Journal of Environmental Engineering
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/30/2008
Publication Date: 7/1/2008
Citation: Liu, S.X., Hermanowicz, S.W. 2008. Empirical correlation of volumetric mass transfer coefficient for a rectangular internal-loop airlift bioreactor. Journal of Environmental Engineering. 7(4):411-415.
Interpretive Summary: Internal-loop airlift bioreactors are a class of novel reactors that consist of a reaction vessel divided into two vertical chambers with instrumentation for temperature, dissolved oxygen, and gas mass flow measurement, and a cold water supply for cooling purposes; the gas that powers both motion of the fluid in the reactor and the reaction in the vessel. They are widely used in biotechnology such as fermentation where a certain degree of agitation is required without the use of mechanical stirrers due to the nature of reactants handled, such as the cultivation of biological organisms and enzymatic bioconversion. Designing and optimizing internal-loop airlift bioreactors require basic understanding of underlying system under different operating conditions. Among many design parameters of internal-loop airlift bioreactors, volumetric mass transfer coefficient is the most important factor in determining gas transfer in the reactor hence the conversion rate of raw materials to products. This study employed fluid hydrodynamics theories with existing experimental data to develop a semi-empirical model that may be used for future airlift bioreactor design. This work could benefit the design and operation of bioreactors used for enzymatic processing of cellulosic and hemi-cellulosic biomass for non-cereal biofuel production.
Technical Abstract: An empirical correlation of volumetric mass transfer coefficient was developed for a pilot scale internal-loop rectangular airlift bioreactor that was designed for biotechnology. The empirical correlation combines classic turbulence theory, Kolmogorov’s isotropic turbulence theory with Higbie’s penetration theory. The simulation results based on the correlation suggested that the loading of polyethylene granules (for microbial colony support) in the bioreactor had little effect on the mass transfer coefficient of oxygen gas in the reactor, however, the gas superficial velocity was showed to affect the mass transfer coefficient substantially. These simulation results are comparable to the experimental results from a similar, albeit smaller in volume, three-phase internal-loop rectangular reactor in the literature.