Mass transfer evaluation and analytical modeling using composite hollow fiber membrane for syngas fermentation to biofuels

Mass transfer of synthesis gas (syngas) (primarily, carbon monoxide and hydrogen) in the aqueous phase is one of the major drawbacks associated with syngas fermentation. One way of addressing this issue is improving reactor design in order to achieve a higher volumetric mass transfer coefficient (kLa). The overall goal of this project was to evaluate the gas-liquid mass transfer of syngas constituents using various reactor configurations and analytical modeling of composite hollow fiber (CHF) membrane for potential applications in syngas fermentation.;Membranes are currently being employed extensively in water and wastewater treatment applications. There is a significant potential of using membranes in mass transfer for improving the efficiency of syngas fermentation. The novelty of this study is the evaluation of mass transfer and modeling of CHF membranes for syngas fermentation. Moreover, the dissolved CO in the aqueous phase was measured using a novel myoglobin (Mb) - protein bioassay.;The highest volumetric mass transfer coefficient (Ka) of 946.6±64.4 l/h for CO was observed using the CHF membrane module. Similarly, a maximum Ka value of 544.6±18.4 l/h for H2 was obtained using the same reactor configuration. Moreover, model equations: Sh=0.05 P-0.22 Re0.24P0.48 Sc0.33 and Sh=0.21*10 -2* P0.49 Re0.45P0.25 Sc0.33 for CO and H2, respectively, were developed for scaling up the CHF membrane bioreactor. The validation of the model was conducted using polydimethyl siloxane (PDMSXA-2500 and PDMSXA-8300) membrane modules. An acceptable agreement between the overall volumetric mass transfer coefficients determined experimentally (Kaexp) and using models (Kamodel), with a reliability of nearly, 85% was observed.;The study demonstrated the reliability of Mb-protein bioassay for CO analysis, and the potential of CHF membranes in improving the mass transfer of syngas in the aqueous phase for syngas fermentation. Further, the analytical modeling data will be useful for scaling-up syngas fermentation to industrial scale. Moreover, the developed models could be applied to examine the gas-liquid mass transfer coefficients in other systems such as wastewater treatment, syngas to methane, and syngas to carboxylic acid conversions.