Modeling and optimization of membrane gas separation based bioreactor plant for bio-hydrogen production by CFD-RSM combined method

A membrane gas separation based bioreactor (MGSBR) as a novel configuration of membrane bioreactors (MBRs) for biohydrogen production is proposed and simulated in this study. A coupled transient Computational Fluid Dynamic (CFD)-biokinetics (modified Gompertz equation) model was developed to simulate the batch stirred fermenter integrated to the Pd-Ag membrane unit. The turbulent gas-liquid fluid dynamics, substrate consumption, cumulative H2 production, and volumetric mass transfer coefficient were predicted by the numerical simulations. A slight increase is seen in biohydrogen production by sparging the MGSBR with CO2-concentrated recycle flow, indicating no significant mass transfer limitations in the system. Finally, the established CFD model was coupled with response surface methodology (RSM) to find the best operating conditions for pH, inlet gas flow rate, and impeller speed to maximize the biohydrogen production. The CFD-based RSM results gave the optimum conditions as pH = 6.2, impeller speed of 115, and inlet gas flow rate of 2.4 × 10- 5 that leads to maximum hydrogen production of 24.09 L. This work confirms the potential interest of the proposed MGSBR for biohydrogen production and the applicability of the coupled CFD-RSM modeling for the optimization of the studied system avoiding expensive and time-consuming experiments