Theoretical study of flue gas CO2conversion to microalgae Chlorella vulgarisbiomass in a bubble column photobioreactor: Tanks-in-series approach, kinetic modeling, and dynamic optimization

The current theoretical research is focused on using flue gas CO2as carbon source to cultivate the microalgae Chlorella vulgarisin a bubble column photobioreactor. The tanks-in-series approach is used to model this semi-batch process. A kinetic model is deployed taking account of light irradiance as well as dissolved CO2and inorganic nitrogen concentrations in the liquid phase. Model parameters are evaluated based on the experimental data reported in the literature. The developed model allows for detailed evaluation of concentration variations of key components along the photobioreactor over the whole process time. Using this method, variables can be distinguished and categorized into two groups: those with considerable spatial distributions and those that are assumed to be lumped and volume-averaged under certain conditions. Simulation results demonstrate a considerable aqueous CO2concentration gradient along the photobioreactor for moderate liquid backflows unlike biomass and dissolved inorganic nitrogen. After performing sensitivity analysis, a multi-objective optimization problem is formulated and solved using parallelized differential evolution to enhance carbon capture rate and biomass productivity. The proposed approach for modeling and optimization improves the carbon capture rate with a reasonable biomass productivity. This method paves the way for developing more efficient and sophisticated bioprocess design procedures.