Mathematical model of the CO₂ solubilisation reaction rates developed for the study of photobioreactors

Abstract

The transfer of CO2 between the gas and liquid phases is one of the most important processes that occur during cultivation of microalgae in photobioreactors. A key factor that influences the rate of mass transfer is the concentration of CO2 in the liquid phase, which, in turn, depends on the rates of the reactions involved in CO2 solubilisation. This work presents a mathematical model for the rate of these solubilisation reactions with correlations that allow the calculation of the model parameters at temperatures from 5°C to 40°C. The model was validated using data of CO2 mass transfer from the literature obtained with two experimental systems: a bubble column for CO2 absorption and a flat‐panel photobioreactor. The model was further used to show that the increase in the rate of CO2 absorption that occurs at higher pH values is due to increased consumption of CO2(aq) in the solubilisation reactions and not to an increase in kLa. The pH decreases as CO2 is solubilised, therefore, when pH is controlled, the mass transfer rate is higher than it would be without pH control. Our model can be used as a tool to guide the operation, control and scale‐up of photobioreactors for the cultivation of microalgae.

Oxygen Suppresses Light-Driven Anodic Current Generation by a Mixed Phototrophic Culture

“…The pH of the anolyte was controlled via dosing of 1 M HCl solution to maintain a pH of 8.0 ± 0.2, using a pump connected to programmable logic controller (PLC) system to provide optimum condition for a microbial consortium performance as biocatalyst, 20 to decrease riboflavin photodegradation in the presence of sodium bicarbonate buffer 21 and to increase solubilization of CO 2 . 22 Analytical Methods. The current density was calculated by dividing the observed anodic current, as recorded by a multichannel potentiostat (CHI1000B, CH Instruments), by the projected anode surface area.…”

Feasibility of a microalgal wastewater treatment for the removal of nutrients under non‐sterile conditions and carbon limitation

“…It has been established that microalgae can treat wastewater by removing excessive nutrients and metals . However, given that microalgae require CO 2 to grow, the consumption of high amounts of dissolved CO 2 can result in an imbalance of the carbonate system in aqueous systems, potentially leading to significant changes in pH and alkalinity. Maintaining the pH of the system is essential, as this also influences whether the NH 3 or NH 4 + species predominate in the system.…”

Dynamic Modeling of the Microalgae Cultivation Phase for Energy Production in Open Raceway Ponds and Flat Panel Photobioreactors

“…The flat panel reactors are positioned vertically, closely spaced, to reach a higher photosynthetic efficiency through selfshading of the panels (Rawat et al, 2013). As for the open raceway pond, the main geometric characteristics have been taken from the literature (Janssen et al, 2003;Sierra et al, 2008;Pruvost et al, 2011;Ruiz et al, 2013;Kochem et al, 2014;Sugai-Guérios et al, 2014) and presented in Table 2 and Figure 2.…”