Thermal analysis of extractive fed-batch ethanol fermentation with CO2 stripping: modeling and simulation

Ethanol production from sugarcane is an exothermic process. The heat generated during the fermentation is removed by heat exchangers, using cooling water. However, it is difficult to keep the fermentation process close to the optimum yeast temperature, especially in hot months. In this work, extractive fermentation with CO2 stripping was evaluated as a way to overcome this operational problem besides reducing the water demand in the process. A mathematical model was developed to describe conventional and extractive fed-batch ethanol fermentation processes. Simulations were performed to determine the effect of different gas flow rates on heat removal from fermentations at different must substrate concentrations (Csm). With a Csm of 285.7 g/L and a CO2 flow rate of 0.7 vvm, the consumption of cooling water in the extractive fermentation decreased by up to 62.1% compared to the conventional process, keeping the broth temperature constant. Thus, the potential of this technique to increase the total ethanol content and reduce the cooling water consumption was demonstrated. Furthermore, there were decreases in the amount of vinasse and steam consumption in the distillation step.