Modeling and simulation of continuous extractive fermentation with CO2 stripping for bioethanol production

摘要

The major bottleneck in industrial alcoholic fermentation is inhibition by the product, which limits the ethanol yield and productivity. An efficient way of overcoming this problem is to use gas stripping to remove the ethanol during the process. In this work, the production of ethanol from sugarcane using extractive continuous fermentation with CO2 stripping was modeled and simulated. The ethanol stripping performance was first evaluated experimentally, varying the specific CO2 flow rate (phi(CO2)), the solution temperature (T-sol), and the initial ethanol concentration (C-EO). The parameters phi(CO2) and T-sol showed positive influences on the stripping kinetics. The proposed CO2 stripping model considered the removal of ethanol and water, as well as changes in the solution volume, and was able to accurately describe the process. Modeling and simulation of the continuous fermentation were performed considering different conditions of feed substrate concentration and cell recycling. The results indicated that ethanol inhibition could be alleviated by CO2 stripping. In addition, the combined use of stripping and cell recycling enabled the use of feed musts containing up to 400 gL(-1) of sucrose, with high substrate conversion, ethanol productivity of 10.79 gL(-1) h(-1), and total ethanol amount produced of 174.80 gL(-1) (22.2 degrees GL), which is about twice the value achieved in an industrial process without ethanol removal by CO2 stripping. This strategy is very promising, compared to traditional processes used in Brazilian distilleries, and has the potential to reduce the global process costs, since it decreases the energy consumed for product recovery and allows the use of smaller fermenters. (C) 2017 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.