Estudo do desempenho de eliminadores de névoa na fermentação alcoólica extrativa

• Autor(a) principal: Martins, Taise Bonfim
• Data de Publicação: 2021
• Tipo de documento: Tese
• Idioma: por
• Título da fonte: Repositório Institucional da UFSCAR
• Texto Completo: https://repositorio.ufscar.br/handle/ufscar/15096
• topic: Produção de etanol; Fermentação extrativa; Arraste gasoso com CO2; Biorreatores pneumáticos; Eliminadores de névoa; Ethanol production; Extractive fermentation; Gas stripping with CO2; Pneumatic bioreactors; Mist eliminators; ENGENHARIAS::ENGENHARIA QUIMICA

The ethanol removal by gas stripping with CO2 offers a potential way to minimize the inhibitory effects of ethanol on yeast cells during the alcoholic fermentation, allowing higher ethanol volumetric productivity compared to the conventional process. In the present study, the hydrodynamics and mass transfer characteristics of ethanol stripping with CO2 were evaluated for different models and working volumes of pneumatic bioreactors, 2.0, 5.0 and 10.0 L. Furthermore, mist eliminators were investigated in order to increase the liquid-gas mass transfer as well as to decrease the entrainment of the droplets carried along with the gas stream, allowing a higher ethanol enrichment in the vapor phase. Firstly, the ethanol removal from alcoholic solutions by gas stripping was evaluated for a 2.0 L pneumatic bioreactor operated in bubble column (BC), concentric-tube airlift (CTA), and split-cylinder airlift (SCA) configurations in order to determine the model that allows higher mass transfer coefficients. The results showed that the three pneumatic reactor models promoted the removal of similar amounts of ethanol in the range of specific gas flow rate investigated. The same behavior was observed for the three scales, although the 10.0 L bioreactor allowed a decrease in the water removal. Then stripping experiments in alcoholic solutions were performed using a 10.0 L bubble column reactor and different prototypes of mist eliminators. It was observed that the mist eliminators were able to enhance the mass transfer, resulting in higher ethanol removal coefficients (kE) and ethanol entrainment factors (FAE), compared with the assays carried out without the device. Finally, extractive ethanol fermentations were conducted in a batch mode using the mist eliminator on the top of the reactor. Monitoring the liquid phase during the extractive fermentation showed an increase in ethanol productivity compared to that obtained in the conventional process. This result was due the use of stripping technique along the cultivation, but it was not because of the mist eliminator effect. On the other side, monitoring the vapor phase revealed that the mist eliminator prototype composed by glass spheres decreased the entrainment of the liquid droplets carried along with the gas phase, resulting in lower water content in the gas stream leaving the reactor, compared to that observed in the extractive fermentation performed without the prototype. Therefore, mist eliminators can increase the ethanol selectivity of this separation process, allowing a decrease in the costs concerning the recovery and concentration of the product removed by gas stripping.