Comparison between Single and Multi-Effect Evaporators for Sugar Concentration in Ethanol Production
Prado, C.
Souza, O.
Sellin, N.
Marangoni, C.
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Prado C., Souza O., Sellin N., Marangoni C., 2015, Comparison between Single and Multi-Effect Evaporators for Sugar Concentration in Ethanol Production, Chemical Engineering Transactions, 43, 541-546.
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Among lignocellulosic materials, the waste generated in banana cultivation, such as the discarded fruit, peels, leaves and pseudostem demonstrates great potential for ethanol production. After hydrolysis, a concentration step of the hydrolyzate material is carried out to increase the amount of sugar available for the subsequent fermentation process, which is directly related to ethanol production. Despite being widely employed, the concentration continues to demonstrate certain limitations with respect to its use for cellulosic materials in second generation ethanol production due to the high energy consumption. Besides, the use of banana waste is not completely established, so studies concerning this process are important to evaluate all productive routes. Based on this, simulations of concentration of sugar from hydrolyzed lignocellulosic banana waste were carried out using the software Aspen HYSYS ®, aiming to obtain a concentrated broth containing 65 g/L of sugars with a simple evaporation system operating an atmospheric pressure. Same conditions were used to compare these results with a multi-effect evaporation system. Glucose concentration, the total amount of available sugars and inhibitors concentration were evaluated. Results have demonstrated that the energy consumption with multi-effect evaporator system is low with all residues: discarded fruit (636 kJ/h), banana peels (720 kJ/h) and pseudostem (734 kJ/h). Similar behavior was found for steam requirement: respectively 0, 2397 kg/h 0.3317 kg/h 0.3385 kg/h. As it is known, this is due to the fact that the steam generated in the first effect is used as heating fluid of the next effect. Even the multi-effect system proposed did not reach the 65 g/L of glucose with all residues, it is considered better than a single evaporator because the hydrolyzate streams contain additional sugars that can also be metabolized to ethanol during fermentation.
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