Risk Analysis Applied To Bioethanol Dehydration Processes: Azeotropic Distillation Versus Extractive Distillation

Production of anhydrous ethanol in large scale has been made by extractive distillation using solvents such as ethylene-glycol or glycerol. In this work, azeotropic distillation is studied to dehydrate bioethanol using n-octane as entrainer. We use a procedure to account for risk and safety, in addition to economic evaluations, in the process design. A probabilistic methodology is applied for the evaluation of a distance likely to cause death as a risk index. The safety assessment combines a frequency and consequence analysis to calculate process total risk. The approach is applied to the design of ethanol dehydration processes, for which azeotropic and extractive distillation systems are compared. The properties of the solvents affect the inherent process safety. The comparison between the two alternatives is done in terms of individual risk, CO2 emissions and total annual cost. The results show that the azeotropic distillation using n-octane as entrainer presents lower total energy consumption and risk compared to the purification process with extractive distillation using ethylene glycol. The product of the proposed separation scheme is a dehydrated mixture of ethanol and n-octane with 81 % mol (61% vol) ethanol, which can be used to produce gasohol.