Design and Optimization of Thermally Coupled Distillation Sequences for Purification of Bioethanol

An important problem in the bioethanol production process is the purification of ethanol from a dilute solution, i.e., approximately 10% ethanol in water. The key factor in the purification process is the formation of the ethanol-water binary homogeneous azeotrope, and an additional process is required to obtain high purity ethanol that can be used in motor vehicles. This study examines the design and optimization of three extractive distillation options (two with thermal coupling) for the purification of a representative mixture of ethanol and water. These extractive arrangements can produce ethanol as distillate with the required purity and energy savings, reduction in CO2 emissions, high thermodynamic efficiencies and good control properties.