Comparison among various configurations of hybrid distillation–membrane setups for the energy efficiency improvement of bioethanol distillery: a simulation study

BACKGROUND: Hybrid distillation–membrane setups have attracted attention in recent years due to their lower energy usage for ethanol purification. Membrane separation processes operate without heating that reduces energy demand. However, it is somewhat challenging to select the optimal material and process for a membrane purifying ethanol, especially to get an ethanol purity of 99.99% with maximum recovery. RESULTS: In this study, three different configurations of hybrid distillation–membrane setups are proposed consisting of distillation–pervaporation/vapor permeation processes by considering ceramic, polymeric and composite membranes. The design of hybrid processes is performed by coupling the membrane model built in Aspen Custom Modeler with a simulator of a distillation column. It was observed that distillation–membrane setups exhibited relatively lower operating energy requirement compared to state-of-the-art distillation with near 70% energy savings for the case of distillation–vapor permeation. In terms of the process, we found that vapor permeation is more feasible than pervaporation due to its lower operating cost. Furthermore, it was determined that ceramic membranes exhibit low areas (about 1.64 to 2.62 m²) for ethanol purification compared to polymeric membranes (about 162.94 to 278.47 m²). It is concluded that hybrid processes are less energy intensive compared to the conventional process for ethanol purification. CONCLUSIONS: The results of the sensitivity analysis revealed that the best configuration to get 99.99% pure ethanol with maximum recovery and least operational cost and capital investment would be distillation and vapor permeation configured with NaA zeolite. These findings would be a useful contribution to process intensification concerning ethanol purification plants.