Reduction of the energy demand of a second-generation bioethanol plant by heat integration and vapour recompression between different columns

The distillation separation technology of an existing second-generation bioethanol production plant is investigated by simulation with a professional flowsheet simulator. The plant contains three distillation columns in series with increasing pressure. Our aim is to compare different Heat Integration (HI) possibilities for the reduction of external heating and cooling energy demands. Besides ethanol and water, 13 further organic pollutant components are taken into account, which were usually neglected in the literature. Several levels of Heat Integration options are studied: first only streams are integrated (HI-A), then a reboiler and a condenser of two different columns are coupled (HI-B). After that streams and columns are heat integrated (HI-C), finally a vapour recompression heat pump is also applied (HI-C + VRC) in a new configuration. The external energy demand and total annual cost of the different configurations are compared. Considerable energy saving can be achieved by all configurations, but the application of a heat pump is not economical in this case. The influence of changing the pressure of the ethanol concentrating column on the different Heat Integration configurations is also investigated. (C) 2020 The Authors. Published by Elsevier Ltd.