Systematic study of energy-saving bioethanol distillation process with sidestreams: Design and control

Bioethanol is regarded as a sustainable alternative to fossil fuels; however, large-scale production is challenging owing to high energy consumption. In this study, some existing side-stream processes are analyzed and optimized to demonstrate their suitability; consequently, binary side-stream processes are proposed. Two types of sidestream processes are considered: a two-column process with a vapor sidestream (VSP) and that with a liquid sidestream (LSP). The merits and demerits are compared, and a novel three-column distillation process with binary vapor and liquid sidestreams (LVSP) is presented. LVSP incorporates heat integration (LVSP-HI) and combines vapor and liquid sidestreams; the vapor sidestream provides heat to concentrate the liquid sidestream, thus conserving energy. Upon eliminating the liquid sidestream, LVSP is simplified to VSP, whereas eliminating the vapor sidestream results in LSP. This approach offers the most substantial energy-saving performance, as energy consumption is decreased by 28.4-37.3% compared to the other processes. Furthermore, dynamic control simulations confirm that the proposed control strategy within LVSP-HI ensures stable flow, concentration, and temperature control. The results of this study are expected to be applied industrially to bioethanol concentration processes.