Enhanced Efficient Extractive Distillation by Combining Heat-Integrated Technology and Intermediate Heating

In order to make full use of the sensible heat of the heavy entrainer adopted in the extractive distillation, an industrial separation case that focuses on the separation of benzene/cyclohexane mixture using sulfolane as entrainer is studied in this work. Furthermore, several retrofitted processes are proposed using the basic case. A side reboiler that utilizes the self-heat or external heat as the heat source is introduced in the separation system to reduce the energy requirement. The economic feasibilities of these sequences are estimated by calculating the total annual cost. Moreover, the thermodynamic analysis and carbon dioxide emissions indexes are also considered to evaluate the energy efficiency and environmental impacts of the modified designs. The simulation results show that the extractive distillation with heat integration 2 (EDHI2) design, which utilizes the entrainer stream to heat the side reboiler and the bottom reboiler, is the most energy-conserving sequence. In addition, the EDHI2 sequence also shows apparent benefits on: economics and environment aspects.