Improving the economy and energy efficiency of separating water/acetonitrile/isopropanol mixture via triple-column pressure-swing distillation with heat-pump technology

摘要

The separation of water/acetonitrile/isopropanol ternary mixture is difficult to achieve with conventional distillation. However, pressure-swing distillation (PSD) is one of the most effective methods. This study investigates two PSD processes with different separation order where the W-A-I separation sequence has a better performance in economy, energy consumption and environment. Several energy-saving methods, including heat integration, heat-pump and heat exchanger network, have been introduced for using the sensible heat and latent heat of the process. In addition, the T-S diagrams of overheads from each column in processes with heat-pump are utilized for discussing the feasibility of dry compression. Among all the processes, the PSD process with triple-heat-pump and heat exchanger network (PSD-THP-HEN) requires the lowest cost and energy and emits the lowest CO_2, SO_2 and NO_x. Compared with the PSD-HEN process, 71.4% of TEC and 57.59% of TAC are saved in PSD-THP-HEN, respectively.