Pressure-Swing Dividing Wall Column with Multiple Binary Azeotropes: Improving Energy Efficiency and Cost Savings through Vapor Recompression

This work introduces a novel thermal integration scheme for a pressure-swing distillation train used to separate a mixture of methanol/ benzene/acetonitrile. This mixture typically forms three azeotropes as shown through developing its residue curve map with two distillation boundaries at atmospheric pressure. This ternary mixture is traditionally separated via a triple column pressure-swing distillation (TCPSD) scheme, in which, all columns operate at different pressures. Here, the first two columns of the TCPSD are proposed to be replaced by a single column having a dividing wall that allows heat transfer through it. Thus, the resulting scheme is called pressure swing dividing wall column (PSDWC). Aiming to improve its performance, further advancement is subsequently made by developing the heat intensified PSDWC (HiPSDWC) and vapor recompressed PSDWC (VRPSDWC). The performance of these proposed schemes is evaluated in the context of energy saving and total annual cost (TAC). Among these configurations, it is investigated that the VRPSDWC secures the best performance, providing a 75.67% savings in external energy consumption, which is 2.45 times that of the HiPSDWC. The attractiveness of the best performing VRPSDWC is further quantified by a 13.25% TAC savings and a reasonably short payback time of 2.97 years (3.91 years with considering penalty of 10%).