Optimisation of the higher pressure of pressure-swing distillation of a maximum azeotropic mixture
László Hégely, Péter Láng
Abstract
The pressure-swing distillation separation of a maximum azeotropic mixture, water-ethylenediamine, is simulated and optimised. In contrast to our previous works, the top pressure of the high-pressure column (HPC) is considered as an optimisation variable. The total annual cost (TAC) is minimised first without heat integration (NHI), then different energy demand reduction options are applied and optimised: partial (PHI) and full (FHI) heat integration and vapour recompression (VRC) heat pumps. For heat pumps, working fluid flow rate is optimised to minimise the work and thus the compressor costs. Environmental impacts are also considered by calculating CO2 emissions and Eco-indicator 99 (EI99) values. The application of HI does not significantly change the pressure optimum. The lowest TAC is obtained by the optimal PHI, which decreases TAC by 16% compared to the optimal NHI process. Applying VRC is uneconomical, but very favourable environmentally: CO2 emissions and EI99 are reduced by 44 and 95%, respectively.