Thermodynamic efficiency enhancement of pressure-swing distillation process via heat integration and heat pump technology

Pressure-swing distillation was investigated to separate ethanol/acetonitrile binary azeotrope. The parameters were optimized based on the minimum total annual cost. To implement cost saving, heat pump technology was applied to pressure-swing distillation process and two new pressure-swing distillation processes were explored and studied. The heat-pump-assisted pressure-swing distillation, which only needs a small amount of fresh heat steam, saves 62.8% of the operating cost compared with the pressure-swing distillation. The other process called double-heat-pump-assisted pressure-swing distillation, which needs no fresh heat steam, achieves an operating cost saving by 59.9%. To further analysis of thermodynamic efficiency, the temperature-enthalpy (T-H) diagram and stage-exergy and stage-deficit were studied. Payback period was introduced to evaluate the economy of the processes. The results showed that the payback periods of the new pressure-swing distillation processes are shorter than the suggested 15-year payback period by at least 7.5 years. Both the processes perform well on operating cost saving and they were economical for separating the ethanol/acetonitrile binary azeotrope.