Process design, intensification and control of triple-column pressure-swing distillation for the separation of methyl acetate/methanol/ethyl acetate

Abstract

In this article, the design, intensification and control of triple-column pressure-swing distillation (PSD) for the separation of valuable methyl acetate, methanol and ethyl acetate are explored from the aspects of economy, environmental index and thermodynamic efficiency. Firstly, based on feed composition and thermodynamic features of methyl acetate/methanol/ethyl acetate, we feed the methyl acetate product back to PSD columns and propose two novel triple-column PSD processes combining pure azeotropic agents (ATPSD). Then a parallel genetic algorithm is used to finish the global optimization of developed processes. The heat-integrated ATPSD (ATPSD-HI) can be further developed according to pressure arrangement. Additionally, the heat pump assisted technology is introduced. The comparison results of twelve alternatives demonstrate that ATPSD1 can achieve 14.8% total annual cost (TAC) reduction in comparison with conventional PSD process. The heat pump assisted processes have the highest thermodynamic efficiency show significant advantages of energy saving and reduction of CO₂ emission, while the impact of the payback period needs to be considered when evaluating their TAC. More importantly, ATPSD1-HI significantly saves total energy cost 58.3%, TAC 49.8%, reduces CO₂ emission by 59.7% and increases the thermodynamic efficiency by 101.0%. Finally, a robust control structure with the composition control and recycled methyl acetate flow control is developed.