Compared novel thermally coupled extractive distillation sequences for separating multi-azeotropic mixture of acetonitrile/benzene/methanol

In this paper, extractive distillation applies to separate acetonitrile/benzene/methanol, the medicine is a compounding of multi-azeotropes via introducing chlorobenzene as a solvent. In order to achieve the purpose of energy saving and CO2 emission reduction, ten novel thermally coupled separation sequences including direct sequences, indirect sequences, hybrid sequences and solvent splitting sequences are established and explored based on extractive dividing wall column (EDWC) and side-stream extractive distillation column (SSED). The corresponding optimal parameters are determined by effective and convenient sequential iterative optimization procedures on the basis of minimized total annual cost (TAC) and meanwhile CO2 emissions are calculated to evaluate environmental impact. The comparison results illustrate that the solvent splitting SSED sequence has more advantages in energy consumption, environment impact and economic cost than others, reducing at most 38.44%, 32.84% and 38.41% in terms of total reboiler duty, TAC and CO2 emissions.