Insight into separation of azeotrope in wastewater to achieve cleaner production by extractive distillation and pressure-swing distillation based on phase equilibrium

Abstract

There are a large number of azeotropes in the binary system of alkanes and alcohols in the industrial wastewater from the reaction of vanadium pentoxide with alkanes to produce alkylvanadate. In order to protect the environment, utilize resources and clean production, the extractive distillation process with high boiling solvent as extractant is usually used to separate the azeotropes in industrial products. However, some intermediate-boiling solvents compared with the two key components to be separated are used as extractant in extractive distillation. In this work, the binary azeotropic system of n-heptane and isoamyl alcohol in wastewater was separated by extractive distillation with intermediate-boiling solvents, pressure-swing distillation and pressure-swing distillation with thermal integration. The binary interaction parameters of isoamyl alcohol and butyl acetate were obtained by correlating and regressing the experimental data of vapor-liquid equilibrium at atmospheric pressure. Taking total annual cost minimum as the objective function, the optimal design parameters of the three processes were obtained by sequential iteration method. Compared with the extractive distillation and pressure-swing distillation, pressure-swing distillation with thermal integration can save the cost up to 29.38%, increase the thermodynamic efficiency up to 445.39%, reduce the global warming potential up to 39.34% and the decrease the acidification potential up to 39.34%. This work provides an effective reference for better separation of azeotropes and wastewater treatment.