Energy-saving investigation of organic material recovery from wastewater via thermal coupling extractive distillation combined with heat pump based on thermoeconomic and environmental analysis

Cyclohexane and sec-butyl alcohol are widely used in the pharmaceutical and chemical industries. The separation of cyclohexane/sec-butyl alcohol/water azeotropic mixture is of great significance for mitigating environmental risk, recycling solvents, and maintaining developmental sustainability. Based on the COSMO-SAC model, the infinite dilution activity coefficients of the components were calculated, and the final solvent was further obtained by relative volatility and solvent power screening. Taking the total annual cost as the objective function, the extractive distillation process is optimized based on a sequential iterative optimization algorithm. To further reduce the process energy consumption, several energy-saving processes were explored. Energy-saving processes are compared in terms of total annual cost, CO2 emissions, and thermodynamic efficiency. It was found that the total annual cost and thermodynamic efficiency of the processes show an increasing trend, while CO2 emissions show a decreasing trend. The results of stage-exergy indicate that the processes with heat pump are relatively small. The heat pump combined with the thermal coupling extractive distillation process exhibits better thermoeconomic and environmental performance. It provides theoretical guidance for improving the separation and recovery of value organics and energy-saving optimization of processes, which conforms to the theme of sustainable and environmental development. (C) 2020 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.

Automated summary

The study focuses on the separation of cyclohexane and sec-butyl alcohol, optimizing the extractive distillation process and exploring energy-saving processes. The results show a decrease in energy consumption, an increase in total annual cost and thermodynamic efficiency, and a reduction in CO2 emissions.