Design and multi-objective optimization of reactive-extractive dividing wall column with organic Rankine cycles considering safety

Abstract

It is challenging and inevitable for the separation of ternary azeotropic mixture with multiple azeotropes in wastewater. Previous research proposed a hybrid double column reactive-extractive distillation (DCRED) process to separate ternary azeotropes in wastewater, which inspires the investigation into the reactive-extractive dividing wall column (REDWC) in this study. However, the design and waste heat recovery of REDWC have not been fully studied. To this end, two hybrid distillation processes, the REDWC process and the REDWC with feed preheating (REDWC-FP) process, are developed to separate ethyl acetate/ethanol/water ternary azeotropic mixture. The design parameters of the two hybrid distillation processes are optimized based upon the maximum total annual cost (TAC), CO2 emissions and minimum process route index (PRI) through the multi-objective genetic algorithm (MOGA) considering safety. In view of massive waste heat in the REDWC process, several new configurations combining the REDWC and Organic Rankine cycles (ORCs) are further proposed. The optimal ORC system is determined via MOGA with the annual net profit, ORC thermodynamic efficiency and PRI as objective functions. Compared with the existing DCRED process, the TAC and CO2 emissions of the REDWC process are reduced by 8.15% and 4.49%, respectively. The TACs of the ORC1-REDWC process with working fluid cyclohexane and the ORC2-REDWC process with working fluid benzene are reduced by 27.50% and 26.32%, respectively.