Process Simulation And Optimization Of Extractive Distillation For CO₂ And Hydrocarbons Mixtures

Large amounts of gas mixtures of CO₂ and hydrocarbons are generated in the CO₂enhanced oil recovery（CO₂-EOR）process,and their separation is very challenging due to the formation of a minimum boiling temperature azeotrope of CO₂ and ethane.Hence,in this work,an intensified triple-column extractive distillation（ITCED）process is developed by closely referring to a previous study by Ebrahimzadeh et al.,（Appl.Therm.Eng.2016,96,39-47）and optimized by using a mixed-integer nonlinear programming（MINLP）method in terms of the minimal total annual cost（TAC）to separate the CO₂-hydrocarbons mixture effectively.Furthermore,based on ITCED,two types of extractive dividing-wall column（EDWC）processes,i.e.,vapor split EDWC（VSEDWC）and liquid split EDWC（LSEDWC）,are developed and optimized.Then,the thermodynamic efficiency and CO₂ emissions of these processes are calculated to evaluate their energy efficiency and environmental impact,showing the advantage of LSEDWC over the other processes.Finally,a heat integrated LSEDWC（HI-LSEDWC）process is proposed and demonstrated to be able to substantially improve the original tripe-column extractive distillation process with 33.04%decrease in TAC from118.93×10⁶$/year to 79.63×10⁶$/year,78.07%increase in thermodynamic efficiency from 12.28%to 21.87%,and 37.22%reduction of CO₂ emissions from 82.56×10³ kg/h to 51.84×10³ kg/h.