Process design of carbon dioxide and ethane separation using ionic liquid by extractive distillation

BACKGROUNDCarbon dioxide and ethane easily form a binary azeotrope under liquefied conditions. An extractive distillation process for the separation of carbon dioxide and ethane using the ionic liquids [bmim][Tf2N], [emim][Tf2N] and [emim][EtSO4] as solvents was explored. The thermodynamic and physical property parameters of each ionic liquid and their thermo-physical properties that correlated with the experimental data were used to create the ionic liquid components and conduct the process simulation. RESULTBased on the analysis of its physical properties and relative volatilities, [emim][Tf2N] is the best option as a solvent for extractive distillation separation compared with other ionic liquids. Based on the sensitivity analysis optimization procedure, the minimum total annual cost, carbon dioxide emissions and thermodynamic efficiency were calculated. Compared with traditional extraction distillation, the total annual cost and carbon dioxide emissions of the process using [emim][Tf2N] as a solvent decreased by 62% and 31%, respectively. The thermodynamic efficiency () of the electricity generated from hydropower increase by 0.7%. CONCLUSIONThe results show that an ionic liquid extractive distillation process using an ionic liquid as the entrainer performs better than a process using traditional organic solvents in terms of economics. Due to the non-volatility of ionic liquids, a flash tank was used instead of a solvent recovery column to efficiently realize solvent recovery. (c) 2017 Society of Chemical Industry