Generalized Ease Of Separation Index And Quantitative Rules For Selection Of Optimal Ternary-distillation Configuration

Distillation is the most widely used separation process in chemical production,but a high energy consumption and low thermodynamic efficiency process as well.Ternary distillation is a very common distillation type and has a large number of applications in industry.Recent appearance of new energy saving distillation schemes,including thermally-coupled distillation,dividing wall column,and multi-effect distillation etc.,has provided increasing number of possible ways for ternary-distillation,and led to the increase of the number of alternative distillation configurations.It is therefore essential to screen out effectively the optimal ternary distillation schemes with the best economic performance from among the numerous alternatives.In the present work,the dependences of the economic performance of ternary distillation configurations on feed composition,relative volatilities,separation requirements and latent heat were demonstrated by using rigorous simulation and optimization with four different ternary mixtures.Seven distillation configurations,including heat-integrated sequences,thermally coupled configurations,and DWC,were investigated.The comprehensive effect of feed composition and relative volatility,latent heat of the mixtures,and separation requirements on the selection of optimal ternary distillation configuration was investigated,and the results were interpreted via a composition triangle map for the ternary mixtures.A generalized ease of separation index(GESI),was proposed for the first time to embed the effects of all the feed composition,relative volatility,latent heat,and separation requirements on the economic performance of the separation configurations.The results showed that,for the feeds with similar volatility ratio,the optimal distillation schemes alter if the GESI values are different,demonstrating the effectiveness of the proposed GESI in selecting optimal ternary distillation configuration.It was shown that the selection of an optimal ternary distillation configuration should be done considering the feed composition,relative volatility,latent heat of the mixtures,and separation requirements.Finally,an empirical rule based on GESI and feed composition was proposed,which can be used to screen out the optimal configuration for ternary distillation,and thus provides an effective reference for the design of industrial ternary distillation processes.