Study On A New Pressure-Swing Distillation Process Via Introducing Azeotropic Entrainer

Pressure-swing distillation is a commonly used method for separating azeotrope.However,conventional pressure-swing distillation is only feasible for the separation of pressure sensitive systems.In this paper,in order to broaden the application range of pressure-swing distillation,a three-column and a two-column pressure-swing distillation process with azeotropic entrainer were developed for the separating of non-pressure sensitive azeotrope systems.A global optimized iterative sequence based on total annual costs was proposed.How to remove and recover pyridine from toluene is a subject worth of study.The new developed pressure-swing distillation process via introducing azeotropic entrainer was applied to the separation of toluene-pyridine system.The appropriate entrainers such as ethanol,isopropanol and tert-butanol were screened.For these three entrainers,design,optimization and comparative analysis of the three-column pressure-swing distillation process and two-column pressure-swing distillation process were carried out.Through comparison and analysis,it is found that the two-column processes had the obvious advantages compared with the three-column process.In addition,the partial thermal integration of the three-column process and the two-column process could significantly reduce energy consumption and total annual cost.The optimal solution for the separation of toluene-pyridine was the two-column process with partial thermal integration using tert-butanol as the entrainer,which had the smallest energy consumption and total annual cost.Taking the azeotropic system of n-propanol-water as an example,tetrahydrofuran was screened out as the suitable entrainer.Design and optimization study of the three-column pressure-swing distillation process and two-column pressure-swing distillation process were carried out.The comparison results showed that the two-column process had obvious advantages in energy savings and total annual costs.In addition,the partial thermal processes could significantly reduce energy consumption and total annual costs.Compared with the extractive distillation separation process,the two-column process with partial thermal integration could reduce the total annual cost by 34.2%.