Design and control analysis of the side-stream extractive distillation column with low concentration intermediate-boiling entrainer

Abstract

Side-stream extractive distillation (SSED) column has attracted increasing attentions due to its simple structure for separating the binary azeotropes using intermediate-boiling entrainer. However, the high-concentration intermediate-boiling entrainer may lead to a disadvantage of high energy consumption. To address this issue, an improved design of the SSED column with low-concentration intermediate-boiling entrainer is proposed to improve economic performances without adversely affecting its controllability for separating binary azeotropes. Economic optimization and sensitivity analysis are employed for designing SSED column using low-concentration intermediate-boiling entrainer for separating the methanol/toluene azeotrope, in which the advantages of cost reduction and energy saving have been observed. Following that, multiple case studies have been conducted to demonstrate the superiority of low-concentration intermediate-boiling entrainer in energy saving. Finally, dynamic control analysis illustrates that the SSED column using low-concentration intermediate-boiling entrainer can react effectively against the feed flowrates fluctuations and compositions disturbances by adopting control structures with composition controller.