Design and control of a novel single-column extractive distillation with internally circulated intermediate boiling entrainer

Abstract

The effective separation of binary azeotropic mixtures is one of the main difficult problems for distillation processes. For the azeotropic mixture separation, additional columns and energy are always needed compared with the non-azeotropic mixture separation. To reduce the equipment cost and energy consumption of the extractive distillation, a novel single-column extractive distillation with internally circulated intermediate boiling entrainer is proposed in this paper. In the proposed distillation column, the entrainer has no need to be withdrawn and recycled into the column, and the binary minimum boiling point azeotropic mixture can be separated completely by one distillation column. Due to there is no outside recycled stream, the entrainer cannot be added into the column directly in its steady state design. To solve this problem, a two-column model is proposed to simulate the whole column in this paper. Three binary minimum boiling point azeotropic mixture separation cases show that the proposed column has high separation and energy efficiencies. In addition, the effective control strategies of the proposed column are studied in three cases, and excellent control performances are achieved by the proposed control strategies. This work proposes a new energy saving way for the extractive distillation to separate the binary azeotropic mixtures.