Design and control of a novel side-stream extractive distillation column for separating methanol-toluene binary azeotrope with intermediate boiling entrainer

Abstract

It is innovative and important to perform complex binary azeotrope separation via single distillation column. In the article, design and control of a novel and simple side-stream extractive distillation (SSED) column with extraction and solvent recovery function is investigated for the separation of methanol and toluene binary azeotrope with intermediate boiling triethylamine (Et3N) as solvent. The steady-state design parameters of the novel SSED column are optimized and obtained with the objective of minimal total annual cost (TAC) via conventional sequential iterative procedure. On the basis of steady-state design, four single-end temperature control structures (STCS), four dual-temperature control structures (DTCS) and four dual-composition control structures (DCCS) are developed and established successively to overcome the operation and control challenges caused by the novel scheme. To seek the robust control, the dynamic performance analysis on account of the above control structures is conducted for the SSED column, which is evaluated for feed flowrates and composition disturbances. The results show that the control performance of DCCS is significantly superior to that of STCS and DTCS while the integral squared error (ISE) and energy-consuming effect are equivalent, and can take shorter time to bring the product purities back to the original steady state in coping with specified feed disturbances.