Design and control of an extractive distillation process for separating isopropanol and water with side-stream extraction

Abstract

Innovating distillation technology to improve the efficiency of distillation equipment, reduce energy consumption, and increase product purity is an important challenge for the rapid development of the distillation industry. In this paper, steady-state simulations are developed for the separated isopropanol and water systems, and the sensitive temperature stage locations are determined using sensitivity and singular value decomposition (SVD). An open-loop steady-state gain analysis of the isopropanol/water system was performed, and a series of dynamic control schemes were designed and optimized to resist ±10% feed flow disturbances and ±5% feed composition disturbances, comparing the performance of the control schemes one by one through IAE error analysis. The results show that the side-stream extractive distillation separation of isopropanol and water system using a single temperature fixed reflux ratio control loop suffers from a large product shift problem. One of the key control loops is to control the isopropanol purity by controlling the bottom of the column flow rate, and the scheme performs well under both single-temperature control and dual-temperature control, effectively resisting ±10% feed flow disturbances and ±5% feed composition disturbances. The improvement of product purity can be seen from the component controllers play an important role, while the feed-forward effect under certain conditions can also enable the system to quickly restore stability and improve the system response speed.