Control Study to Enhance the Controllability of Heterogeneous Extractive Distillation: Cyclohexane/Cyclohexene Separation

Abstract

Control strategy is crucial for the smooth operation of distillation systems, especially when the design flowsheet is complicated. In this work, a control strategy is proposed for a recently published heterogeneous extractive distillation system separating cyclohexane and cyclohexene. During the investigation of control strategy, a closed-loop sensitivity test is adopted to analyze the controllability of this distillation system, and the results show that some modifications for the steady-state design must be made to facilitate the implementation of suitable control structure. After redesigning the separation process, closed-loop sensitivity test is again performed for the purpose of successfully setting up a single-temperature control scheme for two distillation columns and also determine which variable/ratio is to be fixed. The results of open-loop and closed-loop sensitivity tests are taken into consideration together for the sake of selecting the appropriate stage for temperature control. In addition, a closed-loop sensitivity test is also used for the preinvestigation of throughput disturbance rejection to devise feedforward control action. According to the closed-loop dynamic responses, the proposed control strategy enables the heterogeneous extractive distillation system to properly reject ±20% feed composition disturbances and ±10% throughput changes.

Effective Control of Vapor Recompression-Assisted Dividing Wall Column with a Middle Partition

“…To find proper variables for the effective control structures, closed-loop and open-loop sensitivity tests are performed. , Before doing the dynamic control, some inventory and regulatory control loops must be set. The fresh feed is flow-controlled.…”

Complete separation of benzene-cyclohexene-cyclohexane mixtures via temperature-dependent molecular sieving by a flexible chain-like coordination polymer

“…Unfortunately, such agents suffer from low selectivity and poor solubility. As a result, multiple extraction cycles are required to achieve targeted purity (>99%) at the cost of high equipment expense and extensive energy consumption 12 – 14 . To address these pitfalls, adsorptive separation techniques based on tailored nano-space of porous adsorbents are considered as an alternative and desirable solution for energy- and cost-efficient separation of benzene-cyclohexene-cyclohexane mixtures 15 , 16 .…”