A dynamic control structure of liquid-only transfer stream distillation column

doi:10.1016/j.cjche.2022.12.009

Abstract

Abstract: The intention of this fundamental work is to explore the manipulation of a mixture of benzene, toluene and o-xylene separated from liquid-only transfer divided-wall column (LTS-DWC). First, two control structures are clearly proposed, including seven component control loops (CS1) and seven temperature control loops (CS2). However, two control structures can handle ±10% feed disturbances rather than larger feed disturbances. Subsequently, an equivalent four-column model by introducing withdraw ratio is developed to discuss the effect of two liquid-only side-stream on the overall reboiler duty. It is indicated that the second liquid-only side-stream withdraw ratio strongly affects the overall energy consumption. Hence, six-component control loops within the fixed second liquid-only side-stream withdraw ratio (CS3) is proposed and the purity of products returns to set value even as facing ±20% feed disturbances. Finally, based on the above results, it is established a temperature control structure (CS4) for controlling fixed second liquid-only side-stream withdraw ratio, which can cope with ±15% disturbances. Inspired by these findings, an insight into the dynamic control of LTS-DWC promotes the industrial implementation of DWC through new liquid-only side-stream configurations.

Key words: Separation, Divided-wall column, Liquid-only transfer stream, Optimal design, Dynamic modeling

摘要： The intention of this fundamental work is to explore the manipulation of a mixture of benzene, toluene and o-xylene separated from liquid-only transfer divided-wall column (LTS-DWC). First, two control structures are clearly proposed, including seven component control loops (CS1) and seven temperature control loops (CS2). However, two control structures can handle ±10% feed disturbances rather than larger feed disturbances. Subsequently, an equivalent four-column model by introducing withdraw ratio is developed to discuss the effect of two liquid-only side-stream on the overall reboiler duty. It is indicated that the second liquid-only side-stream withdraw ratio strongly affects the overall energy consumption. Hence, six-component control loops within the fixed second liquid-only side-stream withdraw ratio (CS3) is proposed and the purity of products returns to set value even as facing ±20% feed disturbances. Finally, based on the above results, it is established a temperature control structure (CS4) for controlling fixed second liquid-only side-stream withdraw ratio, which can cope with ±15% disturbances. Inspired by these findings, an insight into the dynamic control of LTS-DWC promotes the industrial implementation of DWC through new liquid-only side-stream configurations.

关键词: Separation, Divided-wall column, Liquid-only transfer stream, Optimal design, Dynamic modeling

Borui Liu, Tao Zhang, Yi Zheng, Kailong Li, Hui Pan, Hao Ling. A dynamic control structure of liquid-only transfer stream distillation column[J]. Chinese Journal of Chemical Engineering, 2023, 59(7): 135-145.

Borui Liu, Tao Zhang, Yi Zheng, Kailong Li, Hui Pan, Hao Ling. A dynamic control structure of liquid-only transfer stream distillation column[J]. 中国化学工程学报, 2023, 59(7): 135-145.

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