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

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.