Novel control strategy of intensified hybrid reactive-extractive distillation process for the separation of water-containing ternary mixtures

Novel control strategy by just using temperature measurements for an intensified hybrid reactive-extractive distillation system used to separate water-containing ternary mixtures is developed in this work. Due to the complicated interaction between reaction and vapour-liquid equilibrium in the same reactive-extractive distillation column, it is inherently challenging to design a control structure for this design configuration. Furthermore, the flow rate of ethylene oxide (EO), used as a dehydrating agent in the design configuration, needs to be manipulated accurately to the expected value so that on one hand, this highly flammable substance would not be released out of the system; on the other hand, water would not become the excess impurity in product streams. Without using expensive composition controllers, the results of closed-loop sensitivity tests and corresponding profiles of temperature deviations in columns under various feed composition disturbances are used to develop only temperature and temperature-difference control loops as surrogates of quality control loops. The best control structures also demonstrate that they are resilient to measurable throughput disturbances as long as setpoints of temperature-related control loops can be adjusted according to different throughput changes. The procedure of developing the best overall control strategy is demonstrated on two separation systems of TBA/ EtOH/H2O and THF/EtOH/H2O, which have different characteristics on the number of azeptropes in the system.

Automated summary

A novel control strategy is developed in this work for an intensified hybrid reactive-extractive distillation system using only temperature measurements, addressing the challenging issues in the design configuration. By using temperature and temperature-difference control loops as surrogates for quality control loops, the best control structures are demonstrated to be resilient to measurable throughput disturbances and adaptable to different system characteristics.