Energy-saving columns: Design and control of a Kaibel and a multi-sidestream column for separating hydrocarbon mixture.

Graphical abstract Highlights • This paper addresses the design of Kaibel and multi-sidestream column. • The multi-sidestream column is the most energy-efficient configuration. • The control structure of three distillation system is presented. Abstract Due to the conventional sequence has a disadvantage of high energy consumption, this paper proposes the optimal design and control of the Kaibel and multi-sidestream column for separating five-component hydrocarbon mixture. First, three processes are simulated by steady-state simulation. The three distillation structures are designed by minimizing the total annual cost (TAC) and the results show that the multi-sidestream column is the most energy-efficient configuration, with savings of 29.5% to the conventional sequence, and 12.2% to the Kaibel dividing wall column (KDWC). Second, the suitable control of three processes are designed. The temperature controller is used in multi-sidestream column and the component controller is used in KDWC. The results show that the response time towards disturbance of the KDWC is longer and the purity of the multi-sidestream column is not up to the requirement. Finally, aiming at the problem above, the control structures of KDWC and multi-sidestream column are optimized. Temperature controller is added in the KDWC instead of the component controller. Under the control of temperature, it can return to stable in a short time. A double temperature controller is added in multi-sidestream column based on defects of basic control structure. Its product purity can attain above the designed value. Compared to the multi-sidestream column process, the control structure of KDWC can handle feed disturbance more effectively, and the purity is closer to the design value. [ABSTRACT FROM AUTHOR]