New distributed-action control strategy with simultaneous heating and cooling in trays of a pilot-scale diabatic distillation column

• Published in: Chemical engineering research & design Vol. 159; pp. 424 - 438
• Main Authors: Mello, Geysa Nataly, Battisti, Rodrigo, Urruth, Nícolas Soares, Machado, Ricardo Antonio Francisco, Marangoni, Cintia
• Format: Journal Article
• Language: English
• Published: Rugby Elsevier B.V 01.07.2020; Elsevier Science Ltd
• Subjects: Cooling; Diabatic distillation; Distributed-action control strategy; Flow velocity; Heat transfer; Heating; Internal flow; Reduction; Simultaneous heating and cooling; Strategy; Stripping (distillation); Temperature; Transient time minimization; Trays; Vacuum distillation; Simultaneous heating and cooling; Transient time minimization; Diabatic distillation; Distributed-action control strategy
• ISSN: 0263-8762; 1744-3563
• DOI: 10.1016/j.cherd.2020.05.001

[Display omitted] •A new distributed control strategy was performed for a distillation process unit.•Simultaneous heating (stripping) and cooling (rectifying) in trays were applied.•Transient times had a reduction over 70% against feed temperature disturbances.•The amount of out-of-specification product and overshoot were considerably reduced.•The strategy provides a soft distribution of control action increasing productivity. In order to minimize operation transient times, a new distributed control strategy was performed in a distillation unit. Acting simultaneously by heating in tray 11 (stripping section), and cooling in tray 3 (rectifying section) of a distillation column, the control strategy was implemented using Aspen Hysys® with experimental validation. The new distributed control strategy showed a reduction of 0.32h (19min) in the transient time when a negative disturbance in the feed temperature was applied (−14°C), and 0.37h (22min) when a positive disturbance in the feed temperature was applied (+14°C), compared to conventional control. Variations in internal flow rates, as well as temperatures and compositions, were punctual (just where there is control action) and did not affect the steady-state after the disturbance rejection, when compared to conventional control. Distributed-action approach reduced heat amount transferred in the reboiler and reflux flow rate, due to the association with the heat added/removed in trays, evidencing the soft distribution of the control action along the entire column height. Thus, this new distributed control strategy with simultaneous corrective action between top and bottom of the distillation unit allows a significant reduction in transient times, improving plant productivity.