An energy‐efficient cost‐effective transient batch rectifier with bottom flashing: Process dynamics and control

Abstract

Exploring an internal heat source through bottom flashing route, this work introduces a dynamic batch column configuration within the framework of mechanical heat pump system. This batch rectifier with bottom flashing (BRBF) scheme attempts to use the reboiler liquid as a heat exchanging medium in the overhead condenser, thereby avoiding the use of any external coolant stream and reducing the consumption of hot utility in the reboiler. Aiming to operate the proposed transient process unit at an optimal state of energy use, we formulate an online open‐loop control policy that estimates the multiple control actions simultaneously. Furthermore, in order to achieve constant product purity, a gain‐scheduled closed‐loop control system is synthesized with keeping the stability margin constant. Simulating a multicomponent reactive system, the novel BRBF arrangement is evaluated in the aspects of energy savings and cost under both the open‐loop and closed‐loop control modes. © 2015 American Institute of Chemical Engineers AIChE J, 61: 3699–3707, 2015