A Discrete-Steepest Descent Framework for the Simultaneous Process and Control Design of Multigrade Reactive Distillation Columns

Abstract

The simultaneous optimization of continuous and discrete design variables, operating conditions, and controller's tuning parameters of reactive distillation (RD) columns is investigated in this work. For this purpose, the capabilities of a recently proposed modular economic optimization strategy based on a Discrete-Steepest Descent (D-SDA) framework are investigated. The D-SDA is a decomposition method that aims to improve an initial design by systematically modifying its discrete decisions, e.g., number of stages, until a design that optimizes the process economics while meeting the desired specifications is found. A case study involving the production of ethyl tert-butyl-ether (ETBE) in a RD unit was considered. The simultaneous design and control of the RD column was solved under two scenarios, i.e., product changeovers between four different grades and the production of a single grade of ETBE under a step disturbance in the feed composition. The results show that the modular strategy can specify economic design and control schemes in reasonable computational times.