Separating Mixture Glycols in DWC with Flow Rate-Composition Cascade Control Structure

Abstract

Dividing wall column (DWC) is an advanced technology which could decrease energy consumption. As the vertical wall inserted in DWC increases the degree of freedom of systems, the control becomes more difficult than the conventional columns. In this study, the mixture glycols (1, 2-propanediol+ 1, 3-butanediol+ 1, 4-butanediol) were taken as feed, an optimized DWC structure was proposed, and three control structures for DWC were tested by ± 10% feed disturbances. The temperature control structure (CS1) was hard to control the system while composition control structure (CS2) and flow rate-composition cascade control structure (CS3) had good performance on controlling the DWC. It showed that CS3 was superior to CS2, as CS3 could stabilize the DWC within 4 hours, and the maximum deviations of the three products, namely 1, 2-propanediol, 1, 3-butanediol and 1, 4-butanediol, were 0.07%, 1.44%, and 0.46% respectively, while CS2 could realize the stability within 7 hours, and the corresponding numbers were 0.35%, 2.78%, and 0.41%, respectively.