Dynamics and Control of Reactive Distillation Columns with Double Reactive Sections: Feed-Splitting Influences

作者：Cao, Yang; Huang, Kejin^*; Yuan, Yang; Chen, Haisheng; Zhang, Liang; Wang, Shaofeng

来源：Industrial & Engineering Chemistry Research, 2017, 56(28): 8029-8040.

DOI：10.1021/acs.iecr.7b01488

• RELATIVE VOLATILITY RANKING
• EXTERNAL RECYCLE
• DESIGN
• SYSTEMS

Reactive distillation columns with double reactive sections (RDCs-DRS) at the top and bottom are especially favorable for the separations of reacting mixtures featuring the most unfavorable ranking of relative volatilities. In this article, their dynamics and control are studied in great detail, with special attention given to the influences of feed splitting on process dynamics and controllability. Because of the totally refluxed and totally reboiled operation mode plus an intermediate-product withdrawal, the RDC-DRS is generally characterized by severe under-dampness between the intermediate-product compositions and the reboiler heat duty (i.e., the regulation path) and by severe asymmetry between the intermediate-product compositions and the heaviest reactant feed flow rate (i.e., the disturbance path), consequently posing a great challenge to tight product quality control. With feed splitting of the lightest and heaviest reactants in the RDC-DRS (RDC-DRSFS), the simultaneous suppression of the under-dampness in the regulation path and the asymmetry in the disturbance path is attained, thereby presenting favorable influences to process dynamics and controllability. Two reactive distillation systems, executing a hypothetical reversible reaction, A + B <-> C + D (alpha(A) > alpha(c) > alpha(D) > alpha(B)), and the lactic acid esterification with methanol, are employed to inspect the dynamics and controllability of the RDC-DRS and RDC-DRSFS. Although the RDC-DRS can be maintained as stable, rather sluggish tracking responses are noticed because the under-damped and asymmetrical behaviors restrict tight controller tuning. The RDC-DRSFS, on the other hand, shows greatly improved tracking performance with even enhanced disturbance rejection capabilities. The comparison endorses the great significance of feed splitting for the RDC-DRS, namely, not only an effective strategy for process retrofitting but also a potential booster for process dynamics and controllability.

• 出版日期2017-7-19
• 单位北京化工大学