Equation-Oriented Optimization of a Distillation Column Considering Stage Hydraulics

Abstract

Accurate prediction of pressure drops around trays or packing sections is crucial for the optimal design of distillation columns. However, simultaneous optimization of all operating and structural parameters with the rigorous hydraulics consideration in MESH model is still difficult because of both the convergence for the stage number and integer optimization problem. In the present work, a rigorous equilibrium stage-based pseudotransient distillation model considering stage hydraulics is developed in the equation-oriented environment. By applying the steady-state optimization algorithm assisted by pseudotransient models [Ma, Y.; Luo, Y.; Ma, X.; Yang, T.; Chen, D.; Yuan, X. Fast Algorithms for Equation-Oriented Flowsheet Simulation and Optimization Using Pseudo-Transient Models. Ind. Eng. Chem. Res. 2018, 57 (42), 14124–14142], and the bypass efficiency method [Dowling, A. W.; Biegler, L. T, Rigorous Optimization Based Synthesis of Distillation Cascades without Integer Variables. In Computer-Aided Chemical Engineering; Klemeš, J. J.; Varbanov, P. S.; Lieu, P. Y., Eds.; Elsevier: Amsterdam, Netherlands, 2014; Vol. 33, pp 55–60], the convergence problem and stage number optimization problem are effectively solved. In addition, an optimization framework for DWCs is proposed, which can consider simultaneously tray hydraulic conditions and find the optimal position of the dividing wall by systematically balancing the pressure drops of the column sections in the two sides of the wall.