Enhanced separation of mixing diols by distillation in dividing wall column

Abstract

Dividing wall column (DWC) was used to separate the system (1,2-propylene glycol + 1,3-butanediol + 1,4-butanediol). No research in a DWC has focused on such systems which were difficult to be separated for their great similarity in both molecular structures and properties. The rigorous steady-state and dynamic simulations, as well as the optimization of DWC alternative were performed with Aspen Plus and Aspen dynamics. Sequential quadratic programming (SQP) optimization method and the efficient sensitivity analysis tool were used to minimize the total reboiler and condenser duties. Moreover, a flow rate-composition cascade control structure was first developed to maintain targeted product purity under various external disturbances as feed flow rate and side product composition changed. DWC was compared with both a side rectifier configuration and conventional two-column distillation sequence in energy requirements and total annual costs (TACs) with the same number of stages. It showed that the energy requirements and TAC by DWC were reduced 47.60 % and 35.40 % respectively, compared with conventional distillation sequence, energy savings of 48.00 % and 34.11 % lower TAC compared with side rectifier configuration. This study provided a potential solution for the distillation of the systems with similar molecular structures and properties in a DWC.