Divided-wall column (DWC) has many advantages over conventional columns

such as energy saving potential and low investment cost. A new DWC sequence for separating benzene

toluene

o-xylene and 1

3

5-trimethylbenzene quaternary mixture was proposed and simulated in this study. Rigorous distillation column models in Aspen Plus were employed in all simulations. Under the same targets of purity and yield

the energy consumed by DWC can be reduced by 18.9% and the total annual cost can be saved by 13.0% compared to that of conventional direct separation (DS) sequence. The reason for the energy saving is that DWC could prevent the remixing of intermediate compounds

which often happens in DS sequence. Using Aspen Dynamic

composition controlled structure for DWC is proposed

which controls the new DWC separation sequence and minimizes the energy consumption in DWC. The dynamic simulation shows that the composition controlled structure provides effective control of product purity for fluctuations of feed flow rate and composition.