(492e) Structural Design Approach for the Divided Wall Distillation Column Using the Sloppy Distillation Arrangement

Distillation is most widely applied separation process and will continue to be an important process for the future because there is currently no other industrially viable alternative. Dividing Wall Columns (DWC) for distillation is currently receiving a lot more attention from industry because of their energy saving capability and capital cost reduction. These reductions occur due to the fact that only one column, reboiler and condenser are needed, as compared to two complete conventional columns when a middle-cut is required.

A divided wall column has a vertical partition that divides the column shell into a prefractionator and side draw section. The DWC and the Petlyuk column are thermodynamically identical, the difference between them being that the prefractionation section in a Petlyuk column is external and in a DWC it is contained within one shell. It is appropriate to model a DWC as a Petlyuk column when heat transfer effects across the wall are not significant. The purity of the middle product from a DWC is superior to that from a conventional side product column because the middle distillates usually form a strong split above and below the partition and the product is removed from the side of the partition remote from the feed.

In the proposed study an efficient design method is proposed for determining the optimal design structure of a dividing wall column (DWC). The structure that gives superior energy efficiency in the shortcut sloppy case also brings superior energy efficiency in the DWC, while the optimal internal flow distribution of the DWC is different from that obtained from the sloppy configuration. Based upon an extensive simulation study the optimal DWC structure is first determined by applying the shortcut method to the sloppy configuration; the optimal internal flow distribution is then found from the corresponding DWC configuration.

The simulation study shows that the DWC designed by the proposed method gives a near-optimal structure.