(157b) Dividing Wall Columns - Novel Applications with Case Studies

Reduction of CO2 emissions related to distillation applications necessarily involves reducing the energy demand. Dividing wall column technology can play an important role toward this goal as it can achieve significant energy savings of up to 50% compared to conventional designs.

Dividing wall columns were first described in the first half of the 20th century in two U.S. patents [1,2]. The concept combines the heat-integrated connection of two columns in one apparatus to save energy. Later, thermodynamic and simulation improvements [3,4,5] allowed for a simple and fast simulation of a dividing wall column.

The first commercially used dividing wall column was built and put into operation in the mid-1980s. The column was equipped with internals by Julius Montz GmbH. The combination of thermodynamical knowledge of the operating company and the hydraulic knowledge of column internals by Montz was a decisive contribution to the proper usability of a dividing wall column.

A good understanding of the hydraulic behavior is critical for a proper design of a dividing wall column. For instance, improper distribution of the vapor flow below the dividing wall to each side of the wall will result in the actual separation being significantly different from the simulation results.

Initially, the challenges of dividing wall column design and unfounded concerns about the difficulty of controlling such columns led to the fact that only a few large petrochemical and chemical companies were willing to design, build and operate dividing wall columns.

Even today, opinion persists that dividing wall columns are only a marginal phenomenon in distillation and that even the mechanical challenges are too great to bring dividing wall columns to a wider range of applications. To counter this view, we will present two case studies featuring dividing wall columns, one containing packing and the other trays. These case studies will show that for almost every theoretical obstacle to the design of a dividing wall column, a mechanical solution already exists that has also been tested and proven on an industrial scale.

In conclusion, the recommendation to all operators of distillation plants is to realize the potential energy savings of up to 50% compared to a conventional column system, and to also consider the use of dividing wall columns for existing processes.

References

1. D. A. Monroe, Fractionating Apparatus and Method of Fractionation, 2,134,882, United States Patent Office (1935).
2. R. O. Wright, Fractionation Apparatus, 2,471,134, United States Patent Office (1946).
3. F. B. Petlyuk, V. M. Platonov, D.M. Slavinskii, Thermodynamically optimal method for separating multicomponent mixtures, Int. Chem. Eng. 5, 3 (1965), 555-561.
4. I. Dejanovic, Lj. Matijasevic and Z. Olujic, Dividing wall column – A breakthrough towards sustainable distilling, Chem. Eng. Process. 49 (2010), 559-580.
5. I. J. Halvorsen and S. Skogestad, Minimum Energy Consumption in Multicomponent Distillation. 2. Three-Product Petlyuk Arrangements, Ind. Eng. Chem. Res. 42 (2003), 605-615