A new application of dividing-wall columns for the separation of middle-boiling impurities

• New DWC setup allows removal of middle-boiling impurities from close-boiling mixture.
• By the proposed setup product loss is reduced by more than 50%.
• Less energy consumption and reduced investment costs compared to single side-column.

There is growing interest in dividing-wall column (DWC) technology, and its simplicity lies at the heart of its appeal. Compared to conventional multicolumn arrangements a DWC can generate capital cost savings of up to 40% simply because less equipment is required. With their greater thermodynamic efficiency, dividing-wall columns can also reduce operating costs by around 30% (Asprion and Kaibel, 2010). The actual savings that can be realized will depend on the specific application.In general, the use of DWCs is recommended for multicomponent liquid mixtures that are to be separated into at least three fractions with high purity requirements. Further, DWCs are especially favorable for the separation of small quantities of light and heavy boilers from the main middle-boiling product (Dejanović et al., 2010 and Niggemann et al., 2010).In this paper, a new configuration of divided wall column is presented, which is most effective for the separation of a feed containing low concentrations of middle-boiler (about 1% or less) into a pure distillate and a pure bottoms fraction, while the impurity is concentrated in the side-stream. Product loss in the side-stream is a major cost-driver. In the DWC-configuration proposed here, product loss can be cut in half compared to a single side-stream column.Experiments at pilot scale have confirmed the simulation results, proving a new opportunity to profit from the vertical wall inside the distillation column.