Dividing-Wall Columns: Lessons Learned from Naphtha Upgrading

Dividing-wall columns (DWCs) improve the energy efficiency and reduce capital cost requirements by approximately 20–30% relative to conventional distillation towers. The unique feature of a DWC is a vertical wall (or walls) within the column that eliminates remixing of components, which is common in a traditional tower and constrains the energy efficiency of the separation. DWC technology is quite versatile and well-established, and DWCs have been enjoying resurgence recently in the distillation community. Because no two DWC installations are the same, we can benefit by reviewing lessons learned from previous DWC projects. This article discusses the commercialization of DWC technology in a depentanizer column in the naphtha-upgrading unit of the largest refinery in India. It reviews the process design problems the refinery faced and explains how DWC technology mitigated those problems to achieve new design objectives.