Published September 2003
Distillation is the primary separation method in the petroleum refining, petrochemicals and gas separation industries. Distillation is well known to be energy intensive and inefficient. For separation of three or more components, two or more columns are usually cascaded. However, fully thermally coupled distillation (Petlyuk distillation) is one scheme for three or more products that can save significant amounts of energy by reducing thermodynamic losses. The divided-wall column is one mechanical implementation of fully thermally coupled distillation that is increasingly finding applications.
After decades since its conception, divided-wall distillation recently reached commercial acceptance. It is estimated over 35 columns are in service. Divided-wall columns are used commercially so far in niche applications in fine chemicals, petrochemical, gas separation and refining industries. The divided-wall column is applicable to some ternary separations where the mid boiling component is desired in high purity along with high purity lighter and heavier boiling products. One divided-wall column can replace two or more conventional columns. The divided-wall column offers capital, energy and plot area savings compared to the conventional column configurations.
Not all ternary separations are good candidates for fully thermally coupled or divided-wall distillation. Also, for suitable separations, a real or perceived price of the energy and capital savings may render a specific application impractical. We present some guidelines for the selection of the divided-wall column and for preliminary column design.