Divided-Wall Colum Design by Mathematical Programming Approach

The divided-wall distillation column (DWC) is one of the energy integrated distillation columns that has an more additional wall located in the middle of the column as compared with the traditional one. This feature makes DWC applicable to ternary mixture separation. In contrast to traditional sequence of ternary mixture separation, DWC is more efficiency in energy use and entails less capital cost.

This work, a superstructure that incorporates all possible schemes of DWC is first built, based on the superstructure, a general mathematical model in the form of a Mixed-Integer Nonlinear Programming is formulated. It is desired to determine the optimum type and operating conditions of a DWC. The objective functions include the minimization of utility and minimization of total annual cost.

This work takes the separation of ternary mixtures as an example, determining the optimum configuration of DWC under different relative volatilities and feed compositions. To make sure the accuracy of optimization, the result is compared with that from using commercial software Aspen Plus. Furthermore, discussions are made on whether it is advantageous to use non-optimum structures.