Optimization-based design of dividing wall columns with extended and multiple dividing walls for three- and four-product separations

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While dividing wall columns can be considered an established technology and success story of distillation process intensification, the application of the technology is still limited in relation to the vast number of existing distillation columns. This can at least to some extent be traced back to potential controllability issues and the complexity of the process design. While the first issue is especially related to internal vapor splits, which require an accurate design and consideration of column hydrodynamics, the latter issue becomes more severe with an increasing number of products and column sections, for which the number of degrees of freedom and design alternatives increase exponentially. While modified design concepts for dividing wall columns that allow for an external control of vapor splits have been proposed, similar to four-product dividing wall columns, there is still a lack of computationally efficient tools for the design and optimization of these energy-efficient thermally coupled distillation processes. The current article presents an optimization-based approach for the design of such complex and integrated distillation processes, enabling a case-specific economic assessment and benchmarking. The application is demonstrated for different case studies, including the separation of an azeotropic quaternary system in a multi-dividing wall column.