(214d) Synthesis of New Dividing Wall Columns for Thermally Coupled Distillation

Novel and equivalent dividing wall columns (DWCs) can be obtained by converting ‘thermal couplings to liquid-only transfer streams’¹. In this paper, we first convert thermal couplings on a fully thermally coupled (FTC) configuration to liquid-only transfer streams. We describe the full set of resulting FTC DWCs with n-2 dividing walls that can be used to separate mixtures with n-components. The literature only describes one DWC for FTC distillation of any mixture, whereas we find many equivalent DWC implementations are possible. For example, for 4-component mixtures, we identify thirty five new DWCs. A subset of these DWCs have an attractive feature that, during operation, vapor flow in every section of the DWC can be regulated by means external to the column. This feature makes it possible to build and operate the DWCs near optimality while also ensuring purity of the product streams. We propose rules to identify this subset of DWCs, and develop a formula to accurately determine the number of such DWCs for n-component FTC distillation. For 4-component FTC distillation, there are fifteen externally regulatable DWCs. We also extend the framework to a general thermally coupled configuration, and demonstrate the application of the conversion strategy on the same.

1. Agrawal R. Thermally Coupled Distillation with Reduced Number of Intercolumn Vapor Transfers. AIChE J. 2000;46(11):2198- 2210.