Collocation Methods for Distillation Design. 2. Applications for Distillation

We present applications for a collocation method for modeling distillation columns that we developed in a companion paper. We discuss implementation of the model, including discussion of the ASCEND system, which enables us to create complex models with simple building blocks and interactively learn to solve them. We first investigate applying the model to compute minimum reflux for a given separation task, exactly solving nonsharp and approximately solving sharp split minimum reflux problems. We next illustrate the use of the collocation model to optimize the design a single column capable of carrying out a prescribed set of separation tasks. The optimization picks the best column diameter and total number of trays. It also picks the feed tray for each of the prescribed separations.