Relaxing the constant molar overflow assumption in distillation optimization

The constant molar overflow (CMO) framework, while useful for shortcut distillation models, assumes that all components have the same latent heats of vaporization. A simple transformation, from molar flows to latent-heat flows, allows shortcut models to retain the mathematical simplicity of the CMO framework while accounting for different latent heats, resulting in the constant heat transport (CHT) framework for adiabatic distillation columns. Although several past works have already proposed this transformation in the literature, it has not been well utilized in recent times. In this article, we show the utility of this transformation in upgrading various applications such as identifying energy-efficient multicomponent distillation configurations based on heat duty rather than surrogate vapor flow. The method transforms the V-min diagram to a Q(min) diagram. Furthermore, we derive new and insightful analytical results in distillation, such as cumulative latent-heat stage fractions having monotonic profiles within a distillation column under the CHT framework.