Assessment of separation efficiency modeling and visualization approaches pertaining to flow and mixing patterns on distillation trays

Distillation columns are essential to chemical process industries, and most of them are fitted with crossflow trays due to their versatility. Since these columns are expensive in terms of cost and energy consumption, an accurate determination of their separation efficiency is a prerequisite to optimization of their performance by design modification and revamping. This would further reduce the extra trays, added to account for the uncertainties, during the column design. There have been several attempts in the past to understand the nature of liquid mixing and flow patterns on the trays through experiments and CFD simulations, and to relate them with their separation efficiency through CFD, empirical and theoretical models. The present work aims at reviewing the experimental and the simulational studies accomplished to characterize the flow and the mixing patterns on column trays. In particular, a comprehensive review of the existing theoretical efficiency prediction models along with the critical analysis of their strengths and weaknesses is presented. The dependence of the tray efficiency on system and flow properties is also discussed. In addition, a concise strategy on how to process and utilize the experimental data in tandem with mathematical models is proposed. The future of the tray efficiency modeling is anticipated to feature hybrid approaches, i.e. using theoretical models supplemented with fluid dynamics information from experimentally validated CFD models. Thus, knowledge of the existing theoretical approaches is imperative for their improvement and development of the new ones for better tray efficiency predictions.