Flow phenomena and flooding limitations in a phase transition extraction column

The flooding limitations of liquid–liquid countercurrent two-phase flow in a phase transition extraction (PTE) column were investigated both experimentally and theoretically. The solvents used in the PTE process are partially miscible and posses a critical point of miscibility. In the experiments, the effect of the settlers’ inclination on the onset of flooding in non-isothermal PTE column was investigated. It was found that flooding conditions in the column can be postponed by using off-horizontal settlers. This led to the development of a novel structure of a PTE column with improved throughputs.A model is suggested for predicting flooding conditions in the PTE column. It combines a recently developed two-fluid model with improved theory-based closure relations for laminar stratified flow, with a non-isothermal model for evaluating the composition in the mixing section and the internal streams in the column. The results of the combined model favorably predict the experimental flooding flow rates.