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. (c) 2006 Elsevier Ltd. All rights reserved.