A simple scheme to determine the minimum solvent flow rate for counter-current extraction columns is obtained and its validity is verified using two case studies. An infinite number of equilibrium stages are simplified to a single equilibrium stage. The first case study considers the extraction of a solute using a system made of only three compounds and a non-reactive extraction column to verify the results by rigorous simulation, i.e. aqueous acetic acid. The second case study is focused on biodiesel synthesis in a hybrid reactive extraction column.
