The simulation of liquid-liquid extraction columns based on a droplet population balance approach provides a useful means for getting more insight into the transient and the steady state behavior of such an extremely important unit operation. This numerical simulation is carried out based on a recently developed algorithm for solving the population balance equation. The algorithm is implemented via a computer program called liquid-liquid extraction column module (LLECMOD). The LLECMOD is designed in a flexible way that allows the user to define the breakage and coalescence frequencies, droplet terminal velocity, and the other internal geometrical details of the column. The user input dialog makes the LLECMOD a user-friendly program that enables the user to select the simulation parameters and functions in an easy way. The program is reinforced by a parameter estimation package for the droplet coalescence models. In this work, a sample of small laboratory and pilot plant simulations as compared to the experimental data is presented as carried out by the LLECMOD. (c) 2005 Elsevier B.V. All rights reserved.