The numerical simulation of the distillation and absorption/desorption process is made possible by coupling a transient two-phase simulation in a structured packing with a model for the simulation of the species transfer. The two-phase flow is modeled by the volume of fluid (VoF) method. The simulation of the locally resolved species transfer is conducted using the generalised continuous species transfer (GCST) model. The simulation data are evaluated for the separation efficiency of the tested packing by calculating the HETP value.