A novel simulation model for the two phase flow on column trays has been developed. The flow is divided in a liquid continuous region with bubbles on the tray and a gas continuous region with flying droplets above it. These two layers are coupled through empirical correlations for the probability distribution of the droplet starting velocities and the mass fluxes of liquid being ejected as droplets into the gas continuous region. The liquid continuous layer is modelled using an unstructured finite volume formulation for the depth averaged conservation equations for mass and momentum whereas the effect of the droplets in the gas continuous region above the liquid continuous layer is taken into account using a Monte Carlo approach. Valve models, which can be placed at arbitrary positions on the tray, are used to calculate the gas distribution in the liquid continuous layer. The flying droplets not only redistribute mass but their momentum also influences the flow on the tray. Special boundary conditions for weirs, inlets, walls and guide vanes have been implemented. The model has been tested using data for liquid distributions above a tray from literature as well as from FRI tests. Good agreement between simulations and experimental data has been found. Results for real trays are shown with emphasis on effects that influence the efficiency or capacity of trays such as the residence time distribution of the liquid flowing into the downcomer or the L/V ratios for different flow pathes.