Two computational fluid dynamics (CFD) modeling approaches, the discrete phase model (DPM) and the combination of volume of fluid (VOF) and DPM, are developed to simulate the phase separation phenomenon in four pilot-plant-scale separators. The incipient vapor phase velocity, at which liquid droplet carry-over occurs, and separation efficiency plots are used as criteria for evaluating the developed CFD models. The simulation results indicate that the VOF-DPM approach is a substantial modification to the DPM approach in terms of the predicted separation efficiency data and diagrams. CFD simulation profiles demonstrate that all the separators are essentially operating at a constant pressure. The CFD results also show that mist eliminators may operate more efficiently in horizontal separators than in vertical separators.