Dust emission due to air entrainment in falling solids/particle plumes is a common and serious environmental issue in industry. The prediction of the flowrate of air induced by falling particles is pivotal for the design of dust removal equipment in practice but until now there is still limited reliable correlations available. In this work, the process of air entrainment in falling plumes of particles is numerically studied by a combined approach of Computational Fluid Dynamics (CFD) and Discrete Element Method (DEM) (CFD-DEM). A 2D CFD-DEM model is first compared against two 3D models. Then the 2D model is validated against experiments qualitatively at small scale and quantitatively at large scale. Finally the model is used to predict the effect of various important variables including drop height and solids mass flowrate at an industrial scale.