Induced draft fans extract coal fired boiler combustion products, including particles of un-burnt coal and ash. As a consequence of the particles, the axial fan blades’ leading edges are subject to erosion. Erosion results in the loss of the blade leading edge aerodynamic profile and a reduction of blade chord and effective camber that together degrade aerodynamic performance. An experimental study demonstrated that while the degradation of aerodynamic performance begins gradually, it collapses as blade erosion reaches a critical limit. This paper presents a numerical study on the evolution of blade leading edge erosion patterns in an axial induced draft fan. The authors calculated particle trajectories using an in-house computational fluid dynamic (CFD) solver coupled with a trajectory predicting solver based on an original finite element interpolation scheme. The numerical study clarifies the influence of flow structure, initial blade geometry, particle size, and concentration on erosion pattern.