A Computational Fluid Dynamics (CFD) model is developed for prediction of erosion rates in tube banks of bagasse-fired boilers. The model predicts the flow field, combustion processes, ash particle trajectories and erosion of pipe tubes. Computational efficiency within tube banks is achieved by domain decomposition; the tube banks are treated globally as a porous medium and then detailed modelling is carried out around individual pipe surfaces. Erosion rates are predicted from particle trajectory impact energy. The CFD model predictions are compared with furnace flow measurements and pipe erosion rates obtained by weight loss measurements. There is generally good agreement with the limited data.