The knowledge of particles that remain in the furnace is important for the efficiency of a thermal particle treatment process. These particles mainly stick to the combustion chamber wall and represent a material loss. To predict the amount of particle-wall contacts in such furnaces, a numerical model based on transient multiphase flow calculations is presented in this work. The proposed model differs from the current state-of-the-art CFD models as follows: Instead of using the commonly used RANS turbulence models (realizable-k-ε model, Reynolds stress model) and steady state calculations, large eddy simulations (LES) of the multiphase flow in the furnace in combination with a type of RANS mesh were performed. Furthermore, the applicability of the LES technique was evaluated by comparing the numerical results to measurements. It was found that the proposed numerical model provides more accurate prediction performance than applying common RANS turbulence models.