Shaft furnaces are widely used in high-temperature processes for granular materials due to their high energy efficiency. The modeling of these furnaces is challenging because of large domains and long process times. Small geometric details like the natural gas burner nozzles demand a fine grid on the computational fluid dynamics (CFD) side, resulting in a grid size smaller than the particle size. Resolving a discrete element particle over several cells is computationally expensive. Interpolation methods on non-structured grids are complex. In order to provide a fast and simple solution, the volume fraction smoother was developed, and to shorten the calculation time, the time scale splitting method, which separates the time steps for CFD and the discrete-element method (DEM), was introduced.