Current developments in the energy sector increasingly demand the consideration of fuels with much larger particle sizes, either from alternative sources or due to a reduced pre-processing effort. In numerical simulations of such systems the particles can no longer be considered as non-colliding material points. Municipal waste incineration on grates or wood pellet combustion in domestic boilers are such examples, where the Discrete Element Method (DEM) can be applied to extend the Lagrange tracking of moving particles to a mechanically and thermally fully interacting flow of reacting granular material. In some situations where sufficiently large time scale differences between the processes in the gas phase and in the solid phase exist, distinctive interfaces can be identified between domains, thus allowing a different modelling in these regions. The treatment of the radiative heat transfer between such domains poses particular difficulties at the interfaces. Based on the two exemplary applications mentioned, details of the modelling
approach are discussed and corresponding results presented
