Dysfunctions observed in thermochemical conversion reactors, like dead zones and short- circuits, generally lead to inaccurate pricing of energy resources and air pollution, and originate in the air flow conditions in these aeraulic reactors.([1-3]) Therefore, they can be prevented by better control of flows. In this work, we propose to develop a new tool for determining the distribution of residence time of the solid phase, based on the luminescence of particles previously coated with phosphorescent pigments. This optical method, which is non-intrusive and flexible, has been implemented at a laboratory scale, on an aeraulic test bench.([3]) On the other hand, we have developed a numerical model allowing the determination of the distribution of the residence time. This development aims to master the flows at the exit of surrounding walls, which optimizes them and allows their extrapolation to the industrial scale. Our analytical approach is based on modelling by coupling MFN by finite volume types via the Code Saturn, and DEM by discrete elements of the solid behaviour by means of the code SIGRAME. Finally, a confrontation of the RTD of the digital model with the experimental RTD has been conducted.