A numerical three-dimensional model of a 50 MW industrial incinerator is presented in this communication. The analysed device exploits a new combustion technique, defined as flameless oxidation, that seems to largely hinder thermal NOx formation during the combustion process. This study concerns both fluid-dynamical and thermo-chemical analysis of the reactor. In particular, it highlights the relevant radiating effect on the internal heat transfer related to the presence of grey gaseous participating media inside the control volume of the combustion process. The proposed numerical model, able to analyse the thermodynamics of the reactor for different operative conditions (as other fluids or other inlet velocities) may be an helpful tool, avoiding expensive experimentations, for industrial applications.