The mathematical model of the pulverized coal combustion of technical firing systems, as has been applied in the CFD-programme FIRE-VDS-1.3, is introduced. The Combustion model is divided into several sub-models. A very exact model is described and used which was composed with the aid of Literature. The results of the combustion simulation of a modern Large-scale combustion plant ate presented. It concerns an all-wall firing with four burner Levels and a twofold air-staging.