PREDICTION OF NITRIC OXIDE FORMATION IN A TURBULENT PREMIXED PULVERISED COAL FLAME

Abstract

A mathematical model of the formation of nitric oxide from coal nitrogen has been applied to a turbulent, non-swirling, premixed flame. Volatile nitrogen is assumed to form both HCN and NH3 directly during devolatilisation with the ratio of HCN/NH3 being a function of the fuel O/N ratio. Quaternary nitrogen is released directly as ammonia. A conversion efficiency for char nitrogen to NO is applied, based on a separate single particle model. Ammonia may be formed in the gaseous phase by the conversion of hydrogen cyanide into the NH radical. The effects of hydrocarbon radicals and soot in the flame on the formation of nitric oxide are considered. The inclusion of hydrocarbon reduction and the ammonia reactions gives acceptable results. When a soot formation routine is introduced it is found to have a negligible influence on the reduction of NO. Overall the model gives reasonable predictions of HCN, NO, NH3 and particle temperature.