Numerical Modelling of Nitrogen Oxides Formation During Combustion of Pulverised Fuel

Abstract

Pollutants originating from pulverised solid fuel combustion systems are investigated with numerical simulations augmented by data from the fundamental experimental research. Nitrogen oxides formation model, with fuel nitrogen as a main pathway mechanism, was implemented in the computational fluid dynamics model for coal combustion. Partitioning of nitrogen contained in fuel is among the main characteristics influencing the final production of pollutants, but it is highly dependent on fuel type and combustion parameters. The experimental determination of intermediate chemical species during the pyrolysis of a coal sample was performed on a thermogravimetric analysis-mass spectrometry system, and it shows that the fuel nitrogen is uniformly emitted as hydrogen cyanide and ammonia-52.2% and 47.8%-while the hydrogen cyanide production pathway from char is dominant over the volatiles-84.3% and 15.7% respectively. The obtained results on the ratio of ammonia to hydrogen cyanide during fuel nitrogen devolatilisation were used as input parameters in numerical simulations. The improved model shows good results in simulating pyrolysis, making it suitable for modelling and optimisation of thermal utilisation processes on industrial scales.