Effect of Co-firing Ammonia on Coal Volatile Flame Characteristics and Particulate Matter Formation Behaviours

Co-firing “zero-carbon, hydrogen rich, high nitrogen” ammonia (NH3) fuel in coal-fired power plant is an important technical route to mitigate CO2 emission. To explore the impacts of co-firing ammonia fuel on coal combustion and pollutant formation behaviour, the coal-ammonia co-firing experiments were carried out on a McKenna type flat-flame burner system. Combined with visible-light camera, flue gas analyser and thermophoresis probe sampling system, the influence of co-firing ammonia on the flame properties, gaseous pollutant and particulate matter formation was explored. The results show that the ammonia fuel ignites ahead of coal, and the additional heat released from ammonia combustion promotes the pyrolysis of coal and the release of volatile. Thereafter, it promotes the ignition and combustion of volatile, resulting in the increase of flame height and temperature. The added NH3 is partially converted into NO in the volatile flame, resulting in a notable increase in NO concentration. Adding NH3 improves the equivalent ratio of gaseous fuel, which promotes the conversion of volatile to soot, and finally increases the yield of soot particles.