Release of nitrogen oxides during combustion of model coals

To study nitrogen oxides release, two model coals, which contain pyrrolic or pyridinic nitrogen, are prepared and burned in an entrained flow combustion system during 800-1300 degrees C. The influences of temperature, mineral, interaction between the two nitrogen forms, and oxygen concentration are discussed. The results show that NO is the dominant species, and its release increases drastically as temperature rises. N2O is only detected at 800 and 900 degrees C. The interaction between the two nitrogen forms gives rise to an increase of NO release at low temperatures but a decrease at high temperatures. For pyrrolic nitrogen, Ca and Na promote NO release above 900 degrees C, and Fe increases NO release for all temperatures investigated. As for pyridinic nitrogen, all minerals inhibit NO release above 900 degrees C. The NO release decreases when catalyst load rate increases. NO release rises with increasing oxygen concentration first and then decline. More NO2 is released when oxygen concentration is above 20%. (C) 2016 Elsevier Ltd. All rights reserved.