THE INFLUENCE OF MINERAL MATTER AND CARBONIZATION CONDITIONS ON NITROGEN RELEASE DURING COAL COMBUSTION

This paper describes an investigation of the influence of carbonization conditions and mineral matter on the release of NO during the combustion of a low volatile (14.6 wt% daf) Spanish coal. Temperature programmed combustion studies were carried out in a thermogravimetric analyser coupled with mass spectrometer using a 20% oxygen argon mixture. Fractions of coal, with a range of mineral matter contents, were prepared by flotation techniques. The fractions were carbonized at high heating rates in an entrained flow reactor, and at low heating rates in a conventional laboratory carbonization system. The results show that mineral matter in this particular coal had little effect on the conversion of coal and char nitrogen to NO, even when effects attributed to catalysis of the carbon gasification reactions were observed. However, carbonization conditions had a marked effect on the conversion of fuel nitrogen to NO. The amount of nitrogen converted to NO decreased with increasing nitrogen content and reactivity. The results are discussed in terms of the reduction of primary char nitrogen oxidation product, NO. on the carbon.