RELEASE OF NO FROM THE COMBUSTION OF COAL CHARS

The emissions of nitrogen oxides during coal combustion contribute to acid rain and are a major environmental problem. In this investigation , the release of nitric oxide during the combustion of coal chars prep ared from a wide range of coals in an entrained flow reactor was inves tigated over a range of combustion temperatures (823 - 1323K) using a thermogravimetric analyzer coupled with a mass spectrometer. The conve rsion of char nitrogen to NO (NO/char-N) was studied in relation to co al and char structural characterization parameters. The results show t hat higher levels of conversion of char-N to NO were observed for the high-rank coal chars at lower combustion temperatures, where the react ion is under chemical control. As the combustion temperature increased , there was a decrease in the NO/char-N conversion ratio. Chars with l ow surface areas and low reactivities tend to have higher levels of co nversion of char-N to NO during combustion. The implications for the m echanism of NO reduction on the char surface and in the pores are disc ussed. Copyright (C) 1996 bq The Combustion Institute