The effect of the textural properties of bituminous coal chars on NO emissions

Abstract

NO is the primary product of the oxidation of char nitrogen, and in some combustion processes the NO can be reduced on the char surface to give N 2O and/or N 2. In this study a range of bituminous coals (low, medium and high volatile matter content) were pyrolysed in a fixed bed reactor at various heating rates. Textural characterisation was carried out by measuring true (He) and apparent (Hg) densities and N 2 (−196°C) and CO 2 (0°C) adsorption isotherms. Pore volume distributions and surface areas were obtained for the chars studied. A thermogravimetric analyser coupled to a quadrupole mass spectrometer (TG-MS) was used to study the combustion behaviour of the samples and the nitrogen compounds evolved during temperature-programmed combustion. Results are discussed in terms of the influence of both textural properties and reactivity on NO emissions and on the heterogeneous reduction of NO.