Nitrogen release during reaction of coal char with O-2, CO2, and H2O

The chemistry of char-N release and conversion to nitrogen-containing products has been probed by studying its release and reactions with O-2, CO2, and H2O. The experiments were performed in a fixed bed flow reactor at pressures of up to 1.0 MPa. The results show that the major nitrogen-containing products observed depend on the reactant gas; with O-2, NO2 and N-2 being the major species observed. Char-N reaction with CO2 produces N-2 with very high selectivity over a broad range of pressures and CO2 concentrations. and reaction with H2O gives rise to HCN, NH3, and N-2. Observed distributions of nitrogen-containing products are little affected by pressure when O-2 and CO2 are the reactant gases, but increasing pressures in the reaction with H2O results in the formation of increasing proportions of NH3. Formation of NH3 is also promoted by increasing concentrations of H2O in the feed gas. The results suggest that NO and HCN are primary products when O-2 and HO2 respectively, are used as the reactant gases, and that the other observed products arise from interactions of these primary products with the char surface. (c) 2004 The Combustion Institute. Published by Elsevier Inc. All rights reserved.