Numerical studies of the heterogeneous combustion of char using detailed chemistry

The oxidation of graphite is used as a model system for the combustion of c har. In order to understand this oxidation process a stagnation-point flow of an oxygen stream on a graphite surface is investigated numerically. The chemical reactions in the gas phase as well as on the surface are modelled by a series of elementary steps. The surface reactions take into considerat ion the different surface complexes formed, the influence of the geometry o f the graphite surface and the interaction of gas-phase molecules with surf ace complexes. The rate coefficients used are estimated by applying methods of the microkinetic analysis of heterogeneous catalytic reactions. The: me chanism is used to simulate the combustion rate of a graphite surface and t he ratio of CO to CO2 formed un the surface. The simulation results are com pared with experimental data and a good agreement is achieved. Furthermore, the fraction of char-bound nitrogen converted to N-2 and N2O is calculated . (C) 2001 Elsevier Science Ltd. All rights reserved.