Effect of Solid Structural Change on the Rate of NO Formation During Char Combustion

Abstract

During the combustion of coal, the solid structure changes significantly. In particular, the changes in the porosity and surface area affect most of the heterogeneous combustion reactions. The effect of such changes on the rate of NO formation during char combustion is studied. It is shown that a detailed structural model is required to analyse the important features of NO formation. Using a random-pore model, the simultaneous formation and reduction of NO in a single particle are analysed. Then the model is extended to calculate the profiles of NO, O₂ and carbon conversion in a tubular furnace. It is found that, with structural effects included, a simple reaction scheme gives predictions in good agreement with experimental data, The results also explain why fuel nitrogen is only partially converted to NO even when there is excess oxygen in the bulk gas.