A kinetic study of the high temperature NO-char reaction

The heterogeneous reaction between NO and a coal char was studied in the temperature range 1273-1573 K in a drop tube furnace. The char was prepared at high temperature and its surface and porosity was measured. The parameters investigated were the concentration of NO, the temperature and the solid concentration. It was observed that the experimental results support the first-order reaction assumption with respect to NO and surface area. In order to extract an intrinsic kinetic law from these measurements, a complete two-dimensional simulation of the two-phase flow in the drop tube furnace was built using FLUENT software. This model allowed to take into account the group effects and the influence of radial gradients on the global reaction rate. A description of the diffusion limitation in the porous structure of the particle was added to the fluent heterogeneous reaction sub-model. From these simulations, we were able to obtain a good agreement between the measured and computed NO reduction yield with the kinetic constant k = 88 exp(-14,4001T) m/s which correspond to an activation energy of 120 kJ/mol. (C) 2004 Elsevier Ltd. All rights reserved.