Effect of Pressure on NOx Emission from Char Particle Combustion

Abstract

The effect of pressure on NOx emission during char particle combustion was examined in chemical-reaction control and diffusion control regimes. A fixed bed was used for batch testing under 0.1−1.6 MPa. It was found that with increasing pressure, NOx emission decreased extremely, when char combustion rate was controlled by reactant gas diffusion into the char particle at high temperature. The extent to which NOx was reduced in char particles strongly influenced the NOx emission from char pressurized combustion. Pressure increased residence time for diffusion of NOx throughout the char particle and consequently further increased the reduction of NOx in the char particle. Both pressure and temperature strongly influenced the conversion of fuel-N in char to NOx. When pressure was raised from 0.1 to 1.1 MPa, the conversion of fuel-N to NOx fell from 0.18 to 0.06 at 973 K, and from 0.68 to 0.13 at 1173 K. NOx emissions were lower when large char particles were combusted than when small ones were combusted. It was also observed that practically no N2O was formed in to any extent in the char particle.