Effect of Char Particle Size on NO Release during Coal Char Combustion

Abstract

In this study, the effect of particle size on the release of NO during the char combustion under particle packed-layer conditions was investigated at combustion temperatures of 900 °C~1400 °C. The results show that after pyrolysis, the small size char favored more pores and specific surface area. No significant variations of the intrinsic reactivity of O2 and NO with char particle size were measured. By increasing char particle size, more NO conversion from nitrogen in char (char-N) was found regardless of the combustion temperature and bulk oxygen concentration. This can be explained as follows. By increasing char particle size, less O2 penetrated into the pores and more NO formed because of a less accessible pore surface area and a decreased NO reduction time. The effects of reaction temperature and bulk oxygen concentration were also discussed. A quantified description using a first-order reaction model shows that the char particle size will finally influence the accessible pore surface area and depth ...