A comparison of NO release from coals and entrained-flow reactor chars during temperature-programmed combustion

Abstract

A comparison was made of the temperature-programmed gasification in 20% oxygen in argon of six coals covering a wide range of rank and the chars produced from the coals in an entrained-flow reactor (EFR) at 1000 °C. The temperature-programmed oxidative gasification of the coals has two main regions, representing mainly gasification of the volatiles released and of the char formed during pyrolysis. The NO gas evolution profiles reach a maximum after the corresponding CO and CO 2 profiles for both the coals and EFR chars. The temperature at which these peaks occur increases with increasing rank. In the lower-temperature range where the primary devolatilization of the coal occurs, the NO CO 2 and NO CO ratios decrease with increasing temperature. For the low-rank coals, a peak due to HCN is also detected in this region as well as at the initial char formation stage. In the char gasification region of the coals and for the EFR chars, the NO CO 2 and NO CO ratios increase with increasing temperature and extent of burnoff. The ratio of NO released during gasification to the total nitrogen varies from 0.14 to 0.44 for the EFR chars and from 0.31 to 0.57 for the coals. It is apparent that there are similarities in the release of nitrogen during the combustion of coals of a wide range of rank and of EFR chars derived from these coals.