Advanced reburning measurements of temperature and species in a pulverizedcoal flame

An experimental program has been completed where detailed measurements of a pulverized coal flame with advanced reburning have been obtained. Maps of species (CO, CO2, O-2, NO, HCN, and NH3), temperature, and velocity have be en obtained consisting of approximately 60 measurements across a cross sect ional plane of the reactor. Two maps at a single operating condition were o btained and are compared. In addition to the mapping data, effluent measure ments of gaseous products were obtained for various operating conditions, w hile investigating the affect of reburning zone stoichiometric ratio (SR), ammonia nitrogen to NO ratio (NSR), ammonia injection location, and burner swirl. Advanced reburning was achieved by injecting natural gas downstream of the primary combustion zone to form a reburning zone followed by ammonia inject ion and then tertiary air. The data showed advanced reburning was more effe ctive than either reburning or NH3 injection alone. At one advanced reburni ng condition (SR = 1.05, Swirl = 1.5, NSR = 2.5) over 95% NO reduction was obtained. Ammonia injection was most beneficial when following a reburning zone which was slightly lean, SR = 1.05, but was not very effective when fo llowing a slightly rich reburning zone, SR of 0.95. In the cases when advan ced reburning was most effective (reburning SR = 1.05), higher NSR values i mproved NO reduction, but the effect of NSR was secondary to NH3 injector l ocation. The optimal location for injection was found to coincide with chan ges in the temperature field. The mapped temperature, species and velocity data for advanced reburning sh owed that the largest drops in NO occurred in a region where the O-2 concen tration was between 0.7 and 3.0%, NH3 was between 0 and 2961 ppm, and tempe ratures were between 1274 and 1343 K. These are similar to optimal conditio ns known for SNCR. Significant NO reductions were seen when NSR values were near one, suggesting NH3 was very effective at NO reduction when surroundi ng temperature and species conditions were favorable. Because this was only one detailed set of data, it is difficult to conclude that these condition s are optimal or need to exist for optimal NO reduction. More detailed mapp ing data at other operating conditions would be useful in identifying optim al advanced reburning conditions. (C) 2000 Elsevier Science Ltd. All rights reserved.