Nitrogen pollutant formation in a pulverized coal combustor: Effect of secondary stream swirl

Concentrations of NO, NH3, and HCN, together with coal particle burnout and gas composition, were measured during combustion of a bituminous coal. Control of incoming secondary gas swirl level and overall stoichiometric ratio led to significant reductions in nitrogen oxide pollutant concentration. In‐situ measurements showed that coal particles were confined near the reactor center during rapid particle reaction. This took place in a locally fuel‐rich environment, producing near‐quantitative conversion of fuel‐nitrogen to NH3 and HCN, with some NO. Subsequent gas phase reactions of these nitrogen species were identified as important in establishing the ultimate NO concentration.