The article describes the use of a 15.3 x 25.4 cm thick bed reactor with refractory walls to investigate the influence of bed-region (first-stage) stoichiometry on fuel nitrogen evolution and reaction in coal-fired mass-burning stokers. The combustor operated in a batch mode providing a Lagrangian simulation of the time/temperature/environmental history of a small bed segment traveling through a larger combustion facility. Typically, as a run proceeded, both the superficial burning rate and NO exhaust emissions increased, reached a maximum, and then decreased toward the run termination. However, under locally fuel-rich conditions, the NO emissions peaked prior to the maximum combustion rate. Inflame measurements suggested that fuel nitrogen evolution probably occurs at about the same rate as carbon oxidation. Overall, staging the combustion air resulted in a substantial decrease in exhaust NO emissions.