The aim of the present work was to evaluate the performance of a pulverized-coal-fired furnace with air staging. New data are reported for gas phase species concentration, temperature and particle burnout for two primary zone stoichiometric ratios, 1.15 (unstaged flame) and 0.95 (staged flame), other operating conditions being fixed. The results revealed that the reduction in primary zone stoichiometric ratio caused a decrease in NO_x emissions from 421 to 180 mg/Nm~3@6 percent O_2, an increase in CO emissions from 51 to 168 mg/Nm~3@6 percent O_2 and a reduction in particle burnout from 81.8 percent to 76.5 percent. It was concluded that the reduction of the O_2 availability in the primary zone inhibits the NO formation, mainly via the fuel mechanism, but it affects negatively both the CO and the char oxidation processes because, under staging conditions, both processes tend to occur in the vicinity of the over fire air injection region, where the temperatures are relatively low.
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