Mechanisms that govern the formation and destruction of nitrogenous sp
ecies in fuel rich zones caused by air staging and reburning were expl
ored in a laboratory coal combustor. The objective was to determine wh
ether the same simplified, but fundamentally based, gas phase mechanis
m would predict time resolved profiles of all nitrogenous species, for
both NO(x) abatement procedures. Experimentation was conducted on a 1
7 kW down-fired pulverized coal combustor, burning a variety of coals,
under various air staged and fuel staged configurations. In the fuel
rich pulverized coal post-flame, HCN appearance in the bulk gas phase
was not due to the slow release of nitrogen from the coal residue, as
was previously hypothesized. HCN formation and destruction in fuel ric
h regimes were governed by homogeneous gas phase kinetics alone. The f
ixation of N2 by hydrocarbons to form HCN, together with reactions of
hydrocarbon radicals with either NO or N atoms, could explain HCN form
ation, during both air and fuel staging. The interconversion of nitrog
enous species in the fuel rich zones of air or fuel staging configurat
ions could be adequately described by a simplified mechanism based on
known detailed gas phase reactions and partial equilibrium assumptions
. Profiles of NO, HCN and NH3 were adequately predicted for both air a
nd fuel staged NO(x) abatement configurations, and the proposed mechan
ism should prove useful for incorporation into more complicated furnac
e models to predict NO emissions from practical coal combustion system
s.