Complete distributions of all major products and nitrogen species are
reported for the oxidative pyrolysis and combustion of premixed suspen
sions of subbituminous, Pittsburgh No. 8 hvA bituminous, and a low-vol
atile bituminous coal after 150 ms. As inlet O-2 levels were progressi
vely increased from 0 to 15% in successive tests, the process chemistr
y moved through oxidative volatiles pyrolysis, volatiles combustion, s
oot combustion, and char oxidation. However, the different fuel compon
ents were consumed sequentially only with the low-volatility coal. Cha
r, soot, and noncondensible fuels burned simultaneously with the subbi
tuminous coal and, to a lesser degree, with the Pittsburgh No. 8, Cons
equently, hydrocarbon gases from these coals, particularly CH4 and C2H
2, were present while most of the char and its residual fuel-N was con
verted into gases. With all coals, the persistence of gaseous hydrocar
bons profoundly affects the conversion of all fuel-N species in the ga
s phase, As long as detectable amounts of CH4 and C2H2 are present, NO
is absent with all coal types and total fixed nitrogen (TFN = HCN + N
H3 + NO) is composed of only HCN with both bituminous coals, plus appr
eciable amounts of NH3 during intermediate stages with the low-rank co
al. But after the hydrocarbons are consumed, HCN and NH3 vanish and mo
st of the remaining char-N and soot-N are converted into NO, so TFN is
composed of only NO. The extent of carbon conversion up to the NO inc
eption point is the primary coal rank index for early NO production in
coal flames, falling from 38% with the subbituminous to 12% with the
low-volatility coal.