In pulverized coal flames, the products of primary devolatilization ar
e radically transformed by secondary chemistry after they escape into
the gas phase, but before they burn. This laboratory study aims to cla
rify the macroscopic combustion characteristics of coal volatiles, esp
ecially the way that burning rates increase as tar is converted into s
oot during secondary pyrolysis. Mixtures of the noncondensible fuel co
mpounds released under simulated pulverized fuel firing conditions are
generated in a novel coal flow reactor that independently regulates t
he extent of secondary pyrolysis. After tars, soot, and char particles
are filtered out, the fuel mixtures are blended with oxygen and ignit
ed in a combustion bomb. Laminar burning velocities are assigned from
transient pressure measurements during flame propagation. Burning velo
cities are reported for (fuel) equivalence ratios from 0.5 to 1.5 at t
wo dilution ratios for noncondensible volatiles from four coals repres
enting ranks from subbituminous through low volatile bituminous. For a
ll coal types, burning velocities triple as the extent of tar conversi
on into soot increases from 50 to 100%. This tendency is consistent wi
th conversion of all of the oxygen and hydrogen in tar into H2 and CO,
and of all light hydrocarbons into acetylene. The burning velocities
for volatiles from the bituminous coal are two-and-one-half times grea
ter than those for the volatiles from the subbituminous coal, consiste
nt with the abundance of oxygen in the subbituminous coal, and its cor
respondingly higher yield of CO and lower yields of H2 and hydrocarbon
s. A correlation for this database is developed from the thermal theor
y of premixed laminar flame propagation and a generic skeletal mechani
sm for hydrocarbon combustion. This scaling is also used to assign nom
inal burning rates from the measured burning velocities. The rates are
up to an order of magnitude faster than burning rates of soot. Nomina
l burning rates also gauge the combined influences of coal loading, ra
nk-dependent yields and heating values, and extent of secondary pyroly
sis.