Micronized coal reburning with 14%
reburn fuel reduced NOx emissions from
the 0.35 lb/million Btu baseline level to
0.25 lb/million Btu, a 28% reduction,
which was within the target range. The unburned
carbon-in-ash, also referred to as
loss-on-ignition (LOI), was maintained
under 4%. During testing, it was found that
excess air is the single most important parameter
that affects NOx emissions, higher
excess air resulting in higher NOx, but
lower LOI. Increasing coal fineness improved
NOx emissions only marginally,
but lowered LOI. Increasing the percent
reburn fuel slightly decreased NOx, but
increased LOI.