NOx Emissions from Cement Mfg - US Environmental Protection ...

emission rates may thus be attributed to the difference in the
energy consumption rates in these two types of kilns.
The preheater type of kilns was reported to produce NO x
emissions in the range of 2.5 to 11.7 lb NO /ton of clinker with
x
an average of 5.9 lb NO /ton of clinker. The highest values of
x
8.1 and 11.7 were incidently found in gas burning kilns. As
expected, the energy consumption of preheater kilns was much
lower, about 3.8 MM Btu/ton. In addition, combustion of a part
of the fuel at a lower preheating temperature is expected to
reduce the NO emissions as compared to burning all the fuel in
x
the hot kiln burning zone. These two factors account for the
lower NO emissions in preheater kilns as compared to long wet or
x
dry kilns.
The precalciner kilns produced the least NO emissions ranging
x
from 0.9 to 7.0 with an average of 3.4 lb NO /ton of clinker.
x
These kilns were also the most energy efficient with an average
energy consumption of 3.3 MM Btu/ton of clinker. In precalciner
kilns, the proportion of the fuel burned at the calcining
temperature is much greater as compared to the preheater type
kilns leading to lower NO emissions.
x
The literature data indicate substantial spread in the
reported NO emissions with significant overlap for different
x
kiln types. The four different cement kiln types, however, do
appear to have different levels of NO emissions and different
x
characteristics influencing NO formation. The emission factors
x
based on the information obtained during this study will be used
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