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

from 2 to 9 lb/ton of clinker, and precalciner-kiln emissions
ranged from 2 to 7 lb/ton of clinker.
During preparation of this ACT document, NO emissions data
x
were collected from major cement companies in the United States.
Out of 48 cement kilns providing NO emissions data, 22 were from
x
long wet kilns, 8 were from long dry kilns, 8 were from preheater
kilns, and 10 were from precalciner type cement kilns. Table 4-3
presents these most recent data on NO emissions along with the
x
kiln types and fuels burned.
As seen from Table 4-3, in general, wet kilns were found to
produce the highest NO emissions ranging from 3.6 to 19.5 lb
x
NO /ton of clinker with an average of 9.7 lb NO /ton of clinker.
x x
Wet kilns also consume the most energy among different cement
kiln types. The energy consumption of wet kilns was found to be
in the range of 4.9 to 8.8 MM Btu/ton of clinker with an average
of 6.0 MM Btu/ton. Wet kilns burning gas were found to produce
greater NO emissions as compared to those burning coal. Also in
x
some cases, high secondary combustion air temperatures were
present with high NO emission rates. Twelve of the wet kilns
x
reported burning WDFs in significant quantities. Five of these
kilns used "mid-kiln" firing of the solid and liquid waste fuel
and the other seven kilns injected liquid waste in the hot kiln
burning zone. The kilns with mid-kiln firing reported much
greater NO emissions ranging from 9 to 18.3 lb/ton of clinker,
x
whereas other waste fuel burning wet kilns reported much lower
NO emissions ranging from 3.6 to 8.1 lb NO /ton of clinker. NO
x x x
emissions data from these kilns prior to introducing waste fuels,
however, were not available to directly assess the effect of
waste fuel burning on NO emissions.
x
The long dry kilns were found to consume significantly less
energy than wet kilns (about 4.5 MM Btu/ton on average) and also
were found to produce less NO emissions in the range of 6.1 to
x
10.5 lb NO /ton of clinker with an average of 8.6 lb NO /ton of
x x
clinker. The long wet and dry kilns are similar in terms of
structure and firing of fuels. The difference in the NO x
4-22