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

eductions ranged from 470 tons/year to 1,550 tons/year, whereas
annual NO emissions reductions of 210 tons/year to 510 tons/year
x
are expected with the low NO burner technology for the eight
x
model plants.
The low NO burner technology is not expected to have any
x
measurable impact on CO emissions and its impact on hydrocarbon
emissions is not known. For the postcombustion NO control
x
approaches of SCR and SNCR, generally a little excess of reagent
is used than that required stoichiometrically to ensure the
desired percent reduction of NO . This results in ammonia
x
emissions which is usually referred to as "ammonia slip" which
are normally below 10 ppm. These techniques are not likely to
affect the formation of other pollutants.
No data are available to determine the energy impacts of the
low NO burner technology. Because of problems related to
x
catalyst fouling, an SCR system may need to be installed
downstream of a particulate control device. Since the SCR
process requires gas temperature to be about 400 to 500 EC (750
to 930 EF), the gas stream may need to be reheated causing an
additional energy cost. Additional energy is also needed due to
the pressure drop across the catalyst bed. With no heat recovery
in the flue gas reheater, additional energy required for flue gas
reheating may be as high as 25 percent of the energy consumed in
the cement-making process. With an energy recuperative type
process heater with an energy recovery of 60 percent the energy
requirement for the flue gas reheating would be approximately 10
percent of that consumed in the cement manufacturing. Additional
electrical energy required to operate ammonia or urea solution
pumps in the SCR or SNCR technologies is negligible.
2-11