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

in existing direct-fired kilns ranged from $267,000 for the small
dry kiln to $423,000 for the large long wet kiln.
6.2.1.4 Secondary Combustion of Fuel. As discussed in
Section 5.1.4, secondary combustion of fuel is expected to reduce
the thermal NOx formation in cement kilns. The amount of fuel
NOx generated during the secondary combustion determines the net
effectiveness of this technique for NOx control. The costs
associated with this process are those for kiln modifications
necessary to facilitate secondary combustion of fuels as well as
those for a conveying system required for the secondary fuel.
Typically, the secondary combustion approach would also allow
burning waste-derived fuels and, as such, would reduce the
overall cost for the fuel. Modification of a long kiln for
secondary combustion is a recent technology and very limited
information is available regarding costs involved. According to
one source, the cost of kiln modifications is approximately
$25,000 with additional $25,000 for seals.13,14 According to the
same supplier, the cost of fuel metering and conveying system
depends upon the degree of automation desired and also on the
type of fuel burned. For a completely automated system for
injecting tires or containerized solid or liquid fuels, the
equipment cost could be as much as $250,000 for a typical wet
kiln with a 40 ton/hr clinker capacity, whereas for a completely
automated coal-feeding system the capital cost can be as much as
$100,000.13,14 The cost of a fuel conveying system can be
considerably lower for a semiautomatic, labor intensive system
and may be expected to depend to a small extent upon the fuel
conveying capacity needed. These costs are not applicable to
preheater or precalciner type kilns.
Approximate capital costs were developed by assuming a total
of $300,000 equipment cost for kiln modifications and fuel
conveying and metering system to provide 40 percent of heat
requirement of a 40 ton/hr long wet kiln. The heat duty provided
by mid-kiln-fired fuel in this example would be about 100 MM
Btu/hr. The equipment cost may be scaled to the four long kiln
model plants using the 0.6 power rule:
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