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

6.1.3.7 Administrative Charges. The administrative charges
were calculated as 2 percent of the total capital cost of the
control system, consistent with Reference 2.
6.1.3.8 Capital Recovery. In this cost analysis the
capital recovery factor (CRF) is defined as2:
where
CRF ' i(1%i) n /((1%i) n & 1) ' 0.1315
i is the annual interest rate = 10 percent, and
n is the equipment life = 15 years.
The CRF is used as a multiplier for the total capital cost to
calculate equal annual payments over the equipment life.
6.2 COSTS OF NOx CONTROL APPROACHES
As discussed in Chapter 5, feasible NOx control approaches
include both in-combustion and postcombustion control techniques.
In-combustion approaches considered include combustion zone
process control, use of low NOx burners, and secondary combustion
of part of the fuel. Postcombustion approaches considered
include selective catalytic and noncatalytic reduction of NOx
using either ammonia or urea.
6.2.1 Combustion Control Approaches for Reduction
in NOx Formation
6.2.1.1 Combustion Zone Control of Temperature and Excess
Air. Approaches aimed at improving the energy efficiency of the
process indirectly reduce NOx emissions per ton of the clinker
product. These approaches rely on continuous monitoring of NOx,
O2, and CO emissions for controlling the excess air, fuel rate,
and the combustion zone temperature. These measures are usually
undertaken to increase process energy efficiency by reducing
over-burning of the clinker. Maintaining the combustion zone
temperature to a necessary minimum value using process control
systems minimizes both the process energy requirement and NOx
emissions and increases refractory life. Because continuous
monitoring of emissions is necessary for efficient process
control, the cost of monitors is not considered as a NOx control
cost. The optimum kiln operating conditions provide a baseline
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