Oklahoma Gas & Electric Muskogee Generating Station Best ...

Oklahoma Gas & Electric
Muskogee Generating Station – BART Determination
May 28, 2008
reduce overall NOx emissions from Muskogee Units 4 & 5 by approximately 3,456 tpy
(compared to advanced combustion controls); however, the incremental cost associated with
this reduction is approximately $57,407,600 per year, or $16,611/ton.
As part of the BART rulemaking, EPA established presumptive NOx emission limits applicable
to EGUs greater than 200 MW at power plants with a generating capacity greater than 750
MW. The presumptive NOx emission limits were based on control strategies that EPA
considered to be generally cost-effective for such units (see, 70 FR 39134). The presumptive
NOx emission limit applicable to Muskogee Units 4 & 5 (tangentially-fired units firing
subbituminous coal) is 0.15 lb/mmBtu. For all types of boilers, other than cyclone units, the
presumptive limits were based on the use of combustion control technologies. EPA estimated
that the “costs of such controls in most cases range from just over $100 to $1000 per ton” (see,
70 FR 39135).
The average cost effectiveness of combustion controls (LNB/OFA) on Muskogee Units 4 & 5 is
similar to the BART cost-effectiveness developed by EPA for NOx control on large EGU
boilers. Both the average and incremental cost effectiveness of SCR on Muskogee Units 4 & 5
are significantly greater than the cost effectiveness of NOx control at other BART-applicable
units. The costs associated with SCR would result in significant economic impacts on the
Muskogee Generating Station (approximately $57,407,600 per year additional costs).
Therefore, SCR should not be selected as BART based on lack of cost effectiveness. Although
SCR does not appear to be cost effective, it will be included in the evaluation of the remaining
factors to assure that the BART determination considers all relevant information.
3.4.2 NOx Control Technologies – Environmental Impacts
Combustion modifications designed to decrease NOx formation (lower temperature and less
oxygen availability) also tend to increase the formation and emission of CO and VOCs.
Therefore, the combustion controls must be designed to reduce the formation of NOx while
maintaining CO and VOC formation at an acceptable level. Other than the NOx/CO-VOC
trade-off, there are no environmental issues associated with using combustion controls to
reduce NOx emissions.
Operation of an SCR system has certain collateral environmental consequences. 13 First, in
order to maintain low NOx emissions some excess ammonia will pass through the SCR.
Ammonia slip will increase with lower NOx emission limits, and will also tend to increase as
the catalyst becomes deactivated. Ammonia slip from an SCR designed to achieve a controlled
13 See, Hinton, W.S., Cushing, K.M., Gooch, J.P., “Balance-of-Plant Impacts Associated with SCR/SNCR
Installations”, proceedings of the ICAC Forum, 2002.
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