EPA/600/A-94/259
N0X CONTROL TECHNOLOGY REQUIREMENTS UNDER
THE UNITED STATES' 1990 CLEAN AIR ACT AMENDMENTS
COMPARED TO THOSE IN SELECTED PACIFIC RIM COUNTRIES
C. Andrew Miller
Robert E. Hall
Richard D. Stern
Air and Energy Engineering Research Laboratory
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
Abstract
The 1990 Clean Air Act Amendments (CAAAs) require reduction of nitrogen oxide
(N0X) emissions under two provisions: Title I requires control of N0X from all
source types for the purpose of attaining ambient air quality standards for N0X and
ozone; and Title IV requires control of NQX from coal-fired utility boilers for the
reduction of acid rain precursors. Title IV is the more straightforward of the
two, and sets national emission standards for dry-bottom wall-fired and
tangentially fired boilers based on low N0X burner technology (LNBT), defined by
EPA to include separated overfire air (OFA). Emission standards for other boiler
types are to be promulgated by 1997.
NOx controls under Title I are more complex, and are based on reductions necessary to
reduce local and regional ambient levels of NOx and ozone. Control technology requirements
under Title I are based on Reasonably Available Control Technology (RACT) as defined by
EPA's Office of Air Quality Planning and Standards; however, emission levels are set by the
states according to local conditions. Technologies defined as RACT include low NOx burner
technology, selective non-catalytic reduction (SNCR), and selective catalytic reduction (SCR).
These and other combustion modifications and flue gas treatment technologies are described.
NOx emission regulations and technology requirements in the U.S. are compared to those in
selected Pacific Rim countries.
I. Introduction
The 1990 Clean Air Act Amendments (CAAAs) were put into law in the United States
on November 15, 1990,1 resulting in air pollution control requirements that are applied to a
much broader scope of sources and pollutants, and setting more stringent pollutant emission
levels than previous air pollution control legislation. The CAAAs not only introduced the
concept of trading emission credits in the case of sulfur dioxide (SO2) emissions, but also
applied limits to emissions of both SO2 and NOx to existing utility sources for the purpose of
reducing acid precipitation. The CAAAs also require control of 189 hazardous air pollutants
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(HAPs) from all sources, and require states to move more quickly to improve ambient air
quality, both as a means of reducing risks to human health. Although the CAAAs have
affected a much larger range of sources and pollutants than previous legislation, and have
made some significant changes to the traditional approaches to regulating air pollution
control, the CAAAs' provisions relating to NOx control are relatively straightforward.
Pollution control regulations for individual sources can take two primary approaches:
setting limits on the amount of a pollutant that can be emitted, leaving the method of
achieving these limits to the individual sources; or mandating the use of a particular control
technology to ensure a certain percentage reduction in emissions. The first approach is
"emissions-based," and the second is "technology-based." In addition to these approaches,
agencies can also create regulations using two other approaches: "stack emission" regulation,
which specifies technologies or emission limits at a particular source; or the setting of ambient
pollutant levels, which specifies a certain level of pollutant in the environment of interest. The
second "other" approach can lead to "stack emission" regulations, or to total mass emissions
designed to prevent sources from emitting pollutants in such quantities that the desired
ambient pollutant levels are exceeded.
The CAAAs incorporate to some degree each of these concepts into the NOx control
provisions of the CAAAs. The acid rain provisions of the CAAAs are set forth in Title IV, and
specify NOx emission limits for utility boilers. However, Title IV also bases the emission limits
on a certain technology, giving the final regulation a combined "emission-based" and
"technology-based" twist. NOx emissions are also subject to limitation under Title I, which is
concerned with attaining ambient air quality. Title I can require sources to control NOx
emissions to achieve air quality standards for both nitrogen dioxide (NO2) and for ozone (O3).
Thus, Title IV is an example of the "stack emission" control strategy for a specific group of
sources, while Title I is based on ambient air quality which implies control of all sources in a
given area. Other differences between the two provisions and the implications for control
technology requirements are discussed in the following sections.
In many Pacific Rim countries, NOx emission regulations are mainly emissions-based
but, as in the case of the Title I requirements, are usually set with certain control technologies
as the basis for the emission levels.
II. NOx Control Provisions of the 1990 Clean Air Act Amendments
A. Title IV
Title IV of the CAAAs provides for NOx emission reductions under Section 407,
"Nitrogen Oxides Emission Reduction Program." Title IV requirements were designed to
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reduce NOx and SO2 emissions from coal-fired utility boilers for the purpose of reducing total
national emissions of acid precipitation precursors. The mandated NOx emission reductions
vary according to boiler type and compliance date, with compliance dates tied to the SO2
reduction provisions. Boilers are categorized by two criteria under Section 407. First, 261
boilers (including 5 oil-fired units) are identified in the CAAAs as Phase I units based on their
total SO2 emissions, and are subject to emission limitations beginning January 1, 1995. All
remaining coal-fired utility boilers greater than 25 MWe are defined as Phase II units, and are
subject to emission limitations beginning January 1, 2000. Second, boilers are divided into
Groups 1 and 2 based on the type of boiler. Group 1 boilers are defined as tangentially fired
boilers and dry-bottom wall-fired boilers, excluding units that use cell burner technology.
Group 2 is composed of all other boiler types (e.g., cyclones, wet-bottom wall-fired units, and
cell burner units). Both Phase I and II units include both Group 1 and 2 boilers.
Under this section, the CAAAs place responsibility for regulating NOx emissions from
utility boilers with the U.S. Environmental Protection Agency (EPA). The CAAAs also state
that Phase I utility units are subject to maximum annual average emission rates of 0.45 lb/106
Btu (194 ng/J) for tangentially fired (T-fired) boilers, and 0.50 lb/106 Btu (215 ng/J) for dry-
bottom wall-fired boilers, except for those applying cell burner technology. The final rule
promulgated by EPA used these values in the subsequent regulation, making it appear to be
an "emissions-based" regulation. However, the CAAAs also require that these limits are to be
achieved using "low NOx burner technology" (LNBT), giving the regulation a combination
emissions- and technology-based approach. This combination has resulted in significant
disagreement over the exact definition of LNBT, with EPA determining that overfire air is
appropriately included in the definition. This determination is being contested by the utility
industry, and the case is scheduled to be presented to the U.S. Court of Appeals in October.
B. Title I
Title I requirements are aimed at a significantly different problem, and therefore take a
significantly different approach than does Title IV. Title I is designed to bring ambient air
quality into attainment with the National Ambient Air Quality Standards (NAAQS), and
therefore does not target specific sources for reduction, but seeks to reduce total emissions
from all sources in order to reduce ambient levels of air pollution. In addition, since
nonattainment of the NAAQS is localized, the resulting emission standards are also localized,
and fall under the authority of regional, state, and local regulatory bodies. The role of the EPA
under Title I is to set the NAAQS and to provide guidance to the regulatory agencies as to
technologies that are reasonably available for application to the sources that require control.
The state agencies must submit to the EPA for approval their State Implementation Plans
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(SIPs), which are the regulatory requirements that each state feels will provide the means for
attaining the NAAQS.
The control technology requirements under Title I are therefore determined not by EPA,
but by the various state agencies. However, EPA plays a significant role in determining these
requirements by publishing a guidance document that defines Reasonably Available Control
Technology (RACT) that states use in setting their technology requirements.
III. Standards and Control Technology Requirements in the Pacific Rim Countries
A. g
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and often require the use of a post-combustion control technology such as SNCR or SCR. In
one case, the Electric Power Development Company met emission levels of 50-60 ppm using a
combination of combustion modification and SCR.8 More common are agreements that lower
emission standards to 200-300 ppm, allowing compliance using combustion modification
alone. An overview of Japanese emission standards is presented in Table 2.
C. Australia
In Australia, the emission limits for NOx are structured similar to the U.S. Title I
requirements, with one significant difference. While the U.S. government sets required
ambient air quality standards that the states are responsible for meeting, the Australian federal
government sets national advisory guidelines for ambient pollutant levels and emissions. As in
the U.S. Title I, the Australian state and territorial governments are responsible for setting the
actual limits for emissions.9 Table 3 shows both the national guidelines and the mandatory
state limits for NOx emissions in two of Australia's states. There is no control technology
9
requirement for meeting these emissions; Australia relies on emissions-based rather than
technology-based standards. However, the emissions-based standards are derived from the
use of combustion modification control technologies (e.g., low NOx burners).
IV. Overview of NOx Control Technologies
NOx control technologies can be divided into two primary types, combustion
modifications and post-combustion controls. As the name implies, combustion modification
controls act through changes in the combustion process, and have been very effective at
control of NOx emissions from fossil fuels. Post-combustion controls do not change the
combustion process, and can be applied to other than combustion sources. In general,
combustion modification controls rely on changing the combustion process to reduce the
formation of NOx, while post-combustion controls destroy the NOx that has been formed
during the combustion process; this generalization does not hold for reburning, as explained
below. In addition, the discussion below does not provide fuel-specific information, but is
only a very general overview. For many of the technologies discussed below, the type of fuel
can make a significant difference in the applicability and performance of the particular
technology.
A- Combustion Modification Controls
Combustion modification controls are based on changing the combustion process to
reduce the formation of nitrogen oxide (NO) or, in the case of reburning, a combination of
reducing formation of NO and destroying NO formed in the primary combustion zone.
Preventing the formation or achieving the destruction of NO is important, since NO comprises
most of the NOx emitted by combustion processes. Combustion modifications can be as
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simple as reducing the level of excess air or can involve significant redesign of the combustion
system. Combustion modifications are designed to achieve two primary objectives: (1) to
minimize the peak flame temperature and thereby minimize the reaction of atmospheric
nitrogen with atmospheric oxygen to form NO; and (2) to force solid fuels to devolatilize in an
oxygen deficient atmosphere to minimize the oxygen available to react with nitrogen found in
the fuel. In both instances, the net result is to reduce the formation of NO. The primary
method used to accomplish these objectives is staging, or an incremental mixing of fuel and
air, the most common form of which is staging of the combustion air (as opposed to staging of
the fuel).
The simplest forms of combustion modification are low excess air (LEA) operation,
burners out of service (BOOS), and biased firing. These modifications typically do not require
any modification to the boiler, but are achieved by altering the air and fuel flows in order to
reduce the oxygen available to react with fuel-bound nitrogen. LEA simply reduces the level
of excess oxygen available by operating a boiler as near to stoichiometric conditions as
possible, with the limiting factor being the level of unburned fuel that exits the furnace. LEA
can be applied to most boilers without modification of equipment or significant changes in
operability. LEA can achieve NOx reductions of about 15%.10
BOOS is effective in furnaces that have burners arranged in more than one horizontal
row, and is accomplished by introducing only air through one or more of the upper row of
burners. This requires that combustion conditions for the lower rows of burners range from
slightly above to slightly below stoichiometric, with the remainder of the necessary
combustion air being provided by the upper burners injecting only air. Biased firing is similar
to BOOS, but does not eliminate all the fuel flow from the upper burners. Biased firing alters
the individual stoichiometries to create more fuel-rich conditions in the lower burners and
correspondingly fuel-lean conditions in the upper burners to achieve the desired overall
furnace stoichiometry. A disadvantage of BOOS and biased firing can be a limit on the
maximum load a unit is able to attain under these conditions. BOOS and biased firing are
most commonly applied to wall-fired boilers, and can attain NOx reduction levels of about 20
to 30% compared to normal operating conditions.10
To minimize the impact on boiler load, dedicated air injection ports can be installed so
that each existing burner can maintain its rated capacity. The use of these ports is most often
referred to as overfire air (OFA). OFA can be applied to most dry-bottom boilers, and is
particularly suitable for wall-fired and tangentially fired units. Some efforts are underway to
apply OFA to wet-bottom units as well. OFA can achieve NOx reductions of 20 to 30% when
compared to uncontrolled NOx levels.11'14
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The combustion modification techniques described above rely on the entire furnace
combustion zone for application of the staging process. This is similar to the low NOx
combustion modification most commonly applied to tangentially fired units, in which coal and
air nozzles are placed in the corners of the furnace to create a large swirling flame in the
furnace center. The interior section of this flame is fuel-rich, with the air necessary for
completion of the combustion added at higher levels. This "rich fireball" concept is the basis
for most low NOx combustion systems commercially available for tangentially fired units, and
the majority of improvements to the process have been in changes to the location of the upper
air injection ports.
For wall-fired units, the application of aerodynamic burner staging has been the basis
for most new combustion modification designs. Aerodynamic burner staging alters the flows
of the coal and air from the cylindrical burners to create burner flames characterized by a fuel-
rich core surrounded by increasing levels of air to achieve the desired overall stoichiometry.
Creating this arrangement of combustion conditions within the more localized volume of the
individual burner flames results in suppressing the formation of NOx. In some applications,
these low NOx burners (LNBs) can be operated in conjuction with OFA as an integrated
system to achieve further NOx reductions. In these instances, the burners are operated
substoichiometrically, with the necessary burnout air supplied by the OFA ports located above
the burners.
LNBs are the most common form of combustion modification NOx control technology.
Many designs utilize OFA ports as an integral part of the design, particularly with tangentially
fired units. Most LNB systems can achieve NOx reductions of 35 to 40%, with reductions of
over 50% achieved where baseline NOx emissions are high. Greater reductions are possible
when LNBs are combined with reburning or post-combustion controls (described below).11"14
Reburning is another combustion modification technique used for reducing NOx
emissions. Reburning is based on a different process than the staging of air, and acts to
destroy NOx already formed in addition to reducing its formation. The chemical process of
reburning is complex, and is based on the reduction of NO by the addition of hydrocarbon
combustion radicals. Such radicals are introduced into the furnace by breaking the
combustion process into three stages. Stage 1 is primary combustion, in which the fuel and air
are combusted under standard or low excess air conditions. Where possible, LEA or other
combustion modification technique is used to minimize the formation of NOx in this (primary)
zone. Only a portion (usually 85-90%) of the total required heat input is generated in this
region, with the remainder coming from the addition of the reburn fuel. Stage 2 is the
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reburning zone, where an amount of fuel required to reach the total required heat input of the
furnace is added. In this zone, no additional air is provided, resulting in high levels of
hydrocarbon radicals that react with the NO present to form nitrogen (N2) and carbon
monoxide (CO), water (H20), or carbon dioxide (CO2). Because of the oxygen deficient, or
reducing, conditions in the reburn zone, stage 3 (the burnout zone) is required to completely
convert the CO and other combustibles to CO2 and H2O. Natural gas is often used as the
reburning fuel, since it contains no fuel-bound nitrogen and, therefore does not create any
additional NO from the reaction of such nitrogen and combustion oxygen. However,
demonstrations of reburning using coal or oil as the reburn fuel have shown that it is not
necessary to use natural gas, and that nitrogen-containing fuels can be successfully used as
reburning fuels. Reburning has consistently achieved NOx reductions of 50%, with some
applications showing reductions as much as 65%.15-16
In some applications, flue gas recirculation (FGR) is used to transport the reburn fuel
and provide the momentum necessary to ensure adequate penetration of the fuel into the flue
gases. Research is being conducted to develop advanced reburn designs, to eliminate the use
of OFA and FGR. These design changes would greatly reduce the capital cost of reburn
application. Other advanced reburn designs incorporate injection of reducing agents, such as
ammonia, to provide further NOx reduction. The goal of advanced reburn design is to
improve the NOx reduction potential to the 75-85% range and to reduce the cost of the
systems.
B. Post-Combustion Controls
Post-combustion controls are characterized by low-temperature conversions of NO to
other compounds, i.e., temperatures below those typically found in the combustion zones of
furnaces. The two most effective post-combustion controls are selective noncatalytic reduction
(SNCR) and selective catalytic reduction (SCR). In both, the injection of a nitrogen-containing
reagent is required. The term post-combustion controls should not be construed to mean that
these technologies apply only to combustion sources. Since the emphasis here is on
combustion sources of NOx, the term post-combustion control provides a clear distinction
between these technologies and combustion modification methods. However, both SNCR and
SCR can be applied to other NOx sources if the temperature and chemical composition of the
exhaust gases are suitable for these technologies. In addition, both technologies can be applied
to combustion sources other than large utility or industrial boilers. Both technologies can be
used as a control technique for stationary diesel and gas-turbine engines, if the proper
temperatures and residence times are available in the exhaust.
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SNCR works by injecting the reagent into a relatively high post-combustion zone in the
furnace, where the nitrogen in the reagent combines with the nitrogen in the NO to form N2
and other nonpolluting compounds (primarily H2O). A temperature range of 1600-2100T
(870-1150°C) is normally required for the reactions to occur. The amount of chemical required
to convert the NO depends upon the reagent used, and is based on the ratio of nitrogen in the
reagent to NO. Injection rates are usually less than N/NO = 2. SNCR typically uses ammonia,
urea, or cyanuric acid as the reagent, although several vendors have developed proprietary
reagents to improve levels of NOx reduction or to modify the effective temperature window.
NOx reductions using SNCR are typically in the 40-60% range, depending upon the
uncontrolled NOx level, and the process variables such as injection rate and available time at
the required temperatures; some demonstrations have achieved 70% reductions.
Disadvantages to SNCR include the formation of nitrous oxide (N2O), ammonia slip (in which
ammonia that does not react with NO is released), the deposition of ammonium bisulfates
formed by the reaction of sulfur trioxide and ammonia, and the presence of a visible plume of
ammonium chloride formed by the reaction of ammonia and hydrogen chloride.17
SCR relies on reactions similar to those with SNCR, and also requires the injection of a
nitrogen-containing chemical. However, SCR operates at significantly lower temperatures,
relying on a catalyst to increase the reaction rate. SCR can achieve NOx reductions of up to
80% where the uncontrolled NOx levels are high (> 800 ppmv). Such high reductions
significantly reduce the catalyst life, however, and in instances where large reductions are
required, the usual practice is to use SCR as the final step in a series of NOx reduction
processes beginning with some form of combustion modification followed by the use of SCR.
The SCR system then acts as a polishing system to bring NOx levels to the final desired level.
SCR and SNCR are both applicable to sources in which the use of combustion modification
methods is not feasible, or where combustion modifications cannot achieve the required NOx
reductions alone.
V. Conclusions
Most of the NOx emission standards in the Pacific Rim countries discussed here are not
"technology-based," requiring specific equipment to be installed. Rather, they are "emissions-
based," with emission limits often set such that certain technologies can be used to achieve
those limits. It may appear that setting a standard so that one or more specific technologies
must be applied to achieve that standard is the same as requiring its installation, but there is an
important difference. When technology-based standards are used, there is little, if any, room
for improving the state of the art beyond minimizing costs and performance impacts. When
emissions-based standards are set, however, there is considerable flexibility allowed in
achieving those standards over the long term. This can allow new technologies to be
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developed and applied, which can significantly improve performance and reduce both capita)
and operating costs.
A significant portion of past research on NOx control technology has focused on coal
and utilities. As the need to reduce NOx becomes more important as an ozone control
strategy, the types of fuels and sources from which NOx must be controlled will become much
broader. This will require combustion modification and post-combustion control technologies
that are more flexible and less expensive in order to make their performance and economical
application possible for very small sources as well as the larger coal and utility sources.
VI. References
1. Clean Air Act Amendments of 1990, Public Law 101-549, November 15,1990.
2. Private communication with U.S. EPA Office of Policy Analysis and Review regarding
"The Competitive Impacts of the Clean Air Act Amendments and EPA's Strategy to
Address Them," Report to Congress under CAAA Section 811, Draft, August 1994.
3. WHO/UNEP, "Urban Air Pollution in Megacities of the World," World Health
Organization, United Nations Environmental Programme, Blackwell, Oxford, 1992.
4. "Megacities of the Pacific Rim and the Burden of Air Pollution," Conference
Proceedings, Jakarta, Indonesia, February 1993.
5. L.S. Cochran, R.A. Pielke, and E. Kovacs, "Selected International Receptor-Based Air
Quality Standards," Journal of the Air and Waste Management Association, V. 42, No.
12, pp 1567-1572, December 1992.
6. H.N. Soud, "Emission Standards Handbook, Air Pollutant Standards for Coal-Fired
Plants," IE A Coal Research, IEACR/43, December 1991.
7. K.R. Smith, M.G. Apte, M. Yuqing, W. Wongsakiarttuat, and A.Kulkarni, "Air Pollution
and the Energy Ladder in Asian Cities," Energy, The International Journal, V. 19, No. 5,
pp. 587-600, May 1994.
8. J. Ando, "Recent Developments in SO2 and NOx Abatement Technology for Stationary
Sources in Japan," U.S. EPA, Air and Energy Engineering Research Laboratory,
Research Triangle Park, NC, EPA-600/7-85-040 (NTIS PB86-110186), September 1985.
9. K.D. Bon, Assistant Secretary for Standards and Chemicals, Australian Commonwealth
Environmental Protection Agency, Queen Victoria Terrace, Australia, Personal
communication, June 16,1994.
10. J.M. Beer et al., "Pulverized Coal Combustion: Pollutant Formation and Control, 1970-
1980," U.S. EPA, Air and Energy Engineering Research Laboratory, Research Triangle
Park, NC, EPA-600/8-90-049 (NTIS PB90-229253), May 1990.
11. R.E. Hall and J.S. Bowen, "State-of-the-Art Combustion Modification NOx Control for
Stationary Combustion Equipment," in Air Pollution bv Nitrogen Oxides. T. Schneider
and L. Grant, eds., Elsevier Scientific Publishing, 1982.
12. T. Beggs, "Nitrogen Oxide Control for Stationary Combustion Sources," U.S. EPA, Air
and Energy Engineering Research Laboratory, Research Triangle Park, NC, EPA/625/5-
86/020 (NTIS PB91-211862), July 1986.
13. D. Eskinazi, J.E. Cichanowicz, W.P. Linak, and R.E. Hall, "Stationary Combustion NOx
Control," JAPCA, V. 39, p. 1131, August 1989.
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14. O. Rentz and J. Ribeiro, "Operating Experience with NOx Abatement at Stationary
Sources," Economic Commission for Europe, NOx Task Force, December 1992.
15. R.C. LaFlesh, R.D. Lewis, R.E. Hall, V. R. Kotler, and Y.M. Mospan, "Three-Stage
Combustion (Reburning) Test Results from a 300-MWe Boiler in the Ukraine," U.S. EPA,
Air and Energy Engineering Research Laboratory, Research Triangle Park, NC,
Presented at EPA/EPRI Joint Symposium on Stationary Combustion NOx Control, May
24-27,1993, Bal Harbor, FL.
16. R. Borio, R. Lewis, D. Steen, and A. Lookman, "Long Term NOx Emissions Results with
Natural Gas Reburning on a Coal-Fired Cyclone Boiler," presented at EPA/EPRI Joint
Symposium on Stationary Combustion NOx Control, May 24-27,1993, Bal Harbor, FL.
17. "State of the Art Assessment of SNCR Technology," EPRI Report TR-102414, Electric
Power Research Institute, Palo Alto, CA, 1993.
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Table 1. Summary of NOx emission standards from selected Pacific Rim countries.
(Source: Refs. 2-9.)
Country/Source
Standard
ppm(a)
Control Technology
U.S. (b)
Dry-bottom T-fired
Dry-bottom wall-fired
0.45 lb/106 Btu
0.50 lb/106 Btu
400
445
LNBT (c)
LNBT (c)
Japan (d)
Boilers < 32 MWt (e)
Boilers 32-560 MWt
Boilers > 560 MWt
720 mg/dscm
515 mg/dscm
410 mg/dscm
350
250
200
No requirement -
use combustion
controls and SCR
Canada
New coal-fired utility
Oil-fired utility
Gas-fired utility
0.395 lb/106 Btu
0.300 lb/106 Btu
0.200 lb/106 Btu
350
250
200
No requirement -
stds can be met
using combustion
modification
Mexico
Coal- and oil-fired util.-
10.0 lb/m3 coal(f)
890
LNBT (c)
South Korea
Coal-fired utilities
0.4 lb/106 Btu
350
No requirement -
stds can be met
Oil-fired utilities
0.3 lb/106 Btu
250
using combustion
Gas-fired utilities
0.4 lb/106 Btu
400
modification
Australia (g)
New industrial plants
New utility plants <30 MWt
New utility plants >30 MWt
New plants >250 MWt
535 mg/dscm
535 mg/dscm
860 mg/dscm
535-2680 mg/dscm
260
260
420
No requirement -
stds can be met
using combustion
modification
New Zealand
Combustion plants
2050 mg/dscm
1000
No requirement
Taiwan
New utility plants
Existing utility plants(h)
720-1025 mg/dscm
720-1025 mg/dscm
350-500
350-500
No requirement
Notes:
(a) Approximate conversion from lb/106 Btu
(b) Title IV requirements only
(c) Low NOx Burner Technology
(d) More stringent limits in some areas - see Table 2
(e) Thermal MW
(0 Estimated at approximately 1.0 lb/10^ Btu
(g) Limits vary by state - see Table 3
(h) Proposed
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Table 2. NOx emissions limits for Japan.8
Type of Boiler
Capacity (1,000 Nm3/h)
Emission Standard (ppm)
Coal-fired
<40
300
(6% 02 basis)
40-700
250
>700
200
Oil-fired
<10
180
(4% 02 basis)
10-500
150
> 500
130
Gas-fired
<10
150
(5% 02 basis)
10-10
130
40-500
100
>500
60
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Table 3. NOx emissions guidelines and limits for Australia and the two most populous
Australian states.9
Standard (a)
ppm (at stated 02)
National Guidelines
Steam boilers
Liquid and solid fuels, units < 30
0.5 g/m3 (at 7% 02)
244
MW
Liquid and solid fuels, units > 30
0.8 g/m3 (at 7% 02)
390
MW
Gaseous fuels
0.35 g/m3 (at 7% 02)
171
Gas turbines
< 10 MW
0.09 g/m3 (at 15% 02)
44
> 10 MW
0.07 g/m3 (at 15% 02)
34
Other fuels
<10 MW
0.09 g/m3 (at 15% 02)
44
> 10 MW
0.15 g/m3 (at 15% 02)
73
New South Wales
Any trade, industry, or process
2.5 g/m3 as NQ2 (new
1218
emitting NOx
installations subject to tighter
limits by license conditions,
typically 0.5 to 1.0 g/m3)
Victoria
Fuel-burning units (other than IC
1.0 g/m3 at 7% 02
487
engines and glass manufacturing
plants) heat input > 150,000
MJ/hr
New units
Gaseous fuels
0.35 g/m3
171
Liquid or solid fuels
0.5 g/m3
244
Power station boilers
0.7 g/m3 (may be relaxed to
341
> 250 MWe
0.78 g/m3 depending on fuel,
(380)
existing emission control
technology, and safety)
(a) Volumes at 0°C and 101.325 kPa
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AEERL-P-1216
TECHNICAL REPORT DATA
(Please read InUmetions on the reverse before completer
1 REPORT NO.
EPA/600/A-94/259
4. TITLC AND SUBTITLE
NOx Control Technology Requirements Under the
United States' 1990 Clean Air Act Amendments Com-
pared to Those in Selected Pacific Rim Countries
7, AUTHORŪ
C.A.Miller, R.L.Hall, and R. D. Stern
8. PERFORMING ORGANIZATION REPORT NO
3. R
6. REPORT DATE
6. PERFORMING ORGANIZATION CODE
9. PERFORMING ORGANIZATION NAME AND ADDRESS
10. PROGRAM ELEMENT NO.
See Block 12
11. CONTRACT/GRANT NO.
NA (Inhouse)
12. SPONSORING AGENCY NAME AND ADDRESS
EPA, Office of Research and Development
Air and Energy Engineering Research Laboratory
Research Triangle Park, NC 27711
13. TYPE OF REPORT AND PERIOD COVERED
Published paper; 9/93~9/94
14, SPONSORING AGENCY CODE
EPA/600/13
15.supplementary notes AEEKL project officer is C. Andrew Miller, Mail Drop 65. 919/
Presented at Pacific Rim International Conference on Environmental Con-
541-2920.
trol of Combustion Processes. Maui. HI. 10 VM
i6. abstract papCr compares nitrogen oxide (NOx) control technology requirements
under the U.S. 1990 Clean Air Act Amendments (CAAAs) with those in selected Paci-
fic Rim countries. The CAAAs require reduction of NOx emissions under Titles I
(requiring control of NC* from all source types for the purpose of attaining ambient
air quality standards for NOx and ozone) and IV (requiring control of NOx from coal-
fired utility boilers for the reduction of acid rain precursors). Title IV sets national
emission standards for dry-bottom wall-fired and tangentially fired boilers based on
low NO < burner technology, defined by EPA to include separated overfire air. Emis-
sion standards for other boiler types are to be promulgated by 1997. Title I controls
based on reductions necessary to reduce local and regional ambient levels of NOx and
ozone, involve Reasonably Available Control Technology (RACT) as defined by EPA's
Office of Air Quality Planning and Standards; however, emission levels are set by the
states according to local conditions. Technologies defined as RACT include low NO*
burner technology, selective non-catalytic modifications, and selective catalytic re-
duction. These and other combustion modifications and flue gas treatment technolo-
gies are described.
17.
KEY WORDS AND DOCUMENT ANALYSIS
a. DESCRIPTORS
b.identifiers/open ended terms
c. cosati Field/Group
Pollution Boilers
Nitrogen Oxides Catalysis
Emission Flue Gases
Ozone
Coal
Combustion
Pollution Control
Stationary Sources
Acid Rain
Reasonably Available
Control Technology
(RACT)
13B 13 A
07B 07D
14 G
21D
2 IB
13. DISTRIBUTION statement
Release to Public
19. SECURITY CLASS (This Report)
Unclassified
21, NO. OF PAGES
20. SECURITY CLASS (This page)
Unclassified
22. PRICE
EPA Form 2220-1 (9-73)
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