GUIDELINE SERIES
OAQPS NO. 1.2-048
OOOR76010
SIP PREPARATION MANUAL FOR NO.
US. ENVIRONMENTAL PROTECTION AGENCY
Office of Air Quality Planning and Standards
Research Triangle Park, North Carolina
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SIP PREPARATION MANUAL FOR NOV
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OAQPS NO. 1.2-048
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August 1976
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I U. S. Environmental Protection Agency
Office of Air Quality Planning and Standards
Control Programs Development Division
Research Triangle Park, N. C.
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INTRODUCTION
| The Clean Air Act, as amended in 1970, provided that for each
national ambient air quality standard (NAAQS) promulgated by the
Administrator, a State Implementation Plan (SIP) for each Air Quality
Control Region (AQCR) was to be developed which was to contain emission
control measures that would provide for attainment and maintenance
of national standards, generally within three years of the approval
of the SIP. Experience has shown that not all SIP's developed by the
States in early 1972 were adequate to provide for attainment and main-
tenance of the nitrogen dioxide (N02) standard by July, 1975. Further,
1t is now believed that continued growth of nitrogen oxide (NO ) emis-
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I sions from mobile and stationary sources in a number of cases will make
it difficult to maintain national standards in some areas where they
are not presently being exceeded. Thus, additional NO emission control
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It measures may be necessary in some areas to assure attainment and
maintenance of national standards. This SIP Preparation Manual for
NOX has been prepared to provide guidance to EPA Regional Offices and
State and local control agencies on the development of an approvable
I control strategy for nitrogen oxides.
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FORMAT
The SIP Preparation Manual for NO is separated into four
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sections. Section I provides an overview of various factors that
must be considered in the development of an approvable control strategy I
for NO . Section II sets forth a fairly concise step-by-step procedure
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able control strategy. Section III provides, in question-and-answer
format, additional information on recommended procedures outlined *
in Section II. Section IV provides a more thorough discussion of NO
background information along with references to additional sources of
information. |
This manual will be revised from time to time as new information
becomes available.
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TABLE OF CONTENTS
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Section I: Overview of NOX Control Programs 1
Section II: Summary of Procedures Required for the Development
of a State Implementation Plan Control Strategy for
Nitrogen Oxides 5
Section III: Questions Frequently Asked Concerning NDx 17
(A) Control Strategy Development 17
- What is the NAAQS for N02? 17
- Should a SIP control strategy revision be delayed
simply because no NO^ reference measurement technique
has been promulgated at this time? 17
- How large an ambient NOp data base is needed to
develop a control strategy? 17
- Are available NO emission factors satisfactory for
control strategy development work? 18
- What automotive emissions factors should be used to
estimate the anticipated impact of the FMVCP on auto-
motive emissions of NO ? 18
- Can NO emission reductions be expected to result
from Transportation Control Measures (TCM) implemented
to reduce CO and/or Oj concentration? 18
- Should TCM's be adopted solely for NOX control? ... 19
- Does the rolidack model which is recommended for NO
control strategy development work satisfactorily
considering the different stack height of NO sources
in an urban area? 19
- Should ambient NO background concentrations be con-
sidered in control strategy development work? .... 20
(B) Ambient Air Quality Monitoring for N02 21
- What is the status of the development and promulgation
of a new reference technique for NO,? 21
- What NO- ambient measurement techniques are satisfac-
tory to provide ambient data to be used for SIP control
strategy development work? 21
- Must a correction factor be applied to relate NO^
data from one measurement technique to another? ... 23
- How much ambient air quality data exists in EPA's
SAROAD system? 23
- Historically, what type of ambient N02 air quality
trends have been observed? 25
(C) NOX Emission Data 27
- What are tne major sources of NO in the nation? ... 27
- What NO emission data are needed to develop a control
strategy? 29
- How is NO produced during the fuel combustion process? 30
- Should the impact of stationary source fuel switches
required by the Energy Supply and Environmental Coor-
dination Act of 1974 (ESECA) be considered in the
development of the NOX control strategy? 31
- Historically, what type of NO emission trends have
been observed? 33
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(D) NOX Control Technology 35
- What Is considered to be reasonably available con-
trol technology for stationary sources of NO ? . . 35
- Can significant NO emission reductions be expected
to result from comoustion modifications to existing
utility type boilers? 35
- What is considered to be achievable NO control
technology for stationary sources? 37
- If achievable NO emission limitations in conjunc-
tion with the FMVCP are not adequate to provide for
attainment of the NAAQS for N0?, what type of addi-
tional control measures should be adopted? .... 38
- Will the application of combustion modifications to
reduce NO emissions from utility type boilers
effect emissions of other criteria pollutants? . . 39
(E) Miscellaneous . . .- 41
- How is NO converted to N02 in the atmosphere? . . 41
- Does HC control have any effect on ambient N02
. concentrations? . . 41
- Are any existing stationary sources required to
continuously monitor NO emissions? If so, which
sources? 41
- Are new stationary sources of NO required to
monitor emissions? 42
Section IV: Support Information
History of NOX Control Under the Clean Air Act . . . Section A
Current Status of Ambient fKL Measurement Methods -. Section B
NO- Formation Processes and Control Strategy
Modeling Section C
Control of Oxide of Nitrogen for Stationary Sources Section D
Motor Vehicles Section E
Transportation Control Plans Section F
Field Observations Section G
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ABBREVIATIONS AND SYMBOLS
Act - the Clean Air Act as amended
AP-42 - Compilation of Air Pollutant Emission Factors, EPA
APTIC - Air Pollution Technical Information Center
AQCR - Air Quality Control Region
CO - Carbon Monoxide
EGR - Exhaust Gas recirculation
EMSL - Environmental Monitoring and Support Laboratory, EPA
ESECA - Energy Supply and Environmental Coordination Act
FGR - Flue Gas Recirculation
FGT - Flue Gas Treatment
FMVCP - Federal Motor Vehicle Control Program
HDVD - Heavy Duty Vehicles-Diesel Powered
HDVG - Heady Duty Vehicles-Gasoline Powered
I/M - Inspection/Maintenance
LOT - Light Duty Trucks
LDV - Light Duty Vehicles
LEA - Low Excess Air
NAAQS - National Ambient Air Quality Standards
NMHC - Non-methane Hydrocarbons
NO - Nitric Oxide
N02 - Nitrogen Dioxide
NOX - Nitrogen Oxides (NO + N02)
NSPS - New Source Performance Standards
Ox - Oxidants
02 - Oxygen
03 - Ozone
OSC - Off-stoichometric Combustion
RACT - Reasonably Available Control Technology
SIP - State Implementation Plan
SAROAD - Storage and Retrieval of Aerometric Data
TCM - Transportation Control Measure
TCP - Transportation Control Plan
TEA - Triethanolamine
TGS - Triethanolamine-guaiacol-sulfite
VMT - Vehicle Miles Traveled
VSAD - Vacuum Spark Advance Disconnect
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SECTION I
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OVERVIEW OF NO CONTROL PROGRAMS
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I The following statements summarize the current knowledge concerning
m the nature and extent of the N02 problem and the technical information
available to assist in the development of approvable NOV control
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measures.
1. The primary and secondary National Ambient Air Quality Standard
for N0? is 100 jjg/m annual arithmetic average. The need for an addi-
tional short-term standard has been reviewed. Based on available
m information, it is thought unlikely that a short-term N02 standard
will be promulgated in the immediate future. Therefore SIP revisions
for NOo should address the present annual standard and do not need to
consider short-term N02 concentrations.
2. Although limited, valid N02 data indicate that only a few areas of
I the country have ambient N02 concentrations in excess of the NAAQS for N02.
K On an overall national basis, the N02 problem appears much less severe and
pervasive than the total suspended particulate (TSP) or oxidant (Ox) problem.
fl| 3. Difficulties with ambient N02 monitoring techniques have been
principally resolved in the following manner:
| (a) The original Federal Reference Method for NO^j the
Jacobs-Hochheiser 24-hr, bubbler technique, has been revoked and should
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* no longer be used.
(b) The continuous chemi luminescence measurement principle
and associated calibration procedure was proposed in the Federal Register
| on March 17, 1976, as the basis for the new Federal Reference Method
for N02.
(c) The (1) TGS (triethanolamine-guiacol-sulfite) and
(2) sodium arsenite orifice 24-hr, bubbler methods are also
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satisfactory for NC^ ambient monitoring and will be tested for designation
as equivalent methods. J
(d) The (1) continuous colorimetric (Saltzman) analyzer,
(2) TEA (triethanolamine) and (3) sodium arsenite frit 24-hour bubbler
methods are thought at this time to be capable of producing accurate
air quality data and data collected by these methods can be used for
control strategy development work. However, the likelihood of any of I
these methods producing valid data over a year's time is not as great
as for the previously mentioned methods. 9
(e) Data from the (1) Jacobs-Hochheiser or (2) Saltzman M
24-hr, bubbler techniques should not be used.
4. With a few exceptions, the typical annual N0? problem, where I
it does exist, is in an urban area where observed NO- concentrations are
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either slightly above or below the NAAQS. Such conditions generally |
represent a potential problem of maintenance of the NAAQS rather than «
attainment of such standards.
5. Stationary source control measures will become increasingly V
important as mobile source controls become more fully implemented.
Studies have been conducted that predict future violations of the NC^ |
standard will occur in some areas regardless of automotive NO emission m
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standards because of growth of stationary source emissions.
6. On a national basis, stationary sources and mobile sources
contribute 60% and 40% of the NOV emissions, respectively. In both
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emission categories, the vast majority of NO emissions is produced
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by fuel combustion (fossil fuel-fired power plants, industrial boilers, _
commercial/residential space heating units, gasoline-powered automobiles,
diesel-powered trucks, aircraft, etc.).
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7. At this time the rollback model (basic or modified) is the
^ recommended source/receptor relationship for NOV control strategy
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review and/or development work.
8. Although the magnitude of the N02 problem and required
reduction in NC) emissions is not large, in general NOV control tech-
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I niques are limited (not reasonably available for all source categories).
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9. The greatest activity in developing NOV control technology
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has been with utility type boilers and nitric acid plants. NO control
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techniques are more advanced for gas and/or oil-fired boilers than
coal-fired boilers. Reasonably available control measures for these
source categories include:
(a) For utility type boilers (greater than 250 x 106 BTU/hr
heat input) - Combustion modifications
tm (1) Lower excess air
(2) Staged combustion
(3) Burner modification or replacement
(4) Flue gas recirculation (for gas or oil-fired boilers
with recirculation provisions)
(b) Nitric Acid Plants - Catalytic Decomposition
10. NOV control techniques which are not widely applied at the
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present time or which are not presently available but which are expected
to be available (i.e., achievable) in the next few years include the
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(a) Utility type boilers (greater than 250 x 106 BTU/hr heat
input) - Combustion Modification
jl (1) Water or steam injection (oil or gas-fired)
(2) Preheat reduction
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(3) Derating can be considered as a potential NO M
control measure but it should be reviewed on a case-by-case basis
considering its effectiveness and feasibility.
(4) Firebox enlargement. jtt
(b) Small and medium-size Commercial/Industrial boilers
(less than 250 x 10 BTU/hr heat input) - Burner modification or I
replacement.
(c) Gas turbines *
(1) Water and steam injection m
(E) New combustor designs
(d) Stationary internal combustion engines - exhaust gas
recirculation, turbo-charging with after cooling
(e) Chemical process (ammonium nitrate, fertilizer, explosive
production, etc.) - caustic scrubbing, NO incineration in reducing m
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atmosphere, etc.
(f) Industrial combustion processes (metallurgical, kilns,
glass production) - combustion modification
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SECTION II
SUMMARY OF PROCEDURES REQUIRED FOR THE DEVELOPMENT
I OF A STATE IMPLEMENTATION PLAN CONTROL STRATEGY FOR
NITROGEN OXIDES
ft The following section discusses the nine major steps required
in the development of a SIP control strategy revision for N0?. The
ft amount of work involved in each step will vary from area to area
_ depending on available data, magnitude of N09 problem, types of NO
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9 sources, etc. The nine steps can be summarized as follows:
STEP 1 - Determine if available N02 data indicate the NAAQS for
N02 is being exceeded or has the potential of being exceeded in the
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STEP 2 - Determine if the available ambient air quality data is valid,
ft STEP 3 - Determine the maximum representative N02 concentration.
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STEP 4 - Determine the area to be addressed by the NO control
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strategy.
STEP 5 - Determine the sources of NO .
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STEP 6 - Determine the growth potential for the study area.
STEP 7 - Using the proportional model, determine the NO emission
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reduction requirements.
STEP 8 - Determine NO reduction expected to result from existing
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ft NOX regulation (FMVCP, NSPS, etc.).
STEP 9 - Considering RACT and achievable control technology,
| develop a control strategy to attain and maintain NAAQS for N02- If
j| needed, other control measures should also be incorporated into the
NO control strategy.
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Listed below and discussed in more detail are the nine principal I
steps for developing a State Implementation plan Control Strategy
for NO . I
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STEP 1: Review available N02 air quality data to determine if sufficient data m
are available to provide evidence that the national standards are not
being attained or will not be maintained. Are sufficient data avail- I
able to calculate valid annual average concentrations within the study
area? Valid data from at least one site with one year of data should J
be available, however, 3 years or more of data are preferable. Data m
should be available for areas of expected maximum concentrations;
however, lack of such data should not preclude the development of a I
control strategy if available data indicate valid violations of national
standards. (Note: Predictive models do not exist to estimate ambient |
N02 air quality levels.) ^
STEP 2: If data exist to indicate a potential attainment or maintenance problem,
review the ambient air quality data to determine its validity and B
representati veness.
(a) Review the location of the N02 monitors. Are they properly located J[
in accordance with siting criteria?* Are sites biased toward local condi-
tions such that they do not represent areawide problems? (Note: Local
problems should not be ignored, however, the objective of the review is
to determine the sources and geographical area to be considered in the
control strategy analysis.) |
*OAQPS presently plans to distribute a supplement to OAQPS Guideline
1.2-012 (Guidance for Air Quality Monitoring Network Design and Instru- |
ment Siting) by late 1976 which will update existing N02 monitoring
guidelines. m
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(b) Determine if a satisfactory measurement procedure was used to
collect N02 data being analyzed. The following measurement procedures
are acceptable as indicated. If data are collected by an unacceptable
measurement technique, data should not be used.
Measurement Method
(Method Code)
Instrumental
(11) Modified Saltzman
Colorimetric
(12) Saltzman Colorimetric
(13) Coulometric
(14) Chemiluminescence
Bubblers -
Comment
Data can be used with caution *
Data can be used with caution
Data can be used with caution
Proposed Federal Reference Method
Data can be used
(71, 81, 91) Jacobs-Hochheiser - Data must not be used
(72, 82, 92) Saltzman Bubbler - Data must not be used
(84) Sodium Arsenite Orifice
(94) Sodim Arsenite - Frit
(95) TEA
(96) TGS
Candidate Federal Equivalent Method
Data can be used
Data can be used with caution
Data can be used with caution
Candidate Federal Equivalent Method
Data can be used
*User should be aware of the problems associated with the method and be
assured that proper procedures were used in collecting data.
(c) Analyze the available NCL air quality data to assure its validity
and reliability.
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(1) Determine if the data were collected by monitors that are
properly operated, maintained and that adequate quality control proce- £
dures were utilized to assure validity of data. _
(2) Review specific data for determination of abnormal values.
Obtain frequency distributions of NOp data. Air quality statistics £
such as geometric mean, arithmetic meanfl standard deviation, and fre-
quency percent!les may suggest abnormal values. For example: g
- Both the standard deviation and the magnitude of the difference ^
between the geometric and the arithmetic mean are more sensitive to a -
few extremely high values than to many moderately high values.
- Inspection of the higher percentile values also will identify
abnormal high values.
- Generally the standard deviation should not vary much from year
to year.
(3) The collecting agency should attempt to validate any suspicious »
data and to generally acknowledge that all the data have been reviewed
and are considered valid and useable for control strategy development
work. Where necessary, this review should include:
A. Review of strip charts and laboratory reports, and V
field log books for notations concerning operations and maintenance m
activities.
B. Review basic d-^ta to assure temporal balance of air quality
data (e.g., a missing quarter of air quality data).
C. Have any changes been made in sampling methodology, p
maintenance procedures, calibration procedures or quality control practices? m.
(4) If abnormally high values have been measured and are considered
suspect, it may be useful to review operating parameters for other
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I instruments at the same monitoring site to determine whether electrical
problems or heating/air conditioning problems may have caused abnormal
m values.
f (5) Review data from nearby monitoring sites and compare the
concentrations measured by the other instruments at those sites with
m the concentrations measured by sampling instruments at the site in question.
(d) To determine if N00 air quality concentrations are representative,
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review the N02 air quality trend at each site for the area being studied.
_ To the degree possible, determine if unusual events may have caused
' high NCL concentrations (e.g., industrial accident at nitric acid plant
fl or severe meteorological conditions that may cause unusually high N02
concentrations.
| (1) Review the NOo trend at each site to identify fluctuation in
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N02 levels.
(2) Review parameters that would help explain trend.
- Review NOV emissions inventory, growth projections, construe-
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tion permits, and compliance information to determine if any significant
changes (increases or decreases) in regional NOX emissions have taken
place. NOTE: The purpose of Step 2 is to insure that the data which
will be used as the basis of a control strategy are valid, or can reason-
A ably be assumed to be valid. If it is believed that the data are question-
able and factors exist that could reasonably challenge the data validity,
then such data should not be used as the basis of a control strategy.
If on the other hand, all reasonable measures have been followed in the
collection of the data, and unless the validation efforts prove the data
to be invalid, then such data should be assumed valid and usable.
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STEP 3: Determine the maximum measured ambient level that best represents
ambient air quality levels in the area. Determine if such air quality
data are of sufficient magnitude that a further analysis of existing B
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and anticipated emissions data should be conducted to determine if
national standards will be attained and maintained. This analysis
should be conducted if ambient air quality levels are equal to or
exceed national standards. Also, in those areas where growth of new B
emission sources is expected, the analysis should be conducted even if ^
national standards are being attained on a marginal basis. "
STEP 4: Determine the geographic area to be considered in the analysis. From W
available data, determine the geographic area where national standards
are violated or are anticipated to be violated due to growth of emission
sources. It is not necessary to use an entire AQCR or county. The fc
area does not have to be a political entity. Some consideration should "
be given to political boundaries, however, since the regulations which
implement the control strategy will ultimately be enforced by local
governments. Although some advantages accrue to the use of a commonly
identified geographical area, as long as the area is clearly defined,
it is appropriate for development of a control strategy. The area of
concern should be "future-oriented," in that strong consideration should
be given to growth of emission sources.
More specifically, data indicate that areas slightly downwind from V
the major urban center but within the urban area are the .expected
areas of maximum annual NOo levels. Ambient NCL levels 20 miles or more m
distant from the urban fringe are affected to a very minor degree by f
urban NOX emissions. Similarly, sources generally located more than
20 miles from the urban areas will minimally impact air quality within thp
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urban area. It is recommended therefore that the geographic area to
be considered for NO control strategy for attainment purposes include
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the urban area and the adjacent counties. Of course from a maintenance
point of view, growth of sources throughout some area larger than the
current urbanized area may need to be considered. In such cases, areas
of expected growth should be considered in'defining the geographical
area to be addressed by the NO control strategy.
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STEP 5: Determine the sources of NO emissions in the area and calculate the
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emissions from each source. Data are needed for two purposes:
(a) To assess where the ambient N02 problem originates.
(b) To determine the emissions reduction impact of various possible
control regulations on source emissions.
Most emission inventories are adequate to provide for the assessment of
the sources of NOV emissions in the area, however, for certain emission
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categories such as fuel combustion sources, available data may not be
m adequate for possible control strategy development. Specifically,
detailed information on fossil fuel-fired steam generators (e.g., excess
air usage, boiler configuration, number of burners, fuel specifications,
etc.) is needed to determine a boiler's emission reduction potential.
I Similarly, detailed information for mobile sources such as vehicle
m mix ratio (LDV, LDT, HDVG & LDVD) and age distribution for the area under
study may be necessary to determine the impact of the FMVCP and/or
various transportation control measures. Since this type of information
is not commonly associated with existing emission inventories, it may
P be necessary to collect some additional data.
_ More specific procedures for compiling an emission inventory are
contained within Guide for Compi 1 i ng a_ Comprehensive Emission Inventory
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(EPA/APTD 1135, March 1973). Further, specific information, as well
as emission factors that can be used to calculate NOV emissions from
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various mobile and stationary sources, are contained in Compilation of I
Air Pollutant Emission Factors (AP-42).
STEP 6: Determine the expected increase of NO emissions due to growth (generally
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over the next 20 year period). Growth is an inherent part of air
pollution control; and consideration of growth is thus paramount
in the development of a control strategy. The adjustment of the emissions V
inventory to account for growth is essentially a projection of the levels
of economic and demographic activity and its impact on air quality in 9
the area of concern.
The information needed to develop growth factors originates
from Federal agencies, from State and local governments, and from private
business interests. Fairly specific information should be obtained from
State and local planning agencies if possible. If unavailable, the
growth projections of the Office of Business Economics (QBE), presently m
the Bureau of Economic Analysis of the U. S. Department of Agriculture
can be used. These projections, called "OBERS projections" are avail-
able at the EPA Regional Offices. Since most NO is produced from
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on these source categories (power plants, industrial boilers, commercial/ »
residential space heating, mobile sources, etc.).
Numerous guidelines have been prepared by EPA with regard to V
projecting growth in emissions and allocating such growth. These
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techniques are too detailed to summarize here. The reader is referred
M to the following documents for additional information:
Air Quality Maintenance Guidelines:
ti Vol. 3, Plan Preparation (EPA-450/4-74-003)
Vol. 7, Projecting County Emissions (EPA-450/4-70-008)
Q Vol. 13, Allocating Projected Emisssions to Sub-County AQMA
(EPA-450/4-74-004)
STEP 7: Using the proportional model, determine the degree of control needed
to attain and maintain the NAAQS. The modified rollback is also recom-
mended for NO control strategy development work.
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The Modified Rollback can be expressed as:
. = l QiV future
where X, = SIP design value (representative maximum annual average
N02 concentration in base year)
X2 = NAAQS for N02 (100 yg/m3)
B = annual N02 background concentration (8 yg/m3)
9 Q. = annual NO emission rate per source category
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m G.J = a growth factor, e.g., the ratio of N02 emissions at attainment
data or during maintenance period to N02 emissions in the base
ff year per source category
N = the number of source categories
I i = a particular source category, e.g., light-duty vehicles,
stationary sources, etc.
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X2
- B
X R
N
2 (
i = 1
N
n' base year
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In cases where the area-wide NO emissions result from a variety of
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(a) Consider the impact of the FMVCP on NOV emissions. Figure II-l
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source types with differing emissions and growth rates and where »
various control strategies are to be investigated, the modified roll-
back model will allow the situation to be studied in more detail than
the rollback procedure.
To apply this technique, the left side of the equation is evaluated
with available data to determine an allowable NO emission rate. The
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right side of the equation is then evaluated for various control strate- m
gies until a strategy which demonstrates attainment and assures mainte-
nance is developed.
STEP 8: Determine how large an NOV emission reduction can be achieved by full
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implementation of existing adopted control regulations.
presents a plot of projected national NOV emissions from motor vehicles.
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Additionally, AP-42 can be used to develop city specific curves if
needed.
(b) Consider the impact on NOV emissions (both increases and decreases) |
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that may result from (1) compliance with existing control regulations, »
(2) ESECA or other fuel switches, (3) TCM or I/M program for CO or Ox.
STEP 9: If additional controls are needed, consider the application of (a) reason- V
ably available control technology and if needed (b) achievable control
measures (technology forcing). The term "achievable" is intended to J
require reasonably "technology forcing" control measures if necessary, «
rather than simply "off-the-shelf technology." SIP revisions submitted *
by July 1977 shall require all achievable control technology for stationary M
sources (as needed) to provide for attainment of the national standard.
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1.4
1.2
c *
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1.0
(b
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O)
s_
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N
0.8
0.6
0.4
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0.
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1970
FIGURE II-l
NORMALIZED MOTOR VEHICLE EMISSIONS
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1975
Assumptions:
1980 1985
CALENDAR YEAR
1990
1995
1. National average automobile and truck age distribution
2. Low altitude, standard conditions
3. 3% Compounded (annual) growth rate
4. National average vehicle mix (LDV 80.4%; LOT 11.8%; HDG 4.6%; HDD 3.2%)
5. 1970 composite emission factor 4.6 g/mi
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Additionally, if needed, "other" control measures, including
land use and transportation control measures, should be adopted and
submitted by July 1978.
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SECTION III - QUESTIONS FREQUENTLY ASKED CONCERNING NOX
- Control Strategy Development -
QUESTION - What is the NAAQS for N02?
ANSWER - The primary and secondary NAAQS for N02 is 100 jjg/m annual
fl arithmetic mean measured as N02- Recently a review was performed to
* determine the need for an additional short-term NO- NAAQS. Based on
fl available information, it is thought unlikely that a new short-term
standard will be developed in the immediate future. SIP revisions
should only address the present annual NAAQS for N02.
QUESTION - Should a SIP control strategy revision be delayed simply
because no NOo reference measurement technique has been promulgated
at this time?
ANSWER - No. Detailed studies of ambient N02 measurement techniques
have been completed which assess each measurement technique. The
results of these studies indicate that valid data can be obtained using
various methods. Control strategy development work should be initi-
ated using representative N02 air quality data.
QUESTION - How large an ambient N02 data base is needed to develop a
control strategy?
ANSWER - As a minimum, valid annual air quality data from at least one
m site is required. Although the seasonal variability of N02 is minor in
M most areas, N02 air quality data should be available for all four quar-
ters of the year of interest to accurately determine the annual arithme-
tic mean. Additionally, 2 or 3 years of valid data from a monitoring
site are preferred to a single year's data. Further, data from more
| than one site is preferable, including a site at the area of probable
maximum concentration.
17
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ADDITIONAL INFORMATION - See Section G - Field Observations
QUESTION - Are available NO emission factors satisfactory for control I
x VI
strategy review or development work?
ments be used for NO control strategy development work.
/\
I
ANSWER - Generally, yes. NO emission factors are satisfactory for a
s\
regional assessment of total NOV emissions but may be less accurate for
/\
estimating some individual source emissions. For example, NO emission
X
factors for coal combustion (and fuel oil in some cases) represent
average emissions for typical conditions and at this time do not directly
allow for consideration of the variable nitrogen content of coal. In |
many cases 50% but in extreme cases up to 80% of the NO emitted from H
I
coal combustion is associated with the nitrogen in the fuel. The nitrogen
content of U. S. coals can vary from 1.0% to 2.0%. It is recommended I
that emission factors contained in AP-42 and its associated update supple-
I
QUESTION - What automotive emission factors should be used to estimate _
the anticipated impact of the FMVCP on automotive emissions of NO ? *
X
ANSWER - The automotive emissions regulations (FMVCP) associated with V
ESECA are in effect. Congress is currently considering Act amendments
and may revise them. Until the amendments are completed, the current £
exhaust emission limitation associated with the FMVCP should be used _
for SIP control strategy work. Additionally, procedures and data
described in AP-42 can be used to develop city specific automotive emis-
sion factors.
QUESTION - Can NOX emission reductions be expected to result from
Transportation Control Measures (TCM) implemented to reduce CO and/or
03 concentration?
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ANSWER - Some NO emission reductions can be realized from some of
X
I the CO-0 TCM's but the measures used in the CO-0V TCM's must be
X X
carefully analyzed to assess the amount of NO control achieved. For
I
example, reductions in vehicle miles travelled (VMT), retrofit of
exhaust gas recirculation (EGR) or vacuum spark advance disconnect (VSAD)
can directly reduce NOV emissions. However, inspection/maintenance
X
I programs (I/M) for CO-0 TCM's may have little effect on NOV emissions.
X X
ADDITIONAL INFORMATION - See Section F - Transportation Control Measures.
I QUESTION - Should TCM's be adopted solely for NO control?
T ... X
ANSWER - Reductions in NOV emission from CO and/or Ov TCM's should be
X X
determined and incorporated into the NO control strategy as applicable.
/\
At this time it is thought unlikely that NO reduction would become a
key determinant of TCM policy, however in certain areas, such measures
m in conjunction with stationary source control may be required to provide
for attainment of N00 standards.
I
strategy development work satisfactorily consider the different stack
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QUESTION - Does the rollback model which is recommended for NO control
"~~JT ~ ' " X
height of NOV sources in an urban area?
/\
ANSWER - Yes, generally 1 to 3 hours is required for NO to N02 conver-
sion, thus NO emitted from low and high level sources in the problem
area is constantly diffusing and mixing while N02 is forming and results
fl in NO source contributions being nominally related to stack height.
Therefore in most cases the proportional model will satisfactorily
| describe the urban NOX emission - N02 air quality relationship on an
m annual basis and is the best readily available model for NO control
I '
w strategy development work at this time.
ADDITIONAL INFORMATION - 1. See Section C - NOX Formation Processes
and Control Strategy Modeling.
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QUESTION - Should ambient NOp background concentrations be considered
in control strategy development work? I
3
ANSWER - Yes. An annual average N02 background concentration of 8 ug/m
should be assumed for control strategy development if other background "
concentration data are not available. Natural background concentrations
are a result of natural bacterial and plant actions.
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- Ambient Air Quality Monitoring for NCL -
mj QUESTION - What is the status of the development and promulgation of
a new reference technique for ML?
fl ANSWER - The Environmental Monitoring and Support Laboratory, EMSL, has
completed its study of ambient NOV measurement methods. The chemilumin-
|X
escence measurement principal and associated calibration procedure was
proposed to the public in the Federal Register on March 17, 1976, as the
* basis for the new NO^ reference method. The schedule for other actions
is listed below:
Date Action
3/76 Propose continuous chemiluminescence measurement principle and
calibration procedure (40 CFR Part 50).
I 3/76 Propose reference and equivalency requirements (40 CFR Part 53).
10/76 Promulgate measurement principle and calibration procedure:
promulgate reference and equivalency requirements.
2/77 Designate reference methods (40 CFR Part 53) and identification
of acceptable commercial instruments.
I 3/77 Designate equivalent methods (40 CFR Part 53). (Arsenite and TGS
j| are expected to be designated as equivalent methods.
ADDITIONAL INFORMATION - Current Status of Ambient N02 Measurement Methods
| QUESTION - What NO^ ambient measurement techniques are satisfactory to
provide ambient data to be used for SIP control strategy development
| work?
- ANSWER - Three ambient N02 monitoring methods are reliable and capable
of producing valid N02 air quality data on an annual basis for control
P strategy development work. The methods are (1) the continuous chemilumin-
escence measurement principle and associated calibration procedure,
21
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(2) TGS (triethanolamine-guiacol-sulfite) and (3) sodium arsenite orifice _
24-hr, bubbler methods. The continuous chemiluminescence measurement
principal and associated calibration procedure has been proposed in the
Federal Register on March 17, 1976, as the basis for the Federal Reference
Method for N02> The TGS and sodium arsenite orifice 24-hr, bubbler methods I
will be tested for designation as equivalent methods. B
At this time it is also thought that three other methods when m
properly used can also produce valid air quality data for control m
strategy development work. However, the likelihood of any of these
methods producing valid data for an annual average is not as great as
for the previously mentioned methods. These less reliable methods are
the (1) continuous colorimetric (Saltzman) analyzer, (2) TEA (triethanola- |
mine) and (3) sodium arsenite frit 24-hr, bubbler methods.
I
ADDITIONAL INFORMATION - See Section A - History of NO Control Under the
""" ~ X
Clean Air Act. Section B - Current Status of Ambient N02 Monitoring l[
Methods. The following reports from EPA's Environmental Monitoring
Series are also available from the Air Pollution Technical Information |
Center (APTIC): _
1. EPA-650/4-74-019-a: Collaborative Testing of Methods for
Measurement of N0~ in Ambient Air, Volume 1 - Report of Testing. ff
2. EPA-650/4-74-031: Evaluation of Triethanolamine Procedure
for Determination of Nitrogen Dioxide in Ambient Air.
3. EPA,-650/4-74-046: Collaborative Test of the TGS-ANSA Method g
for Measurement of Nitrogen Dioxide in Ambient Air.
4. EPA-650/A-75-011: Collaborative Test of the Continuous Color-
metric Method for Measurement of Nitrogen Dioxide in Ambient Air.
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5. EPA-650/4-74-047: An Evaluation of TGS-ANSA Procedure for
Determination of Nitrogen Dioxide in Ambient Air.
6. EPA-650/4-74-048: An Evaluation of Arsenite Procedure for
-
* Determination of Nitroqen Dioxide in Ambient Air.
7. EPA-650/4-75-019: Evaluation of Effects of NO, C02, and
Sampling Flow Rate on Arsenite Procedure for Measurement of N02 in
| Ambient Air.
_ 8. EPA-650/4-75-021: Evaluation of Gas Phase Titration Technique
* as Used for Calibration of Nitrogen Dioxide.
9. EPA-650/4-75-022: Evaluation of Continuous Colormetric Method
for Measurement of Nitrogen Dioxide in Ambient Air.
I 10. EPA-650/4-75-023: Comparison of Methods for Determination
of Nitrogen Dioxide in Ambient Air.
' QUESTION - Must a correction factor be applied to relate N02 data from
one measurement technique to another?
ANSWER - No correction factor is required to relate N0? data from
| different measurement techniques assuming they have been operated
_ properly. Each acceptable monitoring technique provides reliable
information with respect to ambient N02 levels.
B QUESTION - How much ambient air quality data exist in EPA's SAROAD system?
ANSWER - Listed in Table III-l are summary statistics of the 1974 N02
| data contained in SAROAD as reported in the 1974 Monitoring and Air
Quality Trends Report. More current data are generally available from
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TABLE III-l
NO AMBIENT AIR QUALITY MONITORS IN USE-NATIONAL TOTAL
£t
-\
Measurement Method
(Method Code)
instrumental
11) Modified Saltzman Colorimetric
[12) Saltzman Colorimetric
[13) Coulometric
14) Chemiluminescence
TOTAL
iubblers
(84& Sodium Arsenite
94) (Orifice & Frit)
(95) TEA
(96) TGS
TOTAL
GRAND TOTAL
u f (1)
Number of
Monitors Reporting
131
10
8
72
221
1196
0
5
1201
1422(2)
AQCR's Reporting
39
5
8
35
87
158
0
1
159
168
Total No. of
AQCR's Reporting
Based on 1974 Trends Report (updated) and does not include Jacobs-Hocheiser
or Saltzman Bubbler data.
Note that only 610 sites (106 AQCR's) of the 1422 sites (168 AQCR's
reporting) have reported enough ambient NO? air quality data to calculate
an annual mean.
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I SAROAD and State agencies. The Regional Offices, State and local
air pollution control agencies are encouraged to submit any additional
| N02 air quality data obtained to SAROAD so that it can be stored for
. future reference.
QUESTION - Historically, what type of NO,, air quality trends have been
fl observed?
ANSWER - Trends in ambient N02 concentrations at CAMP sites have been
| analyzed for Chicago, Cincinnati, and Philadelphia. The N02 graphs
and regression lines (See Figure III-l) indicate, for the most part,
9 an increase in annual average concentration with time.
I Further, it is now believed that continued growth of NO emissions
X
from stationary sources in a number of cases will make it difficult
to maintain the NAAQS for NO^ in some areas where they are not presently
being exceeded. Thus, additional control of NO emissions may be
|X
necessary in some areas to restrict the upward trend of NO emissions
to assure the attainment and maintenance of the NAAQS for NOp.
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FIGURE III-1
N02 Air Quality Trends at CAMP Sites*
a
u
200
100
0
100
50
0
100
50
0
100
50
0
100
50
CHICAGO
CAMP
CINCINNATI
CAMP
DENVER"
CAMP
PHILADELPHIA'
CAMP
ST. LOUIS"
CAMP
1962 1963 1964 1965 1966 1967 1968 1969 1970 1971
YEAR
Station
Chicago
Cincinnati
Denver
Philadelphia
St. Louis
CAMP average
Annual Average N02
Concentration (/jg/m3)
1962-66
86.1
62.0
66.0
67.7
58.5
68.1
'1967-71
101.2
60.1
67.9
77.6
54.2
72.2
Percent
Change
+18
- 3
+ 3
+15
v- 7
+ 6
D Valid annual average
o Indicates average based on incomplete data
*Measurements made with Modified Saltzman (colormetric) Method, the
National Air Monitoring Program: Air Quality and Emission Trends:
Annual Report: Volume I: EPA-450/1-73-001-a.
26
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I- NO EMISSION DATA -
X
_ QUESTION - What are the major sources of NO in the nation?
I
" ANSWER - Nitrogen oxides (NO ) are formed by nature and as a result of
1 ' " A
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urban areas. Natural emissions of NO are considerable when the entire
A
I man's activities. Both sources principally emit NO in the form of
x
nitric oxide (NO). Although the natural emissions which occur as a
Jj result of bacterial and plant actions exceed man-made emissions by a
factor of 10 on a worldwide basis, man-made emissions predominate in
geographical land area of the nation is.considered, but because of their
low emission density (tons N0x/square mile), they only result in a N0?
background concentration in the order of 8 ug/m . Man-made NOX emissions
in 1972 amounted to 24 million tons within the United States.
On a national basis, 60% of the man-made NOV is generated by station-
A
ary sources and the remaining 40% by mobile sources (see Figure III-2),
but the distribution can vary for specific AQCR's. For example, based
upon emission data in NEDS the stationary/mobile source ratio is 76% - 24%
for the St. Louis AQCR and only 43% - 57% for the Denver AQCR.
Most NO stationary source emissions are generated by the combustion
A
of fuel. On a national basis, utility and industrial boilers emit 67%
(49% utility and 18% industrial) of the stationary source NO emissions.
A
Other sources of NO include stationary internal combustion engines (prin-
cipally used for natural gas transmission pipeline pumping stations
| located in nonurban areas, 19%) and commercial/residential space heating
(7%). Non-combustion NOX sources which include nitric acid production,
TNT production, etc., contribute only 7% of the national NO emissions.
A
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STATIONARY - '10'iILE SOURCES
lndintrl.1 Prx>c«» licit (31)
C«s Tu.blnt (?t)
Non-combuitlon (1JJ
InelncriUon (< Tt)
STMIOMARY SOURCES
Figure III- 2
MOBILE SOURCES
NATIONAL DISTRIBUTION 01 NO EMISSION SOURCES (197?)
28
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X
generated by gasoline-powered motor vehicles (light duty - 59%, heavy
duty - 13%, and off-road 4%). Additionally, diesel-powered motor vehicles
contribute another 20% (heavy duty - 14% and off-road - 6%) of the
nation's NO emissions. The remaining 4% of the national emissions are
A
contributed by railroad, aircraft, vessels, etc. Because diesel-powered
trucks are not commonly used in urban areas, gasoline-powered motor
vehicles are the major urban mobile source of NOV emissions.
A
QUESTION - What NO emission data are needed to develop a control
A
strategy?
ANSWER - On a national basis, stationary sources contribute approximately
60% and mobile sources contribute about 40% of the total NOV emissions
X
(principally as NO). Thus an emission inventory for the problem area
should include both categories of sources. In order to access the mobile
| source emission rates, data should be obtained on mobile source population
g by category, expected growth rates, age distribution, information on
* vehicle miles traveled (VMT) and fuel consumption information. Additional
I information may be required if mobile source controls (i.e., TCM* for
carbon monoxide (CO) or oxidants Ov)) in addition to the Federal Motor
|X
Vehicle Control Program (FMVCP) are being evaluated.
For stationary sources, information on the location of large point
* sources and emission density of area sources is required to determine
their impact on ambient N02 concentration. Although some processes
such as nitric acid production emit enough N02 at one plant to be a point
I source, most NO point sources will probably be large industrial boilers
A
m or power plants. Specified data on each large industrial or utility
*TCM - Transportation Control Measures
29
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Both the NO emission inventory and ambient N00 data base used for
A c
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boiler will be required if the control strategy is to address these
sources. Specific data should include information on the type of fuel
(specifications), firing configuration, excess air controls, number I
of burners, burner arrangement, availability of new low NO producing
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replacement burners, secondary air ports, etc. In some cases, such as
coal-fired boilers, individual sources may have to be studied to deter-
mine NOX control potential. The emission inventory should accurately
describe NOX emissions for the year of record and identify any scheduled I
increases or decreases in emissions.
I
control strategy development work should be for the same year of record. m
If the current NO emission inventory is deficient and an update is
A
required, it may be possible to efficiently and accurately develop the I
inventory by principally addressing the major emission sources in the
study area. g
ADDITIONAL INFORMATION - See Section D - Control of NO for Stationary
Sources.
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QUESTION - How is NOV produced during the fuel combustion process?
ANSWER - As previously indicated, the principal stationary and mobile
sources of NOX emissions are fuel combustion processes (utility boilers, V
industrial boilers, motor vehicles, etc.). These processes generate NO
by two formation mechanisms. The principal formation method is the high |
temperature oxidation of the nitrogen in the combustion air supply to _
produce NO. Thermal NO is formed in all combustion processes, but predomin-
ates for cleaner fuels (low nitrogen content fuels) such as gasoline
(mobile sources) and natural gas and light oil (stationary sources). For
other fuels with greater nitrogen content (lie., heavy oil and coal used J
30
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I by larger boilers), NO is also formed by the oxidation of the nitrogen
in the fuel. For coal, approximately 50% of the NOV emissions are
|X
formed in this way and in extreme cases up to 80% of the NO in the
g exhaust gas is associated with the fuel nitrogen.
Because of different specific heats, nitrogen content, excess air
requirement, etc., of different fuels, each fuel has a different NO
formation potential per BTU. As shown in Table 111-2, the combustion
I of coal (high nitrogen and excess air requirement) produced more NO per
J\
BTU than a clean gaseous fuel such as natural gas. Thus for the same
heat input rate (10 BTU/hr) a coal-fired combustion unit would typically
produce greater NOV emissions than a natural gas or oil-fired unit.
X
QUESTION - Should the impact of stationary source fuel switches required
I by the Energy Supply and Environmental Coordination Act of 1974 (ESECA)
be considered in the development of the NO control strategy?
I
ANSWER - Since the N02 problem is typically an urban problem and most
ESECA fuel switches will be required for utility boilers, the location
of power plants in the study area should be reviewed to determine if
they will impact the urban area. Power plants 20 miles or more from
an urban problem area generally will have minor impact on the urban
problem area on an annual basis. If the source is expected to impact
I upon the problem area, the increase in NO emissions resulting from
X
oil or gas-to-coal fuel switches should be considered as an emission
increase that must be offset by other NO emission reductions. One
factor to consider is that boilers which are combusting oil or gas but
I
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were originally designed for coal-firing emit substantially less NO than
/\
a furnace designed for oil or gas-firing. This is because the combustion
31
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TABLE III-*
NO EMISSIONS PER BTU OF HEAT PRODUCED
A
Fuel
(Nitrogen
Content)
Coal
(1-22N)
on
(0.1-
0.5%N)
Gas
(Negligi-
ble %N)
Type of Unit
Utility/Large Industrial
Cyclone (Pulverized)
Wet Bottom (Pulverized)
General (Pulverized)
Indus trial /Commercial
Domestic
Utility
General
Tangential
Indus tri al /Commerci al
Horizontal
Tangential
Domestic
Utility
Industrial
Commercial
Domestic
Emissions-Potential
(#NO Y/10b BTU)
/\
2.08
1.25
0.75
0.63
0.25
0.75
0.36
0.57
0.28
0.09
0.57
0.11 - 0.22
0.11
0.08
32
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chamber designed for coal firing would be much larger than needed for
oil or gas combustion and this large size tends to reduce NO emissions
A
because of the reduced flame temperature. The important point is that
if these low NO producing boilers switch to coal, this will result in a
A
greater increase in NO emission rate than expected based on established
A
emission factors. This is because the baseline NO emissions for the
A
gas or oil-fired boiler (designed for coal) is substantially less than
indicated by emission factors for gas or oil-firing of boilers designed
for these fuels (See Table III-3).
TABLE III-ijJ
UTILITY BOILERS* - FUEL SWITCHING
(NOV Emissions Ibs NO/106 BTU)
A A
Fuel
Coal
Oil
Apparent Emission
Increase from
Fuel Switch
Actual
Percent Increase
Boiler Designed for
Referenced Fuel
0.9
0.7
0.2
28.5%
Boiler Designed
For Coal Firing
0.9
0.3
0.6
200%
*Front Wall Fired
QUESTION - Historically, what type of NO emission trends have been
A
observed?
ANSWER - NOX emission rates have generally increased since 1940 princi
pally because of the increase in number of motor vehicles and fossil
fuel-fired stationary sources in use (see Figure III-3).
33
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For the overall period 1940 to 1970, the average growth rate of NOY
/\
emissions from motor vehicles and stationary fuel combustion sources
were very similar, being 4.8 percent per year, respectively. Over the
period 1940 - 1960, however, the average road vehicle emission growth
rate was 4.9 percent and the stationary fuel combustion source growth
rate was only 2.0 percent. During the period 1950 to 1970, these trends
were reversed, and the road vehicle emission growth rate decreased
to 4.6 percent while the rate for stationary fuel combustion sources
increased to 7.3 percent. Over the last 10 years through 1970, NO
A
emissions from steam-electric power plants increased at a rate of
7.4 percent per year.
1950 I960
YEAR
1970
Figure III- 3- Nationwide emissions
for N0₯ (1940 - 1970). *
/\
*A much more detailed discussion, including tables and methodology,
is presented in Nationwide Air Pollutant Emission Trends, 1940 - 1970,
Ap_115
34
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- N0x Control Technology -
I
coal-fired boilers. Listed below are reasonably available NO control
X
QUESTION - What is considered to be reasonably available control tech-
nology for stationary sources of NO ?
X
ANSWER - The greatest activity in developing NO control technology has
been with utility type boilers and nitric acid plants. Reasonably
available control technology exists for both of these source categories.
Utility type boilers are typically the largest NO stationary source
emission category and in those areas where additional control is needed,
these sources should be analyzed for NOV control potential. NO control
X X
techniques are more advanced for gas and/or oil-fired boilers than
I
techniques:
* (a) Utility type boilers (greater than 250 x 106 BTU/hr heat input) -
Combustion modifications
1. Lower excess air
Jj 2. Staged combustion
3. Burner modification or replacement
* 4. Flue gas recirculation (for gas or oil-fired boilers with
recirculation provisions)
(b) Nitric Acid Plants - Catalytic Decomposition
| QUESTION - Can significant NOX emission reduction be expected to result
from combustion modifications to existing utility type boilers?
ANSWER - Generally, yes. Table III-| lists typical NOX emission reduc-
reduction in NOV emissions).
A
tion factors that can be expected to be achieved (up to 50% or greater
I
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36
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QUESTION - What is considered to be achievable NO control technology
for stationary sources?
ANSWER - NO control techniques which are not widely applied at the
*~~ X
present time or which are not presently available but which are
expected to be available (i.e., achievable) in the next few years
include the following:
(a) Utility type boilers (greater than 250 x 10 BTU/hr heat
input) - Combustion Modification
(1) Water or steam injection (oil or gas-fired)
(2) Preheat reduction
(3) Derating can be considered as a potential NO control
X
measure but it should be reviewed on a case-by-base basis considering
its effectiveness and feasibility.
(4) Firebox enlargement
(b) Small and medium-size Commercial/Industrial boilers (less
| than 250 x 10 BTU/hr heat input) - Burner modification or replacement
(c) Gas turbines
(1) Water and steam injection
I (2) New combustor designs
(d) Stationary internal combustion engines - exhaust gas recircu-
| lation, turbo-charging with after cooling
(e) Chemical process (ammonium nitrate, fertilizer, explosive
.
*
I
production, etc.) - caustic scrubbing, NO incineration in reducing
X
I atmosphere, etc.
(f) Industrial combustion processes (metallurgical, kilns, glass
production) - combustion modification
37
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QUESTION - If achievable NO emission limitations for stationary sources
A
in conjunction with the FMVCP are not adequate to provide for attainment
of the NAAQS for N(L, what type of additional control measures should
be adopted?
ANSWER - All achievable NO control technology for existing NO sources
A A
must be carefully analyzed to assess the amount of NOV control achieved.
X
NO emissions.
X
38
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must be required if necessary and be submitted by July 1, 1977.
All other measures needed to attain and maintain must be submitted
no later than July 1, 1978. These "other measures" should be comprehen-
sive and innovative where needed, and should include items such as land I
use measures, transportation controls, transit improvements, zoning
ordinances, building codes, inspection/maintenance programs for station-. g
ary and mobile sources. _
Transportation Control Measures (TCM's)
Although it is thought unlikely that NOV control will be a key
X
determinant in the foreseeable future, NOV emission reductions can be
X
obtained from some of the TCM's for CO and/or Ox but the measures used |
1.
For example, retrofit of exhaust gas recirculation (EGR), vaccum spark
advance disconnect (VSAD), or gaseous fuel conversion can directly
reduce NOV emissions. However, inspection/maintenance programs (I/M),
A
if not specifically designed for NO , may have little or no effect on I
A
NOX emission reductions can also be obtained from reductions in
vehicle miles traveled (VMT). Methods to reduce VMT include traffic I
restrictions, limited access zones, traffic-free zones, street closing
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and other similar measures. VMT can also be reduced through mass
transit improvements such as express bus-carpool lanes, improved bus
service, and rapid rail service. See Section F - Transportation Control
Plans for more detailed information on this subject.
Stationary Source Control Measures
NO reductions from stationary combustion sources must be required
as necessary. Such measures may include innovative energy conservation
m, measures such as requiring (1) increased thermal insulation and storm
windows and doors, (2) the use of power plant reject heat, (3) the use
of central heating units for residential and commercial space heating
and other energy saving measures. Additionally, a fuel tax on the
| nitrogen or BTU content of fuel may be useful to encourage conservation
_ measures.
ADDITIONAL INFORMATION - See Air Quality Maintenance Planning and Analysis,
Volume 4: Land Use and Transportation Considerations (EPA-450/4-74-004).
I
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QUESTION - Will the application of combustion modifications to reduce
NO emissions from utility type boilers effect emissions of other criteria
X
pollutants?
ANSWER - The application of reasonably available NOV control techniques
°°~~~ * " * /\
I (combustion modifications) to fossil fuel-fired steam generators are
usually related to changes in the design of the boiler and/or burner
| configuration. Any of the combustion modifications presented in this
I document can usually be used to reduce NOV emissions to meet most NO
X X
emission limitations. The flue gases leaving the boiler (firebox) area
can be treated for other pollutants as required. One of the techniques
39
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for NO control, reduction of excess air, may increase smoke but the
amount does not become significant unless very low excess air rates are I
used. This is balanced by the fact that as these pollutants increase,
boiler efficiency is reduced, which is a waste of BTU's and the danger ^
of explosion increases. This situation is usually watched closely
and not tolerated by boiler operators, especially today. Utility boilers
are less affected than industrial or smaller boilers because they nor- I
mally have higher heat release rates. The use of reasonable and achievable
combustion techniques for NO control should not affect the operation or
A
efficiency of a control device used to control other pollutants.
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40
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- Miscellaneous -
QUESTION - How is NO converted to NQ2 in the atmosphere?
ANSWER - Although there are many atmospheric reactions involving
NO - N02 transformation, only a few of the mechanisms are predominate
I in the basic conversion processes. The NO emitted into the atmosphere
by sources combines with oxygen (0~), ozone (Oo) or some type of organic
I
compound to form N02. The NOo in the atmosphere can be photodisassociated
by sunlight to form NO. While these NO - N02 reactions are in process,
both NO and N0? may also be removed from the reactive mechanisms by
I combining with organic and/or inorganic radicals to form nitrates
(such as PAN) which are photochemically unreactive.
I QUESTION - Does HC control have any effect on ambient N02 concentrations?
ANSWER - Available laboratory studies have indicated that changes in the
non-methane hydrocarbon/nitrogen oxides (NMHC/NO ) ratio for an area may
X
I influence N02 concentrations. The studies indicated that if HC reduc-
I
_
tions exceed NOV reductions, thus reducing the NMHC/NOV ratio, peak NO
X X
concentrations may be reduced but the annual average NOo concentration
may increase. However, the NMHC/NOX relationship is preliminary, hence it
is not recommended that HC emissions be considered in an NOX control strategy
at this time.
QUESTION - Are any existing stationary sources required to continuously
| monitor NO emissions? If so, which sources?
X
j ANSWER - Yes. On October 6, 1975, the Agency promulgated regulations
(40 FR^ 46240) requiring the revision of SIP's to include requirements for
I the continuous monitoring of emissions from certain categories of
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stationary sources. Included in these regulations was the requirement
for the monitoring of NO emissions from fossil fuel-fired steam gener-
f\ ^^^
ators and from nitric acid plants in AQCR's where the Administrator has _
specifically determined that a_ control strategy for NOo is_ necessary.
6
A minimum size of 1,000 x 10 BTU/hour heat input for boilers and 300
tons/day (100% acid) production capacity for nitric acid plants was also
established for these monitoring requirements. The regulations are
complex and the reader is referred to applicable Federal Register for
specific details. Any NOY SIP revisions that have been determined to
/\
be needed shall include emission monitoring requirements for regulated
sources.
Revisions to SIP's to require continuous emission monitoring must
be submitted by the States to Regional Offices by October 6, 1976. The
State regulations may allow an additional 18 months after EPA approval
of the SIP revisions for sources to procure, install, and begin operating
the monitoring instruments. Quarterly reports of (1) emissions in excess
of SIP emissions limitation, and (2) the monitoring system downtime must
be submitted by the sources to the States.
I
ANSWER - Yes. The October 6, 1975, Federal Register (40 FR_ 46250) -
contains regulations under 40 CFR, Part 60, New Source Performance Stan-
QUESTION - Are new stationary sources of NOV required to monitor emissions?
1 X
dards, requiring all new fossil fuel-fired steam generators greater
than 250 x 10 BTU/hour heat input and new nitric acid plants to continu-
ously monitor their emissions of NO . Certain boilers, those capable
X
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of demonstrating operation during performance tests at below 70% of the _
emission standard» are exempted from the NO monitoring requirement.
/\
Sources must submit quarterly reports of excess emissions and monitoring
system downtime to EPA Regional Offices.
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I SECTION A
_ HISTORY OF NO CONTROL UNDER THE CLEAN AIR ACT
I
I Under the mandate of Section 109 of the Clean Air Act as amended
(1970), the Administrator, on April 30, 1971, promulgated in the
| Federal Register (36 FR_ 8186) as Part 410 of 42 CFR, national ambient
£ air quality standards (NAAQS) for particulate matter, sulfur oxides,
~ carbon monoxide, photochemical oxidants, hydrocarbons (oxidant guide),
and nitrogen dioxide. These air quality standards were to be attained
and maintained in all AQCR's through the implementation of various
I emission limitations as specified by each State in their State Implemen-
tation Plan (SIP) for each Air Quality Control Region (AQCR) within a
State. The NAAQS set for nitrogen dioxide were 100 jjg/m (0.05 ppm),
I annual average, for both the primary and secondary standard conditions.
3
A 24-hour average standard for N0? of 250 jjg/m (0.13 ppm) was proposed
but not promulgated because "No adverse effects on public health or
welfare have been associated with short-term exposure to nitrogen dioxide
I at levels which have been observed to occur in the ambient air", at
that time. A subsequent recodifi cation on November 25, 1971, resulted
in the NAAQS being contained in 40 CFR 50.11.
SIP's
SIP requirements were published on August 14, 1971, as 42 CFR,
Part 420 and were recodified as Part 51 of 40 CFR on November 25, 1971.
| These requirements included, in Section 51.14, the requirement that all
AQCR's where measured annual arithemetic average ambient N0? concentrations
were greater than 110 AJa/m, be designated Priority I. It was assumed that
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emission reductions resulting from the Federal Motor Vehicle Control «
Program (FMVCP) would reduce ambient levels to the standard (100 juc
by 1975, thereby not requiring control strategies to be developed for
those AQCR's only slightly in excess of the NftAQS for N02 (110 wg/m3 vs.
100 ,ug/m ). Ambient air quality data used in determining the priority |
classification of the AQCR's in relation to N02 were generally based ^
on the Jacobs-Hochheiser measurement technique. In the absence of
measured air quality data, priority classifications were to be determined
by population, i.e., AQCR's with an "urban place" population (1970) of
greater than 200,000 would be classified Priority I for N02- A total I
of 47 AQCR's (19%) of the 247 AQCR's were classified Priority I, 25 (53%)
of those AQCR's being interstate AQCR's. All other AQCR's were classi- I
fied Priority III.
CONTROL STRATEGY REQUIREMENTS FOR NITROGEN DIOXIDE
Each Priority I AQCR was required to submit a plan which set forth I
a control strategy that provided the degree of emission reduction
necessary for attainment and maintenance of NAAQS.
The emission reductions necessary to attain NAAQS for N02 standards
were to be calculated with the use of the proportional model. Control
strategy requirements for N02 were based upon the following measures (as |
needed): «
(a) the utilization of the FMVCP for NO:
/\
(b) consideration of any additional reduction in NO that would be
an indirect result of a transportation control plan designed either for
the control of carbon monoxide or photochemical oxidants; and |
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(c) the application of reasonably available control technology
(RACT) on stationary sources of NO (e.g., power plants and nitric
acid plants).
Should the combination of measures (a) (b) and (c) not demonstrate
attainment and maintenance of the N0£ standard, the original SIP control
strategy was to also include the use of RACT for the control of stationary
sources of hydrocarbons. If these measures were adopted, it was expected
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that the NCL standard would be attained.
It should also be noted that no TCP's*were required solely for
the control of NOV. It was believed that automotive emissions of NO
X A
did not contribute a large enough portion of the total NO emissions
X
in an area such that a TCP designed specifically for Ntk would be an
I
efficient method to address NOV control.
j\
The NO control strategy requirements were amended late in 1971
X
I (36 FR_ 25233, December 30, 1971) to delete the requirement for RACT for
M control of hydrocarbons from stationary sources. This change was based
upon a reappraisal of information on the role of hydrocarbons in the
I atmospheric conversion of NO to NO^ resulting in the conclusion that
the reduction of hydrocarbons from stationary sources did not play a
| significant role in the reduction of long-term (annual) ambient N02 con-
« centrations. With the deletion of this requirement, it was assumed
* that the NO^ standard would be achieved if control measures (a) (b) and
(c), identified above, were implemented.
*TCP = Transportation Control Measures
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APPROVAL/DISAPPROVAL OF SIP's _
On May 31, 1972, EPA published in the FIR (37 F£ 105, at 10842)
notifications of approval and disapproval of State Implementation Plans
submitted by States earlier in the year. Included in the Federal
Register were notices of disapproval for the NO control strategies I
/\ ^^"
for the 21 AQCR's listed in Table A-l. The predominate reason for these
disapproval actions was that the SIP did not require the application V
of RACT for stationary sources of N0x within AQCR's with N02 problems.
To correct the inadequacy of these SIP's, EPA proposed regulations
on June 14, 1972 (FJ^ 11826), to require the use of RACT in AQCR's I
requiring N0v control strategy. The AQCR's in Table A-l would be made
I
subject to EPA promulgated regulations if the State did not adopt approv- jj
able regulations before EPA promulgation. In this same FR_notice, EPA M
acknowledged that there was some difficulty with the routine field
use of the Jacobs-Hochheiser ambient monitoring technique and, because I
of that fact, the proposed regulations would not go into effect until
July 1, 1973. Similarly, States that had adopted NO regulations would J|
not be expected to require compliance before any EPA promulgated regula- _
tions. In the interim, further ambient measurements would be made to
affirm the validity of the Jacobs-Hochheiser method.
MEASUREMENT CONTROVERSY
I
In the FR^ of June 14, 1972, at 11826, the Administrator took note
of the fact that there were problems associated with the routine field
use of the Jacobs-Hochheiser method, the method designated as the federal
reference method for NO (see Appendix F, 40 CFR, Part 50). The problem |
/\
with the reference method was caused by two factors that had become
A-4
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TABLE A-l
21 AQCR'S WITH DISAPPROVED N0v CONTROL STRATEGIES AS OF MAY 31, 1972*
/\
AQCR AQCR NAME
NO.
015 Phoenix-Tucson
024 Los Angeles
042 Hartford-New Haven-Springfield
0.43 New York-New Jersey-Connecticut
045 Philadelphia
070 St. Louis
085 Omaha-Council Bluffs
115 Baltimore
123 Detroit-Port Huron
151 Scranton
160 Rochester
162 Buffalo
195 Altoona
196 Harrisburg, PA
197 Pittsburgh
214 Corpus Christi-Victoria
215 Dallas-Fort Worth
216 Houston-Galveston
220 Salt Lake City
223 Norfolk
225 Richmond
AFFECTED STATES
Arizona
California
Massachusetts
New York, New
Pennsylvania,
Missouri
Nebraska
Maryland
Michigan
Pennsylvania,
New York
New York
Pennsylvania
Pennsylvania
Pennsylvania
Texas
Texas
Texas
Utah
Virginia
Virginia
Jersey
New Jersey
New Jersey
*The control strategies for Atlanta (GA), Washington, D.C. (MD),
Flint (MI), Toledo (NI), Memphis (TN), and Seattle (WA) AQCR's
were also disapproved but were later approved (Sept. 22, 1972 and
Oct. 28, 1972) after the respective states submitted additional
information.
A-5
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A-6
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apparent during a revaluation of the method. First, the method was
found to have a variable collection efficiencythe range was from
about 50% to 70% at low levels of N02 to about 15% at high levels of
N0?. The second problem was a nositive interference from NO that could
cause NOp readings to be more than 100% greater than the actual value.
After an intensive laboratory and field investigation of the Jacobs-
Hochheiser method (and other methods believed to be more accurate), it
was concluded that the Jacobs-Hochheiser method was unreliable and should
no longer be the reference method. Hence, in the FR_ on June 9, 1973, m
at 15174, EPA proposed to delete the Jacobs-Hochheiser method as the
reference method. Three other reference methods, or "tentative candidate
methods" were proposed. These included the arsenite bubbler (orifice),
continuous chemiluminescence, and continuous Saltzman. Of these, the
method with the greatest potential accuracy was considered to be the |
chemiluminescence technique. _
Comments were solicited from the public and scientific community *
on the proposed new methodologies while lab and field investigations I
continued to determine the accuracy of the three candidate methods and
other methodologies . J
IMPACT OF MEASUREMENT CONTROVERSY ON SIP's
In addition to deleting the Jacobs-Hochheiser method as the federal
reference method, the Agency took three other significant SIP related |
actions in the Federal Register in June, 1973, necessitated by the «
faulty Jacobs-Hochheiser data base upon which SIP's were based.
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First, EPA prooosed, on June 8, 1973 (38 FFM518Q) to reclassify
_ 43 of the 47 Priority I AQCR's for N02 from Priority I to Priority III.
This was necessitated because current and valid N02 data was collected
which indicated that no N02 problem existed in the 43 AQCR's. The
remaining Priority I AQCR's were Los Angeles, Chicago, New York-New
I Jersey-Connecticut, and Wasatch Front (Salt Lake City). Because ambient
N0? levels were significantly above the NCL standard in Los Angeles
and Chicago, these AQCR's remained as Priority I AQCR's. Since the two
remaining Priority I AQCR's (i.e., New YorkrNew Jersey-Connecticut
and Salt Lake City) had ambient levels only slightly above the national
standards, it was proposed that additional information be collected in
these AQCR's before any action was taken to either reclassify them to
Priority III or to request a revised control strategy. Additionally,
3
valid ambient data above 110 ug/m had become available for Denver,
which had originally been classified Priority III. Since the data were
inconclusive, no action was taken at that time to reclassify Denver.
However, it was proposed that additional data be collected in Denver.
Secondly, in the same FR_ action, EPA proposed to rescind its
m emission control regulations proposed on June 14, 1972, for 17 AQCR's
and approve the State submitted control strategies for the attainment
of N02 standards within these AQCR's. However, disapprovals of nitrogen
oxides control strategies were retained for New Jersey-New York-Connecticut
| and the Wasatch Front AQCR's.
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were encouraged to rescind such NO control regulations. This action
X
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EPA held in abeyance the proposed regulations in these two AQCR's
until final decisions could be made on the classification of these
AQCR's. The Federal Register notice also indicated that States which I
had submitted NO regulations in AQCR's now classified Priority III
I
|
was taken since the regulations were developed on an inaccurate data
* I
base and current valid data did not support the need for such control.
Thirdly, EPA oroposed to change 51.14 (i.e., the requirements for
approvable NO control strategy) so as to require an explicit demon -
'
stration that the national standard for NOV would be attained in Prior- |
X
ity I AQCR's. States would still be allowed to take credit for any NO B
I
reductions to be obtained through the FMVCP and any TCP necessary for m
I
controlling CO and/or 0 . Further, the Preamble to the proposed changes
X
to Part 51 indicated that if a State could demonstrate NO reductions
that may result through the use of hydrocarbon emission control, then I
such reductions could be considered in the demonstration of attainment _
of the NAAQS.
On May 8, 1974, at 39 FR_ 15344, the Administrator promulgated
these three proposals with one exception. During the comment period,
additional data had become available for the Baltimore AQCR which I
marginally indicated that that AQCR should not be reclassified Priority
III. The data, however, were not conclusive that the AQCR should be
designated Priority I. Hence, Baltimore was grouped with Denver,
Salt Lake City and New York as AQCR's which required additional infor-
mation prior to final reelassification. I
*To date there have been few submittals for rescinding of NO control
regulations. .
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As a result of the promulgations, control plans were
needed for the two Priority I AQCR's (e.g., Los Angeles and Chicago).
Hence the State of Illinois was required to submit within 4 months
a demonstration that the approved control strategy for the Metropolitan
Chicago AQCR was adequate to attain and maintain the national standard
for nitrogen oxides. With respect to the Los Angeles AQCR, EPA had
previously disapproved California's control strategy for nitrogen oxides,
carbon monoxide and photochemical oxidants, and promulgated a transpor-
tation control plan. On February 6, 1974, the State of California
submitted a plan revision for Los Angeles which provided a transportation
control plan and a control strategy for nitrogen oxides. At the time
of the Federal Register action, EPA (Region IX) was reviewing the plan
to determine its adequacy in fulfilling the requirements of the revised
§51.14 to demonstrate the attainment and maintenance of the nitrogen
I oxide standard for Los Angeles. Hence no further control strategy was
required for Los Angeles at that time. In the July 12, 1976, Federal
Register EPA called for a revision of the SIP NO control strategy for
I Los Angeles.
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SECTION B
CURRENT STATUS OF AMBIENT N02 MEASUREMENT METHODS
Since the announcement that the Jacobs-Hochheiser method was poten-
I tially inaccurate, EPA has used other nitrogen dioxide measurement tech-
niques in conjunction with the routine activities of the Continuous Air
Monitoring Program (CAMP), the National Air Surveillence Network (NASN)
and the Community Health and Environmental Surveillance System (CHESS).
Data from these methods, as well as from laboratory investigations have
I been used to investigate the various methodologies. Four 24-hour bubbler
methods have been operated at approximately 200 NASN sampling sites for
| various periods during 1972-73-74. These include: (1) sodium arsenite
(orifice), (2) sodium arsenite (frit), (3) the triethanolamine- guaiacol-
sulfite (TGS), and (4) triethanolamine (TEA) methods. In 1972, continu-
ous chemi luminescence instruments were placed in 41 AQCR's and operated
for approximately one year. Additionally, 20 chemi luminescence
| instruments were operated in various AQCR's with three additional
instruments operated in Los Angeles under the CHESS network.
Continuous Colorimetric (Saltzman) have been used at each of the six
CAMP sites. In addition to these EPA sponsored monitoring projects,
the state and local agencies have begun to expand the NO 2 ambient moni-
| toring networks with various valid monitors.
M In addition to collecting NO 2 information by various methodologies,
work has continued to determine a new reference method for N0£ to replace
I the Jacobs-Hochheiser method. Since the major problem with the Jacobs-
Hochheiser method was the variable collection efficiency of the absorbing
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reagent, six alternate absorbing methods have been examined. These I
methods have undergone two independent studies at the Environmental
Monitoring and Support Laboratory. I
As a result of these studies, the chemiluminescence measurement
principle and calibration procedure was proposed in the Federal
Register on March 17, 1976, as the basis for the new reference method. The |
chemiluminescent technique was selected over the manual-type candidate methods
primarily because analyzers based on this principle would have the
capability of generating continuous, real time data rather than integrated
data representing 24-hour time periods as in the case with the Arsenite
and TGS manual methods. Technical evaluations and comments from the I
monitoring community were also considerations in the selection. It
should be noted however that for determining compliance to the National |
Ambient Air Quality Standard for NCL - an annual arithmetic mean - mm
integrated 24-hour bubbler measurements are adequate.
In addition, two 24-hour bubbler methods were found to be reliable |
and capable of producing valid air quality data. These are the TGS and _
sodium arsenite orifice methods. These two bubbler methods will be tested
for equivalency as soon as a reference method is designated.
Data collected under proper operating conditions for these three
methods, i.e., chemiluminescence, TGS, and arsenite orifice can be used J
directly in development of NO control strategies. Additionally, there _
I
are other methods in field use which are thought at this time.' to be m
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I capable of producing valid air quality data under the proper operating
conditions, i.e., TEA, sodium arsenite frit and continuous Saltzman
I colorimetric. However, the likelihood of these methods providing valid
_ data for an annual average is not as great as with the sodium arsenite
* orifice, TGS, or chemi luminescence methods. Therefore care should be
taken to assure that the air quality data used for the control study is
valid. If bubbler methods are to be used in SIP networks, the use of
arsenite orifice and TGS bubblers should be encouraged. If continuous
methods are to be employed, chemi luminescent analyzers should be encouraged
although data collected with Saltzman colorimetric analyzer can be used
if it is judged valid. (See Table B-l.)
In the case of the TEA method, it was found that the collection effi-
ciency is low (around 50% with an orifice) and that a frit is necessary
to obtain a more desirable high constant collection efficiency of 80%.
Although data from this method would be acceptable for use in strategy
analysis, other methods are available which have high constant collection
efficiencies without the use of a frit. The frit is undesirable for the
I following reasons: it can become clogged which would result in inaccurate
flow measurements; the use of pre-filters to capture particulate would
interfere with SO^ measurements if an N02/S0? sampling train was being
used; and it is more expensive.
In the case of the sodium arsenite frit method, it was determined
that the frit increased the collection efficiency by only approximately
5%. Because of the problems mentioned above with the use of frits, this
method should be discouraged, although data already collected under proper
operating conditions can be used for emission control strategy analysis.
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TABLE B-l
N02 AMBIENT MEASUREMENT METHODS
Measurement Method
(Method Code)
Instrumental
(11) Modified Saltzman
Colorimetric
(12) Saltzman Colorimetric
(13) Coulometric
(14) Chemiluminescence
Bubblers .
(71, 81, 91) Jacobs-Hochheiser
(72, 82, 92) Saltzman Bubbler
(84) Sodium Arsenite Orifice
(94) Sodim Arsenite - Frit
(95) TEA
(96) TGS
Comment
Data can be used with Caution *
Data can be used with caution
Data can be used with caution
Proposed Federal Reference Method
Data can be used
- Data must not be used
- Data must not be used
Candidate Federal Equivalent Method
Data can be used
Data can be used with caution
Data can be used with caution
Candidate Federal Equivalent Method
Data can be used
*User should be aware of the problems associated with the method and be
assured that proper procedures were used in collecting data.
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In the case of continuous colorimetric (Saltzman) analyzers, results
of tests indicate a method bias, slow response time (about 15 minutes) and
I negative ozone interference for certain monitors. Because of these problems,
_ the use of chemi luminescent analyzers should be encouraged. However, data
obtained from analyzers using this measurement principle may still be valid
for use in emission control strategy analysis for the following reasons:
1. Since the ozone interference noted in some monitors is negative,
any NOp values obtained will tend to be conservative.
2. The ozone interference is significant only at high OgrNCL ratios
(32% negative interference at 3:1 O-^NCk ratio) which occur over a limited
part of the day and usually over one or two seasons of the year. Thus,
the impact of this interference on annual averages of NCL should be
small in many areas of the country.
3. A slow response time is not important when only annual averages
are of interest. The impact would be insignificant on the annual average.
However, short-term averages (e.g., 1-hr.) could be affected significantly.
4. Some users of analyzers (i.e., California/Los Angeles) using
the colorimetric principle claim they have been unable to detect significant
ozone interferences. Thus, it is possible that specific models may not
I be as prone to ozone interference as others.
Any data collected from instruments using the Jacobs-Hochheiser proce-
dure should not be used for strategy analysis. Anyone using Jacobs-Hoch-
heiser bubblers should be encouraged to switch to the Sodium arsenite
orifice or T6S procedure as soon as possible. A more detailed discussion
| of ambient NCU measurement method can be found in Comparison of Methods
for Determination of Nitrogen Dioxide in Ambient Air (EPA-650/4-75-023) .
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The following section contains a more complete discussion of each
method.
N02 MEASUREMENT METHODS
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1. Sodium Arsenite Procedure (ARS), orifice- Bubbler (Method No. 84)
Principle and Applicability
Nitrogen dioxide is collected by bubbling ambient air through a sodium
hydroxide-sodium arsenite solution to form a stable solution of sodium nitrite.
The nitrite ion (N0£) produced during sampling is reacted with phosphoric acid,
sulfanilamide, and N-l-(naphthyl) ethylienediamine dihydrochloride to form an azo-
dye and then determined colorimetrically.
The method is applicable to the collection of 24-hour samples in the
field and their subsequent analysis in the laboratory. I
Interferences
Nitric oxide (NO) is a positive interference. The presence of NO can I
increase the NO ?response by 5 to 15 percent of the N0£ sampled.
The interference of sulfur dioxide is eliminated by converting it to
sulfate ion with hydrogen perioxide before analysis.
Evaluation
The method when followed is a precise procedure for measurement of I
NOg on a 24-hour average basis, and is sufficiently accurate provided the
average 24-hour NO and/or C02 concentrations do not exceed 310 J4g/m and/or
500 ppm, respectively. The probability of these concentrations being exceeded
in ambient air is low (less than 5%). Data from this method are considered
valid and can be used as the basis of a control strategy. I
2. TGS-ANSA Procedure - Bubbler (Method No. 96)
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I Principle and Applicability
Nitrogen dioxide (NOp) collected by bubbling air through a solution of
triethanolamine (T), 0-methoxyphenol (guaiacol) (G), and sodium metabisulfite (S)
The nitrite ion (N02) produced during sampling is determined colorimetrically by
reacting the exposed absorbing reagent with sulfanil amide and 8-anilino-l-
naphthalenesulfonic acid ammonium salt (ANSA). The method is applicable to
the collection of 24-hour samples in the field and subsequent analysis in the
m laboratory.
Interferences
At a NCL concentration of 100 jug/m3, the following pollutants, at the
levels indicated do not cause interferences: ammonia, 205 jug/m3; carbon
monoxide, 154,000 >jg/m3, formaldehyde, 750 /jg/m3; nitric oxide, 734 jjg/m3;
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phenol, 150 jug/m ; ozone, 400 yug/m ; and sulfur dioxide, 439/jg/m .
A temperature of 40°C during collection of sample had no effect
on recovery.
I Evaluation
The method is an accurate, precise procedure for measurements of NO,,
in ambient air when the specified analysis procedure is followed closely.
f The method has more than adequate sensitivity for ambient measurement for
24-hour sampling periods. However, the method does not appear to be sensitive
enough for shortfeterm sampling. Data from this method are considered valid
and can be used as the basis of a control strategy.
| 3. Chemiluminescence Method - Instrumental (Method 14)
Principle and Applicability
Atmospheric concentrations of nitric oxide (NO) can be measured by
the chemiluminescent reaction of ozone (03) with NO at reduced or near
atmospheric pressure. Nitrogen dioxide (NOg) is measured as NO in the system
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after conversion of NOg to NO. Air samples are drawn directly into the
analyzer to establish a NO response; then a switching valve directs the sample
air through the converter where the N02 is converted to NO. The photomultiplier
measures the light energy resulting from the chemiluminescent reactions of NO I
and 03. By subtracting the NO signal from the NO+N02(NOX) signal, the amount of *
N02 is determined. The subtractive process is accomplished electronically.
Total time for both measurements is less than 1 minute. Q
The method is applicable to the measurement of NOg, at concentrations m
in the atmosphere ranging from 9.4 to 18,800 ug/m3 (0.005 - 10'ppm). *
Interferences jl
The chemiluminescent detection of NO with 0^ is not subject to inter-
ference from any of the common air pollutants, such as Og, N0£, carbon monoxide
(CO), ammonia (NHg), or sulfur oxides (SOX). _
When the instrument is operated in the NO* mode, any compounds that
may be oxidized to NO in the thermal N02 converter are potential interferents.
The principal compound of concern is ammonia; however, this is not an inter-
ferent for converters operated at less than 330°C. Unstable nitrogen compounds
such as peroxyacetyl nitrate (PAN), organic nitrites, decompose thermally to ^
form NO and may represent minor interferences in some polluted atmospheres.
Evaluation
The chemiluminescent method is a precise and accurate procedure for
measurement of NO. in ambient air when used by an experienced operator. The
method has more than adequate sensitivity for ambient measurements. Data from this
method are considered valid and can be used as the basis of a control strategy.
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" 4. Colorimetric Method (Saltzman) - Instrumental (Method 11)
Principle and Applicability
This method is based on a specific reaction of nitrite ion (NOg) with
diazotizing-coupling reagents. The absorbance of the azo-dye is directly
m proportional to the concentration of N0£ absorbed.
This method is applicable to the measurement of N02 at concentrations
in the ambient air from 18.8 to 1880 ^ig/m3 (0.01 - 1 ppm).
Interferences
Interferences from other gases that might be found in the ambient air
ha've been reported to be negligible ; however, most interferent studies have
been done on manual procedures and may not be applicable to continuous methods.
ft Recent studies indicate that ozone (0^) produces a negative interference
as follows: ratio of 0^ to N0? 1:1 = 5.5 percent, 2:1 = 19 percent, and
3:1 = 32 percent.
Evaluation
» The results of the collaborative test demonstrates a collaborator
dependent method bias which cannot be quantitated. The method has a slow
response time and possesses a negative ozone interference. The method does
have an acceptable lower detectable limit and adequate precision. Until
the problems discovered in the collaborative test are resolved, additional
m monitoring using this method should not be initiated. However, after reviewing
data available from this method, it may be found satisfactory for control
strategy development.
Status of Selection of New N02 Reference Method
As a result of these tests, the chemiluminescen ce measurement
I principle and an associated calibration procedure was proposed as the basis
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for a method to supercede the original reference method. The chemilumi
nescent technique is recommended over the manual-type condidate methods ^
primarily because analyzers based on this principle would have the capa- Ij
bility of generating continuous, real time data rather than integrated
data representing 24-hour time periods as in the case with the arsenite p
and TGS manual methods. Technical evaluations and comments from the ^
monitoring community were also considerations in the selection. It *
should be noted however that'for determining compliance with the National
Ambient Air Quality Standard for NCL - annual arithmetic mean- integrated
24-hour bubbler measurements are adequate. V
The continuous chemiluminescence measurement principle and calibra-
tion procedure were proposed in the Federal Register on March 17, 1976, *
as the new reference method. This proposed action specified only a A
measurement principle and calibration procedure, not a reference method
per se. For a specific analyzer to be designated as a reference method m
for N0?, it would be required to utilize the measurement principle and
calibration procedure, meet all specifications and other requirements of |
Part 53 (i.e., EPA reference and equivalency requirements that will also M
be promulgated shortly) and be designated as a reference method under
provisions of Part 53. Analyzer manufacturers would test their own respec-
tive analyzers against the specifications and requirements and then would
submit the results to EPA. Analyzers satisfying all of the Part 53 J
requirements would be designated as reference methods. It would, there- «
fore, be possible to have several reference methods for NCL. In addition,
other methods or measurement principles will be designated as equivalent
methods. A three-month period is being allowed for manufacturers to
best their instruments and submit them with the test results for reference
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Method designation. If no instruments are submitted in that period,
EPA will designate an instrument which EPA itself will have tested and
found satisfactory as the reference method. The FEDERAL REGISTER
action schedule needed to accomplish these tasks is outlined below.
Schedule for Establishing NCL Reference Method
Action
Date
3/17/76
3/17/76
10/76
2/77
3/77
Propose continuous chemiluminescence measurement principle
and calibration procedure (40 CFR Part 50).
Propose reference and equivalency requirements (40 CFR Part 53),
Promulgate measurement principle and calibration procedure;
promulgate reference and equivalency requirements.
Designate reference methods (40 CFR Part 50) and identification
of acceptable commercial instruments.
Designate equivalent methods (40 CFR Part 53). (Arsenite and
TGS 24-hr, bubbler methods are expected to be designated as
equivalent methods.)
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I SECTION C
N02 FORMATION PROCESSES AND CONTROL STRATEGY MODELING
Emissions of NO and NO- Formation
A C-
J Most man-made sources of nitrogen oxide, NO , emit primarily nitric
_ oxide, NO. Some point sources, such as nitric acid plants and TNT
* plants, however, directly emit mostly nitrogen dioxide, N02Jinto the
atmosphere. The reaction mechanism for the conversion of NO to N02
conversion is complex and is a function of many factors including the
g hydrocarbon concentrations, hydrocarbon reactivity, ultraviolet radiation
and ambient temperature.
The importance of hydrocarbons in the conversion of NO to N02
is the photochemical production in the air of organic radical species
^ and ozone which oxidize the NO to N02. Ultraviolet light acts both to
1 photochemically dissociate N02 to NO and at the same time to help
produce the species that oxidize NO to N02. As a result, ambient air
* never has just NO or just N02, although summer afternoon air often has
10 to 15 parts of N02 per part of NO. The conversion of NO. to N02 is
slower in the winter than in summer because of lower temperatures.
1 A parameter that has been identified in laboratory studies as important
in the conversion process is the hydrocarbon to NO ratio. It appears
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I more than the NO emissions, the peak N0~ concentrations will decrease
x t
but the nonpeak N02 concentrations may actually be increased due to the
I lessening of the extent of removal processes with the hydrocarbons.
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It is not known how the 24-hour and annual average concentrations will be
affected. Although insufficient data is currently available to require I
consideration of the hydrocarbon to NO ratio in control strategy
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development work, the hydrocarbon reduction associated with the oxidant m
control strategy may become of interest in the future and eventually may M
need to be considered with respect to its possible impact on the N02
control strategy. I
Under most conditions, NO is mostly converted to N0~ within a few
hours. During this period, NO emitted into the atmosphere is constantly (
dispersing while the N02 is forming. In an urban area this fact can allow
a portion of the NO emitted from tall stacks to be brought to the ground
A
and a portion of the NO emitted from motor vehicles to disperse upward
A
before the N0-N0? conversion is completed. As the NQ9 is formed in large
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urban areas, it becomes rather uniform in concentration in relation to |
the area due to the significant NO emissions throughout the urban area. m
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For the 24-hour average and for the annual average, sharp NO^ concen-
tration gradients are therefore not observed in urban areas in contrast I
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to the situation for directly emitted pollutants such as CO and S0?.
Isolated point sources outside of urban areas, whether large or jjf
small NO emitters, have their greatest impact near the source with m
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relatively less impact on distant cities where NO attainment problems w
: ~ ' ' ~ /\
are generally experienced. Generally, most isolated fossil fuel -fired
power plants have a minor local impact and a negligible impact on annual
average NO- concentrations at a distance greater than 20 to 30 miles. |
The time period required for NO-NOp conversion and transport to a ~
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I metropolitan area allows for diffusion of the NCL to such an extent
that its impact on the urban area is minor. Thus, sources of NO
£ emissions 20 or more miles distant from the fringes of an urban area generally
need not be considered as an important emission source in relation to the
urban area, even though their emission rates may be large. Large emission
reductions from such isolated sources usually will not be effective
in reducing IW^ concentrations in the urban area. Other factors such
I as wind persistence, topographical features restricting transport in
_ certain directions, etc., should also be considered in analyzing NO - N0?
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" source receptor relationships and defining "isolated" sources.
Natural background concentrations of N02 resulting from bacterial
and plant actions should also be considered in strategy development.
| Such concentrations are generally about 8 yg/m (.004 ppm)2 annual
*
average.
CONTROL STRATEGY MODELING
| A key element in the evaluation of a control strategy is an
« adequate methodology for relating pollutant emissions to ambient air
quality. A commonly used technique is an atmospheric simulation model
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which is a mathematical description of the pollutant transport, dis-
persion and transformation processes that occur in the atmosphere.
In its simplest form, such a model relates ambient pollutant concen-
trations (x) to pollutant source emissions rates (Q) and a background
concentration (B).
1 x = KQ + B
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The variable K is a function of atmospheric conditions and the spatial
relationships between a source and a receptor.3
With the aid of a simulation model, it is possible to estimate |
systematically the variations in pollutant concentration which would m
result from alternative degrees and types of emission control. If each
control strategy can be stated in terms of specific emission reductions, 9
then a simulation model can be used to investigate the cost effective-
ness of each strategy. Although simulation models may not be capable
of indicating the air quality impact of individual control strategies
with precision, simulation models provide a measure of the range and
relative significance of air quality changes which may result from
various strategies.
The simplest of the models used to project air quality is the I
proportional or rollback model. In the past this model has been used
for NO control strategy review and development for urban areas. It is 9
recommended that this simple model along with measured air quality flj
data continue to be used as the basis for NO planning. While other
X
models may be applicable to special cases, such as isolated point sources, M
or may attempt to explicitly account for the photochemical production
of NOp, such models have not been adequately validated at this time. m
The proportional model assumes that the dispersion parameter (K) ft
does not vary with time or with the source-receptor relationship and that
changes in NO emissions will be uniform across the area. Thus the I
relationship of emissions (Qp) and air quality (xp) at some future time
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to base year emissions (Q, ) and air quality (XT) can be expressed
by the following proportionality which accounts for the natural back
Ji ground NO^ concentration (B) .
X2 - B 0
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cause and effect relationship between the rate of emission of the pollu-
* tant and its concentration in the atmosphere. If, for example, the rate
of emissions is reduced by 95 percent, it is expected that the non-
background component of atmospheric concentrations will be reduced by
95 percent. The use of this linear relationship does not imply that
_ the chemical relationships leading to NC^ formation in the atmosphere
' are linear. It is, therefore, not necessary to know what percent of NO
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4 is converted to NCL. The implicit assumption is that the ratio between
emitted NO and ambient N0? is fixed and that it will not change from
A. C.
I year to year as NO concentrations change.
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in NO emissions which are necessary to reduce N0? ambient concentrations
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from XT to xo if no change in N02 background occurs. To calculate
the percent reduction in NO emissions, R, the proportional model
A
I can be rewritten in the rollback form, as follows:
m ^i v? xi x?
R = -i-^ x 100 = b x 100
QI x-| - B
where XT = SIP design value (representative annual average N09 con-
I' *
centrations in base year).
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B = N02 background concentration (8 yg/m ) I
X2 = C = NAAQS for N02 (100 yg/m3)
R = Percent reduction in NO emissions required *
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The rollback model is applicable to annual N02 concentrations
on an urban area basis for which appropriate data are available. Input
to the rollback model requires total area-wide emissions for the base
year and for the future year of interest. An annual NOp concentration
representative of air quality for the area of interest is also 9
necessary. It should be noted that the proportional model can only be <
used to estimate concentrations at sites where representative air
quality data are available. However, because of the small NOp gradients V
observed in most urban areas, this limitation becomes of much less
importance for N02 than for other pollutants. m
Because of the number of different types of sources which emit m
NO , an expansion of the simple rollback equation has been made. This
expansion is called Modified Rollback (See Appendix A - Modified V
Rollback). Modified Rollback is a technique for considering a variety
of NO source categories and growth factors. It can be expressed as V
N N g
-T~B" i=l 'base year = ^ ^i rfuture
where
G = a growth and control factor, i.e., the ratio of NO emissions
at or after the attainment date versus the NO., emissions
... ,,__. ,
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N = the number of source categories,
i = a particular source category, e.g., light-duty vehicles,
V trucks, power plants and other stationary sources, etc.
I In cases where the area-wide NO emissions are contributed by a variety
of source types with differing emissions, growth rates and applicable
I controls, the modified rollback model permits a consideration of a
variety of control strategies.
| To apply this technique, the left side of the equation is evaluated
I with available data to determine an allowable NO emission rate. The
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right side of the equation is then evaluated for various control strategies
H until a strategy which demonstrates attainment is developed. Growth
rates for mobile sources and for stationary combustion sources can
| usually be obtained from local planning agencies. Future emission
^ reductions for mobile sources can be estimated from Supplement 5 to AP-42.
Expected emission reductions for stationary sources depend on new source
II performance standards and local regulations for NO emissions on the
date that these regulations take effect.
Q The rollback models are applicable anywhere for which there are
« basic data on area-wide emissions and representative air quality for
a particular base year. The simple rollback model can be applied
V with hand calculations and is widely used. Modified rollback has
been computerized and documented. A computer program and associated
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documentation on the "Modified Rollback Computer Program" have been
made available to all EPA Regional Offices.
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APPLICATION I
Figure C-l presents projections and trends for nitrogen dioxide
for Los Angeles and Philadelphia (Camp Stations). These annual average
N02 concentrations were developed using the modified rollback technique.
In general, Figure C-l demonstrates that the modified rollback model
and assumptions used with it provide an adequate representation of the »
actual air quality trends. The projections are smooth curves, whereas m
the measured air quality may change randomly from year to year because
of meteorological factors. Any deviation between the projected values
and the measured air quality may be due to errors in estimating and
projecting emissions and changes in air quality. *
OTHER MODELS |
Because of the limitations of existing N0-N02 modeling techniques,
MDAD, OAQPS is continuing to review available models to assure the "
best "state of the art" models are made available for N02 control *
strategy review and develonment work. The proportional model previously
discussed is currently the method which is recommended for control V
strategy development work. If other superior NO models are identified
x i
by future OAQPS reviews, they will be made available to the Regions as
soon as possible. AQDM, COM, or other models may be used when evaluating
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140
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FIGURE C-l
OBSERVED AIR QUALITY VS. MODIFIED ROLLBACK PROJECTIONS
O
O
Los Angele
Philadelohia
1964 1966
Parameter
1968 1970
YEAR
1972
1974
Observed N02 Concentrations (Modified Saltzman Method)
Projected N02 Concentrations (Modified Rollback Model)
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REFERENCES
1. Martinez, E. L., and N. C. Possiel, "Report of N0? Distribution j|
in Cities" Memo, October 10, 1975.
2. Air Quality Criteria for Nitrogen Oxides, AP-84, pp. 3-1 (1971).
3. Appendix A-40 CFR Part 51.
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CONTROL OF OXIDES OF NITROGEN
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SECTION D
- OXIDES OF
FOR STATIONARY SOURCES
Table of Contents
Page
BOILERS AND HEATERS D- 1
fl Utility Boilers D- 2
Tangenti ally-fired boilers D- 3
| Front-wall firing furnaces D- 4
Horizontally-opposed firing furnaces D- 4
Cyclone furnaces D~ 4
Split or divided furnaces D- 4
Commercial, Residential, and Industrial Boilers (CRI) D- 5
I COMBUSTION MODIFICATIONS D- 7
^ Low excess air combustion (LEA) D- 7
Off-stoichiometric or staged combustion D- 8
fl Flue gas recirculation (FGR) D- 8
Water or steam injection D- 9
J Preheat reduction D- 9
Firebox enlargement D- 9
Derating D- 9
Burner designs D- 9
Costs of Combustion Modifications D- 12
I FLUE GAS TREATMENT (NO ) D- 13
^v X
, Dry Flue Gas Treatment D- 13
" Wet Flue Gas Treatment D- 15
GAS TURBINES D- 16
STATIONARY INTERNAL COMBUSTION ENGINES D- 18
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INDUSTRIAL PROCESSES D-19 |
Nitric Acid D-19 _
Catalytic Decomposition D-19 *
Scrubbing D-20
Molecular Sieves D-20
Extended Absorption D-21 £
Other Chemical Processes D-21 _
PETROLEUM AND NATURAL GAS PRODUCTION D-23
METALLURGICAL PROCESSES D-23
CEMENT, LIMESTONE, CERAMIC, AND GLASS PRODUCTION D-24
OTHER STATIONARY SOURCES D-24 . §
SUMMARY OF NOV CONTROLS D-25 m
x ...|
GLOSSARY D-27 ,
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List of Tables '
List of Figures
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List of Tables
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Table D-l. Analyses of Typical U. S. Coals and Lignite
Table D-2. Analyses of Typical Fuel Oil
Table D-3. NOV Emission Levels from Uncontrolled Utility Boilers
A
Compared to the New Source Performance Standards
Table D-4. Typical Baseline Emission Levels From Commercial and
Residential Heating
i Table D-5. NOX Levels and Typical NOX Reductions with Combustion
Modification to Utility Boilers
Table D-6. Summary of Combustion Modification Techniques for
Large Boilers
Table D-7. Estimated Investment Costs for Retrofitting Low Excess
Air Firing to Existing Utility Boilers
Table D-8. Major Flue Gas Treatment Plants in Japan Using Selective
Catalytic Reduction (Dry Process)
Table D-9. Major Flue Gas Treatment Plants in Japan Using Wet Scrubbing
Table D-10. Effectiveness of Combustion Modification on Gas Turbines
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List of Figures ,
Figure D-1. Tangentially Fired Boiler |
Figure D-la. Details of Tangentially Corner Firing Systems and Flame Pattern .
Figure D-2. Front Wall Fired Boiler *
Figure D-3. Front Wall Fired Boiler W
Figure D-4. Horizontally Opposed Fired Boiler
Figure D-5. Schematic Drawing of Cyclone Furnace J
Figure D-6. Cyclone Fired Boiler ^
Figure D-7. 1973 Installed Equipment Costs of NOX Control Methods "
for New Tangentially, Coal-Fired Units
Figure D-8. 1973 Installed Equipment Costs of NOX Control Methods
for Existing Tangentially, Coal-Fired Units J
/
Figure D-9. Typical Gas Turbine Base Load NOX Emissions ' m
Figure D-lO. Effectiveness of Water or Steam Injection in Reducing
NOX Formation in Gas Turbines
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CONTROL OF OXIDES OF NITROGEN
* FOR STATIONARY SOURCES
I
Control technology for stationary sources can address NO by
/\
process changes or tail gas treatment. Process changes tend to be
specific to source characteristics. Tail gas treatment has potential
applicability to many sources but except for nitric acid plants, its use
has been extremely limited to date. The greatest activity in NO control
f
has been with utility boilers and nitric acid plants.
Process changes are commonly termed "combustion modifications". While
still being refined, they are used widely for large boilers and other
combustion sources in the United States. Flue gas treatment (FGT) systems
are being investigated in the United States but most of the development
m work is being conducted in Japan.
BOILERS AND HEATERS
Nitric oxide (NO) is formed during combustion either from thermal
fixation of molecular nitrogen in the combustion air (thermal NO) or from
oxidation of chemically bound nitrogen in fuels (fuel NO). In the atmosphere,
NO reacts slowly *ri±h oxygen ID fora nitrogen dioxide (N02). The main factors
affecting NO formation in combustion sources are characteristics of the fuel
burned, flame temperature, length of time the combustion gases are subjected
to peak flame temperatures and excess oxygen.
Effect of Fuel Nitrogen
II 2 3 4 5/
Recent studies ' * ' ' ' indicate that as much as half of the nitrogen
in the fuel (oil and coal) can be converted to NO. It was also shown that
the fraction of fuel nitrogen converted to NO decreases with increasing
ff nitrogen content even though the magnitude of the NO increases. Excess air
(oxygen) appears to have a strong effect on fuel nitrogen conversion but con-
| version is relatively insensitive to temperature. Much of the U. S. supplies
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of residual oil and coal are relatively high in nitrogen; therefore, it H
is Important to give consideration to fuel characteristics when discussing
combustion modifications. Tables D-l and D-2 show the range of fuel nitrogen
for various coals and fuel oil.
An extremely wide range of devices can be classified as boilers or P
heaters. For this document, only a minimal review of boiler terminology ^
is presented such that the reader can differentiate between those factors
that materially affect NO emissions. Many other publications treat I
boiler and heater technology in depth.
In broad categories, boilers and heaters can be differentiated by Q
usage, fluids heated or vaporized, size, fuels burned, firebox design, _
firetube versus watertube, by the use or non-use of air preheaters, and
I
by the manner in which they are constructed (field erected or packaged).
Many of these factors affect NO emissions as do operational characteristics
such as excess air, degree of air preheat, and firing rate. H
For purposes of this paper we have segregated boilers and heaters into ._
two groups which we term "utility boilers" and "commercial, residential,
and industrial (CRI) boilers". There is some overlap since large industrial V
boilers are grouped with utility boilers and the smallest utility boilers
are occasionally of the same design as CRI boilers. |
Utility Boilers _
Utility steam generators and large industrial boilers are differentiated
I
from other types of boilers and heaters since they are much larger and produce
significantly greater concentrations and quantities of NO than CRI boilers.
1
These large units (generally greater than 250 million Btu per hour heat input) |
employ air preheaters such that firebox peak temperatures are about 500°F ^
hotter than with CRI designs. Also utility boilers are almost always field *
'. D-2 *
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are limited but by and large those offered for new units reflect
consideration of NO reduction techniques. Some designs inherently produce
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more or less NO . Typical new utility boilers are of 500 megawatts
A *~
I erected, watertube designs as opposed to packaged units (built in the
« factory) typical of CRI installations. Furthermore, essentially all
* U. S. utility boilers are manufactured by four firms, Babcock and Wilcox,
I Combustion Engineering, Riley Stoker, and Foster Wheeler. Utility designs
I
(output) capacity (4.5 x 109 Btu per hour heat input) and most are
coal-fired. The largest industrial boilers are of about 750 million Btu
per hour heat input. Units of 100 million Btu per hour and greater tend
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levels. They are manufactured by Combustion Engineering.
Figure 1 shows a typical corner-fired boiler. Figure la shows jj
details of a corner firing system configuration and flame pattern.^
Front-wall firing furnaces (Figures 2 and 3) are designed with
all burners firing horizontally from one wall normally considered
the front of the furnace.
Horizontally-opposed firing furnaces (Figure 4) are designed with |
rows of burners firing horizontally from the front wall and other
rows of burners firing horizontally from the rear wall. "
Cyclone furnaces (Figures 5 and 6) are a type of slagging furnace
in which coal and combustion air are introduced in a tangential
pattern. Burning occurs at high heat release rates such that ash I
becomes molten and is tapped from the bottom of the boiler. Cyclone
furnaces require coal with ash of low softening point. They produce
greater concentrations of NOX than almost any other design and for
this reason are seldom installed at new sites.
Split or divided furnaces are divided by a wall of steam or water I
tubes. Such furnace* are -usually front-wall fired or horizontally-
opposed fired.
Uncontrolled emissions from utility boilers tend to be lowest for
tangentially fired units and highest for cyclone furnaces. Other factor
being equal, NOX emissions are lowest for gas firing and greatest for
coal burning. However because of constraints on natural gas and fuel oil,
almost all new utility boilers probably will be fired with solid fuel.
Ranges of uncontrolled emissions are listed in Table D-3 for principal utility *
boiler designs. The relationship between NO concentration and the NSPS is a
A
function of fuel heat content and chemical makeup (the latter governs the volume
of products of combustion generated by a unit weight of fuel). The coal
D-4
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cited in Table D-3 is of relatively high heating value (13,100 BTU per
I pound) and doesn't necessarily reflect the coal burned in the boilers
at which the data were measured.
I Commercial, Residential, and Industrial (CRI) Boilers
I Commercial and residential boilers, small and medium size industrial
units, and residential warm air furnaces are almost always assembled at
| the factory and shipped to the user as a package. For the most part the
_ boilers are of firetube design but the largest and smallest often are of
watertube construction. Until the recent oil crisis, all except the oldest
CRI boilers were fired with natural gas or fuel oil.
Because of the absence of air preheating and because of their smaller
g size (shorter residence time at high temperature) CRI boilers inherently
produce less NO than their larger counterparts. There have been only
I
* limited efforts until recently to characterize emissions from CRI boilers.
IB It is known that there are wide variations in CRI firing rates and in
burner maintenance and adjustment. The firing rate and firebox characteristics
I probably have a strong effect on NO emissions but the influence of these
factors has not been evaluated for the many CRI designs available in the
" United States. Also there is little uniformity in such important design
M parameters as firebox heat release rate. However, in comparison to utility
boilers, CRI units probably are fired at lower rates, i.e., lower percentages
| of manufactures maximum load rating; this factor tends to reduce NOX emissions
below those which would be predicted from emission factors.
In addition, CRI boilers normally receive less maintenance and operator
care than utility boilers such that combustion is less complete and heat
transfer is less efficient. Precision adjustments, such as are necessary with
Q many combustion modification techniques, are generally not workable for rptrn-
fitting CRI boilers. The effect of maintenance and operator care on NOX emission
I
Jx
D-5
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I
in unclear. Where combustion is incomplete, NO formation is likely _
to be inhibited. On the other hand, the extremely wide variation
of excess air often observed at CRI boilers might produce more or
less NO emissions.
/\
Baseline or uncontrolled emission levels for typical commercial I
and residential heating boilers are listed in Table D-4. These values
represent units of less than 100 x 10 BTU heat input, some appreciably
smaller.
D-6
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COMBUSTION MODIFICATIONS
Principal combustion modifications are measures that reduce maximum
flame temperatures, minimize oxygen concentration, or reduce residence
I time at peak temperatures. Combustion modifications include: (1) low
excess air (LEA), (2) off-stoichiometric combustion (OSC), (3) flue gas
" recirculation (FGR), (4) water or steam injection, (5) preheat reduction,
(6) burner design, (7) firebox enlargement or revamping, and (8) derating.
Of these options, LEA and OSC are the most frequently employed since
they are applicable to most existing boilers, are less costly than other
options, and represent no fuel penalty (in fact they can improve fuel
efficiency). FGR is the next most likely alternative particularly for
new boilers or those already equipped with FGR components. Options (4)
and (5) present measurable energy penalties. Option (6)--burner design
I is in reality a broad area in which LEA, OCS, and FGR principles are
usually employed within the burner. Options (7) and (8) are corollaries
with firebox modification usually applicable to new boilers only; derating
is a means of achieving the same effectless heat release per unit volume
at existing boilers. It should be pointed out that option (7) and (8) are
unattractive from an economic point of view.
Low excess air (LEA) combustion has been used successfully with all
fuels in a variety of furnaces. By reducing oxygen availability
at the burner(s), both thermal and fuel NO levels are reduced.
The degree of reduction is a function of furnace design and fuel
characteristics as well as excess air. Practical excess air levels
are limited by the formation of incomplete combustion products
| (CO, partially oxidized hydrocarbons, and carbon). Care must be taken
in reducing oxygen to avoid unacceptably low levels where boiler vibrations,
slagging, fireside corrosion, and in extreme cases explosions (CO) can
be encountered.
D-7
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I
Off-stoichiometric or staged combustion covers a wide- range of
techniques designed to limit the availability of oxygen during I
combustion. Two-stage combustion is a type of OSC which involves _
reducing air through the main burners to about 90 to 95 percent
of stoichiometric and adding the balance of the combustion air
through separate ports beyond (usually above) the highest burner
zone. OCS variations are (1) to fire lower sets of burners in |
a fuel rich mode and upper burners fuel lean and (2) to use
staggered configurations of fuel rich and fuel lean burners with 9
some burners acting only as air ports. On existing boilers, a
load reduction will result if the active fuel burners do not have
the capacity to carry the fuel required for full load. Most g
furnaces constructed recently (1970's) are or have been designed
with overfire air ports so that all fuel burners are active even *
with OCS in operation.
Flue gas recirculation (FGR) is accomplished by recycling part
(typically 15 to 30 percent) of the exhaust gases through the £
burners into the primary combustion zone. This method is generally _
restricted to low nitrogen fuels (gas and low-nitrogen fuel oils)
because FGR is most effective for thermal NO. FGR reduces the flame
zone temperature and the concentrations of oxygen needed for NO
production. Flue gas recirculation requires greater capital invest- g
ment than LEA and OCS methods because of the need for high temperature _
fans and ducts and large space requirements for the modifications.
However, for those boilers originally designed with FGR (for superheat
control), costs of retrofitting are reasonable.
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D-8
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Water or steam injection is used primarily on oil or gas-fired
systems where thermal NO predominates. Water or steam injected
into the combustion zone reduces flame temperatures and prevents
the formation of thermal NO. This technique has the greatest
operating costs of the combustion modification schemes with a
fuel and efficiency penalty of about 3 to 5 percent.
Preheat reduction is an NO reduction technique that has been used
0 only sparingly because of the energy penalty. It is applicable only
_ to utility steam generators and large industrial boilers which
* employ heaters to impart about 500°F incremental heat to combustion
air. With present boiler designs, reducing air preheat would cause
significant reductions in thermal efficiency and fuel penalties of
I up to 14 percent. This technique would be feasible if means other
than air preheat were developed to recover heat from 300 to 800°F gases.
* Firebox enlargement is a design change usually feasible only for new
boilers because of economic penalties. At any given heat input, increasing
the cooling rate in the furnace tends to lower peak temperatures and
J| reduce NO formation. Firebox enlargement like derating is most effective
where high heat release rates are employed. It is usually not feasible
for slagging furnaces.
Derating will reduce NO formation in almost all types of boilers
provided the same or lower excess air rates are maintained. Nonetheless,
g this method reduces heat or power output. It does not adversely affect
_ 'neat rate, in fact, thermal efficiency is normally improved by derating.
Burner designs of a wide variety have been offered to reduce NO formation.
For the most part, they are designed for Commercial /Industrial boilers
and employ LEA, OCS, or FGR principles. The aim is to strike a
D-9
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.
balance between minimum NO formation and acceptable combustion .
of carbon and hydrocarbons in the fuel.
The Japanese appear to lead the way with several commercial low- ft
NOW burner designs in operation and under development. Considerable
I
development work is underway in the U. S. by several companies, some p
under EPA contracts- To date, new optimized design burners appear to
have the capability of reducing NO concentrations 40 to 65 percent from
A
conventional burner designs on gas and oil fuels. No data were avail- ft
able for coal burners but preliminary studies indicate a substantial
reduction will be achieved by new coal burner designs. The new burners ft
are designed to attain good controlled mixing of fuel and air in a
pattern that keeps the flame temperature down and dissipates the heat *
quickly. Burners can be designed to control flame patterns thus ft
minimizing peak temperature reaction time between nitrogen and oxygen.
Other designs internally recirculate part of the combustion gases or have ft
fuel rich and fuel lean sections within a burner to reduce flame «
temperatures and oxygen availability. New burner designs, especially *
for large utility type boilers, have not been completely proven. Addi- I
tionally, the effectiveness of replacement burners for small domestic
heating units has not been fully determined. ft
Burner design modifications have the major advantages of not. »
requiring redesign of boilers or combustion chambers, not necessitating
load reduction, and possible applicability to many types of boilers. ft
The disadvantages are that some burners may have to be custom designed
for specific fuels, some designs (large burners) are difficult to ft
manufacture, and some may only be applicable to a limited number of m
boilers. However, improved burner design may well replace the external
combustion modifications now in use and achieve significantly lower NOX ft
emissions.
-- - D-10
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m For the most part, burner designs are considered applicable to
CRI boilers. Nonetheless, Babcock and Wilcox, one of the principal
I U. S. vendors of utility boilers, has indicated its intent to use a
dual register burner as the prime means of achieving NSPS
requirements for NO in new boilers.'
I Table D-5 summarizes NCL reductions that can be achieved with
utility boilers. The combination of low excess air and off-stoichiometric
I firing is seen to provide over 50 percent reductions in many instances.
Nonetheless, the degree of reduction is affected strongly by
| the base line NO level before combustion modifications were performed.
/\
For those cases where levels were initially low, reductions of only 20
to 30 percent were accomplished.
I The summary in Table D-6 lists several pertinent aspects of combustion
modification techniques applied to utility-size boilers.
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Costs of Combustion Modifications
Cost data have been developed principally for utility boilers with p
emphasis on coal firing. The least expensive technique, low excess air, g
represents a capital cost of less than $1.00 per installed kilowatt and has ~
no energy penalty. Cost of LEA are presented in Table D-7 for gas, oil, and
II ~
coal firing.-/
Costs of more extensive combustion modifications are presented in |
Figures D-7 and D-8. This information was developed in a 1973 study by _
Combustion Engineering Company and relates principally to tangentially
fired boilers.-' However, it is believed reasonable to apply the cost
figures to wall-fired boilers as well.
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D-12 I
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FLUE GAS TREATMENT (NOX)
Flue gas treatment (FGT) processes reduce NOX emissions from combustion
sources either by decomposing it to nitrogen and water or oxygen or by
removing it from the gas stream. Work on these systems in the United States
is being funded by EPA but the major work is being conducted in Japan both
for wet and dry FGT methods. FGT is not considered a reasonable control tech-
nology at this time. FGT is more advanced for clean gas streams (gas-fired
I boilers) than dirty gas streams (oil or coal-fired), but the decreased use of
natural gas for firing utility type boilers will reduce its potential applica-
I bility. For "dirty gas streams", (S02 and particulate), FGT are still in the
« developmental stage.
Dry systems are operated at about 700°F and generally employ flue gas
additives and catalysts. Wet systems employ a wider variety of chemicals
and are operated at 100 to 120°F, the same temperatures as scrubbers use
| to remove SOp-
m Dry Flue Gas Treatment
Dry processes are more developed than wet systems, particularly for "clean"
flue qas streams, that is, gases from the burning of natural qas or LPG. Large
clean gas streams in Japan have been in operation for over a year. However,
V dirty gas streams have been piloted successfully and several prototype
£ plants are now being constructed to treat gases from oil and coal-fired
boilers.
fl The dry systems which have been developed in Japan are catalytic reduction
(selective and non-selective), catalytic decomposition, electron, beam radiation,
I and absorption. Selective catalytic reduction has been the most widely used
m process, however, selective non-catalytic reduction of NOX with ammonia has
been demonstrated commercially in Japan reducing NO emissions by 70 percent.^/
A
The selective catalytic reduction (SCR) process normally uses ammonia and
a metal catalyst to reduce NOX selectively to nitrogen and oxygen. It is
D-13
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termed "selective" because it affects only NOX. SCR can reduce NOX «
concentrations in a clean gas stream by more than 90 percent. Particulates
cmd S02 tend to poison the catalysts. Compared to the wet process, the dry
process is simple, requires less space, presents no troublesome by-products,
and requires no reheating of tail gases. However, the dry process has yet
to prove itself on a dirty gas stream of commercial scale. If the dirty
gas is scrubbed to remove S02 before FGT, it will have to be reheated from
about 100°F to 700°F. Excess ammonia may combine with S0,/S02 and cause
a visible plume. Ammonium bisulfate is also corrosive to mild steel.
Large amounts of ammonia may be required which means an increased consumption
of natural ga« {to produce ammonia).- ti-ke -wet processes, "ammonia requirements m
are proportional to the quantity of NO removed. Thus, combustion modifications
A
are likely to be used to reduce NOX levels as much as possible before treatment I
in FGT systems.
Table 0-8 shows the selective catalyst reduction processes on commercial |
and pilot plants in operation or in the construction stage in Japan. Two f
large plants, being constructed by Sumitomo Chemical and Hitachi Shipbuilding
will treat "dirty gas" streams. I
A pilot plant on "dirty gas" (oil fired) has been operated by Sumitomo
for over 4,000 hours reportedly without serious problems. Electrostatic V
precipitators are used to remove dust and prevent contamination of the m
catalyst. More than 85 percent NO removal has been reported for this
pilot unit.
Alkaline scrubbing, molecular sieve absorption, and catalytic reduction
processes have been identified as possible NO control techniques. Most I
of these hold promise primarily for specialized applications where NO m
* I
concentrations are high or where local considerations require stringent
cont ol. '
A selective noble metal catalyst process using ammonia was explored
on a pilot scale through an,EPA contractor. The pilot plant using natural
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gas accumulated about 2,000 hours of testing and achieved NO reductions
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of 90 percent with essentially no catalyst degradation. Further tests have
been conducted using fuel oil and/or sulfur-containing flue gases. These
tests indicate that platinum is not satisfactory for flue gases containing
SO-. A final report is in preparation.
Another study for EPA has been conducted for the technical and economic
assessment of various catalytic processes for NOV control. Lab scale
X
m tests on simulated flue gas (no fly ash) investigated several operating vari-
ables and catalysts. The major emphasis was on selective NO -ammonia, non-
A
noble catalyst systems. These parametric studies indicated NO reductions of
60 to 95 percent at inlet concentrations of 250 to 1,000 ppm.
I Wet Flue Gas Treatment
g In Japan, the wet processes generally use an oxidation step and many
yield by-products, i.e., nitric acid, potassium nitrate, ammonium sulfate,
fl calcium nitrate, and gypsum, some of which have questionable marketability.
Some wet processes reduce NO to the elements and yield no by-products.
|X
Currently, the Japanese are investigating flue gas treatment processes aimed
_ at the elimination of both NO and SO ; this may be the major advantage of
^^1 A A
a wet system. Wet systems are better suited than dry systems for use on
dirty gas. Major disadvantages of wet systems are (1) expensive oxidizing
agents and/or energy inputs are needed in proportion to the quantity of NOX
I removed, (2) some processes create a wastewater problem, (3) demand for by-
_ products may be limited, and (4) many processes require S02 removal first to
reduce consumption of NO removal chemicals.
A
In 1975, there were 12 different wet processes being developed in Japan
at pilot plants and small commercial plants (100 to 25,000 cubic meters per
hour). The largest systems reportedly are treating 32,000 to 100,000 cubic
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D-15
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meters per hour of flue gas. No firm data are available as to NO removal
X
efficiencies but the range appears to be from 60 to 90 percent. Japanese
I
systems are directed at meeting stringent levels which are dictated by
ambient air quality standards. Table 9 lists plants in Japan using wet
process FGT systems.
GAS TURBINES
Gas turbines for stationary application range from 40 to 87,000 horse-
power (about 65 Mw) with larger units being designed. Uncontrolled NO emis-
sions are a function of turbine size and fuel type. Increasing the turbine
size increases the NOW concentrations primarily due to higher combustion
.
atures. Oil-fired turbines have higher NO concentrations than gas-
' I
fired units. Typical uncontrolled NO concentrations for No. 2 fuel oil
X
and gas-fired turbines are shown in Figure 9. Variances between turbines of
equal size are attributed to design differences and/or fuel characteristics.
Most combustion modifications for turbines using gas or distillate oils V
are based on methods to reduce peak temperatures since the majority of NO
I
emissions from these fuels are thermal. However, some gas turbines are
being designed to fire residual oils where the conversion of fuel nitrogen
to NO could be significant.
NSPS studies being conducted by EPA indicate that water or steam |
injection results in the least NOV emissions. Significant reductions in NO m
X X ^H
can be achieved using these methods but some turbine efficiency (1-3 per- *
cent) is lost when using water. Further, the water used in turbines tt
D-16
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has to be very clean (less than 5 ppm total solids) requiring water
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_
*
preparation facilities. Providing water or steam of acceptable
quality to turbines at remote locations may be a problem.
NO reduction is strongly influenced by the water or steam to fuel
A
I ratio. Equally important is the injection technique. With optimum
injection techniques and a water or steam to fuel ratio of 0.6 to 1.0,
I NO reductions of 50 to 75 percent have been achieved with oil firing
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f and 60 to 90 percent with gas firing (Figure D-5).-' Table 10 shows the
effectiveness of combustion modifications on gas turbines using the various
I techniques. Cost data for NSPS are being developed and will be available
in the near future.
| The proposed new source performance standard for gas turbines, i.e.,
M 55 ppm (gas) and 75 ppm (oil) at 15 percent 02, should be achievable by
adjustments in injection ratios for the size turbines discussed in this
fl section.
There are about 14 dry control techniques or combinations thereof
,| under development for gas turbines; however, none have been put into field
operation. The dry 'teUmlnina are* primary zone leaning; exhaust gas
recirculation; premixed, prevaporized, and well -stir red combustors; variable
flj geometry; and external combustors. Development work on dry control techniques
is being aggressively pursued by turbine manufacturers because it is felt
| that they will be more economical and attractive to users. Development
data indicate that dry control systems may consistently achieve concentrations
of 15 to 25 ppm NO at 15 percent oxygen. Gas turbines may also be amenable
A
fl to control by FGT systems. However, for a given heat input, FGT will be more
costly than for boilers since turbines use appreciably greater ratios of
I excess air.
D-17
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STATIONARY INTERNAL COMBUSTION ENGINES
Stationary internal combustion engines (ICE) sizes range f'^m a
fractional horsepower (lawn mower type) to large multi-cylinder unics cr
over 1,000 horsepower. Diesel engines are included in thij category.
NO emissions from these sources can range from 100 to 3,000 ppm
depending upon engine type, size, design, fuel, load, fuel to air
127
stoichiometry$ etc. In fact, NOV emissions from ICE probably are
x
subject to more variables than any other stationary combustion source. m
Control techniques for ICE are many and varied but only two are being
applied to production ICE and these only infrequently. They are exhaust
gas recirculation on gas/gasoline engines and turbo-charging with after-
cooling mainly on large diesel engines.
Other methods being studied to reduce NO emissions ere derating., water
I
injection, modified fuel injection timing, variable compression ratio, optimum
fuel/air ratio, retarding ignition, catalytic converters, and exhaust treatment.
Laboratory studies indicate that 35 to 60 percent reductions of NO concen-
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trations may be achieved; however, the effectiveness of many of the methods
has yet to be demonstrated in actual operation and little is known if these
methods are reasonable for existing sources. Proposed NSPS for stationary
internal combustion engines will probably be stated in grams NO per horse-
127
power per hour.
Preliminary annualized cost estimates on the exhaust gas recirculation
system are approximately $200 per ton of NO removed Cost estimates for
/\
other control techniques were not available for this report.
D-18
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INDUSTRIAL PROCESSES
I
Compared to other major sources, NO emissions from these processes
I are considered minor. They often represent highly concentrated emissions
(1,000 to 10,000 ppm NO ) in low volume streams.
I '
Nitric Acid
A typical uncontrolled nitric acid plant will release NOX in the
range of 1,000 to 3,000 ppm. Emissions above 3,000 ppm are considered
uneconomical and can be reduced by simple process improvements. All the
_ control technology systems to be discussed could be installed on many
existing pressurized plants with costs the controlling factor as to which
one to use for any particular plant.
Standards of performance for new nitric acid plants were promulgated
I in August 1971 allowing 3.0 pounds NO per ton of acid produced. The NSPS
X
_ was based on catalytic decomposition systems as other control schemes were
not developed. Today, other systems are available.
g Catalytic Decomposition. Catalytic decomposition of NOX to the
_ elements nitrogen and oxygen is still the most prelevant control method
used in the United States. All catalytic reduction processes use some
type of fuel-reducing agent with natural gas and hydrogen being the most
common. Energy generated from the exothermic reaction is usually
| recovered and used in the acid process. The catalytic reduction systems
are basically designed for streams containing about 3,000 ppm. At lower
concentrations, the processes may not be economically attractive because of
lower energy recovery. Operating costs for 100 and 1,000 TPD plants are
estimated respectively to be $0.97 to $0.70 per ton of acid; capital costs
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are estimated to be $207,^00 and $830,000. Operating costs are directly
related to the cost of fuel.
Scrubbing. Caustic scrubbing removes NOX but few commercial _
installations use this process because of problems in disposing of the
spent nitrate solutions which can create a serious water pollution
problem. Removal of 90 percent of NOV emissions have been reported
/\
by this process. |
The Masar process uses a solution of urea to scrub NO ; the nitrated
I
solution finds use as a nitrogen fertilizer. Two commercial installations
are using the process. Originally, the plants were reported operating at
one commercial installation, 99 percent plus NO removal was achieved
J\
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exit levels of about 200 ppm NO . Further tests conducted by an EPA
J\
contractor and an independent test laboratory showed NO concentrations I
in the range of 55 to 60 ppm from uncontrolled levels of about 1,800 ppm.
The operating cost of this process is reported to be about 30 cents per ton |
of acid produced (1974 cost data). Ability to use the by-product is a major
advantage.
Molecular Sieves. Two commercial plants use molecular sieves for I
NOX control. They reportedly work well in acid plants where the tail
gas is bone dry. The sieve converts NO to N0£ which is absorbed in the
sieve. Desorption produces an enriched N02 which is reused to produce
more nitric acid. The increase in nitric acid production is reportedly
about 2 to 3 percent]-/ |
A vendor has reported that during three-day performance tests on
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and outlet concentrations ranged from less than one ppm to 7 ppm. Since m
then, the typical daily average outlet concentration has been less than
50 ppm with instantaneous concentrations ranging from 0 to 104 ppm NO . fl
D-20 I
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A second installation is reporting outlet levels of about 180 ppm NOX>
| EPA is funding monthly testing of these installations for two years to
M confirm the vendor's guarantee. At one installation a plant malfunction
damaged the sieve such that it probably will not meet the guarantee but
may still meet NSPS./
Operating costs for plants of 100 and 1,000 TPD are estimated to be
| $1.75 and $1.35 per ton, respectively; the capital costs are about $500,000
- and $4,100,000.^
Extended Absorption. The extended absorption process has a second
fl absorption tower to receive tail gases from the first absorber and continue
the absorption process. Unconfirmed reports indicate that emissions from
I this process will meet NSPS. For 100 and 1,000 TPD plants, operating costs
M are estimated to be $1.53 and $0.61 per ton, respectively and capital costs
about $1,200,000 and $6,100,000./
I
At small nitric acid plants, batch processes, storage facilities, or
| other specialty processes NO may be controlled by incineration. The
emissions are burned by adding excess fuel; the NOV acting as an oxidant
is reduced to nitrogen. NO reductions of 75 to 90 percent have been
/\
estimated but not confirmed in plant operation. Fuel requirements are
13 14/
probably the main disadvantage of this system.!
I Other Chemical Processes
_ Other chemical processes which are sources of NO include the production
I
of ammonium nitrate, adipic acid, terephtholic acid, nitrobenzene toluene
dissolyanate, commercial and military explosives, fertilizers, and other
nitro-nitrate compounds.
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Emissions usually occu. i,« any of these processes at the step in
which the nitric acid and other compound(s) are mixed or .^acted.
Emissions from ammoniated processes are usually negligible because the
reactivity of ammonia is much higher than nitric acid and because a
slight excess of ammonia is usually required for product formation
(NH.NOo). In most other processes, it is economically attractive to
capture all or most of the NO emissions for reuse because nitric acid
represents one of the prime material costs.
In these specialty processes, caustic scrubbing or NO incineration I
A
in a reducing atmosphere may be used. Scrubbing with urea solutions may «
also be suitable. Control technology is sometimes difficult because the
operations are intermittent in character. The specialty processes are
relatively small but may cause local problems. Costs may vary widely.
NOV emissions from industrial and military explosives (ammonium . '
A
nitrate, TNT, nitroglycerin, others) are reported to range from 2.5 to 12 m
pounds NO per ton of product. Previous control techniques discussed can
be applied to these processes.
NO can fce released Tram fertilizer processes which use nitric acid
for acidulation with phosphate rock. Only a few manufacturers produce
nitric phosphates making this an infrequent problem. The reaction of the H
nitric acid with the carbon or organic material in the phosphate rock
produces the NO emissions. The use of calcined rock will prevent the
production of NO . For the acidulation step in fertilizer production
I
scrubbers are used to remove particulates and fluorides; however, the scrubbers
are not effective in controlling NOX emissions. No emissions data are
available but brown fumes which appear to be NOo are reported to occur.
One company reported that urea (discussed previously) added to the
D-22
-------
I
acidulation mixture reduced fuming and eliminated the brown plume.
I Ammonium nitrate fertilizer (ammoniating processes) was discussed
I
I
147
previously.
NO is evolved from metals pickling, bright-dipping copper,
A
absorption, catalytic reduction, and NO incineration.
A
I and the manufacture of tungsten filaments. Emissions reportedly
can be reduced through the proper use of chemicals as well as charcoal
I
* PETROLEUM AND NATURAL GAS PRODUCTION
B Oil and gas production, pipeline transportation, gas plant operation,
I and petroleum refining may be significant sources of NO emissions. NO
A A
emissions result from the combustion of fuel in boilers, heaters, CO
I boilers, internal combustion engines, and gas turbines. NO control
technology for boilers and heaters, I.C. engines, and turbines has been
discussed previously.
METALLURGICAL PROCESSES
NO from steel and metallurgical processes has to date drawn less
X
flj attention from pollution control agencies than other pollutant emissions.
NO emissions can be traced primarily to the combustion of fuels. At steel
|X
plants, NO is generated at the blast furnaces (stove), open hearth furnace;
A
_ coke plants, sinter plants, cupola furnaces, basic oxygen furnaces (EOF),
and soaking pit furnaces. The phasing out of open hearth furnaces and the
switch to electric steel production will reduce these emissions. This
would transfer some NOX generation to the power plant where effective
| NO control probably can be achieved.
x
D-23
-------
Most of the NO produced in metallurgical furnaces is believed to b°
A
I
I
due to nitrogen fixation but fuel nitrogen may be important also. Little
attention has yet been directed to the control of NO at steel plants but I
combustion modifications should be an effective technique.
CEMENT, LIMESTONE, CERAMIC, AND GLASS PRODUCTION
Cement, limestone, and ceramic kilns and glass manufacturing are
other sources of NO that could be of significance. Little information jj
on NOX control or emissions is available. The majority of NO emissions _
comes from the large quantity of fuels burned at temperatures (1700° -
2900° F) usually needed for the operation of the processes. Combustion
modifications to reduce peak temperatures would be expected to reduce ND
A
emissions. However, since high temperatures are required on some of the |
processes switching to gas, modification of firing design, low excess air,
incineration, or electric heating may be effective techniques.
I
OTHER STATIONARY SOURCES
Other sources of NO emissions are: refractory fiber material furnaces,
A
perlite production furnaces, baking and drying ovens, spray driers, and
welding machines (electric arc and oxyacetylene). Most of these processes
create high temperatures conductive to the formation of NO. However, I
I
(7-40 ppm). Combustion modifications (mainly low excess air) or other
treatment methods mentioned previously may be effective in reducing NOX
I
D-24
limited ava.lable data indicate that most of these are low NOY emitters
-------
emissions.
I
I
SUMMARY OF NO.. CONTROLS
Boilers and Heaters
I
I
I
1. Combustion modification techniques:
are available for new utility size boilers and to a lesser degree
for retrofit of existing utility boilers,
are more advanced for gas and oil firing than for coal firing,
provide reductions of 30 to 60 percent in NOX emissions from
utility boilers, and
' are more limited for CRI than for utility boilers with burner
adjustments and new burner designs offering more promise to
CRI operators than techniques which have been effective with
g utility boilers.
2. Burner adjustment and maintenance programs to improve combustion
at existing CRI boilers may not reduce NOX emissions and could
increase them.
3. Flue gas treatment -for HO t
rt
I is not considered a reasonable control technology for NO .
/\
won't be available for oil and coal-fired boilers in the near
future, and it is uncertain whether the processes can be
perfected for use in the presence of S02,
probably will reduce NOV levels by 80 or 90 percent,
A
may be extremely costly where inlet NO levels are
greater than 250 ppm,
will have direct (wet processes) or indirect (dry processes) energy
penalties,
D-25
-------
I
will have to be further investigated to determine their
compatibility with flue gas desulfurization systems, I
may create ozone, ammonium-sulfur compounds, or other
undesirable compounds in stack gases, and
may generate liquid wastes containing nitrate or nitrite
pollutants.
Gas Turbines I
4. Water and steam injection can provide 50 to 75 percent reductions in
NO from oil fired turbines and 60 to 90 percent for gas-fired turbines
A
but only at fuel penalties of 1 to 3 percent.
5. Proposed new source performance standards can be achieved without water
or steam injection.
Internal Combustion Engines
6. Limited study indicates that 30 to 60 percent NO reductions can be
/\
realized at internal combustion engines.
Nitric Acid Plants
7. Several techniques are available to achieve the new source performance I
standard level.
Other Sources
8. Many of the NOX control schemes used for nitric acid plants are applicable
to other industrial sources, particularly those sources which are operated
under high pressures. I
9. Flue gas treatment systems which are being developed for combustion
sources should be applicable to almost all NOX sources.
I
I
D-26
-------
Glossary
m Clean Gas Stream - Exhaust gases containing only negligible fractions
of S02 and participate, as from burning natural gas or LPG.
Combustion Modification - An alteration of the normal burner/firebox
configuration or operation employed for the purpose of reducing the
formation of nitric oxide.
Cyclone Furnace - A type of wet bottom furnace in which combustion takes
place in cylindrical cyclone-separator-like burners. Ash becomes molten
in the cyclone burners and flows to the bottom of the boiler where it is
periodically tapped.
Derating - Reducing the heat input and power or steam output of a boiler
I below the level for which it was designed.
M Dirty Gas Stream - Exhaust gases containing significant SCk and/or
particulate, as from an oil or coal-fired combustion device.
I Dry-Bottom Boiler - The common type of pulverized coal furnace employed
at most new power plants. Temperatures in the firebox are maintained
I at a sufficiently low level that melting or slagging of the ash does not
m occur. Bottom ash is removed from the firebox in the dry state.
Excess Air - Any increment of air greater than the stoichiometric fuel
requirement. With gas, oil, and coal-fired boilers, some excess air is
used to assure optimum combustion.
I Flue Gas Recirculation - A combustion modification in which a portion of
HJ the boiler exhaust gases are recirculated to the burners to inhibit NO
formation. (FGR)
8 Flue Gas Treatment - A process which treats tail gases chemically to remove
NOX before release to the atmosphere. (FGT)
D-27
I
-------
I
Fuel Nitrogen - Nitrogen that is chemically bound in the fuel. _
Heat Release Rate - The rate of combustion oer unit volume of firebox, ~
typically in terms of Btu's per hour per cubic foot. I
Low Excess Air - A combustion modification in which NO formation is
inhibited by reducing the excess air to less than normal ratios.
Off-Stoichiometric Combustion - A combustion modification in which NO
25 x 10 Btu per ton provides a heat input of 250 x 106 Btu per hour.
_
*
formation is inhibited by delaying the introduction of part of the
combustion air, also termed staged combustion. I
Stoichiometric Air - That quantity of air which supplies only enough
oxygen to react with the combustible portion of the fuel. |
Two-Stage Combustion - A type of off -Stoichiometric combustion. _
Wet-Bottom or Slagging Furnace - A type of furnace often used with
older utility boilers in which the ash becomes molten and is tapped I
from the bottom of the furnace in the molten state.
Field-Erected Boiler - All components of a boiler are delivered to I
the site and assembled in the field. Mainly pertains to utility
and large Industrial toilers.
Packaged Boilers - These are usually CRI boilers that are smaller I
and more economically assembled at the plant, shipped to the boiler
site, as one integral unit ready for operation after connection to I
water, steam, and power.
Heat Input - The product of the fuel feed rate and the higher heating
value, e.g., 10 tons per hour of coal with a higher heating value of
I
I
D-28 -
-------
Heat Output - The quantity of heat contained in the steam and/or hot
water generated in the boiler, usually the product of the steam rate
and the enthalpy of the steam.
I Boiler Efficiency - Heat Output x 100.
m Heat Input
I The overall figure reflects combustion efficiency, radiation and convection
losses from the boiler and heat lost in exhaust gases.
| Gross or Higher Heating Value - The heat generated by complete combustion
of a fuel, always referenced to baseline temperature, e.g., 60°F. Heat
available at the reference temperature is included in the higher heating
value even if it is not practically available, i.e., heat of condensing
water vapor.
| Net or Lower Heating Value - The heat that is practically available from
_ a fuel to generate steam or otherwise raise the temperature of the media
* receiving energy. The net heating value assumes complete combustion.
It differs from the higher heating value in that heat of vaporizing
water of combustion is considered an recoverable loss.
I
I
I
I
I
I
I
M D-29
-------
Rank
Table D-l. Analyses of Typical U. S. Coals an^ ' ignite*
Anthracite Bituminous Subbituminous Lignite
Analysis:
Moisture, %
Volatile
matter, %
Fixed carbon, %
Ash, %
Heating value,
103 Btu/lb
Sulfur, %
Nitrogen, %
2-5
5-12
70-90
8-20
12-14.5
<1
0.5-1
2-15
18-40
40-75
3-25
10-14
0.5-5
1-2
15-30
30-40
35-45
3-25
8-10.5
1.5-3
1-1.5
25-45
25-30
20-30
5-30
5.5-8
0.5-2.5
0.5-1.5
*Research Triangle Institute, "Effects of Transient Operating Conditions I
on Steam-Electric Generator Emissions", EPA-600/2-75-022, August 1975.
D-30
-------
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
Table U-2. Analyses of
Distillate Oil
Grade No. 1 No. 2
Analysis
Gravity, °API 35-42 30-35
Viscosity,
Saybolt sec. - 33-37
Heating value,
0
10"3 Btu/gal 134-138 136-144
Sulfur, % 0.1-0.3 0.2-0.8
Hydrogen, % 12-14 12-14
Carbon, % 86-88 86-88
Nitrogen, % <0.01 <0.01
Ash, % 0.01 0.01
*Research Triangle Institute, "Effects
Conditions on Steam-Electric Generator
2-75-022, August 1975.
n_-?i
Typical Fuel Oil*
Residual Oil
No. 4 No. 5 No. 6
23-25 18-22 12-16
45-125 150-700 900-9000
143-146 145-149 149-152
1-3 1-3 1-5
11-12 10-12 10-12
86-88 86-88 85-88
0.1-0.5 0.1-0.5 0.1-0.5
0.01-0.1 0.01-0.1 0.01-0.3
of Transient Operating
Emissions", EPA-600/
-------
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D-32
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Table D-4. Typical Baseline Emission Levels
From Commercial and Residential Heating7-/
Emission Concentration, ppm 3%
NOX as
Unit Fuel N°2 C0 HC
Residential Gas 70 15 3
Residential No. 2 Oil 115 65 13
Commercial Gas 80 20 9
Commercial No. 2 Oil 100 4 3
Commercial No. 4 Oil 390 7 3
Commercial LSR* 260 3 5
Commercial No. 5 Oil 290 16 4
Commercial No. 6 Oil 415 10 5
*Low Sulfur Residual Oil
-------
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I Table D-7. Estimated Investment Costs for Retrofitting
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Low Excess Air Firing to Existing Utility Boilers -
Unit Size Investment Costs, $/KVJ
MW Gas & Oil Coal
I 1,000 0.12 0.48
. 750 0.16 0.51
' 500 0.21 0.55
250 0.33 0.64
120 0.53 0.73
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EFFECTIVENESS OF
*
Combustion
Modification
Interim
Primary Zone
Leaning
Exhaust Gas
Recirculation
Water/Steam
Injection
Advanced Combustors
Premi xed ,
prevapon'^ed,
well stirred,
variable geometry,
external combustors
Table D-10.
COMBUSTION MODIFICATION ON GAS lu^BINES---1--7
Emissions
NOX CO HC Smoke"
10 - 30% Small Small Reduction
reduction reduction reduction
v30% Negligible Negligible Negligible
reduction effect effect effect
50 - 75% Some Small Small
reduction reduction rpduction inrroaco
(oil) or in- or small possible
60 - 90% crease increase
reduction
(gas)
70 ppm 40 ppm 5 ppm Invisible
achievabl-e achievable achievable
*Prototype unit; catalytic combustor may be able to achieve 5.0 ppm NO .
/\
*
D-40
1
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Figure D-l.
Tangentially Fired Boiler
rr-ir~T J-T-rf *-.T~ »' . -
' :: . . ' " ,, "
- -hiTT T~l n »
DRAWING FURNISHED THROUGH THE COURTESY OF
COMBUSTION ENGINLI:KING. INC.
D-41
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WtMOWX
KCONOAMY AIM
DAwrlKS
SICONOAMV AIM-
DAMFER DMIVC
UNIT
Kf
rj)^
w
Nomcs
S>Ot IGNITOM
MOBILE
SJCONOABT Am
COAI Nomcs
a-
OH GUN
Tangential firing system incorporating overfire air for
NO, control coo/ firmg
Figure la.
Tangential flame pattern viewed from top of furnace
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tl
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D-42
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Figure D-2.
Front Wall Fired Boiler
EL. l724'-f.'
EL. ITOS'-S"
\...
60'tO SPRM CONTR'. HCAOUi
T - v
---" ----.. ~" -* .',,' , C-'jril-M.rATER OUHET
^ ^v^~^f*:^^--/-f'i yy ~i """"1 !
"~i ^-i-^r?.:;-^4;.;!j./\~:-4;-ry7.e:-Jii|
TEB
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, f^QWlQIOM V'Ml^j. ' * '' I'..-1-
\ ?/.,..,;-*>
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i
| I] EL Ii87;0'
PUljV tRIZIjRS | |1
i PMD-1584-8
DRAWING FURNISHED THROUGH THE COURTESY OF
THE FOSTER WHEELER CORPORATION
'- °~43 ; '
-------
Figure D-3.
Front Wall Fired Boiler
m'-o"
DRAWING FURNISHED THROUGH THE COURTESY OF
THE BABCOCK AND WILCOX COMl'Ai.T
D-44
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F-igure D-4.
Horizontally Opposed Fired Boiler
=f
db=
r ' 1 ' f
'=?,. |UX-3"|jrlT| K ArTEM^A1!
' ill ...,,^-lJ..., , llt 1 s.1{ .1 ..__._JJ
II
"/PfRATOR
T
2ZJ'-O"
-m^.rjiJii-:, .\! | ; jj '
= "1WIST f"1
| - . -. - *--=-_ SpiXeyf, FH^rrfJ "~--s---- i's <
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-; -; jH*' 4-^.^^r^HrrxV%f*~~^'~»'{fH'
piiiilifflifii
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;,.: ,<.! .'-.»'-'' HI LiJ w-x} i r' A 1
- ;;, -;."-v.-H'iLp/RMr^TrR (^ |- ,\-'
lini^^'^^ir'^n
m-f i'T?.fl^-:-v>,--;ft
wr-t' .---.'-' : ' '''' fl
^'-bf^TTTTr^'LU
-"!-. A ^ iiri1 x' / ; = --
..i4:^4J::!! _.__.v.J"-
DRAWING FURNISHED THROUGH THE COURTESY OF
THE BABCOCK AND WILCOX COMPANY
D-45
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|:
1:
TANGENTIAL SECONDARY
AIR
PRIMARY AIR
COAL
PRIMARY FURNACE
-HOT GASES
CYCLONE SLAG-
TAP HOLE
^
PRIMARY FURNACE
SLAG-TAP HOLE
Figure D-5. Srlicmat i<- draw in}; (if cyclone furn.'H'C'. Usually si-vora
ryclones are used on a sinj;!1-" primary furnace.
D-46
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Figure D-6.
Cyclone Fired Boiler
£3~f- ... }.
SECONDASV SUPERHEATER , , ,
OUIUT HEADER
- ECONOMIZER
ECONOMIZER
i INIET HEADER
ECONOMIZER
OUTLET HEADER
DRAWING FURNISHED THROUGH THE COURTESY
OF THE BABCOCK i WILCOX COMPANY
D-47
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<*
106Btu
10'Btu
$
KM
_ KW
200
300
400
500
600
700
Windbox Gas
Recirculation
Overfire A1r
Combined Overfire
Air and Wind-
ox Gas Re-
circulation
as Recircula-
tion thru Mills
Windbox Water
Injection
800
Figure D-7.
UNIT SIZE
(MW)
I
1973 installed equipment costs of NOx control methods for new
tangentially, coal-fired units (included in initial design).*
*Based on: 5400 hrs/yr at rated MW and net plant heat rate
of 10" Btu/KWhr (Reference 4-3).
*Aerotherm Division, Acurex Corporation, "NOX Combustion Control
Methods and Costs for Stationary SourcesSummary Study", EPA-
600/2-75-046, September 1975.
D-48
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106Btu
11
10
9
8
7
6
5
4
3
2
1
0
13
12
11
10
9
8
7
10'Btu 5
4
3
2
1
0
6.0
Windbox Gas
Recirculation
Overfire A1r
Combined Overfire
Air and Windbox
Gas Recirculation
Gas Recirculation
Thru Mills
Water Injection
Including Fan &
Duct Changes
Water Injection Without
Fan & Duct Changes
I
Unit Size
(MW)
Figure D_g. 1973 installed equipment costs of NOX control methods for existing
tangentially, coal-fired units (heating surface changes not included).*
PG&E Portrero #3 *Based on 5400 hrs/yr at rated MW and net plant heat rate of 10" Btu/fcwhr
PG4E Pittsburg #7 (Reference 4-2).
*Aerotherm Division, Acurex Corporation, "NOX Combustion Control
Methods and Costs for Stationary SourcesSummary Study", EPA-
600/2=75-046, September 1975.
-------
F
280
240
200
160
120
X
i 80
SJMPIC CYCIL^
NATURAL GAS
J I 0
720
600
480
3GO
240
120
o
x.
-a
-p
OJ
o
ro
0 10 20 30 40 50 60 70 80
BASF. LOAD, HW
Figure D-9. Typical Gas Turbine Base Load NOX Emissions'
D-50
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fD
O
I
(D
O
73 (0
n> =j
CL ft)
c «/>
O in
tn
ft)
n -j
o
3 -S
r+ co
- c*-
o n>
^s -
n>
o
n-
PERCENT NOX REDUCTION
ro
o
o
en
O
Co
o
rr I
»^
o
o
o
D-51
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References
1. Shaw, J. T., and A. T. Thomas, NTIS No. PB 229-102/AS, "Oxides
of Nitrogen in Relation to Combustion of Coal", 7th International
Conference on Coal Science, Prague, Czechoslovakia, June 1968.
I
I
2. Martin, G. B., and E. E. Berkau, "An Investigation of the Conversion _
of Various Fuel Nitrogen Compounds to Nitrogen Oxides in Oil Combustion",
AIChE/Symposium Series, Air Pollution and Its Controls Volume 68 (1972).
3. Turner, D. W., R. L. Andrews, and C. W. Siegmund, "Influence of
Combustion Modification and Fuel Nitrogen Content on Nitrogen Oxides
Emissions from Fuel Oil Combustion", Presented at the 64th Annual
AIChE Meeting, San Francisco, California, November 1971.
4. Cato, G. A., et al., "Field Testing: Application of Combustion
Modifications to Control Pollutant Emissions from Industrial
Boilers - Phase I", EPA-650-2-74-078a, October 1974. 1
5. Hobelt, W. W. and B. M. Howell, "Control of NOX Formation in
Tangentially Coal-Fired Steam Generators", Presented at Electric .
Power Research Institute NOX Control Technology Seminar, San Francisco, |
California, February 1976.
6. Brackett, C. E., and J. A. Borsen, "The Dual Register Pulverized Coal . t £
Burner - An N0>, Control Device", Presented at Electric Power Research
Institute NO Control Technology Seminar, San Francisco, California,
February 1976.
7. Bowen, Lachapelle, and Stern, "Overview of EPA's NOX Control Technology
from Stationary Sources", Control Systems Laboratory, U. S. Environmental
Protection Agency, Research Triangle Park, North Carolina, December 4, ' p
1974.
8. Blakeslee, C, £., and A. P. Selker, "Program for Reduction of NOX
from Tangential Coal-Fired Boilers, Phase I", EPA-650/2-73-005,
August 1973.
9. Lyon R. K. and J. P. Longwell, "Selective, Non-Catalytic Reduction of .
NOX with Ammonia", Exxon Research and Engineering, Presented at the
Electric Power Research Institute NOX Control Technology Seminar,
San Francisco, California, February 1976. I
10. Jumpei, Ando and Heiichiro Tokata, "NOX Abatement Technology in Japan
for Stationary Sources", Faculty of Science and Engineering, Chuo |
University, Kasuga, Bunkyo-Ku, Tokyo, Japan, March 1975.
11. Draft of Standards Support and Environmental Impact Statement for
Standards of PerformanceStationary Gas Turbines, U. S. Environmental
Protection Agency, OAQPS, MD-13, Research Triangle Park, North
Carolina 27711, March 1975.
D-52
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12. Seiffert, Randy D. and Frank Collins, "Drafts of Standards
Support Document for an Investigation of the Best Systems of
Emission Reduction for Stationary Internal Combustion Engines",
U. S. Environmental Protection Agency, OAQPS, MD-13, Research
Triangle Park, North Carolina 27711, September 1975.
13. Battelle Columbus Laboratories, "Molecular Sieve NOX Control
Process in Nitric Acid Plants", EPA-600/2-76-015, January 1976.
14. Control Techniques for Nitrogen Oxides from Stationary Sources,
NAPCA Publication No. AP-67, March 1970.
15. Roessler, W. U. et al., "Assessment of the Applicability of
Automotive Emission Control Technology for Stationary Engines",
EPA-650.2-74-051, July 1974.
D-53
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I
Addendum References I
1. Bartok, W. et al., "Systems Study of Nitrogen Oxide Control Methods _
for Stationary Sources, Volume II", Prepared for the National Air
Pollution Control Administration, NTIS Report No. PB 192-789,
Esso, 1969.
2. Zeldovitch, Y. B., P. Y. Sadonikov, and D. A. Frank-Kamenetskii,
"Oxidation of Nitrogen in Combustion", Academy of Sciences of
USSR, Institute of Chemical Physics, Moscow-Leningrad, 1947.
3. Heap, M. P., T, M. Lowes, R. Walmsley, and H. Bartelds, "Burner
Design Principles for Minimum NOX Emissions", EPA Coal Combustion
Seminar, Research Triangle Park, North Carolina, June 1973.
4. Pershing, D. W., G. B. Martin, and E. E. Berkau, "Influence of
Design Variables on the Production of Thermal and Fuel NO from
Residual Oil and Coal Combustion", Presented at the 66th Annual I
AIChE Meeting, Philadelphia, Pennsylvania, November 1973.
5. Hall, R. E., J. H. Wasser, and E. E. Berkau, "A Study of Air |
Pollutant Emissions from Residential Heating Systems", EPA-
650/2-74-003, January 1974. -
6. Dickerson, R. A., and A. S. Okuda, "Design of an Optimum Distillate
Oil Burner for Control of Pollutant Emissions", EPA-650/2-74-047,
June 1974.
7. Shoffstall, D, R. and D, H, Larson, "Aerodynamic Control of Nitrogen
Oxides and Other Pollutants from Fossil Fuel Combustion", EPA-650/
2-73-033a, October 1973.
I
8. Browa, TL A.~o -ft. 1L 'Basxm, araSH. J. Schreiber, "Systems Analysis _
Requirenffittts for Nitrogen Oxide Control of Stationary Sources",
EPA-650/2-74-091. September 1974.
9. McGowin, C. R., "Stationary Internal Combustion Engines in the
United States", EPA-R2-73-210, April 1973. "
10. Bartok, W. et al., "Systematic Field Study of NOX Emissions Control
Methods for Utility Boilers", Esso Research and Engineering Company, |
Linden, New Jersey. Report GRU.4GNOS.71, Prepared for the Office of
Air Programs, Environmental Protection Agency, Research Triangle Park, _
North Carolina, December 31, 1971.
11. Jain, L. K., E. L. Calvin, and R. L. Looper, "State of the Art for
Controlling NOX Emissions, Part I: Utility Boil
Catalytic, Inc., EPA-R2-72-072a, September 1972.
Controlling NOX Emissions, Part I: Utility Boilers", Final Report, M
12. Berkau, E. E., and D. G. Lachapelle, "Status of EPA's Combustion
Program for Control of Nitrogen Oxide Emissions from Stationary |
Sources", Presented at the Southeast APCA Meeting, Raleigh, North
Carolina, September 19, 1972. _
D-54 *
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1
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13. Crawford, A. R. et al., "Field Testing: Application of Combustion
Modification to Control of NOX Emissions from Utility Boilers",
EPA-650/2-74-066, June 1974.
14. Levy, A. et al., "A Field Investigation of Emissions from Fuel
Oil Combustion for Space Heating", Conducted by Battelle Columbus
Laboratories for the American Petroleum Institute, API Publication
4099, November 1, 1971.
15. Barrett, R. E. et al., "Field Investigation of Emissions from
Combustion Equipment for Space Heating", EPA-R2-73-084a, June 1973.
16. Crits, G. J., "Economic Factors in Water Treatment", Industrial
Water Eng., 8(8), 22 (1971).
17. Tyco Laboratory Final Report, "Development of the Catalytic
Chamber Process", EPA-R2-72-038, September 1972.
18. Esso Research Report, "Development of the Aqueous Processes for
Removing NOX from Flue Gases", EPA-R2-72-051, September 1972 and
Addendum, EPA-R2-73-051a, June 1973.
D-55
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SECTION E
MOTOR VEHICLES
I
1. NO Emissions
A
the major NO emission categories of highway vehicles.* Within each
X
Automobiles, light-duty trucks, and heavy-duty trucks comprise
I
I
of these categories different engine types and fuel variations result
in significantly different emission characteristics. In addition,
different exhaust emission standards and compliance dates apply to
different vehicles. Because of these variations, highway vehicle
emissions change with time and must be calculated for a specific time
oeriod, normally one calendar year. The major reasons for this time-
M dependence are (1) the gradual replacement of vehicles without emission
control equipment by vehicles with control equipment, and (2) the gradual
I deterioration of vehicles with control equipment as they accumulate
age and mileage. Detailed information is contained within AP-42 which
£ will allow the reader to consider these factors in calculating motor
_ vehicle emissions.
Other factors that influence overall motor vehicle emissions include
the vehicle mix ratio (LDV, LOT, HDVG & HDVD) , vehicle age distribution,
average vehicle speed, ambient temperature and hot vs. cold operation.
J After considering these factors, as well as expected VMT growth, a
composite emission factor can be developed to estimate overall motor
vehicle emissions from the entire mobile emission class.
Figure E-l presents a national composite motor vehicle (LDV, LOT,
HDVG and HDVD) emission rate projected through 1995, based on the current
Federal Motor Vehicle Control Program** (FMVCP). Incorporated into this
*Automobiles = Light Duty Vehicles = LDV
Light Duty Trucks = LOT
Heavy Duty Trucks = Heavy Duty Vehicles (Gasoline) = HDVG
Heavy Duty Vehicles (Diesel) = HDVD
**ESECA (1974)
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composite motor vehicle emissions projection is a 3% annual VMT growth
rate which is typical of ma*"- urban areas. As illustrated, a 14% reduction
in NO emissions from motor vehicles is expected on a nacunal basis during
/\ ^^"
the 1975-1980 time period. Congress is reviewing the Clean Air Act and
if changes are made to the present motor vehicle emission standards3 associ-
ated changes will be observed in the NO emissions projections.
X I
The development of accurate VMT growth projections to be incor-
porated into the composite emission rate projections is paramount. I
Growth factors over a 10-year or longer period are very significant
and are one of the principal factors influencing the overall effective-
ness of motor vehicle control program. Figure E-2 illustrates various M
growth factors associated with different annual growth rates (0.5% to 4.0%
per year). As shown by Figure E-2, automotive VMT growth factors are
extremely sensitive to the change in growth rates. Therefore, it is
desirable to accurately determine the expected areawide VMT growth for
the area under study and, if necessary, to correct Figure E-l FMVCP
projections from a 3% annual VMT growth to the applicable growth rate.
The correction factor can be developed by dividing the applicable growth V
factor by the 3% growth factor.
Another important factor which influences the composite emission
projection is the vehicle age distribution for an area. Similar to
VMT growth information, locally specific information on motor vehicle
age distribution should be obtained if needed. Figure E-3 illustrates
how vehicle use varies with vehicle age and presents (1) a national
age distribution and (2) an age distribution for Detroit. As ill us-
trated in Figure E-3, there is a much higher percentage of newer in-use m
motor vehicles (less than 3 years old) in Detroit than are in use on
a national basis. Because auto use patterns are associated with the
auto replacement rate, the total effect of an auto emission standard
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is not fully achieved until 5 to 10 years after a standard is
fl implemented. In areas such as Detroit, the high motor vehicle
g replacement rate will tend to result in a more rapid reduction in
composite NOX emissions than predicted nationally. However, in areas
I with lower replacement rates, NO reductions may be achieved later
x
than predicted nationally. On a national basis less than 15% of the
| in-use vehicles are of the current model year and less than 50 percent
_ were manufactured in the last five years. In addition to the slow auto
replacement rate, motor vehicle emissions typically increase as an
automobile gets older (2% per year for pre-1975 vehicles for first
10 years) which also tends to reduce the immediate impact of motor
| vehicle emission standards.
Another important factor influencing overall composite NO emission
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factors is the motor vehicle mix ratio. More specifically, this factor
represents the ratio of LDV:LDT:HDVG:HDVD . The mix ratio is important
because (1) it represents the weighting factors for the different motor
vehicle emission categories which have significantly different NO emis-
x
sion rates and (2) it can vary greatly from area to area.
Figure E-4 illustrates the projected composite NO emission factors
/\
j for the four major motor vehicle classes based on the FMVCP considering
standard conditions and considering emission control equipment deteriora-
tion. As illustrated, on a per vehicle basis, the NO emissions from
HDVG or HDVD are significantly greater than LDV emissions. However, as
illustrated in Figure E-5, the much greater total VMT for LDV results
I in LDV's having the major impact on NO emissions in urban areas.
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2. Composite Emission Fac ors
The development of composite emission factors is discussed in
greater detail in AP-42 but the procedure is based on weighted
averaging of emission factors for in-use vehicles for the year of
interest.
Listed below in the basic summation equation which is used to
develop composite emission factors:
c m v z
enpstw ~ _ cipn min vips zipt riptw
i=n-12
nominally 75°F; for speed, 19.6 mph; for hot/cold ratio, 20% cold operation.
E-4
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Where: enpstw = Composite emission factor in g/mi (g/km) for calendar year (n), pollutant (p), average
speed (s), ambient temperature (t), and percentage cold operation (w) B
c. = The FTP (1975 Federal Test Procedure) mean emission factor for the i I
v model year vehicles during calendar year (n) and for pollutant (p) "
m. = The fraction of annual travel by the i model year vehicles during
1 calendar year (n)
v. = The speed correction factor for the i model year vehicles for m
p pollutant (p) and average speed (s) p
z. . = The temperature correction factor for the i model year vehicles «
p for pollutant (p) and ambient temperature (t)
r. . = The hot/cold vehicle operation correction factor for the i model
p year vehicle for pollutant (p), ambient temperature (t), and
I
percentage cold operation (w)
A review of this composite emission factor (enpstw) summation
equation indicates the vehicle emission factor (c. ) is weighted
by a VMT use factor (m ) and corrected for speed (v. ), ambient I
in ips
temperature (z. .) and percent hot/cold operation (r. . ) if nonstandard
1P C Ip uW M|
contitiorfs exist. Standard conditions are: for temperature, 68°F - 86°F,
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The temperature correction factors are available over a range of
20°F-80°F; the speed correction factors ere in two parts, the "normal"
speed correction from 15-45 mph, and the "low speed" corrections for
I 5 and 10 mph; the hot/cold correction factor is usable from 0-100%
cold operation (it should be pointed out that, for cars after 1975
| equipped with catalysts, the net/cold correction includes another
_ factor, hot start percentage, to account for the variation in emissions
from catalyst equipped vehicles that have had less than 1 hour to cool
before being restarted). All of the above correction factors are
discussed in more detail in AP-42,
I In general the above correction factors will effect projected NO
X
emissions to a lesser extent than growth factors. For example, most
whereas the difference between a 2% and 3% annual growth rate over a
I
operational correction factors effect NO emissions by less than 20%
/\
twenty year period will make a 30% difference in NO emission projections.
X
Because of the different relative importance of the various factors, they
should be considered on a priority basis starting with the factor which
In relation to the specific operational correction factor, Figures
will effect NO emission calculations the most.
X
E-6, 7, and 8 present speed correction factors (V. ). As illustrated
N0v emissions increase both as average vehicle speed is increased or
decreased from standard conditions (19.6 mph). The ambient temperature
correction (Z. .) factor (Figure E-9) increases as the ambient tempera-
ture is reduced from standard conditions (75°F). The final correction
factor, the hot/cold operational factor (r- t ) is a function of two
variables (see Figure E-10). The first variable is percent cold
operations (w). The NO correction factor reduces with increased cold
|X
operation. The second variable is ambient temperature which also causes
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the hot/cold correction factor to be reduced at lower temperatures.
In summary, the NO emission rate for motor vehicles is maximized at
A
high speeds, low ambient temperature, and steady state conditions an'4
minimized at medium speed, high ambient temperatures and short-term
operations. I
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E-6
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1.4
1.2
to
C£
c *
° 1.0
^ 0.8
o
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o
0.6
S-
o
0.4
0.2
o.o1
1970
FIGURE E-1
NORMALIZED MOTOR VEHICLE EMISSIONS RATE
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I
1975
Assumptions:
1980 1985
CALENDAR YEAR
1990
1995
1. National average automobile and truck age distribution
2. Low altitude, standard conditions
3. 3% Compounded (annual) growth rate
4. National average vehicle mix (LDV 80.4%; LOT 11.8%; HDG 4.6%; HDD 3.2?
5. 1970 composite emission factor 4.6 g/mi
E-7
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FIGURE E-2
GROWTH FACTORS (GF) vs TTMF (T)
GR = annual growth rate (%}
GF = , GR
I
2.2 ..
GR = 4%
2.0
1.8
00
o:
o
§1.6
o
o;
1.4
1.2
GR = 3%
i.a
GR = 2%
10 15
YEARS (T) E-8
20
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20
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FIGURE E-3
LDV TRAVEL BY MODEL YEAR (min)*
National
Average
(AP-42)
*Based on 1972 Data
468
Automobile Age (LDV)
E-9
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20
15
E
\
CO
s
o
c
o
10
1970
FIGURE E-4
rACTOR FOR L
VS. CALENDAR YEAR
COMPOSITE NOV EMISSION FACTOR FOR LDV, LOT, HDV, AND HDD
A
T
T
HDVD
LDV = Light-Duty Vehicle
LOT = Light-Duty Truck
HDVG = Heavy-Duty Vehicle
HDVD - Heavy-Duty Vehicle
Gasoline
Diesel
HDVG
I
1975
*Low altutude; 49 state
vehicles, standard conditions
1980 1985
CALENDAR YEAR
1990
1995
E-10
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An NO emission limitation for light duty vehicles (LDV) (i.e.,
X
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3. Motor Vehicle Emission Standards
Light Duty Vehicles
any motor vehicle with a gross vehicle weight (GVW)* of 6,000 Ibs.
or less and used principally for transportation of people) was . v.
established by Section 202 of the Clean Air Act (CAA) of 1970 as
amended. The Act required EPA to establish regulations that would
require 1976 model LDV's to reduce NO emissions by 90% of their
X
uncontrolled 1971 emission rate. On July 2, 1971 (at 36 FFM2652)
later recodified on November 15, 1972 (at 37 FR 24250) the Administra-
tor established the following emission standards for NO emissions:
|X
1973 model year - 3.0 grams per vehicle mile
_ 1974 model year - 3.0 grams per vehicle mile
1975 model year - 3.1 grams per vehicle mile
1976 model year - 0.40 grams per vehicle mile
On July 31, 1973 (at 38 FR_ 20365) after testimony by automobile
| manufacturers, control equipment suppliers and the National Academy
« of Science which had indicated that the statutory standards could not
* be met by the required attainment date with acceptable reliability,
and after the Administrator had determined that full 90% control was
not generally needed to attain national standards, except in Los
| Angeles (June 8, 1973, F£ at 15183) the Administrator under the
^ suspension provision of Section 202(b)(5)(D) granted a one-year
extension (until 1977) for compliance with the statutory standard to
some automobile manufactuers. In conjunction with the extension, the
I*
Total weight of vehicle and maximum load as rated by the manufacturer.
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Administrator or. July 305 1973, established a national interim I
standard of 2.0 grams/mile for 1976 model motor vehicles and postponed
the 0,4 grams/mile standard to 1977 model vehicles (August 21, 1973 at |
F_R 22474), At that time it was generally believed the 1976 interim
standard was the lowest emission level that LDV could achieve without
the use of a reduction catalyst. fl
In June 19749 the Energy Supply and Environmental Coordination
Act (ESECA) modified and postponed these emission rates by legislative |
decree,, Specifically ESECA suspended all automotive emission standards
I
for an additional year; i.e., the NO statutory standard of 0.4 grams/
A
mile was postponed to 1978. The 1976 interim standard of 2.0 grams/mile
was postponed to 1977 and the 1975 standard of 3.1 grams/mile was main-
tained for 1976 model vehicles. The present standard (i.e., for 1976 |
models) is thus 3J grams/mile. These standard and proposed changes
are summarized in Table E-l 1.
EPA has recommended to Congress changes in NO standards for
X I
automotive sources. On March 5, 19759 the Administrator recommended
that the NO automotive standards be established at 2.0 grams/mile I
X ^B
for vehicle models 1977-1982. Final action on automotive emission
standards by Congress is anticipated during
An analysis was conducted by OAQPS which predicted air quality
levels in ten cities resulting from eight different emission standards
combinations (options). The ten cities (Phoenix; Los Angeles; San Francisco; I
Denver; New York City; Philadelphia; Washington, D.C.; Chicago; Baltimore;
and Salt Lake City) represented the "worst-case" situations (considering
air quality and growth) from a list of about thirty urban areas for
which 1972 data were available. The analysis indicated :hat future N00
E-18
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E-19
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levels will exceed the air quality standards in most of the ten
cities under all eight of the automotive control options, primarily
because of the growth of stationary sources which will constitute
the major contribution of NO emissions. Variations in the control
I"
each of the ten cities studied by affecting the rate the N02 air m
quality level deteriorated. Under the strictest option (i.e., 0.4
gram/mile), an average increase in ambient NO concentrations of 6 fl
percent by 1980 would be experienced in the 10 cities examined, and
under the most lenient option (i.e., 3.1 gram/mile), the average |
increase would be 16 percent by 1980. ^
Light Duty Trucks (LOT - gasoline powered)
Uncontrolled NO emissions from gasoline powered LDT's range I
X ^H
between 1.6 to 5.3 grams/mile, depending upon age of the vehicle and
whether the vehicle is operated at low or high altitude. Presently
the LOT standard is identical to the LDV standard; i.e., an emission
limitation of 3.1 grams/mile beginning with model year 1975.
An NO emission standard of 2.3 grams/mile beginning in 1978 for
light duty trucks was proposed in the Federal Register in February 1976.
The proposal will also change the distinction between light and heavy V
duty trucks from the present 6,000 Ibs GVW to 8,500 Ibs. GVW. This
proposed LOT standard is significantly below the uncontrolled emission
rate of N0x, which was approximately 3.5 grams/mile in 1967 prior to I
the introduction of HC and CO controls and which caused the average NO
emission rate to increase to 5.3 grams/mile in 1973. I
E-20 I
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Heavy Duty Trucks (HOT)
I Uncontrolled NO emissions from gasoline-powered HOT range from 4.1
x
to 12.6 grams/mile depending upon the age of the vehicle and whether
the vehicle is operated at high or low altitude. Additionally, the NO
/\
emission rate from diesel powered HOT is approximately 21 grams/mile.
The current standard in effect (see November 15, 1972 FR^ at 24287) is
combined HC and NO emission limitation of 16 grams/brake horsepower
hour. This standard applies to vehicles of model years 1974 through
I
1977. In addition, a combined standard for hydrocarbon and NOV of
X
10 grams per brake horsepower hour beginning with 1979 model vehicles
horsepower hour for NO .
X
was proposed for heavy duty trucks in the May 24, 1976, Federal Register.
This standard is approximately equal to a standard of 9 grams per brake
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E-21
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SECTION F
TRANSPORTATION CONTROL PLANS
: The need to reduce automotive emissions in some areas below the levels
resulting from Federal Motor Vehicle Control Program (FMVCP) was specifically
recognized in the Clean Air Act. After review of the SIP's, EPA required
certain states to submit plans containing various transportation control
measures to reduce automotive emissions in 27 Air Quality Control Regions.
On June 8,'1973, the Administrator promulgated regulations to amend 40 CFR,
Part 51, to clarify the requirements for transportation control strategies.
Transportation control measures included in SIP's are of two basic types;,
i.e., measures that reduce emissions from individual vehicles and measures
that reduce general automobile use (vehicle-miles-traveled or VMT). The
first type of control measure includes inspection/maintenance and retrofit,
programs. The second type includes transit improvements, carpool programs,
disincentives to the use of low-occupancy automobiles and parking restric-
tions.
Impact of_ Various Transportation Control Measures on_ NOx Emissions
The principal thrust of transportation measures to date has been aimed
at reducing levels of carbon monoxide (CO) and photochemical oxidants (Ox).
In some cases those actions result in concomitant increases or decreases in
NCx emissions.
Auto-used and emissions reductions achieved by transportstion controls
derive from the effects of the .entire group of measures included in a tran-
sportation control plan, rather than the effects of individual measures.
Moreover, the effectiveness of specific auto-used reduction approaches is
strongly dependent on local conditions. Hence, in any consideration of NOx
reductions identified with specific control measures, it is necessary to
view these reductions as rough estimates which are subject to change when
placed in the operating framework of the entire TCP for a particular area.
(a) Non-VMT measures.
Several control measures are available to reduce emissions from in-
dividual vehicles. Since these control measures require that individual
vehicle emissions be reduced by a certain amount, it is relatively erisy
(when compared to VMT reductions) to quantify emission reductions that may
result from the implementation of these control measures.
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Inspection and Maintenance
Inspection and maintenance (I/M) programs, which provide For in- |
spection at least once a year to primarily check HC and CO emission rates
of motor vehicles, do not significantly affect NOx emissions. Analyses ' «
of two studies by Olson Laboratories showed that I/M increased annual I
emissions of NOx by 0.8 and 1.4 percent respectively. Neither of these
increases was statistically significant, even though fleet sizes were larger
(600 and 144 vehicles). These negligible increases in NOx levels are
due principally to increased temperatures accompanying improved combus- '
tion efficiency.
Retrofit I
Retrofit means the addition or removal of an item of equipment, or a «
required adjustment, connection, or disconnection of an existing item of ' I
equipment, on an in-use vehicle for the purpose of reducing emissions.
Retrofit devices can be used singly or in combination with other retrofits .
to optimize control of NOx, HC and CO emissions for both light duty and
heavy duty vehicles. Studies on both light and heavy duty vehicles have
demonstrated the potential for retrofit devices to be very effective in
reducing NOx emissions, all of which are contained in the exhaust gases.
,NOx,.retrofits can be used on both controlled (1968-1974) and on pre- .
1968 uncontrolled vehicles. Of the two approaches currently certified M
for use in California, one uses exhaust gas recirculation (EGk) plus
vacuum spark advance disconnect (VSAD) and the other uses only VSAD.
The NOx control devices used for the California retrofit program for
1966-1970 vehicles were designed to reduce NOx emissions by at least 40
percent without increasing HC or CO emissions. *
The central technical problem in controlling NOx emissions by retrofit
is to optimize the choice among various combinations of retrofit devices con-
sidering the pollutant problems at hand. Another major variable affect-
ing the optimization of retrofit devices is altitude. Studies in Denver,
Colorado r have shown additional reduction in NOx emissions from retrofit : |
at high altitude although simultaneously increasing HC and CO emissions.
The choice of retrofit options is thus a delicate balance among the three _
pollutants, the feasible technical approaches, and the estimated use of the, I
vehicle. '
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Additionally, the California retrofit problem encountered stiff public I
opposition. Therefore, a light duty vehicle retrofit program must be viewed
as one of the lesser politically feasible measures.
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_ Measures
VMT reduction measures most frequently found in TCP's approved or
promulgated by EPA include: transit improvements, carpooling'programs ,
priority 'treatment for buses and carpools on streets and freeways (e.g.,
exclusive bus lanes), and parking restrictions. These interrelated
measures reduce VMT, hence reduce the amount of fuel burned and con-
sequently the amount of NOx emissions.
v
The maximum emission reductions f^om transportation measures will
result from coordinated measures designed to discourage low occupancy
auto use and to encourage transit and carpool use. However, transit and
carpool incentives by themselves are insufficient for achieving signifi-
cant emission reductions. Programs that do not incorporate parking
restrictions, surcharges, or other disincentives are unlikely to achieve
emission reductions greater than 5 to'10 percent. For further information1
on specific measures refer to the attached list of reference materials.
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EPA-460/3-74-021
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References/Bibl iography
£f Control Strategies for In -Use Vehicles, EPA , December 1 974 , jj
*
2- Applications for Accreditation of NOx Control Devices, State of California,
'Air Resources Board (undated)
3. Transportation Controls to Reduce Automobile Use and Improve Air Quality
n C PA - --
in Cities, EPA, November 1974, EPA-400/1 1-74-002
4. An Evaluation of Retrofit Devices for Heavy Duty Vehicles,, (Draft),
New York City Department of Air Resources, December 1975
5. Effectiveness of Short Emission Inspection Tests in Reducing Emissions,
through Maintenance, Olson Laboratories for EPA, July 1973, EPA-460/3-
73-009 . "
6. Degradation Effects on Motor Vehicle Exhaust Emissions , (Draft), Olson
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laboratories for California Air Resources Board, 1976
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SECTION G
FIELD OBSERVATIONS
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_ Recently a study of short-term NO concentration distributions
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over urban/suburban areas was conducted. A review of available air
quality data indicated that only St. Louis (25 sites) and Los Angeles
(24 sites) had sufficient data for analyzing the spatial character of
I NOp. Three days of hourly data were analyzed for each city with days
of relatively high NOX concentrations selected for analysis.
A review of the 24-hour NOp concentrations in St. Louis indicated
that the highest NQ0 concentrations were recorded in an area along the
prevailing wind direction and slightly downwind p_f_ the major industries
clustered near the center of the city. On each day, the concentrations
would rapidly decrease with increasing downwind distance Such that sub-
urban NOp concentrations at 25 miles downwind were only one-fourth to
m one-half of the city center value. (See Figures G-l, G-2, and G-3.,)
In Los Angeles the 24-hour NOp concentrations patterns were more
complex than in St. Louis. It is expected that the day/night land/sea
airflow patterns and complicating topographical features in the Los
| Angeles Basin tend to channel and inhibit surface air flow and result
in complex wind flow patterns. For the days analyzed similar concentra-
tion patterns were observed. On each day there appeared to be four
B different areas of high N02 concentrations with all four maxima located
downwind of the Los Angeles city center. The 24-hour N0? concentrations
in the basin dropped rapidly with increasing downwind distance with an
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approximate gradient of 20 wg/m (0.01 ppm) per mile. The analysis
also indicated that N0£ concentrations in Los Angeles may be twice as
high in the fall and winter as in the spring and summer.
A review of the 1-hour NOp data for St. Louis indicated that peak
1-hour N02 concentrations also occurred downwind of major city sources
from 8:00 p.m. to 10:00 p.m. on 2 days and 4:00 a.m. to 8:00 a.m. at I
the center city sites on the third day. (See Figure G-4.) The general
urban area (excluding the center city) reached its maximum concentration
at 10:00 p.m. on the third day. In Los Angeles maximum 1-hour concen-
trations occurred during the mid-morning to noontime along the coast and
center city, but during the evening in suburban and inland sites. I
In summary, the analysis indicated that high short-term N02 concen-
trations tend to occur in and immediately downwind of the city center |
and decrease rapidly with distance outward toward rural areas. These _
findings imply that the maximum annual NOg concentrations in an urban *
area would be expected to occur slightly downwind of the center city I
industrial complex along the most persistent wind directions.
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G-4
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G-6
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