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Subpart V—Nitric Acid Production

§ 98.220 Definition of source category.

A nitric acid production facility uses one or more trains 

to produce weak nitric acid (30 to 70 percent in strength). A 

nitric acid train produces weak nitric acid through the 

catalytic oxidation of ammonia.

§ 98.221 Reporting threshold.

You must report GHG emissions under this subpart if your 

facility contains a nitric acid train and the facility meets the 

requirements of either §98.2(a)(1) or (a)(2).

§ 98.222 GHGs to report.

(a) You must report N2O process emissions from each nitric 

acid train as required by this subpart.

(b) You must report under subpart C of this part (General 

Stationary Fuel Combustion Sources) the emissions of CO2, CH4, 

and N2O from each stationary combustion unit by following the 

requirements of subpart C.

§ 98.223 Calculating GHG emissions.

(a) You must determine annual N2O process emissions from 

each nitric acid train according to paragraphs (a)(1) or (a)(2) 

of this section.

(1) Use a site-specific emission factor and production data 

according to paragraphs (b) through (i) of this section.
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(2) Request Administrator approval for an alternative 

method of determining N2O emissions according to paragraphs 

(a)(2)(i) and (a)(2)(ii) of this section.

(i) You must submit the request within 45 days following 

promulgation of this subpart or within the first 30 days of each 

subsequent reporting year.

(ii) If the Administrator does not approve your requested 

alternative method within 150 days of the end of the reporting 

year, you must determine the N2O emissions for the current 

reporting period using the procedures specified in paragraph 

(a)(1) of this section.

(b) You must conduct an annual performance test for each 

nitric acid train according to paragraphs (b)(1) through (b)(3) 

of this section.

(1) You must conduct the performance test at the absorber 

tail gas vent, referred to as the test point, for each nitric 

acid train according to §98.224(b) through (f). If multiple 

nitric acid trains exhaust to a common abatement technology 

and/or emission point, you must sample each process in the ducts 

before the emissions are combined, sample each process when only 

one process is operating, or sample the combined emissions when 

multiple processes are operating and base the site-specific 

emission factor on the combined production rate of the multiple 

nitric acid trains.
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(2) You must conduct the performance test under normal 

process operating conditions.

(3) You must measure the production rate during the 

performance test and calculate the production rate for the test 

period in tons (100 percent acid basis) per hour.

(c) Using the results of the performance test in paragraph 

(b) of this section, you must calculate an average site-specific 

emission factor for each nitric acid train “t” according to 

Equation V–1 of this section:

Where:

EFN2Ot = Average site-specific N2O emissions factor for 

nitric acid train “t” (lb N2O/ton nitric acid 

produced, 100 percent acid basis).

CN2O = N2O concentration for each test run during the 

performance test (ppm N2O).

1.14 × 10−7 = Conversion factor (lb/dscf-ppm N2O).

Q = Volumetric flow rate of effluent gas for each 

test run during the performance test 

(dscf/hr).

P = Production rate for each test run during the 

performance test (tons nitric acid produced 

per hour, 100 percent acid basis).

n = Number of test runs.

(d) If nitric acid train “t” exhausts to any N2O abatement 

technology “N”, you must determine the destruction efficiency 
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for each N2O abatement technology “N” according to paragraphs 

(d)(1), (d)(2), or (d)(3) of this section.

(1) Use the manufacturer's specified destruction 

efficiency.

(2) Estimate the destruction efficiency through process 

knowledge. Examples of information that could constitute process 

knowledge include calculations based on material balances, 

process stoichiometry, or previous test results provided the 

results are still relevant to the current vent stream 

conditions. You must document how process knowledge (if 

applicable) was used to determine the destruction efficiency.

(3) Calculate the destruction efficiency by conducting an 

additional performance test on the emissions stream following 

the N2O abatement technology.

(e) If nitric acid train “t” exhausts to any N2O abatement 

technology “N”, you must determine the annual amount of nitric 

acid produced on nitric acid train “t” while N2O abatement 

technology “N” is operating according to §98.224(f). Then you 

must calculate the abatement utilization factor for each N2O 

abatement technology “N” for each nitric acid train “t” 

according to Equation V–2 of this section.

Where:
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AFt,N = Abatement utilization factor of N2O abatement 

technology “N” at nitric acid train “t” 

(fraction of annual production that abatement 

technology is operating).

Pt = Total annual nitric acid production from 

nitric acid train “t” (ton acid produced, 100 

percent acid basis).

Pt,N = Annual nitric acid production from nitric acid 

train “t” during which N2O abatement technology 

“N” was operational (ton acid produced, 100 

percent acid basis).

(f) [Reserved]

(g) You must calculate N2O emissions for each nitric acid 

train “t” according to paragraph (g)(1), (g)(2), (g)(3), or 

(g)(4) of this section.

(1) If nitric acid train “t” exhausts to one N2O abatement 

technology “N” after the test point, you must use the emissions 

factor (determined in Equation V–1 of this section), the 

destruction efficiency (determined in paragraph (d) of this 

section), the annual nitric acid production (determined in 

paragraph (i) of this section), and the abatement utilization 

factor (determined in paragraph (e) of this section) according 

to Equation V–3a of this section:

Where:

EN2Ot = Annual N2O mass emissions from nitric acid 

train “t” according to this Equation V–3a 

(metric tons).
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EFN2Ot = Average site-specific N2O emissions factor for 

nitric acid train ”t” (lb N2O/ton acid 

produced, 100 percent acid basis).

Pt = Annual nitric acid production from nitric acid

train “t” (ton acid produced, 100 percent acid 

basis).

DF = Destruction efficiency of N2O abatement 

technology N that is used on nitric acid train 

“t” (decimal fraction of N2O removed from vent 

stream).

AF = Abatement utilization factor of N2O abatement 

technology “N” for nitric acid train “t” 

(decimal fraction of annual production during 

which abatement technology is operating).

2205 = Conversion factor (lb/metric ton).

(2) If multiple N2O abatement technologies are located in 

series after your test point, you must use the emissions factor 

(determined in Equation V–1 of this section), the destruction 

efficiency (determined in paragraph (d) of this section), the 

annual nitric acid production (determined in paragraph (i) of 

this section), and the abatement utilization factor (determined 

in paragraph (e) of this section), according to Equation V–3b of 

this section:

Where:

EN2Ot = Annual N2O mass emissions from nitric acid 

train “t” according to this Equation V–3b 

(metric tons).

EFN2O,t = N2O emissions factor for nitric acid train “t” 

(lb N2O/ton nitric acid produced).
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Pt = Annual nitric acid produced from nitric acid 

train “t” (ton acid produced, 100 percent acid 

basis).

DF1 = Destruction efficiency of N2O abatement 

technology 1 (decimal fraction of N2O removed 

from vent stream).

AF1 = Abatement utilization factor of N2O abatement 

technology 1 (decimal fraction of time that 

abatement technology 1 is operating).

DF2 = Destruction efficiency of N2O abatement 

technology 2 (decimal fraction of N2O removed 

from vent stream).

AF2 = Abatement utilization factor of N2O abatement 

technology 2 (decimal fraction of time that 

abatement technology 2 is operating).

DFN = Destruction efficiency of N2O abatement 

technology N (decimal fraction of N2O removed 

from vent stream).

AFN = Abatement utilization factor of N2O abatement 

technology N (decimal fraction of time that 

abatement technology N is operating).

2205 = Conversion factor (lb/metric ton).

N = Number of different N2O abatement technologies.

(3) If multiple N2O abatement technologies are located in 

parallel after your test point, you must use the emissions 

factor (determined in Equation V–1 of this section), the 

destruction efficiency (determined in paragraph (d) of this 

section), the annual nitric acid production (determined in 

paragraph (i) of this section), and the abatement utilization 

factor (determined in paragraph (e) of this section), according 

to Equation V–3c of this section:
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Where:

EN2Ot = Annual N2O mass emissions from nitric acid 

train “t” according to this Equation V–3c 

(metric tons).

EFN2O,t = N2O emissions factor for nitric acid train “t” 

(lb N2O/ton nitric acid produced).

Pt = Annual nitric acid produced from nitric acid 

train “t” (ton acid produced, 100 percent acid 

basis).

DFN = Destruction efficiency of N2O abatement 

technology “N” (decimal fraction of N2O removed 

from vent stream).

AFN = Abatement utilization factor of N2O abatement 

technology “N” (decimal fraction of time that 

abatement technology “N” is operating).

FCN = Fraction control factor of N2O abatement 

technology “N” (decimal fraction of total 

emissions from nitric acid train “t” that are 

sent to abatement technology “N”).

2205 = Conversion factor (lb/metric ton).

N = Number of different N2O abatement technologies 

with a fraction control factor.

(4) If nitric acid train “t” does not exhaust to any N2O 

abatement technology after the test point, you must use the 

emissions factor (determined in Equation V–1 of this section), 

and the annual nitric acid production (determined in paragraph 

(i) of this section) according to Equation V–3b of this section:

Where:

EN2Ot = Annual N2O mass emissions from nitric acid 

train “t” according to this Equation V–3d 

(metric tons).
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EFN2Ot = Average site-specific N2O emissions factor for 

nitric acid train ”t” (lb N2O/ton acid 

produced, 100 percent acid basis).

Pt = Annual nitric acid production from nitric acid 

train “t” (ton acid produced, 100 percent acid 

basis).

2205 = Conversion factor (lb/metric ton).

(h) You must determine the annual nitric acid production 

emissions combined from all nitric acid trains at your facility 

using Equation V–4 of this section:

Where:

N2O = Annual process N2O emissions from nitric acid 

production facility (metric tons).

EN2Ot = N2O mass emissions per year for nitric acid 

train “t” (metric tons).

m = Number of nitric acid trains.

(i) You must determine the total annual amount of nitric 

acid produced on each nitric acid train “t” (tons acid produced, 

100 percent acid basis), according to §98.224(f).

§ 98.224 Monitoring and QA/QC requirements.

(a) You must conduct a new performance test according to a 

test plan as specified in paragraphs (a)(1) through (3) of this 

section.

(1) Conduct the performance test annually. The test should 

be conducted at a point during the campaign which is 

representative of the average emissions rate from the nitric 
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acid campaigns. Facilities must document the methods used to 

determine the representative point of the campaign when the 

performance test is conducted.

(2) Conduct the performance test when your nitric acid 

production process is changed, specifically when abatement 

equipment is installed.

(3) If you requested Administrator approval for an 

alternative method of determining N2O emissions under 

§98.223(a)(2), you must conduct the performance test if your 

request has not been approved by the Administrator within 150 

days of the end of the reporting year in which it was submitted.

(b) You must measure the N2O concentration during the 

performance test using one of the methods in paragraphs (b)(1) 

through (b)(3) of this section.

(1) EPA Method 320 at 40 CFR part 63, appendix A, 

Measurement of Vapor Phase Organic and Inorganic Emissions by 

Extractive Fourier Transform Infrared (FTIR) Spectroscopy.

(2) ASTM D6348–03 Standard Test Method for Determination of 

Gaseous Compounds by Extractive Direct Interface Fourier 

Transform Infrared (FTIR) Spectroscopy (incorporated by 

reference in §98.7).

(3) An equivalent method, with Administrator approval.
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(c) You must determine the production rate(s) (100 percent

acid basis) from each nitric acid train during the performance 

test according to paragraphs (c)(1) or (c)(2) of this section.

(1) Direct measurement of production and concentration 

(such as using flow meters, weigh scales, for production and 

concentration measurements).

(2) Existing plant procedures used for accounting purposes 

(i.e. dedicated tank-level and acid concentration measurements).

(d) You must determine the volumetric flow rate during the 

performance test in conjunction with the applicable EPA methods 

in 40 CFR part 60, appendices A–1 through A–4. Conduct three 

emissions test runs of 1 hour each. All QA/QC procedures 

specified in the reference test methods and any associated 

performance specifications apply. For each test, the facility 

must prepare an emission factor determination report that must 

include the items in paragraphs (d)(1) through (d)(3) of this 

section.

(1) Analysis of samples, determination of emissions, and 

raw data.

(2) All information and data used to derive the emissions 

factor(s).

(3) The production rate during each test and how it was 

determined.
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(e) You must determine the total monthly amount of nitric 

acid produced. You must also determine the monthly amount of 

nitric acid produced while N2O abatement technology is operating 

from each nitric acid train. These monthly amounts are 

determined according to the methods in paragraphs (c)(1) or (2) 

of this section.

(f) You must determine the annual amount of nitric acid 

produced. You must also determine the annual amount of nitric 

acid produced while N2O abatement technology is operating for 

each nitric acid train. These annual amounts are determined by 

summing the respective monthly nitric acid quantities determined 

in paragraph (e) of this section.

§ 98.225 Procedures for estimating missing data.

A complete record of all measured parameters used in the 

GHG emissions calculations is required. Therefore, whenever a 

quality-assured value of a required parameter is unavailable, a 

substitute data value for the missing parameter shall be used in 

the calculations as specified in paragraphs (a) and (b) of this 

section.

(a) For each missing value of nitric acid production, the 

substitute data shall be the best available estimate based on 

all available process data or data used for accounting purposes 

(such as sales records).
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(b) For missing values related to the performance test, 

including emission factors, production rate, and N2O 

concentration, you must conduct a new performance test according 

to the procedures in §98.224 (a) through (d).

§ 98.226 Data reporting requirements.

In addition to the information required by §98.3(c), each 

annual report must contain the information specified in 

paragraphs (a) through (p) of this section.

(a) Nitric Acid train identification number.

(b) Annual process N2O emissions from each nitric acid train 

(metric tons).

(c) [Reserved]

(d) Annual nitric acid production from each nitric acid 

train during which N2O abatement technology is operating (ton 

acid produced, 100 percent acid basis).

(e) Annual nitric acid production from the nitric acid 

facility (tons, 100 percent acid basis).

(f) Number of nitric acid trains.

(g) Number of different N2O abatement technologies per 

nitric acid train “t”.

(h) Abatement technologies used (if applicable).

(i) Abatement technology destruction efficiency for each 

abatement technology (percent destruction).
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(j) Abatement utilization factor for each abatement 

technology (fraction of annual production that abatement 

technology is operating).

(k) Type of nitric acid process used for each nitric acid 

train (low, medium, high, or dual pressure).

(l) Number of times in the reporting year that missing data 

procedures were followed to measure nitric acid production 

(months).

(m) If you conducted a performance test and calculated a 

site-specific emissions factor according to §98.223(a)(1), each 

annual report must also contain the information specified in 

paragraphs (m)(1) through (7) of this section.

(1) Emission factor calculated for each nitric acid train 

(lb N2O/ton nitric acid, 100 percent acid basis).

(2) Test method used for performance test.

(3) Production rate per test run during performance test 

(tons nitric acid produced/hr, 100 percent acid basis).

(4) N2O concentration per test run during performance test 

(ppm N2O).

(5) Volumetric flow rate per test run during performance 

test (dscf/hr).

(6) Number of test runs during performance test.

(7) Number of times in the reporting year that a 

performance test had to be repeated (number).
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(n) If you requested Administrator approval for an 

alternative method of determining N2O emissions under 

§98.223(a)(2), each annual report must also contain the 

information specified in paragraphs (n)(1) through (n)(4) of 

this section.

(1) Name of alternative method.

(2) Description of alternative method.

(3) Request date.

(4) Approval date.

(o) [Reserved]

(p) Fraction control factor for each abatement technology 

(percent of total emissions from the nitric acid train that are 

sent to the abatement technology) if equation V–3c is used.

§ 98.227 Records that must be retained.

In addition to the information required by §98.3(g), you 

must retain the records specified in paragraphs (a) through (g) 

of this section for each nitric acid production facility:

(a) Records of significant changes to process.

(b) Documentation of how process knowledge was used to 

estimate abatement technology destruction efficiency (if 

applicable).

(c) Performance test reports.

(d) Number of operating hours in the calendar year for each 

nitric acid train (hours).
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(e) Annual nitric acid permitted production capacity 

(tons).

(f) Measurements, records, and calculations used to 

determine reported parameters.

(g) Documentation of the procedures used to ensure the 

accuracy of the measurements of all reported parameters, 

including but not limited to, calibration of weighing equipment, 

flow meters, and other measurement devices. The estimated 

accuracy of measurements made with these devices must also be 

recorded, and the technical basis for these estimates must be 

provided.

§ 98.228 Definitions.

All terms used in this subpart have the same meaning given 

in the Clean Air Act and subpart A of this part.