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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 nitric acid. A nitric 

acid train produces 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.

(2) Request Administrator approval for an alternative method of determining N2O 

emissions according to paragraphs (a)(2)(i) through (a)(2)(iv) of this section.

(i) If you received Administrator approval for an alternative method of determining N2O 

emissions in the previous reporting year and your methodology is unchanged, your alternative 

method is automatically approved for the next reporting year.
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(ii) You must notify the EPA of your use of a previously approved alternative method in 

your annual report.

(iii) Otherwise, you must submit the request within 45 days following promulgation of 

this subpart or within the first 30 days of each subsequent reporting year.

(iv) 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 (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.

(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:
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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 for each N2O abatement technology “N” according to 

paragraphs (d)(1), (2), or (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.
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(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:

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:
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where:

EN2Ot = Annual N2O mass emissions from nitric acid train “t” according to this Equation 

V-3a (metric tons).

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:

where:
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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).

EFN2Ot = Average site-specific N2O emissions factor for nitric acid train ”t” (lb N2O/ton 

acid produced, 100 percent acid basis).
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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 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 
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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.

(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 (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.
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(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.

(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).

(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.
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In addition to the information required by § 98.3(c), each annual report must contain the 

information specified in paragraphs (a) through (q) of this section.

(a) Nitric Acid train identification number.

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

(c) [Reserved]

(d) Reserved.

(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) and date of installation of abatement 

technology.

(i) Reserved.

(j) Reserved.

(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) Reserved.

(2) Test method used for performance test.
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(3) Reserved.

(4) Reserved.

(5) Reserved.

(6) Reserved.

(7) Number of times in the reporting year that a performance test had to be repeated 

(number).

(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 (4) of this section.

(1) Name of alternative method.

(2) Description of alternative method.

(3) Request date.

(4) Approval date.

(o) [Reserved]

(p) Reserved.

(q) Annual percent N2O emission reduction for all nitric acid trains combined.

§ 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 (h) 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.
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(d) Number of operating hours in the calendar year for each nitric acid train (hours).

(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.

(h) Verification software records. You must keep a record of the file generated by the 

verification software specified in § 98.5(b) for the applicable data specified in paragraphs (h)(1) 

through (10) of this section. Retention of this file satisfies the recordkeeping requirement for the 

data in paragraphs (h)(1) through (10) of this section.

(1) Annual nitric acid produced from each nitric acid train (tons nitric acid produced, 

100% acid basis).

(2) Indicate which equation was used to calculate emissions for each nitric acid train.

(3) N2O concentration per test run during the performance test (ppm N2O) (Equation V-1

of § 98.223).

(4) Volumetric flow rate of effluent gas per test run during the performance test dscf/hr) 

(Equation V-1).

(5) Production rate per test run during the performance test (tons nitric acid produced per 

hour, 100 percent acid basis) (Equation V-1).

(6) Annual nitric acid production from each nitric acid train during which each N2O 

abatement technology was operational (tons nitric acid produced, 100 percent acid basis) 

(Equation V-2 of § 98.223).
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(7) Destruction efficiency of N2O abatement technology that is used on each nitric acid 

train (decimal fraction of N2O removed from vent stream) (Equation V-3a of § 98.223).

(8) Destruction efficiency of each N2O abatement technology that is used on each nitric 

acid train (decimal fraction of N2O removed from vent stream) (Equation V-3b of § 98.223).

(9) Destruction efficiency of each N2O abatement technology that is used on each nitric 

acid train (decimal fraction of N2O removed from vent stream) (Equation V-3c of § 98.223).

(10) Fraction control factor of each N2O abatement technology that is used on each nitric 

acid train (decimal fraction of total emissions from nitric acid train "t" that are sent to abatement 

technology "n")(Equation V-3c).

§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.