To: Alexis McKittrick, Mausami Desai 

From: Natalie Tang 

Date: 1/29/2015 

RE: Strong Nitric Acid Facilities in the U.S 

Summary 

El Dorado Chemical Company produces both weak (53% -63% concentration) and concentrated (strong) 

nitric acid (98% or greater concentrations). This facility does not use the Uhde process to produce 

concentrated nitric acid. Instead, it uses a chemical dehydrating method using the NACSAC® process. 

This method is not known to produce additional N2O emissions on top of the production of the weak 

nitric acid feedstock. Weak nitric acid production is covered by the GHGRP, thus associated emissions 

from strong nitric acid production at El Dorado Chemical Company should already be included under 

Subpart V of the GHGRP. 

There is currently one other known strong nitric acid producer also using the NACSAC® process in the 

United States with the possibility of two other strong nitric acid plants at existing facilities becoming 

operational as early as the end of 2015. The latter two plants are being designed and built by 

ThyssenKrupp Uhde and therefore will use the Uhde process for nitric acid production. All three of these 

facilities currently report to GHGRP. 

Background 

Weak nitric acid production is defined as having a 30% to 70% strength in a solution as defined by the

Greenhouse Gas Reporting Program (GHGRP).1 Based on the 2010 Best Available Control Technology 

(BACT) paper published by EPA, it is produced by a three-step high-temperature catalytic ammonia 

oxidation process: 

4 NH3 + 5 O2  4 NO + 6 H2O (Reaction 1) 

2 NO + O2  2 NO2 (Reaction 2) 

3 NO2 + H2O  2 HNO3 + NO (Reaction 3) 

Strong nitric acid is defined as nitric acid of 95% to 99% concentration. It can be produced in two ways: 2 

1) Uhde process (direct strong process or DSN), produced directly from ammonia 

2) Dehydrating, bleaching, condensing, and absorption of weak nitric acid 

According to the 2010 BACT paper, El Dorado Chemical Company is the only strong nitric acid plant in 

the United States and uses the strong direct process and there are no known US plants utilizing the 

second method.3 

El Dorado Chemical Company 

LSB industries, the parent company of El Dorado Chemical Company, defines their nitric acid commercial

blends as “aqueous solution up to 89%” and also offer concentrated nitric acid, described as “aqueous 

solution up to 99% concentration.”4 However, El Dorado Chemical Company suffered major damage to 

their DSN 98% concentrated nitric acid plant during an explosion on May 15, 2012. It was determined 

that repairs to this plant were not feasible and that that a new plant would be required.5

 
According to El Dorado Chemical Company’s Arkansas Draft Air Permit, the company uses a Nitric Acid 

Concentration and Sulfuric Acid Concentration (NACSAC) process that “concentrates weak nitric acid 

(56%-65% strength) to strong nitric acid (greater than 98% strength) by extracting water from the weak

nitric acid with sulfuric acid.6 Based on this description and on NACSAC process flow diagram from the 

manufacturer7, El Dorado Chemical Company no longer uses the Uhde process and instead uses a 

chemical dehydrating method to produce concentrated nitric acid. 

The secondary production of high strength acid from weak is not known to result in additional N2O 

emissions8. Thus, any emissions during production of strong nitric acid occur in the production of the 

weak nitric acid feedstock, which is covered by Subpart V of the GHGRP. 

Their permit also confirms that they also produce nitric acid at concentrations of 56%-65%. 

Uncertainties 

• Only a draft of the Air Permit was available online. Further research indicates that the permit 

was awarded in 2013 after which construction on the expansion could commence.9 From the 

draft air permit an expansion is only mentioned for a second D.M. Weatherly Nitric Acid Plant, 

however, conflicting information is found in news sources regarding components of the 

expansion.10 It is unclear if the NACSAC® is currently operating or is still being constructed. 

• El Dorado Chemical Company’s permit suggests that they only produce weak nitric acid at 56% 

to 65% concentrations and strong nitric acid at 98% or above concentrations. However, their 

company website advertises that they are able to produce commercial nitric acid blends as 

“aqueous solution up to 89%” and it is unclear how they are achieving nitric acid concentrations 

greater than 65% but less than 98% and emissions from production of these concentrations may 

not be reported to GHGRP. 

Other Strong Nitric Acid Plants in the U.S. 

Another GHGRP reporting facility, Radford Army Ammunition Plant (GHGRP ID: 1001818) also uses the 

NACSAC method to produce strong nitric acid.11 This plant has been in operation from 2010. Emissions 

from strong nitric acid production should already be reported to the GHGRP. 

ThyseenKrupp Uhde is the manufacturer of the equipment that uses the Uhde process to produce nitric 

acid and offers four types of equipment12: 

Process Product

Uhde medium-pressure process Produces one type of nitric acid with a max. concentration 

of 65% or two types of acid with different concentrations, 

e.g. 60% nitric acid and 65% nitric acid 

Uhde high- pressure process Produces one type of nitric acid up to 67% or two or more 

acids with different concentrations 

Uhde dual-pressure process Nitric acid concentrations of more than 68% can be 

achieved with two or more product streams of different 

concentrations. “external streams of weak nitric acid can 

be processed if required” 

Uhde azeotropic nitric acid process

 (extended dual pressure process) 

“Nitric Acid with elevated concentrations of 68%” No weak 

acid co-production 
ThyssenKrupp Uhde has been selected by CF Industries to provide engineering and supply services to 

their Donaldsonville (GHGRP ID: 1002301) and Port Neal (GHGRP ID: 1006005) fertilizer producing 

facilities. The new plants are scheduled to come on stream in 2016.13 14 It is not clear what 

concentration of nitric acid that these plants will be producing using the Uhde process. 

Limitations of the Definition of Weak Nitric Acid and Strong Nitric Acid 

Commercial use nitric acid usually has a strength of 53%- 68%, although can have concentrations up to 

99%. During this research, nitric acid was most commonly available in concentrations of 68%, 72%, and

98%. Concentrations of 98% and higher appear to produced using chemical dehydration of weak nitric 

acid, however, it is unclear how concentrations between 68% and 97% are produced. More research 

should be considered if concentrations above 68% and between 97% are being produced in the United 

States or, on the other hand, available for distribution only. As mentioned in the background section of 

this document, the GHGRP defines weak nitric acid as having concentrations between 30% - 70% and 

OAQPS defines strong nitric acid as having a concentration of 95% - 99%. Current definitions of weak

and strong nitric acid do not cover all the concentrations that are produced. 

 

1

 Office of Air, U.S. Environmental Protection Agency. “40 CFR Part 98: Mandatory Reporting of Greenhouse 

Gases,” §98.220. http://www.ecfr.gov/cgi-bin/text-idx?tpl=/ecfrbrowse/Title40/40cfr98_main_02.tpl January 28, 

2015. 

2

 Office of Air Quality Planning and Standards (OAQPS), U.S. Environmental Agency. “Available and Emerging 

Technologies for Reducing Greenhouse Gas Emissions from the Nitric Acid Production Industry,” U.S. 

Environmental Protection Agency, December 2010, p.7. http://www.epa.gov/nsr/ghgdocs/nitricacid.pdf January 

28, 2015. 

3

 OAQPS, p.6-7. 

4

 LSB Industries.” What Our Products Are Used For,”2012, LSB Industries. 

http://www.lsbindustries.com/chemical?phpMyAdmin=bd47d61ca5ff3d7349b86f5ab8f66958 January 28, 2015. 

5

 Magnolia Reporter, “El Dorado Chemical will build new nitric acid plant, replacing facility lost to explosion,” July 

12, 2012. http://www.magnoliareporter.com/news_and_business/local_business/article_034649e2-cbf4-11e1-

913f-001a4bcf887a.html February 3, 2015. 

6

 Arkansas Department of Environmental Quality, Draft Operating Air Permit. Permit No. 0573-AOP-R16, Valid 

between November 24 2010 and November 23, 2015. 

http://www.adeq.state.ar.us/ftproot/Pub/WebDatabases/PermitsOnline/AirDrafts/0573-AOP-R16.pdf January 26, 

2015. 

7

 Plinke, “Nitric Acid,” brochure, http://www.plinke.de/fileadmin/user_upload/pdf/Flyer/PLINKE_HNO3_08-

2012.pdf February 2, 2015. 

8

 OAQPS,p. 7. 

9

 Magnolia Reporter, “LSB Industries gets air quality permit for El Dorado construction,” November 22, 2013. 

http://www.magnoliareporter.com/news_and_business/local_business/article_d2c20e5a-533d-11e3-ae0f0019bb2963f4.html February 2, 2015. 

10 Magnolia Reporter, “LSB Industries will build new $120 million nitric acid plant in El Dorado,” December 2, 2102. 

http://www.magnoliareporter.com/news_and_business/local_business/article_433f8472-3e6e-11e2-9e1a001a4bcf887a.html February 3, 2015. 

11Case, Joy, “Radford AAP celebrates new nitric-sulfuric acid facility” U.S. Army, October 12, 2010. 

http://www.army.mil/article/46470/Radford_AAP_celebrates_new_nitric_sulfuric_acid_facility/ February 3, 2015. 

12 ThyssenKrupp Uhde, “Nitric Acid,” brochure. http://www.thyssenkrupp-industrialsolutions.com/fileadmin/documents/brochures/uhde_brochures_pdf_en_4.pdf January 26, 2015. 

13 CHEManager, “ThyssenKrupp Uhde Wins Contract for Fertilizer Plants in USA, November 12, 2012. 

http://www.chemanager-online.com/en/news-opinions/headlines/thyssenkrupp-uhde-wins-contract-fertilizerplants-usa February 3, 2015. 
 

14 ThyssenKrupp Uhde, “ThyssenKrupp receives mega-order for fertilizer plants in the US exceeding 1 billion 

euros,” press release, November 2, 2012. 

http://www.thyssenkrupp.com/en/presse/art_detail.html&eid=TKBase_1351847416160_1211657050 February 3, 

2015. 

All from N2O emissions nitric acid production are associated with weak nitric acid, which is sold 

commercially and used as feedstock for concentrated nitric acid.