### Date: December 16 , 2009

Subject: Using EPA Method 7E for Measuring NO X 

### Emissions from Nitric Acid

Production Facilities

Nitric Acid NSPS Review

EPA Contract No. EP

- D

- 06

- 118; Work Assignment No. 3

- 22 RTI Project No. 0210426.0 03.022

From: Melissa Icenhour

To: Bill Neuffer

OAQPS/SPPD/MMG (D243

- 02) U. S. Environmental Protection Agency Research Triangle Park, NC 27711

Introduction

The EPA is required by section 111(b)(1)(B) of the C lean Air Act (C AA ) to review and , if appropriate, revise existing New Source Performance Standards (NSPS) at least every 8 years.

The nitric acid NSPS (part 60, subpart G) has been reviewed in the past but the last review was more than 8 years ago. As a result of this, EPA has received a citizen suit from Sierra Club and Environmental Integrity Project prompting review of the standards before the end of the year

2010.

NSPS (40 CFR part 60) Promulgation date Previous review dates Nitric Acid (subpart G) December 23, 1971 (36 FR 24876 ) Reviews dated June 19, 1979; April 5, 1984. No changes. Minor testing/ monitoring changes made

- October 6, 1975 [40 FR 46258], April 22, 1985 [50 FR 15894], and February 14, 1989 [40
FR 6666]2



### Options for NSPS review

The purpose of an NSPS review is to determine if the standards reflect the “degree of emissions limitation achievable through application of the best system of emission reduction which (taking into account the cost of achieving such reduction and any nonair quality health and

environment al impact and energy requirements) the Administrator determines has been adequately demonstrated.”

Potential outcomes of the review process include one or more of the following:

- No changes

- Clarifying amendments

- Changes to emissions limits or other rule requirements

- Add emission limits for additional pollutants (i.e., N 2 

### O)

EPA w ill collect and validate data to determine what changes to the NSPS may be needed. In discussions with industry, most of the NO X 

### data collected by industry has been analyze d using Method 7E, “ Determination of Nitrogen Oxides Emissions f rom Stationary Sources (Instrumental Analyzer Procedure)

. ”

Using Method 7E for Measuring NO X 

### E missions from Nitric Acid Production Facilities

The nitric acid NSPS ( Subpart G ) specifies that Method 7, 7A, 7B, 7C, or 7D be used to
determine the NO X 

### concentration

. Method 7E is not offered as an alternative method.

According to the Applicability Determination Index (A D I) [ http://www.epa.gov/compliance/monitoring/programs/caa/adi.html ]

, Method 7E was approved

for use at the DuPont nitric acid plant in Victoria, T exas
, in 2000 under Control Number

0000006

. The method was approved by Texas Natural Resource Conservation Commission (TNRCC).

Th e alternative method was approved under the condition s that the chemiluminescent nitrogen oxides analyzer be calibrated with nitrogen dioxide and that the analyzer pass a converter efficiency test. The facility submitted data “dem onstrating that its nitrogen oxides CEMS, when calibrated with nitrogen dioxide, is positively biased with respect to reference method 7.” John Hepola (Chief of Air Toxics and Inspection Coordination Branch of TNRCC) responded to the facility, “this bias would be removed if reference M ethod 7E were used for the certification of relative accuracy of the nitrogen oxides CEMS, since reference M ethod 7E is an instrumental analyzer procedure using a chemiluminescent nitrogen oxides analyzer.”

When the Metals a nd Minerals Group (MMG) became aware of the use of Method 7E by the nitric acid industry, Bill Neuffer contacted Bill Grimley of the Measurement Technology Group (MTG) for guidance. The ramifications of Method 7E being used throughout the industry brought up two issues: should Method 7E be explicitly allow ed for NO X 

### testing by adding it to Subpart G and could emissions data collected using Method 7E be used to set a ne w NO X 

### emission limit for new sources under Subpart G ?3



### According to members of MTG and the Measurement Policy Group (MPG)

, the alternative

method request should have been reviewed and approved through their group s; TNRCC did not have the authority to grant the approval. However, after being published in the ADI, most of t he

nitric acid prod uction plants in the United States began using Method 7E for NO X 

### testing

.

In response, the following comment was added by Bill Grimley to the ADI under Control

Number 0000006:

This letter should not be used as precedent. Only the Office of Air Quali ty Planning and Standards or the appropriately delegated authority is authorized to approve alternative test methods. Additionally, an incorrect test method is

described in this letter. Parties interested in an alternative to the test methods

listed in 4 0 CFR Subpart G for compliance determination and relative accuracy testing of NOx CEMS may send a source

- specific request to the Administrator's delegated authority as explained in guideline GD 22 at

h ttp://www.epa.gov/ttn/emc/guidlnd.html and 40 CFR 60.8(b)(3).



### Additional Method 7E Provisions for Nitric Acid Production Facilities

June 2009

EPA’s Measurement Technology Group and Measurement Policy Group issued a statement, dated June 15, 2009, that Me thod 7E would no longer be allowed for NO X 

### testing in the nitric acid production industry. The statement is included as Attachment 1 and outlines the reasons that Method 7E may not be applicable for use by nitric acid production facilities.

July 2009

Duri ng discussions with industry representatives from The Fertilizer Institute (TFI) and American Chemistry Council (ACC), EPA asked for further information on the use of Method

7E for NO X 

### testing within the nitric acid production industry

.

During a telephone conversation with Jim Schellhorn of Terra Industries (a member company of TFI) , Bill Neuffer summarized why TFI preferred to use Method 7E to measure NO X 

### from nitric acid plants. Jim explained that :

• Method 7E i s the standard stack method for conducting NO X 

### analyzer performance tests and RATAs, most of which are conducted by stack test companies for fuel combustion sources ;

• Method 7E is the method of choice for stack testers because it doesn’t rely on wet chemistry ;

• All stack emissions testing companies are prepared to use Method 7E ; and

• 

### The cost for Method 7E is $3,000 compared to $4,500 for Method 7D.4



### Also, Jim estimated that 20

– 30% of the NO X 

### from typical NSPS nitric acid plants operating at steady state conditions is NO 2 

### and t here is little moisture (0.5

- 2.0%) in the stack of nitric acid plants

. He said the industry would be willing to do concurrent Method 7D and 7E tests if that would be helpful to demonstrate the accuracy of Method 7E for nitric acid performance tests.

Later, MTG and MPG discussed the possibility of allowing the nitric acid production industry to use Method 7E if certain additional provisions were followed. The se includ e performing dynamic spiking procedures using NO 2 

### spike gas and ensuring that the gas stream does not come in cont act with any condens at e.

August 2009

On August 1 1 , 2009, MTG and MPG issued the first version of the provisions:

Title: Use of Method 7E for NO

x Measurements

- NSPS review for Nitric Acid

Plants

To be suitable for use by EPA, NO

x emissions measurements m ust be of verified quality. Because of the propensity of NO 2 to be absorbed by water, the sampled gas must not contact any condensate, and the efficiency of any NO 2 to NO converter (if needed by the detection principle of the instrument) must be

determine d and documented as described in the method. For wet basis measurement systems, the tester must measure and report temperature data to show that the sample line and all sample transport components up to the inlet of the analyzer (and, for hot

- wet extracti ve systems, also the analyzer) were maintained above the stack gas dew point. Use of a dilution probe to reduce the dew point is an acceptable procedure, if documented. Section 8 of Method 7E describes the measurement system performance tests and documen tation required by the method, both prior to and following sampling. NO 2 calibration gas must be substituted for NO calibration gas in the performance of system bias checks. The alternative mentioned in Section 8.6 to follow the dynamic spike procedure in Section 16.1 is acceptable, but only with NO 2 spike gas. The dynamic spiking procedure is strongly recommended.5



### September 2009

On September 16, 2009, Bill Herz of TFI responded with the following, via email :

In response to our call on September 9, 200 9 regarding EPA Test Method 7E, as used at nitric acid plants, and concerns raised by EPA regarding NO 2 absorption in water during this test procedure, we discussed this issue with some emissions testing companies and TFI member company personnel. EPA's c oncerns are expressed in the attached June 15, 2009 memorandum [Attachment 1] and one paragraph Word

document [September 16, 2009 paragraph above]

.

As we understand it, and as set forth in the June 15, 2009 memorandum, the premise set forth by EPA for con cerns with the use of Method 7E at nitric acid plants is that "Nitrogen dioxide is very soluble in water." This conclusion, however, is very misleading and, from a technical standpoint, is incorrect. The uptake into water of

NO 2 from a gas stream is pred ominantly a bulk

- phase process that is governed by Henry’s Law. See Chemicals in the Atmosphere

- Solubility, Sources and Reactivity, P.G.T. Fogg, J.M. Sangster, John Wiley & Sons Ltd. (2003) at 190, 191. The

maximum concentration of NO 2 in an aqueous solu tion should be governed not by solubility, but by the partial pressure of the NO 2 in the gas stream.

Given the very low partial pressure of NO 2 in the exhaust gas from a nitric acid plant, along with the low moisture content available to condense out in th e conditioning apparatus (based on discussions with TFI members, the highest moisture content we’ve encountered is 1.5%, with many below 1.0%), losses of NO 2 in the condensate should be insignificant and should not form the basis for invalidating Method 7E for use at nitric acid plants. For any given stack test run, given the known quantities of condensate recovered, losses of NO 2 during Method 7E sampling can be estimated using well established and published Henry’s Law constant data.

During our call, you indicated that EPA has several emissions test results from tests run using Method 7E. These data should enable one to calculate NO 2 losses to conditioning apparatus condensate using Henry’s Law constant data. To the extent that EPA has performed this ev aluation already, we would appreciate the opportunity to review the Agency’s results. Currently, we are aware of EPA’s conclusion, but have not seen the underlying data to support this conclusion.

If the data support EPA’s conclusion, we believe the next step should be utilization of a dynamic spiking procedure performed during a Method 7E test to quantity NO 2 losses to condensate, or use of an indirect electric chiller to limit the quantity of NO 2 that comes in contact with any condensate.. Such a test w ould allow EPA to verify the results of empirical calculations and, as necessary, determine what controls may be necessary (if any) to ensure that Method 7E used at nitric acid plants produces

reliable results.

To presume that (1) NO 2 is absorbed in conden sate, and (2) such absorption results in inaccurate performance test results using Method 7E, without calculations and testing to confirm same, is arbitrary and not based on sound science.6

Please advise what work has been performed by EPA to date regarding this issue. If you think that a call would assist in advancing the evaluation, please let me know.



### October 2009

T he Method 7E provisions were updated as follows on October 8, 2009:

Emissions Testing and Continuous Emissions Monitoring for Nitric Acid

NSP S (Subpart G) Review

Limitations for Use of Method 7E for (1) Performance Test or CEMS RATA in Amendments to Subpart G and (2) Current Data Request

• Must conduct system bias checks in Sections 8.2.5 and 8.5 with NO 2 gas, not NO gas; and

• Must use one of the following approaches to effectively eliminate loss of

NO 2 in water:

§ For a wet

- basis measurement system, measure and report temperature of sample line and components (up to analyzer inlet) to demonstrate that the temperatures remain above the sample gas dew point at all times during the sampling,

• A dilution probe may be used to reduce the dew point of the sample gas; § Use a permeation

- type sample conditioning device to continuously remove condensate from sample gas while maintaining minimal contact between c ondensate and sample

gas; or § Conduct dynamic spiking with NO 2 gas according to Section

16.1 in Method 7E.

CEMS Requirements in Amendments to Subpart G

• Must use one of the following approaches to mitigate loss of NO 2 in

water in CEMS:

§ For a wet

- basis measur ement system, measure and report temperature of sample line and components (up to analyzer inlet) to demonstrate the temperatures remain above the stack gas dew point at all times during the sampling; or

• A dilution probe may be used to reduce the dew point of the stack gas; § Use a permeation

- type sample conditioning device to continuously remove condensate from sample gas while maintaining minimal contact between condensate and sample

gas.7



### The above draft was sent to TFI via email on October 8, 2009. Bill Herz responded that day with the following (also via email ) :

This imposes requirements on the use of Method 7E without scientific or engineering justification for same. Regarding the e

- mail we sent two weeks ago describing why we believe 7E to be compar able to 7; your response does not

address the issues we raised

.

Until we better understand EPA’s rationale; we cannot recommend to a member that they perform a concurrent test to validate 7E v. Method 7.



### On October 20, 2009, EPA (Bill Neuffer, Peter Wes tlin, Robin Segall, Bill Grimley and Ed Brown) responded via email to the issues from Bill Herz as follows:

Comment byTFI

- NO 2 absorption in water during Method 7E procedure.

As we understand it, and as set forth in the June 15, 2009 memorandum, the premi se set forth by EPA for concerns with the use of Method 7E at nitric acid plants is that "Nitrogen dioxide is very soluble in water." This conclusion, however, is very misleading and, from a technical standpoint, is incorrect. The uptake into water of NO 2 from a gas stream is predominantly a bulk

- phase process that is governed by Henry’s Law. See Chemicals in the Atmosphere

Solubility, Sources and Reactivity, P.G.T. Fogg, J.M. Sangster, John Wiley & Sons Ltd. (2003) at 190, 191. The maximum concentratio n of NO 2 in an aqueous solution should be governed not by solubility, but by the partial pressure of the

NO 2 in the gas stream. Given the very low partial pressure of NO 2 in the exhaust gas from a nitric acid plant, along with the low moisture content

av ailable to condense out in the conditioning apparatus (based on discussions with TFI members, the highest moisture content we’ve encountered is 1.5%, with many below 1.0%), losses of NO 2 in the condensate should be insignificant and

should not form the bas is for invalidating Method 7E for use at nitric acid plants. For any given stack test run, given the known quantities of condensate recovered,

losses of NO 2 during Method 7E sampling can be estimated using well established and published Henry’s Law consta nt data.

EPA Response

The discussion of Henry's Law, while thought

- provoking, is not applicable in this case. The chemical engineering textbook, Elementary Principles of Chemical Processes, (Felder & Rousseau, 1st edition) clearly states that Henry's Law i s valid only for dilute solutions where the solute does not dissociate, ionize, or react in the liquid phase. If this were the case for NO 2 , it wouldn't be used to make nitric acid. Essentially, once chemical reactions and equilibria enter into the pictur e, all bets are off on trying to model or estimate NO 2 losses, even when "using well established and published Henry’s Law constant data" (which vary from 0.007 M/atm to 0.041 M/atm, depending on which publication you read).8

The argument about low stack m oisture doesn't fit with what we've seen (and done) in the field. The "NOx condensers" that we used back in the 1990s appear to still be in use today. They're essentially an ice bath with a coil of TeflonTM and some knockout jars. The knockout jars usually have dip

- tubes in them, and quite often start out with some water in them (essentially a small impinger); in fact, the water improves the moisture removal, just as it does in impinger trains.

These condensers were never used for SO 2 because of the knockou ts; instead, there was a similar condenser with one or two small knockout traps that were continuously drained by a peristaltic pump. This was used to maintain minimal contact between the condensate and the sample gas" as dictated in the original

Method 6C

.

Comment by TFI

If the data support EPA’s conclusion, we believe the next step should be utilization of a dynamic spiking procedure performed during a Method 7E test to quantity NO 2 losses to condensate, or use of an indirect electric chiller to limit

th e quantity of NO 2 that comes in contact with any condensate. Such a test would allow EPA to verify the results of empirical calculations and, as necessary, determine what controls may be necessary (if any) to ensure that Method 7E used at nitric acid plan ts produces reliable results.

EPA Response

We agree. As stated in our Summary of Procedures (to be used when applying Method 7E at nitric acid plants), which was emailed to you on August 11, 2009, dynamic spiking is to be conducted with NO 2 gas accordin g to section 16.1 in Method 7E each time it is used at a nitric acid plant.9

Comment by TFI

During our call, you indicated that EPA has several emissions test results from tests run using Method 7E. These data should enable one to calculate NO 2 losses

to conditioning apparatus condensate using Henry’s Law constant data. To the extent that EPA has performed this evaluation already, we would appreciate the opportunity to review the Agency’s results. Currently, we are aware of EPA’s conclusion, but have not seen the underlying data to support this conclusion. To presume that (1) NO 2 is absorbed in condensate, and (2) such absorption results in inaccurate performance test results using Method 7E, without calculations and testing to confirm same, is arbitrary and not based on sound science.

EPA Response

We do not agree with the "not based on sound science" statement; see comments above about the applicability of Henry’s law in testing NOx emissions from nitric acid plants.. EPA’s reference method development s trategy is not to presume that a problem always exists, but rather to employ performance

- based methodology so as to preclude such problems. In this case, EPA is not presuming that a significant amount of NO 2 gas is always present to be absorbed in condens ate, or that such absorption always results in significantly inaccurate performance test results using Method 7Ebut, instead, that the test method perform in such a manner to minimize the potential for any such interference. As to the test data you refere nce, we have evidence that appreciable amounts of NO 2 gas can be present in nitric acid plant emissions. For purposes of our reviewing Method 7E test data that could be used to establish a national emission standard, and that has been generated by client

- focused testing firms, that possibility means that 7E requirements for those tests must have been modified, especially for nitric acid plants, to insure a full and accurate accounting of all NOx emissions.10



### On October 28, 2009, Peter Westlin made a few add itional changes to the Method 7E provisions.

Emissions Testing and Continuous Emissions Monitoring for Nitric

Acid NSPS (Subpart G) Review

Limitations for Use of Method 7E for (1) Performance Test or CEMS RATA in Amendments to Subpart G and (2) Current Dat a Request

• Must conduct system bias checks in Sections 8.2.5 and 8.5 with

NO 2 gas; and

• Must use one of the following approaches to mitigate loss of

NO 2 in water:

§ For a wet

- basis measurement system, measure and report temperature of sample line and component s (up to analyzer inlet) to demonstrate that the temperatures remain above the sample gas dew point at all times during the sampling,

• A dilution probe may be used to reduce the dew point of the sample gas; § Use a refrigerated

- type condenser or similar devic e (e.g., permeation dryer) to continuously remove condensate from sample gas while maintaining minimal contact between condensate and sample gas; or § Conduct dynamic spiking with NO 2 gas according to Section

16.1 in Method 7E.

CEMS Requirements in Amendment s to Subpart G

• Must use one of the following approaches to mitigate loss of

NO 2 in water in CEMS:

§ For a wet

- basis measurement system, measure and report temperature of sample line and components (up to analyzer inlet) to demonstrate the temperatures remain above the stack gas dew point at all times during the sampling; or

• A dilution probe may be used to reduce the dew point of the stack gas; § Use a refrigerated

- type condenser or similar device (e.g., permeation dryer) to continuously remove condensate from

s ample gas while maintaining minimal contact between condensate and sample gas.

November 2009

On November 18, 2009, EPA met with representatives from TFI to discuss emission data from TFI members. Method 7E and its additional provisions were not further d iscussed.11

December 2009

EPA has decided that all NO X emission data used to determine any potentially updated emission standards under the reviewed NSPS must either be conducted using Method 7, 7A, 7B, 7C, and 7D or a modified Method 7E with the above pro visions.

As part of the data gathering effort, EPA received test data from Nathan Frank of Region V ( see memorandum entitled “Using EPA Method 7E for Measuring NO X Emissions from Nitric Acid

Production Facilities” dated December 16, 2009). . Most of the test data were gathered using Method 7E

before the Method 7E provisions were issued. EPA is planning to conduct an Information Collection Request (ICR) under Section 114 authority in order to gather a sufficient amount of NO X data for use in potentially updating the NO X emissions standards in the NSPS.12 

### Attachment 1

Memorandum : Use of Method 7E at Nitric Acid Plants and Method

6C at Sulfuric Acid Plants