E

C

/R Incorporated Providing Environmental Technical Support Since 1989

501 Eastowne Drive, Suite 250  Chapel Hill, North Carolina 27514 

Telephone: (919)484-0222  Fax: (919) 484-0122 

MEMORANDUM

Date: August 31, 2010 

To: Anita Lee, U.S. EPA/Region 9 

From: Nancy Jones and Stephen Edgerton, EC/R Incorporated 

Subject: Impact of Ammonia in Fly Ash on its Beneficial Use 

1. Purpose 

 This memo describes the qualitative impacts of ammonia adsorption to fly ash in 

response to a comment EPA received from the Salt River Pima-Maricopa Indian Community 

(SRPMIC) on the Advanced Notice of Proposed Rulemaking (ANPR) of the Best Available 

Retrofit Technology (BART) for the Four Corners Power Plant (FCPP) located on the Navajo 

Nation, near Farmington, New Mexico. SRPMIC expressed concern about adverse economic 

impact on their fly ash business unit at FCPP if selective catalytic reduction (SCR) were required 

to meet BART. Although the comment letter did not provide further detail on the nature of the 

adverse economic impacts, we assume their concerns relate to the possibility that the use of 

ammonia for SCR would result in ammonia contamination in the fly ash they obtain from FCPP 

and make it unusable for certain applications. 

 In addition to the qualitative discussion of how SCR at FCPP may affect SRPMIC’s fly 

ash business, we also present information about their business and on fly ash beneficial uses in 

general. We also present an estimate of the amount of ammonia in fly ash from FCPP. 

 SRPMIC’s comment letter is included in this memorandum as Attachment 1. Note that 

the commenter referred to previous testimony that was not readily available for review. 

2. Background 

 Fly ash is a fine, glass-like powder recovered from gases created by coal-fired electric 

power generation. U.S. power plants produce millions of tons of fly ash annually, which is 

usually landfilled at costs estimated by the Electric Power Research Institute (EPRI) to range 

from $5 to $60 per ton. However, there is a market for fly ash to ready-mix concrete plants, 

wallboard manufacturers, agricultural soil amendment distributers, roadway builders, and others, 

with sales prices ranging from $10 to $20 per ton.1

 

 

1

http://portfolio.epri.com/ProgramTab.aspx?sId=GEN&rId=166&pId=55730 
2 

 

 The interests of SRPMIC relate to the use of fly ash in cement manufacturing. Fly ash is 

an inexpensive replacement for portland cement used in concrete, while it actually improves 

strength, segregation, and ease of pumping of the concrete. As an admixture, fly ash functions as 

either a partial replacement for, or an addition to, portland cement and is added directly into 

ready-mix concrete at the batch plant. 

 Phoenix Cement Company owns the Clarkdale cement manufacturing plant and has 

manufactured portland cement since 1959 at its Clarkdale facility, located 100 miles north of 

Phoenix. Phoenix Cement Company is one of Arizona’s leading manufacturers of portland 

cement and other building products. Founded in 1959 by the American Cement Company to 

supply materials for the development of Glen Canyon Dam, Phoenix Cement Company has been 

a division of SRPMIC since 1987.2

 Phoenix Cement Company has four fly ash sources: the Escalante Plant is located 

approximately 90 miles west of Albuquerque, New Mexico; the Cholla Plant near Holbrook, 

Arizona; FCPP near Farmington, New Mexico; and the San Juan Plant, also near Farmington - 

all of which are within 150 miles of each other. Its distribution territory includes the states of 

Arizona, California, Colorado, Nevada, New Mexico, Texas, and Utah. In addition to fly ash, 

the company markets other coal combustion products, seven types of portland cement products, 

and agricultural gypsum. 

3. Effect of SCR on Fly Ash and Subsequent Beneficial Uses 

 Post-combustion NOx controls such as SCR result in a certain level of inefficiency in 

regards to the ammonia reducing process. This inefficiency results in unreacted ammonia, called 

“ammonia slip,” in the exhaust gases. Some or all of the ammonia slip ultimately may be 

adsorbed or deposited on the fly ash. Typically, SCR systems operate with ammonia slip values 

in the 2 to 5 parts per million by volume (ppmv) range, while SNCR systems operate 

considerably higher. Ammonia slip can be expected to vary widely depending on changes in 

operating conditions. 

 A 2001 EPRI White Paper3 on the impacts of ammonia contamination on fly ash disposal 

and use addresses the problems associated with ammoniated ash as a result of increased use of 

ammonia-based environmental control technologies. The White Paper notes that these processes 

can result in a fly ash with ammonia content greater than currently acceptable in the concrete 

industry, which represents the largest market for the ash. The sale of fly ash is an important 

component of ash management at many utilities. It represents both revenue enhancement and 

reduced disposal costs. A 1996 EPRI study4 investigated the impacts of the post-combustion 

NOx technologies on ash use. Key findings of this study reported in the White Paper relative to 

the ammonia issue were as follows: 

• Ash with high ammonia levels may not be acceptable as a cement feedstock. Although 

the ammonia does not impact the strength of the resulting concrete, its presence generates 

 

2

http://www.aggregateresearch.com/articles/415/Phoenix-Cement-Company-Acquires.aspx 

3

http://mydocs.epri.com/docs/public/000000000001004609.pdf 

4

 Assessment of Impacts of NOx Reduction Technologies on Coal Ash Use, “Volume 1: North American 

Perspective,” TR-106747 V-1, EPRI, November, 1996.
3 

an odor, and hence, nuisance conditions for workers during placement. Construction and 

other bulk applications are not impacted unless personnel exposure in enclosed spaces is 

possible. 

• With suitable mitigation measures, ash containing ammonia can still be used in existing 

pozzolan and concrete markets—albeit at a cost. 

• Disposal costs for ash containing ammonia can increase due to lower bulk density. The 

lower density requires more water for compaction and greater volumes; landfills will not 

last as long. 

• Methods are known for treating ammonia-contaminated fly ash. 

 

 The acceptance of ammoniated ash by the ready–mix concrete industry is a function of 

both technical and economic factors, as well as institutional barriers. The relative supply of ash 

that does not have an ammonia odor will influence its acceptance. If clean ash is available at the 

same price and quantities, then the ammoniated ash will not be accepted. The ash marketers 

were surveyed by EPRI in August 2001 to obtain an update on the acceptance of the ashes from 

NOx control systems. They found the acceptable level of ammonia in ash that the marketplace 

will accept is in the range of 20 to 60 ppm. This compares to the level of 50 to 100 ppm that is 

standard practice in Europe. Although ash buyers have expressed “philosophical concerns” 

about the presence of ammonia on ash, there does not appear to be a significant impact on ash 

quality or beneficial use potential. 

 A 2005 EPRI report indicates that there has been no extensive implementation of 

ammonia removal technologies, reflecting the generally low levels of ammonia contamination in 

ash that are currently being experienced by the industry, which in turn reflects the relatively 

small amount of service hours on the installed catalyst. This implies that the majority of SCR 

installations are operating within their design criteria. However, certain individual sites have 

found a need for ammonia removal and several full-scale installations are in place covering 

several technologies. This trend is expected to strengthen as the fleet of SCRs ages and as the 

issue of ammonia contamination receives higher priority.5

 

 In further research on ammonia-contaminated fly ash, EPRI conducted a survey in early 

2007 to which 44 SCR-equipped units responded, which were believed to offer a good 

representation of the domestic SCR-equipped fleet as a whole. The responding SCR-equipped 

units were typical of the current "standard" high-dust type SCR design, having high NOx

removal efficiency and guaranteed ammonia slip on the order of 2 ppmv. Overall the survey 

indicated that the adverse impacts associated with ammonia contamination of fly ash are 

minimal, at least based upon the responding units. The survey overwhelmingly indicated that 

ammonia contamination is not impacting the ability of plants to sell ash, although it was common 

for the ash marketer to place maximum limits on the allowable ammonia contamination for ash 

intended for sale and to independently measure the ammonia concentration.6

4. Estimate of Ammonia Concentration in Fly Ash if SCR Were Installed at FCPP

 We estimated the ammonia concentration in ppm by weight (ppmw) that might occur if 

SCR were installed at FCPP. We based this estimate on site-specific information regarding 

 

5

http://my.epri.com/portal/server.pt?Abstract_id=000000000001008310

6

http://my.epri.com/portal/server.pt?Abstract_id=000000000001014269
4 

Unit 5 at the facility that was submitted by the facility as part of their BART analysis,7 as well as 

the following assumptions: 

• 5 ppmv ammonia slip. 

• As-fired ash content of the coal used at the facility is 25% by weight. 

• 100% of ammonia ends up in the fly ash. 

Finally, to estimate the mass of fly ash, we used the appropriate emission factor for particulate 

matter from EPA’s AP-42, Compilation of Air Pollutant Emission Factors.

8

 Our analysis resulted in an estimated ammonia content of 245 ppmw in the fly ash.9 We 

believe this to be a conservative analysis in that we used an ammonia slip of 5 ppmv, whereas 

many modern SCR systems operate closer to 2 ppmv. In addition, our analysis assumed that 

100% of the ammonia ends up in the fly ash, while it is typically assumed that only 70 to 80% is 

retained in the fly ash. Although high, the ash content assumed for the facility is representative 

of the coal combusted at FCPP. 

5. Effect of Alternative NOx Reduction Technologies on Fly Ash 

 Combustion modification techniques, such as Low-NOx burners (LNB), are the 

alternative to post-combustion treatments, such as SCR or selective non-catalytic reduction 

(SNCR) systems, for reducing NOx formation and emissions. Combustion modification 

techniques also have an impact on fly ash by increasing the unburned carbon contained in the fly 

ash, which can raise other fly ash quality issues. Termed “level of ignition” (LOI), the increased 

carbon in the fly ash impacts its use in cement and other uses and requires treatment to reduce 

the carbon level before the fly ash can be used. Several combustion modification techniques 

obtained from the U.S. Department of Energy10 are presented below. 

Low-NOx Burners are designed to control the mixing of fuel and air to achieve what 

amounts to staged combustion. This staged combustion reduces both flame temperature 

and oxygen concentration during some phases of combustion and, in turn, reduces both 

lower thermal NOx and fuel NOx production. 

Overfire Air (OFA) is air that is injected into the furnace above the normal combustion 

zone. Generally when OFA is employed, the burners are operated at a lower than normal 

air-to-fuel ratio, which reduces NOx formation. OFA, which is frequently used in 

conjunction with LNBs, completes the combustion process at a lower temperature. 

In the reburning process, part of the boiler fuel input (typically 10-25%) is added in a 

separate reburn zone. The fuel-rich reducing conditions in this zone lead to the reduction 

of NOx formed in the normal combustion zone. OFA is injected above the reburn zone to 

 

7

“Arizona Public Service Company Four Corners Generating Plant Units 1 through 5 Best Available Retrofit 

Technology Engineering Analysis,” Appendix A Design Basis, Black and Veach, December 4, 2007. Docket 

Number EPA-R09-OAR-2009-0598-0004.3. 

8

 AP-42, “Compilation of Air Pollutant Emission Factors,” Volume I, Chapter 1, Section 1.1, U.S. EPA, 1998. 

9

 The calculations are included in the docket for the FCPP BART determination, filename 

FCPP_ammonia_ppmw.xlsx. 

10 http://www.netl.doe.gov/technologies/coalpower/ewr/nox/NOx-reduct.html 
5 

complete combustion. Thus, with reburn there are three zones in the furnace: (1) a 

combustion zone with an approximately normal air-to-fuel ratio; (2) a reburn zone, where 

added fuel results in a fuel-rich condition; and (3) a burnout zone, where OFA completes 

the combustion. Coal, oil, or gas can be used as the reburn fuel. 

Flue Gas Recirculation (FGR), in which part of the flue gas is recirculated to the furnace, 

can be used to modify conditions in the combustion zone (lowering the temperature and 

reducing the oxygen concentration) to reduce NOx formation. FGR is also used as a 

carrier to inject fuel into a reburn zone to increase penetration and mixing. 

Operational Modifications involve changing certain boiler operational parameters to 

create conditions in the furnace that will lower NOx production. Examples include 

burners-out-of-service (BOOS), low excess air (LEA), and biased firing (BF). In BOOS, 

selected burners are removed from service by stopping fuel flow, but airflow is 

maintained to create staged combustion in the furnace. LEA involves operating at the 

lowest possible excess air level without interfering with good combustion, and BF 

involves injecting more fuel to some burners (typically the lower burners) while reducing 

fuel to other burners (typically the upper burners) to create staged combustion conditions 

in the furnace. 

6. Example Commercial Methods for Removal of Ammonia (and Carbon) from Fly 

Ash 

 When ammonia contaminated fly ash is wetted as part of a concrete mixture, the gas is 

released, exposing concrete workers to varying levels of ammonia, but there is no quality issue 

with the cement. However, under certain conditions, unburned carbon in fly ash can cause 

quality control issues such as interfering with the concrete’s ability to reliably entrain correct 

amounts of air. Discussed below are a few examples of general and proprietary methods for 

treating fly ash that contains high levels of carbon or ammonia. Some methods to reduce carbon 

are also effective at reducing ammonia that results from SCR and SNCR NOx reduction 

techniques. 

 Carbon Burn-Out (CBO) has long been known as a very robust system for carbon 

removal for various types of ash feedstocks. Ash feedstocks containing carbon contents as high 

as 90% have been successfully processed. To date, over 200,000 tons of CBO processed fly ash 

has been produced. CBO processed ash exhibits excellent pozzalanic activity, consistent air 

entrainment, and carbon levels of 21⁄2 % and has gained excellent market acceptance in its market 

areas. CBO’s fluid bed technology provides heat and residence time dictated by conditions for 

optimal combustion of carbon found in fly ash. Fly ash residence times of 45 minutes and 

temperatures in the 1300 degrees Fahrenheit range are characteristic of the CBO process. 

Kinetic theory suggests that CBO conditions should be ideal for ammonia removal. Ammonium 

Sulfate and Ammonium Bisulfate are the two prominent ammonia compounds found in coal fly 

ash. Both compounds exhibit low decomposition temperatures and should readily decompose 

within the operational conditions of CBO.11

 

11 http://www.netl.doe.gov/publications/proceedings/00/ubc00/GIAMPA.PDF 
6 

 A commercial scale carbon separation and ammonia removal system designed by 

Separation Technologies (ST)12 is operating at the Tampa Electric Big Bend Power Plant and 

10 other power stations throughout the U.S., Canada, and the United Kingdom. A three-stage 

carbon separation process maximizes the fuel value recovered from the company’s ProAsh® and 

EcoTermTM products. ProAsh® has been approved for use by over 20 state highway authorities. 

The ammonia process reduces the ash ammonia level from ~2,000 ppm to the less than 75 ppm 

needed to meet market requirements, and it can handle up to 52 tons of fly ash per hour. 

 Headwaters Resources’13 proprietary carbon fixation technology is used to pre-treat fly 

ash using a liquid reagent to coat unburned carbon particles and hinder their impact on the 

concrete mix. Carbon is not removed, but its effects on air entrainment are minimized. The 

technology also renders some ash products usable for the first time without having any impact on 

the quality of finished concrete. Headwaters Resources’ new technology uses a chemical reagent 

to mitigate ammonia effects. When water is added to the concrete mix containing ammoniated 

fly ash, the reagent converts ammonia to harmless compounds. The treatment reagent can be 

added and blended with the dry fly ash at any point between the fly ash collection system at the 

power plant and final delivery to the ready mixed concrete producer. 

 Carbon BlockerTM 14 is a Patent Pending fly ash treatment process that conditions fly ash 

so that desired levels of air entrainment can be achieved in concrete products applications. 

Carbon Blocker works across a broad range of fly ashes even with elevated levels of carbon. 

Carbon Blocker is used to treat fly ash at more than 10 power plants in Kentucky, Indiana, Ohio, 

Pennsylvania, and West Virginia. Fly ash from these plants can now be used at elevated carbon 

levels when treated with Carbon Blocker. 

 In addition, there are products that can be added to the combustion process to reduce fly 

ash LOI in systems with LNB and OFA. For example, Biofriendly Corporation markets 

hydrocarbon fuel combustion catalysts (Green Plus®) for reducing NOx and SO2 emissions and 

lowering LOI while maintaining or improving fuel use efficiency. 

7. Impact of Other EPA Programs on Beneficial Use of Fly Ash 

 On June 21, 2010, EPA proposed to regulate the disposal of coal combustion residuals 

(75 FR 35128) generated from the combustion of coal at electric utilities and by independent 

power producers. Under the Resource Conservation and Recovery Act (RCRA), EPA’s Office 

of Solid Waste (OSW) currently regulates coal combustion residuals (CCR) as non-hazardous 

waste under the Bevill Amendment that covers high volume, low toxicity wastes. As a result of 

the damage caused by a breach and spill of a large CCR sludge impoundment in Tennessee, the 

proposal contains two options for tightening the regulations for CCRs. Under one option, CCR 

would be listed as hazardous waste under subtitle C of RCRA, while under the other option CCR 

would continue to be regulated as nonhazardous waste under subtitle D of RCRA, but EPA 

would issue national minimum criteria to regulate disposal of CCR. In either case, EPA is 

proposing to establish dam safety requirements for CCR disposed of in surface impoundments. 

 

12 http://www.flyash.info/2009/116-gasiorowski2009.pdf 

13 http://www.flyash.com/ccpquality.asp 

14 http://www.flyashdirect.com/carbonblocker/index.asp 
7 

 However, EPA is not proposing to change the May 2000 Regulatory Determination for 

beneficially used CCRs. As a result, it is anticipated the costs for disposal of fly ash as waste 

will rise and desire for power producers to increase the beneficial use of fly ash will increase. 

8. Discussion 

 SCR and SNCR use ammonia post combustion to reduce NOx emissions from coal-fired 

power plants. Due to ammonia slip, a small amount of the ammonia is emitted to the atmosphere 

or adsorbed to the fly ash. The resulting ammoniated fly ash is less desirable for use in the 

cement and other industries because of the odor. The other option for reducing NOx emissions 

from coal-fired power plants are combustion modification techniques. These techniques can 

result in higher carbon content in the fly ash. Unburned carbon in fly ash can interfere with 

concrete’s ability to reliably entrain correct amounts of air. There are post-treatments available 

for both ammonia and carbon in fly ash. 

 SRPMIC is concerned that if EPA imposes SCR as BART for the FCPP it will have an 

adverse economic effect on its business of buying and reselling fly ash for beneficial uses. 

Figures are not available on what portion of the fly ash sold by SRPMIC originates at FCPP, but 

FCPP is the largest of the four power plants from which the fly ash is obtained. Questions that 

figure into the impact of SCR as BART for FCPP on SRPMIC include: 

• Will the ammonia have an impact on the market for their fly ash? 

• Will they be able to replace the FCPP fly ash with a supply from existing or other 

sources? 

• Will treatment of the fly ash be required and, if so, what will be the cost for treatment? 

• What are the impacts on the tribe if SCR is installed at FCPP? 

 It appears that while the ammonia results in odor problems, especially for workers 

pouring the concrete, there is not an adverse effect of ammonia on the properties of the concrete 

or on human or ecological health. As the concrete dries, the ammonia is released at higher levels 

initially and then more slowly until completely dry.

15 Ammonia odors can return when concrete 

is rewetted with the highest concentrations occurring within enclosed areas such as basements; 

however, in the desert Southwest, wet basements may be expected to be less of a concern. 

Additionally, as more facilities are required to control NOx emissions, ammoniated fly ash is 

likely to become the norm. 

 As discussed above, EPRI researchers have found that ammonia contamination resulting 

from the use of SCR has is not impacting the ability of plants to sell ash. Nevertheless, our 

conservative estimate of the ammonia content that could result from the use of SCR at FCPP 

indicates at least the potential that ammonia contamination could be above the acceptable level. 

If this were the case, SRPMIC could be forced to replace the fly ash from FCPP with other 

sources. As an alternative, FCPP or SRPMIC could process the fly ash to remove excess 

ammonia. 

 

15 Rathbone, B. and Tyra, M., University of Kentucky Center for Applied Energy Research. (2003) 

http://www.caer.uky.edu/coalash/posters/pcc2002.pdf 
8 

 Regarding alternative sources of fly ash, it is not known whether SRPMIC could replace 

the fly ash from FCPP with ash from its other three sources. If not, the OSW proposed rule, 

which would impose more rigid management requirements and potentially reclassify fly ash as a 

hazardous waste, appears likely to result in an increased amount of fly ash available for sale from 

power plants, because selling fly ash would represent an attractive alternative to disposal at a 

high cost. However, obtaining fly ash from other power plants would force changes in 

SRPMIC’s current processing and distribution system. 

 Regarding removal of ammonia from the fly ash, Section 6 above discusses some 

potential methods. Clearly, this would increase the cost to ready FCPP fly ash for sale. It is not 

known whether this increased cost would be borne by SRPMIC or FCPP. As noted above, the 

OSW rulemaking on power plant ash will affect the economics of disposal, which will provide 

incentive to utilities to sell as much of the ash as possible. 

 In addition to use in concrete manufacturing, fly ash containing ammonia can be used for 

other purposes as well. For example, the largest use of ammonia in the U.S. is in the agricultural 

industry either applied directly to soils or used in the production of fertilizer. Fly ash has been 

used in the agricultural industry as a weed preventative around trees in orchards. The addition of 

the ammonia to the fly ash would have a beneficial effect as a fertilizer for the trees. Other uses 

are covers at animal feed lots and dairy operations to provide a more solid surface than the 

underlying soil that would become mud when wet. Landfills use fly ash as daily cover. In both 

the animal and landfill operations, the odor of ammonia from the fly ash would not be expected 

to be greater than the ammonia odor from the animal wastes or the multiple odors from landfilled 

materials. Thus, it appears that ammonia-contaminated fly ash might still be marketable for 

some uses. 

 Numerous tribes recommended combustion modification techniques, rather than SCR, as 

BART for FCPP. As described earlier, the option of substituting combustion modification 

techniques for SCR carries impacts as well. Our qualitative analysis suggests the impact of 

increased carbon in the fly ash resulting from combustion modification would be greater than the 

impacts from SCR. Based on the challenges associated with higher LOI from LNB and the 

higher ammonia slip rates from SNCR, we expect that the lowest negative impact to fly ash 

would be if SCR is installed at FCPP compared to LNB or SNCR. Although not related to any 

air pollution project, the impact of OSW’s proposed rule could result in a positive impact on the 

tribe’s fly ash operation. 
Attachment 1 

Salt River Pima-Maricopa Indian Community Comment Letter