February 29, 2012 

Memorandum to the North Dakota Regional Haze File 

Docket ID # EPA-R08-OAR-2010-0406 

Subject: Supporting Material for the North Dakota Regional Haze FIP Concerning 

Selective Non Catalytic Reduction (SNCR) and Ammonia Slip Mitigation 

for Lignite Fly Ash at Great River Energy’s (GRE) Coal Creek Station 

From: EC/R, Inc. 

Issue: The ability of SNCR systems to operate in an ammonia slip controlled condition. 

Summary: On February 21, 2012, Doug Grano of EC/R received an e-mail from 

Bill Cummings of Fuel Tech, Inc. concerning ammonia slip from SNCR systems. 

Mr. Cummings stated that all Fuel Tech SNCR systems are capable of operating 

in a slip controlled condition and that the ammonia on ash and subsequent balance 

of plant impact(s) are well understood.

Issue: The performance of SNCR on subcritical versus supercritical units.

Summary: On February 2, 2012, Dr. Jim Staudt of Andover Technology Partners 

provided EC/R with draft responses to GRE’s November 21, 2011 comments on 

the proposed FIP. In these draft responses, Dr. Staudt stated the following: 

“GRE claimed in their November 2011 comments that data on supercritical units 

does not provide an indication of SNCR performance at CCS because CCS does 

not have supercritical units. This is an incorrect statement that does not consider 

the key process variables of SNCR. Supercritical units typically operate at higher 

furnace temperatures than subcritical units. The higher furnace temperature 

makes NOx reduction with SNCR more difficult due to the competing urea 

oxidation reaction that causes NOx reduction to drop off at high temperatures. As 

a result, one would expect SNCR performance to generally be better at a 

subcritical unit than a supercritical unit – all other factors being equal.” 

Issue: Effectiveness of ammonia mitigation for lignite fly ash. 

Summary: Dr. Staudt provided information on the effectiveness of ammonia 

mitigation for lignite fly ash in the February 2, 2012 draft comment responses 

referenced above. Dr. Staudt referenced three tangentially fired units that use 

lignite coal and control NOx emissions to under 0.14 lb/MMBtu; Big Brown Unit 

1 and Monticello Units 1 and 2. Dr. Staudt stated that “According to The Fly Ash 

Resource Center, both the Big Brown Plant and the Monticello Plant market their 

fly ash through Boral Materials. The Monticello fly ash was an approved material 
by the Arizona Department of Transportation (July 2012 and Georgia Department 

of Transportation (January 2012). Clearly, this fly ash does not seem to be 

adversely impacted.” 

 

Recent information obtained by EC/R indicates that the Texas, Florida, and 

Louisiana Departments of Transportation (DOT) have approved Big Brown’s fly 

ash;1,2,3 however, EC/R could not verify that Arizona or Georgia DOT approved 

Big Brown’s fly ash. 

Dr. Staudt concluded that “The assumption that GRE has made, that the Coal 

Creek plant would be unable to market its fly ash while other tangentially-fired 

boilers that use lignite coal and are controlling to below 0.14 lb/MMBtu are 

capable of marketing fly ash, appears to be unjustified and overly conservative. 

While there is a possibility that some portion of the Coal Creek fly ash may not be 

marketable without additional treatment, to assume that a treatment method would 

not be effective at all is also an overly conservative assumption. For this reason 

GRE’s claim that a significant amount of fly ash would be unmarketable appears 

unreasonable.” 

 

1

ftp://ftp.dot.state.tx.us/pub/txdot-info/cmd/mpl/flyash.pdf 

2

ftp://ftp.dot.state.fl.us/fdot/smo/website/sources/cementsource.pdf

3

http://www.dotd.la.gov/highways/construction/lab/qpl/qpl%2050%20fly%20ash.pdf