11011 CODY

OVERLAND PARK, KS 66210 

PHONE 913 / 451-8900 FAX 913 /451-1686 

CURTIS D. LESSLIE, PE 

VICE PRESIDENT, ENVIRONMENTAL AFFAIRS WRITER’S DIRECT LINE – 913/319-6065 

APRIL 22, 2010 

VIA ELECTRONIC MAIL

Mr. Peter Tsirigotis 

Director, Sector Policies and Programs Division 

US EPA 

Research Triangle Park, NC, 27711 

Dear Peter: 

During our last meeting, you requested that Ash Grove provide you with a number for the floor 

and beyond the floor for the high mercury limestone subcategory composed of Ash Grove’s 

Durkee, OR kiln and Lehigh’s Tehachapi, CA kiln. Additional comments and data related to 

THC from in-line coal mills are also provided in the letter. 

Mercury Floor and Beyond the Floor for High Mercury Limestone Subcategory 

Data from a spreadsheet provided by Keith Barnett to Hector Ybanez on 2/25/2009 was used as 

the best available data representing daily mercury values for the 89 kilns for which EPA has data. 

The Durkee and Tehachapi kiln worksheets were taken from that spreadsheet and all calculations 

were performed using that data. Days for which there were no limestone mercury values were 

removed from the daily average value calculated for each kiln. 

The daily average for each kiln was computed and the daily average of the two kilns was 

determined to be 1,581 lb/MM ton raw feed. The square root of the sum of the squared standard 

deviations was used to compute the total variance for the two data sets. Since the data set 

involved was relatively small, the floor was computed by adding 3 times the total variance 

(663.58) to the average. The “floor” value for the high mercury limestone subcategory using this 

method results in 3,572 lb/MM ton raw feed (5,894 lb/MM ton clinker). 

Ash Grove believes that it is reasonable to then impose a minimum control efficiency of 85% as a 

beyond-the-floor requirement for all kilns in the high mercury limestone subcategory, regardless 

of their emission rate. This results in a maximum controlled emission rate of 535.8 lb/MM ton 

feed (884 lb/MM ton clinker). The 85% control efficiency value was selected based on the upper 

range of control shown from the Ash Grove Durkee pilot study, which is the highest level of 

control known to ever be demonstrated on a cement kiln. 
Mr. Peter Tsirigotis 

April 22, 2010 

Page 2 

As proposed previously by Ash Grove, all kilns in the high mercury limestone subcategory 

should be required to install the best known add-on controls, restrict off-site sources of raw 

materials with elevated mercury content, and to implement shuttling of main baghouse dust to the 

finish mill to the extent allowed by product specifications. By imposing these advanced control 

technologies, administrative controls and techniques through beyond-the-floor requirements, the 

sources in the high mercury limestone subcategory will achieve the highest level of control 

possible at all times, regardless of the emission rate specified in the rule. 

Early Reduction Credits 

In addition to the beyond-the-floor requirements noted above, EPA should encourage all kilns 

(not just those in the high mercury limestone subcategory) that would be required to make 

reductions under the new standards to take early action to reduce mercury emissions by providing 

incentives for doing so. One such incentive would be to offer sources more time to comply with 

the standard in exchange for making verified reductions early. This would encourage more kiln 

owners to take immediate steps towards making reductions even though there is no current 

federal requirement to do so. 

Sources that take these early actions should be allowed to use a portion of the early reduction 

credits toward demonstration of compliance with the standard when a standard does apply, to the 

extent that total emissions for that source over the long term are reduced. Early reduction credits 

should be applied only to a specific source; that is, they should not be traded among sources. 

Over the term of the allowed credit use, the source must demonstrate that there is an overall net 

reduction when the legal compliance deadline and emission rate are compared to the early 

implementation and extended compliance date. While the early emission reductions at Durkee 

will likely result in more than the equivalent of 25 years worth of emissions under the proposed 

limit of 43 lb/ MM ton clinker, Ash Grove would support an extended compliance deadline of up 

to 8 years from the final compliance date, analogous to the amount of time allowed under section 

112(j)(6). 

Regardless of actual final compliance deadline or emission limit imposed in the final rulemaking 

for existing sources, it is advantageous to health and environment for EPA to encourage early 

mercury reductions. Allowing credits for early reduction efforts would also likely result in 

technological advances in the cement industry being made sooner rather than later. 

THC Subcategorization for Kilns with In-Line Coal Mills 

As noted in Ash Grove’s September 2009 comments on the proposed rulemaking, Ash Grove 

data supports the need to subcategorize the THC standard to recognize the inherent difference 

between kilns that do and those that do not have in-line coal mills. First, in-line coal mills that 

utilize kiln gas and vent directly to atmosphere were not evaluated when EPA set the floor for 

kiln exhaust, so it appears to have been an oversight to simply impose the kiln standard on in-line 

coal mill exhaust. Ash Grove provided historical data with its original comments showing that 

THC from in-line coal mill stacks are substantially higher than 7 ppmv. The configurations were 

not properly accounted for in establishing the proposed standard. The data demonstrates that inline coal mills must be considered further as part of the final rule. 

Ash Grove has completed additional testing since our September 2009 comments, documenting 

as much as a 10 fold increase in THC across the coal mill. See the summary table below. Note 
Mr. Peter Tsirigotis 

April 22, 2010 

Page 3 

that the coal mill inlet concentration is representative of kiln exhaust gas concentrations at the 

main stack, since the coal mill inlet gas is a slip stream of the kiln exhaust. 

Plant Test Date(s)

Average Coal

Mill Inlet THC

(ppmv, Wet)

Average Coal

Mill Outlet

THC

(ppmv, Wet)

Average Coal Mill

Outlet THC

(ppmv, Dry @ 7% O2)

Chanute, KS Oct '09 ‐ Mar '10 4.68* 56.65 N/A

Durkee, OR Nov '09 ‐ Apr '10 N/A 336.4 N/A

Louisville, NE (Humbolt Kiln) March 28‐29, 2010 9.5 254 528.2

Leamington, UT March 18‐19, 2010 2.9 589 1368

Seattle, WA Dec 16‐17, 2009 30 60 122

*The Chanute by‐pass THC represents coal mill inlet concentrations, expressed at dry @ 7% O2

Furthermore, as illustrated in the graph below, there was a 5 fold increase in THC emissions (35 

ppmv wet versus 150 ppmv wet) at the Chanute coal mill exhaust when the source of the coal 

changed (Oklahoma coal versus Colorado coal). It should be noted that the type (both are subbituminous) of the coal did not change, only the mine. 

0

50

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RLT

16:00:00 tt12:00:00 tt

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3/5/2010

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3/10/2010

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3/15/2010

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3/20/2010

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3/25/2010

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3/30/2010

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4/4/2010

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Coal Mill Outlet DUCT THC (ppmv, uncorrected)

CMDUCT_THC Oklahoma Coal Versus Colorado Coal
Mr. Peter Tsirigotis 

April 22, 2010 

Page 4 

This is consistent with USGS data on various coal mines, concluding that methane emissions 

from coal mines varies dramatically with depth, age, and type of coal, among other factors. 

Clearly there is a basis upon which to subcategorize in-line coal mill THC emissions based on 

coal type and for kilns with combined stacks, the THC standard must account for the influence of 

the in-line coal mill. Kilns were configured this way for two reasons – 1) energy efficiency gains 

through recovery of waste heat from the process and 2) increased safety for coal mills operated at 

a low oxygen environment. To our knowledge, EPA has not yet considered the impact of in-line 

coal mills on the main stack and this is a significant shortcoming of the THC floor proposed on 

May 6, 2009. 

Thank you for your consideration of our additional comments on this rulemaking. Please let me 

know if you have any questions and to what extent you can utilize additional data beyond the 

summary data provided in this submittal. Please feel free to call me directly at (913) 319-6065. 

Sincerely, 

Curtis D. Lesslie, P.E. 

Vice President, Environmental Affairs 

Ash Grove Cement Company 

C Keith Barnett