11011 C ODY O VERLAND P ARK

, KS 66210

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

CURTIS D

. LESSLIE

, PE

V ICE P RESIDENT

, E NVIRONMENTAL A FFAIRS WRITER ’ S DIRECT LINE

– 913/319-6065



### A PRIL 

### 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 limes tone 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 fo r High Mercury Limestone Subcategory

Data from a spreadsheet provided by Keith Barne tt 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 wo rksheets were taken from that spreadsheet and all calculations were performed using that data. Days for wh ich 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 varian ce 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 th e 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 lim estone subcategory, regardless

of their emission rate. This results in a maxi mum controlled emission rate of 535.8 lb/MM ton feed (884 lb/MM ton clinker). The 85% control efficiency value was sel ected 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 k ilns in the high mercury limestone subcategory should be required to install the best known a dd-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 sp ecifications. By imposing these advanced control technologies, administrative controls and techni ques through beyond-the-floor requirements, the sources in the high mercury limestone subcategor y 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 requirement s 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 re ductions early. This would encourage more kiln owners to take immediate steps towards maki ng 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 th e standard when a standard does apply, to the

extent that total emissions for that source over th e 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 sour ce 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, anal ogous 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 hea lth 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 industr y being made sooner rather than later.

THC Subcategorization for Kilns with In-Line Coal Mills

As noted in Ash Grove’s September 2009 comme nts on the proposed rulemaking, Ash Grove data supports the need to subcategorize the TH C 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 oversi ght 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 propo sed 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 TH C across the coal mill. See th e summary table below. Note

### Mr. Peter Tsirigotis April 22, 2010 Page 3

that the coal mill inlet concentration is representa tive 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, th ere was a 5 fold increase in THC emissions (35 ppmv wet versus 150 ppmv wet) at the Chanute co al mill exhaust when the source of the coal changed (Oklahoma coal versus Colorado coal). Itshould be noted that the type (both are subbituminous) of the coal did not change, only the mine.

0 50 100 150 200 250 300 350 400 450RLT16:00:00tt12:00:00tt8:00:00tt4:00:00tt3/5/201020:00:00tt16:00:00tt12:00:00tt8:00:00tt4:00:00tt3/10/201020:00:00tt16:00:00tt12:00:00tt8:00:00tt4:00:00tt3/15/201020:00:00tt16:00:00tt12:00:00tt8:00:00tt4:00:00tt3/20/201020:00:00tt16:00:00tt12:00:00tt8:00:00tt4:00:00tt3/25/201020:00:00tt16:00:00tt12:00:00tt8:00:00tt4:00:00tt3/30/201020:00:00tt16:00:00tt12:00:00tt8:00:00tt4:00:00tt4/4/201020:00:00tt 

### 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, th e 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 a nd 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 signi ficant 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