www.AndoverTechnology.com 1

August 2, 2012

To: Doug Grano

Fm: Jim Staudt

Re: Response to Comments Regarding Ash Grove Cement and Holcim Cement Kilns

Responses to Ash Grove Cement Comments

Ash Grove Comment: Ash Grove stated that they did not object to EPA’s conclusion that BART should be 

based in the installation of LNB and SNCR. However, the company stated that they objected to the 

assumptions made about what SNCR can achieve. Ash Grove stated that they explained in the prior 

correspondence that the company did not believe that it is appropriate to assume that the Montana City 

kiln can achieve 50% control effectiveness. Ash Grove stated that as the data in Table 10 of the 

preamble clearly showed, only one of the three kilns at Ash Grove’s Midlothian plant is able to achieve 

50% control effectiveness. The other two kilns had an average control efficiency of 37.7% and 40.5% and

Ash Grove stated that no other credible evidence is provided for EPA’s conclusion as to SNCR NOx control 

efficiency. Ash Grove stated that EPA referenced studies from other industry sectors and a marketing 

brochure from Cadence stating that “control efficiency of up to 50% can be achieved on long wet kilns” 

and that this quote states the upper end of what might be achievable. Ash Grove stated that it does not 

state that 50% control efficiency can be achieved on all long wet kilns and that Cadence’s experience 

with SNCR on long wet kilns is what is shown in Table 10 as it was Ash Gove’s partner in developing the 

Midlothian SNCR – the only wet kilns in the United States with any track record of SNCR use. Ash Grove 

stated that even after years of optimization on the Midlothian kilns, the data show that it has not been 

possible to bring all three kilns up to a 50% control efficiency and that the Midlothian NOX reduction data 

reflect not only the benefits of SNCR, but also the mid-kiln firing of tires, use of a mid-kiln fan and other 

technologies that are not available to the Montana City kiln, but that were implemented concurrent with 

the SNCR installation/optimization at Midlothian to reduce NOx emissions. Ash Grove explained that in 

considering the Midlothian data, one needs to account for the direct control efficiency these technologies 

provide, in addition to the synergistic effects of using more than one control device/technique at a time 

at Midlothian and that these benefits would not be available at Montana City and should not be 

assumed. 

Ash grove summarized that they continued to believe that a SNCR system at Montana City cannot be 

assumed to reach greater than 35% control efficiency and that EPA has produced no credible evidence in 

the record for supporting a different conclusion. Ash Grove stated that they recognized that their initial 

BART submittal listed 50% control as achievable for the combination of a low NOx burner and SNCR at 

the Montana City kiln but now believe they cannot get to that level on all three kilns at Midlothian. Ash 

Grove stated that they are willing to not contest the 8.0 lb/ton clinker limit, and they anticipate that 

compliance could require additional control technologies/strategies; therefore, they need the maximum 

time allowable to find ways to consistently maintain NOx at or below that level. 
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Response: 

For the reasons described below, I disagree that SNCR cannot achieve a 50% control effectiveness at Ash 

Grove’s Montana City kiln. The data in Table 10 of the proposed FIP, 77 FR 24003, show the control 

effectiveness that was achieved with SNCR on Ash Grove’s three Midlothian, TX kilns (shown in Figure 1

below), but it was not intended to imply that this is the upper bound of what might be achieved. From 

Figure 1 it appears that these kilns are virtually identical in design, and one might expect that they 

would have similar performance. Ash Grove did not submit any information explaining why these three 

kilns, of apparently the same design, have significantly different performance when using SNCR for NOx 

control. SNCR was used at the three Midlothian kilns to comply with the emission limit established at 

Texas Administrative Code (TAC) 117.3110 (a)(1)(B) of 4.0 lb/ton clinker. TAC 117.3110(b) allowed an 

owner or operator of a long wet kiln to comply with the 4.0 lbs/ton clinker emission limit on the basis of 

a weighted average for multiple cement kilns. Thus, it is not necessary for each individual kiln to achieve 

the maximum percentage reduction possible but only for the three to average an emission rate below 

the limit of 4.0 lbs/ton clinker. 

Figure 1. Ash Grove’s Midlothian, TX Kilns

The data from Table 10 of the proposed FIP is reproduced in Table 1 below along with additional 

statistics. Table 1 shows the data of Table 10 of the proposed FIP with kiln capacity and date in service 

and calculated standard deviation of the three kiln NOxlevels over the period and the coefficient of 

variation (COV = standard deviation divided by the mean or average). Figure 2 graphically depicts the 

data. The three kilns are apparently of similar design (all the same capacity of 291 TPY), were built

within six years of one another, utilize the same raw materials, and they have very similar uncontrolled 

emissions. From Figure 1, the kilns appear to be virtually identical in design. As a result, it is expected 

that all three kilns should be capable of similar performance in any given period, and this is confirmed by 
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the very similar NOx emissions for each of the kilns exhibited in any given month in 2006. As shown, the 

COV was about 5% on average in 2006 and was at about 10% or below for each of the three months in 

2006. Kiln 1 was generally the highest NOx emitter during the 2006 period, but in the same range as the 

other two kilns (as confirmed by the low COV during this period). However, the COV for the same three 

months in 2008 was over 20% on average (almost 4 times the COV for the same period in 2006) and 12% 

in the month with the lowest COV (see COV data in red). This difference demonstrates that the kilns, 

which appear to be of similar design and operated at a similar NOx emission rate in 2006, were clearly 

operated at very different NOx rates in 2008. For the three month period in 2008, kilns 2 and 3 have 

nearly identical NOx emissions rates. Therefore, higher COV in 2008 was almost entirely due to the fact 

that Kiln 1 was consistently operated at a much lower NOxlevel than the other two kilns, which is 

unexpected if the kilns are all of the same or similar design and were being operated in the same way 

with respect to NOx control. Because SNCR is a “dial up” technology in the sense that additional reagent 

will provide additional NOx reduction and one would expect similar NOxlevels in 2008 if the three kiln 

SNCR systems were being operated in the same way, it appears that kiln 1’s SNCR system was not being 

operated in the same manner as kilns 2 & 3 during the 2008 period. This seems to indicate that kilns 2 

and 3 were capable of greater NOx reductions than were being realized during the 2008 period, at least 

comparable to the NOx reductions achieved on kiln 1.

Table 1. NOx Emission Rate Data from Ash Grove Midlothian Kilns, lb/ton clinker

In service

2006 2008

Kiln

TPY June July Aug. Avg. Std. 

Dev COV June July Aug. Avg. Std. Dev COV

1 291 1966 5.2 5 4.5 4.9 0.36 7.36% 1.7 1.6 2.2 1.8 0.32 17.9%

2 291 1969 5 4.1 3.9 4.4 0.59 13.3% 2.7 2.6 2.8 2.7 0.10 3.70%

3 291 1972 5 4.4 4.2 4.5 0.42 9.25% 2.9 2.6 2.5 2.7 0.21 7.71%

Average 5.07 4.50 4.20 4.60 0.44 9.57% 2.43 2.27 2.50 2.40 0.12 5.01%

Standard Deviation 0.12 0.46 0.30 0.26 -- 0.64 0.58 0.30 0.52 --

Coefficient of Variation 

(COV) 2.28% 10.18% 7.14% 5.75% -- 26.4% 25.5% 12.0% 21.7% --

TPY and In Service from 2006 US and Canadian Portland Cement Industry: Plant Survey, Portland Cement 

Association

Figure 2. NOx Emission Rates from Ash Grove Midlothian Kilns

0

1

2

3

4

5

6

June July Aug

Emission Rate, lb/ton clinker

kiln 1, 2006

kiln 2, 2006

kiln 3, 2006

kiln 1, 2008

kiln 2, 2008

kiln 3, 2008

kiln Average, 2006

kiln Average, 2008
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As a technology with the ability to respond to changes in NOxlevels, SNCR has the potential to reduce 

NOx emission variability of the kiln. The ability of the SNCR system to reduce variability in emissions is 

shown in the column that shows standard deviation of the monthly data for each kiln in 2006 and in 

2008. As shown, in every case the standard deviation dropped. The month to month variability of each 

kiln’s NOx emissions (as indicated in the COV data in blue) dropped significantly for kilns 2 and 3, and the 

overall month-to-month variability of NOx emissions for all three kilns dropped. This demonstrates that 

SNCR can be used to reduce variability in emission rates as well as reducing them overall.

On the other hand, Ash Grove has not submitted any data to demonstrate that SNCR was optimized in 

an attempt to achieve the lowest emissions possible, and the data in Table 1 appears to confirm that at 

least kilns 2 and 3 were not optimized to achieve the lowest emissions. 

The emissions rate data for the Midlothian kilns from June – August in the years 2006 through 2010 

where available is shown in Figure 3. The 2009 and 2010 emission rates are significantly higher than the 

emission rates from June to August 2008 (an average of 1.8 lbs/ton clinker for kiln 1, 2.7 lbs/ton clinker 

for kiln 2, and 2.7 lbs/ton clinker for kiln 3). An increase in NOx emissions over time would not be 

expected if the SNCR were being operated in an optimized fashion, and if changes in feed properties 

were the explanation, I would expect the same trends for all kilns, but that is not the case. As shown in 

Figure 3, for all years where there is data, kiln 2 and kiln 3 have similar emission rates. And, in 2006, 

before applying SNCR all three kilns have similar emission rates. However in 2009 and 2010 the trends 

in kilns 1 and 2 differ, with kiln 2 having a the same steady NOx emission rate in both years and kiln 1 

having a much lower rate in 2010 than in 2009. The trends in Figure 3 indicate that the SNCR systems of 

the three similar (if not virtually identical) kilns were being operated in very different ways, and 

therefore they could not all be optimized.

Figure 3. June-Aug Midlothian kiln NOx Emission Rate Data 2006-2010.

With regard to Ash Grove’s claim that EPA should account for the direct control efficiency of other 

technologies that are not available to the Montana City Kiln, the tire-derived fuel system was already 

being used at Midlothian in 2006 and is already accounted for in the 2006 baseline to which the 2008 

0.00

1.00

2.00

3.00

4.00

5.00

6.00

2005 2006 2007 2008 2009 2010 2011

Emission Rate, lb/ton clinker

kiln 1

kiln 2

kiln 3

note: data not available for kiln 3 in 2009 due to shut down
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post-SNCR emissions are compared.1 Thus, no further adjustment is necessary. Ash Grove has not 

provided data to demonstrate that a synergistic effect has occurred between mid-kiln firing of tires and 

SNCR at Midlothian. 

Ash Grove has not submitted data to support their claim that only 35% reduction can be achieved with 

SNCR at the Montana City kiln. All of the Midlothian kilns were able to achieve greater than 35% 

reduction with SNCR and there is no information to demonstrate that SNCR was optimized to its 

maximum potential. The BART Guidelines state, " In assessing the capability of the control alternative, 

latitude exists to consider special circumstances pertinent to the specific source under review, or 

regarding the prior application of the control alternative. However, you should explain the basis for 

choosing the alternate level (or range) of control in the BART analysis. Without a showing of differences 

between the source and other sources that have achieved more stringent emissions limits, you should 

conclude that the level being achieved by those other sources is representative of the achievable level 

for the source being analyzed." 70 FR 39166. Ash Grove has not demonstrated the differences between 

their Montana City kiln and the Midlothian kilns.

With regard to Ash Grove’s statement that EPA did not produce credible evidence in the record for 

supporting a greater than 35% control effectiveness for SNCR, EPA provided a detailed explanation in 

their proposed FIP at 77 FR 24003. Ash Grove has used SNCR at its Midlothian kilns where it was shown 

to achieve the reductions ranging from 37.7% to 62.5% and these are within the range of control 

effectiveness demonstrated at other kilns. As described earlier, similar performance would be expected 

for each of the three Midlothian kilns if the SNCR systems were being operated in a similar manner and 

because the kilns could average under their permit, it was not necessary to control all kilns to the same 

degree. So, it appears that the higher NOx reduction is a better representation of what the SNCR system 

is capable of for the Midlothian kilns. Moreover, considering that control effectiveness (in terms of 

percent reduction) is greater when initial NOx concentrations are greater, and that the baseline NOx

emissions of the Montana City kiln are significantly greater than the Midlothian kilns, the Montana City 

kiln would be expected to achieve even greater control effectiveness when compared to the Midlothian 

kilns. 77 FR 24003 and 77 FR 24004. 

Ash Grove’s comment that they are willing to not contest the 8.0 lb/ton clinker limit is noted. With 

regard to Ash Grove’s comment that they anticipate that compliance could require additional control 

technologies/strategies and, therefore, they need the maximum time allowable to find ways to 

consistently maintain NOx at or below that level, I disagree that additional control 

technologies/strategies are necessary. The final FIP does not require specific control 

technologies/strategies to be used. The final FIP allows for the maximum time available to comply with 

the 8.0 lb/ton clinker limit. 

 

1 Letter from Molly Cagle to Chance Goodwin, Initial Control Strategy Development for DFW Ozone 

Nonattainment Area, July 30, 2010, p. 1.
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Responses to Holcim Cement Comments

Holcim Comment A.1.a : An SNCR system at Trident will not be as effective as EPA assumed.

Holcim argues that the Texas kilns cited by EPA in the FIP are not representative and two of the three 

kilns did not achieve 50% NOx reduction. Holcim cites several site-specific factors that impact SNCR 

performance that they state that EPA did not adequately consider, including turbulent mixing, heat 

transfer, spray droplet size, spray drop evaporation, devolatilization and others. Holcim also argues that 

the CO levels at the Trident kiln are much lower than the CO levels at the Texas kilns, which they argue 

will adversely impact NOx reductions and ammonia slip at the Trident kiln relative to the Texas kilns. 

Holcim additionally argued that EPA did not adequately consider NOx emissions variability in setting the 

limit because of the limited time frame considered for the data from the Texas kilns.

Response:

EPA has assumed that 50% reduction is possible with SNCR; however, this does not rule out the 

possibility that Holcim may determine that other means may be better than SNCR alone in terms of cost 

or other factors for achieving 50% NOx reduction. For example, Holcim may determine that 50% 

reduction is more effectively achieved through combination of SNCR with another technology. In any 

event, 50% NOx reduction is achievable with SNCR and this is supported by the data cited in the 

proposed FIP. See response to comments from Ash Grove Cement for more on this.

In the proposed FIP EPA also assumed that a combination of SNCR with LNB would provide 58% 

reduction (50% from SNCR and 15% from LNB, which is reasonable because LNB with indirect firing has 

been shown to provide greater than 15% NOx reduction on average.

2

) Although LNB and SNCR is a 

viable approach that should provide NOx reductions in the range EPA assumed and at a cost similar to 

what they assumed in the proposed FIP, it may be possible that Holcim determines that other 

approaches used in combination with SNCR will be less expensive overall than indirect firing with LNB. 

For example, in the proposed FIP EPA ruled out Mid Kiln Firing (MKF) because it was uncertain if tires 

could in fact be burned in the kiln due to Montana permit requirements; however, this would not 

preclude MKF of coal or pet coke rather than tires, which would provide the same NOx reduction (30%), 

albeit, without the benefit of the revenue realized from burning tires. If MKF provides greater NOx

reduction than indirect firing, there would be an offsetting benefit in the form of a reduction of SNCR 

reagent costs.

With regard to Holcim’s specific comments, Holcim also noted that SNCR performance depends upon a 

wide range of site-specific factors. They list rate-limiting processes, including turbulent mixing, heat 

transfer, spray droplet size, spray drop evaporation, devolatilization and others.

 Spray droplet size is clearly related to evaporation rate and reagent devolaltilization. Spray droplet 

size is something that the SNCR system designer can control and tailor to the needs of the system.

 

2

NOX Control Technologies for the Cement Industry, FINAL REPORT, EPA Contract No. 68-D98-026, Work 

Assignment No. 2-28, EC/R Project No. ISD-228, September 19, 2000 at p. 7
www.AndoverTechnology.com 7

 Turbulent mixing may or may not be within the SNCR system designer’s ability to impact. For 

example, it may be possible to utilize something like Cadence Recycling Mixing Air technology3to 

improve turbulent mixing for the SNCR system.

Increased turbulence improves mass transfer (contacting the ammonia with the NOx), which will reduce 

mass transfer limitations on the chemical reaction. SNCR can be limited from the chemical kinetic 

perspective also, as described in detail by Muzio and others.

4

 This effect is illustrated in Figure 4 that 

shows the calculated effect of temperature and residence time on the controlled NOxlevel for ammonia

SNCR. As shown, NOx reduction seems to be best within a temperature window of about 1600-1950°F 

for ammonia SNCR, but reaction time at that temperature plays a role as well, especially at the lower 

end of the temperature range. At the lower end of the temperature range, reaction time makes a large 

difference in the outlet NOx achieved. For urea SNCR similar results would be observed, but at a higher

temperature range than for ammonia. Therefore, more reaction time is advantageous for SNCR as is 

more turbulence.

Figure 4. Effect of Reaction Temperature and Reaction Time on NOx Reduction for Ammonia SNCR4

The concentration of carbon monoxide (CO) is another factor raised in Holcim’s comments. As Holcim 

notes, CO tends to cause the SNCR reaction to behave in a manner as if the temperature was higher –

allowing urea or ammonia injection at a lower temperature than otherwise possible because the CO will 

mitigate ammonia slip. This effect is shown in Figure 5. As shown, without CO present, NOx reduction is 

best with an initial temperature around 1000°C and with 1000 ppm of CO present, NOx reduction is best 

 

3

Cadence Recycling Web site: http://www.cadencerecycling.com/mixingtechnology.html

4 Muzio, L., Montgomery, T., Quartucy, G., Teixeira, D., “The Effect of Residence Time on SNCR Processes”, 1993 

Joint Symposium on Stationary Combustion NOx Control, Miami, FL, May 1993.
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with a starting temperature around 850°C. Holcim argues that the difference in CO emissions between 

one kiln and another will impact how performance at one kiln may be related to another. However, if 

the CO at the Trident kiln is much lower than at the Texas kilns referred to in the comments, as Holcim 

describes, this simply means that the SNCR reagent should be introduced at a point in the process where 

the gas temperature is higher than the injection point used at the Texas kilns where the CO levels are 

higher. This would mean injecting the reagent farther upstream in the process (from a gas-flow 

perspective rather than solids perspective) at the Trident kilns than the location used at the Texas kilns 

referred to in the comments, which is also advantageous from a NOx reduction and ammonia slip 

perspective because it enables the reaction to occur over a longer period of time in the kiln. And, as 

demonstrated in Figure 5, there is no disadvantage in terms of NOx reduction performance by injecting 

at a higher temperature and lower CO level. Therefore, with regard to the impact of lower CO levels in 

the Trident kilns, these may in fact improve (and certainly will not harm) performance relative to

facilities with higher CO emissions because greater reaction time is likely to be possible as the injection 

point is moved farther upstream in the kiln gas flow.

Figure 5. Effect of CO on NOx Reduction using SNCR 5

NOx emission variability is another factor raised by Holcim in their comments. First, the data used by 

EPA in Table 10 of the proposed FIP covers a three month period which should be adequate time to 

address normal operating changes that would impact NOx. Second, SNCR can be used to mitigate 

variability in NOx emissions. If NOx emissions change over time due to operating changes, the percent 

 

5

Horton, J., Linero, A., Miller, F., “USE OF SNCR TO CONTROL EMISSIONS OF OXIDES OF NITROGEN FROM CEMENT 

PLANTS”, 1-4244-0372-3/06/ (c)2006 IEEE
www.AndoverTechnology.com 9

reduction that is possible will also change because of the well-established fact that NOx reductions from 

SNCR are generally higher from higher NOx baselines. The effect of temperature and baseline NOxlevel 

on percent NOx reduction is shown in Figure 6 for urea SNCR. For ammonia SNCR a similar trend would 

be observed except at lower temperature levels. Because of the phenomenon shown in Figure 6, 

higher NOxlevels will typically permit greater levels of NOx reduction so that similar emission rates may 

be achievable. Therefore although baseline NOx emissions may vary, with SNCR it is possible to respond 

to the variability in NOx emissions by variation of treatment rate. This is confirmed by the data on the 

Midlothian kilns that is in the proposed FIP and as described in Response to Comments from Ash Grove 

Cement. For every kiln, the standard deviation in the monthly NOx emission rate was lower after the 

application of SNCR than before, indicating a lower variation in NOx emissions.

Figure 6. Effect of Baseline NOx on Percent Reduction Using Urea SNCR6

Holcim Comment A.1.b: An SNCR system cannot be operated year-round at Trident

Holcim argues that a detached plume may result from operation of the SNCR in the winter months, which 

will make it necessary to not operate the SNCR system or to allow a condition where visibility is adversely 

impacted to continue. The detached plume could be the result of the formation of ammonium salt 

reactions with sulfate or chlorides.

 

6

Hofmann, J., Sun, W., “Process for Nitrogen Oxides Reduction to Lowest Achievable Level”, US Patent 5,229,090, 

July 20, 1993.
www.AndoverTechnology.com 10

Response:

As discussed by Miller, 7there are several factors that contribute to visible detached plume, and these 

include moisture, temperature, and availability of the constituents that contribute to the plume –

ammonia, sulfates and chlorides. Ammonia slip from the SNCR process can be well controlled in a 

cement kiln, while ammonia contributed by raw materials probably cannot be well controlled and would 

not be affected by the SNCR system.

Sulfates and chlorides are largely the result of impurities in the raw materials, and ammonia can be 

contributed by raw materials. Holcim’s SO2 emission rate, which is sufficiently low that additional 

controls are not needed for BART, indicates low levels of sulfates in the exhaust. Therefore, the risk of 

an ammonium sulfate plume, even with ammonia present, is small. The presence of chorides will 

depend upon the raw materials and whether the chlorides become bound to alkaline material before 

being emitted up the stack.

Chlorides, if present, will typically preferentially be bound to alkaline material that is present than be 

emitted. Holcim did not provide any information on stack chloride emission levels at this site to support 

their concerns about detached plume from ammonium chloride.

Because of the importance of impurities in the raw materials in contributing to the chemical 

constituents that form a plume, the experience at one kiln cannot be directly applied to another without 

more information. Therefore, while there may be a risk of a plume at the Trident kiln, Holcim has not 

provided enough data to indicate that addition of an SNCR system would increase this risk significantly.

Holcim Comment A.2: EPA failed to consider the NOx control technology already installed at Trident. 

EPA did not properly consider the technology installed at the kiln, which includes a new multichannel 

burner and indirect firing of Pet coke (not indirect firing of other fuels), which resulted in a 13% NOx

reduction. Holcim believes that indirect firing for other fuels will not provide a NOx benefit and that 

EPA’s analysis did not properly take into account the reductions from the burner change in developing its 

proposed NOxlimit. In the proposed FIP, EPA assumed 15% NOx reduction from LNBs and indirect firing 

would achieve a 15% NOx reduction, but Holcim’s Trident kiln already achieves 13% reduction, which 

indicates that additional reductions can only be achieved through SNCR, and EPA’s analysis is therefore 

erroneous and should be disregarded.

Response:

As the June 9, 2009 letter from Mr. Greg Gannon of Holcim to US EPA Region 8 notes, “a low NOx burner 

modification would require low primary air and, thus, a conversion of Trident’s firing system from a 

direct to an indirect system. This modification would require several changes including but not limited 

to installation of a baghouse, additional explosion prevention, pulverized coal storage and dosing 

equipment in addition to the low NOx burner”. The Trident kiln has not installed an indirect firing 

system for coal, and therefore does not meet the definition in Mr. Gannon’s letter. As a result, the 

burner is not capable of operating at low primary air levels on pulverized coal and cannot achieve the 

 

7

. Miller, F. M., “Management of Detached Plumes in Cement Plants”’ 2001 IEEE-IAWPCA Cement Industry 

Technical Conference Vancouver, British Colombia, Canada April 2001
www.AndoverTechnology.com 11

NOx reductions that an indirect firing system would achieve. For this reason there is no reason for EPA 

to assume that the NOx reductions associated with a low NOx burner modification, as described in the 

June 9, 2009 letter, have been achieved. Moreover, data from the March 2, 2012 letter from John Goetz 

to Vanessa Hinkle does not support a 13% reduction in NOx emission rate from the burner that was 

installed.

In the proposed FIP, EPA did assume 15% NOx reduction from LNB and indirect firing; however, this was 

a conservative assumption used for the purpose of estimating cost effectiveness. LNB with indirect 

firing was found to provide an average emission reduction of 27% (a range of 4%-47%) from an average 

emission rate of 9 lb/ton of clinker.8 Even if the Trident kiln had achieved 13% NOx reduction from the 

burner changes they have made (and EPA does not see support for this claimed reduction in Holcim’s 

NOx emission rate), there is good reason to believe that an indirect firing system would provide 

significant additional NOx reduction due to the ability to reduce primary air levels.

Holcim Comment A.3.a: EPA underestimated the costs of installing and maintaining an SNCR system. 

Holcim estimated the direct annual cost of commercial SNCR to be $443,341 and the indirect annual 

costs for commercial SNCR to be $227,538 for a total of $670,879, while EPA estimated a total annual 

cost of $271,216 in the proposed FIP, despite the fact that EPA cited Holcim’s earlier estimate. It is 

unclear how EPA derived its cost estimate and Holcim requests clarification. EPA also used a 20-year 

amortization schedule rather than 15-year as used by Holcim. Holcim also believes that if SCR is required 

in subsequent reasonable progress planning periods, the 20-year amortization period would not 

accurately represent the cost of the SNCR system. Also, Holcim’s recently installed SNCR system at its 

Hagerstown, MD kiln cost $1,920,000 installed and operating costs have been in the range of $1.40 per 

metric ton of clinker.

Response:

EPA has revised its estimate for the cost of SNCR and has determined that the total annualized costs 

would be $650,399 resulting in an average cost effectiveness of $1,170/ton. These are very consistent 

with Holcim’s estimated costs for SNCR. If Holcim’s costs are used for SNCR ($670,879 per year) then 

the cost effectiveness of the NOx reduction (556 tons per Table 39 of the proposed FIP) is $1206/ton, 

which is well within the estimated cost effectiveness values for other BART sources affected by the 

proposed FIP. For SNCR - EPA relied on capital and annual cost from Holcim except that EPA used a CRF 

corresponding to 7% and 20 years (0.0944). (77 FR 24015). 

Regarding Holcim’s information on the costs of SNCR at Holcim’s Hagerstown, MD kiln, Holcim’s 

Hagerstown, MD kiln is much larger than the Trident kiln. The Trident kiln is permitted at 425,000 tons 

per year of clinker production. (Montana Air Quality Permit #0982-11, Condition II.B.6). The Hagerstown 

kiln is rated at 630,114 tons per year of clinker production capacity (PSD Permit Application For 

Approval, Holcim Hagerstown, October 30, 2008). Also, the Hagerstown kiln – a dry kiln - likely has 

different emission rates than the Trident kiln. Also, without more information it is not possible to 

 

8

NOX Control Technologies for the Cement Industry, FINAL REPORT, EPA Contract No. 68-D98-026, Work 

Assignment No. 2-28, EC/R Project No. ISD-228, September 19, 2000 at p. 7
www.AndoverTechnology.com 12

determine how much of the claimed $1,920,000 capital cost of the Hagerstown kiln SNCR system would 

be costs that are permissible for inclusion in a BART cost estimate. For these reasons without more 

information the costs of the SNCR system at the Hagerstown kiln are not useful for estimating the costs 

at the Trident kiln.

Holcim Comment A.3.b.: EPA failed to give proper weight to the costs of installing indirect firing and 

ignored the lack of visibility benefits.

Holcim believes that EPA underestimated the costs of indirect firing at the Trident kiln and used a lower 

cost than used in Holcim’s estimate.9 However, even using EPA’s estimate of cost and an assumption of 

15% NOx reduction, the incremental cost effectiveness is such that it does not warrant a determination 

as BART. Because the majority of emission reduction would result from SNCR, the average cost of NOx 

reductions from the combination of indirect firing and SNCR are much lower than the incremental cost 

effectiveness of the indirect firing alone and make the combination seem reasonable. EPA’s estimate of 

$4279/ton for the incremental cost of indirect firing is outside the range of what EPA has considered to 

be reasonable for BART and EPA’s estimate of the incremental cost effectiveness of LNB+SNCR at $8,029 

is well outside the range that EPA has considered reasonable under BART.

As a result of the high incremental cost of indirect firing plus SNCR over the cost of SNCR alone and the 

low NOx reduction from indirect firing which offers only 0.125 deciview improvement at the Gate of the 

Mountains Wilderness Area (proposed FIP at 24017), it is unreasonable for EPA to require indirect firing. 

A 58% reduction in NOx would result in only 0.424 deciview improvement in visibility at Gate of the 

Mountains Wilderness Area (proposed FIP at 24017), which is below the 0.50 threshold for a perceptible 

change in visibility 70 Fed. Reg. at 39119-20, n. 28, but the Agency uses the deciview metric precisely 

because a change of 1 deciview is generally the limit of human perceptibility. See 64 Fed. Reg. 35714, 

35725 (July 1, 1999) (“A one deciview change in haziness is a small but noticeable change in haziness 

under most circumstances when viewing scenes in Class I areas.”). Given that, it would be unreasonable 

to require Trident to install indirect firing as it would result in no perceptible improvement in visibility.

Response:

For LNB - EPA relied on capital cost and annual cost from Holcim except that EPA used a CRF 

corresponding to 7% and 20 years (0.0944) and EPA used a retrofit factor of 1 instead of 1.5 for the 

indirect installation costs. (77 FR 24014). The effect of this was to reduce the capital cost from 

$4,958,209 to $4,385,307 and to reduce the annualized cost from $846,061 to $714,629. This results in 

a 12% reduction in estimated capital cost and a 16% reduction in annualized cost. The cost effectiveness 

value is also impacted by the assumed level of NOx reduction. Although EPA assumed 15% reduction in 

the proposed FIP, EPA believes that higher levels of NOx reduction are likely from addition of indirect 

firing with an LNB. Some sources showed an average emission reduction of 27%, nearly double that 

assumed in the proposed FIP.10 This would reduce the incremental cost effectiveness of NOx 

reductions from an indirect firing conversion roughly in half. It would also increase the visibility 

improvement. Therefore, there is the likelihood that the visibility improvement cited in the FIP that is 

attributable to LNB (with indirect firing) is low and that the cost effectiveness value is high.

 

9

June 9, 2009 letter from Mr. Greg Gannon of Holcim to US EPA Region 8

10 NOX Control Technologies for the Cement Industry, FINAL REPORT, EPA Contract No. 68-D98-026, Work 

Assignment No. 2-28, EC/R Project No. ISD-228, September 19, 2000 at p. 7