Vinson&Elkins
 

Molly Cagle mcagle@vclaw.con1 

Tel 512.542.8552 Fax 512.236.3280 

Via Regular and Electronic Mail 

Chance Goodin 

Texas Commission on Environmental Quality 

12100 Park 35 Circle 

MC-206 

Austin Texas 78753 

C~( lodin«f:tceq.slak.lx. us 

Re: Initial Control Strategy Development for DFW Ozone Nonattainment Area 

Dear Mr. Goodin: 

We are writing on behalf of Ash Grove Texas, L.P., which appreciates TCEQ's 

interest in gathering infonnation as early as possible in its next round of air quality planning 

for the DFW ozone nonattainment area. Ash Grove operates one of three cement 

manufacturing plants in Midlothian, Ellis County, which is located within the designated 

DFW nonattainment area. Ash Grove's kilns use the wet process, the others use dry. We are 

submitting these informal comments in the interest of reminding TCEQ about Ash Grove's 

history of controlling its NOx emissions, and to provide current information about NOx 

control options for cement plants generally. Those seeking purportedly easy solutions for 

DFW's ozone nonattainment often tout yet further controls on Ash Grove's kilns, but such 

controls are neither easy nor solutions. 

I. Ash Grove History 

Ash Grove's Midlothian Plant has a proven history of reducing NOx emISSIOns. 

From 1996 (a year before EPA promulgated the current 0.08 ppm ozone standard) until 2006, 

the Plant reduced its annual NOx emissions by around 45%. These emission reductions 

occurred as a result of methodical and judicious implementation of various technologies, 

such as optimized computer controls for the kilns, improvements to kiln burners, and 

installation of one of the most successful tire-derived fuel systems in the country. The use of 

tire-derived fuel, injected mid-kiln, not only reduces NOx emissions generated at the burning 

zone of the kiln, but safely eliminates millions of scrap tires that otherwise might end up in 

Texas landfills and illegal dumpsites. 

But Ash Grove's NOx reductions did not end in 2006. In 2007, after substantial 

investigation of the French cement plant that pioneered the first use of Selective Noncatalytic Reduction (SNCR) on wet-process cement kilns, Ash Grove purchased and installed 

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\/&£	 Chance Goodin July 30, 2010 Page 2 

an SNCR system on its three Midlothian kilns. Ash Grove started operating this SNCR 

system-the first ever pm a wet cement kiln in the U.S.--during the 2008 ozone season, one 

full year before it was required under the 2007 SIP. SNCR operation has resulted in an 

additional 35% reduction in NOx emissions, on top of the roughly 45% reduction achieved 

from the other control measures already discussed. 

As a result of Ash Grove's efforts, the Midlothian Plant is among the best-controlled 

cement plants in Texas, measured in amount of NOx emissions per ton of cement produced: 

Only 3 of 21 operating kilns in Texas did any better in 2008. Ash Grove was the first in the 

U.S. and now is among the very few wet process kilns in the world to successfully run 

SNCR. As compared to the experience of those who have experimented with Selective 

Catalytic Reduction (SCR) technology, it is clear that Ash Grove made the right choice. 

II. SNCR Is the Best Available NOx Control Technology for Cement Kilns 

Ash Grove did not install SNCR on all three of its kilns without carefully evaluating 

all options available to reduce NOx emissions. In 2006, Ash Grove representatives visited 

the cement plants in Europe that pioneered each of the two competing technology options 

under consideration, SCR at the Solnhofen Plant in Germany and SNCR at the Lumbres 

Plant in France. As a result of these visits and after carefully evaluating the technical 

challenges, costs, and expected results associated with each technology option for its 

Midlothian Plant, Ash Grove concluded that SNCR was the best option, for several reasons: 

•	 Catalyst Degradation is a Major Problem for Cement Kiln Application of SCR. 

SNCR does not rely on a catalyst to reduce NOx emissions, so there is no degradation 

of reduction efficiency over time. Ash Grove observed this degradation during its 

site visit to the Solnhofen Plant, and the problem has persisted to the point that 

Solnhofen instead has been operating an SNCR system instead of SCR since 2006. 

The SCR system operated only for very short periods, and required extensive offline 

repairs and replenishment. As a result, the highest rate of compliance with the 

applicable NOx limit jumped from 90.8 percent in 2005 using SCR, to 96.4 percent in 

2006, when the plant switched to using SNCR. 

•	 Catalytic Systems Generate Unintended Emission Consequences. For SCR to 

work at the Midlothian Plant, the gas leaving the kiln would need to be reheated from 

its current exhaust temperature of around 350 OF, to the catalysis temperature of 

around 650 OF. It is not possible to increase the temperature of the exhaust gases 

from the kiln by several hundred degrees by choosing to run the kiln hotter, at least 

without severely affecting the operational performance of the kiln. Accordingly, any 
V&£ Chance GoOdin July 30, 2010 Page 3 

SCR installation also would require a reheat system, with its attendant fuel costs and 

higher emissions. 

The catalyst used in all SCR systems also contributes to the production of sulfuric 

acid gas, at least if there is S02 gases present in the kiln exhaust stream. The 

expected increase in sulfuric acid production would require the installation of a 

scrubber system at a significant capital and operating cost. 

• Capital Costs of SNCR are Substantially Lower. An SNCR system does not need 

a catalyst or a catalyst tower. The SNCR reagent used at Ash Grove (water-based 

solutions of ammonia or urea) is pumped into a point in the kiln where the 

temperature of the gases already is hot enough to allow NOx reductions to occur 

without affecting the process. The capital cost to install an SNCR system were 

significantly lower than for SCR, and the operating and maintenance costs also are 

lower. Of course the incremental cost associated with SCR now would be 

astronomical in terms of NOx removal because Ash Grove's SNCR is operating so 

efficiently. And because there is no catalytic production of sulfuric acid with an 

SNCR system, there is no need to install yet another emission control device for this 

unintended co-product. 

• SCR Has Not Been Demonstrated at All in Any Substantially Similar 

Application. Any rational consideration of a major capital expenditure requires 

proof that the technology to be purchased will work in the application for which it is 

being considered; indeed, demonstration of the technology is a major consideration in 

any BACT analysis conducted for new source permitting. Even worldwide 

experience offers no such demonstration. 

If the Solnhofen experience demonstrates anything, it is that SCR does NOT work 

consistently on cement plants. And whatever Solnhofen had demonstrated would not 

likely be useful to Ash Grove's Midlothian Plant due to the substantial differences in 

kiln design and raw materials. 

SCR has been installed on two other plants in Europe, but neither of these provides a 

demonstration of likely success if applied to Ash Grove's Midlothian Plant. Like 

Solnhofen, each is substantially different from Ash Grove in terms of design and raw 

materials. 

The experience with the high-dust SCR system at Monselice, Italy, a small preheater 

kiln plant, parallels that of Solnhofen. The Monselice SCR started around the time 
V&E
 Chance Goodin July 30, 2010	 Page 4 

that Solnhofen gave up (in June 2006). A primary purpose of the catalytic system 

was to control ammonia (and odor), not NOx. Like Solnhofen, Monselice also has 

experienced significant problems with dust buildup on the catalyst, and has had to 

replace and regenerate the catalyst often and perform manual cleaning: 

June 2006 SCR began operation. 

July 2007 Catalyst was removed and sent for regeneration. New 

catalyst installed. 

February 2008	 The second set of catalyst was removed, and the 

regenerated catalyst was installed. 

The SCR was modified to reduce the catalyst bed from 

24 m3 to 16 m3 in an attempt to reduce pressure drop 

across the catalyst. 

October 2008	 Installed a larger pitch catalyst in the first layer. 

Installed heated compressed air cleaning system to try 

to reduce sticky buildup on the catalyst particularly 

during the winter months. 

April 2009	 Replaced second and third catalyst .layers with larger 

pitch. System still requires catalyst bypass 2 to 3 times 

per year for manual removal of the dust buildup on the 

catalyst. These cleaning periods are approximately 72 

hours in duration. 

Monselice, in short, remains in the shakedown mode more than five years after 

installing SCR, and has been unable to achieve sustained operations and performance 

using that technology. 

The other European cement plant to try SCR, in Sarche, Italy, is a 700 ton per day 

Lepol kiln, much smaller and of much different design than Ash Grove's Midlothian 

Plant. A Lepol kiln consists of a shorter kiln system with a traveling grate heater 

preceding the kiln. None of the kilns in Texas are of this type. The Sarche SCR 

system started operation in 2007, primarily to control ammonia emissions and odors 

and to reduce visible emissions; that is, the catalyst was installed to reduce ammonia 

gases generated from the processing of the raw materials available to that facility. 

Because the kiln process generates NOx as well, ammonia is reduced by reacting with 

NOx in the SCR unit. The same could occur in an SNCR reaction if the ammonia and 

NOx were in contact at the right temperature. However, most of the ammonia at the 

Sarche facility is released at a temperature too low for the non-catalytic reduction of 

NOx and ammonia. Therefore, Sarehe needed to use catalyst to achieve its objection 
.. TQ...r'

\:~L Chance Goodin July 30. 2010 Page 5 

of reducing ammonia. The Midlothian Plant's exhaust, 

substantial reheating. 

In contrast, would need 

In addition to fundamental design differences, raw material differences also prevent 

reliance on any successful performance of SCR in Europe to draw conclusions about 

performance at facilities in Texas. None of the three SCR units in Europe are 

installed on kilns that process high-sulfur raw materials, such as those in Midlothian. 

The sulfur in raw materials exits the kilns, regardless of kiln type, as sulfur dioxide 

(SOz) in the kiln gases. The SCR catalyst will oxidize the SOz to S03. The S03 then 

reacts with moisture in the stack gases to form HzS04, which corrodes duct work and 

steel stacks. There are catalyst formulations to minimize the conversion of SOz to 

S03, but some conversion will occur. Therefore, the Midlothian kilns would likely 

require a wet scrubber to address SO)!HzS04, at a significant additional cost. 

Ash Grove is aware of a dry process cement plant located in Joppa, Illinois, that has 

agreed to install an SCR system as part of a consent decree with EPA. If built, this 

will be the only full-scale application of SCR on a cement kiln in the U.S. But the 

technology is certainly not yet proven: Under the terms of the consent decree, the 

Joppa SCR is not required to be installed until 2013, which means that it is at best still 

is design phase, and not yet proving anything about actual performance. 

But even if it were put into successful operation, it would not prove up SCR for Ash 

Grove's Midlothian Plant any more than do the cxperiences in Europe. As with the 

European plants, the designs are not comparable: Ash Grove has only wet kilns in 

Midlothian, whereas the Joppa plant consists of two long dry kilns. As noted, Ash 

Grove would need to reheat the exit gas to achieve catalysis temperatures, whereas 

Joppa already operates with much higher exhaust gas temperatures and so will not 

have to reheat its exhaust gases. 

And there is no guarantee that the new SCR at Joppa-if installed and operated-will 

achieve NOx levels as low as those already achieved with SNCR at Ash Grove. The 

Joppa consent decree compels no specific level of NOx reductions; instead, the 

facility is required to monitor the performance of the SCR unit and establish a new 

NOx limit based on site-specific conditions. Ash Grove already has demonstrated the 

ability to achieve NOx emission rates lower than those achieved by SCR-equipped 

plants, cven during the periods when those SCR systems are working. 

• Ash Grove's SNCR System Achieves Lower NOx Emission rates than the SCR 

Systems Attempted in Europe. It makes no sense to impose any further technical 
Chance Goodin July 30, 2010 Page 6 

risk or cost in search of lower NOx emissions from Ash Grove's Midlothian Plant, 

when SNCR works so well. Ash Grove's Midlothian Plant achieves an outlet NOx 

emission rate of about 280 mglNm3 using SNCR. Even when their SCR systems 

actually function, none of the SCR systems tried in Europe are able to do as well: 

Ash Grove's emission rate is over 40 % less than achieved by Solnhofen (500 

mg/Nm3

), 30% less than Monselice (400 mg/Nm3), and almost 50% less than Sarche 

(540 mg/Nm3

). 

•	 Ash Grove's Decision to Choose SNCR is Affirmed by National Practice. No 

BACT determination has compelled installation ofSCR on a cement kiln anywhere in 

the U.S., no doubt because ofthe various factors discussed above. 

III.	 Any Further Reductions in NOx Emissions from Midlothian Cement Plants 

Offer No Marginal Ozone Attainment Benefit. 

Regulation should never impose undemonstrated technology at great cost, especially 

when-as hert>-it would accomplish none of the intended goals of the regulation even if the 

technology succeeds. TCEQ and other experts have understood that, historically, the ozone 

monitoring sites that drove DFW's ozone status were dominated by concentrated mobile 

source emissions. Even total elimination of Ash Grove's NOx emissions had no meaningful 

effects on the DFW ozone design values. Even the maximum attributed ozone reduction 

(eliminating all of Ash Grove's NOx emissions) is far below the ability of the monitor to 

even detect, and amounts to modeling "noise," at best. 

IV.	 Conclusions 

Although the impact from Ash Grove's NOx emissions on the attainment status of the 

region is immeasurable, Ash Grove has continued to reduce its emissions by implementing 

emission control technologies that are economically sustainable and reliable. Ash Grove's 

Midlothian Plant has achieved 60% reductions in its NOx emissions over the last decade. As 

a result, its NOx emissions per unit of product are now among the lowest of any kiln in the 

State. The Midlothian Plant not only produces a product essential to the growth and 

maintenance of the region, but contributes significant positive effect on the State's 

environment by providing reuse of millions of scrap tires. When considering additional NOx 

reductions from Ellis County cement kilns, TCEQ should continue to consider the modeled 

impact of such reductions on ozone design values, and weigh that against the very real 

economic and operational impact on the facilities that need to comply with even tighter NOx 

emission limits. 
T rfl--I:"' 

V~L	 Chance Goodin July 30. 2010 Page 7 

Although SCR has been promoted in the past as an alternative or even superior 

technology to SNCR in controlling NOx emissions at cement plants, in practice, SCR is 

significantly more difficult to implement, requires more capital investment, is likely to 

require significant catalyst maintenance, and-ultimately-it has not been shown to 

consistently and reliably offer Ellis County kilns a better solution than SNCR to reduce NOx 

emissions. 

Again, we are grateful for the opportunity to help inform your judgment, as TCEQ 

continues its efforts to achieve ever-lower ozone standards in the DFW area. Should you 

have any questions, please contact me at (512) 542-8552, or Curtis Lesslie at (913) 319­

6065. 

Very truly yours, 

MOllYCa~

0~~

cc:	 Curtis Lesslie 

]acqueline Clark 

Francisco Pinto 

Eric Groten 

US 493781 v.1