### VIRGINIA DEPARTMENT OFENVIRONMENTAL QUALITY Valley Regional Office INTRA-AGENCY MEMORANDUM 441 I Early Road

- P. O. Box 3000 Harrisonburg, VA 22801-3000

PermitWriter 

### Laura RJustin Date 

### 12/23/09 Air PermitManager

### (j~/o1 

# 7<- Date

Deputy Regional Director Date Memo To Air Permit File Date Description Registration Number 80252 County-Plant I.D. 51-171-0003 UTM Coordinates (Zone 17) 731.3 Elevation (feet) 630 Distance to Nearest Class I Area (select one) -22 FLMNotification Required (YIN) 

### Y AIRS Classification Before permit After permit (A,SM, B) A Action A Action Pollutants for Which the Sourceis Title V S02, NOx, 

### Before permit S02, NO" After permit Major PM-lO, CO action PM-I0, CO Action PSD Major Source Before pel'mit Afterpermit (YIN) 

### Y action Y Action Pollutants for Which

The Source is PSD S02, NOx, 

### Before permit S02, NOx, 

### After permit Major PM-I0, CO action PM-lO, CO Action

### I. Introduction O-N Minerals (Chemstone) Company

- Strasburg Facility Engineering Memo for BART Determination Page 2

On July 1, 1999, the U. S. Environmental Protection Agency (EPA) promulgated its Regional Haze Rule (40 CFR Part 51). The objective ofthe rule is to improve visibility in the 156 national parks and wilderness areas around the countryknown as Class I areas. There are two Class I areas within Virginia: Shenandoah National Park (SNP) and the James River Face Wilderness Area (JRFWA). According to the Regional Haze Rule, states must require certain older, large facilities to install emission controls as part ofthe state's strategy to meetregional haze improvement goals. The requirement applies to suchplants emittingpollutants that contribute to visibility degradation and is known as the BestAvailable Retrofit Technology (BART) requirement. EPApublished amendments to the Regional Haze Rule and final BART guidelines July 6, 2005. According to the guidelines, there are three criteria for determining which sources are potentially subject to BART (i.e., "BART-eligible" sources): 1. The emission unit musthave been in existence prior to August 7, 1977 and begun operation after August 7, 1962. 2. The emission unit must be located at a facility which falls into one of26 categories.
3. The aggregate potential emissions ofall emissionunits identified in Items 1 and 2 must be greater than or equal to 250 tons per year ofany visibility impairing pollutant. Thepollutants thatreduce visibility include particulate matter (PM-10 and PM2.5), and compounds which contribute to PM2.5 fOlmation, such as nitrogen oxides (NOx), sulfur dioxides (S02), and under certain conditions volatile organic compounds, and ammonia. After the BART eligible units in the state were identified, each facility had the option ofeither conducting BART exemption modeling to detelmine the aggregate impact of the BART eligible emissions units orproceeding straight to the BARTpermitting process.
The O-N Minerals (Chemstone) Company

- Strasburg Facility (Chemstone) is a lime manufacturing plant located on State Route 629 in Shenandoah County. Lime manufacturing is one ofthe 26 categories identified byEPA for BART eligibility. Chemstone received its first airpermit in 1973. The aggregate potential emissions of NOxexceed 250 tons peryear (tpy). Two BART-eligibleunits at Chemstone were identified: the rotary and calcimatic kilns.
In September 2006, Chemstone submitted a BART Applicability Analysis that included refined modeling (Attachment A). According to the analysis, the predicted visibility impacts attributable to its kilns exceeded the threshold (0.5 deciview) above which a source is considered to contribute to visibility degradation. Accordingly, Chemstone wasO-NMinerals (Chemstone) Company

- Strasburg Facility Engineering Memo for BARTDetetmination Page 3 required to submit a permit application identifying the BART-eligible emissions units and the appropriate BART controls. Since Chemstone's potential emissions ofS02 and PM-I0 exceed the de minimis tlll"esholds, BART analyses arerequired for S02 and PM10 as well as for NOx• According to EPA's BART guidelines, for each BART-eligible source and each pollutant, the BART analysis should identify the best system ofcontinuous emission reduction taking into account: 1. The available retrofit control options;
2. Anypollution control equipmentinuse at the source; 3. The costs ofcompliance with control options;
4. Theremaining useful life ofthe facility;
5. The energy and non-air quality environmental impacts ofcontrol options; and
6. Thevisibility impacts analysis.

Once the BART determination for each emissions unit/pollutant is made, the requirements are to be written in a state operatingpermit as federally enforceable conditions and submitted to EPA as part the Virginia StateImplementation Plan (SIP).

OnFebruary 26, 2007, Valley Regional Office (VRO) received Chemstone's permit application and accompanying BART determination analysis. Supplemental information was also received, submitted inresponse to requests byDEQ, dated April 27, 2007, May 31,2007, July 12, 2007, August 30, 2007, September 27,2007, October 30, 2007, December 5, 2007, January 7,2008, March 17,2008, July 15, 2008, April 3, 2009, May 8,2009, and June 4, 2009. The submittals are appended (Attachments B through Land Q). 

### II. Emission Units I 

### Process Descriptions
Chemstone operates two limekilns that are subject to a BART analysis: a rotarykiln and a calcimatickiln. Thevisibility impairingpollutants emittedfrom theunits are NO" PM10 andS02. The rotary kiln system, constructed in 1974, consists ofa preheater, kiln and cooler. Approved fuels for the rotary kiln are coal, distillate oil and natural gas. Its rated capacityis 50 tons per hourlimestone feed input (25 tons limeper hour output). Chemstone's application indicates that the heat input capacityfor thekiln variesO-N Minerals (Chemstone) Company

- Strasburg Facility Engineering Memo for BART Determination Page 4 according to fuel used as follows: 135 MMBtu/hr for coal, 125 MMBtu/hr for gas and 115 MMBtuIhr for oil. A multicyclone and baghouse control particulate matter. Operation ofboth controls is required in the facility's July 31, 2000 minor new source review (NSR) permit and in its Title V federal operating permit. The product cooler is not being separately evaluated for BART, because its emissions are routed through the rotarykiln and to the baghouse (i.e., its emissions are included in the rotary kiln's BART evaluation). The calcimatic kiln system was constructed before 1972 and its approved fuels are distillate oil, recycled oil and natural gas. Its rated capacity is 16.6 tons/hr limestone feed input (8.3 tons/hr output). Heat input capacity for the kiln is 60 MMBtuIhr for either gas or oil. Particulate matter emissions are controlled bymultiple cyclones and a Venturi scrubber. Operation ofthe controls are enforceable requirements in the facility's May 1, 2002 minorNSRpermit and in its Title V permit. III. RegulatoryReview

- BestAvailableRetrofitTechnology (BART) review Review ofChernstone's BART analysis has been conducted in accordance with EPA guidance issued July 6, 2005. According to 9 VAC 5-80-800 C, DEQ mayissue a State Operating Permit (SOP) to establish a source-specific emission standard or other requirements necessaryto implement the federal Clean Air Act or the Virginia Air Pollution Control Law. Thus, a SOP is issued to establish BART for subjectunits. BART for Chemstone, as approved byDEQ, will be enforced through issuance ofa SOP that will be submitted to EPA as part ofVirginia's State Implementation Plan (SIP). A. Summary ofproposed BART The BART analysis has resulted in the following control determinations:O-NMinerals (Chemstone) Company

- Strasburg Facility Engineering Memo for BARTDetelmination Page 5 Table 1. ChemstoneBARTdetermination SUIIIlIlaJY Emission Proposed Pollutant Proposed Visibility Class I area unit BART controlled BART improvement impacted emission on 98th limit* percentile day (delta deciview) Combination ofinherent dry 0.29Ib/tsf, Shenandoah sClUbbing in S02 14.71bslhr 0.11 National Park kiln and wet (SNP) sClUbber Rotary kiln Good (U5) combustion I.74 lbs/tsf, practices; NO, 87.01bslhr None SNP indirect firing system Multicyclone PMlPM-IO 0.12Ibsltsf, None SNP & baghouse 6.0lbslhr Venturi S02 0.16Ib/tsf, None SNP scrubber 2.6lbs/hr Good 0.61Ibs/tsf, Calcimatic kiln combustion NOx None SNP (Ul2) _practices 9.81bslhr Multicyclones 0.60 lbs/tsf, & Venturi PMlPM-1O None SNP scrubber 9.6lbslhr 

### *Calculated as a 24-hour average for S02 and as a three-hour average for NOli: and PMlPM-lO. B. BART-eligible emission units subject to MACT staudard According to EPA's BART guidance at 70 FR 39163-39164, states mayrely onMACT standards for purposes ofBART, unless there are new technologies subsequent to the MACT standard's promulgation which would lead to cost-effective increases in the level ofcontrol. EPA's rationale is that it is unlikely that states will identify emission controls more stringent than the MACT standards that are not found to be cost-prohibitive. The National Emission Standards for Hazardous AirPollutants from Lime Manufacturing (Lime MACT) were promulgated on January 5, 2004 (40 CFR 63 SubpaliAAAAA). The LimeMACT limits PM emissions from lime kilns to 0.12 Ibs/ton stone feed (tsf) ifa dry control device is used or 0.60 Ibs/tsfifa wet scrubber is used. Chemstone has submitted stacktesting results indicating thatthe Strasburg facility is not a major source ofhazardous airpollutants (HAPs) and is therefore not subject to the Lime MACT. Previous stacktesting ofboth kilns hadindicated that emissions ofPMlPM-10 were below the MACT standards. The rotarykiln uses a fabric filter to control emissions, so the applicable MACT standard would be 0.12 lbs/tsf. The calcimatic kiln controls emissions using a wet scrubber, so the appropriate MACT standard is 0.60 Ibs/tsf.O-N Minerals (Chemstone) Company- Strasburg Facility Engineering Memo for BARTDetermination Page 6
No new control technologies for PMlPM-10 from lime kilns have emerged since the promulgation oftheLime MACT. Accordingly, the PM emission standards in 40 CFR 63 Subpart AAAAA constitute a BART level ofcontrol for both lime kilns. The permit limits bothPM andPM -10 to the Subpart AAAAA PM emission levels. The following table compares previously-reported actual emissions from eachkiln with the appropriate MACT standard. Table 2 Actual emission rates vs MACTstandards Emission unit Actual emission rate (lb/tsi) 

### PM PM-IO Rotary kiln (U5) 0.01285' 0.0090' Calcimatic kiln (U12) 0.5716'

a Based on 12/7/04 stack and particle size testmg b 40 CFR 63 SubpartAAAAA standard for lime kilns controlled byfabric filter

CBased on 10/18/01 stack and particle size testing 0.442'

d 40 CFR 63 Subpart AAAAA standard for lime kilns controlled by wet scrubber Applicable MACT 

### PM rate (Ib/tsi) 0.12" 0.60a

In October 2008, Chemstone submitted a repOli ofresults from stacktesting conducted in August 2008 on the rotary kiln. PM results from the test are in excess ofthe MACT (proposed BART) limits. No explanation has been offered for the discrepancybetween the 2004 and 2008 rotarykiln test results. However, a properly operating fabric filter shouldbe able to meetthe corresponding MACT limit, so the fact that the August 2008 test results exceed the limit will notpreclude use ofthat limit as BART. However, the draft BARTpermit includes a six-month compliance extension for the PMlPM-lO limits, to allow Chemstoneto conduct maintenance on the control devices (i.e., the PMlPM-lO limits are effective 180 days after thepermit effective date). The pelmitrequires Chemstone to conduct stack testing within 180 days ofthepermit issuance date to show compliance with the PM limits. C. Baseline conditions and visibility impacts for BART-eligible units Details concerning the baseline conditions modeled to determine visibility impacts and the visibility modeling results were provided in Chemstone's September 2006 repOli ("Best Available Retrofit Technology Applicability Analysis, O-NMinerals (Chemstone) Company"). The 2006 refined analysis indicated a 98th percentile impact of0.744 deciview (dv), which is above the contribution threshold of0.5 dv at SNP. The analysis is attached (Attachment A). Stacktesting voluntarily conductedby Chemstone for S02 emissions from the rotarykiln on October 30, 2007, indicated that S02 emissions were orders ofmagnitude higher than therates indicated byprevious stacktesting (2001) and onwhich the original BART proposal was based. At DEQ's request, Chemstonerevised its BART-applicability modeling analrsis to reflect the higher baseline emissions ofS02. Therevised analysis indicated a 98t percentile impact of0.80 dv. The report ofthe revised analysis is attached (Attachment I).O-N Minerals (Chemstone) Company

- Strasburg Facility Engineering Memo for BARTDetermination Page 7

In October 2008, Chemstone submitted a report ofresults ofrotarykiln stacktesting conducted in August 2008. Thereport indicated PM emissions exceeding those usedin the BART-applicabilitymodeling (the PM emissions levels modeled were based on a 2004 stack test). As explained in Section m.B above, the rotarykiln is controlledbya multicyclone and baghouse and Chemstone has proposeduse ofthe Lime MACT (40 CFR 63 Subpart AAAAA) PM limits as BART limits; DEQ has concurred with the proposal. EPA's BART guidelines allow use ofa MACT limit as BART (40 CFR 51, Appendix Y, Section

### N.C). Accordingly, the BART determination for PM (fabric filter control and the MACT emissions level) would be the same ifthe visibility impact were higher. Therefore, DEQ did not require Chemstone to revise its modeling to reflect the PM emissionrate measured during the August 2008 test. D. BART analysis for**BART~eligible** emission units 1. Rotary kiln (US)



### a. NOx (1) Step 1: Identify all available retrofit control technologies (a) Existing controls: Therotary kiln currently is controlledbyproperkiln design and operation and byuse ofan indirect firing system. In the indirect firing system, the coal mill air is separated from the pulverized fuel, which is stored in a tank. Thepulverized fuel is conveyed to the burner with the quantity ofair that is optimal for flame considerations. Indirect-fired cementkilns are believedto emit 20 to 30% less NOx than those that are direct-fired; itis notknown whether this level of control is achieved in lime kilns. Chemstone's actual NOx emissions from the rotary kiln are as low, on a lb/tsfbasis, as those ofrecent lime kilns listed inEPA's RACTIBACT/LAER Clearinghouse (RBLC) (see Attachment M). (b) Available retrofit control tecllllologies (i) Selective Catalytic Reduction (SCR) (ii) Selective Non-Catalytic Reduction (SNCR) (iii) Non-Selective Non-Catalytic Reduction (NSNCR) (iv) Low-NOxburner (LNB) (v) Properkiln design and operation (vi) Water/steam injection (vii) Reburn at the burner (fuel staging) (viii) Mid-kiln firing (MKF) (2) Step 2: Eliminate technically infeasible optionsO-N Minerals (Chemstone) Company

- Strasburg Facility Engineering Memo for BARTDetermination Page 8

(a) Selective Catalytic Reduction (SCR): Selective catalytic reduction (SCR) is a post-combustion technique that involves the injection of ammonia into the flue gas upstream ofa catalystbed. 

### Inthe presence ofa catalyst, the ammonia reacts with the flue gas to reduceNO, to nitrogen and water. When operated within an optimum temperature range of480 to 800 

### of, this technology can result inbetween 70 and 90 percentNO, emission reductions on some combustion units. The rate ofNO.removal increases with temperature, up to a maximum removal rate at a temperature between 700 

### of and 750 

### of. As the temperature increases above the optimumtemperature, theNO. removal efficiencybegins to decrease. Efficient operation ofthe SCR process requires fairly constant exhausttemperatures. Fluctuations in exhaust gas temperature reduce removal efficiency. Ifthe temperature is too low, ammonia slip occurs. Ammonia slip is causedby low reaction rates and results inboth higher NO. emissions and appreciable ammonia emissions. Ifthe temperature is too high, oxidation ofthe ammonia to nitric oxide can occur. Also, at higher removal efficiencies (beyond 80 percent), an excess ofammonia is necessary, therebyresulting in some ammonia slip. Other emissions possibly affectedby SCRinclude increased paliiculatematter emissions (from ammonia salts in a detached plume) and increased sulfur trioxide emissions (from oxidation ofS02 onthe catalyst).
To avoid fouling the catalyst bed with the particulate matter in the exhaust stream, a SCRunit should be located downstream ofthe particulate matter control device. However, due to the low exhaust gas temperature exiting the rotary kiln's fabric filter, the exhaust stream would need to bereheated (potentiallywith a heat exchanger) to the desired reaction temperature. The source ofheat in the heat exchanger would be the combustion offuel that would generate additional NO,. Therefore, in addition to storage and handling equipment for the ammonia, the required equipment for the SCR system will include a catalyticreactor, heat exchanger, and potentially additional NOx control equipment for the emissions associated with the heat exchanger fuel combustion.
In addition the handling and disposal ofspent catalysthas been recognized as an environmental risk and a potential health hazard. Additional concerns with a SCR system include the safety and environmental hazards involved with storage and use oflarge quantities ofammonia. This technology is not listed in the RBLC for kilns in the lime industry and has neverbeen commercially demonstrated on a lime kiln. The Ozone Transport Commission has concluded that SCR is an infeasible control option for lime kilnsO-NMinerals (Chemstone) Company

- Strasburg Facility Engineering Memo for BARTDetelmination Page 9 ("Summary ofOzone TranspOli Commission (OTC) Candidate Control Measures

- Control Measure Summary for Lime Kilns" (5/3/06)). Accordingly, SCRhas been eliminated as technically infeasible for further consideration for BART. UpdatefOllowing FLMcomments providedduring its 60-day review period: OnMarch 2,2009, Don Shepherd ofthe National Park Service (NPS) submitted comments on the draft BARTpermitprovided to the FLMs for their 60-dayreview period. In the comments, NPS questioned the technical infeasibility ofSCRuse priorto the baghouse and, asserting thatpost-baghouse SCRuse is technically feasible, requested a cost analysis for SCRfollowing thebaghouse. Following receipt ofNPS' comments, VRO requested that Chemstone address the issues raised. A summary ofVRO's conclusions follows. NPS' comments are attached as Attachment P.

• Pre-baghouse SCR: NPS questioned why a high-dust SCRunit would notbe technically feasible for the rotarykiln when such units have been successfullyused to control pulverized coal boilers (PCBs). Asreported in Chemstone's May 8, 2009 response (attached as Attachment Q), the particulate matter control device loading typical for a PCB is approximately 10 glNm3

, whereas the dust loading for a lime kiln prior to a baghouse is typically several times higher, in excess of80 glNm 3• A lime kiln's higher dust loading combined with the fact that the dust from a lime kiln is primarily calcium oxide (CaO), known to deactivate conventional catalysts byits conversion to calcium sulfate, further distinguishes the process from a typical PCB application. Furthermore, there is no record ofSCRhaving ever been used to control a lime kiln. There has been verylimiteduse ofSCR to control cementkilns in Germany (one plant) and Italy (two plants), while SCRhas not yet been employed in the U.S. to control a cementkiln. The mostrecent information available on the Gelman facility indicates that the SCR is no longer operating (replaced instead by SNCR) due to various technical issues, including inability to achieve the required reduction efficiency. Thelimited data available on one ofthe Italian plants does not establish the SCRunit's ability to consistently meet the desired reduction efficiency; there is nopubliclyavailable testing data for the second Italian plant.
Because SCRhas neverbeen used to control a lime kiln, itis likely that extended pilot-scale trials would berequired prior toO-NMinerals (Chemstone) Company

- Strasburg Facility Engineering Memo for BART Determination Page 10 its application on a lime kiln. Accordingly, SCR maynot meet the definition of"available"technology for a lime kiln given in the BART guidelines. As stated inEPA's final BART guidelines (at 70 FR 39164): "Technologies which have not yet been applied to (orpermitted for) full scale operations need not be considered as available; we do not expect the source owner to purchase or construct a process or control device that has not already been demonstrated inpractice." Due to its lack of successful demonstration on the few cementkilns to which it has been applied and given EPA's guidance, SCRis not an appropriate candidate atthis point for technologytransfer consideration for BART control ofa lime kiln. Based on the high dust concentrationinthe lime kiln's exhaust stream, the content ofthe dust, and the lack ofcommercial demonstration on lime kilns, we find that SCRuse prior to the baghouse is not a technically feasible control option for Chemstone's rotary kiln.

• Post-baghouse SCR: In its comments, NPS requested that the economic feasibility ofSCRuse following the baghouse be evaluated. Inresponse to NPS' comments, VRO asked Chemstone to conduct a cost analysis for post-baghouse SCR control ofNOx . Chemstone's analysis indicates a cost effectiveness of 

### $7,400Iton, a costperton exceeding thatresulting from any BART determination ofwhich VRO is aware. As noted above, we are unaware ofany SCRuse on a lime kiln. The cost effectiveness calculation did not include pilottesting that would therefore likelybe required in any proposed application ofSCRto a lime kiln. VRO finds post-baghouse SCRto be economically infeasible for control ofthe rotary kiln. Additionally, the lack ofdemonstration on a lime kiln cited above makes questionable the technical feasibility at this time as a BART control. Chemstone's responses regarding the FLM comments are appended as Attachment Q. VRO's response to the FLMs following evaluation of Chemstone's submittals is in Attachment 

### R. (b) Non-Selective Non-Catalytic Reduction (NSNCR) (Also referred to as staged combustion air): NSNCR is comprised ofan initial bumzone (oxidizing), a secondary bum zone (reducing), and a final bum zone (oxidizing). Inthe initial bumzone, there is a slight excess air. TheO-N Minerals (Chemstone) Company

- Strasburg Facility Engineering Memo for BARTDetennination Page 11 highest temperatures are reached here, which generate thermal NOx. In the secondaryburn zone, a secondary burner injects additional fuel into the marginally lean air, creating stronglyrich air. In this reducing atmosphere, NO is reacted to N as the hydrocarbons and CO scavenge oxygen. Theoretically, NSNCR can result in NOxreductions of20 to 50 percent in kilns. Only a few cement kilns use this technology and there is no infonnation that any lime kiln uses this technology. Process differences between cement and lime production are the reason this technology has notbeen applied to the lime industry. A multi-stage preheater and cyclones, which the subject lime kiln does not have, are necessary to apply this control technology. As this lime kiln does notpossess the requisiteprocess equipment for this control technology, the control technology is technicallyinfeasible. (c) Low-NOx burner (LNB): LNBs reduce the amount ofNOx initially formed in the flame. Theprinciple ofall LNBs is the same: stepwise or staged combustion and localized exhaust gas recirculation (i.e. at the flame). LNBs are designed to reduce flame turbulence, delay fuel/air mixing, and establish fuel-rich zones for initial combustion. Due to fuel-rich conditions and lack ofavailable oxygen, formation of thelmal NOx and fuel NOx are minimized. The RBLC lists one facility for which LNB is the listed control for a lime kiln. However, the source has not commenced operation and the resulting NOx emissions rate, as listed in the RBLC, is higher than Chemstone's actual emission rate as demonstrated through stack testing. As applied to combustion sources such as boilers, this technology requires staged combustion in the primary fuel burning zone. This fOlm ofcombustion has notbeen achieved in a limekiln. One reason for this is that the requiredproduct temperature in a lime kiln is approximately 2000 of, so a veryhot flame temperature is required. This operating requirement is generally not compatible with limiting the flame temperature, which is a key aspect ofLNB technology. Accordingly, this technologyis not considered technically feasible for lime kilns. (d) Water/steam injection: Injection ofwater or steam into the main flame reduces the flame temperature and the generation ofNOx. In some industrial applications, NOx can be reduced byas much as 75 percent through water/steam injection. Water/steam injection is effective for reducing thelmal NOxin natural gas fired boilers and turbines.O-NMinerals (Chemstone) Company

- Strasburg Facility Engineering Memo for BARTDetermination Page 12
Because oflow initial costs, buthigh operating costs, this technique is considered particularly effective for small, single-burnerpackaged boilers that are operated infrequently. Water/steam injection reduces flame temperature by absorbing the latent heat ofvaporization, which results in decreased process efficiency. Itis mainlyrecommended as a temporary control measure to reduce NOx during peakingperiods. The limekiln at this facility is operated closeto 8760 hours peryear and primarilyfueled by coal or coal/fuel oil. Although this technology is effective for natural gas fired boilers and turbines that are operated infrequently, it has not beenutilized on a coal/fuel oil fired lime kiln that is operated year-round. Since water/steam injection can decrease process efficiency, interfere withproductquality, increase CO emissions generation, and has not been commerciallydemonstrated on a lime kiln, it is considered technically infeasible. (e) Rebul'll at the bUl1ler (fuel staging): Reburn is a NOx control technologythat involves diverting a portion ofthe fuel from the bUl1lers to a second combustion area (rebul1l zone) above the main combustion zone. TheNOx produced in the main combustion zone is reduced downstream in a second combustion zone. The major requirements ofrebul'll are to have the fuel feed rate to the main combustion zonebereduced and have an equivalent amount offuel being fed to the reburn burners in the rebul1l zone. Reburning would require major changes for a lime kiln, which could impactthe quality ofthe lime being produced. A lime kiln does nothave a "rebul'll zone", therefore, this technology has notbeen previously applied to rotary lime kilns. Reburn is nottechnically feasible. (f) Mid-kiln firing (MKF): MKF is a form ofstaged combustion offuels. A specially designed fuel injection system introduces a second fuel source at a mid point in the kiln. This system is typicallyused in cementkilns and allows the fuel to beburned at a material calcination temperature of 1,100 of to 1,650 of, whichis much lower than the burning temperature of 1,950 of to 2,050 of in the lime kiln. Although MKF canreduceNOx emissions incementkilns, it is technically infeasible for lime kilns because the addition offuel to the lime will have a negative effect on the quality ofthe limeproduced. (3) Step 3: Evaluate control effectiveness ofremaining control technologies (a) Selective Non-Catalytic Reduction (SNCR): Selective non-catalytic reduction (SNCR) is a post-combustion control technique that involves injecting ammonia orurea into specific temperature zones in the upper ful1lace orconvectivepass. The reagent reacts with theNOx to form 

### N

### z , C02 (using urea), and water. In order for SNCRto be technicallyO-N Minerals (Chemstone) Company- Strasburg Facility Engineering Memo for BARTDete!mination Page 13 feasible, the location for ammonia/urea injection must meet the following criteria: placement ofthe injector to ensure adequate mixing ofthe ammonia orurea with the combustion gases, residence time of the ammonia with the combustion gases, and temperatureprofile for ammonia injection. There is basically one location in a rotary lime kiln where the ammonia/urea injection could occur- after the particulate matter control device. Ammonia or urea could be injected after the fabric filter ifit is feasible to install heat exchangers after the fabric filter to reheat the exhaust gases backup to the required temperature ofbetween 1,600 of and 2,100 of. No data was found on the level ofemission reduction to be expected for SNCR ifapplied to a lime kiln. However, the Ozone Transport Commission indicates that SNCR would achieve a 60% reduction in NOx when applied to cement kilns ("Identification and Evaluation ofCandidate Control Measures", FeblUary 28, 2007). Inthe absence oflime kiln-specific information, the estimate for cementkiln control will be assumed to applyto a lime kiln. (b) Properkiln design and operation (good combustion practices): Part of Chemstone'skiln design is the indirect firing system, described in III.D.I.a(1)(a) above, whichreduces NOx formation byminimizing excess air delivered to the combustion chamber. According to Chemstone's application, EPAhas indicated that indirect-fired cement kilns can emit 20-30% less NOx than direct-fired ones. No information on reductions achieved in lime kilns was found. (4) Step 4: Evaluate impacts and document results (a) Impact analysis part I: Costs ofcompliance (i) SNCR: At the request ofDEQ, Chemstone provided a cost per ton estimate for controlling NOx using SNCR. Indoing so, Chemstone states that use ofSNCRhas not been successfully demonstrated or achieved in practice on anyknown lime kilns orrelated process industries. Based on the estimated natural gas and ammonia reagent costs, using a conservative assumption of$I,OOO,OOO capital costs, and the expected 60% control effectiveness, the resulting costperton is $17,210, annualized!. Chemstone indicates that it is likelythat the capital costs would bemuch higher than $1,000,000 considering the lack ofprevious application ofthis technology to the industry. DEQ concurs with Chemstone's conclusion that SNCRis not economically feasible.

I The May 31, 2007 SNCR cost analysis, indicating a costper ton of$12,800, was based on an incorrect rotmykiln exhaust flowrate. The May 2009 cost analysis adjusted the original data to both correctthe kiln exhaust flowrate and reflect recent decreases in natural gas pricing and resulted in a cost effectiveness of$ 17,21O/ton.

### O-N Minerals (Chemstone) Company

- Strasburg Facility Engineering Memo for BARTDetermination Page 14 (ii) Proper kiln design and operation (good combustion practices): No cost to implement, as proper kiln design and operation, including an indirect firing system, is currentlyused on the rotarykiln. (b) Impact analysis part 2: Energy impacts (i) SNCR: The primary energy impact from SNCRuse is the fuel (natural gas) that would berequired to operate the control device. The costs associated with the natural gas required were factored into the costs ofcompliance to derive the costper ton to control NOx• 

### Additionally, Chemstone's analysis indicates thatburning the natural gas would result in 4.8 tons peryear additional NOx 

### emissions (assuming 10w-NOx 

### burners). (ii) Proper kiln design and operation (good combustion practices): NI A (currently used) (c) Impact analysis part 3: Non-air quality environmental impacts (i) SNCR: None were identified inthe application. (ii) Proper kiln design and operation (good combustion practices): NI A (currently used) (d) Impact analysis part 4: Remaining useful life (i) SNCR: The remaining useful life ofthe unit was not considered in the evaluation. (ii) Proper kiln design and operation (good combustion practices): NI A (currentlyused) (5) Step 5: Visibilityimpacts (a) SNCR: Since SNCR was found to be cost prohibitive, visibility impacts resulting from its use were not evaluated. (b) Proper kiln design and operation (good combustion practices): N/A (currentlyused) (6) Step 6: Propose BART The evaluation ofavailable control measures for NOx 

### from lime kilns demonstrates thatproper kiln design and operation (good combustionO-N Minerals (Chemstone) Company

- Strasburg Facility Engineering Memo for BARTDetelmination Page IS practices) is the only control that is bothtechnically feasible and cost effective. In addition to proper kiln design and operation, Chemstone's rotary kiln employs an indirect firing system and the resultingNOx emission rate is as low as recent RBLC listings for lime kilns. Accordingly, ithas been determined thatuse ofproperkiln design and operation (good combustion practices) and the indirect firing system constitutes BART for NO, from the rotary kiln.
b. S02 (I) Step I: Identify all available retrofit control technologies (a) Existing controls: As a preheaterrotarykiln, the unit is expected to achieve a significant level ofS02 adsorption onto the lime during the lime production process. Newpreheaterkilns typically achieve a reduction ofgreater than 90% through suchinherent dry scrubbing. Recent listings in EPA's RACTIBACTiLAER Clearinghouse (RBLC) indicate that a minimum 92% reduction has beenrequired for new preheaterkilns. Chemstone's initial BARTproposal for S02 (which proposedbasecase or inherent scrubbing as BART) was based on the assumption that the unit was achieving S02 reductions greater than 99% through inherent scrubbing (based on a 2001 stacktest). Stack testing conducted in October 2007, however, indicated much higher than expected S02 emissions and a removal rate of55%, considering sulfur input from fuel only. (Chemstone's October 2007 stack test report did not indicate the sulfur content ofthe limestone feed used during the test. Depending on the limestone sulfur content, it is possible that the rotarykiln's inherent removal rate is greater than 55%.)
To date, Chemstone has provided no clear explanation for the apparent increase in S02 emissions (and apparent decrease in inherent scrubbing) from the rotary kiln. Further stacktesting conductedin August 2008 indicated a much lower S02 emissionrate, indicative ofa higher level ofinherent scrubbing closer to the 2001 test results. Itis clear from the disparate test results that the level ofinherent S02 adsorption is variable and dependent on a combination ofprocess parameters. Further testing will be conductedinthe future (as required bythe BARTpermit). Forthe present; the level ofS02reduction achieved in the kiln through inherent scrubbing appears to be less than that typically experienced in preheaterrotarykilns. (b) Available retrofit control technologiesO-NMinerals (Chemstone) Company

- Strasburg Facility Engineering Memo for BARTDetelmination Page 16 (i) Wet sClUbbing with lime (ii) Inherent dry sClUbbing (process) (iii) Semi-wet sClUbbing (spray dryer adsorber) (2) Step 2: Eliminate technically infeasible options
All ofthe identified retrofit technologies are technically feasible for controlling S02 from the rotarykiln. (3) Step 3: Evaluate control effectiveness ofremaining control technologies (a) Wet scrubbing withlime: Wet S02 sClUbbers operatebyflowing the gas to be sClUbbed upward tlU'ough a large reactor vessel thathas an alkaline reagent (limestone or lime) flowing down from the top. A series ofspraynozzles distribute the reagent throughout the sClUbber chamber and thereby mix the gas stream withthe alkaline liquid. The calcium in the reagentreacts with the S02 in the gas streamto form calcium sulfite and/or calcium sulfate that is removed from the sClUbber with the sludge and disposed. Wet scrubbing with lime has been known to achieve greater than 95% efficiency for acid gas removal. (b) Inherent dry scrubbing (process): In a lime kiln, S02 that is released during lime production will react with the lime in the kiln. The amount ofS02 adsorbed inthe system is a function ofnot only the sulfur in the fuel, but also the sulfur in the limestone feed, the amount ofsulfur in the product, and the degree ofcalcium oxidation that takes place in the kiln (greater oxidation generallyresults in more sulfur removal). Fornewpreheaterkilns, inherent dry sC11lbbing can provide control efficiencies greater than 90%. According to onerecent stack test (October 2007), Chemstone's rotary kiln appears to be achieving approximately 55% removal efficiencyfrom inherent sClUbbing. As detailed above, othertests have indicated higherremoval rates. (c) Semi-wet sClUbbing (spray dryer adsorber): Spray dryer systems operate byinjecting a moist sorbent (normally lime orcalcium hydroxide) into the sC11lbber. As the hot gas stream mixes with the sorbent, water is evaporated. The surfaces ofthe solid sorbent react with S02. Theprocess fOlms a dry wasteproduct that is collected in a baghouse. The semi-wet system is sensitive to operating conditions, particularly temperature fluctuations. High-temperature gas streams reduce theperformance ofthe sC11lbbing system. The semi-wet sC11lbber system would needto be locatedpriorto therotarykiln baghouse, where the gas stream temperature is approximately 500 OF. Semi-wet sClUbbers have beenknown to achieve up to 90% removal

### O-N Minerals (Chemstone) Company

- Strasburg Facility Engineering Memo for BARTDetelmination Page 17 efficiency. Chemstone's analysis indicates that the rotarykiln outlet gas stream mayneed to be cooled to enable a semi-wet scrubber to achieve that removal level. (4) Step 4: Evaluate impacts and documentresults (a) Impact analysis part 1: Costs ofcompliance (i) Wet scrubbing with lime: In its January 7,2008 submittal, Chemstone calculates annualized costs perton for wet scrubbing with lime at $4,090 (at 95% removal) and $4,317 (at 90% removal), eachbased on control ofthe proposed emissions level and assuming seven percent interest and an equipment life of 15 years. DEQ staffadjusted the calculations to reflect the guidelines inEPA's Control Cost Manual and detelmined annualized costs 

### of$4,007/ton (95% removal) and 

### $4,225/ton (90% removal). (ii) Inherent dry scrubbing (process): No cost ofcompliance, as this method ofcontrol is inherent to the process and is currentlyused. (iii) Semi-wet scrubbing (spray dryer adsorber): In its 117108 

### submittal, Chemstone calculated an annualized cost for semiwet scrubbing of$5,218 perton, based on 90% control of proposed emissions, seven percent interest and a 15-year equipment life. The calculations do not appear to include the cooling system likely needed to reduce the temperature ofthe rotary kiln outlet (inlet to adsorber). (b) Impact analysis part 2: Energy impacts (i) Wet scrubbing with lime: Electricity would be required to operate the wet scrubber. Electrical costs were accounted for in calculating the annualized costperton for wet scrubbing. (ii) Inherent dry scrubbing (process): NI 

### A (currentlyutilized). (iii) Semi-wet scrubbing (spray dryer adsorber): Electricitywould berequired to operate the spray dryer adsorber. Electrical costs ofoperating the adsorber were factored into the annualized cost per ton. (c) Impact analysis part 3: Non-air quality environmental impactsO-N Minerals (Chemstone) Company

- Strasburg Facility Engineering Memo for BARTDetelmination Page 18 (i) Wet scrubbing with lime: Chemstone's 11/30/07application addendum identified sludge handling and disposal issues as non-air quality environmental impacts ofwet sClUbbing. Specifically, the need to handle the sludge so as to avoid groundwater contamination and the need to permanently set aside from future surface uses the area used for sludge disposal, as the disposed sludge cannotbear weight from uses such as buildings or cultivated agriculture. (ii) Inherent dry sClUbbing (process): 

### NI A (currentlyutilized). (iii) Semi-wet sClUbbing (spray dryer adsorber): Chemstone's 11130/07application addendum lists the production ofdry waste requiring landfilling and water usage as non-air quality environmental impacts ofsemi-wet sClUbbing. (d) Impact analysis part 4: Remaining useful life (i) Wet sClUbbing with lime: Theremaining useful life oftheunit was not considered in the evaluation. (ii) Inherent dry sClUbbing (process): 

### N/A (currentlyused). (iii) Semi-wet sClUbbing (spray dryer adsorber): The remaining useful life ofthe unit was not considered in the evaluation. (5) Step 5: Visibility impacts (a) Wet sClUbbing with lime: In its 11/30/07 application addendum, Chemstone evaluated visibilityimpacts at SNP associated with two S02 control scenarios: 80% reduction and 90% reduction. The scenarios were not associated with a specific control device butrather applied to either wet or semi-wet scrubbing. The analyses were conducted using CALPUFF andrepresented base-case (no control) and base-case with 80 and 90 percent S02 removal applied. Visibility improvement was calculated as the difference between the existing visibility impairment (base case) and the visibility impairment for the controlled emission rates as measured bythe 98th percentile modeled visibility impact. The (higher) S02 emission rate determined in the October 2007 rotary kiln stack test was used in the visibility impact modeling. Other pollutants were modeled at the same rates as in prior (i.e., BART applicability) modeling analyses. The visibility improvement modeling analysis was reviewed byboth DEQ and NPS staff.O-NMinerals (Chemstone) Company- Strasburg Facility Engineering Memo for BARTDetermination Page 19

The visibilityimpact analysis compared the 98 1h percentile modeled imr.actresulting from base case (no add-on control) conditions to the 98 11 percentile modeled impacts resulting fi'om 80% control ofS02 and 90% control ofS02. Thebase case analysis used the actual S02 emission rate determined in the October 30, 2007 stacktest (66.1 lbs/hr). The analyses determined that the visibility improvement predicted for 80% control was 0.04 dv and that the improvement predicted for 90% control was 0.05 dv. Chemstone also analyzed the visibility impact associated with both control levels when the base case was Chemstone's proposed BART S02 emission limitation (79.3 lbs/hr). Inthat case, Chemstone reported visibility improvement of 0.06 dv resulting from either control level. On Febtuary 26, 2008, DEQ staff, after consultation with theNPS (FLM), requested several clarifications and refinements to bemade to Chemstone's analyses. Requested adjustments included use ofa higher ammonia background concentration, use ofa PM speciation background value that varies based on monthly average relative humidity, and modeling a reduction in primary sulfate emissions linear to the projected S02 reductions. Chemstone's response, dated March 17, 2008, indicated a revised visibility improvement of0.11 dv resulting from 90% S02 (and primary sulfate) control. (b) Inherent dry sctubbing (process): 

### N/A (currentlyused). (c) Semi-wet sctubbing (spray dryer adsorber): Please see discussion of visibility impact analysis for wet scrubbing above. (6) Step 6: Propose BART The following table summarizes the impacts analysis described above.O-NMinerals (Chemstone) Company

- StrasburgFacility EngineeringMemo for BARTDetermination Page 20 

### To hi 

### 3 S

a e UlIll1lary 0 

### I Impacts analysIs

- 

## so fi 2 rom rotmy 

### k"l I n Inherent dry Semi-wet Wet scrubbing scrubbing scrubbing with lime (process) (spray dryer (base case) adsorber) Expected 

### I Ibs/hr 4.0 79.3' 7.93 emission rate 

### I tons/yr 17.4 347 34.7 % pollutant removed' 95 55 90'

Expected emissions 330 NIA 312 rednction (tons/yr) TAC' 1,322,423 NIA 1,631,421 Costs of ($) compliance4 $/ton 4,007 NIA 5,218 $/dv' 12MM NIA 14MM Energyimpacts Electricity to NIA Electricity to operate operate Non-air quality Sludge handling NIA Landfilling of dry waste; environmental impacts & disposal waterusage Modeled visibility improvement' (dv) 0.11 NlA 0.11

I Inherent dry scmbbmg represents base case. The pounds-pel-haUl emiSSIOns level IS the BARTlimit proposed by Chemstone and is based on October 2007 stack testing (66.1 Ibs/hr) with a 20% margin ofcompliance added.

, Base-case (inherent dry scrubbing) removal percentage is based onpercent sulfur in fuel used versus mass ofsulfur emitted in October 2007 stack test (sulfur content oflimestone feed was not indicated in stack test report; percent removal maybe higher depending on limestone sulfur content). Percent removal for wet and semi-wet scrubbing is based on removal ofSO, inkiln outlet gas stream (i.e., after base-case removal shown). J For a semi-wet scrubber to achieve this level ofreduction, it would likelyrequire cooling ofkiln outlet stream. Costs ofcooling gas stream were not evaluated. 4 Incremental cost effectiveness was not evaluated because the most stringent control (wet scrubber) had lower total amlUalized costs than the alternative add-on control (semiwet scrubber). 5 TAC = total annualized cost (sum ofdirect annual costs and indirect ammal costs) 6 Based on 90% control.

The impact analysis summarized above indicates that wet sClUbbing with lime constitutes BART for S02 from the rotarykiln. The finding is based on the following considerations:

• Ofthe add-on control altematives evaluated, wet sClUbbing with lime has higherremoval efficiency and lower costs than semi-wet sClUbbing (spray dryer adsorption). Accordingly, no further consideration is given to semi-wet sClUbbing.

• The cost effectiveness ofwet sClUbbing ($4,007/ton at 95% efficiencyand $4,225/ton at 90% efficiency) is notO-N Minerals (Chemstone) Company

- Strasburg Facility Engineering Memo for BARTDetelmination Page 21 consideredprohibitive. The BART determination for another Virginia facility, Georgia Pacific, is control ofS02 with a wet sClUbber at a costper ton that is slightly higher than that indicated for Chemstone.

• The variable and at times low level ofcontrol achieved inherently in the kiln, as indicated byrecent testing. Newer preheaterrotarykilns typically achieve greater than 90% removal ofS02 tlll'ough inherent dry sClUbbing. The control level listed for inherent dry sClUbbing for most preheater kilns in the RBLC is 92 percent. Forreasons that are not yet clear, Chemstone's rotary kiln appears to be operating at times at a significantly lower level ofinherent removal (55%). In terms oflbs S02/tsfor Ibs**SO~ton** lime, Chemstone's rotary kiln emission rate is higher than most kilns listed in the RBLC. As a result, inherent dry sClUbbing alone does not meet BARTrequirements, given that an economically feasible alternative is available. TheBARTlimits for S02 from the rotary kiln are 14.7 Ibslhr and 0.29 Ibs/tsf. The limits are based on 95% control ofS02 emitted assuming all sulfur in the limestone feed and fuel is emitted as S02 and assuming a maximum coal sulfur content ofonepercent (calculations in Attachment N). Uncontrolled emissions have been conservatively based on raw material and fuel sulfur mass balance because there are insufficient data available onwhich to determine the percentage removed through inherent sClUbbing. Two performance tests on the rotary kiln indicate inherent removal as high as above 99% (April 2000) and as low as 55% (October 2007, considering fuel sulfur only). No explanation has yet been offered for the fluctuation in dry sClUbbing efficiencybetween the tests. Further testing and data collection are needed before a reliable inherent removal rate canbe determined for the kiln. Given the limited and highlyvariable test results, DEQ has no confidence that the October 2007 testing represents the maximum S02 emissions rate from the kiln. Accordingly, the BART limits have been based not on the October 2007 test results but rather on the maximum sulfur in the kiln (from limestone and fuel), as this determines the potential S02 that needs to be controlled. Chemstone's cost analyses were based on controlling the emissions level determined in the October 2007 testing, adjusted for a 20% margin ofcompliance. The level ofcontrol (95%) determined to be cost effective at this lower emissions level has been applied to the potential emissions (based on sulfur mass balance) to derive the BART limits. Calculations are in AttachmentN. (Note that, as explained below, the permitrequires Chemstone to operate a Continuous Emissions Monitoring System (CEMS) to monitor S02 emissions.)O-N Minerals (Chemstone) Company

- Strasburg Facility Engineering Memo for BART Determination Page 22

The BARTpermit also restricts maximum sulfur content to onepercentby weight; prior to the BARTpermit, the sulfur content limit was 1.5% by weight. In discussions with DEQ staff, Chemstone has indicated a willingness to accept a 1.0% S limit on its rotary kiln coal. TheBART pelmit enforces the limit and thereby further reduces potential S02 emissions. The BARTpermitrequires that S02 from the rotarykiln be controlled bya wet scmbber or, upon DEQ approval, an alternative control technology (including inherent process scmbbing) capable ofmeeting the BART emissions limits. The limits are based on an overall control efficiency of 95%, meaning that between the inherent dry scmbbing within the kiln and the wet scmbber, emissions will be reduced to 14.7 Ibs SO:J]u· and 0.29 lbs/tsf. The production-based limit (lbs/tsf) applies at all times except during startup, which is defined in the permit. The hourly emission limit (lbs/hr) applies at all times, including startup. The permitrequires that the S02 emissions limits be met no later than September 10,2010 and that the wet scmbber, ifneeded to meet the emissions limits, be installed by August 1, 2012. The effective date ofthe emissions limits was chosen for consistencywith terms ofa pending EPA enforcement settlement. 2. Calcimatickiln (UI2)



### a. NOx (1) Step 1: Identify all available retrofit control technologies (a) Existing controls: The calcimatic kiln controls NOx emissions by proper kiln design and operation (good combustion practices). The kiln employs a 27-burner system having a multi-channel burner at each ofthe 27 locations. Recycled oil or fuel oil is mixed with combustion air and atomizing air at each location to produce the most efficient burn possible and to minimize emissions. Each bumerlocation can be fine-tuned individually as needed. The gases are monitored by an oxygen/combustible analyzer to ensure proper combustion. (b) Available retrofit control technologies The control technologies available for the calcimatic kiln are the same as those identified for the rotarykiln: (i) Selective Catalytic Reduction (SCR) (ii) SelectiveNon-Catalytic Reduction (SNCR) (iii) Non-SelectiveNon-Catalytic Reduction (NSNCR)O-N Minerals (Chemstone) Company

- Strasburg Facility Engineering Memo for BARTDetermination Page 23 (iv) Low-NOx burner (LNB) (v) Proper kiln design and operation (vi) Water/steam injection (vii) Reburn at the bU11ler (fuel staging) (viii) Mid-kiln firing (MKF) (2) Step 2: Eliminate technically infeasible options The rationale for determining technical feasibility for the calcimatic kiln is the same as that for the rotarykiln. Please refer to discussion of technically infeasible control options for the rotary kiln in Section IILD.I.a(2). (3) Step 3: Evaluate control effectiveness ofremaining control technologies The control effectiveness ofthe remaining feasible technologies, SNCR and proper kiln design and operation, are the same as indicated for the rotarykiln in Section III.D.I.a(3). (4) Step 4: Evaluate impacts and document results (a) Impact analysis patt I: Costs ofcompliance At DEQ'srequest, Chemstone conducted a cost analysis for controlling NOx from the rotary kiln using SNCR. The resulting average annual cost per ton was deemed cost prohibitive when compared to recent costs for controllingNOx encountered bythe agency. NOx emissions from the calcimatic kiln are limited by a minornew source review pelmit to 41.4 tpy. Assuming 60% control, use ofSNCR would reduce NOx emissions from the calcimatic kiln by 24.7 tpy. Given the results ofthe cost analysis for the rotary kiln (whichhas potential emissions over 300 tpy), itis reasonable to infer that a SNCR cost analysis for a 24.7 tpyreduction would result in a finding that the control was not economically feasible for the calcimatic kiln. (b) Impact analysis patt 2: Energy impacts Energyimpacts are similar to those described for the rotarykiln in Section IILD.I.a.( 4)(b). (c) Impact analysis palt 3: Non-air quality environmental impacts (i) SNCR: None were identified in the application.O-N Minerals (Chemstone) Company- Strasburg Facility Engineering Memo for BART Detennination Page 24 (ii) Proper kiln design and operation (good combustion practices): 

### NI A (currentlyused) (d) Impact analysis patt 4: Remaining useful life (i) SNCR: Theremaininguseful life ofthe unit was not considered in the evaluation. (ii) Properkiln design and operation (good combustion practices): 

### NI A (currentlyused) (5) Step 5: Visibility impacts (a) SNCR: Since SNCRwas found to be cost prohibitive, visibility impacts resulting from its use were not evaluated. (b) Proper kiln design and operation (good combustion practices): N/A (cUlTently used) (6) Step 6: Propose BART The evaluation ofavailable control measures for NOx from lime kilns demonstrates thatproperkiln design and operation (good combustion practices) is the only control that is both technically feasible and cost effective. Chemstone's calcimatickiln is designed to allow tuning of individual burners as needed to optimize combustion efficiency and minimize emissions. The calcimatic kiln is subject to BACT limits for NOx of9.82 Ibs/hr and 41.4 tpy (minorNew Source Review permit dated May 1, 2002). Considering the 16 tsJThr capacity ofthekiln, the BACT limits are equivalent to 0.611bs NOx/tsf, which is lower than recent limits on lime kilns in the RBLC. Accordingly, it has been determined that use ofproperkiln design and operation (good combustion practices) constitutes BART for NOx from the calcimatic kiln.

(1) Step 1: Identify all available retrofit control technologies (a) Existing controls: The calcimatickiln is controlledby a Venturi scrubber. The scrubber was installed primarily for PM control but also achieves S02 removal. The calcimatickiln is subject to minorNew Source Review pennit limits of7.52Ibs S02/br and 31.7 tons 

### S02/yr. The calcimatic kiln is limited to use oflow-sulfurfuels (natural gas, distillate oil (maximum 0.5% S) andrecycled fuel oil (maximum 0.5% S). The minorNSRlimits were derived assuming all sulfur in boththeO-NMinerals (Chemstone) Company- Strasburg Facility Engineering Memo for BARTDetermination Page 25
limestone feed and the fuel was emitted and a S02 removal efficiency of85.9%. The 85.9% removal efficiency was based on data submitted by Chemstone from stack testing at an Oregon facility and apparently reflected a combination ofinherent scrubbing and wet scrubber control. Testing conducted in 2001 on the Chemstone calcimatic kiln indicated an emissions rate of0.04 Ibs S02ihr. The emissions rate presumablyresults from a combination ofinherent dry scrubbing within the kiln and wet scrubbingbythe Ventnri scrubber. (b) Available retrofit control technologies (i) Inherent dry scrubbing (process) (ii) Semi-wet scrubbing (spray dryer adsorber) (2) Step 2: Eliminatetechnically infeasible options
All ofthe identifiedretrofit teclmologies are technically feasible for controlling S02 from the calcimatickiln. (3) Step 3: Evaluatecontrol effectiveness ofremaining control teclmologies (a) Inherent dry scrubbing (process): Accordingto Chemstone's 11130107 submittal, inherent scrubbing in the calcimatickiln wouldbe expected to remove less than 80percent ofS02. Note that the calcimatic kiln does nothave a preheater and therefore the inherent scrubbing potential is lower than that for the (preheater) rotary kiln. (b) Semi-wet scrubbing (spray dryer adsorber): A semi-wet scrubber can achieve removal efficiencies up to 90%. Please see item III.D.1.b(3)(c) above for details (discussion ofsemi-wet scrubbing under rotary kiln evaluation). (4) Step 4: Evaluate impacts and document results (a) Impact analysis part 1: Costs ofcompliance Since the calcimatickiln is controlledbythe most stringent technology, no cost analyses were conducted. (b) Impact analysis part 2: Energyimpacts Energyimpacts were not evaluated because the calcimatic kiln is controlledbythe most stringent technology. (c) Impact analysis part 3: Non-air quality environmental impactsO-N Minerals (Chemstone) Company

- Strasburg Facility Engineering Memo for BARTDetermination Page 26

Non-air quality environmental impacts were not evaluated since the kiln is controlled bythe most stringent technology. (d) Impact analysis part 4: Remaining useful life Theremaining useful life ofthe kiln was not considered inthe evaluation. (5) Step 5: Visibility impacts Since the calcimatic kiln is controlledbythe most stringent control alternative, no visibility impact analysis was conducted. (6) Step 6: Propose BART Chemstone's 11/30107analysis concluded that use ofa wet scmbber (such as the Venturi scmbber currently employed) constitutes BART for S02 from the calcimatic kiln. DEQ concurs with the conclusion. However, the level ofS02 removal (85.9%) currentlyrequired bythe minorNSRpennit does not meet BARTrequirements. As indicated in Chemstone's 11/30107 analysis, wet scmbbing can achieve up to 95% removal and the October 2001 stack testing ofthe calcimatic kiln demonstrated such removal. Accordingly, BART limits have been established based on 95% removal ofS02, assuming all fuel and limestone feed sulfur is emitted as S02. The limits included in the BARTpennit are 2.61bs S02/hr and 0.16 lbs SOz/tsf. Calculations are attached (Attachment 0). IV. ComplianceDemonstration Except for the rotarykiln (US) S02 and PMlPMto limits, compliance with the BART emission limits and supporting provisions is required following the effective date ofthe permit. Compliance with the rotary kiln S02limits is required by September 10, 2010. Compliance withthe rotary kiln PM and PMto limits is required 180 days after the pelmit effective date. Thepennitprescribes several means ofcompliance demonstration, including continuous monitoring ofemissions (rotary kiln S02) and ofcontrol device parameters, recordkeeping, testing and repOlting. Themonitoring required bythepermitincludes:

• Rotarykiln fabric filter pressure drop is to be continuouslymeasured; the measurement is to be observed at least once each operating day and a log kept ofthe observations. • Calcimatickiln Venturi scmbber'spressure drop, liquid flow rate and exit gas temperature is to be continuouslymeasured; the measurements are toO-N Minerals (Chemstone) Company

- Strasburg Facility Engineering Memo for BARTDetermination Page 27 be observed at least once each operating day and a log kept ofthe observation results. • A BARTMonitoring Plan is required to be developed within six months ofpermit issuance. Theplan is required to detail procedures for proper operation and maintenance ofeach kiln, procedures for monitoring and proper operation ofmonitoring equipment and corrective action to be taken when necessary. • The permitrequires that eachkiln be monitored in accordance with the BART monitoring plan. • The combustion apparatus on both kilns are to be tuned annuallyto minimize emissions ofNOx• • Use ofa Continuous Emissions Monitoring System (CEMS) onthe rotary kiln to measure S02 emissions by September 10, 2010 (the S02 compliance date for the rotarykiln). The CEMS is to be installed, calibrated, maintained and operated in accordance with 9 VAC 5-40-41. A performance evaluation ofthe CEMS is to be conducted and a CEMS quality control program implemented. Records required to bekept (for each kiln) include amount ofeach fuel consumed, throughput oflimestone, operating hours, fuel supplier certifications, emissions calculations to verify compliance with all emission limits, CEMS data, operational and control device monitoring records (including records ofmonitoring required bythe BARTmonitoring plan and a copy ofthe plan), scheduled and unscheduled maintenance and stack test results. The permitrequires performance testing to be conducted on each kiln for NOx, S02 and PM to demonstrate initial compliance with the emission limits. The tests are to be conducted according to EPAReference Methods 7 or7E (NOx), 6 or 6C (S02) and 5 (PMlPM-10). RM5 has been specified for PMlPM-10 compliancebecause it is the test method prescribed bythe Lime MACT (40 CFR 63 SubpattAAAAA) for demonstration ofcompliance with the MACT's PM limits. The MACT PM limits have been used as Chemstone's BARTdetermination (the emission level has been applied to both PM and PM-IO). Testing for S02 from the rotarykiln is required within 60 days ofSeptember 10, 20I0 (S02 limit compliance date). The remaining tests are required to be completed within 180 days ofthe effective date ofthe permit. Forthe calcimatic kiln (UI2), which is not currently operating, initial testing is required to be conducted within 90 days after the unit resumes normal operation.
To show continuing compliance with the limits, the permitrequires that an annual stack test for NOx be conducted for eachkiln. After three consecutive stack tests showing compliance with the NOx limits, the required frequency oftesting is reduced to once every five years. Ifany subsequent stack test indicates noncompliance with the NOx limits, stack testing frequency reverts to onceperyear. The permitrequires that compliance withthe S02 limits for the rotary kiln be shown byuse ofa CEMS. TheO-N Minerals (Chemstone) Company

- Strasburg Facility Engineering Memo for BARTDetermination Page 28 permit also requires additional stacktesting at least once every five years for PM and upon request ofDEQ. The permittee is required to report its emissions ofeachpollutant from both kilns semiannually, in writing.
V. Public Participation According to 40 CFR 51.308(i)(2), Federal Land Managers (FLMs) are to be provided a 60-dayreviewperiod for consultation on implementationplans related to regional haze, which includes proposed BARTpermits. Therefore, the FLMs were giventhe opportunity to review and comment on the draft permit beginning January 15,2009. Comments were received from theNational Park Service (NPS) onMarch 2, 2009 (see Attachment P). VRO responded in a letter dated September 22, 2009 (see Attachment R). The draft permit was placed onpublic notice inthe Harrisonburg Daily News-Record from October 15,2009; the public commentperiod began October 16,2009 and ended November 16,2009. Two comments were received: one from the National Park Service and one from Chemstone. Bothletters are appended as Attachment S. VRO's response to the comments received is attached (Attachment T). There were no requests for a public hearing. As a result ofpublic comment, the following changes have been made to the permit:

• Condition 4 was changed to allow additional time for installation ofa wet scrubber. The original condition required that scrubber installation be completed by September 1, 2010. Inits comments provided during the public comment period, Chemstone requested that the scrubber installation deadline be extendedto September 1, 2012 (see Attachment S for full request). VRO agreed that it was appropriate to allow more time to complete scrubber installation, butextended the deadline to August 1, 2012 to comply with Virginia's BART Rule (see 9 VAC 5-40-7590). It should be noted that the compliance date for the S02 limit was not changed: the permit still requires Chemstone to meet the BART S02 emissions limits by September 1, 2010. Condition 4 now reads: Emission Controls: Rotary 

### Kiln

- No later than September 10,2010, sulfur dioxide (S02) emissions from the rotary kiln (US) shall be controlled to achieve the S02limitsin Condition 23. Unless the Director, Valley Regional Office, approves inherent process scrubbing as an alternative control technology by September 10,2011, a wet scrubber shall be installed by August 1, 2012. The wet scrubber or other technology employed to meet the S02 limits shall beprovided with adequate access for inspection and shall be inoperation when the rotary kiln is operating. (9 VAC 5-80-850, 9 VAC 5-40-7580, 9 VAC 5-40-7590 and 9 VAC 5-40-7650)O-N Minerals (Chemstone) Company

- Strasburg Facility Engineering Memo for BARTDetermination Page 29

• The recordkeeping condition has been changed to correspond to the extended scrubber installation date in revised Condition 4. Condition 26J now reads: Beginning on August 1, 2012, control device monitoring records for the wet scrubber serving the rotary kiln (U5) as required in Conditions 9 and 14.

• Therotarykiln S02 stack test condition has been revised to require testing within 60 days ofthe compliance date in Condition 23. The original condition required testing within 60 days ofthe compliance date orfollowing scrubber installation, whichever occurred first. Since the scrubber installation deadline has been changed, there is no question that the compliance date in Condition 23 (September 1, 2010) will occur first. Condition 28now reads: StackTest: Rotary KiIn- Initial perfOlmance tests shall be conducted for S02 from the rotarykiln (U5) using EPA Reference Method 6 or 6C (40 CFR 60 Appendix A) to determine compliance with the emission limits contained in Condition 23. Thetests shall beperformed and demonstrate compliance within 60 days after the compliance date in Condition 23. Tests shall be conducted and reported and data reduced as set forth in 9 VAC 5-40-30 and the test methods and procedures contained in each applicable section or subpmt listed in 9 VAC 5-50-410. The details ofthe tests are to be arranged with the Director, ValleyRegional Office. The pelmittee shall submit a test protocol at least 30 days priorto testing. A copy of the test results shall be submitted to the Director, ValleyRegional Office, within 60 days after test completion and shall conform to the test report format enclosed with this permit. (9 VAC 5-80-850 and 9 VAC 5-40-7660)

• At Chemstone's request, the word "caustic" has beenremoved from all references to the scrubber throughoutthe permit.

VI. Conclusions TheBART analysis submitted by Chemstone for its rotary and calcimatic kilns has been reviewed in accordance with guidelines provided in 40 CFR 51 Appendix Y. The BART detelminations for each pollutant and each kiln are summarized in Table 1 and the underlying rationale has been documented in Section III.D. A state operating permithas been drafted to make enforceable the emission limitations, monitoring, testing, recordkeeping and reporting requirements needed to implement the BART determination, in accordance with 9 VAC 5 Chapter 40, Article 52. AttachmentsA:

B:

C:

D:

E:

F:

G:

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### N: O-NMinerals (Chemstone) Company

- StrasburgFacility Engineering Memo for BARTDetermination Page 30
BestAvailable Retrofit TechnologyApplicabilityAnalysis submittedby O-N Minerals (Chemstone) Company, September 2006
BestAvailable Retrofit TechnologyDetermination submittedby O-NMinerals (Chemstone) Company, Febmary2007
Letter dated April 27, 2007, submittedby Chemstone in support ofits BART determination (response to VRO 30-day letter)
Letter dated May 31, 2007, submittedby Chemstone in support ofits BART determination (SNCRevaluation)
Letter dated July 12, 2007, submittedbyChemstone in support ofits BART detelmination
Letter dated August 30, 2007, submittedbyChemstone in support ofits BART determination (application for de minimis S02limits)
Letter dated September 27, 2007, submitted byChemstone in SUppOlt ofits BART detelmination (comments on draft permit) October 30, 2007 rotarykiln emissions test summaryreport (cover letter dated 11112/07)
November 30, 2007 revised S02 BARTproposal (cover letter dated 12/05/07)
Letter dated January 7,2008, submittedby Chemstone in SUppOlt ofits BART determination (response to VRO 30-dayletter for revised S02 BARTproposal)
Letter dated March 17, 2008, submittedby Chemstone in SUppOlt ofits BART determination (response to DEQ and FLM modeling comments)
Letter dated July 15, 2008, submittedbyChemstone in support of its BART detelmination (response to June 2008 draft permit)
Recent listings for limekilns in EPA's RACTIBACT/LAER Clearinghouse (NOx) Calculations showing derivation ofBART S02 limits for rotary kiln0:

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T: O-N Minerals (Chemstone) Company

- Strasburg Facility Engineering Memo for BART Determination Page 31

Calculations showing derivation ofBART S02limitsfor calcimatic kiln Comments dated March 2, 2009 from Don Shepherd (NPS) on draft BARTpermit
Letters dated April 3, 2009, May 8, 2009 and June 4, 2009 submitted by Chemstone inresponse to VRO request to address FLM comments Letter dated 09/22/09 from VRO to FLMresponding to FLM comments Comments received on the draft permit during the public comment period (from NPS and Chemstone) VRO's Response to Comments received