## CLIFFS

CLIFFS NATURAL RESOURCES INC. 200 Public Square, Suile 3300, Cleveland, 01-1 44114
·2315 P216.694.5700 clillsnolumlrcsourcos.com



### November20,2012

VIAELECTRONICMAIL(hcdman.susan@epa.gov)


### Dr. SusanHedman, Ph.D. Regional Administrator 

### U.S. EPARegion 5 77 W

.Jackson Boulevard Mail Code: R-19J Chicago, IL 60604-3507 

### Rc: Cliffs Natural Resources' Regional HazeProposalforTaconiteFacilities
DearDr. Hedman:
Thank you for your time and attention concerning the effect of the proposed Regional Haze Federal Implementation Plan for the taconite industry (the "BART FIP") on the four affected facilities operated by Cliffs Natural Resources (Notihshore, Hibbing Taconite, United Taconite, and Tilden Mining)

. Based on our most recent discussion, Cliffs has prepared new information that Cliffs' requests EPAconsider, and thatcontainsthe following elements: (1) Commits to natural gas and other low-sulfur fuels to displace coal; and (2) Accepts low-NOx burners as a "presumptive BART" technology with a commitment to evaluate and install these bumers on a trial basis to confirm that they can meetpellet quality and energy efficiency benchmarks for feasible use as BARTatCliffs' taconite furnaces; and (3) Agrees to install Advanced Process Controls to facilitate implementing LNB while potentially mitigating a portion ofany potential adverse impacts to pellet quality and energy efficiency; and (4) Agrees to continuous emission monitors to capture the NOx reduction benefits from innovations and to provide a basis for establishing appropriate NOx emission limits in the future.
This proposal provides a pathway for achieving the S02 and NOx reductions anticipated in the proposed BART FIP while protecting the taconite industry from changes that can adversely affect two attributes critical to our global competitiveness: pellet quality and energy efficiency. The attachment to this letter provides the details that you have requested for these conceptual proposals and identifies the new information that supportsthe changesto the proposed BARTFIP.
Cliffs believes that this proposal provides a mutually beneficial alternative to the current proposed BART FTP and we ask that EPA incorporate Cliffs' proposal into the final BART FIP rule to

### Ms. SusanHedman November 20, 2012 Page 2

mitigate the serious risk of both technical and commercial uncertainty for Cliffs' taconite operations, while meeting EPA'sregulatory responsibilities.

Ifyou, oryour staff, have any questions regarding Cliffs' proposal, please do nothesitate to contact me.

# Si~~ 

# C.JJL@

DavidT

. Cartella 

# • CLIFFS

DAVID T. CARTELLA VP, Global Environmental Affairs & Counsel P216.694.4380 (O) 216.212

.7817 (M) David.Cartella@CiiffsN R

.com CLIFFS NATURAL RESOURCES 200 Public Square, Suite 3300, Cleveland, OH 44114



### cc: David Thornton, MPCA LynnFiedler, MDEQ MaryGade Michael Long Scott Gischia Douglas 

### A. McWilliams

### Cliffs NaturalResources' RegionalHazeProposalfor TaconiteFacilities
This document presents a regional haze proposal for EPA's consideration in response to the proposed Regional Haze Federal Implementation Plan for the Taconite Industty published August 15, 2012 (the Proposal). The Proposal protects Cliffs' taconite facilities from installing new burner technology that undercuts the pellet quality and energy efficiency attributes critical to Cliffs' global competitiveness. Cliffs' Proposal is summarized in the table belowand explained in detail in the narrative thatfollows thetable for eachofCliffs' affected taconite furnaces.



### NOxLimit NO/ mmbtu 1.2 lbNO/ mmbtu 1

.2lb NO/ mmbtu 1.2 lb NO/ mmbtu (effective (eff ective 6 m onths after (effective 6 monthsafter (cft"cc tive 6 months after immediat el

y) installation within 30,42, installation within 48 and 54 installation within 36 54 months, subjectto months, subject t o months, subject to presumptiveBAR T pr esumptive BART pr esumptive BART feasibility de monstration) f easibility demonstration) feasibility demonstration)

S02Limit 19

.5 lbnlf 88 lb/ hr Combine d limi tof529 lb/ hr I 00% Gas
- Line I 30-da yrolling averagebasis (effective (effective immediately) within 54 months for Line I (effective within 12 immediately) and Line 2 (base d on 155 lbs months, S02 limit base d S02 /h

r for Line I and 374 lbs S02 /hrfor Line 2) using on CEMS within Iyear) existing CEMs.

Advanced Notrequired First line: Within 24 First line: Second lin e: PrototypeInstalled Process months Within 24 Within 36 (within 12 months) Controls months months Second line: Within 36 months (depending (depending on (Energy on prototype Efficiency Third line 3:Within 48 prototype installation Program) months installation success) success) (depe nding on prototype insta lla

tion success)

CEMS NO, installed on NO, installed on waste Currently installed and NO, & S02 installed on wast e gas stacks gas slacks operating waste gas stacks (wi thin 18 (within 18 months) (within 18months) months)

1In summary, Cliffs proposes to achieve S02 emission reductions by transitioning from high sulfur coal to natural gas and other low sulfurfuels. Cliffs proposes NOx reductions by installing lowNOx burner technology (LNB) on one straight grate furnace and on one grate kiln furnace to determine ifthey can be demonstrated as feasible for Cliffs' furnaces. IfLNB is demonstrated to be feasible, Cliffs will install LNBs where necessary to meet the BART limits. Key elements ofthe feasibility determination include:
1. Cliffs proposes to demonstrate whether LNB technology can cost-effectively achieve NOx reductions while maintaining pellet quality at each of the two primmy types of furnaces.' Cliffs will conduct feasibility engineering for the straight grate furnaces at Hibbing Taconite within 12 months. This repmt will include anticipated cost, NOx rate, energy penalty, pellet quality issues, and the projected installation and permitting schedule based onthe burner design. Cliffs will proceed with feasible LNB design specifications to fabricate and install LNB technology on one ofthe lines at Hibbing within the next 12 months following feasibility engineering? Cliffs will collect information on actual energy penalty, quality impacts, NOx rates and costs per ton of NOx reduced and submit a demonstration repmt within six months after installation (a total of

### 30 months from acceptance ofthis proposal).2
2. Cliffs will concurrently proceed with a similar grate-kiln furnace trial at Tilden Line I. The grate-kiln furnace feasibility evaluation is expected to need more time. The feasibility engineeringreport covering the criteria indicated above will be complete within 18 months. The design and installation ofthe trial LNB will be complete within 

### 30 months. The demonstration report will be submitted six months after installation (36 months from acceptance ofthis proposal). Ifthe LNB demonstrations are successful, Cliffs will install feasible LNB technology on one additional straight grate furnace and one additional grate kiln furnace eve1y year after completingthe demonstrations.
3. Ifthe successful LNB demonstrations prove that the technology can meet 1.2 lbs NOJMMBtu as proposed by EPA, these limits will become effective six months after LNB installation is complete to allow time for shakedown periods and process optimization adjustments. Ifthe successful LNB demonstrations prove the technology reduces NOx but cannot cost-effectively achieve 1.2 lb NOJmmbtu consistently while meeting the criteria for pellet quality and energy efficiency, Cliffs will propose an alternate NOx emission limit reflecting what LNB can consistently achieve. If the LNB demonstration concludes that the technology is not feasible for a furnace type, Cliffs will propose an alternate NOx

1 Cliffs provided new information in its comments from EPA's LNB vendors that indicate the data from LNB testing and installations performed to date are insufficient to generalize that LNB is feasible for all taconite furnaces. The vendors agree that the furnace-specific analysis offered by Cliffs above is necessary before we can determine if LNB technology causes unacceptable pellet quality, energy penalty, or unacceptable costs for taconite furnaces. See sections IV.C, E.2.a, & F.1 of Cliffs' 9/28/12 comments and Attachments F, I, Y, U & AA (EPA-R05-0AR-2010- 0037-0045, -0047, -0052) 2 Installation schedules are based on reasonably expected conditions that do not include delays beyond Cliffs' control. LNB installations are expected to require more fuel, which may trigger significant air permitting requirements for other pollutants that may require more time than has been allotted in the above schedule. Any enforceable milestone schedule should account for these and other potential delays beyond Cliffs' reasonable control.

2emission limit using valid CEMs data that reflects the use ofgood combustion practices with any newAdvanced Process Controls (APC) that can be effectively implemented. Cliffs proposes to install a prototype system for APC at Tilden within 12 months and will implement APC on two additional furnaces each year thereafter if the systems are successful. The APC are designed to improve process stability, which should improve energy use and combustion efficiency. They are also expected to reduce NO, emissions and should serve as a valuable tool to improve LNB performance and help mitigate any adverse pellet quality impacts due to LNB.
4. The following three objective criteria will be used to determine ifLNB is feasible for Cliffs' furnaces:

a. Furnace-specific degradation in pellet quality from baseline statistical performance using pellet quality specifications expressed in objective values for compression, before tumble sizing, after tumble sizing, R40 reducibility, lowtemperature disintegration, swelling and contraction.
b. An energy penalty greater than 30% over baseline energy consumption before LNB installation. This high energy penalty reflects additional fuel demand that undercuts energy efficiency and generates greenhouse gas (GHG) emissions and other pollutants that may trigger independent regulatmy requirements or permitting obligations. Increased energy use to this degree is not consistent with good energy policy.

c. The cost per ton ofNOx reduced must remain within EPA's cost effectiveness thresholds. Some additional costs may be incurred to mitigate energy penalty or pellet quality impacts. At some point, additional costs may render LNB costineffective in a patticular application. EPA will provide a cost-effectiveness threshold consistent with other regional haze precedent benchmarks for this objective criterion.3
5. Under this proposal, EPA would determine based on the demonstration provided by Cliffs whether the LNBs meet the criteria for feasibility set forth above for Cliffs' straight-grate furnaces at Hibbing and separately for Cliffs' grate-kiln furnaces at Tilden and United. EPA would also determine based on the alternate NOx limits submitted how to revise the NOx emission limitations in the implementation plan to reflect this new information. Each of these determinations would be a final agency action subjecttojudicial review.
Cliffs' proposal is designed to be implemented within five years ofplan approval in accordance with 40 CFR 51.302(c)(4)(iv). Ifemission limitations must be revised or established after the rule is finalized, the agency will have time within the five-year period to amend the implementation plan to reflectthe appropriate emission limits. Therefore, interim limits are not believed to be necessary.

3 One relevant regional haze cost-effectiveness benchmark is in EPA's proposed partial approval ofthe Michigan Regional Haze SIP. EPA proposes to find that no additional control equipment constitutes BART for

### so, after concluding that$3,500 perton for dryflue gas desulfurization was not cost effective for St. Mary's Cement. 77 Fed. Reg. 46912, *46921 (August 6, 2012)

3Cliffs acknowledges that additional emission reductions for regional haze pollutants may be necessary at one or more ofits facilities to meet the one-hour S02 and one-hour NO, National Ambient Air Quality Standards (NAAQS). Minnesota's approved long term strategy (LTS) for regional haze includes an express obligation for each Minnesota facility to develop modeling and plans for achieving any necessary emission reductions to meet its NAAQS obligations by June 30, 2017. Cliffs anticipates additional regional haze emission reductions will be motivated by its NAAQS obligations. MPCA's long term strategy has established an enforceable mechanism for securing these additional regional haze emission reductions.
The following sections apply Cliffs' Proposal to each ofCliffs' fumaces subject to BART under the Regional Haze provisions ofthe Clean AirAct.
NORTHSHORE MINING: Northshore operates two straight-grate fumaces and two process boilers subjectto BARTthatbum natural gas as their primmy fuel. I) Northshore will immediately meet the proposed BART FIP limit of 1.2 lbs NO)MMBtu (30- day rolling average) for Fumaces 11 and 12 and demonstrate compliance within the 18-month timeline in the proposed BART FIP rule based on newly installed continuous emission monitors (CEMs) on the waste gas stacks. 2) Northshore will also meet the proposed BART FIP limit of0.085 lb NOjMMBh1 (30-day rolling average) for Process Boiler#I and Process Boiler#2 within the 60-month timeline in the proposed BARTFIP rule. 3) Northshore will meet a 19.5 lb S02 /hr emission limit (30-day rolling average) for Furnace 11 and Furnace 12 by burning natural gas. This limit uses the same emission factor that EPA used in its proposed FIP rule (0.0651 lb S02 /long ton pellet produced) but we multiply the factor by maximum production capacity. EPA's proposed FIP limits (16.3 and 17.1 lb S02 /hr respectively) are multiplied by average production rates, which inappropriately reduce production capacity at Northshore.' Cliffs proposes that EPA remove the 80% minimum S02 control efficiency obligation for these fumaces, which EPA does not impose on any other natural gas-fired taconite furnace as a separately enforceable obligation.' 5) Cliffs will demonstrate compliance with the S02 limits by periodic stack tests.6 Northshore can demonstrate S02 compliance immediately ifCEMs are notrequired in the final rule.

HIBBING TACONITE: Hibbing operates three straight-grate taconite pelletizing fumaces of similardesign burning natural gas. 1) Cliffs and EPA agree that existing scrubber controls constih1te BART for the Hibbing natural gas-fired fumaces, but the S02 emission limits must reflect the full variability ofthe ore body. Cliffs provided new test data over an extended period oftime to help EPA develop a large enough database to

4 See section IV.D.3 ofCliffs' 9/28/12 comments (EPA-R05-0AR-2010-0037-004S). 5 BART is defined as the "emission limitation based on the degree of reduction achievable through the application ofthe best system ofcontinuous emission reduction

..." 40 CFR 51.301. Northshore's SO, emission limitation is all that is required. Also requiring a demonstration of control efficiency is unnecessary and beyond what BART requires. See alsop. 35 ofCliffs' 9/28/12 comments (EPA-ROS-OAR-2010-0037-004S). 6 See section V.A ofCliffs' 9/28/12 comments (EPA-R05-0AR-2010-0037-0045).

4mn a statistical analysis to determine the upper predicted limit (UPL) for S02 when properly operating BART controls.7 Since the three furnaces at Hibbing are the same type and size and the ore is from the same mine, Cliffs combined the test data and the statistical analysis to produce an emission limit of88 lbs SO,/hr on a 30-day rolling average basis for each furnace. This is preferable to the proposed BART FIP limit, which is based on the average value from a single stack test for each furnace and is not representative ofnormal process variability. 2) Cliffs will demonstrate compliance with the S02 limits by periodic stack tests. Hibbing can demonstrate S02 compliance immediately ifCEMs are not required in the final rule.' 3) Cliffs and EPA have no data on the pellet quality effects ofinstalling low NOx burners on straight grate furnaces. EPA relies on pilot testing conducted by Fives Nmth America for the Essar installation, which did not introduce pellets and is not a retrofit application. Essar was able to design its furnace with LNB, while Hibbing will need to make retrofit burners work in its existing furnace design constraints.' Cliffs agrees that the Essar test results are a positive development and we have engaged Fives to workwith furnace design engineer, Metso, to develop a way to test LNBs on pellets for Hibbing. Metso has warned Cliffs that the retrofit application for the Hibbing furnaces could have a significantly higher energy penalty than the new furnace designed for Essar. Cliffs is willing to conduct the testing necessary to evaluate pellet quality impacts and energy penalty. Ifthese criteria can be resolved within the bounds of preserving pellet quality, minimizing energy penalty and cost-effectiveness, Cliffs will install LNBs on all three ofthe Hibbing furnaces.
Cliffs proposes that LNBs be designated as the presumptive BART determination for Hibbing Line I, Line 2 and Line 3, with a presumptive emission limit of 1.2 lb NOxfMMBtu on a 30-day rolling average basis using CEMs. These presumptive limits will become effective within 6 months after installing LNB. As indicated above, LNB will be installed on a trial basis o1i the first line within 30 months. IfEPA's presumptive BART is validated aftertesting, Cliffs will have installed LNB on the first line 

### 1 and will proceed to install LNBs on the second line within 

### 12 months and the third line within 

### 24 months of EPA's approval ofthe demonstration repmt excluding permitting and other delays beyond Cliffs' control.
If the successful LNB demonstrations prove the technology reduces NOx but cannot costeffectively achieve 

### 1.2 lb NOxfmmbtu consistently while meeting the criteria for pellet quality and energy efficiency, Cliffs will propose an alternate NOx emission limit reflecting what LNB can consistently achieve. Ifthe LNB demonstration concludes that the technology is not feasible for Hibbing based on the objective pellet quality criteria representing Hibbing's baseline statistical performance for the criteria listed above or the energy penalty exceeds 30% with cost-effective mitigation measures, Cliffs will propose an alternate NOx emission limit using valid CEMs data that reflect the use ofgood combustion practices with any new advanced process controls thatcan be effectivelyimplemented.
Cliffs is scheduled to install advanced process controls atHibbing at the first line in 

### 24 months, at the second line in 36 months, and at the third line in 48 months, if the prototype at Tilden proves successful. The Advanced Process Controls are designed to improve energy and combustion efficiency and they are expected to reduce NOx emissions, improve LNB performance, and help mitigate potential adverse pellet quality impacts due to LNB. Any alternate NOx limit proposed by Cliffs is expected to reflectNOx performance with the benefitofthese advanced process controls.

7 See section IV.D.3 of Cliffs' 9/28/12 comments and Attachment N (EPA-R05-0AR-2010-0037-0045, -0051). 8 See sections V.A. and BofCliffs' 9-28-12 comments and Attachments R-T (EPA-R05-0AR-2010-0037-0045, -0051, -0052). 9 See section C.2.a ofCliffs' 9-28-12 comments and Attachment G(EPA-R05-0AR-2010-0037-0045, -0047).

5UNITED TACONITE: United Taconite is the most complex ofthe four Cliffs' facilities. It operates two grate-kiln furnaces on mixed solid and gaseous fuels. Based on new information provided during the commentperiod, installing add-on controls for S02 is not cost-effective for the United furnaces when the baseline emission rates reflect the amount ofnatural gas in the current and projected fuel mix. 10 Though add-on controls will not be required, Cliffs is achieving significant S02 reductions with its lowsulfur fuel mix. United completed a complicated permitting process for the Green Production Process (GPP) in 2011, which imposed NO, limits and natural gas restrictions to control NO, emissions. United is interested in increasing natural gas usage even further as part ofits dual strategy to increase production and meet the one-hour S02 NAAQS, and will rely on NO,reductions from LNBs, iffeasible, and a GPP permitmodification to increase natural gas usage as needed. 1) Cliffs proposes low-sulfur fuels as BART for United Line 1 and Line 2.ll United will meet a combined BART S02 limit of529 lbs S02 /hr within 54 months (based on 155 lbs SO,!hr for Line 1 and 374 lbs S02 /hr for Line 2) on a 30-dayrolling average basis using existing CEMs. These limits reflectthe use oflow sulfurfuels, more natural gas, and they utilize the higher sulfur emission factor for the standard (acid) pellets produced by United as documented in the comments ofUS Steel. 12 The schedule reflects the time needed to address permit limits that currently restrict the use ofnatural gas. 2) Cliffs cannot assume that LNB will work based on EPA's data from the Minntac installation ofLNB technology because the United grate-kiln furnaces are significantly different in material respects. First, Minntac has not generated data for its LNBs on solid fuels, which are essential for United given its current GPP permit constraints on using natural gas. 13 Second, Minntac achieves a significant amount of its NO, reductions in the preheat zone with smaller burners that have limited effect on pellet quality. 14 United's design does nothave preheat burners, so all ofits NO, reduction must come from the retrofit ofa

10 See section E.2.b, E.3 of Cliffs' 9-28-12 comments and Attachment BB (EPA-R05-0AR-2010-0037-0045- 0052). Cliffs provided new information regarding the actual baseline S02 emission rates that reflect the current use of lower-sulfur fuels for the grate-kiln furnaces at United and Tilden. When the actual baseline emissionrate is used consistent with EPA guidance, add-on S02 controls are not cost effective for Cliffs' grate kiln furnaces. See sections IV.E.2.b, E.3 of Cliffs' 9/28/12 comments and Attachments L& BB (EPA-R05-0AR-2010-0037-0045, -0050, -0052). This offers EPA the opportunity to treat Cliffs' grate kiln furnaces comparably to the US Steel grate-kiln furnaces at Keetac and Minntac. The proposed BART FIP currently requires S02 controls for Cliffs but not for US Steel resulting in lb/ton S02 rates on Cliffs' grate-kiln furnaces that are four times more stringent than the Keetac lb/ton S02 emission rates. See 77 Fed. Reg. 49308, 49319, 49324-25 (Aug. 15, 2012). 11 Cliffs provided new information on its intent to continue to use a lower-sulfur mix of fuels at the United and Tilden lines subject to BART in order to meet regional haze and the S02 NAAQS obligations. See section IV.E.4 of Cliffs' 9/28/12 comments (EPA-R05-0AR-2010-0037-0045). 12 See section 5 of US Steel's 9/28/12 comments (EPA-R05-0AR-2010-0037-0044). 13 See U.S. Steel Minntac, line 6 Low NO, Main Burner Final Report & Facility NOx Management at 12 (Dec. 2011) (EPA-R05-0AR-2010-0037-0039); U.S. Steel Minntac, line 7 Low NO, Main Burner Final Testing Report at 7-8 (May 2011) (EPA-R05-0AR-2010-0037-0039). 14 Minntac invested capital to retrofit the design of furnaces in the late 1980's to include preheat burners for its grate-kiln furnaces which facilitated a significant portion of the furnace's NO, reduction while mitigating energy, heat balance and quality parameters associated with a kiln burner LNB retrofit. See section IV.D.2 of Cliffs' 9/28/12 comments (EPA-R05-0AR-2010-0037-0045). The existing design of United and Tilden do not have preheat burners, so 100% ofany NO, reduction must come from the primary burner in the grate kiln furnace, a much more challenging proposition. This reduces vendors' options for mitigating energy penalty and increases the potential pellet quality ramifications for Cliffs' grate-kiln furnaces. This is furtherjustification for the furnace-specific testing referenced above.

6single burner that alone dictates combustion parameters that affect pellet quality. 15 Cliffs agrees that the results at Minntac are a positive development, but Cliffs and EPA need more data to establish that LNBs constitute BART for United's two grate kiln furnaces. Cliffs has engaged the Minntac burner design company, Coen, to work with furnace design engineer, Metso, to develop a way to test LNBs on pellets for the grate-kiln furnaces at United and Tilden. Metso has warned Cliffs thatthe retrofit applications for the United and Tilden grate-kiln furnaces could have a significantly higher energy penalty and more significant pellet quality impacts than Minntac's application. Cliffs is willing to conduct the testing necessmy to evaluate pellet quality impacts and energy penalty. Ifthese criteria can be resolved within the bounds ofcost-effectiveness, Cliffs will install LNBs on the two United furnaces.
Cliffs proposes that LNBs be designated as the presumptive BART determination for United Line I and Line 2, and impose the 1.2 lb NOJmmbtu emission limit on a 30-day rolling average basis based on CEMs. These presumptive limits will become effective six months after Cliffs conducts a trial ofLNB technology on one of its grate kiln furnaces. As indicated above, Cliffs will conduct feasibility engineering within 18 months and install feasible LNB on a trial basis on one of Cliffs' grate kiln furnaces within 30 months. If EPA's presumptive BART is validated for the grate-kiln furnace after testing, Cliffs will install LNB on the second grate kiln within 12 months of EPA's approval ofthe demonstration repott, and within 18 months ofEPA's approval ofthe LNB demonstration report for the third grate kiln furnace.
Ifthe successful grate kiln LNB demonstration proves the technology reduces NO, but cannot cost-effectively achieve 1.2 Ib NOJmmbtu consistently while meeting the criteria for pellet quality and energy efficiency, Cliffs will propose an alternate NO, emission limit reflecting what LNB can consistently achieve. Ifthe LNB demonstration concludes that the technology is not feasible for United, Cliffs will propose an alternate NO, emission limit using valid CEMs data that reflects the use ofgood combustion practices with any new advanced process controls that can be effectively implemented. Cliffs is scheduled to install advanced process controls atUnited on the first line in 24 months and at the second line in 36 months, if the prototype installed at Tilden proves successful. Any alternate NOx limit proposed by Cliffs is expected to reflect NO, performance with the benefit ofthese advanced process controls.

TILDENMINING (Michigan): Tilden's Line I is agrate-kiln furnace thatburns a combination ofsolid and gaseous fuels to make a fully fluxed pellet. Tilden is processing iron ore from an ore body in Michigan that contains more sulfur that the ore processed by taconite mining operations in northeast Minnesota. I) Cliffs is willing to limit Tilden Line I to natural gas fuel as an alternative for 

### S02 control. Cliffs has vety limited data for 

### S02 emissions when burning I00% natural gas. Cliffs proposes that Tilden collect one year's worth ofCEM data and use the UPL calculated for that database to set the new 

### S02 emission limit. Tilden will submit the alternate 

### S02 emission rate to EPA within 60 days after the CEM has collected one year's worth ofvalid data and EPA will proceed to amend the regional haze rule to include this numeric 

### S02emission limit reflecting natural gas operation ofLine I. 2) Cliffs proposes that LNB be designated as the presumptive BART determination for Tilden Line I and that the presumptive emission limit be 1.2 Ib NOJmmbtu on a 30-day rolling average basis based on CEMs. The presumptive limit will become effective 6 months after the LNB grate kiln

15 See section C.1 of Cliffs' 9-28-12 comments and Attachments H & Y (EPA-R05·0AR-2010·0037·0045, -0047,

- 0052).

7demonstration has been validated by EPA and LNB is installed on Tilden Line I (expected 36 months afterthe effective date ofthe rule).
Ifthe successful grate kiln LNB demonstration proves the technology reduces NOx but cannot cost-effectively achieve 1.2 lb NO,/mmbtu consistently while meeting the criteria for pellet quality and energy efficiency, Cliffs 

### will propose an alternate NOx emission limit reflecting what LNB can consistently achieve. Ifthe LNB demonstration concludes that the technology is not feasible for Tilden Line I, Cliffs will propose an alternate NOx emission limit using valid CEMs data that reflects the use of good combustion practices with any new advanced process controls that can be effectively implemented. Cliffs proposes to install prototype advanced process controls at Tilden in the next 12 months. Any alternate NO, limit proposed by Cliffs is expected to reflect NO, performance with the benefit ofthese advanced process controls.

8