## Minnesota Pollution Control Agency
520 Lafayette Road North I 5t.Paul,MN 55155-4194 I 651-296-6300 I 800-675-3843 651-282-5332 TTY www.pca.state.mn.us

January 12, 2010



### Mr. ScottColeman,

General Manager US SteelCorporation MinnesotaOreOperations P.O. Box 417 Mountain Iron, MN 55768



# . RE: NitrogenOxidesControlTechnology PilotTesting DearMr. Coleman: This letter is to summarizethe progress US Steel (USS) has madeto date in meeting the nitrogen oxides (NOx) emissions reduction requirements ofUSS Minntac's (Minntac) air emissions permit,_Minntac's air emissions permit requires pilot testing and implementation of NO x emission reduction technologies, with a goal of greaterthan 70 percent reduction in NOx emissions comparedto the initial permit limit of 13,300ton per year NOx, The Minnesota Pollution Control Agency (MPCA) received the letter dated November 30, 2009, from Minntac in response to the MPCA's November 6,2009, requestfor information on potential pilot testing of Selective Catalytic Reduction (SCR) and Low Temperature Oxidation (LoTOx) technologies at Minntac. The November 30, 2009, letter contained information concerning problems pilot testing SCR, including two letters from SCRvendors declining 10bid, discussion of optimal operating temperatures for SCR systems,and identification of potential SCR catalyst poisons in the exhaustgas stream at Minntac. In the letter Minntac requesteda meeting with the MPCA to discuss issuesrelated to LoTOx pilot testing, including timing, permitting, cross media impacts, and technical feasibility. On the morning of December 15,2009, representativesfrom the MPCA, Minntac, the US Forest Service, and the National Park Service met with Babcock Power (Babcock) to discuss Regenerative Selective Catalytic Reduction (RSCR) technology and its potential application at Minntac. Minntac representativesdistributed copies of a Babcock RSCR bid dated April 24, 2009, for pilot and full scale application of RSCR at Minntac. This bid was not previously provided to the MPCA, despite our November 6,2009, requestfor any additional information or correspondencewith SCR pilot testvendors. The Minntac permit identifies RSCR asa type of 

### SCR. Representatives from the MPCA, Minntac, and the US Forest Service met on the afternoon of December 15,2009, to discussprogress on current requirements of the Minntac air permit, including current and potential pilot tests of air pollution control equipment.

St. Paul I Brainerd I Detroit lakes I Duluth I Mankato I Marshall I Rochester I Will mar I Printed on 100% post-consumer recycled paper

### Mr. ScottColeman

Page 2
The following is a brief summary of the current statusof the NOx reduction technologies discussed by Minntac andthe MPCA: 

### Low NOx Main Burners



### 1. Minntac contracted with Hatch, anengineering and project management company, to analyze potential NOx reduction technologies. According to Hatch's January30, 2009, Project Report, which analyzed potential NOx reduction technologies for Minntac, Selective Non-Catalytic Reduction (SNCR), and low N9x main burners in combination had the potential to achieve NOx reductions approachingthe 70 percent reduction goal for the Minntac air permit. In a February 27,2009, letter, Minntac proposed pilot tests for SNCR and a low NOx main burner. In a letter datedApril 16,2009, the MPCA authorized Minntac to proceed with a pilot test of a low NOx main burrier, in combination with computational fluid dynamics (CFD) modeling and Mobotec technology. Hatch's January2009 Project Report estimateda 30 percent reduction in NOx formation from installation of a low NOx main burner in combination with CFD modeling and Mobotec. The MPCA approved the specific installation of a low NOx main burner on Line 7 at Minntac in a letter dated November 20,2009. Minntac plans to install the burner in April 2010, in accordancewith the MPCA-approved schedule for the pilot test. 

### 2. SelectiveNon-Catalytic Reduction The MPCA received a letter dated December9, 2009, from Minntac discussingthe feasibility of SNCR as a technology to reduce NOx emissions at Minntac. A full report on SNCR from NALCO Mobotec was attached.The report was prepared after pilot testing SNCR, as required by Minntac's 2009 air emissions permit. In the letter and attachedreport Minntac and NALCO Mobotec concluded that SNCR was not a feasibleNOx control technology for full scale implementation at Minntac. The MPCA has completed a preliminary review of the report and preliminarily acceptsMinntac's proposal not to implement a full-scale SNCR demonstration project atthis time. Demonstrated NOx reductions in the pilot testwere less than 10 percentandthe December9, 2009, report identified technical problems adapting the technology to an application at Minntac. At this tim~, the MPCA has not madea determination regarding the technical feasibility of SNCR.



### 3. Selective Catalytic Reduction Minntac supplied technical information on potential application of traditional "clean side" and "dirty side" SCR applications that would be installed either before ("dirty side") or after ("clean~ side") existing control equipment. Minntac statedthat severalvendors declined to bid on a pilot test project dueto technical problems suchasthe presenceof catalyst poisons in the pre-control equipment gas streamand reheatrequirements of the gas streamfor effective post-control applications. The MPCA has not madea determination regarding the technical feasibility of "clean side" or "dirty side" SCR. There are other potential control technologies with better chancesof success,including RSCR. At this time, the MPCA will work with Minntac onthosetechnologies.

### Mr. ScottColemanPage

3
Babcock prese~tedthe technical details ofRSCR technology and potential application at Minntac at the December 15,2009, meeting. RSCRequipment is designedfor installation after other pollution control equipment and requites significantly less energy for gas streamreheating than "dirty side" SCR technology. Babcock concluded in its December 15,2009, presentation and April 24,2009, letter to Minntac that RSCR was technically feasible. Issuesraised by Minntac in writ~encorrespondenceand/or or~l discussioninclude:



## ..

# . Required amounts of ammonia for proper systemoperation.

The presenceof catalyst poisons in the gas streamand their effects onthe RSCR catalyst. Dust levels in the gas streamand engineering of water flushing to remove dust from the



## . equIpment.Capital and operating costs forbumers to reheatthe gas stream. Babcock representativesestimated that an RSCR systemcould reduce NOx emissions by 70 percent or more, depending on thesy~tem design. Based on discussionsbetweenBabcock, the MPCA, Minntac, and others present,the MPCA has determined that anytechnical issuesrelated to RSCR could be studied,in a pilot test and are likely to be factors affecting cost but not technical feasibility of the technology. Minntac' s permit requires that technologies be selected for pilot testing based on technical feasibiliry rather than cost.



### 4. Low Temperature Oxidation

In its January 30, 2009',engineering analysis on potential NOx reduction technologies atMinntac,

Hatch estimated LoTOx could achieve 80 percent reduction in NOx emissions. Bas~don th,e;

information provided in the January, 2009~atch report, the MPCA hasconcluded that a LoTOx pilot test is technically feasible. In a November 6,2009, letter, the MPCA requested from Minntac a scheduleto pilot test LoTOx. As discussed in the letter, technical feasibility is the only criteria allowed by Minntac's permit for consideratio,nwhen examining technologies for potential pilot testing. Issuesassociatedwith full scale LoTOx implementation; specifically crossmedia pollution impacts and system energy demands, canbe studied in a pilot test and evaluated when determining whether LoTOx is appropriate for a full-scale demonstrationproject.



### 5. ProcessOptimization

A report outlining the findings of Minntac's CFD studies is due to the MPCA in February, 2010. Potential process optimization projects recommended in the CFD report or otherwise developed by Minntac should be discussedwith the MPCA as soonas practicable following submittal of the 

### report. Path Forward Given the results of the SNCR pilot test, it is .likely that pursuit of technologies other than SNCR will.bemore productive at this time. Technical analysessubmitted by Minntac and others suggestthat either I;oTOx or RSCRmay achieve 70 percent or greaterreductions in NOx emissions from Minntac's operations.

### Mr. ScottColeman

Page4

As discussed in MPCA's November 6, 2009, letter, Minntacis obligated by its air permit topropose and conduct technically feasible pilot teststhat will leadtQfull scale implementation of NOx emissions reductions attheir facilitY; Therefore, by February 15,2010, pleasepropose pilot test schedules for LoTOx and RSCR for the MPCA 'sreview and approval.

. For your planning purposes,the MPCA has cont~ctedvendors for LoTOx and RSCR. BOC Linde requires three months to prepare its LoTOx equipmentfor a pilot test. Minntac's proposed pilot test for LoTOx should include a commencementdatefor pilot.testirig no later thanJune 15,2010. Babcock requires sevenmonths tQfabricate andrleliver a pilot scale RSCR system.As a result,

. Minntac's proposed pilot test schedule for RSCR should include a commencementdate for pilot testing no later than October 15, 201 O.Potential RSCR pilot testsshould be conducted on Line 6 or 7 at Minntac to most appropriately studythe effects of multiple fuels onthe control system. Per the requirements of Minntac's air emissionspermit, upon receipt of the proposed schedule,the MPCA will review the 'Proposaland approve anenforceableschedulefor pilot testing.

Finally, the MPCA requestsall information collected or generatedby USS, in whatever format,

that has not already beenprovided regardingallNOx emission reduction technologies thatUSShas considered or investigated to date, including testdata, written exchangeswith vendors and bids. Submit information tiy February 15,2010. Minn. Stat..§ 116.091 (2008). 

### The MPCA looksforwardto continuing to work with Minntac onpotentialNOx reduction technologies.

Please contact mewith anyquestions

orconcerns

at651-757-2603. Si
Christopher

J.Nelson,P.E..,

Manager Metallic Mining Sector Industrial Division CJN/SV:rm

cc: Tishie Woodwellt US Steel

Mike Dzurinkot US Steel Chrissy Bartovicht US Steer



## . Ryan SlatstUS Steel Stephanie Campbellt US Steel SuzanneBaumannt MPCA Owen Seltzt MPCA Hongming Jiangt MPCA