Question#1 

### Provide a written description summarzzzng all challenges which U S. 

### Steel faced during installation, start-up, and normal operation with the low nitrogen oxide burners (LNB) attempting to run with coal or coal and gasfitel on Line #6 and Line #7. 

### Include in the description 

### ifU S. 

### Steel believes operations on Line #6andLine #7

### can be run solelywith solid fitel combustion. Please address separately for coalandbiomass.
U S. 

### SteelResponse All of the infotmation below details the issues observed during the stmi-up and shakedown periods afterinitial installation ofthe lowNOx burners onLines 6 and 7.
Coal 

### Line 7 The Line 7 burner was installed in May 2010 and was stmied after completion ofthe Major outage. Belowis anoutline ofthe issues thathave occunedduring stmi-up ofthe burner: 

### • Problems with lighting theflame. This was due to issues withthe flame scanner, pilot light, etc. The issues have been documented and measures have been implemented to conectthe issues. • Spalling ofthe refractory onthe discharge end ofthe kiln occuned during the start-up from the May 2010 and February 2011 Major outage. This issue has been resolved by changingmaintenance and operatingpractices. 

### • Losing the flame during heat-up. The manufacturer provided assistance with addressing some of the issues; however, challenges still existed. The operators watched the heat-ups very closely and adjusted the gas and combustion air manually during heat-up. Upon continued success with heating up the process and learning how and when to make adjustments to the gas and combustion air, the controls have nowbeen automated. During stmi-up ofcoal, the air to fuel ratio was evaluated. The proper air to fuel ratio is critical for optimizing the burner's perfotmance with respect to NOx emissions. The primary issue observed when running coal was a bushy flame. A tight flame shape is desired, which is seen when burning natural gas. After investigating the issue, it was found that the coal mill backpressure was lower with the new low NOx burner than before. It was determined that a restriction needed to be added to the coal annulus to improve the coal delivery. The following are items thathavebeen done in an attemptto correctthis issue:

• A coal tip insert was installed in July 2010 to restrict the coal displacement at the burner tip. The addition ofthe coal tip inse1i did improve the coal mill backpressure to typical levels and allowed testing to determine the proper stoichiometric ratio to efficiently run coal. • A coal cone was installed in November 2010 to deflect the coal to the center ofthe flame. A 20% improvement inNOxwas anticipated. • The actions implemented inbullets one and two above improved the flame shape, but the expectedNOxreductions were notrealized.Line 6 

### Due to the issues on the Line 7 bumer, two design changes were implemented on the Line 6 bumerin an attemptto improve NOx performancewhenrunning coal. 1. The coal annulus was sized so that the coal mill backpressure would be at typical levels. 2. The coal and combustion air annuluses were switched. The thought behind this is that the combustion air on the outside would improve the flame shape and improve NOx reductions on Line 6.
The Line 6 lowNOx main bumer was installed in April 2011. The coal stmi-up was delayed on Line 6 due to safety concems related to the coal mill. The safety concems were related to the coal mill and not the bumer. Coal testing was stmied in early June.
After evaluatingthe trial results, it was determined thattheNOxreductions were not as favorable as the reductions seen on Line 7. The bumer manufacturer was consulted multiple times regarding this issue. It

### was determined that Line 6 combustion air had 20% less thrust than Line 7 combustion air when running coal. The decrease in air thrust resulted in a poorer flame shape and higher NOx emissions. As a result, the manufacturer recommended installing rings on the inner and outer edges ofthe combustion air annulus to increase the air thrust. The modification, whichtook several days, was made to thebumerinmid September2011. Upon additional testing, NOx emissions improvedhowever were still not as low as whenrunning 1

00% natural gas. The bumer manufacturer was consulted again about the issue. It 

### was detetmined that the higher NOx when running coal with natural gas is directly related to the fuel bound nitrogen contribution (SummaryReport for USS OnNOxreduction for Kilns #6 and 7, S. Londerville 10/26/11).
Biomass Line 7 

### The new low NOx bumer has not been able to achieve the desired feed rate ofbiomass due to plugging issues. This issue was investigated and it has been concluded that the biomass is settling in the bumer pipe due to low flow velocity. A design change was made on the Line 6 lowNOx bumerto address this issue.
Line 6 

### The Line 6 lowNOx bumerwas not able to consistently delivery more than 50% ofthe designed feed rate. The manufacturer was consulted onthis issue and they recommended that changes be made to the biomass system to improve delivery. The biomass supplier completed the recommendations in June 2011, but no improvements were seen in the volume of biomass throughthe bumer. In addition, the biomass supplier assistedinadditional testingby supplying a constant material ofoat hulls, which has a more consistent size distribution. This is different than typical biomass feed which is not a constant material. Again, this did not improve performance.
Due to these issues, the bumertip was inspected in July 2011 to detetmine ifthere was plugging and it was found that the biomass line was deformed. The bumer manufacturer investigated thecause ofthe defmmation and found that it was a burner designmalfunction. The burner biomass pipe was designed to be a divisionplate, but the location ofthe tabs resulted in the thin biomass pipe wall to see excessive stresses which caused itto deform.
No further biomass testing was planned until the biomass line was repaired. The repair was extensive as the burner needed to be removed from the kiln, disassembled, reassembled and reinstalled. The burner manufacturer provided the recommendations for the repair. Due to the time necessary to design the modification and lead time to construct, the modification was completed duringthe majorrepair outage inMarch2012.
On April 11, 2012, biomass testing was performed on the repaired Line 6 low NOx burner to determine ifwe could achieve the designed feed rate. Twotests were performedto determine the maximum biomass feed rate that could be achieved before plugging issues occmTed. The fuels burned during the testing were a combination ofnatural gas and biomass. The biomass burned during the testperiod was a combination ofoat hulls and wood. Comparing the testresults from April 11th, 2012 with the repaired biomass annulus to the tests performed in 2011 with the deformed biomass annulus, there was no improvement in biomass throughput with the repaired burner. Plugging issues in the biomass pipe/burner annulus continued to occur at 50% ofthe designed feed rate.
The plugging issue is believedto be a biomass delivery issue and not an issue withtheburner. In order to determine where the plugging is occuning, a pressure leg was installed off of the biomass line. Testing is tentatively scheduled for the end ofSeptember2012 to determine where the plugging is occuning.
The Line 6 and 7 low NOx burners cannot operate solely on solid fuels due to the following reasons: • Coal- Natural gas is needed when running coalto ensure a stable flame. The designs for Line 6 and 7 burners are different and affectthe stability ofthe flame differently. • Line 6

- The combustion air is on the outside ofthe flame; therefore, the coal is ignited and stabilizedbythenatural gas flame. • Line 7

- The coal is on the outside ofthe flame and the coal is ignited by the hot secondary air. Natural gas also helps to stabilizetheflame. • The natural gas is a dual gas gun consisting ofannulus gas and core gas. See Figure 1 and 2 below that outline the burner tips. When burning any amounts ofnatural gas, the natural gas gun protrudes from the burner. By simply using a ce1iain amount of natural gas, the burner tip is cooled by the flow of natural gas. The burner manufacturer recommends a minimum MSCFH ofgas through the burner to ensure the burner does not overheat. Ifno gas is used, the gas gun needs to beretracted. The retraction ofthe gas gun is done by a manual turnbuckle onthe burner. This does not allowfor a seamless transitionbetween switching from coalto natural gas.

### Figure 1: Line 7Low NOx BurnerTip**,-- --~**  Coal Annulus

,---- Combustloil Air Annulus

. 

### . ,---- Biomass Annulus Atornizing Air Anriulus Gas Core Gas fuQI Oil Gun



### Figure2: Line 6Low NOx BurnerTipQuestion#2 Provide a written description summarizing all externalities, including but not limited to afitel penalty and an increase in emissions on Line #6 and Line #7 after the installation ofLNB technologies. Please confirm 

### if such externalities do notexist or have been able to be resolved.
U 

### S. SteelResponse After the initial installation ofthe low NOx burner on Line 7, there was a temporary 10.5% fuel mcrease. During the shakedownperiod, the fuel increase was alleviated by:

• Process optimization. There was a learning curve due to the fact that this was the first lowNOx burner installed on an iron oreprocessingline. • Balancing the process airflow. The waste gas fan on Line 7 was running at maximum before the burner installation and with the addition ofcombustion air, the process efficiency decreased and safety issues were created. The waste gas fan airflow capacity was increased to balance the airflow out ofthe process. The waste gas fan capacitywas increased inFebruary 2011 onLine 7

. The end result is there is no increase inprocess fuel due to the installation ofthe Line 7 lowNOx burner.
The Line 6 lowNOx burner was installed in April 2011 and due to what we learned during the shakedown period on the low NOx burner on Line 7, no increase in process fuel was realized after the installation ofthe lowNOx burner. The Line 6 waste gas fan capacity was increased in the same timeframe thatthe lowNOxburnerwas installed onthe line.
U. S. Steel researched the collateral pollutant emissions associated with the LNB installation for a LNB trial petmit applicability determination submitted to the Minnesota Pollution Control Agency (MPCA). Both Hatch and Coen determined that the LNB would cause no increases in collateral pollutants. Correspondence between U

. S. Steel and MPCA is attached for your revtew. Question #3 Provide a written description summarizingallpelletquality issues resulting from the installation of LNB technology onLine #6andline #7.
U 

### S. SteelResponse Impactto pellet quality was a keyparameterin dete1miningtechnical feasibility for lowNOx burners. U.S. Steel observed no adverse pellet quality issues resulting from the installation ofthe LNB technology onLine 6 and 7. Impact to Pellet Quality- Line6 Four quality parameters were examinedto determine ifthere was an impactto final pellet quality on Line 6 due to the low NOx burner. These four parameters were reviewed because they are affected by the kiln and cooler section ofthe process. The four quality parameters are after tumble, compressions, reducibility, and low temperature disintegration (LTD). For all ofthe parameters, a higher value represents better quality. The table below shows the values before

### and after the installation ofthe Line 6 lowNOx burner. More recent quality data has also been included to show quality remains to be acceptable. Compressions have decreased, but this is observed on all process lines, including lines without lowNOx burners. This indicates there is an issue withprocessingthe feed material.
Line 6 QualityBefore and Afterthe low NOx BurnerInstallation After Tumble Compression Reducibility LTD Before (11/1/10- 4/3/11) 96.0 416 1.15 87.30 After (4/20/11

- 10/31/11) 96.0 417 1.22 85.58 1/1/12-9/1/12 96.2 410 1.22 86.11


### An improvement was seen in the reducibility and is believed to be due to improved heat distribution in the kiln from the lowNOx burner. A decrease in LTD was seen and is due to the issue ofdumping hot from the cooler. When material is dumping hot, water is added and the hot pellets are cooled too quickly. When pellets are not allowed to cool slowly enough, the LTD decreases. The graph below shows that the LTD has been increasing since the Line 6 lowNOx burner installation in April 2011. This improvement is a result of resolving the issues of dumpinghot from the cooler.
Line 6 Low Temperature Disintegration LowTemperature Disintegration (LTD)
89.0 88.0 87.0 86.0 85.0**~** 0 84.0 83.0 82.0 81.0 80.0 79.0 May-11 Jun-11 Jul-11 Aug-11 Sep-11 Oct-11


### Impactto Pellet Quality-Line 7 In the Line 7 final burner report, it was stated that Line 7 compressions were lower after the installation ofthe burner. It

### also stated that the compressions were low on all ofthe lines which indicate an issue on all of the lines in processing the feed material. Therefore, the low compressions on Line 7 are not believed to be due to the installation ofthe lowNOx burner. In addition, no other quality issues were observed on Line 7 after the installation ofthe low NOx burner.

### Conclusion The pellet quality specifications have not changed since the installation ofLow NOx 

### Bumers. There have been zero off-spec shipments to date. There have been no adverse pellet quality issues related to installation and operation ofthe lowNOxmainbumers. Question#4 Provide a written description summarizing the timeline ofinstalling LNB technology at the facility's remaining fitrnaces. The response schedule must include a time estimate for engineering, purchasing, installation and start-up in weeks. What would be the shortest reasonable time, 

### ifdifferent fi·om your schedule, that it 

### would take to install this LNB technology?
U S. SteelResponse
U. S. Ste.el Minntac- Lines 4 & 

### 5 Task Time I. Receive permit without appeal 6-12 months (approximately 26-52 weeks)* 2. Appropriate projectfunds 1-2 months afterreceiving permit without appeal (approximately 4-8 weeks) 3. Procure and manufacture LNB 6-9 months (approximately 26-36 weeks)** 4. Install LNB 3weeks 5. Shakedown ofLNB

- Optimize LNB for 6months (approximately 26 weeks)*** maximum NOxreductions TotalTime 22-29 months (approximately 85-125 weeks)**** * A permit apphcatwn has been submitted to theMPCA. A permit 1s reqmred for mstallatwn due to the language inthe PSD permit. This applicationwas received byMPCA on August 1, 2012. ** The longest lead time items are for the pmis to increase the waste gas fan capacity. These items include a newmotorand fan wheel. ***A shakedown period is needed oneach line to ensure compliance. **** The LNB will be installed during a major outage. These timeframes could potentially be longer in orderto match upwith a scheduled major outage. 

### U. S. SteelMinntac- Line 3 Task Time I. Prepare and submitpermit application 2 months (approximately 8weeks) 2. Receive permitwithout appeal 12-18 months (approximately 52-78 weeks)* 3. Appropriate projectfunds 1-2 months afterreceivingpennitwithout appeal (approximately 4-8 weeks) 4. Procure and manufacture LNB 4-8 months (approximately 16-32 weeks)** 5. Install LNB 3 weeks 6. Shakedown ofLNB

- Optimize LNB for 6months (approximately 26 weeks)*** maximum NOx reductions Total Time 26-37months**(~roximate!Y_**109-155 weeks)**** * A NOx lilmt w!llneed to be set upon the permittmg ofthe Lme 3 LNB due to the language m the PSD pennit. Itis anticipated thatthe Line 3 permittingtimeframe will be longerthanLine4 and 5. Also, Line 3 permit application will be initiated upon a successful installation ofLine4 or 5. **Atthistime, it is not anticipatedto haveto increasewaste gas fan capacity. ***A shakedownperiod is needed on each lineto ensure compliance. **** The LNB will be installed during a major outage. These timeframes could potentially be longer in orderto matchup with a scheduled majoroutage.

### U.S. Steel Keetac Task Time 1. Detailed LNB engineering 6 months (approximately26 weeks) 2. Preparepermit applicability determination 1month (approximately4 weeks) 3. Receivepermit applicability determination 1-2 months (approximately4-8 weeks)* fi"omMPCA 1-2 months afterreceivingpermit applicability 4. Appropriate project funds determination ofno pennitnecessary from MPCA (approximately 4-8 weeks) 5. Procure and manufacture LNB+procure new 1year (approximately 52 weeks)** fans to balance air flow throughprocess 6. Install LNB 3 weeks 7. Shakedown ofLNB

- Optimize LNB for 6 months (approximately26 weeks)*** maximumNOx reductions Total Time 2 years 6 months (130 weeks)**** *U.S. Steel does notbelieve a permit is required to install a LNB at Keetac. ** The pre-heat fans are currently operating atthe maximum airflow capacity. Therefore, new fans will needto be purchasedto increase the airflow capacity. The pre-heatfans are the longest lead time item. ***A shakedown period is needed on each line to ensure compliance. **** The LNB will be installed during a major outage. These timeframes could potentially be longer in orderto match up with a scheduled major outage.


### Question#5 Provide a written description summarizingany challenges U 

### S. Steel hasfacedwhen attempting to secure vendor and/or engineeringguarantees on reducing nitrogen oxide emissions with LNB technology, and

### if any, to whatextenthave they been overcome. U S. SteelResponse 

### U. S. Steel- Minntac was required to trial NOxreduction technologies in accordance with Title V Operating Permit #13700005. Minntac's Title V operating permit contains a NOx emissions reduction goal. Selective Non-Catalytic Reduction (SNCR) was the first technology trialed, and SNCR was determined to be technically infeasible. Consequently, U. S Steel proposed to trial a Low NOx main burner (LNB). The purpose of trialing the LNB was to evaluate the NOx emissions reduction and, ifnecessary, to detetmine an appropriate add-on control to achieve the additional emissions reduction necessary to meet the NOx emissions reduction goal in Minntac's Title V operating permit. Minntac obtained the permit that required a LNB trial in December 2008. An evaluation ofthe LowNOx MainBurner trial results revealed that Minntac could meet the NOx emission reduction goal without additional add-on controls. U. S. Steel did request a vendor guarantee for a NOx emissions reduction, but the vendor declined to provide a specific NOx emissions reduction guarantee. Although the vendor declined to provide a NOx emissions reduction guarantee, the trial evaluation showed it was not necessary. Question#6 Provide a ·written description summarizingany challenges U 

### S. Steel hasfacedwhen attempting to secure vendor and/or engineering guaranteesforpellet quality with LNB technology, and 

### if any, to what extenthave they been overcome.U 

### S. SteelResponse U. S. Steel did not pursue a vendor guarantee for pellet quality with LNB technology. A vendor would not be likely to provide a guarantee due to not having control over other aspects ofthe process that affect quality. However, pellet quality was a factor in determining the feasibility of the LNB technology. Ifthe impact to pellet quality was unacceptable, the pilot test would have been deemedunsuccessful. Question #7 Provide the approach thatyou will be usingto establish S02 limits, including thepotential use of a lbs/MMBTUlimit.
U 

### S. SteelResponse U. S. Steel will use a basic statistical analysis that includes establishing a standard deviation and a 99% confidence interval utilizing available CEMS data over a period of time to capture changes in ore variability. The statistical analysis will be used to establish alb S02/hr limit that U. S. Steel is comfmiable it can meet. We have done a cursory evaluation ofestablishing an S02 limit as a lb/MMBTU. Since the majority ofthe sulfur is coming from the ore as opposed to the fuel, it does not make sense inthis particular applicationto use a fuel based limit.