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 gas fitel on Line #6 and Line #7. Include in the 

description if U S. Steel believes operations on Line #6 and Line #7 can be run solely with solid 

fitel combustion. Please address separately for coal and biomass. 

U S. Steel Response 

All of the infotmation below details the issues observed during the stmi-up and shakedown 

periods after initial installation of the low NOx burners on Lines 6 and 7. 

Coal 

Line 7 

The Line 7 burner was installed in May 2010 and was stmied after completion of the Major 

outage. Below is an outline of the issues that have occuned during stmi-up of the burner: 

• Problems with lighting the flame. This was due to issues with the flame scanner, pilot 

light, etc. The issues have been documented and measures have been implemented to 

conect the issues. 

• Spalling of the refractory on the discharge end of the kiln occuned during the start-up 

from the May 2010 and February 2011 Major outage. This issue has been resolved 

by changing maintenance and operating practices. 

• 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 

now been automated. 

During stmi-up of coal, 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 that have been done in an attempt to correct this issue: 

• A coal tip insert was installed in July 2010 to restrict the coal displacement at the 

burner tip. The addition of the 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 of the 

flame. A 20% improvement in NOx was anticipated. 

• The actions implemented in bullets one and two above improved the flame shape, but 

the expected NOx reductions were not realized. 
Line 6 

Due to the issues on the Line 7 bumer, two design changes were implemented on the Line 6 

bumer in an attempt to improve NOx performance when running 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 low NOx 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 evaluating the trial results, it was determined that the NOx reductions 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 of the combustion air annulus to increase the air thrust. The modification, 

which took several days, was made to the bumer in mid September 2011. 

Upon additional testing, NOx emissions improved however were still not as low as when running 

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 (Summary Report for USS On NOx reduction 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 of biomass 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 

low NOx bumer to address this issue. 

Line 6 

The Line 6 low NOx bumer was not able to consistently delivery more than 50% of the designed 

feed rate. The manufacturer was consulted on this 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 

through the bumer. In addition, the biomass supplier assisted in additional testing by supplying a 

constant material of oat 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 bumer tip was inspected in July 2011 to detetmine if there was plugging 

and it was found that the biomass line was deformed. The bumer manufacturer investigated the 
cause of the defmmation and found that it was a burner design malfunction. The burner biomass 

pipe was designed to be a division plate, but the location of the tabs resulted in the thin biomass 

pipe wall to see excessive stresses which caused it to 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 during the major repair outage in March 2012. 

On April 11, 2012, biomass testing was performed on the repaired Line 6 low NOx burner to 

determine if we could achieve the designed feed rate. Two tests were performed to determine the 

maximum biomass feed rate that could be achieved before plugging issues occmTed. The fuels 

burned during the testing were a combination of natural gas and biomass. The biomass burned 

during the test period was a combination of oat hulls and wood. Comparing the test results 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% of the 

designed feed rate. 

The plugging issue is believed to be a biomass delivery issue and not an issue with the burner. 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 of September 2012 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 coal to ensure a stable flame. The designs 

for Line 6 and 7 burners are different and affect the stability of the flame differently. 

• Line 6 - The combustion air is on the outside of the flame; therefore, the coal is 

ignited and stabilized by the natural gas flame. 

• Line 7 - The coal is on the outside of the flame and the coal is ignited by the hot 

secondary air. Natural gas also helps to stabilize the flame. 

• The natural gas is a dual gas gun consisting of annulus gas and core gas. See Figure 1 

and 2 below that outline the burner tips. When burning any amounts of natural 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 of gas through the burner to ensure 

the burner does not overheat. If no gas is used, the gas gun needs to be retracted. The 

retraction of the gas gun is done by a manual turnbuckle on the burner. This does not 

allow for a seamless transition between switching from coal to natural gas. 
Figure 1: Line 7 Low NOx Burner Tip 

,----~ Coal Annulus 

,---- Combustloil Air Annulus . . ,---- Biomass Annulus 

Atornizing Air Anriulus 

Gas 

Core Gas 

fuQI Oil Gun 

Figure 2: Line 6 Low NOx Burner Tip 
Question #2 

Provide a written description summarizing all externalities, including but not limited to a fitel 

penalty and an increase in emissions on Line #6 and Line #7 after the installation of LNB 

technologies. Please confirm if such externalities do not exist or have been able to be resolved. 

U S. Steel Response 

After the initial installation of the low NOx burner on Line 7, there was a temporary 10.5% fuel 

mcrease. During the shakedown period, the fuel increase was alleviated by: 

• Process optimization. There was a learning curve due to the fact that this was the 

first low NOx burner installed on an iron ore processing line. 

• Balancing the process airflow. The waste gas fan on Line 7 was running at 

maximum before the burner installation and with the addition of combustion air, 

the process efficiency decreased and safety issues were created. The waste gas 

fan airflow capacity was increased to balance the airflow out of the process. The 

waste gas fan capacity was increased in February 2011 on Line 7. 

The end result is there is no increase in process fuel due to the installation of the Line 7 low NOx 

burner. 

The Line 6 low NOx 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 of the low NOx burner. The Line 6 waste gas fan capacity was increased in 

the same timeframe that the low NOx burner was installed on the 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 summarizing all pellet quality issues resulting from the installation 

of LNB technology on Line #6 and line #7. 

U S. Steel Response 

Impact to pellet quality was a key parameter in dete1mining technical feasibility for low NOx 

burners. U.S. Steel observed no adverse pellet quality issues resulting from the installation of the 

LNB technology on Line 6 and 7. 

Impact to Pellet Quality- Line 6 

Four quality parameters were examined to determine if there was an impact to 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 of the process. The four quality parameters are after 

tumble, compressions, reducibility, and low temperature disintegration (LTD). For all of the 

parameters, a higher value represents better quality. The table below shows the values before 
and after the installation of the Line 6 low NOx 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 low NOx burners. This indicates there is 

an issue with processing the feed material. 

Line 6 Quality Before and After the low NOx Burner Installation 

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 low NOx burner. A decrease in LTD was seen and is due to the 

issue of dumping 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 low NOx 

burner installation in April 2011. This improvement is a result of resolving the issues of 

dumping hot from the cooler. 

Line 6 Low Temperature Disintegration 

Low Temperature 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 

Impact to Pellet Quality- Line 7 

In the Line 7 final burner report, it was stated that Line 7 compressions were lower after the 

installation of the burner. It also stated that the compressions were low on all of the 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 of the low NOx burner. In 

addition, no other quality issues were observed on Line 7 after the installation of the low NOx 

burner. 
Conclusion 

The pellet quality specifications have not changed since the installation of Low NOx Bumers. 

There have been zero off-spec shipments to date. There have been no adverse pellet quality 

issues related to installation and operation of the low NOx main bumers. 

Question #4 

Provide a written description summarizing the timeline of installing 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, if different fi·om your schedule, that it would take to install this LNB 

technology? 

U S. Steel Response 

U. S. Ste.el Minntac- Lines 4 & 5 

Task Time 

I. Receive permit without appeal 6-12 months (approximately 26-52 weeks)* 

2. Appropriate project funds 1-2 months after receiving permit without appeal 

(approximately 4-8 weeks) 

3. Procure and manufacture LNB 6-9 months (approximately 26-36 weeks)** 

4. Install LNB 3 weeks 

5. Shakedown of LNB - Optimize LNB for 6 months (approximately 26 weeks)*** maximum NOx reductions 

Total Time 22-29 months (approximately 85-125 weeks)**** 

* A permit apphcatwn has been submitted to the MPCA. A permit 1s reqmred for mstallatwn due to the 

language in the PSD permit. This application was received by MPCA on August 1, 2012. 

** The longest lead time items are for the pmis to increase the waste gas fan capacity. These items 

include a new motor and fan wheel. 

***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 

order to match up with a scheduled major outage. 

U. S. Steel Minntac- Line 3 

Task Time 

I. Prepare and submit permit application 2 months (approximately 8 weeks) 

2. Receive permit without appeal 12-18 months (approximately 52-78 weeks)* 

3. Appropriate project funds 1-2 months after receiving pennit without appeal 

(approximately 4-8 weeks) 

4. Procure and manufacture LNB 4-8 months (approximately 16-32 weeks)** 

5. Install LNB 3 weeks 

6. Shakedown of LNB - Optimize LNB for 6 months (approximately 26 weeks)*** maximum NOx reductions 

Total Time 26-37 months (~roximate!Y_ 109-155 weeks)**** 

* A NOx lilmt w!llneed to be set upon the permittmg of the Lme 3 LNB due to the language m the PSD 

pennit. It is anticipated that the Line 3 permitting timeframe will be longer than Line 4 and 5. Also, Line 

3 permit application will be initiated upon a successful installation ofLine 4 or 5. 

**At this time, it is not anticipated to have to increase waste gas fan capacity. 

***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 

order to match up with a scheduled major outage. 
U.S. Steel Keetac 

Task Time 

1. Detailed LNB engineering 6 months (approximately 26 weeks) 

2. Prepare permit applicability determination 1 month (approximately 4 weeks) 

3. Receive permit applicability determination 1-2 months (approximately 4-8 weeks)* fi"omMPCA 

1-2 months after receiving permit applicability 

4. Appropriate project funds determination of no pennit necessary from MPCA 

(approximately 4-8 weeks) 

5. Procure and manufacture LNB + procure new 1 year (approximately 52 weeks)** fans to balance air flow through process 

6. Install LNB 3 weeks 

7. Shakedown of LNB - Optimize LNB for 6 months (approximately 26 weeks)*** maximum NOx reductions 

Total Time 2 years 6 months (130 weeks)**** 

*U.S. Steel does not believe a permit is required to install a LNB at Keetac. 

** The pre-heat fans are currently operating at the maximum airflow capacity. Therefore, new fans will 

need to be purchased to increase the airflow capacity. The pre-heat fans 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 

order to match up with a scheduled major outage. 

Question #5 

Provide a written description summarizing any challenges U S. Steel has faced when attempting 

to secure vendor and/or engineering guarantees on reducing nitrogen oxide emissions with LNB 

technology, and if any, to what extent have they been overcome. 

U S. Steel Response 

U. S. Steel- Minntac was required to trial NOx reduction 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, if necessary, 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 of the Low NOx Main Burner 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 summarizing any challenges U S. Steel has faced when attempting 

to secure vendor and/or engineering guarantees for pellet quality with LNB technology, and if 

any, to what extent have they been overcome. 
U S. Steel Response 

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 of the 

process that affect quality. However, pellet quality was a factor in determining the feasibility of 

the LNB technology. If the impact to pellet quality was unacceptable, the pilot test would have 

been deemed unsuccessful. 

Question #7 

Provide the approach that you will be using to establish S02 limits, including the potential use of 

a lbs/MMBTU limit. 

U S. Steel Response 

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 of establishing 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 in this particular application to use a fuel based limit.