NALCO Mobotec Nalco Mobotec Final Report October 26, 2009

**Confidential & Proprietary Information** This information is proprietary and confidential and shall not be copied, discl osedor shared

with parties other than those addressed without specific written authorization by NALCO Mobotec. All state and federal laws governing such

information, copy writes, and trademarks shall apply. All rights reserved.

1 of 10

US Steel Minn Tac Line 7

Final Report

October 27, 2009
NALCO Mobotec Nalco Mobotec Final Report October 26, 2009

**Confidential & Proprietary Information** This information is proprietary and confidential and shall not be copied, discl osedor shared

with parties other than those addressed without specific written authorization by NALCO Mobotec. All state and federal laws governing such

information, copy writes, and trademarks shall apply. All rights reserved.

2 of 10

Table of Contents

Table of Contents 2

1. Project Background 3

1.1. Contract Description 3

1.2. Unit Description 3

1.3. CFD Modeling 3

2. Nalco Mobotec System Description 4

3. Summary of engineering, construction and testing performed. 4

4. Summary of Tuning results 6

5. Temperature Traverse 7

6. SNCR applicability Summary 8

7. Recommendations 9

7.1 Cooling the kiln exit flue gas temperature by injecting water spray

into the kiln 9

7.2 Flue gas recirculation into kiln burner 9

7.3 Low-NOx kiln burner 9

8. Conclusion 10
NALCO Mobotec Nalco Mobotec Final Report October 26, 2009

**Confidential & Proprietary Information** This information is proprietary and confidential and shall not be copied, discl osedor shared

with parties other than those addressed without specific written authorization by NALCO Mobotec. All state and federal laws governing such

information, copy writes, and trademarks shall apply. All rights reserved.

3 of 10

1. Project Background

1.1. Contract Description

US Steel Issued Purchase Order 00797286 to Nalco Mobotec to perform Computation

Fluid Dynamic Modeling on agglomerator line 5 per Nalco Mobotec Proposal dated

March 25, 2009.

Nalco Mobotec performed the contracted CFD modeling and presented the results to US

Steel at the plant on March 17, 2009.

Following CFD presentation, Nalco Mobotec submitted a revised proposal dated April 3,

2009 to engineer, supply, start up andtune a NOx only demonstration. USS Steel

awarded purchase order00824682 dated April 7, 2009 to Nalco Mobotec to install SNCR

System on line 6 or line 7. In later discussions, US Steel clarified that the SNCR

demonstration would be applied to line 7.

1.2. Unit Description

US Steel operates an iron ore pelletizing plant at their Minnesota Ore Operation

(Minntac) facility, including five pelletizing lines designated as Nos. 3, 4, 5, 6 and 7.

These facilities emit tremendous NOx from fuel combustion and mercury from iron ore

pelletizing process. To meet pollutant emission limitations, US Steel is currently

investigating the feasibility of reducing NOx and mercury emissions from these

indurating processes, focusing initially on Line No.5. NOx emission control would be

installed onthe other lines once the technologies prove to be effective.

The indurating process at Line No.5 is a “grate-kiln” type system,which employs a

traveling grate, a rotary kiln and an annular cooler. The green pellets are dried and

heated in an oxidizing atmosphere at an incipient fusion temperature of approx. 2400-

2600 F depending on the type of pellet. Acid pellets are generally heated to the lower

end of the temperature range, while flux pellets are heated to the higher end of the

temperature range. Drying of the green pellets and partial induration occurs at the

grate, while final induration is finished in the rotary kiln. The pellets are cooled in an

annular cooler that is designed to operate with counter-current cooling air flow.

1.3. CFD Modeling

The objective of the CFD study was to analyze combustion performance and NOx/Hg

reduction resulting from the application of Nalco Mobotec Rotamix®designed for

Minntac pelletizing lines. Multiple CFD models have been performed for baseline and

Rotamix®cases. All models focused on Line 5 only. The accuracy of the baseline model
NALCO Mobotec Nalco Mobotec Final Report October 26, 2009

**Confidential & Proprietary Information** This information is proprietary and confidential and shall not be copied, discl osedor shared

with parties other than those addressed without specific written authorization by NALCO Mobotec. All state and federal laws governing such

information, copy writes, and trademarks shall apply. All rights reserved.

4 of 10

results have been validated against the testing data. Through careful study, analysis

and review the following conclusions have been drawn from the CFD study:

• Rotamix®system designed for NOx reduction has multiple injection ports on the

furnace walls between rotary kiln and preheater. The Rotamix®air pressure is designed

for 15 inwg.

• The modeling results showed that more than 50% NOx reduction can be

achieved by Rotamix®urea injection with an NSR of 1.0-1.3. Further reduction is

possible by injecting more urea.

2. Nalco Mobotec System Description

Following award of purchase order 00824682, Nalco Mobotec began engineering of the

Nalco Mobotec Rotamix®SNCR System for application on Line 7. The system consists

of a Rotamix®Air system and a urea pumping and delivery system. Components

included:

 Rotamix® fan

 Ductwork and supports

 Trailer tanker for temporary urea storage

 Dilution tank for mixing demineralized water with the urea.

 Pump station.

 Distribution piping

 Rotamix®Injection lateral and lances.

 Instrumentation.

US Steel provided electrical design and all installation labor.

3. Summary of engineering, construction and testing performed.

Nalco Mobotec began Engineering on April 8, 2009 and mobilized the site for beginning

of construction the week of June 22, 2009. Construction was completed and

commissioning began the week on July 21, 2009. Nalco Mobotec performed tuning

Summary of Tuning Performed

From July 24 through August 7, Nalco Mobotec performed SNCR tuning. Following

tuning period, Nalco Mobotec and US Steel had several conference calls to explore what

systems modifications could be made to improve the NOx reduction. Nalco Mobotec

and US Steel agreed that additional temperature data was required. As a result, Nalco

Mobotec remobilized and on September 24, 2009 performed a temperature traverse of

the injection plane. Details of testing are discussed below.
NALCO Mobotec Nalco Mobotec Final Report October 26, 2009

**Confidential & Proprietary Information** This information is proprietary and confidential and shall not be copied, discl osedor shared

with parties other than those addressed without specific written authorization by NALCO Mobotec. All state and federal laws governing such

information, copy writes, and trademarks shall apply. All rights reserved.

5 of 10
NALCO Mobotec Nalco Mobotec Final Report October 26, 2009

**Confidential & Proprietary Information** This information is proprietary and confidential and shall not be copied, discl osedor shared

with parties other than those addressed without specific written authorization by NALCO Mobotec. All state and federal laws governing such

information, copy writes, and trademarks shall apply. All rights reserved.

6 of 10

4. Summary of Tuning results-line 7

The urea injection ports are located at the entrance of the preheater (exit of the kiln).

The ports are adjacent to the Zone 2 burners. Ten ports are installed for the urea

injection: four ports are located on top of the preheat entrance and three ports are

located on each of the side walls. Figure 1 shows the general location of the ports and

in reference to the burners. Port numbering is also presented in the figure.

Figure 1: Port position and numbering

Nalco Mobotec performed the tuning from July 26 to August 7, 2009. The variables

that were adjusted during the tuning include

 different combinations of lance injection

 air pressure of Rotamix®fan

 urea concentration in the solution

 solution flow rates

No NOx reductions were seen with Zone 3 burners in service. The best NOx reduction

was realized with Lances9 and 10 in service. The other ports showed no significant

NOx reduction. Under most operating conditions, the NOx reduction was in the range

of 8 – 10%. A final test using a 10% urea concentration resulted in a 15% reduction.

However, the test was held for a relatively short time and should be repeated to

validate the results.
NALCO Mobotec Nalco Mobotec Final Report October 26, 2009

**Confidential & Proprietary Information** This information is proprietary and confidential and shall not be copied, discl osedor shared

with parties other than those addressed without specific written authorization by NALCO Mobotec. All state and federal laws governing such

information, copy writes, and trademarks shall apply. All rights reserved.

7 of 10

Nalco Mobotec also tested injecting urea solution through the view ports located above

the grate in the preheat section. In all cases, the urea injection resulted in an increase

in NOx production. The temperature of the gas above the grate is elevated because of

its proximity to the Zone 1 and Zone 2 natural gas burners. The high temperature

caused the urea to react with the high O2 concentration and produce NOx.

5. Temperature Traverse

During the tuning, Nalco Mobotec used its IRthermocouple to measure the flue gas in

the preheat section of line 7 through the numerous view ports. The temperatures were

higher than desired, mainly ranging between 2100 and 2500oF. (The ideal temperature

range for SNCR is 1900 to 2100oF.) The view portswere downstream of the injection

location. Also, a limitation of the IR thermocouple is that the reading is an average

temperature value.

To determine the actual flue gas temperature around the injection location, Nalco

Mobotec brought an 8-foot thermocouple totraverse the preheat duct through the

injection ports. The temperature results are presented in Table 1, with Zone 3 burners

out of service.

Table 1: Temperature readings of traverse measurement

Top Ports West Ports East Ports

Port # 4 5 6 7 2 1 3 8 9 10

Time Start 10:06 10:20 10:38 11:28 14:21 14:37 15:31

8 1933 1965 1979 2019 2141 2185 2157

7 1920 1938 1959 2002 2133 2146 2143

6 1909 1913 1934 1998 2110 2031 2077

5 1910 1906 1929 1994 2095 1982 2023

4 1874 1852 1933 1980 1980 1964 2010

3 <1000 <1000 <1500

2

D

e

pth (ft)

1

End Time 10:20 10:38 10:50 11:44 14:37 14:56

Plu

g

ged

15:54

Plu

g

ged

Plu

g

ged

The first three feet of the probe were in the refractory section. Therefore, the

temperature readings were of the five feet closest to the preheat walls, which has

dimensions of 16 X 10 ft. Three portswere plugged and could not be traversed,

including ports 9 and 10, which resulted in the bulk of NOx reduction when urea was

injected.
NALCO Mobotec Nalco Mobotec Final Report October 26, 2009

**Confidential & Proprietary Information** This information is proprietary and confidential and shall not be copied, discl osedor shared

with parties other than those addressed without specific written authorization by NALCO Mobotec. All state and federal laws governing such

information, copy writes, and trademarks shall apply. All rights reserved.

8 of 10

The temperatures measured from the top ports were between 1900 and 2020oF, which

is the desired temperature range for urea injection. However, the side ports show

temperatures higher than 2100oF. The temperature is higher deeper inside the duct.

Therefore, the gas temperature away from the preheat walls is expected to be even

higher than the measured values (i.e. greater than 2100oF). This temperature is

beyond the best temperature windows for SNCR which is between 1900-2100oF, which

is believed to be the main reason for low NOx reduction achieved. The lack of NOx

reduction from the ports on the top of the preheater is due to short residence time for

the urea reaction before reaching preheat burners in Zone 2, while the limited NOx

reduction from the side ports is due tothe higher flue gas temperatures.

6. SNCR applicability Summary

Nalco Mobotec installed ten ports for urea injection to reduce the NOx emissions of

Line 7. The portswere located at the entrance of the preheat section. Two important

factors forthe SNCR effectiveness in NOx reduction are flue gas temperature (ideally

between 1900 and 2100oF) and sufficiently long residence time.

In the majority of the flue gas duct, the temperatures are believed to be too high for

SNCR to effectively reduce NOx. When Zone 3 burners are out of service, only the top

five feet of the duct (approximately the top third of the duct) appears to be in the right

temperature regime. In the region of elevated temperatures, NOx reduction was

limited to only 8 – 10% (from Ports 9 and 10).

The flue gas at the top of the duct travels longer distances(through length of the

preheater) before finally passing through the grate. The required reaction time for

SNCR is short (fractions of a second). However, because of the fast flue gas velocities

in the preheater and the presence of natural gas heaters, the residence time may not

be sufficient for complete SNCR reaction. Any urea that does not react to reduce NOx

will quickly react in the presence of high temperatures and high O2 concentrations to

produce NOx, resulting in an overall negligible NOx reduction.

The conditions necessary for SNCR were not present to reduce NOx sufficiently. NOx

was reduced by 8 – 10%, with one short test yielding a 15% reduction. SNCR is more

like ly to work if more burners in the preheat were taken out of service. Unfortunately

that would greatly affect the quality of the taconite green balls and is therefore not a

viable solution. SNCR may still be possible in taconite lines where preheaters do not

have burners (such as lines where there are no limestone fluxing, and therefore a lower

heat requirement).

It is noted from the historical plant operational data that the kiln exit temperature of
NALCO Mobotec Nalco Mobotec Final Report October 26, 2009

**Confidential & Proprietary Information** This information is proprietary and confidential and shall not be copied, discl osedor shared

with parties other than those addressed without specific written authorization by NALCO Mobotec. All state and federal laws governing such

information, copy writes, and trademarks shall apply. All rights reserved.

9 of 10

Line 7 that we injected urea in is hotter than Line 5 that was originally tested by HVT

and modeled. Line 5 is much suitable for SNCR injection from temperature standpoint.

7. Recommendations

With the discussions Nalco Mobotec has hadwith US Steel, finding an effective NOx

reduction strategy will be a challenge. The economics, technical difficulty and operating

issues of an SCR clearly make that technology seem unreasonable. We still believe that

there are potential solutions tothe US Steel NOx reduction goals that may be

economically and technically feasible. However; additional time and investigation will

be required.

Some of the options we consider possible are as follows:

7.1 Cooling the kiln exit flue gas temperature by injecting water spray into the kiln

Mixing water spray with flue gas will cool down the gas temperature to an

appropriate point for SNCR injection. In order for flue gasto be well mixed, the

water injection points have to be upstream 5-10 ft from the kiln exit, and the

injection ports shall be on the kiln cylinder. To maintain the same heat flux to

the pellets in the preheater, the preheater burners have to burn harderto

compensate for the loss of flue gas heat capacity due to water injection. We

understandthat injection of water into a gas stream to then reheat it is an

efficiency loss, however; the temperature drop required making SNCR work

appears to be relatively small compared to the overall temperature. This layout

can be field tested. US Steel needs to consider whether this is acceptable by the

process operation.

7.2 Flue gas recirculation into kiln burner

The majority of NOx is formed from thermal NOx when natural gas is fired

through the kiln burner. One way to reduce the NOx is to reduce the flame

temperature of kiln burner. Kiln burner is a diffusion flame; flue gas recirculation

has proved to be able to effectively reduce the peak flame temperature by

reducing the O2 concentration of the secondary air before its mixing with fuel

from the kiln burner. This design is not overly complicated and can be designed

and implemented in a relatively short time frame.

7.3 Low-NOx kiln burner

A conventional low-NOx burnercan be applied to the kiln. If US Steel desired

Nalco Mobotec would work with a burner manufacturer to provide a burner
NALCO Mobotec Nalco Mobotec Final Report October 26, 2009

**Confidential & Proprietary Information** This information is proprietary and confidential and shall not be copied, discl osedor shared

with parties other than those addressed without specific written authorization by NALCO Mobotec. All state and federal laws governing such

information, copy writes, and trademarks shall apply. All rights reserved.

10 of 10

design appropriate for the process. It is important to keep in mind that Nalco

Mobotec has done low NOx burner modifications in conjunction with combustion

modifications in order to optimize NOx reduction. Nalco Mobotec’s ROFA system

is an alternative to typical low-NOx burners that has always shown higher NOx

reduction while maintaining good combustion (recognized by the US EPA) and

may be an option, but due to the rotation of the kiln and configuration it would

be a challenging design that requires detailed design up front and cannot be pilot

scale tested as the SNCR application was.

8. Conclusion

Nalco Mobotec is more than willing to work with US Steel on a solution if US Steel

desires. Investigation of the options stated above may yield additional solutions not yet

examined, but potentially highly successful.