Project Report



# United States Steel Corporation

Minntac Plant



# NOx Reduction Analysis

For


# Minntac Iron Ore Pelletizing Operation

H-332002
Rev. 0 January 30, 2009ISO 9001 H-332002 , Rev. 0, Page i

C:\carl40268\US STEEL\332002 Minntac Iron Ore Pellet Operation\PR332002-01 US Steel Minntac - NOx Reduction Technology Report Rev 0.doc © Hatch 2006/03 a H-332002 

### Project Report Rev. 0, Page i January 30, 2009



## United States Steel

Minntac Iron Ore Pelle tizing Operation

DISTRIBUTION



## NOx Reduction Analysis

Table of Contents

1. Introduction ................................................................................................................... ......................... 1

2. Pelletizing Process Description ................................................................................................ ............... 1

3. NOx Emissions from Indurating Process .......................................................................................... ....... 3

3.1 Design Basis for NOx Emission Analysis at Indurating Line 5 ......................................................... 3

3.2 NOx Emission Estimate for Line 5 Indura ting Process – Based on AP-42 (EPA) ............................... 3

3.3 NOx Emission Estimate for Line 5 – Based on Stack NOx Monitor................................................. 4

4. Indurating Process NOx Reduction Technology Analysis........................................................................ 4

4.1 Low NOx Burner Technology and Indurating Process Changes ...................................................... 4
4.1.1 Low NOx Burners in Preheat Section of the Grate................................................................ 5
4.1.2 Low NOx Main Burner in the Rotary Kiln............................................................................. 5
4.1.3 Combustion Air Distribution and Mixing Upgrades (Rotary Kiln).......................................... 6

4.2 Selective Non-Catalytic Reduction (SNCR) ..................................................................................... 6
4.2.1 SNCR Utilizing Urea ............................................................................................................ 6
4.2.2 SNCR Utilizing Aqueous Ammonia...................................................................................... 8
4.2.3 SNCR Design Concepts........................................................................................................ 8
4.2.4 SNCR Equipment Concepts ................................................................................................ 11
4.2.4.1 Urea Storage Tank: ................................................................................................... 11
4.2.4.2 Urea Day Tank: ........................................................................................................ 11
4.2.4.3 Water Tank:.............................................................................................................. 11
4.2.4.4 Pump Skids:.............................................................................................................. 11
4.2.4.5 Urea Injection Lances:.............................................................................................. 11
4.2.4.6 Compressed Air System: ........................................................................................... 11
4.2.4.7 Control System: ........................................................................................................ 11
4.2.5 SNCR Equipment Suppliers ................................................................................................ 12
4.2.5.1 Nalco Mobotec......................................................................................................... 12
4.2.5.2 Energy Systems Associates (ESA)............................................................................... 12
4.2.5.3 BACT Process Systems, Inc....................................................................................... 13

4.3 Selective Catalytic Reduction (SCR) Technology........................................................................... 13
4.3.1 SCR Utilizing Urea............................................................................................................. 13
4.3.2 SCR Design Concepts......................................................................................................... 14
4.3.3 SCR Equipment Concepts................................................................................................... 18United States Steel - Minntac Iron Ore Pelletizing Operation NOx Reduction Analysis

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C:\carl40268\US STEEL\332002 Minntac Iron Ore Pellet Operation\PR332002-01 US Steel Minntac - NOx Reduction Technology Report Rev 0.doc © Hatch 2006/03 a 4.3.3.1 Electro-Static Precipitator System .............................................................................. 18
4.3.3.2 Reactant Storage and Feed System:........................................................................... 18
4.3.3.3 Reactant Dilution and Injection System: ................................................................... 18
4.3.3.4 Compressed Air System: ........................................................................................... 18
4.3.3.5 SCR Catalyst System: ................................................................................................ 19
4.3.3.6 Exhaust Fan and Motor System: ................................................................................ 19
4.3.3.7 Instrumentation and Controls System:....................................................................... 19
4.3.4 SCR Equipment Suppliers ................................................................................................... 19
4.3.4.1 Branch Environmental Corp...................................................................................... 19
4.3.4.2 Mitsubishi Power Systems ........................................................................................ 20

4.4 Low Temperature Oxidation (LoTOx) - NOx Reduction Technology ............................................ 20
4.4.1 LoTOx Technology Overview ............................................................................................ 20
4.4.2 LoTOx Design Concepts..................................................................................................... 21
4.4.3 LoTOx Equipment Concepts............................................................................................... 24
4.4.3.1 Oxygen Plant............................................................................................................ 24
4.4.3.2 Ozone Generator System.......................................................................................... 25
4.4.3.3 Ozone Reaction Chamber ........................................................................................ 25
4.4.3.4 Wet Scrubber System................................................................................................ 26
4.4.3.5 Exhaust Fan and Motor Drive ................................................................................... 26
4.4.3.6 Exhaust Stack............................................................................................................ 26
4.4.3.7 Wastewater Treatment Plant ..................................................................................... 27
4.4.3.8 Control System ......................................................................................................... 28
4.4.4 LoTOx Equipment Supplier ................................................................................................ 28

5. Hatch Recommendations .......................................................................................................... ............ 29

Appendices:

Appendix A – Indurating Process Flow Diagram Appendix B – Line 5 Operating Data Appendix C – NOx Reduction Technology Comparison for Existing Installations Appendix D – NOx Reduction Vendor ComparisonUnited States Steel - Minntac Iron Ore Pelletizing Operation NOx Reduction Analysis

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## 1. Introduction

U.S. Steel contracted Hatch to provide a Conceptual Engineering analysis of the potential technology options for reducing NOx emissions from the indurating furnaces at the Minntac facility. There are five pelletizing lines at the Minntac facility and U.S. Steel requested that Line No.5 be the focus of Hatch’s
evaluation.

U.S. Steel stated that a current estimate for NOx emissions from the five indurating lines at U.S. Steel Minntac is approximately 13,300 tons/yr. U.S. Steel also stated that a preliminary target of 3,990 tons/yr NOx emissions has been established, which is a reduction of approximately 70%.



## 2. Pelletizing Pro cess Description

The pelletizing operation is the last major step in taconite ore processing at Minntac. Immediately upstream of the indurating process, iron concentrates, along with water and a binder are rolled into marble-sized, “green” balls inside a balling mill (rotating cylinder).

The pelletizing operation at Minntac produces two types of pellets, which are acid pellets and flux pellets. Acid pellets are produced from iron ore c oncentrates and a binder (bentonite) only, while flux pellets are produced by adding between 1 and 10 percent limestone to the mix before the agglomeration process. The bentonite binder is added to the iron concentrates to improve the green ball formation at approximately 10 to 20 lbs/ton of wet concentrate.

Next the agglomerated “green balls” are dried and heat ed in the indurating process as the final step in the pelletizing process at Minntac. The grate-kiln-c ooler type indurating system includes a traveling grate, a rotary kiln and an annular cooler. Drying of the green pellets and partial induration occurs on the traveling grate, while final induration occurs at the rotary kiln and pellet cooling in the annular
coolers.

U.S. Steel provided 2007 pellet production information pertaining to the indurating operations at Minntac, which is outlined below in Table 2-1 (Line No.5 information highlighted in yellow for clarity).

Table 2-1 Pellet Production (Indurating Process)

Based on information provided by Minntac, Hatch prepared a simplified process flow diagram for the indurating process at Minntac’s Line No.5, which is outlined below: 

### U.S. Steel Minntac - 2007 Indurating Pellet Production (per Minntac)

Line Pellets Produced Operating Ti me % Time Average Production

Line 3 784,101 LT/yr 3,395 hours/yr 38.8% 231 LT/hr Line 4 3,520,968 LT/yr 8,396 hours/yr 95.8% 419 LT/hr
Line 5 2,953,534 LT/yr 7,805 hours/yr 89.1% 378 LT/hr Line 6 3,131,607 LT/yr 8,010 hours/yr 91.4% 391 LT/hr Line 7 3,089,753 LT/yr 8,028 hours/yr 91.6% 385 LT/hrUnited States Steel - Minntac Iron Ore Pelletizing OperationNOx Reduction AnalysisGreen PelletsIron PelletsWaste Gas Preheat Recoup Cooler VentGas Side Analysis StackAir Flow Stack Zone 1 Zone 2/31. Gas Flow Rates:(1A & 1B) (FAN 3A) (FAN 3B)- standard: (scfm) 500,000 265,000 110,000 108,000 174,000 206,0002. Mass Flow Rates:- dry gases: (lbs/min) 32,000 19,750 7,620 7,580 12,380 14,720- water vapor: (lbs/min) 2,600 155 150 100 130 1603. Gas Temp.: (deg F) 120 600 1,630 930 70 704. Gas Density: (lbs/ft3) 0.063 0.038 0.018 0.027 0.072 0.0725. Static Pressure: ("wg) 0.5 -15.2 -0.6 0.3 -2.1 -2.1Pellet Analysis Dryer D1 Dryer D2 Preheat Rotary/Kiln Cooler 1 Cooler 2/36. Pellet Temp* (deg F) 100 650 1100 2450 800 250* estimated pellet temperatureCooler Indraft AirUS Steel Minntac – Line 5Hatch Project No. 332002SK1 - Process Flow Diag.RotaryKilnCoolerZone 1CoolerZone 2CoolerZone 3Cooler VentStackScrubberSystemWaste GasFanWaste GasStackPreheatExhaustFan1A & 1BInputs:- Biomass- NaturalGas- Fuel Oil3ExhaustFan 3A541212356Dryer D2Dryer D14ExhaustFan 3B6Waste Gas Preheat Recoup Cooler VentGas Side Analysis StackAir Flow Stack Zone 1 Zone 2/31. Gas Flow Rates:(1A & 1B) (FAN 3A) (FAN 3B)- standard: (scfm) 500,000 265,000 110,000 108,000 174,000 206,0002. Mass Flow Rates:- dry gases: (lbs/min) 32,000 19,750 7,620 7,580 12,380 14,720- water vapor: (lbs/min) 2,600 155 150 100 130 1603. Gas Temp.: (deg F) 120 600 1,630 930 70 704. Gas Density: (lbs/ft3) 0.063 0.038 0.018 0.027 0.072 0.0725. Static Pressure: ("wg) 0.5 -15.2 -0.6 0.3 -2.1 -2.1Pellet Analysis Dryer D1 Dryer D2 Preheat Rotary/Kiln Cooler 1 Cooler 2/36. Pellet Temp* (deg F) 100 650 1100 2450 800 250* estimated pellet temperatureCooler Indraft AirUS Steel Minntac – Line 5Hatch Project No. 332002SK1 - Process Flow Diag.RotaryKilnCoolerZone 1CoolerZone 2CoolerZone 3Cooler VentStackScrubberSystemWaste GasFanWaste GasStackPreheatExhaustFan1A & 1BInputs:- Biomass- NaturalGas- Fuel Oil3ExhaustFan 3A541212356Dryer D2Dryer D14ExhaustFan 3B6United States Steel - Minntac Iron Ore Pelletizing Operation NOx Reduction Analysis

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## 3. NOx Emissions from Indurating Process

There are basically two types of NOx generated for this application, thermal NOx and fuel NOx. Thermal NOx is formed by the high temperature reaction of nitrogen and oxygen as follows: (Zeldovich mechanism)

N2 + O = NO + N

N + O2 = NO + O

N + OH = NO + H

Hatch believes almost all of the NOx from Line 5 is thermal NOx generated in the rotary kiln, due to the high process gas temperatures ranging between 2500-2600 deg F.

Fuel NOx can be a factor when oil, coal or other fuels are utilized based on the potential for these fuels to contain organically bound nitrogen. Line 5 utilizes na tural gas and biomass in the combustion process at the rotary kiln, and bound nitrogen in the biomass fuel is expected to be relatively minor.



### 3.1 Design Basis for NOx Emission An alysis at Indur ating Line 5

As outlined in Section 1 above, U.S. Steel stated that the current estimate for NOx emissions from the five indurating lines at U.S. Steel Minntac is approximatel y 13,300 tons/yr and that a preliminary target of 70%
reduction has been established.

It was also established by U.S. Steel that the NO x emissions for the Line 5 portion of the pelletizing production at U.S. Steel Minntac is estimated to be 25 00 tons NOx/yr, which would translate to a required NOx reduction of 1750 tons/yr (70% reduction) at Line 5.



### 3.2 NOx Emission Estimate for Line 5 Indur ating Process – Based on AP-42 (EPA)

Based on the production information outlined above in Table 2-1, Hatch prepared an estimate for NOx emissions that are expected based on an emission factor of 1.5 lbs NOx/ton pellets produced as outlined in AP-42. The results are outlined below in Table 3-1, which shows an average hourly NOx emission rate of approx. 624 lbs/hr for the Line No.5 indurating line (highlighted in yellow for clarity).



### Emission Factor NO x 

### Emissions (per AP-42) (AP-42) Annual Basis Hourly Basis

Line 3 1.5 lbs NOx/ton 647 tons/yr 381 lbs/hr Line 4 1.5 lbs NOx/ton 2,905 tons/yr 692 lbs/hr
Line 5 1.5 lbs NOx/ton 2,437 tons/yr 624 lbs/hr Line 6 1.5 lbs NOx/ton 2,584 tons/yr 645 lbs/hr Line 7 1.5 lbs NOx/ton 2,549 tons/yr 635 lbs/hr Totals: 11,121 tons/yr

Table 3-1 Estimated NOx Emissions from Indurating ProcessUnited States Steel - Minntac Iron Ore Pelletizing Operation NOx Reduction Analysis

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### 3.3 NOx Emission Estimate for Line 5 – Based on Stack NOx Monitor

Hatch reviewed data supplied by U.S. Steel pertaining to NOx emissions from Li ne 5 as measured via the continuous emission monitor (CEM), which is located in the scrubber system exhaust stack. This data shows that the average level of NOx emissions was approximately 470 lbs NOx/hr for the time period from October 2007 thru June 2008.

The 470 lbs/hr (average) NOx emission rate measured at Line 5 translates to an emission factor of approx. 1.13 lbs NOx/ton. Utilizing this “measured” emission f actor to estimate emissions at each of the five lines results in total NOx emissions of 8,400 tons/yr.



## 4. Indurating Process NOx Redu ction Technology Analysis

Hatch investigated the following potential options for reducing NOx emissions from the indurating process

at Minntac:

• Low NOx burners at the rotary kiln/pre-heating sections of the indurating process and indurating process changes with respect to the rotary kiln combustion, including Mobotec’s ROFA system.

• Selective Non-Catalytic Reduction (SNCR) technology.

• Selective Catalytic Reduction (SCR) technology, including dirty-side and regenerative.

• Low Temperature Oxidation (Lo-TOx)

Note a majority of the NOx reduction technology that has been installed has been directed to the power, oil refining and cement plant industries. Hatch is not aware of any of these NOx reduction technologies being installed on an indurating process in North Americ a. LKAB in Sweden has recently installed an SCR type NOx reduction system on their indurating process line KK4. Hatch was able to find very little information pertaining to this system, which was installed in 2008.



### 4.1 Low NOx Burner Technology a nd Indurating Process Changes

Hatch investigated several potential applications of low NOx burners to reduce NOx emissions generated in the rotary kiln, including the following:

• Install low NOx burners in the preheat section of the traveling gate, upstream of the rotary
kiln.

• Upgrade the main burner in the rotary kiln to a low NOx burner.

• Upgrades to improve the combustion air distribution, mixing and efficiency of the kiln burner system.

Hatch believes these potential “process” type changes have the potential to reduce NOx emissions generated from the indurating process by approximately 20-30%. In addition, it is anticipated that these “indurating process” type upgrades are likely to be the most cost effective of all the potential NOx reduction options.United States Steel - Minntac Iron Ore Pelletizing Operation NOx Reduction Analysis

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C:\carl40268\US STEEL\332002 Minntac Iron Ore Pellet Operation\PR332002-01 US Steel Minntac - NOx Reduction Technology Report Rev 0.doc © Hatch 2006/03 a For example, less NOx generated means that the sizing of the downstream NOx reduction systems will be reduced, including reagent consumption, electrical power consumption, equipment systems, etc. Lastly, all of these options can be utilized in conjunction with other NOx reduction systems (i.e. SNCR, SCR, Lo-TOx, etc). Each of these potential concepts is described in more detail below.



### 4.1.1 Low NOx Burners in Preheat Section of the Grate

Hatch understands that Minntac is in the process of inst alling low NOx burners in the preheat section of the traveling grate upstream of the rotary kiln. The objective was to provide additional energy in preheating the pellets, thereby reducing the energy input requirements at the rotary kiln.

Lower energy input and slightly lower flame temperature at the rotary kiln burner were expected to lower the NOx emissions generated in the kiln. Minntac has stated that initial installations have been successful from several aspects, including the following:

• Lower NOx emissions generated from the i ndurating process based on the lower flame temperatures inside the kiln. In the absence of test data and NOx emission results from Minntac for these installations, Ha tch estimates a 10% NOx reduction.

• Improved process efficiency and improved product characteristics inside the kiln based on more uniform heat distribution, gas temperatures, etc. (i.e. less material build-ups on the walls of the kiln).

• Reduced fuel consumption for the indurating process.



### 4.1.2 Low NOx Main Burner in the Rotary Kiln

The existing main kiln burner is not a “low NOx” bur ner, but a standard, multi-fuel burner manufactured by Conamera/Aecometric Corp.

Hatch’s discussions with one potential burner supplier shows that they believe that upgrading the main kiln burner with low NOx type burner will provide a si gnificant reduction in the amount of NOx emissions generated in the rotary kiln (estimated to be 10- 20% reduction). Hatch’s review of the low NOx burner literature shows that the potential NOx reduction and cost savings are significant enough to merit additional modeling and investigation. The key w ill be to verify that the low NOx burner will not negatively affect the indurating process.

FCT, Inc. proposes to replace the existing main burne r in the rotary kiln with a Gyrotherm low NOx dual fuel burner. FCT is an Austrailian based company that specializes in burner technology and has significant experience in kiln burner design. FCT also appears to have significant capabilities for providing CFD modeling and bench scale testing of the rotary kiln.

Other potential “low NOx” burner suppliers manufactur e similar burners and should be investigated prior to implementing this approach.United States Steel - Minntac Iron Ore Pelletizing Operation NOx Reduction Analysis

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### 4.1.3 Combustion Air Distribution and Mixing Upgrades (Rotary Kiln)

In 2001 U.S. Steel Minntac retrofitted one of their rotary kilns with a “ported kiln” air-injection system and currently two of Minntac’s five indurating lines possess the “ported kiln” technology.

The ported kiln technology (patented by Metso Minerals) injects air under the bed of pellets in the rotary kiln, causing rapid oxidation of the magnetite pellets. This rapid oxidation of the magnetite pellets reduces the kiln temperatures, fuel consumption, heat lo ad on the downstream annular cooler and produces improved pellet quality. This “ported kiln” technology is also expected to reduce NOx emissions generated in the rotary kiln.

Another potential option to reduce NOx emissions generat ed in the rotary kiln is to improve the air flow/circulation throughout the rotary kiln. Nalc o Mobotec proposes to impr ove the combustion process by upgrading the kiln with a Rotating Opposed Fired Ai r (ROFA) System. Mobotec states this system is a state of the art furnace staging and NOx reduction system. By increasing the circulation and turbulence of the air-flow throughout the kiln, it is expected that th e efficiency of the combustion process is improved. Mobotec believes that this improved efficiency will re duce NOx generated in the kiln by approximately 10-

20%.

Energy System Associates (ESA) stated that they believe some low NOx features can be incorporated into the existing combustion system design, which will redu ce NOx emissions by approximately 25%. The ESA proposal includes modifications to the burner tip.

The potential for each of these technologies to reduce NOx emissions while minimizing the costs associated with “end of the pipe” type solutions merits that each of these potential options should receive additional consideration via CFD modeling and testing.



### 4.2 Selective Non-Catalytic Reduction (SNCR)

Selective Non-Catalytic Reduction (SNCR) is utilized for reducing NOx emissions by injecting urea (or aqueous ammonia) directly into a high temperat ure gas stream. These NOx reduction concepts are described briefly below:



### 4.2.1 SNCR Utilizing Urea

Urea is utilized to reduce NOx emissions by chemic ally reducing the NOx to harmless nitrogen gas in accordance with the following simplified reaction: *

(NH 2 ) 2 CO + 2NOx + 1⁄2O 2 

### → 2N 2 + 2H 2 O + CO 2

* Note that there is an intermediate reaction in which the urea reacts to form ammonia.

Key design parameters in optimizing the NOx reduc tion efficiency of the SNCR system include the following:

• Reagent injection rate.

• Flue gas residence time of 0.3 seconds or more.

• Good mixing and contact between the urea and the gas stream (NOx).United States Steel - Minntac Iron Ore Pelletizing Operation NOx Reduction Analysis

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C:\carl40268\US STEEL\332002 Minntac Iron Ore Pellet Operation\PR332002-01 US Steel Minntac - NOx Reduction Technology Report Rev 0.doc © Hatch 2006/03 a • Reaction temperature between 1800 and 2000 deg F.

• No presence of a flame.

As stated above, the temperature of the flue gas needs to be kept within the range of 1800-2000 deg F in order to be effective in reducing NOx emissions. Figu re 4-1 shows that the for gas temperatures on the left side of the peak, NOx removal efficiency increases with increasing gas temperature (i.e. reaction rates increase with temperature). Residence time typically limits NOx reduction in this range.

At temperatures below 1800 deg F, the reaction betwee n the ammonia and the NOx is reduced to the point that little reaction takes place. This can result in un-reacted ammonia (ammonia slip) exiting the stack or
result in an ammonia reaction with sulfates and/or chlori des to form ammonium salts. These salts can foul downstream equipment (scrubber system) and/or cause a whitish colored opaque plume at the exhaust
stack.


### At gas temperatures above the 2000 deg F, the a mmonia tends to preferentially react with oxygen in gas stream to form NOx, thereby increasing NOx emissions in lieu of helping to reducing the emissions. Figure 4-1 shows theoretical NOx reduction efficiency for SNCR technology below:

SNCR NOx Reduction Efficiency

0 10 20 30 40 50 60 70 80

1700 1800 1900 2000 2100

Gas Temperature, Deg FReduction Efficiency,%

Figure 4-1 SNCR NOx Reduction Efficiency w/ Urea

Note that based on Hatch’s analysis, this theoretical reduction efficiency appears to be relatively optimistic and is contingent on “ideal” conditions for the reduction reaction. Hatch’s literature review and discussions with various equipment suppliers sugges t that a 30-50% NOx reduction is a more realistic
target.United States Steel - Minntac Iron Ore Pelletizing Operation NOx Reduction Analysis

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### 4.2.2 SNCR Utilizing Aqueous Ammonia

Utilizing aqueous ammonia to reduce NOx emissions is similar to utilizing urea, with the reaction described below: (simplified):

2NH 3 + 2NOx + 1⁄2O 2 → 2N 2 + 3H 2 O

The optimal range for the flue gas temperature is s lightly lower for aqueous ammonia when compared to urea at approx. 1650-1850 deg F. The biggest issue with utilizing aqueous ammonia is that it often requires special safety precautions when shipping, handling and storing. Note that the EPA has classified aqueous ammonia at concentrations greater than 20% as a regulated toxic substance (hazardous chemical).



### 4.2.3 SNCR Design Concepts

As outlined in the NOx Reduction Comparison Table (A ppendix C), a majority of the SNCR installations identified by Hatch were designed for utility boiler applications. Hatch’s review of these SNCR installations showed the following:

• Gas volumes for these boiler applications were relatively large (100,000 scfm to 1,000,000 scfm), which is similar to the 265, 000 scfm gas stream at Minntac’s Line 5.

• Inlet NOx concentrations were typically in th e 200-500 ppm range, which is similar to the 420 ppm NOx loading in the Preheat section of the traveling grate at Minntac.

• SNCR installations showed an average NOx reduction efficiencies of 34%.

• Gas temperatures were typically in the 1900 to 2500 deg F range, which similar to the gas stream temperature in the Preheat section of the traveling grate at Minntac.

Although Hatch was not able to identify any previous SNCR installations on an indurating process, Hatch believes that the SNCR technology is a viable option for this application. The key factor in successfully implementing the SNCR technology is identifying a ur ea injection point that will provide optimal gas temperature and residence time. Preliminary design parameters are outlined below:

• Urea to be injected in the preheat section dow nstream of the rotary kiln as necessary to provide the acceptable gas temperature (1800-2000 deg F).

• Injection nozzles shall be designed to provide good contact between the urea sprays and the gas stream exiting the kiln (approximately 10-16 nozzles required).

• Urea usage is expected to be approx. 150 gal/hr (50% solution) based on the NOx loading outlined in Section 3 above (i.e. 2500 tons NOx/yr).

• Urea consumption for Line 5 at Minntac is expected to be approx. 1,200,000 gal/yr (50% solution by weight).

• Compressed air usage at 2700 scfm and 80 psig to atomize the urea sprays.

• NOx reduction is expected to be in the 30-50% range, with a preliminary target of forty percent (40%), which translates to a reduction of 1000 tons NOx/yr at Line 5.United States Steel - Minntac Iron Ore Pelletizing Operation NOx Reduction Analysis

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C:\carl40268\US STEEL\332002 Minntac Iron Ore Pellet Operation\PR332002-01 US Steel Minntac - NOx Reduction Technology Report Rev 0.doc © Hatch 2006/03 a Gas Analysis at Injection Point: (preliminary)

Gas Volume:

Standard: 265,000 scfm

Gas Temperature: 2000 deg F

Gas Analysis: (% volume basis)

- Nitrogen 73%

- Carbon Dioxide 8%

- Oxygen 16%

- Moisture 3%

- Dust Load 8 gr/dscfUnited States Steel - Minntac Iron Ore Pelletizing OperationNOx Reduction AnalysisISO 9001C:\carl40268\US STEEL\332002Minntac Iron Ore Pellet Operation\PR332002-01 US Steel Minntac - NOxReduction Technology Report Rev 0.docUS Steel Minntac – Line 5Hatch Project No. 332002SNCR - Process Flow Diag.CoolerZone 1CoolerZone 2CoolerZone 3Cooler VentStackScrubberSystemWaste GasStackPreheatDryer D2Dryer D1Urea Flow: 150 gal/hrUrea Temp.: 70 deg FComp. Air: 2700 scfm50% UreaStorage TankUrea Feed SystemRotaryKilnWaste GasFanGas Volume: 265,000 scfmGas Temp.: 2000 deg FNOx Load: (ave.) 630 lbs/hrDust Load: 8 gr/dscfGas Volume: 500,000 scfmGas Temp.: 120 deg FNOx Load: (ave.) 380 lbs/hrDust Load: 0.015 gr/dscfPellets Produced412 tons/hrUS Steel Minntac – Line 5Hatch Project No. 332002SNCR - Process Flow Diag.CoolerZone 1CoolerZone 2CoolerZone 3Cooler VentStackScrubberSystemWaste GasStackPreheatDryer D2Dryer D1Urea Flow: 150 gal/hrUrea Temp.: 70 deg FComp. Air: 2700 scfm50% UreaStorage TankUrea Feed SystemRotaryKilnWaste GasFanGas Volume: 265,000 scfmGas Temp.: 2000 deg FNOx Load: (ave.) 630 lbs/hrDust Load: 8 gr/dscfGas Volume: 500,000 scfmGas Temp.: 120 deg FNOx Load: (ave.) 380 lbs/hrDust Load: 0.015 gr/dscfPellets Produced412 tons/hrUnited States Steel - Minntac Iron Ore Pelletizing Operation NOx Reduction Analysis

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### 4.2.4 SNCR Equipment Concepts

The equipment systems required to implement the SNCR technology at Minntac appear to be relatively simple and this NOx reduction technology is least likel y to negatively impact the indurating process. Key equipment design concepts for the SNCR installation at Minntac are as follows:

• Design, quantity and location of the urea injection nozzles.

• Instrumentation, controls and valves utilized in delivering the right amount of urea to
the nozzles.

• Instrumentation utilized to monitor the NOx emissions.

Typical SNCR equipment systems include the following:



### 4.2.4.1 Urea Storage Tank: One 15,000 gallon storage tank (approx. 14 ft. dia. x 28 ft tall) to receive the 50% urea solution. Tank to be constructed from fibreglass reinforced plastic (F RP), insulated and include level monitoring system. Heating panels may be required to maintain a liquid temperature above 70 deg F.



### 4.2.4.2 Urea Day Tank: One 5,000 gallon day tank to store the urea solution at a lower concentration and feed the urea solution to the injection nozzles. Tank to be constructed from polyethylene.



### 4.2.4.3 Water Tank: One 5,000 gallon water tank for diluting the 50% urea to final injection concentration. Tank to be constructed from polyethylene.



### 4.2.4.4 Pump Skids: One pump skid to pump the 50% urea solution from the urea storage tank to the day tank. Two (2) pumps shall be provided (1 operating; 1 stand-by) and shall include all required valves for switching between the two pumps.

Two pump skids with necessary valves and instruments to deliver the urea solution to the atomizing spray nozzles. Each pump skid will have two pumps (1 operating; 1 stand-by).



### 4.2.4.5 Urea Injection Lances: Urea injection nozzles and lances complete with contro l valves and pressure transmitters in each nozzle.



### 4.2.4.6 Compressed Air System: Compressed air system to provide the high pressure ai r required to atomize the urea solution at the spray nozzles. Preliminary compressed air requirements are estimated to be 2700 scfm at 80 psig.



### 4.2.4.7 Control System: The SNCR system will be controlled by an Allen-Br adley programmable logic controller (PLC) with all necessary instrumentation, controls and monitoring equipment.United States Steel - Minntac Iron Ore Pelletizing Operation NOx Reduction Analysis

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### 4.2.5 SNCR Equipment Suppliers

Hatch obtained proposals from several potential suppliers. Each of the proposals were reviewed and the highlights are outlined below.



### 4.2.5.1 Nalco Mobotec Nalco Mobotec proposal offers to reduce NOx emissions in two ways:

• Rotating Opposed Fired Air (ROFA), which invo lves improvements to the mixing and air distribution inside the rotary kiln.

• Rotamix system, which is Mobotec’s SNCR technology.

The ROFA system utilizes ROFA boxes (fans) that are strategically placed along the kiln walls to provide turbulent mixing and improved air distribution inside the kiln. The ROFA air is injected in a manner
such that it creates a rotational air flow in the kiln combustion zone. Mobotech states that the ROFA system will reduce NOx generated in the rotary kiln by approximately 10-20%.

The Rotamix system proposed by Mobotech is a SNCR sy stem that is in accordance with the equipment system outlined above in Section 4.2.4. Mobotech’ s proposal estimates a urea usage rate of 200-320 gallons/hr at 50% urea solution. Additional equipment requirements include systems to supply demineralised water and compressed air, which are required for their Rotamix system. Mobotech estimates that their Rotamix system will reduce NOx emissions by approximately 35-55%, in addition to the 10-20% for the ROFA system. This equates to a total of a 45-75% reduction.

Lastly, Mobotech proposes to provide CFD modeling of the rotary kiln operation in order to refine the design of both their ROFA and Rotamix systems.



### 4.2.5.2 Energy Systems Associates (ESA) Energy Systems Associates’ (ESA) proposal offe rs to reduce NOx em issions in two ways:

• Low NOx combustion modifications to the existing burner system.

• SNCR technology based on urea injection.

The low NOx combustion system mod ifications basically center on modifying the existing main burner by adding a modified burner tip. The modifications are expected to include some combination of swirl or splitter vanes designed to improve the efficiency of the burner system. ESA states that the combustion modifications are expected to reduce NO x emissions by approximately 20-30%.

The SNCR system proposed by ESA is generally in accordance with the equipment system outlined above in Section 4.2.4. ESA’s proposal estimates a urea us age rate of 80 gals/hr @ a 50% urea solution, which would be further diluted to 20% prior to injection.

Additional equipment requirements include provisions to supply filtered water and compressed air, which are required for the SNCR system. ESA estimates that their SNCR system will reduce NOx emissions by approximately 25-40%, in addition to th e 20-30% for the burner modification. This equates
to a total of a 45-70% reduction.United States Steel - Minntac Iron Ore Pelletizing Operation NOx Reduction Analysis

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Lastly, ESA proposes an on-site pilot testing demonstration for their SNCR system that is to be designed based on the concepts defined by their CFD modeling and baseline tests.



### 4.2.5.3 BACT Process Systems, Inc. BACT Process System’s (BACT) proposal offers to re duce NOx emissions by installing an SNCR system. The SNCR system proposed by BACT is generally in accordance with the equipment system outlined above in Section 4.2.4. BACT’s pr oposal estimates a urea usage rate of 350 lbs/hr, which translates to approx. 400 gallons/hr.

Additional equipment requirements include provisions to supply filtered water and compressed air, which are required for the SNCR system. BACT estimates that their SNCR system will reduce NOx emissions by approximately 60%.

BACT also proposes to provide CFD modeling of the rotary kiln operation in order to refine the design of their SNCR NOx reduction system.



### 4.3 Selective Catalytic Reduction (SCR) Technology

Selective Catalytic Reduction (SCR) is a NOx reduction technology that is similar to SNCR in that a reductant such as urea (or aqueous ammonia) is utilized to chemically reduce the NOx emissions to nitrogen and water. Unlike SNCR, however, SCR utilizes a vanadium based catalyst to facilitate the chemical reaction at a lower gas temperature, typically in the range of 600-900 deg F.

A majority of the SCR installations are employed to reduce NOx emissions generated from large utility boilers, where a NOx reduction efficiency of 60-80% can be expected. The SCR NOx reduction concepts are described briefly below:



### 4.3.1 SCR Utilizing Urea

Urea is utilized to reduce NOx emissions by chemic ally reducing the NOx to harmless nitrogen gas in accordance with the following simplified reaction: *

(NH 2 ) 2 CO + 2NOx + 1⁄2O 2 

### → 2N 2 + 2H 2 O + CO 2

* Note that there is an intermediate reaction in which the urea reacts to form ammonia.

Key design parameters in optimizing the NOx reduction efficiency of the SCR system include the following:

• Effective monitoring of NOx emissions and appropriate reagent injection rate.

• Flue gas residence time of 0.3 seconds or more.

• Good mixing and contact between the urea and the gas stream (NOx).United States Steel - Minntac Iron Ore Pelletizing Operation NOx Reduction Analysis

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• Relatively clean gas stream (< 1 gr/dscf) to minimize fouling of the catalyst surfaces.

• Proper design, layout and selection of the catalyst.

Figure 4-3 Typical SCR Process Concepts



### 4.3.2 SCR Design Concepts

As outlined in the NOx Reduction Comparison Tabl e (Appendix C) a majority of the previous SCR installations identified by Hatch were installed downstream of a utility boiler or in a cement plant application. Hatch’s review of these SCR installations showed the following:

• Gas volumes for these boiler applications were relatively large (500,000 scfm to 5,000,000 scfm), which is the same order of magnitude as the 265,000 scfm gas stream

at Line 5.

• Inlet NOx concentrations were typically in the 200-500 ppm range, which is similar to the 420 ppm NOx loading downstream of the Preheat section of the traveling grate at

Minntac.

• SCR installations showed an average NOx reduction efficiencies of 75%.United States Steel - Minntac Iron Ore Pelletizing Operation NOx Reduction Analysis

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C:\carl40268\US STEEL\332002 Minntac Iron Ore Pellet Operation\PR332002-01 US Steel Minntac - NOx Reduction Technology Report Rev 0.doc © Hatch 2006/03 a • Gas temperatures were typically in the 600 to 900 deg F range, which similar to the gas temperature downstream of the Preheat section of the traveling grate at Minntac.

Although the SCR technology is clearly an effective NOx reduction technology, Hatch has several concerns associated with utilizing the SCR technology on the indurating lines at Minntac, including the following:

• Locating the SCR equipment downstream of the existing wet scrubber system would minimize the dust loading and associated fouling of the SCR equipment (catalyst bed). However, this concept would require a major energy input of approximately 270 MM Btu/hr to heat the relatively cold exhaust from approximately 120 deg F to the required temperature range of 600-900 deg F. Based on the high energy input required Hatch does not believe this “clean side” SCR concept is feasible.

• Most likely location of the SCR system equipment is downstream of the preheat section of the traveling grate equipment based on the gas stream temperature of approximately 900 deg F. A relatively high dust load of approximately 6 gr/dscf is expected in this gas stream, which is a relatively high dust load for the SCR system equipment.

• In addition to reducing the NOx reduction efficiency, material build-up on the catalyst surfaces will increase the gas-side pressu re drop across the SCR system. This would have the potential to reduce the ventilation volume directed to the indurating process, which would be unacceptable.

• A precipitator type dust collection system shall be located upstream of the SCR system to reduce the dust load to minimize the catalyst fouling and ensure effective operation of the SCR system in lowering NOx emissions. The 900 deg F gas temperature is at the high end of the temperature range for precipitator systems, which has the potential negatively affect the dust collection efficiency and will likely require high temperature
materials of construction.

• The catalyst bed is expected to last approximately five years before the catalyst becomes chemically in-active (poisoned) and the NOx reduction efficiency will be reduced. This will require that the catalyst bed be replaced and will require additional maintenance

attention.

• The process flow diagram (PFD) for the proposed SCR System is outlined below. This system has the potential to negatively impact the indurating process based on the fact that the precipitator and SCR system are intertwined in the indurating ventilation system.

Clearly, the most important factors in successfully implementing the SCR technology is maintaining the gas temperature in the acceptable range (600-900 deg F) and minimizing the potential material build-up on the catalyst surfaces.United States Steel - Minntac Iron Ore Pelletizing Operation NOx Reduction Analysis

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• Urea to be injected in the area downstream of the preheat section of the grate feeder based on required gas temperature range (600-900 deg F).

• Injection nozzles shall be designed to provide good contact between the urea sprays and the gas stream exiting the kiln (approx. 10-16 nozzles required).

• Urea usage is expected to be approximately 150 gal/hr based on the NOx loading outlined in Section 3 above (i.e. 630 lbs/hr).

• Annual urea consumption for Line 5 is expe cted to be approximately 1,200,000 gal/yr.

• Compressed air usage at 2700 scfm at approx imately 80 psig as required to atomize the

urea sprays.

• NOx reduction is expected to be in the 75% range, which translates to a NOx reduction of approximately 1875 tons NOx/yr at Line 5.

Gas Analysis at Injection Point: (preliminary)

Gas Volume:

- Standard: 265,000 scfm

- Dry Standard: 255,000 dscfm Gas Temperature: 700 deg F Gas Analysis: (% volume basis)

- Nitrogen 70%

- Carbon Dioxide 8%

- Oxygen 18%

- Moisture 4%

- Dust Load 0.1 gr/dscfUnited States Steel - Minntac Iron Ore Pelletizing OperationNOx Reduction AnalysisISO 9001C:\carl40268\US STEEL\332002Minntac Iron Ore Pellet Operation\PR332002-01 US Steel Minntac - NOxReduction Technology Report Rev 0.docUS Steel Minntac – Line 5Hatch Project No. 332002SCR - Process Flow Diag. ACoolerZone 1CoolerZone 2CoolerZone 3Cooler VentStackScrubberSystemWaste GasFanWaste GasStackPreheatDryer D2Dryer D1RecycleFan50% UreaStorage TankUrea FeedSystemRotaryKilnSCR Systemc/w TiO2-V CatalystUrea Flow: 150 gal/hrUrea Temp.: 70 deg FComp. Air: 2700 scfmGas Volume: 265,000 scfmGas Temp.: 800 deg FNOx Load: (ave.) 630 lbs/hrDust Load: 6 gr/dscfGas Volume: 500,000 scfmGas Temp.: 120 deg FNOx Load: (ave.) 160 lbs/hrDust Load: 0.005 gr/dscfElectrostaticPrecipitatorPellets Produced412 tons/hrUS Steel Minntac – Line 5Hatch Project No. 332002SCR - Process Flow Diag. ACoolerZone 1CoolerZone 2CoolerZone 3Cooler VentStackScrubberSystemWaste GasFanWaste GasStackPreheatDryer D2Dryer D1RecycleFan50% UreaStorage TankUrea FeedSystemRotaryKilnSCR Systemc/w TiO2-V CatalystUrea Flow: 150 gal/hrUrea Temp.: 70 deg FComp. Air: 2700 scfmGas Volume: 265,000 scfmGas Temp.: 800 deg FNOx Load: (ave.) 630 lbs/hrDust Load: 6 gr/dscfGas Volume: 500,000 scfmGas Temp.: 120 deg FNOx Load: (ave.) 160 lbs/hrDust Load: 0.005 gr/dscfElectrostaticPrecipitatorPellets Produced412 tons/hrUnited States Steel - Minntac Iron Ore Pelletizing Operation NOx Reduction Analysis

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### 4.3.3 SCR Equipment Concepts

The key components of the SCR equipment systems are the urea injection system and the catalyst bed. Key equipment design concepts for the SCR installation at Minntac are as follows:

• Design, quantity and location of the urea injection nozzles.

• Instrumentation, controls and valves utilized in delivering the right amount of urea to
the nozzles.

• Instrumentation utilized to monitor the NOx emissions.

• Selection and layout of the catalytic bed as required to provide the proper distribution and velocity of the gas stream across the catalyst surfaces.

Typical SCR equipment systems include the following:



### 4.3.3.1 Electro-Static Precipitator System One (1) electrostatic precipitator system shall be provided to reduce the dust load in the gas stream upstream of the SCR system. ESP system shall be de signed to handle the following gas stream from the exit of the preheat portion of the traveling grate:

Gas Volume:

- Standard: 265,000 scfm

- Dry Standard: 255,000 dscfm

Gas Temperature: 800 deg F

Pressure Drop ( ∆ P): 6-8” wg

Solids Loading:

- Inlet Dust Load 6.0 gr/dscf

- Outlet Dust Load 0.1 gr/dscf



### 4.3.3.2 Reactant Storage and Feed System: A 1m diameter tank at 3m high to supply the reducta nt (ammonia, or urea) to the injection points in the SCR reactor. An estimated 0.6 lbs of ammonia will be required for each pound of NOx to be removed, which translates to approx. 282 lbs/hr of ammonia solution.



### 4.3.3.3 Reactant Dilution and Injection System:

In order to atomize the ammonia solution is it to be diluted with distilled water and mixed with compressed air and distributed before the catalyst bed.



### 4.3.3.4 Compressed Air System: The SCR system will require compressed air as necessary to atomize the reductant sprays. Preliminary requirements are estimated to be 2700 scfm and 80 psig.United States Steel - Minntac Iron Ore Pelletizing Operation NOx Reduction Analysis

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### 4.3.3.5 SCR Catalyst System: The catalyst shall be a titanium oxide vanadium ma terial blend and arranged in a honeycomb type configuration. There will be a 6” wear panel supplied by the vendor and larger honeycomb area to resist wear and prolong catalyst lifespan.



### 4.3.3.6 Exhaust Fan and Motor System: The existing preheat recycle fan shall be upgraded to provide the increased static pressure required to accommodate the precipitator and SCR equipment systems.

Gas Volume:

- Standard: 265,000 scfm

- Dry Standard: 255,000 dscfm

Gas Temperature: 600 deg F

Static Pressure: 15” wg

Power: 2000 BHP



### 4.3.3.7 Instrumentation and Controls System: The SCR system shall be controlled by an Allen-Bradley programming logic controller (PLC) with all necessary instrumentation, controls, and monitoring equipment



### 4.3.4 SCR Equipment Suppliers

Hatch obtained proposals from several potential suppliers. Each of the proposals were reviewed and the highlights are outlined below.



### 4.3.4.1 Branch Environmental Corp. Branch Environmental Corp. proposal offers to inst all an SCR system to reduce NOx with an optional reheat section directly upstream of the scrubber. It will require a space approximately 34 foot square by 25 feet tall and will be a vertical type SCR system to reduce the wear induced by the presence of particulate matter in the flue gas.

Branch Environmental Corp. proposal states that a minimum efficiency of 50%-60% will be achievable given the initial conditions stated on the bid specification document issued by Hatch.

The SCR system shall consume approximately 0.6 lbs of ammonia/lb of NOx removed. This translates to approximately 282 lbs/hr of ammonia at an efficiency of approximately 50%.

The reheat section will be designed to produce up to 270 MM Btu/hr of necessary heat to raise the temperature from the inlet of the SCR to the desired operating condition of 600 o F. Branch Environmental Corp. is confident of recovering 50% of the energy in use through the installation of a plate heat exchanger within the duct which will be installed by the vendor.

Branch Environmental Corp. proposal does not include any CFD modeling but will require time on site to find the ideal location of the SCR system. Additional equipment to supply compressed air and
demineralised water are also needed.United States Steel - Minntac Iron Ore Pelletizing Operation NOx Reduction Analysis

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### 4.3.4.2 Mitsubishi Power Systems Mitsubishi Power Systems proposal offers to insta ll an SCR system after the dryer D1 (shown on the process flow diagram issued by Hatch) within the duct. This will include the reactor housing, engineering. The approximate footprint of the SCR reactor is 33’ x 30’ and is 85’ high with 3 catalyst layers.

Hatch discussions with Mitsubishi Power Systems representatives have concluded a minimum reduction efficiency of 60% given an ammonia consump tion or 230 lbs/hr or 44.66 gallons/hr.

The catalyst used will be of a vanadium and titanium oxide blend and is guaranteed for 63 months, or for 43,800 hrs of regular operation. Mitsubishi Power Systems proposal does not include any inlet or outlet ductwork, support structures, loading platforms, ammo nia storage tank, or any of the associated utilities needed for this SCR system i.e. power, demineralised water, or compressed air.



### 4.4 Low Temperature Oxidation (LoT Ox) - NOx Reduction Technology

LoTOx is a patented low temperature oxidation pr ocess utilizes ozone to reduce NOx emissions. Like SCR technology, the LoTOx system is relatively effic ient at reducing NOx emissions with a typical NOx reduction efficiency of approximately 80%.

LoTOx utilizes ozone (O 3 ) as a reagent to convert the NOx emissions to form soluble N 2 O 5 , which is highly soluble and reacts rapidly to form nitric acid , which is easily scrubbed from the gas stream via a wet scrubber. LoTOx can also be utilized to remove other airborne pollutants such as Mercury and SO 2

.



### 4.4.1 LoTOx Technology Overview Ozone reacts rapidly with NOx to form nitric acid in accordance with the following reaction sequence:

NO + O 3 Æ NO 2 + O 2 (1)

2NO 2 + O 3 Æ N 2 O 5 + O 2 (2)

N 2 O 5 + 2H 2 O Æ 2HNO 3 + O 2 (3)

Nitric acid is highly soluble in water and is readily removed via a wet scrubber system and neutralized via caustic addition to the scrubber effluent scrub water. In addition, a high dust load can be tolerated with the LoTOx technology and removed via the wet scrubber portion of the system.

Key design parameters involved in optimizing the NOx reduction efficiency of the LoTOx system
include:

• Providing a residence time of approximately 5 seconds to allow for the gas phase reaction to go forward.

• Gas stream temperature of approximately 300 deg F.

• Pure oxygen supply via onsite oxygen generation plant or supplied commercially and
stored on-site.

• Onsite generation of ozone from oxygen gas.

• Cooling water for both oxygen and ozone generators in the region of 2600 gpm.United States Steel - Minntac Iron Ore Pelletizing Operation NOx Reduction Analysis

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### 4.4.2 LoTOx Design Concepts

As outlined in the NOx Reduction Comparison Tabl e (Appendix C) a majority of the previous LoTOx installations identified by Hatch were installed downstream of a utility boiler or in an oil refinery plant application. Hatch’s review of these LoTOx installations showed the following:

• Gas volumes for these applications ranged from 4,000 to 300,000 scfm, with a majority of these installations being less than 100,000 scfm. Note that this is a much smaller gas stream volume than the 500,000 scfm gas stream at Line 5.

• LoTOx installations showed an average NOx reduction efficiencies of 80%.

• Gas temperatures were typically in the 300 deg F range, which similar to the gas temperature immediately upstream of the existing scrubber system at Line 5.

Although the LoTOx technology is clearly an effe ctive NOx reduction technology, Hatch has several concerns associated with utilizing the LoTOx technology on the indurating lines at Minntac, including the following:

• LoTOx has not been utilized on an indurating furnace and it is not clear how effective this technology will be when applied to the indurating process.

• Potential for the ozone (O3) to react with iron oxides in the gas stream, which will require higher than expected amounts of ozone to be injected and consumed.

• Power requirements to operate the LoTOx system will be very high, particularly for oxygen supply system and the ozone generating equipment (approx. 11 MW).

• Equipment systems will be relatively large and will require significant plant space, particularly the oxygen plant facility and wastewater treatment plant facilities.

• Residence time of 5 seconds required from the ozone injection point to the catalyst bed, which will likely require a significant run of ductwork (300 ft.) or a large reaction
chamber to meet the residence time.

• LoTOx system will require a new scrubber based on the requirement to remove the nitric acid in the gas stream. Caustic addition will be needed to control pH in the scrub

water.

• The exhaust fan and motor drive will need to be upgraded to provide the static pressure and horsepower necessary based on the LoTOx equipment concepts and layouts.

• A new wastewater treatment facility will be required to handle the 4000 gpm for the scrubber system, as well as to neutralize the nitric acid scrubbed from the gas stream.

The most important criteria for the LoTOx system to be effective is the ample supply of ozone into the reaction chamber. The ability of the system to brea k NOx down into soluble nitric acid is proportional to the amount of ozone injected into the reaction chamber.United States Steel - Minntac Iron Ore Pelletizing Operation NOx Reduction Analysis

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• Residence time of the flue gas within the reaction chamber is approximately 5 seconds.

• Gas temperature must be approximately 300 d eg F to maintain an effective environment
for the NOx reaction.

• Ozone usage is expected to be approx. 1600 lbs/hr based on the NOx loading outlined
in Section 3 above.

• Annual ozone consumption for Indurating Li ne 5 is expected to be approx. 6,000 tons/yr.

• Annual oxygen supply to the ozone generati on system is approx. 56,000 tons O2/yr

• NOx reduction is expected to be approximately 80%, which translates to a NOx reduction of 2000 tons NOx/yr at Line 5.

• Neutralization of the nitric acid scrubbed from the gas stream via caustic addition, as well as wastewater treatment system desi gned to meet nitrate discharge limits.United States Steel - Minntac Iron Ore Pelletizing OperationNOx Reduction AnalysisISO 9001 H-332002 , Rev. 0C:\carl40268\US STEEL\332002Minntac Iron Ore PelletOperation\PR332002-01 US Steel Minntac - NOxReduction Technology Report Rev 0.doc© Hatch 2007/03aUS Steel Minntac – Line 5Hatch Project No. 332002LoTOx - Process Flow Diag.CoolerZone 1CoolerZone 2CoolerZone 3Cooler VentStackNewScrubberSystemExhaustStackPreheatDryer D2Dryer D1Ozone Flow: 1600 lbs/hrRotaryKilnNew Waste GasExhaust FanGas Volume: 500,000 scfmGas Temp.: 300 deg FNOx Load: (ave.) 630 lbs/hrGas Volume: 500,000 scfmGas Temp.: 120 deg FNOx Load: (ave.) 127 lbs/hrDust Load: 0.015 gr/dscfPellets Produced412 tons/hrOzone ReactorOzoneProductionFacilityTo New WWTPOxygenProductionFacilityChilling Water:2600 gpmNOxÆNO2ÆN2O5ÆHNO3US Steel Minntac – Line 5Hatch Project No. 332002LoTOx - Process Flow Diag.CoolerZone 1CoolerZone 2CoolerZone 3Cooler VentStackNewScrubberSystemExhaustStackPreheatDryer D2Dryer D1Ozone Flow: 1600 lbs/hrRotaryKilnNew Waste GasExhaust FanGas Volume: 500,000 scfmGas Temp.: 300 deg FNOx Load: (ave.) 630 lbs/hrGas Volume: 500,000 scfmGas Temp.: 120 deg FNOx Load: (ave.) 127 lbs/hrDust Load: 0.015 gr/dscfPellets Produced412 tons/hrOzone ReactorOzoneProductionFacilityTo New WWTPOxygenProductionFacilityChilling Water:2600 gpmNOxÆNO2ÆN2O5ÆHNO3United States Steel - Minntac Iron Ore Pelletizing Operation NOx Reduction Analysis

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### 4.4.3 LoTOx Equipment Concepts

The are several major equipment components that co mprise the typical LoTOx system, including the oxygen generating plant, the ozone generating system, the ozone reactor, the new scrubber system and the wastewater treatment systems. Also note that the electrical supply and distribution system will likely require major upgrades as necessary to pr ovide the electrical power required for the ozone generating and oxygen plant equipment.

The key components of the LoTOx equipment systems are briefly described below:



### 4.4.3.1 Oxygen Plant The LoTOx system will require approx. 56,000 tons/yr of oxygen gas to feed the ozone generating system, which in turn will be converted to ozone. This will require a significant amount of electrical power consumption of approximately 3 MW. In addition, if all five indurating lines were to install LoTOx systems, the oxygen requirements would be increased to approximately 270,000 tons/yr. This is a major amount of oxygen, which will likely require the installation of an oxygen plant. Major equipment systems for the oxygen plant will be as follows:

Air Compressor and Pre-Cooling Systems

Multistage intercooled turbo compressor system to co mpress the gas stream to the required pressure of approximately 90 psig. Air from the last compressor stage is cooled and washed in a direct contact process air cooler in counter-flow with water injected at two levels. In the lower section the air is pre-cooled with recycled cooling water. In the upper section, the air is further cooled by chilled water from the evaporation cooler.

The descending cooling water also scrubs the water soluble impurities from the process air stream. A wire mesh on top of the process air cooler removes the water mist from the process air.

Purification System

The air purification system includes two cyclic operating molecular sieve type adsorbers. Passing through an adsorber vessel, moisture, and potentially hazardous hydrocarbons are adsorbed from the gas stream. While one of the adsorbers is purifying the air, the other is regenerated.

During the heating cycle, the regenerated gas is heated by a steam heater with an additional electric
heater and desorbs the water from the molecular sieve. During the cooling cycle, the adsorbents are cooled with dry impure nitrogen gas. After comple tion of the regeneration sequence, the adsorber is pressurized before being switched over to the adsorption cycle.

Process Refrigeration

The main stream of purified air enters the coldbox, where it is cooled in the main heat exchanger to the liquefaction temperature. It is then fed to the bottom section of the pressure column for
rectification.United States Steel - Minntac Iron Ore Pelletizing Operation NOx Reduction Analysis

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In the pressure column, the air is pre-separated into pure nitrogen yielded at the top and into oxygen enriched liquid at the bottom. The required reflux for rectification is provided by condensing the gaseous nitrogen in the heat exchange against boiling oxygen in the main condenser/reboiler. Part of the condensed nitrogen is cooled in an integrated subcooler and subsequently fed as reflux to the top of the low pressure column.

The final air separation occurs in the low pressure column, with the pure oxygen at the bottom of the column and the nitrogen at the top of the column.

Storage Tank

Liquid oxygen product is withdrawn from the bottom of the low pressure column, sub-cooled and transferred to a storage tank via a transfer pump. Liquid oxygen product is pumped from the storage tank to the required product pressure via a centrifugal pump. The compressed liquid stream is fed back, evaporated and warmed up in the main heat exchanger against the boosted air stream. It is then fed to the pipeline as high pressure gaseous oxygen.



### 4.4.3.2 Ozone Generator System Ozone gas is very reactive and unstable and as a result the ozone must be produced where and when it is needed (i.e. cannot be stored). As such an ozone generator system shall be utilized to convert the oxygen gas from the oxygen plant to ozone gas (O 3 ).

Ozone is produced from oxygen gas in an ozone gener ator by means of an electrical discharge. A high voltage is applied between two concentrically arranged electrodes, which are separated from each other by a dielectric and two discharge chambers. A portion of the oxygen molecules in the inlet gas stream break down in the electric field and attach themselves to free oxygen molecules, forming ozone.

The efficiency of the ozone generation is related to a number of factors, including the quality of the oxygen, strength of the electric field, generator design, etc. Ozone yields of approximately 5-10% by weight are typically achieved.

Electrical power consumed is expected to be a pproximately 7 MW based on the ozone requirements
outlined above.



### 4.4.3.3 Ozone Reaction Chamber An ozone reaction chamber shall be provided to accomplish the contact between the ozone and the NOx laden gas stream from the indurating process. The inlet ductwork and reaction chamber shall be sized to provide the necessary five second residence time for the NOx oxidation reaction as
described above.

Ductwork (13’-0” diameter) will connect the ozone reaction chamber with the new wet scrubber
system.United States Steel - Minntac Iron Ore Pelletizing Operation NOx Reduction Analysis

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### 4.4.3.4 Wet Scrubber System A low energy, venturi scrubber shall be provided to remove nitric acid and solid particulates from the gas stream downstream of the ozone reactor. Preliminary scrubber system design shall be as
follows:

Inlet Gas Volume: 500,000 scfm

Gas Temperature: 250 deg F

Scrubber Pressure Drop: 15” wg

Inlet Dust Load: 6 grains/dscf

Outlet Dust Load: 0.01 grains/dscf

Nitric Acid Removal: 1350 lbs/hr

Caustic Addition: pH control

Scrub Water Flow: 4,000 gpm

Scrub Water Solids (TSS) 100 ppm

Pump Motor: (2 operating; 1 stand-by) 500 Hp



### 4.4.3.5 Exhaust Fan and Motor Drive One exhaust fan shall be provided as required to provide the additional static pressure to accommodate the new system equipment, including the ozone reaction chamber, venturi scrubber and ductwork system. Preliminary fan and motor system design shall be as follows:

Inlet Gas Volume: 500,000 scfm

Gas Temperature: 120 deg F

Static Pressure: 24” wg

Fan Brake Horsepower: 2800 BHP

Motor Size: 3000 Hp



### 4.4.3.6 Exhaust Stack One exhaust stack shall be provided to discharge the cleaned gas stream to atmosphere. Preliminary sizing of the exhaust stack shall be a 15’-0” diameter by 150’ height. Interconnecting ductwork between the various equipment systems shall be provided. Ductwork shall be sized at approx. 4000 fpm, which should be approx. 13’0” diameter.United States Steel - Minntac Iron Ore Pelletizing Operation NOx Reduction Analysis

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### 4.4.3.7 Wastewater Treatment Plant Wastewater treatment plant shall be provided to re move solid particulates and dissolved salts from the effluent water from the scrubber before recycling the water back to the scrubber. In addition, the water treatment system shall provide neutralization of the nitric acid from the LoTOx process via caustic addition and shall remove the nitrates formed, such as sodium nitrate. Wastewater treatment system shall include the following major equipment systems:

Cyclone Separators

Two cyclone separators shall be provided to remove the first cut of the heaviest solids from the effluent scrub water. This equipment shall be provided to lower the solids loading and improve the performance of the downstream wastewater system equipment.

Classifier

Two screw augers shall be provided to dewater the heaviest solids from solids removed via the cyclone separators as described above. The augers shall be sized to handle the cyclone underflow water stream at approx. 300-400 gpm.

Neutralization Tank

One neutralization tank shall be provided as a reservoir for caustic addition as required for pH monitoring and control. The tank shall include a mixer and shall be sized to provide a retention time of approximately 15 minutes. Tank shall be sized as follows:

Tank Size: 120,000 gallons

Tank Dimensions: 35’-0” dia. x 18’0” height

Material: Coated Steel

Mixer (turbine type): 50 Hp

Thickener

One thickener shall be provided to remove entrai ned solids via settling. Preliminary sizing of the thickener shall size at a rise rate of approximat ely 0.5 gpm/ft2 or a diameter of approx. 120 ft. Thickener shall include a center-well type design with rake.

Vacuum Filter System

Air diaphragm type pumps shall be provided to pump the thickener underflo w to the vacuum filters for additional dewatering and solids removal. Three drum type vacuum filters (2 operating; 1 standby) shall be included.United States Steel - Minntac Iron Ore Pelletizing Operation NOx Reduction Analysis

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Three venturi supply pumps (2 operating; one stand-by) shall be provide to pump the clean thickener effluent water back to the venturi scrubber system. Pump design shall be as follows:

Water Flow Rate: 2,000 gpm

Motor Horsepower: 250 Hp

Discharge Pressure: 120 psig



### 4.4.3.8 Control System The LoTOx system will be controlled by an Allen-Bradley programmable logic controller (PLC) with all necessary instrumentation, controls and monitoring equipment.



### 4.4.4 LoTOx Equipment Supplier

Hatch obtained a proposal from BOC Linde ba sed on a budgetary specification prepared by Hatch. BOC Linde has proposed the installation of a LoTOx system at US Steel Minntac (as per the process flow diagram provided by Hatch) and shall include at new wet scrubber and wastewater treatment system. Linde estimates the NOx reduc tion to exceed 90% given the initial conditions set forth by the bid specification document issued by Hatch.

The Linde proposal scope includes a site review, basic engineering package, process review during the detailed engineering phase, details of the ozone distribution system upstream of the scrubber, and supervision and support during the commissioning and start-up phases of the installation. Linde will expect US Steel to supply the ozone generator skid, ozone and oxygen flo w controls as well as the injection manifold, oxidation reactor, existing wet scrubber system, controls and instrumentation, an electrical connection and power for the ozone generator and instrumentation, cooling water, and engineering specifications for pipi ng, foundations and structures.

Hatch has determined that in order to achieve the NOx reduction Linde has proposed a ozone plant would need to supply 1600 lbs/hr of ozone. In addition, the wastewater treatment plant would be required to remove approximately 1350 lbs/hr of nitric acid.

Linde has also proposed a demonstration period of a smaller scale LoTOx system. This system is capable of operating on a slip stream gas flow of 50 to 200 scfm. Test results will provide accurate date for fine tuning the required residence time, gas temperature and ozone reaction model so that the demonstration plant can be successfully applied to the full scale indurating line process. The testing period will also provide key insight into the operating experiences of previous LoTOx installations to US Steel staff, as well as characterizing the key process variables.

It has also been proposed by Linde that the installation of low NOx burners would provide a less concentrated flue gas stream to the LoTOx syst em, thus reducing the usage of oxygen, power and

ozone.United States Steel - Minntac Iron Ore Pelletizing Operation NOx Reduction Analysis

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## 5. Hatch Recommendations

U.S. Steel stated that a current estimate for NOx emissions from the five indurating lines at Minntac is approximately 13,300 tons/yr. U.S. Steel also stated that a preliminary target of 3,990 tons/yr NOx
emissions has been established or a reduction of approximately 70%. The current Line 5 portion of
the NOx emissions baseline was established at 2500 tons/yr. This translates to a 750 tons/yr NOx emission limit necessary to meet this 70% reduction. In addition, it would require that either the SCR or the LoTOx control technology would be re quired to meet the 70% NOx emission reduction
target.

However, Hatch’s review of the actual NOx emission data from the continuous emission monitor (CEM) in the stack shows a current average emission rate of 470 lbs NOx/hr at Line 5. This translates
to a current annual emission rate of 1850 tons NOx/ yr in lieu of the 2500 tons/yr that was utilized as the basis for this analysis. Therefore, a 60% re duction would be needed to meet the NOx emission limit of 750 tons NOx/yr (as outlined above).

This means that it would be feasible to meet the 750 tons/yr NOx emission target at Line 5 with upgrades to the indurating process coupled with the installation of SNCR technologies outlined in this report.

As a result, Hatch concludes that the best approach to NOx emission reduction at Minntac is to pursue the following upgrades:

• Upgrades to the indurating process as outlined in Section 4.1 of this report, with an estimated reduction of NOx generated from the pelletizing operations of approximately 30%. Specifically, Minntac should investigate installation of a low NOx main burner on the kiln, CFD modeling and Mobotec.

• SNCR technology as outlined in Section 4.2 of this report to further reduce the NOx emissions by approximately 40%.

Short term, Hatch recommends that each of these potential options be verified and further refined via on-site testing and CFD modeling of the Line 5 i ndurating process (as recommended by several of the potential suppliers).

Hatch also believes that it is important that at least two of the vendors be selected to perform independent analysis of the indurating process due to the fact that none of the proposed vendors have significant experience in this application. Based on our discussions with the various vendors, Hatch would recommend the following two vendors:

• Nalco Mobotec

• Energy Systems Associates

Hatch recommends on-site baseline testing to provide the data necessary to proceed with the conceptual design of the NOx reduction concepts. Hatch also recommends that the vendors provide additional details pertaining to their plan and/or objectives for the on-site testing.United States Steel - Minntac Iron Ore Pelletizing Operation NOx Reduction Analysis

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C:\carl40268\US STEEL\332002 Minntac Iron Ore Pellet Operation\PR332002-01 US Steel Minntac - NOx Reduction Technology Report Rev 0.doc © Hatch 2007/03 a Long term, Hatch strongly recommends that Minntac pursue all available technology and potential options pertaining to reducing the amount of NOx emissions generated in the rotary kiln, including:

• Low NOx burners located in the Preheat Secti on of the grate as outlined in Section 4.1.1

• Low NOx main burner in the Rotary Kiln as outlined in Section 4.1.2

• Upgrades outlined in Section 4.1.3 to improve the air distribution, mixing and efficiency of the rotary kiln burner system.

These upgrades have the potential to improve the iron pelletizing operations from an efficiency and production standpoint, while significantly reducing NOx generated. There are multiple benefits associated with these upgrades as compared with any of the “end of pipe” reduction technologies (i.e. SNCR, SCR, etc.) including energy efficiency and a reduction of cross-media impact.

However, based on the fact that the process changes outlined above are not likely to achieve U.S. Steel’s target of 750 tons NOx/yr, Hatch also recommends pursuing the SNCR technology.

The most important factor in determining how well the SNCR technology will work is identifying a point for urea injection which will provide the following:

• An acceptable temperature window of 1800-2000 deg F required for efficient NOx
reduction reaction.

• Residence time necessary to complete the reaction (>0.3 seconds).

The on-site testing and CFD modeling will allow Mi nntac to determine whether this technology is feasible, and will allow for the vendors to refine the additional data associated with the SNCR technology to determine if the technology would be deemed successful for this application.United States Steel - Minntac Iron Ore Pelletizing Operation NOx Reduction Analysis

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# Appendix A Indurating Process Flow DiagramWaste Gas Preheat Recoup Cooler VentGas Side AnalysisStackAirFlowStackZone 1Zone 2/31. Gas Flow Rates:(1A & 1B)(FAN 3A) (FAN 3B)- standard: (scfm) 500,000 265,000 110,000 108,000 174,000 206,0002. Mass Flow Rates:- dry gases: (lbs/min) 32,000 19,750 7,620 7,580 12,380 14,720- water vapor: (lbs/min) 2,600 155 150 100 130 1603. Gas Temp.: (deg F) 120 600 1,630 930 70 704. Gas Density: (lbs/ft3) 0.063 0.038 0.018 0.027 0.072 0.0725. Static Pressure: ("wg) 0.5 -15.2 -0.6 0.3 -2.1 -2.1Pellet Analysis Dryer D1 Dryer D2 Preheat Rotary/Kiln Cooler 1 Cooler 2/36. Pellet Temp* (deg F) 100 650 1100 2450 800 250* estimated pellet temperatureCooler Indraft AirUS Steel Minntac – Line 5Hatch Project No. 332002SK1 - Process Flow Diag.RotaryKilnCoolerZone 1CoolerZone 2CoolerZone 3Cooler VentStackScrubberSystemWaste GasFanWaste GasStackPreheatExhaustFan1A & 1BInputs:- Biomass- NaturalGas- Fuel Oil3ExhaustFan 3A541212356Dryer D2Dryer D14ExhaustFan 3B6United States Steel - Minntac Iron Ore Pelletizing Operation NOx Reduction Analysis

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# Appendix B Line 5 Operating DataHDATE Nox Emissions Stack Flow LINE Pellet Grate Feed Green Ball Pellet Produced GrateTotal Fuel OIL(lb/hr) (1000 scfm)No.Type(LTPH)Factor(LTPH)Operation(MM Btu's)%MMBTUS%MMBTUSMMBTUS%Minimum:3 13080 0.82 67 0.3 4.2 4.5% 0.0 0.0% 70.3 0.0 0.0%Maximum:1,232 701528 0.86 454 1.9 352.4 100.0% 242.0 95.5% 461.9 1.0 0.5%Averages:467 380448 0.84 375 1.0 163.5 57.4% 117.6 42.6% 281.1 0.0 0.0%10/1/07 0:35 353.8 441 5 FLUX 472 0.820 387 1.0 130.3 48.3% 139.4 51.7% 269.7 0.0 0.0%10/1/07 1:35 340.4 440 5 FLUX 462 0.820 379 1.0 114.2 44.9% 140.3 55.1% 254.5 0.0 0.0%10/1/07 2:35 341.2 441 5 FLUX 461 0.820 378 1.0 108.1 43.7% 139.5 56.3% 247.6 0.0 0.0%10/1/07 3:35 308.9 440 5 FLUX 462 0.820 379 1.0 121.8 49.5% 124.5 50.5% 246.3 0.0 0.0%10/1/07 4:35 417.3 438 5 FLUX 464 0.820 380 1.0 104.9 42.8% 140.1 57.2% 245.0 0.0 0.0%10/1/07 5:35 490.4 436 5 FLUX 464 0.820 381 1.0 138.9 49.7% 140.3 50.3% 279.2 0.0 0.0%10/1/07 6:35 487.5 439 5 FLUX 464 0.820 381 1.0 137.2 49.4% 140.3 50.6% 277.5 0.0 0.0%10/1/07 7:35 474.9 439 5 FLUX 460 0.820 377 1.0 136.9 49.5% 139.6 50.5% 276.6 0.0 0.0%10/1/07 8:35 450.8 437 5 FLUX 456 0.820 374 1.0 135.7 49.2% 139.9 50.8% 275.6 0.0 0.0%10/1/07 9:35 481 436 5 FLUX 452 0.820 371 1.0 135.8 49.2% 140.0 50.8% 275.8 0.0 0.0%10/1/07 10:35 351.6 399 5 FLUX 436 0.820 358 1.0 130.2 48.1% 140.2 51.9% 270.4 0.0 0.0%10/1/07 11:35 393.6 436 5 FLUX 400 0.820 328 1.0 106.6 47.1% 119.9 52.9% 226.5 0.0 0.0%10/1/07 12:35 320.8 439 5 FLUX 442 0.820 363 1.0 108.1 43.7% 139.3 56.3% 247.4 0.0 0.0%10/1/07 13:35 323 442 5 FLUX 462 0.820 378 1.0 100.1 41.7% 140.0 58.3% 240.1 0.0 0.0%10/1/07 14:35 470.7 438 5 FLUX 460 0.820 377 1.0 96.0 40.7% 140.1 59.3% 236.1 0.0 0.0%10/1/07 15:35 360.2 441 5 FLUX 462 0.820 379 1.0 136.5 49.3% 140.2 50.7% 276.7 0.0 0.0%10/1/07 16:35 346.7 440 5 FLUX 465 0.820 381 1.0 108.2 43.4% 140.9 56.6% 249.1 0.0 0.0%10/1/07 17:35 348.3 438 5 FLUX 473 0.820 388 1.0 100.0 41.3% 142.2 58.7% 242.1 0.0 0.0%10/1/07 18:35 349.1 439 5 FLUX 473 0.820 388 1.0 101.9 41.8% 141.8 58.2% 243.7 0.0 0.0%10/1/07 20:35 299.3 422 5 FLUX 326 0.820 267 0.9 115.2 50.5% 113.0 49.5% 228.1 0.0 0.0%10/1/07 21:35 396.7 443 5 FLUX 445 0.820 365 1.0 106.2 42.7% 142.3 57.3% 248.5 0.0 0.0%10/1/07 22:35 317.4 443 5 FLUX 471 0.820 386 1.0 122.7 46.4% 141.6 53.6% 264.3 0.0 0.0%10/1/07 23:35 311 443 5 FLUX 471 0.820 386 1.0 112.4 44.2% 141.9 55.8% 254.3 0.0 0.0%10/2/07 0:35 387.5 447 5 FLUX 465 0.820 382 1.0 114.0 44.5% 141.9 55.5% 255.8 0.0 0.0%10/2/07 1:35 421.7 436 5 FLUX 460 0.820 377 1.0 147.3 50.8% 142.7 49.2% 290.0 0.0 0.0%10/2/07 2:35 316.3 446 5 FLUX 456 0.820 374 1.0 107.5 43.2% 141.5 56.8% 249.0 0.0 0.0%10/2/07 3:35 317.6 439 5 FLUX 455 0.820 373 1.0 98.9 41.0% 142.1 59.0% 241.0 0.0 0.0%10/2/07 4:35 307.8 443 5 FLUX 455 0.820 374 1.0 99.3 41.2% 141.9 58.8% 241.2 0.0 0.0%10/2/07 5:35 424.3 442 5 FLUX 455 0.820 373 1.0 113.2 44.3% 142.4 55.7% 255.6 0.0 0.0%10/2/07 6:35 422.1 443 5 FLUX 451 0.820 370 1.0 137.2 49.1% 142.4 50.9% 279.6 0.0 0.0%10/2/07 7:35 331.1 432 5 FLUX 449 0.820 368 1.0 99.3 41.3% 141.3 58.7% 240.6 0.0 0.0%10/2/07 8:35 370.4 383 5 FLUX 445 0.820 365 1.0 94.6 40.4% 139.6 59.6% 234.2 0.0 0.0%10/2/07 9:35 370.4 372 5 FLUX 363 0.820 298 1.0 88.1 40.2% 131.2 59.8% 219.3 0.0 0.0%10/2/07 10:35 616.9 412 5 FLUX 405 0.820 332 1.0 157.1 77.7% 45.2 22.3% 202.3 0.0 0.0%10/2/07 11:35 594 423 5 FLUX 411 0.820 337 1.0 192.0 100.0% 0.0 0.0% 192.0 0.0 0.0%10/2/07 12:35 482.3 360 5 FLUX 405 0.820 332 1.0 176.1 86.8% 26.9 13.2% 203.0 0.0 0.0%10/2/07 13:35 339 364 5 FLUX 350 0.820 287 1.0 124.7 67.1% 61.1 32.9% 185.8 0.0 0.0%10/2/07 14:35 280.6 384 5 FLUX 363 0.820 298 1.0 108.0 55.9% 85.1 44.1% 193.1 0.0 0.0%10/2/07 15:35 256.6 381 5 FLUX 399 0.820 327 1.0 94.9 41.7% 132.5 58.3% 227.4 0.0 0.0%10/2/07 16:35 269.6 388 5 FLUX 398 0.820 327 1.0 84.4 38.9% 132.7 61.1% 217.0 0.0 0.0%10/2/07 17:35 237.5 381 5 FLUX 400 0.820 328 1.0 91.4 40.8% 132.4 59.2% 223.8 0.0 0.0%10/2/07 18:35 236.1 397 5 FLUX 397 0.820 326 1.0 91.3 40.8% 132.4 59.2% 223.7 0.0 0.0%10/2/07 19:35 257.2 386 5 FLUX 399 0.820 327 1.0 89.9 40.4% 132.6 59.6% 222.5 0.0 0.0%10/2/07 20:35 244.6 388 5 FLUX 399 0.820 327 1.0 86.8 39.6% 132.3 60.4% 219.1 0.0 0.0%10/2/07 21:35 232.6 382 5 FLUX 398 0.820 326 1.0 90.4 40.5% 132.7 59.5% 223.1 0.0 0.0%10/2/07 22:35 244.5 375 5 FLUX 390 0.820 320 1.0 108.3 45.0% 132.6 55.0% 240.9 0.0 0.0%10/2/07 23:35 305.4 435 5 FLUX 400 0.820 328 1.0 110.4 45.4% 132.8 54.6% 243.2 0.0 0.0%10/3/07 0:35 343.6 440 5 FLUX 437 0.820 359 1.0 115.8 46.6% 132.8 53.4% 248.6 0.0 0.0%10/3/07 1:35 342.8 435 5 FLUX 452 0.820 371 1.0 132.8 50.1% 132.2 49.9% 265.0 0.0 0.0%10/3/07 2:35 308.1 430 5 FLUX 453 0.820 371 1.0 128.2 49.1% 132.7 50.9% 260.9 0.0 0.0%10/3/07 3:35 309.5 432 5 FLUX 455 0.820 373 1.0 115.3 46.6% 132.3 53.4% 247.6 0.0 0.0%10/3/07 4:35 303.7 437 5 FLUX 458 0.820 376 1.0 104.8 44.1% 132.9 55.9% 237.7 0.0 0.0%Nat. Gas Input Biomass FuelUS Steel Minntac - Line 5 NOx Emissions (revised)01002003004005006009/15/2007 11/4/2007 12/24/2007 2/12/2008 4/2/2008 5/22/2008 7/11/2008Date

Grate Feed Rate (tonnes/hr) and Natural Gas/Biomass (MM Btu)020040060080010001200 Stack Flow (Kscfm), NOx (lbs/hr)Pellet Production Rate (LT/hr)Natural Gas Input (MM Btu's)Biomass Fuel Input (MM Btu's)NOx Emissions (lbs/hr)Stack Flow Rate (kscfm)United States Steel - Minntac Iron Ore Pelletizing Operation NOx Reduction Analysis

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# Appendix C NOx Reduction Technology Comparison for Existing InstallationsUS Steel MinntacHatch Project No. H-3320021/22/2009, rev.1Appendix C - NOx Reduction Technology Comparison for Existing InstallationsApplication/Oxygen Ammonia Catalyst InjectionTechnology Location Volume Temp.∆P Dust Load Inlet Outlet Removal Basis Slip Material Point(scfm) (deg F)(in wg)(gr/dscf) (ppm) (ppm) (%) (%) (ppm)SCRJapan (Shimonoseki) - ReplacementCoal Fired Boiler, 175MW342,000 698 3.25 240 570 285 50% 3% <5 V/Ti Dirty SideSCRJapan (Shimonoseki) - DemonstrationCoal Fired Boiler, 175MW549,000 734 3.25 160 340 115.6 66% 3% <10 V/Ti Dirty SideSCRJapan (Isogo) - Pilot TestCoal Fired Boiler, 265MW930 662 3.25 320 180 36 80% 3% <5 V/Ti Dirty SideSCRUSA (Pensacola, FL) - Pilot TestCoal Fired Boiler, 75MW420 700 3.25 160 400 80 80% 3% <5 V/Ti Dirty SideSCRKing George Country, VACoal Fired Utility Boiler, 220 MW506,000 680 6 8 54 24 56% 3% <5 V/Ti Dirty SideSCROrlando, FLCoal Fired Utility Boiler, 425 MW977,500 680 3.25 8 102 54 47% 3% 2 V/Ti Dirty SideSCRCarneys Point, NJCoal Fired Utility Boiler, 260 MW598,000 680 <1 8 102 42 59% 3% <5 V/Ti Dirty SideSCRSwedesboro, NJCoal Fired Utility Boiler, 225 MW517,500 680 0.8 8 112 45 60% 3% <5 V/Ti Dirty SideSCRIndiantown, FLCoal Fired Utility Boiler, 330 MW759,000 680 3.25 8 80 48 40% 3% <5 V/Ti Dirty SideSCRConcord, NHCoalFired Utility Boiler, 330 MW759,000 680 3.25 8 848 246 71% 3% <2 V/Ti Dirty SideSCRSomersetCoalFired Utility Boiler, 675 MW1,552,500 649 2.8 5 340 34 90% 3% 3 V-Mb/Ti Dirty SideSCRRoxboroCoal Fired Utility Boiler, 735 MW1,725,300 735 1.3 0.04 278 58.5 79% 3.25% 2 V-Mb/Ti Clean SideSCRHawthornCoal Fired Utility Boiler, 550 MW1,291,041 695 2 14.3 135 59.2 56.1% 3.5% 2 V-Mb/Ti Dirty SideSCRCementeria Di Moselice - DesignKiln Capacity 2400 tpd94,172 635 6.0 43 Max 1652 165.2 90.0% 2.5% 4 V/Ti Dirty SideSCRCementeria Di Moselice - ActualKiln Capacity 1800 tpd64,744 635 2.0 43 Max 1118 55.9 95.0% 2.7% 4 V/Ti Dirty SideSCRFurnace HeaterCalifornia, USA730,000 626 1.5 8 100 35 65% 3% <5 V/Ti Dirty SideSCRFurnace HeaterCalifornia, USA1,122,000 726 3 8 57 5.5 90% 3% <5 V/Ti Dirty SideSCRHeat Recovery Steam GeneratorMontana, USA3,796,000 583 2 8 25 4 84% 3% <5 V/Ti Dirty SideSCRHeat Recovery Steam GeneratorConnecticut, USA3,157,000 622 3.5 8 25 2 92% 3% <5 V/Ti Dirty SideSCRUtility Boiler (Natural Gas)Canada1,350,000 530 5 8 150 15 90% 3% <5 V/Ti Dirty SideSCRUtility Boiler (Natural Gas) California,USA1,687,000 650 2 8 97 8.8 91% 3% <5 V/Ti Dirty SideSCRUtility Boiler (Oil)California, USA1,827,000 660 2 8 158 27.6 83% 3% <5 V/Ti Dirty SideSCRUtility Boiler (Coal)Georgia, USA5,189,000 757 6 8 366 37 90% 3% <5 V/Ti Dirty SideSCRUtility Boiler (Coal)Minnesota, USA5,390,000 735 6 8 545 55 90% 3% <5 V/Ti Dirty SideSCRGas Turbine (Simple Cycle)California, USA2,320,000 1020 6.5 8 42 4 90% 3% <5 V/Ti Dirty SideAverage Removal Efficiency = 75%Nox EmissionsGas Stream for Nox Reduction TreatmentUS Steel MinntacHatch Project No. H-3320021/22/2009, rev.1Appendix C - NOx Reduction Technology Comparison for Existing InstallationsApplication/Oxygen Ammonia Catalyst InjectionTechnology Location Volume Temp.∆P Dust Load Inlet Outlet Removal Basis Slip Material Point(scfm) (deg F)(in wg)(gr/dscf) (ppm) (ppm) (%) (%) (ppm)Nox EmissionsGas Stream for Nox Reduction TreatmentSNCRFort Martin Unit 1 1,030,000.00 2400 ~ 0 3200 165 17.5%3.8 <5 N/A Dirty SideSNCRFort Martin Unit 2 1,060,000.00 2200 ~ 0 3200 150 25.0%3.8 <5 N/A Dirty SideSNCRAvon Lake Unit 9 1,170,000.00 2400 ~ 0 3290 225 22.5%4 <5 N/A Dirty SideSNCRElrama 1, 2, & 3 250,000.00 2000 ~ 0 2320 248 22.5%6 <5 N/A Dirty SideSNCRElrama 4420,000.00 2200 ~ 0 2330 239 27.5%4.5 <5 N/A Dirty SideSNCRNew Castle Units 3 & 4 200,000.00 2000 ~ 0 2250 181 27.5%3.2 <5 N/A Dirty SideSNCRNew Castle Units 5 300,000.00 2000 ~ 0 2270 203 25.0%3.2 <5 N/A Dirty SideSNCRNiles Units 1 & 2 220,000.00 2200 ~ 0 1440 308 30.0%3.5 <5 N/A Dirty SideSNCRShawville 1 & 2 280,000.00 2300 ~ 0 1350 254 27.5%5 <5 N/A Dirty SideSNCRShawville 3 & 4 400,000.00 2500 ~ 0 1250 213 15.0%4 <5 N/A Dirty SideSNCRBayfront 1 & 2 Wood Fuel 55,000.00 1850 ~ 0 0.5140 95 32.5%4.5 <5 N/A Dirty SideSNCRBayfront 1 & 2 Coal Fuel 55,000.00 2000 ~ 0 0.5210 116 45.0%4.5 <5 N/A Dirty SideSNCRBayfront 1 & 2 Wood Fuel 55,000.00 1850 ~ 0 0.5220 88 60.0%4.5 <5 N/A Dirty SideSNCRBayfront 1 & 2 Coal Fuel 55,000.00 2000 ~ 0 0.5420 137 67.5%4.5 <5 N/A Dirty SideSNCRHonam Power Plant 1 (test a), KoreaCoal Fired Utility Boiler, 250 MW575,000 2100 ~ 0 2 462 270.7 41.4% 6% 9.8 N/A Dirty SideSNCRHonam Power Plant 1 (test b), KoreaCoal Fired Utility Boiler, 250 MW575,000 2100 ~ 0 2 384 230.0 40.1% 6% 2.6 N/A Dirty SideSNCRHonam Power Plant 2 (test a), KoreaCoal Fired Utility Boiler, 250 MW575,000 2100 ~ 0 2 416 243.8 41.4% 6% 4 N/A Dirty SideSNCRHonam Power Plant 2 (test b), KoreaCoal Fired Utility Boiler, 250 MW575,000 2100 ~ 0 2 333 208.5 37.4% 6% 2.9 N/A Dirty SideAverage Removal Efficiency = 33.6%LoTOxStainless Steel Pickling 4,0003000 100 96.7%LoTOx25 MW Coal Fired Boiler 90,000200 20 90.0%LoTOxLead Smelting26,000150 10 93.3%LoTOx1000 HP Natural Gas Fired Boiler 10,00040 4 90.0%LoTOxFCC145,00070 2071.4%LoTOxFCC185,000120 2083.3%LoTOxFCC260,000120 2083.3%LoTOxFCC40,00070 2071.4%LoTOxSulfur Acid Regeneration50,00090 1088.9%LoTOxFCC200,000120 2083.3%LoTOxFCC300,00085 2076.5%LoTOxFCC250,00080 2075.0%LoTOxFCC85,000250 2092.0%Average Removal Efficiency = 80.6%SCR Selective Catalytic ReductionSNCR Selective Non-Catalytic ReductionLoTOxLoTOx TechnologyUnited States Steel - Minntac Iron Ore Pelletizing Operation NOx Reduction Analysis

ISO 9001 H-332002 , Rev. 0

C:\carl40268\US STEEL\332002 Minntac Iron Ore Pellet Operation\PR332002-01 US Steel Minntac - NOx Reduction Technology Report Rev 0.doc © Hatch 2007/03 a 

# Appendix D NOx Reduction Vendor ComparisonUS Steel Minntac Iron Ore Pelletizing Plant - NOxReductionHatch Project No.332002January 15, 2009Appendix D - NOx Reduction Vendor ComparisonNALCOBRANCHBOCMOBOTEC BACT ESA ENVIRONMENTAL MITSUBISHI LINDE FCT1. PROPOSED TECHNOLOGYa. Low NOx BurnerYesYesb. Combustion Air ModificationsYesc. SNCRYesYesYesd. SCRYesYese. LoTOxYes2. PROCESS ANALYSISa. Gas Volume (scfm)265,000 265,000 265,000 265,000 265,000 500,000b. Gas Temperature (deg F)2000 2000 2000 800 800 300c. Dust Loading (gr/dscf)8 8 8 6 6 6c. Pressure Drop,∆P ("wg)1 1 1 10 10 10d. NOx Reduction- % of Inlet Load60% 60% 60% 70% 70% 80% 20%- Line 5 Reduction (tons NOx/yr)1500 1500 1500 1750 1750 2000 5003. EQUIPMENT SYSTEMSa. Kiln Combustion Process- Low NOx Burner UpgradesBurner StagingBurner Tip- Combustion Air UpgradesROFA Systemb. SNCR System- Urea Supply SystemRequiredRequiredRequired- Spray NozzlesRequiredRequiredRequired- ControlsRequiredRequiredRequired- Compressed Air SystemRequiredRequiredRequiredc. SCR System- Urea Supply SystemRequiredRequired- Spray NozzlesRequiredRequired- ControlsRequiredRequired- Compressed Air SystemRequiredRequired- Reactor w/ CatalystRequiredRequired- Precipitator Dust CollectorRequiredRequired- Exhaust Fan/MotorRequiredRequiredd. LoTOx- External Reactor SystemRequired- Ozone Generator SystemRequired- Oxygen Supply SystemRequired- Cooling Water SystemRequired- Scrubber SystemRequired- Wastewater Treatment SystemRequired- Exhaust Fan/MotorRequired4. UTILITY REQUIREMENTSa. Compressed Air (scfm @ 80 psig)2700 180027002700 2700b. Urea Consumption (gal/hr)260 400200320 320c. Heat Energy Input (Btu/hr)270,000,000d. Electrical Energy (kW)600 500 60015,000e. Cooling Water (gpm)2,6005. Pilot Plant/CFD Modelinga. CFD ModelingYesYesYesb. Field Testing and Data CollectionYesYesYesc. Pilot Plant DemonstrationYesYesYesYesGateway View Plaza, 1600 West Carson Street, Suite 1 Pittsburgh, PA, USA 15219 1031 Tel (412) 497 2000  Fax (412) 497 2212