Project Report

United States Steel Corporation

Minntac Plant

NOx Reduction Analysis

For

Minntac Iron Ore Pelletizing Operation

H-332002 

Rev. 0 

January 30, 2009 
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H-332002 

Project Report 

Rev. 0, Page i

January 30, 2009

United States Steel 

Minntac Iron Ore Pelletizing 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 Indurating 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................................................................................................... 18
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NOx Reduction Analysis

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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 Comparison 
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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 Process 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 concentrates 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 heated in the indurating process as the final step in 

the pelletizing process at Minntac. The grate-kiln-cooler 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 Time % 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/hr 
United States Steel - Minntac Ir

Green Pellets 

Waste Gas Preheat Recoup Cooler Vent

Gas Side Analysis Stack Air Flow Stack Zone 1 Zone 2/3

 1. Gas Flow Rates: (1A & 1B) (FAN 3A) (FAN 3B)

- standard: (scfm) 500,000 265,000 110,000 108,000 174,000 206,000

 2. Mass Flow Rates:

- dry gases: (lbs/min) 32,000 19,750 7,620 7,580 12,380 14,720

- water vapor: (lbs/min) 2,600 155 150 100 130 160

 3. Gas Temp.: (deg F) 120 600 1,630 930 70 70 4. Gas Density: (lbs/ft3) 0.063 0.038 0.018 0.027 0.072 0.072 5. 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 2/3 6. Pellet Temp* (deg F) 100 650 1100 2450 800 250* estimated pellet temperature

Cooler Indraft Air

Rotary

Kiln

Cooler

Zone 1

Coole

Zone 

Scrubber 

System

Waste Gas

Fan

Waste Gas 

Stack

Preheat

Exhaust 

Fan

1A & 1B

Inputs:

- Biomass- Natural 

Gas

- Fuel Oil

3

Exhaust 

Fan 3A

5

1

2

1 2 3 5 6

Dryer D1 Dryer D2

4

6

Waste Gas Preheat Recoup Cooler Vent

Gas Side Analysis Stack Air Flow Stack Zone 1 Zone 2/3

 1. Gas Flow Rates: (1A & 1B) (FAN 3A) (FAN 3B)

- standard: (scfm) 500,000 265,000 110,000 108,000 174,000 206,000

 2. Mass Flow Rates:

- dry gases: (lbs/min) 32,000 19,750 7,620 7,580 12,380 14,720

- water vapor: (lbs/min) 2,600 155 150 100 130 160

 3. Gas Temp.: (deg F) 120 600 1,630 930 70 70 4. Gas Density: (lbs/ft3) 0.063 0.038 0.018 0.027 0.072 0.072 5. 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 2/3 6. Pellet Temp* (deg F) 100 650 1100 2450 800 250* estimated pellet temperature

Cooler Indraft Air

Rotary

Kiln

Cooler

Zone 1

Coole

Zone 

Scrubber 

System

Waste Gas

Fan

Waste Gas 

Stack

Preheat

Exhaust 

Fan

1A & 1B

Inputs:

- Biomass- Natural 

Gas

- Fuel Oil

3

Exhaust 

Fan 3A

5

1

2

1 2 3 5 6

Dryer D1 Dryer D2

4

6
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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 natural 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 Analysis at Indurating 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 approximately 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 NOx emissions for the Line 5 portion of the pelletizing 

production at U.S. Steel Minntac is estimated to be 2500 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 Indurating 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 NOx 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 Process 
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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 Line 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 factor to estimate emissions at each of the five lines 

results in total NOx emissions of 8,400 tons/yr. 

4. Indurating Process NOx Reduction 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 America. 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 and 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. 
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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 installing 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 indurating 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, Hatch 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” burner, 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 significant 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 will be to verify that the low NOx burner will not 

negatively affect the indurating process. 

FCT, Inc. proposes to replace the existing main burner 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 manufacture similar burners and should be investigated prior 

to implementing this approach. 
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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 load 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 generated in the rotary kiln is to improve the air 

flow/circulation throughout the rotary kiln. Nalco Mobotec proposes to improve the combustion process 

by upgrading the kiln with a Rotating Opposed Fired Air (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 the efficiency of the combustion process is improved. 

Mobotec believes that this improved efficiency will reduce 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 reduce 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 temperature gas stream. These NOx reduction concepts are 

described briefly below: 

4.2.1 SNCR Utilizing Urea 

Urea is utilized to reduce NOx emissions by chemically reducing the NOx to harmless nitrogen gas in 

accordance with the following simplified reaction: * 

(NH2)2CO + 2NOx + 1⁄2O2 → 2N2 + 2H2O + CO2

* 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 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). 
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• 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. Figure 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 between 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 chlorides 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 ammonia 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 F

Reduction 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 suggest that a 30-50% NOx reduction is a more realistic 

target. 
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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): 

2NH3 + 2NOx + 1⁄2O2 → 2N2 + 3H2O 

The optimal range for the flue gas temperature is slightly 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 (Appendix 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 the 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 urea 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 downstream 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. 

 
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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/dscf 
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Cooler

Zone 1

Cooler

Zone 2

Scrubber 

System

Waste Gas 

Stack

Dryer D1 Dryer D2 Preheat

Urea Flow: 150 gal/hrUrea Temp.: 70 deg FComp. Air: 2700 scfm

50% Urea 

Storage Tank

Urea Feed System

Rotary

Kiln

Waste Gas 

Fan

Gas Volume: 265,000 scfmGas Temp.: 2000 deg FNOx Load: (ave.) 630 lbs/hrDust Load: 8 gr/dscf

Gas Volume: 500,000 scfmGas Temp.: 120 deg FNOx Load: (ave.) 380 lbs/hrDust Load: 0.015 gr/dscf

Cooler

Zone 1

Cooler

Zone 2

Scrubber 

System

Waste Gas 

Stack

Dryer D1 Dryer D2 Preheat

Urea Flow: 150 gal/hrUrea Temp.: 70 deg FComp. Air: 2700 scfm

50% Urea 

Storage Tank

Urea Feed System

Rotary

Kiln

Waste Gas 

Fan

Gas Volume: 265,000 scfmGas Temp.: 2000 deg FNOx Load: (ave.) 630 lbs/hrDust Load: 8 gr/dscf

Gas Volume: 500,000 scfmGas Temp.: 120 deg FNOx Load: (ave.) 380 lbs/hrDust Load: 0.015 gr/dscf
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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 likely 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 (FRP), 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 control valves and pressure transmitters in each nozzle. 

4.2.4.6 Compressed Air System: 

Compressed air system to provide the high pressure air 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-Bradley programmable logic controller (PLC) with all 

necessary instrumentation, controls and monitoring equipment. 
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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 involves 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 system 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 offers to reduce NOx emissions in two ways: 

• Low NOx combustion modifications to the existing burner system. 

• SNCR technology based on urea injection. 

The low NOx combustion system modifications 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 NOx 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 usage 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 the 20-30% for the burner modification. This equates 

to a total of a 45-70% reduction. 
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ESA also proposes to provide CFD modeling of the rotary kiln operation in order to refine the design of 

both their low NOx combustion system modifications and their SNCR system. ESA stated that they have 

done previous CFD modeling of Minntac’s rotary kilns, which would help them improve the accuracy of 

the modeling effort. 

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 reduce 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 proposal 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 chemically reducing the NOx to harmless nitrogen gas in 

accordance with the following simplified reaction: * 

(NH2)2CO + 2NOx + 1⁄2O2 → 2N2 + 2H2O + CO2

* 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). 
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• Reaction temperature between 600 and 900 deg F. 

• 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 Table (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%. 
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• 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 pressure 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. 
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Preliminary design parameters are outlined below: 

• 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 expected to be approximately 1,200,000 gal/yr. 

• Compressed air usage at 2700 scfm at approximately 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/dscf 
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UHS

Cooler

Zone 1

Cooler

Zone 2

Scrubber 

System

Waste Gas 

Fan

Waste Gas 

Stack

Dryer D1 Dryer D2 Preheat

Recycle

Fan

50% Urea

Storage Tank

Urea Feed 

System

Rotary

Kiln

SCR System

c/w TiO2-V Catalyst

Urea FloUrea TemComp. A

Gas Volume: 265,000 scfmGas Temp.: 800 deg FNOx Load: (ave.) 630 lbs/hrDust Load: 6 gr/dscf

Gas Volume: 500,000 scfmGas Temp.: 120 deg FNOx Load: (ave.) 160 lbs/hrDust Load: 0.005 gr/dscf

Electrostatic

Precipitator

UHS

Cooler

Zone 1

Cooler

Zone 2

Scrubber 

System

Waste Gas 

Fan

Waste Gas 

Stack

Dryer D1 Dryer D2 Preheat

Recycle

Fan

50% Urea

Storage Tank

Urea Feed 

System

Rotary

Kiln

SCR System

c/w TiO2-V Catalyst

Urea FloUrea TemComp. A

Gas Volume: 265,000 scfmGas Temp.: 800 deg FNOx Load: (ave.) 630 lbs/hrDust Load: 6 gr/dscf

Gas Volume: 500,000 scfmGas Temp.: 120 deg FNOx Load: (ave.) 160 lbs/hrDust Load: 0.005 gr/dscf

Electrostatic

Precipitator
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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 designed 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 reductant (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. 
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4.3.3.5 SCR Catalyst System: 

The catalyst shall be a titanium oxide vanadium material 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 install 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 600o

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. 
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4.3.4.2 Mitsubishi Power Systems 

Mitsubishi Power Systems proposal offers to install 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 consumption 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, ammonia 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 (LoTOx) - NOx Reduction Technology 

LoTOx is a patented low temperature oxidation process utilizes ozone to reduce NOx emissions. Like 

SCR technology, the LoTOx system is relatively efficient at reducing NOx emissions with a typical NOx 

reduction efficiency of approximately 80%. 

LoTOx utilizes ozone (O3) as a reagent to convert the NOx emissions to form soluble N2O5, 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 SO2. 

4.4.1 LoTOx Technology Overview 

Ozone reacts rapidly with NOx to form nitric acid in accordance with the following reaction sequence: 

NO + O3 Æ NO2 + O2 (1) 

2NO2 + O3 Æ N2O5 + O2 (2) 

N2O5 + 2H2O Æ 2HNO3 + O2 (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. 
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4.4.2 LoTOx Design Concepts 

As outlined in the NOx Reduction Comparison Table (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 effective 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 break NOx down into soluble nitric acid is proportional to 

the amount of ozone injected into the reaction chamber. 
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Primary design parameters are outlined below: 

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

• Gas temperature must be approximately 300 deg 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 Line 5 is expected to be approx. 6,000 

tons/yr. 

• Annual oxygen supply to the ozone generation 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 designed to meet nitrate discharge limits. 
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Cooler

Zone 1

Coole

Zone 2

New

Scrubber 

System

Dryer D1 Dryer D2 Preheat

Ozone Flow: 1600 lbs/hr

Rotary

Kiln

Gas Volume: 500,000 scfmGas Temp.: 300 deg FNOx Load: (ave.) 630 lbs/hr

Gas Volume: 50Gas Temp.: NOx Load: (ave.) Dust Load: 0

Ozone Reactor

Ozone 

Production 

Facility

To New WWTP 

Oxygen 

Production 

Facility

Chilling Water: 2600 gpm

NOx Æ NO2 Æ N2O5 Æ HNO3

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Zone 1

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Zone 2

New

Scrubber 

System

Dryer D1 Dryer D2 Preheat

Ozone Flow: 1600 lbs/hr

Rotary

Kiln

Gas Volume: 500,000 scfmGas Temp.: 300 deg FNOx Load: (ave.) 630 lbs/hr

Gas Volume: 50Gas Temp.: NOx Load: (ave.) Dust Load: 0

Ozone Reactor

Ozone 

Production 

Facility

To New WWTP 

Oxygen 

Production 

Facility

Chilling Water: 2600 gpm

NOx Æ NO2 Æ N2O5 Æ HNO3
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4.4.3 LoTOx Equipment Concepts 

The are several major equipment components that comprise 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 provide 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 compress 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 completion 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. 
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Air Separation

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 (O3). 

Ozone is produced from oxygen gas in an ozone generator 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 approximately 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. 
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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. 
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4.4.3.7 Wastewater Treatment Plant 

Wastewater treatment plant shall be provided to remove 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 entrained solids via settling. Preliminary sizing of the 

thickener shall size at a rise rate of approximately 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 underflow to the vacuum filters 

for additional dewatering and solids removal. Three drum type vacuum filters (2 operating; 1 standby) shall be included. 
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Venturi Supply Pumps

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 based 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 reduction 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 flow 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 piping, 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 system, thus reducing the usage of oxygen, power and 

ozone. 
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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 required 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% reduction 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 indurating 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. 
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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 Section 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 Minntac 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. 
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Appendix A 

Indurating Process Flow Diagram 
Waste Gas Preheat Recoup Cooler Vent

Gas Side Analysis Stack Air Flow Stack Zone 1 Zone 2/3 1. Gas Flow Rates: (1A & 1B) (FAN 3A) (FAN 3B)

- standard: (scfm) 500,000 265,000 110,000 108,000 174,000 206,000

 2. Mass Flow Rates:

- dry gases: (lbs/min) 32,000 19,750 7,620 7,580 12,380 14,720

- water vapor: (lbs/min) 2,600 155 150 100 130 160

 3. Gas Temp.: (deg F) 120 600 1,630 930 70 70 4. Gas Density: (lbs/ft3) 0.063 0.038 0.018 0.027 0.072 0.072

 5. 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 2/3 6. Pellet Temp* (deg F) 100 650 1100 2450 800 250* estimated pellet temperature

Cooler Indraft Air

Rotary

Kiln

Cooler

Zone 1

Cooler

Zone 2

Scrubber 

System

Waste Gas

Fan

Waste Gas 

Stack

Preheat

Exhaust 

Fan

1A & 1B

Inputs:

- Biomass- Natural 

Gas

- Fuel Oil

3

Exhaust 

Fan 3A

5

1

2

1 2 3 5 6

Dryer D1 Dryer D2

4

E

6
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Appendix B 

Line 5 Operating Data 
HDATE Nox Emissions Stack Flow LINE Pellet Grate Feed Green Ball Pellet Produced Grate 

(lb/hr) (1000 scfm) No. Type (LTPH) Factor (LTPH) Operation (MM Btu's)

% MMBTUS

Minimum: 3 130 80 0.82 67 0.3 4.2 4.5% 0.0 0

Maximum: 1,232 701 528 0.86 454 1.9 352.4 100.0% 242.0 95

Averages: 467 380 448 0.84 375 1.0 163.5 57.4% 117.6 42

10/1/07 0:35 353.8 441 5 FLUX 472 0.820 387 1.0 130.3 48.3% 139.4 5110/1/07 1:35 340.4 440 5 FLUX 462 0.820 379 1.0 114.2 44.9% 140.3 5510/1/07 2:35 341.2 441 5 FLUX 461 0.820 378 1.0 108.1 43.7% 139.5 5610/1/07 3:35 308.9 440 5 FLUX 462 0.820 379 1.0 121.8 49.5% 124.5 5010/1/07 4:35 417.3 438 5 FLUX 464 0.820 380 1.0 104.9 42.8% 140.1 5710/1/07 5:35 490.4 436 5 FLUX 464 0.820 381 1.0 138.9 49.7% 140.3 5010/1/07 6:35 487.5 439 5 FLUX 464 0.820 381 1.0 137.2 49.4% 140.3 5010/1/07 7:35 474.9 439 5 FLUX 460 0.820 377 1.0 136.9 49.5% 139.6 5010/1/07 8:35 450.8 437 5 FLUX 456 0.820 374 1.0 135.7 49.2% 139.9 5010/1/07 9:35 481 436 5 FLUX 452 0.820 371 1.0 135.8 49.2% 140.0 50

10/1/07 10:35 351.6 399 5 FLUX 436 0.820 358 1.0 130.2 48.1% 140.2 5110/1/07 11:35 393.6 436 5 FLUX 400 0.820 328 1.0 106.6 47.1% 119.9 5210/1/07 12:35 320.8 439 5 FLUX 442 0.820 363 1.0 108.1 43.7% 139.3 5610/1/07 13:35 323 442 5 FLUX 462 0.820 378 1.0 100.1 41.7% 140.0 5810/1/07 14:35 470.7 438 5 FLUX 460 0.820 377 1.0 96.0 40.7% 140.1 5910/1/07 15:35 360.2 441 5 FLUX 462 0.820 379 1.0 136.5 49.3% 140.2 5010/1/07 16:35 346.7 440 5 FLUX 465 0.820 381 1.0 108.2 43.4% 140.9 5610/1/07 17:35 348.3 438 5 FLUX 473 0.820 388 1.0 100.0 41.3% 142.2 5810/1/07 18:35 349.1 439 5 FLUX 473 0.820 388 1.0 101.9 41.8% 141.8 5810/1/07 20:35 299.3 422 5 FLUX 326 0.820 267 0.9 115.2 50.5% 113.0 4910/1/07 21:35 396.7 443 5 FLUX 445 0.820 365 1.0 106.2 42.7% 142.3 5710/1/07 22:35 317.4 443 5 FLUX 471 0.820 386 1.0 122.7 46.4% 141.6 5310/1/07 23:35 311 443 5 FLUX 471 0.820 386 1.0 112.4 44.2% 141.9 55

10/2/07 0:35 387.5 447 5 FLUX 465 0.820 382 1.0 114.0 44.5% 141.9 5510/2/07 1:35 421.7 436 5 FLUX 460 0.820 377 1.0 147.3 50.8% 142.7 4910/2/07 2:35 316.3 446 5 FLUX 456 0.820 374 1.0 107.5 43.2% 141.5 5610/2/07 3:35 317.6 439 5 FLUX 455 0.820 373 1.0 98.9 41.0% 142.1 5910/2/07 4:35 307.8 443 5 FLUX 455 0.820 374 1.0 99.3 41.2% 141.9 5810/2/07 5:35 424.3 442 5 FLUX 455 0.820 373 1.0 113.2 44.3% 142.4 5510/2/07 6:35 422.1 443 5 FLUX 451 0.820 370 1.0 137.2 49.1% 142.4 5010/2/07 7:35 331.1 432 5 FLUX 449 0.820 368 1.0 99.3 41.3% 141.3 5810/2/07 8:35 370.4 383 5 FLUX 445 0.820 365 1.0 94.6 40.4% 139.6 5910/2/07 9:35 370.4 372 5 FLUX 363 0.820 298 1.0 88.1 40.2% 131.2 59

10/2/07 10:35 616.9 412 5 FLUX 405 0.820 332 1.0 157.1 77.7% 45.2 2210/2/07 11:35 594 423 5 FLUX 411 0.820 337 1.0 192.0 100.0% 0.0 010/2/07 12:35 482.3 360 5 FLUX 405 0.820 332 1.0 176.1 86.8% 26.9 1310/2/07 13:35 339 364 5 FLUX 350 0.820 287 1.0 124.7 67.1% 61.1 3210/2/07 14:35 280.6 384 5 FLUX 363 0.820 298 1.0 108.0 55.9% 85.1 4410/2/07 15:35 256.6 381 5 FLUX 399 0.820 327 1.0 94.9 41.7% 132.5 5810/2/07 16:35 269.6 388 5 FLUX 398 0.820 327 1.0 84.4 38.9% 132.7 6110/2/07 17:35 237.5 381 5 FLUX 400 0.820 328 1.0 91.4 40.8% 132.4 5910/2/07 18:35 236.1 397 5 FLUX 397 0.820 326 1.0 91.3 40.8% 132.4 5910/2/07 19:35 257.2 386 5 FLUX 399 0.820 327 1.0 89.9 40.4% 132.6 5910/2/07 20:35 244.6 388 5 FLUX 399 0.820 327 1.0 86.8 39.6% 132.3 6010/2/07 21:35 232.6 382 5 FLUX 398 0.820 326 1.0 90.4 40.5% 132.7 5910/2/07 22:35 244.5 375 5 FLUX 390 0.820 320 1.0 108.3 45.0% 132.6 5510/2/07 23:35 305.4 435 5 FLUX 400 0.820 328 1.0 110.4 45.4% 132.8 54

10/3/07 0:35 343.6 440 5 FLUX 437 0.820 359 1.0 115.8 46.6% 132.8 5310/3/07 1:35 342.8 435 5 FLUX 452 0.820 371 1.0 132.8 50.1% 132.2 4910/3/07 2:35 308.1 430 5 FLUX 453 0.820 371 1.0 128.2 49.1% 132.7 5010/3/07 3:35 309.5 432 5 FLUX 455 0.820 373 1.0 115.3 46.6% 132.3 5310/3/07 4:35 303.7 437 5 FLUX 458 0.820 376 1.0 104.8 44.1% 132.9 55

Nat. Gas Input Biomass F

US Steel Minntac - Line 5 NOx Emissions (revised)

0

100200300400500600

9/15/2007 11/4/2007 12/24/2007 2/12/2008 4/2/2008 5/22/2008 

Date

Grate Feed Rate (tonnes/hr) and 

Natural Gas/Biomass (MM Btu) 

PelNatBioNOSta
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Appendix C

NOx Reduction Technology Comparison for 

Existing Installations 
US Steel Minntac

Hatch Project No. H-3320021/22/2009, rev.1Appendix C - NOx Reduction Technology Comparison for Existing Installations

Application/ Oxygen Am

Technology Location Volume Temp. ∆P Dust Load Inlet Outlet Removal Basis 

(scfm) (deg F) (in wg) (gr/dscf) (ppm) (ppm) (%) (%) (

SCR Japan (Shimonoseki) - Replacement Coal Fired Boiler, 175MW 342,000 698 3.25 240 570 285 50% 3% 

SCR Japan (Shimonoseki) - Demonstration Coal Fired Boiler, 175MW 549,000 734 3.25 160 340 115.6 66% 3% 

SCR Japan (Isogo) - Pilot Test Coal Fired Boiler, 265MW 930 662 3.25 320 180 36 80% 3% 

SCR USA (Pensacola, FL) - Pilot Test Coal Fired Boiler, 75MW 420 700 3.25 160 400 80 80% 3% 

SCR King George Country, VA Coal Fired Utility Boiler, 220 MW 506,000 680 6 8 54 24 56% 3% 

SCR Orlando, FL Coal Fired Utility Boiler, 425 MW 977,500 680 3.25 8 102 54 47% 3% 

SCR Carneys Point, NJ Coal Fired Utility Boiler, 260 MW 598,000 680 <1 8 102 42 59% 3% 

SCR Swedesboro, NJ Coal Fired Utility Boiler, 225 MW 517,500 680 0.8 8 112 45 60% 3% 

SCR Indiantown, FL Coal Fired Utility Boiler, 330 MW 759,000 680 3.25 8 80 48 40% 3% 

SCR Concord, NH Coal Fired Utility Boiler, 330 MW 759,000 680 3.25 8 848 246 71% 3% 

SCR Somerset Coal Fired Utility Boiler, 675 MW 1,552,500 649 2.8 5 340 34 90% 3% 

SCR Roxboro Coal Fired Utility Boiler, 735 MW 1,725,300 735 1.3 0.04 278 58.5 79% 3.25% 

SCR Hawthorn Coal Fired Utility Boiler, 550 MW 1,291,041 695 2 14.3 135 59.2 56.1% 3.5% 

SCR Cementeria Di Moselice - Design Kiln Capacity 2400 tpd 94,172 635 6.0 43 Max 1652 165.2 90.0% 2.5% 

SCR Cementeria Di Moselice - Actual Kiln Capacity 1800 tpd 64,744 635 2.0 43 Max 1118 55.9 95.0% 2.7% 

SCR Furnace Heater California, USA 730,000 626 1.5 8 100 35 65% 3% 

SCR Furnace Heater California, USA 1,122,000 726 3 8 57 5.5 90% 3% 

SCR Heat Recovery Steam Generator Montana, USA 3,796,000 583 2 8 25 4 84% 3% 

SCR Heat Recovery Steam Generator Connecticut, USA 3,157,000 622 3.5 8 25 2 92% 3% 

SCR Utility Boiler (Natural Gas) Canada 1,350,000 530 5 8 150 15 90% 3% 

SCR Utility Boiler (Natural Gas) California, USA 1,687,000 650 2 8 97 8.8 91% 3% 

SCR Utility Boiler (Oil) California, USA 1,827,000 660 2 8 158 27.6 83% 3% 

SCR Utility Boiler (Coal) Georgia, USA 5,189,000 757 6 8 366 37 90% 3% 

SCR Utility Boiler (Coal) Minnesota, USA 5,390,000 735 6 8 545 55 90% 3% 

SCR Gas Turbine (Simple Cycle) California, USA 2,320,000 1020 6.5 8 42 4 90% 3% 

Average Removal Efficiency = 75%

Gas Stream for Nox Reduction Treatment Nox Emissions
US Steel Minntac

Hatch Project No. H-3320021/22/2009, rev.1Appendix C - NOx Reduction Technology Comparison for Existing Installations

Application/ Oxygen Am

Technology Location Volume Temp. ∆P Dust Load Inlet Outlet Removal Basis 

(scfm) (deg F) (in wg) (gr/dscf) (ppm) (ppm) (%) (%) (

Gas Stream for Nox Reduction Treatment Nox Emissions

SNCR Fort Martin Unit 1 1,030,000.00 2400 ~ 0 3 200 165 17.5% 3.8 

SNCR Fort Martin Unit 2 1,060,000.00 2200 ~ 0 3 200 150 25.0% 3.8 

SNCR Avon Lake Unit 9 1,170,000.00 2400 ~ 0 3 290 225 22.5% 4 

SNCR Elrama 1, 2, & 3 250,000.00 2000 ~ 0 2 320 248 22.5% 6 

SNCR Elrama 4 420,000.00 2200 ~ 0 2 330 239 27.5% 4.5 

SNCR New Castle Units 3 & 4 200,000.00 2000 ~ 0 2 250 181 27.5% 3.2 

SNCR New Castle Units 5 300,000.00 2000 ~ 0 2 270 203 25.0% 3.2 

SNCR Niles Units 1 & 2 220,000.00 2200 ~ 0 1 440 308 30.0% 3.5 

SNCR Shawville 1 & 2 280,000.00 2300 ~ 0 1 350 254 27.5% 5 

SNCR Shawville 3 & 4 400,000.00 2500 ~ 0 1 250 213 15.0% 4 

SNCR Bayfront 1 & 2 Wood Fuel 55,000.00 1850 ~ 0 0.5 140 95 32.5% 4.5 

SNCR Bayfront 1 & 2 Coal Fuel 55,000.00 2000 ~ 0 0.5 210 116 45.0% 4.5 

SNCR Bayfront 1 & 2 Wood Fuel 55,000.00 1850 ~ 0 0.5 220 88 60.0% 4.5 

SNCR Bayfront 1 & 2 Coal Fuel 55,000.00 2000 ~ 0 0.5 420 137 67.5% 4.5 

SNCR Honam Power Plant 1 (test a), Korea Coal Fired Utility Boiler, 250 MW 575,000 2100 ~ 0 2 462 270.7 41.4% 6% 

SNCR Honam Power Plant 1 (test b), Korea Coal Fired Utility Boiler, 250 MW 575,000 2100 ~ 0 2 384 230.0 40.1% 6% SNCR Honam Power Plant 2 (test a), Korea Coal Fired Utility Boiler, 250 MW 575,000 2100 ~ 0 2 416 243.8 41.4% 6% SNCR Honam Power Plant 2 (test b), Korea Coal Fired Utility Boiler, 250 MW 575,000 2100 ~ 0 2 333 208.5 37.4% 6% 

Average Removal Efficiency = 33.6%

LoTOx Stainless Steel Pickling 4,000 3000 100 96.7%

LoTOx 25 MW Coal Fired Boiler 90,000 200 20 90.0%

LoTOx Lead Smelting 26,000 150 10 93.3%LoTOx 1000 HP Natural Gas Fired Boiler 10,000 40 4 90.0%

LoTOx FCC 145,000 70 20 71.4%

LoTOx FCC 185,000 120 20 83.3%

LoTOx FCC 260,000 120 20 83.3%

LoTOx FCC 40,000 70 20 71.4%

LoTOx Sulfur Acid Regeneration 50,000 90 10 88.9%

LoTOx FCC 200,000 120 20 83.3%

LoTOx FCC 300,000 85 20 76.5%

LoTOx FCC 250,000 80 20 75.0%

LoTOx FCC 85,000 250 20 92.0%

Average Removal Efficiency = 80.6%

SCR Selective Catalytic Reduction

SNCR Selective Non-Catalytic Reduction

LoTOx LoTOx Technology
United 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 Comparison 
US Steel Minntac Iron Ore Pelletizing Plant - NOx Reduction

Hatch Project No.332002January 15, 2009Appendix D - NOx Reduction Vendor Comparison

NALCO BRANCH 

MOBOTEC BACT ESA ENVIRONMENTAL MITSUBISHI 

1. PROPOSED TECHNOLOGY a. Low NOx Burner Yes  b. Combustion Air Modifications Yes c. SNCR Yes Yes Yes d. SCR Yes Yes e. LoTOx 2. PROCESS ANALYSIS a. Gas Volume (scfm) 265,000 265,000 265,000 265,000 265,000  b. Gas Temperature (deg F) 2000 2000 2000 800 800  c. Dust Loading (gr/dscf) 8 8 8 6 6  c. Pressure Drop, ∆P ("wg) 1 1 1 10 10  d. NOx Reduction  - % of Inlet Load 60% 60% 60% 70% 70%  - Line 5 Reduction (tons NOx/yr) 1500 1500 1500 1750 1750 3. EQUIPMENT SYSTEMS a. Kiln Combustion Process - Low NOx Burner Upgrades Burner Staging Burner Tip - Combustion Air Upgrades ROFA System b. SNCR System - Urea Supply System Required Required Required - Spray Nozzles Required Required Required - Controls Required Required Required - Compressed Air System Required Required Required c. SCR System - Urea Supply System Required Required - Spray Nozzles Required Required - Controls Required Required - Compressed Air System Required Required - Reactor w/ Catalyst Required Required - Precipitator Dust Collector Required Required - Exhaust Fan/Motor Required Required d. LoTOx - External Reactor System R - Ozone Generator System R - Oxygen Supply System R - Cooling Water System R - Scrubber System R - Wastewater Treatment System R - Exhaust Fan/Motor R4. UTILITY REQUIREMENTS a. Compressed Air (scfm @ 80 psig) 2700 1800 2700 2700 2700 b. Urea Consumption (gal/hr) 260 400 200 320 320 c. Heat Energy Input (Btu/hr) 270,000,000 d. Electrical Energy (kW) 600 500 600  e. Cooling Water (gpm) 5. Pilot Plant/CFD Modeling a. CFD Modeling Yes Yes Yes b. Field Testing and Data Collection Yes Yes Yes c. Pilot Plant Demonstration Yes Yes Yes 
Gateway View Plaza, 1600 West Carson Street, Suite 1 

Pittsburgh, PA, USA 15219 1031 

Tel (412) 497 2000  Fax (412) 497 2212