fives north american 

Reducing NOx from Pelletizing 

Furnaces 

2012 SME- Minnesota Section Conference 

Apri/17, 18 2012 

Fives NA Driving Progress in Combustion 
• Pelletizing Process 

• NOx Primer 

• Pelletizing furnace conditions are ideal for generating NOx 

• FivesNA and Essar Steel Minnesota have collaborated to design the 

lowest NOx pelletizing furnace in the world 

• A unique configurable test-rig was built to simulate the combustion 

process in a pelletizing furnace at 1

/4-scale 

• The result is a reduction of 95°/o in combustion NOx emissions. 

• The new furnace will reduce NOx emissions to the environment by 

8000 to 1 0000 tons/year compared to conventional technology 

Fives North American 2 
Beneficiated iron ore~ fines are processed with binders such as limestone 

and bentonite into small round pellets, then indurated (hardened) in a 

furnace. 

The result is hardened pellets of 67°/o to 72°/o iron suitable for use in blast 

furnaces and other steel processes. 

The indurating process requires firing the pellets at high temperatures 

and high oxygen levels to harden the pelle ts. 

Pelletizing furnaces have developed to deliver the required conditions at 

high production rates in a highly energy efficient process. 

Fives North American 3 
Oravo-Lurgi 

PROCESS GAS FLOW 

Fives North American 4 
Diagram of Essar Steel Minnesota 

Pelletizing Furnace 

COREM POT GRATE 

TEST RESULTS 

T-987; P-58 

COREIII POTTESTRESULTS 

TOOON7:P-"' TEIIPEIIAlURfS 

Temperature 

"F 

Fives North American 

TfiiPEMlURf, '!' 

ESSAR • .. NNESOTA STEEL· 4.1 IITPY PELLET PLANT WITH FOUR INACTIVE WINDBOXES 

5 5 
High temperatures (2200- 2400 F) and high oxygen rates (12°/o-18°/o) 

are delivered to the pellets by using air to recover the heat stored in the 

pellets in a cooling section. 

Air from the hottest part of the cooling section is preheated to 1600-1800 

F before being heated to process temperatures by combustion of fuel in 

the heating section. 

Air from the final part of the cooling. section and exhaust from the heating 

sections are used to dry and preheat the pellets. 

The result is a very efficient process but one which creates ideal 

conditions for formation of NOx in the heating zone. 

Fives North American 6 
Reducing NOx in Pelletizing Furnaces: 

A Difficult Problem 

NOx Drivers: 

High temperature and high 

oxygen level in Products Of 

Combustion 

Combustio 

2400 F 

17°/o 02 (dry) 

Preheated Air 

1700 F 

21 o/o 02 

NOx Driver: 

Diffusion -type flame with large interface 

area between flame and high-oxygen 

Products Of Combustion 

Fives North American 

NOx Driver: 

Very high air preheat 

Temperature 

(Results in very high 

peak flame temperatures) 

Burner Cooling air 

80 F 

Natural Gas 

7 
Reducing NOx in Pelletizing Furnaces: 

A Brief NOx Primer 

Equilibrium Model o~f NOx Formation 

[N 0] = Kp(T) [ 02] 112 [N2] 112 

To minimize NOx 

we need to minimize KP (T) 

and the product of [02]112[N2]112 

Fives North American 8 
Reducing NOx in Pelletizing Furnaces: 

A Brief NOx Primer 

1: 24ooo -,-----.----..----r-------..--------. 

z 

............ E 2oooo -~---- ~--------~ 

... Vl 

850 C Air Temperature 

1100 C Air Temperature 

c 

0 

~ 1300 C Air Temperature 

E 12000 ~---+ ~--4-----+----~ UJ 

X 

0 

z 

E 

::J 

~ 

..c 

!oilers 4000 Pelletizing 

Furnaces 

::J 

0"' 

UJ ~~~~--~--~~--r+--~~~ ~ 

25 20 15 10 5 0 

Oxidant Oxygen,% 

Fives North American 9 
Reducing NOx in Pelletizing Furnaces: 

A Difficult Problem 

Combustion Factors that contribute to NOx Formation: 

• High Peak Flame Temperatures 

o High Process Tem1peratures 

o Large Tem1perature Flam1e Tem1perature Gradients 

o High Air Preheat Temperatures 

• High Oxygen Concentration in Products Of Combustion 

• Long Residence Time at High Temperature 

All of These Factors Exist in Pelletizing Furnaces! 

Fives North American 10 
Reducing NOx in Pelletizing Furnaces: 

A Difficult Problem 

• Methodls typically usedl to control combustio n NOx 

emissions at the source include: 

- Reduce local temperature 

-Reduce local oxygen level 

- Minimize residence time 

Fives North American 11 
Reducing NOx in Pelletizing Furnaces is 

difficult: Most traditional methods don't work. 

Traditional methods for Reducing NOx from Combustion: 

Flue Gas Recirculation 

Air Staging 

Simple Fuel Staging 

Precessing Jets 

Fives North American 

No source f Low 0 2 Flue Gas 

Ineffective because of high 0 2 in 

POC 

Ineffective because o~f high 0 ·

2 in 

POC and large excess of 

preheated air 

Don't work well with high excess 

12 
Reducing NOx in Pelletizing Furnaces: 

Post-Treatment usually isn't a good option. 

Post Tre.a~ment methods f~r NOx removal are expensive 

andl d1ff·1cult to apply or Ineffective for pelletizing 

Furnaces: 

Selective Catalytic 

Redluction (SCR) 

Selective NonCatalytic. Redluction 

(SCNR) 

Fives North American 

Lack ideal temperature window to 

apply; c.atalyst -7 high operatin~g 

costs 

Lack ideal tem1perature window to 

apply; Toxic. bypro~dlucts -7 high 

o·perating costs 

Unproven; 

xygen generatio n -7 high cost+ 

high electrical energy consumption 

13 
How Can NOx Emissions from Pelletizing 

Furnaces Be Reduced? 

FivesNA Low NOx Combustion 

-New Combustion Technology 

-Existing Technologies Applied in New Ways 

-Lower Capital and Operating Costs than 

After-treatment 

Fives North American 14 
NOx Emissions from 

Standard Pelletizing Burners 

NOX vs. Process Temperature for Pelletizing Burners 

:I 

.... 

co 4 

~ 

~ 

~ 

"' c 

.Q 3 "' 

."' E 

.... 

X 

0 

z 

2 

• NOX for Standard Pelletizin Burner Firing Natural Gas 

1 

l 

0 

2,200 

Fives North American 

2,250 

I 

2,300 2,350 2,400 

POC Temperature, F 

2,450 

15 
• October 2007- MPCA issued Air Emissions Permit No. 06100067-001 

to Minnesota Steel Industries (MSI). 

- Furnace NOx limit~ 629 lbs/hr for 35 months after initial start-up. 

- Evaluation of after-treatment (LoTOx) for technical and economic 

feasibility. 

- 35 months after initial start-up, if determined by the Commissioner to be 

technically and economically feasible through application of LoTOx, the 

total furnace NOx limit is 211 lbs/hr . 

- Essar Global, Ltd purchases MSI and renames Essar Steel Minnesota, 

LLC (ESML) 

• September, 2008-Aker Solutions (now Jacobs Engineering) and Fives North 

American Combustion (FivesNA) are engaged by ESML to study feasibility of 

a solution to reduce the NOx produced by natural gas combustion in a 

pelletizing furnace that can produce 7.0 MTPY of pellets. 

Fives North American 
• September 2008 -Fives North American jointly with the O.E.M. 

furnace builder were engaged by the plant owner to present a 

solution that reduces combustion NOx formation in a straightgrate indurating furnace. 

- Study Scope Included: 

• Listing of relevant experience, data and references for similar 

applications of the proposed technology 

• CFD Modeling and other technical information to substantiate 

the estimated NOx emission rates associated with providing 

process gas at approximately 2400 F to feed into the iron ore 

bed 

• Bench-Scale Laboratory NOx testing 

• Estimated fuel usage and oxidant flows 

• Preliminary arrangement drawings 

Fives North American 17 
• Simulate the environment present in a downcomer of a Pelletizing Furnace 

- High temperature oxidant: 1600-1900 F 

- High oxygen content: 21 °/o in Oxidant, 18-19°/o in exhaust 

- High (lean) volume and mass ratio of oxidant to fuel 

• Rough simulation of basic geometry compatible with bench scale: 

- 90° turn at burner location (flow non-uniformity) 

- Similar velocity (== 50 fps vs. == 80 fps) 

- Large scale factor ( -60:1 flow, 8 :1 geometry) Results qualitative in 

nature 

• Compare base case burner and LE Low NOx burner configurations 

• Geometry simple enough for meaningful comparison with CFD 

Fives North American 18 
Low NOx Pelletizing Study Included 

Bench-Scale Lab Tests and CFD Analysis 

PeOeiiZmg 

Bumer 

S1mulator 

0Xyg<!f1 

lflOC!Or 

14 '" 

0 

0 

0 

0 

0 

0 

17400 

SCFH 

21%02 

1850F 

~ 

76 SCFH 

Nat Gas 

Pl-emtied O•v- Enndlad Air and 

Natural Gas 

Natural Gas 

825SCFH 

Air 

139\7 SCFH 

O<ygen 

1813 SCFH 

I 

48" Long x 8 625• 10 

Modules 

Test Ports 

, 

0 

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AI<STS FLLENT 12 0 lld, ,...,., ~. '"") 

DK01 , 2009 

,~~trNSVS FL.lJENT 120(3d, iXJM,, -c- I'Dl 

Engineering Study Conclusion: 85-90°/o Reduction in NOx is Feasible. 

Fives North American 19 
The Essar Steel Minnesota Project Moves 

Forward 

• The results of the bench-scale testing were very promising: 88°/o 

reduction in NOX was achieved in the bench-scale tests. 

• It was clear to ESML, FivesNA, and the MPCA that an investment of 

-1 billion dollars and issuance of environmental permits to a potential 

major emissions source required more than bench-scale testing and 

CFD simulation. 

• Therefore, Essar and FivesNA proceeded with a joint $2Million 

investment in a test rig to simulate a straight-grate pelletizing furnace 

down comer and burner at a much larger scale: 

- 1/4-scale energy and flow 

- V2-scale diameter 

- Approximately full-scale time (length) 

Fives North American 20 
26 MMBtu/hr (LHV) LE Burner Installation 

in a Pelletizing Furnace Downcomer 

800,000 SCFH --t ----; ' Process Air at 1700 F ...... ~~ 

' 

825,000 SCFH 

Process Air at 2400 F 

Fives North American 21 
Pelletizing Burner Test Rig; 1

/4 Scale Input; 

V2 Scale Geometry 

Fives North American 

200,000 SCFH 

Process Air at 

1700 F 

206,000 SCFH 

Process Air at 2400 F 

I ' 

22 
1

/4 Scale Pelletizing Burner Test Chamber 

and Hot Air Generator 

Fives North American 23 
Test Chamber for 1

/4-Scale Pelletizing 

Burner Test Rig 

Fives North American 24 
Fives North American 25 
Test Chamber for 1

/4-Scale Pelletizing 

Burner Test Rig 

Fives North American 26 
Hot Air Generator: 

• Delivering required air quantity: 200,000 to 300,000 SCFH 

• Delivering required air quality: 20.85-20.94°/o Oxygen 

• Delivering required air temperature: > 1720 F 

Te,st-Chamber and LE Burner: 

• 114-scale model of burner and pelletizing furnace down comer 

• Flow restriction of pellet bed simulated with matrix of honeycomb 

ceramic modules 

• PLC-based burner air and fuel controls as specified for actual 

furnace. 

• Electronic data-acquisition system monitoring flows, temperatures, 

and emissions. 

• Test Chamber and Burner can be re-configured to simulate other 

types of furnace, burner, and process. 

Fives North American 27 
• 1st Stage: Optimize Burner Design Parameters 

1. Primary/Secondary Fuel Ratio 

2. Secondary Fuel Injector Configuration 

3. Secondary Fuel Pressure 

• 2nd Stage: Determine Sensitivity of NOx emissions to 

operating parameters: 

1. Variation in Process Air Temperature 

2. Variation in Burner Fuel/Air Ratio 

3. Variation in Premix/Injector Fuel Ratio 

4. Variation in Burner Air Temperature 

5. Variation in System Firing Rate compared to Process Air Flow Rate 

Fives North American 28 
I 

Center Fuel Injection Tests: Basis for Test 

Conditions 

Parameter Design Value 

Windbox Air Flow 28,93,2 SCFM _ ____J 

Downcomer Air Flow (2 Downcomers/Windbox) 

Downcomer Air Temperature 

Burner Input, LHV basis 

Burner Combustion Air Flow 

Burner Combustion Air Temperature 

Burner Radial Air Flow 

Calculated Temperature of POC to Pellet Bed 

Fives North American 

868,000 SCFH 

1720 F 

24.16 MMBtu/hr 

252,000 SCFH 

650 F 

10,500 SCFH 

2410 F 

29 
Radial 

Gas Inlet_....,... 

r 

Secondary 

Radial 

Air Inlet 

Gas Inlet / 

Primary 

Gas Inlet 

Main Combustion 

Air Inlet 

Anti-Flashback 

Mixers 

Fives North American 

Secondary 

Combustion 

(stoichiometric) 

Primary Reaction Zone 

( 

/ 

r30 
Center Fuel Injection Tests: 

Test Parameters 

Parameter 

Downcomer Air Flow, SCFH: 

Downcomer Air Temperature, F: 

Burner Input, LHV basis, MMBtu/hr: 

Burner Combustion Air Flow, SCFH: 

Burner Radial Air Flow, SCFH: 

Measured Average Temperature above 

Bed, F: 

Average Burner Excess Air 

(incl. Burner Radial Air), 0

/o: 

Fives North American 

Test 1 

213,885 

1,702 

6.09 

63,931 

1,212 

2,276 

2.04°/o 

Test 2 Test 3 

21 0,9'94 211 '163 

1,700 1,701 

6.09 6.10 

63,855 63,818 

2,295 2,274 

- .--- -

1.89°/o 1.72°/o 

31 
Center Fuel Injection Tests: 

Test Results 

Parameter Test 1 Test 2 Test 3 

Average NOx Emissions Factor, lb/MMBtu: 0.235 0.214 0.218 

Average 02 in POC: 16.94°/o 16.59°/o 16.91 °/o 

Average CO in POC (uncorrected), PPM: 0.00 0.00 0.00 

Average NOx in POC (uncorrected), PPM: 42.9 42.4 40.1 

NO Calibration Span Gas, PPM: 50.5 50.5 50.5 

I 

NOx analyzer zero offset, beginning of test, PPM: 0 0 0 

NOx analyzer zero offset, end of test, PPM: 0 0 0.1 

NOx analyzer total zero drift during test, 0/o of span: Oo/o Oo/o 0.20°/o 

NOx analyzer span, beginning of test (reading/offset), PPM: 54.9/4.4 53.6/3.1 50.3/-0.2 

NOx analyzer span, end of test (reading/offset), PPM: 53.7/3.2 53.9/3.4 49.6/-0.9 

NOx analyzer total span drift during test, 0/o of span: -2.38°/o -0.59°/o -1.39°/o 

Test Duration, minutes: 180 172 178 

Fives North American 32 
Center Fuel Injection Tests: Stoichiometric 

Ratio, 3 Hour Test 

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... 

Q 

... 

Ql 

c 

... 

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CQ 

80,000 

70,000 

60,000 

50,000 

40,000 

30,000 

20,000 

10,000 

0 

NOx vs. Time for Test 1 

Spe.cial LE Burner 

Stoichi,ometric Air /Fuel Ratio 

• Burner Dry Air Flow 

8 NOx 

11:02:24 AM 11:32:04 AM 12:01:44 PM 12:31:24 PM 1:01:03 PM 1:30:43 PM 2:00:23 PM 

Fives North American 

0.8 

0.7 

0.6 

0.5 

0.4 

0.3 

0.2 

0.1 

0 

... = 

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33 
Center Fuel Injection Tests: Stoichiometric 

Ratio, 3 Hour Test 

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QJ 

1: 

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80,000 

70,000 

60,000 

50,000 

40,000 

30,000 

20,000 

10,000 

0 

NOx vs. Time for Test 2 

Special LE Burner 

Stoichiometric Air /Fuel Ratio 

• Burner Dry Air Flow 

• NOx 

2:24:00 PM 2:53:40 PM 3:23:20 PM 3:53:00 PM 4:22:39 PM 4:52:19 PM 5:21:59 PM 5:51:39 PM 

Fives North American 

0.8 

0.7 

0.6 

~ 0.5 .. 

CD 

~ 

~ 

0.4 

....... 

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0.3 

0.2 

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34 
Center Fuel Injection Tests: Stoichiometric 

Ratio, Three Hour Test 

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cu 

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80,000 

70,000 

60,000 

50,000 

40,000 

30,000 

20,000 

10,000 

0 

9:30 

Fives North American 

10:00 

NOx vs. Time for Test 3 

SpeciaiLE Burner 

Stoichiometric Air /Fuel Ratio 

10:30 11:00 11:30 

• Burner Dry Air Flow 

• NOx 

12:00 12:30 

0.8 

0.7 

0.6 

:::s 

0.5 co 

-:E 

:E 

....... 

0.4 :e 

x 

0 

z 

0.3 

0 .2 

0.1 

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35 
• Upon completion of burner 

optimization and 

characterization, three tests, 

each of 3 hours duration, were 

performed, and the results 

presented to the MPCA. 

• In June, 2011, Essar, Jacobs 

Engineering, and the MPCA 

met at the FivesNA 

·facility to 

review the test-data, and to 

witness the test facility and 

burner in operation. 

Fives North American 36 
• Optimum LE Burner operating parameters and injector 

co nfiguratio n were not wedl-predicted by 1 :60 Scale bench 

rig testin g, althou gh achievable 0

/o reduction in NOx was 

well-predicted. 

• NOx Emissions were reduced fro m ~ 1 .0 to ~o .2 lb/Mmbtu 

from beginning to nd of te sting at 1

!4 scale. 

• NOx Emissions consistent with established objectives were 

de monstrated on the V4 scale rig. 

• Rem1aining Test Objectives: So~lidify and demo~nstrate 

results achieved and engineer a deliverable burner and 

combustion system package. 

Fives North American 37 
• Worst case NOx emissions have been demonstrated at 

0.22 lb/MMBtu(HHV) for the highe,st te:mperature, highest 

firing rate furnace down comer in the Essar furnace. 

• This represe·nts a 95°/o re·duction in NOx from 

conventional inspirating burne,rs, typically used in straight 

grate pe lletizing furnaces. 

• It is also 56°/o lowe:r than the· (2007) MSI controlled permit 

level for lb/h NOx, while achieving a 60°/o incre·ase· in 

pe,llet production. 

Fives North American 38 
FivesNA Has Low NOx Pelletizing 

Solutions for Every Situation 

Each application is unique with it's own challenges, for 

example: 

• Significant NOx reductions with lower-cost retrofit with1out 

furna.ce shutdowns 

• Major retrofits or new furnaces needing 50°/o NOx reductions 

without operating penalties 

• 90°/o to 95°/o NOx reductions with much lower capita.! and 

operating costs than after-treatment 

• Different furnace configurations 

• Straight-Grate 

• Grate-Kiln 

• Rota.ry 

Fives North American 39 
NOx Emissions Results from 1

/4-Scale 

Testing: Natural Gas 

7 

NOx vs. Process Temperature for Pelletizing Furnaces 

Firing Natural Gas 

NOX ErrlissionsJ Standard Burners 

5 

t 

5 

E 

"" ox 

z 3 

2 

1 

0 

2,225 2,250 

Fives North American 

2,275 2,300 2,325 2,350 2,375 2,400 2,425 

Process Temperature, F 

2,450 2,475 2,500 2,525 

40 
The Environmental Benefits of Low NOx 

Pelletizing Burners are Significant 

... 

"' 

~ ... 

cu 

c. 

VI 

c 

~ Ill .. 

c 

0 

'iii 

.la 

E 

w 

X 

0 

z 

14,000 

12,000 

10,000 

8,000 

6,000 

4,000 

2,000 

0 

2200 

Annual Burner NOx Emissions for a 6.5 MTPY Pelletizing Furnace 

Firing Natural Gas 

- NOX Emissions, Standard Burners 

- NOX Emissidns Standard Burners with Low NOX Insert 

NOX Emissidns LE Ultra Low NOX Burners 

2250 2300 2350 2400 

Process Temperature, F 

Fives North American 

2450 

41 
The pelletizing furnace e·nvironment typically favors very 

high NOx levels. 

NOx levels can be reduce·d by an order of mag1nitude 

through appro priate burner technology. 

NOx re!ductions were proven using a unique laboratory 

test rig, capable of simulating pelletizing furnace 

conditions at useful scales. 

NOx reductions o!f 95°/o have· been proven in testing 1f2 

at 114 sc.ale (1f2 ·Qe·ometric. scale) o~m pared to· 

commercial straight-grate pelletizing furnace· down 

comers. 

Fives North American 42 
fives north american 

Providing World Class Solutions 

Combustion 

Technology, Experience, Products, Services 

To talk more about Low NOx Combustion Solutions, 

Visit FivesNA at Booth # 2 

Fives NA Driving Progress in Combustion