# fives north american Reducing NOx 

# from Pelletizing Furnaces 2012 SME- Minnesota Section Conference Apri/17 , 18 2012

F i ves 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 10000 tons/year compared to conventional technology

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### 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 3Oravo-Lurgi

PROCESS GAS FLOW

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# 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.

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# Reducing NOx 

# in Pelletizing Furnaces: A Difficult Problem
NOx Drivers : High temperature and h i gh 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 Tempe r ature (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[N 2 ]112

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# 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**~** 1 300 C Air Temperatur e 

### 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 ,%
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## Reducing NOx 

## in Pelletizing Furnaces: A Difficult Problem Combustion Factors that contribute to NOx Formation: • High Peak Flame Temperatures o 

### High Process Tem 1 peratures o 

### Large Tem 1 perature Flam 1 e Tem 1 perature Gradients o 

### High Air Preheat Temperatures • High Oxygen Concentration in Products Of Combustion • Long Residence Time at Hi g h Temperature All of These Factors Exist in Pelletizing Furnaces!

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## Reducing NOx in Pelletizing Furnaces: A Difficult Problem
• Method ls typically usedl to control**combustio n**  

### NOx emissions 

## at the source include:

- Reduce local temperature -Reduce local oxygen level

- Minimize residence time

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## 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 pre h eated 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 metho** **ds f~r**  

## NOx removal are expensive and l d1ff· 1cult to apply or Ineffective for 

## pelletizing Furnaces: Selective Catalytic Red luction (SCR) Selective NonCatalytic. Red luction (SCNR)

Fives North American 

## Lack ideal temperature window to apply; c. atalyst 

## -7 high**operatin~g** 

## costs Lack ideal tem 1 perature 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**Comb ustion** **Te chnology**  

# -Existing Technologies Applied in New Ways -Lower Capital and Operating Costs than After-treatment

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## NOx 

# Emissions from Standard Pelletizing Burners
NOX vs. Proces s Temperature for Pelletizing Burners

:I .... co 4**~ ~** **~** 

### "' c

.Q 3 "' "' . E

.... X 0 z 2

• N OX for Sta n d a r d Pell e t i z in Burner F iring N at ura l 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 s t art- u p .

- Evaluation of after-treatment (LoTOx) for technical a n d 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 prod u ced 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 an d other technical information to substantiate the estimated NOx emission rates associated with providing p rocess gas at approximately 2400 F to fee d into the iron ore bed • Bench-Scale Laboratory NOx testing • Estimated fuel usage and oxidant flows • P reliminary 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 Ox i dant , 18-19°/o in exhaust

- High (lean) volume and mass ratio of oxidant to fuel • Rough simu l ation of basic geometry compatible with bench scale :

- 90 ° turn at burner location (flow non-un i formity)

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

- Large scale factor ( -60:1 f l ow , 8 : 1 geometry)**Results** qualitative in nature • Compare base case burner and LE Low NOx burner configurations • Geometry simple enough for meaningful compar i son with CFD

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# Low 

# NOx Pelletizing Study Included Bench-Scale Lab Tests and CFD Analysis

PeOeiiZmg

B umer S1mulator 0Xyg<!f1 l flOC!Or**14 '"**  0 0 0 0 0 0 17400 SC F H 21%02 1850F**~** 76 SCFH Nat Gas Pl-emtied O•v- Enndlad Ai r and

Natural Gas

Natu ral Gas 825SCFH Air 139\7 SCFH O<ygen 1813 SCFH 

# I 48" Long x 8 625• 10 Modules

Test Ports 

## ,

0 '"""' ,...... '1'0t·OI ,...... ="6·""'**0!~06** 2 101 · 0' ,...... '""'""' '"'""' ,.,.

## ..**1~-0i** '""""'**1~ 0l**  ooc..as '""'""' 

# . ..,.... ....

# --

# ....... . ·""""" · 311C&C6 ,......,. O<Ot•CCI DBc01 200SI 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.
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# 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 ma j or 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 stra ight-grate pelletizing furnace down comer and burner at a much larger scale :

- 1 

### /4-scale energy and flow

- V 2-sca l e diameter

- Approximately full-scale time (length)

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# 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

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## 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 '

221 /4 

## Scale Pelletizing Burner Test Chamber and Hot Air Generator

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## Test Chamber for 1 

## /4-Scale Pelletizing Burner Test Rig

Fives North American 24Fives North American 25

## Test Chamber for 1 

## /4-Scale Pelletizing Burner Test Rig

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### Hot Air**Generato r:**  

### • 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: • 1

### 14-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 Se n sitivity of NOx 

## emissions to operating parameters: 1. Variation in P rocess Air Temperat ure 

### 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 Ame r ican 28I 

## 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

29Radial Gas I nlet_....,... 

# r Secondary Radial Air Inlet

Gas Inlet / Primary Gas Inl et Main Combustion Air In let

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: O o /o O o/

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

J: 

## ... u II') 'i 0 t:i:
... 

### < > ... Q 

### ... Ql c ... :s 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 = 

### ... co**~ ~**  

# - :e )(' 0 z

3 3

## Center Fuel Injection Tests: Stoichiometric Ratio, 3 Hour Test

:z: I.L. u 1,1)**~** 0**~ ~** **~** > ... 0 

### ... QJ 1: 

### ... ::J co 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 ....... :2 ><"' 0 z 0.3 0.2 0 . 1 0 34

## Center Fuel Injection Tests: Stoichiometric Ratio, Three Hour Test

l: u.. u V')**~**



### .. 0**~** 

### ... 

### < > 

### ... 0 

### ... cu c 

### ... j**~** 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 0
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** **achie vable**  0 

## /o reduction in NOx was well-predicted. • NOx Emissions were**re duced** **fro m** **~** 

### 1 .0 to**~o .2**  

### lb/Mmbtu from**be ginning**  

### to**nd** 

### of**te sting**  

### at 1

## !4 scale. • NOx Emissions consistent with established objectives were**de monstrated**  

### on the 

## V4 scale rig. • Rem 1 aining Test Objectives:**So~lidify** 

### and**demo~nstrate** 

### results achieved and engineer a deliverable burner and combustion system package. Fives North Ame r ican 37

### • Worst case NOx emissions h ave been demonstrated at 

## 0.22 lb/MMBtu(HHV) for the h ig h e, 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 straig h t 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 with 1 out 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 Burner s 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
02200 Annual Burner NO x Emissions for a 6.5 MTPY Pellet i zin g Furnace Firing Natural Gas

- NOX Em is s ion s, Standard Burners

- NOX Em i ssi d n s Standard Burners with Low NOX Insert NOX Em i ssi d ns LE Ultra Low NOX Bu r n ers

2250 2300 2350 2400 Pro c ess 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 mag1 n itude through**appro priate**  

## burner tech nology. NOx re! ductions were prove n using a unique laboratory test rig, capable of simulating**pe lletizing**  

## furnace**co nditions**  

## at useful scales. NOx reductions o ! f 

## 95°/o have· bee n proven i n testing 

## 1f2 at 

## 1 14 sc. ale 

## (1f2 · Qe· ometric. scale)**o~m pared**  

## to· commercial straight-grate pelletizing furnace ·**do wn**  

## comers.

Fives North American 42

# fives north american Providing World Class Solutions Combustion T

echnology, Experience , Products , Services 

## To talk more about Low NOx Combustion Solutions , Visit FivesNA at Booth 

## # 2
Fives NA Driving Progress in Combustion