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Copyright © 2001, Praxair Technology, Inc. All rights reserved.

O2 EnhancedCombustion forNOx Control

2002 Conference on SCRand SNCR for NOx Control

Pittsburgh PA,

May 15-16, 2002

2

Acknowledgements

The authors wish to thank DoE NETL forproviding funding for this program.

Participants in this program include:

L. Bool, H. Kobayashi, KT Wu, D. Thompson - Praxair

E. Eddings, R. Okerlund - University of Utah

J.O.L Wendt - University of Arizona

M. Cremer, D. Wang - Reaction Engineering International

N. Nsakala, C. Maney, G. Richards, R. MacWhinnie - Alstom Power

S. Plasynski, DoE NETL

3

Discussion Points

� Where has oxygen been used before?

� What role can oxygen play in utilityboilers?

� What is the effect of oxygen enhancedcombustion on NOx?

� What is the cost impact of using oxygen?

4

Conventional O2 Use

� High temperature oxy-fuel flames� welding, flame polishing, cutting, etc.

� Oxygen addition for production rateincrease

� by O2 lancing� by O2 enrichment� by auxiliary oxy-fuel burners

� Full furnace conversion to oxy-fuel firing� fuel savings, NOx reduction, capital reduction� CO2 capture and sequestration

5

Typical Advantages ofOxygen� Increased efficiency (lower sensible heat

loss)� less fuel required

� Throughput increase

� Lower capital requirements

� Potential for pollution reduction

6

Where is O2 Used Now?

Industry Furnace/Kiln Applications

Steel Reheat, Soaking Pits, Ladles, Forging, EAFGlass MeltingCopper Smelting, AnodeAluminum Remelting, Coke CalciningPulp&Paper Lime kiln, Black LiquorCement Cement kilnPetroleum Fluid Cat. Cracker Regen., Claus SulfurChemical Incinerator, Sulfuric AcidClay Brick Kiln

Primarily High Outlet Temperature Processes

7

Known Benefits of O2 inBoilers� Conventional benefits

� increased efficiency

� Boiler operation benefits� capacity recovery after fuel switching� overcome fan limitations

8

Barriers to O2 Use inBoilers� Cost

� Site safety concerns

� Siting requirements for on-site oxygenplants or large storage tanks

9

Oxygen for NOxReduction� Oxygen use can reduce NOx formation in

the primary combustion zone� promote flame attachment� enhance effectiveness of staged combustion

� Oxygen can enhance NOx destructiontechnologies in secondary combustionzone

� enhance coal-based reburning� enhance natural gas reburning and SNCR

� Oxygen reduces LOI/Unburned Carbon

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Oxygen with StagedCombustion

� O2 anchors coal flame

� O2makes gas phase morefuel rich

� O2 increases temperaturewhich enhances pyrolysisand accelerates NOxreduction kinetics

� O2 allows more fuel richoperation

O2enriched

firststage

OFA

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Approach

� Use an expert team to address criticalissues

� Praxair (oxy fuel combustion)� U of A (NOx formation)� U of U (combustion , burner development)� REI (CFD modeling)� ALSTOM (burner development)� Utility advisory panel (commercial application)

� Move from small-scale studies to pilot-scale testing, and finally large-scale burnertesting

12

Program Timeline

Lab-

scal

e

CFD

Pilo

t-sca

le

Burn

er T

est

Dem

onst

ratio

n

Lab-

scal

eC

FD

1/00 1/01 1/02 1/03

Pilo

t-sca

le

CFD

Pilo

t-sca

le

13

UA Experiments

� 17kW “premixed” pulverizedcoal downflow combustor

� Staged combustion

� Parametric study� response surface

methodology� O2 enrichment in first stage� SR in first stage� first stage residence time� O2 enrichment at staging

point

� Measurements� water cooled, water quenched

probe for gases� gas species NO, CO, CO2, O2

� ash for carbon burnoutAsh Trap

Exhaust

MistEliminator

Water CaptureSystem

PrimaryCondenser

NaturalGas Combustion Air

LowerSamples

0.0 / 1540

Timesec

//

TempK

UpperSamples

CoalTransportAir

0.5 / 1450

2.2 / 1140

Baghouse

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UA Experiments

0.00

0.10

0.20

0.30

0.40

0.50

0.60

First stage Stoichiometric ratio

NOx

(lb/M

MBt

u)

Oxygen addedAir alone

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Kinetic Model

� Proprietary model used to evaluateconcept

� Model of UA furnace agreed well withdata

� Model indicates O2 addition reducesNOx

� Parametric mixing studies suggestedNOx emissions below 0.10 lb/MMBtu

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REI Model

� Existing boiler model used to evaluateeffectiveness of oxygen

� NOx control� LOI

� Method of oxygen addition based onexperimental data

� Different burner type, including differentcoal spreader, that explored experimentally

� evaluate sensitivity to burner type

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CFD Modeling Resultsfor O2

2000

500K

Gas temperature (Side view, Centerline of the burners on the RHS)

Burner B

Burner C

Burner A

Burner D

OFA

AirNOx reduction: ---%LOI Reduction: ---%

A% replacementNOx reduction: 17%LOI Reduction: 12%

2A% replacementNOx reduction: 24%LOI Reduction: 24%

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L1500 - Furnace

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Results From L1500Testing

0.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35

0.40

0.45

Burner SR

NO

x at

out

let (

lb/M

MB

tu)

AirA% replacement2A% replacement3A% replacement

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ISBF Test Overview

� Well characterized boiler simulator at Alstom Powerhas been used to demonstrate oxygen enhancedcombustion using a full scale commercial burner.

� Various proprietary oxygen injection techniques wereevaluated

� Various parameters were measured: NOx, FOT,

CO, UBC

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Industrial Scale BurnerFacility

ISBF

SOFA 1 SOFA 2

HeatExchanger

33'-2"

TC

TC

TCTC

Water Jacket

FlameBurner

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Results From ISBFTesting

0.10

0.11

0.12

0.13

0.14

0.15

0.16

0.17

0.18

0.19

0.0% 2.0% 4.0% 6.0% 8.0% 10.0% 12.0% 14.0% 16.0%O2 replacement (%)

NO

x (lb

/MM

Btu

)

Phase I condition APhase I condition BPhase II

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Summary of Results

0%

5%

10%

15%

20%

25%

30%

35%

A% 2A% 3A%

Percent replacement of stoichiometric air

Redu

ctio

n fr

om a

ir c

ase

REIU. ArizonaU. UtahAlstom

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O2 Supply for UtilityOperation� Oxygen supply from

either onsite plant orproduct pipeline

� Oxygen plant can beeconomically scaledto accommodateunits from < 100 MWto 1,000 MW

� Well proven, reliabletechnology

Two bed Praxair VPSA plant

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But can we afford it?

� Minor burnermodificationrequired

� Other benefits� reduced LOI� increased

efficiency� reduced fan limits� technology

additive

Typical Economics*

*based on 5 month operation

0

500

1000

1500

2000

2500

3000

3500

4000

NOxCredits

SCR SNCR O2

$/to

n NO

x re

mov

ed

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Conclusions

� Testing and modeling indicate oxygenaddition can significantly reduce NOxemissions

� Even when initial NOx concentrations arelow O2 addition reduces NOx even further

� Oxygen is an economically attractivealternative to purchasing NOx credits orconventional technologies (SCR and SNCR)

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"This presentation was prepared with the support of the U.S. Department of Energy, under Award No. DE-FC26-00NT40756. However, any opinions, findings, conclusions, or recommendations expressed herein are those of the author(s) and do not necessarily reflect the views of the DOE".