Pilot-Scale Evaluation ofPilot Scale Evaluation of Oxycoal Firing in Circulating-

Fluidized Bed and PulverizedFluidized-Bed and Pulverized-Coal-Fired Test Facilities

Eric G. Eddings, Ryan OkerlundEric G. Eddings, Ryan OkerlundUniversity of Utah

Lawrence E BoolLawrence E. BoolPraxair, Inc.

OverviewOverview

• Summary of Current Oxycoal ResearchSummary of Current Oxycoal Research Activities at University of Utah

• Conversion of Pilot-Scale CombustionConversion of Pilot Scale Combustion Facilities for Oxyfiring

• Experimental ResultsExperimental Results– Circulating Fluidized Bed Operation– Pulverized Coal Fired Operationu e ed Coa ed Ope at o

• Observations/comparisons between CFB- and PC-fired systemsy

Oxy-Coal Combustion Test F ili i U i i f U hFacilities at University of Utah

Larger Scale• Pilot-scale (1.5 MW) Pulverized-coal (PC) fired

test facility• Retrofit of existing facility - funded by Praxair, Inc.

• Pilot-scale (0.30 MW) Circulating Fluidized Bed (CFB) test facility(CFB) test facility

• Retrofit of existing facility - funded by Praxair, Inc.• Bench-scale (100 KW) Oxy-Fuel Combustor

(OFC) for flame characterization• New construction – funded by U.S. DOE, university funds

S ll S l Smaller Scale• Lab-scale Oxygen Transport Membrane (OTM)

Based Combustor• New construction – funded by Praxair, Inc., U.S. DOE

• Single Particle Fluidized Bed Reactor• Single-Particle Fluidized Bed Reactor• New construction – funded by U.S. DOE

• Laminar-Flow Drop-Tube Reactor• Existing facility

• Lab-Scale Pulverized Coal Burner• New construction – funded by U.S. DOE

Summary of Larger-Scale Oxy-Coal Research ProgramsResearch Programs

• Oxycoal Combustion in Circulating Fluidized Beds

– Funding by U S DOE Utah Clean Coal ProgramFunding by U.S. DOE, Utah Clean Coal Program• Advanced Oxyfiring of Coal in Entrained-Flow

and Fluidized Bed Combustors– Funding by Praxair, Inc.

Ch t i ti f O C b ti I t i• Characterization of Oxy-Combustion Impacts in Existing Coal-fired Boilers

– Funding by U.S. DOE, team: Reaction Engineering International; University of Utah; Praxair, Inc.; Siemens; VattenfallSiemens; Vattenfall

• Near-Field Aerodynamics of Oxy-Coal Flames with Directed Oxygen and Minimum Flue Gas Recycle

Funding by U S DOE Utah Clean Coal Program– Funding by U.S. DOE, Utah Clean Coal Program• Ash Partitioning Mechanisms for Oxy-Coal

Combustion with Varied Amounts of Flue Gas Recycle

F nding b U S DOE Utah Clean Coal Program– Funding by U.S. DOE, Utah Clean Coal Program• Diagnostics for Oxy-Coal Combustion (U.S. DOE)

– Funding by U.S. DOE, Utah Clean Coal Program

Summary of Larger-Scale Oxy-Coal Research Programs Today’s DiscussionResearch Programs

• Oxycoal Combustion in Circulating Fluidized Beds

– Funding by U S DOE Utah Clean Coal Program

y

Funding by U.S. DOE, Utah Clean Coal Program• Advanced Oxyfiring of Coal in Entrained-Flow

and Fluidized Bed Combustors– Funding by Praxair, Inc.

Ch t i ti f O C b ti I t i• Characterization of Oxy-Combustion Impacts in Existing Coal-fired Boilers

– Funding by U.S. DOE, team: Reaction Engineering International; University of Utah; Praxair, Inc.; Siemens; VattenfallSiemens; Vattenfall

• Near-Field Aerodynamics of Oxy-Coal Flames with Directed Oxygen and Minimum Flue Gas Recycle

Funding by U S DOE Utah Clean Coal Program– Funding by U.S. DOE, Utah Clean Coal Program• Ash Partitioning Mechanisms for Oxy-Coal

Combustion with Varied Amounts of Flue Gas Recycle

F nding b U S DOE Utah Clean Coal Program– Funding by U.S. DOE, Utah Clean Coal Program• Diagnostics for Oxy-Coal Combustion (U.S. DOE)

– Funding by U.S. DOE, Utah Clean Coal Program

Summary of Smaller-Scale Oxy-Coal Research ProgramsResearch Programs

• Single Particle Oxy-CO2 Studies –Fluidized Bed

– Funding by U.S. DOE, Utah Clean CoalFunding by U.S. DOE, Utah Clean Coal Program

• Single Particle Oxy-CO2 Studies ––Pulverized Coal

Funding by U S DOE Utah Clean Coal– Funding by U.S. DOE, Utah Clean Coal Program

• Ash Partitioning Mechanisms during Oxy-Coal Combustion

– Funding by U.S. DOE, Utah Clean Coal Program

• Development of Coal Combustor for Oxygen Transport Membrane (OTM) T h lTechnology

– Funding by Praxair, Inc.; U.S. DOE• Advanced Diagnostics for Oxy-Coal

Combustion (U S DOE)Combustion (U.S. DOE)– Funding by U.S. DOE, Utah Clean Coal

Program

Summary of Oxy-Coal CFD Research ProgramsResearch Programs

Current Areas of Oxycoal Si l ti R&D*Simulation R&D*:– Oxy-Coal Combustion Large Eddy

Simulations (LES)S b id S l P i l L d– Subgrid-Scale Particle-Laden Mixing and Reaction Modeling

– Particle-Laden Radiation ModelingGas Phase Reactions– Gas-Phase Reactions

– Single Particle Model w/Reaction– Non-Reacting LES Models &

AlgorithmsAlgorithms– LES-DQMOM Simulation of a Pilot-

Scale Fluidized BedOxycoal

flame image LES

Simulation of

* Funding provided by U.S. DOE, Utah Clean Coal Program

gfrom UofU

100 KW Combustor

UofU 100 KW

CombustorQuickTime Movie

Retrofit of Pilot-Scale FacilitiesRetrofit of Pilot Scale Facilities for Oxy-Coal Firing

Circulating Fluidized Bed Test F ili M difi i *Facility Modifications*

• 0 30 MW• 0.30 MW• 6.4 m height, 0.25 m ID • Flue gas recirculation

– Same blower for air and RFGRFG

– Flue gas recirculated after baghouse

– Reheat up to 425 C (800 F)• Oxygen lines• Oxygen lines

– Multiple oxidant streams– Flow control and flow

measurement• Heat removal• Heat removal

– In-bed lances– Jacketed solids return line– Flue gas before baghouse

* Funding for modifications provided by Praxair, Inc.

L1500 Pulverized Coal Test F ili M difi i *Facility Modifications*

• 1.5 MW, refractory-lined12 l 1 1 i t l

• Flue gas recirculationS bl f i d RFG• 12 m long, 1 m x 1m internal cross-

section• Dual-register, swirl burner• Oxygen lines

– Multiple oxidant streams

– Same blower for air and RFG– Flue gas recirculated after baghouse– Reheat up to 425 C (800 F) prior to

oxygen addition• Heat removal

– Multiple oxidant streams– Flow control and flow measurement – In-furnace cooling panels

– Flue gas before baghouse

* Funding for modifications provided by Praxair, Inc.

Industrial Gas Supply*Industrial Gas Supply Oxygen

• 6000 gallon (22,700 liter) liquid O2supply with vaporizers

• Delivery gaseous O2 up to 150 SCFM (4250 SLPM) for oxycoal studies(4250 SLPM) for oxycoal studies

• Additional Trifecta unit for delivery of pressurized oxygen up to 350 psi for pilot-scale gasifiers

Carbon Dioxide• 400 gallon (1500 liter) liquid CO2

supply with vaporizerU f th h l t di• Use for once-through oxycoal studies at 100 KW (when no FGR)

• For pulsing in pulsed jet baghouses• For loop seal motive fluid in CFBp

* O2 and CO2 provided by Praxair, Inc.

Results – Oxy-Coal CFBResults Oxy Coal CFB Testing at 0.30 MWth

Typical Temperature ProfileTypical Temperature Profile

Baseline Air FiringUtah Bituminous Coal

1700

1800

1900

1400

1500

1600

1700

pera

ture

(F)

1100

1200

1300

1400

Tem

p

1000Section 1 Section 2 Section 3 Section 4 Section 5 Transition Cyclone

OutletLoop Seal

Retrofit Strategies - CFBRetrofit Strategies CFB• Constant O2 concentration in flue2

– Global stoichiometric ratio is lower than air-fired case– Oxidant flowrates decreased with increasing O2

concentration in oxidant– reduces bed velocity– Fluidization/solids recirculation rates impacted?

• Bed velocity constant– Global stoichiometric ratio increases with O2 concentration inGlobal stoichiometric ratio increases with O2 concentration in

the oxidant– Concentration in the flue increased O2 with increasing O2

concentration in the oxidant– ‘wastes oxygen’

• Alstom and Foster Wheeler have specific strategies for commercial retrofits/new buildso co e c a et o ts/ e bu ds– Our study is based on fundamentals

CFB Temperature Profile with Oxy-Coal Firing

CFB Firing Rate 0.22 MW, Utah Bituminous Coal

1700

1800

)

1500

1600

mpe

ratu

re (F

)

1300

1400

rage

bed

tem

1100

1200

Ave

r

09 data - air

09 data constant O2

100015% 20% 25% 30% 35%

Overall O2 concentration in Oxidant (wet)

NOx EmissionsNOx EmissionsCFB Firing Rate 0.22 MW, Utah Bituminous Coal

0.40

0.45

0.50tu

)Air baseline

Constant O2 - measured

Constant velocity - measured

0 25

0.30

0.35

ns (l

b/M

MB

t

0.15

0.20

0.25

NO

x Em

issi

o

0.00

0.05

0.10N

15% 20% 25%O2 in oxidant (wet basis)

SO2 EmissionsSO2 Emissions0.90

CFB Firing Rate 0.22 MW, Utah Bituminous Coal

0.70

0.80

Btu

)Air baseline

Constant O2 - measured

Constant velocity - measured

0 40

0.50

0.60

sion

s (lb

/MM

0.20

0.30

0.40

SO2 E

mis

s

0.00

0.10

15% 20% 25%O i id t ( t b i )O2 in oxidant (wet basis)

No limestone – bed consists of quartz bed material and coal ash

SO2 EmissionsSO2 Emissions100%

08 data air

CFB Firing Rate 0.22 MW, Utah Bituminous Coal

70%

80%

90%08 data constant mass

09 data - air

08 data - const O2

50%

60%

70%

Cap

ture 09 data constant O2

30%

40%SO2

0%

10%

20%

0%1300 1400 1500 1600 1700 1800 1900

Average Bed Temperature (F)

Effect of Bed Temperature on SO E i i *SO2 Emissions*

CFB Firing Rate 0.22 MW, Utah Bituminous Coal

4000

4500

5000

1900

1950

2000Increased bed oxygen level

3000

3500

n (p

pm, d

ry)

1800

1850

atur

e (F

)

SO2 (UV)

1500

2000

2500

Con

cent

ratio

n

1650

1700

1750

Tem

pera SO2 (IR)

Sect. 1 Temp

0

500

1000

1500

1550

1600

014:00 14:15 14:30 14:45 15:00 15:15

Time

1500

*Note: Two different SO2 analyzers used, with two different upper limits

Results – Oxy-Coal PC-FiredResults Oxy Coal PC Fired Testing at 1.5 MWth

NOx Emissions vs. Burner Swirl

1.00AirAir firing

PC Firing, 0.9 MW, Utah Bituminous Coal, 23% O2 Overall

0.70

0.80

0.90

u)

RFG in primary, FGR+O2 in burner

FGR+O2 all streams

gOxycoal Strategy AOxycoal Strategy B

0 40

0.50

0.60

x (lb

/MM

Btu

0.20

0.30

0.40

NO

x

0.00

0.10

0 20 40 60 80 100

Burner Swirl Setting (%)

• 75% swirl settings provided lowest NOx for all conditions considered.

Burner Swirl Setting (%)

NOx SO2 Emissions vs O2NOx, SO2 Emissions vs. O2PC Firing, 0.9 MW, Utah Bituminous Coal, Swirl Setting = 75%

0.80

0.90

1.00NOx - Air

NOx - oxy-coal

SOx - Air

SOx - oxy-coal

0.60

0.70

MM

Btu

)

0.30

0.40

0.50

NO

x (lb

/M

0.10

0.20

0.0020.0% 25.0% 30.0% 35.0%

Average O2 Concentration (vol%, dry)

Operational Observations – Oxy-C l CFB PC Fi iCoal CFB vs. PC Firing

• Common ConsiderationsCommon Considerations– Transition from air-firing to oxy-firing became routine

• Transition period ~ 10-15 minutes• No gross differences in operating (bed behavior/agglomeration)• No gross differences in operating (bed behavior/agglomeration)

between air firing and oxy-firing for same T• System perturbations required significant time to regain steady

state due to recirculation loop(s)

Operating under slightly positive pressure precluded air– Operating under slightly positive pressure precluded air infiltration in ‘normal’ leak points

• Air ingress likely due to leaks in the blower itself• N2 concentrations ~ 8 – 10%N2 concentrations 8 10%

– Reductions observed in NOx and SO2 emissions when switching to oxycoal conditions

• Both CFB- and PC-fired testing

Operational Observations – Oxy-C l CFB PC Fi iCoal CFB vs. PC Firing

• CFB-Specific IssuesC t l f th t i d f l tt ti d t th lti l– Control of the system required careful attention due to the multiple recirculation loops

– Trade-offs between changing oxygen level and bed velocity• When bed velocity is held constant bed temperatures lower than baseline -

did not increase rapidly with O concentration due to dilution by extra RFGdid not increase rapidly with O2 concentration due to dilution by extra RFG– Bed temperature control critical when varying oxygen levels, especially

for fixed exit O2 scenario• Agglomeration issues• Sulfur retention in bedSulfur retention in bed

• PC-Specific Issues– Good burner stability

• Helped maintain attached flame, and thus low NOx, over wide range of p gburner conditions

– Control of system challenging due to fuel “spikes” when refilling coal hopper

• Perturbation “recycled” for long time

Concluding CommentsConcluding Comments• Modifications were made to two University of Utah facilities to

allow study of oxy coal firing under pulverized coal andallow study of oxy-coal firing under pulverized-coal and circulating-fluidized-bed conditions– Several test campaigns completed with oxy-coal firing of the 0.30

MW CFBI iti l t t i l t d ith 1 3 MW PC fi d f ilit– Initial test campaigns completed with 1.3 MW PC-fired facility

– considerable PC-fired campaigns completed at 100 KW scale (separate presentations)

• Both PC and CFB facilities showed good operation on oxygen-g p ygenriched RFG– Temperature could be controlled– Low air in-leakage

• Mass based emissions for NOx SO much lower than air fired• Mass-based emissions for NOx, SO2 much lower than air-fired baseline

• Considerable additional work scheduled this year for both firing systems to evaluate strategies to optimize oxygen use

25

AcknowledgmentsAcknowledgmentsThe authors gratefully acknowledge the financial and technical support of Praxair Incsupport of Praxair, Inc.

The University of Utah oxycoal effort is partially supported by the U.S. Department of Energy under Award Numbers FC26-08NT0005015 and DE-NT000528808NT0005015 and DE-NT0005288.

DISCLAIMERThis report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government northe United States Government. Neither the United States Government nor any agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe pri atel o ned rights Reference herein to an specific commercialprivately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof. The views and opinions of authors expressed herein do not g y p pnecessarily state or reflect those of the United States Government or any agency thereof.