CFD Modeling For Entrained Flow Gasifiers - globalsyngas.org · burning a range of fuels including...
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CFD Modeling For Entrained Flow Gasifiers
DOE Vision 21 Program Cost Shared Agreement DE-FC26-00NT41047
Mike Bockelie, Martin Denison, Zumao Chen, Temi Linjewile, Connie Senior and Adel Sarofim
Reaction Engineering International
Neville Holt Electric Power Research Institute
Gasification Technologies Conference 2002October 27-30, 2002, San Francisco, CA USA
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Vision 21 - Computer Simulation• Enabling Technology• Benefit
– reduce time, cost and technical risk to develop new energyplex systems
• 100 MW plant ~ 100 – 150 M$• Challenges
– need for improved component models• robust, high fidelity physics based models (CFD)• not available for many components for Vision 21
spectrum of conditions
Vision 21
gasifiergasifier
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Gasifier Model• Model Development
– Computational Fluid Dynamic (CFD) + Process models• Allows modification of
– Process conditions, burner characteristics– Fuel type, slurry composition– gross geometry
• Generic Configurations: – downflow / upflow– 1 stage / 2 stage
• Define Parameters with DOE– Improved physical models
• reaction kinetics – high pressure and gasification
• slag, ash, soot, tar• air toxics (metals, PM2.5)
• Collaboration– N. Holt (EPRI)– T.Wall,…. (Black Coal CCSD) – K.Hein (IVD)
downflow
upflow
Vision 21
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Modeling Opportunity- Gasifier RAM
See Gasification Technologies 2001:� Stiegel, Clayton and Wimer� HoltSee Clearwater 2002� Dogan
• Carbon Conversion & Syngas Quality– Fuel Switching
• Coal, Petcoke, Wastes, Oil, Biomass, Dirt, Blends– Fuel Feed System
• Dry (N2, CO2); Wet (H2O); Pre-heat; Grind size• Oxidant: Air vs O2
– System Modifications / Scale Up• Injectors (location, quantity, orientation, spray)• Volume (L/D ratio)• System pressure
• Slag and Ash Management– Viscosity, composition, flux mat’l– Carbon content: slag vs flyash
• Refractory Wear– Heat extraction
• Transient Operation – start-up / shutdown / switching
Vision 21
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Qualifications! >130 boilers, process furnaces and
incinerators in several countries burning a range of fuels includingcoal, oil, gas, wood, straw, petcoke, tires, hazardous waste
! Complementary relationships withboiler owners, OEMs andservice/equipment providers to develop solutions in areas including:
• NOx Control• Corrosion and Deposition• Heat flux• SOx Control• CO, hydrocarbon emissions• Carbon-in-flyash• Opacity• Air toxics (fine particulate, mercury, soot)
! Independent evaluation
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CFD Model
• Geometry• Wall Properties• Fuel & Oxidant
– Properties– Composition
• Ultimate, proximate• Ash composition
– Temperature– Particle grind– Splits
• Multiple Injectors• Quench
• Carbon Conversion• Flow Patterns & Velocities• Gas & Surface Temperatures• Gas Species Concentrations
– Major : CO2, CH4, H2, H2O, N2, O2– Minor: H2S, COS, NH3, HCN,….– Reducing vs oxidizing
• Wall Heat Transfer– Incident, net flux– Backside cooling
• Particle / Droplet Trajectories and Reactions– Time temperature histories– Wall deposition– Flyash (Unburned carbon)– Slag
• Temperature, viscosity, thickness• composition
Inputs Outputs = Predicted Values
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CFD Model• Computer model represents
– Gasifier geometry – Operating conditions– Gasification processes
• Accuracy depends on– Input accuracy– Numerics– Representation of
physics & chemistry
Turbulence
ParticleReactions
Surface Properties
Gasification & CombustionChemistry Radiation &
Convection
Fuel Conversion
NOxChemistry
CO, Sulfur, Air ToxicsChemistry
See Pittsburgh Coal Conference 2002Paper for model details
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Flowing Slag Model• Model accounts for:
– Wall refractory properties– Back side cooling– Fire side flow field + heat transfer– Particle deposition on wall
• Local Deposition Rate• Fuel ash properties• Composition (ash, carbon)• Burning on wall
• Slag model computes– Tcv = critical viscosity
• ash composition– Slag surface temperature– Liquid & frozen slag layer thickness– Heat transfer through wall
Hot GasS
Liquid Slag
xy
u (x, y)
RefractoryLining
Metal Wall
Coolant
Qradiation
Hot ParticlesSolid Slag Layer
Qconvection
TAmbient
Tw
Ts
TiTw1
Tw2
Hot GasHot GasS
Liquid Slag
xy
u (x, y)
RefractoryLining
Metal Wall
Coolant
Qradiation
Hot ParticlesSolid Slag Layer
Qconvection
TAmbient
Tw
Ts
TiTw1
Tw2 Tw
Ts
TiTw1
Tw2
Based on work by [Benyon], [CCSD], [Senior], [Seggiani]
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Flowing Slag ModelCritical Viscosity: Predicted vs Measured
Where α = SiO2/Al2O3 and β = Fe2O3 + CaO + MgOSiO2 + Al2O3 + Fe2O3 + CaO + MgO = 100 [weight%]
22cv 860. + 8.67 - 5.74 + 5.519 - 4523 = [K] T ββαα Measured data from
Patterson et al, 2001
1000
1200
1400
1600
1800
2000
1300 1400 1500 1600 1700 1800Measured TCV (K)
Pred
icte
d TC
V (K
)
+15%
-15%
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Example – Slag Flow Model• Firing Conditions
– [Benyon, 2002], [Seggiani, 1998]– Pressure = 25 atm.– 2600 tpd dried bituminous coal
• 22% ash– Dry feed
• N2:Coal (lb) = 0.075– Oxidant
• 76% O2 , 11% H20, 10% N2, 3% Ar• O2:C (molar) = 0.46• Inlet Stoichiometry ~ 0.4
L
0.2 D
0.75 D
D
0.1 D
0.4 D
L/D = 1.75D = 3.7m Injector
Orientation
4.7--Deposition (%)
4622(4248)(4431)HHV (Btu/lb)-
-
--
1.83.2
76.51803
Seggiani
(91.5)
-
--
1.810.070.9
(1650)Benyon
~100Carbon Conversion(%)
80.5Cold-Gas Efficiency (%)
REIExit Conditions
3.2H2O (wt %)10.1N2 (wt %)
1.9H2 (wt %)6.0CO2 (wt %)
76.8CO (wt %)1790Gas Temp (K)
water jacketcooled
(…) = estimated value
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Slag Model SummarySlag SurfaceTemperature
Liquid Slag Thickness
Solid Slag Thickness
0
1
2
3
4
5
6
7
8
1400 1700 2000 2300 2600
Slag surface temperature, K
Gas
ifier
hei
ght,
m
0
1
2
3
4
5
6
7
8
0 0.005 0.01 0.015 0.02
Liquid slag thickness, m
0
1
2
3
4
5
6
7
8
0 0.02 0.04 0.06 0.08
Solid slag thickness, m
Seggiani
Benyon
REI
Gas temperature, K
CO
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Slag Thickness
• curve = camera path• ball on curve = camera location
• displayed = solid slag thickness
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Example: Two Stage – Up Flow• Firing System
– 4 fuel injectors / level– Fuel Injectors ~ pipes
D
• Vision 21 Firing Conditions – Pressure = 28 atm.– 3000 tpd Illinois #6
• H2O 11%, Ash 10%– Recycle 100 tpd char + ash– Slurry: 74% solids (wt.)– Slurry Distribution
• 39%, 39%, 22% (upper)– Oxidant
• 95% O2, 5% N2• O2:C (molar) = 0.43• Inlet Stoichiometry ~ 0.50
6 D
Upper injectors
LowerInjectors
Jet centerline
D
0.5 D
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Flow FieldGas Temperature, K Axial Velocity, m/s
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Gas Composition
H2 CO H2O CO2 O2
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Particles and Droplets
Volatiles Mass Fraction Char Mass Fraction Water Droplet Trajectories
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ComparisonExit FGR / Cool NETL
Exit Temperature, K 1611 1335 1311*Carbon Conversion, % 97.7 -
Exit LOI, % 0.4 -Deposit LOI, % 28.6 -Deposition, % 6.3 -
PFR Residence Time, s 1.24 -Particle Residence Time, s 0.63 -Water Droplet Res. Time, s 0.01
Mole Fraction: CO 43.2% 43.4% 43.5%H2 29.2% 29.6% 32.5%
H2O 16.7% 16.7% 13.6%CO2 8.3% 8.5% 8.6%H2S 0.8% - -
COS 0.0% - -N2 1.7% 1.7% 0.9%
Exit Mass Flow, klb/hr 483 - 489*HHV of Syngas, Btu/lb 4622 - -
HHV of Syngas, Btu/SCF 237 - 250*Cold-Gas Efficiency 78.0% - -
V21 “Design” Conditions– DOE-NETL flow sheet
analysis of “DESTEC-style” 2 stage gasifier in an IGCC plant
– Syngas:• At Gasifier exit (*):• Gas Composition after GCU:
Minor Species:
NH3, HCN, O, OH, CH, CH4, C2H2, H, N, HCl, H2S, COS < 1 %
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Single Stage – Down Flow• Vision 21 Firing Conditions
– Pressure = 32 atm.– 3000 tpd Illinois #6
• H2O 11%, Ash 10%– Slurry: 74% solids (wt.)– Oxidant
• 95% O2, 5% N2• O2:C (molar) = 0.46• Inlet Stoichiometry ~ 0.51
D = 2.2m
L = 2D
0.25 D
0.6 D
D
oxidant
slurry
slurryoxidant
oxidant
fuel injector model
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Gas, Particle and Droplet Flows
Particle Coal Fraction
Axial Gas Velocity, m/s
Particle Char Fraction Water mole fraction
Gas Temp., K
Particle Coal Fraction
Axial Gas Velocity, m/s
Particle Char Fraction Water mole fractionH2H2
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Compare• V21 “Design” Conditions
– DOE flow sheet analysis of “Texaco-style” 1 stage gasifier in an IGCC plant
– Syngas:• At Gasifier exit (*):• Gas Composition after GCU:
– T = 843 K (1060F)
Exit cool/clean NETLExit Temperature, K 1641 - 1650*
Carbon Conversion, % 98.3 - -Exit LOI, % 6 - -
Deposit LOI, % 33 - -Deposition, % 3 - -
PFR Residence Time, s 1.41 - -Particle Residence Time, s 0.20 - -Water Droplet Res. Time, s 0.01 - -
Mole Fraction: CO 43.3% 41.3% 41.8%H2 28.2% 30.8% 30.8%
H2O 17.3% 15.1% 15.3%CO2 8.6% 10.1% 10.2%H2S 0.8% - -
COS 0.0% - -N2 1.7% 1.7% 0.9%
Exit Mass Flow, klb/hr 525 - 524*HHV of Syngas, Btu/lb 4508 - -
HHV of Syngas, Btu/SCF 236 - 240*Cold-Gas Efficiency 78.8% - -
Minor Species:
NH3, HCN, O, OH, CH, CH4, C2H2, H, N, HCl, H2S, COS < 1 %
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Fuel Switch – PetcokeIll. #6 Petcoke
Exit Temperature, K 1641 1610Carbon Conversion, % 98.3 97.9
Exit LOI, % 6 11Deposit LOI, % 33 40Deposition, % 3 2
PFR Residence Time, s 1.41 1.69Particle Residence Time, s 0.20 0.17Water Droplet Res. Time, s 0.01 0.01
Mole Fraction: CO 43.3% 53.4%H2 28.2% 28.5%
H2O 17.3% 9.4%CO2 8.6% 5.8%H2S 0.8% 1.2%
COS 0.0% 0.1%N2 1.7% 1.5%
Exit Mass Flow, klb/hr 525 463HHV of Syngas, Btu/lb 4508 5026
HHV of Syngas, Btu/SCF 236 267mmBtu/hr 2367 2278
Cold-Gas Efficiency 78.8% 83.4
• New Firing Conditions– Match syngas BTU/hr from
Illinois #6 case– Flow rates:
Inputs Illinois#6 Petcoke %ChangeFuel (tpd) 3089 2569 -16.8%
Oxidant (tpd) 2535 1965 -22.5%O2:C Mole Ratio 0.459 0.365 -20.5%
H2O:C Mole Ratio 0.465 0.499 7.3%
Ill. #6 PetcokeProximate Analysis As-Rec'd (wt%) As-Rec'd (wt%)Moisture 11.12 7.00Ash 9.70 0.48Volatile Matter 34.99 12.40Fixed Carbon 44.19 80.12TOTAL 100.00 100.00HHV (Btu/lb) 11666.00 14282Ultimate Analysis As-Rec'd (wt%) As-Rec'd (wt%)Moisture 11.12 7.00Carbon 63.75 81.37Hydrogen 4.5 2.55Nitrogen 1.25 0.92Sulfur 0.29 4.81Ash 9.7 0.48Oxygen (by difference) 6.88 2.87TOTAL 100.00 100.00
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Gasifier Process Model• Fast running Process Model
for Gasifier– Design inputs for CFD model – indicator for proper slag flow
• Consists of two submodels– Zonal Equilibrium model– Particle burnout model
• Iterate between the submodels Coal
Unburned Carbon
Particle Burnout Model
Temperature
Residence Time: τ
T = 2600 – 2900°F
Oxidant
CoalUnburned Carbon
Transport Fluid
Qloss
Refractory
Zonal Equilibrium Model
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• CFD models for entrained flow gasifiers– Mechanistic based approach– Analysis tool to address broad range of operational and design
problems for gasifiers• Comparisons to available information
…getting better …• Next ?
– Improve• slag (mineral matter, heat extraction), soot, air toxics• gasification kinetics
– Applications• Operations: fuel switching (Petcoke, blends)• R+D questions: feed type, volume,…
– Impact of syngas on downstream equipment & process
Summary
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AcknowledgementsDOE NETL (COR=John Wimer, PM = Larry Ruth, DE-FC26-00FNT41047)
REIDave Swensen (Software Lead), Martin Denison (Modeling Lead)Zumao Chen, Temi Linjewile, Connie Senior, Adel Sarofim, REI Technical Staff- Develop component models, workbench, ….
CollaboratorsNeville Holt (EPRI)
Gasifier System Configurations & ValidationTerry Wall, Peter Benyon, David Harris, John Kent and others (CCSD, Australia)
Coal Gasification Data and Mineral Matter Sub-modelsKlaus Hein, Bene Risio (U. Stuttgart/IVD, RECOM)
transient gasifier simulations, gasification in the EU