Application of Solid Bed Application of Solid Bed Combustion Models Combustion Models Sangmin Choi Department of Mechanical Engineering Department of Mechanical Engineering KAIST Thermal Engineering Lab
Application of Solid Bed Application of Solid Bed Combustion ModelsCombustion Models
Sangmin ChoiDepartment of Mechanical EngineeringDepartment of Mechanical Engineering
KAIST
Thermal Engineering Lab
THERMAL ENGINEERING FOR INDUSTRIES
POWER WASTE INCINERATION IRON & STEEL
Design Development (Needs & Parameter)
Analysis(Needs & Parameter)
Identification
Integrated System Design
Modeling of Combustion System
Bed Combustion Modeling
F l Ch t i tiIntegrated System Design
Design & Off Design Point Operation
Fuel CharacterizationComputational Fluid Dynamics
Physical Model TestsPhysical Model Tests
Process Simulation
Modeling of Dioxin Emissions
Thermal Engineering Lab
g
Combustion Modeling of Solid BedsCombustion Modeling of Solid Beds
Combustion of solid fuel bedC b i f h i l i l I i b h i lCombustion of the single particle + Interaction between the particles
Major phenomenaMaterial flow: Gas, Solid, Multiple Componenetsate a o Gas, So d, u t p e Co po e etsReactions : Solid-gas reaction, Gaseous reactionHeat transfer : Conduction, Convection, RadiationPh i l d t i l hPhysical and geometrical changes
• Generation of internal pore, Change of particle size• Bed structural change : Porosity, height• Melting, Sintering…
Reactors containing solid bedIron-making process
• Coke oven, Sintering bed, Blast furnaceWaste incinerators (grate type)
Thermal Engineering Lab
Waste incinerators (grate type)
Waste Incinerator Waste Incinerator
Bed combustion of mixed waste (solid fuel)
Waste heat boiler
Stoker typeStoker type
Rotary kiln
Thermal Engineering LabTraditional stoker-type incinerator Advanced incinerator : Stoker-type + Rotary kiln type
Iron Making ProcessIron Making Process
Coking coal
Iron ore
Coking coal
Coke oven
SinteringBlast furnace
I M ki P
Thermal Engineering Lab
Iron Making Process
Iron Ore Sintering BedIron Ore Sintering Bed
Iron ore sintering process90% f i Ph i l h f i (i ) i i~90% of inert : Physical changes of inert (iron ore) is important
Self-sustaining combustion (no external heat source) once ignitedNo pyrolysis, very slow progress of coke combustionpy y y p g
CHARGING
+COKE, LIME etcPSEUDO-PARTICLES +WATER
CHARGING
+COKE, LIME etc+COKE, LIME etcPSEUDO-PARTICLES +WATER
YARD
CHARGING
COG BURNERSTACK
ORE BINREROLLING MIXING YARDYARD
CHARGING
COG BURNERSTACK
ORE BINORE BINREROLLING MIXING
SINTERING BED
EP
HEARTH BEDWIND BOXES SINTERED ORE
SINTERING BED
EPEP
HEARTH BEDWIND BOXES SINTERED ORE
HOT CRUSHING
COOLINGCOLD CRUSHINGSCREENINGRETURN FINE
FAN HOT CRUSHING
COOLINGCOLD CRUSHINGSCREENINGRETURN FINE
FAN
Thermal Engineering Lab
BLAST FURNACEBLAST FURNACE
Iron Ore Sintering
Sintering bedSize
L th 100• Length : 100m• Height : 0.7m• Width : 5m
Sintering time : about 1400s
Thermal Engineering Lab
Coke OvenCoke Oven
Each slice – Batch type oven
Charge : 27.8 ton/ovenPUSHER
CHARGING CAR
Coking time : about 20 hours
QUENCHING
COAL
PUSHER
CAR
16.0m
Charging
coal6m . . . . 6.7m
Thermal Engineering Lab
0.45m fuel air0.70m More than 100 slices
Blast FurnaceBlast Furnace
Blast Furnace
Iron ore+ Coke+ Limestone
<10 mIron ore+ Coke+ Limestone
<10 m
Gas flow
+ Limestone
Gas flow
+ Limestone
LumpyZone
Maxim
um : ~1
LumpyZone
Maxim
um : ~1
CohesiveZone Dripping
Zone
110m
CohesiveZone Dripping
Zone
110m
Hearth Raceway
TuyereMolten
Iron
Hearth Raceway
TuyereMolten
Iron
Thermal Engineering Lab
Blast Furnace ProcessBlast Furnace Process
Phenomena in Blast FurnaceS kStack zone
• Alternate coke/ore layers• Ore layer is heated up and partially reduced
( tit F O)
Stack zone
(wustite, FeO).Cohesive zone
• Ore layer is softened and agglomerates. Cohesive zone• Low permeability of ore layer – “coke slit”• Wustite is transferred to Fe.
Dripping zone Dripping zonepp g
• Ore starts to melt and fall down.Raceway – Reducing gas by coke combustionDeadman - Stagnant coke zoneDeadman Stagnant coke zone
DeadmanRaceway
Thermal Engineering Lab
Raceway
Advanced TechnologyAdvanced Technology
FINEX Process
Thermal Engineering Lab
Modeling Approach
Thermal Engineering Lab
Applicability to Various SystemsApplicability to Various Systems
Reactors with bed of solid material : Solid flow: batch or continuousCommon governing mechanism and physical/chemical phenomena but differ in the dimension, the boundary conditions and additional physical changes
Solid material Oxidizer
Solid material
Solid material Oxidizer
Solid material
Solid Solid
materialSolid Solid
materialmaterialmaterial
• Fixed bed combustorOxidizer
• Co-current fixed
Oxidizer
• Count-current fixed
Oxidizer
• Grate-type incineratorI i t i b d
• Fixed bed combustorOxidizer
• Co-current fixed
Oxidizer
• Count-current fixed
Oxidizer
• Grate-type incineratorI i t i b d
Thermal Engineering Lab
• Direct melting furnace• Coke oven
bed gasifier bed gasifier• Blast furnace
• Iron ore sintering bed• Direct melting furnace• Coke oven
bed gasifier bed gasifier• Blast furnace
• Iron ore sintering bed
Approach: Solid-Gas Material Flow ModelingApproach: Solid Gas Material Flow Modeling
Solid MaterialLocally homogeneous & Porous Media
Gas FlowContinuousLocally homogeneous & Porous Media
Multiple componentsAssumed to be continuum
G i E ti f PDE
ContinuousFlow through porous media
• Governing Equations of PDE
ACTUALFUEL BED
UNSTEADY1-D MODEL
UNSTEADY2-D MODEL
UNSTEADY3-D MODEL
ACTUALFUEL BEDACTUALFUEL BED
UNSTEADY1-D MODELUNSTEADY1-D MODEL
UNSTEADY2-D MODEL
UNSTEADY3-D MODELFUEL BED
yz
x (time)
y
1 D MODEL
x
y
2 D MODEL
x
yz
3 D MODELFUEL BED
yz
FUEL BED
yz
yz
x (time)
y
1 D MODEL
x (time)
y
x (time)
y
1 D MODEL
x
y
x
y
2 D MODEL
x
yz
x
yz
3 D MODEL
xtime x (time)xtimextimeACTUALFUEL BED
UNSTEADY3-D MODEL UNSTEADY
2-D MODEL
xtime xtime xtime x (time)x (time)x (time)xtime xtimextime xtimeACTUALFUEL BED
UNSTEADY3-D MODEL UNSTEADY
2-D MODELWaste IncineratorIron Ore Sintering BedFixed-bed Gasifier
oror
Fixed-bed Gasifier
Coke OvenBlast Furnace
Thermal Engineering Labx
yz
time x
y
time r
y
timex
yz
time x
yz
time x
y
time x
y
time r
y
time
Applicability to Various Systems (Cont’d)Applicability to Various Systems (Cont d)
Flexibility in computation - In the model, user can defineS lid d iSolid components and gaseous speciesCombustion/reaction types and their ratesBoundary conditionsyPhysical and geometric propertiesNumerical Scheme
Extension of 1-D, transient model to 2-D modelFor moving bed, with constant traveling speed
time
y
time
y
Thermal Engineering Lab
t=0 tmaxt+∆ t timett=0 tmaxt+∆ t timet
Numerical Models : ConceptsNumerical Models : Concepts
Solid Phase and Gas PhaseS lid h
N
SOLID PHASE, K
NSOLID PHASE, I
SOLID PHASE, J N
SOLID PHASE, K
NSOLID PHASE, I
SOLID PHASE, J
Solid phase• Assumed as the porous media : Combustion and radiation• Combustion : Drying – Pyrolysis - Char combustion• Heat and mass transfer : Conduction Convection Radiation
P
S
EW
P
S
E
N
W
P E
N
WN
SOLID PHASE, IP
S
EW
P
S
E
N
W
P E
N
WN
SOLID PHASE, I
• Heat and mass transfer : Conduction, Convection, Radiation• Physical changes
Gas phase : ReactionsI t ti bt T h
S
SP
S
EW
GAS PHASE
S
SP
S
EW
GAS PHASEInteractions btw. Two phases• Heat transfer• Mass transfer and transport Gas phase
Mass transportSolid-gas reactions- drying & condensation Gas-gas reactions
Gas phaseMass transport
Solid-gas reactions- drying & condensation Gas-gas reactions
GAS PHASEGAS PHASE
Governing Equations (PDE)Mass, energy, component
pby solid-gas reactions - combustion
- water-gas shift reactions
gas conductionSolid phase J
drying & condensation- char reactions(combustion,gasification)- Limestone decomposition
Gas gas reactions
- convection
Heat transfer btw. solid and gas
pby solid-gas reactions - combustion
- water-gas shift reactions
gas conductionSolid phase J
drying & condensation- char reactions(combustion,gasification)- Limestone decomposition
Gas gas reactions
- convection
Heat transfer btw. solid and gas
Solid phase
p
Solid phase KGeometrical changes of solid particles
- radiation- heat of reaction
Solid phase
p
Solid phase KGeometrical changes of solid particles
- radiation- heat of reaction( ) ( ) ( )V
eff
fu S
t φ
ρ φρφ φ
∂+∇⋅ = ∇⋅ Γ ∇ +
∂r
Thermal Engineering Lab
Solid phaseI Solid-solid interaction
(radiative and conductive heat transfer)
-slumping- internal pore- sintering- melting
Heat transfer btw. solid phases
Solid phaseI Solid-solid interaction
(radiative and conductive heat transfer)
-slumping- internal pore- sintering- melting
Heat transfer btw. solid phases
Mathematical Model – Governing EquationsMathematical Model Governing Equations
Governing equationsS lid h I M E CSolid phase I : Mass, Energy, Component
( ) ( ), , , ,,
s I V I s I s Isolid gas reactions I J
phase JI J
f vM
t yρ ρ
− →
≠
∂ ∂+ =
∂ ∂ ∑ &
I J≠
( ) ( ) ( ), , , , , , ,, , , , , , , , , 1
V s I s I s I s I s I v IV s I s I JI s I s J s I conv g I s I g s I rad
J
f h v h T ff k h A T T h A T T q
t y y y
y M H M C T
ε−
∂ ∂ ∂⎛ ⎞∂+ = + − + − +⎜ ⎟∂ ∂ ∂ ∂ −⎝ ⎠
⎛ ⎞+ ∆ ⎜ ⎟
∑
∑ ∑& &, , , , , ,s s
s s
I s I r r s I r p I s Ir r
y M H M C T+ ∆ − ⎜ ⎟⎝ ⎠
∑ ∑& &
( ) ( ), , , , , , , ,, , , s
s
s I V I s I k s I s I s I ks I k r
r
f m v mM
t yρ ρ∂ ∂
+ =∂ ∂ ∑ &
Gas phase : Mass, Energy, Species
, ,g g g
s I r
vM
ρ ε ρ∂ ∂+ = −
∂ ∂ ∑∑ &, , s
s
s I rI rt y∂ ∂ ∑∑
( ) ( ) ( ), , , , , , , , ,(1 )s s s
s s
g g g gg conv g I s I s I g I s I r r s I r p I s I
I r r
h v h Tk h A T T y M H M C T
t y y yε
ε −
∂ ∂ ⎛ ⎞∂⎛ ⎞∂+ = + − + − ∆ + ⎜ ⎟⎜ ⎟∂ ∂ ∂ ∂⎝ ⎠ ⎝ ⎠
∑ ∑ ∑& &
Thermal Engineering Lab
( ) ( ), ,, , , , ,s g
s g
g g k g g g ks I k r g k r
r I r
m v mM M
t yρ ε ρ∂ ∂
+ = +∂ ∂ ∑∑ ∑& &
Submodel - ReactionsSubmodel Reactions
Solid – gas reactions & Gaseous reactions
Solid-gas reactions
solid solid gas gas solid solid gas gassolid gas solid gas
M M M Mν ν ν ν′ ′ ′′ ′′+ → +∑ ∑ ∑ ∑
gDrying : Boling(>373K) and Diffusion(<373K) :
( )1min , (by boiling)in s moistureQ m
Hρ ε⎧ ⎧ ⎫−⎪ ⎪−⎪ ⎨ ⎬⎪ ∆⎪ ⎪
∑&
Pyrolysis A v W C d
( )2H O
, ( y g)
(by diffusion)
fgmoisture
g p p wg wp wg
H tM
C W d n D X X
⎪ ⎨ ⎬⎪ ∆= ⎪ ⎪⎨ ⎩ ⎭⎪ −⎪⎩
&
Char reactions : C(s)+O2, H2O, CH4, CO• Competitive reactions : Arrhenius rate + diffusion
Limestone decomposition
,,
1 1 1s s char g i po g
i
r m eff
A v W C dR
k k kζ
=+ +
Limestone decomposition
( )( )
2 2
*
2 4.18681
l l CO COl
p p l pl
n d C CR
d d d dK
π −=
− ⎛ ⎞⋅+ + ⎜ ⎟
3 2CaCO CO CaO→ +
Thermal Engineering Lab
m l s l s lk d D k RT d+ + ⎜ ⎟
⎝ ⎠
Submodel – Reactions(Cont’d)Submodel Reactions(Cont d)
Iron ore reduction : Fe2O3(s), Fe3O4, FewO, + CO3 interface shrinking core model• 3 interface shrinking core model
2
2
,,,
1,4
6 CO gg CO gi in n m m
mi i CO CO
fR a Kd W M M
ωρ ωεφ =
⎡ ⎤⎛ ⎞⎛ ⎞= −⎢ ⎥⎜ ⎟⎜ ⎟ ⎜ ⎟⎢ ⎥⎝ ⎠ ⎝ ⎠⎣ ⎦
∑
Solution loss : C+CO2->2CO• Competitive reactions : Arrhenius rate + diffusion
( ) ( )2 2 2
11 1, film, 5g CO g CO s COR M A k kρ ω η
−− −⎡ ⎤= +⎢ ⎥⎣ ⎦p
Melting ( )1,
, inflow
cell0
j s face facej melt j
nj j
G AT TR
T M Vol
ω−= ⋅
∆ ⋅
∑cell0j j
Thermal Engineering Lab
Submodel- Heat transfer & Geometrical changesSubmodel Heat transfer & Geometrical changes
Heat TransferC d i I l d d i h iConduction : Included in the energy equationsConvections : Wakao and Kaguei(1982)’s equation
or Ranz-Marshall equation qRadiation : 2-flux model(Shin and Choi, 2000)Among solid phases
( )q h A T T= −( )( )
, , , ,
, ,,2where
ss IJ IJ s I s J s I
V I s I s ps g g pgI V JIIJ
V I s g V I
q h A T T
f k C k C fh
f t t f
ρ ε ρ
επ
= −
⎡ ⎤+⎢ ⎥
= ⎢ ⎥+⎢ ⎥
∑∑
Geometrical changesParticle diameter
, ,V I s g V II
f f⎢ ⎥⎣ ⎦
∑
( ) 1/33 31d F d Fd⎡ ⎤= +⎣ ⎦Particle diameterGeneration of the internal pores , , , ,
, , ,V I ip I s ip I comb i
ip i ip loss Ii i
f v Mf
t yε ε
ερ
∂ ∂+ = − +
∂ ∂ ∑&
&
( )1p u rd F d Fd⎡ ⎤= − +⎣ ⎦
Thermal Engineering Lab
Bed structural changes : packing parameter, n1 n o
V s Vf f f−=
Characteristics of the reactors summarized in this studyCharacteristics of the reactors summarized in this study
Waste Incinerator
Iron Ore Sintering Bed
Coke Oven Blast Furnace
Bed type Moving bed Moving bed Fixed bed Counter-current Fixed bedFixed bed
Feeding Continuous Continuous Batch Continuous.Solid
materialSolid waste Iron ore
+LimestoneCoking coal Sintered ore+Coke
+CokeMode of
gas/air flowBlowing air Suction air Discharge of
pyrolized gasBlowing of
preheated blast air(or gas)air(or gas)
Heat source Volatile/Char combustion
Coke combustion External Wall Heating, latent
Heat of Pyrolysis
Coke & PC(pulverized coal)
combustionPhysical change
Change of bed height by
combustion
Melting/sinteringNegligible change
of bed height
Swelling, shrinkage
Melting of iron ore, coke diameter
change(combustion)
Thermal Engineering Lab
Waste Incinerator
Thermal Engineering Lab
Waste Incinerator (II)Waste Incinerator (II)
Major phenomena within the bed in waste incineratorsI i i b di i f ll/hIgnition by radiation from wall/hot gasDrying – Pyrolysis – Char combustionCombined closely with the gas flow in the incineratory g
SECONDARYSECONDARYSECONDARYSECONDARYSECONDARYAIR
RADIATION
SECONDARYAIR
RADIATION
(1) Raw waste(2) Drying(3) Pyrolysis(4) Char reaction( )
SECONDARYAIR
RADIATION
SECONDARYAIR
RADIATION
(1) Raw waste(2) Drying(3) Pyrolysis(4) Char reaction( )
WASTEFEEDER WASTE BED
COM BUSTION GASRADIATION
WASTEFEEDER WASTE BED
COM BUSTION GASRADIATION
(1) (2) (3) (4) (5)
(5) Ash
WASTEFEEDER WASTE BED
COM BUSTION GASRADIATION
WASTEFEEDER WASTE BED
COM BUSTION GASRADIATION
(1) (2) (3) (4) (5)
(5) Ash
ASHHOPPER
PRIM ARY AIR
GRATESFEEDER
ASHHOPPER
PRIM ARY AIR
GRATESFEEDER (5)
ASHHOPPER
PRIM ARY AIR
GRATESFEEDER
ASHHOPPER
PRIM ARY AIR
GRATESFEEDER (5)
Thermal Engineering Lab
Waste Incinerators – Calculation ParametersWaste Incinerators Calculation Parameters
Single solid phaseBed height : 0.68 mThe particle size and porosity are not changed during the process
Bed height change is very importantBed height change is very importantCalculation time : 6000 sec
Bed height (m) 0.68O idi
Type Air# f ll 150 T 300K
Combustion
Waste incinerator (Moving bed, Continuous feeding)Ignition by radiation
from hot gas or wall (2) Combustion
Waste incinerator (Moving bed, Continuous feeding)Ignition by radiation
from hot gas or wall (2)
Oxidizer# of cells 150 T 300Ktmax (sec) 6000 vave 0.136m/s∆t (sec) 1
IgnitionType Radiation
Size 30mm Value CFD resultsa
Solid waste (30~60%
combustible)
Combustion gas
Ash
Solid waste (30~60%
combustible)
Combustion gas
AshSolidmat.
(i l di
resultsMoisture 45%
PyrolysisA 1.5×104
Volatile 39% E 30kcal/kmol
Char 6%Char
A 2.3
Time = 0 Time = t1 Time = tmaxAirTime = 0 Time = t1 Time = tmaxAir
(includingmass-basecomposition)
CharAsh 10% E 22kcal/km
ol
εo 0.54
Gaseous
Volatile+O2→CO+H2
LHVa 1790 CO+H2O↔CO2+H
Thermal Engineering Lab
reactionLHV 1790
2
n 1 H2+0.5O2→H2OShrinkage of grid YES
Waste Incinerators - Calculation ResultsWaste Incinerators Calculation Results
Model is well describing the physico-chemical process in the waste bedT di ib i d i iTemperature distribution and gas composition
RADIATIONRADIATION0.4
0 4
0.6
(m) 3.73
13
0 4
0.6
(m) 3.73
13
COMBUSTION GAS
RADIATION
COMBUSTION GASCOMBUSTION GAS
RADIATION
0.3
OH Oon
O2 CO2 H2O CO H2 CxHyOz
0.2
0.4
Bed H
eight
(
14
80
0.2
0.4
Bed H
eight
(
14
80AIRAIRAIR 0.1
0.2
O2
H2
CO2
H2O
Mol
e Fr
actio
0 2 4 6 8 10 120.0
Location on the grate (m)
4681013
0 2 4 6 8 10 120.0
Location on the grate (m)
4681013AIRAIRAIR
0 1000 2000 3000 4000 5000 60000.0
CO
Ti ( )
Predicted temperature distribution (x100k) Predicted gas composition (x100k)
Time(sec)
Thermal Engineering Lab
Application of the Model : Combined Simulation MethodApplication of the Model : Combined Simulation Method
FURNACE ENCLOSURE
CFD
GAS FLOW FIELD :Mass, Energy, Momentum andSpecies Conservation Equations
Temperature, Heat TransferVelocity, Turbulent Mixing, Chemical Species and Reaction
CFD +Turbulence, Radiation, Reaction Models
MGAS, TGAS, VGAS
FUEL BEDCOMBUSTION FUEL BED:
QRAD
COMBUSTION MODEL
x = 0 Grate Length Grate Length
Fuel Components and TemperatureGas Species and TemperatureBed Height, etc.
FUEL BED:Combustion, Gas ReactionHeat Transfers
Thermal Engineering Lab
x = 0( t = 0 ) PRIMARY AIR(x)
x = Grate Length(tmax: Fuel Residence Time)x = Grate Length(tmax: Fuel Residence Time)
Simulation Results for Waste IncineratorSimulation Results for Waste Incinerator
TEMPERATURE
12001300
TEMPERATURE[ UNIT : K ]
1500 Tgas
1100
TEMPERATURE[ UNIT : K ]
700
1100
empe
ratu
re (K
)
0.2CO2
Mole 1500Tgas
1400300
Gas
T
0.0
0.1CxHyOz+CO+H2
Fraction
x=0.8m ( t=6.6 min )
1200
700
1100
0 1
0.2CO2
1500
1550
SECONDARYAIR
13000.35
0.70
Heigh
t (m)
0.35
0.70
Heigh
t (m)
0.35
0.70
Heigh
t (m)
0.35
0.70
Heigh
t (m)
0.35
0.70
Heigh
t (m)
300
0.0
0.1CxHyOz+CO+H2
1500 1500
1400
1400
5000
0.004 8 12
Bed H
Distance (m)0
0.004 8 12
Bed H
Distance (m)0
0.004 8 12
Bed H
Distance (m)
0.004 8 12
Bed H
Distance (m)4 8 12
Bed H
Distance (m) 0.70
(m)
0.70
(m)
0.70
(m)
0.70
(m)
0.70
(m)
0.70
(m)
Thermal Engineering Lab
7001100
00.00
4 8 12
0.35
Bed H
eight
(
Distance (m)
13
13
1211
00.00
4 8 12
0.35
Bed H
eight
(
Distance (m)0
0.004 8 12
0.35
Bed H
eight
(
Distance (m)0
0.004 8 12
0.35
Bed H
eight
(
Distance (m)
0.004 8 12
0.35
Bed H
eight
(
Distance (m)4 8 12
0.35
Bed H
eight
(
Distance (m)
13
13
1211
Iron Ore Sintering
Thermal Engineering Lab
Iron Ore Sintering Iron Ore Sintering
Major Phenomena in the sintering bedAIRAIR
AIRAIR COOLING
AIR
COOLING
AIR
COMBUSTION SINTERED
IGNITIONAIR
RAW COMBUSTION SINTERED
IGNITIONAIR
RAW
COOLING
COMBUSTION
SINTERED ZONE
SINTERING
COOLING
COMBUSTION
SINTERED ZONE
SINTERING
RAW MIX ZONE
COMBUSTIONZONE ZONERAW
MIX
Hearth Bed
RAW MIX ZONE
COMBUSTIONZONE ZONERAW
MIX
Hearth Bed RAW MIX ZONE
ZONE CHAR COMBUSTION
O S CO S O
MOISTURE EVAPORATIONRAW MIX
ZONE
ZONE CHAR COMBUSTION
O S CO S O
MOISTURE EVAPORATION
xy
COMBUSTION GASxy
COMBUSTION GAS
ZONE
HEARTH BED
MOISTURE CONDENSATIONZONE
HEARTH BED
MOISTURE CONDENSATION
COMBUSTION GASCOMBUSTION GAS
Thermal Engineering Lab
Iron Ore Sintering Bed – Calculation ParametersIron Ore Sintering Bed Calculation Parameters
Iron ore sintering bed (Moving bed, Continuous feeding)Iron ore sintering bed (Moving bed, Continuous feeding)
Bed height (m) 0.57Oxidizer
Type Air
# of cells 57 T 300Ktmax (sec) 1500 vave 0.450m/s
Solid materiala
Air
feeding)Ignition by burner
Sintered ore
Solid materiala
Air
feeding)Ignition by burner
Sintered ore
∆t (sec) 1 Ignition
Type Gas burner
SolidSize(mm) 1.6/3.2 Val
ue 4 m/s, 1400K
Moisture 7 0% P l A
Time = 0 Time = t1 Time = tnaxCombustion gas
Time = 0 Time = t1 Time = tnaxCombustion gas
Solidmat.
(includingmass-basecompositi
Moisture 7.0% Pyrolysis
A -Coke 3.8% E -
Iron ore 83.2%Char
A 2.3Limeston
e 13.0% E 22kcal/kmol ga : Iron ore + Coke + Limestone (~4% combustible)
ga : Iron ore + Coke + Limestone (~4% combustible)compositi
on)e 13.0% E 22kcal/kmol
εo 0.4 Gaseous reaction
CO+0.5O2↔CO2n 0.6Shrinkage of grid Nog g
Thermal Engineering Lab
IRON ORE SINTERING BED – COMPARISON WITH SINTERING POT TEST RESULTS
Bed Type: Fixed Bed of Mixed Materials without a Gas PlenumExtension of 1-D Unsteady Model to 2-D Steady Model
AirairQ&
AirairQ&
AirairQ&
AirairQ&
Air
R-type T/C
Sintering
y=490mm
m
Air
R-type T/C
Sintering
y=490mm
m
Air
R-type T/C
Sintering
y=490mm
m
Air
R-type T/C
Sintering
y=490mm
mSintering bed
gasQ&P∆
bedT
y
y=300mm
y=110mm
600m
m
ID=205mm
Sintering bed
gasQ&P∆
bedT
y
y=300mm
y=110mm
600m
m
ID=205mm
Raw MixSintered Ore
Raw MixSintered Ore
Sintering bed
gasQ&P∆
bedT
y
y=300mm
y=110mm
600m
m
ID=205mm
Sintering bed
gasQ&P∆
bedT
y
y=300mm
y=110mm
600m
m
ID=205mm
Raw MixSintered Ore
Raw MixSintered Ore
Raw MixSintered Ore
Raw MixSintered Ore
Suction
Grate Bar
T/C
P∆
gasT
Suction
Grate Bar
T/C
P∆
gasT
y
Raw Mix
Combustion y
Raw Mix
Combustion Suction
Grate Bar
T/C
P∆
gasT
Suction
Grate Bar
T/C
P∆
gasT
y
Raw Mix
Combustion y
Raw Mix
Combustion y
Raw Mix
Combustion y
Raw Mix
Combustion
GasAnalyzer
BlowerWind Box GasAnalyzer
BlowerWind Boxtimet=0 tmaxt+ ∆ttt=0 tmaxt+ ∆tt
zone
x = time × traveling speed
timet=0 tmaxt+ ∆ttt=0 tmaxt+ ∆tt
zone
x = time × traveling speedGas
Analyzer
BlowerWind Box GasAnalyzer
BlowerWind Boxtimet=0 tmaxt+ ∆ttt=0 tmaxt+ ∆tt
zone
x = time × traveling speed
timet=0 tmaxt+ ∆ttt=0 tmaxt+ ∆tt
zone
x = time × traveling speed
timet=0 tmaxt+ ∆ttt=0 tmaxt+ ∆tt
zone
x = time × traveling speed
timet=0 tmaxt+ ∆ttt=0 tmaxt+ ∆tt
zone
x = time × traveling speed
Thermal Engineering Lab
Concept and schematic diagram of sintering pot
IRON ORE SINTERING BED – COMPARISON WITH SINTERING POT TEST RESULTS
1800
2000
Computed
25
O2-Computed
1200
1400
1600
1800y=0.11my=0.30m
y=0.49m
atur
e(K
)
p Measured
15
20
ition
(Vol
.%)
CO2-Computed CO-Computed O2-Measured CO2-Measured CO-Measured
400
600
800
1000
Tem
pera
5
10
Gas
com
pos
0 200 400 600 800 1000 1200 1400
400
Time (sec)
0 200 400 600 800 1000 1200 14000
Time(sec)
Temperature profile flue gas composition in the sintering bed
4
5
ec)
Extingushed
m/m
in) 1600
2000
Sintering timeFlame front speed (FFS) and Sintering time for various air velocities and particle diameters
2
3
Sin
terin
g Ti
me
(s
me
Fron
t Spe
ed (c
m
Coke diameter : 1.2mm
800
1200
FFSQuantification of the Combustion Propagation
diameters
Thermal Engineering Lab0.2 0.3 0.4 0.5 0.6 0.7 0.8
1
Flam
Averaged Air Velocity (m/s)
Coke diameter : 1.4mm Coke diameter : 1.6mm
0
400Combustion Propagation(Flame Front Speed, Sintering Time)
Characterization of Bed CombustionCharacterization of Bed Combustion
Flame Front Speed (FFS)Combustion Zone Thickness (CZT)Melting Zone Thickness (MZT) : for an Iron Ore Sintering BedMaximum Temperature (MaxT) CZT : Combustion Zone ThicknessMaximum Temperature (MaxT)
yy
35
40MZT : Melting Zone Thickness
CZT(AirV=0.26m/s) CZT(AirV=0.32m/s) CZT(AirV=0.45m/s) CZT(AirV=0.52m/s)MZT(AirV=0 26m/s)
1800
2000
K)
MaxT(AirV=0.26m/s) MaxT(AirV=0.32m/s) MaxT(AirV=0.45m/s)MaxT(AirV=0.52m/s)
Sintered Zone
CZTSintered Zone
CZT 20
25
30
ss (c
m)
MZT(AirV=0.26m/s) MZT(AirV=0.32m/s) MZT(AirV=0.45m/s) MZT(AirV=0.52m/s)
1400
1600
empe
ratu
re (K
MaxT(AirV 0.52m/s)
Melting ZoneCombustion Zone
CZT
Melting ZoneCombustion Zone
CZT
10
15
20
Thic
knes
1200
1400
Max
imum
Te
Raw Mix
empe
ratur
e
MZT
MaxT
Raw Mix
empe
ratur
e
MZT
MaxT
0 400 800 1200 1600 20000
5
800
1000
Thermal Engineering Lab
1373K1000K
Te
1373K1000K
Te 0 400 800 1200 1600 2000
Time (sec)
Quantified results : CZT, MZT, MaxT (for various air supply)
Coke Oven
Thermal Engineering Lab
Coke OvenCoke Oven
Plastic
(1) Wet Coal(<100oC)
(2) Dried Coal
(1) Wet Coal(<100oC)
(2) Dried Coal
layer
Flue Flue
(100~400oC)(3) Semi-Coke(4) Coke
(4)(4)
Hea
(100~400oC)(3) Semi-Coke(4) Coke
(4)(4)
Hea
(1)(2)(3)
(4)
Fro
nt
g Fr
ont
(1)(2)(3)
(4)
Fro
nt
g Fr
ont
at From H
eati
(1)(2)(3)
(4)
Fro
nt
g Fr
ont
(1)(2)(3)
(4)
Fro
nt
g Fr
ont
at From H
eati
Cok
ing
Boi
ling
Cok
ing
Boi
ling ng W
allCok
ing
Boi
ling
Cok
ing
Boi
ling ng W
all
Thermal decomposition of bituminous coal with final temperatures of
Air Fuel Air FuelCoal Coke
Thermal decomposition of bituminous coal with final temperatures of about 900℃ in the absence of air0.45m width, 6m height and 16m length, Slot -type furnace
Thermal Engineering Lab
Oven wall is heated by fuel gas combustion in the combustion chamber
Coke Oven – Calculation Parameter and resultsCoke Oven Calculation Parameter and results
Height (6m) is much longer than width(0.45m) 1D model
Charging coal is assumed to be not a coal
Bed width (m) 0.22Oxidizer
TypeNo oxidizer# of cells 44 T
tmax (sec) 54000 vave∆t (sec) 10
IgnitionType - Charging coal is assumed to be not a coal
blend but a single coalInput data - Elemental/Proximate analysis data
Ignition
Solidmat.
(includingb
Size 3mm Value -Moisture 7%
PyrolysisA 1.5×104
Volatile 24.2% E 30kcal/kmolChar 60.5%
CharA -
Homogeneous porous mediamass-basecomposition)
CharAsh 8.3% E -εo 0.4
Gaseous reaction -n 1
Shrinkage of grid Nog g
Heat Gas
Coke oven (Batch type fixed bed)
Heat Gas
Coke oven (Batch type fixed bed)
from hot wall Raw
coking coal
Coke
from hot wall Raw
coking coal
Coke
Thermal Engineering Lab
Time = 0 Time = t1 Time = tmaxTime = 0 Time = t1 Time = tmax
Coke Oven - Temperature ProfileCoke Oven Temperature Profile
Experimental data Temperature distribution within the oven
Time
700800900
10001100
e (o C
)
300
350
400
450
ure
(mm
H2O
)
#2 charging hole#3 charging hole
1coke plant No. 2, No. 2 ovenMoisture : 5.8%
200300400500600
Tem
pera
ture
50
100
150
200
250
tern
al g
as p
ress
u
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19Time (h)
0100
0
50 In
Temperature change at the center Temperature change at the wall
1000
1200
1400
atur
e(K
)
LV(0.15) MV(0.25) HV(0.35)
1000
1200
1400
ture
(K)
LV(0.15) MV(0.25) HV(0.35)
400
600
800
Tem
pera
400
600
800
Tem
pera
Thermal Engineering Lab
0 5 10 15 20200
Time (hour)0 5 10 15 20
200
Time (hour)
Blast Furnace
Thermal Engineering Lab
Blast Furnace – Modeling & Calculation ParameterBlast Furnace Modeling & Calculation Parameter
Modeling2D axi-symmetric model2D axi-symmetric modelAssumptions
• 2 phases - Gas and solid phases• Layer structure is obtained by Lo/Lc data & solid velocity
Sh f h i i d fi d b f lid t t (1050 C 1350 C)• Shape of cohesive zone is defined by range of solid temperature (1050oC~1350oC)• Shape of deadman(stagnant zone) is assumed• Layer properties (Dp, porosity) are function of locations• Raceway is treated as a boundary condition
# of cells 24x76 Reduction Rate
Size 20.0mma
50.0mmb3Fe2O3+CO
->2Fe3O4+CO2
0 36a Fe O +CO
Sold material : sintered ore + coke + flux(limestone)Blast furnace gas
. .. . ... .. .Solidmat. [17]
ε0.36a
0.45b
0.10c
Fe3O4+CO->FeO+CO2FeO+CO->Fe+CO2
Feeding rate(kg/s)
180.8 a
36.7 b 1/4Fe3O4+CO3/4F CO
. ... .
. ... . .. .. . . ...
... ... . .
. ... . .. .... .
.. . .cokeore...... .
->3/4Fe+CO2
Blast air
T(oC) 1191
P(MPa) 0.42 Solution-loss Rate
V(Nm3/min) 6150 C+CO2->2CO [18]GG
...
. .... . ..
. .. .. .. . .
.. ... . ..
Solid flow
Thermal Engineering Lab
PCRd(kg/s) 15.9 -GasGas
Liquid : pig iron + slaga: Iron ore, b: Coke, c: Cohesive zone, d: Pulverized coal rate
SimplificationSimplification
Profilemeter29.5
30
30.5
O SProfilemeter
28
28.5
29
Hei
ght(m
) O.S
Coke+Ore
O.L
C.COKE
O.S
27
27.5
0 1 2 3 4
R di ( )
COKE
Radius(m)
8
29
29.5
30
t(m)
5
6
7 Lo/Lc sm oothing of Lo/Lc
ORE
27
27.5
28
28.5
Hei
ght
1
2
3
4
Lo/L
c
COKE
ORE
Thermal Engineering Lab
270 1 2 3 4
Radius(m) 0 1 2 3 4
0
Radius(m )
Lo/Lc data & Layer DistributionLo/Lc data & Layer Distribution
7 Case ACase B
4
5
6Case B Case C
Lc
2
3
4
Lo/L
0 1 2 3 4 50
1
Radius(m)
Lo/Lc data (Case A : Base)
Thermal Engineering Lab
Case A Case B Case C
Result - Temperature Distribution within the FurnaceResult Temperature Distribution within the Furnace
Thermal Engineering LabCase A Case B Case C
Mass Fraction of OreMass Fraction of Ore
Thermal Engineering Lab
Fe2O3 Fe3O4 FewO Fe
Mass Fraction of Ore & Gas (r/R=2/3)Mass Fraction of Ore & Gas (r/R 2/3)
0 8
1.0
Fe2O3
0.35
0.40 CO2
CO
0.6
0.8
ract
ion
Fe2O3
Fe3O4
FewO Fe
0.20
0.25
0.30
ract
ion
0.2
0.4
Mas
s fr
0.10
0.15
Mas
s Fr
10 15 20 25
0.0
5 10 15 20 25 30
0.00
0.05
Height(m) Height(m)
Mass Fraction of Ore Mass Fraction of Gas
Thermal Engineering Lab
Chemical ReactionChemical Reaction
• 3 InterphaseReactions of Indirect Reduction
2 3 3 4 23 ( ) ( ) 2 ( ) ( )Fe O s CO g Fe O s CO g+ → +
• 3 Interphase•Shrinking Core Model
3 4 23( ) ( ) ( ) ( )
4 3 4 3 ww Fe O s CO g Fe O s CO g
w w+ → +
− −
( ) ( ) ( ) ( )F O CO F CO+ → + 2( ) ( ) ( ) ( )wFe O s CO g wFe s CO g+ → +
3 4 21 3( ) ( ) ( ) ( ) ( 848 )4 4 sFe O s CO g Fe s CO g T K+ → + <
2
2
,,,
1,4
6 CO gg CO gi in n m m
mi i CO CO
fR a Kd W M M
ωρ ωεφ =
⎡ ⎤⎛ ⎞⎛ ⎞= −⎢ ⎥⎜ ⎟⎜ ⎟ ⎜ ⎟⎢ ⎥⎝ ⎠ ⎝ ⎠⎣ ⎦
∑
( ) ( ) ( ) ( )( )( ) ( ) ( )( )( )( ) ( ) ( )
1,1 3 2 2 3 2 2 3 1,2 2,1 3 2 3 2 3
2,2 1 1 2 3 3 3 3 2,3 3,2 1 1 3
*3,3 1 1 2 2 3 2 2 3 3,1 1,3 2 3
( )a A A B B F A B B F a a A B B F B B F
a A B B A B F A B F a a A B B F
a A B A B B F A B B a a A B F
= + + + + + + = = − + + + +⎡ ⎤⎣ ⎦= + + + + + + = = − + +
= + + + + + + = = − +
Thermal Engineering LabBack to the contents…
Chemical Reaction (cont’d)
( )
( )
1 2 32
1
3 4
film, 2
1 11 31 1 2
11 1 1,1 2 1,2 2 4 1
Fe O Fe On n i w
n n n n n s sn
Fe O
CO s
d dX X dn nk K X X D d dX
dk d
A B X X
W A B a A a F X X
+
+
−+= ⋅ = ⋅ = =
= + − = = =
( ) ( ) ( )33720 50.2 141002 4
1 1 18.3146 10exp 7.255 10 exp 3.16 10 exp 8.76
s ssT TTK k D−
− −×
= + = − = −
( ) ( ) ( )34711 40 72002 4
2 2 28.3146 10exp 5.289 10 exp 2.09 10 exp 2.77
s ssT TTK k D−
− −×
= − = − = −
( ) ( ) ( )2879 61 4 88002 43 127 10 5 42 10 5 09K k D− −( ) ( ) ( )32879 61.4 88002 4
3 3 38.3146 10exp 3.127 10 exp 5.42 10 exp 5.09
s ssT TTK k D−×
= − + = − = −
( )981.53 4 1 4 2exp 1.032
sTK k k D D= − + = =
13TD ⎡ ⎤⎛ ⎞ T T12 2 2
2
2 2
,film,
,
2 0.39 Reave
ave
TCO N g
CO ig Ts g CO N
Dk
d Dµ
ρ
⎡ ⎤⎛ ⎞⎢ ⎥= + ⎜ ⎟⎜ ⎟⎢ ⎥⎝ ⎠⎣ ⎦
2s g
ave
T TT
+=
1321F O F Od ω⎛ ⎞
⎜ ⎟
132 31F O F O F Od ω ω⎛ ⎞
⎜ ⎟
132 31F O F O F O F Od wω ω ω⎛ ⎞
⎜ ⎟2 3 2 3
2 3
21Fe O Fe O
s Fe O
dd M
ωσ
⎛ ⎞= ⎜ ⎟⎜ ⎟
⎝ ⎠
3 4 2 3 3 4
2 3 3 4
2 31Fe O Fe O Fe O
s Fe O Fe O
dd M M
ω ωσ
⎛ ⎞= +⎜ ⎟⎜ ⎟
⎝ ⎠
2 3 3 4
2 3 3 4
2 31w w
w
Fe O Fe O Fe O Fe O
s Fe O Fe O Fe O
d wd M M M
ω ω ωσ
⎛ ⎞= + +⎜ ⎟⎜ ⎟
⎝ ⎠
2 3 3 43 2 3wFe O Fe O Fe O Fe
wω ω ω ω+ + +
Thermal Engineering Lab
2 3 3 4
2 3 3 4
3 w
w
Fe
Fe O Fe O Fe O FeM M M Mσ = + + +
Back to the contents…
Chemical Reaction (cont’d)Chemical Reaction (cont d)
Solution loss2( ) ( ) 2 ( )C s CO g CO g+ →
( ) ( )2 2 2
11 15 , film, 5g CO g CO s COR M A k kρ ω η
−− −⎡ ⎤= +⎢ ⎥⎣ ⎦
5 1 3(1 ) 82 056 10k
k T
6(1 )s
s s
Ad
εφ−
=
2
5,1 35
5,2 5,3
(1 ) 82.056 101 s g
CO CO
k Tk P k P
ρ ε −= − ⋅ ×+ +
( )2 2 2film, , ShaveT
CO CO N s s sk D d φ=
( ) ( )1 66350 21421
( )0.5ave g sT T T= +
( ) ( )( ) 3
1 66350 214215,1 5,260 1.987 1.987
82.056 10881685,3 ,1.987
exp 19.875 exp 6.688
exp 31.615
s s
g g
s j
T T
Tj j gT M
k k
k P ρ ω−×
= − = − +
= − =
0.55Sh 1.5 Res sg=( )
η = −⎛
⎝⎜
⎞
⎠⎟
1 13
13Φ Φ Φtanh
2 2
5
,6 ave
s sT
s CO N
d kDδ
ζΦ =
Thermal Engineering LabBack to the contents…
CONCLUSIONSCONCLUSIONS
A Unified Approach in the Numerical Modeling of the Bed Combustion R i fl f lid li id d h f l i lReacting flow of solid, liquid and gas phase of multiple componentDiscretization of the solid flow in the same manner as the usual discretization of gas phaseCommon governing equations for gas and solid phasesEasy to accommodate various configurations of gas and solid flow by treating them as boundary conditionsyUser can define the dimension, phenomena, boundary conditions, etc.
Examples of the ApproachMoving bed in waste incineratorI i t i b dIron ore sintering bedCoke ovenBlast furnace
Thermal Engineering Lab
CONCLUSIONS (cont’d)CONCLUSIONS (cont d)
Strong Points of the Mathematical Modeling of Complex ProcessesStrong Points of the Mathematical Modeling of Complex ProcessesPhysics–based Computational Model: Critically beneficial for design and operationA li bl t i t t i iApplicable to very important engineering processesValidity shown for application in incinerators, sintering, coking and blast furnaceMaybe applicable to food and bio processing
Weak Points of the Mathematical Modeling Sub-processes are not comprehensively modeledDifficult to validate: measurable quantities are limitedDifficult to validate: measurable quantities are limited
Thermal Engineering Lab
THANK YOUTHANK YOU
Thermal Engineering Lab
Temperature in RacewayTemperature in Raceway
Obtained from the heat and mass balance in the racewayBoundary condition of the energy equation of gas phase
• A : Base, B: High PCR, C: High Productivity
In high PCR, temperature in raceway is lowest Since temperature of PC is 300K while temperature of coke is 1800K
Thermal Engineering Lab
Since temperature of PC is 300K while temperature of coke is 1800K
Temperature DistributionTemperature Distribution
Measured Results
Thermal Engineering Lab
Base High PCR High productivity
Position of CZPosition of CZ
Distance from tuyere level to Ts=1050oC
18
(m)
BaseHi h PCR
18
(m)
BaseHi h PCR
14
16
uyer
e le
vel High PCR
High Productivity
14
16
uyer
e le
vel High PCR
High Productivity
8
10
12
form
the
tu
8
10
12
form
the
tu1 2 3 4 5
6
8
Dis
tanc
e
1 2 3 4 5
6
8
Dis
tanc
e
Measured result Simulated result
Radius(m) Radius(m)
Thermal Engineering Lab
Pressure DropPressure Drop
Pressure drop in the wall
0.35
0.36
Measurement0.55
0.60
Base High PCR High Productivity
0.32
0.33
0.34
sure
(MP
a)
0.40
0.45
0.50
sure
(MPa
)
0.29
0.30
0.31
Pres
s
0.25
0.30
0.35Pre
ss
2.1 3.2 4.4 5.6 6.7 7.9 9 10.2 11.3 12.5 14.5 17.6 --0.28
Distance form tuyere level (m)
Calculated data Measurement data
0 5 10 15 20
Distance form the raceway (m)
A major portion of pressure drop occurs in a cohesive zone
Thermal Engineering Lab
Simulation Condition
<Operation condition> <Calculation cases>
Simulation Condition
Top gas pressure (MPa) 0.277 Blast volume (Nm3/min) 6150Blast pressure (MPa) 0 4192
• Case A : 기준
• Case B : 중심류 억제 (0.5m내진)
• Case C : 중심류 억제 (1.0m내진)Blast pressure (MPa) 0.4192Blast temperature (oC) 1191Production rate of pig iron(t/d) 9284PCR (kg/t) 147.6O2 t (N 3/h ) 20000
Case C : 중심류 억제 (1.0m내진)
O2 rate (Nm3/hr) 20000Blast moisture(g/Nm3) 22.3R.R (kg/t) 489.2Ore ratio (-) 1.683
Layer Particle diameter (m) Shape factor (-) Voidage (-)
<Layer property>Layer Particle diameter (m) Shape factor ( ) Voidage ( )Ore layer 0.0214 0.84 0.36Coke layer 0.0477 0.90 0.45Cohesive layer 0.0214 0.84 0.10Raceway 0 0477 0 90 0 80
Thermal Engineering Lab
Raceway 0.0477 0.90 0.80Deadman zone for gas 0.0477 0.90 0.10