application of solid bed combustion modelsamigas.kaist.ac.kr/data/choi_japanese combustion...

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


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)


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


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


BLAST FURNACEBLAST FURNACE

Iron Ore Sintering

Sintering bedSize

L th 100• Length : 100m• Height : 0.7m• Width : 5m

Sintering time : about 1400s


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


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


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


Raceway

Advanced TechnologyAdvanced Technology

FINEX Process


Modeling Approach


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


• 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


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


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 −

∂ ∂ ⎛ ⎞∂⎛ ⎞∂+ = + − + − ∆ + ⎜ ⎟⎜ ⎟∂ ∂ ∂ ∂⎝ ⎠ ⎝ ⎠

∑ ∑ ∑& &


( ) ( ), ,, , , , ,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→ +


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


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⎡ ⎤= − +⎣ ⎦


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)


Waste Incinerator


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



(1) (2) (3) (4) (5)

(5) Ash





(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)


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


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)


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


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)


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


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


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


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



zone



zone



zone



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


1373K1000K

Te

1373K1000K

Te 0 400 800 1200 1600 2000

Time (sec)

Quantified results : CZT, MZT, MaxT (for various air supply)

Coke Oven


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


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


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


0 5 10 15 20200

Time (hour)0 5 10 15 20

200

Time (hour)

Blast Furnace


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


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


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)


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


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


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+ + +


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


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


THANK YOUTHANK YOU


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


Since temperature of PC is 300K while temperature of coke is 1800K

Temperature DistributionTemperature Distribution

Measured Results


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)


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


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


Raceway 0.0477 0.90 0.80Deadman zone for gas 0.0477 0.90 0.10

application of solid bed combustion modelsamigas.kaist.ac.kr/data/choi_japanese combustion...

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