CFD MODELING FOR HIGH RATE PULVERIZED COAL INJECTION (PCI)

IN THE BLAST FURNACE

Overview of Project Progress

Chenn Q. ZhouProfessor of Mechanical Engineering

Purdue University CalumetHammond, IN 46321

PROJECT OVERVIEWParticipants:

ArcelorMittal USA-Indiana Harbor DofascoStelco Inc.US SteelUnion gas Purdue University Calumet

Duration: 24 +7 MonthsStart Date: May 2005Funding Agent: AISI/DOE and Indiana 21st Century Research and Technology Fund

PROJECT GOALS

To help the steel industry in using advanced technology for optimizing the PCI process to

increase PCI rate improve fuel efficiencysave energyreduce pollutant emission

To lay a solid foundation for developing a comprehensive model for the whole blast furnace to optimize the operationTo enhance education program at PUC

PROJECT OBJECTIVES

To develop a state-of-the-art three-dimensional CFD model of PCI to BF To use the CFD model to provide a better understanding of PCI combustionTo provide CFD model-based strategies to increase the replacement ratio and PCI rate

Top GasCO, CO2, H2, H2O, & N2

Hot Air, & PCI

RacewayTuyere

Pellets, Sinter& Coke

Blow pipe

PROJECT TASKSTask 1: Development of Computer Simulation for PCI into BF

Subtask 1.1 Simulation of Gas-Solid Flow in the RacewaySubtask 1.2 Simulation of the combustion and gasification of Coal and Coke Subtask 1.3 Modeling of Subspecies Subtask 1.4: Complete Simulation of PCI to BF Subtask 1.5: Code Validation

Task 2: Parametric Studies and Optimization Task 3: Technology Transfer

Task 3

Task 2

Task 1.5

Task 1.4

Task 1.3

Task 1.2

Task 1.1

Task 1

242322212019181716151413121110987654321Months

APPROACHStep-by-Step

Heat transfer, natural gas combustion, coal devolatilization and combustion before entering the raceway (lance and tuyere)Raceway formationNatural gas, Coal and coke combustion in the raceway

Combination of in-house code and Fluent©

In-house code: multiphase reacting flow inside racewayFluent: raceway formation

Validation and VerificationComparison with experimental dataComparison with analytical solution

Close Interactions with Industry

SUMMARY OF ACCOMPLISHMENTS

Developed multiphase PCI CFD Models and In-House codeValidated the multiphase PCI CFD Models and In-House codeSimulated different furnaces for ArcelorMittal, Dofasco, Stelco, and USS casesConducted parametric studies

PART I

LANCE AND TUYERE

LANCE AND TUYEREFluent is used

3-dimensional, TurbulentHeat transferMultiphase flowMultispecies reactionsCoal combustionNatural gas co-injection

Cases studied for ArcelorMittal: Coal devolatization in the lance; Effects of PCI rate, PCI carrier gas flow rate, Oxygen lance flow rate, and blast air temperature, etc.StelcoDofasco

STELCO CASES

Lance DesignParametric Effects:

Natural gas flow ratePCI carrier gas flow rateOxygen enrichment in blastOxygen enrichment through oxygen lance

0.30760.30760.28640.2970.30760.3076Oxygen mass fraction in blast

0.0570.0570.0570.0570.0460.057PCI carrier gas rate (kg/s)

0.03670.04280.07330.0520.01170.0117Mass fraction steam in blast

137212551372137213721372Blast temperature (K)

0.1800.1440.1140.1460.1800.180NG rate (kg/s)

0.3080.3080.3080.3080.3080.308PCI rate (kg/s)

0.07110.10670.10670.10670.10670.1067Lance oxygen rate (kg/s)

3.123.123.123.123.123.12Wind rate

(kg/s)

case5case4case3case2case1base caseParameter

SIMULATION CONDITIONS

RESULTS OF BASE CASE

Mass Fraction CH4 Temperature (K)

Devolatilization Rate (kg/s)

0.050

0.055

0.060

0.065

0.070

0.0711 0.107Oxygen Flow Rate Through Lance (kg/s)

Tota

l Dev

olat

iliza

tion

(kg

EFFECTS OF CARRIER AIR RATEAND OXGEN FLOW RATE

0.050

0.054

0.058

0.062

0.066

0.058 0.046Carrier Air Flow Rate (kg/s)

Tota

l Dev

olat

iliza

tion

(kg

As carrier air mass flow rate is increased, devolatilization rate decreases due to less residence time before entering raceway. As oxygen lance flow rate is increased, devolatilization rate decreases due to oxygen cooling and decreased residence time.

Basecase

Case 1 Case 5

Basecase

EFFECTS OF N.G. FLOWRATE

As natural gas flow rate is increased, devolatilization rate increases due to higher temperatures.As natural gas flow rate is increased, oxygen lance temperature increases.

0.0480.0500.0520.0540.0560.0580.0600.062

0.18 0.15 0.12Methane flow rate (kg/s)

Tota

l Dev

olat

iliza

tion

(kg

Case 2

Case 3

Basecase

1495

1500

1505

1510

1515

1520

0.181 0.147 0.115Methane flow rate (kg/s)

Max

. Lan

ce T

empe

ratu

re

EFFECT OF BLAST AIR TEMPERATURE

0.050

0.055

0.060

0.065

Blast Air Temperature (K)

Tota

l Dev

olat

ilizat

ion

(kg/

s)

1372 K (base) 1255 K (case 4)1500

1502

1504

1506

1508

1510

1512

1514

1516

1518

1520

Blast Air Temperature (K)

Max

imum

Oxy

gen

Lanc

e Te

mpe

ratu

r

1372 K (base) 1255 K (case 4)

As blast air temperature is increased, devolatilization rate and oxygen lance temperature increases due to increased temperatures.

DOFASCO CASESEFFECT OF PRESSURE

Contours of Temperature (K) Contours of Devolatilizaiton (kg/s)

P = 5.813 atm

P = 3.313atm

EFFECT OF PRESSURE

0

500

1000

1500

2000

2500

3000

0 0.1 0.2 0.3 0.4 0.5

Distance from Lance Tip (m)

Tem

pera

ture

(K)

Base CaseP = 5.813 atm

0.00E+00

2.00E-05

4.00E-05

6.00E-05

8.00E-05

1.00E-04

1.20E-04

1.40E-04

0 0.1 0.2 0.3 0.4 0.5

Distance from Lance Tip (m)

Dev

olat

iliza

tion

(kg/

s)

Base CaseP = 5.813 atm

0

0.01

0.02

0.03

0.04

0.05

0.06

Base 5.813 atm

Tota

l Dev

olat

iliza

tion

(kg/

s)

Temperature vs. Distance from Lance Devolatilization vs. Distance from Lance

Total Devolatilization in the Tuyere

As blast pressure is increased, devolatilization rate and residence time increase.

PART II

RACEWAY FORMATION

RACEWAY FORMATION KINETICSFluent is used

3-D transient gas-particle flow simulationsEulerian approachA multi-fluid granular model is used to describe the flow behavior of the fluid-solid mixture.

RACEWAY FORMATIONUS Steel cases

Effects of Tuyere velocity, Tuyere Diameter, Tuyere Depth inside the furnace, Deadman Permeability, and Burden Distribution

ArcelorMittal Steel cases:Effects of coke size, blast velocity, etc.

Stelco cases: Effects of methane flow rate, PCI carrier gas flow rate, Oxygen lance flow rate, and blast air temperature

Dofasco cases:Effects of pressure etc.

RACEWAY FORMATION

Measured Raceway as per Hiroshi Nogami et al

CFD

Validation and Verification

“Raceway design for the Innovative Blast Furnace”, Hiroshi Nogami, Hideyki Yamaoka, Kouji Takayani, ISIJ 2004.

VALIDATION“ Prediction of Raceway size in Blast Furnace from 2D experimental correlations”, S Rajneesh, S Sarkar and G.S Gupta, ISIJ international, Vol 44(2004)Empherical equations used:

0.82 20.25164 g b T

r w Teff p

v DD D

gd HWρ

μρ

−⎛ ⎞

= ⎜ ⎟⎜ ⎟⎝ ⎠

1.2

1.4

1.6

1.8

2

2.2

170 180 190 200 210 220

Velocity, m/s

Rac

eway

Dep

th, m

ExperimentalCFD

1

1.2

1.4

1.6

1.8

2

2.2

0.35 0.45 0.55 0.65

Initial Porosity

ExperimentalCFD

1.1

1.3

1.5

1.7

1.9

2.1

0.02 0.025 0.03 0.035 0.04

Coke Diameter, m

Experimental

CFD

RACEWAY FORMATION DYNAMICSARCELORMITTAL AND USS

3 tuyeres located 9°apart, with a diameter of 0.15m at a downward angle of 6°Parametric Effects: Tuyere velocity, Tuyere Diameter, Tuyere Depth inside the furnace, Deadman Permeability, and Burden Distribution

EFFECT OF BLAST VELOCITY

Raceway is defined as the boundary where the coke volume fraction is equal to the initial porosity near the tuyereV , Raceway size

EFFECT OF TUYERE SIZE

Length , Raceway depth Diameter , Raceway size

EFFECT OF DEADMAN POROSITY AND COKE PARTICLE SIZE

Porosity , Raceway depth Particle size , Raceway size

EFFECT OF BURDEN DISTRIBUTION

DOFASCO CASES

Dimensions are based on BF#4 of Dofasco

PART III

RACEWAY COMBUSTION

Main Features of In-House PCI CFD Code3-dimensionalTurbulentMultiphase flow (gas, pulverized coal, and coke particles)Heat transferMultispecies reactionsCoke combustionCoal combustion Natural gas co-injection

RACEWAY COMBUSTION

CFD ModelEulerian approach

k-ε Turbulence modelCoal moisture evaporation rateCoal devolatilization rateChar combustion rateCoke combustion rateNatural gas combustion rate

RACEWAY COMBUSTION

Pgφφφφφ )()()()()()( SSz

Γzy

Γyx

Γx

wz

vy

ux

++∂∂

∂∂

+∂∂

∂∂

+∂∂

∂∂

=∂∂

+∂∂

+∂∂ φφφφρφρφρ

PgφPφP

φPP

φPP

φPPPPPPPPPP )()()()()()( SSz

Γzy

Γyx

Γx

wz

vy

ux

++∂∂

∂∂

+∂∂

∂∂

+∂∂

∂∂

=∂∂

+∂∂

+∂∂ φφφ

φρφρφρ

RACEWAY COMBUSTIONValidation

00.10.20.30.40.50.60.70.8

0 0.1 0.2 0.3 0.4 0.5 0.6

Distance from the tuyere nose (m)

Mas

s fr

actio

n (-)

N2

CO

O2

CO2

Data from: H. Nogami et al: ISIJ 2004, No.12: 2150

RACEWAY COMBUSTIONValidation

Φ8

Φ12

Φ18 Φ30

Φ34

coal +carrying air primary air secondary air

reactor tube (Ф200mm)

burner

0

5

10

15

20

25

0 0.3 0.6 0.9 1.2 1.5

Distance from burner [m]

O2

[vol

%] Experimental

Predicted

0

4

8

12

16

20

0 0.3 0.6 0.9 1.2 1.5

Distance from burner [m]

CO

2 [v

ol %

]

Experimental

PredictedExperimental Setup (Zhang Y. Wei X L, Zhou L X, Sheng H Z. Simulation of coal combustion by AUSM turbulence –chemistry char combustion model and a full two-fluid mode. Fuel 2005; 84: 1798-1804)

RACEWAY COMBUSTION CASESStelco cases:

Coke, coal, and natural gas combustionEffects of methane flow rate, PCI carrier gas flow rate, Oxygen lance flow rate, and blast air temperature

ArcelorMittal USA cases:Coke combustion onlyEffects of coke size, blast velocity, etc.

Dofasco cases:Coke combustion onlyEffects of pressure etc.

METHODOLOGY OF SIMULATION

Tuyeres

Dripping Zone

Chimney

Coke Bed

Dead man

Liquid level

Cohesive Zones

NG lance

Coal lance

Blowpipe

Tuyere

Oxygen pipe

(a) Simulation of NG+coal inside a tuyere

(b) Obtain the raceway shape and size

(c) Schematic of Race way combustion

0.30760.30760.28640.2970.30760.3076Oxygen mass fraction in

blast

0.0570.0570.0570.0570.0460.057PCI carrier rate (kg/s)

0.03670.04280.07330.0520.01170.0117Mass fraction steam in

blast

137212551372137213721372Blast temperature (K)

0.1800.1440.1140.1460.1800.180NG rate (kg/s)

0.3080.3080.3080.3080.3080.308PCI rate (kg/s)

0.07110.10670.10670.10670.10670.1067Lance oxygen

rate (kg/s)

3.123.123.123.123.123.12Wind rate (kg/s)

case5case4case3case2case1base caseParameter

SIMULATION CONDITIONS AND CASES

INLET CONDITIONS FOR RACEWAY COMBUSTION –base case

Tg Pressure Mean molecular weight

X- velocity Y-velocity Z- velocity

GAS TEMPERATURE AND GAS SPECIES (base case)

Tg

CH4 O2

CO2

EFFECT OF CARRIER AIR RATE

0

0.2

0.4

0.6

N2 0.512715148 0.515384959

co 0.472829876 0.470091232

H2 0.014454976 0.01452381

cokeconsumption(kg/s)

0.467 0.46

base case1

base

case1

0.150.200.250.300.350.400.450.500.550.60

base case2 case3

Mas

s fra

ctio

n

0.012

0.0130.014

0.0150.016

0.017

0.0180.019

0.020

H2

mas

s fra

ctio

n

N2cocoke consumption(kg/s)H2

EFFECT OF NATURAL GASFLOW RATE

Coke consumption rate increases with the decreasing of the NG flow rate;CO and H2 increases with the decreasing of the NG flow rate

0

0.1

0.2

0.3

0.4

0.5

0.6

base case5

Coke consumption rate, kg/sCOH2N2

EFFECT OF OXYGEN LANCE FLOW RATE AND BLAST TEMPERATURE

base case4

0

0.1

0.2

0.3

0.4

0.5

0.6

coke consumption

CO

H2

N2

OUTLET GAS TEMPERATURE

1800

1850

1900

1950

2000

base case1 case2 case3 case4 case5

cases

Tg, K

DOFOSCO CASESP= 3.313 atm P= 5.813 atm

BASE CASE RESULTS

1400

1700

2000

2300

2600

0.0 0.5 1.0 1.5 2.0 2.5

Tem

pera

ture

(K)

0.00

0.10

0.20

0.30

0.40

Mas

s Fr

actio

ns

Tg

O2

Co

CO2

Distance from tuyere inlet central point

ARCELORMITTAL CASES

BASE CASE RESULTS

tg

CO O2

CO2Tg

EFFECT OF BLAST INLET VELOCITY

Vb=156 Nm/s Vb=170 Nm/s Vb=184 Nm/s

EFFECT OF COKE SIZE

Dp=0.04m Dp=0.03m

X [m]

SUMMARYDeveloped and validated the multiphase PCI CFD Models and In-House code

heat transfer, devolatilization and combustion of injected coal before entering racewaysRaceway formationCoal and coke combustion in the racewayNatural gas and coal co-injection

Conducted parametric studies for ArcelorMittal, Dofasco, Stelco, and USS casesResults have been used for understanding and improving PCI process More parametric studies are on-going

AISI/DOE Indiana 21st Century Research and Technology FundIndustrial CollaboratorsPurdue Calumet Research Team Members

ACKNOWLEDGEMENT