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Modeling Coal-Particle Modeling Coal-Particle

Fragmentation inside a Moving

Bed Gasifier

Dipl.-Ing. Franz Holzleithner

Flow Sheet:

Introduction: COREX ®-Process

Melter-Gasifier:

2Dipl.-Ing. Franz Holzleithner

Motviation:

Particle Size Distribution (PSD) effects:

• Flow of Gas, Liquid Metal and Slag

• Heat Transfer

• Drying

• Pyrolysis

Introduction: Motivation & Objectives

• Gasification

Objectives of the Research-Project:

• Evolution of PSD

• Heat Transfer

• Drying

• Pyrolysis

• Gasification

• Gas-Phase-Reactions

within the modelling domain 3Dipl.-Ing. Franz Holzleithner

For

each

carb

onca

rrie

r

For

each

size

clas

s

Model-Outline

Models for Coal Conversion:

Drying: Single first order reaction, onset of evaporationdependent on water-vapour saturation pressure.

Devolatilization: Volatiles composition: determined by elemental balances(C,H,O,N,S) and closing relations.

Drying:H2O

Devolatilization:CH4, CO, CO2, H2O, H2, Tar, …

(C,H,O,N,S) and closing relations.Kinetics of volatiles release: system of parallel singlefirst order reactions.

Gasification: Shrinking particle behaviour, O2, H2O, CO2

Particle Energy Balance: Heat transfer, heats of reaction

Gasification:

O2, H2O, CO2

CO, CO2, H2, Ash

Model-Outline

Coal Particle Fragmentation:

Five process variables are driving forces:

• Shear stress

• Solids pressure

• Rate of drying

• Rate of devolatilization

Fragmentation-Breakage :

Fragmentation-Attrition:

5Dipl.-Ing. Franz Holzleithner 5Dipl.-Ing. Franz Holzleithner

• Rate of devolatilization

• Rate of gasification

Gasification-Diameter Reduction:

Model-Outline

Coal Particle Fragmentation:

Species-Balance Size Class j:

MassjonGasificati

MassjPyrolysis

MassjDrying

Massjreaction SSSS ,,,,

ɺɺɺɺ ++=

1,,.,. −+ jjBreakagejredDiam MM ɺɺ

Size Classes (SC):

MassjreactionjBreakagejredDiamjredDiam

j SMMMdt

dM,,1.,..,.

ɺɺɺɺ +++−= +

kijb ,

kiSkiK

…Breakage-Matrix, Process k, SC=i,j

…Frequencyfactor, Process k, SC=i

…Process Quantity, Prozess k, SC=i

6Dipl.-Ing. Franz Holzleithner 6Dipl.-Ing. Franz Holzleithner

Energy-Balance Size Class j:

j-1Mj-1

0M0

……… j+1Mj+1

………jMj

NMN

0,, jBreakageMɺ

∑

∑=

= =

SC

i k

ki

ki

kijijBreakage KSbMM

0

5

0,,

ɺ

NjBreakageM ,,ɺ

Enthalpyjreaction

EnthalpyjerHeatTransfjBreakagejjredDiamjjredDiam

j SSHhNhNdt

dH,,,11....

ɺɺɺɺɺ ++++−= ++

Get Data

Heat Transfer

Drying

Devolatilization

Computational Approach 1 Lagrange-Solid:

Output:

Continuum-Solid:

PorosityMass-BalanceMomentum-Balance Time Integration

Solver: CVODE

Loop overSize-Classes

Loop over Carbon Carriers(Iron Carriers analogously)

Gasification

Fragmentation

Send Data

7Dipl.-Ing. Franz Holzleithner 7Dipl.-Ing. Franz Holzleithner

Output:PSD,Sourceterms:Mass,Species,Energy

Continuum-Gas:

Mass-BalanceSpecies-BalanceMomentum-BalanceEnergy-BalanceGasphasereactions

[1] Committee on Reaction within Blast Furnace, Joint Society on Iron and Steel Basic Research, The Iron and Steel Institute of Japan

Blast Furnace Phenomena and Modelling. Elsevier Applied Science, 1987.

Model-Outline

Parameter Estimation for Coal Conversion Submodels:

Necessary since parameters are heaviliy

dependent on coal/coke type

Drying, Pyrolysis, Gasification:

Experiments have been performed

by IEHK-RWTH Aachen.

Coal Particle Fragmentation:

Experiments have been performed by ARP/ECV GESMBH (Leoben)

First Simulations-Boundary Conditions

Geometry and Boundary Conditions:Solid-Inlet:

3 Carbon Carriers (1 Coke, 2 Coals)

1 Iron Carrier + Additives

4 Size Classes (1mm-5mm-16mm-31.5mm), homogeneous mixture

Inlet-Temperatures: 25°C and 800°C

Mass flow rate-Outlet: acc. to CO Massflow Rate

Solid-Inlet

99

Mass flow rate-Outlet: acc. to CO Massflow Rate

Gas Inlet:

Massflow Rate: 50 kg/s,100% CO

Temperature: 3000 °C

Considered Processes:

• Heating

• Drying

• Pyrolysis

• Particle fragmentation

• Homogeneous reactions (Water-Gas-Shift-Reaction, Methane and Tar decomposition)

• Heating of prereduced Iron Carrier + Additives (solid and inert)

Gas-Inlet

First Results

Volume Fraction of Gas [-]: Sauter‘s Diameter-Carbo n Carriers [m]:

with Particle Fragmentation

Important for flow of liquid metal and slag.

10Dipl.-Ing. Franz Holzleithner

Particle Size Distribution-Volumefraction of Size Clas ses [-]:

(Averaged over all charged Carbon Carriers)

1 mm 5 mm 16 mm 31.5 mm

First Results

Mean Coal Temperature [°C]:

(Averaged over Coals and Particle Sizeclasses)

w/o Particle Fragmentation: with Particle Fragmentati on:

Coal Gas Coal Gas

11Dipl.-Ing. Franz Holzleithner

First Results

Coal - Particle Temperature [°C]:

Coal 1:1 mm 5 mm 16 mm 31.5 mm

with Particle Fragmentation

Coal Gas Coal Gas Coal Gas Coal Gas

12Dipl.-Ing. Franz Holzleithner

Coal 2:

1 mm 5 mm 16 mm 31.5 mm

Coal Gas Coal Gas Coal Gas Coal Gas

Status and Outlook

Completed:

• Models (3D-domain):

Fragmentation, Heat Transfer, Drying, Pyrolysis, Gas ification (O 2,H2O,CO2),

Homogeneous Reactions

• Validation of Single Particle Model (TGA-Measurement s)

• Validation of Fragmentation Model (Drying and Pyrolys is)

13Dipl.-Ing. Franz Holzleithner

Outlook (Follow-Up-Project 07.2012-07.2015):

• Inclusion of solids charging

• Inclusion of an existing solids flow model

• Inclusion of models for iron ore-particles (final reducti on and melting)

• Inclusion of models for calcination of additives

• Inclusion of models for flow of liquid iron and slag

• Inclusion of raceway

• Simulation of 3D-Slowly Moving Fixed Bed of an existing COREX®-MG

The research program of the Competence Center for Excellent Technologies in “Advanced Metallurgical and Environmental Process Development” (K1-MET) has been financially supported within the Austrian competence centreprogramme COMET (Competence Center for Excellent Technologies) by the Federal Ministry of Economy, Family and Youth; by the Federal Ministry for Transport, Innovation and Technology; by the provinces of Upper Austria, Styria and Tyrol, by the Styrian Business Promotion Agency and by the Tiroler Zukunftsstiftung.

grant-aided by

Acknowledgment

grant-aided by

14Dipl.-Ing. Franz Holzleithner