Ischia, 24-27 June 2007

ANALYSIS OF MULTIPHASE REACTING

TURBULENT JETS: CASE STUDY ON CARBON

INJECTION IN SIDERURGIC FURNACES

1Centro Interdipartimentale di Fluidodinamica e Idraulica &

2Dipartimento di Energetica e Macchine, Università di Udine

3Dip. Ingegneria Chimica, Chimica Industriale e Scienza dei Materiali, Universitò di Pisa

M. Campolo1, M. Andreoli1, L. Tognotti3, A. Soldati1,2

IcheaP-8

The eight International Conference on Chemical & Process Engineering

A successful story?

Targets of injection & Industrial challenge…

1. Heating Scrap (oxy-methane lance)

2. Feeding consumables to control slag/bath composition (carbon injection system)

Why not a multipurpose injector?

Innovative design of multipurpose injector

Features:

1. Coherent supersonic annular oxygen stream

2. Sonic methane stream

3. Inner (low velocity) particle laden flow

Research Objectives

1. Virtual testing of injector performaces

carbon injection yield

2. Identification of rules for field installations

maximum injector distance from bath

carbon characteristics (size, quality)

3. Identification of guidelines for performance optimization

mechanisms controlling performances

Modelling challenges…

Supersonic flow O2

Sonic flow CH4

Combustion CH4 /O2

Transport of C particles

Radiative/Reactive environment

C Oxydation & Devolatilization

… and modelling tools

Finite volume solver Navier-Stokes equations

1. Flow field characterization

2. Basic characterization of chemico-thermal environment

Lagrangian tracking

1. characterization of chemico-thermal environment seen by carbon particles

Reactor Network Analysis

1. Precise modeling of oxidation/devolatilization

2. Evaluation of injection performances

Numerical details -1

oFlow solver: StarCD (FV)

oBoundary conditions:

•fixed mass flow rate (O2, CH4, Air, Air extraction)

•temperature & emissivity profiles (electrodes, slag & wall)

oTurbulence model:

Modified k-ε (+ compressibility effect - Sarkar et al. 1991)

oCombustion model:

CH4+1.5 O2 CO+2H2O

CO+0.5 O2 CO2

Numerical details -2

oLagrangian tracking

•One way coupling, drag + inertia forces

•Non spherical shape (Crowe, 1998)

•Eddy interaction model (Gosmann & Ioannides, 1983, Graham, 1998)

oReactor Network Analysis:

•Gas phase reaction (Ranzi et al.,2001, Falcitelli et al., 2002)

•Heterogeneous reaction

Char oxidation

Char devolatilization

Flow field

Temperature field

Lagrangian tracking: radial dispersion

Traditional configuration

Innovative configuration

Particle thermo-chemical history

Most critical conditions for RNA

Results from RNA

Most critical conditions for RNA

0.09%

0.11%

0.02%0.03%

Very high injection efficiency is obtained

• for large injection distances (L2=1300 mm from slag)

• For all commercial types of carbon

Industrial results: field tests(Duferco La Luvriere S.A.)

Quality/metallurgical results

Traditional Injector

Hi-jet injector

Production yield

92% 94% LargerProductivity

Ferrum content in slag

28% 22% LowerWaste

Metallic charge composition

86% scrap, 14% pig iron

96% scrap, 4% pig iron

LowerRaw Material

Costs

Yes!