Ischia, June 2007 ANALYSIS OF MULTIPHASE REACTING TURBULENT JETS: CASE STUDY ON CARBON INJECTION IN SIDERURGIC FURNACES 1 Centro Interdipartimentale di Fluidodinamica e Idraulica & 2 Dipartimento di Energetica e Macchine, Università di Udine 3 Dip. Ingegneria Chimica, Chimica Industriale e Scienza dei Materiali, Universitò di Pisa M. Campolo 1, M. Andreoli 1, L. Tognotti 3, A. Soldati 1,2 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 O 2 Sonic flow CH 4 Combustion CH 4 /O 2 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 (O 2, CH 4, Air, Air extraction) temperature & emissivity profiles (electrodes, slag & wall) oTurbulence model: Modified k-ε (+ compressibility effect - Sarkar et al. 1991) oCombustion model: CH O 2  CO+2H 2 O CO+0.5 O 2  CO 2

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

Lagrangian tracking: radial dispersion RR-A RR-B 250 mm 750 mm 1250 mm Radial position Particles are focused by the supersonic jet

Lagrangian tracking: radial dispersion RR-A RR-B 250 mm 750 mm 1250 mm Axial velocity Small particles are accellerated more by the supersonic jet and spend less time into the furnace Travel time distribution RR-A RR-B

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%Larger Productivity Ferrum content in slag 28%22%Lower Waste Metallic charge composition 86% scrap, 14% pig iron 96% scrap, 4% pig iron Lower Raw Material Costs

Yes!