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Hot Metal Desulfurization by CaO-Mg Co-Injection in Usiminas Steel Shop 2

Jose Flavio Viana Metallurgical Engineer Usiminas BR381KM21O CEP 35160-900 Ipatinga-MG-Brazil tel: 55-31-829-2657 fax: 55-31-829-3429 Sergio Luiz de Souza Costa Metallurgical Engineer, DSC. Usiminas BR381 KM21O CEP 35160-900 Ipatinga-MG-Brazil tel: 55-31-829-3020 fax: 55-31-829-3429 Alessandro Prenazzi Metallurgical Engineer Usirninas BR381 KM21O CEP 35160-900 Ipatinga-MG-Brazil tel: 55-31-829-3308 Douglas C. Lee Vice President-Technology ESM II Inc. 300 Corporate Parkway-216 N Amherst, New York 14226-1207 tel: 716-446-8810 fax: 716-446-8868 Key words: hot metal, Mg, desulfirization, thermodynamics lime,

INTRODUCTION

The use of Mg as a desulfi.u-izing agent of hot metal is not new. During the sixties, Mg in the form of mag-coke was used in various plants in the world. Deep injection of Mg in the hot metal transfer ladle is widely practiced throughout the world and continues to be adopted by integrated steel plants. There are four different types of Mg injection presently in use; lime/ Mg co-injectioq [email protected] co-injection and sequence injection, lime/Mg and [email protected] blend injection and monoinjection of Mg reagents. The co-injection processes with lime and CaCz have proved superior for modern BOF shops due to the minimization of transport gas required with high addition rates of Mg reagents which reduces hot metal turbulence. The high production rates of modern BOF Shops are striving for 60 to 75 heats per day and greater thus the transfer ladle desulfimization process needs to have maximum injection treatment times less than 10 minutes even for high hot metal S analysis. The other reason that the lime or CaCz co-injection process is technically superior to the monoinjection blend products is that the Mg reagent addition is accurately measured by the injection process equipment which is not possible in the blend products; thus, predictability of the blend process is generally unsatisfactory for most applications. The lime/Mg co-injection process is the topic of study for this paper. Theoretical Aspects of the Process Table I shows the calculated Q content in equilibrium with the elements present in the hot metal. The hot metal, before the desulfimizing treatment, arrives at the station with a theoretical average content of 56 ppm of Q, which is determined by the silicon content, since this is the stronger deoxidizer.

1999

STEELMAKINGCONFERENCE PROCEEDINGS

361

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HOT METAL DESULFURIZATION BY CAO-MG CO-INJECTION IN USIMINAS STEEL SHOP 2

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