NUMERICAL MODELING OF ENERGY EFFICIENT SOLUTIONS OF CARBON REMOVAL AND SLAG MODE IN ELECTRIC ARC FURNACE

Abstract

In the framework of modern two-stage liquid steel production, electric arc furnace (EAF) is a unit for intensive smelting of intermediate product, with subsequent finishing to specified steel grade by methods of the ladle metallurgy. The EAF technological regulations provide for obtaining a low-carbon melt in the energy-saving mode of slag foamed with gas bubbles. Reduction of the shape factor of steel melting bath (diameter to depth ratio) with an unchanged liquid steel capacity is aimed at increasing the energy efficiency of the EAF due to reduction of heat losses by radiation of the melt surface on the working space water-cooled panels. The transition to a “deep” bath also contributes to the intensification of heat and mass exchange processes under the conditions of forced mixing of the melt, in particular, purging with inert gas. The effect of a “deep” bath on the process of carbon removal on argon and CO bubbles and formation of foamed slag during intensive technology, from the standpoint of the EAF energy efficiency, a numerical study was carried out. The single bubble model and known empirical relations for mass transfer coefficients of reactants under the conditions of diffusion stoichiometry are used. For industrial 120- tons EAF it is shown that reducing the bath shape factor to the optimum, according to the energy efficiency criterion, leads to an increase in the rate of metal decarburization by 5–18% due to the intensification of the mass transfer processes of reagents in the system of iron-carbon melt-floating gas bubble. On the base of known experimental data, under conditions of optimal surface tension and viscosity of the slag, a regression equation was obtained for the height of stable slag foam on process gas flow rate through metal-slag interface. Using a numerical model of radiation heat transfer, is shown that a “deep" bath factor, in this context, contributes to the reduction of radiation heat losses with water by 4% due to more effective shielding of electric arc radiation on water-cooled EAF panels with foamed slag.