One of the main differences in the operative practices between carbon and stainless steels is that in carbon steels, large quantities of oxygen and carbon are injected toward the end of the batch with the target of creating a foamy slag layer on the top of the liquid metal which can be sufficiently deep to cover the electric arc. It can be said that stainless steels tend to be produced with more scrap than carbon steel. Furthermore, the operational practices to produce a batch of steel also vary considerably from meltshop to meltshop and are strongly dependent on whether carbon steel or stainless steel is produced. This is because industrial gases and DRI are cheaper than electricity and scrap. EAFs in countries with high electricity and scrap costs tend to use more chemical energy and to use more direct reduced iron (DRI) as raw material. Some of the most influential factors in the operations are the costs of the raw materials and of electric power. The way in which steel is produced in EAFs depends on the geographical location and the type of steel produced. First, to create oxy-fuel flames with temperatures over 3,000 K that aid the melting of the solid scrap and second, to inject oxygen in the liquid metal pool, promoting its decarbonization. On the other hand, natural gas burners and oxygen lances are used for two purposes. On the one hand, the electric energy is used to generate plasma jets that can reach temperatures of up to 17,500 K. The latent and sensible heat that is required for the phase transition of the metal is mainly provided by electric energy and supported by chemical energy. A modern EAF can be viewed as a batch reactor in which metal scrap is melted, and its composition is partially or completely refined. Although the technology has a history of over 100 years, a full understanding of the process has not yet been accomplished, and industrial operations still rely strongly on empirical models and on the experience of the operating crews. Steel production via electric arc furnaces (EAFs) is a very energy-intensive process that accounts for almost 25 pct of the total crude steel production worldwide. Based on the model, time-dependent energy efficiency curves for the various contributions and for the overall process are computed and discussed.Ĭarbon Steel vs Stainless Steelmaking Processes In comparison with existing EAF models, the model presented here describes the dynamic behavior of the melting process more realistically. The model contains the melting rates and the efficiency of the oxygen lancing as free parameters their values were computed by a least squares fit to process data of an industrial Ultra-High-Power EAF. (d) The energy exchange from the bath to the solid phase due to splashing is modeled using relationships and experimental data that are available in the literature. (c) The amount of heat released by the oxidation of solid metal is described by the quadratic corrosion formula. (b) The energy input from the oxy-fuel burner is modeled using simplified geometries for which heat transfer relationships are known. The different mechanisms of heat exchange are represented in the model as follows: (a) the radiative heat exchange from the arc to the other phases is computed using the DC circuit analogy, where the view factors are calculated using exact formulae and Monte-Carlo algorithms. The energy exchange between the liquid and the solid phase due to liquid metal splashing is also considered. It assumes that the energy demand of the process is satisfied by six sources, the electric arc, the oxy-fuel burners, the oxygen lances, the combustion of coal, and the oxidation of metal in the liquid and in the solid phase. The model is suited for process simulation, optimization, and control applications. This paper presents a comprehensive model of an industrial electric arc furnace (EAF) that is based upon several rigorous first-principles submodels of the heat exchange in the EAF and practical experience from an industrial melt shop.
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