Steel scrap is of great benefit for environmental protection. In converter steelmaking, bottom carbon injection was applied to enhance the scrap ratio and in EAF steelmaking, submerged carbon powder injection was used to accelerate the smelting of scrap. In these two cases, carbon powder is directly injected into molten metal to improve the scrap melting with effective carburization capacity and intense stirring effect. In this study, the induction furnace experiments were carried out to study the melting characteristics of steel scrap with different carbon contents and bottom-blowing gas flow rates. The results show that larger carbon content and faster fluid flow can promote scrap melting because the carburizing reaction can be accelerated by larger carbon concentration gradient and the heat transfer can be enhanced by larger stirring intensity. Finally, the convective mass transfer coefficient and heat transfer coefficient between steel bar and molten metal were also calculated.
As an efficient oxygen supplying technology, coherent jets are widely applied in electric arc furnace (EAF) steelmaking processes to strengthen chemical energy input, speed up smelting rhythm and promote the uniformity of molten bath temperature and compositions. Recently, the supersonic coherent jets with CO 2 and O 2 mixed injection (COMI) was proposed and through industrial experiments, it can be found that the supersonic coherent jets with COMI showed remarkable advantages in reducing the dust production during EAF steelmaking. In this study, based on the eddy dissipation concept (EDC) model with the detailed chemical kinetic mechanisms (GRI-Mech 3.0), a computational fluid dynamics (CFD) model of supersonic coherent jets with COMI was built. Compared with one-step combustion reaction, GRI-Mech 3.0 consists of 325 elementary reactions with 53 components and can predict more accurate results. The numerical simulation results were validated by the combustion experiment data. The jet behavior and the fluid flow characteristics of supersonic coherent jets with COMI at steelmaking temperature 1 700 K was studied and the results show that the chemical effect of CO 2 significantly weakens the shrouding combustion reactions of CH 4 and the relative importance of the chemical effect of CO 2 increases with CO 2 concentration increasing. The potential core length of supersonic coherent jets decreases with the volume fraction of CO 2 increasing. Moreover, it also can be found that the potential core length of supersonic coherent jets can be prolonged with higher ambient temperature.
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