Flat Bath Research Articles

NUMERICAL SIMULATION OF ENERGY-EFFICIENT SOLUTIONS OF THE ARC FURNACE STEEL MELTING BATH

Numerical modeling of hydrodynamics and heat and mass transfer in the arc furnace (EAF) steel melting bath under pneumatic stirring conditions demonstrates that the introduction of a «deep» bath with a form factor (ratio of diameter to depth) of 2.5 against the traditional 5.0 provides an energy-efficient bubbling mode of purging at higher inert gas flowrate. An increase in the diameter of the porous plug and the volume of the two-phase region in the "deep" bath allows in 150-ton EAF to increase the mixing power and the coefficient of convective heat transfer in liquid steel by 2-2.2 and 1.4 times on average, respectively. In the context of the «flat bath» process, it is shown the possibility of intensifying the convective melting of scrap in the bath by 24% in average and, thus, increasing productivity and, accordingly, improving the energy efficiency of the EAF.

Page curve and island in EGB gravity

In this paper, the information paradox on lower-dimensional Gauss–Bonnet gravity, known as a three-dimensional EGB black hole, is studied using the quantum extremal island approach. For that, we connect an auxiliary flat bath system to this timelike singularity spacetime and estimate the entropy of hawking radiation in its asymptotic regions when gravity is weak. The addition of island areas to the entanglement wedge of radiation causes its entropy to obey the Page curve, as shown. The quantum extremal surface, or island boundary, is outside the horizon. This yields a time-independent equation for Hawking radiation fine-grained entropy compatible with the appropriate Page curve. We also discover the modifications to this entropy and Page time.

Islands in Kerr–de Sitter spacetime and their flat limit

We use quantum extremal island method to study the information paradox on certain cosmological setups known as three dimensional Kerr-de Sitter spacetimes. To do so, we couple an auxiliary flat bath system to this spacetime in timelike singularity and measure entropy of hawking radiation in its asymptotic regions where the gravity is weak. We show that adding island regions to the entanglement wedge of radiation causes its entropy to obey Page curve. The boundary of island i.e. quantum extremal surface is located outside the cosmological horizon in the region connected directly to the bath. Taking the flat-space limit from the location of island and its related calculation in the Kerr-de Sitter sapcetime results in the flat-space cosmology (FSC) island, scrambling time and also Page time that were obtained in our previous paper. We repeat the same calculation for the pure de Sitter spacetime and show that our setup which neglects the effect of backreaction, leads also to a quantum extremal surface outside the cosmological horizon. We calculate the scrambling time and confirm the idea that pure de Sitter spacetime is a fast scrambler.

Islands in flat-space cosmology

Flat-space cosmologies (FSC) are solutions to three dimensional theories of gravity without cosmological constant that have cosmological horizons. A detector located near the time-like singularity of the spacetime can absorb Hawking modes that are created near the horizon. Continuation of this process will eventually cause the entropy of the radiation to be larger than the entropy of the FSC, which leads to the information paradox. In this paper, we resolve this paradox for the FSC using the island proposal. To do this, we couple an auxiliary flat bath system to this spacetime in timelike singularity so that Hawking modes are allowed to enter the bath and the entropy of radiation can be measured in its asymptotic region where gravity is also weak. We show that adding island regions that receive the partners of Hawking modes cause the entropy of radiation to follow a Page curve which leads to resolving the information paradox. Moreover, we design a quantum teleportation protocol by which one can extract the information residing in islands.

Energy efficient solutions of DC Electric Arc Furnace Bottom Electrode

Analysis of recent research and publications. The problems of thermal state of billet-type bottom electrode (BE) in liquid bath of DC electric arc furnace (EAF) are associated with limited thermal conductivity of the rod in the absence of available alternative to copper-steel pair. There isn’t enough data on values of convective and Joule components of heat flux, passing through BE, initiated by electrovortex flows (EVF); regarding influence of thermophysical characteristics of transition copper-steel zone and cooling rate of BE copper part on the position of phase transition surface of steel part. Problems are considered, especially related to innovative “flat bath” steelmaking technologies, in which the possibilities of dead time pauses for periodic renewal of the BE body due to “EVF-off” are significantly limited.Purpose. To investigate the effect of EVT on the thermal state of bottom electrode and to develop on this base the energy efficient BE solutions.Methodology. Numerical simulations of BE thermal state and an industrial testing of essentials. Findings & Originality. For the first time, the joint effect of EVF, Joule heat, and characteristics of BE transition zone copper – steel on the position and equilibrium thickness of solid steel part of the BE, which determines the energy efficiency of DC EAF operation, was comprehensively studied.Research implications. Numerical simulations of EVF in DC EAF steelmaking bath and heat transfer with a phase transition through BE were carried out. The heat flux density and local EVF velocity in anode well are 1.8–2 MW/m2 and 0.75 m/s, respectively. Equilibrium thickness of solid steel BE part is critically dependent on the width of copper-steel transition zone, should not exceed 20-25 mm. Contribution of Joule component of total thermal load on the BE does not exceed 20%. Intensification of cooling rate above ≥ 20 kW/(m2K) practically doesn’t affect the BE solid steel part thickness.Practical implications. Manufacturing technology of BE with a narrow transition zone by the method of two-stage electro-slag welding of copper on a steel billet, which ensures stable DC EAF operation and increases energy efficiency, has been improved.

Modern electroslag technologies of electrode remelting and processing of liquid metal (review)

Objective. The results of the analysis of advanced technologies of electroslag remelting are presented. Results It is shown that ESR today is the main and most challenging in obtaining of high quality metal. Protection of the melting chamber and the electrode from the atmosphere by inert gas (IESR) or melting under pressure (PESR) prevents oxidation, which is especially important during remelting of the steels and alloys with high content of easily oxidizable elements. Refusal to use a consumable electrode in the classical ESR in favor of liquid metal, provided by the use of current-suppling mold, is an effective solution to the problem of its manufacture (manufacturing price reaches 40-60% of the cost of ingot production, and in some cases impossible) and reduce energy costs. Scientific novelty. During ESR LM, there is a decrease in temperature of slag and overheating of metal in comparison with classical ESR , the volume of liquid metal bath decreases that followed by improving conditions of ingot formation, at the expense of decrease in development of segregation processes and gives the chance to receive metal of homogeneous composition and structure. Practical significance. The advantages of the new ESR processes are a wide variation of the metal feed rate, less metal overheating and a flat bath, which provides molding with a homogeneous and defect-free internal structure and a smooth surface.

Computational Fluid Dynamics Simulations for Understanding and Optimizing the AOD Converter

Computational fluid dynamics (CFD) has constantly evolved in the last decades and nowadays play an important role in the design and development of modern steelmaking converters. Although the flow inside the converter is highly complex and comprises many physical phenomena, like chemical reactions, heat transfer, and the flow of gas bubbles in the liquid melt, it is possible to capture major effects for the design of new converters with modern simulation tools. It is well known that the decarburization reaction is strongly influenced by the partial pressure of CO. To ensure a low partial pressure of CO, a flat bath design with low bath height shows advantages. On the other hand, the bath height needs to be sufficient to ensure enough time for the reactions of the rising gas plume with liquid melt as well as proper mixing. Primetals Technologies has used extensive numerical simulations to compare various bath geometries for a 120 t AOD to improve bath mixing and the interaction between slag and steel phase. As a result, an optimized flat bath geometry could be found, which was an intermediate configuration between deep bath and flat bath design that ensures both high mixing efficiency for the reduction phase and low partial pressure for the decarburization phase. In this paper the most important aspects of numerical modelling of the flow and mixing inside an AOD converter are described, followed by a detailed comparison of different vessel geometries and presentation of an optimized version.

Theoretical Estimation of Peak Arc Power to Increase Energy Efficiency in Electric Arc Furnaces

This research work introduces the concept of “useful arc power” and the thermal model, first introduced by Dittmer and Krüger, to establish the arc length at any stage of the heat in Alternate Current Electric Arc Furnaces (AC-EAF), based on the estimation of the fraction of the energy transferred to the metallic load by radiation. Radiation is the most effective way to transfer heat in an arc furnace in presence of metallic scrap (bore-in and early meltdown). On the other hand, if the arc is not adequately covered with slag, radiation is extremely dangerous to the furnace integrity. When the furnace is fully loaded, scrap protects the walls and cooling panels and then arc radiation must be maximized. To increase energy efficiency, and at the same time reduce circuit power losses, the arc length should be controlled. However, arc instability prevents to increase radiation, as desired, and a compromise must be reached between arc length and arc stability. In this work AC-EAF electric circuit is modeled and analyzed under different heat stages. Electrodes, anode and cathode, fall regions can be considered as energy losses and their associated power may be deducted for the estimation of the “useful arc power” and for the definition of the operational currents in the heat process, particularly during flat bath conditions (late meltdown and refining). As a result of the present study it is proved that current setpoints play an important role for energy saving at any stage of the heat. Finally, experimental results obtained from an industrial steel factory validate this approach to optimize the electrical energy consumption per ton of liquid steel in AC-EAF.

Dip coating with an interaction potential normal to the substrate

Dip coating in the presence of a substrate-liquid interaction potential normal to the substrate, previously theoretically investigated by R. Krechetnikov and G. M. Homsy [Phys. Fluids 17, 038101 (2005)], was revisited. Their solution procedure leads to predictions of the entrained film thickness $h_\infty ^*$h∞* that deviate substantially from the classical Landau-Levich law because of the impossibility to identify meniscus solutions satisfying the proper boundary conditions of zero thickness and zero apparent contact angle on the solid substrate (L-L BC’s). In contrast, in the present analysis, by choosing a different method of integration and requiring the satisfaction of the boundary condition of flat bath for large, but finite, meniscus thickness, we obtain solutions subject to L-L BC's for the same parameter range studied in Krechetnikov and Homsy's paper. Thus, the matching follows a modified Landau-Levich law, where $h_\infty ^*$h∞* is inversely proportional to the meniscus curvature at the substrate. Since the interaction potential changes considerably this curvature, the entrained film significantly thickens for attractive interactions or thins for repulsive ones. Similar results are also found for a potential of the Debye-Hückel form.

Application of a dynamic metallurgical model to the electric arc furnace

CRM has developed a dynamic model of the EAF. Combined with a complete acquisition of process parameters and of events occurring during a heat, the model continuously assesses the mass and thermal balances; it simulates the scrap movement inside the furnace during melting down as well as the foaming slag. It is in daily use at Carsid-Marcinelle since two years. Its second application is at the furnace of ProfilArbed at Esch-Belval. The model allows to determine the optimum time for the charging of the second scrap basket, to control the heating during the flat bath phase and to predict the end point of the melting. The model is also an efficient tool for the optimization of the electric furnace.

Effect of oxyfuel burner ratio changes on energy efficiency in electric arc furnace at Co-Steel Lasco

Trials were conducted on Co-Steel Lasco's electric arc furnace (EAF) to evaluate the effect of oxyfuel burner ratio changes on furnace energy efficiency and productivity. Carefully controlled trials with the collection of numerous process and sample data over 331 heats provided statistically significant results. The oxygen available for post-combustion in the furnace was increased by 19%. As the burners were operating at their maximum oxygen constraint, this was achieved by decreasing the natural gas consumption by 43%. Results of this study indicate that decreases in terms of specific electrical energy consumption (4·0%), power on time (5·0%), and tap to tap time (4·5%) were realised. Slag chemistry, electrode consumption, and yield were not affected. Measurement data support the finding that more heat was transferred into the steel with the post-combustion burners: a flat bath was achieved earlier; high bath temperatures were reached more quickly; power on time was reduced, leading to reduced electrical energy consumption. Analysis suggests that furnace thermal energy losses were reduced by less air inleakage, less incomplete methane combustion, and earlier achievement of foamy slag conditions.