Bottom Blown Process Research Articles

Numerical simulation of continuous bubbles motion behavior with different lance spacings

The lance is a critical component of the bottom-blowing pool melting process, and its placement has an important impact on the pool?s gas-liquid two-phase flow. In this study, a mathematical model of the bottom-blowing process is established, and the flow pattern, trajectory, wake vortex, and velocity of bubbles under four lance spacings are simulated. Results show that there are three basic bubble flow patterns appear in the flow field: bubbles coalesce before leaving the nozzle (Pattern ?), bubbles coalesce after leaving the nozzle (Pattern ?), and no coalescence during the rise of bubbles (Pattern III). The bubble pattern varies from Pattern I to Pattern III with the increase in lance spacing. The intensity of the influence of the wake vortex on the bubbles decreases. The Q (the Q is the second Galilean invariant of the velocity gradient tensor ?v) value of the wake vortex is small, but the vortex structural distribution is complex. Moreover, there is a large velocity difference between gas and liquid at the beginning of gas injection, but the velocity difference between them decreases after gas injection, so the average turbulent kinetic energy in the pool initially increases sharply, and then approaches dynamic equilibrium. The top and bottom velocities of the bubbles are consistent, and the velocity fluctuation is orderly. Moreover, the greater the lance spacing is, the greater the disturbance in the pool is. The mixing effect of D = 0.2 m is the best among the four spacings.

Numerical Simulation of Bottom-Blowing Stirring in Different Smelting Stages of Electric Arc Furnace Steelmaking

Electric arc furnace (EAF) steel bottom-blowing can effectively improve the temperature and composition uniformity of the molten pool during smelting process. To explore the effect of molten-steel characteristics on bottom-blowing at various stages of smelting, we divided the smelting process of the EAF into four stages: the melting stage, the early decarburization stage, the intermediate smelting stage, and the ending smelting stage. The numerical simulation software ANSYS Fluent 18.2 was used to simulate the velocity field of molten steel under the condition of bottom-blowing stirring in different stages in EAF steelmaking process. The properties of bottom-blowing and the kinetic conditions of the steel-slag at this interface were investigated. Our results showed that at a bottom-blowing gas flow rate of 100 L/min, the average flow rates of the four stages were v1 = 0.0081 m/s, v2 = 0.0069 m/s, v3 = 0.0063 m/s, and v4 = 0.0053 m/s. The physical model verification confirmed the results, that is, the viscosity of molten steel decreased as the smelting progressed, and the flow velocity of the molten steel caused by the agitation of bottom-blowing also decreased, the effect of bottom-blowing decreased. Based on these results, a theoretical basis was provided for the development of the bottom-blowing process.

Physical simulation of bubble refinement in bottom blowing process with mechanical agitation

In order to increase the contact area and promote the mass transfer process of gas and liquid, the process of the bubble refinement in a metallurgical reactor with mechanical agitation was studied by physical simulation. Based on the capillary number, a prediction equation for the bubble refinement was established. The effects of the gas flow rate, the stirring speed and the stirring depth on the bubble refinement in the reactor were discussed in detail. The distribution of the bubble diameter in the reactor was obtained under different conditions. The results show that when the stirring speed reaches 300 r/min, the bubble diameter mainly distributes in the range of 1–2 mm. A higher gas flow rate may increase the number of bubbles in the melt and promote the bubble refinement process. The mechanism of bubble refinement under mechanical agitation was analyzed, and the results indicated that the stirring speed, the blade area and the blade inclination are the main influencing factors.

Cold model on bubble growth and detachment in bottom blowing process

Abstract The bubble growth and detachment behavior in the bottom blowing process were investigated. Four multi-hole nozzle configurations with different opening ratios were assessed experimentally using high-speed photography and digital image processing. For these configurations, the experiments reveal that the bubble growth consists of a petal-like stage, an expansion stage and a detachment stage. The petal-like shape is qualitatively described through the captured images, while the non-spherical bubbles are analyzed by the aspect ratio. The bubble size at the detachment is quantified by the maximum caliper distance and the bubble equivalent diameter. Considering the dependence on the opening ratio, different prediction models for the ratio of maximum caliper distance to hydraulic diameter of the nozzle outlet and the dimensionless bubble diameter are established. The comparative analysis results show that the proposed prediction model can accurately predict the bubble detachment size under the condition of multi-hole nozzles.

Mixing Behaviors in the Horizontal Bath Smelting Furnaces

In the copper smelting process, sulfides are oxidized by the injected oxygen in the liquid bath. The reaction rate is predominantly determined by the stirring conditions of the bath. Single lance mixing experiments were carried out in a horizontal cylindrical vessel with different gas blown angles to simulate the smelting furnaces gas blown from side and bottom. The mixing behaviors were studied by quantifying the mixing time of the bath under different conditions. The results show that the increase of gas flow rate decreases the mixing time rapidly before it reaches a plateau. In the side blown furnace, mixing time was also shortened significantly by increasing bath height up to certain values, followed by minor promotions of mixing time if further increasing the bath heights. In comparison to the side blown process with the same gas flow conditions, the bottom blown process took more time for the bath to reach homogeneity under the same operating conditions.

Physical, chemical and thermal histories of an oxygen bubble in bath during bottom blown process

A mathematic model has been developed for an oxygen bubble rising in metal during a bottom blown process. The model successfully coupled local reactions and mass transport with heat transport between metal and the bubble surface, and between the latter and the bubble interior. This novel method reveals the physical, chemical and thermal histories of an oxygen bubble during a bottom blown process. An oxygen bubble rising in Fe–3%C metal under conditions of the oxygen bottom blown process was described by the modelling. The results show (1) the heat supplied to the bath is sourced from the secondary combustion in the bubbles rather than from the decarburisation at a bubble surface; (2) the temperature of a bubble surface reached a maximum of few degrees higher than the bath at few centimetres above the nozzle; (3) the maximum heat supplied to the bath by a bubble midway along the bubble trajectory is much more than the total heat supplied by the bubble reaching the bath surface; (4) the energy in the process-off gas is as high as three-fold of that received by the bath; and (5) iron is unlikely to be oxidised in front of the nozzle.

Bottom-Blown Stirring Technology Application in Consteel EAF

Bottom blown stirring technology application in EAF was studied in this paper. The basic principle of bottom blowing process was researched, the bottom blown stirring can give strong stirring effect on the molten steel bath, thus bath mixing time was shortened, decarburization and dephosphorization were improved, however over stirring would lead to liquid steel incontact with atmosphere air. Reasonable process was considered on Consteel EAF. results show that: with bottom-blown stirring technology, decarburization and dephosphorization increase significantly; oxygen and lime consumption decrease; content of FeO in final slag reduces; and heat time becomes short.

Development and Verification of Accretion Similarity Conversion Method for Gas Bottom-Blowing Process inside Pyrometallurgical Vessels

In this research, a water model with an extra low temperature (-177°C) gas blown-in system was established to simulate the phenomena inside pyrometallurgical vessels for investigating effects of gas bottom blowing conditions on the shape and dimensions of solid accretion sitting on the refractory lining near gas tuyeres. In addition, Buckingham Pi theorem was adopted to derive the important dimensionless parameters for correlating conditions of accretion formation in the similar systems. Then, by combining dimensionless parameters with heat transfer equations that describe the heat transfer across the accretion, quantitative relations based on the similarity conversion of the similar systems was established. The method mentioned above is called Accretion Similarity Conversion Method (ASCM). Meanwhile, the experimental work of a wax model was conducted to evaluate the accuracy of ASCM. The results indicate that the size of solid accretion inside the wax model under a specific condition can be reasonably estimated by ASCM.

Selected Refractory Advances in Steel-Handling Systems

The iron and steel industry is constantly undergoing technological changes in improving its processes to produce the highest quality world-class steels. As a consequence, the refractories industry has been challenged to keep in lock-step with the iron and steel industry to enhance, not detract from these processes.Certain internal combinations have enabled these refractories changes. Three expositions can display the sophistication to which refractories have advanced, so this article will explore refractories for primary steelmaking, ladles, and slide-gate devices for continuous casting.The start-up of the first top-blown oxygen vessel at the Linz Works in Austria 37 years ago was a historical milestone in the evolution of steelmaking. At that time the open-hearth process was the dominant steelmaking technology in the world. Ten to 12 hours were required to produce one batch of steel in the open-hearth furnace, but only one hour is needed to refine the same amount of steel in a basic oxygen furnace (BOF). In a top-blown BOF all oxygen required for refining is introduced into the vessel through the oxygen lance inserted through the top of the vessel.Toward the end of the 1960s, bottom-blown processes, such as OBM and Q-BOP, became very important in oxygen steelmaking. In the bottom-blown process, oxygen and lime are blown into the steel batch through bottom tuyeres.

上底吹き転炉におけるCOガス底吹き法の開発と冶金反応特性

上底吹き転炉におけるCOガス底吹き法の開発と冶金反応特性

Mathematical Model of End Point Control for the Top and Bottom Blowing Process in BOF

For the endpoint control of the top and bottom blowing process in BOF, a simplified mathematical model which is suitable for the online application has been established by the following procedure.(1)The basic equations for the rates of oxygen consumption and temperature increase, which have the comprehensive characteristics in both the ranges of low and carbon high carbon contents, have been derived in the current work.(2) On the basis of the basic equations, the fundamental curves of oxygen consumption and temperature increase, which show the progress of blowing, have been determined by the analysis of the actual operational data. The fundamental curve of dephosphorization has also been determined in the same way.(3) A control model for the endpoint carbon content and the endpoint temperature of metal has been established by the use of the fundamental curves.At No. 2 BOF shop in Kashima Steel Works, Sumitomo Metal Industries, Ltd., the model is now being used for the automatic blowing and contributes to the reduction of reblow ratio and furnace refractories.

転炉複合吹錬終点制御モデルの開発

転炉複合吹錬終点制御モデルの開発

Mass transfer between gas and liquid in bottom blown process.

Desorption of carbon dioxide from water during bottom blowing of nitrogen was studied. Volumetric mass-transfer coefficient of carbon dioxide was evaluated by following the change of carbon dioxide concentration in the bath. The volumetric mass-transfer coefficient was found to increase with the increase in the flow rate of nitrogen gas. A model for the estimation of volumetric mass-transfer coefficient was developed. The model uses Higbie equation for the estimation of mass-transfer coefficient. The prediction of the model is in reasonable agreement with the experimental observations.

The Formation of Iron Oxide Fume

Previous work on this subject is reviewed briefly. It is shown that the rate of vaporization of a metal increases linearly with increasing oxygen partial pressure of the atmosphere up to a limiting rate. An attempt is made to explain the role of carbon in steel in enhancing or hindering the formation of iron oxide fumes by the top- or bottom-blowing process.