Desulfurization Of Steel Research Articles

ENERGY EFFICIENT SOLUTIONS FOR STEEL REFINING IN FOUNDRY CLASS ELECTRIC ARC FURNACE

Analysis of recent research and publications. The technological period in foundry class electric arc furnaces (EAF) is usually long term, is determined by desulfurization of steel and accompanied by significant energy loss through emissive surface of shallow steelmaking bath. Known mathematical models of Sulphur removal do not take into attention the impact of hydrodynamics factors due to deepening of the steelmaking bath of the same volume. Purpose. The task is to show feasibility of energy savings in foundry class EAF due to implementation of “deep” bath with forced pneumatic mixing. Method. Numerical modeling of sulfur removal in the steelmaking bath under conditions of forced pneumatic mixing. Research findings. Mathematical model takes into account removal of sulfur on interfacial surface of thin steel film, covering gas bubbles, geometry of bath and two-phase region, hydrodynamics, coalescence of bubbles. Simulation showed that in a “deep” bath, having shape factor (diameter to depth ratio) 2.5, rate of desulfurization, increases up to 5-6.7 times compared with a standard not forcibly stirred bath with shape factor 4.5, due to amplification of mass transfer in two-phase region and film desulfurization, reaching at least 23-28 % in overall process. Rise of porous plug radius contributes to increase sulfur removal velocity due to enlargement of threshold flowrates, corresponding to transition bubble - jet mode and bath "breakdown” mode. Effect of bath deepening in overall improvement of desulfurization kinetics is on average 23%. Practical significance. The obtained results allow to expect a shortening of the technological period due to increase of sulfur removal processes by an average of 1.5 times. Taking into account the share of the technological period in the total duration of melting on average 25-30%, the reduction of melting time will be 8-10%, and the saving of electricity, with an average specific consumption in small-capacity arc furnaces of 850 kWh/t, is expected to be 60-70 kWh per ton of crude steel.

Effect of Liquid Fraction on Reaction Rate of Molten Steel Desulfurization Using Solid-Liquid Coexisting Slag

Effect of Liquid Fraction on Reaction Rate of Molten Steel Desulfurization Using Solid-Liquid Coexisting Slag

Kinetic Analysis for Steel Desulfurization during Ruhrstahl–Heraeus Process

A kinetic model for the Ruhrstahl–Heraeus (RH) desulfurization process is established based on the FactSage Macro Processing. The desulfurizer addition, the desulfurization reaction, the steel mixing, the flow circulation, and the desulfurizer floating during the RH refining process are considered in the model. Simulated results agree well measured results, indicating that the current model can be used to predict the desulfurization reactions during the RH refining process. The CaO activity increases with a higher CaO/Al2O3 ratio and a lower SiO2 content, which exhibits a similar tendency with the desulfurization ratio. It is indicated that it is necessary to increase the CaO activity in the desulfurizer to improve the desulfurization ratio. The S content in the molten steel decreases with time and a higher ratio of the powder blowing. The cost increases with time due to the refractory erosion and the steam consumption. The cost of the desulfurizer added by the powder blowing is lower than that of the gravity sinking.

Effects of Liquid Fraction on Reaction Rate of Molten Steel Desulfurization Using Solid-liquid Coexisting Slag

Effects of Liquid Fraction on Reaction Rate of Molten Steel Desulfurization Using Solid-liquid Coexisting Slag

Statistical Inference Modeling Using Pearson Correlation Filters and Best Subset Selection Applied to Steel Desulfurization Preliminary to Ladle Furnace Treatment

Statistical Inference Modeling Using Pearson Correlation Filters and Best Subset Selection Applied to Steel Desulfurization Preliminary to Ladle Furnace Treatment

Numerical studies of the kinetics of steel desulfurization with pneumatic stirring

Analysis of recent research and publications. In the conditions of mini-mills, the removal of sulfur in a number of cases is the limiting link in the production of steel. The kinetics of desulfurization is determined by the specific stirring power of the steel melting bath. The influence of the geometry of the bath on the efficiency of pneumatic mixing and desulfurization of steel at a fixed mass has not been sufficiently studied. Purpose and method. The purpose of the work is increasing the energy efficiency of steel production in the conditions of a mini-mill due to the minimization of steel desulfurization time. The method consists of numerical modeling of the desulfurization kinetics taking into account the geometric parameters of the steel melting bath and regime parameters of pneumatic mixing. Novelty and scientific significance of research. In the context of the kinetics of steel desulphurization, an understanding of the energy component of the process was developed through the specific power of pneumatic mixing of the liquid bath Nmix. The finiteness of the isothermal expansion model of the rising gas bubble for determining Nmix in industrial conditions through argon flow rate is shown. A mathematical model for estimating Nmix when purging the bath with argon in jet-bubble mode through the averaged speed of liquid steel movement and Archimedes’ force as a function of the gas content ratio in the two-phase region is proposed. The model allows optimizing argon flow rate according to the criterion of the maximum specific power of pneumatic mixing. This mode ensures the minimum duration of steel desulfurization for the given slag parameters and geometry of the steel melting bath-bottom porous plug system. Practical value. Determining the optimal flow rate of argon to ensure the maximum specific power of pneumatic mixing of a steel melting bath of a certain geometry and mass in the context of minimizing the duration of desulfurization contributes to increasing the energy efficiency of the steel production technology in the conditions of mini-mill operation.

Deep Steel Desulfurization Practice

This article is aimed to study theoretical knowledges related to deep steel desulfurization and their practical application in specific production conditions. The main goal of this study was to verify the efficiency of added CaSi to processed heats in two batches, i.e., first for deep desulfurization at the beginning of the secondary metallurgy and then in a second smaller batch at the end of that process for final modification. At the beginning of the secondary metallurgy process, it was crucial to prepare a suitable chemical composition of ladle slag with advantageous properties for good assimilation of sulfur-based inclusions from desulfurization reactions. Samples were taken of final basic oxygen furnace slag, ladle slag before the deep desulfurization process at the beginning of secondary metallurgy and ladle slag at the end of processing. Detailed cleanliness analyses of steel samples taken from mold during the casting were performed using the Automated Steel Cleanliness Analyses Tool. For better understanding and interpretation of the obtained cleanliness results and their relationship, the following defined parameters were used: ratio of “Ca/Al” oxide inclusions, percentage of “liquid” inclusions and area of CaS inclusions.

Steel desulfurization on RH degasser: physical and mathematical modeling

Due to the high-quality steel demand, especially for ultra-low Sulfur steel, RH desulfurization has been practiced. Based on this, mathematical and physical modeling have been applied to study steel desulfurization by reagent addition in the RH degasser vacuum chamber. The main result of cold modeling, using water and oil emulating steel and slag, respectively, was to assess the influence of density difference between the continuous and disperse phases on oil droplet behavior. It is shown that its flow tends to be more restricted near the down snorkel when the density difference increases. Moreover, these results provide the basis for CFD modeling validation, which enabled the determination of slag drop residence time inside steel on RH and the average value of the rate of dissipation of turbulent kinetic energy inside the RH ladle. These two parameters were used to develop a kinetic model, which reaches a good agreement with industrial trial results available in literature. The optimum desulfurization degree of 31.44% was achieved for a gas flow rate of 90 Nm3/h, according to the kinetic model. This value can be useful in some steel grade production, where the required S content is less than 10 ppm. Even in common steel grade production, if some punctual chemical adjustment is necessary, this technique is also useful. The main kinetic parameter for steel desulfurization is the steel circulation rate. For best results, it should be reduced in the desulfurization stage, and after that, the normal operation can be resumed, so that the production cycle is not affected.

Modeling of the influence of the bath blowing mode on mass exchange processes and slag formation in the oxygen converter

Рurpose. Establish rational modes of bath blowing and slag formation when using traditional and experimental materials that ensure effective refining of steel from harmful impurities. To investigate the influence of the change in the hydrodynamic state of the converter bath on the stability of the lining of problem areas of the converter and the loss of metal with removal, emissions, with metal balls merging with the slag. Method. The work uses methods of cold and high-temperature modeling of the steel smelting process. When conducting experiments on cold modeling, the mode of penetration of gas jets into the liquid on the sample and the model was observed with the provision of Lrz/Nv (model) = Lrz/Nv (converter). Nv is the depth of the bath on the model and the wor king converter. Lrz - the length of the reaction zone in high-temperature simulations was determined as the length of the primary reaction zone, and in the cold one - as the length of the jet section formed when the gas jet penetrates the liquid. These conditions, together with ensuring the similarity of the geometry of the model and the sample, were consi dered necessary and sufficient for obtaining data for qualitative and quantitative assessment of both the hydrodynamic state of the converter bath and the effect of changing the method and parameters of blowing the bath on the physicochemical features of steel refining according to the time of the process. An additional condition is compliance with the condition of equality of the ratio of the plane of the bath to the plane of the internal section of the nozzle of the blowing nozzle: (Sbaths/Snozzles) model=(Sbaths/Snozzles) sample on the model and sample. Scientific novelty. Theoretically substantiated and experimentally confirmed the expediency of using to determine the effect on physico-chemical processes and conversion in the converter bath of the blowing mode, for the characteristic of which the parameter - hydrodynamic factor equal to the ratio LrzI/Nv was chosen. In turn, the length of the reaction zone that remains when the gas jet enters the bath depends on the intensity of blowing: Lrz ~ K q0.4. For the first time, the parameter that determines the state of mixing of the bath during its oxygen blowing - LrzI/Nv - was used to determine the intensity of sulfur conversion into slag during the oxygen blowing of the iron-carbon melt of the converter bath for the range of changes in the carbon content in it 3.0...0.25. where LrzI is the length of the primary reaction zone, which is formed when the oxygen jet penetrates the metal melt. The primary reaction zone is the source of the formation of CO bubbles according to the reaction FeO + C = Fe + CO, which are responsible for the intensity of mixing of the bath through the formation of circulating flows of metal in the bath, which in turn are responsible for the transport of impurity elements to the metal-slag boundary. It is shown that in the given range of changes in the content of carbon in the metal melt, the dependence of the removal rate of sulfur from the metal into the slag on the hydrodynamic parameter LrzI/Nv is extreme. At this time, when the maximum mixing effect of the bath is achieved, in the presence of the necessary basicity of the slag phase, the speed of the desulfurization reaction for these conditions is maximum. In the future, in the case of the implementation of the traditional conversion scheme, which is characterized by a sharp increase in the content of iron oxides in the slag (15...17%), the speed of the desulfurization reaction decreased even with a sufficient speed of metal flows. Practical significance. Reducing the intensity of metal bath blowing in the conditions of steel smelting in a laboratory oxygen converter with upper oxygen blowing from 4.0 m3/t•min to 3.2 m3/t•min, while increasing the blowing time by 17.8%, increased the desulphurization rate . Bringing the desulfurization reaction to its fuller completion was achieved due to the rational organization of mixing the melt in the converter bath: the appropriate and effective rate of metal delivery to the reaction surface from the point of view of the completion of steel desulfurization ensured a higher speed of the desulfurization reaction at the border compared to more intensive blowing of the bath with oxygen metal-slag distribution. At the same time, the value of the indicator Ls =(S)/[S] increased from 6.4 to 10.5.

Desulfurization of molten steel with molten slag using the electrochemical method

The desulfurization in metallurgical process is electrochemical reaction in nature. Desulfurization using the electrochemical method was proposed with the CaO-MgO-Al2O3 molten slag covering molten steel. Effect of an applied external DC voltage, which varied from 0 to 8V, was discussed. The results indicated that sulfur in molten steel could be removed effectively with applied external voltage. According to the mechanism analyses of the desulfurization under the applied external voltage, kinetics formulae were developed, and the model calculated results that were in agreement with the experimental values. The transfer coefficient of sulfur in molten slag under electromigration conditions was approximately 2.09?10-5 m?s-1?V-1. The desulfurization of molten steel with molten slag can be promoted by increasing the applied voltage, reducing the partial pressure of atmospheric oxygen, strengthening the stirring intensity of the reaction system, and optimizing the composition and properties of the slag.

Reducing the Cost of Steel Desulfurization during Secondary Refining in a Ladle-Furnace Unit

Reducing the Cost of Steel Desulfurization during Secondary Refining in a Ladle-Furnace Unit

Сучасний досвід десульфурації сталі

Modern technological schemes of steel production do not allow to achieve low (< 0.01 % S) and ultra-low (<0.005 % S) sulfur content on the production of in the metal directly. That is why out-of-furnace steel treatment is often used to remove sulfur. Desulfurization process of steel depends on the chemical composition of the slag, the time of its formation in the ladle, metal oxidation, conditions of mixing of steel in a ladle, additional technological operations and ladle metal processing. Methods are widely used for desulfurization of steel treatment of steel with solid slag-forming mixtures, synthetic slag, lime-aluminous slag, silico-calcium and other powdered materials. Modern approaches to the process of steel desulfurization in conditions steel production are analyzed in the Study. In particular, the Ukrainian (on the example of PJSC ‘Azovstal Iron & Steel Works’ and PJSC ‘Dneprovsky Integrated Iron & Steel Works named after Dzershinsky’) and foreign (on the example of PJSC ‘Severstal’ and PJSC ‘Magnitogorsk Iron & Steel Works’) experience of desulfurization under oxygen converter production. The use of technological complexes ‘Installation of pig iron desulfurization steel making unit’ and ‘Cast iron desulfurization installation steel making unit is ‘oven-bucket’ installation’ provides a deeper desulfurization of steel, the possibility of optimizing the cost of steel production, expands range of scarce products and eliminates a number of restrictive conditions that complicate current production. The analysis of steel C80D desulfurization process is given in the conditions of JSC ‘Moldova Steel Works’, in which partial sulfur removal occurs in an arc steel making furnace, and the ultra-low content is achieved by creating a highly basic refining slag in the process out-of-furnace processing of steel. The study of the kinetics of the desulfurization process of 20GL steel in the conditions of JSC ‘Tashkent Mechanical Plant’ with the use of solid slag-forming mixtures and modification of steel with rare-earth metals is analyzed. The issue of desulfurization of electric steel in the conditions of OJSC ‘Byelorussian Steel Works’ with injection of powdered materials through the installation ‘Velko’ during out-of-furnace processing of steel is considered. Keywords: steel desulfurization, desulfurizer reagent, degree of desulfurization, cast iron desulfurization installation, out-of-furnace processing of steel, ‘‘oven-bucket’’ installation.

Aluminum-Free Steelmaking: Desulfurization and Nonmetallic Inclusion Evolution of Si-Killed Steel in Contact with CaO-SiO2-CaF2-MgO Slag

In some applications, deep desulfurization and deoxidation of steels without the use of aluminum are required, using Si as a deoxidant instead, with double-saturated slags in the CaO-SiO2-CaF2-MgO system. This work studied the desulfurization and nonmetallic inclusion evolution for the system using an induction furnace and compared the results with FactSage kinetic simulations. Steel samples were taken from the steel melt and analyzed with ICP-MS and combustion analysis for chemistry, and SEM/EDS for nonmetallic inclusion quantity, size, and composition. The results indicate that the steel was deeply desulfurized, with a final sulfur partition coefficient of 580; MgO was reduced from the slag, yielding dissolved [Mg] that transformed liquid Mn–silicate inclusions into forsterite and MgO. Intentional reoxidation of the melt with oxidized electrolytic iron demonstrated a significant concentration of dissolved [Mg] in the steel, by the formation of additional forsterite and MgO upon reoxidation.

Deep Steel Desulfurization during Chamber Degassing

Deep Steel Desulfurization during Chamber Degassing

Elaboración de escorias sintéticas con residuos de mármol y óxido de aluminio utilizados en el proceso de desulfuración de acero

El objetivo de este trabajo es investigar el proceso de desulfuración del acero utilizando escorias sintéticas que contienen residuos de mármol y óxido de aluminio. Las pruebas se realizaron usando un acero SAE 1020 que contenía 80 ppm de azufre. La temperatura fue 1600 °C bajo un flujo de argón de 1NL/minuto. Cada prueba de desulfuración duró 30 min. Se retiraron muestras de acero del baño cada 5 min. Posteriormente, cada muestra se caracterizó en un espectrómetro infrarrojo LECO CS240 para determinar el contenido de azufre. Los resultados indicaron un rendimiento de desulfuración de 78,7% y 70% en peso para escorias que contienen óxido de aluminio y residuos de mármol, respectivamente. Con estos resultados fue posible concluir que la fracción de la fase líquida influye en el rendimiento de desulfuración. El rendimiento máximo de desulfuración se alcanzó con 83,2% y 82,0% en peso de la fase líquida para escorias que contenían óxido de aluminio y residuos de mármol, respectivamente. Además, en las escorias que contienen cal, el rendimiento máximo de desulfuración se alcanzó con 85,0% en peso de la fase líquida. Las pruebas también demostraron que en los procesos de desulfuración es necesario contener una fase sólida de CaO en la composición de escoria sintética para alcanzar el rendimiento máximo de desulfuración. Por lo tanto, el uso de óxido de aluminio en lugar de fluorita es una alternativa interesante para la desulfuración del acero, así como el reemplazo de la cal por los residuos de mármol.

Development of a calculation method for evaluating technological parameters of the desulphurization process in a ladle

To fulfil the requirements for pipe steels of strength group D in terms of sulfur content, the metal is subjected to ladle desulfurization. In the course of desulfurization, in order to reduce its duration, steel is mixed in the ladle by blowing with argon. To optimize the desulfurization process, a methodology has been developed for evaluating its technological parameters, which allows determining under production conditions the intensity of steel blowing in the ladle. As initial data for comparative calculations of the technological parameters of the process of desulfurization of pipe steel in a ladle according to the developed method, the indicators of industrial melts were used, including the chemical composition of steel and the main technological data characterizing the production parameters of desulfurization of pipe steels of strength group D. The algorithm for using the proposed technique provides for the calculation of sulfur activity and the coefficient of sulfur activity in a steel melt of a given composition; determination of the oxidizing potential of the slag-metal system and the sulfide capacity of the slag; calculation of the equilibrium sulfur distribution coefficient between steel and slag, as well as the volumetric mass transfer coefficient under equilibrium and production conditions. To determine the thermodynamic characteristics of the interaction of sulfur dissolved in a metal with slag, the sorption ability of the slags of the analyzed melts with respect to sulfur was calculated. Data are presented on the effect of sulfur activity in experimental melts on the final sulfur content in steel. The rational limits of the value of the integral indicator of the composition of refining slags and volumetric mass transfer coefficient, which provide the best indicators of the process of desulfurization of steel, were determined. The dependences of the influence of the volumetric mass transfer coefficient on the duration of the process and the final sulfur content in the metal were established. The proposed methodology for assessing the technological parameters of steel desulfurization can optimize the duration of its individual stages and, thereby, reduce the cost of the process as a whole.

Prospects for the Use of Hollow Electrodes for Deep Desulfurization of Steel in the Ladle-Furnace Unit

The article discusses the possibilities of intensifying the process of desulfurization of molten steel in the process of after-furnace treatment of molten steel in the ladle-kiln unit. As one of the techniques, it was proposed to heat the melt with the help of hollow electrodes with argon feed during the operation of the electric arc plant. Comparative thermal balances of the installation in the basic and experimental versions and on the basis of the proposed mathematical model for calculating the mass-average temperature of the melt are given, and graphs of temperature changes during processing are plotted. To assess the efficiency of the desulfurization process, arrays of heats were processed in the basic and experimental mode and original three-parameter graphs were built, allowing to estimate the degree of desulfurization in both modes as a function of processing parameters.

Effective Materials from Recycled Aluminum Waste for Steel Ladle Treatment

The paper presents the results of research on the use of recycled aluminum waste (RAW) for steel ladle treatment. It has been established that simultaneously with the deoxidation of refining slags before desulfurization of steel, their liquid mobility increases, which eliminates the need for using fluorspar for these purposes. A thermodynamic analysis of possible reactions of formation of aluminates and calcium aluminosilicates in the refining slag has been carried out. The composition of briquettes based on RAW for liquefaction of refining slags is proposed.

Analysis of the influence of the solid and liquid phases on steel desulfurization with slags from the CaO–Al2O3 systems using computational thermodynamics

Normally, CaO is used in steel desulfurization in slags from the systems: CaO–CaF2, CaO–Al2O3, and CaO–SiO2. Among these, the CaO–CaF2 slags are more efficient. This paper uses computational thermodynamics to study the influence of solid and liquid phases in the efficiency of desulfurizing slags in the CaO–Al2O3 system. Desulfurizing slags were prepared to produce steels with sulfur levels below 20ppm. Simulations using computational thermodynamics were made to determine the properties of the slags at 1600°C. The experimental tests were carried out in an induction furnace at 1600°C. The experimental results showed that slags from CaO–Al2O3 system can be as efficient as slags from CaO–CaF2 system, reaching final sulfur contents lower than 10ppm. The conclusion was that slags containing higher quantities of liquid phase are more efficient. However, the presence of some amount of solid CaO is necessary to keep the liquid phase of slag always saturated in CaO and its activity equal to unity. A Steel Desulfurization Factor was proposed as an easy way to estimate the desulfurization efficiency.

An impact of the ladle lining on the refining of reinforced steel when blowing with powders

When refining steel by blowing powders, the ladle lining material plays a serious role. The dependency graphs of the degree of desulfurization on the consumption of silicocalcium powder during blowing in ladles lined with various materials have been presented. It has been noted that the amount of FeO in the slag seriously affects the average degree of desulfurization. With a large amount of FeO in the slag, the degree of resulfurization is greatly increased. The placement plan of the unit for refining the liquid steel in the ladle has been illustrated. Simultaneously, for powder blowing, a device diagram of the ladle furnace fitted with equipment for blowing liquid steel with powders has been presented. In this equipment, powder lining can be used and steel blowing with silicocalcium based powders can be carried out. The degree of desulfurization is also seriously affected by the initial amount of sulfur in the metal charge for steelmaking The presence of a roof in the pouring ladles improves the conditions for metal blowing, oxidation and metal loss are reduced. It has been observed that the process of refining liquid steel in a ladle is complex and depends on many factors. The amount of sulfur in the primary metal charge, the lining of the ladle, the composition of the powder of the blown material and the technological parameters of the blowing are important. The complete desulfurization of steel by blowing with powders primarily depends on the initial amount of sulfur in the metal. It has been found that there is a linear dependence of the final sulfur content on its initial content in steel when metal is blown in a ladle with a mixture of 70 % MgO, 20 % CaO, and 10 % CaF 2 . The desulfurization of steel by blowing with powders, especially by blowing magnesium and calcium alloys, can be significantly affected by ladle lining