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This paper investigates the influence of biochar, either as an individual component or in combination with high-temperature coke, on the slag foaming behavior. High-temperature coke serves as a reference. Three scenarios were considered to study the slag foaming behavior, each characterized by different slag chemical compositions. The results indicate that biochar can promote steady foaming for specific slags when the basicity (CaO/SiO2) falls within a range of 1.2 to 3.4. Experimental findings also reveal that stable foaming can be achieved when a mixture containing biochar and coke with a ratio of 1:1 is employed, with a minimum slag basicity of 1.0 and FeO content of 25 wt.%. The foaming range obtained using different FeO contents (15 wt.% to 40 wt.%) in the mixture surpasses the range observed with the individual application of coke or biochar. The X-ray diffraction (XRD) analysis showed that unrelated to the carbon source applied, the general pattern was that the phases larnite (Ca2SiO4) or dicalcium silicate were detected for slag foams with high basicity. Monticellite (CaMgSiO4) and magnesium iron oxide (Fe2MgO4) were predominant in slag foam samples, with the highest MgO content. The presence of monticellite and merwinite (Ca3MgSi2O8) occurred in samples with the lowest basicity. Eventually, the application of the mixture of coke and biochar showed the potential to obtain stable foaming across a wide range of slag compositions. [ABSTRACT FROM AUTHOR]

The influence of different carbon sources, including anthracite, calcined petroleum coke, three samples of high-temperature coke, biochar, and a mixture of 50 wt.% biochar and 50 wt.% coke, on slag foaming behavior was studied. The slag's composition was set to FeO-CaO-Al2O3-MgO-SiO2, and the temperature for slag foaming was 1600 °C. The effect of the carbon sources was evaluated using foaming characteristics (foam height, foam volume, relative foaming height, and gas fraction), X-ray diffraction (XRD), chemical analysis of the slag foams, Mossbauer spectroscopy, observation by scanning electron microscope (SEM), and energy-dispersive spectroscopy (EDS) mapping. Different foaming phenomena were found among conventional sources, biochar as a single source, and the mixture of coke and biochar. Biochar showed the most inferior foaming characteristics compared to the other studied carbon sources. Nevertheless, the slag foaming process was improved and showed slag foaming characteristics similar to results obtained using conventional carbon sources when the mixture of 50 wt.% coke and 50 wt.% biochar was used. The XRD analysis revealed a difference between the top and bottom of the slag foams. In almost all cases, a maghemite crystalline phase was detected at the top of the slag foams, indicating oxidation; metallic iron was found at the bottom. Furthermore, a difference in the slag foam (mixture of coke and biochar) was found in the presence of such crystalline phases as magnesium iron oxide (Fe2MgO4) and magnetite (Mg0.4Fe2.96O4). Notwithstanding the carbon source applied, a layer between the foam slag and the crucible wall was found in many samples. Based on the SEM/EDS and XRD results, it was assumed this layer consists of gehlenite (Ca2(Al(AlSi)O7) and two spinels: magnesium aluminate (MgAl2O4) and magnesium iron oxide (Fe2MgO4). [ABSTRACT FROM AUTHOR]

Understanding the micro mechanism of foaming behavior is urgently required for regulating metallurgical processes and preparing porous ceramics. In this study, we performed high-temperature simulation experiments on the foaming of CaO–SiO 2 -Fe x O-MgO-based slag induced by a slag/metal reaction. The evolution of the melt structure with changes in the chemical composition of the molten slag was analyzed using Raman spectroscopy. The micro mechanism of slag foaming was interpreted using the melt structure characteristics. As the w (CaO)/ w (SiO 2) and P 2 O 5 content varied, the maximum foaming height exhibited a positive relationship with the degree of polymerization of the experimental slag. In the bulk phase of the liquid film, an increase in the degree of polymerization of the experimental slag hindered the drainage of slag from the liquid film and reduced the solubility of the liquid film for CO gas in the bubble, leading to an increase in the maximum foaming height of the molten slag. Moreover, the increase in the degree of polymerization of the structural units at the liquid film/CO interface improved the elasticity of the liquid film and decreased the permeability of the liquid film for CO in the bubble, resulting in an increase in the maximum foaming height of the molten slag. The new perspective of ''chemical composition—melt structure—slag foaming'' also inspired studies on industrial processes that readily form foam, including glass manufacturing, oil recovery, and froth flotation. [Display omitted] [ABSTRACT FROM AUTHOR]

The electric arc furnace (EAF) has the potential to significantly contribute to the decarbonization of the iron and steel industry. However, during EAF steelmaking, carbon still needs to be injected into the molten slag to initiate slag foaming, which is beneficial to the energy efficiency and protection of the furnace. To move away from fossil carbon, biocarbon has gained attention as an injection carbon agent. In this study, two biochar candidates were added to the molten slag layer of an induction furnace for steel melting, to simulate EAF steelmaking conditions. The resultant slag foaming height was measured, and a ranking in comparison to two fossil carbon candidates was developed. The results indicate that the injection biochar sample, in the form of a bio-briquette, has a considerable degree of slag foaming capacity. More work is ongoing to develop a standardized testing methodology of ranking various injection biochar candidates for their suitability and qualification for use on a larger scale. [ABSTRACT FROM AUTHOR]

Previous studies have shown that alkali metals catalyse the pyrolysis and gasification processes of biomass. However, whether alkali metals have the same catalytic effect on the reduction reaction of biochar with iron oxide has not been investigated. In this article, the effect of alkali metals on the reduction behaviour of biochar with iron oxide was investigated. It was shown that adding alkali metal carbonate could increase the reaction rate of CSC reduction stages 1 and 2, but it played an inhibitory role for the first and middle periods of stage 3. Moreover, adding alkali metals resulted in higher total CO2 gas production and reduced total CO gas production for the reduction reaction. The GB1 model was the best mechanistic model for stages 1 and 2 of the CSC-2K and CSC-2Na reduction reactions, while the C1 model was the best mechanistic model for stage 3. [ABSTRACT FROM AUTHOR]

The control of slag foaming is important for optimising basic oxygen furnace (BOF) performance. Acoustics systems monitoring wide frequency bandwidths have been applied to BOF monitoring for the purpose of understanding slag foam height and density but there is limited information about their accuracy and repeatability. Improved understanding of the fundamental behaviour of sound in slag foam could help resolve these issues. In this cold physical model study using, aqueous foams generated in a cylindrical vessel were used to study the attenuation of sound in large samples of foam. Sound pulses over the range of 201 to 1801 Hz were transmitted through varying aqueous foam heights of 100 to 250 mm and acoustic signals detected via a measurement microphone were analysed. The results indicated aqueous foams consisting of smaller bubbles in the range of 0.4 to 0.75 mm with visibly thicker outer films displayed a stronger correlation between the attenuated sound and the stationary foam heights. It was also observed that frequencies above 1009 Hz were more sensitive in terms of their attenuation in varying foam heights and the time-dependant drainage of bubbles compared to lower frequencies. These frequencies were generally higher than those used for industrial slag foam monitoring systems. [ABSTRACT FROM AUTHOR]

This paper investigates the influence of biochar, either as an individual component or in combination with high-temperature coke, on the slag foaming behavior. High-temperature coke serves as a reference. Three scenarios were considered to study the slag foaming behavior, each characterized by different slag chemical compositions. The results indicate that biochar can promote steady foaming for specific slags when the basicity (CaO/SiO2) falls within a range of 1.2 to 3.4. Experimental findings also reveal that stable foaming can be achieved when a mixture containing biochar and coke with a ratio of 1:1 is employed, with a minimum slag basicity of 1.0 and FeO content of 25 wt.%. The foaming range obtained using different FeO contents (15 wt.% to 40 wt.%) in the mixture surpasses the range observed with the individual application of coke or biochar. The X-ray diffraction (XRD) analysis showed that unrelated to the carbon source applied, the general pattern was that the phases larnite (Ca2SiO4) or dicalcium silicate were detected for slag foams with high basicity. Monticellite (CaMgSiO4) and magnesium iron oxide (Fe2MgO4) were predominant in slag foam samples, with the highest MgO content. The presence of monticellite and merwinite (Ca3MgSi2O8) occurred in samples with the lowest basicity. Eventually, the application of the mixture of coke and biochar showed the potential to obtain stable foaming across a wide range of slag compositions.

Electric arc furnaces (EAFs) are used for steel production, particularly when recycling scrap material. In EAFs, carbonaceous material is charged with other raw materials or injected into molten slag to generate foam on top of liquid metal to increase energy efficiency. However, the consumption of fossil carbon leads to greenhouse gas emissions (GHGs). To reduce net GHG emissions from EAF steelmaking, the substitution of fossil carbon with sustainable biogenic carbon can be applied. This study explores the possibility of the substitution of fossil material with biogenic material produced by different pyrolysis methods and from various raw materials in EAF steelmaking processes. Experimental work was performed to study the effect of biogenic material utilization on steel and slag composition using an induction melting furnace with 50 kg of steel capacity. The interaction of biogenic material derived from different raw materials and pyrolysis processes with molten synthetic slag was also investigated using a tensiometer. Relative to other biogenic materials tested, a composite produced with densified softwood had higher intensity interfacial reactions with slag, which may be attributed to the rougher surface morphology of the densified biogenic material.

An electric arc furnace (EAF) is a furnace that utilizes mainly electric energy to melt scraps into liquid. Above the liquid steel is called the freeboard, and combustion that happens here can significantly heat the furnace wall, resulting in overheating issues on water‐cooling panels. In this study, a comprehensive computational fluid dynamics (CFD) model is developed to predict the side wall temperature distribution of an EAF. The comprehensive CFD model is integrated into a coherent jet, a DC electric arc, and a slag foaming models. [ABSTRACT FROM AUTHOR]

The influence of different carbon sources, including anthracite, calcined petroleum coke, three samples of high-temperature coke, biochar, and a mixture of 50 wt.% biochar and 50 wt.% coke, on slag foaming behavior was studied. The slag’s composition was set to FeO-CaO-Al2O3-MgO-SiO2, and the temperature for slag foaming was 1600 °C. The effect of the carbon sources was evaluated using foaming characteristics (foam height, foam volume, relative foaming height, and gas fraction), X-ray diffraction (XRD), chemical analysis of the slag foams, Mossbauer spectroscopy, observation by scanning electron microscope (SEM), and energy-dispersive spectroscopy (EDS) mapping. Different foaming phenomena were found among conventional sources, biochar as a single source, and the mixture of coke and biochar. Biochar showed the most inferior foaming characteristics compared to the other studied carbon sources. Nevertheless, the slag foaming process was improved and showed slag foaming characteristics similar to results obtained using conventional carbon sources when the mixture of 50 wt.% coke and 50 wt.% biochar was used. The XRD analysis revealed a difference between the top and bottom of the slag foams. In almost all cases, a maghemite crystalline phase was detected at the top of the slag foams, indicating oxidation; metallic iron was found at the bottom. Furthermore, a difference in the slag foam (mixture of coke and biochar) was found in the presence of such crystalline phases as magnesium iron oxide (Fe2MgO4) and magnetite (Mg0.4Fe2.96O4). Notwithstanding the carbon source applied, a layer between the foam slag and the crucible wall was found in many samples. Based on the SEM/EDS and XRD results, it was assumed this layer consists of gehlenite (Ca2(Al(AlSi)O7) and two spinels: magnesium aluminate (MgAl2O4) and magnesium iron oxide (Fe2MgO4).

The electric arc furnace (EAF) has the potential to significantly contribute to the decarbonization of the iron and steel industry. However, during EAF steelmaking, carbon still needs to be injected into the molten slag to initiate slag foaming, which is beneficial to the energy efficiency and protection of the furnace. To move away from fossil carbon, biocarbon has gained attention as an injection carbon agent. In this study, two biochar candidates were added to the molten slag layer of an induction furnace for steel melting, to simulate EAF steelmaking conditions. The resultant slag foaming height was measured, and a ranking in comparison to two fossil carbon candidates was developed. The results indicate that the injection biochar sample, in the form of a bio-briquette, has a considerable degree of slag foaming capacity. More work is ongoing to develop a standardized testing methodology of ranking various injection biochar candidates for their suitability and qualification for use on a larger scale.

The development of new materials and their production processes along with the environmental constraints demand new data of high quality, especially thermodynamic and physical property data. As slags play a crucial role in metallurgical processes and recycling, the need of better understanding of the reaction mechanisms between slag and metal is also increasingly felt. High precision data and better understanding of the reaction mechanism require efficient collaboration between the researchers in the laboratory and in the industries. Unfortunately, in some cases, the reported data are not obtained in well‐controlled experimental conditions. Without the knowledge of the experimental conditions, the use of the data in industrial practice would possibly lead to unintended results. In other cases, the measurements themselves, even their principles, are questionable. This review article addresses how to make the laboratory investigation more relevant to the industrial reality. Some existing uncertainties in the laboratory studies are also discussed. To help a sensible discussion, some specially designed experiments are conducted to support the argument. The review is focused on slag properties (namely, sulfide capacity, phosphate capacity, apparent viscosity, and apparent interfacial tension) and studies of interfacial slag phenomena. [ABSTRACT FROM AUTHOR]

The results of basic studies of the physicochemical properties of slags are used as the basis for developing the rational composition of main magnesian slags and the process techniques for their formation by the periods of blowing a basic oxygen furnace (BOF) bath and the periods of smelting in electric arc furnaces (EAFs). The record-breaking durability of furnace linings is ensured by implementing, in the furnace shop of OJSC EVRAZ NTMK, the developed set of process techniques of forming magnesian slags in the main period of blowing and a wear-resistant skull based on the final magnesian slags. These slags produce a low aggressive effect on the lining of furnaces, while maintaining high refining properties. The furnaces' lining durability exceeds 7000 heats; that said, the high process and key performance indicators of the process are maintained. The treatment of low manganese cast irons in the 350-ton heavy furnaces of OJSC EVRAZ ZSMK under magnesian slags allows studying the features of slag formation and changes in the chemical composition of the slag by the BOF bath blowing periods. In the course of treating phosphorous cast irons in the 300-ton BOFs at JSC ArcelorMittal Temirtau, a set of process techniques is developed for forming the magnesian slags of the recommended chemical composition by the periods of phosphorus cast iron blowing and wear-resistant skulls based on moderate-basicity final magnesian slags. The implementation of the developed process techniques ensures the lining stability of BOFs for more than 5000 heatings while maintaining the high process parameters and key performance indicators of the phosphorous treatment phase. The technology of forming rationally composed magnesian slags by the periods of smelting in EAF-135 is developed in the EAF shop of PJSC Seversky Pipe Plant. The adoption of the technology ensures the record-breaking resistance of the refractory lining of the furnace for up to 1900 heats per campaign and the high process parameters and key performance indicators of the process. [ABSTRACT FROM AUTHOR]

Slag foaming directly affects the productivity and quality of steel during the electric arc furnace (EAF) process. Therefore, the slag foaming height needs to be monitored in real-time. However, direct measurement of the slag foaming height is difficult to achieve because the inside of the EAF consists of harsh environments, i.e., high temperature and the presence of gas and dust. A stepwise regression model of the slag foaming height was created using sensor data from the EAF. A total of 272 operational data sets from the EAF process were used to develop and validate the regression model. This data came from 140ton DC-EAF of Dongkuk Steel in Pohang, Korea. We randomly selected 80% of the data for developing the regression model; the remaining 20% of data were used for model validation. The model was validated using the validation benchmark coefficient of determination (R2) and correlation coefficients. As a result, the important variables of slag foaming were statistically selected a priori. Using the regression model, the slag foaming height can be predicted without additional sensors. Based on the developed model, the effects of oxygen injection and carbon injection on the slag foaming height of EAF were predicted and are discussed herein. [ABSTRACT FROM AUTHOR]

Current research on using biochar as foaming agents in electric arc furnace (EAF) steelmaking is limited to pyrolysis biochar treated with nitrogen. Therefore, this study used pyrolysis corn stalk biochar treated with nitrogen (PN) as a reference, the physical and chemical properties, the ability to reduce iron oxide, and the reaction mechanism of pyrolysis corn stalk biochar treated with superheated steam (PSS) and hydrothermal corn stalk biochar (HC) were investigated. HC contains a large number of hydrogen-containing functional groups, which can release large amounts of H 2 during the reduction of iron oxide, while PSS has a higher fixed carbon content and produces higher amounts of CO and CO 2 gas. Dividing the thermogravimetric results into three reduction stages, the results show that the large amount of volatile fraction contained in HC contributes to Stage 1 and that the gasification reaction ability of PSS is stronger than that of PN. The results of the kinetic analysis showed that the best reaction mechanism for the three reduction stages of the three biochars was the Jander diffusion equation. This work provides theoretical guidance for the use of PSS and HC as foaming agents in EAF steelmaking. [ABSTRACT FROM AUTHOR]

This paper is concerned with semi-batch foams generated by injecting gas bubbles in a vertical column containing a liquid phase at rest. Its aim is to better understand the physical mechanisms responsible for foam formation at the liquid free surface and to predict the superficial gas velocity for onset of foaming. The model for predicting the onset of foaming is derived from the one-dimensional drift-flux model for gravity driven flow in the absence of wall shear. The analysis is based on experimental data reported in the literature and covers a wide range of physico-chemical properties, bubble sizes and shapes, and flow regimes. It identifies the inhibition of coalescence between rising bubbles and bubbles at rest at the free surface as a key mechanism responsible for the onset of foaming. A semi-empirical correlation for high viscosity fluids has been developed and good agreement with experimental data is found.

The CaO-SiO2-MgO-5Al2O3-30FeO five (oxide) components slag system was studied by varying the magnesium oxide (MgO) content (5.7–13.6 wt.%.% MgO) and keeping the basicity constant). The data were analyzed using the FactSage software. It was observed that the liquid network structure and precipitation of solid particles had an impact on high-temperature viscosity and foaming life. Under the same basicity (mass ratio CaO/SiO2 = 1.5) and at a temperature of 1500 °C, the MgO content was varied as 5.7 wt.%, 7.4 wt.%, 9.6 wt.%, 11.5 wt.%, and 13.6 wt.% in A0~A5. The solid fractions of different samples were estimated with FactSage software and found to be A0–A2 (0 wt.%), A3 (2.77 wt.%), A4 (6.92 wt.%), A5 (11.7 wt.%). The viscosities of A0–A5 measured at 1500 ·C were 22, 47, 40, 76, 363, and 1088 mPa×s, respectively, and the foaming life was 2.0 min, 7.7 min, 6.2 min, 13.4 min, 16.8 min, and 18.0 min, respectively. It was found that A5 exhibits the best effective foaming life under these environmental conditions because it can ex-hibit a double foaming effect formed by the precipitation of solid particles. The Si-O-Si network in liquid slag also contributed to foaming life, when there was only liquid slag bonding in the slag, the effective foaming life was 7.7 min. In the absence of these factors, the foaming life was only 2 min.

Abstract The heavy use of coal-derived coke (CDC) in steel industry makes it a major contributor to the greenhouse emissions. With the impact of global warming knocking our doors, the CDC has experienced supply shortages and increasing costs. Such scenario has raised the need to find a sustainable and renewable replacement to CDC. Hard-wood biomass has emerged as a promising alternative to the CDC. While such sources of virgin biomass remain at high cost, other types of agro-industrial residues constitute an opportunity for further sustainable utilization. In the current work, we have assessed the suitability of an abundant source of biomass waste, i.e., lignin-rich press mud (LPM), for steel industry. Hard carbons were obtained from LPM through a thermal treatment at a wide range of temperatures, and the chemical content (i.e., impurity) of all carbons was compatible with the steel making process. Before fitting the LPM-derived carbons (LPMCs) for such purpose, several carbon properties (e.g., chemical content and reactivity) and carbon-steel interactions (e.g., iron oxide/slag reduction, steel carburizing) were comprehensively studied and evaluated. The LPMC obtained at high temperature has particularly demonstrated an excellent reduction performance and desirable slag interactions compared to a typical metallurgical coke. The diffusion of S from LPMC into steel was an issue raised and discussed in this study. The reduction of S in LPMC was demonstrated and a subsequent enhanced C uptake in steel of 2.38% was achieved. Graphical abstract Image 1073 Highlights • Lignin biomass was transformed into hard carbon. • The resulting carbon was used for iron oxide and slag reduction. • Enhanced reduction efficiency was achieved with the biomass-derived carbon. • Desirable interactions were observed between the resulting carbon and the slag. [ABSTRACT FROM AUTHOR]

Environmental aspects and the sustainable manufacturing of steels require producers to pay more and more attention to the efficient utilization of materials and waste products during steelmaking. This study is focused on the evaluation of possibilities for the recovery of metals (such as Fe, Ni and Cr) from waste products used for slag foaming in the Electric Arc Furnace (EAF) process. Two types of industrial briquettes were produced by mixing mill-scale from the hot rolling of stainless steels with anthracite and pet-coke, respectively. Thereafter, an assessment of the metal reduction processes in briquettes at high temperatures (1500 °C) was made by using laboratory thermo-gravimetric reduction experiments in an argon atmosphere. The amounts of metal, slag and gas obtained from the briquettes were estimated. In addition, the velocity and time for the removal of metal droplets from the liquid slag depending on the size of the metal droplets was estimated. It was found that up to 97% of metal droplets can be removed from the slag during the first 30 min. Moreover, results showed that most of the Cr, Ni and Fe (up to 93−100%) can be reduced from oxides of these metals in briquettes at 1500 °C. Moreover, the anthracite and pet-coke in the investigated briquettes have similar reduction capabilities. It was found that up to 330 kg of Fe, 28 kg of Ni and 66 kg of Cr per ton of added briquettes can be recovered from waste products by the industrial application of those briquettes for slag foaming in EAF.

The crucial role of foamed slag in improving the effectiveness of the arc-furnace process is beyond any doubt. However, there is no consistent approach to the description of the slag foaming mechanism despite the wide application of this process in modern electric-arc furnaces. Aspects of assessing the effectiveness of slag foaming are considered. A new index characterizing the slag foaming rate is introduced. It allows determining the superficial gas velocity that ensures effective foaming of slag depending on its physical and chemical properties. [ABSTRACT FROM AUTHOR]

This article provides an analysis of the effect of adding hot-briquetted iron (HBI) on the main smelting production indices, DSP-150 lining working layer life, and refractory material consumption for servicing under PAO Tagmet electric steel smelting workshop conditions. Various schemes are considered for HBI charge fractions to a furnace and the optimum version is determined. Changes in slag composition are analyzed with use of HBI. Recommendations are proposed for furnace lining servicing under conditions of using HBI on the example of DSP-150 operated on a solid charge in order to improve its life. The economic saving effect of introducing the recommendations is demonstrated. [ABSTRACT FROM AUTHOR]

One of the current trends in resource saving in steel making is replacement of conventional carbonaceous materials by recycled carbonaceous materials (RCM), such as end-of-life tires containing carbon black. A 'cold model' is used to study the foaming of steelmaking slag, the structure and morphology of products of thermal degradation of RCMs and their effect on the foaming process. The energy efficiency of the foaming process where conventional carbonaceous materials are partially replaced by RCMs is evaluated. [ABSTRACT FROM AUTHOR]

A new method of preventing slopping is proposed in this paper, by simply blowing gas at the top of the foam surface. The physical experiment results show that the foam height can be effectively decreased by the top blowing air. The maximum decrease of the foam height can reach around 70 mm with an initial foam height of 145 mm in the current setup, around a 48% decrease. The first 40 mm of the foam height is easy to destroy with a low flow rate from the top. However, it is increasingly difficult for a further decrease in the foam height. Different types of nozzles show a large difference in the role of destroying the foam. The air flow velocity from the nozzle outlet is found to be the key factor for a decreased foam height. Overall, three foam destruction mechanisms are proposed. When the top air flow velocity is small, the drag and pressure destruction mechanisms are the main reasons for the decrease in foam height. However, when a large top air flow velocity is used, the coalescence and breakup mechanisms due to a high turbulence and the shear force on gas bubble shape deformation become important. [ABSTRACT FROM AUTHOR]

End of life tyres are discarded at an alarming rate reflecting the strength of developing countries economy and the intensity of trade and transportation. Conversely, environmental concerns are increasing the need for alternative materials in steelmaking industries. The solution to this problem involves the development of environmentally-friendly technologies that would utilize these waste products. The present study investigates carbon/slag reactions, including slag foaming and FeO reduction, for a range of coke/rubber blends.

Nowadays, an effective application of energy required for stainless steel production in the electric arc furnace (EAF) by a slag foaming practice and recycling of waste products play two of the most significant roles for a sustainable steel production. In this study, briquettes were used to obtain a combined slag foaming and waste product reduction in the EAF process. Briquettes with different densities produced partly from waste products were tested in an industrial scale to study slag foaming in the EAF process during stainless steel production. The slag foaming tendency was determined based on visual estimations of slag foaming, evaluations of the slag density before and after addition of different briquettes, and by calculating a foaming index. The influence of the main parameters of briquettes (composition, density) and the furnace slag (composition, basicity, and, etc.) on slag foaming was studied. It was found that both heavy and light briquettes can be used for slag foaming. The heavy briquettes, with FeCr, produce about half the amount of gas compared to the light briquettes, without FeCr. The main part of the gas, >80%, was generated during the first 2-3 min, Moreover, the highest slag foaming rate was obtained for slags with a basicity in the range of 1.31-1.49. [ABSTRACT FROM AUTHOR]

The modern sustainable stainless steel making industry is characterized by different factors such as an efficient utilization of energy in the Electric Arc Furnace (EAF) by a slag foaming practice and an utilization of waste products from its own production facilities. In this study, the foaming briquettes applied for a combined slag foaming and waste product reduction in the EAF are characterized. The recipes of the briquettes were made based on a literature review and previous experience. Afterwards, the composition and density of briquettes were estimated and compared to calculated data. Moreover, weight reduction experiments were made on a laboratory scale at temperatures up to 1500 °C in an argon atmosphere in order to characterize the products (metal, slag, and gas). Based on these results, the calculations were compared with experimental data. The following main results were found: (i) the density of briquettes can be successfully verified, (ii) briquettes have different mechanical properties depending on the materials used for production of briquettes, and (iii) the briquettes yield in different amounts of metal and gas. Moreover, it was found that light briquettes (without FeCr) produced almost double the amount of gas in comparison with heavy briquettes (containing FeCr); valuable metals can be recovered from briquettes, and recipes of briquettes can be optimized based on the amount of metal droplets in briquettes and the total utilization of carbon. [ABSTRACT FROM AUTHOR]

Development and assimilation of a production method for smelting periods in an EAF with rational composition magnesia slags are described. A set of engineering methods for improving EAF operating efficiency is developed and introduced. [ABSTRACT FROM AUTHOR]

Abstract: A computational fluid dynamic (CFD) model has been developed for the simulation of slag foaming on bath smelting slag (CaO–SiO2–Al2O3–FeO) by considering foam as a separate phase. The CFD model has been used to predict the foam height, bubble number density and the multiphase flow phenomena in the system. The height of foam is dynamically balanced by the formation of foam due to transformation of both gas and liquid into foam and its destruction due to liquid drainage and bursting of bubbles, transforming foam back to liquid and gas. The bubble break-up and coalescence were considered in gas–liquid dispersion whereas in the foam layer, the bubble coalescence due to film rupture was incorporated. A population balance modeling was used to track the number density of different bubble classes and fixed pivot method was used to discretize the population balance equation. The model predicted the foam height of the slag system (CaO–SiO2–Al2O3–FeO). The content of FeO was changed and its effect on the foam height predicted. The foaming index was calculated and the results from the model predict that the foaming index decreases with increase of FeO content in slag. The CFD model also predicts that the foaming index of a slag with Al2O3 is higher than that of slag without Al2O3. Dimensionless analysis was performed based on the model available in the literature to correlate the foaming index with the physical properties of the slag. The predicted results from the present study are in reasonable agreement with available experimental data. [Copyright &y& Elsevier]

Metal foams have potential for variety of applications such as ultra-light weight structural components, heat insulations and energy absorber. Commercially available metal foams are made mostly by aluminum alloys, which are manufactured using titanium hydride as a foaming agent. Iron based metal foam has several advantages over aluminum alloy foam such as high strength, high energy absorbability and low cost. However, it is hard to manufacture iron foam using conventional foaming agents because of a significant difference between their decomposition temperatures and melting point of iron. Further, even if good foaming agent can be utilized, it is also difficult to obtain iron foam with high porosity. In this study, therefore, new manufacturing method of porous iron by foaming of molten oxide and reduction of foamed oxide was studied. This foaming phenomenon is very famous in the field of steel making, while it should be suppressed. The tablet of Fe, Fe2O3, Al2O3, and CaCO3 was heated rapidly in the crucible to foam the molten oxide by carbon dioxide generated from carbonate in the inert atmosphere. The target oxide system is FeO-Fe2O3-CaO-Al2O3. The time, at which maximum porosity was obtained, became longer with decreasing the foaming temperature. This is because the decomposition rate of CO2 from CaCO3, which is foaming agent of this method, decreases with decreasing temperature. Maximum porosity of the oxide was approximately 57% at 1350 °C, and the pore shape obtained in this study was spherical. After reduction of the iron oxide in the obtained foam to the reduction degree of 95%, the composite material of metallic iron, oxide, and pore was obtained with higher porosity than this oxide. [ABSTRACT FROM AUTHOR]

Selected IMPHOS (IMproving PHOSphorus refining) heats ([], []: Millman et al. in Proc. Scanmet 3, 2008; and Millman et al. in Ironmak Steelmak 38:499, 2011), have been used to make observations on decarburizing and dephosphorising performance characteristics during BOS refining. If it is assumed that decarburization takes place solely in the slag/metal emulsion then maximum metal residence time in the emulsion is just under 9 sec and at peak decarburisation time, the maximum amount of metal in the emulsion is ~ 50 % of the total metal content in the converter. To evaluate the effects of changes in slag component chemistry on phosphorus refining it is necessary to account for changes in slag weight, which can change substantially throughout a heat and be significantly different heat-to-heat. Dephosphorising performance depends on the thermodynamic stability of slag phases that are able to take-up phosphorus and the distribution of phosphorus between these thermodynamically stable phases. The application of proprietary thermodynamic models such as MTDATA and FACTSage has helped to clarify such events. The stability of the foamy slag/metal emulsion changes over the period of the blow. Slag height increases with an increase in FeO (tot) wt% and decreases with a decrease in decarburisation rate and the collapse of the foamy slag. [ABSTRACT FROM AUTHOR]

Abstract: In this communication, the advantages and difficulties of the slag foaming process control are presented, highlighting the thermodynamic simulations role in the design of isothermal solubility diagrams (which express the relationship between MgO and FeO contents, in weight percentage, for a specific basicity and temperature). These diagrams can predict the liquid composition changes required in order to induce a longer foam lifetime at the upper surface of molten slags. Mathematical models and experimental tests have been used to understand the slag foaming phenomenon, however they do not simultaneously consider all variables involved in this process. Thus, a comparison between some experimental results and isothermal solubility diagrams was made in this work. According to this evaluation, the use of thermodynamic simulations can be a good alternative to help keeping the slag foam generation while some equipment is being used in the steel production. The use of isothermal solubility diagrams provides a clear image of which adjustments can be made in order to attain stable foam, reducing the needs for some additional experimental analyses. [Copyright &y& Elsevier]

Electric Arc Furnace (EAF) steelmaking uses different carbon based materials as foaming agents. Depending on cost and availability, anthracite and metallurgical coke are among the conventional injecting materials. Considering the energy and green house gas emissions requirements, alternative carbon sources are put on the spot to replace, at least partially, the conventional materials, i.e. waste materials such as rubber and high density polyethylene (HDPE) plastics may react with gas and slag phases resulting in devolatilization, combustion and iron oxide reduction reactions. The addition of waste tyres and waste plastics in EAF steelmaking has been studied in detail by our groups at UNSW and OneSteel is developing a method for EAFs to use blends of different proportions of rubber/HDPE plastics and coke as a slag foaming agent. Initially, laboratory investigations were carried out to establish the feasibility of carbon and polymer blends as foaming agents. The enhanced slag foaming performance compared to coke was found to be in good accordance with the results obtained in the laboratory indicating an increased slag volume when using polymeric blends. Following the successful installation of materials handling systems at both plants, the use of a rubber and coke blend is no longer considered a trial and is instead standard practice. [ABSTRACT FROM AUTHOR]

A study of the typical characteristics of electrical arc furnace (EAF) slags in the production of the stainless steel (AISI 304L) was carried out. Twenty-eight slag samples were taken from 14 heats. Simultaneously with each slag sampling, the temperature of the steel was measured, and one steel sample was taken. The selected slag samples were studied both using SEM–EDS and light optical microscopy. Computational thermodynamics was used as a tool to predict the equilibrium phases in the top slag as well as the amount of these phases at the process temperatures. It was observed that, at process temperature, the stainless EAF slag generally consists of liquid oxides, spinel particles and metallic droplets. Under normal operation, the amount of spinel particles is 2–6 wt-%. In addition, the influence of the slag temperature, basicity, MgO content and Cr2O3 content on the amount of spinel precipitates and thereby on the foaming index of the top slag is also illustrated and discussed. More specifically, it was found that, within the compositional range of the slag samples, the critical parameter affecting the amount of solid spinel particles in the slag is the chromium oxide content. [ABSTRACT FROM AUTHOR]