Slag foaming in bath smelting
01 Aug 1991-Metallurgical and Materials Transactions B-process Metallurgy and Materials Processing Science (Springer-Verlag)-Vol. 22, Iss: 4, pp 481-489
TL;DR: In this article, the foaming index of bath smelting-type slags (CaO-SiO2-FeO, CaO-MgO-Al2O3-NiO) was measured at 1773 K. The results showed that the foam stability decreases with increasing FeO (FeO > 2 pct) content.
Abstract: Slag foaming measurements in terms of the foaming index (∑) were conducted on bath smelting-type slags (CaO-SiO2-FeO, CaO-SiO2-MgO-Al2O3-FeO) at 1773 K. It was found that the slag foam stability decreases with increasing FeO (FeO > 2 pct) content and basicity. For the slag system (CaO-SiO2-FeO), no stable foam was observed at very low FeO content (<2 pct). As pct FeO increases, the slag foaming index goes through a maximum and then decreases; a similar phenomenon was observed for CaO-SiO2-NiO slags with respect to the NiO content. The foaming index determined from the normal small-scale experiments (3.8-cm ID diameter) were confirmed on a larger scale (9.2-cm ID diameter), indicating that the foaming index is independent of container size. Measurements were also made for the actual compositions for bath smelting slags. For these slags, the foaming index is higher than those of simple CaO-SiO2-FeO slags, because MgO and Al2O3 may increase their viscosities. The foam index is believed to be a function of the physical properties of the slag. Consequently, a dimensional analysis was performed, and a correlation was developed relating the foaming index to the viscosity, surface tension, and density of the slag. An estimation of slag foaming in actual pilot plant trials was also made from the results of the present study. Good agreement was observed between the predicted and observed foam heights and indicated coke in the slag can reduce the foam height by more than 50 pct.
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TL;DR: This review focuses on the current knowledge regarding (i) the mechanisms governing foamability and foam stability, and (ii) models for the foam column kinetics, and critically review and summarize the models that describe macroscopic foam behaviors within the context of the mechanisms involved.
206 citations
30 Jul 2013-Metallurgical and Materials Transactions B-process Metallurgy and Materials Processing Science
TL;DR: In this paper, the effect of flux (lime) addition on the reduction behavior of iron oxide in copper slag by solid carbon at 1773 K (1500 °C) was investigated.
Abstract: We investigated the effect of flux (lime) addition on the reduction behavior of iron oxide in copper slag by solid carbon at 1773 K (1500 °C). In particular, we quantified the recovery of iron by performing typical kinetic analysis and considering slag foaming, which is strongly affected by the thermophysical properties of slags. The iron oxide in the copper slag was consistently reduced by solid carbon over time. In the kinetic analysis, we determined mass transfer coefficients with and without considering slag foaming using a gas holdup factor. The mass transfer of FeO was not significantly changed by CaO addition when slag foaming was ignored, whereas the mass transfer of FeO when slag foaming was considered was at a minimum in the 20 mass pct CaO system. Iron recovery, defined as the ratio of the amount of iron clearly transferred to the base metal ingot to the initial amount of iron in the slag phase before reduction, was maximal (about 90 pct) in the 20 mass pct CaO system. Various types of solid compounds, including Mg2SiO4 and Ca2SiO4, were precipitated in slags during the FeO reduction process, and these compounds strongly affected the reduction kinetics of FeO as well as iron recovery. Iron recovery was the greatest in the 20 mass pct CaO system because no solid compounds formed in this system, resulting in a highly fluid slag. This fluid slag allowed iron droplets to fall rapidly with high terminal velocity to the bottom of the crucible. A linear relationship between the mass transfer coefficient of FeO considering slag foaming and foam stability was obtained, from which we concluded that the mass transfer of FeO in slag was effectively promoted not only by gas evolution due to reduction reactions but also by foamy slag containing solid compounds. However, the reduced iron droplets were finely dispersed in foamy and viscous slags, making actual iron recovery a challenge.
96 citations
01 Aug 1995-Metallurgical and Materials Transactions B-process Metallurgy and Materials Processing Science
TL;DR: In this article, the foam stability in terms of the foam index for a bath-smelting type of slag (CaO-SiO2-Al2O3-FeO) was determined for different bubble sizes.
Abstract: Slag foams have been investigated with smaller bubbles than those used in the previous studies.[5,6,7] The bubbles were generated by argon gas injection with the nozzle of multiple small orifices and by the slag/metal interfacial reaction of FeO in the slag with carbon in the liquid iron. The foam stability in terms of the foam index for a bath-smelting type of slag (CaO-SiO2-Al2O3-FeO) was determined for different bubble sizes. The average diameter of bubbles in the foam was measured by an X-ray video technique. When the foam was generated by the slag/metal interfacial reaction at 1450 °C, it was found that the average bubble diameter varied from less than 1 to more than 5 mm as a function of the sulfur activity in the carbon-saturated liquid iron. The foam index was found to be inversely proportional to the average bubble diameter. A general correlation is obtained by dimensional analysis in order to predict the foam index from the physical properties of the liquid slag and the average size of the gas bubbles in the foam.
94 citations
TL;DR: In this article, the surface phenomena effect on bubble formation from a single orifice (1 mm diameter) submerged in water with air blowing at an extremely small flow rate (2 cm3 min−1).
82 citations
TL;DR: In this article, a novel aluminothermic smelting reduction (ASR) process was investigated for cleaning waste copper slag; this process is not only able to recover valuable iron, but also eliminates hazardous elements from the end-of-life slag product.
73 citations
References
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Book•
01 Jan 1979
TL;DR: Szekely et al. as discussed by the authors presented Fluid Flow Phenomena in Metals Processing, which outlines the fundamentals of fluid flow theory, emphasizing the potential applications of fluidflow concepts that are illustrated by actual problems drawn from the metallurgical literature.
Abstract: 458 pages 2012 Julian Szekely Fluid Flow Phenomena In Metals Processing 032314957X, 9780323149570 Elsevier, 2012 Fluid Flow Phenomena in Metals Processing outlines the fundamentals of fluid flow theory, emphasizing the potential applications of fluid flow concepts that are illustrated by actual problems drawn from the metallurgical literature.This book is divided into 10 chapters. Chapters 1 to 4 are devoted to the fundamentals of fluid flow, while Chapters 5 to 9 are concerned with the application of basic concepts to specific systems, such as electromagnetically driven flows, surface tension and natural convection driven flows, multiparticle systems, gas bubbles, and impinging jets. The discussion on flow measurements and introduction to physical modeling are provided in the last chapter.This publication is suitable for a one semester graduate level course for metallurgy and chemical engineering students. file download nugus.pdf
249 citations
TL;DR: In this paper, the authors proposed an experimental model based on accurate data for pure binary and ternary melts, using a simple hypothesis on the behaviour of unusual compounds, it is possible to estimate the viscosity of a complex melt.
Abstract: The viscosity of silicate melts and slags is a property difficult to measure accurately using sophisticated apparatus, it is both time consuming and expensive. The use of models to estimate the viscosity is the first step to be carried out, mainly with metallurgical slags involving numerous components. The proposed model is an experimental one based on accurate data for pure binary and ternary melts. From this data, using a simple hypothesis on the behaviour of unusual compounds, it is possible to estimate the viscosity of a complex melt. This estimation is used as a first approximation and can be amended, if necessary, by only a few direct measurements.
218 citations
01 Aug 1989-Metallurgical and Materials Transactions B-process Metallurgy and Materials Processing Science
TL;DR: In this paper, the effect of slag composition on foaming in iron and steelmaking processes was quantitatively studied for CaO-SiO2-FeO slags in the temperature range of 1250 °C to 1400 °C.
Abstract: In order to understand the effect of slag composition on foaming in iron and steelmaking processes, slag foaming was quantitatively studied for CaO-SiO2-FeO slags in the temperature range of 1250 °C to 1400 °C. It was found that slag foaming could be characterized by a foaming index (Σ), which is equal to the retention or traveling time of the gas in the slag, and the average foam life ( τ). The effects of P2O5, S, MgO, and CaF2 on foaming were studied. As expected, slag foaming increased with increasing viscosity and decreasing surface tension. It was found that suspended second-phase solid particles such as CaO, 2CaO SiO2, and MgO stabilized the foam and had a larger effect on foaming than changes in viscosity and surface tension for the slags studied.
138 citations
130 citations