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The viscosity of CaO–SiO2–FeOt–Al2O3–BaO steel slag with the BaO substitution for CaO is measured. Calculation of the corrected optical basicity and the apparent activation energy of the steel slag are executed. The effect of substituting CaO with BaO on structure evolution is studied. The measured results show that the viscosity of molten slag increases with the BaO substitution. The values of corrected optical basicity decrease from 0.63441 to 0.62329 with the BaO substitution. The apparent activation energy shows an upward trend from 152.78 to 160.62 kJ mol−1 with the BaO substitution. The Fourier transform infrared reflection analysis indicates that the structure complexity of the [SiO4] and [AlO4] tetrahedrons is increased with the BaO substitution. The Raman analysis indicates that the translation of Q0 and Q1 to Q2 and Q3 is advanced with the substitution of BaO for CaO in molten slag. The conversion of O2− to O0 is promoted with the substitution of BaO for CaO using X‐Ray photoelectron spectrometer analysis. The complexity of the molten slag network structure and the degree of polymerization are all increased by the substitution of BaO for CaO, which sits comfortably with measured viscosity results. [ABSTRACT FROM AUTHOR]

In this study, the wetting and corrosion behavior of slags containing vanadium (V) and titanium (Ti) on the oxidized surface of MgO–C refractory (MO), were investigated. The microstructures and phase compositions were analysed at the interface between the slag and MO substrates, alongside an examination of the corrosion mechanism. The findings unveiled that adding V2O3 and TiO2, whether individually or in tandem, reduced the slag's melting point and the contact angle between the slag and MO substrate. The molten slags mainly penetrated the MO substrates through pores, cracks, and grain boundaries, forming silicate, and vanadate phases at the slag–MO interface. In particular, the V–containing slag demonstrated stronger susceptibility to corrode the MO substrate due to the capacity of V to form low–melting point phases with MgO. This led to deeper penetration and a larger corroded area within the substrate. These findings offer valuable insights for the design and optimization of slags containing V and Ti and MgO–C refractory materials in metallurgical processes. [ABSTRACT FROM AUTHOR]

The present study investigates the wetting and corrosion behaviour of slags on dense Al2O3 ceramics, focusing on the influence of varying vanadium- and titanium oxide content. Physicochemical properties of the slag were assessed by measuring wetting angles, heights and diameters of the molten slags on the alumina at different temperatures. Microscopic observations and elemental composition analysis were conducted on the interface between the corroded Al2O3 ceramics and the slags. Our findings demonstrated that the V2O3 addition in the slag leads to its oxidation to V2O5, which further reacts with Fe2O3 and MnO to form low melting point phases such as FeVO4 and MnVO6. Consequently, the melting point of the slag decreases significantly, resulting in a decreased wetting angle with the Al2O3 ceramics. The presence of unsaturated alumina in the slag leads to the dissolution of aluminium ions from the ceramics into the slag, which reacts with Fe2O3 and MnO to form spinel phases, contributing to material loss of the ceramics. Infiltration of the slag into the Al2O3 predominantly occurs through the alumina grain boundaries. Two types of infiltration are identified: one involving reactions with alumina to form low melting point phases like Fe2O3 and the other involving inherent low melting point phases such as MnVO6. In contrast, the penetration of SiO2 into the alumina substrate is limited. Additionally, the dissolution of Al2O3 into the slag creates pathways for further infiltration. This study highlights the significant influence of Ti and V content on the physicochemical properties of the slag and provides insight into the corrosion mechanism of Al2O3 ceramics by Ti and V containing slags.

Molten slag has different properties depending on its composition. The relationship between its composition, structure, and properties has been the focus of attention in industrial manufacturing processes. This review describes the atomistic scale mechanisms by which oxides of different compositions affect the properties and structure of slag, and depicts the current state of research in the atomic simulation of molten slag. At present, the research on the macroscopic properties of molten slag mainly focuses on viscosity, free-running temperature, melting point, and desulphurization capacity. Regulating the composition has become the most direct and effective way to control slag properties. Analysis of the microevolution mechanism is the fundamental way to grasp the macroscopic properties. The microstructural evolution mechanism, especially at the atomic and nanoscale of molten slag, is reviewed from three aspects: basic oxides, acidic oxides, and amphoteric oxides. The evolution of macroscopic properties is analyzed in depth through the evolution of the atomic structure. Resolution of the macroscopic properties of molten slag by the atomic structure plays a crucial role in the development of fundamental theories of physicochemistry. [ABSTRACT FROM AUTHOR]

Centrifugal granulation is one key step to enable waste heat recovery from the molten slag in the iron and steel industry. Yet, it remains unknown about the granulation characteristics of molten slag with different chemical compositions, especially at high throughput. In this work, we provided an experimental study on centrifugal granulation with four types of molten slags. The stage-specific centrifugal granulation was recorded and analyzed at first. Both effects of atomizer configuration and chemical compositions on granulation were investigated in detail. The cup-type atomizer favors film-mode disintegration and possesses better anti-adhesion capacity although the final granule size was not strongly affected by the atomizer configuration. Most importantly, centrifugal granulation has been demonstrated with appreciable adaptability to composition-specific blast furnace (BF) slag with binary basicity of 0.9–1.3. The present study not only sheds light on the modest effect of the chemical composition of molten slag on centrifugal granulation characteristics, but also gains credit for the adaptivity of CGATER.

Effect of MgO content on wetting and corrosion behaviour of corundum substrate by CaO–SiO2–MgO (−15%Al2O3) molten slags was investigated at 1450°C via joint application of a sessile drop technique, SEM–EDS detection and FactSage thermodynamic software. All slags exhibit good wettability on the substrate, and the contact angle values are small. Increasing MgO content from 7% to 9% in CaO-SiO2-MgO slags can increase the contact angle between the droplet and the substrate, while the substrate dissolution thickness and the slag penetration depth tend to decrease. Increasing MgO content from 8% to 15% in CaO-SiO2-MgO-15% Al2O3 slags can also increase the contact angle, but significantly decrease the slag penetration depth. The indirect dissolution thickness increases instead due to the formation of a large amount of MgAl2O4 by the interface reaction. The wettability can give an indication of the slag penetration depth in the substrate but not the dissolution thickness of the substrate. [ABSTRACT FROM AUTHOR]

The viscosity of steel slag plays an important role in mass transfer, steel-slag reaction rate and slag discharge. The viscosity of CaO–SiO2–FeOt–(Al2O3)–BaO slag with different Al2O3 content was measured. The effect of Al2O3 on structure evolution was investigated. The results showed that the viscosity of steel slag increased by the addition of Al2O3. The FTIR and Raman analysis all showed that the structures of [SiO4] symmetric tetrahedron and [AlO4] asymmetric tetrahedron were more complex by the addition of Al2O3. The XPS analysis the showed that the overall relative fraction of O0 increased from 34.72% to 38.05%, O- decreased from 55.55% to 54.07%, and O2- decreased from 9.73% to 7.88% with the Al2O3 content from 0% to 6wt%. The above analysis meant the degree of polymerization (DOP) increased by the addition of Al2O3, which are agree well with the results of viscosity measurement. [ABSTRACT FROM AUTHOR]

The viscosity of steel slag has an important influence on phosphorus mass transfer in dephosphorization process and slagging-off after dephosphorization. In current work, the viscosity of steel slag was measured and the influence of BaO on viscosity and structure evolution of steel slag was studied. The results showed that the viscosity of steel slag decreased with the addition of BaO. The Fourier transform infrared spectroscopy (FTIR) analysis showed that the degree of polymerisation (DOP) of steel slag is reduced by the addition of BaO. The Raman spectra quantitative analysis revealed that the convertion of Q² and Q³ to Q0 and Q¹ was promoted by the addition of BaO. The X-ray photoelectron spectroscopy (XPS) analysis indicated that the general relative fraction quantity of O0 decreased and that of O2- increased with the addition of BaO. The above analysis are agree well with the results of viscosity measurement. [ABSTRACT FROM AUTHOR]

The entrained flow gasification has been identified as the most promising gasification technology. Serious environmental pollution and waste of land resources are caused by the increasing amount of storage and production of coal gasification slag. The aim of this work is to explore the feasibility of high-temperature combustion and melting technology for treating coal gasification fine slag and determine the important parameters of system operation. The flow properties and molten slag structure characteristics of three fine slags from different entrained flow gasifiers were studied. Depending on the melting mechanism of melt-dissolution, the melting time of fine slags is short. Three fine slags all produce glassy slags, which is conducive to slag discharge. The degree of polymerization of silicate melt is proportionate to the amount of SiO2 in the slag. A part of Al3+ exist in the form of [AlO4]5− because of the effect of CaO and Na2O, as the network former. Finally, the degree of polymerization of the three type molten slag was calculated by considering the role of Si and Al in molten slag and the property of each one. [ABSTRACT FROM AUTHOR]

Molten slag has different properties depending on its composition. The relationship between its composition, structure, and properties has been the focus of attention in industrial manufacturing processes. This review describes the atomistic scale mechanisms by which oxides of different compositions affect the properties and structure of slag, and depicts the current state of research in the atomic simulation of molten slag. At present, the research on the macroscopic properties of molten slag mainly focuses on viscosity, free-running temperature, melting point, and desulphurization capacity. Regulating the composition has become the most direct and effective way to control slag properties. Analysis of the microevolution mechanism is the fundamental way to grasp the macroscopic properties. The microstructural evolution mechanism, especially at the atomic and nanoscale of molten slag, is reviewed from three aspects: basic oxides, acidic oxides, and amphoteric oxides. The evolution of macroscopic properties is analyzed in depth through the evolution of the atomic structure. Resolution of the macroscopic properties of molten slag by the atomic structure plays a crucial role in the development of fundamental theories of physicochemistry.

Traditional methods of disposing of oil-based drill cuttings do not provide the much-needed benign treatment. In this study, a skid-mounted thermal plasma processing device was developed with a designed maximum processing capacity of 0.8 kg/min. When the input power of the plasma torch is 10–50 kW, the temperature measured by the thermocouple is 385–1979 °C. After plasma treatment, the morphology of oil-based drill cuttings changes from jelly-like to vitreous state solid structure, and the content of organic matter decreases with the decrease in weight. Mass and volume reductions of 40.98–61.49% and 25.02–68.81%, respectively, were achieved in a treatment period of 0.5–3 min. The total organic compound reduction of 73.08–98.12% was equally achieved in the same treatment period. Due to the special structure of the glassy state residue, the leached concentration of toxic metals is far below the Chinese standard for landfill leachate discharge. This effectively solves the problem of secondary pollution of solid waste. Therefore, thermal plasma technology is an effective alternative method to treat oil-based drill cuttings. [ABSTRACT FROM AUTHOR]

Approximately 35 % high-temperature waste heat in the steel industry is carried by blast furnace slag and steelmaking slag, and thermal radiation is a primary pathway for this waste heat to dissipate into the ambient environment. Thermophotovoltaic (TPV) systems can convert short-wavelength thermal radiation into electrical energy, but the long-wavelength radiation is still wasted. Here, this work introduces a concept of spectral-splitting (SS) for full-spectrum thermal radiation utilization, allowing simultaneous waste heat recovery by TPV and heat-to-power methods such as Stirling engine (SE). To further demonstrate this concept, an SS TPV-SE system is designed. An optical transmission window of 0–1.7 μm is applied for TPV, and an over 5 μm absorption window is applied for SE. Results show that, with a 0.1 × 1 m molten slag chute, the SS TPV-SE system yields an output power of over 1300 W and achieves an overall efficiency of around 19 %, resulting in an about 58 % improvement compared to the standalone TPV system, and leads to a CO 2 emission reduction of 7516 kg/year. Provided the improved energy efficiency and environmental sustainability, the spectral-splitting concept presented in this work provides a promising approach to enhancing waste heat recovery in the steel industry. • A novel concept of spectral-splitting and cascade utilization of thermal radiation is introduced. • A SS TPV-SE structure for waste heat recovery in steel industry is developed and evaluated. • Numerical simulations are performed to optimize the operating parameters of the SS TPV-SE system. • A comparison is conducted between the SS TPV-SE system and existed WHR methods in terms of efficiency and output power. [ABSTRACT FROM AUTHOR]

• The interaction behavior of slag-iron-carbon multiphase flow has been investigated. • The wetting behavior of molten iron on the graphite is controlled only by its own carbon content. • The wetting behavior of slag on the graphite is influenced by both the carbon content of the molten iron and the composition of the slag. • The reduction ability of dissolved carbon is significantly stronger than that of solid carbon. The interaction between molten slag, liquid iron, and carbon is one of the most typical and complex multiphase flow behaviors in the high-temperature zone of blast furnace. The wetting behavior among these phases is the most fundamental characteristic that determines their interactions. This research focuses on the co-wetting behavior of molten slag and iron on graphite, using high-temperature experiments and atomistic simulations. The results revealed that the multiphase cooperative reaction wetting process is influenced by multiple factors. The wettability of molten iron is mainly affected by its initial carbon content, while the wettability of slag is influenced by both the initial carbon content of the molten iron and its own compositional changes. The initial carbon content in molten iron affects the carburizing reaction, which in turn influences the wetting mechanism between molten iron and graphite. Additionally, it alters the reaction of FeO in the slag, thereby modifying the properties of the slag-carbon interface and affecting the overall co-wetting process. Meta-dynamic calculations showed that the reduction of molten iron oxide by dissolved carbon is significantly more effective than that by solid graphite carbon, demonstrating that the behavior of carbon between iron and slag is a key factor in the multiphase cooperative reaction process. [ABSTRACT FROM AUTHOR]

It remains a longstanding challenge to recover the waste heat from molten slags in pursuit of lower energy and carbon intensity in the metallurgical industry. To tap the heat from molten slag, the enabling technology i.e. centrifugal-granulation-assisted thermal energy recovery (CGATER) has been proposed and evolved from the laboratory concept into technological embodiment. Further development and deployment of CGATER necessitate a thorough, informative understanding of the multiscale CGATER physics; this is often enabled by modelling. Yet, the availability of informative CGATER physics is very limited due to the insufficiency and complexity of CGATER models. It is thus nontrivial to understand the current CGATER models and most importantly, the challenges and opportunities in future CGATER development. Herein, we first introduce the fundamental physics of CGATER. Second, we provide an overview of the CGATER models in the recent decade. Finally, we further analyze the missing pieces in current CGATER models and suggest future development of the CGATER models. According to the authors' opinion, revisiting current CGATER models is essential. In the future, joint efforts from academia and industry are advocated to develop multiscale, multiphase CGATER models which are expected to accelerate the large-scale implementation of CGATER in the metallurgical industry. • This work provides the most complete summary of the CGATER models. • The complexity of multiscale CGATER physics is elaborated with viable solutions proposed for the multiscale problems. • The gap between the CGATER modelling and CGATER experimental trials is stressed. • New perspectives for future research directions are highlighted towards the industrial-scale CGATER practices. [ABSTRACT FROM AUTHOR]

This paper presents the scientific and technological principles of electrochemical removal of diffusible hydrogen by reactions of hydroxyl and hydrogen in molten aluminum fluoride slag and in the gas phase. A model was proposed for the electrochemical processes in the weld pool with the formation of aluminum fluoride polymer clusters in TiO2–CaF2–Na3AlF6 slag to reduce the content of diffusible hydrogen, decrease the volume of slag inclusions, and improve the mechanical properties of bainitic steel welded joints. [ABSTRACT FROM AUTHOR]

Hydroponic farming promotes high-efficiency water, fertilizers, and high productivity under a controlled environment. However, the use of this system needs consistent application of fertilizers, increasing the cost of operations. Molten Slag (MS), a waste from the Municipal Solid Waste Incineration has essential nutrients that can be used as fertilizer. The objective of this study was to clarify the releasing process of nutrients by molten slag to be applied as a substrate in hydroponic system. For this, anion and cation contents of three varieties of Molten Slag (MS1, MS2, MS3) were determined in the laboratory by a shaking method. The nutrient content, P2O5, K2O, MgO and CaO were in MS1, MS3 and MS2. The quantification ion released was performed at 1, 6, 12 and 24 hours. It was observed that MS3 had performed the best condition in the releasing process of K+, Mg+, SO4 2- and Cl-. Although MS1 had higher nutrient content, MS3 released higher contents of those minerals among the samples. According to the result of this study, it was confirmed that MS3 has a high potential for hydroponic farming. [ABSTRACT FROM AUTHOR]

High-gravity technology was applied to the dissolution process between molten slag and solid modifiers to accelerate the modification of hot slag. In this study, MgO and SiO 2 rods were chosen as typical modifiers, and the effects of high-gravity (G = 800) and normal-gravity (G = 1) fields on the dissolution process between molten slag and solid modifiers were researched. The effects of high-gravity forces on the penetration depth and boundary layer of the dissolution process of the rod in molten slag were investigated using optical micrographs, X-ray fluorescence, X-ray diffraction, scanning electron microscopy, and electron probe microanalysis. Under high gravity conditions, the penetration depth of the slag melt into the solid rod was larger because the melt could enter deeper and smaller cracks and gaps, which increased the contact area and accelerated the dissolution process. The penetration depth increased from 0.1 mm to 1.07 mm in the MgO rod system and from 0.55 mm to 1.99 mm in the SiO 2 rod system. Moreover, the boundary layer of ions between the solid rod and slag melt became thinner, which promoted the diffusion of ions; the boundary layer thicknesses were reduced from 1.91 μm to 0.45 μm in the MgO rod system and from 96.88 μm to 51.63 μm in the SiO 2 rod system. In addition, high centrifugal forces could remove pores by pushing air bubbles from inner liquid–solid interfaces to the surface of the molten slag. The elimination of bubbles at the interfaces favored the penetration and dissolution processes. This study provides a rapid and effective new modification method to reduce the energy loss of molten slag and increase the output of modified slag. [ABSTRACT FROM AUTHOR]

The wetting and corrosion behavior of the corundum substrate anode by CaO–SiO 2 –MgO molten slag was investigated via the joint application of the sessile drop method with applied voltage and SEM-EDS technique. The slag drop exhibited a good wettability on the corundum substrate. The apparent contact angle at zero voltage slightly exceeded that at a 1 V applied voltage but was lower than those at 1.5 V and 2 V ones. Low applied voltage of 1 V had little effect on the corundum substrate's direct dissolution corrosion processes; high ones of not less than 1.5 V caused the electrode reaction to occur. The stirring effect of O 2 bubbles from the anode reaction aggravated the substrate's direct dissolution and physical stripping. It was found that the applied voltage could inhibit the slag penetration, and the apparent contact angle had no obvious relation with the direct dissolution thickness and penetration depth. A thin but almost continuous MgO⋅Al 2 O 3 (MA) layer could form at the slag/substrate interface at the applied voltage of 1.5 V. These results indicate the positive effect of applied voltage on the distribution of interfacial products and the molten slag penetration in reducing the corrosion of corundum anode under certain conditions. However, when the applied voltage was too high, the vigorous electrode reaction could aggravate the direct dissolution and physical stripping of the corundum anode, and damage the continuation of the formed interface product layer with a high melting point. [ABSTRACT FROM AUTHOR]

Chemical and physical analysis was performed to identify the molten slag composition and its ability to be used as alternative catalyst in pyrolysis of waste cooking oil. The implementation such type of catalytic material could be useful in reducing the process cost. To increase the efficiency (increase the active site) of molten slag, it was modified by acid washing that resulted in an increase in the acidity from 159 to 1224 µmol/g. The results showed that the yield of bio-fuel was increased and the product selective to n-C15 upon the modification of molten slag by acid treatment. Copyright © 2020 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).

Turning molten slag into a solid state involves a complex cooling history that significantly influences the quality of the final product. It is crucial to unveil the crystallization dynamics of molten slag during practical cooling, particularly in the post-cooling course with temperature rise. In this work, we employed the single hot thermocouple technique to visually investigate the crystallization behavior of blast furnace slag. A series of control experiments were conducted to quantify the effects of temperature rise features and chemical composition on incubation time (τ o - τ l), crystallization temperature region (T o ∼ T e), and the average crystal growth rate (Vα). The results proved that the governing factor of V α changed from nucleation growth rate to nucleation rate, resulting in a significant difference in crystallization phenomena between the continuous cooling condition and temperature rebounding condition. Considering the post-peak temperature, temperature rise rate, and corrected optical basicity exerted remarkable effects on the crystallization behaviors, we established correlations for predicting τ o - τ l , T o , T e , and V α by fitting experimental data. These correlations offer valuable insights for optimizing cooling parameters in dry slag treatment, contributing to a comprehensive understanding of crystallization dynamics in high-temperature slag subjected to intricate cooling histories. [ABSTRACT FROM AUTHOR]

This research aims to investigate the influence of the slag basicity from 1.40 to 1.83 on dephosphorization of the hot metal with a CaO–FeO–SiO2–MgO–Al2O3 molten slag at the low temperature of 1653 K. The results indicated that the dephosphorization ratio was increased with the increase of basicity. Even at the low basicities of 1.73 and 1.83, the dephosphorization ratios can be as high as 77.3 and 80.7%, respectively. With the increase of basicity, the contents of P2O5 and total iron in the slag were increased, whereas the content of MnO was decreased. The distribution ratio of phosphorus (L P) was expressed as log ⁡ L P = 19.4 Λ − 6381 T + 5.244 + log ⁡ f P + 5 4 log ⁡ P ( O 2) . The L P values calculated by the present method are well consistent with the measurement values. Besides, the dark grey phase B and the light grey phase D could be considered as the phosphorus-rich phases containing C2S solid particles. [ABSTRACT FROM AUTHOR]

Water quenched blast furnace slag is an excellent hydrated material. However, dry granulation is a new treatment method for molten blast furnace slag that has numerous advantages compared to water quenching. This study investigated the size distribution of slag particles obtained from the dry granulation of molten slag. In addition, the effect of using the slag obtained from dry granulation in slag cement blends was analyzed. All the results showed that there was a wide size distribution range of blast furnace slag particles in ligament formation. The mean diameter of the solid particles decreased as the rotating speed increased. Meanwhile, the glass content in slag particles decreased for a fixed diameter of the metal collecting tray. The strength of slag cement concrete was low at a low rotating speed. In contrast, obtaining slag particles at a high rotating speed was beneficial for producing a compact structure in the slag cement blend. Unlabelled Image • The mean diameter of solid particles decreased with an increase in rotating speed. • It is easy to form compact structure in slag cement at high rotating speed. • The strength of slag cement was determined by slag powder size distribution. [ABSTRACT FROM AUTHOR]

The structural properties of molten CaO–SiO2–P2O5–FeO slag system with varying slag basicity have been investigated by molecular dynamic (MD) simulations using the pairwise potential model. The result shows that more than 95 % Si and 98 % P are four coordinated and form tetrahedral structures. Non-bridging oxygen occupies a predominant position in the system. With basicity increasing from 0.6 to 1.5, the proportion of non-bridging oxygen increases from 66.3 % to 77.3 %, whilst the bridging oxygen decreases from 30.1 % to 10.2 %. Both the result of MD simulations and Raman spectroscopic analysis show the proportion of Q0 increases with increasing slag basicity, whilst Q2 and Q3 decrease. The degree of polymerization of CaO–SiO2–P2O5–FeO system decreases with increasing slag basicity.

Chemical and physical analysis was performed to identify the molten slag composition and its ability to be used as alternative catalyst in pyrolysis of waste cooking oil. The implementation such type of catalytic material could be useful in reducing the process cost. To increase the efficiency (increase the active site) of molten slag, it was modified by acid washing that resulted in an increase in the acidity from 159 to 1224 μmol/g. The results showed that the yield of bio-fuel was increased and the product selective to n-C15 upon the modification of molten slag by acid treatment. [ABSTRACT FROM AUTHOR]

Due to the large radiation and difficulties in determining the solid fraction, conventional methods are not appropriate to measure the thermal conductivity of high-temperature molten slag. This paper presents a method to measure the thermal conductivity of molten slag above 600 °C. Solidification of molten slag was implemented by using copper finger dip test. A mathematical model was established to describe the heat transfer process during solidification. Results indicate that when the temperature is between 600 and 800 °C, the thermal conductivity decreases with the increase in temperatures. In the initial stage of solidification, molten slag will transform from liquid to glass under rapid cooling process. As solidification proceeds, the cooling rate decreases gradually with time, and crystals begin to precipitate from liquid. For molten slag with short incubation time, the high nucleation rate of crystals will lead to large amount of crystals in the solidified layer and the higher thermal conductivity. [ABSTRACT FROM AUTHOR]

The distributions of Sb and Sn between slag and matte in equilibrium with tridymite in the Cu-Fe-O-S-Si system at 1200 °C (1473 K) have been measured. The experimental technique involves high-temperature equilibration in sealed quartz ampoule, rapid quenching, and direct measurement of phase compositions using Electron Probe X-ray Microanalysis (EPMA). The closed system equilibration approach was used to minimize the evaporation of Sb and Sn from the samples. The experimentally-determined distribution coefficients of Sb and Sn between slag and matte were found to increase with increasing Cu concentration in matte above 40 wt%. The new data have been used to refine the computational thermodynamics model for the system containing Sb and Sn at dilute concentrations. The molten slag phase is described using the Modified Quasichemical Model in the Quadruplet Approximation. Liquid matte and metal phases were modelled using single solution built within the Modified Quasichemical Model in the Pair Approximation. The thermodynamic model can be used to assess and predict the deportments of Sb and Sn between the slag and matte phases in the high-temperature pyrometallurgical production, refining and recycling of copper. [ABSTRACT FROM AUTHOR]

Abstract At present, centrifugal granulation has become the most promising method for waste heat recovery of molten slag. This paper investigates the effects of rotary disk configurations on particles characteristics with molten aluminum as the working medium. Four types of rotary disks and two kinds of particles characteristics which included particles size distribution and particles mean size were studied. It can be seen that the main particles sizes are populated in the range of 2.0~4.0mm for all disk configurations. Due to the special surface structure, the particles produced by curved-block disk and arc-edge disk configurations are more concentrated compared to other two types of disks. Besides, the results shown that the mean size of particles generated by curved-block disk is smaller. All the conclusions will be helpful for future development of the high-temperature molten slag dry granulation systems. [ABSTRACT FROM AUTHOR]

In order to improve the recovery of iron resource in molten basic oxygen furnace (BOF) slag through carbothermal reduction, bottom blowing argon gas is used to promote the mixing efficiency between molten slag and graphite particles in the converter. In the present work, computational fluid dynamic-discrete particle model (CFD-DPM) method coupled with the reduction kinetic model of FeO in molten slag by graphite particle is employed to simulate the multiphase system composed of molten slag, graphite particle and argon gas. The motion and dispersion characteristics of graphite particles in a bottom-blown converter were mainly investigated, and the decrease of graphite particle diameter caused by the reduction reaction was considered. A particle dispersion index was also proposed to evaluate the distribution uniformity of graphite particles in the molten slag. In addition, the effects of initial particle diameter and bottom tuyere arrangement on the dispersion characteristics of graphite particles were further discussed. The results show that the proportion of large-sized particles is higher in the inactive-flow zone and the motion trajectory of graphite particles can be divided into two regimes. Graphite particles with an initial diameter of 5 mm and the converter with six bottom-blown tuyeres are more conducive to the homo-dispersion of graphite particles. The dispersion characteristics of graphite particles in a bottom-blown converter were investigated for molten BOF slag reduction. Based on the migration distance and particle size decrease, the motion trajectory of graphite particles can be divided into two regimes. Graphite particles with an initial diameter of 5 mm and the converter with six bottom tuyeres are more conducive to the particle homo-dispersion and reduction of molten BOF slag. [Display omitted] • Reduction reaction-induced decrease in graphite particle diameter is studied. • The motion trajectory of graphite particles can be divided into two regimes. • A dispersion index is proposed to assess graphite particle distribution uniformity. • 5 mm particle diameter and 6 tuyeres are conducive to the particle homo-dispersion. [ABSTRACT FROM AUTHOR]

A granulated slag, which goes to a dump, forms in the metallurgical enterprise near Novoshakhtinsk (Primorye Territory, Far East) upon processing of the germanium-containing raw materials of the Pavlovsk brown coal deposit. The reclamation of this technical waste needs an energy efficient ecologically safe method that meets the requirements of ecological norms. According to modern requirements, the problem of reclamation of the slag of cyclone smelting should be solved before the beginning of operation of the enterprise. The project documentation recommends using the slag of cyclone smelting in building or the production of building materials. The chemical and granulometric compositions of the slag and the properties of the material during interaction with water should be determined to find the direction of reclamation of the slag of cyclone smelting. Using reduction-sulfidizing cyclone smelting with flux and sulfidizer additives, we formed a granulated slag, the properties of which are close to those of the commercial slag of cyclone smelting, under laboratory conditions. Samples are prepared for a further investigation. Using modern experimental techniques, we determined the composition and properties of the slag and performed chemical analysis to find macrocomponent contents and X-ray diffraction analysis for an ecological estimation. The physicochemical and organoleptic characteristics of the slag are determined according to the existing standards. For example, the maximum particle size in the slag is 10 mm and the content of the particles the size of which is more than 5 mm is 9.7%, which corresponds to GOST 5578–94. The density and humidity of the slag are determined. The solution that forms during interaction with water has a weak alkaline reaction, which does not prevent the use of the material in an industrial process. The slag is shown to be suitable for further reclamation. [ABSTRACT FROM AUTHOR]

Abstract The wetting and spreading phenomena of molten slag were observed in situ on dense MgO and MgO-C refractory substrates. Parameters associated with wetting and spreading of molten slag, such as the contact angle, droplet height, diameter, and volume, were measured and calculated. The microstructure and chemical composition of the corroded dense MgO and MgO-C refractory were studied using SEM and EDS analysis. The droplet volume of molten slag on dense MgO declined faster than that on MgO-C refractory during the first 90 s of the testing period, whereas the droplet volume exhibited little difference across the two cases after 150 s. Molten slag penetrated the dense MgO and MgO-C refractory through grain boundaries and the channels which were formed by the dissolution of MgO. Besides, the slag also penetrated into the MgO-C refractory through the pores and channels formed by the redox reaction between slag and carbon, and a reaction product (Fe) was found at the interface. The dissolution of MgO and redox reactions changed the wetting process and increased corrosion of the MgO-C refractory. [ABSTRACT FROM AUTHOR]

Thermal energy recovery of pyrometallurgy slags is a worldwide problem that is widely concerned for decades. As chemical recovery method, molten slag cascade recovery method (MS-WHCR) is proposed in this work. As typical endothermic chemical reactions, pyrolysis, gasification, calcination and reforming reactions are applied in this method. Gasification-pyrolysis system, calcination-pyrolysis system, enhanced pyrolysis system (R-SEP) and fixed carbon gasification and sorption-enhanced pyrolysis system (CG-SEP) systems of MS-WHCR method are designed. Based on the first law of thermodynamics and second law of thermodynamics, enthalpy-exergy compass analysis method is applied to analyze the exergy efficiency, consumption of reactants and products of designed MS-WHCR method, compared with traditional water quenched (WQ) method and gravity bed waste heat recovery (GWHR) method. As calculation example, 1000kg copper slag is used in this paper. The results showed that the exergy efficiency and exergy loss of WQ method are 20.7% and −947 MJ respectively. By WQ method, energy quality of molten copper slag is discounted. Copper slag particles should be fast cooled during granulation process. Thus, lots of air is blown in to make enough heat transfer with copper slag particles, which generate some exergy loss. And exergy efficiency of GWHR method is 76.9%. Using chemical endothermic reactions, MS-WHCR method improves the exergy efficiency of molten slag waste heat recovery. There is a slight fluctuation of exergy efficiency by MS-WHCR method for four kinds of systems from 66.6 to 70.1%. Fixed carbon and combustible syngas are acquired by MS-WHCR. And enhanced pyrolysis process in proposed R-SEP and CG-SEP systems improves hydrogen contents in syngas. [ABSTRACT FROM AUTHOR]

Highlights • Analogue experiments of molten slag granulation in various rotary disk configurations are carried out. • A correlation for predicting the particle size for four types of disks is determined. • The majority of the particles size is populated in the range of 2.0∼4.0 mm. • The curved-block/arc-edge disks can produce particles with smaller size. • Fibers generation is determined by Q , ω and liquid film breakup model. Abstract Rotary disk centrifugal granulation is one of the most promising methods for molten slag recovery with lower power consumption, compact and coupling with a variety of waste heat devices easily. In this paper, high temperature analogue experiments were performed by four types of disks with molten aluminum as the working fluid. The particles characteristics which include particles size distribution, particles mean size and fiber mass fraction were studied. The results show that the majority of the particles size is populated in the range of 2.0 mm∼4.0 mm for all the ω and Q. Both theoretic and experimental analyses indicate that the ω has more impact on particles size than Q. The particles produced by curved-block disk and arc-edge disk configurations are more concentrated than the other two types of disks. Besides, the mean size of particles generated by curved-block disk is smaller. A simple correlation of d m for four types of disks is proposed, which agrees well with the experimental data (R2 = 0.9172). Meanwhile, when the Q is relative low, a lower ω can contribute to the reduction of produced fiber. The main conclusions drawn from this work will be helpful for future development of the high-temperature molten slag dry granulation systems. [ABSTRACT FROM AUTHOR]

Centrifugal-granulation-assisted thermal energy recovery (CGATER) is one of the most promising routes to enable waste heat harvest from molten slags. However, it remains a grand scientific and technological challenge to produce fine particles from the bulk high-temperature molten slag, especially at large slag throughput. In this work, we established an improved model to simulate the centrifugal granulation at the large flowrate comparable to the laboratory- pilot-scale trials. For the first time, film fragmentation has been successfully reproduced by modelling. On this basis, we elucidated the intricate film fragmentation by quantifying the off-atomizer film characteristics at various operational conditions, with a strong focus on the metrics of the off-atomizer slag film. The present study provides an important and valuable CFD model to approach the underlying physics of film fragmentation. Most importantly, it opens up new possibilities for predicting slag droplet formation at experimentally unavailable operational conditions. A new CFD model is established to model the film fragmentation mode which is favored to produce large-quantity slag particles at industrial-scale applications. [Display omitted] • An updated CFD model is established to simulate the tones-per-hour centrifugal granulation of molten slag at high temperatures. • The film fragmentation mode is reproduced by modelling for the first time. • The characteristics of film fragmentation have been quantified at various operational conditions. [ABSTRACT FROM AUTHOR]

In order to optimize the removal of boron during the refining of slag to obtain solar grade silicon, the density of molten slag was measured by an improved Archimedean method within a temperature range from 1073 to 1373 K. It was found that the density of molten slag at 1723 K can be deduced by linear fitting, and that the slag density decreases with increasing temperature. However, a reduction in slag density occurs with decreasing CaO concentration. An increase in the molar volume of slag was also observed with increasing temperature.

A fully-Lagrangian numerical model was applied for understanding packed bed structures containing non-spherical solids, such as coke, and the high-temperature melt trickle flow characteristics of such beds. Smoothed-particle hydrodynamics (SPH) simulations can track the motion of liquids without discriminating between continuous and dispersed phases, and the extended discrete element method (DEM) is employed as a highly accurate method for simulation of non-spherical solid-particle motion. Based on this model, we carried out large-scale trickle flow simulations using more than 10 million particles, investigated case studies of statistical processing, and evaluated the effects of packed bed formed from various non-spherical coke samples. We found that the pathway that the passing rivulet takes down depends on the structure of the void and the neck size between two voids. If the connecting neck is larger than the capillary length λ = σ / ρ g , the slag will drain. The shape of pathway was related that the solids shape factor which is considered by the projected area in the direction of gravity. Even if cokes with similar size were obtained by sieving, low sphericity cokes block slag flow through channeling voids, i.e., as the projected area of the non-spherical solid shape increased, the liquid hold up showed a tendency to increase. [ABSTRACT FROM AUTHOR]

Reduction of FeO-bearing molten slag using solid-carbon, existing in primary slag of blast furnace (BF), consumes much BF energy. It is also a limit for BF efficiency. In this paper, reduction kinetics behavior of FeO-CaO-SiO2-MgO-Al2O3 molten slag (primary slag of BF) was investigated, and the restrictive step of the reaction was identified. It has been found that the reduction process of FeO-CaO-SiO2-MgO-Al2O3 BF slag using solid-carbon is a second-order reaction. And the reduction process is controlled by both diffusion of FeO and gasification reaction of carbon in molten slag. The apparent activation energy of reaction is 342.37 kJ/mol, the diffusion activation energy of FeO in molten slag is 355 kJ/mol, and the gasification reaction activation energy of carbon is 152.98 kJ/mol. Additionally, it is also concluded that reduction rate is influenced by temperature (T), mass fraction of FeO ( w(FeO)), and basicity (R) of the slag. Moreover, a reduction model of this slag system was established and verified by a series of experiments. [ABSTRACT FROM AUTHOR]

A new purification method of removing boron from metallurgical grade silicon (MG-Si) using a high baisicity slag was developed in this paper. The typical impurities Al, Ca, Ti, B, P etc in MG-Si can be removed by the binary calcium sillicate slag and it is especially efficient for removing impurity Boron. It was found that the maximal distribution coefficient of boron between calcium sillicate slag and silicon reaches to 1.57 when the mass ratio of CaO/SiO2 was 1.5 and the composition was 60%CaO-40%SiO2. It showed that the oxidizability of calcium sillicate slag was affected and restricted by the basicity and the mass ratio of acid oxide SiO slag according to the thermodynamic relationship. The boron concentration in MG-Si can be reduced from 18x10-6 to 4.5x10-6 and 1.4x10-6, respectively, when using the ternary slags 40.5%CaO-49.5%SiO2-10%Li2O and 32CaO-38%SiO2-30%Li2O.

Recently, a solid fertilizer with condensed nutrients was manufactured using molten slag from municipal solid waste and dried cow dung. This novel substratum was used for the afforestation of Sargassum alternato-pinnatum Yamada in the subtropical Amami Ohshima Island since 2010. Seedlings were attached to discoidal, fertilized, molten slag (DFMS) blocks by hanging fertile thalli within a cage unit (4 m), deployed at a depth of 4-5 m from March to April. The attached germlings grew rapidly from November and thalli of a total length of >1 m filled the cage by the next reproductive period the following year. Water temperature varied between 17.6 and 31.9 °C in 2013-2014; the water was oligotrophic (i.e., nitrogen-deficient). To measure the nutrients liberated from the DFMS blocks (28 × 5 cm; diameter × width), a batch experiment ( N = 3) was undertaken using 15-L seawater plastic containers with weekly water exchange. High concentrations of NH-N (16.3-90.0 μmol L) and SiO-Si (5.9-256.9 μmol L) exuded out of the blocks for a period of 3 months and lower concentrations exuded for another 3 months, even after the block was dried for 7 months. To clarify the fertilizer effects of exudates from the DFMS blocks on algae, S. alternato-pinnatum juveniles (0.7 g) were cultured in 300-mL flasks for 1 month. The juveniles produced new leaves and increased in weight in both enriched seawater and control treatments, but the color of the thallus was darker than normal. To visualize the effects more clearly, introduction of the yellowed (nitrogen-starved) thalli of the red alga, Chondracanthus intermedius, was useful because the color of its thallus turns red under enriched conditions. [ABSTRACT FROM AUTHOR]

The structural properties of molten CaO--SiO2--P2O5--FeO slag system with varying slag basicity have been investigated by molecular dynamic (MD) simulations using the pairwise potential model. The result shows that more than 95% Si and 98% P are four coordinated and form tetrahedral structures. Non-bridging oxygen occupies a predominant position in the system. With basicity increasing from 0.6 to 1.5, the proportion of non-bridging oxygen increases from 66.3% to 77.3 %, whilst the bridging oxygen decreases from 30.1% to 10.2 %. Both the result of MD simulations and Raman spectroscopic analysis show the proportion of Q0 increases with increasing slag basicity, whilst Q² and Q³ decrease. The degree of polymerization of CaO--SiO2--P2O5--FeO system decreases with increasing slag basicity. [ABSTRACT FROM AUTHOR]

For a better utilization of Zhundong coals which have high fouling and slagging tendency, the slag-tap boiler has attracted much attention. To avoid the high sensible heat loss of discharged molten slag, an air-cooling waste heat recovery system is proposed. Energy and economic analyses are conducted to investigate the effectiveness of heating the desulfurized flue gas by hot air and the influences of partially substituting the secondary air by hot air on heat transfer of air preheater and thermal efficiency of boiler. A case study is performed by referring to a typical 50 MW cyclone boiler with nine types of low fusion temperature coals. The results show that for coals with low ash content, the temperature increment of desulfurized flue gas can be over 7 ℃. While for coals with high ash content, the flue gas temperature can be heated to more than 70 ℃, and the surplus hot air can be sent to the furnace. When the hot air is introduced to partially substitute the secondary air, an instantaneous impact on the air preheater will give rise to a decrement of quantity of heat transferred and increments of temperatures of exit flue gas and hot secondary air. The variations of these thermodynamic parameters become smaller with increasing hot air temperature. After introduction of hot air, the thermal efficiency of boiler can increase, resulting in a decrease of fuel consumption rate. In addition, the heating surface area of air preheater can be reduced. [ABSTRACT FROM AUTHOR]

Heat transfer of molten slag under high temperature is significant for industrial processes. Unlike other phase change materials, the phase change temperature of molten slag is always not a constant during cooling process. In this case, the basis of judging different phases could not be accurately obtained, which brings difficulties for the calculation of radiation-solidification coupled heat transfer. In present work, the coupled conductive and radiative heat transfer of molten slag during solidification is investigated by the zonal method with fixed grid and moving area. In order to determine the liquid fraction of molten slag during phase change, the enthalpy method is improved by using crystallization kinetics. In addition, ray tracing method based traversal algorithm is developed to analyze the multiple reflection among three layers. The results indicate that the diffuse radiation in multi-layer could be described by tracking the path of reflections. However, the ray tracing method is time-consuming for computation. Compared with the ray tracing method, it is more efficient to calculate the radiative heat flux by solving a system of linear equations established according to the energy balance on each surface element. In initial stage of solidification, radiation is the main way of heat transfer. After solid slag is formed, heat transfer is dominated by conduction, and the proportion of the radiative heat flux in the total heat flux is lower than 30%. [ABSTRACT FROM AUTHOR]

In consideration of great need for the physicochemical properties of slag systems in metallurgical process estimation, this work examined the possibility of predicting multi-properties by one model. The mass triangle model was applied to evaluate the density, viscosity, surface tension and sulfide capacity of CaO-'FeO'-SiO2 system at 1,673 K. Good agreements were achieved between calculated data and experimental data in the various properties. Meanwhile, the calculated contour lines successfully predicted the properties of slag within the limited solubility area. The new model thus is competitive and flexible when an integrated knowledge of a certain system is necessary. [ABSTRACT FROM AUTHOR]

The granulation for molten slag produces a large amount of sensible and recoverable heat. In this paper, a system was proposed to simultaneously produce glassy slag and reuse the heat for production of hydrogen-rich gas via biomass catalytic pyrolysis. A variety of parameters, including slag temperature, mass ratio of slag to biomass (S/B), particles size, and rotor speed, were evaluated for their effects on pyrolysis product yields and gas characteristics. The catalytic activity of blast-furnace (BF) slag for improving tar cracking was also addressed. The conditions of 1000 °C of slag temperature and 0.6 of S/B achieved a complete pyrolysis of biomass. When the S/B value increased to 0.8, a lower slag temperature (700 °C) can afford a complete pyrolysis of biomass. The maximum gas yield was gained at a rotor speed of 16 rpm/min, when slag particles in reactor showed a “cascading” movement. BF slag exhibited a catalytic activity in tar cracking and C n H m reforming during biomass pyrolysis process. Furthermore, decreasing the slag particle size favored to produce more light gases, and less char and condensate. However, the effect of slag particle size became not evident in the subsequent catalytic reforming process. [ABSTRACT FROM AUTHOR]

The aim of the present study is the CALPHAD modeling of the systems CaO-SiO2-M2O (M=K,Na) based on a careful review of the available literature data – phase diagram and thermodynamics – as well as own experiments. The heat capacities (Cp) of three compounds, CaSiO3, K2Ca2Si2O7 and K8CaSi10O25 (determined using drop calorimetry), were included in the optimization of the ternary phase diagram CaO-SiO2-K2O.