Smelting Research Articles

Application of a Magnetic Field in Metal Melting

Application of a Magnetic Field in Metal Melting

Electrochemical investigation of scorodite synthesis for arsenic fixation using hematite as an iron source: Elucidation of reaction acceleration by Fe2+ using a local-cell model

Owing to the chemical stability of scorodite, the synthesis of scorodite for arsenic fixation has gained interest as a treatment method for arsenic-containing wastewater generated at nonferrous metal smelting plants and other facilities. Diverse synthesis processes have been investigated such as hydrothermal, oxidation, and solid iron oxide methods. The solid iron oxide method using hematite as an iron source is particularly promising owing to its many advantages. Though the overall reaction equation for this process does not include Fe2+, the reaction is influenced by Fe2+ in the solution, significantly increasing the reaction rate. In the present study, we examine the mechanism of this reaction electrochemically to elucidate the role of Fe2+. By analyzing the open-circuit potentials and the polarization behaviors of each local reaction and conducting short-circuiting experiments based on the predicted local-cell model, we demonstrate the electrochemical nature of the reaction, which involves the reduction of hematite and the oxidation of Fe2+. In addition, the multistep reaction involved in the formation of scorodite is discussed using potential–pH diagrams based on thermodynamic reference data.

Numerical simulation of pure metal melting and solidification with coupled multiphysics analysis

Numerical modeling of the melting and solidification process is a complex phenomenon. It involves the coupling of various physics, such as thermal, structural & fluid flow. This article examines the solidifying of structural steel metal simulated by coupled thermal, structural, and fluid flow physics was taken in to account and run in COMSOL Multiphysics software. In this present study, both solid and fluid phases are taken in a single domain and separated with a fusion temperature boundary. With the help of Stefan energy balance condition, the moving front (interface boundary of solid & liquid region) through time is calculated. A coupled heat transfer and laminar flow distribution and phase transition by a moving boundary interface were considered. Later, structural analysis is coupled with the study of stress distribution. Numerical modeling of transient coupled multiphysics is used for investigating the thermal distribution, velocity profiles, and stress distributions during the solidification process.

Effect of thermal treatment of chromium iron melts on the structure and properties of castings

The article describes the results of experimental studies for the effect of thermal treatment (TTM) of G-X300CrMo27-1 high-chromium cast iron samples in the solid–liquid and liquid state on the structure, phase composition, and properties of ingots. For ingots with a carbon content of 2.8 to 4.5 wt%, cooled at a rate of 3.3 * 10−2 deg s−1, the dependencies of the structure, phase composition, composition of primary, eutectic carbides and matrix, hardness HV and microhardness of its individual phases and resistance to abrasive wear from the temperature of isothermal holding at TTM. A significant effect of the TTM temperature of melts on the structure and properties of high-chromium cast iron ingots was detected. The temperatures of inflection on the plotted curves for the characteristics of the structure and properties of the ingots were associated with a phase transition in iron at 1400 °C and with a point on the phase diagram liquidus of the Fe-Cr system. This as well as an increase in the concentration of chromium in the composition of primary carbides with an increase in the TTM temperature up to 1480 °C, made it possible to assume that (Cr, Fe)7C3 clusters stable in composition were formed in the melt of such cast irons below ∼1500 °C. The reasons for the decrease in the size of primary carbides during G-X300CrMo27-1 molten chromium iron overheating above 1500 °C were substantiated based on these data. During the TTM of fine-crystalline ingots made of hypereutectic cast iron in the temperature range between the liquidus and solidus lines, it was detected that the primary carbides (Cr, Fe)7C3 recrystallized resulting in a significant decrease in the chromium content and an increase in the iron content in them. At the same time, their sizes did not change significantly. Their share increased, and the share of eutectic carbides decreased. Such a process also had a significant impact on the properties of the resulting ingots. The most preferable temperatures of hot metal cast irons in the liquid and solid–liquid states were identified based on the results of the studies.

Carbon Storage in Earth's Deep Interior Implied by Carbonate‐Silicate‐Iron Melt Miscibility

AbstractCarbonate melts have been proposed to exist in the lower mantle, but their interaction with other lower mantle melt compositions is poorly understood. To understand miscibility in the carbonate‐silicate‐metal melt system, we simulate endmember, binary, and ternary melt mixtures and study how their Gibbs free energies of mixing evolve with pressure. We find that carbonate‐metal and carbonate‐silicate melts have miscibility gaps that close with increasing pressure, while silicate‐metal melts are immiscible at all lower‐mantle pressures. Extending this analysis to the core‐mantle boundary, we suggest three miscible melt fields near the endmember carbonate, silicate, and iron melt compositions. Analysis of the densities of these miscible melt compositions indicates that some carbonate‐rich and some silicate‐rich melt compositions are gravitationally stable at the core‐mantle boundary and could be candidate compositions to explain ultra‐low velocity zones. Additionally, we evaluate the speciation of an example immiscible melt composition at various pressures throughout the mantle and identify reduced carbon species that would be expected to form in the melt. Our analysis reveals that a majority of Earth's carbon could have been transported to the core during core‐mantle differentiation and that much of Earth's carbon may be stored in the deep interior today.

The positive effect of designing a gas fired reverberatory furnace in recycling aluminum scraps in our environment

A furnace is a device for high furnace heating, through (fuel or gas combustion, co-generation, electric or induction). A gas fired reverberator furnace was designed,a reverberator furnace is mainly used for the extraction of tin, copper, aluminum and nickel metals as well as in the production of certain concretes and cements. It is a metallurgical or process furnace that isolates the materials being processed from contact with fuel, but not from contact with combustion gases.The furnace was fired with liquefied petroleum gas (butane) at a constant temperature of 660.3 degrees was maintained in order to melt metals efficiently. The reverberator furnace side walls were lined with refractory bricks and glass fibers to reduce heat loss to the amount. The device was observed to use only one-third(1/3) of the time used by the conventional bituminous coal charged. Addition of oxygen enhances the combustion rate, thereby reducing the time in melting. An efficiency of about 76% was obtained from design analysis as melted scraps were used in the production of simple tools.

Study on the dissolution diffusion behavior of Al in Sn melt

The Al-Sn alloys with a large melting point difference and large density are widely used in sliding bearings in the aerospace and automobile industries. But the problem of insufficient alloying easily occurs during the preparation process due to the physical properties. This paper investigates the dissolution and diffusion behavior of Al in Sn Melt. The dissolution rates of Al in Sn melts at different temperatures were calculated. The research results show that the Al/Sn diffusion is dominated by the diffusion of Sn into Al, the Sn melt penetrate into the solid Al to form diffusion channel leading to the exfoliation and aggregation of the unmelted Al particles. Then, an electromagnetic field treatment technology was introduced to improve sufficient alloying by regulating the flow field of the metal melt. It can accelerate the diffusion and redistribution of elements at the Al/Sn solid-liquid interface, as well as change the dissolution mechanism of Al/Sn interface.

Tracking the multiple Hg sources in sediments in a typical river-lake basin by isotope compositions and mixing models

In this study, total mercury (THg) contents and Hg isotope compositions in sediments were investigated in the Lianxi River, Zijiang River and South Dongting Lake to identify and quantify multiple Hg sources and evaluate the Hg environmental processes. The THg contents, δ202Hg and Δ199Hg values in sediments were 48.22 ∼ 4284.32 µg/kg, − 1.33 ∼ 0.04‰ and − 0.25 ∼ 0.03‰, respectively. Relatively distinct Hg isotope characteristics of sediments were presented in the Lianxi River, Zijiang River and South Dongting Lake, indicating the dominant Hg sources considerably varied in these regions. Source apportionment based on MixSIAR proved that Hg in sediments mainly originated from industrial activities, and the ternary mixing model concluded non-ferrous metal smelting was the dominant industrial Hg contributor in the Lianxi River. Compared with the Lianxi River, the relative contribution of Hg in sediments from industrial activities significantly decreased, while the relative contributions of Hg from background releases significantly increased in the Zijiang River and South Dongting Lake. Nonetheless, the contribution of industrial Hg in this study area deserves more attention. These results are conducive to further manage Hg pollution.

Capture gaseous arsenic in flue gas by amorphous iron manganese oxides with high SO2 resistance

In non-ferrous metal smelting, the problem of gaseous arsenic in high-sulfur flue gas is difficult to solve. Now we have developed oxygen-enriched amorphous iron manganese oxide (AFMBO) based on the unique superiority of iron-manganese oxide for arsenic capture to realize the effective control of gaseous arsenic in the non-ferrous smelting flue gas. The experimental results show that the arsenic adsorption capacity of AFMBO is up to 102.7 mg/g, which has surpassed most of the current adsorbents. In particular, AFMBO can effectively capture gaseous arsenic even at 12% v/v SO2 concentrations (88.45 mg/g). Moreover, the spent AFMBO possesses pronounced magnetic characteristics that make it easier to separate from dust, which is conducive to reducing the secondary environmental risk of arsenic. In terms of mechanism study, various characterization methods are used to explain the important role of lattice oxygen and adsorbed oxygen in the capture process of gaseous arsenic. Moreover, the reason for the efficient arsenic removal performance of AFMBO is also reasonably explained at the microscopic level. This study provides ideas and implications for gaseous arsenic pollution control research.

Removal of C, Si, Mn, S and P in Iron Melt under Hydrogen Plasma

Removal of C, Si, Mn, S and P in Iron Melt under Hydrogen Plasma

Redefined interface error, 2D verification and validation for pure solid-gallium phase change modeling by enthalpy-porosity methodology

For simulating phase change process of pure solid gallium, previously published literature contains some key problems, including the inappropriate definition & computation for interface errors, and the unsatisfactory numerical verifications & validations. Herein, the 2D verifications and 2D validations for the enthalpy-porosity modeling of pure gallium melting starting from a vertical end wall have been reported comprehensively. The well-known and classic experimental data presented in literature are used to verify and validate the model. The groundbreaking contributions in this work are that: i) The definition and computational method of the interface-position errors between the numerical and experimental results are revisited and proven carefully; ii) The numerical schemes as well as major parameters of 2D modeling gallium melting are selected with overall interface error <9%. However, these schemes and parameters are not appropriate for the solidification modeling of gallium due to the irregular and non-reproducible interface shapes caused by highly anisotropic properties of solid crystal gallium as experimentally reported in literature; iii) The 2D validations of enthalpy-porosity modeling of gallium melting are investigated in detail, and the maximum interface error is within the limits of ±12%. Moreover, the simulated liquid volume fractions and dimensionless heat transfer coefficients are well correlated in terms of related criteria parameters, and they are compared with correlations available in literature. It is concluded that to solidly validate the modeling of pure metal melting, both the global parameters (e.g., volume-averaged liquid fraction) and the local parameters (e.g., interface position) need to be considered together.

Effect of simulated root exudates on the distribution, bioavailability, and fractionation of potentially toxic elements (PTEs) in various particle size fractions of zinc smelting slag: Implication of direct revegetation

Direct revegetation is a promising strategy for phytostabilization of metal smelting slag sites. Slag comes into direct contact with root exudates when slag sites undergo direct revegetation. The slag particle size fractions are considered the key factor influencing the geochemical behaviour of potentially toxic elements (PTEs). However, the effects of root exudates on the geochemical behaviours of PTEs in various slag particle size fractions remain unclear. Here, the effects of simulated root exudates of perennial ryegrass (Lolium perenne) directly revegetated at a zinc smelting slag site on the distribution, bioavailability, and fractionation of PTEs (Cu, Pb, Zn, and Cd) in various slag particle size fractions were investigated. The results showed that PTEs mainly occurred in the <1 mm slag particles; the mass loads of PTEs in the <1 mm slag particles were higher than those in the >1 mm slag particles. The bioavailability of Cu, Zn, and Cd rather than Pb in the slag increased as the particle size decreased. There was a decrease in the <0.25 and 1–2 mm slag particles and an increase in the 0.25–0.5, 0.5–1, and >2 mm slag particles in the presence of root exudates. Root exudates enhanced the transformation of acid-soluble PTEs into other more stable fractions in various slag particle size fractions. Root exudates enhanced the aggregation of slag particles associated with the migration of PTEs, causing differences in the geochemical behaviour of PTEs in various slag particle size fractions. These findings are beneficial for understanding the geochemical behaviour of PTEs in metal smelting slags undergoing direct revegetation and provide an important basis for the guidance of environmental risk management of the revegetated metal smelting slag sites.

Improved catalog of NOx point source emissions (version 2)

Abstract. We present an updated (v2) catalog of NOx emissions from point sources as derived from TROPOspheric Monitoring Instrument (TROPOMI) measurements of NO2 (Products Algorithm Laboratory (PAL) product) combined with wind fields from ERA5. Compared to version 1 of the catalog (Beirle et al., 2021), several improvements have been introduced to the algorithm. Most importantly, several corrections are applied, accounting for the effects of plume height on satellite sensitivity, 3D topographic effects, and the chemical loss of NOx, resulting in considerably higher and more accurate NOx emissions. In addition, error estimates are provided for each point source, taking into account the uncertainties of the individual retrieval steps. The v2 catalog is based on a fully automated iterative detection algorithm of point sources worldwide. It lists 1139 locations that have been found to be significant NOx sources. The majority of these locations match power plants listed in the Global Power Plant Database (GPPD). Other NOx point sources correspond to cement plants, metal smelters, industrial areas, or medium-sized cities. The emissions listed in v2 of the catalog show good agreement (within 20 % on average) to emissions reported by the German Environment Agency (Umweltbundesamt, UBA) as well as the United States Environmental Protection Agency (EPA). The data are publicly available at https://doi.org/10.26050/WDCC/No_xPointEmissionsV2 (Beirle et al., 2023).

An experimental investigation on debris bed formation from fuel coolant interactions of metallic and oxidic melts

During postulated severe accidents in a light water reactor (LWR), the core melt (corium) may relocate to the lower head and fail the reactor pressure vessel (RPV). The corium is expected to undergo fuel coolant interactions (FCI) if the reactor cavity is flooded with water. Both FCI energetics and resulting debris bed coolability are of paramount importance to reactor safety, since the ex-vessel corium poses a threat to the containment integrity if steam explosion occurs or the debris bed is uncoolable, leading to release of radioactive fission products to the environment. The present study is intended to quantify the characteristics of a debris bed resulting from FCI, which are crucial to debris bed coolability. Different from the previous studies with only oxidic materials, various materials, including metallic ones of Sn, Sn-Bi and Zn as well as oxidic one of Bi2O3-WO3, were employed as the simulants of corium (mixture of UO2/ZrO2/Zr/Fe) in the present study to investigate the effects of melt materials, melt superheat and coolant subcooling on debris bed formation in a water pool. High-speed photography was applied to visualize melt jet breakup, droplets fragmentation, as well as fragments sedimentation on the pool floor. Other obtained data are debris bed shape (profile) and porosity, as well as morphology and size distribution of debris particles. The comparative results of various tests provided insights toward filling the knowledge gap on debris bed characteristics under different melt materials and compositions.

Investigation of a novel ceramic coating for graphite electrodes in electric ARC furnaces using numerical simulation, experimental method, and industrial testing

Electric ARC furnaces (EAF) are referred to as a set of furnaces in which the process of melting metal materials takes place using an electric ARC. The temperature of melting and discharging in these furnaces is different and can vary between 1600 and 3000 ℃. These furnaces can use lime, fluorine, iron, etc., and ferroalloys to produce metal products such as steel or cast iron. The production of EAF metal products depends on various factors, including graphite electrodes. Electric electrodes are one of the main components of EAF, which transfer the current by creating an electric ARC from the electrode arms to the furnace load. Nowadays, a growing need is felt for using graphite electrodes in electric ARC furnaces (EAF). The validity of SiO2/ TiO2 productive coating is evaluated to decrease the corrosion resistance of graphite electrodes through the experiments. The corrosion of the graphite samples was simulated using finite element (FE) simulation in ANSYS software. FE simulation was used to model the actual working condition of electrodes in the EAF. The validity of SiO2/TiO2 productive coating is evaluated to decrease the corrosion of electrodes by using numerical simulation, experimental methods, and industrial testing in the EAF. All the tests and experiments performed in this study were to obtain a more precise consideration of the corrosion of electrodes. Also, using the TGA (Thermo-gravimetric analysis), the results show that this ceramic coating has a prominent role in decreasing the corrosion of electrodes at high temperatures. Finally, it was realized that coating the surface of graphite electrode with two layers of SiO2/ TiO2 would effectively decrease the consumption of graphite electrodes.

A New Approach to the Study of Archaeological Charcoal: The Case of Metallurgical Furnaces of the Southeastern Altai

In recent years, dendrochronological analysis in archaeology has undergone a substantial transformation, offering an opportunity to use samples of wood that were previously considered uninformative. One striking example is the analysis of charcoal excavated from archaeological sites. We have studied 448 samples of charcoal collected from metallurgical (iron smelting) furnaces in the Kurai and Chuya basins of the Russian Altai Mountains. Earlier methods of preparing such samples were slow and ineffi cient. Our approach guarantees fast, simple, and high-quality preparation of a large number of samples of virtually any size and shape. Its advantages include low cost of apparatus, high quality measurement of annual rings, the possibility of effi cient remote measurement, no need for verifi cation, and a wider range of measured parameters of the annual ring. Hopefully, the new approach will help to solve the critical problem relating to the construction of a tree-ring chronology in the arid zone of Southern Siberia. Such a c hronology will be highly prospective for assessing the age of wood from numerous mounds in the intermountain depressions of the Altai- Sayan region, and year-by-year reconstructions of the humidity regime; and for revealing extreme droughts and other climatic phenomena in this territory.

Temperature and key element content prediction based on BP neural network optimized by genetic algorithm

In the process of metal smelting, the precise control of temperature and key element content has important significance in improving the performance of metal smelting. This paper uses the values of 2048 light intensity to predict the flame temperature and the content of the key elements in the raw materials in real time.First, Feature extraction of optical information data based on polynomial fitting model is established to find the characteristics of optical information data, and then these features will be extracted.Then, establish the prediction model based on the BP neural network to probe the relationship between Kelvin temperature T and key element content C.

Internal differentiation and volatile budget of Mercury inferred from the partitioning of heat-producing elements at highly reduced conditions

Understanding the behavior of elements under highly reduced conditions is fundamental to explain the differentiation, crust formation, and volatile budget of Mercury. Here we report experiments on a synthetic composition representative of the bulk silicate Mercury (BSM), at pressure up to 3 GPa, temperature up to 1720 °C, and under highly reduced conditions (∼IW − 8 to ∼IW − 1, with IW the iron-wüstite oxygen fugacity buffer). We determined partition coefficients for >30 minor and trace elements between silicate melt, metal melt (FeSi), sulfide melt (FeS), and MgS solid sulfides. Based on these results and published literature, we modeled the behavior of heat-producing elements (HPE: U, Th, and K) during Mercury's early differentiation and mantle partial melting and estimated their concentrations in the mantle and crust. We found that U, K and especially Th are principally concentrated in the BSM and did not partition into the core because they are not siderophile elements. Uranium is chalcophile under highly reduced conditions, and so our model suggests that an FeS layer at the core-mantle boundary formed during Mercury's primordial differentiation would likely have incorporated large amounts of U, significantly increasing the Th/U ratio of the BSM. However, this is inconsistent with the chondritic or slightly sub-chondritic Th/U ratios of Mercury's lavas. In addition, the likely presence of mantle sulfides, such as MgS, would have also fractionated U and Th, increasing the mantle Th/U. It is possible to have an FeS layer if Mercury formed under less reduced conditions, or if the building blocks of Mercury had Th/U ratios close to the lower end of chondritic data. If, as suggested by our model, no FeS layer formed during differentiation, it means that the majority of HPE are concentrated in Mercury's thin silicate part. Based on the compatibility of U, Th and K, we also show that surface K/Th and K/U ratios are respectively 2–4 times and 3–6 times lower than expected for initial K/Th and K/U ratios similar to enstatite chondrites, implying that the planet suffered an important volatile loss via mechanisms that remain undetermined.

Falling Angle of Fe‐C‐Based Alloy Droplet on Coke and Graphite

The hold‐up of molten pig iron and slag melt in the coke packed bed of blast furnace (BF) causes a decrease of void between coke lumps and inhibits gas permeability. Smooth dripping of those liquids in the coke bed is desirable to keep the productivity of BF. Herein, the conditions for smooth flowing of molten iron on coke surface are calrified, and the falling angles of Fe‐C and actual pig iron droplets on coke and graphite are measured at high temperature. It is found that Fe‐C droplet easily slids down on coke because of small falling angle, and the falling angle of actual pig iron is even smaller, while those droplets adhere to a graphite substrate. The carbon in iron has only a small effect on the static contact angle with coke, but has a great influence on the falling angle. From the viewpoint of the roughness of coke surface, the variation of static contact angle and falling angle is discussed.

Morphological and compositional changes of chromite as it descends in the black top of a platinum group metals smelter

The decomposition of chromite ore in platinum group metal (PGM) concentrates and the further partitioning of chromium between PGM matte and gangue were investigated under conditions typically found in the black top of primary PGM smelters. UG–2 and Platreef PGM concentrates were fired under isothermal conditions at eight different temperatures from 800 up to 1480 °C, in sealed steel capsules. The microstructural and chemical evolution of chromite, as well as the partitioning of chromium, was studied by characterizing the PGM concentrates before and after firing, using SEM–EDS analysis. Results showed that between 800 and 1100 °C (i.e., below the solidus temperature of the silicate portion of the concentrates), the chromite particles exhibited limited reduction of Fe3+ to Fe2+ at the chromite surface, similar to the early stages of chromite reduction observed in the ferrochrome industry. After heating at 1200 °C and above, the formation of a liquid silicate was confirmed. This liquid phase acts as a solvent for the spinel components, which are subsequently transported through this liquid silicate phase to the sulfide phases and undissolved enstatite particles. At temperatures of 1300, 1400 and 1480 °C, the dissolved Al2O3 and FeO diffuse away from the chromite surface. This leads to the saturation of the adjacent liquid silicate in MgO and Cr2O3, and subsequently, MgCr2O4–rich spinel crystals precipitate. A maximum of 1.1 mass% Cr was found in the matte at 1480 °C. Chromium was transferred to the matte through reaction of the liquid matte with solid chromium-containing spinel phases and through partitioning between the liquid silicate gangue and the liquid matte.