Materials Processing Fundamentals 2018

This study aimed to elucidate the effect of a sulfur addition on the formation and behavior of CaS inclusions in steel melts during a secondary refining process without a Ca-treatment. Samples were taken during production for two different steel grades, namely a low-S steel (S = 0.005%) and a high-S steel (S = 0.055%). Thereafter, the inclusion characteristics were determined using an SEM combined with an EDS. The results show that the CaO content in the inclusions decreased and the CaS content increased after a sulfur addition during an RH process for the high-S steel. Furthermore, CaS-covered inclusions were frequently detected in the high-S steel samples after the S addition. Thermodynamic calculations were also performed to compare the CaS formation behavior in the two steels. The results showed that a CaS phase can thermodynamically be formed in the high-S steel melt even without a Ca-treatment. Also, it was indicated that a CaS phase can be formed in two ways, namely a reaction between Ca and S and a reaction between CaO in inclusions and S. From the viewpoint of interfacial features, inclusions covered by a CaS phase are thought to possess low contact angles to steel melts. Therefore, CaS-covered inclusions tend to remain in a steel melt. According to the results of this study, CaS inclusions can be formed and deteriorate the castability of high-S containing steels even without a Ca-treatment.

In order to maximize the use of copper slag, a new idea that copper slag is reduced to smelt copper-containing antimicrobial stainless steel was proposed. But copper-iron reduced from copper slag contains a large number of copper matte, making sulfur content high. In this article, desulfurization of copper-iron was studied. The Fact-Sage software was used to calculate ΔG of the desulfurization reaction. Calcium oxide, calcium carbide and ferromanganese were used as desulfurization agent. The results show that desulfurization capacity of calcium oxide is poor, but with addition of carbon, desulfurization effect of calcium oxide will be enhanced. Calcium carbide and ferromanganese have good desulfurization effect.

Aging treatment is the primary method to control the strength of nanoprecipitates-strengthened ferritic steels and excellent mechanical properties could be obtained by optimal combination of the size and the density of nanoclusters. In this study, the aging treatments with different time and temperatures are used to control the microstructure, size and density of nanophases. In addition, the distribution of the nanophases and dislocation pattern are observed. It is found that the strength shows an obvious transformation with the aging time and temperatures. However, the microstructures and ductility have not significantly changed with altering aging process. Furthermore, the relationship between the nature of nanophase and mechanical properties is discussed.

The liquid metal battery is composed of two liquid metals with different electronegativity separated by molten salt. The three layers self-segregate based on density allowing for easy manufacturing and scaling. Lithium (Li) is one of the most widely researched anode materials, and when coupled with bismuth (Bi) cathodes, it gives a liquid metal battery that has an open circuit voltage of 0.9 V. Such a system has demonstrated impressive rate capabilities, ultra-long life cycle, and low energy cost. Here we present a two-dimensional physics-based model for Lithium-Bismuth liquid metal batteries. The model takes into account dynamical changes in the battery, including surface concentration and fluid flow. By solving the convection-diffusion equation in Bi electrodes, we are able to investigate the effect fluid flow on kinetic losses and concentration profiles in real time. The outcome of this work allows us to link electrochemistry and fluid dynamics in liquid metal batteries. Moreover, the model can also be used to guide future development of battery management systems.

Side-blown process is regarded as an efficient, energy-saving, environment-friendly copper smelting technology. The arrangement of nozzles has significant impact on the distribution of emulsion droplets and flow pattern, which mainly decide the efficiency and result of the smelting process. In this paper, physical model was set up based on the same modified Froude number between model and industrial production. Effects of three kinds of nozzles on the size of emulsion droplet, field flow pattern and mixing time were analyzed. The results show: the SMD (Sauter mean diameter) of emulsion droplets turns normal distribution and the average SMD ranges from 2 to 4 mm. The size of emulsion droplets will decrease and the mixing time will be shorter when nozzles are more intensive. Two circulations exist in the fluid and the dead region (velocity below 0.05 m/s) will shrink when nozzles are arranged intensively.

Stirring plays an important role in the metallurgical process. Enhancing the agitation of materials can strengthen the turbulence in multiphase flow, which can shorten uniform mixing time and reaction time. In order to improve leaching reaction and heat transfer efficiency, a novel self-stirring tubular reactor driven by pressure energy used in bauxite digestion process is presented originally by Northeastern University, which combines the advantages of autoclaves and conventional tubular digestion equipment. According to the principle of dimensional analysis, the dimensionless equation between input power and various factors is established, and it is corrected to obtain input power, through verified, the calculated values are basically consistent with the experimental results.

The numerical investigation of common heat treated A356 as-cast parts was successfully exhibited by several authors for T4, T6 and T7 tempers. However, for non-uniform or local heat treatments (e.g. welding) the common procedure of estimating the material properties cannot be used. Therefore, a new methodology was developed in order to overcome the weak point in the kinetic calculation and to enable the prediction of the material properties in 3D. The single steps of the methods are described while mentioning interesting aspects briefly. Subsequently, a local heat treated structural A356 component case is presented while taking care about remelting and yielding. At the end possible areas of applications are given in which the new method can be applied.

Phase equilibria and thermodynamics in the Ag₂SnS₃–SnS–Sn₂S₃–FeS system were investigated using differential thermal analysis, X-ray diffraction, and EMF methods. Determined phase relations were used to express the forming chemical reactions for compounds Ag₂FeSn₃S₈ and Ag₂FeSnS₄. The forming chemical reactions were performed by applying electrochemical cells of the types: (–) C | Ag | Ag₃GeS₃I glass | Ag₂FeSn₃S₈, SnS, Sn₂S₃, FeS | C (+) and (–) C | Ag | Ag₃GeS₃I glass | Ag₂FeSnS₄, SnS, Ag₂FeSn₃S₈, FeS | C (+). Based on the measured EMF versus temperature relations, experimental thermodynamic data of the quaternary phases Ag₂FeSn₃S₈ and Ag₂FeSnS₄ were derived for the first time.

Aluminum based alloy can serve as anode materials for air battery that has great potential for use in electrical vehicles and other green energy applications. In this paper, effects of heat-treating Al-0.2 Mg-0.2 Ga-0.4In-0.15Sn anode materials on their electrochemical performance and corrosion behavior have been investigated. The results show that the discharge voltage of the as-cast alloy anode at 20 mAcm⁻² is higher than that of the pure Al (about 300 mV on average) in 4 M KOH solution. In general, electrochemical performance is improved with increased temperature and processing time in heat treatment. The high energy density (about 3180 Whkg⁻¹) and discharge voltage (about 1.62 V) can be obtained with heat treatment at 550 °C for 12. SEM observation reveals that the micro cracks due to the corrosion around the grain boundaries of the Al alloy anodes appear after the discharge performance in 4 M KOH solution, which may reduce the charge transfer resistance crossing the reaction layer on the anode surface.

Copper electrowinning is an important recovery method in the copper industry, which accounts for a growing proportion of the world copper production. In copper electrowinning, not all the current is used for the deposition of Cu, in large part because of the existence of dissolved iron in the electrolyte. The reduction of ferric ions is often the main factor that causes the current efficiency to decrease. The current efficiency is influenced by parameters such as electrolyte temperature, current density, iron concentration, copper concentration, etc. To obtain optimal operating conditions, thus minimizing energy consumption, a copper electrowinning current efficiency model was established using empirical formulas and electrode kinetics. Electrochemistry, gas-liquid flow, transport phenomena and comparisons to experimental data are considered to enhance the accuracy of the model. The model can predict the current efficiency under a variety of conditions to provide valuable guidance for the optimization of process parameters.

Currently, there is an increasing interest to produce energy mainly from renewable sources such as biomass. However, fouling, slagging and corrosion threaten long-term operation availability and costs of biomass power plants. Alkali metal elements in the biomass fuel and the ash fusion behavior are the two major origins contributing to slagging during high-temperature biomass combustion. Accumulated slags decrease thermal efficiency of superheaters. These slags often constitute a considerable percentage of complex inorganic phases such as K₂Ca₂(SO₄)₃. However, thermodynamic properties of these inorganic phases and their combined effect, which would help to solve the fouling, slagging and high-temperature corrosion related problems in biomass combustion processes, are not well known. In the present work, thermodynamics and phase equilibria of selected phases in the K₂SO₄–CaSO₄ system were both critically reviewed and experimentally studied. The obtained results are presented and discussed.

The JX Nippon Mining & Metals Corporation engages in copper mining, copper smelting and refining, electronic-materials production and used material recycling. The characteristic of its recycling business is applying “Zero-Emission Policy” without landfill, with operating a unique metal recovering system consists of pyro- and hydro-metallurgical processes, and with employing efficient scrap treatment system utilized from its copper smelting technology. In 2010, we constructed a pilot plant for recovering valuable metals from waste lithium-ion batteries and its cathode materials. The process consists of leaching, solvent extraction and electro-winning to recover electrolytic cobalt and electrolytic nickel as main products, and lithium and manganese carbonate as byproducts. We have changed its mind to processing mainly the waste batteries because of the difficulty of collecting waste cathode materials. This paper describes the technical changes and development, and also shows the recent operating conditions of the plant.

The Platinum Group Metals (PGMs) are of substantial technological prominence. They are also extremely rare, because of their low natural existence and their complicated extraction and refining process. To meet the future demand and preserve resources, it is essential to process end-of-life platinum-containing materials, such as catalytic converters. PGMs recovery from catalytic converters scrap commonly carried out by pyro/hydrometallurgical processes that involved thermal treatment followed by leaching and solvent extraction. This paper reviews current methods in used in the recovery of PGMs out of waste catalytic converters in Australia and discusses some of the key factors and opportunities in improving the existing methodologies. Emerging trends that are likely to affect the current or future PGM recovery are also explored.

A preliminary leaching recovery of silver metal from waste radiographic films with potassium hydroxide (KOH) in a water bath was investigated. The rinsed and cleansed films were sized into squares before being dried in an oven at 20 °C for 30 min. Silver oxide was precipitated with potassium hydroxide at varying concentrations at 90 °C in a water bath by agitated leaching. The leach solutions were filtered and the filtrates obtained analyzed for silver with Atomic Absorption Spectrophotometer. The results obtained showed that the leach liquors assayed 648.27, 984.86 and 1017.82 mg/L for KOH solutions of molar concentrations 0.02, 0.5 and 1.0 M, respectively. The silver oxide precipitate obtained after filtration was also thermally decomposed at 450 °C. Future research will include analysis for the silver content of the residue resulting from thermal decomposition. The study showed that silver metal in waste radiographic films can be leached with potassium hydroxide in a water bath at 90 °C and thus further confirm waste radiographic films as a secondary resource for silver recovery.

This project investigated alternative lixiviants for leaching copper from chalcopyrite and conichalcite, two highly refractory Cu ore minerals. Chalcopyrite (CuFeS₂) is the most abundant of the copper sulfide minerals; conichalcite (CaCuAsO₄OH) is less well known but contributes to supergene Cu inventory in high-As deposits. Neither leaches well in sulfuric acid. Sulfurous acid, glycine, methanesulfonic acid (MSA), and thiourea (for conichalcite leaching test) were tested as lixiviants for chalcopyrite- and conichalcite-bearing ores with ferric sulfate or hydrogen peroxide as oxidant. The highest Cu extraction from chalcopyrite was obtained by MSA (47% Cu recovery in 30 g/L of MSA with 5 g/L Fe³⁺ at 75 ℃ within 96 h; nearly 100% Cu extraction in 30 g/L MSA with 3% hydrogen peroxide at 75 ℃ within 72 h). Glycine recovered 20.7% of copper from chalcopyrite at room temperature within 96 h. All these compare favorably to the results of sulfuric acid leaching of chalcopyrite (1.5% recovery at 96 h). Conichalcite proved less refractory to sulfuric acid (46–71% extraction in 10 g/L H₂SO₄ with 3 g/L Fe³⁺ in 24 h) and leached almost as well in MSA (45–67% extraction in 20 g/L MSA with 3 g/L Fe³⁺ in 24 h), but glycine, thiourea, and sulfurous acid did not effectively leach conichalcite.

Presently, several copper mining plants in Chile are treating by solvent extraction aqueous solutions that contain high concentrations of chloride ions. The effect of chloride ions on the extraction of copper from chloride-sulfate solutions using the commercial extractants LIX 984N and Acorga M5910 was investigated. Copper extraction isotherms were determined at 25 and 35 ℃ for aqueous solutions of pH 2, containing 6 g/l of Cu(II), 5 g/l of Fe(II) and 2 g/l of Fe(III) with 0, 60 and 110 g/l of chloride ions. The organic solutions used were 26%v/v solutions of LIX 984N or Acorga M5910 in Escaid 110. It was determined that the presence of chloride ions affected negatively the copper extraction equilibria for both extractants, while a temperature increase from 25 to 35 ℃ produced only a small increment in the copper extraction. On the other hand, a temperature increase affected negatively the stripping equilibria.

Complex copper sulfide concentrates normally contain As, Sb, Bi, Zn, Pb, as the main impurities. Because of the high levels of these impurities, conventional smelting due to the high risk of environmental pollution cannot treat these concentrates. Oxidizing roasting has been used to remove the unwanted impurities through the gas phase, a process where arsenic is removed effectively but antimony and bismuth removal is very deficient. Because of the poor removal of antimony in oxidizing roasting, an alternative chloridizing roasting of pure stibnite and complex MH copper concentrate (Ministro Hales mine, CODELCO, Chile) has been studied. In roasting in the range of 500–650 ℃, temperature and oxygen concentration affected significantly the Sb volatilization in the case of solely Sb₂S₃–CaCl₂ sample. At 600 ℃ and 10% oxygen, antimony volatilization was 60% in 30 min. The volatilization proceeded through intermediate oxides and formation of nonvolatile antimony oxide Sb₆O₁₃ as confirmed by XRD spectroscopy. In roasting the MH concentrate at 600 ℃ and 5% oxygen, arsenic from enargite can be eliminated in less than 20 min most likely as a mixture of arsenic trichloride and trioxide. Oxygen concentration in the gas phase affects not only the rate of weight loss due to volatilization of arsenic, but also the rate of formation of non-volatile compounds.

As an important treatment method of processing the sphalerite, the technology of pressure acid leaching has many benefits, such as process flow short, no waste pollution, low production costs, high leaching rate of Zn, and S output in elemental form, which can be sold as a product. This paper takes the high indium sphalerite provided by Kunming Metallurgical Research Institute as the research object. A metallurgical behavior of sulfur conversion process is studied under high temperature and high pressure. The results indicate that the conversion rate of sulfur increases with the increasing liquid-solid ratio, leaching temperature, initial acid concentration and partial oxygen pressure in a certain range. With increasing leaching time, the conversion rate of sulfur increases first and then decreases. Considering all the aspects, the optimum parameters in the condition of conventional electric heating and microwave heating of the process are as follows: liquid-solid ratio 8:1, leaching temperature 423 K, initial acid concentration 120 g/L, partial oxygen pressure 1.0 Mpa, leaching time 90 min. The conversion rate of sulfur reaches 72.00% under the condition of conventional electric heating, 65.74% under the condition of microwave heating.

Considering the complicated and harsh conditions in the electric arc furnace (EAF) steelmaking process, the precise endpoint control technology is a crux that influences the product quality and production costs of the molten steel because precise endpoint control can control the endpoint carbon content and the endpoint oxidation. In this paper, a new hybrid prediction model was established to predict the endpoint carbon content in EAF steelmaking, which included the mechanism model based on the mass transfer process and the Extreme Learning Machine (ELM) optimized by the Evolving Membrane Algorithm (EMA). The mechanism model was calibrated with corrected parameters obtained from the ELM-EMA algorithm. As a result, the shortages that the mechanism model can’t work precisely and that the single mathematical algorithm model lacks the analysis of the metallurgy process were overcome by the hybrid prediction model. Meanwhile, modifying ELM algorithm by EMA algorithm can improve the generalization performance of single-hidden-layer feed-forward neural networks. The experiments on a 50t EAF demonstrated that the proposed model had a good generalization performance and good prediction accuracy.

Spontaneous inter-particle percolation is a common phenomenon in nature and industries. Dispersion of cohesionless particles has been investigated by means of various physical and numerical experiments. However, many granular materials are in cohesive or wet state in metallurgical and mineral processes, and the previous works have a lack of understanding the effect of cohesive force on particle dispersion behaviour. Thus, the present work systematically studies the dispersion of cohesive particles by spontaneous inter-particle percolation in a packed bed using discrete element method (DEM). The results indicate that the vertical velocity of percolating particles increases with increasing the cohesive force from 0 to 2 mg (the gravity force of percolating particle, given by ρ gπd ³/6). While for a higher cohesive force, e.g. f _c = 8 mg, insufficient percolation occurs and percolating particles stick in the packed bed. Percolating particles in the packed bed shows a diffusivity for the cases of smaller cohesive force, and the diffusion property can be described by Einstein-Smoluchowski equation. The transverse dispersion of f _c = 2 mg is smaller than that of f _c = 0, while the longitudinal dispersion becomes larger when the cohesive force changes from 0 to 2 mg. This study provides a fundamental understanding on dispersion behaviour of cohesive particles in a packed bed, and is useful for processes understanding and optimization in cohesive particles handling and mixing.