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By E. Fregeau-Wu

The major obstacle in recycling steelmaking slags to the blast furnace is their phosphorus content. Removal of the phosphorus, which is primarily associated with the silicate and phosphate phases, would allow for greater recycle of these slags for their iron, manganese, and lime contents. Calculations show that separation of the silicates from the oxide phases would remove nearly 90% of the phosphorus from the slag. The variable grain size of the as-received slag made liberation by fine grinding difficult. Therefore, slow-cooling experiments were undertaken to improve the grain size distribution. The grain size distributions were determined using in-situ image analysis. The samples were ground to their apparent liberation size and high gradient magnetic separation was used to separate the magnetic oxides from the nonmagnetic silicates and phosphates. Liberation analysis and modeling was performed on selected separation products for discussion of benefication characteristics.

Jan 1, 1995

By Paul L. Wichlacz

A mathematical model of growth and ferrous iron oxidation for attached bacteria was applied to rotating biological contactor (RBC) units treating acidic mine drainage. The model describes attached bacterial growth as a saturation function, where the rate of substrate utilization is determined by a maximum substrate oxidation rate constant, a half saturation constant, and the concentration of substrate within the RBC. The maximum oxidation rate constant was proportional to flow rate and the substrate concentration in the reactor varied with influent substrate concentration. The model was tested at three separate sites and with three different size RBC units. The ability of the model to predict the rate of iron oxidation under all test conditions was significant. The accuracy of the model was found to be affected by unit size and vary with specific test site.

Jan 1, 1985

By Joseph C. Rota

The Carlin Trend is one of the most significant gold mining districts in North America. Located in northeastern Nevada, a total of over 17 million ounces of gold have been produced since 1965 at Newmont Gold Company's open-pit and underground operations. Oxidized portions of the sediment-hosted, disseminated gold deposits at Carlin generally consist of finely disseminated concentrations of sub-micron sized native gold particles hosted in Paleozoic siliciclastic or carbonate rock. Oxide ore is commonly amenable to dump leach or heap leach processing, yielding an average 50 to 70% recovery of total contained gold. Refractory unoxidized ore requires some form of pretreatment oxidation to ensure economic gold recovery. Geologic ore control is typically combined with standard assay and engineering techniques to maintain both grade and metallurgical control ofleach grade ores. Mine geologists provide a vital function through field observation and recording ofmineralogic data during daily, visual blasthole logging. Intricately mixed refractory materials must be separated from oxide ore to ensure highest possible gold recoveries. Geologic information is combined with assay data to create mine polygons in an engineering computer database. Mining selectivity is further enhanced by in-pit ore control geologists who are available to make production decisions based on direct mineralogic observations at active mine faces.

Jan 1, 1997

By C. J. McKee

A gold-silver-lead-zinc deposit at Montana Tunnels, Jefferson County, Montana is located in a diatreme of middle Eocene age (45 to 50 m.y.). Sulfide minerals within the diatreme occur as disseminations, veinlets, and locally as breccia matrix. Principal sulfide minerals are pyrite, sphalerite, and galena. The diatreme is a matrix-rich quartz latitic breccia with a fine grained rather soft matrix and heterolithic clasts. The ore deposit contains approximately 50 million tons of ore at a grade of 0.025 oz/ton Au, 0.5 oz/ton Ag, 0.25 % Pb, and 0.65 % Zn. Mining is by open pit methods. The original process flowsheet included flotation and cyanide leaching. Problems with the leaching circuit led to a change to the straight flotation process which is presently in use. To maintain a reason-ably uniform feed material, blending of ore is required for grades of four metals as well as for ore hardness and oxidation.

Jan 1, 1988

By Li Qian

Mechanisms of bio-dephosphorization from iron ore was investigated in this Paper. The results show that there are two bio-dephosphorization ways from iron ore, the one is that Acidithiobacillus ferrooxidans directly derive phosphorus from the ore, the other is phosphorus is able to be leached acid produced during metabolizing of Acidithiobacillus ferrooxidans, and the latter is more important than the other. Adding suitable pyrite can enhance the bio- dephosphorization process through providing nourishment and producing acid directly due to S 3oxidized or indirectly due to Fe3 as oxidant. The potential varies in the range of 0.434~0.498V and pH is in the range of 2.5 ~ 1.25 during bio-leaching process. It can be founded that, according 2+to the E-pH graph of Fe-H2O system, Fe wouldn?t be oxidized under sterile system in this potential and pH ranges. It can be obviously concluded that the Acidithiobacillus ferrooxidans are 2+able to reduce the potential for the oxidization of Fe and make the oxidization occur in the above pH and potential zone, so the bio-leaching process can proceed. the investigation of E-pH graph of P-H2O system show that H3PO4 can exist steadily.

Jan 1, 2009

By Robin D. Rogers

Room temperature ionic liquids (RTIL) can replace certain traditional organic solvents in liquid/liquid extraction of metal ions from aqueous systems. The very low vapor pressure and non-flammable nature of RTIL warrant consideration of these neoteric solvents for new processing technologies which will reduce pollution, Increase safety, and lower costs. Metal ion separations in RTIL, however, will typically require the use of an extractant and research is needed to identify suitable selective extractants which have appreciable solubility in the RTIL and low solubility In the aqueous phase. Choice of extractant should also take into account the toxicity, expense, and disposal of the ligand.

Jan 1, 1999

By Fan Xiao-Hui, Jiang Li-Juan, Chen Xu-Ling

"In order to solve air leakage of sintering testing cumbersome, inaccurate results, and other issues, the sinter machine air leakage characteristics were studied, and combining the mathematical modeling and the field detection. The temperature before air leakage was calculated by mathematical model, energy balance equation was established according to sintering process, using Adams prediction correction method which has stronge stability and high precision, to solve hyperbolic partial differential equation with astringency problem. The temperature after air leakage is detected by instruments, according to energy conservation calculation the sintering air leakage rate. According to the sintering continuity and periodicity, sintering air leakage location diagnosis expert system was established to judge specific air leakage locations.IntroductionStrengthening of modern blast furnace production depends on the quality of the raw material preparation to a large extent [1]. Technical and economic index of modern blast furnace production is advanced; the most important reason is the use of concentrated feed. Sintering plant is the ""kitchen"" of blast furnace’s concentrate. As we all know, sintering plant is major energy consumption of steel plant, in sinter process energy consumption, the solid fuel consumption of total energy consumption is 75%~80%, power is 13%~20%, ignition and combustion is 5%~10%. To reduce the air leakage of sintering plant is an effective measurement to save energy consumption. At present, our air leakage of sintering compared to the other developed countries is still a long way to go. Japan’s air leakage rate is about 30%, and 35%~60% air leakage of sintering machine at home, a big gap exists between the plants. At present the determination of air leakage is all for manual operation, long measuring period, considerable manpower and resources, and the results are significantly affected by operation. For air leakage of sintering control lag issues, research and development of diagnosis expert system for on-line monitoring model for air leakage and, through this research can reduce the use of detection equipment, detect sintering air leakage, improve the yield and quality of sintering production, reduce energy consumption, and extend equipment life span."

Jan 1, 2012

By Jayagopal Uchil, M. Krishna, Shanta Sastcy

"Damping behaviour of aluminite particulate reinforced ZA-27 alloy metal matrix composites processed by compocasting method is studied. The weight percentage of particulate reinforcement is 0,1,2,3, and 4%. A dynamic mechanical· analyzer is used ·to measure the damping capacity and dynamic modulus at the natural frequency of the specimen over a temperature range of 30°C to 300 °C both in the heating and cooling cycle. The damping capacity of the material is found to increase with increase in temperature and weight percentage of aluminite reinforcement although this is accompanied by a decrease in dyliamic modulus.The damping capacity and dynamic young's modulus exhibit a sharp decrease in their values around 300 °C a8 ZA-27 alloy undergoes a first order phase transition in this region which is confirmed by Differential scanning calorimetric studies. Several damping mechanisms have been evaluated theoretically for the material under study. The damping capacity at low temperatures is attributed primarily to coefficient of thermal expansion mismatch induced dislocations and high intrinsic damping of the matrix. At higher temperatures the damping capacity is attributed to ZA-27/aluminite interface, phase transformations and thermoelastic damping.IntroductionMetal matrix composites. (MMCs) offer designers many added benefits, as they are particularly suited for applications requiring good strength at high temperature, good structural rigidity, dimensional stability, and lightweight [1-5]. At present, the usage of ceramic particles as reinforcement in MMCs has attracted considerable interest from scientists and engineers. The MMCs show substantially improved elastic modulus, strength, stiffiless, and tribological properties with low coefficient of thermal expansion compared with the unreinforced matrix material."

Jan 1, 2000

By Chen Wen, Li Zhao-jia, Zhao Qiang, Ning Shun-ming, Tang Sanchuan, Wang Hong-qiang

"The carbon-burdened and cold-bonded pelletizing-electrosmelting process is used to dispose low-grade manganese, and the qualified rich-manganese slag is obtained. On the condition that reduction roasting temperature was 1000?, reduction time was 45min, particle-size was -1mm, reductant dosage was 1.6%, basicity was 0.3, smelting temperature was 1410?, smelting time was 60min, it had a good effect on the melting between slag and metallographic phase, the manganese content was 32.58%, manganese recovery was 92.16% in the slag; while the iron content was 94.40%, iron recovery was 95.32% in the metallographic phase. It was proved by the demonstration tests.IntroductionManganese is an important raw material for steelmaking, which is extensively utilized in modern industry, the consumption of manganese for iron and steel industry accounts for 90% to 95%. After mining over 30 years, the high-grade manganese resources drop markedly, especially with the hypergrowth of steel industry, the domestic manganese is far from the requirement, as a result, we have to buy significant quantities of manganese overseas. Besides, the property of imported manganese is more and more complex, and the high-grade and lump manganese decrease year by year, while the fines and high-crystal water manganese are on the increase. Therefore, how to make effective use of domestic low-grade manganese and intensify the manganese’s smelting is an effective approach to reduce the cost of manganese series ferroalloy and improves market competitiveness[1-4]. It has important practical meaning."

Jan 1, 2012

By Wenxian Zhu, Xuema Li, Patrick R. Taylor

"Experiments were performed in a non-transferred arc, thermal plasma flow reactor to investigate the synthesis of ultra fine boron nitride (BN) powder from the reaction system of boron oxide (Bz03), methane (CH4), ammonia (NH3) and hydrogen (H2). Argon (Ar) and nitrogen (N2) were used as plasma gases. The thermodynamics and kinetics of the synthesis reactions were examined and a chemical reaction mechanism was proposed. The powders produced under certain operating conditions had high purity and good conversions. All the products were extremely fine powders (< 30nm) and were uniform in size distribution. The powder products were analyzed by chemical and physical characterization. The effects of the reaction variables on the conversions from B203 to BN and the purity of the products were investigated.IntroductionIn the past few decades, boron nitride (BN) has attracted a great deal of interest because of its excellent thermal, chemical and electrical properties (1-4) It has a high thermal stability and thermal conductivity. Chemically, it is very stable and is not wetted by most molten metals and slag. It is also an excellent low loss insulator. Since hexagonal boron nitride (h-BN) is light in weight, strong and easily fabricated, it has applications in a variety of specialized high temperature areas, such as a high temperature lubricant, crucibles for molten metals, thermocouple protection tubes, break rings for horizontal continuous casting of steel, and friction reducing coatings. In cubic form, boron nitride is one of the hardest materials known, second only to diamond, and it is an excellent material for tools in which the use of carbon based materials is limited by oxidation or reaction with metals."

Jan 1, 1998

By P. Gray

Process and engineering development of the Warner Zinc Process over the past two decades has proceeded alongside the world-wide collection and analysis of operating and cost data of current processing practices from sulphide ores to refined metals. Study of these data shows that recoveries are dependent on mineralogical characteristics of the sulphide matrix and point to the inadequacy of differential flotation as a tool for preparing feed for smelters. The paid-for return at the mine on the combined metal values in zinc rich sulphide ores rarely exceeds 80% and increasingly runs as low as 50-60%. Surveying the possible alternative ways of improving these performances leads to the conclusion that the Warner Process is the only technology in sight that could meet a target of 90% paid-for recovery and that its development has now reached a point where it can be a fully practicable process for all mixed sulphide ores.

Jan 1, 2000

By E. T. de Groot, D. L. Verhelst

With the successful start-up of Cominco's new KIVCET smelter, the final key component is now in place for Trail Operations to operate efficiently as a modern integrated zinc-lead facility. Unique metallurgical, operational, planning and management issues apply to this operation. Along with presenting the current flowsheet for Trail Operations, this paper discusses issues such as the impact of recycles, operational re-stabilization following significant process changes, plant operation with just-in-time inventories, real-time process optimization, and management philosophy.

Jan 1, 2000

By N. Menad

The formation of the dioxins can be dependent on the quantities of carbon, hydrogen, chlorine and oxygen present in a given system, as well as on parameters such as temperature and pressure. Inadequate supply of combustion air ( incomplete oxidation ), low combustion temperatures ( incomplete combustion ), and insufficient turbulence in the combustion are factors which can favour their formation. Dioxins were produced also calatytically from chlorinated phenol precursors, non-chlorinated compounds that were chemically, and reaction of phenol with inorganic chloride. In this paper different precursors such as combination of C, H, 0, Cl, rapid formation/combustion intermediates and routes to PCDFs are reviewed, and the influence of PVC amount on the formation of these isomers is discussed.

Jan 1, 2000

By Vincent Canaguier

Methane is increasingly considered as a promising reductant for metal oxides, including chromite. To assess the possibilities of such reduction route, the gas-solid reactions between Ar–CH4–H2 gas mixtures and synthetic chromites are studied between 950 and 1050 °C. The influence of Mg and Al additions on the reduction-caburization of (Fe,Mg)(Cr,Al)2O4 solid solution is investigated thermodynamically, structurally and kinetically. The product phases are examined by x-ray diffraction (XRD), scanning electron microscopy (SEM), and electron probe microanalysis (EPMA). The reaction rate is derived from real-time exhaust gas measurements and post-reaction product analyses such as oxygen analysis. Kinetic models are proposed based on the product phase morphologies and confronted with the empirical data.

By Shizhe Liu, Bing Li, Heng Wang, Zuxin Zhao

In this paper, cyclic voltammetry and chronoamperometry have been applied to investigate the effects of Nd2O3 concentration on the anode effects, critical potential for the anode effects and Nd2O3 reduction in LiF-NdF3-Nd2O3 melts at 950℃. The results show that the oxidation peaks in the potential of about 2.7V are attributed to the oxygen ions oxidation and the peak current density increases with Nd2O3 concentration increase from 0 to 0.5wt%. The critical potential caused the anode effects shifts to 0.3V more positive value as Nd2O3 content in the melts decreases from 0.01wt% to 0.5wt%. The cyclic votammograms on W electrodes in the LiF-NdF3-Nd2O3 melts present two pairs of reduction and oxidation peaks, indicating that the reduction of Nd ions in the LiF-NdF3-Nd2O3 melts in two steps rather than one step.

Jan 1, 2014

By Youn-Bae Kang, Jong-Jin Pak, Min-Kyu Paek

The critical evaluation and thermodynamic optimization of Mn-Si-C and its sub-binary systems have been carried out over the whole composition range from room temperature to above the liquidus temperature. The solution properties of the liquid systems have not been clearly described because the liquid solution exhibits a high degree of short-range-ordering. In order to predict the thermodynamics of the liquid solution, the liquid phases were optimized by the modified quasichemical model. The model parameters of the solid phases were also optimized by the compound energy formalism to best reproduce the phase diagram and important thermodynamic properties in Mn-Si-C system. Using the model parameters, various thermodynamic calculations were carried out. The present database will be a part of larger thermodynamic database for the ferromanganese alloy database.

Jan 1, 2014

By Y. A. Chang, L. M. Pike, C. R. Kao

"Knowledge of the site preference of ternary solute additions is essential to developing an understanding of how these solutes affect the properties of B2 intermetallic compounds. A quasichemical model will be presented which is able to predict the site preferences of dilute solute additions to tliple defect B2 compounds. The only parameters required are enthalpies of formation at the stoichiometric composition. General equations are developed which can be used to determine site occupations and defect concentrations for dilute as well as non-dilute solute additions. These equations use atom pair bond enthalpies as the parameters. It is found that the site preferences of dilute additions are not always in agreement with predictions based on the solubility lobes in ternary Gibbs isothelms. Predictions for dilute additions to NiAl and FeAl are compared to expel1mental results found in the literature. Satisfactory correlation is found between the model and the experimental results. In addition, the predictions from the model on vacancy concentrations in Fe doped NiAl are compared to recent experimental results by the authors.1.0 IntroductionIntennetallic compounds with the B2 crystal structure such as NiAl and FeAl have been investigated recently for possible use as structural materials in high temperature, oxidizing, and/or corrosive environments. The major limiting property of these materials has been a lack of sufficient room temperature ductility. Attempts to improve the ductility have often been made through ternary or higher order alloying. For B2 compounds, substitutional alloying additions can occupy either of the two sublattices and this site occupancy can be crucial in determining how the alloying addition affects the properties of the alloy. In this manuscript we will discuss the use of thelmodynamic modeling to predict the site occupancies of ternary alloying additions in B2 compounds with the triple defect structure."

Jan 1, 1996

By V. Blet

Rare earth elements (REE) are regarded today as highly critical raw materials but currently lack suitable recycling processes. A combined hydro- and pyrometallurgical process aimed at REE recovery from used NdFeB permanent magnets was recently developed by the CEA. The process integrates the physico-chemical treatment of magnets, followed by a solvent extraction step for the recovery and intra-REE separation using a selective extractant. A subsequent pyrometallurgical treatment via molten chloride salt electrolysis allowed the isolation of pure Dy metal. Technical-economic assessment and life-cycle analysis were also conducted. Following this first successful demonstration, a new project aimed at the recovery of REE from end-of-life nickel-metal-hydride batteries is currently being developed in association with industrial and academic partners. The project aims at evaluating from an experimental and economic perspective different processes converging at the production of value-added products such as cermet materials for catalytic applications, purified REO concentrates, or metallic alloys.

By Zeng Zheng, Liu Chen, Yu Xing-Fu, Tian Su-Gui, Zhang Chao

"Single crystal nickel-base superalloy is prepared by using the various withdrawing rates. By measuring creep properties and microstructure observation, the influence of the element segregation on creep properties of the superalloys is investigated. Results show that the dendrite spacing and the segregation extent of the elements decrease with the enhancing withdrawing rate. The superalloy with smaller dendrite spacing has lower segregation of the elements and better creep resistance. The dislocations climbing over the rafted y’ phase is thought to be the deformation mechanism of the alloy during steady state creep. In the later stage of creep, the fact that some dislocations shear into the rafted y’ phase may twist the rafted y’ phase. As the creep goes on, the initiation and propagation of the cracks occur up to occurring creep fracture, which is thought to be the fracture mechanism of the superalloy during creep.1. IntroductionSingle crystal nickel-based superalloys consist of high volume fraction of ?? strengthening phase and ? matrix, and possess the excellent high-temperature mechanical and creep properties, therefore, they have become the main material to make the blades of the advanced aeroengines[1-3]. Some literatures report that the temperature-bearing and creep-resistance properties of the single crystal nickel-based superalloys can be remarkably improved as the increases content of the refractory elements, such as W and Re[4-6]."

Jan 1, 2012

BHP Hartley Platinum operates an electric smelting furnace to treat Cu-Ni-PGM concentrate at its plant in Selous, Zimbabwe. The furnace, originally built by others, has experienced problems including severe refractory erosion of the sidewall. Hatch Associates has designed several important improvements to the furnace, including: ? water-cooled copper cooling elements in the slag zone ?air-cooled copper cooling fins at the metal level ?water-cooled copper tapholes ?binding system providing vertical refractory compression ?electrode seals ?new feed pipes Novel construction techniques employed on this project to reduce shutdown duration are discussed.

Jan 1, 1999