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By H. Shang

The materials science and metallurgical engineering communities have expended enonnous resources in developing high fidelity process models. Exploiting these Models for Predictive Optimization (MPO) and Control (MPC) is a new frontier in Materials Process Engineering that will lead to exceptional process perfonnance. This paper will begin with a short survey of the development of high quality process models available in the literature and a discussion of how these could be used to improve process operation. A summary of the current "state-of-the-art" in process automation technologies and the traditional framework in which these technologies are deployed will be presented. An illustration of the use of MPO in process design and operations will be presented for the continuous casting of steel. In addition, a simple run-out table simulation will be used to demonstrate the power of the MPC technique.

Jan 1, 2003

By Musa Karakus

The sedimentary iron ores of Alsace-Lorraine, France have very high phosphorous contents that average 0.7% and are as much as 2.19% P. Ores from the Tucquegnieux and Joeuf mines have been studied by cathodoluminescence microscopy, X-ray diffraction, scanning electron microscopy, and electron microprobe analysis in order to fully characterize the mineralogy, size, shape, and distribution of the deleterious phosphate grains. The phosphorous occurs as collophane, a carbonate fluorapatite, in ten morphological forms, most abundantly as microcoprolites, but also as intraclasts, concentric layers, and cortices in ooids, phosphate replaced ooids and bioclasts, phosphatiC shells, fossil infillings and internal molds, fish teeth, phosphatiC laminae, and cements between the goethite ooids. About 95% of the phosphate grains are sufficiently large that relatively fine grinding fol'lowed by reverse flotation would be expected to be effective in significantly diminishing the phosphorous content of the concentrates.

Jan 1, 1989

By Yi Tan, Kazuki Morita, Yaqiong Li

Molten Si-Al alloy, with the addition of Sn, was used for metallurgical grade Si purification by a low-temperature solidification method, with the aim of improving the recovery rate of Si. In this ternary melt, bulk Si was grown with a planar front by a directional solidification process under a well-controlled thermal gradient and growth rate conditions, thereby reducing the contamination of solvent metals. Effects of cooling rate, amount of Sn addition, and temperature gradient on the quality of bulk Si were determined. The criterion for constitutional supercooling for single-phase growth from multicomponent melts was employed to evaluate the growth process.

Jan 1, 2015

By Charles H. Bucknam

A gold sampling optimization study was carried out in support of open pit gold mining operations for the Newmont Gold Company Bootstrap-Capstone deposits in Northeastern Nevada. Six bulk samples were tested using fire refining techniques at field particle size, to determine coarse particle heterogeneity of the ores, and by gravity .concentration methods at 10 mesh particle size, to observe any particulate gold liberation. An overall sampling model is presented for the deposit based on the pooled test information, to reconcile the results of coarse particle heterogeneity testing and the fine particle 'liberation testing. The sampling model is used to recommend procedures to control the variability of gold grade estimation due to the fundamental error (nugget effect) during sampling, sample preparation and assaying of the ores and other fundamental variances. The technique of simplified quantitative risk analysis (SQRA) is used to provide an economic justification for implementation of. recommended improvements to field sampling practices.

Jan 1, 1999

By J. Wong

We report a successful use of x-ray absorption spectroscopy to probe the chemical and structural environment of trace elements in coal. When applied to vanadium in coal, it was found that vanadium exists in at least two environments: a trivalent site 6-fold coordinated by oxygens at ca. 2.0~ and a tetravalent site 5-or 6-fold coordinated also by oxygens, one of which forms a short V=O bond at ca. 1.6a. No evidence of nitrogen (porphyrin)1'or sulfide environment was found. It was also found that the vanadium environ-ments in the raw coal did not survive unchanged in a liquefaction process. These findings have implications for coal cleaning processes and for trace element release into liquefaction process streams.

Jan 1, 1982

By Gordon Lewis

A complex mixture of hydrated reaction products is obtained from hydrothermally treated refractory cements and castable concretes. TGA can be used both to identify the product phases in the mixture and to determine a quantitative relationship among the phases. When reacted mixtures contain compounds that decompose simultaneously, or nearly so, additional assumptions must be introduced in order to develop a quantitative phase analysis. It is the purpose of this paper to examine some of these assumptions and to demonstrate their application, particularly to refractory cement systems.

Jan 1, 1982

By S. W. Marcuson

Smelting of nickel-copper sulfide ores at Vale Inco’s Sudbury operations commenced in 1888 and the first converting plant went into operation in 1892. As the demand for nickel grew, the smelting operations expanded and by the 1960’s the Copper Cliff Smelter featured the longest converter aisle in the world with space for nineteen Peirce-Smith converters. During this long period, different converting techniques and vessels were employed. The evolution of converting is reviewed with special emphasis on the modifications made to the Peirce-Smith vessel to accommodate the metallurgical and process needs of the changing times.

Jan 1, 2009

By Christopher Gammons

In developing countries throughout the world, gold ores are being processed by mercury amal-gamation, a technique long banned in the U.S. - unless a retort operation is used for mercury recovery - due to mercury toxicity and its effects on the environment. Amalgamation is a simple process that involves contacting a ground, slurried concentrate or ore with mercury in a slightly agitated vessel, usually for several hours, The amalgamated mercury is separated by gravity and then filtered through a fine cloth to collect the gold amalgam as a sponge, which is then fired to remove the final remnants of mercury and produce high quality gold. However, in Peru and other developing countries in South America and throughout the world, tailings are simply discarded into uncontrolled drainages and ponds and the sponge is fired in the open air. Clearly, in this case, environmental friendly and, to make matters worse, is typically conducted by family members of all ages without proper protection. Furthermore, the technique is inefficient, yielding approximately 50% gold recovery. For the past two years, faculty members from Montana Tech in Butte, MT, USA and the Universidad Nactonal del Altiplano in Puno, Peru have teamed to study the La Rinconada Mine Complex located in southern Peru approximately 100 kilometers north of Lake Titicaca and 25 kilometers west of Bolivia. The mining complex is over 5,000 meters above sea level and exists at the foot of a receding glacier in the Andes Mountains. A suite of soil and water samples collected in 2001 documented extensive Hg contamination in the Rinconada area [1]. The present paper summa¬rizes a follow-up investigation in July-2002, in which water samples were collected at numerous locations along the 200 km length of the Rio Ramis, from the Rinconada mine com¬plex to Lake Titicaca, In addition, we report new results of Hg analyses of fish from Lake Titi¬caca, The results of this study have relevance to safety and health concerns for the miners as well as people in downstream communities.

Jan 1, 2003

By Tiejun Chun, Jian Pan, Deqing Zhu, Vinicius Mendes

"Fine manganese fines are characterized by large amount and low price compared to lump manganese ores. However, fine manganese must be agglomerated as EAF (electric arc furnace) feed. In this paper, high quality fired pellets were produced by simulating grate-kiln process to supply the feed for EAF from some imported manganese ore fines containing high combined water. Manganese ore fines assaying 44.47wt%Mn, 5.89wt%Fe, 12.09%LOI and with 72.7wt% ranging between 0.5mm and 8mm, are pretreated up to the particle size of 84.7wt% passing 0.074mm by HPGR (high press grinding roller) twice in open circuit. The finely ground manganese fines were mixed with 1.2wt% bentonite, balled at 15% moisture for 7min in disc pelletizer. The drop numbers, compressive strength and thermal shock temperature of green balls reach 11 times/0.5m, 11 N/pellet and 360oC, respectively. After the green balls drying in the oven, the dry pellets were preheated at 1050oC for 12 min and then fired at 1300oC for 12 min in electric tube furnace. The compressive strength of fired pellets reaches 2621 N/pellet. Therefore, these pellets are high quality burden for blast furnace or EAF due to high mechanical strength and high Mn grade of 49.11wt% and low detrimental elements.IntroductionManganese, mainly using as deoxidizing agent, desulfurization agent and alloying elements, is widely used in the steel company. With the rapid development of iron and steel industry in China, domestic manganese ores cannot meet the requirement, resulting large quantities manganese ores import to China [1-4]. Compared to lump manganese ores, fine manganese ores containing high combined water are characterized by large amount and low price. However, they must be agglomerated as EAF (electric arc furnace) feed. There are three ways to agglomerate the manganese fine ores, sintering, briquetting and pelletizing [5-6]. Compared to the other two methods, pelletizing technology possesses the following superiorities, such as uniform size distribution of product, stabilizing chemical composition of product and lower energy consumption in producing. Therefore, pelletizing is a superior way to treat the fine manganese ores [7]. The systematic research of producing manganese oxide pellets by fine manganese ores containing high combined water was studied in this paper."

Jan 1, 2011

By Avijit Moitra

The behavior of the solidifying shell in the early stages of solidification has an important influence on the final quality of continuously-cast steel slabs. In order to understand the thermal and mechanical behavior of the shell, a two-dimensional transient piecewise-coupled finite-element model has been developed. The model simulates a transverse section of the slab as it moves down through the mold and incorporates the effects of heat conduction, solidification, shrinkage, turbulent fluid flow, thermal distortion of the mold and the visco-plastic behavior of the steel. Coupling between the thermal and the mechanical model is based on the mutual dependence of heat transfer across the interface between the shell and the mold and the size of the gap. The effects of mold distortion and taper on the gap size are also included. The effect of fluid flow has been incorporated via a heat flux imposed at the solid-liquid interface, which is obtained from a separate fluid flow model. The high temperature creep and plasticity of the steel is incorporated through a unified constitutive law defining the inelastic strain rates as a function of temperature, time and stress state. The model can be applied to various problems in continuous casting, such as the formation of surface defects and the design of mold taper.

Jan 1, 1992

By P. N. Anyalebechi

"The as-cast microstructure of two commercial-size ingots of aluminum alloy 3004 produced by the electromagnetic casting process was quantitatively characterized. This involved the quantitative determination of through-thickness and across-width variations in dendrite cell size, grain size, macrosegregation of alloying elements, interparticle spacing, and the types, volume fractions, and sizes of the constituent or second phase particles. More than ninety-five percent of the constituent phases in the ingots consisted of the A16(Mn,Fe) phase; the desirable a-Al 12(Fe,Mn)3Si phase was not detected in any of the ingots by Guinier X-ray diffraction analyses or electron probe X-ray microanalyses. A significant microstructural heterogeneity through the thickness and across the width of both ingots was observed. For example, macrosegregation, and the sizes of the constituent phase particles, dendrite cells, and grains increased concomitantly from edge to mid-width and from surface to center of the ingots. There was a -20% depletion (negative macrosegregation) of Mg and a +54-87% enrichment (positive macrosegregation) of Ti in the center of the ingots. With the exception of grain size, there was no significant microstructural difference between the two ingots examined. The causes and practical implications of the observed microstructural heterogeneity in the ingots are discussed.IntroductionThe first step in the fabrication of majority of wrought products of aluminum and its alloys is the casting of large ingots or billets of simple shapes (round or rectangular). The sizes of the ingots vary from 10 mm to 450 mm diameter or 25 mm to 780 mm thick. The quality of the finished products is established at the ingot casting stage. This is because the microstructural characteristics, such as secondary dendrite cell size or arm spacing, amount of alloying elements retained in solid solution, macrosegregation, and the characteristics of second phases, produced during casting cannot be reversed by subsequent processing. Up until twenty-five years ago, the effect of as-cast microstructure of large ingots on the structure and behavior of thin sheets (0.34 mm thick) during drawing and ironing processes was incorrectly assumed to be minimal or nonexistent. This was based on the erroneous notion that the thermal treatments and large reduction (>99.94%) and strain that the ingot undergoes during production of the sheets completely destroys the original ingot structure and its inherent heterogeneity. However, the effects of ingot structure can, a priori, be deduced from the observed effects of constituent phase particle size, type and volume fraction on recrystallization, development of texture during annealing and deformation, and earing. In fact, careful examination of the behavior of products produced from different size ingots or castings have shown that the original microstructure of the ingot has a direct impact on the properties and performance of the end products."

Jan 1, 2011

By W. K. Connor, O&apos

The Bureau of Mines has conducted beneficiation, carbothermic reduction, and leaching tests of Mn oxide ores as part of its evaluation of the Mn and Co resources of the West- Central Arkansas District. The major Mn oxides in the ore include cryptomelane, psilomelane, pyrolusite, and lithiophorite. Cobalt is contained within the Mn oxides. Nonbeneficiated ore was reduced at 800' C with coal and leached in ammonium sulfate and ammonium carbonate leach liquors. Ore concentrates were calcined at 600" C prior to reduction under the same conditions as the raw ore. Head analyses reported up to 21 ptt Mn and 0.11 pct Co. Extractions of 70 to 90 pct Mn and 40 to 60 pct Co were achieved.

Jan 1, 1992

By Alicia Esther Ares

This study was conducted to investigate the directional solidification of Zn-20%A1 and Zn20% A1-1O%Si-3o/oCu alloys under different conditions of heat transfer at the metal/mould interface. The type of structure obtained in both cases was analyzed and related to the solidification thermal parameters such as cooling rate, growth rate, thermal gradient and recalescence which were determined from the temperature versus time curves. These parameters were correlated with the structure-like length of columnar grains and size of equiaxed grains. The metallographic analyses were done performing quantitative metallography and composition analysis of the different alloying elements along the cast samples by SEM (Scanning Electron Microscopy) and EDXA (Energy Dispersive X-Ray Analysis). Correlations between properties, structures and thermal parameters were found.

Jan 1, 2008

By E. G. Noble

The potential for using heterotrophic microorganisms to solubilize manganese from low-grade domestic ores is being assessed at the Reno Research. center, U.S. Bureau of Mines. More than 90 pct of the manganese has been extracted from a variety of oxide ores in shake-flask tests using molasses as a source of .. nutrients for the microorganisms. It has also been demonstrated that high recoveries of manganese can be obtained from a domestic wad ore using column bioleaching. 'l'he isolation and identification of organisms responsible for manganese extraction is discussed, as are the mechanisms responsible for manganese solubilization.

Jan 1, 1991

By Shengqi Chen

The reduction smelting of nickel laterites produces slag, consisting principally of the chemical components MgO, "FeO", SiO2, and A12O3, and ferro-nickel alloy. Despite the fact that the phase equilibria for the ternary MgO-"FeO"-SiO2 up to 1500°C is well established limited experimental data are available in the MgO-"FeO"-SiO2-Al2O3 system, which is relevant to commercial operation of the process. A methodology has been developed for the experimental investigation of the liquidus temperatures for the multi-component system MgO-"FeO"-SiO2-Al2O3-Cr2O3 in equilibrium with metallic iron. Experiments have been carried out using high temperature equilibration, quenching, followed by electron probe X-ray microanalysis (EPMA). Liquidus temperatures have been determined in the silica primary phase field in the composition ranges directly relevant to the Cerro Matoso S.A. ferro-nickel smelting slag. Liquidus isotherms have been determined for temperatures between 1450 to 1600°C. The study enables the liquidus to be described for a range of MgO/FeO ratios. It was found that liquidus temperatures in the silica primary phase field decrease significantly with the addition of AI2O3. Keywords: Liquidus temperature, ferro-nickel, pyrometallurgy, smelting

Jan 1, 2004

By Zhao Guangwen, Wu Tan, Qiuzhan Tian, Duan Shuzhen

"A thorough study of lost currents in bipolar cells has been made for the development of the great potential of bipolar cells in energy saving. A proper equivalent circuit for bipolar cells has been found, and mathematic methods for computing lost currents at all kinds of polarization have been developed.At linear polarization, the lost currents can be computed by solving either a tridiagonal matrix or an ordinary differential equation of second order. This kind of values can be used to evaluate the minimal lost currents at given conditions. At other kinds of polarization, the lost currents can be computed by the same methods as above if the necessary experiments of measuring the cell voltages of every electrolytic compartment have been made. This kind of values can be used to design bipolar cells at practical conditions.Extensive experiments have been made to evaluate the effects of electrode polarization, emf of galvanic cell for the formation of electrolyzed substance, gaseous products, geometric dimensions of electrolytic cells, special resistance of electrolyte used, and the total and ordinal number of electrolytic compartments on lost currents. It is the first time to make such a systematic research by experiments in the world. Experiments showed that theoretic models were in good agreement with measured data. Experiments also showed that D.C. energy consumption of 0.45 kwh/kg of Pb for lead electrolysis from molten chlorides could be achieved in a cell with 7 bipolar electrodes.IntroductionIt is very promising to apply bipolar electrolytic cells to electrolysis of aluminum, magnesium, lead, zinc and perchlorinates for their great potential of energy saving for example, bipolar cells had been used in the production of magnesium and saved more than 30% of energy, being one of the three main techniques of energy saving in the production of titanium sponge (1)."

Jan 1, 1988

By W. K. Choi

Stainless steel exposed to wet environments at ambient temperature is subject to the formation of a surface biofilm. Depending upon the prevailing environmental conditions (dissolved oxygen, pH, Eh, concentration of cationic/anionic species), the biofilm may stimulate corrosion through formation of differential aeration zones and concentration cells. Corrosion significantly impacts the United States economy, since on a yearly basis, corrosion induced losses are estimated to be over $200 billion. A large portion of this corrosion is imputable to bacterial activity, and basic information is needed for a better understanding and control of the biocorrosion phenomenon. The present study has investigated the influence of Thiobacillus ferrooxidans in the corrosion of American Iron and Steel Institute (AISI) 304, 316 and 416 stainless steel samples. The formation of biofilm and microstructural changes on the surface of stainless steel samples and their weldments were assessed by microscopic examination, and the changes in the mechanical properties by stress-strain measurements. The significance of the results will be discussed.

Jan 1, 1993

By Baozhong Zhao

The direct smelting of copper concentrates to copper metal in a single furnace offers environmental and energy advantages over conventional two-stage copper smelting processes. However, the direct copper making results in unacceptably high level impurities (As, Sb and Bi) in the anode copper. Experimental studies have shown that it is possible to remove these impurities from molten copper by injection of sulfur-hexafluoride. This paper discusses the experimental findings on the influence of various factors on the rate of removal of impurities, such as the impurity inter-effects, initial oxygen content in the metal and injection rate of SF6.

Jan 1, 1995

By J. R. Goode

Up to one half of neodymium and praseodymium production, key ingredients in permanent magnets, is produced illegally. About 60% of cobalt production, critical in lithium-ion batteries and other applications, comes from central African states, and much of it is produced illegally. Tantalum, important in modern electronics, is also primarily sourced from central Africa and, again, much of it illegally. Illegal mineral production, as exemplified here, is often used to fund armed conflict. Furthermore, it is typically conducted with scant regard for human rights and environmental protection. It also leads to depressed prices which in turn limits the possibility of legitimate producers entering the market. Systems of traceability and provenance, along with cooperative supply chain participants can limit the production of illegitimate material and thereby improve conditions in the countries of origin and reduce downward pressure on prices.

By A. Kontopoulos

Refractory sulfide gold ores or concentrates require an oxidation pretreatment step to yield the contained gold amenable to the subsequent leaching step. The process options for oxidation pretreatment can be broadly classified as follows: roasting, high or low pressure oxidation bacterial oxidation, chemical oxidation, each with a number of alternative suboptions. Roasting and high pressure oxidation are being applied on an industrial scale; the stage of development of the other options range from preliminary laboratory to advanced pilot plant- In this paper, the major technical, environmental and economic aspects of the above processes are being discussed. Future industrial trends will also be considered. Particular emphasis will be placed on the treatment of arsenical ores and concentrates, where safe plant operation as well as, handling and disposal of the arsenic containing products and/or effluents 'and residues is of paramount importance.

Jan 1, 1990