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By Sheng-li Wu, Guo-liang Zhang, Bo Su

The mineralogical characteristics of iron ores can influence their high temperature sintering performance. In this study, eight iron ore samples from Brazil, Australia, and South Africa were characterized by their chemical composition, mineral types, particle morphology, and gangue dispersity. Meanwhile the influence rules between the mineralogical characteristics and the high temperature characteristics were evaluated and analyzed. The results showed that the effect of SiO2 on assimilation characteristic of iron ores was relatively complex, Al2O3 and LOI of iron ores had negative correlation with assimilation temperature of iron ores, the dense slab-flaky mineral granule restrained to the assimilation characteristics of iron ores; liquid phase of iron ores with high SiO2 content and low Al2O3 content had high fluidity, and the higher dispersity of gangue minerals in iron ores was good to the fluidity of liquid phase.

Jan 1, 2015

By Theo Lehner

"During my first contact with industrial metallurgy as a summer vacation worker at the Steelplant at Luleå, Sweden, I came during a visit to MEFOS into contact with works of Prof. Worner caried out during the piloting of the Worcra continuous steelmaking process. These tests are still today remarkable as an innovative step in the art of metalmaking. By that they involved the necessary ingredients for the development of our art: seeing, knowing and doing. Industrial injection as applied during slag fuming will be discussed below.Phenomena of injection metallurgyPhenomenon according to Collins dictionary is"" anything that can be perceived as an occurrence or facts by the senses"". To open the senses for the interesting phenomena in pyrometallurgy must be the main task of any educator. The investigations by Engh et al. around the mixing phenomena of the WORCRA process are an early example of combining senses with knowledge. To see what you model must be a crucial part in any development. This can also involve to see and control that one is subject to the same conditions as in published models. Below the need ""to see"" will be illustrated by some recent investigations around slag fuming. In the literature various models for reactions occuring during the fuming of slags are presented. Two recent models hint ·ata) the occurrence and importance of iron for the fuming processb) the occurrence and importance of lead droplets during respectively."

Jan 1, 1996

By Xiao Caimei

The method of Substance Flow Analysis (SFA) provides a helpful tool for the study of the industrial metabolism of a certain metal within a regional level, such as copper, lead etc. In this paper the flows and inventory of cobalt in China, 2008, were traced with the STAF model, and the situations of production, fabrication and manufacturing, use and waste management in China were introduced. The result revealed that the resource of cobalt in China was so poor that a large amount of cobalt material or cobalt products needed to be imported, and there was lack of recycling of cobalt resources.0

Jan 1, 2010

By Broggi Andrea

Condensates produced by SiO(g) and CO(g) have a crucial importance in silicon production. Condensation will follow the reactions 3 SiOðgÞ+COðgÞ→ 2 SiO2 + SiC and 2 SiO ðgÞ→Si+SiO2. Solid compounds generated during silicon production contain Si, SiO2 and SiC in different microstructures and amounts. In industrial systems, condensates limit the SiO(g) escape to the off-gas system. On the other hand, they can block the gas flowing from the high temperature zone, hence the necessity of studying an optimized condensation process. This review discusses SiO(g) condensation and its interaction with CO(g). The report gives an overview of the condensates found both at laboratory and at industrial scale. The two main compounds are the Si–SiO2 and the SiOx–SiC mixtures. The hypothesis on the mechanism of formation of SiC–SiOx condensates is presented through a wide selection of performed works. The advantages and disadvantages of the former experimental procedures are discussed.

By A. Patti, S. Reutzel, D. M. Herlach, L. Ratke, I. Egry

Cu-Co shows a metastable miscibility gap in the region of the undercooled melt. Undercooling of the melt below the binodal leads to separation of the melt into a Co-rich LI-phase and a Curich L2-phase. Experimentally, undercooling into the metastable miscibility gap is realised by means of electromagnetic levitation (EML), processing in drop tube (DT) and by melt flux embedding. As undercooling is large in these experiments, the velocity of the solidification front is high and the microstructure is frozen in instantaneously. Samples have been undercooled and solidified in the TEMPUS-facility (container less electromagnetic processing under weightlessness) during parabolic flight under reduced gravity conditions. Microstructures of solidified samples have been analysed and compared to those processed under gravitational conditions. The influence of convection on phase growth is much lower in reduced gravity. The microstructure shows spherical droplets of the minority phase, statistically dispersed in the majority phase.

Jan 1, 2004

By Herbert Pöllmann

Waste disposals are needed for safe deposition of different kinds of materials which can not be used as secondary raw materials. Often high contents of heavy metals must be bonded tightly to cristalline compounds to protect the environment from contamination. Therefore it is important. to find minerals which are capable to incorporate different heavy metals and protect the ground water. The power of resistance against leaching out effects of highly water-soluble salts can be increased. Mineral groups of metal hydroxy salts, ettringites, apatites, sodalites and calciumchlorosilicates and their hydrates are recommended for their formation in mineral reservoirs. Different wastes as red mud, gasification ash, garbage combustion ash and fluidized bed ashes were included in this study. The formation of different new compounds and their properties were determined.

Jan 1, 1991

By Susumu Okabe

Mitsubishi Continuous Copper Converter employs the top blowing lance system for the continuous supply of reaction gases into the molten bath. In order to avoid the excessive refractory wear caused by the melt splash without loss of the reaction efficiency, the furnace design and the blowing condition should be optimized. Empirical equations which correlate the splashing rate on the' side wall with the dimensions of the furnace, lance position, lance size, gas velocity and bath properties were obtained by by the physical model study, and compiled into a computer program. The computer program is effectively utilized for the analysis of the actual operation and for the optimum design of new furnaces.

Jan 1, 1998

By B. Q. Li, Y. Shu, K Lynn

"This paper discusses the effects of magnetic field and internal radiation on the melt flow and solidification morphology during solidification processing of oxide crystals for optoelectronic and remote sensing applications. The numerical solution of the integral differential equation characterizing the internal radiation and the magnetohydrodynamic equations describing the magnetic and transport phenomena is obtained by applying the combined discontinuous and continuous finite element method. The results show that both internal radiation and an externally applied magnetic field can have important effects on the melt flow and solidification behavior during the melt processing of oxide materials.IntroductionOptical single crystals are widely used in optical and electronic devices. These crystals are often grown from high temperature oxide melts under strictly controlled conditions. As in the well-known single crystal growth processes for semiconductor wafers, thermal gradient in the melt is a major contributing fuctor to the oxide melt pool. Unlike the semiconductor single crystal growth processes, however, the oxide melt is semitransparent and internal thermal radiation plays an important role in redistributing the thermal energy in the melt pool. Our recent experience with pilot-scale plant measurements also shows that the oxide melt is electrically conducting, although its electrical conductivity is considered much lower than the liquid metal or semiconductor melt.The fact that the oxide melt is absorbing and emitting in the thermal radiation frequency range makes it difficult to study the thermal energy transport in the melt pool. This is because thermal radiation is governed by a hyperbolic differential equation, which is different from those describing the transport processes in liquids. Also, our understanding of how thermal radiation interacts with other transport mechanisms such as convection and conduction is rather limited at point in time, in particular in high temperature oxide melts for optical single crystal processing."

Jan 1, 2004

By Brent W. Madsen

The acid-ferric sulfate leaching of low-grade sulfide copper mine waste provides more than 10 percent of the U.S. supply of new copper, but recoveries and leaching rates are very low. In Federal Bureau of Mines research to improve the leaching process, experiments on 5- to 10-ton lots of mine-run ore were more revealing than bench-scale tests on fine ore. This report discusses the results obtained by leaching run-of-mine and minus 6-inch plus 112-inch samples of low-grade chalcocite-bearing mine waste. The samples were leached for 461 days and 61.6 and 37.7 percent of the copper was extracted from the minus 6-inch plus -112-inch and run-of- mine samples, respectively. A mixed kinetics model was applied successfully to the leaching of the sample with the fines removed where bulk solution transport was not rate controlling. The model, when applied to the run-of- mine ore, gave somewhat higher predicted copper extractions than experimentally determined. Subsequently, oxygen was introduced into the run-of- mine ore, leaching continued for an additional 312 days, and an additional 53.0 percent of the copper was extracted. Before the leaching experiment was dismantled and the residue sampled, the ore was treated with sulfur dioxide and its permeability was improved markedly. The results of each of these procedures are interpreted in relation to the attendant condition of the test.

Jan 1, 1976

By D. M. Hausen

Microscopic point-counting of polished sections, in combination with x-ray diffraction analyses of representative whole rock samples, provides an efficient means to compare the modal mineralogic composition of different rock types. Major gangue minerals, e.g., quartz, feldspars, micas, amphiboles, chlorite, clays, etc., are estimated semiquantitatively by x-ray diffraction techniques, utilizing optimum grind, gridded sample surfaces and a sample spinner during scanning. Opaque to semi-opaque oxide and .sulfide phases are estimated by microscopic "point-count" and "gross-count" scanning. Total mineralogic compositions are calculated and normalized to 100 percent from XRD and microscopic data by computer programming. Comparative mineral analyses for different rock types, as well as quantitative microscopic data for various parameters, including particle and crystal sizes, textures, degree of alteration, paragenesis, etc., provide useful guides in mineral exploration, both in early stages of geologic mapping and later stages of economic evaluation. Several case histories are described.

Jan 1, 1981

By Anthony C. Mulligan

Metals have historically been used in mining since they offer an excellent combination of hardness, toughness and cost and can be fabricated to form a variety of shapes. However, for many applications the metals used today have limited performance in the environments in which they are needed. This is particularly true for geothermal environments where the brines are highly siliceous causing corrosion and accelerated wear of many components. Geothermal sources are increasingly being explored for their high thermal value as well as possible sources for future minerals. While advanced ceramics have historically been expensive to produce in comparison with metals, they offer significantly greater corrosion resistance and hardness and can improve the overall performance when used in selected ?problem? areas. One of the major drawbacks in the use of ceramics in high impact areas has been their brittle nature and propensity to fracture and spall (fail) when loaded. Recent advances in the fabrication of ceramics have combined hard (strong) ceramics with more ductile ceramics in a architecturally designed microstructure, thus allowing ceramics to perform well in these high impact regions. Additionally, ceramics are significantly more inert to corrosion from either alkaline or acidic environments and can typically be used for significantly longer periods in these environments than their metallic counterparts.

Jan 1, 2006

By Celaletdin Ergun, Ibrahim Erden, Gurbuz Gunes, Thomas J. Webste, Huinan Liu, Abdurrahman Bahadll

"B, Ti, Ag, AI and Cu substituted hydroxyl apatites were synthesized via precipitation method. Then the samples were air-sintered at 1300°C for 2 hrs and characterized with XRD, SEM, FTIR, and cell adhesion behaviors.IntroductionSynthetic hydroxylapatite (HA, Ca10(P04)6(0H)2) has a similar composition and structure to biological apatite. Therefore, it has been safely and extensively used as an implant material for bone substitute. However, synthetic HA has been used for a various applications including medical or non-medical applications, such as matrices for drug release control, bone cements, tooth paste additive, blood purification agent, monolithic implants or coatings on metallic implants, packing media for column chromatography, gas sensors, catalysis and host materials for lasers and luminescent materials, etc. [1-9].The major factors affecting the performance of HA on these applications are crystal morphology, density, porosity, pore size and distribution, chemical composition, and surface structure. As provided by the high flexibility of the apatite structure a great variety of cationic and anionic species can be substituted into HA structure which is specifically considered as an effective method to modify the properties of HA [10,11]."

Jan 1, 2012

By S. Y. Tan

The thermal stability of fully silicided NiSi with arsenic doping on silicon was investigated. The aims of the work were to investigate the Ni silicide phase-related issues associated with arsenic dopant and thermal annealing on Ni-FUSI/HfO2/Si and Ni-FUSI/HfSiO/Si gate stacks. It was found that arsenic-incorporation demonstrated some improvement in both morphology and phase stability of nickel silicided films at high processing temperatures regardless underlying gate dielectrics. The correlations of Ni-Si phase transformation and arsenic doapnt with their electrical and physical changes were established by sheet resistance measurements, X-ray diffraction (XRD), atomic force microscopy (AFM), and X-ray photoelectron spectroscopy (XPS) analysis. Furthermore, the modulation of the work function (WF) of Ni fully silicided gates by arsenic impurity is presented, comparing the effects of dopant (As) on the WF and silicide phases (NiSi and NiSi2). It confirmed that the work function of NiSi can be tuned by implanting arsenic dopant, but it ineffective for NiSi2 phase.

Jan 1, 2010

By Orhan Gokce Goksu

It has been shown that metallic tungsten powder can be obtained by electrochemical reduction of solid CaWO4 in molten CaCl2-NaCl eutectic mixture at 600oC. In this study, constant and pulse voltage electrolysis experiments were performed to optimize reduction kinetics and obtain information about the mechanism of above process. It was found that pulse voltage applications yield faster reduction rates when average voltage of pulse voltage application was the same as constant voltage application. In addition, analysis of the current vs. time graphs of constant and pulse voltage electrolysis studies showed that reduction occurs at potential differences higher than about 2.2 V between CaWO4 cathode and graphite rod anode.

Jan 1, 2010

By J. L. Liow

Studies have been carried out on the causes and effects of slopping in an annular cylindrical geometry such as the top submerged combustion reactor. Properties of standing waves formed such as the wave profile, period, pressure distribution and velocity have been derived analytically. The wear profile due to wave erosion was calculated based on the assumption of linear motion and that the wear is a dissolution process. The use of the j, factor showed that the wear was proportional to the square root of the wave velocity at any point. Using the dimensions of the lsasmelt reactor given by Errington et al. (1987)[11, the wear profile due to wave erosion was calculated using the analytical solution. The wear profile calculated was shown to have a maximum just below the initial bath surface. The wear was found to be concentrated in the region where the first asymmetric standing wave was most active. The results showed that the refractory near the bath surface will be affected by wave erosion, more so than any other parts of the reactor. The contribution of wave erosion on wear must be accounted for in assessing the total refractory wear of a vessel in which slopping exists.

Jan 1, 1991

By Zhuoqing An, Qi Li, Zhancheng Guo, Yanling Zhang

Fluidized bed is an important iron-making reactor, especially for the finely sized iron-bearing materials. However, defluidization caused by sticking between particles extremely limited its wide spread commercialization. In this paper, apparent viscosity was put forward to express the ability of particles to resist movement, which is reasonably considered as the comprehensive results of interaction between particles. Meanwhile, an experimental measuring method of apparent viscosity of particles was proposed, during which the torque exerted on the rotating blade in a particle layer is measured, and then the apparent viscosity is obtained based on the motion equations of powder particles. Further, the apparent viscosity of iron particles was measured by using of this method, and the effects of shape, size, and temperature were examined. The data can provide important information for understanding when and why defluidization happened.

Jan 1, 2015

By Matthias Frommer, Carl-Peter Reipl, Reinhard Flende

"Today there is a growing demand for strip of superior steels with specifically tailored technological properties. Especially strips of high-strength, micro-alloyed steel grades applied to manufacture longitudinally and spiral-welded pipes are a growth market. Tubes are generally required to have high strength and sufficient toughness values and thus favour specific hot strip microstructures. The correlation of chemical analysis, process parameters and mechanical properties with microstructural features is still a challenging task. During the last decades, scanning electron microscopy (SEM) and electron backscatter diffraction (EBSD) have become useful tools for the characterization of complex microstructures. The EBSD data provides an immense variety of post-processing possibilities, e.g. related to grains, grain boundaries, misorientations or texture. This paper highlights the results of an advanced analysis of microstructures representing industrial produced hot-rolled strips and presents an approach to define and quantify some essential microstructural parameters.IntroductionHigh-strength microalloyed steels have been used for the production of welded pipes for more than 30 years. However, the alloy design of pipeline grades is being continuously modified and the process technology optimized because of the increasing high strength-toughness combination requirement for pipeline steels. Compact strip production (CSP®) technology is an upcoming promising route for the production of high-quality pipeline steel grades [1]."

Jan 1, 2012

By Patrick R. Taylor

Sub-micron sized boron carbide powders have been synthesized in a non-transferred arc thermal plasma reactor. Precursors for this synthesis are boric acid or boron oxide powders and methane. The powders produced were characterized in terms of size, shape and purity. Methods to increase the purity of the product were evaluated and included hot water leaching to remove unreacted oxides and controlled temperature, air roasting to remove excess carbon. Theoretical results are also presented on the thermodynamics and mechanisms of the synthesis reactions.

Jan 1, 1994

By F. J. Arriagada

Where gold is present in a finely disseminated form within sulfide particles, the porosity and surface area of the calcined material strongly influence leaching since they control the penetration of solution inside the gold-bearing grains. On the basis of a stability diagram for the Fe-O-S in the temperature range of 400 to 750aC, the expected sequence chemical transformations associated with the oxidation of pyrite is discus-sed. By using analytical techniques which include scanning electron microscopy, X-ray diffraction and BET gas adsorption, the chemical and structural changes experienced by auriferous pyrite-arsenopyrite concentrates and pure pyrite samples are studied under an oxidizing roasting atmosphere of com-position 80% N + 20% O2 in the temperature range of 450 to 750°C. The results indicate that as the roasting temperature increases, the surface area of the calcines decreases sharply after a maximum value attained at about 450-500°C. SEM micrographs show that the needle-shaped tips which characterize the surface of the oxide product become wider and the size of the pores between them is decreased when the roasting temperature is in-creased from 550 to 750°C. This effect suggests that the formation of a more "closed" hematite product at higher temperatures is due to sintering associated with a faster growth and crystallization of the oxide. A strong correlation is shown between increasing roasting temperature and increase in gold lost in cyanidation tailings, an effect which may be partly attributed to the loss in surface area of the calcines.

Jan 1, 1982

By J. Grogan

Leaching of galvanized steel coatings allows the steel substrate to be used as a zinc-free scrap source to steel and iron furnaces. In this study the behaviors of sulfuric acid leaching solutions are investigated. The ranked significance of the variables are shown to be acid concentration > temperature > zinc concentration. Examination of the leaching mechanism finds the rate-limiting step to be the cathodic hydrogen reduction reaction. This rate is not only influenced by acid concentration, but also by the hydrogen reduction exchange current density. Dezincing leaching rates are improved by taking advantage of the higher exchange current density of the iron substrate versus the zinc coating. This is accomplished in practice by increasing the exposed interfacial zinc:iron surface area through shredding. Also, a leach control mechanism is proposed through online monitoring of the zinc-iron couple mixed potential.