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By Onuralp Yücel, Mehmet Bugdayc, Murat Alkan

"In this study, iron based alloys (Fe-Mo, Fe-Cr-Ni, etc.) were produced by using aluminothermic methods starting from Mill Scales obtained continuous casting processes. Mill scales are an oxidised layer of steel alloys containing iron oxide, which includes + 2, + 3 values, on the surface of slabs and billets occurring during annealing in heating furnace at integrated iron and steel milling plant, and continuous casting unit. In the metallothermic experiments, different ratios of starting mixtures and addition of the oxide powders (Alz03, Si02, CaO, MgO) were examined, and their effects on the metal recovery and alloy compositions were carried out. The samples were characterized by using chemical analysis (AAS), XRD, XRF and SEM/EDS techniques.IntroductionSelf Propagating High Temperature Synthesis process (SHS) has many favour compared to the furnace applications, such as low energy requirement, low cost, very short processing time and simple operation, [l, 2]. In a SHS process, the ignition starts the combustion and propagates throughout the reactant mixture yielding the desired product. However, the disadvantages of the process such as inhomogeneous or unreacted products due to undesirable reaction rates needs to be overcome by changing some parameters such as ignition temperature, particle size, additive, atmosphere etc. [3, 4]. Mill scale is a layer of iron oxide which forms on ferrous materials cooling after being processed in hot rolling or continuous casting plants. Mill scale contains iron (II) and iron (III) oxides, which result in a 70% total iron content in oxide form. Not being able to reuse this material will prevent the raw material entering the production plant from being fully utilized [5]. This study aimed to produce Fe-based alloys via SHS (Self Propagating High Temperature Synthesis) metallurgy which is attractive process technique regarding fast and low-cost production ability of cast alloys by using high metallic iron content by reducing continuous casting mill scale."

Jan 1, 2013

By V. D. Tathavadkar

Natural chromite mineral is a solid solution of spinet end members namely: chromite (FeCr2O4), hercynite (FeA1204), magnetite (Fe3O4), magnesio-chromite (MgCr2O4), (MgA12O4), and magnesio-ferrite (MgFe2O4). A phase transformation in chromite minerals occurs in oxidising conditions during the soda-ash roasting reaction. This phase transformation plays an important role in improving the extraction efficiency of Cr3+ from mineral phase. The extraction efficiency of chromium (Cr3+) from chromite to a water¬soluble sodium chromate (Cr6+) salt depends upon the decomposition kinetics of the spinet phase. An investigation of the phase changes in chromite ores in the absence of sodium carbonate was carried out in air, argon, and in argon +5 % hydrogen gas mixture. The thermodynamics of phase transformation reaction in chromite solid solution phase is discussed using the solution model proposed by Sack and Ghiorso [1]. The microstructural changes and the changes in elemental compositions of different phases were examined by SEM and electron probe microanalysis (EPMA) respectively. The experimental results indicate that the solid solution spinet phase in chromite mineral undergoes spinodal decomposition under the influence of oxygen partial pressure and temperatures. The structure of phases formed and their morphologies suggest that the phase decomposition may be similar to those observed by Burkert et. a]. 121, although the scale of phase separation in chromite appears to be strongly dependent on oxygen partial pressure.

Jan 1, 2001

By Ann M. Hagni

"Ceramic matrix composites are inorganic materials that are particularly resistant to heat and abrasion. A magnesia (MgO) and aluminum nitride (AlN) based composite is formed by exposing a magnesia preform to a metallic alloy block in a nitrogen atmosphere at 950°C. The metallic alloy, which is composed primarily of aluminum, is wicked into the preform. Aluminum nitride matrix is grown between MgO particles as the wicked metallic aluminum reacts with nitrogen. Unused metallic alloy, remnant metallic alloy (carcass), and composite produced after 8 hours, 50 hours, and 225 hours of processing are characterized mineralogically. Reflected light microscopy, transmitted light microscopy, scanning electron microscopy, energy dispersive spectroscopy, and X-ray diffraction techniques reveal that in addition to anhedral to euhedral AhNi, AbSbSr, and Al crystallizing in the metallic alloy carcass, AIN and (Al,Si)N have formed as well. Nitride rings and nodules in the carcass may hinder AIN growth in the composite. Fine-grained residual AhNi and AhShSr are dispersed throughout the composite matrix. The nitride matrix is composed of AIN and (Al,Si)N. Rim replacement of MgO by spine! occurs in the composite. Aluminum nitrides in the metallic carcass cathodoluminesce deep violet-blue, unlike non-luminescent AIN in the composite matrix. This distinction in cathodoluminescence suggests a different mode of formation for composite AIN than for carcass AIN. Phase interpretations and textural characterizations deduced from the implementation of sophisticated mineralogical techniques have contributed to the understanding, and will aid in the improvement, of MgO/ AlN-based ceramic matrix compositeprocessing."

Jan 1, 1999

By Peter K. Everett

One of the major driving forces behind the development of the Intec Copper Process has been the increasingly stringent regulations governing SO2 emissions and, in some parts of the world, a declining H2SO4 market. Other incentives include operating cost (9.2 US c/lb Cu), capital cost (US $1400/annual tonne Cu compared with smelter cost of US$3-4000/annual tonne Cu) and the ability to treat low grade and contaminated concentrates. With such advantageous features, widespread use of the process is expected over time, leading to the production of large amounts of residues containing around 25% elemental sulfur, together with approximately 50-60 % akaganeite (FeOOH) and the ganggue minerals originally present in the concentrate feed. This paper briefly describes the Intec process chemistry involved in the formation of elemental sulfur, thereby avoiding atmospheric sulfur dioxide pollution, and the investigations to be carried out either to extract it or to turn the residue into a valuable by-product while minimising any adverse environmental effects, The process is being developed jointly by a group of fifteen major international mining companies.

Jan 1, 1996

By Junzo Hino

Most of the waste that contains a small portion of copper is landfilled. The recycling process of copper from the waste, such as shredder residue, should be developed in order to save mineral resources and prevent environmental pollution. Shredder residue, generated from disposed automobiles and electric appliances, consists of many types of plastics, glasses and metals. The combustion heat of plastics is efficiently used for smelting in the recycling process that consists of melting and reduction. Because the waste contains numerous components the knowledge of the distribution behaviors of the main components is necessary to develop the recycling process. The distribution behaviors in the recycling process are evaluated by using the thermodynamic calculation program, HSC Chemistry. The calculation results are compared with the practical operation data of the recycling process and discussed.

Jan 1, 2003

By Fabio J. Esper, Guillermo R. Martín-Cortés, Francisco R. Valenzuela-Díaz, Cassio P. Carvalho, Giorgio Grotti, Reginaldo B. Santos

"Rejected sands from smelting metallurgical process because contain lead and others heavy metals are a problem to dispose as waste in all the countries. A procedure that is being proposed for it is to incorporate it on common clay bodies in the fabrication of structural ceramic products as bricks, blocks and roof tiles. The main goal of this paper is to present the results obtained with mixtures of sands from smelting metallurgical process with common clay from Jundiaí, São Paulo, Brazil. Preliminary incorporation tests (1,0% in weight) were made with hand formed spherical samples. With the higher compression strength of the spheres after drying and firing (950ºC) experiments on bricks production were made for quality technological test. Seven hundred hallow blocks containing 1,0% waste were produced and presented ceramic properties similar to those without sand incorporation. Introduction In last the fifteen years the LMPSol - Raw Materials & Non-metallic Solids Laboratory – Metallurgic Eng. & Materials Depto. – Polytechnic School - University of São Paulo comes studying the possibilities of incorporate industrials waste materials to the production of bricks and other products of construction aiming at to remove pollution products of the environments and to user the properties of the same ones in the structural ceramics products. Examples are the study of the influence of rejected steel furnace dusts in structural ceramic [1], another example is the main subject of the present paper: use of rejected sand from smelting metallurgical process in the production of bricks an other products of structural ceramics. Antecedents More or less one year ago, specialist and members from the direction board of METALÚRGICA GROFE LTD. Company contacted researchers and professors of the LMPSol – PMT – EPUSP seeking for a solution to their concern with the disposal of rejected sand from smelting metallurgical process."

Jan 1, 2008

By Batric Pesic

Recovery of gold from refractory ores was studied by pressure oxidation as the method of ore pretreatment followed by bromination of oxidized residues. Three different ores were examined, Au-Ag, Au-Ag-Te, and Au-silver free ore. Pyrite was the major host mineral for gold in these ores. The effect of pressure oxidation parameters (temperature, pressure of oxygen, time, and pulp density) on subsequent bromination under standard conditions was examined. Bromination of residues produced under standard pressure oxidation conditions was examined as a function of: temperature, bromine and sodium bromide concentration, and time. Recovery of gold on activated carbon, from the pulp after bromination, was studied too. Recovery of gold from silver containing ores was lower (87-91%) than the recovery of gold from silver free gold ore (97%). In each studied case, the presence of activated carbon in the pulp further increased the recovery of gold.

Jan 1, 1992

By E. Daniel Baker

"The term ""oxide disseminated gold deposits"" refers to near surface, gold-bearing veins, faults, and shear zones that typically contain appreciable amounts of oxidized ore or gossanous material, resulting from oxidation of sulphides.The concept of oxide gold deposits underwent a dramatic change after the discovery of the Carlin gold mine in north-central Nevada in the early 1960's. Now the term implies large tonnage, low-grade bulk minable deposits that are processed by milling and/or heap leach methods.Oxide gold deposits may now be classified into two types: (1) primacy ores derived directly from the effects of hydrothermal alteration on host rocks, and (2) secondary oxide ores derived from the supergene oxidizing effects of circulating post-mineral meteoric waters on gold-bearing sulphides. Each type of deposit has unique diagnostic mineralogic and metallurgical characteristics that must be addressed to achieve successful exploration strategies and viable metallurgical exploitation.The author would like to thank the management of Newmont Metallurgical Services and Newmont Mining Company for allowing presentation of this paper. Thanks are due Sevkett Acar, Donald M. Hausen, Jerry R. Odekirk, and D. Erik Spiller for their critical review of the manuscript. Also, thanks are extended to all those cited and uncited whose hard work and dedication have led to the discovery and exploitation of near-surface oxide gold deposits. Our knowledge would be greatly limited without the dedication and research of many others."

Jan 1, 1997

By Zhen Zhang, Jiang Diao, Xuan Liu, Tao Zhang, Bing Xie, Hong-Yi Li

Extracting vanadium from vanadium containing hot metal by LD process has been proven an effective solution for the utilization of vanadium-titanium magnetite ore, but the systematic analyses of vanadium extraction rate and mechanism by basic slag are seldom reported. In this study, mathematical model of vanadium transfer from metal to slag was formulated and the rates of vanadium extraction of hot metal with basic slag were investigated. The results indicated that the apparent vanadium extraction rate constant, kp, were in the range of 1.33~9.07×10-4g/(cm3·s). And the rate constant was increased with the increase of final slag basicity, reaction temperature and stirring gas flow. The apparent of mass transfer parameter decreases significantly from 0.13 cm3/ s to 0 cm3/ s in 20min, and the data changed as negative due to the decrease of slag oxidation and recovery of vanadium from slag to metal.

Jan 1, 2015

By K. Nona C. Liddell

There is a significant amount of early work that has been largely forgotten that deals with the validity of the pseudo-steady approximation for liquid-solid reactions. Much of this was originally published in the chemical engineering literature but is highly relevant to hydrometallurgical processes. The purpose of this paper is to summarize some criteria that were been developed by various authors for determining the error associated with use of shrinking core models for liquid-solid systems.

Jan 1, 2002

By M. Furuta, M. Hasimoto, Y. Komoda, K. Haiki

"Tamano Smelter & Refinery started its operation in 1972 with high current density electrolysis (350Nm2 of maximum) applying PRC technology. After the start up, four times of expansion have been done, the cathode production capacity has increased from- 84,000 t/y to 191,000 t/y. However, recent refining technology with permanent stainless steel cathode enabled to increase current density up to 300 Nm2 or more without PRC method. In order to increase current density more than 350 A/m2 , experimental work using commercial size cell has been carried out at several conditions, such as current density, PRC conditions, electrolyte composition and electrode condition. As a result, it was found that high quality (LME A grade) cathode can be produced at such a high current density as 405 A/m2•IntroductionWhen considering the production increase of electrolytic copper, what becomes important is the improvement of productivity per unit of production facility. Conventionally, production had been expanded by increasing the number of cells but a huge investment required for this had a influence to the business profitability. Because of this, increase of current density, which is one of the methods to improve unit productivity, 'was expected and this method at the same time has another advantage of shortening the retention time of copper and other precious metals in the cells. At present, the average current density at Tamano during full capacity production is around 350 A/m2 and this used to be the limit throughout the world (1)."

Jan 1, 2000

By Tim B. Vander Wood

Standard methods of determining clay mineral powder aspect ratios involve manual scanning electron microscopy analyses of shadowed particles in order to measure both platelet thickness and diameter. We present a method whereby the diameters of platelets are quickly determined by automated scanning electron microscopy and their images are recorded and digitally transferred to a transmission electron microscope equipped for parallel electron energy loss spectroscopy. Thickness' of platelets whose diameters are known from the previous analyses are determined by measurement of the ratio of scattered and unscattered electrons in the beam after it has been transmitted through the platelet.

Jan 1, 1995

By Michael I. Morris

The U.S. Department of Energy's (DOE's) Transuranic and Mixed Waste Focus Area (TMFA), funded from fiscal year (FY) 1996 though FY 2002, was tasked with finding solutions for the mixed waste treatment problems of the DOE complex. During TMFA's initial technical baseline development process, three of the top four technology deficiencies identified were the need for amalgamation, stabilization, and separation/removal technologies for the treatment of mercury-contaminated mixed waste. The Mercury Working Group (HgWG), a selected group of representatives from DOE sites with significant mercury waste inventories, assisted TMFA in soliciting, identifying, initiating, and managing efforts to address these areas. Solicitations and contract awards were made to the private sector to demonstrate both the amalgamation and stabilization processes using actual mixed wastes. The goal was to develop separation and removal processes that will address DOE's needs. This paper discusses the technology selection process, development activities, and the accomplishments of TMF A through these various activities.

Jan 1, 2003

By F. H. Froes, O. N. Senkov, N. Srisukhumbowornchai

"Mechanical alloying (MA) and thermohydrogen processing (THP) approaches were used to synthesize amorphous or nanocrystalline powders of the titanium-aluminide-based alloys and composites. Fully dense samples with nanocrystalline and bimodal structures were produced from these powders by hot isostatic pressing. The stability of the microstructures during continuous heating at high temperatures was studied. Characterization techniques including X-ray diffraction, scanning and transmission electron microscopy, energy dispersive spectroscopy, and differential thermal analysis were used in this work.IntroductionAs performance demands increase, so do the demands for enhanced mechanical property combinations at reduced overall weight; and reduced weight can most efficiently be realized by the use of low-density metals with high specific strength, such as titanium alloys and titanium-aluminum intermetallics [l]. The TiAl-based alloys are attractive for high temperature applications, however, they exhibit poor ambient temperature ductility and fracture toughness [2-4]. Incremental improvements can be obtained using ingot metallurgy processing [1,2] but more substantial developments require ""far from equilibrium"" (FFE) synthesis [5-8] which allows development of novel constitutional and microstructural effects, leading to enhanced physical and mechanical properties. Improved ductility of titanium aluminide intermetallics can be achieved by disordering, grain refinement and deoxidation of the matrix, while good elevated temperature properties are achieved due to a dispersion of fine, thermodynamically stable, second phase particles.The approaches for producing nanocrystalline and amorphous TiAl-based alloys and composites used in this work included FFE powder metallurgy techniques such as rapid solidification, mechanical alloying and thermohydrogen processing. The rapid solidification (RS) technique allows extension of solubility limits, production of novel phases, and much more refined microstructures (down to nanostructure or even amorphous range) than is possible using the ingot metallurgy technique [9]. Mechanical alloying (MA) is a process in which heavy working of powder particles results in intimate alloying by repeated deformation, fracturing and welding. This process can produce greater departure from FFE than RS, leading to greater refinement effects; and additionally allows production of a dispersion of second phase particles [10]. Thermohydrogen processing involves hydrogen as a temporary alloying element in titanium to facilitate processes, refine microstructure, and improve final mechanical properties [11]; it was used in the present work to improve MA process. The combination of these three processes was expected to control the final microstructure even better than either process used alone."

Jan 1, 1998

By William D. Riley

The U. S. Bureau of Mines has developed technology to recover by-product materials from aluminum scrap using engineered scavenger compounds (ESC). ESCs are structural oxides with a channel or tunnel structure that allows them to hold ions of a specitksizes and charges. The scavenging reaction is easily reversible allowing the ESC to be recharged for continued use and the ion is recovered as an electro deposit. Key features of this novel technology are; a) ESC ,systems are designed to have a high degree of selectivity for a desired ionic species. b) The recovered mater.ial requires little or no additional reprocessing prior to reuse. Two current uses for the ESC technology that are described in this paper are the removal and recycle oflithium (Li) from lithium aluminum (Li-AL) alloys; and, using ESCs as a replacement for the conventional demaging (magnesium removal) technology used by the secondary casting industry. Research indicates that the ESC technology proposed for both these applications has either 'distinct economic and/or environmental advantages over previously employed methods of recovering. metal values from aluminum scrap.

Jan 1, 1995

Segregation roasting tests were carried out on Zaire cobalt oxide ores assaying about 2% Co and 3.5 to 6.5% Cu. The major parameters tested during the laboratory investigations were temperature, dosage and type of reducing agent, dosage and type of chloridizing agent, and particle size. Results showed that standard conditions suited to the segregation of copper ores, i.e. low temperature and low dosages of reducing and chloridizing agents, resulted in the segregation of copper only, while conditions suited to the segregation of lateritic nickel, i.e. higher temperature and increased dosages of reducing and chloridizing agents, led to a successful segregation of both copper and cobalt. Under the best conditions, 88% of the cobalt and 98% of the copper could be recovered in a concentrate assaying 32.5% Cu and 8.5% Co. Alternatives to process such a concentrate are briefly reviewed.

Jan 1, 1993

By Shenghui Guo, Jianbo Lan, Hongying Xia, Jinhui Peng, Lihua Zhang, Libo Zhang

Spent Hawaii nut shell was converted into a high-quality activated carbon via steam physical activation. Analysis of the experiment including activation temperature, activation duration, steam flow rate on the adsorption capability and yield of activated carbon were identified. Response surface methodology showed that the activation temperature was identified as 866 , an activation duration of 36 min and a steam flow rate of 2.5mL/min with the methylene blue adsorption number of 195 mg/g and yield of 77.75%. The key parameters that characterize quality of the activated carbon such as the BET surface area, total pore volume and average pore diameter were estimated to be 1125m2 /g, 0.94mL/g and 5.21 nm, respectively. Additionally, by the SEM analyses of char and activated carbon, the surface of activated carbon has large number of pores of irregular and heterogeneous morphology.

Jan 1, 2016

By H. Saint-Raymond, F. Gruy, P. Gardin, M. Cournil

"The control of inclusion elimination is getting more and more important to obtain clean steel. This paper presents a methodology under development for predicting cluster growth and elimination in ladle - RH system. The first key point is to express the collision efficiency, which is very specific for alumina cluster due to the non-wetting fluid. Second, a description of the two-phase flow in the system is necessary. In our calculations with Fluent CFD package and Lagrangian approach for bubbles, bubble growth is implemented, which improves the predictions. Using global reactor decomposition makes possible the prediction of the time evolution of cluster distribution. Important effect of fractal dimension is demonstrated.IntroductionElaboration of new steel grades requires not only to have a high purity in terms of C, O and N content but also to eliminate particles such as alumina or slag droplets. Flow optimisation making easier inclusion elimination is then a key figure to satisfy cleanliness requirements. Mathematical models of flow and inclusion behaviour are widely used for this purpose (1, 2). But having a predictive tool is still a challenge, because the number of phases is important in steelmaking industry: liquid steel, slag layer, bubbles and inclusions (with a large range of composition and rheology). The paper presents the methodology which is developed at IRSID to predict oxygen content evolution during RH degassing.The main mechanisms which have to be considered are :-inclusion growth by turbulent aggregation of elementary inclusions (keeping in mind that liquid steel is a non-wetting medium for inclusions); the difficulty is to express collision efficiency for alumina particles,-inclusion removal by flotation; the difficulty for alumina clusters stems from the complex morphology of particle; fortunately, the use of fractal concept makes it possible to cope with this problem.The paper describes the general modelling of inclusion removal taking into account the previous mechanisms. Hydrodynamic parameters are obtained by means of Fluent CFD package and a specific coding is developed for cluster growth."

Jan 1, 2001

By Mikhail Mikhaylenko

Natural and technogenic sources of rare earth elements (REE) and other rare and scattered metals are remarkable for their chemical diversity. The pregnant solutions going to processing for the valuable metals have very complex compositions. Both targeted elements and competing impurities are present in the solutions in different chemical forms. Thus processing of such materials demands application of different technological tools addressing numerous specific tasks on the way to the final product. Screening work was undertaken to identify the best resins among developmental and commercial products addressing typical cases in the hydrometallurgy of scandium and REE. The cases outline typical sources of scandium and REE, such as streams of TiO2 production, extracted phosphoric acid, barren uranium solutions and others. Specially designed ion exchange resins can be effective tools.

By E. Fregeau-Wu

The mineralogy and grain size distribution of phases in a steelmaking slag and experimental products from the heating of the slag under various conditions were determined to explore the possibility of recycling of the iron and manganese to the blast furnace. The steelmaking slags consisted of three major phases: dicalcium silicate, dicalcium ferrite, and Mg-Mn-wustite. Most of the phosphorus was contained in the dicalcium silicate and to lesser extent in the dicalcium ferrite. Due to the fine grain size of the dicalcium silicate, grinding and magnetic separation required pretreatment to increase the grain size and hence the liberation. Experiments on a steelmaking slag were conducted by heating the slag to 1633-1748°K( and slow-cooling in an inert atmosphere at various rates with or without the addition of fluorspar (CaF2) as a flux. Grain size distribution analyses of the starting material and the slow-cooled products were performed using the SEM-IPP area scan method and the QEM*SEM linear scan method. Comparable and reproducible results were obtained on the same sample using both methods. A size versus volume percent plot showed the increased grain growth most effectively. Examples of the grain size distributions obtained were used to show that a higher soaking temperature prior to slow-cooling, a slower cooling rate, and the addition of fluorspar to the slag promoted grain growth.

Jan 1, 1989