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By Rolando Campos

Until 1970, the Caletones Smelter of CODELCO-CHILE, División El Teniente, operated under the conventional pyrometallurgical process used by most of copper smelters. The annual copper production varied around 165.000 tons. The failure in the commissioning of the "oxygen smelting" technology in Peirce- Smith converters (1970-1972), forced further introduction of transcendental changes in the Caletones smelter operating scheme. Implemented technological innovations were based on wide studies and research works performed by División El Teniente. This paper presents a summary of technological modifications introduced, their impact on production and energetic performances, and short and medium terms improvement plans.

Jan 1, 1993

By R. C. Hubli

A panial equilibrium model? to simulate the dissolution of millerite (NiS) in aqueous solutions containing copper(II) chloride as the oxidizing species has been developed. The predominant copper(I) and copper(II) species are CuQ3 and CUO2 respectively. The model computes the initial concentrations of the species present in the aqueous phase under the specified input conditions, prior to the simulation of dissolution. During the dissolution of millerite, nickel enters the leach liquor as NiH and it has been found that the H+ decreases as a function of NiS dissolution. The simulation has been accomplished under conditions prevailing during actual dissolution, with only one mineral undergoing dissolution. The model can be applied for the simulation of co-dissolution of two or more sulfides. Under the given conditions, the precipitation of Cu1(OH»)O is negligible but loss of Cu(1l) could be significant if the initial H+ is lower than 0.03 M. The results of the simulation compare favorably with experimental observations.

Jan 1, 1996

By S. E. James

EAF dust has been listed as a "hazardous waste" due to the presence of lead and cadmium, and at times chromium. The 550,00 tpy production of . .EA]' dust, estimated for the United States alone, contains more than 10,000 tpy of lead and about 250 tpy of cadmium in addition to nearly 1'00,000 tpy zinc. Even though the listing of .EAF dust as a hazardous material stimulated extractive metallurgical work worldwide, process development efforts have focused only on the recycle of the potentially-valuable zinc units. However, the recycle of the lead and cadmium, while not lucrative, is the more critical effort. Horsehead Resource Development Company, Inc. (HRD), in conjunction with its sister company, Zinc Corporation of America (ZCA), has taken a unique approach to total recycle of the toxic heavy metals found in the EAF dust. Impure oxide, produced by either a Waelz kiln or FLAME REACTOR Process and containing the lead and cadmium, is calcined in a rotary kiln at Palmerton, Pennsylvania, to produce a refined zinc-rich intermediate for ZCA's electrothermic zinc plant at Monaca, Pennsylvania. During the calcining operation, lead and cadmium are concentrated in a fume product and shipped to ZCA's electrolytic plant at Bartlesville, Oklahoma. At Bartlesville, a new hydrometallurgical circuit has been constructed and the existing cadmium plant expanded. The combined facilities permit the total recovery of cadmium to refined metal and the lead to .a silver-rich intermediate, which is sold to lead smelters. In this paper the Waelzing, calcining and new leaching facilities will be described.

Jan 1, 1990

By Shengli Wu, Jinming Zhu, Wei Huang, Xinliang Liu

The sinter of high basicity would interact with lump ores or acid pellets in the cohesive zone of blast furnace due to the difference of chemical composition and micro structures. The results of this work showed that the softening-melting properties of lump ores and acid pellet would be obviously improved by the high temperature interaction. However, the high temperature interaction index (INI) would be influenced by many factors, such as chemical composition, porosity, interaction interface and so on. The INI between sinter and porous limonite lump ore (L-2) was much higher than that of dense hematite lump ore (L-1) and acid pellet (P-1). In addition, though the softening and melting properties of L-2 were poorest in respective iron ores, the softening and melting properties of integrated burden B (consist of sinter and L-2) were not worse than other integrated burdens due to the strong high temperature interaction.

Jan 1, 2015

By G. G. Richards

"The slag fuming process has operated for close to 70 years to recover zinc from lead blast furnace slag. The process is normally carried out through the batch treatment of slag by submerged injection of coal and air. Within the bath the coal acts as both a reductant, to reduce Zno to zinc vapour, and a fuel, to maintain bath temperature during the endothermic reduction process. The partition of coal between the slag, combustion and bypass is dependent on factors such as bath depth and injection pressure. The option of continuous fuming has been pursued at the D. Blagoev smelter in Bulgaria using heavy fuel oil as reductant/fuel. There has, however, been little attempt at commercial continuous fuming with coal. This paper presents an analysis of a coal-based continuous slag fuming furnace. The data on the Plovdiv fumer is used as a reference point. Critical design criteria for continuous fuming include the slag feed rate, degree of coal combustion and furnace size. Mathematical modelling analysis suggests that continuous fuming with coal can achieve respectable zinc/coal ratios.IntroductionThe slag fuming process was developed in the early part of this century to recover zinc from non-ferrous smelting slags [1-3]. The majority of installed furnaces were put in place to fume zinc from lead blast furnace slag on a batch basis. In most cases coal is used to effect reduction of zinc oxide, but one furnace uses natural gas [4] and, in a curious twist, a continuous fumer was developed based on fuel oil [5].Given the general nature of blast furnace lead smelting, it is not surprising that slag fuming has remained a batch process, in spite of the advantages that could be gained by moving to continuous fuming. Blast furnaces are usually operated as relatively independent units, and tapping has traditionally been done into ladles. The presence of a crane aisle makes direct coupling of the blast furnace to a slag fumer difficult, especially in a retrofit situation. Furthermore, steady-state blast furnace operation is not easy to achieve. The size of these furnaces and the nature of their feed make it difficult to guarantee constant operation."

Jan 1, 1996

By P. Peczak

A Monte Carlo simulation technique has been used to study dynamic recrystallization in polycrystals. A continuum microstructure of the polycrystal is modeled employing a discrete lattice. The response of the material to hot deformation is simulated by adding stored energy and recrystallization nuclei continuously with time. The experimentally observed nonuniform character of deformation substructures is modeled by employing a phenomenological expression for inhomogeneous distribution of the stored energy. All simulations were performed on HP-Apollo 9000 Series 700 workstations. A program written in FORTRAN with use of PHIGS graphics library calls was used to interactively monitor the current state of the matrix and all relevant parameters: deformation stress, average grain size and effective nucleation rate. Visual analysis of the simulated microstructure allows a better understanding of the data developed by averaging over a number of very long Monte Carlo runs. Since the essential features of dynamic recrystallization are accurately reproduced by the model, it is used to discuss the role of the controlling mechanisms of the dynamic recrystallization in real polycrystal.

Jan 1, 1993

By Bo Jiang, Jiusan Xiao, Hongmin Zhu, Kai Huang, Shuqiang Jiao

Carbothermal selective reduction of simulative titanium slag and various titanium raw materials were presented and SiO2 was found to be partially reduced, forming a series of Fe-Si alloys during the process. Thermodynamic analysis of the selective reduction between TiO2 and SiO2 was performed using HSC 6.0 software, then a series of equilibrium experiments were designed and presented. The activity of Si reduced from SiO2 was affected by the presence of Fe reduced from FeOx and the generation of Fe-Si alloys, promoting the reduction of SiO2 in the whole process. The results of experiment are in great accordance with the calculated data obtained from thermodynamic analysis.

Jan 1, 2016

By Ann M. Hagni

Microscopic and sub-microscopic gold commonly occurs in the sulfides pyrite (FeS2) and arsenopyrite (FeAsS). To recover refractory gold from pyrite and arsenopyrite, these sulfides are roasted to create porosity and permeability prior to cyanide leaching. A new technique of adding Ca(OH)2 and roasting. lime roasting. is being tested for retention of contaminant sulfur and arsenic and effectiveness of gold extraction. The lime roasting of pyrite at 500°C contains anhydrite (CaS04). oldhamite (CaS). calcium sulfite (CaS03). hematite (Fe2O:J), magnetite (Fe304). and minor amounts of pyrrhotite (Fe1.xS) and pyrite. At 600°C. 650°C and 700°C. the main constituents are anhydrite. oldhamite. and hematite. At 750°C. 800°C. and 850°C. anhydrite and hematite are the predominant phases with minor oldhamite. The roasted arsenopyrite at 450°C contains arsenic sulfides. calcium sulfite. hematite. and minor oldhamite. magnetite. and pyrrhotite. At 650°C. 700°C, 750°C. and 800°C, anhydrite, oldhamite. arsenic sulfides, and hematite are present. At 850°C. the same minerals are present with only minor oldhamite. The textures indicate excellent porosity and permeability at high temperatures. At lower temperatures, rims of low porosity and permeability surround many of the pyrite and arsenopyrite particles, and the complete oxidation process from pyrite to pyrrhotite to magnetite to hematite can be observed in individual particles. Additional process mineralogy techniques employed in this study are electron spectroscopy for chemical analysis (ESCA) and cathodoluminescence microscopy (CIM) in the determination of the calcium-sulfur-oxygen phases. Automated scanning electron microscopy-energy dispersive spectroscopy was utilized to analyze particles for gold content. Reflected light microscopy (RIM) revealed arsenopyrite and pyrite encapsulated in quartz particles of the gold-bearing concentrate, gold roast calcine, and cyanide leach residue.

Jan 1, 1991

By Ann M. Hagni

Microscopic and sub-microscopic gold commonly occurs in the sulfides pyrite (FeS2) and arsenopyrite (FeAsS). To recover refractory gold from pyrite and arsenopyrite, these sulfides are roasted to create porosity and permeability prior to cyanide leaching. A new technique of adding Ca(OH)2 and roasting, lime roasting, is being tested fro retention of contaminant sulfur and arsenic and effectiveness of gold extraction. The lime roasting of pyrite at 500°C contains anhydrite (CaS04), oldhamite (CaS), calcium sulfite (CaS03), hematite (FenOs), magnetite (Fe304), and minor amoupts of pyrrhotite (Fel.,S) and pyrite. At 600°C, 650°C and 700°C the main constituents are anhydrite, oldhamite, and hematite. At 750°C, 800°C, and 850°C anhydrite and hematite are the predominant phases with minor oldhamite. The roasted arsenopyrite at 450°C contains arsenic sulfides, calcium sulfite, hematite, and minor oldhamite, magnetite, and pyrrhotite. At 650°C 700°C 750°C and 800°C, anhydrite, oldhamite, arsenic sulfides, and hematite are present. At 850°C, the same minerals are present with only minor oldhamite. The textures indicate excellent porosity and permeability at high temperatures. At lower temperatures, rims of low porosity and permeability surround many of the pyrite and arsenopyrite particles, and the complete oxidation process from pyrite to pyrrhotite to magnetite to hematite can be observed in individual particles. Additional process mineralogy techniques employed in this study are electron spectroscopy for chemical analysis (ESCA) and cathodoluminescence microscopy (CLM) in the determination of the calcium-sulfur- oxygen phases. Automated scanning electron microscopy-energy dispersive spectroscopy was utilized to analyze particles for gold content. Reflected light microscopy (RLM) revealed arsenopyrite and pyrite encapsulated in quartz particles of the gold-bearing concentrate, gold roast calcine, and cyanide leach residue.

Jan 1, 1993

By H. V. R. von Rhaden

Systematic quantitative X-ray diffraction analyses performed on diamond-drill cores originating from the Aandenk formation at the Loraine Gold Mine, located in the Welkom goldfield, Orange Free State, South Africa, have revealed the presence of a number of phyllosilicate mineral assemblages which have not hitherto been reported from this region. Rectorite, a regularly interstratified 1:1 mica-montmorillonite "swelling clay", is found to occur together with paragonite, muscovite, pyrophyllite, kaolinite, and chlorite in highly-altered friable rocks. The presence of rectorite in mill feeds may have potentially serious implications with respect to gold recovery. Quantitative X-ray diffraction analysis for phyllosilicates can be used as an aid to correlation, and also to guide the widths of stopes in underground mining. Rectorite has a unique mode of origin, which is discussed.

Jan 1, 1991

By Cynthia Belt

"Energy management is critical to aluminum processing given the high energy requirements of melting and processing aluminum. Energy costs have always been a high percentage of the total production costs within this industry. Energy management at many plants relied on better technology that many times required high capital. As carbon management has grown in importance and project payback becomes more critical, a larger view of a plant's process is required. This paper looks at the energy requirement due to current typical practices in overall product recovery, metal loss, utilization, and technology to understand potential methods of reducing overall energy within a plant and within the aluminum processing industry.IntroductionFor many companies that process aluminum, energy is a major portion of their costs that can surpass the cost oflabor. Aluminum processing can include secondary processing of scrap and prime aluminum into sows and/or molten aluminum or casting aluminum by various methods such as direct chill, continuous casting, low or high pressure casting, mold casting, and extrusions. In the case of this paper, we are considering only plants that include the melting process as a portion of their process. The process of melting aluminum takes energy. In most cases, the aluminum must then be heat treated one or more times. Post processing of the aluminum includes rolling mills used for making sheet, extrusion lines, and machining such as saw cuts, drilling, or surface finishes that all take additional energy.While these high energy costs directly affect the profits of the company, energy management within the metals industry is still not widespread. A co=on misconception is that the solution to high energy costs is high cost capital equipment. While state-of-the-art equipment can certainly improve energy efficiency, it is not the only solution. To obtain a truly energy efficient plant, several directions needs to be addressed through an energy management thought process with a wider scope. Impact on potential savings is possible through: product recovery, metal loss, utilization, and new technologies. An understanding of the potential costs and savings from these means is important. Several of these methods provide low cost approaches to saving energy.The background data used in this paper is not a random sample within aluminum processing but yearly averages from various plants in different aluminum processing industries. As is normal in this industry, the plants have been under different corporate management over the years with different strategies for energy management. This data is not meant to be accurate for the entire industry but to suggest areas for energy efficiency work."

Jan 1, 2012

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 Andreas Siegmund

During the decade of the nineties the conventional method of primary lead smelting (sinter machine/blast furnace) was successfully challenged by the introduction of novel direct and continuous smelting processes. In combination with a significant shift in market structure, as well as more stringent government regulations these modem technological innovations like the QSL, Kivcet, and Isa/Ausmelt processes became more than major competitors. They have proven to be economically and environmentally viable. The intensification of the metallurgical reaction by applying oxygen enriched or pure oxygen bath or flash smelting principles resulted in cost savings and a higher flexibility with respect to raw materials and additives usage. By synchronizing individual auxiliary plant sections with the smelting process a virtually waste- free production and low-emission mode of operation with nearly optimum energy exploitation is achieved. The primary lead industry will gradually substitute the sinter -blast furnace operation with novel high-energy efficient technologies in the new millennium.

Jan 1, 2003

By Kazuki Morita

A new route to produce solar grade silicon (SOG-Si 6N) from metallurgical grade (MG-Si 98%) has been developed in Japan, which may satisfy the increasing demand for solar cells in the near future. Since some elements such as P and B have very large segregation coefficients, solidification refining is not effective for their removal and costly processes, such as electron beam vacuum melting and oxidation plasma refining, are required. According to our previous results which showed the effectiveness of leaching procedure with Ca addition for Fe and Ti removal, possibility of P and B removal by acid leaching was focused expecting that their affinities for Ca in molten silicon might be considerable. Hence, the effects of Ca addition on the thennodynamic properties of P and B in molten silicon alloys have been investigated for overall control and optimization of the SOG-Si production process in the present study. The interaction parameters between Ca and P, and Ca and B were determined by chemical equilibration techniques at 1723 K. Although the interaction parameter between Ca and B was slightly negative, that between Ca and P showed a large negative value. Also, the results for the leaching test with various amount of Ca addition revealed that the removal fractions of both elements, especially P, drastically increased with increase in the Ca content, which showed very good agreement with the prediction from the interaction parameters derived in the present work. The present results suggest that the preliminary leaching procedure can reduce the processing time and energy for SOG-Si refining. Keywords: Silicon, Solar Cell, Refining, Acid Leaching, Thennodynamics. Interaction, Phosphorus, Boron, Calcium

Jan 1, 2003

By L. Sh. Tsemekhman

The results of laboratory, large-scale laboratory and commercial scale investigations regarding the process of slag melts cleaning by oxidizing-reduction gas mixtures with a wide range of Po2 and the use of matte of various compositions as an extracting phase are presented. The copper, nickel and cobalt behavior during the cleaning process has been studied based on SEM and x-ray Microprobe of the quenched slag melts. The general cleaning mechanisms have been found. On the basis of the obtained data the most efficient cleaning methods have been proposed.

Jan 1, 2003

By Katsunori Yamaguchi

A new technique for the removal of tramp-elements from steel scrap has been required from the viewpoint of saving energy and protection of environment. In order to obtain fundamental information on the removal of copper, tin and zinc from molten iron, the extraction method by using of phase separation in the liquid Fe-Pb-C system was investigated at 1453K. A mixture of iron, lead and carbon melted in a carbon crucible separates into two phases of lead and iron containing carbon. The compositions on the miscibility gap in the Fe-Pb-C system are 95.4%Fe-4.5%C-0.1 %Pb and 99.9%Pb-0.I%Fe. The distribution ratios of copper, tin and zinc between the lead and the iron phases, Lx [mass%X in molten Pb]/(mass%X in molten Fe), are 2.2, 2.2 and 1.4, respectively. Seventy percent of copper and tin from iron scrap can be eliminated with comparable lead addition. Gold, silver and palladium are enriched in the lead rich phase, on the contrary platinum and rhodium are more distributed to the iron rich phase than to the lead phase.

Jan 1, 2003

By T. C. Goel, A. Venna, R. G. Mendiratta

"Processing of ferrites has gained tremendous importance in recent times to meet the high performance demands on ferrites in keeping with the fast emerging· technologies. The quality of ferrite powders has strong influence on ·the performance of final device. Fabrication· of high performing ferrite components requires starting ferrite powders of precise stoichiometry, purity and microstructure. It is difficult to obtain these attributes by the conventional ceramic method. The key to obtaining quality powders lies in the· solution techniques. With this in view soft ferrites have been prepared by a wet chemical process, known as the citrate precursor method, which involves the formation of citrate complexes of the constituent cations. The advantages of this process are the ease of preparation and close control of composition, homogeneity, purity and particle size. Electrical and magnetic measurements on lithium ferrites have shown resistivity higher by more than two orders of magnitude compared to that observed for samples prepared by the conventional ceramic method, and low magnetic losses, making the ferrites specially suitable for high frequency applications.IntroductionProperties of ferrites are known to be sensitive to .their processing technique. A small deviation in the compositional stoichiometry of the ferrite affects its properties greatly. Soft ferrites such as Ni-Zn, Mn-Zn and Mg-Mn. are well known ferrites covering wide-ranging applications [1,2]. Lithiiim ferrites have also assumed technological importance for microwave applications and are potential substitutes for the expensive garnets [3]. Lithium ferrites are often doped with zinc to tailor the saturation magnetization required at high frequencies. Lithium and lithium-zinc ferrites, however, present difficulty to processing due to the volatile nature of both the cation components, namely Li and Zn. These ions are volatile at temperatures > 1000°C which makes their processing difficult. One of the main considerations of high frequency performance of ferrites is the high eddy current losses which prevent the interaction of the magnetic field with the ferrite component and hence impair device performance. These losses can be reduced by having a material of high resistivity. Electrical conductivity in lithium ferrite has been attributed to electron hopping [4] between the two vaience states of iron, Fe2+ <=> Fe3+, on octahedral sites. Maintaining the + 3 valence state of otahedral- Fe ions is thus a prerequisite for achieving high resistivity. The resistivity of ferrites is normally found to be low when processed by the conventional solid-state or the ceramic method [5]. This is attributed to (a) extensive ball-milling employed in the method to mix the component oxides results in non-stoichiometric compositions due to introduction of additional Fe ions on abrasion of steel balls during milling, (b) high processing temperatures involved which result in significant volatilization of Li and Zn ions creating thereby oxygen non-stoichiometry which results in reduction of Fe3 + to Fe2 +, (c) large and non-uniform grain sizes. In the present work, preparation of Li and Li-Zn ferrites by a non-conventional method known as a citrate precursor method [6, 7] which requires lower processing temperatures and duration is reported. The method gives stoichiometric compositions on account of homogeneous atomic-scale mixing of the constituent cations via the formation of metal-citrate complexes mixed in solution state. The method is also capable of giving small grain size which aids the oxidation ofFe2+ ions."

Jan 1, 2000

By Nicholas E. Vanderborgh

Projections show that domestic coal will serve for the majority of energy supplies during the next decades. Thorough chemical cleaning of this coal can be accomplished in long-residence time, slurry-transport systems to produce high-quality fuel product. Concurrently, mineral recovery from coals will supplement existing ores. This paper describes this concept and gives preliminary engineering considerations for mineral recovery during transport operations.

Jan 1, 1982

By Christian Wögerer

For material or process development as well as for quality checking of materials, thermal diffusivity measurement may be the tool of choice in many applications. Especially if diffusivity is measured locally resolved, a lot of information can be read out of such a ?diffusivity image?. This paper explains the method to measure coplanar specimen like plates and lists some interpretations of diffusivity images, like inhomogeneity of sintered materials, structural voids or inclusions. Diffusivity is a material property, describing transportation of heat in solids in spatial and temporal terms. With thermo cameras it is possible, to measure diffusivity of larger areas simultaneously. The result is an area of diffusivity values that may be plotted or displayed like an image. Locations with lower diffusivity values could be caused by the presents of structural differences in the material, by decomposition of the material components or by inclusions of other material like air.

Jan 1, 2009

By James A. Voigt

The efficient separation of metal species from aqueous streams by precipitation techniques requires &apos;a fundamental understanding of the various processes that occur during precipitation. These processes include particle nucleation, particle growth by solute deposition, agglomerate formation, and agglomerate break-up. The application of the population balance approach has been used to develop a kinetic model that accounts for these competing kinetic processes. The usefulness of the model is illustrated through its application to the precipitation of yttrium hydroxynitrate, YHN. The kinetic parameters calculated from the model equations and system-specific solution chemistry are used to describe several aspects of the effect of pH on the precipitation of the YHN. Implications with respect to the simultaneous precipitation of more than one cation type are also discussed through use of example systems: The effects of solution chemistry, precipitator design, and solvent choice are considered.

Jan 1, 1996