Search Documents

By Tomas Astorga

APEC, the Asia Pacific Economic Cooperation is the forum of 21 countries having approximately 56% of the total world income, and over 45% of global trade. In 1997, APEC economies produced 67% of the world copper output, 55% of gold, and over 45% of other base metals. Mining in APEC captures more than 60% of the total mining investment in the world. New and emerging economies are now appearing in the demand scenery, such as China. New trends in the international environmental regulations are posing questions related to the use of copper in different industrial and consumption applications. These may have a strong impact on future trade of copper. New applications are also appearing based in new technology fields. The paper examines the growth potential of the copper market in main consumer ad highly populated economies of APEC, incorporating analysis of various interrelated factors. It also analyses the outlook of the copper supply. Its conclusions point to the need to implement demand outlook models. Finance and economic reforms will open important avenues for trade growth in basic metals, particularly copper. Changes in the consumption patterns of highly populated countries will add to better perspectives of copper demands. The recovery of a fast pace of economic growth in the APEC region will bring new demands for copper, especially as a consequence of high tech applications. More extended policies focused in the need for developing energy efficiency programs and schemes will add to this picture.

Jan 1, 1999

By David K. Melgaard

Electroslag Remelting (ESR) is a complex process used to produce high quality specialty alloy materials. The quality can be directly correlated to variances in melt rate and immersion depth. Conventional ESR furnaces control these quantities using two independent control loops using proportional changes in current for melt rate and driving the electrode up and down to match a voltage set point for immersion depth. However it is well known that the control loops are highly coupled, i.e. changing the current to account for melt rate deviations changes the voltage depth relationship and vice verse. In addition the noise in measurements of the ESR process can be considerable, forcing conventional controllers to use highly damped responses. A new model-based controller has been developed to embody the coupling and improve responsiveness by using estimates from a reduced-order linear ESR model and the typical process measurements to control melt rate and immersion depth simultaneously. Kalman filtering is used to optimally combine the model estimates of eight process states and the measurements of voltage, current, position and mass to estimate the instantaneous melt rate and immersion depth. Several ESR melts under steady state and transient conditions were conducted to evaluate the performance of the new controller. This paper will discuss the design of the new ESR model and controller and will present experimental results demonstrating its much improved control and responsiveness. While this controller was developed for the ESR process, the effectiveness of model-based control in managing such a complex process with relatively simple equations suggests the approach could be employed for many other processes as well.

Jan 1, 2006

By Abhoy Mukherjee

The Luanshya Smelter is a traditional Reverberatory Smelter which once worked with up to three coal-fired reverbs, and now operates one Reverb and one hot Peirce- Smith Converter, projected to produce approximately 42.000 tons per year of copper anodes. The aim of this study is to select a smelting technology which best fits the upgrading of the Smelter, such that low capital and operating costs are achieved for the projected design production capacity of 60.000 tpy, limited by the available supplies of concentrates. An equally important requisite is the compliance of present and future environmental regulations, which determines the need to install and Acid Plant to treat the smelter primary gases. In the process selection study, the following technologies were analyzed, at a Conceptual Engineering level: the Oxy-fuel Burner Reverb, the Teniente Converter, the CONTOP Cyclone Smelting Reactor, and further, the Ausmelt Furnace, the engineering of which was provided by the proprietary firm. The engineering of the other processes was developed by INDEC, which also integrated the comparative analysis of the four options. The analysis of a comprehensive set of technical factors, including integrated smelter metallurgical models, together with the evaluations of economical features, led to the selection of the CONTOP Smelting Technology for the modernization of the Luanshya Smelter.

Jan 1, 1999

By Rivera Jose Antonio Ore

Top Submerged Lance (TSL) smelting technology is currently used in a wide range of applications in the non ferrous and waste product treatment industries. The use of TSL technology for tin concentrates smelting has been successfully applied at the Minsur Tin Smelter and Refinery at Pisco, Perú. The process is based on the air-cooled top entry submerged Sirosmelt lance, developed by Dr. John Floyd at the CSIRO division of Mineral and Process Engineering in the 1970?s. Advantages of the process include flexibility to operate the lance, main burner of the Sirosmelt furnace, with different levels of combustion stoichiometry which allows us to get from highly reducing to highly oxydising atmospheres in the smelting reactor according to the type of feed we are processing, ability to utilize cheap energy sources such as natural gas, low capital cost and an environmentally friendly operation. This presentation summarises the application of the Submerged Sirosmelt technology for smelting tin concentrates and a variety of tin containing materials like iron dross, copper dross, tin residues, low tin/antimony slags by applying recent metallurgical developments at the Minsur smelter. The impact of new feed conditions and level of impurities on reactor performance with features of process and operation control are described. As a result of these recent advances in tin smelting using TSL technology, the Minsur Tin Smelter and Refinery improved its overall tin recovery, substantially reduced tin inventories and became the second largest tin smelter in the world, currently producing more than 40,000 metric tones of refined tin per year.

Jan 1, 2006

By Qixing Yang, Björn Haase, Fredrik Engström, Anita Wedholm

"MiMeR, the Minerals and Metals Recycling Research Centre at Luleå University of Technology, Sweden, started industry-related research work to stabilize an EAF slag from Höganäs AB with of CaO/SiO2 values near to 3.2. The intention was to determine the suitability of the EAF slag as construction material after stabilization. Some of the stabilizers effective for preventing disintegration of AOD slag were examined in laboratory tests for stabilization of the EAF slag. The EAF slag samples were mixed together with stabilizers for melting at 1600ºC and then cooling in a crucible system. With a laboratory granulation system, the liquid EAF slag was cooled rapidly using air. Samples from the tests were characterized by different techniques, including XRD and SEM. Some of the results from the work may be useful for preventing slag disintegration and, thus, enhancing utilization of the EAF slag as construction material, thereby saving valuable natural resources.IntroductionAt steel plants of some MiMeR member companies, steel grades with low carbon contents were produced in Electric Arc Furnaces (EAF). EAF slag was tapped out of the furnace to slag pots for transport to slag yards, where the slag was poured on the ground. Very often, the EAF slag disintegrated during cooling on the ground. Fines from the slag disintegration were often difficult to handle and use as material for road construction [1, 2]. The EAF slag disintegration was rather similar to the disintegration occurring in the slag tapped from some AOD (Argon Oxygen Decarburization) converter heats.Literature studies show that formation of dicalcium silicate (C2S) is the main reason for the disintegration or dusting of AOD slag from production of stainless steel [1-4]. The C2S can form while the content ratio of CaO to SiO2 of the slag, CaO/SiO2, exceeds 1.4 [1]. Values of CaO/SiO2 for the AOD slag are often near to 2.0, making the C2S a predominant slag component. The ß phase of C2S, ß-C2S, transforms into its low temperature ? form in the temperature range of 400-500°C, inducing a volume expansion of nearly 12% [1-4]. The volume expansion disintegrates the AOD slag."

Jan 1, 2008

By F. Mucciardi

With the increasing trend to continuous smelting and converting, granulation of copper matte is gaining prominence as a means of decoupling the smelting and converting operations. Moreover, granulation is also being seen as a possible avenue to using higher grade oxygen in converters. By feeding cold solid matte, the oxygen concentration can be increased to compensate for the lower enthalpy feed. This leads to a higher grade of SO2 in the off gas and a lower total flow rate. Current granulation technology relies on the cooling of a falling matte film by water jets. This technology while effective has several drawbacks including those related to safety. Noranda and McGill University have developed a new process (patent pending) for solidifying copper matte (or slag). It overcomes many of the negatives of current technology. The system is based on an air cooled twin roll caster. This: new system uses no water and instead incorporates heat pipe technology to transfer the heat from the solidifying matte to the cooling air to produce a thin strip of 1 to 2 mm in thickness. Testing of a prototype unit demonstrated its viability. This paper describes this newly developed, twin roll casting system that is completely waterless. The advantages of this process as well as the findings from several tests are also detailed.

Jan 1, 1999

By T. A. Chepushtanova, B. Mishra, E. O. Kilibayev, V. A. Luganov

"The paper contains the results of studying about modification of pyrite and arsenopyrite specific surface and porosity at their thermal decomposition. The studying of specific surface was carry out by B.E.T. – adsorption of nitrogen at his boiling-point. In our work were using the electron-microscopical, X-ray structure analysis and chemical analysis. There was established that the decomposition of pyrite and arsenopyrite accompany by increasing of pores volume from 0.303 · 10-3 to 1.23 · 10-3 at increasing of pyrite degree of decomposition about 41 % and then decrease about 0.131 · 10-3 m3/g at degree of decomposition near 100 %. The surface area of pores increase from 0.31 to 1.085 m2/g with following lowering due to enlargement and confluence of minor, small pores. Increasing of porosity accompany with increasing of particles windage that appear the result of heightened dust-furnace partially decomposing pyrite and arsenopyrite particles by air flow from furnace reaction zone. This explains heightened contention of sulfide sulfur in roast dust of sulfide concentrate. 1. INTRODUCTION As a result of ore base exhaustion of ferrous and nonferrous metallurgy at metallurgical treatment are involving more complicated and less qualitative ores. Magnetiting ores content considerable quantity of pyrite complicative the technology of iron extraction. At the same time the pyrite concentrates wining at dressing content different nonferrous metals in industrial quantities. Extracting ores of nonferrous metals are contenting considerable quantity of arsenic at the present time. Extraction of base metals from complicated raw materials demands new technologies. Arsenic contenting in ores is necessary to utilize (waste burial) in more ecological compatible form. Arsenic on acting metallurgical and chemical enterprises from technological cycle is withdrawing in the form of arsenate – arsenite cakes, burial of their may lead to seriously ecological problems as times goes by. In Kazakh National Technical University is carry out the cycle of researching by pyrite, arsenopyrite and arsenate – arsenite cakes treatment with the object of arsenic withdrawal in sulfide form – in more ecological and safe form and with the object of preparation of initial ore raw materials to following pyro- and hydrometallurgical treatment. As a result of sulfidizing of arsenate – arsenite cakes by pyrite are forming the volatile arsenic forms and pyrrhotite of variable structure."

Jan 1, 2008

By Felipe P. D. Lopes, Jr. dos Santos, Sergio N. Monteiro, Frederico M. Margem

"Continuous and aligned fiber composites provide the highest possible reinforcement for a polymeric matrix. In particular, the impact resistance is significantly increased in comparison with a low energy absorbed brittle polymer. For this reason, investigations have been carried out with both synthetic and natural fibers as a way to improve the toughness of polymeric composites. Among the natural fibers, ramie was not yet been studied for its reinforcement effect to make tougher polyester composites. Thus, the present work assesses the impact toughness of polyester composites incorporated with different amounts of ramie waste fibers.IntroductionIn most engineering and other technological areas, the use of materials associated with low energy processing conditions is gaining attention for the possible environmental benefits. This offered an incentive towards the substitution of natural renewable and biodegradable materials for the traditional energy intensive synthetic materials [1]. Natural fibers from both origins: animal, such as silk and wool, and vegetable, such as cotton and jute, are typical examples of those environmentally friendly materials. Low cost and highly reduced processing machinery wear are important advantages of the natural fibers over the most common synthetic ones such as glass fiber and nylon. For these reasons, polymeric composites reinforced with natural lignocellulosic fibers have nowadays been the subject of investigation [2,3].The mechanical strength is one important property of lignocellulosic composites to access the possibility of uses like structural materials for building parts such as doors and panels, as well as furniture. In this case, mechanically strong fibers like sisal, jute, curaua and ramie [4-7] are most convenient. Moreover, the relatively low fiber/matrix interfacial shear stress in these composites is associated with higher impact energy. In fact, a greater energy has to be expended for the rupture of a weak interface. The many cracks that are formed by impact tend to branch during the fiber pullout from the matrix [8]. A larger number of cracks correspond to a greater fracture surface and consequently higher toughness."

Jan 1, 2008

By Cristián Araya L.

A dynamic agglomeration, heap leaching, solvent extraction and electrowinning software, called NICO, has been developed in order to either design or simulate copper ore recovery plants. NICO contains a library of routines, each representing a unit operation or piece of equipment, which are assembled like a meccano to match almost any wet plant configuration. Routines include agglomeration or curing either in drums or belts, belt conveyors, heap stacking and reclaiming, heap leaching of oxide, sulfide or mixed copper ores, heap irrigation, drainage, ponds, mixer-settlers, filters, columns, coalescers, tanks, electrowinning cells, pumps, and all connections and related piping. All models are semi- phenomenological, i.e., they include all physical-chemical, mass, thermal, transport equations, which are required to represent as closely as possible the equipment or unit operation. However, operating experience has been incorporated into the model in order to make it simpler, faster and reliable. This experience has been tested in several plants in Chile since 1992. Site meteorological data is simulated also; in this way the model is responsive to weather conditions (temperature, solar radiation, ambient humidity, atmospheric pressure, wind velocity, etc). NICO has been used recently for design and optimization studies in copper plants in Chile like Radomiro Tomic, Collahuasi and Zaldivar. A user-friendly interface allows fast and comprehensive simulations. The entire plant is shown in a single graphic screen, so the user can see all the relevant information, and soft-keys are provided in order to change parameters on-line and watch their effect in final copper production in cathodes. Model also calculates and reports operating parameters, as well as estimated investments and operating costs.

Jan 1, 1999

By A. Warczok

The oxidation and smelting of chalcopyrite, bomite, chalcozine and pyrite has been studied under simulated flash smelting conditions. The results of copper sulphide oxidation show that under constant oxidation conditions, the degree of oxidation drops sharply when the particle size is increased above a given range. This critical size range varies typically between 200 and 500 pm depending on the oxygen content in the gas phase. For bomite, chalcopyrite and pyrite, the critical size range increases with increasing iron content in the mineral and with increasing oxygen content in the gas phase. The extreme case is observed for pyrite in pure oxygen, where there is no effect of the particle size on the degree of oxidization. Microscopical observations of the oxidized products show the influence of different factors on the mechanism of oxidation and fragmentation of the sulphide particles. Based on microscopical analysis and phase identification of the oxidized products, a model has been proposed for the oxidation and smelting of copper sulphide particles in suspended state. The mathematical model describing the sulphide particle oxidation is supported by the obtained results. Using this model, it is possible to describe the role of particular factors in the sulphide minerals oxidation.

Jan 1, 1992

By Jie Ma, Shun-Li Zhao, Jian Zhao, Jie-Yu Zhang

"Microstructural morphology evolution of Ni-45wt.%Mo droplets during rapid solidification process was investigated using an advanced modified 3D cellular automaton-finite element(CAFE) model by CALCOSOFT software. The model was modified by User-defined functions (UDFs) and validated with experimental solidification microstructural morphology of Ni-45wt.%Mo droplets available in the literature. Then, the influences of convection heat transfer coefficient, superheat of the alloy droplets and droplets size were investigated during the rapid solidification process. The predictions show that microstructural morphology is obviously sensitive to convection heat transfer coefficient and droplet size. With the decrease of convection heat transfer coefficient, the grain density decreases. In addition, the decrease of the droplet size could obtain refined microstructure. However, decrease the superheat ofNi-45wt.%Mo droplets has little effect on microstructural morphology.IntroductionFor several decades, much attention has been paid to undercooled alloy droplets of rapid solidification process for which can obtain refined microstructure, decreased microsegregation and extended solubility of alloying elements [1-3]. Extensive prior work shows that solidification of droplets plays an essential role in advanced material properties [ 4]. Consequently, it is very important to investigate the microstructural morphology evolution, especially for dendrite growth during non-equilibrium solidification process, for dendrite growth reflected the kinetics of the crystal growth process."

Jan 1, 2013

By Wayne Bell, Shivanand A. Borkar, Anish Upadhyaya, Matthew D. Andriese, Jiann-Yang Hwang, Zhiwei Peng

"A refractory ore body located in Michigan’s Upper Peninsula contains high concentrations of nickel and copper chiefly occurring in the minerals pyrrhotite, chalcopyrite, and pentlandite. Refractory ore bodies are difficult to treat by conventional mineral processing methods so microwave pre-treatment of the ore is employed to increase metallic-particle/host rock liberation by making use the differential thermal expansion properties of the mineral phases that absorb microwave energy. The Curie temperature measurement of metallic-bearing particles is in agreement with the known value for pyrrhotite occurring at 325°C. A nickel-rich iron sulfide mineral is found to be in occurrence and also appears to be magnetic under BSE imaging. It is shown the ore particles heat rapidly when exposed to microwave radiation for short durations of time mainly due to the high concentration of ferromagnetic mineral phases. Rapid heating causes thermal expansion of constituent mineral phases that produce cracks within ore particles. SEM imaging shows fracture occurring along grain boundaries and throughout host rock matrix. Ball milling experiments show an increased grindability of the ore resulting in a decrease in work index values.IntroductionCrushing and grinding operations consume 50-70% amount of energy used in mineral processing operations [1]. All these processes involve high energy impact of surfaces to develop compressive stresses that produce cracks to initiate breakage of particles. Microwave pre-treatment of certain types of ore might provide an energy savings to these type grinding processes by taking advantage of the tensional forces produced by selectively heating microwave absorbing type mineral phases. The heating of ore particles produces cracking by thermal expansion of the constituent mineral phases. Conventional heating has been investigated and shown to positively aid in grinding processes but determined energy inefficient to be used commercially."

Jan 1, 2011

By F. J. Tavera

Recently Jameson cell technology has gained acceptance in both mineral and non-mineral applications, mainly because of the high degree of contact between the involved phases in the downcomer, fact that leads to an efficient collection performance. The key for an acceptable performance of the downcomer operation depends on the stability of the jet zone, the mixing zone, and the plug flow zone. in this work the behaviour of the downcomer of a laboratory Jameson cell is reported, as a function of gas hold-up, superficial gas velocity, superficial liquid (or slurry) velocity, and length of the operating zones. The presence of carbon is evaluated in terms of its effect on the gas hold-up and bubble surface area flux. The influence of the downcomer operating conditions on the gas-liquid disengaging cell is presented. Keywords: Jameson cell, downcomer, gas hold-up, mixing, plug flow, conductivity.

Jan 1, 2003

By Yue Tian, Shengqian Wang, Lifeng Zhang

This paper is to discuss the removal of non-metallic inclusions from molten steel using a high frequency magnetic field. In experiments, a certain amount of aluminum was added to the molten steel in a crucible to generate aluminum inclusions. A layer of aluminum clusters were observed close to the wall of the crucible after the electromagnetic (EM) field was imposed. Three dimensional EM field and fluid flow simulation were performed and showed that over 91% inclusions transported to the skin depth (2.31 mm) of the molten steel. The calculation of inclusion removal agreed well with the experimental observation. The separation mechanisms of inclusions from the molten steel by the high frequency EM field were discussed.

Jan 1, 2014

By A. Ohno

"A new near net shape casting process, OHNO Continuous Casting (OCC), has been recently developed. In this process, molten metal is fed into a heated mold maintained at a temperature above the solidification temperature of the metal being cast. Solidification begins from the central core of the casting rather than the wall of the mold. With the heated mold, the formation of crystals on the mold wall is prevented and solidification occurs out of contact with the mold surface. This produces near net shaped products with smooth, mirror-like surfaces and unidirectional grain structures free from cavities, porosity and segregation. Any crystals formed at the beginning of solidification decrease in number as solidification progresses and eventually a single crystal product is obtained. This process is applicable to any metal alloys, converting them into new materials with superior properties and quality.IntroductionAs a result of growing technical demands for more advanced and diversified materials, the OHNO Continuous Casting (OCC) technology has found many new applications in industry. Considerable interest in the process has been shown in Japan and other countries because of its distinct ability to:produce a single crystal, (1)produce a remarkably clean cast surface without a witness mark,provide extremely good ductility,and reduce casting defects and segregation.This paper provides an overview of the principle of the OCC process and describes the remarkable characteristics of the material produced by this method."

Jan 1, 1988

By Stein Tore Johansen

Some ferro-silicon furnaces have heat-recovery equipment. Here, the recovery of electric energy from the off-gases can be increased by increasing the off-gas temperature. This is easily done by reducing the amount of air which usually is mixed into the?off?gas to cool the gas mixture. If the off-gas becomes too hot problems with severe fouling or clogging of the gas channels close to the furnace is observed. The result is irregular stops to clean the off-gas channels. The paper focuses on the nature of the clogging phenomena and some of the ways to avoid clogging. A detailed experimental study was carried out at the Elkem Thamshavn Plant. Theoretical studies were performed to understand the particle deposition, turbulent multiphase fluid flow and off gas combustion in the off-gas channels. The study has resulted in reduced clogging.

Jan 1, 1992

By Go-Gi Lee, Jae-Young Jung, Myung-Duk Seo, Hyun-Na Bae, Seon-Hyo Kim

"Bubbles form at the anode during the electrowinning of magnesium and cause hydrodynamic acceleration and electrical field disturbance. A three-dimensional computational model was developed to investigate the effects of the geometry of the electrochemical chamber and the size distribution of bubbles on the fluid flow in the pilot plant. The results are validated by measurements of the surface characteristics of molten salt and the bubbles formed. Fluid flow at the surface was recorded with a high speed camera, and the distribution of bubble size is determined by inspecting the video images frame by frame. The measured size distribution of the bubbles is entered into the computer simulation of a multi-phase flow. A sloped roof is installed above the electrodes, to enhance the flow of the molten salt, thus resulting in higher current efficiency, lower energy consumption, and higher quality of magnesium metal.IntroductionTitanium's excellent properties of low density, high specific strength, high temperature strength, and exceptional resistance to corrosion are highly beneficial to diverse applications including aerospace, automotive, construction, and medical implants. Although the Kroll process[l] and Hunter process have been used for the extraction of titanium in the 20th century, their complicated engineering stages and high production cost, have led to further research into new processes such as FCC Cambridge, Armstrong and TiRO. Despite these intense research efforts, no process has yet been developed that is more economical than the Kroll process, by which most of the global commercial titanium is still being produced."

Jan 1, 2011

By Luis Hoyos-Reyes, Jesus Gonzalez-Trejo, Adriana Cervantes-Clemente, Marco Gutierrez-Villegas, Manuel Palomar-Pardave, Cesar Real-Ramirez

Recent improvements on Peirce-Smith Converters (PSC) have combined numerical and physical simulations. However, most of the physical simulations have been carried out in cold-water models with only one tuyere. Several authors have proved that 2D numerical simulations do not reproduce the hydrodynamic behavior observed in physical simulations. On the other hand, most of the 3D numerical models have used a PSC thin slice with only one tuyere, but symmetric boundary conditions on the virtual walls have been imposed in order to reproduce the behavior of the whole converter. Therefore, there is no coincidence with the rigid walls of the physical models. The aim of this work is to quantify the effect of the virtual walls boundary conditions of a PSC thin slice and to determine the minimum number of tuyeres to characterize the fluid flow behavior of the entire converter.

Jan 1, 2009

By S. N. Lekakh

Experimental work and thermodynamic simulations of cast iron refining were carried out using various additions of alkali and rare earth metals. The refining reactions for sulfur and oxygen removal were studied for melts treated with Mg, Ca, and Ce. The measured data and the results of the computer simulations were in agreement. Experimental kinetic data, together with the thermodynamic calculations, were used for optimization of the amount and sequence of the addition of nodulizers for ductile iron production.

Jan 1, 2009

By M. Rubinstein, N. C. Koon, B. N. Das, V. G. Harris

"Copper and gold - based alloys having giant magnetoresistance properties were produced by melt spinning from arc melted and cast rods. The ribbon width varied between 1 and 2 mm and the ribbon thicknesses were in the range of 30 to 50 11m. The uniform microstructure of the cast rods indicated the composition homogeneity in the starting material. The ribbons showed composition uniformity across the cross section from EDX analysis. However, the spun ribbon microstructure changed from a 'frozen in' region near the wheel side to a nanosize spherically precipitated phase towards the freely frozen surface. The evolution of the microstructure from the spun ribbon state to the annealed ones was studied by optical microscopy, SEM and TEM. The structural information of the spun and annealed specimens was obtained from X - ray, electron diffraction, electron microscopy and ferromagnetic resonance. Magnetoresistance was measured by the four point probe method.IntroductionRecently. Giant Magnetoresistance. GMR. has been observed in sputtered thin films alloys of Ag. Au and Cu with Co and Fe [1. 2. 3]. The sputtered films are produced by condensation of the alloys from the vapor phase. These Ag. Au and Cu alloys are miscible and homogeneous in the vapor and liquid phase (except Ag alloys which exhibit phase separation even in the liquid phase) but immiscible and heterogeneous in the solid phase. In our work we have produced thin ribbons of the Cu and Au alloys about 30 µm thick from the miscible state in liquid phase by rapid solidification melt spinning. The microstructural development of the ribbons was investigated in the as - spun condition and on annealing. The other properties such as magnetization. GMR and Mossbauer Spectroscopy were also investigated in the various microstructural conditions of the ribbons."

Jan 1, 1994