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By Muammer Kaya

This paper reviews the existing and state of art knowledge for electronic waste (e-waste) recycling. Electrical/electronic equipments (EEEs) which are unwanted, broken or discarded by their original users are known as e-waste. The main purpose of this study is to provide a review of e-waste problem, give e-waste management strategies and introduce various physical e-waste recycling processes with special attention towards extraction of both metallic values and nonmetallic substances. The hazards arise from the presence of heavy metals (e.g. Hg, Cd, Pb etc.), brominated flame retardants (BFRs) and other potentially harmful substances in e-waste. Due to the presence of these substances, e-waste is generally considered as hazardous waste and may pose significant human and environmental health risks if improperly managed. This review paper describes the potential hazards and economic opportunities of e-waste. First of all, an overview of e-waste/printed circuit board (PCB) components and substances are given. Current status and future perspectives of e-waste and waste PCB recycling techniques are described. E-waste characterization, dismantling, liberation, classification and separation processes, are also covered. Manual selective dismantling after desoldering and metal-nonmetal liberation at −150 μm with two step crushing are seen to be the best techniques. After size reduction, mainly physical separation processes employing gravity, electrostatic, magnetic separators etc., which are commonly used in mineral processing, have been critically reviewed here for separation of metals and nonmetals. The recovery of pure metals from e-waste after physical separation can be performed by pyrometallurgical, hydrometallurgical or biohydro metallurgical routes, which are not covered here. Suitable PCB recycling flowsheets for industrial applications are also given. E-waste recycling will be a very important sector in the near future from economic and environmental perspectives for both developing and developed countries. Recycling technology aims to take today’s waste and turn it into conflict-free, sustainable polymetallic secondary resources (i.e. Urban Mining) for tomorrow. Recycling technology must ensure that e-waste is processed in an environmentally friendly manner, with high metal/nonmetal recovery efficiency a lowered carbon footprint. Taking into consideration our depleting natural resources, this Urban Mining approach offers quite a few benefits; it provides a substantial secondary resource, while also ensuring that the environment is kept free from harmful toxins in e-waste. This results in increased energy efficiency and lowers demand for mining of new raw materials.

Mar 1, 2017

By A. R. Laplante

Recent developments in gold metallurgy are used to illustrate how the interface between gravity recovery and hydrometallurgy has evolved in recent years. Of particular interest is the use of gravity recovery to produce high-grade concentrates that can be subjected to intensive cyanidation. It is expected that a growing proportion of gold production, possibly close to 50% in certain countries, will follow this route. Other examples of the interaction between gravity recovery and cyanidation are also provided. Implications for new and renewed research directions are discussed.

Jan 1, 2003

At its Copper Cliff Smelter, Inco Limited processes a bulk copper-nickel concentrate in two Inco oxygen flash furnaces, The furnace matte is converted to low iron matte for further processing, and the molten converter slag is recycled to the flash furnaces. The flash furnace slag is discarded. Natural gas or coke supplies a minor proportion of the process heat requirements, thus limiting the flash furnace matte grade to the target 45% CuNiCo. Coke addition to the furnace offers a potential means of establishing a reducing barrier on the surface of the molten bath. Such a practice would be conducive to producing sulfur deficient (partially metallized) matte. At the same iron content, the iron activity of sulfur deficient matte is higher than that of regular matte. A supernatant coke barrier could, therefore, be expected to lead to higher nickel and cobalt recoveries, reduction or even elimination of magnetite furnace bottom build-up and increased sulfur elimination as S02 in the flash furnace. Preliminary experiments were conducted in a miniplant flash furnace to investigate the effect on process metallurgy of the suggested modified scheme. This paper presents the experimental results and discusses key aspects of the possible operation of the Inco flash furnace with a coke barrier separating the freeboard from the molten bath.

Jan 1, 2003

By P. Kim, M. Tangstad, T. Larssen, R. Kawamoto

The reduction rates of MnO and SiO2 were investigated for various charge compositions. The empirical activation energies of MnO and SiO2 reduction from SiMn slags were calculated between 1500 and 1650 °C under CO atmospheric pressure. The amounts of metal produced at different temperatures were compared, and the Arrhenius plots were described for each slag A, slag B and synthetic slag, which shows that the raw material have significant influence on the reduction rate. The rate of Mn-produced in slag A was faster than slag B despite of the relatively lower driving force. The lower rate constant in slag B implies that other kinetic factors, such as viscosity, affects the reduction rate. The estimated activation energies of MnO were 920, 304 and 975 kJ/mol MnO for slag A, slag B and synthetic slag, respectively. The rates of Si-produced were similar and slow for all slag types. However, the different activation energies of SiO2 between industrial ores and synthetic materials implied that the trace elements can have catalytic effects toward SiO2 reduction in SiMn slags. The estimated activation energies of SiO2 reduction were around 800 kJ/mol for slag A and slag B.

Mar 1, 2017

By Jim Sarvinis, Rory Hynes, Elizabet Cruz, Kerry McKenna, Maytinee Vatanakul

"Energy efficiency improvements achieved using heat recovery processes offer benefits to both the business case and environmental impact of metallurgical facilities. Global demand drives the development of lower and lower grade ore bodies. This trend results in higher energy intensity and consequently increased waste heat. Waste heat boilers and Organic Rankine Cycle (ORC) processes are becoming cost competitive methods of utilizing this waste heat.This study analyzes heat recovery from available sources to produce power using, • High grade: waste heat boiler and steam turbine generator. This system will produce electricity, and/or process steam.• Low grade: ORC to produce electricity. The cycle is well adapted to low- moderate temperature heat sources.Processes used in metallurgical plants, such as hot exhaust streams, cooling and condensers could benefit from application of these systems.The study demonstrates:• The energy and cost saving potential of waste heat recovery technologies,• The environmental benefit.IntroductionIn recent decades, process intensification has resulted in increased productivity from unit operations such as kilns, fluidized bed reactors and smelting furnaces and decreased unit operating costs. In the coming decades, the industry’s challenge will be to continue this trend while at the same time decreasing the consumption of fossil fuels and further reducing the environmental impact of its processes.The U.S. Department of Energy reports that available waste heat sources in industry, which is approximately seven quadrillion BTU (~7,400 PJ/y), exceeds the current production of all renewable power sources combined. In Canada there are about 2,300 PJ/y of available waste heat, with the pulp and paper, metallurgy, chemical/petrochemical and oil refining industries the main players. Natural Resources Canada (NRCan)9 has estimated that about 25% of that heat could be recoverable using existing technologies, which in turn, represents a reduction of 27 Mt/y of Green House Gas (GHG) emissions, plus considerable water savings due to lower water cooling requirements and less fossil fuel consumption."

Jan 1, 2011

By Henry L. Ehrlich

This survey compares bioleaching and biobeneficiation by autotrophic bacteria with that by heterotrophic bacteria and fungi Some physiological principles are reviewed. Advantages and disadvantages of autotrophic and heterotrophic leaching are discussed. Principles of anaerobic leaching by autotrophs and heterotrophs are introduced. and the advantages? over aerobic heterotrophic leaching are discussed. Examples of useful organisms in the autotrophic and heterotrophic categories are cited.

Jan 1, 1991

By Reza Ghomashchi

Casting is the most economical route to transfer raw materials into readily usable components. The economics of casting would be more pronounced and better realized, if there are no or limited necessary post fabrication treatments. Therefore, there is an urge towards near or net-shaped casting as there are significant advantages over conventional casting including reduction of component weight, excellent surface finish, higher strength and integrity of the as-cast parts, closer tolerance, and the ability to produce pore-free parts by controlling the solidification shrinkage. The concept of near or net-shaped casting is currently employed for both semi-finished products such as strip-casting and finished shaped casting, as in case of high pressure die casting or squeeze casting. The full potential of this process yet to be explored and is expected to be realized within the next 10 years, especially in case of strip casting. The current article discusses different near or net-shaped casting routes currently employed for fabrication of high integrity finished products with main emphasis on aluminum-silicon alloys. In this regard, attempts will be made to identify the key parameters during fabrication and highlight the importance of process control and optimization in fabricating premium quality cast products. Keywords: Near Net Shape casting, Solidification, die casting, squeeze casting, rheocasting, thixocasting

Jan 1, 2003

By Arthur E. Morris

Fifty years ago when Professor Yazawa began his career, the field of process simulation and modeling was in its infancy. Since then, tremendous progress has been made in our ability to model metal production flowsheets from mine to refined metal. This progress has come about by parallel developments in basic understanding of process chemistry and in computational techniques, This paper will review the progress made in process understanding and modeling in lead, zinc, and copper metallurgy from its inception to the present, and the role of Professor Yazawa's work in furthering this progress. Specific examples will be given for the sintering of lead concentrates, slag fuming, zinc concentrate roasting, flash smelting of copper, and pyro-extraction of zinc. Factors limiting further progress will be described.

Jan 1, 2003

By Zuomei Jin

The Mineralogical form of Silver in a Ag-rich complex ore was determined. In the complex sulfide ore, acidic thiourea leaching resulted in 35% extraction of silver directly. In the same complex sulfide ore, under the effect of ultrasonic treatment, 65% of silver can be ex¬tracted. After the above ore had been roasted and acidically leached of Zn and Cu, the silver extracted from this Pb-Ag residue was 96.8%. The effets of temperature, thiourea and ferric ion concentrations and partical size were examined. The leaching rate of silver from the Pb-Ag residue was diffusion controlled. The activation energy was calculated to be 10. 49%KJ/mole. The kinetic model for the thiourea leaching of silver from Pb-Ag residue was obtained and is given by, The kinetics of silver cementation by aluminium in thiourea solutions was also investigated. The activation energy was calculated to be 65. 13KJ/mole, which is reasonable fora rate-limiting surface reaction.

Jan 1, 1995

By Mike Trovant, Stavros A. Argyropoulos

"A fixed grid numerical model for phase change problems is proposed. The model solves for heat transfer and fluid flow, via the coupled solution of the energy, continuity and momentum equations. In addition, the numerical scheme accounts for temperature varying thermophysical properties and determines the shrinkage profile resulting from phase and density change. Simulations are run to determine the effect of varying model parameters and wall cooling rates on the location and shape of the shrinkage void formation in cylindrical casts. Results are shown for both aluminum and magnesium.IntroductionThe mathematical modeling of phase change processes (be they solidification or melting problems) entails solving for many interrelated phenomena. A comprehensive numerical simulation of the casting of a metal, for example, would have to account for: (a) heat transfer in both the solid and liquid portions of the metal and in the mold, (b) the release of latent heat during phase change, (c) fluid flow behavior in the liquid portion of the metal, (d) temperature induced shrinkage caused by liquid contraction and solidification contraction, and (e) the development of thermal stresses with accompanying shrinkage in the solid portion of the cast and mold. A schematic of the relationships that exist between the coupled equations which govern solidification is shown in Figure 1."

Jan 1, 1994

By Jinxing Ji

Several fundamental aspects related to the nickel electrowinning from chloride electrolytes have been addressed in this paper. The thermodynamic study includes the activity coefficient of the hydrogen ion and the speciation diagram of NiCI2 solutions. The activity coefficient of the hydrogen ion (YH+) was calculated and estimated experimentally using a combination glass pH electrode. It was found that YH+ was greater than one in concentrated NiCl2 solutions and increased significantly with increasing NiCl2 concentration. The speciation diagram for NiCl2 solutions was plotted with YH+ and the effect of the ionic strength on the equilibrium constants being taken into account. It was discovered that the predominant nickel species in the acidic region were Ni2+ and NiCI+ in 0.937 M NiCl2 solution at 25°C. Electrodeposition tests demonstrated that higher Nit' concentration in the electrolyte improved the current efficiency of nickel electrodeposition (CENi). The additions of H3BO3, and NH4Cl increased very little the current efficiency of nickel electrodeposition at pH 1.5 and temperature 60°C. However, the addition of sulfate decreased the current efficiency of nickel electrodeposition. Nickel electrodeposition was also found to be a steady-state process since the amount of acid added to the electrolyte at a constant pH increased linearly with time during galvanostatic electrodeposition. The cathode surface pH during nickel electrodeposition was measured using a flat-bottom combination glass pH electrode and a 500-mesh gold gauze as cathode. The cathode surface pH was found always to be higher than the pH in the bulk electrolyte, and if the current density was sufficiently large, it would eventually reach a level causing precipitation of insoluble Ni(OH)2(s) on the cathode surface. Rotating disc electrode studies revealed that the rate of nickel electrodeposition was first order with respect to the activity of nickel ion and zero order with respect to the activities of chloride and hydrogen ions. The rate of hydrogen evolution was found to be first order with respect to the activity of hydrogen ion and to be zero order with respect to the activities of nickel and chloride ions. These findings indicate that nickel deposition and hydrogen evolution proceed independently.

Jan 1, 1995

By Shengli Wu, Feng Chang, Hua Lu, Jianliang Zhang

Kinetic studies of the blast furnace dust (BFD) reduction process have been carried out under non-isothermal conditions. BFD pellets were made with bentonite as the binder. A Comprehensive Thermal Analyzer (TG-DSC) was used to determine the mass loss of pellets, which were heated at three heating rates of 10, 20, 30 K/min up to 1493 K. Furthermore, the metallization rate and mineral composition of BFD pellets heated to several different temperatures were analyzed by chemical analysis and X-ray diffraction (XRD). It was found that, with its inherent carbon resources as the reducing agent, the metallization rate of BFD pellets could reach 88% at most. The reduction and weight loss process of iron oxides mainly happens above 1273 K. In addition, from application of the Coats-Redfern equation the apparent activation energy of the reduction from wustite to Fe was 443 kJ/mol and the mechanism was interface reaction R..

Mar 1, 2017

By Vinicius Alves Gomes, Jean Igor Margem, Frederico Muylaert Margem, Sergio Neves Monteiro, Marina Rangel Margem

The interface between the matrix and the reinforcing fiber plays an important role in the efficiency by which an applied load is transmitted through the composite structure. The shear stress at the fiber/matrix interface can be associated with this load transference and, consequently, affects the composite strength. In the present work, pullout tests were used to evaluate the interfacial shear stress of malva fiber in epoxy matrix composites. A small critical length was found for the malva fiber embedded in epoxy, which corresponds to a relatively weak fiber/matrix bond and lower interfacial strength.

Jan 1, 2015

By Florian Kongoli

"Lime ferrite" slag with limited silica content has proven to be a valuable choice in the modem processes of copper smelting and converting due to several advantages that this slag offers compared to classical silicate slags. Nevertheless the liquidus surface of this slag has been experimentally measured only at low oxygen potentials such as in equilibrium with iron or hear it and in air. Although most of the smelting and converting processes that use this slag occur at intermediate oxygen potentials, the liquidus surface of this slag is not known at these conditions and the effect of oxygen potential and silica has not been correctly understood. This has brought some confusion in literature as well as in the industrial practice. In this work the liquidus surface of the calcium ferrite slags has been quantified by the means of a new thermophysicochemical model and a new type of liquidus surface diagrams which are very convenient for any industrial process that uses calcium ferrite slags. These diagrams can be easily used to select the lowest liquidus temperature of calcium ferrite slags at a minimum cost and can help design several fluxing strategies in copper smelting and converting processes. The effect of the oxygen potential and silica is also quantified and important industrially related conclusions are drawn.

Jan 1, 2003

By Huimin Lu, Neale R. Neelameggham, Guangzhi Wu

In China’s Inner Mongolia Tuquan County, 1.4 billion tons of reserves of serpentine deposits were found. Because serpentine belongs to magnesium silicate, there is no good reducing agent to reduce magnesium. In the local there is also a large reserves of high-aluminum bituminous coal for thermal power, power plants each year produce a large number of high-aluminum fly ash. The aluminum-silicon alloys obtained from this high-aluminum fly ash as the raw material by carbothermal reduction method can reduce the magnesium from the serpentine. In this paper, first, the feasibility of producing aluminum-silicon alloys by carbothermal reduction of high-alumina fly ash was studied, the hypereutectic aluminum-silicon alloys were obtained; and then the investigation on aluminum-silicon alloy as a reducing agent to reduce of metal magnesium from serpentine was carried out. According to the previous investigation, the optimized technical process for the extraction of metal magnesium from serpentine was proposed.

Mar 1, 2018

By Tuomas Hirsi

The world’s first large scale modular solvent extraction plants have been delivered by Outotec. The first of these is now in operation and has proven that the VSF®X technology can deliver the excellent performance of the Outotec VSF® solvent extraction process. Modular delivery allows site work to be minimized and the manufacturing done in a controlled environment, allowing for serial production manufacturing benefits. Container based delivery was found to be a highly efficient way of utilizing the standardized transportation methods on a global scale. Site work with modular units was found to be efficient and highly predictable. In this paper, we present the first successful Outotec VSF®X deliveries and discuss the benefits of the modular delivery and design compared to the standard solvent extraction installation’s delivery. The process performance of the VSF®X is also discussed with experiences from the first industrial reference presented.

By Cesar Garban

The samples of the washings are characterized of the ore for physical, chemical and metalurgical properties for representivity. the optimum values are determined for the recuperation of gold of the washings of the gold ore from the zone El Callao, Venezuela by acidic solutions of thiourea of the following parameters: Ph , contact time, composition of the liquid mixture, ratio of solid to liquid, grade of liberation, in an apparatus designed for contacting solid powder of the mineral with liquid solution of thiourea mantained in suspension by bubles of compressed air. The experimental results showed that the velocity of lixivation in primier time of (20) minutes is rapid and practically 2/3 part of the reaction is completed. For experimental design of parameters, the optimum conditions of recuperation of gold determind in this experimental investigation are:

Jan 1, 1999

By Sylwia Zymankowska-Kumon, Rafal Danko, Józef Danko, Mariusz Holtzer

"Burning of ceramic materials is carried out at temperatures 900+ 1300°C, in dependence of the required functional properties. The Faculty of Foundry Engineering together with the Faculty of Material Engineering and Ceramics developed the technology of production of burned ceramic materials with using spent moulding and core sands. The mentioned above waste materials of the foundry industry fulfilled -in plastic masses intended for obtaining ceramic materials -the role of the addition weakening clay raw materials. The laboratory investigations were fully verified by the results of industrial tests. It should be pointed out that none negative effects were observed at the stage of mixing raw materials and preparation of plastic masses. The measurements of exhaust gases emissions performed during burning the products containing spent moulding sands as well as during the normal production did not exhibit any significant differences, which could have indicated the harmful impact on the natural environment.IntroductionSands are used by the foundry industry to make metal casting molds and are a mixture of silica sand, bentonite clay and carbonaceous additives or resins. During the casting process, the molten metal cause thermal decomposition of carbonaceous additives or resins, which results in the formation of potentially hazardous organics, that are emitted to the atmosphere and condense in the molding sand. Each year the U.S. foundry industry landfills about 10 million tones of sand because it is no longer suitable to make metal casting molds. A large high-silica sand content in spent foundry sands (SFSs) generates rational premises for their reuse in other than foundry practice fields. Efforts to divert the SFSs from landfills and encourage their beneficial use in manufactured soils, geotechnical applications, the construction industry (road construction, highway construction), the building materials industry (cement, bricks, limestone manufacture), in the filling of mining cavities or in landfill construction (roads on landfills, permanent covers) are make [1-7]."

Jan 1, 2013

By Guo Chen, Yifeng Shi, Xiaobiao Shang, Nanshang Shen, Bangqi Zhang, Jinhui Peng, Junruo Chen

"The energy is introduced directly into the volume of the honeycomb ceramic regenerator due to the complex interaction of microwaves with minerals in microwave gas heating system. A three-dimensional numerical model is developed to simulate the electromagnetic field by solving Maxwell's equations using finite-difference time-domain method. Computational result is presented for the microwave power absorption of the regenerator. Effects of the dielectric constant and the effective loss factor on the microwave power absorption in the regenerator are studied as well. Numerical results show that the heating pattern strongly depends on the dielectric property of the regenerator. The demonstration of the model of electromagnetic field distribution can be applied effectively and efficiently to optimize the fundamental parameters in the microwave heating processing.IntroductionIn recent years, microwave energy has been utilized in many fields, such as food processing, chemical engineering and mineral processing [l]. In contrast to conventional heating, where heat is transferred from a surface to the interior, microwave energy is introduced directly into the volume of minerals due to the complex interaction of the microwave with the mineral. Based on volumetric heating effects, microwave heating has several advantages such as pollution free, rapid heating technique, internal heating, high efficiency over conventional heating [ 1-4]."

Jan 1, 2013

Based on experimental and computer simulation results from our group, we report a systematic, atomic level analysis of carbon dissolution from carbonaceous materials in molten iron. Experimental results on graphite / Fe-C-S system were obtained using carbon dissolution studies, XRD and FESEM investigations and were supplemented with Monte Carlo simulations. Three basic mechanisms, namely carbon atom dissociation rate, interfacial phenomena and mass transfer in the melt were found to be responsible for the overall dissolution process. While mass transfer in the melt is governed by the concentration gradients, melt composition and temperature; impurities present in ash play a significant role in the interfacial phenomena. For less ordered forms of carbonaceous materials, carbon atom dissociation rate depends strongly on the degree of long-range order and is an important rate controlling mechanism in the overall dissolution process. A systematic comparison of dissolution rates for a variety of coal-chars, natural and synthetic graphites has been carried out in an attempt to identify rate-controlling mechanisms. The structure of the carbonaceous material appears to be an important underlying factor in the carbon dissolution process.

Jan 1, 2003