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By J. W. Evans

Mathematical modeling has now become a standard technique in the development of new technology and the improvement of existing technology in the processing industries. Physical modeling has a longer history but a smaller following at present. The paper reviews some examples of the application of both types of modeling in non-ferrous metal extraction, particularly within the copper and aluminum industries. The objective is to show that well founded models can lead to results that have practical consequence in scaleup, design and operation.

Jan 1, 1993

By E. W. Lithgow

Commercial volumes of nickeliferous laterite ores overlie part of a 90 km long belt of peridotites in central Dominican Republic. Protores are serpentinized harzburgites and dunites, with lesser serpentinite. The ore mineralogy consists mostly of goethite, serpentine-group minerals, quartz and poorly crystallized, x- ray amorphous materials. Minor constituents are hematite, gibbsite, olivine and enstatite. In the Ore Dressing plant the mine feed is subjected initially to proper sizing and blending to produce a homogenized mix. Subsequent drying and upgrading, by selective crushing and screening of rock fragments through a Barmac circuit, complete preparation of the ore for pyrometallurgical processing.

Jan 1, 1993

By Satu Strömberg

A single-particle laminar-flow technique was used to study oxidation of two nickel concentrates and a granulated nickel matte (43 wt% of Ni). Experimental conditions were: reaction gas from N2 to N2 + 75 vol% O2; gas preheating temperatures ranging from 500 to 1100°C. The major nickel-bearing minerals in the two concentrates were pentlandite and violarite, respectively. Chemical analysis of the particles was used to determine the oxidation degree of the materials, and optical and scanning electron microscopy were used to detect their morphology and mineralogy. Total desulfurization of the nickel concentrates was achieved under the most oxidizing conditions, while the sulfur removal from the nickel matte was not as efficient, especially with the coarse size fraction. Pentlandite-based concentrate was found to be less reactive than the violarite-based.

Jan 1, 1995

By Xuan Cheng

The electrochemistry of sulfide mineral flotation is reviewed with particular emphasis on galvanic interaction among minerals and grinding media, and its relevance to flotation of complex sulfide ores is discussed. Surface alteration due to galvanic interactions among chalcopyrite, pyrrhotite and mild steel is analyzed in terms of voltammetric and chronoamperometric studies on individual minerals and through galvanic current measurements in 2- and 3- electrode combinations. The results are related to laboratory flotation behaviors of chalcopyrite-pyrrhotite mixtures simulating copper-nickel bearing Duluth gabbro.

Jan 1, 1993

By Gernot Schenker

With the shut-down in the mid-1970s of the last shaft furnaces in the Harz Smelter Plant the long tradition of the Primary Lead Smelter in Oker came to an end. A continuation of the concern was nevertheless possible as a result of the timely commencement with the development and construction of lead production from secondary raw materials. Then as today, the most essential secondary raw material is lead accumulator scrap with over 80 % of the raw material pallet. Already in the 1960?s a method of reclamation lead battery scrap was developed and successfully carr.ied out by Preussag. In 1983 this process was fundamentally modified, also for environmental protection reasons within the framework of a rehabilitation programme of the existing plant. Today Metaleurop's HarzMetall GmbH in Oker is equipped with a modern secondary lead smelter which includes all environmental protection installations required by law. Besides processing battery scrap, the. smelter is in a position to process a ?multitude of other lead bearing residues in an economically useful way, whose waste disposal would otherwise be impossible due to the ever-increasing environmental protection laws or only be achieved at great expense.

Jan 1, 1990

By Lin Li, Wen Shi, Hua Wang

"Specimens of the ultra-low carbon bake hardening steel were soaked for 1 min to 5 min, and then cooled by water quenching. The internal friction experiments were carried out to detect the spectra of the specimens. Results show that Snoek peaks are present in all the specimens, however, an obvious Snoek-Koster peak is found only in the 5 min-annealed specimen. Besides, tensile results indicate that the bake hardening values increase with the annealing time prolonging from 1 min to 3 min, but decrease as the annealing time prolongs further to 5 min. The solute distributions in the specimens were characterized by three dimensional atom probe. Some segregated C and V are found in the 1 min-annealed specimen, and the C and V contents decrease as annealing time prolongs to 5 min.1. IntroductionAs an excellent member of automotive body panel materials, various types of bake hardening (BH) steels have been developed since 1980s. Bake hardening property, as one of the most important mechanical properties, has been studied by many researchers [ 1-5]. As is known, BH phenomenon is generally controlled by the interaction between solute C and dislocations. The Snoek peak of internal friction (IF) is very popular in the investigation of solute C [6-9]. However, result of internal friction cannot suggest the distribution pattern of solute C as well as its influence on BH phenomenon.Three dimensional atom probe (3DAP) can diagnose solute element atoms as well as nano-sized precipitates, and it is the only instrument that currently can identify the identities of individual atoms in a material and measure their spatial coordinates with the resolution close to 0.3 nm [10]. There have been a number of studies about using 3DAP to detect solute elements as well as nanometer sized precipitates [11-19]. For example, Hono et al. [16] used 3DAP to determine the solute elements in an age-hardened Mg-Ca-Zn alloy, and they also obtained the distribution patterns of the observed elements."

Jan 1, 2011

By Susan Fredholm, Randolph Kirchain, Jeremy Gregory

"Jurisdictions across the world have struggled to create and finance systems that can effectively collect and process electronics waste (e-waste). Many different system architectures have been proposed and implemented, but it is difficult for policy-makers and system architects to compare the costs and benefits of different systems, particularly when the systems operate in different contexts. This paper presents a systematic methodology that seeks to address this challenge and uses data from several existing electronics recycling systems across the world to illustrate its implementation. The methodology characterizes three main system characteristics: architecture (e.g., financing and collection methods), context (e.g., jurisdiction population, density, and wages), and performance, both economic and materials collection. A comparison of systems in Europe and North America with different system architectures and contexts illuminates the importance of using the methodology to discern the extent to which architecture and context drive system performance.IntroductionElectronic waste (e-waste) recycling offers several environmental benefits when processing is done responsibly. The controversy around e-waste recycling systems rarely debates such benefits; rather, it focuses on the characteristics of an effective system and whether benefits outweigh costs. Historically, the costs of recycling most electronics have outweighed the value of the scrap recovered. Thus, in the absence of legislation, e-waste recycling systems have been limited to private recycling of high-value waste with minimal consumer participation. E-waste recycling systems now exist in many locations worldwide including Asia, the European Union, Canada and the United States and the amount of related legislation continues to increase. Numerous approaches have been proposed including landfill bans, extended producer responsibility (EPR) and consumer advance recovery fee (ARF) funded recycling systems."

Jan 1, 2008

By Isadora Dias Perez, Monica M. Jimenez Correa, Jorge A. Soares Tenorio, Denise Crocce Romano Espinosa

The generation of mining waste has been the subject of environmental, economic and social concern. Alternative and sustainable methods of recycling metals technologies are desired. The present work focuses on the application of the ion exchange technique for the extraction of metals contained in a lateritic nickel mining effluent. The Purolite S950 chelating resin was used in the present work because it has the ability to adsorb transition metals present in an acidic solution. The experiments were carried out in a batch varying the pH in the range of 0.5–2.0. 1 g of resin was placed in contact with 50 mL of solution and stirred for 120 min at a speed of 200 rpm and temperature at 25 °C. The results demonstrated that the affinity of the resin varied with pH. The adsorbed metals were only copper, manganese, magnesium and zinc. The most extracted metal was copper, corresponding to 37%, when the solution was conditioned at pH 2.0.

Mar 1, 2018

By Mingming Zhang, Marcelo W. Andrade

The evolution of microstructure and mineral phases in iron ore sinters have been investigated by scanning electron microscope and QEMSCAN (Quantitative Evaluation of Minerals by Scanning Electron Microscopy). It was found that MgO, basicity and Al2O3 content play an important role in the formation of mineral phases and microstructure in sinter. The low Al2O3 (<2.0 wt%), medium MgO (2.0–2.5 wt%) and high basicity (>3.0) sinter showed higher low temperature degradation index (LTD) due to the presence of silico ferrites of calcium and aluminium (SFCA), and magnetite phase, and lower pore phase as compared to low basicity iron ore sinter.

Mar 1, 2017

By Q. Cao, A. Pitts, L. Nastac

Accurate prediction of the desulfurization behavior of steel is of great importance for process control during ladle metallurgical furnace (LMF) steel refining. A CFD model capable of simulating multiphase flow with bulk and free surface turbulence phenomena and desulfurization behavior in the gas-stirred ladle has been developed. The fluid flow behavior shows that slag and metal try to entrap each other, forming a two-phase mixing zone. The resulting substantial contact area between the two phases will provide very favorable kinetic conditions for chemical reactions. For reaction kinetics model, the reactions at the metal/slag bath interface as well as the entrapped droplet surface are included. Predicted results show that the sulfur content changing with time in the ladle agrees well with the industrial-scale experimental measurements.

Mar 1, 2017

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 M. J. Adam

The U.S. Bureau of Mines has investigated the partitioning of complex minerals to simpler phases using sulfidation reactions for selective extraction of mineral values. This report describes research in which thermal processing of the complex Ti-bearing mineral ilmenite (FeTi03) resulted in partitioning of the valuable Ti metal to the simpler compound rutile (TiO2). Samples of ilmenite were blended with elemental S for thermal treatment at various temperatures under controlled atmospheres in an effort to dissociate the Fe from the ilmenite complex. Product characterization revealed that the Fe was partitioned &apos;from the ilmenite, forming a rim of pyrrhotite/pyrite (FeS/FeS2) on a rut il e core. The products were agate milled and then subjected to cursory magnetic and flotation techniques in an attempt to physically separate the partitioned phases. Partitioning results and phase concentration data are reported relative to thermal treatment variables and physical separation techniques.

Jan 1, 1991

By Wei Yu, Tiejun Chun, Jian Pan, Deqing Zhu

In this paper, improving the pelletization of Brazilian hematite by adding a boron bearing additive was carried out, and the pelletization parameters were also optimized. The mechanism of boron bearing additive was revealed in the kinetics of crystal grain growth by using LEICA microscopy and its software to measure hematite grain growth. Good qualities of green balls are manufactured with drop numbers above 5.7 times/0.5m, compressive strength higher than 13 N/pellet and thermal shock temperature over 620? under the following conditions: 1.2wt% bentonite, 0.4wt% boron bearing additive, 7wt% moisture and pelletizing in disc for 15 min. When the green balls were preheated at 1000? for 8 min and fired at 1280? for 15 min, the compressive strength of the fired pellets containing boron bearing additive is about 3096 N/pellet, which is far beyond the standard requirement for good quality pellets. Compared to the fired pellets without adding any boron bearing additives, the compressive strength of fired pellets containing boron bearing additive is increased by 1225 N/pellet. It is revealed that adding boron additive into the hematite pellets help to form more liquid phases, lower the activation energy of the hematite grain growth by 135.2 kJ/mol and increase grain growth rate by 33.6%, leading to higher strength of fired pellets due to forming more coarse and dense recrystallized hematite and energy saving by firing at lower temperatures for shorten time.

Jan 1, 2011

By Shu-cai Zhou

"To understand the solidification behavior of austenitic heat-resistant stainless steel (TP34 7) in rotary electromagnetic-field, the influence of electromagnetic stirring in mold (M-EMS) on solidification structure of TP34 7 heat resistant steel in a round billet continuous casting was investigated based on industrial experiments. The results indicate that the excellent billet solidification structure of TP34 7 heat resistant steel can be obtained with appropriate electromagnetic stirring parameters. The solidification structure of TP34 7 heat resistant steel can be remarkably refmed, central porosity and shrinkage cavity can be remarkably decreased and equiaxed grains zone widens was enlarged. The industrial trials verify that the stirring intensity of TP34 7 heat resistant austenitic stainless steel should be higher comparing with plain carbon steel. Due to a higher viscosity, rotating speed of molten stainless steel was 20-30% lower than that of molten carbon steel in the same magnetic flux density.IntroductionIn recent years, the development of ultra super critical (USC) plants is accelerated by the demands of environment protection and energy saving, and USC plants with steam temperature and pressure conditions in excess of 593°C and 24.lMPa respectively were constructed. To achieve the goal, it is important to develop new materials with excellent high temperature strength, superior resistance to oxidation and corrosion at high temperature. Besides, their cost must be low enough to meet the requirement of plants [ 1]. TP34 7H steel is promising austenitic heat-resistant steel, which is used as superheater/reheater tube material and is extensively used for high temperature components and fossil-fired power plants, and suitable to be used in USC boilers plant. This kind steel contains with about 0. 7%Nb and it keeps higher allowable stress and creep rupture strength than TP304 and TP321H [1-2]. TP347H has conventionally been produced by ingot casting followed by forging and rolling. Recently, in order to decrease the production cost, challenging trials to produce these types of alloys by a continuous casting (CC) process have been attempted. However, the solidification structure of austenitic stainless steel is one of the key issues that attract more attention. Due to the low thermal conductivity of TP347H heat resistant stainless steel (much smaller than that of plain carbon steel), pronounced defects during continuous casting of austenitic heat-resistant steel such as coarse columnar, center porosity and coarse bridging, greatly influence mechanical properties of fmished products.A widely used technique in metallurgy is the inductive drive of molten metals using rotational or traveling magnetic fields. Recently, rotary electromagnetic stirring (EMS) has been applied to reducing various defects and improving increase the solidification structure of the metals in the continuous casting of steel, Al-based alloys and Mg-based alloys [3-8]. Electromagnetic stirring of plain carbon and low alloy steel in the continuous casting bloom and slab is well established for improving the quality of cast products [9-11] and is widely used in industry. However, very few literatures on electromagnetic casting of heat resistant stainless steel have reported. In this work, an industrial plant trial was performed to clarify the effect ofM-EMS on the macroscopic quality ofTP347heat resistant steel billet, in which the regularity and mechanism of the influence of EMS on solidification casting billet were discussed."

Jan 1, 2014

By Qiang Zhong, Bin Xu, Qian Li, Yongbin Yang, Tao Jiang

Viscosity of slag determines the production efficiency, energy consumption and distribution of elements between metal and slag, which is very important for pyrometallurgy. Slag of goldantimony ore blast furnace smelting has seldom been studied. In this paper, the viscosities of gold-antimony ore smelting slags of different composition have been studied by the rotating cylinder method. The results showed that, for a slag of 38.95% SiO2, 16.17% CaO, 25.97% FeO, 10.25% Al2O3, 5.17% MgO, the viscosity can be decreased by reducing 3.24%-8.5% SiO2 or increasing 3.31%-9.56% CaO content. Complex SixOy z- from SiO2 acts as the main cause for the high viscosity in a slag of high SiO2. The increasing of CaO causes the decreasing of the amount of SixOy z- and the O2- dissociated from CaO breaks the complex SixOy z-, which can decrease the viscosity. Viscosity of different composition slag in the appropriate range temperature can be calculated from the Arrhenius equation.

Jan 1, 2015

By Giacobbe Braccio, Alessandro Blasi, Assunta Romanelli, Massimo Morgana, Corradino Sposato

The solvent extraction technique is the only industrial way used to separate and purificate yttrium from other rare earths. In order to improve this process several extractants have been tested during last years. In this work, the behavior of sec-octylphenoxy acetic acid (CA-12) in Yttrium recovery from high concentrated heavy rare earth mixture was investigated. Sodium hydroxide solution was used in order to presaponify organic phase composed by CA-12 and Tributyl phosphate (TBP) diluted in kerosene. In the investigated condition, TBP confirmed its role of phase modifier not significantly altering the extraction behavior of CA-12. The CA-12-TBP system showed a high affinity in extraction for lighter rare earths such as Sm, Eu, and Gd, leaving yttrium in aqueous phase. Using a feed concentration (P [RE]) of 1 M, organic mixture is capable to extract around the 70% of metals in a single extraction test showing this extraction sequence Y < Lu < Yb < Tm < Er < Ho < Dy < Tb < Gd < Eu < Sm. Moreover for [CA-12] = 1.79 M and [RE] = 2 M the instability of extraction system occurs.

Mar 1, 2017

By Bin Xu, Qian Li, Qiang Zou, Yongbin Yang, Long Hu, Tao Jiang, Xuefei Rao

The recovery of palladium from the chloridizing leaching solution of spent Pd/Al2O3 catalyst was studied mainly by sulfide precipitation tests and chemical composition analysis. The effects of key parameters including sodium sulfide concentration, pH, addition rate, temperature, and stirring speed on palladium precipitation efficiency are systematically investigated and optimized.

Mar 1, 2017

By Dong-Wei Li, Tao Zhang, Diao Jiang, Zhou Wang

The feasibility of simultaneous vanadium extraction and phosphorus removal from vanadium-containing hot metal was demonstrated with laboratory experimental investigation.The effect of CaO addition on the distribution behavior of vanadium, phosphorus between basic vanadium slag and semi-steel as well as the influence of basicity on the leaching behavior of vanadium, phosphorus was particularly studied. Results show that vanadium oxidation ratio slightly decreases with the increase of basicity, but phosphorus oxidation ratio rapidly increases with the increase of basicity. The leaching of roasted vanadium slag with various CaO contents indicated that the optimal slag basicity for extracting vanadium was 1.5. The maximum leaching efficiency of vanadium could reach 84.02% and the sequence of vanadium leaching efficiency by using different leaching reagents was: 160 g/L Na2CO3 > 100 g/L NaHCO3 > 400 g/L (NH4)2CO3 > 5% H2SO4.

Mar 1, 2017

By Jr. Langhans, J. S. McPartland

"The presence of zinc in cyanide solutions is generally thought to not have an adverse effect on precious metal recovery or recovery rate by heap leach processing. However, analytical interferences of zinc in solution can cause problems in accurately determining and controlling cyanide concentration in the leach solution, leading to increased cyanide consumption. Analytical methods and the chemistry of cyanide in the presence of zinc are reviewed. The effects of solution pH and zinc concentration on the free cyanide determination were evaluated in detail. Use of the standard silver nitrate titration and a modified titration method for controlling cyanide concentration during heap leaching were investigated experimentally. The practical implications of cyanide heap leaching in the presence of cyanide soluble zinc minerals are discussed.IntroductionThe presence of zinc in precious metal cyanidation circuits is not uncommon. Zinc can be introduced into cyanide leach solutions through dissolution of various zinc minerals1>, or through the use of a Merrill Crowe (zinc precipitation) circuit. Zinc minerals typically occur infrequently and in low concentration in gold ores, but are more abundant in silver ores. Merrill Crowe systems are most commonly employed for recovery of precious metals from solution for relatively high silver ores. It is desirable to control the amount of dissolved zinc in a cyanidation circuit for several reasons. Excessive zinc build-up in cyanide leach solution can, under certain circumstances, inhibit precious metal dissolution and adversely affect solution recovery systems. Additionally, high zinc concentrations can lead to excessive in-process cyanide inventories and potentially, to higher cyanide consumption"

Jan 1, 1999

By Shilai Yuan, Huimin Lu, Liyuan Zhao, Zhijiang Gao

"A purification process was developed to removal impurity element boron from metallurgical grade silicon by electromagnetic induction slag melting. Vacuum melting furnace was used to purify boron in both Al2O3-MgO-CaO-SiO2 slag system and Al2O3-CaO-SiO2 slag system. The relationship between different slag chemistry and the removal of boron in silicon were studied using Back Propagation (BP) Neural Network model. The best slag chemistry for the removal of boron was predicted by Genetic Algorithm (GA) contributed by the use of Matlab. The results show that the mass fraction of Boron in silicon is reduced from 11.7496×10-6 to 2.3259×10-6 after slag melting in 28.96%Al2O3-3.43%MgO-36.24%CaO-31.37%SiO2 slag system. The relative error obtained with GA-BP Neural Network model was below 0.35%.IntroductionSolar energy, due to its low green house gas emissions, has been paid great attention. Accordingly, the demand for solar grade silicon (SoG-Si) has been growing rapidly. The quest for developing a low-cost method of producing SoG-Si has been moving forward in the last decade. Refining of metallurgical-grade silicon (MG-Si) attracts research interest due to its low material and energy costs, and more environmentally friendly technology in comparison to the traditional Simens process. As such, impurity elements in MG-Si must be removed to low levels for the photovoltaics (PV) cell to operate at optimum efficiency. Most impurities in metallurgical-grade silicon (MG-Si), especially metal elements, can be separated by directional solidification and the zone refining plasma-arc method [1, 2]. The main focus in refining MG-Si to SoG-Si is on the impurities which are the most difficult to remove. Boron has relatively high segregation coefficients (KB=0.8, concentration of Boron in solid silicon divided by its concentration in liquid silicon) [3] and higher vapor tension (the saturated vapor pressure of boron and silicon are 6.78×10-7 Pa and 0.4 Pa, respectively). The vacuum melting and directional solidification methods hence have no effects on boron removal.Slag refining involves melting MG-Si in the presence of a flux to produce a slag phase that can take up the impurity elements. The mechanism of slag refining is considered to include two main steps: the oxidation of boron and the absorption of boron oxide by slag materials. The oxidation of boron, described by the oxygen potential (PO2), resulting from the equilibrium Si and SiO2. The absorption of boron oxide, described as the slag basicity, is interpreted as expected to facilitate their extraction to alkali and alkali-earth oxides in the slag phase. Thus, effective removal may be obtained for a certain slag composition. Researchers [4-5] examined the effect of boron removal in CaO-SiO2 based ternary systems and showed that the addition of excess CaO can decrease the activity of SiO2. Researchers [6-8] studied the boron behaviors in CaO-SiO2-Al2O3, CaO-SiO2-Na2O, Al2O3-BaO-SiO2, CaO-SiO2-Li2O and Al2O3-CaO-MgO-SiO2 slag systems by adding boron in the silicon to a degree. Li2O, Na2O, MgO and BaO are thought to be associated with B2O3."

Jan 1, 2014