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By F. Begazo

The most common approach to increase production in copper refineries is to increase current densities. However, if these increases are not well thought out beforehand and are not properly and effectively controlled, the end results could be reduced plant performance and a deterioration in cathode quality. Both of these factors result in lower efficiencies and increased costs. At the Ilo Refinery of Southern Peru Copper Corporation, a modernization and expansion program was implemented shortly after the Refinery was purchased from Minero Peru, in 1994. This program was intended to increase production from 195,200 mtpy of cathode to 227,000 mtpy over a 3-year period. Part of this production increase would come from increasing current density. During the period from 1994 to 1997, current density at the Ilo Refinery was increased from 218 A/m2 to 230 A/m2, while plant efficiencies were maintained at consistently high levels. The current efficiencies were maintained at >97.5% and time efficiencies were maintained at >98%. During 1998, additional increases in current density were implemented while the high plant performance was maintained at the same levels. By the end of 1998, the current density was 241 A/m2, while current efficiency and time efficiency of 98% were maintained. This paper describes the control processes used at the Ilo Refinery to maintain high plant performance levels while increasing the current density. Additionally, expected plant performances from extended test programs at current densities up to 280 A/m2, for future production increases, are reviewed and discussed.

Jan 1, 1999

By Mariola Saternus

The quality of the liquid metal has the biggest influence on the quality of the final products. In the metallurgical industry, and especially in aluminium production the refining process is the important technological stage. Today the most popular are refining reactors with impellers like URO ? 200, which can generate small gas bubbles. A rotary impeller also makes the metal bath to be stirred well. There are two basic hydrodynamic parameters: the flow rate of refining gas and the mixing of refining gas (impeller rotation) that influence metal stirring and generating small gas bubbles. The paper presents the influence of the flow rate of refining gas on the hydrogen removal process from aluminium (final hydrogen concentration), taking into consideration the refining process of AlSi7Mg alloy and using URO - 200. The mathematical model of this process is also presented. The equation needed for calculation of the final hydrogen concentration as a function of the equivalent bubble diameter is shown. Basing on this equation the calculations of bubble diameter and optimal refining time are done. This paper presents the physical model (the water one) of aluminium refining process and the gas dispersion taking into account the fact that the gas flow rate is changing from 2,5 to 17,5 l/min and the impeller speed is changing from 0 to 400 rpm. Schemes of gas dispersion in liquid metal in comparison with the model data are shown and the optimal values of the gas flow rate and the impeller speed are chosen.

Jan 1, 2006

By Li Yuhai

Kinetics of non-isothermal precipitate process and crystal growth of perovskite (CaO ? Ti02) phase in CaO-TiOz-Si02-AlP3-MgO system were studied. The experimental results show that the relative volume fraction can be described by the equation given by K. Matusita et at. and the experiential expression of average crystal radius was obtained. The particle coarsening in non-isothermal process has important effects on the crystal growth of perovskite phase.

Jan 1, 2000

By Kohei Yajima

The dusts and fly ash generated from the steelmaking processes and municipal solid waste incineration processes contain metallic elements such as Fe, Zn, Pb and Cd with considerable amount of halogens. In Japan, zinc in dusts is recovered by Waelz kiln or MF process, etc. However, the presence of halogen in the dust affects the evaporation and condensation behavior of zinc and other metals, and disturbs the direct recycling of dust to steelmaking processes, because alkali or heavy metals reacted with halogen vaporize easily as halides and/or oxyhalide compounds in pyrometallurgical process. Recently, the formation mechanism of zinc oxychloride vapor was investigated and the formation of zinc oxychloride such as ZnOCl was proposed. However, considering the practical operation, the effect of water vapor on the evaporation behavior of oxychloride is not fully clarified yet. This study is focused on the investigation of evaporation behavior of ZnO with Ar- O2-HCl-H2O atmosphere.

Jan 1, 2008

By B. Yawney

A copper-nickel sulfide concentrate was leached in water at about 2000C under oxygen pressures of about 0.35 MPa. Oxidation of sulfide to sulfate was virtually complete in about 30 minutes, resulting in greater than 95% copper and 98% nickel extractions. Leaching temperature was shown to be the most important factor affecting metal extractions. Measured rates of oxygen consumption were used to develop batch kinetic data. Mini-plant continuous pressure leaching tests agreed with batch leach results. A proposed overall flowsheet is briefly examined.

Jan 1, 1976

By Alan Branham

The Mike deposit is a large, low grade, oxide, gold-copper system found at the intersection of two major faults that bound the Carlin Window, Eureka County, Nevada. Disseminated gold occurs within metamorphosed and hydrothermally altered silty limestone (Silurian-Devonian Roberts Mountains Formation), beneath 182 m (600 feet) of barren Tertiary sediments and tuffs. A supergene copper oxide blanket occurs beneath and locally overlaps the lower portion of the gold zone. Decalcification argillization, silicification, and brecciation are superimposed on earlier calcsilicate hornfels and marbles. Altered dikes and sills intrude the gold zone and are locally auriferous.

Jan 1, 1995

By Zhihe Dou, Zimu Zhang, Guozhi Lv, Yan Liu, Xiaoli Jiang

"Cyclic heat stewed slag washing water carries high content of alkali and calcium and may cause serious tube scaling and impose an adverse impact on normal production. This study proposes a solution to utilize washing water by absorbing and mineralizing CO2, potentially restraining scaling and being able to create calcium carbonate powders. Effects of water flux on water quality, utilization ratio of CO2 and yield of calcium carbonate powder have been investigated; meanwhile, features of calcium carbonate powder are also represented. On the other hand, effects of factors such as as injection flux, pressure of CO2 on utilization ratio of CO2, morphology and purity of calcium carbonate are also investigated. The results show unambiguously that after soften injection of CO2, calcium ions were removed effectively via precipitation, alleviating the scaling problem. High purity yet fine carbonate powder could be achieved.IntroductionNowadays, 0.34 tons of blast furnace slags will be produced when producing 1 ton of pig iron; ensuing that, 0.12 tons of steel slag will be generated with 1 ton steel production while 1.57 billion tons of steel output all over the world in the year of 2012. It is therefore a critical issue to realize zero discharge of steel slags to achieve sustainable development and cyclic economy of iron and steel industry. In recent years, research institute of MCC and China JINGYE engineering company developed a heat stewed steel slag self-decomposition technology GENERATION III to solve the problem of instability of steel slags and realize the zero discharge. However, the problem of circulation line scaling which may cause the clogging, even exploding, need to be solved. The principles of the technology are: directly spraying water to the high temperature steel slag when it is poured into the hot closed pot, realizing the selfdecomposition via utilizing the waste heat of steel slag. The washing water is recycled to achieve a cyclic utilization. The process is shown in Figure 1."

Jan 1, 2014

By Xi-Shan Li, Qian Li, Yong-bin Yang, Li-na Cui, Tao Jiang, Jie Ge

"With regard to control environment pollution in the roasting pretreatment of sulfur & arsenic-bearing gold concentrate, roasting of double-layered pellet was proposed. In the paper, the characteristics of double-layered pellet roasting were studied. Removal and solidification rates of sulfur and arsenic were investigated as primary factors. The result indicated that the removal and solidification rates of arsenic reached up to 95.91 % and 98.95% while the sulfur was 97.19% and 97.90% respectively on the premise of adopting slaked lime as solidified agent at temperature of 6000, the package proportion of 2.14 and roasting time of 3h. However, pyrite and arsenopyrite were transformed to hematite and magnetite and product of solidification mainly consisted of calcium sulfate, calcium arsenate and calcium sulfite within optimum roasting parameters.IntroductionUtilization of refractory gold resources has been gradually concentrated on with the depletion of the gold resources which are easy to deal with in the world [1]. Sulfur and arsenic-bearing gold ore is a typical refractory gold one, in which ultrafme gold is encapsulated in the structure of metal sulfide minerals [2,3], so it gives poor recovery through direct cyanide leaching. These refractory ores need pretreatment before the process of cyanide leaching to undermine lattice structure of pyrite and arsenopyrite containing gold [4] so that the gold could touch with cyanide solution [5]. Among various methods of pretreatment, conventional roasting method is most effective, but this process generates gases such as S02 and As203 harmful to environment. Therefore solidification roasting was proposed to solve this problem occurring in the conventional roasting at the end of last century."

Jan 1, 2013

By Bin Xu, Qian Li, Ya-xuan Wang, Yong-bin Yang, Xi Zhang, Tao Jiang

The effects of common associated sulfide minerals including pyrite, arsenopyrite, galena and sphalerite on thiosulfate leaching of gold were studied in this work. Sulfide minerals had significant effects on gold leaching because that the dissolved products of sulfide minerals precipitated on gold surface to form coating layer. The degree of sulfide minerals impact on gold dissolution decreased in the order of pyrite ≈ galena > arsenopyrite > sphalerite, while the degree of effects on thiosulfate consumption decreased in the order of pyrite > arsenopyrite > sphalerite > galena. The additive CMC (Carboxymethyl cellulose) could not only reduce thiosulfate consumption but also increase gold dissolution. The mechanism of this might be that CMC could restrict the decomposition of thiosulfate by cupric ions and the precipitates on gold surface.

Jan 1, 2015

By Chang Wei, Fan Zhang, Zhigan Deng, Minting Li, Cunxiong Li, Gang Fan, Xingbin Li

Marmatite is an important resource of zinc, which exist in forms of high iron and high indium. In order to recycle the valuable metal from these ores, the testwork of simultaneous leaching on neutral residue mixed with zinc concentrate of high iron and high indium has been conducted. The primary objectives are to leach the zinc and indium remaining in the neutral leach residue as ferrite using acid, and to reduce the ferric iron in solution to the ferrous by zinc concentrate, thereby extracting the zinc and indium in the zinc concentrate. The results indicated that in the following conditions, mass ratio of neutral residue to zinc concentrate of 1:0.25, particle size of 74-58 μm, initial sulfuric acid concentration of 150 g/L, liquid to solid ratio of 8 L/kg, temperature of 90°C, reaction time of 4h, the leaching efficiency of zinc and indium were over 95%, nearly 90% Fe was Ferrous in the leaching solution. This process effectively extracted zinc and indium and converted Fe3+ into Fe2+ in solution, and simplified the traditional process of reduction after leaching.

Jan 1, 2016

By Biao Zhou, Qian Li, Kuo-Chih Chou, Yi-Long Liang, Jie-Yu Zhang, Qun Luo

"In this work, the phase transformational behaviors and microstructural characteristics of 60Si2CrVAT spring steel were systematically investigated as a function of applied cooling rates in the range of 0.l-10°C/s. A quenching deformation dilatometer was used to austenize and quench. The dilatometric curves between length changes and temperature of samples suggest three characteristic stages could be identified as different ranges of cooling rates, which meets well with metallographic examination and the measured hardness results. As the cooling rate increases, the structure transformed from pearlite, granular bainite to finally martensite. The F + P and B zones are completely overlapping in continuous cooling transformation (CCI) curve, which indicates that this steel is difficult to become single bainite and shows good hardenability.IntroductionThe 60Si2CrVAT, a high-carbon low ally super-high strength steel developed from the ?OCT 60C2XFA and 60Si2MnA, is often used for coil spring of heavy vehicles and high-speed railway by hot deformation or cold deformation [1-3]. The addition of Si improves relaxation resistance significantly, through the refinement of tempered carbides as the result of the retardation of E -carbide conversion to cementite during tempering. Due to its deleterious effects on decarburization and toughness, the maxinJum content of Si has limited to 1.5 or 2.0% [4-5]. Additionally, V and Cr can improve sag resistance due to the precipitation of fine carbonitrides during hot rolling [6-7]. To best of our knowledge, the strengthening by precipitation of alloy carbides of Cr and V often referred to secondary hardening [8]."

Jan 1, 2013

By M. Sripathy, K. V. Sharmal

"The conventional fiber reinforced plastic does not participate in the plastic deformation or enter the large plastic deformation state during collision. On the other hand, sandwich structure allows more plastic deformation, which improves the energy absorption efficiency. The objective of this study is focused on the investigation of the crushing of sandwich structure made from sisal / coir / bamboo/ glass fabrics as reinforcement and with polyester resin to form the composites skin and with polyurethane foam as the core. Experiments were conducted, showing that the underlying crushing mechanism of sandwich structures is very different from that of solid-section thin-walled structures. When a sandwich is subjected to crushing, the core deforms in the shear mode and the face bends independently. The damage is through the width zone of crushed foam core accompanied by a residual crushing in the foam. It is shown that such damage causes a significant reduction of compressive strength. Results show that glass/polyester and bamboo/polyester skin based sandwich structures have superior compressive strength. Coir /polyester based sandwich structure come next to glass/polyester sandwich structures in this aspect which is then followed by Sisal /polyester based sandwich structures.IntroductionCellular polymeric foam sandwich structures are often employed in shock mitigating applications. The cellular polymeric foam has several favorable properties, such as, low density, relatively high strength-to weight ratio and a significant degree of crushability. This high crushability is the result of the large void ratio in such materials, which also facilitates the collapse of cell walls via bending and buckling [1]. A few feasibility studies on FRP sandwich panels show that the panels efficiently provided high mechanical performance for minimum weight [2]."

Jan 1, 2012

By Carlos A. Nogueira

Spent Ni-Cd batteries contain in the electrode materials heavy metals like Ni, Cd and Co, which must be recycled due to environmental problems. Pyrometallurgy is normally used for recycling these end-of-life products, but alternative processes by hydrometallurgy, integrating also physical operations, can be used. Hydrometallurgy seems to be useful, because metals can be efficiently recuperated in chemical forms with commercial value. The economical viability of this recycling process can be improved increasing the treatment capacity, through the application to different types of residues with similar characteristics like Ni-MH and domestic batteries, or other residues containing Ni/Co, like sludges, dusts or spent catalysts. Spent Ni-Cd batteries were first physically processed using shredding and wet sieving operations. Best results were achieved using an output of 6 mm in the shredder and 1.4-2 mm in the physical separation by wet sieving, resulting a fine fraction containing 70% of the initial electrode material and only 6% of the initial scrap. The acid leaching of the obtained material in the previous operation was studied, being the parameters like: temperature, H2SO4 concentration and the liquid/solid ratio (L/S) optimized. The values attributed to the factors which concerned the best results obtained on the leaching process were mainly influenced by Ni recovery. In opposition, Co and Cd were easily leached in a wide range of conditions. To attain an overall recovery, with minimum costs, of the three metals, the values of T~100ºC, [H2SO4]=2.3-2.7 M and L/S=8-10 L/kg were considered the most appropriate.

Jan 1, 2006

By Tanm Engin, Ali Riza Tarakcilar, Derya Dispinar

"Nowadays, the casting industry is developing parallel with the information technologies (IT). Particularly the casting simulation software is being frequently used in foundry floors for casting quality control and optimisation. In this study, the filling and solidification analysis of a rolling roll manufactured by spherical graphite cast iron were carried out by Vulcan casting simulation software. The appropriate defect relieving suggestions were presented by anticipation of defects that may form during the casting process.IntroductionThe optimisation of a casting process has long been the most focused area in manufacturing plants. Many of the work involve not only the process itself but the cost as well. When it comes to the process, it is important to be able to control the defects that may form during casting.The casting process begins with the melting of a charge; followed by pouring into the mould cavity. One of the most important factors is the difference in the liquid/solid density which may lead to porosity. On the other hand, turbulence during filling is another significant factor in casting operations [1].During solidification, due to the density difference between liquid and solid, porosity might form which leads to crack-like defects. There are several other factors that may determine the quality of a casting such as segregation, inclusions, grain size and etc. However, porosity is one of the first parameters that can be easily determine and controlled by the help of simulation software. Simulation is a cost-effective tool in the optimization of process parameters and castings can be visually observed. Time loss and economic expenses could be minimized [2]."

Jan 1, 2012

By Ibrahim Yusufoglu, Ahmet Orkun Kalpakli, Cem Kahruman, Sedat Ilhan

"The effects of oxalic acid concentration, temperature, stirring rate and particle size on the dissolution rate of synthetically prepared calcium molybdate were investigated. Dissolution of calcium molybdate in oxalic acid solutions takes place as a series - parallel type reaction. In the first reaction step, which proceeds according to the ""Langmuir - Hinshelwood Mechanism"", calcium aqua oxalato molybdate is formed as a complex chelate intermediate product. In the second reaction step, molybdic acid is formed during the slow hydrolysis of calcium aqua oxalato molybdate, and it reacts rapidly with oxalic acid to form the polymeric hydrogen oxalate dimolybdate chelate as an end product. Activation energies were calculated as 41.4 and 49.9 kJ mol-1 for the first and zero order reactions. The fractional conversion versus time relationship can be given by the following equation.IntroductionMolybdenum is used widely in electric-electronic, metal working, aerospace and aeronautic, nuclear, glass and petrochemical industries because of its high melting temperature and resistance against chemical effects. However, the largest molybdenum consumers are the iron-steel and super alloy industries where molybdenum is used as an alloying element. Industrially important molybdenum minerals are limited to molybdenite (M0S2), powellite (CaMo04) and wulfenite (PbMo04), which are considered as primary molybdenum resources. Secondary molybdenum resources are spent catalysts and scrap [1-4].Molybdenum has been produced by pyrometallurgical processes in the past. Since it is possible to process low grade molybdenum ores and industrial wastes by hydrometallurgical processes, which are more environmentally friendly than pyrometallurgical processes, the importance of the use of hydrometallurgical processes has increased in the molybdenum production industry."

Jan 1, 2012

By V. A. Luganov

During the treatment of raw materials containing arsenic and antimony, problems in the distribution of these elements in the process products occur. In a number of cases in processing of copper-bearing materials, it is possible (or necessary) to obtain speiss. The purpose of the present research is to study the theoretical aspects and analyze the technological possibilities of producing copper-bearing speiss and the subsequent electrometallurgical processing with copper extraction as well as arsenic and antimony utilization. Copper arsenide (Cu3As) and copper antimonide (Cu3Sb) are the main components of the speiss. A thermodynamic analysis of the electrochemical oxidation of Cu3As and Cu3Sb, carried out using Pourbaix diagrams, showed that in a pH range from 0 to 2, oxidation potential 0.45-0.55V, ions of copper and arsenic and antimony trioxide are in the equilibrium. The kinetic study has shown, that with an increase in the polarization potential, the dissolution process changes from chemical to diffbsion control. An increase in temperature stabilizes the electrolysis process due to dissolution of arsenic trioxide forming on the anode. Electrolysis of speiss using a cathode diaphragm with the solution pH = 1-2, current density 150-200 A/m2 and temperature 60-70°C makes it possible to obtain cathode copper with a current efficiency of 95-96% and to remove the arsenic from the process during the electrolyte cleaning process. The arsenic content in the cathode copper did not surpass 0.002%. As the result of the research, a technological flowsheet for copper-lead speiss processing was developed. At the present time this technology is undergoing pilot testing.

Jan 1, 1999

By Elsa Agante

Recycling of solid wastes, a common practice nowadays, requires the separation of the different materials in order to increase the products added value. The separation of one plastic from mixtures of different types of plastics is not easy due to their similar physical properties, but different techniques are available, from automatic sorting systems based on optical sensors to techniques adapted from mineral processing, namely gravity, froth flotation and electrostatic processes. In the last decade, many researchers have addressed the separation?s problem of different polymers, like Polyethylene Terephthalate (PET) and Polyvinyl Chloride (PVC), two polymers commonly used in packaging which have similar density. One proposed technique is the classical froth flotation performed in agitated cells. Froth flotation is a versatile and relatively cheap process widely used in mineral separation. It is based on the different behaviour of particles in the presence of an inter-phase air-water, which depends on the materials surfaces properties. Froth flotation can be affected by some variables such as impeller speed and air flow rate. Agitated cells, when used with low density materials, like plastics, can produce overstated turbulence that prevents the adhesion and collection of particles in the froths. In this case, separation is favoured by column flotation smoother hydrodynamics. This paper proposes the separation of PET from PVC by column flotation. The experimental work was carried out in a column of 9cm diameter and 1m high. The effects of some operating conditions, such as depressor and frother concentration, air flow rate and feed grain size on products grade and recovery were evaluated and the best flotation conditions for the separation of these plastics were established.

Jan 1, 2006

By T. A. Edison

A distinct hydrocarbon maturation anomaly coincides with the Gold Acres open pit, Nevada (Figure 1). Both atomic hydrogen to carbon (H-C) ratios and reflectance measurements of contained organic matter indicate significantly higher maturity in samples collected within the confines of the open pit than in samples from the surrounding region (not shown in Figure 1).

Jan 1, 1987

By Sung Jin Han

Magnesia-based refractory is generally used in an electric arc furnace (EAF) due to its relatively high corrosion resistance and strength at high temperatures. However, the magnesia refractory is attacked by EAF slag and thus the lining life continuously decreases. Thus, it is significant to identify the interfacial reaction between magnesia refractory and FeO-rich EAF slags. In the present study, the influence of FeO-rich slag on the corrosion behavior of MgO refractory was evaluated. The (Fe,Mg)Oss layer was observed at the slag-refractory interface and its thickness increased with increasing content of FeO in the slag. The specific reaction phenomena and formation behavior of (Fe,Mg)Oss layer were evaluated by thermochemical computing program, FactsageTM7.0.

By Xiangru Chen, Qijie Zhai, Haicheng Li, Chao Yang, Zhang Wei

The Nb-rich phase generated by the addition of trace amounts of Nb(<0.1wt%) \ and the effects of different content of Nb on the morphology and distribution of graphite in ductile iron were studied in this paper. The results showed that when the content of niobium less than 0.1wt%, the two-dimensional morphology of Nb-rich phase existed in microalloyed ductile iron were mainly regular pattern such as square, triangle, polygon etc. Besides, Nb-rich phase in large size distributed in the matrix with a certain distance from graphite. With the increasing amount of niobium, the dispersion degree of graphite diameter, average diameter and roundness increased slightly, and the number of graphite decreased slightly.

Jan 1, 2015