Search Documents

By Courtney A. Young

All cyanide species are considered toxic and can be found predominantly in industrial effluents generated by metallurgical operations. For example, cyanide's strong affinity for metals makes it favorable as an agent for metal finishing and treatment and as a lixivant for metal leaching, particularly gold. These technologies are environmentally sound but require safeguards to prevent water contamination. Various methods of cyanide remediation by separation and destruction are available, but certain methods are more effective than others depending on the cyanide species being remediated. Photolytic destruction is regarded as the one technique that is independent of the cyanide species involved. The destruction of various cyanide species by several photolytic techniques has been investigated for the past few years. A literature survey suggests heterogeneous photocatalysis with anatase (TiO,) should behave similarly to homogeneous photolysis with hydrogen peroxide (H,O,) since proposed reaction mechanisms for both processes involve hydroxyl radicals. However, experimental evidence on a suite of cyanide species suggests otherwise. A new mechanism for the photocatalytic destruction of cyanides, especially SAD species, is therefore proposed.

Jan 1, 1998

By M. Z. Mubarok

Effect of single addition of a lignin-based biopolymer additive, DP 2782, at various dosages as well as in combination with thiourea on cathode polarization during copper deposition was investigated by performing potentiodynamic and galvanostatic measurements using a potentiostat. The result of electrochemical measurements was compared with the behaviour of cathode deposition with glue and thiourea additives. Surface micro-appearance of the copper deposit after 1 h galvanostatic scan under current density of 330 A/m2 and various additive type and dosage was evaluated by scanning electron microscopy (SEM) examination. It was found that the addition of 2.5 mg/l biopolymer gave sufficiently polarizing effect of copper deposition. SEM examination of the cathode surface after galvanostatic scan revealed that the combination of the biopolymer with thiourea (2.5 and 3.5 mg/l) resulted in a compact deposit which is comparable with that resulted from the test with glue and thiourea.

By George Kachaniwsky

Until mid-1982 the Mines Gaspe copper smelter consisted of a fluid bed roaster, a reverberatory furnace, two Peirce-Smith converters of which only one was blowing at any one time, anode casting facilities, and a single contact sulphuric acid plant treating both roaster and converter gases. Reduced concentrate supplies have led to the shutdown of the roaster and, as a result, it was necessary to adapt the converter and acid plant operation to the new operating mode: green concentrate smelting with resulting lower matte grades and acid plant treatment of off-gases from only one blowing converter. Therefore, modifications were carried out to existing equipment and methods of operation and control. This paper describes the result of work done to obtain steady, maximum strength, converter off-gas flow and an efficient acid plant operation. Topics covered include: optimization of converter operation, tightness of hood and off-gas ducting, improvements in acid plant/converter communications and modifications of acid plant operation and control to cope with the fluctuations in converter gas flowrates and strengths.

Jan 1, 1983

By H. P. Wang, E. M. Perry

"Analytical solutions for investigating the solidification of casting problems with initial superheat and natural boundary conditions have been derived using an integral method. There are two moving interfaces in the solution field, one for the phase change line and the other for the superheat line. Two coupled nonlinear differential equations, representing two moving layers, were calculated by the Runge-Kutta numerical integration scheme. The solutions are in terms of six dimensionless parameters: phase change number, two Biot numbers for interfaces, diffusivity ratio, and dimensionless superheat temperature and time. Parametric studies on these parameters have been conducted to provide generic information about this phase change problem. This analytical information is extremely useful for validating numerical solutions. A simplified I-D finite element model was constructed for the purpose of comparison. The excellent agreement between the analytical and finite element solutions has proven that they are mutually validated.This validated finite element modeling tool was then used for modeling an investment casting process of a super-alloy with a simple geometry: a two-step plate. The nonlinear latent heat release, a common property of alloy materials, was approximated by several piecewise linear segments. The transient temperature response of this 2-D finite element solution, including a metal/mold gap resistance, shows excellent agreement with experimental data.This fundamental work provides a solid basis for further work on the development of a process modeling tool for the complex investment casting process.IntroductionAt present, the investment casting process is used in a variety of industries. In the aircraft engine industry, in particular, investment casting is used to produce parts ranging from turbine blades to engine frames. Because a large single casting can replace many component parts that require machining, fabrication, and assembly, this one-piece casting approach becomes a very cost-effective manufacturing process.The main constraint in using this process for mass production is the long design-to-production lead time. The standard rigging design is still an art, based on the experience of casting experts, rather than on scientific methods. Many trials are often required before making a sound final casting. In order to .reduce the number of expensive casting trials, the development of computer-aided tooling technology is needed.The fundamental physics describing this manufacturing process can be simply described. They reduce to a solid/liquid phase change problem, with two parts - first, the thermal balance of the initial superheat temperature of the molten metal and the preheat temperature of the ceramic shell through heat conduction, and second, the energy release from the mold surface to the ambient by radiation."

Jan 1, 1986

By Toshihide Ito, Jie Liu, Takashi Nishiyama

"Human society evolved from an agricultural to industrial and, subsequently, to a service society. As the resource requirements for each stage of this development differ, trends of metal and energy consumption are related to shifts in society. The increase pattern of supplemental energy is similar to that of mineral production throughout the world. Low positive and stable long-term increasing occurred before 1950, whereas they increased quickly after 1950, especially between 1950 and 1973. A substantial decline in· the growth of energy and mineral production began in 1973 and lasted until the early 1980s. Production of energy resources has recently begun to increase again at a high growth rate in the world. Observing the consumption trends of energy and key metals, it is clarified that increasing patterns can be thought in three stages.IntroductionHuman society evolved from an agricultural to industrial and, subsequently, to a service society. As the resource requirements for each stage of this development differ, trends of metal and energy consumption are related to shifts in society [1-3]. Humphreys [4] described that both the non-ferrous metal consumption and the construction material consumption showed a similar trend dropping markedly in the UK over the period 1960-1992. On the other hand, per GDP (Gross Domestic Product) consumption, that is, the intensity of use of construction materials has declined sharply over the past 30 years, more so than the intensity of metal use in the USA [5]. Nishiyama [6] observed that increase pattern of supplemental energy is similar to that of mineral production throughout the world."

Jan 1, 2000

By Yuzo Hiroshige, Masayuki Kyoi, Tomonori Saeki, Masahide Okamoto, Toru H. Okabe, Yu Miyamoto, Tomohiko Akahori, Takeshi Nemoto

We report Hitachi's approach to establish the recycling process for rare-earth metals in magnet. We have developed a process to disassemble the used electric products to collect the magnets, a process to remove the surface plating film of the magnet, and processes to separate rare-earth metals from the magnet. All processes are operated without chemical solutions in order to minimize the environmental impact due to the waste water emission. For the disassemble process, we have developed an equipment to generate continuous shock on the electric products to loosen screws. A sand blast technique is applied for the plating removal process. Rare earth metals in the magnets are extracted by immersion of the magnets in molten magnesium. The extracted rare-earth metals are separated from Mg by evaporation of Mg. The overall yield of recovery is 86.8 %. The purity of the final rare-earth metal is 98.8 %.

Jan 1, 2014

By G. G. Krishna Murthy

Several experiments were conducted to determine the rates of heat transfer coefficients of CaO-SiO2-A1203-FeO slags at temperatures in the range 1623-1823 K The experimental technique involved measuring heating rates of a solid specimen, sub¬merged in slag phase, using a temperature probe made of Pt\ 10%Rh-Pt. Effect of %FeO (3-10%), %FeS (0.1-0.68%), %P205 (0.2-3.0%), %MgO(5-6%), and %MnO (0.96-3.84%) present in the slag on overall heat transfer coefficient, U, of slags was investigated. Simple first order heat balance equation in combination with experimental plots rising temperature of solid specimen versus time were employed to determine the values of U. The values of U determined in the present investigation were present in the range of 70-260 cal/Ks.m2. The value of U increased with increasing the slag temperature. The values of U were not effected by increased amounts of sulfur in the slag phase. The increased concentrations of MgO, FeO, MnO, and P205 in the slag phase decreased the values of U. On the other hand, the increased amounts of Fe2O3 in the slag phase increased the value of U. Comparison of the results, obtained using the slag bath stirred by argon injection, with those determined without any stirring indicated that both radiative and conductive heat transfer mechanisms are important even at high temperatures.

Jan 1, 1993

By Batric Pesic

Dissolution of gold with elemental bromine was studied by using a rotating disc technique. The main parameters studied were: bromine concentration, stirring speed, pH, and temperature. Additionally, effect of copper, iron, and manganese was also examined. A special attention was paid to elucidate the role of cations, primarily Na+, during gold dissolution. It was found that gold dissolution with bromine was characterized with two pH regions. Below pH=7, gold dissolution was independent of pH, and above this value, gold dissolution decreased with pH increase. Gold dissolution rates were proportional with concentration of bromine. Two regions, diffusional and kinetic, were observed with respect to stirring speed. with respect to the role of Na+, and cations in general, they play absolutely no role during gold dissolution with bromine, unless they are in their lower oxidation state and become oxidized by bromine. In that case they have a negative effect because of bromine consumption.

Jan 1, 1991

By Xue Ping

Sm2Fe17 alloy is an important precursor for the preparation of Sm2Fe17Nx magnet, which possesses a higher Curie temperature, larger anisotropy field, better resistance to oxidation and thermal stability. In this paper, the wet chemical co-precipitation was developed for synthesis of the Sm-Fe alloy oxide precursor. Based on the principles of simultaneous equilibrium and mass balance, a series of thermodynamic equilibrium equations of Sm(III)-Fe(II)-NH3-C2O4 2--H2O system at ambient temperature were deduced theoretically and the thermodynamic diagrams of lg[M2+]T (M=Sm, Fe) versus pH at different solution compositions were drawn. Then, the experiments were done to address the various effects on the wet chemical process, including solution pH value, reactant concentration, reaction temperature and aging time, etc. It is found that by precise control of the process, the Sm-Fe alloy oxide precursor was synthesized with fine crystallization and special size &size distribution.

Jan 1, 2008

By Atsushi Shibayama

The aim of this research was to develop a copper recovery process from mine tailings (0.34%Cu) using flotation followed by high-pressure oxidative leaching (HPOL) and solvent extraction. The results of HPOL using the concentrate of mine tailings obtained by flotation under the optimal conditions of the previous study shown that an efficient copper dissolution of 94.4% was achieved in an H2O media, while the copper concentration of PLS reached to be 2.9 g/L. The solvent extraction of PLS obtained from the optimal HPOL showed that 91.3% copper was recovered in stripped solution under the determined optimum conditions, in which the copper concentration achieved to be 44.8 g/L. Finally, a proposed copper recovery process from the concentrate of mine tailings was developed by combination of HPOL and solvent extraction, while a total copper recovery of 86% was achieved.

By John Anawati

Bauxite residue is an environmentally unfriendly byproduct of alumina manufacturing, produced worldwide in large quantities. This material contains 50– 100 ppm of scandium, a critical material for the production of stronger, weldable, corrosion resistant, and heat tolerant aluminum products. Aircraft manufacturers are particularly interested in Al–Sc alloys because of its ability to form weldable alloys that could potentially reduce aircraft weight by 15–20%. Because of its abundance and low cost, bauxite residue has the potential to be used as an efficient feedstock for valorization processes to recover its scandium content, while in turn degrading this problematic waste. In this project, we developed an efficient process to recover scandium and rare earth elements from a Canadian bauxite residue with high extraction yields, using industrially scalable and economical techniques. The process employs a modified version of sulfuric acid leaching and subsequent impurity removal by selective precipitation. This article outlines the current progress and design rationale in the development and optimization of this innovative and sustainable recovery process.

By James J. Komadina, Robert R. Beebe

"Heap leaching of gold ores has enjoyed wide acceptance in the arid and semi-arid regions of the western U.S., Australia and South America. There are areas, however, where cold weather or excessive precipitation can limit the usefulness of heap leaching. Even in Nevada difficulties can be encountered which call for special operating procedures.The paper discusses the general climatological limitations and some of the techniques used to extend heap leaching into colder conditions. A case history of the Cripple Creek and Victor Gold Mining Company operation in Colorado examines 'valley-fill"" technology as an ideal cold-climate solution, where topographical conditions permit.AcknowledgementsThe authors gratefully acknowledge the management of Independence Mining Company for their permission to present this paper. The contributions of Golder Associates; Pikes Peak Mining Company Environmental Affairs Department staff, and the Colorado Department of Mines and Geology were all invaluable in successfully concluding this project.BackgroundWhen heap leaching of oxidized gold ores was introduced in the rnid-1970s it was aimed at large tonnages of low-grade material which could not, in general, be developed via conventional milling. Normally, the reasons for this were economic rather than technical: capital and operating costs for milling were simply too high. At first, grade was almost the only criterion, but deposits too small to justify milling were also potential targets for heap leaching.Renewed interest in gold was centered in the western United States and Australia, where exploration for milling-grade deposits had never really died. When heap leaching came along, it was in these areas that the first developments took place. Coincidentally, these same areas were favorable for heap leaching: climates were temperate for most of the year and competing land uses were limited. Even so, in the western United States in particular, winter temperatures were low enough to complicate operations. Precipitation was less a problem, although heavy snowfalls could periodically interfere as well."

Jan 1, 1997

By Jianxun Song, Hongmin Zhu, Qiuyu Wang, Jungang Hou, Shuqiang Jiao, Xiaobo Zhu

This work presents the results of a study on the Ti3+/Ti2+ couple redox potentials vs. Cl–/Cl2 at the temperature range (673 to 1073 K) in fused LiCl-KCl eutectic by direct potentiometric method. Initial concentrations of TiClx in solvents did not exceed 5.0 mol%. Basic thermodynamic properties of the reactions TiCl2+1/2Cl2(g)=TiCl3 were calculated using the temperature dependencies of apparent standard potentials of the couples E* Ti3+ /Ti2+.

Jan 1, 2014

By Kunio Nakahara, Kashiwagim Junichi, Takao Hayashi

"There are many problems for electronic devices and parts which were caused electrostatic damage by static electricity. It is necessary for prevention of electrostatic charge to decrease surface resistivity of material using electroconductive coating. Mitsui Mining & Smelting Co., Ltd. developed metal oxide type electroconductive pigment PASSTRAN (trade mark) Type-IV which is barium sulfate coated with SnOz(Sb) thin electroconductive layer. This paper shows about pigment characteristics and film condition of antistatic transparency paint which contained PASS TRAN.L.IntroductionRecently rapid development of electronics technology diffused electronic devices and products to Office, Factory, Laboratory and our life. But the other side, there are many problems for electronics parts which were caused electrostatic damage under static electricity. Demand of antistatic materials were become lager by this situation.There is close relationship between surface resistivity of material and static electricity. If the surface resistivity of object is enough low (under 109 Q /Sq), static electricity is dissipated quickly. So it is necessary for prevention of electrostatic charge to decrease surface resistivity of material using electroconductive coating.1) There are many type of electroconductive materials, for example, carbon black, metal powder, electroconductive polymer and so on. Especially, carbon black is used for general purpose by reason of its low cost, but it has big problem of black color. It can not get any color without black, and it caused contamination of carbon.In recent years, metal oxide electroconductive pigment (ECP) was developed and used for special purpose which demands transparent coating or easy dispersion to make ECP paint or endurance under hard environment and so on. Mitsui Mining & Smelting Co., Ltd. developed electroconductive pigment PASSTRAN Type-IV which is BaS04 coated with electro-conductive Tin oxide layer."

Jan 1, 1998

By Yang Hai-long, FAN Gang, LI Cun-xiong, WEI Chang, LI Min-ting, LI Xing-bin, DENG Zhi-gan

Hydrothermal sulfidation of pure cerussite with elemental sulfur has been reported in the present paper. The variables considered in the study were temperature, time, particle size and elemental sulfur fraction in the reacting mixture. Temperature was the most important factor at temperatures above 180 , PbS and PbSO4 were the only stable reaction products in the sulfidation of cerussite. The experimental data indicated that under the hydrothermal conditions with a particle size of -74+58 μm and sulfur fraction in reacting mixture of 15% at 200 °C for 120 min, and 92% of lead sulfidation rate was achieved.

Jan 1, 2016

By Shoji Taniguchi, Lifeng Zhang, Kaike Cai

"In the present paper, based on the two-phase (Eulerian-Eulerian) model, the 3D fluid flows in gas-stirred systems, i.e., air-stirred water vessel and argon-stirred liquid steel ladle, are simulated. In the Eulerian-Eulerian two-phase model, gas and liquid are considered to be two different continuous fields. The phases are assumed to share space in proportion to their volume fractions. The exchange between the phases is represented by source terms in conversation equations. Turbulence simulated by the k- e model is assumed to be the property of the liquid phase. The following effects of mathematical treatments and operational factors on the fluid flow are discussed, such as interphase drag force, turbulent model, the size of bubble, and gas injection mode.Some interesting results are derived. Except the interphase drag force, the interphase lift force should be taken into accounted in order to exactly simulate the fluid flow in gas-stirred systems. Suitable turbulent model and drag coefficient have effect on the mathematical simulation. Injecting small bubbles can realize a well mixing flow condition. The distance between the two gas-injection nozzles has effect on the fluid flow."

Jan 1, 2000

By Renato G. Bautista

"The development of processing methods for the preparation .of three electronic materials with rare-earth components is discussed. The resulting processing innovations are the results of a search for an economically competitive pilot scale or industrial production flowsheet without compromising the required properties of the final products. The three cases highlighted in this presentation are: 1) The preparation of high energy (Pr-Nd-Ce)FeB magnets for MRI application from a mixed-rare-earth oxide with a narrow range of composition directly prepared from the solvent extraction circuit of bastnaesite ore. 2) The kg production of the giant magnetocaloric effect Gds(SixGe1-x)4 magnetic refrigerant materials from commercial grade gadolinium metal (95 to 98 at. % pure) instead of high purity gadolinium metal (99.8 at. %); and 3). An industrial chemical synthesis flowsheet for the production of the superconductor precursor of YBa2Cu3O7.INTRODUCTIONIn the laboratory discovery stage, the synthesis of a new material is carried out using very high purity components, usually the highest purity available. As the new material is studied and characterized, the effectiveness of its desirable properties becomes better defined and understood. The evaluation of the effectiveness of the .property over the range of a given parameter and other interactions are further studied. Once it's potential application becomes clear, a practical and economical processing method need to be developed. The successful material processing flow sheet does not necessarily have to be a scale up of the laboratory procedure. At this stage, substitution of starting components and with lower purity materials is considered as the economics of the processing becomes a major issue. In addition, other approach to it's synthesis"

Jan 1, 2000

By P. K. Jimack, C. E. Goodyer, A. M. Mullis, P. C. Bollada

"We review the application of advanced numerical techniques such as adaptive mesh refmement, implicit time-stepping, multigrid solvers and massively parallel implementations as a route to obtaining solutions to the 3-dimensional phase-field problem with a domain size and interface resolution previously possible only in 2-dimensions. Using such techniques it is shown that such models are tractable even as the interface width approaches the solute capillary length.IntroductionMulti-scale modelling impinges upon many areas of science, engineering and technology where the interplay between processes occurring on disparate length and/or timescales can affect the properties of systems in a complex, and sometimes unforeseen, manner. One such is the processing of materials where interactions at the atomic scale, through the nano- and microstructural scale can have a profound affect on the macro-scale response of engineering components. Here we focus on one such problem, the crystallisation of alloy melts, to illustrate how a range of advanced numerical techniques make the modelling of such systems tractable.The modelling of solidification structures, in particular the growth of dendritic crystals, is a subject of intense and enduring interest within the scientific community, both because dendrites are a prime example of spontaneous pattern formation and they have a pervasive influence on the engineering properties of metals. For alloy systems, which form the vast majority of engineering materials, solidification involves the rejection of both solute and latent heat from the growing solid, forming a coupled diffusion problem in which both the chemical and thermal diffusion equations should be solved. The multi-scale nature of this problem arises from the disparity between the thermal and solutal diffusivities for most liquid metals, which are typically 10-5 m2 s-1 and 10-9 m2 s-1 respectively. The ratio of these two, referred to as the Lewis number (Le =Dia), is therefore typically of the order 10,000 and gives a measure of the multi-scale nature of the problem. In fact, in many cases the thermal diffusivity is so much larger than its solutal counterpart that thermal diffusion is considered instantaneous, wherein the system can be approximated as isothermal such that the multi-scale calculation does not need to be performed. This is certainly a reasonable approach in most conventional castings. However, there is a class of solidification problem in which this approach is far from satisfactory, namely Rapid Solidification (RS). The application of isothermal phase-field models in such situations are highly likely to produce spurious results or to fail totally, particularly for temperatures below To (the temperature at which the free energies of the solid and liquid phases are equal at the concentration of the bulk alloy), wherein partitionless solidification may occur."

Jan 1, 2013

By Kenichi Moriyama

The Sumitomo Toyo Copper Smelter started operation in 1971, as an epoch-making smelter at which 9996 of the charged sulfur could be captured. In the past ten years, the amount of treated copper concentrate has-been increased from 1,300 l/ day to 1;900 t/ day by the extremely effective application of the oxygen enrichment for a flash smelting furnace and converter furnace. The sulfuric acid production capacity at the acid plant has also been increased up to 1,900 t/ day corresponding to the increase of copper concentrate smelting rate without installing an additional acid plant. Furthermore the sulfur fixed ratio is kept at a high level, more than 99.996. despite the SO. strength fluctuation of the wide range of 596 to 1396 which is attributed to the combination of flash smelting furnace and, P.S. converter. These -operational results at the? acid plant were achieved by several modifications. and two examples are briefly described as follows; (1) Converter modifications in order to cope with the high SO, strength -gas (2) Introduction of the anodically protection shell and tube type acid coolers In addition. the quality of sulfuric acid has been positively increased. For example, the concentration of iron and arsenic, which were the main Impurities in ?sulfuric acid, was successfully .reduced.

Jan 1, 1995

By Naiyang Ma

"High oil concentration is one of the major barriers for recycling of mill scale of steel hot rolling mills. It is of vital importance to find cost-effective technologies of reducing oil concentration in mill scale in order to recycle the mill scale without causing detrimental effects on production and environment. This paper discusses in-process separation of mill scale from oil at steel hot rolling mills. Formation of mill scale and status of oily wastewater at hot rolling mills are reviewed in the first place. A mathematical model is then formulated to relate oil concentration in mill scale to physical properties of mill scale, chemical and physical properties of wastewater and interacting parameters between mill scale particles and wastewater. From this model, three approaches of in-process separation of mill scale from oil are derived: (1) avoiding contacts between mill scale particles and oily wastewater, and (2) maintaining low oil concentration in wastewater, and (3) collecting mill scale in upper streams of wastewater flows. In-process separation of mill scale from oil might have advantages of lower capital cost, lower operating cost and less additional environmental concerns, compared to other strategies of separating mill scale from oil.IntroductionHot rolling is an inevitable step in producing finished steel products. Figure 1 schematically shows a steel hot rolling process. Semi-finished steel products, slabs here, are reheated first, and then the reheated slabs are discharged from the furnaces and transported on hot rolling trains to descaling units for removing scale with pressurized water. After being descaled, the slabs are rolled by roughing mills. After treated with cropping and the second descaling, the slabs are finally rolled into finished products, coils here, by finishing mills."

Jan 1, 2012