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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 Walter Curlook

An improved process of hydrometallurgical treatment of laterite ores of the limonitic type for the recovery of nickel and cobalt using sulphuric acid has been developed and patented [I]. The major improvement is brought about by recycling a significant portion of the "mother liquor" emanating from the pressure leaching reaction back to the feed preparation stage thereby substituting for all or at least a major proportion of the fresh water that must be added. The amount of process effluent waters is correspondingly reduced. Concomitantly with the major savings in fresh water requirements, a degree of reduction in new sulphuric acid requirements is effected, along with a savings in limestone and lime required for subsequent neutralizations. Keywords: Acid pressure leaching; Nickel laterites

Jan 1, 2004

By F. A. Fasoyinu

The mechanical properties of yellow brass (C85800), high strength yellow brass (C86300), and high manganese brasses (C99700 and C99750) cast in permanent molds have been studied. The tensile properties as well as fracture and impact toughness of these alloys are strongly dependent on the chemical composition. Alloys and/or compositions exhibiting relatively high zinc equivalent often exhibited high ultimate tensile strength and yield strength with significant reduction in ductility (% elongation). In order to achieve optimum properties with a good balance between strength and ductility, a calculation of the zinc equivalent before alloy preparation can be useful.

Jan 1, 1999

By Katsukiyo Marukawa, Mashamichi Sano, Shigeta Hara

"Various subject of studies are discussed to develop ·innovative refining processes in the 21st century for cost reduction, production of high quality steel and environmental conservation. The future refining reactor should have abilities of highly efficient mixing and separation of different phases. It is stressed ·that applications of electromagnetic and ultrasound energies, and control of flow fields rate required to create the highly efficient mixing I separation reactor.IntroductionIn recent years, it seems that the research and development in the field of steelmaking has shifted its emphasis to the solidification I ingot-making process in which continuous casting plays the leading role. From a long-range point of view, however, the need for continual development of the refining process will probably increase but is very unlikely to decrease. In order to meet such demands, it is required that problems and issues of the present process should be clearly grasped and that there must be rapid progress in process elements, such as highly efficient mixing and separation of different phases.Applications of electromagnetic and ultrasound energies and flow field control will become important options for resolving the above-mentioned problems. By efficiently and skillfully incorporating these new technologies into high-efficiency mixing/separation reactors, the innovative refining process will be established in the early 21st century."

Jan 1, 2000

By Hani Henein

"Heat transfer between droplets/particles and a gas phase plays an important role in the transport of numerous materials processing operations. These include rapid solidification operations such as gas atomization and spray forming, as well as chemical systems such flash furnaces. Chemical reaction rates and solidification are dependent on the rate of gas-particle or gasdroplet heat transport. Using a heat transport model validated using single fluid atomization of molten droplets; the effect of process variables on heat losses from droplets was examined. In this work, the effect of type of gas, droplet size, gas temperature, gas-droplet relative velocity on the heat transport from AA606 l droplets was examined. The most critical of these process variables to heat transfer is identified and will be presented.IntroductionIn materials processing, droplets are often encountered and used in processing a wide range of liquids and slurries. The small size of the droplet enables high reaction rates or high solidification rates in many systems. In order to capitalize on these high rates of transport processes, sprays are· also developed to maximize throughput. The design of these sprays, however, does not account for the transport steps and rate limiting mechanisms at the droplet surface. Rather, spray design focuses on maximizing the break-up of a stream or slurry into small size droplets or controlling the spread of the spray. Spray systems in industrial use typically generate droplets of wide size distribution leading to a wide range of reaction times for each of the droplets. Often the generation of a spray involves a number of coupled phenomena such as stream break-up, droplet-gas transport, droplet size distribution and spray geometry. Using gas generated sprays, it is not possible to identify how individual process variables contribute and control each of these coupled phenomena. While many mathematical models have been developed of sprays and they attempt to simulate coupled droplet transport, they do not provide insight into the contributions of different mechanisms in heat transfer. This is primarily because the basic fundamental heat transport between droplet and gas cannot be isolated from other gas spray phenomena experimentally such as two-way thermal coupling [l]. Thus, experimental validation of heart transfer of large and complex industrial spray models is not carried out. Hence, the validity of spray models remains in question and the approach required to optimize spray processes cannot be clearly identified"

Jan 1, 2004

By Jimsher N. Aneli

There are many experimental works on the investigation of temperature effect on the conductivity of polymers filled by carbon materials. However frequently the establishment of current nature in the polymer heterogeneous systems becomes difficult. This fact is explained by complexity of calculation of different physical or chemical phenomena passing in materials at variation of the temperature. Among these phenomena it must be noted some morphological changes in the structure of polymers. These changes reflex on the structure of conductive system of composites. So, it has been shown, that the character of temperature dependence of thermal noises level and conductivity of some polymers filled by carbon black essentially depend on some relaxation transition in the polymeric matrix. In this paper the effect of difference transitions in polymer matrix of filled by carbon black some polymers and rubbers have been investigated in a wide temperature range. The importance of such investigation is due to possibility of application of resistive temperature sensors based on conductive polymeric composites (CPC) to measuring technology. The experiments have been carried out in the cavity with regulation of temperature in the range 110-650K. The resistance of samples was measured by four electrodes method. The samples were obtained by hot pressing of dry mixture of powdered components at chosen temperatures, pressures and cooling time in the case of plastics and by peroxide vulcanization of the elastomers in the case of the rubbers. The samples were produced on the basis of the following thermoplastics: low density polyethylene, polytetrafluoroethylene, polycarbonate and polydimethylmethylvinilsiloxane.

Jan 1, 2006

By Andreas Nolte

In 1999 HÜTTENWERKE KAYSER AG (HK) in Germany will produce more than 180,000 t/y of electrolytic refined copper. To achieve this production from materials with copper grades from two to seventy percent and diverse copper alloys, HK operates three blast furnaces, one holding furnace two Peirce Smith converters and two anode furnaces. Technical, metallurgical and economic factors for the ongoing process optimization are outlined. The fluctuating quality and quantity of raw materials renders complex this optimization. The principal variables are the quality and quantity of process consumables: coke, copper-iron, limestone, oxygen, as well as the blending of feedstock and a new organization of the operating crews. The search for new metallurgical process parameters is ongoing. HK started with an intensive research programm in November 1997. As a result it will be possible to cut processing costs by about ten per cent, to increase the blast furnace capacity by ten per cent and to lower the metallurgical losses of copper and tin in the slag by more than ten percent. The presentation concludes with information on future steps to continue the optimization process.

Jan 1, 1999

By Honglei Zhang, Yue Wang, Guotao Xu, Li Liu

The influence of rich oxygen atmosphere on the properties and structure of castables used in the hot wind pipe of blast furnaces was analyzed. Results show that the cold compressive strength of castables is affected by the change of rich oxygen volume in the wind pipe, the bulk density decreases and apparent porosity of castables increases with the addition of rich oxygen in wind pipe. With the addition of rich oxygen, the velocity of heat transfer increase and result of the steel shell become over hot out of safe limit at the thin lining in hot wind pipe.

Jan 1, 2015

By Marko Suput

Titanium is a high-strength, low-density metal nearly immune to corrosion, but limited in use by its high price. The high price is due to the cost of smelting and processing the ore. The research on titanium production using the Solid Oxide Membrane (SOM) process aims to consolidate most of the processing steps required for conventional titanium production into a single step making it an energy-efficient and cost-effective method for producing CP billet and ingot and possibly also powders used to make titanium alloys. In the SOM process experiment, a steel crucible contains MgF2-CaF2-TiO2 flux; an inert metal/carbon rod serves as the cathode; an oxygen-ion-conducting yttrium-stabilized-zirconia (YSZ) membrane in the form of a one-end-closed tube contains either a liquid metal that acts as the anode or liquid MgF2-CaF2 ionic flux that connects the YSZ membrane to an anode. During electrolysis, when the voltage between anode and cathode is higher than the reduction potential of titanium oxide, titanium ions are reduced at the cathode and the oxygen ions pass through the YSZ membrane and are oxidized at the anode. The oxygen ions are oxidized at the anode by a reducing agent, hydrogen gas or carbon, forming steam or CO(g), respectively. To date, a suitable MgF2-CaF2-TiO2 flux has been selected and the operating temperature for the SOM process has been determined. Several electrolysis experiments have been performed. As expected, lower valence deposits of titanium oxides have been witnessed at the cathode prior to depositing pure titanium. Continuing work will aim to extend the electrolysis time in order to pass enough charge to produce a significant amount (100 g) of titanium at the cathode.

Jan 1, 2006

By Xu Zhong

The theoretical limit to smelting rate and possibly the size of a smelter is dependent on the rate of heat transfer, and the chemical kinetics of both sulfur removal and minor element volatilization. The fundamental kinetics of volatilization of minor elements such as As, Sb, Bi, and Pb from matte and white metal is being investigated. It has been shown that the molecular form of trace elements in matte depends on the chemical potential of sulfur and the propensity for the minor element to form a sulfide. The impact of the variable molecular form of the minor elements on the volatilization kinetics is unknown and is under investigation in this study. The experimental technique is reviewed and preliminary results are reported in this manuscript.

Jan 1, 1995

By D. Ducharme, J. Lenz

Operation of the Kidd electrolytic zinc plant commenced in 1972 with a cellhouse capacity of 105,000 tonnes of zinc cathode. The original cellhouse layout consisted of 42 parallel rows for a total of 588 cells. As leaching capacity increased, the cellhouse was expanded to 630 cells. Zinc cathode was manually stripped from plant start-up until the development of a mobile automated stripping system in 1994. Machine development continued until a second unit was placed in production in 1996, from which point, 60 % of the cellhouse was being stripped with the automated system. The final phase of the project was implemented in 1999 with the commissioning of two more automated strippers. This paper describes the implementation of the automated stripping system and its impact on cellhouse productivity.

Jan 1, 2000

By Dirk Bergmann

During the spray forming process, a continuous molten metal stream is atomized by impinging high speed inert gas jets. In the generated spray cone, the resulting metal droplets are rapidly cooled by the huge temperature difference to the surrounding gas phase and thereby partly solidified during flight. After a certain flight and residence time inside the spray cone, the droplets impinge onto the solid substrate and form the product (deposit) by compaction. Material properties of this preform strongly depend on several process parameters and especially on the thermal and kinetic state of the deposited droplets at the point of impingement. Smaller droplets may cool very fast due to their low mass and impinge onto the product in a completely solidified state as solid metal powder particles. Larger droplets with big mass contain a higher amount of thermal energy and impact during the state of phase change or still as completely liquid. It is obvious, that a certain amount of liquid content in the droplets is needed for forming a homogeneous deposit. Therefore, the thermal history of metal droplets during flight in the spray cone is of great importance for overall process modelling and control. Modelling the effects of the impinging droplet mass on the formation and heat balance of the deposit, the thermal conditions of the droplet stream need to be temporary and spatially averaged at different locations. Averaging may be achieved in different ways, giving alternative results. A first method is averaging over the droplets total enthalpy which consists of the thermal content and the remaining latent heat of fusion within the droplets. A second method may yield the average over the heat content and the solid fraction separately. Results of these two methods depend on the application and the kind of information which one wants to achieve and show some deviations, which will be discussed in terms of consolidation and energy conservation of the deposit.

Jan 1, 1999

By Jean-François Domgin

This paper aims at presenting numerical results showing the impact of different parameters on the limitation of entrained slag from ladle to tundish during the ladle drainage. These parameters are process parameters, slag properties or external actuator acting directly on ladle slag behaviour. Numerical simulations based on the use of the CFD Fluent software illustrate the vortexing and non-vortexing phenomena appearing during the ladle drainage. This numerical tool validated by experimental data acquired on water model has been applied to industrial configurations. It shows that the slag properties (viscosity, surface tension?) or some modifications of parameters (slide gate opening, geometry of the ladle bottom?) have a positive effect on the slag entrainment and also on the decrease of the ladle heel. Finally, the modelling of the behaviour of an external actuator injecting some gas in the region of the nozzle reveals interesting possibility for reducing slag entrainment from ladle to tundish during the final steps of the drainage.

Jan 1, 2006

By Jorge Alberto Soares Tenório

Electronic components have precious metals like Au and Ag. These metals have a high performance in electric conductance. The recycling of the scrap, however is too difficult because of the presence of other metals like Fe, Al, Zn, Sn, ceramics and plastics, all together in electronic components. The aim of the present work was to define one way for physical separation to have metallic non-ferrous concentrates. It was used three kinds of scrap. I was used conventional equipment for mineral processing like hammer mill; screens, electrostatic and magnetic separation.

Jan 1, 1997

By Stephan Mulch, Christian His, Patrick M. Stephan, Thibault Champion

"When fuel costs increase dramatically, waste to energy (WTE) conversion technologies become a good alternative to produce energy. The potential energy available in domestic wastes, in developed countries, could be upwards of 4% of their total energy needs. Due to low energy recovery and low level of treated domestic wastes in many countries, the energy coming from waste is generally less than 0.5% of the country needs.Domestic waste incineration can convert heat to electricity for industry and housing and allow waste volume reduction in countries where land fills are a scarce resource.There is a request to improve existing combustion technology by increasing energy recovery with better heat transfer in the boiler and also by increasing lining durability with more resistant materials and technologies.The knowledge of corrosion phenomena and material performance allows Saint-Gobain Group to develop and propose high performance refractory lining solutions.IntroductionThe interest in alternative energy has been growing dramatically in the two last decades due to several combined factors, such as global energy demand, fuels prices evolution (e.g. crude oil, Figure 1) or environmental and geopolitics factors"

Jan 1, 2008

By S. B. . Tyrrell

This paper describes research carried out to develop and optimise a process to extract lithium from the processed waste of spent lithium ution of lithium salts can be used to produce a pure lithium hydroxide solution, From this, lithium carbonate is produced, the major precursor for other lithium chemicals and for new lithium batteries. Hence, the recycle loop can be closed. Significant variation in the composition of the battery waste has been observed. Small amounts of metals other than lithium and certain anions can present technical difficulties such as electrode dissolution and membrane fouling. Pre-treatment of the waste, together with an optimum combination of cell materials and operating parameters has been found to enhance separation and alter the energy consumption of the process.

Jan 1, 1999

By W. John Rankin

The finite and non-renewable nature of mineral resources poses unique challenges for sustainability: How can mineral and material needs of society be satisfied indefinitely? How can the benefits of exploitation of minerals best be captured for present and future generations? How can the environmental problems caused by large scale mining and processing best be ameliorated? These issues are rarely addressed, or if so only incidentally, in traditional courses in geology, mining, metallurgy and materials yet addressing them will increasingly be a major role for professionals in the minerals and materials industry and related sectors and agencies. This paper describes a framework for examining these and other sustainability issues related to meeting future material needs from non-renewable resources. The framework may be useful for educational purposes, either as the basis of a dedicated subject or by including the elements of it throughout a traditional course in relevant subjects.

Jan 1, 2014

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 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 Chao Zhang, Kexin Jiao, Yi Qian, Jianliang Zhang

Now low-grade iron ore were widely used. However, one prominent problem is that the content of trace elements is higher than that in high quality iron ore. For the requirement of the content of Mn, Cr, Ni, Cu, and Ti in hot-rolled steel sheet and strip, the upper limits of these elements in sinter will be studied in this paper. Using the activity model of aggregation of electronic phased slag composition, the distribution ratio of each element in converter is analyzed and the content of each element in hot metal is calculated. Furthermore, through the thermodynamics method, the distribution ratio of each element in BF is analyzed and the content of each element in raw material is calculated. The upper limits of Mn, Cr, Ni, Cu, and Ti in sinter can be determined by calculating, the values are as follows: Mn 0.767%; Cr 0.552%; Ni 0.055%; Cu 0.159%; Ti 0.108%.

Jan 1, 2015