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By Yuzuru Sato

Viscosity has been measured for various molten binary alloys of nickel with iron, cobalt and chromium in order to clarify the behavior of viscous flow of molten nickel alloys. The entire concentration range for iron and cobalt and 0-67at% of chromium content were studied. The measurement method was an oscillating cup viscometry using an alumina crucible that was precisely machined. The temperature was up to about 1880K for all the measurements. The results represented good Arrhenian relationship although some measurements included overcooled temperatures. The isothermal viscosities increased monotonously with an addition of iron and chromium into nickel. The addition of cobalt increased after stationariness. The isothermal viscosities showed concave curves. Activation energies increased monotonously by adding all the elements into nickel. These phenomena were considered to be related to the thermodynamic properties such as the heat of mixing and the structures of mixture melts.

Jan 1, 2003

By David G. Dixon

Although the kinetics of leaching processes are of paramount importance in the design and analysis of nearly all hydrometallurgical flowsheets, these concepts remain poorly understood and, as a result, are only rarely applied to mass and heat balance models. In this second of two papers, we demonstrate how simple yet powerful models of leaching kinetics and other rate processes may be added to mass and heat balance models, and apply these concepts using a spreadsheet model of a simplified pyrite autoclaving flowsheet. In particular, we focus on the interpretation and scale-up of batch leaching data, and on simple means for modeling other phenomena commonly associated with leaching, such as reagent depletion, gas-liquid mixing, and the precipitation of oxides and basic salts.

Jan 1, 2002

By P. Tim Johnson

Relentless increases in demand for nickel and vanadium for uses such as steelmaking, catalysts and battery materials, plus the growing financial and environmental costs of their primary extraction, have led to much interest in potential secondary sources of these metals. The presence of such metals in heavy fuel oils, bitumen and related materials offers both opportunities and challenges for potential extraction methods, especially with the growing production and importance of metal-rich fossil fuels around the world. For several decades, Tetronics’ DC plasma smelting technology has been used for the recovery of metals such as nickel and chromium from stainless steel melt dusts and other wastes in compact, environmentally-friendly and efficient plants. This paper explores the suitability of DC plasma smelting as part of a wider flowsheet with feed preparation and aluminothermic reduction techniques for smaller-scale extraction operations based on this important niche secondary source of these key metals.

By B. J. Vorster

AngloGold South Africa region currently consists of 12 Gold Plants. These plants use a combined total of $20 million of cyanide per annum. Of this, the .major portion (60%) is consumed at two Ergo dump retreatment plants. Historically the primary motivation for cyanide control at Ergo has been one of leachlcost optimisation. However, more recently, with the increased public awareness of cyanide in the environment, a secondary but increasingly important motivation for control has been to ensure that only the minimum amount of cyanide is added to the process whilst not compromising leach performance. Following a brief overview of the Ergo process, the methodology in detennining the amount of cyanide to be added is described. The paper then traces the developments in cyanide control from very basic? manual systems to the current automated control system. In line with the increasingly sophisticated control systems, developments also took place in regards to the method of cyanide analysis. The development of these analysers is also discussed. Whilst cyanide is one of the major drivers, if not the major driver of gold dissolution, it cannot be viewed in. isolation particularly with respect to the relationship between cyanide and oxygen as ascertained from the Elsner's well known equation. Consequently, in order to control cyanide addition, knowledge of the relative cyanide/oxygen profiles is necessary. Various means investigated at Ergo for pulp oxygenation have therefore been included for the sake of completeness. Finally a comparison is made of the control achieved from the current system compared to the? original manual system. The knowledge and experience gained at Ergo is now being used to draw up guidelines for the installation and optimisation work at the other AngloGold plants. The net effect of this will be reduced cyanide consumption for the region, which also, apart from the obvious economic benefit, translates into a reduced environmental; risk.

Jan 1, 1998

By T. Shibasaki, S. Kamio, K. Kanamori

"Mitsubishi Process has been proven through fifteen years operation to be highly productive, cost efficient and easy to abate environmental requirements. However, in order the process to remain competitive from now on, it should also be adaptable to a variety of varying conditions. Various test works have been conducted from such a stand point of view and some of the new concepts have been implemented to the actual operation.The paper discusses the adaptability of the process to the change of concentrate grade with respect to copper and also impurities, acceptability of the secondary materials and the potential to increase unit capacity. IntroductionThe first commercial plant of Mitsubishi Process with 48,000 mt copper annual capacity started its operation at Naoshima Smelter of Mitsubishi Metal Corporation in 1974, and the second plant with 65,000 st annual capacity started in 1981, at Kidd Smelter, Timmins, Ontario, now Kidd Creek Division of Falconbridge Limited 2. These plants have increased their capacities to 90,000 mtpa respectively by adding oxygen and acid plant capacities while maintaining the original furnace design uncharged. Thereby both smelters have established more cost efficient operations. (3), (4)Mitsubishi Process applies so-called multi-furnace continuous system. Figure 1 shows conceptual flowsheet. Backgrounds that required and justified the development of such system are as follows:"

Jan 1, 1988

By A. Kontopoulos

The Olympias Mine in Northern Greece is producing an extremely refractory gold-bearing arsenical pyrite concentrate, containing on the average 41 3 S, 40 3 Fe, 10-12 3 As, 25 ppm Au and 35 ppm Ag. During the process selection stage, more than a dozen alternative technologies? were considered and an in-depth analysis was prepared for the three most promising, ie roasting, pressure oxidation and biological oxidation. Detailed capital and operating cost estimates were prepared, based, where appropriate, on laboratory and pilot-plant tests. A number of criteria was used for process evaluation and selection, including capital and operating costs; environmental impact, gold' recovery, stage of development, etc. Based on the above evaluation, the Sherritt Pressure Oxidation Process was finally selected. A detailed description of the process selection stage, supported with laboratory and pilot-plant test results on many of the processes considered, will be? presented.

Jan 1, 1989

By Kevin L. Gering

A detection method and apparatus have been developed to perform real-time measurement of aqueous free cyanide, C-. A laboratory prototype can measure cyanide ranging from 5 micrograms ,per liter to 100 milligrams per ?liter for analysis times as short as 2 minutes per measurement. Sample size per measurement is typically only a few mI, thus? minimizing the waste volume produced from spent samples. The basis for this detection device is a quantifiable, stable affinity between the electrode material and free cyanide in the sample; The electrode exhibits piezoelectric behavior, allowing it to be used as a microbalance. This technology 'has experienced two generations of laboratory prototypes, and has been thoroughly tested to determine the operational sensitivity toward process variables such as pH, competing reactions, etc. The speed and ,accuracy of this method make it superior to conventional wet chemistry methods used for quantifying cyanide levels in water. A device based on this technology could be useful in areas involving process monitoring and environmental compliance, .particularly in the cyanide-based leach mining industry. Interest for this detector has been shown by the gold mining industry and others. Patent application is in progress.

Jan 1, 1998

By A. H. Rhoades

The modern polarizing microscope with such accessories as cameras, infrared devices, reflectance and/or transmission photometers, indention hardness, and heating stage is used to characterize coal, coke, and other carbon forms. It allows characterization of coke by-products, such as tars and pitches and their insoluble residues. A useful product of the microscopic approach is the coal petrographic analysis which permits the prediction of coke strength carbonization pressure and volume change. Carbonization tests are expensive, time-consuming and require large amounts of coal. Tests on the coke show it to be strong or weak but give no indication of why. Petrographic analysis requires grams of coal and yields data that indicates why the coal produces coke of a given quality. Small samples from drill cores are sufficient for petrographic analysis. These data are also used to optimize blends for coke production. When coke-plant problems occur, ~he microscope can be used to check the coal blend proportions, as well as for weathered coal. Microscopy is useful in spore correlation work which may be a prerequisite to sound coal reserve estimates. Dispersed vitrinoid reflectance studies are used to determine the degree of organic metamorphism which serves to establish oil and gas deadlines. Tars and pitches are examined microscopically for the amount of normal solids as well as the size of undesirable carry-over solids resulting from pollution abatement practices in coke works. The microscope is also used to study coals for gasification and liquefaction.

Jan 1, 1981

By Kelly J. Driscoll

Impure zinc (98.5%) was electrorefined to high purity zinc (99.995%) using a fused salt electrolyte of molar composition 1: 1 : 1 :2 ZnCI2:KCl:NaCl:LiCl with a current efficiency of about 90% at 723 K. A recessed channel electrorefining cell was developed which achieved excellent mixing of both the metal and the electrolyte and by ensuring a very small anode to cathode spacing the voltage drop across the cell was 0.16 V and at a current density of 7kA m-2. The physical characteristics of the cell were observed using a low temperature model which showed the formation of droplets and rivulets which provided mixing. The application of this approach to the refining of other non-ferrous metals is discussed.

Jan 1, 1992

By Andy Judge

"In traditional Permanent Magnet Machines, such as electric motors and generators, power is transmitted by magnetic flux passing through an air gap, which has a very low magnetic permeability, limiting performance. However, reducing the air gap through traditional means carries risks in manufacturing, with tight tolerances and associated costs, and reliability, with thermal and dynamic effects requiring adequate clearance. Using a magnetically permeable, high thermal conductivity material has the potential to improve magnetic performance, while at the same time offering performance advantages in heat transfer.Ferrofluids can be used to improve permeability in the rotor I stator gap. However, there are several tradeoffs in this approach. Fluid immersion comes with an increase in fluid friction loss compared to the windage losses of a traditional system. Isolating the rotating components from the ferrofluid can offset this effect. Also, while the magnetic effect can be positive for gap permeability, leakage flux can increase, and saturation can limit gains. These effects must be taken into account for a system optimized for ferrofluid immersion.IntroductionPermanent Magnet Machines (PMM's) convert electrical energy to mechanical energy in motor applications, or, for generator applications, convert mechanical energy to electrical energy through means of passing alternately polarized magnets past electrical coils. Looking at a simplified version of a PMM, where Rx is magnetic reluctance and <l>x is magnetic flux, we have the circuit shown in Figure 1."

Jan 1, 2013

By Afonso Garcez de Azevedo, Anna Carolina Lopes Rabello, Renan Tavares Vicente, Sergio Neves Monteiro, Amanda Maia Ferreira dos Santos

Civil construction is a sector of extreme impact in the Brazilian economy, with construction and demolition waste (RCD) having an extreme impact on the amount of urban solid waste. In this research it was proposed to propose a way of using these residues in the construction of concrete artifacts for structural use. Concrete specimens with sand substitution by RCD were produced in different percentages as a way to contribute to reduce,recycle and reuse thi large amount of waste from the construction industry. The objective of this work was to study the mechanical properties of structural concrete with total and partial replacement (25, 50, 75 and 100%) in sand mass. The results of the compression test indicate good quality for concretes with mass substitution of up to 75% per RCD.

Mar 1, 2018

By W. Kasprzak

Modern light metals processing technologies are very complex and involve a diverse set of variables that must be quantitatively evaluated. The most effective way to design new casting processes that deliver specified metallurgical and mechanical properties is to develop a method of simulating the "real-time" process within a test sample of sufficient size. The results can then be analyzed and the required optimizations can be performed. This paper presents a novel method of simulating the industrial casting processes in a laboratory environment using an experimental apparatus based on the principle of high frequency induction heating. The applicability and accuracy of the proposed analytical method is demonstrated, for example, by simulation of the solidification and heat treatment of a test sample composed of two dissimilar materials. The simulation can be used to develop a stress model for an engine block made from an aluminum based alloy with iron cylinder liner inserts.

Jan 1, 2002

By P. S. Dunn, A. D. Rollett, H. D. Lewis

"The results of preliminary work on the modeling and measurement of the heat transfer coefficients of metal/mold interfaces is reported. The system investigated is the casting of uranium in graphite molds. The motivation for the work is primarily to improve the accuracy of process modeling of prototype mold designs at the Los Alamos Foundry. The evolution in design of a suitable mold for unidirectional solidification is described, illustrating the value of simulating mold designs prior to use. Experiment indicated a heat transfer coefficient of 2 kW/m /K both with and without superheat. It was possible to distinguish between solidification due to the mold and that due to radiative heat loss. This permitted an experimental estimate of the emissivity, ~ = 0.2, of the solidified metal.IntroductionA feature that distinguishes casting processes from welding processes is the presence of an interface with a low heat transfer coefficient between the mold and the casting. Especially when chill casting, the interface delays the start of solidification and increases freezing times significantly. By comparison welds can be assumed to have a very high heat transfer coefficient. The heat transfer coefficient controls such phenomena as folds and laps on the surface of castings which can be crucial to the acceptability of a casting. The time delay for the start of solidification influences the occurrence of cold shut defects. The standard mold material for uranium casting is high quality graphite which is an excellent refractory when used in vacuum and coated with a refractory wash. Graphite is an effective chill material and has a thermal diffusivity approximately twice that of uranium. Experience has shown that practicable superheat without mold pre-heat is not sufficient for avoiding cold shut defects when casting in graphite molds.TheoryIt is possible to calculate the position of the freeze front s, as a function of time, t, the superheat and interface heat transfer coefficient, h, [1]. However, the value of h cannot be obtained explicitly. The Virtual Adjunct Method (VAM) [2] offers a method for extending the standard equation for an insulating mold where s is proportional to the square root of time. By considering the effect of the interface to be equivalent to finite thicknesses of mold and metal, the following quadratic equation is obtained,"

Jan 1, 1986

By G. Coryell, E. Brack

"Remaining competitive in today's metal markets requires that copper smelters utilize the latest technology offered in process control, data acquisition, and process optimization. State-of-the-art tools like minicomputers, personal computers, and microprocessor based controllers provide real time process information that assist in making proper adjustments to the overall control strategy of an operating plant. The database accumulated by such systems broaden process knowledge, thereby reducing costly errors and plant downtime.IntroductionThe ASARCO Hayden Plant is located approximately 80 miles southeast of Phoenix, Arizona. The plant was commissioned in 1912 for the purpose of smelting copper concentrates from the surrounding mining district. Copper was produced for many years using calcining, reverberatory smelting and copper converting techniques. With the stricter environmental controls of the 1970's, the smelter experienced substantial declines in efficiency and productivity. It became necessary to identify and install a new smelting technology to maintain the viability of the Hayden plant.In 1980, after evaluating several smelting techniques, ASARCO management selected flash smelting as developed by International Nickel Company (INCO). One hundred and thirty-two million dollars was allocated for the project and construction began in 1982. Construction was completed and the new plant came on line in November of 1983."

Jan 1, 1989

By Bradford H. Miller

Separation and Recovery Systems, Inc. (SRS) provides on-site waste minimization and resource recovery using its state-of-the-art MX-1500 centrifuge and MX-2000 thermal desorber. The MX-1500 can process over 450 feed tons of material per day, resulting in centrifuged cake containing 20% to 60% by weight. The MX-2000 is a hollow-flite thermal processor indirectly heated by either steam or hot oil. SRS has dewatered and/or deoiled over 1,000,000 feed tons of material in the refining, chemical, and energy industries using the MX-1500. SRS estimates that over 300,000 barrels of reusable oil have been recovered from that material. Additionally, SRS has dried and/or detoxified over 150,000 wet tons of solids or soil to regulatory or customer-specified limits using the MX-2000.

Jan 1, 1994

By Thomas P. Battle

Titanium is the ninth most common element in the Earth&apos;s crust, yet only in this century has titanium come into use as an engineering material, particularly in aircraft structures, as the metal, and in pigments, as the dioxide. In this presentation, the metallurgical aspects of processing titanium-containing raw materials will be reviewed. Particular emphasis will be given to the ores and beneficiation techniques which lead to the production of titanium dioxide pigment, which accounts for over 90% of world titanium production.

Jan 1, 1993

By Wenbo Luo, Kang Liu, Fusheng Mao, Jilai Xue, Jun Zhu, Chunlei Yang

Extracting alumina from coal fly ash (CFA) is of great interest for both environmental protection and recycling valuable alumina content. In this study, ultrasonic aided leaching process as an effective method was investigated to enhance extracting Al2O3 from CFA via concentrated sulfuric acid sintering. The influence of ultrasonic power and processing time were tested under the conditions as the same as those without ultrasound. It is found that the alumina extraction rate can reach 90.5 % with ultrasound assistance, while the ultrasonic treatment can reduce almost 15 ~ 30 min in leaching time and 5 ~ 10 oC in leaching temperature than those without ultrasonic operation at the same Al2O3 extraction rate. In addition, the ultrasonic can reduce calcium content by 6 ~ 8 % dissolved into the leaching liquid. SEM analysis also shows that the residue particle size with ultrasound is smaller than that without ultrasonic treatment.

Jan 1, 2015

By G. E. S. Lima, J. V. B. Lemes, F. G. D. Machado, J. Alexandre, L. G. Pedroti, L. A. F. Fioresi, W. E. H. Fernandes, R. C. S. S. Alvarenga

Cellulose fibers are extracted from renewable sources and have potential to be used in various fields. In this study, a type of Reactive Powder Concrete (RPC) was produced with the addition of Cellulose Nanofibers (CNF), a biopolymer extracted from lignocellulosic materials. Three different concrete compositions were produced, each with addition of 0.10, 0.20 and 0.25% of CNF in mass, proportionally to the cement’s mass. During the analysis were performed Scanning Electron Microscopic (SEM) tests, compressive strength and Young’s modulus tests after 1, 3, 7 and 28 days of production and shear and flexural strength after 28 days of production. The results showed that the addition of CNF in aqueous solution reduces the concrete’s workability and negatively affects mechanical properties.

Mar 1, 2017

By J. K. S. Tee

Using a novel method, zinc has been selectively removed from galvanized steel scrap on a laboratory scale. The separation is based on thermodynamic principles: during chlorination in air-chlorine (10:l) mixtures at 800 OC, zinc forms a volatile product (zinc chloride) while iron does not chlorinate as its oxides are more stable than the respective chlorides. As much as 92 % of zinc is removed from the surface of steel within 10 minutes. This process overcomes tedious and costly preparatory stages associated with leaching - electrowinning methods.

Jan 1, 1999

By G. A. Irons, D. Guo

"The average spout height and width produced by bottom gas injection in a water model of a steel ladle were measured with an image processing technique. It was revealed that the spout height could be described by a Gaussian curve. A combined SIMPLE -VOF model was developed to simulate the liquid surface and flow. The results showed that, though the model produced reasonable velocity distributions and free surface positions, the spout height due to the dynamic head of the rising liquid was substantially lower than observed, indicating that the bubble dynamics at the bath surface play an important role in spout height.IntroductionDue to the enormous importance of gas injection and stirring in metallurgical processes, there have been numerous publications on water and numerical modeling of such vessels. The free surface of the bath has received considerably less attention, despite its importance. At the free surface there are often important chemical phenomena occurring that require a good understanding of the fluid flow; these would include reoxidation of steel, metal splash and fume formation. Furthermore, to understand the details of slag-metal interactions such as slag entrainment, metal losses to slag and the transport phenomena associated with refining reactions, it is necessary to understand the plume and spout interactions first.There have been few experimental studies of the free surface of liquid in gas-injected ladles [1- 3], and even fewer on numerical modeling. Brimacombe and co-workers [1] studied the gas void fraction in the spout region, using a double-tip electrical resistance probe. This sensor cannot distinguish between gas in bubbles about to break and gas in the freeboard. Thus, it is a matter of judgement as to the position of the free surface. Schwerdtfeger and co-workers [2] used a single probe configuration with a wire and a counter electrode in the liquid, so that the height of the continuous liquid phase was unambiguously determined. Irons and co-workers [3] measured the spout height by ultrasonic and electrical capacitance techniques. These techniques were as reliable as the resistance techniques, but were restricted to low flow rates."

Jan 1, 2001