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By William Petruk

An investigation was conducted to determine whether mineral liberation data obtained by one image analysis technique are the same as data obtained by another image analysis technique. The liberated vs non-liberated, volume % and weight % techniques for measuring mineral liberations by image analysis were tested. The results show significant differences between the values obtained by the different techniques. The lowest liberation values were obtained by the liberated vs non-liberated technique and highest by the weight % technique. It is interpreted that the weight % technique produces the most realistic results. The weight % technique also produces data that can define mineral associations for the unliberated grains. These include (1) mineral quantities in particles that contain different amounts of unliberated mineral, (2) mineral quantities in particles that have different size ranges, and (3) mineral quantities and degrees of liberation for specific minerals in particles of different size ranges.

Jan 1, 1996

By J. A. Holmes

Due to varying and complex mineralogy, the flotation tailings from the Chingola Concentrator have, for some years, contained upwards of 0.4% acid soluble copper. In 1968, an investigation was initiated, to determine a method for recovering this acid soluble copper. This initial investigation concluded with a recommendation to install a leach-solvent extraction-electrowinning plant at Chingola, to treat up to 900 000 tonnes of material per month, for an additional copper production of some 4 500 tonnes per month. The process consists basically of six stages :- Materials reclamation handling and preparation, acid leaching in air agitated pachucas, solid-liquid separation by countercurrent washing in thickeners, solution concentration and purification by solvent extraction, copper recovery by electrowinning, and residue neutralisation and disposal. This paper describes the development of the main parameters for design of each of the six sections, and gives details of the final plant design. Problems encountered in commissioning and initial operations are commented on, particularly insofar as they indicated any errors or misjudgements in the design. The choice of materials of construction is commented on in some detail.

Jan 1, 1976

By G. S. Hill

A large amount of the stereological error associated with liberation studies can he eliminated by assessing areas instead of linear intercepts. The presentation of a simple geometrical model as a stereological 'worst case' allows calculation of the worst possible grade/recovery curve for a given assemblage of areas. The true results are expected to lie in the window between this worst case and the hest possible case, represented by uncorrected data. The width of this window typically corresponds to an error margin of about 5% grade at a given recovery. An indication of where the data lies within the range of possible grade/recovery results may he obtained from a qualitative analysis of the locked section complexity. Assemblages consisting of texturally complex locked sections (ie. containing many mineral nuclei) are likely to exhibit minimal stereological bias and therefore will tend to lie close to the uncorrected side of the grade/recovery window.

Jan 11, 2011

By B. Q. Li

A numerical study of the developing fluid flow and thermal aspects during the staning phase of aluminum continuous casting processes is presented. The deforming finite element method, coupled with a quasi-Lagrangian formulation, is used to represent the growth of an ingot and the dynamic fluid flow and thermal behavior that evolves in the growing ingot. The mathematical formulation of the problem and the numerical treatment are discussed. The algorithm solves the free moving nodes as part of total unknowns with an automatic time step control for time integration. This permits an optimal computing efficiency while still keeping the computational errors under control. A selection of the results obtained using the algorithm is presented. The results are concerned with the evolution of fluid flow, temperature and solidification phenomena during a DC round ingot casting process, as it evolves from the beginning of casting operation to a steady state. These results show that the time-varying, complex fluid flow and thermal phenomena during continuous casting processes can be very well represented by the computational algorithm. The results also illustrate that, during the casting process, ~e fluid flow and temperature fields change drastically at the initial stage but evolve slowly afterwards

Jan 1, 1993

By C. -S. Jiang

In most copper refineries, addition agents are added at predetermined rates with no further monitoring of their activity or concentration in the electrolyte. Increasingly stringent cathode quality requirements, and a desire for better process control in tankhouse operations, have recently directed a number of refineries to search for a better addition agent control strategy. Extensive development work has been carried out at the Noranda Technology Centre for the monitor in of glue and thiourea in copper refinery electrolyte using cyclic voltammetry (cv~. Data from both synthetrc and commercial electrolytes are presented, showing the ability of CV to produce reliable and easily identifiable fingerprints of addition agent concentrations in copper refinery electrolyte.

Jan 1, 1991

By J. W. Lyman

The U.S. Department of the Interior, Bureau of Mines, investigated methods to recover valuable rare-earth materials from NdFeB magnet scrap. Although several processing techniques were evaluated" the best separation of rare earths from the NdFeB magnet ,scrap was obtained by sulfuric acid dissolution followed by precipitation of recyclable rare-earth salts. Both sodium and ammonium intermediate double-salt precipitates' that can be converted to a variety of useful neodymium products were investigated. The sodium system showed a neodymium recovery of 98 pct, while the ammonium system yielded 70 pct during double-salt precipitation. The iron-rich effluent following the rare-earth recovery was treated to produce sodium and ammonium iron jarosites that can be disposed of or converted to hematite. By following this new procedure, many materials handling and economic disadvantages found with fluoride or oxalate direct precipitation were avoided.

Jan 1, 1992

By B. Mishra

The major waste product of the alkaline extraction of alumina from bauxite [Bayer Process] is known as red-mud. Approximately, a ton of red-mud is produced for every two tons of bauxite that is mined. The red-mud produced from Jamaican bauxite is rich in hematite, alumina and titanium oxide. It has been shown that over 90 wt. pct. alumina can be recovered from red-mud by soda-ash sintering and caustic leaching. Hematite can be carbothermically reduced with a degree of metallization of over 94 pct. At this stage, the product could be charged through the tuyeres in an iron blast furnace or smelted to produce pig iron. The mineralogical characteristics of the reduced product are not amenable to magnetic separation for iron recovery. The problems associated with the use of reduced red-mud as an alternative to direct-reduced iron [DRI] has also been discussed. Special attention has been paid to lower the alkali content of the reduced material. If smelted, the concentration of titanium oxide in the slag will be significantly high justifying its recovery by an acid-leach process. This paper describes the successful efforts of iron and alumina recovery.

Jan 1, 2000

By Peter R. Sanford

Cyanides are present as a dilute constituent of streams from a variety of metallurgical and mineral-processing operations. In addition, a cyanide concentration in excess of approximately 100ppb is toxic to aquatic life, and consequently these operations require a waste-treatment process to reduce the already dilute cyanide species by several orders of magnitude. Furthermore, the waste streams may have flowrates in excess of a million gallons per day. The paper reports on research conducted with a laboratory?scale electrochemical porous (graphite felt) electrode (anode) flow-reactor, which was conducted in conjunction with a computer-aided simulation of a mathematical model describing the intrinsic rate-phenomena associate with the electrode processes. The laboratory-scale cell, of rectilinear geometry, was found to be capable of reducing a feed-stream anolyte (KCN-KOH and supporting electrolyte of a single salt ? K2SO4) with a cyanide concentration of 10ppm, to less than 100ppb, at current efficiencies in the neighborhood of 50%. The computer simulation of the cell performance based on the mathematical model (and constraints imposed for tractability) was found to provide only for qualitative agreement.

Jan 1, 1998

By Egil Aukrust

"An American Iron and Steel Institute Task Force evaluated developing direct steelmaking technology worldwide to seek a replacement for the coke-oven, blast-furnace, basic-oxygen process technology now in use. To remain internationally competitive it is essential to move away from the traditional series of batch processes towards continuous processing and the associated energy savings which are possible with high technology process control systems. The group identified in-bath smelting of iron ore pellets or fines with coal as the process most sui table for domestic raw materials (including abundant scrap) and called for research to study operation with varying degrees of preheat and prereduction of the ore by the gases generated from the coal and various degrees of combustion of these gases above the melt.A coordinated, 3-year, $27 million, direct steelmaking research program is proposed. Concurrent projects include design, construction, and experimental operation of an in-bath smelting pilot plant; modeling, simulations, and laboratory-scale experiments at universities on slag-phase and metallicphase reactions and interactions; and large-scale heat transfer and reaction rate trials. Also included are modeling studies and pilot plant trials of on-stream decarbonization and desulfurization; application of circulating fluid bed technology to fine ore reduction and hot gas cleanup; and specific heat transfer and fluid flow research projects.IntroductionThe American Iron and Steel Institute (AISI), based on the Task Force studying direct steelmaking, believes strongly that a coordinated program of research on the reduction of domestic raw materials to liquid steel should be undertaken as part of the Steel Initiative program. To specify the steelmaking process for development best suited to the American steel industry and domestic raw materials, it was important to determine the state-of-the-art of direct steelmaking worldwide, both as practiced and under development, and then, by expert analysis of the processes and their potentials, to choose the process most likely to provide a domestic competitive edge."

Jan 1, 1988

By Shu Xinqian, Zhou Weining, Shan Zhiqiang, Feng Jifu

"Modified calcination conditions on the extraction of rubidium resources from muscovite (KAlz[AlSi301o](OH)2) ore are systematically studied. The impact of various factors on the rubidium leaching rate is also analyzed, including the agent types, roasting time, the mass ratio, roasting temperature, etc. The results indicate that the best agent is a combination of sodium chloride and calcium chloride, its mass ratio ofmuscovite/NaCl/CaClz is 1:0.25:0.25. Calcined at 8500 for 30 minutes, the rubidium leaching rate is up to 90%. The reaction of muscovite ore with the chlorinating agent CaC12 has been studied by TG/DSC, the calcined intermediates are identified by XRD, and the surface morphology before and after leaching is characterized by SEM. Rubidium chloride products can be obtained with a purity of 92% by using t-BAMBP extraction, hydrochloric acid reextraction and purification.IntroductionRubidium is one ofrare alkali metals, which is found in 1981 by German R.W. Bunsen and G.R. Kirchhof. Rubidium includes the following features: atomic number is 37, each atom weight 85, the body-centred cubic lattice, each unit cell has two metal atoms, and the density is 1.532g/cm3. The properties of low melting point (312.46 K) and malleability make rubidium have a strong chemical activity and photoemission. Rubidium provides a main material for manufacturing phototube with a wide range oflight waves, which possess high sensitivity and stability. Efforts are being made to carry out research on rubidium ion gngine, magnetic flux generators and thermoelectric transudcer, etc. Rubidium exists in muscovite ore(KA12[AlSh01o](OH)2 (monoclinic system and hexagonal layered structure) as isomorphism and replace the large radius of the potassium atoms, as well as part of rubidium locate between structure layers. The complex components bring great difficulty in comprehensive recycling."

Jan 1, 2013

By Yongzhong Xiao, Tiejun Chun, Jian Pan, Deqing Zhu

"An innovative process of reverse floatation-direct reduction-low intensity magnetic separation was developed to effectively beneficiate the superfine run-of-mine (ROM) ore mined from Hunan Province, China. Mineralogy was measured that the ROM ore is of superfine low grade hematite ore type, assaying 27.2wt%Fetotal and with main valuable minerals of hematite occurring at size between 3 to 5µm. The upgrading results show that the final iron concentrate, assaying 88.3wt%Fe total and 94.5% metallization degree was obtained at an overall iron recovery of 69.9% under the following conditions: rough concentration by grinding of ROM up to 88.7% passing 0.074 mm and reverse flotation at pH=9.4, 100 g/t starch and 200 g/t dodecylamine (DDA), and coal reducing the rough concentrate pellets containing 12% calcium containing complex additive at 1200 oC for 120 min, and finally magnetic separation of the reduced pellets by grinding up to 89.2% passing 0.043 mm at 0.08 T field intensity.IntroductionWith the rapid development of iron and steel industry in China, there has been a soaring demand for iron ores in the past decade. The imports of iron ores have increased from 148 million ton in 2003 to 628 million ton in 2009 [1]. Iron making industries increasingly demand for high grade raw materials to improve product quality and reduce operation cost. However, availability of high grade natural ores is limited and enrichment of lower grade ores is necessary to meet the demand. Therefore, large quantities of superfine low grade iron resources are necessary to utilize in China at the moment."

Jan 1, 2011

By Guohua Bai, Lin Zhang, Shan He, Xuling Chen, Min Gan, Xiaohui Fan, Yanbin Tang

"For reducing the dust content in flue gas during copper smelting in the Ausmelt, technologies and mechanism of strengthening the pelletizing of copper concentrate were studied. The results show that adding bentonite, organic binder or composite binder can effectively enhance the strength of green pellet and reduce the rate of shedding powder in drying process, and composite binder works best. When adding 1 % of composite binder, the drop strength of green pellet increased from 1.9 times/P to 4.5 times/P, the rate of damage dropping from 2 m reduced from 50.12% to 13.08% and the rate of shedding powder reduced from 60.28% to 25.13% at drying temperature of 400111. In addition, the mechanism of binder absorbed in the surface of mineral was investigated by infrared spectroscopy. The results showed that composite binder absorbed in the surface of copper concentrate was in the form of chemisorptions, which made hydrophilic enhanced, while bentonite absorbed in the surface of copper concentrate was physisorption.IntroductionWith the technologies of copper smelting developing, the equipment of copper smelting steps into a large-scale and efficient level in recent years. As Ausmelt smelting is characterized by being efficient, environmentally-friendly and energy-saving, it is generally recognized by the enterprises of copper smelting [l]. The process of Ausmelt smelting starts with materials mixing, and then pelletizing. From this point onwards, pelletized balls are charged to the top of the furnace, undergoing drying and smelting reaction[2]. Since copper concentrate is fine-grained, directly adding into smelting furnace can make it blown out of the furnace together with the airflow upwards, rendering flue gas high in flue dust, which can cause the loss of concentrate greatly, and make smelting environment poor as well. The concentrate transported into the furnace and smelted after disc balling is conducive to improve the capacity of melting furnace during copper concentrate smelting, reduce the powder shedding rate and improve enterprise benefits."

Jan 1, 2013

By R. M. Reynolds

Engitec Impianti, S?.p.A. of Milan, Italy has successfully designed, constructed and has in operation state-of-the-art battery breaker systems at two European locations. A third facility i:s partially completed in Toronto, Ontario, Canada. The CX system crushes whole batteries, separates the various components and desulfurizes the battery paste. The system also produces sodium sulfate from the sulfuric acid and lead sulfate contained in the batteries. Actual plant operating data indicates that the desulfurized paste contains less than 0. 6 percent sulfur and less than 0. 5 percent antimony. The CX system utilizes mechanical screening and an up-flow hydrodynamic separator to accomplish the component separation. Sodiwn hydroxide or sodium carbonate is used for desulfurization. The sodium sulfate brine is evaporated and crystallized to produce clean anhydrous sodium sulfate suitable for use by detergent or glass manufacturers. Plant data also indicates that an increase in furnace productivity of about 25 to 30 percent is achieved using feed from the CX system. The desulfurized paste is very suitable for electrolytic processing as an alternative to pyrometallurqical processing.

Jan 1, 1990

By R. Lanza, M. Hytros, N. Saka, I. Jureidini, J. H. Chun, D. Kim

"A novel method for delineating the solidification front in metal casting has been developed using the attenuation phenomenon of electromagnetic radiation (y-rays or x-rays) and computed tomography (CT). The densities of the liquid and solid phases that exist during metal casting may differ anywhere from 4 to 12 % depending on the metal. As in the medical imaging field, CT provides an excellent means of mapping this density variation in a solidifying casting into two-or three-dimensional images.In an effort to develop an industrial-scale sensor, laboratory-scale experiments have been conducted using a cobalt-60 (Co60) radioisotope and a sodium-iodide (Nal) scintillation detector. The CT image reconstruction was performed on a crucible containing pure tin in a two-phase state. Although the spatial resolution and data acquisition speed were not optimum, the CT images clearly differentiate the liquid and solid phases of the tin in the crucible. To maximize resolution and minimize data acquisition time, a linear accelerator (linac)-based CT sensor is being developed and tested for application in the continuous casting of steel and aluminum alloys.IntroductionIn all casting processes, the quality of a finished product and its production rate depend upon the shape and movement of the solidification front. From a quality perspective, it is well documented that solidification kinetics (heat and mass transfer, fluid flow, microstructure evolution) greatly influence the final properties of castings [l,2,3]. Product shortcomings, such as surface defects, cracks, macro-and microsegregation, and inclusions are directly controlled by the solidification process. By understanding the role the solidification front plays in the casting process, product quality may be dramatically increased through the reduction of defects."

Jan 1, 1997

By Guohui Zheng

The ever increasing quantities of solid wastes generated by various industries are at the source of the growing need for proper waste disposal methods. Thermal treatment of combustible wastes is a proven technology which permits the reduction of hazardous material having to be landfilled. However, this method is not universally applicable to waste disposal. For example, the transferal of heavy toxic metals into the thermal remediation products is a major issue of public concern. This paper focuses on the analysis of morphology changes from solid sludge to ash which is a product of the sludge combustion. The morphological parameters analyzed were particle size and external surface. They were determined using Jeol 840 Super Probe. The experiments were conducted in a computer-controlled high-temperature combustion system consisting of the thermogravimetric furnace coupled with Fourier transform infrared spectrometer (TGA-FTIR). Sludge particles were made of complex fibers trapped in the aluminosilicate matrix. At low temperatures, up to 680 K, the solid residue looked similar to the initial sludge. Between 680 K and 1180 K the sludge underwent intensive burning and steadily changed into powdered ash. At the temperature of 1050 K the ash was composed of separate, flat flakes with sizes ranging from 5 to 20 um. At 1470 K the flakes aggregated into large particles. The surface observed at 1670 K was a mixture of mullite crystals. Such structure could result from the solidification of the ash material after its melting. Morphological changes influenced the distribution of metals in the solid residue. For example, Cr was concentrated in small aggregates. Such distribution should allow for recovery of valuable metals from the solid waste residue.

Jan 1, 1996

By Zhang Yongzhu

Developments on bioleaching of low grade ores and refractory gold ores by T. Ferrooxidans in China are summarized. Effect of the ions on bacterial growth, bioelectrochemical reaction mechanism of sulfide minerals and bacterial reaction mechanism are also discussed.

Jan 1, 1992

By Yuzhe Zhang, Xiaodi Huang, Xinli Wang, Bowen Li, Matthew Andriese, Jiann-Yang Hwang, Zhiwei Peng, Likun Li

With the development of the world, the waste tires have been a serious environmental problem. There are about 2 billion waste tires produced all over the world every year and about 500 million waste tires are produced in the United States. Most of the waste tires are land filled, which waste a lot of space. It takes hundreds of years to resolve the macromolecules of waste tire into the standard which does not pollute the environment. Microwave irradiation is a thermal processing way for waste tires decomposition. In this study, the relative dielectric loss factor of the tire at various temperatures was determined to understand the behavior of tires under microwave heating.

Jan 1, 2016

By Adam Powell

A Cahn-Hilliard phase field model is formulated to describe transport-limited electrochemical reactions coupled with fluid flow in a metal reduction cell. When the reaction is limited by mass transfer of metal ions from the electrolyte to the cathode, the metal-electrolyte interface at the cathode exhibits a Mullins-Sekerka instability, leading to the growth of dendrite-like "streamers" of liquid metal into the electrolyte, which in turn significantly enhance the apparent mass transfer coefficient there. Model results for iron reduction from ferrous oxide in slag show formation of these streamers. Although the double-layer is not included in this model, the related phenomenon of electrocapillarity can be represented by a gradient penalty term which includes the electric potential gradient, such that interfacial energy is a function of the electric field normal to the interface.

Jan 1, 2003

Several processes are now available for the recovery of free and WAD cyanide from gold plant solutions and pulps. In the past, the incentive for evaluating cyanide recovery in gold plant flowsheets has been economic. In many cases, it has been possible to demonstrate (at least in the laboratory and on paper), an improvement in process economics by; (i) reducing the costs of tailings detoxification, (ii) recycling cyanide at lower cost than the purchase/delivery price of new cyanide, and (iii) generating additional revenue via by¬product sales. Despite these convincing arguments, few cyanide recovery plants have been built at operating gold mines. Also, there is arguably an even more compelling reason for mining companies to consider cyanide recycling. With the growing storm of negative public opinion that the use of cyanide in the mining industry is attracting - following several highly publicized spills over the last couple of years - the time has come for the gold industry to demonstrate environmental diligence and stewardship in the use of this commodity that is so vital for their industry. There is no doubt that the widespread implementation of cyanide recycling will reduce the impact of the cyanidation process on the environment, both by reducing the risk of spills (with less cyanide being transported from manufacturing plants to gold mines), and by reducing the loading of toxic and non-toxic metals and ions in the tailings. In this paper, the various processes that are available for cyanide recovery are discussed, along with the process chemistry. Results of several laboratory and pilot plant trials that have been conducted over the last few years are also presented.

Jan 1, 1998

By D. Mishra

Electric arc furnace dust (EAFD) generated during the recycling of steel- scrap is classified as a hazardous waste for landfilling. This is because it contains leachable heavy metals such as zinc, lead,... Recovery of these metals could result in both resources conservation and resolving waste disposal problems. A study of the thermal reduction of a sample of EAFD was carried out in an inert gas atmosphere using coke as a reducing agent. Preferential volatilization of zinc and lead was achieved during the reduction process at about 800 "C. More than 96 % of both zinc and lead were removed from the dust and were recovered in the condensates. The treatment residue was essentially composed of iron oxides and almost free from heavy metals.

Jan 1, 2002