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By KNona Liddell

Many metal recovery processes Involve heterogeneous reactions In porous media accompanied by fluid flow and mass transfer. Modeling such systems Is difficult because of the number of rate processes Involved and is complicated even further by effects due to the structure of the porous medium. Data on even bulk properties of the medium are often severely limited or unavailable. For many such systems, a cell model may provide, an attractive alternative to models based on transport ,mechanisms in a differential volume. A cell model requires less input data and is computationally efficient. Identical residence time distributions can be obtained with models of both types, and both allow conversion and concentration profiles and histories to be calculated. The formulation and properties of cell models for metals recovery are described in detail.

Jan 1, 1996

By Yang Hong-ying, Yu Juan

Electrochemical behavior of natural chalcopyrite in electrolyte solution at pH value of 6.97 was studied by cyclic voltammetry, X-ray photoelectron spectroscopy and electrochemical impedance spectroscopy. The results showed that the electrochemical processes occurred on electrode surface were controlled mainly by the growth of sulfur species at lower applied potentials (<0.35Vvs.SHE), and the oxidative dissolution of sulfur species and the hydroxylation of iron at higher applied potential (>0.45V). The EIS spectra of oxide product layers could be illustrated by the equivalent circuit of Re(QdlRct(QfRf)), and the degree of hydrophilicity for chalcopyrite was higher when the value of charge transfer resistance Rct. was greater. The optimum potential range for the floatation of chalcopyrite in collectorless solution at pH value of 6.97 was between OCP (0.165V) and 0.35V.`

Jan 1, 2015

By Ted H. Eyde

Natural Zeolites are a less expensive and in certain applications a superior alternative to organic ion exchange resins. Mining and metallurgical waste streams are difficult to treat because the effluents which contain potentially valuable heavy metals such as copper, lead, and silver are often highly acidic and contain significant quantities of suspended solids. Under rigorous operational conditions, certain natural zeolites can remove the metals, which if desired can be recovered by either elution or conventional smelting techniques. There are significant differences in cation exchange rate, selectivity and capacity as well as resistance to either high or low pH, blocking cations and tolerance to elevated or depressed temperature and pressure not only between different zeolite minerals but between the same mineral from different deposits. Applying natural zeolites to the treatment of mining and metallurgical waste streams depends on matching the specific zeolite to the effluent by characterization of the zeolite minerals.

Jan 1, 1993

By W. Kasprzak

Press-fit systems are widely used to seal oil lines in the automotive engine components. In the case studied a ball plug made from the 7075 A1 alloy was inserted into a 319 Al alloy cast component. The oil lines were subjected to the required component service pressure. This paper addresses the analysis of the ball plug/casting hole press-fit performance. The tools used to investigate the plug system included: the SEMIEDS technique for the assessment of the plug and the casting hole wall surface integrity; image analysis methods for the characterization of the ball plug/casting hole interface; matrix microhardness measurements of the plug and casting components; laboratory ball plug insertion, speed and force correlation; as well as the ball shearing mechanism analysis. Laboratory tests indicated that optimization of the aluminum matrix hardness in the 319 A1 alloy cast components resulted in considerable improvement of the press-fit system sealing properties.

Jan 1, 2002

By Herman Wotruba

Mercury emissions and other environmental impacts in small-scale gold mining are a world-wide problem. "Clean" or better: "Cleaner" technologies have -apart from being environmentally sound -to guarantee a higher income and better working conditions for the miners in order to have a chance for long-term acceptance. In small scale primary gold mining in several South American countries, a number of techniques have been adapted and improved so that they not only were accepted due to their efficiency and easy handling, but they could also significantly lower mercury emissions.

Jan 1, 2003

By Marcelo Jimenez Bustos

The Chagres Smelter was the first in Chile to follow environmental regulations to control sulfur dioxide emissions. Because of this, the operation and development plans have had to incorporate environmental planning as part of its policies for almost three decades. The present article shows the development of the environmental standards applied to its operations, investments and operational improvements carried out to meet the regulations and improve competitiveness. Results to-date and future plans are outlined, as well as their impact on operations and the environment.

Jan 1, 1993

By Larry B. Fiske

Elimination of dust and processing of fines for both thermal and metallurgical coals is addressed. The efficiency of treatment with lignosulfonates compares favorably to oil in thermal coal. Effect of treatment with various lignosulfonates upon cokability of metallurgical coal was determined by Free Swelling Index, Gieseler Plasticity and Arnu Dilatation.

Jan 1, 1992

By Vladimir Mindin

Simulation of complex equilibria is usually done in the P-T-X coordinates, where "Xu is the amount of individual chemical components in the system. This approach is not productive in some very important cases: (i) investigation of "open" systems, (ii) determination of coordinates (trajectories) of mono-variant points, among others. To solve these and some other problems, we use the idea of chemical potentials of elements (CPE) of the system. A system of different coordinates axes (CPE-axes ) leads to a new strategy of simulation, observing the results of the simulation, and to efficient technology of compressing and storage the data of the simulation.

Jan 1, 1994

By M. S. Moats

The treatment of oxidized residues of zinc with high iron content continues to present a technical challenge in both the steel and zinc industries. Two main problems are commonly identified and include high treatment costs and environmental concerns about contaminated, iron-bearing residuals. A new approach to this problem is described in which selective separation of the iron and zinc into salable products may be potentially feasible. The waste material is first leached to give a solution having an approximate concentration of 110 g/l Zn, 15 g/1 Fe and 40 g/1 H2SO4 and other impurities such as Pb, Cd, Cu and Sb. A suitable organic, such as D2EHPA, is used to load the majority of the iron. The aqueous phase is then acceptable for zinc electrowinning after standard solution purification. The novel step in the flow sheet is the efficient recovery of the ferric iron from the organic solvent using a solid metal to reduce the iron to the ferrous state. The Fe+2 is easily stripped into an aqueous phase in a relatively pure form, suitable for use in water treatment. Process parameters and possible flow sheet designs are described and discussed.

Jan 1, 1995

Direct electrowinning is an electrochemical process which has been developed for the extractive recovery of copper from dilute, acidic leach solutions. In passing through a thin particulate coke cathode. copper is reduced and electrodeposited in a thin layer forming a solid copper-coke sheet. The product is melted in a furnace to separate the coke, then the molten copper is fire refined to produce a salable product. A description is given of a prototype unit which is designed to treat 20 gpm leach liquor and recover over 100 pounds of copper per day. Economic analyses show that in a commercial facility producing about 25.000 TPY copper.*the direct electrowinning process has lower overall cost than either conventional iron-cementation or the newer liquid ion exchange-electrowinning when the leach liquors contain less than 2 grams per liter of copper.

Jan 1, 1976

By Leonard J. Friedman

Modern smelting systems using continuous, flash and/or oxygen smelting processes have a significant effect on the choice of sulfur dioxide control processes and system arrangements. Based on gases from an enriched air or oxygen smelting furnace and copper converters the paper reviews and analyzes alternate processes and system arrangements for recovery of sulfur dioxide. The work indicates the choice system to include a conventional sulfuric acid plant for converter gas and a liquid SO2 plant to handle the high strength smelting fur¬nace gas. The liquid SO2 plant would be used as a fly-wheel to damper the flow and SO2 concentration variations of the con-verter acid plant. Potential energy recovery alternates and product flexibility are also reviewed.

Jan 1, 1983

By Akira Nishikawa

During the twentieth century the copper smelting industry achieved dramatic expansion corresponding to the vast growth of global economy. This was largely due to innovations in pyro-metallurgical processes, such as autogenous smelting and continuous smelting and converting technologies. However, as copper production capacity increased, its impact on the environment also could not be ignored, and thus with increasing global environmental awareness, many smelting operations either had to renew or rebuild their facilities. In addition to these changes, in places like Japan and Europe, with scarce primary resources, the treatment and recovery of metals from a variety of items such as car shredder dust, used electrical appliances and electronic devices, on top of scraps traditionally treated, is having a profound effect on the reduction of waste and the preservation of primary resources. Thus compared to the days when copper smelting focused on the environmental control in order to break with "Smoke Stack Industry", copper smelting today is making an important contribution to the sustainable development of human society.

Jan 1, 2003

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 T. Alboussiere, O. Paireau

"We have designed an experiment to simulate natural convection in a direct-chill aluminium ingot. In this experiment we induce natural convection within a hemisphere filled with liquid-metal (mercury). The device consists of a copper hemispherical bowl closed by a copper plate. The top is maintained at superheat temperature while the boundary is cooled. While the temperature measurements were found using thermocouples, the velocities were obtained using an original technical procedure that relies on MHD properties. By applying a steady local magnetic field, we measure the velocity. The distribution of temperature and velocity can be separated into a thermally stratified core bounded by thermal wall jets. These wall jets greatly influence the degree of macrosegregation in ingots.1. Natural Convection in Aluminium CastingIt is well known that the quality of the final product in aluminium casting depends on the movements within the liquid metal such as forced or thermogravitational convection. Strong buoyancy-driven flows are known to occur in the liquid metal pool of an aluminium ingot caster. These flows have a significant influence on the metallurgical structure of the ingot through the redistribution of heat, fragmented dendrites and segregated material within the pool. Macrosegregation mechanisms depend on favourable temperature and flow distributions in the sump, and these factors will determine the pattern and degree of macrosegregation. Moreover, for many years, the importance of thermally-driven natural convection in casting has been underlined (Cole & Bolling, 1965). In this way, a precise determination of the velocity and temperature fields is required in order to improve understanding of the macrosegregation mechanisms. That is precisely the aim of this paper, which provides experimental data of the flow and the temperature distributions in a natural convection experiment. We intend, with this laboratory experiment, to determine accurately the velocity field, particularly within the thermal boundary layer where the effects of the flows may have an important role in the transport of crystals."

Jan 1, 1999

By Robert R. Beebe

On the night of August 1&apos;9-20, 1995, seepage was seen at the toe of the Omai tailings dam in Guyana. The mill was immediately shut down, and within two hours the flow, then mostly water, was diverted into an inactive mining pit nearby. At about the same time a second more serious break occurred at a point where water and solids could flow directly into the Omai River. By the time Ii coffer dam could be completed in the early morning of August 24, some 4.2 million cubic meters of tailings water and solids had escaped from the dam, of which nearly2.9 million cubic meters had reached the Omai River. This paper outlines some initial Process considerations and operational decisions which might have contributed to the dam&apos;s failure, describes how the Government of Guyana and the operator, Omai Gold Mines Limited, cooperated in dealing with immediate problems and shows how the Government set about investigating the accident. In particular, the paper details the work of a Process Review Committee comprising Guyanese and foreign experts convened to assess the gold processing and effluent management systems at Omai, and to recommend actions where appropriate.

Jan 1, 1998

By R. J. McClincy

The potential techniques for the direct smelting of copper sulfide concentrates to blister copper were evaluated from the standpoint of commercial application. Many existing smelters are adaptable to direct smelting practice but only with improved control of metallurgical performance. Modified and innovative procedures for slag cleaning and metal refining, prerequisites to direct smelting, are presented and discussed. The ability to smelt directly to blister copper using existing equipment and eliminating the need to convert matte offers ,significant advantages to traditional smelting practice from the viewpoint of cost, &apos;S02 control, and process simplicity.

Jan 1, 1983

By Jean Goldschmidt

Recycling of fine oxidized particles of non-ferrous metals usually cannot be carried out by pyrometallurgical methods. &apos;Hydrometallurgy provides an alternative technology to reintroduce? the resulting products as secondary raw materials into the industrial cycle, thereby saving resources and energy while keeping the environment a little cleaner. The paper summarizes the methods employed by Hydrometal to achieve these objectives and? stigmatizes the latest counterproductive international regulations which create ever more obstacles to environmentally sound recycling.

Jan 1, 1995

By Dean G. Heitt

"The Rain and SMZ mines from 1987 to 1994 produced a total of22.0 t of gold from a pre-mine reserve of 14.24 Mt of ore grading 2.13 g/t Au.Gold at Rain is hosted within the basal portion of the Mississippian Webb Formation. ·Mineralization is closely tied to the Rain Fault which is interpreted to be the main feeder for the deposit. Multiple collapse and hydrothermal breccia events provided permeability for the mineralizing fluids in the otherwise unreactive siltstones. Major alteration events include: decalcification and dolomitization of the Devils Gate Limestone; and silicification, baritization, argillization and oxidation of the Webb Fm. Six ore types based on XRD and visual rock chip Jogging have been identified: siliceous ore containing >40% quartz and <30% barite; siliceous-baritic ore containing mostly silica but >30% barite; baritic ore containing >40% barite; argillaceous ore containing >40% total clays (including alunite); calcareous ore containing mostly calcite and dolomite; and carbonaceous ore which has significant pyrite and organic carbon. Metallurgical testing of the oxide leach grade ores found that recoveries, on -1.3 cm crushed material, were greater than 70%. Results also found that Rain ore has strong grind dependency due to silica encapsulation.The Rain leach pad was commissioned in 1988, and to date 9.3·Mt at an average grade of0.65 g/t Au have been placed. Life to date recovery, through December 1995, is approximately 51 %, for a total of3.87 t of gold produced. Two major factors have contributed to the low leach recoveries at Rain when compared with the metallurgical testing: 1) More argillaceous ore than expected was placed on the pad especially late in the mine life and 2) approximately 50% of the tons placed were run-of-mine with no agglomeration."

Jan 1, 1997

By Robert E. (Bob) Brown

Magnesium was discovered by Davy in 1808. The production processes as they exist are not economically competitive with aluminum The electrolytic magnesium process is divided into two steps; one to make the MgCh feed and the other to apply large amounts of electric current to dissociate the feed into magnesium (450 g) and chlorine (1200 g). The production of fuJIy anhydrous, pure cell feed is a major problem Recently, there has been a growth of thermal processes, mainly the Pidgeon silicothermic production process using FeSi to reduce dolomite in horizontal retorts. Pechiney has a large vertical electrical furnace process that also uses FeSi to reduce calcined dolomite in a molten bath containing alumina. Work is proceeding to develop new or modified processes that will greatly improve magnesium production. The present methods and the research and R&D will be reviewed in this paper.

Jan 1, 2001

By Philip L. LeHoux

"Kennecott Barneys Canyon Mining Co. is a gold heap leaching facility that has been in operation since 1989. In 1994, a flotation plant was commissioned to remove sulphide minerals from refractory sulphide ore. Tailings from the plant are mixed with oxide heap leach material in order to produce a geotechnically stable agglomerate from which the gold is leached and recovered in a conventional heap leach cyanidation process. The experience to arrive at an effective blending methodology is discussed.IntroductionAgglomeration is the practice of binding fine particles to coarser rock or other fines in order to avoid the deleterious effects of mobilizing the fines during the course of heap leaching(l-Chamberlin). Agglomeration has been considered a key component of successful operation at many heap leach sites. If the ore is of sedimentary origin and crushed, there is a high likelihood that the resulting product will contain a significant quantity of fines and a skewed gradation, that i~, a disproportionate amount of coarse and fine particles, with few in the intermediate size range. The exact methodology for determining whether the practice of agglomeration will have to be integrated into the operating scheme has been well discussed. These conditions are primarily geotechnical and geochemical. This paper will deal with the specific experiences of Kennecott Barneys Canyon Mining Company in modifying the agglomeration practices to suit evolving operational requirements."

Jan 1, 1997