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By J. C. Ingles

"A survey of possible methods for controlling cyanide concentration indicated that the simplest method would involve the use of a potentiometric technique. Such a method was suggested by a paper from the laboratory of Mines Safety Appliances, which described a method for determining hydrogen cyanide in air. In this application, the cyanide was absorbed in caustic and a silver electrode immersed in the caustic solution provided a measure of the cyanide concentration. However, our attempts to use the silver electrode in this simple manner to measure the cyanide concentration of solutions were not very successful. A study of the mechanism by which a silver electrode responds to cyanide concentration made it evident why this simple procedure is not satisfactory.Basically, the silver electrode provides an indication of the free silver ion concentration of a solution, and generally speaking, ignores the other ions' present. It can be used to measure an anion if this anion complexes silver. This technique has been used in complexing studies to determine the activities of such anions as acetate, citrate, oxalate and chloride. To do this, the electrode has to be placed in a solution which initially contains a known concentration of free silver ions. Addition of the complexing anion causes a drop in the free silver ion concentration and hence a change in the potential of the silver electrode. The change in potential can be expressed in terms of the concentration of the complexing anion, and used to indicate its concentration in the solution being analysed. The determination of chloride-ion by a silver-silver chloride electrode is an example of an application of this technique. The solubility of the silver chloride with which the electrode is coated provides the initial free silver-ion concentration. Depression of this free silver-ion concentration by the presence of the excess chloride ion of the sample solution results in a change in the potential of the electrode which is proportional to the chloride-ion concentration."

Jan 1, 1965

By Terry J. Briggs, Ian J. Kelso

"Abstract- The Century mine in northwest Queensland,Australia, is a major sediment-hosted zinclead- silver orebody, located within the western Mount Isa Basin. Stratiform, carbonaceous shalehosted mineralization is developed within Proterozoic shale and siltstone sequences of the Lawn Hill Formation. CRA Exploration Pty Ltd (CRAE) discovered the Century deposit in 1990 and open pit mine development commenced in 1998 under the ownership of Pasminco Century Mine Limited (PCML). The deposit contains an identified mineral resource of 105 Mt @ 12.1% Zn + 1.7% Pb + 46 g/t Ag (Broadbent and Waltho, 1998) which is currently being mined at a rate of 5 Mt/y.In December 1998, an exothermic reaction was observed between explosives spilt onto shale drill cuttings from a blasthole. This reaction is referred to as ‘reactive ground’ and has the potential to cause premature detonation of explosives in a charged blasthole with catastrophic consequences. The incident led to a subsequent geological and geochemical assessment of the different rock types at the Century deposit and their potential reactivity with ammonium nitrate-based (AN) explosive products. This assessment was conducted in an attempt to characterize zones safe for blasting with uninhibited AN-based explosive products. A direct result of this study is a set of procedures outlining the use of different AN-based explosives in areas defined as potentially reactive or non-reactive for the different lithologies present. Black shales contained in both the waste and mineralized sequences contain the sulfide mineral pyrite (FeS2), which is thermodynamically unstable with AN contained in commonly used explosives. The potential reactivity of partially weathered pyrite can ultimately result in the decomposition of an AN-based explosive. It was determined that only pyritic black shales showed any potential to react with AN, irrespective of their position in the stratigraphic sequence. Other lithologies present at Century, including Proterozoic sandstone and Cambrian limestone, are classified as non-reactive with AN. This is a geological risk management situation present at the Century mine."

Jan 1, 2001

By Claudio Rocha Rosales

"Peñoles is a mining group with integrated operations for the smelting and refining of non-ferrous metals, and it is also a chemicals producer. Peñoles is the world’s foremost producer of refined silver, metallic bismuth and sodium sulphate. It is also the leading Latin American producer of refined gold, lead and zinc. The Met-Mex Peñoles Zinc Plant commenced operations in 1973 with an annual production capacity of 105,000 t/y zinc. Since then, production capacity has increased, and at present, it stands at 240,000 t/y zinc. In this paper, the leaching process and particularly the operation of the jarosite circuit is reviewed, specifying process improvements to treat high iron calcines.INTRODUCTIONTwenty years ago the Electrolytic Zinc Plant in Peñoles was treating high quality zinc concentrates with low concentrations of iron (~7.5 wt.%) and silica (1.8 wt.%). Nowadays the quality of zinc concentrates is poor with a typical iron content of around 11 wt.% and silica at 2.0 wt.%. This has created numerous processing problems in our roast-leach-purification- electrolysis sections. In order to meet customer requirements it is necessary to find processing solutions to assure the operational continuity of the plant. These processing solutions are the focal point of this paper.REVIEW OF THE LEACHING PROCESSThe purpose of the leaching process is to recover the metals, mainly zinc, through a series of extraction stages with sulphuric acid solutions, which progressively increases the zinc dissolution. After the series of acidification stages, the solution, which is rich in iron, is sent to the jarosite circuit to separate zinc from iron (Garcia & Valdez, 1996). The first step of the leaching process is the neutral leach circuit which produces a zinc sulphate solution that is sent to the purification section for the removal of impurities such as cadmium, cobalt and copper. Then this solution is sent to the tank house to feed the electrolytic cells."

Jan 1, 2016

By J. A. Eisele, D. L. Pool

"The Bureau of Mines has developed a particle agglomeration technique to improve the flow of leaching solution through heaps of low-grade gold-silver ores which contain clays. Benchscale experiments and industrial practice have shown that the percolation rate of cyanide leaching solution is greatly enhanced by mixing the ore with Portland cement as a binder, moistening the mixture, mechanically tumbling to form agglomerates, and aging before heap building and leaching. A slight modification ofthe technique allows its application to precious-metal-bearing tailings, which cannot normally be treated by heap leaching because they are too fine. IntroductionMany low-grade gold and silver deposits and tailing materials from former mining operations in the western United States are potential sources for precious metals. These sources are too low grade or too small to support the capital cost of a conventional cyanidation plant but have stimulated the development of lowcost procedures, such as extraction of the precious metals by heap leaching with cyanide. The Bureau of Mines has investigated methods to improve the recovery ofgold and silver by heap leaching these low-grade materials.For heap leaching to be successful, the crushed and stacked ore must have good permeability so that uniform distribution of the cyanide leaching solution through the heaps can be achieved. Some of the most difficult gold and silver ores to treat by heap leaching are those containing excessive amounts of clays, or fines generated during crushing. Excessive amounts of slimes, generally minus 50-micrometre or 270-mesh Tyler sieve size particles, in the heap feed will slow the percolation of the leaching solution, cause channelling, or produce dormant or unleached areas within the heap, resulting in long leaching periods and low extractions. In extreme cases, the clays or slimes can seal the heap and cause the leaching solution to run off the sides of the heap rather than through it."

Jan 1, 1987

By A. P. Annan, C. Vaughan, J. L. Davis

"The increase in the price of gold in the last decade has led to a significant increase in placer gold exploration around the world. Placer deposits occur in depressions along ancient river and stream channels. In many instances these channels have been covered with materials from subsequent erosion or glacial activity. Use of high resolution geophysical techniques to map the bedrock and soil strata can improve the probability of finding the placer deposits. The buried bedrock surface is often the factor controlling deposition. Ground probing radar (GPR) and seismic sounding are complementary high resolution techniques which can be used to map bedrock topography and soil stratigraphy. Current radar instrumentation operates best in coarse grained soils. Penetration depths of up to 30 m have been attained, and stratigraphic horizons have been mapped with spatial resolutions of better than 0.5 m. Although its spatial resolution is considerably lower than radar, seismic refraction achieves superior penetration in electrically conductive environments such as clay and silt soils. The seismic refraction method thus proves to be complementary to the radar method. The seismic reflection technique is analogous to the radar method. Current seismic instrumentation and energy sources however, provide limited spatial resolution and do not permit the use of seismic reflection for reflecting horizons lying at depths of less than 20 m to 30 m.This paper discusses the use of both radar and seismic methods for placer exploration. The radar and seismic techniques, the field methods, equipment, and data displays are presented. Field examples illustrate the high resolution mapping capabilities of the techniques. The radar data agree very well with the borehole data, and in fact they sometimes detect subtle soil strata variations associated with changes of permeability that were not initially observed in the borehole logging. The radar method can give a continuous profile of water table and bedrock in sandy soils. Seismic soundings are necessary to differentiate between the bedrock and water table reflections observed by the radar."

Jan 1, 1987

By E. J. Marcotte

"INTRODUCTIONThe Upper Canada Mine is located at Dobie, approximately ten miles east of Kirkland Lake, Ontario.The mill contains Upper Canada's cyanide circuit and Upper Beaver's flotation circuit. The combined capacity is 590 tons per day consisting of 415 t.p.d. of Upper Canada gold ore and 175 t.p.d. of Upper Beaver copper-gold ore.The Upper Beaver ore is trucked five miles to the Upper Canada mine site.Crushing:The crushing circuit consists of primary, secondary and tertiary crushing employing one C .A. C. 15 in. x 24 in. Superior jaw crusher, one 4 ft. x 8 ft. Tyler-Niagara double deck screen, one 3 ft. Symons standard cone crusher and one 3 ft. Symons shorthead cone crusher.The -2 in. product from the jaw crusher is fed to the double deck screen. The+ 5/ 8 in. passes over the top deck to the 3 ft. standard cone crusher; the+ 3/ 16 in. material passes over the lower deck to the shorthead cone crusher. The - 3 / 16 in. material pas sing through the lower deck of screens is the product to the mill.The screens used prior to the installation of rubber screen cloths were: one 4 ft. x 4 ft. section with 3/ 4 in. square openings and one 4 ft. x 4 ft. section with 5/ 8 in. square openings on the top deck; two 4 ft. x 4 ft. sections with openings of 3/16 in. x 4 1/2 in. slot on the lower deck. The fine screens were positioned so that the 4 1/ 2 in. slots were parallel to the flow of feed.The crushing circuit is operated on a three shift per day basis by one operator per shift."

Jan 1, 1968

By G. Labonté, J. Truskoski, A. Kerr, A. Bouchard, J. Barrett

"Improving mill grade recovery relationships is always good business. Inco’s Clarabelle mill has just undergone a $16 M process upgrade that was designed to improve nickel recovery by 2%. The “Mill Redesign Project” was completed on time, under budget and delivered the promised improvement in recoveries.This paper describes the methodology of the Mill Redesign Project team, details of the process improvements and the critical success factors that helped the team deliver on its promises.With a payback of under one year, the Mill Redesign Project will play a key role in ensuring a competitive edge as Inco embarks on its second century of operation. IntroductionIt is not uncommon in milling operations to encounter a crisis. That is the point when the process does not behave as expected and fails to respond to the increasingly desperate efforts of the metallurgists and operators. Flowsheet and process changes are attempted and abandoned. With luck, one or more of the changes achieves some mitigation of the original problem or more usually, the original cause of the problem disappears. Regardless, the metallurgist can sit back and bask in the apparent success of his or her endeavours.Less common is when a problem is carefully diagnosed, a team put together to explore all avenues and recommend a path of action that is implemented on time, on budget and immediately delivers on the promises which are sustained over time. This is one such story. It is the story of the Mill Redesign Project at Inco’s Clarabelle mill in Copper Cliff, Ontario."

Jan 1, 2003

By V. Pouyafar

Semi-Solid metal alloys, as used in SSM processing, have a special microstructure of globular solid particles suspended in a liquid matrix, which makes them behave differently in forming processes. The sensitivity of semi-solid slurries to temperature variations and their history and rate dependant behavior, make process design and control difficult. Precise selection of the process parameters is necessary in part production. Therefore, a numerical analysis and simulation of the process can be a valuable tool in process design. In this work we proposed a structural dependent model to account for the thixotropic behavior of semi-solid metals. The parameters of the model were then determined using rheometery tests. The results show a good agreement between the model and the experiments.

Oct 1, 2011

By M. Hosseinzadeh

By changing the quality of consumed refractory bricks in burner zone of sarcheshmeh copper complex anod kiln removing of carbon precipitation phenomenon was studied. For blister deoxygenation LPG is blowing in anod kiln and cause destoring microsturcture and bonding of refractory bricks. Studies are shown that in a part of the bricks which have a temperature of 800 - 1000 °C , iron content phases in magesia - chromite bricks are like catalist and cause increasing the rate of carbon precipitation reactions . In a way that in comparsion of two bricks with best and medium quality with different analysis, this problem is more critical in best quality bricks containing high iron oxide. Therefore special magesia spinel bricks suggested and installed in burning zone.

Jan 1, 2004

By M. R. Coffin

In recent years, improved operation of the Kidd smelter has resulted in an increase in blister production capacity. Due to manpower and equipment limitations anode production and treatment rates could not be increased without incurring significant additional operating expenses. The option chosen to expand casting and refinery capacity to meet the available blister supply was to increase the anode thickness while maintaining the same anode exchange cycle in the refinery. This has resulted in a cathode production increase of almost 10% for minimal expenditure. Equipment and process modifications required to cast and refine the thicker anodes are discussed in this paper, along with the Six Sigma methodologies used to identify them. Key areas covered are Hazelett continuous caster operation, refining process parameters, plating performance and cathode quality.

Jan 1, 2007

By W. Lo, M. Brothers, G. Oprea, G. Richard, T. Troczynski

Magnesia-chrome and chrome-magnesia are the most used refractories in contact with iron-rich non-ferrous smelting slags. The corrosion by slag always brings chromium oxide into the slag, causing the precipitation of crystalline phases at the process temperature. This secondary effect of the chromium-bearing refractory dissolution was studied in this work, emphasizing the effect of the other chemical components of the slag at various temperatures. The experimental results showed that the presence of chromium and lead contribute, although in different ways, to the formation of complex spinel phases and their precipitation at temperatures in the range of 1250-1400°C. The XRD and SEM/EDS results were discussed for refractory-slag mixes containing 0-20% Cr2O3 and 0-11% PbO.

Jan 1, 2004

By K. J. Mintz

Conveyor belts installed in an underground mine can be a potential source of a major fire, thus the need for fife-retardant belting. A Canadian Standard, CAN/CSA-M422-M87, incorporating a small-scale flame test, a drum-friction test, a flame propagation test and an electrical surface-resistance test, has been developed to meet the varied needs of the mining industry. It is recommended that mines use Types A and B belting described in that Standard, because they will have passed the large-scale flame propagation test, rather than Type C, which does not require that test. Belting that has been approved by the U.S.A. Mine Safety and Health Administration (MSHA) may be much less fire-retardant than any Canadian approved belting.

Jan 1, 1992

By L. Jacobsson, J. E. Lindqvist

A series of laboratory tests were conducted to study stress-induced spalling on medium to coarse-grained granite specimens. The specimens made from cylinders had two manufactured notches on opposite sides aimed to represent the tangential loading around a circular opening. Specimens of three different sizes were tested with notch radii, 98.5, 225 and 375 mm, representing 197, 450 and 750 mm diameter holes, to study the effect of notch radius on the spalling initiation stress. The cracking was monitored by acoustic emission sampling. The fracture patterns were investigated visually on polished slabs and by microscopy on thin sections. The crack analysis describes how the cracks propagate in relation to the grain structure in the rock and to the macroscopic stress field.

Jan 1, 2015

By J. L. Rodrigues Bravo

The aim of this paper is to show the results of the study that relate the variations of the bismuth content in the Caraíba Metais' electrolytic copper with the main electrolysis' process variables as electrolyte flow rate and temperature, anode's impurities content, electrolyte composition, current density, etc and their combinations and factors like cathode washing, blend of materials entering rod plant's furnace, analytical methods, shot-circuit inspection, etc. Also, the methodology considered arsenic, bismuth and antimony mass balance in the electrolysis and their electrolyte's molar ratio relations as well as bibliographic references of refineries that operate in similar conditions. The results showed the circumstances with the major probability of causing bismuth content increasing in the electrolytic copper and the main operating conditions that have to be fixed for having less bismuth variation and lower content in the electrolytic copper.

Jan 1, 2007

By Chih-Huey Lin

The Au/?-Al2O3 catalyst prepared by AuCl3 impregnation is subjected to the influence of residual chlorine after an oven drying. A post-impregnation NH4OH treatment was able to eliminate chlorine, and to reduce the cluster size of Au moiety. However, the CO oxidation activity was not increased by this post-impregnation NH4OH treatment. This suggests that certain metal-support interaction (MSI) is the determining factor for the activity of Au catalysts. Thermal treatment under H2, O2 or He was attempted to increase MSI of the prepared catalyst with or without the post-impregnation NH4OH treatment. No significant activity enhancement was found but the TPD analysis suggests that a H2 treatment has a higher chance to induce MSI.

Oct 1, 2003

By M. S. Moats

As smelter feeds become more complex, the impurities that ultimately report to electrorefineries are changing. Many of these impurities collect in the electrolyte and must be controlled. As commercial copper electrorefineries look to expand their capacities by increasing their operating current density, the interaction between electrolyte composition and anode passivation can cause operational difficulties. To improve the industry's understanding of the passivation phenomena, the role of electrolyte composition was evaluated using commercial electrorefining anode samples. The electrolyte composition variables examined were copper, acid, nickel, arsenic, chloride, thiourea and glue. Finally, the role of non-commercially utilized additives, such as bromide and polyethylene glycol were studied. From this investigation, electrolyte parameters that inhibit copper dissolution through copper sulfate precipitation, copper oxide stabilization and/or absorbed species lead to accelerated passivation. Species that prevent passivation have the ability to complex cuprous ions. Possible mechanisms for the role of each.

Jan 1, 2007

By Tom Shumka

All mineral processing facilities that use girth gear driven mills need to inspect the gear teeth on a routine basis, whether it is every six months or every three years. The inspection frequency depends upon gear tooth condition, and the objective is to ensure operational integrity of the gear teeth. Conventional methods such as magnetic particle testing, visual inspection, or dye penetrant examinations rely heavily on interpretation. At best, these techniques can determine whether a defect exists, but are unable to provide information on defect severity. This paper describes the use of combined Eddy Current Array (ECA) and Alternating Current Field Measurement (ACFM) to provide a complete survey of all surface breaking indications on the whole gear tooth depth. This method accurately determines the size, length and depth of any cracks found on the surface.

Jan 1, 2012

By Christopher McElman

Real-time mine management solutions have evolved over time from closed, proprietary solutions, to a "system of systems" that may include a wide variety of off-the-shelf components and technologies. Modular Mining Systems has embraced open standards for their NextGen products to bridge the technology gaps between these systems. However, the remaining logical gaps must be overcome, in order to achieve truly seamless integration between discrete systems. When dealing with volatile real-time management problems, the effectiveness of business process modeling and middle-ware can break down. Scientific principles of military command and control applied to mining domain help to achieve better alignment and reach the highest level of integration. The combination of open standards and off-the-shelf hardware and software with a deliberately structured command-and-control approach provides a clear evolutionary path from ad-hoc connected systems towards real-time management of a seamlessly integrated digital mine.

Oct 1, 2009

By I. M. Santos Moraes

The control of minor impurities (mainly As, Sb and Bi) in copper refineries has been a great challenge. Caraiba Metais' copper refinery produces a very high quality copper, registered in LME as grade A, and recognized as amongst the top ten in the copper world. At Caraiba's Tankhouse Bi and Sb are controlled by means of electrolyte bleed-stream removal after partial decopperizing in a set of electro-winning cells (liberators). Another way of reducing the Sb and Bi content in the electrolyte is by means of the arsenate precipitation chemistry. It is well known that the use of high arsenic concentrations in copper refinery electrolyte has the advantage of causing most of the bismuth and antimony to report in the anode slimes. However, the use of such mechanism of control may contribute to other undesired problems such as antimony and bismuth precipitation in the bulk of the electrolyte, what may cause severe contamination problems. This paper describes a period when some cathode contamination with Sb occurred at Caraiba Metais' Copper Refinery. It also presents an analysis of several process parameters related to the problem, the possible causes for the contaminations as well as the actions taken to correct the problem.

Jan 1, 2007

By D. A. Livingstone

"INTRODUCTORY REMARKS BY PANEL CHAIRMAN - D. A. LIVINGSTONEThe mining industry has progressed significantly from the dusty mines and mills of decades past to the modern processing complexes of today, and improved technology has made great strides in eliminating debilitating lung discuss. More recently, the public's environmental awareness is also working to enforce more stringent regulations and controls in tl1e matter of dust in working places.There are numerous excellent texts and handbooks outlining the principles of collection of dust produced in the various unit operations entailed in the crushing, screening and the transport of ore. However, it is painfully obvious that dust emanating from belt return idlers and scrapers, take-up pulleys, skirting, larger and deeper chutes, clean-up operations, etc., which I choose to refer to as fugitive dust, presents some seemingly unmanageable difficulties, or at least difficulties inordinately costly to correct. Possibly static electricity is adding to the difficulties. In my view, these problems are magnified in many of our B. C. operations where ore from open pit mines in cold climates is frequently crushed in unheated buildings, thereby precluding the simple and obvious use of water sprays for dust suppression.It is hoped that the presentations and discussion which follow will emphasize some of these unusual problerr.s and suggest corrective measures, either tried or planned."

Jan 1, 1976