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By T. Yalcin

"This paper describes the development of a process flowsheet designed to provide high dewatering rates and to bring about savings in tailing disposal costs. The flowsheet comprises a hydrocyclone, a settling cone and a thickener arranged in closed circuit. The mill tailing, after pulp density adjustment, is fed to the hydrocyclone which yields two products. The underflow product is sent to the settling cone for further dewatering. The overflow product, together with the settling cone overflow, goes to the thickener which, with the aid of flocculants, gives a clear effluent and a relatively dilute underflow. The latter combines with the original mill tailing to form the hydrocyclone feed. Solids finally leave the system in the settling cone underflow which can reach pulp densities of up to 78%, making it suitable for direct disposal or for use as mine backfill.Some discussion is included for the selection and sizing of equipment required for this process. INTRODUCTIONDewatering is an essential process for the disposal of mill tailings which forms an added burden in milling practice, often with little or no return. It is, therefore, desirable to conduct this process as economically as possible. One way of reducing costs would be to increase the rate of dewatering so that savings can be made in the size of dewatering unit s which would lead to lower capital and operating expenditures.A common method of dewatering mill tailings is gravity sedimentation which is frequently carried out with the aid of flocculation. In most cases, flocculation greatly enhances the sedimentation process, but only until a pulp density of 50% to 55% is reached in the settled material.Centrifugal sedimentation in hydrocyclones can provide high pulp densities rapidly, but does not result in a clear effluent.This paper outlines a suitable combination of gravity and centrifugal sedimentations that results in an over-all high rate of dewatering. The system developed produces a material of high pulp density while at the same time giving clear effluent."

Jan 1, 1989

By Jan Rosenkranz, Anders Sand, Lisa Malm, Nils-Johan Bolin

Within flotation technology the general trend is towards very large cells. Scale-up is usually done by postulating geometrical similarity, which implies keeping the aspect ratio constant when increasing cell volume. Consequently, the design of flotation circuits typically involves several cells of identical geometry within a bank. Using a few standard sizes in a flotation plant simplifies design, manufacturing and maintenance of the cells, but does not necessarily guarantee optimal performance and selectivity of the flotation process. Geometry parameters for a given cell volume that influence flotation cell performance include cell height, which causes changes in the hydrostatic pressure and suspension hydrodynamics, and also influences the travel distance of particle-bubble agglomerates as well as the homogeneity of the mixing. Also the thickness of the froth layer depends on the aspect ratio of the cell. The objective of this work is to gain a better understanding of material distribution and properties within a flotation cell and, based on this information, elucidate how alterations of the cell geometry can influence separation efficiency. For this purpose systematic measurements and analyses of the spatial distribution of the different phases within a 160 m3 flotation cell have been carried out with a particular focus on an industrial, low-grade copper ore beneficiation process. The concepts for sampling at different vertical and lateral positions of the flotation cell are introduced. The results from the experimental work give an understanding of internal material distribution within flotation cells. Based on the measured phase distribution and concentrations as well as particle properties at various positions within the cell, the implications for an optimized scaling and design of individual flotation cells within a flotation circuit are discussed.

Jan 1, 2016

By C. Chapman, P. Cowx

"INTRODUCTIONTetronics Research and Development Co. Limited has installed several plasma torches for steel heating in continuous caster tundishes. An extensive demonstration program on a 14 tonne tundish reported the following advantages of plasma heating.• close control of steel temperature to ± 5°C;• a reduction of the furnace tapping temperature of up to 20ºC, leading to savings in energy and refractories costs ;• improvement in steel quality, to produce a slab product with an equi-axed crystal structure and a reduced number of large sub-surface slag inclusions;• the virtual elimination of oxygen pickup in the tundish; and• the capability of making ferroalloy trim additions to the tundish to permit a change of steel grade during casting, greatly decreasing inventory costs.The Need for Tundish HeatingIn the continuous casting of steel, the function of the tundish is to transfer the molten metal between the ladle to one or more continuously fed casting moulds. Figure I shows a typical temperature profile of molten steel in the tundish over the first cast cycle. It is observed that a rapid drop in temperature occurs both at the start of the cast, due to the tundish refractories absorbing heat, and also during ladle changeover. In addition, as a result of thermal losses through the ladle sidewalls, there is a gradual decline in the bulk steel temperature over the entire heat cycle. Consequently, in normal tundish operation, it is necessary to cast with a high superheat (25°C to 30°C + above steel liquidus temperature) in order to prevent freeze-up of the strand. Problems of high temperature variation and the potential of the steel solidifying in the tundish are greater for small caster units of low thermal mass . A high steel superheat increases the steelmaking vessel process time and refractory wear and prevents the formation of a uniform equi-axed solidification structure in the cast steel, resulting in centre line segregation and porosity. The large drop in the casting temperature that occurs during unsteady state operation causes an increase in the number of sub-surface inclusions, reducing the value of the product. Accordingly, plasma heating may be employed to maintain the molten steel at an optimum temperature to produce a slab of consistent quality."

Jan 1, 1989

By J. B. Heslop, D. S. Bubar

"The Gondor Zn-Ag-Pb-Cu deposit is a stratabound massive sulphide lens occurring within Archean volcaniclastic rocks of the Yellowknife Supergroup. The deposit is located in the west-central portion of the Slave Structural Province, approximately 350 km north of Yellowknife.Initial diamond drilling at Gondor has outlined a steeply dipping, L-shaped, folded, massive sulphide body, which may be traced over a strike length of approximately 800 m, and to a depth of 350 m. True widths of up to 40 m have been intersected in the thickest part of the deposit. Preliminary estimates suggest that the deposit contains a minimum of 7.5 million tonnes grading 6% Zn, 50 g/tonne Ag and less than I% combined Cu and Pb. In addition, significant gold, grading up to 2.8 g/tonne, occurs in some parts of the deposit. The mineralization is open both down-dip and along strike.The Gondor deposit lies conformably within a predominantly east-west striking, north-facing sequence of felsic to intermediate volcaniclastic rocks. Coarse fragmental rocks are abundant in the hanging wall, whereas ash and lapilli-tuffs predominate in the footwall. The main structural feature in the area is a large-scale, steeply northeast-plunging, Z-shaped fold. The sulphide mineralization lies within the synformal portion of this fold, with the thickest part of the deposit coinciding with its hinge zone. Several episodes of faulting have also affected the local stratigraphy.The wallrocks of the Gondor deposit were hydrothermally altered prior to the onset of medium-grade regional metamorphism. A halo of altered rocks surrounds the massive sulphide lens, with no apparent difference in the degree of alteration between the hanging wall and footwall strata. The alteration zone is characterized by the addition of MgO and K20 and by the depletion of Na20 and CaO. These changes are reflected in the mineralogy of the altered wallrocks by local enrichment in chlorite, biotite, muscovite and cordierite.The mineralized zone is medium- to coarse-grained, well-banded and is composed largely of pyrite, quartz, and sphalerite with subordinate galena and chalcopyrite. Preliminary studies of metal distribution indicate that a lateral zonation is present, with lead enrichment in the central part of the deposit, and copper enrichment toward both ends. Stringer-type copper mineralization has not yet been discovered in the footwall of the Gondor deposit."

Jan 1, 1985

By L. Vollert

"The application of pneumatically-assisted fluidized bed flotation, specifically the ERIEZ HydroFloatTM technology, has found widespread use in non-sulphide processing (particularly phosphate, potash and coal) for the recovery of coarse particles. In gold processing, centrifugal gravity circuits and flash flotation cells are typically employed for the recovery of coarse and near-size liberated gold which tends to accumulate in recycled grinding streams due to bypass to the classifying cyclone underflow streams owing to the higher specific gravity of these gold particles. Early removal of this gold from the grinding circuits contributes toward the reduction of downstream processing losses as a result of overgrinding and particle shape deformation in the case of flotation processing, longer leach residence times in the case of extractive processing, and surface occlusions in the case of both flotation and extractive processing. Furthermore, recovery to bullion attracts higher payment terms by way of comparison to concentrate sales in the case of copper-gold concentrators. This paper assesses the application of pneumatically assisted fluidized bed flotation for the recovery of coarse liberated gold through the analysis of piloting data generated from the operation of a continuously operated 16 inch ERIEZ HydroFloatTM unit treating a sized coarse grinding circuit stream. The paper presents the stage recovery by size performance of the ERIEZ HydroFloatTM unit together with quantitative gold deportment analysis to demonstrate the efficiency with which gold was recovered during this pilot campaign and then compared to more conventional processing units – centrifugal gravity and conventional flotation.INTRODUCTION Newcrest Mining Limited (NML) has identified that an opportunity exists for improving the recovery of coarse composite particles at its current operations, both as a means for improving overall recovery and as an opportunity for early gangue rejection. As such, Newcrest Mining Limited has taken an interest in the application of pneumatically-assisted, fluidized-bed flotation i.e. ERIEZ HydroFloatTM technology. This interest dates back to 2011 with sighter testwork carried out on their Australian-held ore bodies (Kohmuench et al, 2013). Newcrest continues to assess ERIEZ HydroFloatTM potential for coarse composite recovery and, in the case of the topic of this paper, coarse gold recovery based on examples in the literature which demonstrate the efficiency of this technology in this regard (Carmona Franco et al., (2015); Miller et al., (2016); and Kohmuench et al, 2013)."

Jan 1, 2017

By A. Diaz, Minera Los Pelambres, C. G. Salinas, G. Leinenweber, F. Diaz, D. Rojas, R. Bernal, O. Jimenez

"Los Pelambres Mine (MLP) is located in the IV Region of Chile, a semi-arid region where water plays a key role in operations as a scarce resource and is vital for the sustainability of human life, animals and ecosystem. The conventional flow meters installed on pipes at MLP can fail to provide an accurate measurement due to corrosion and/or fouling on the inner wall or presence of elements in the water such as acids, salts and suspended solids. Conventional flow measurement methods require the inner diameter to be known, however it is not always possible to assess its real value due to scaling, fouling, corrosion, etc. Here we present a novel methodology to solve these problems, which consists of the measurement of flow by a method that does not require the internal area of the pipes: the fluorescent tracer dilution method. In addition, the fluid velocity can be determined by the transit time of a radioactive tracer method. With the flow rate and velocity, the equivalent area is determined and thus the equivalent internal pipe diameter as well. This methodology was applied in a recirculation pump station, for mineral processing from the El Mauro tailings dam.This work demonstrated adequate correlation between measurements from fluorescent tracers and velocity measurements from radioactive tracers, both of which lead to the assessment of the internal diameter of pipes with scaling. The results of both methods disagree with the data provided by the flowmeter installed on the line due to its miscalibration. This information is useful in validating and correcting the information provided by online flowmeters of all water and solutions transport processes in filled pipes.INTRODUCTIONPresently, the need to optimize water resources is increasingly ever important, due to various reasons such as water scarcity, community empowerment, an increased use of water for mining processes and environmental considerations. Taking into account those main considerations, Los Pelambres Mine decided to focus on water conservation to avoid losses of this vital element. They decided to demonstrate that all of the systems that used water (flow meters, pipes, pumping stations, lagoons, etc) were in good condition and that no evitable loses of this important resource occurred. A plan was proposed to conduct a “hydraulic assessment” of fluid flux and water speed at different points and courses at the mine, with the purpose of obtaining hard data to support, verify and correct the information provided online from specific instrumentation dedicated to those purposes. The final goal was to manage the water resource basin in a sustainable way, based on cross-checked information. The chosen points are representative of the processes present in the mine, such as recirculating water stations at different operating conditions and surface water courses, where the fresh water capture systems operate."

Jan 1, 2016

By A. A. Lavrinenko, N. I. Gluhova, L. M. Sarkisova, D. V. Makarov

"The investigated sulfide Cu-Ni ores are characterized by low PGE contents and emulgated impregnations of pentlandite and palladium minerals in the main ore-forming mineral pyrrhotite, which hinders their selective separation, requiring a collective flotation of sulfides to concentrate, and hydrometallurgical processing. As revealed by studies of floatability of Pt-Cu-Ni ore in a mixture of butyl xanthate and chelating phosphorus containing reagents, the most effective additive is Aerophine 3416 (a phosphinates mixture) manufactured by Cytec. Using collective flotation with a butyl xanthate – Aerophine 3416 composite in the ratio of 1:3 has afforded to enhance the Pt, Pd, and Ni recovery by 13.6 %, 9.2 %, and 9.4 %, respectively. The optimal ratios of Aerophine 3416 to butyl collector for the collective flotation are the following: 1:1 for Pt and Pd and 3:1 for Ni. The effect of these reagents on the electrode potential and surface hydrophobicity of pyrrhotite, pentlandite, and platinum black has been investigated. The extraction UV spectrophotometry experiments demonstrate that DIBDTPI exists on the pyrrhotite surface mainly in the form of disulfide in weak acid medium and in the form of compounds with Fe on the mineral surface in minute amounts. There appears some disulfide and few amount of (DIBDTPI)2Ni on the surface after interaction of DIBDTPI and pentlanditeINTRODUCTIONXanthates are widely used in flotation of copper-nickel ores containing platinum group metals (PGM) as sulfides collectors which can concentrate the most part of PGM connected with the sulfides. Though xanthates are hardly efficient for flotation of free PGM, the latter are floated more slowly compared to the sulfides of base metals. The reasons for poor floatation of free (mineral) forms of PGM are under-researched, however the key accepted reasons are: fine disseminations of free PGM, insufficient interaction with xanthate and negative influence of blue copperas and sulfur-containing ions which are sulfides oxidation products (Penberthy et al. 1999; Shackleton et al., 2007). That’s why an additional collector, normally dialkyldithiophosphates, is used during flotation of PGM-containing copper-nickel ores. A reagent DP-4 is used for recovery of PGM at Norilsk mining and metallurgical plant. The reagent represents a slightly-soluble organic calcium sulfonate which is given to flotation pulp in the form of water emulsion of 5% - solution in automotive diesel oil."

Jan 1, 2016

By J R. Barber, B. E. Rogers, R. Fukuzawa

Mercury is sometimes present in non-ferrous ores including gold, zinc, copper and lead. The selection and use of appropriate mercury abatement technology is critical for preventing its release to the environment during ore processing and to protect workers from mercury exposure. This paper presents a general decision-making process for mercury abatement technology selection for major emission sources in the gold industry. Mercury abatement can be accomplished through making process changes and/or by adding a process step to an existing system (i.e. "end-of-pipe control"). Advantages and limitations of the technologies along with waste / by-product management options are discussed through case studies of current operating mercury abatement systems.

Jan 1, 2015

By N. Hosking, M. Nichols

Aluminum alloys are increasingly used for automotive body construction but are susceptible to filiform corrosion or paint blistering in service. Filiform corrosion resistance of two 6000-series aluminum alloys was investigated in this work. Test panels were produced with full automotive coating layers and scribed parallel and perpendicular to the rolling direction. The corrosion exposure comprised an inoculation step with acidified salt solution followed by a 6-week exposure period at 95% relative humidity and either 25°C or 70°C. Greatest corrosion activity was measured on the alloy with higher copper content, AA6111. Higher temperature exposure led to greatly enhanced corrosion activity for AA6111 compared to the lower temperature exposure. The 70°C exposure also led to greater mean corrosion-affected area measurements for the low copper aluminum alloy, AA6022, but the effect was not as stark as that observed for AA6111. Rolling direction affected the propagation direction, and possibly mechanism, of the corrosion effects. Cross-sectional analysis revealed dense corrosion products within the filament, comprising mostly aluminum and oxygen but with traces of chloride and sulphate. Development of varying filament and blister types on a single test panel and the progression of corrosion underneath a filament into the substrate indicate that several corrosion mechanisms can develop on the test panel, testament to the complexity of the corroding surface developed on an aluminum automotive body panel.

Jan 1, 2015

Accurately modeling and predicting long term mill throughput is one of the challenges facing metallurgists, geologists and mine engineers in their quest to consistently deliver accurate life of mine business plans. Batu Hijau has systematically improved long and short term mill throughput predictions since feasibility and commissioning in 1999. This has been achieved through a combination of ongoing improvement to the geology ore hardness and grade characterisation model, drill and blast optimisation and, by application of these data to model mill throughput. Batu Hijau has demonstrated the ability to consistently estimate long term mill throughput within ±2% accuracy. Aside from reliably predicting expected production rates with the existing plant configuration, this predictive ability provides a solid foundation for identifying operating and design criteria for short term grinding circuit optimisation and future expansions. This paper discusses ongoing throughput prediction model development at Batu Hijau based on geo-metallurgical characterisation. Also discussed are tools used for day to day production performance management. This includes on line "Mine to Mill" variable monitoring to improve operations parameter ecision making and performance assessment.

Nov 1, 2011

By F. Wirfiyata

"Accurately modeling and predicting long term mill throughput is one of the challenges facing metallurgists, geologists and mine engineers in their quest to consistently deliver accurate life of mine business plans.Batu Hijau has systematically improved long and short term mill throughput predictions since feasibility and commissioning in 1999. This has been achieved through a combination of ongoing improvement to the geology ore hardness and grade characterisation model, drill and blast optimisation and, by application of these data to model mill throughput.Batu Hijau has demonstrated the ability to consistently estimate long term mill throughput within ±2% accuracy. Aside from reliably predicting expected production rates with the existing plant configuration, this predictive ability provides a solid foundation for identifying operating and design criteria for short term grinding circuit optimisation and future expansions.This paper discusses ongoing throughput prediction model development at Batu Hijau based on geo-metallurgical characterisation. Also discussed are tools used for day to day production performance management. This includes on line ""Mine to Mill"" variable monitoring to improve operations parameter decision making and performance assessment."

Jan 1, 2012

By J. Ouellet

The authors participated in a study for a new mine shaft in Saskatchewan?s Athabasca Basin where ground freezing is desired to reduce water inflows. Constraints were imposed on the design in terms of permissible water leakage (less than 10 m3 / hour) inside the shaft. Since the shaft goes through highly permeable formations, water control measures had to be incorporated into the design. Ground freezing was selected as the most reliable and proven method for the sinking and a hydrostatic liner design was implemented. While exploring various technological options available for providing a fully hydrostatic liner, the authors came up with a new design concept that offers a more cost effective solution while meeting all the design constraints. The new liner concept is a composite design using concrete and a sprayed-on membrane system. A proof of concept program comprising laboratory testing and field testing was successfully implemented. This paper presents the innovative liner design, as well as the adapted sinking methodology, developed for this type of project. The new concept offers a new cost effective high performance hydrostatic mine shaft liner comparing favorably with traditional methods. RESUME: Les auteurs ont réalisé une étude pour un nouveau puits de mine dans le Bassin de l?Athabasca en Saskatchewan. Des limites sévères sont imposées sur le design en terme de volume d?infiltration d?eau acceptable (moins de 10 m3 / heure). Comme ce puits de mine traverse des formations très perméables la congélation des terrains a été sélectionnée, une méthode éprouvée et fiable. Un design hydrostatique a été choisi pour le revêtement du puits. Dans le processus de design, les différentes technologies disponibles ont été étudiées. Les auteurs ont développé un nouveau concept de revêtement composite offrant un rapport performance/prix plus avantageux que les technologies conventionnelles. Le nouveau design proposé est composé de béton et d?une membrane projetée. Un programme expérimental a été réalisé pour démontrer la faisabilité du concept. Cet article présente le nouveau concept ainsi que la méthodologie de fonçage de puits adaptée. Ce concept innovateur offre un revêtement hydrostatique performant à un cout avantageux par rapport aux techniques de construction utilisées jusqu'à maintenant.

Jun 1, 2012

By E. Henderson

"This paper outlines the upgrading of a double-drum 2000 hp cage hoist to provide fully-automatic operation from shaft station control panels. The application utilizes programmable controller technology to provide all necessary functions for movement of personnel and material to 22 locations in a 4000 ft shaft.Various functions involving special design considerations such as ""chairing"", ""jogging"", and three modes of ""multi-level calling service"", are outlined. The use of higher level PLC functions to optimize memory utilization and simulate ""elevator service"" required the addition of a comprehensive fault finding software section to aid in troubleshooting.This paper will deal primarily with the automation portion of the project with references made to other pertinent aspects which were prerequisite to automatic operation. It is not intended to deal with every design detail, but rather to provide an overview of what can be done in the area of automation for those considering such an application. INTRODUCTIONEarly hoisting control systems provided only the essential elements of control, leaving many responsibilities with the operator. With advancements in various areas of technology, electromechanical devices were incorporated to enforce slow-down in end zones, control acceleration rates, monitor safety devices, etc. Brake control systems were supplied to allow for ""single-stick"" operator control, regulated deceleration during emergency brake applications, etc.These additions enhanced the over-all performance but were generally confined to speed and current regulation. Some mechanical devices, such as travelling nut limits, etc.; were used to provide ""position"" control to multiple locations within the shaft. These devices, in conjunction with rather extensive relay control panels, did allow for the establislunent of some automatic cage hoists . The hoists were often limited to service from point ""A"" to point ""B""', involving a limited number of levels due to the complexities of the mechanical interfaces employed. Only limited systematic work sequences were possible . .Programmable Logic Controllers (PLCs) were introduced into industry in the mid-70s and have since gained acceptance in mining applications such as pumping, ventilation, ore handling, etc. This technology, being ""software"" based, allows complexities to reside in the program rather than increasing the number of physical control elements. This has opened the door into hoisting systems for automatic loading and hoisting of ore as well as a means to achieve a comprehensive package of automated cage hoisting functions."

Jan 1, 1989

By Kevin P. Plucknett, Z. Memarrashidi

"In the current work, factors influencing the corrosion mechanisms of TiC and Ti(C,N) based cermets are reviewed. Cermets were typically prepared with 30 vol.% of metal binder, in the form of various in-situ reaction-formed Ni3Al alloys. Commercial WC-Co hardmetals were also examined as baseline materials. The assessment of corrosion involved a variety of electrochemical measurements, including open circuit potential and potentiodynamic polarisation. The corrosion potential and current density were determined, following Tafel extrapolation, allowing estimation of the corrosion rates. Post-corrosion characterisation involved scanning electron microscopy analysis and associated energy dispersive X-ray spectroscopy of the sample surfaces. It is demonstrated that the primary corrosion mechanism for this type of cermet is dissolution of the metallic phase during oxidation attack, and thus this response can be expected to increase with the amount of binder in the cermet, although degradation can be subtly affected by composition (i.e. alloy composition, C:N ratio, impurities in the ceramic phase, etc.) and test procedure (i.e. aerated vs. de-aerated electrolytes). It was observed that addition of N content into the ceramic phase is beneficial to the corrosion characteristics of TiC based cermets, through significant refinement in the grain size of the hard phase. Similarly, elimination of impurities, such as W in selected TiC powders, also improves the corrosion resistance.INTRODUCTION Cermets are prepared using the combination of a hard, high elastic modulus ceramic phase with a ductile, high toughness metallic binder. This pairing of hard and ductile components ensures wide application of cermets in demanding wear environments. These materials are consequently used industrially in both bulk and coating form. The most common example of such a composite system is based on the use of tungsten carbide with a cobalt-based binder (WC-Co), which has been widely examined over the past 80 years. However, while WC-Co has been shown to exhibit an excellent combination of high strength and wear resistance, the corrosion and high temperature properties of this material are relatively poor. In addition, WC-Co possesses a high density (~13–14 g/cm3), which makes it a less desirable option when the component mass is a design factor (i.e. use in aerospace). In particular, the aqueous corrosion response of WC-Co limits its use in wear environments where combined corrosive degradation may occur (i.e. tribo-corrosion scenarios). Alternate cermet systems are therefore being actively developed due to these performance limitations."

Jan 1, 2017

By F. Henríquez, V. Iriarte, L. Vinnett, J. Yianatos, F. Díaz

Metallurgical characterizations of the collective (Cu/Mo) and selective flotation plants were carried out in Minera Los Pelambres, Chile. The selective plant allows the valuable minerals of Cu and Mo to be separated. The evaluation involved two surveys consisting of metallurgical sampling as well as residence time distribution (RTD) measurements to determine load distribution. The RTD data were obtained in real-time by means of the radioactive tracer technique. In addition, metallurgical data was reconciled and supported by effective residence times. In the collective plant, a performance comparison of parallel rougher circuits was carried out, which included a bank of six mechanical cells of 250 m3 and banks of nine mechanical cells of 130 m3. In the selective plant, the Cu and Mo evolution along the plant was evaluated. The results in the selective plant allowed for performance evaluation of mechanical and pneumatic cells in primary flotation. In both plants, mineral losses were evaluated and their relationship with circuit configuration (cell types and circuit layout) was determined. The metallurgical characterization was a powerful tool to evaluate circuit performance and to detect improvement opportunities at industrial scale.

Jan 1, 2015

By K. Enns, J. J. Byerley

"While thiocyanate (SCN-) is used in a number of industrial processes (production of polyacrylonitrile filaments, synthesis of agricultural chemicals and certain metallurgical solvent extraction and flotation circuits) it is recognized more as an undesirable by-product associated with ' the metallurgical industry. Thiocyanate is present at low concentrations in some waste streams from the iron and steel industry. Of particular significance is the formation of thiocyanate during cyanidation of gold and silver ores, concentrates, tailing s and residues. The thiocyanate levels present in the resulting effluents may range from a few mg/I to several thousand mg/I.At present, thiocyanate does not appear to be as hazardous in the environment as cyanide (CN-) at the same concentration although its interaction with other species and resulting decomposition of products may be unacceptable. Of course the presence of thiocyanate in the leaching circuit and ultimately in the effluent streams may add considerably to the oxidative requirments of any non-selective treatment process for cyanidation wastes.With respect to the thiocyanate as it relates to the cyanidation process, two aspects are evident. Thiocyanate forms and persists in the cyanidation circuit resulting in a ""fouling"" condition with subsequent loss of leaching activity. In order to reduce or control this problem, it is common practice for some mills to discharge daily as much as 20% of the barren leach liquor. Besides contributing to fouling of the leach liquor the formation of thiocyanate represents an irreversible loss of reagent cyanide. It is noteworthy that in some present or proposed mill practice reagent cyanide loss through thiocyanate formation may reach 50%(1). The purpose of this paper is to discus s the application of controlled electrooxidation of thiocyanate with the view of suggesting a process for regenerating cyanide from waste thiocyanate(2). The paper describes the important theoretical aspects and presents experimental data obtained for thiocyanate electrooxidation using both small and large scale electrochemical reactors. Some economic conclusions are presented."

Jan 1, 1984

By W. N. Roman

This paper will examine the challenges involved in ventilating and cooling South African mines, with particular emphasis on solutions to the issues of heat (generally associated with depth), mechanization and energy efficiency. Comparisons will be made with other international mining areas. Some of the deepest mines in the world are to be found in the South African goldfields. The Mponeng mine is approaching 4,000 m below surface, with virgin rock temperatures (VRT) of between 60°C and 70°C. Mining at these depths has only been possible with the use of large refrigeration plants supplying cold air, water and ice to the workings. In the Bushveld Igneous Complex, where most of South Africa?s platinum mines are located, similar VRTs are being experienced at significantly shallower depths. This is due to the different geothermal properties of the host rock between the two areas. Existing mines are being forced to go deeper and new underground mines are being planned and constructed in other areas with widely differing thermal conditions. South African metal mining has traditionally been labour intensive for historical reasons as well as for the narrow tabular nature of many ore bodies. Due to cost pressures and labour problems, some mines have been investigating the possibility of using mechanized equipment, both diesel and electric, to increase production and to improve efficiency. Studies have been carried out to determine the effect of the additional equipment on the overall ventilation system and some of the conclusions are discussed. The use of diesel equipment adds heat and pollutants to the ventilation air but, although electrical equipment has a lesser effect on the ventilation systems, it is generally less favoured due to claims of lower flexibility/manoeuvrability. Mechanization holds the promise of more concentrated mining activities but, with higher localized ventilation and cooling needs. Systems which will control the provision of air and cooling more effectively are required and are being implemented. In the 1990s and early 2000s, the South African economy experienced significant growth which was not matched by the growth in infrastructure. Consequently, at present there is a shortage of electricity generation capacity which affects large industrial consumers, including mines. Increasing levels of heat and mechanization will require more electrical energy for ventilation and cooling. There are many initiatives underway to save power or to shift consumption to periods of national low demand and these will be described.

Aug 1, 2013

By Donald Roberts

"Parameters f or design and development of an emergency hoist system (Fig. I) were submitted to Timberland Equipment Limited of Woodstock, Ontario by the Potash Corporation of Saskatchewan Mining Limited.The unit is the first of its kind in Canada. Not only does it comply with the province of Saskatchewan's mining regulations, but has the added advantage of being completely mobile and self-contained.As well as being useful in the mining industry, the mobile hoist unit could be used in other emergency situations such as rescuing people trapped in wells.JustificationRevisions to the Mines Regulations under Section 13 of the Occupational Health and Safety Act, 1977, of the Province of Saskatchewan stipulate as follows:"" Section 410 .04(4) The Mine Employer shall make adequate provision at every mine where any worker is hoisted in a shaft not equipped with a manway to enable an y such worker trapped in a conveyance in the shaft to be rescued . "" It was not possible to equip the shafts at PCS Mining' s Divisions with "" manways"" and therefore an alternative was required.BackgroundThe Potash Corporation of Saskatchewan Mining Limited, a subsidiary of the Potash Corporation of Saskatchewan, operates four potash mines. Of these, three, Cory, Rocanville and Lanigan Divisions are wholly owned while the fourth, Allan Division, is 40% owned by Kidd Creek Mines Ltd., but managed by PCS Mining. The four underground operations all have a service and production shaft.From 1979 to 1981 the PCS Mining Division, along with Central Canada Potash, were developing an idea to use the existing ground-mounted timberland hoist at Lanigan as an emergency hoist. This hoist was used in the past for rope-up work at both Rocanville and Lanigan and other potash mine s. The Department of Labour at this time had concerns about the time it would take to load, t ran sport and re-install the hoist on a foundation when needed for an emergency. Weight and size made this particular unit very cumbersome for transporting.In addition, the speed at which this hoist operates is too slow for rescue work. When the Department of Labour expressed concern that this unit would be unsuitable for these rea sons, a search for a suitable unit was initiated.The project responsibility for procuring an emergency hoist for the Potash Corporation of Saskatchewan Mining Limited was assigned to the author, a shaft/ hoist specialist a t PCS Mining."

Jan 1, 1986

By Sandeep Singh Sandhu, Karanvir Singh Ghuman, Manjit Singh

"Cobalt based super alloy stellite 6 was weld cladded on AISI 304 L stainless steel using SMAW process in order to improve the wear resistance for tyre crusher blades. Microstructure characterization and micro hardness testing was performed on stellite 6 cladding. The suitable parameters viz. 80 Amp current with arc weaving technique was selected by performing bead on plate experiment were further used for depositing multipass multilayer cladding to achieve full filler chemistry at the top surface. Further GTAW process was used for re-melting the top surface of the cladding. Comparative evaluation of the claddings showed that TIG re-melting resulted in increased microhardness and wear resistance in comparison to as cladded specimens even with lesser deposition of material. It was observed that TIG re-melting improved the hardness from 603 HV0.5 kg to 712 HV0.5 kg. Micro structures of stellite 6 contained cobalt solid solution matrix along with inter dendrite chromium carbides which resulted in the increased micro hardness values. Pin on disc abrasion tests were carried out at room temperature and the worn out surfaces were characterized using SEM and EDS.INTRODUCTIONThe crusher blades are used in many industries for crushing various types of material and its wider applications in tyre rubber crushing mills, metal-powder crushers industries etc. Most of the crusher blades are damaged by the wear and impact loading conditions. It is because of metal to metal abrasion and the temperature also plays a vital role in blunting the cutting edges of these blades. The wear is the major cause which leads to loss of material and thus the productivity that can never be recovered (Kotechi et al., 1992). The wear can be reduced by coating of various super alloys which could reduce the behavior of metal degradation even in aggressive environments. Cladding of cheaper low alloyed material with expensive superalloys to enhance the performance of components at low cost has been investigated by many scholars (Deng et al., 2010, Kennametal, 2007, Lolla et al., 2014, Singhet al., 2014, J.N et al., 2003, Ramkumar et al., 2012). Many researchers have reported that cladding is an application of build-up deposits of specialized alloys to resist abrasion, high temperature corrosion and impact loadings. Cladding is used for providing required mechanical strength properties as well as inhibition of oxidation and other corrosive degradation. Coatings are used to protect the heat affected areas like tubes of fluidized bed combustor etc. (Kirchbner et al., 2008, Wang et al., 1994, Hocking et al., 1993, Ananthapadmanabhan et al., 1991, Staia et al., 2001). Coating techniques are widely used for the protection of turbine engine and boiler tubes against high temperature corrosion attack, power generation equipment, chemical process equipment, aircraft engines, pulp and paper processing equipment, bridges, rollers and concrete reinforcements, orthopedics and dental, land-based and marine turbines, ships. Coatings of stellite 6 are widely used in steam turbine blades and boiler tubes for power generation because of an excellent combination of impact, wear and other properties. It can maintain its properties even at high temperature and in harsh environments (Kobayashiet al., 1999, Alam et al., 2009, Munehru et al., 2009). The loading and unloading conditions experienced by the material may induce the surface cracks which lead to its breakage and leaving large pits in the surface (Meng et al., 1995). Many researchers have reported that the properties of cladded layers can be increased by various techniques such as controlling the current variations, dilution, heat input, laser and other re-melting processes, addition of special alloying elements, speed of weldingetc(C.M Anaet al., 2002, Kumaret al., 1999, Luo et al., 2012, et al., Madadi et al., 2011, Shin et al., 2003, Kuzucu et al., 1997, Sudha et al., 2008, Sawant et al., 2017, Houdkova et al., 2016, Ciubo"

Jan 1, 2017

By D. M. Maijer, S. L. Cockcroft, A. B. Phillion, P. Fan, C. Reilly

"A numerical model has been developed to study macrosegregation associated with liquid feeding in the Low Pressure Die Casting of A356 aluminum alloy wheels. The model of the wheel casting process has been implemented within the commercial CFD software package, FLUENT, using a User Defined Function (subroutine) to account for Si rejection based on the Scheil approximation. The model has been validated against temperature and microstructural data taken from a commercially cast wheel. The amount of segregation in the wheel has been shown to be significant in a couple of key areas. The implications of accounting for segregation include an improved ability to predict shrinkage porosity, fatigue performance and potentially also hydrogen porosity.INTRODUCTION The aluminum alloy A356 is widely used in the automotive and aerospace industries for various components. Examples include automotive wheels, automotive suspension components and airframe castings. Focusing on automotive wheels, Low-Pressure Die Cast (LPDC) A356 wheels offer significant design freedom and are far more aesthetically appealing to consumers than conventional stamped steel wheels. A356 wheels now dominate the market, appearing in all but the entry level offerings of the OEM manufacturers. However, they are typically over-designed to allow for the various casting related defects that degrade their mechanical performance. Thus, their potential to save weight has not been fully realized. Wheel manufacturers are under constant pressure to ensure their products meet strict mechanical requirements (ductility, fatigue, vibration), tight geometric tolerances and high aesthetic quality. The mechanical properties of the final product are determined by the microstructure – e.g. SDAS – and the defect population (porosity and oxides). Depending on their size and location, both porosity and oxides, can act as crack initiation sites reducing fatigue life (Caton, 2001; Jordan, 2010; Wu, 2015). There are a number of examples appearing in the literature (Atwood, 2000; Carlson, 2007; Lee, 2001; Yao, 2011) of numerical models that have focused on hydrogen-based pore formation that have demonstrated an ability to predict porosity formation and pore size distributions in geometrically simple castings. These models assume that the local gas species diffusion through the liquid metal to the pores is the rate-controlling factor of pore growth. Another common source of porosity is liquid encapsulation (Dantzig, 2009). As the pressure within the isolated liquid drops, pores form first due to the pressure dropping below the equilibrium partial pressure of hydrogen in solution and then second grow substantially as the pressure continues to drop falling below the vapour pressure of Al. One factor that can affect both mechanisms of pore formation is species macrosegregation, which has received comparatively little attention in die-casting."

Jan 1, 2017