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By A. K. Raina

Blast induced damage to the final wall of rockmass in any civil or engineering application is a major concern to the rock excavation engineers. There are at least four distinct techniques practised by blasting engineers to minimise the damage to the parent rock during blasting that are classified as contour blasting. One of the methods to achieve a smooth wall or rock surface in blasting is pre-splitting, where blastholes in the final row are mildly loaded with explosives and fired first in sequence before the rest of the holes in a round of blast to achieve a split in rockmass. Since blasting is one of the most adopted methods for achieving a final wall in a desired shape, while maintaining the rockmass integrity, the design of pre-split blast assumes importance. There are several variables that determine the final shape of the pre-split face including the rock type, the drill diameter, the explosive characteristics, the orientation of major joints with respect to drill hole, the linear charge density, the spacing of drill holes and inclination of the drill holes. This study attempts to determine the importance and sensitivity of variables in pre-split blasting using historical data from open excavations of a hydroelectric project in India. Keeping in view the multitude of variables, low correlation of independent variables with responses and high level of interactions between the variables that define the blast results, it was found suitable to use ANN to determine the importance and sensitivity of the variables involved. A new method to determine the blast induced damage to rockmass, namely, undamaged area (AUD%), is introduced. Half Cast Factor (HCF%) and AUD%were calculated for a high wall and trenches by digital image analysis technique using the Fragalyst software. Joint spacing and linear charge density emerged as most controlling variables in determining the final result of pre-blast. The relative importance of other variables assuming significance in the case of both the designed outputs is also discussed. A comparative analysis of HCF%and AUD%on the basis of results obtained from ANN analysis is also presented. A futuristic approach concept has also been introduced.

May 30, 2021

By S. M. Viduka

This paper presents a numerical investigation of solid separation in jigging device, which is a gravity separation method widely used in ore processing. Separation is recognized as being heavily dependent on fluid motion in the jig. This study explores the effects of the inlet time dependent velocity profile on jigging performance. Modelling of the liquid-solid system is performed through a combination of computational fluid dynamics (CFD) to simulate liquid flow and discrete element method (DEM) to resolve particle motion. The initial packing conditions consist of a binary-density particle system of 1130 particles each 1 cm in diameter. A variety of jigging profiles are implemented in jigging. The saw tooth pulsation profile is selected with three variations in both amplitude and frequency. The performance of each profile variant is compared in terms of solid flow patterns, separation kinetics, energy, and mean particle position. These quantitative comparisons demonstrate significant differences in the segregation rate, energy, and solid phenomena, helping find an alternative optimum operating setting for the system.

Sep 1, 2012

By Gordon Jackson

"There are two accomplishments of air and gas drilling: a new series of economic and mechanical challenges; and, acceptance as a standard drilling and completion tool.The new challenges are related to the concept of using a gaseous circulating medium in drilling for oil or gas. For purposes of discussion, a two part division has been made: the challenge of fluid invasion control and that of equipment and tools. Great strides have been made in the development of materials and techniques to combat formation fluid invasion. Chemicals and the ""mist drilling"" technique, now in use, have the versatility to cope with a wide range of downhole fluid entry conditions.Equipment and tools have been developed to meet the challenges of better, more economic drilling and completion possible with a gaseous circulating fluid. Economic and operational challenges remain.Acceptance of air and gas drilling as a normal operating tool was reached with difficulty. It is now established as a means of reducing costs in exploratory and develop-mental well drilling, exemplified in a recent study of 226 wells covering 419,407 feet of hole in the United States. Air reached the projected depth in 85 per cent of the operations, although formation water was encountered in 48.7 per cent of the holes. Slim hole bit performance and cost all compared for overall bit averages as part of analysis."

Jan 1, 1961

By Gennaro G. Marino

As part of the development of a shopping center in West Virginia, a significant bench had to be cut into a mountainside that was over 700 ft. high. As a result, a steeply stepped, over 400-ft.- high wall was created. The high wall exposed old abandoned room-and-pillar coal workings at the toe of the cut. Because of exposure to the elements, the mine openings began to severely deteriorate with significant potential of undermining of the rock cut face and causing a large rock fall(s). Exacerbating this wall problem was a set of fairly planar sub-parallel and sub-vertical joints creating, in essence, thin rock slabs. Also present were stress relief fractures that were observed in the exposed pillars. Given the proximity of the project building to this high rock face, mitigation of the rock fall potential was deemed necessary. In order to prevent continued damage and deterioration of these exposed mine entries, the rubblized openings were filled with bulkhead grout and pressure injected with grout. The total amount of grout installed in these openings was about 3,945 CY. Also, a rock drape was attached to the entire face to mitigate small rock falls from natural causes. There also existed another level of mining below the ground surface and under an existing building at a depth of about 160 ft. Under a portion of the building, the pillars in these old works were second mined, and the building seemed to have been already affected by limited subsidence above this area. Also, calculated pillar safety factors in this high extraction section of the mine were too low. Consequently, these old works were stabilized by saturation grouting. An indication of overall roof distress was the significant fracturing encountered in the bedrock overburden during the drilling of the injection holes and the volume of grout placed in these holes. The total grout installed in the high extraction section of the lower mine was about 6,660 CY. This paper describes the investigation and the grouting techniques employed at the rock cut face and under the existing building to mitigate continued damage to avoid future subsidence problems at the face and the building premises.

Jan 1, 2013

By J. Hoover

"IntroductionThis chapter will discuss the operational and maintenance aspects of a heavy media cyclone circuits as applied to coal processing and using magnetite as the media. It deals with heavy media bath separators in terms of types of media, equipment, circuits, media recovery, maintenance, and product handling. It will detail heavy media cyclone operation and supplement the previously described topics.The heavy media cyclone was first developed in the Netherlands by the Dutch State Mines in 1945. A cyclone plant was not built in North America until 1961. Traditionally, heavy media cyclones have been used to treat size fractions between 1lz in. (12 .6 mm) and 35 mesh (0.5 mm). High maintenance related to heavy media bath separators has recently prompted some plants to crush all raw coal to minus 2 in. for treatment in heavy media cyclones.The heavy media bath separators utilize only the force of gravity to make the separation between heavy and light particles. This requires lengthy retention time which can lower capacity and also is inefficient for finer particles. A heavy media cyclone utilizes centrifugal forces which are 20 to 200 times greater than the force of gravity. This means the separation between coal and the impurities occurs very quickly, therefore a low retention time is required allowing cyclones to have high tonnage capacities. Also these greater forces allow better separation for the finer particle sizes.Heavy media cyclones are now widely used to produce both metallurgical and thermal coal. Work is in progress to reduce magnetite consumption, extend wear life, increase tonnage capacity, improve separation efficiency and automatically control these cyclone circuits."

Jan 1, 1989

By D. G. Lynch, M. R. Martin, R. J. Coutts

"Broadmeadow Mine is an underground longwall mine located in Central Queensland, Australia. The mine introduced a top coal caving (TCC) longwall face in 2013 but since then has experienced severe convergence events at the start of each panel after 60–70m of retreat, resulting in equipment damage and the longwall almost becoming iron bound. A significant geotechnical monitoring effort during LW10 and LW11 to characterise the caving mechanics and operational changes during LW11 were successful in mitigating the risk posed by these initial convergence events. This paper describes the geotechnical monitoring programme undertaken during LW11, the operational methods used to mitigate these initial convergence events, and the contribution to these events of the TCC technique.A thick sandstone unit close to the extraction roof was likely the cause of the convergence events at the start of each longwall panel. However, stress change monitoring cells, surface extensometers, an inclinometer, and the blockage of holes designed for pre-conditioning using hydraulic fracturing indicated that the convergence events were not caused by the sudden collapse of sandstone bridging across the goaf. Rather, they were caused by the propping action of strong units within the overburden strata. Equipment design modifications were made to allow the longwall to remain operational during the convergence events and an operational strategy was implemented to mitigate convergence in LW11. The initial convergence event was successfully negotiated, and Broadmeadow went on to be the highest producing longwall for CY16 in Australia.INTRODUCTIONBroadmeadow Mine is an underground longwall mine located in Central Queensland, Australia, owned and operated by BHP Mitsubishi Alliance (BMA). The mine is a punch longwall mine using open cut pit access provided by Goonyella/Riverside Mine. Broadmeadow commenced longwall operations in 2005 using a conventional high reach longwall, but later changed to the top coal caving (TCC) method of extraction. Broadmeadow extracts the easterly dipping 5.5–7.5m-thick Goonyella Middle Seam in ranging in depth from 90m to 330m. The coal is washed and blended at the adjacent Goonyella/Riverside open cut mine to produce a premium coking coal product for export."

Jan 1, 2018

By C. R. McClung

"Molybdenum, in the form of molybdenite, is a common byproduct of many copper mining and concentrating operations. While the recovery of most copper sulfide minerals is principally liberation controlled, the recovery of molybdenite is much more complex, with fully liberated particles commonly lost to tailings.A geometallurgical investigation was undertaken of molybdenite from the Bingham Canyon deposit with the aim of determining what effects, if any, mineralogy and the mineralogical attributes of morphology, angularity, liberation and size have on molybdenite recovery in the processing circuit. A set of samples was collected from the ores and products of Rio Tinto Kennecott’s Copperton Concentrator. The samples were analyzed by normal polarized reflected light microscopy, X-ray diffractometry, and scanning electron microscopy using a Mineral Liberation Analyzer, revealing the presence of two distinct types of molybdenite, which are the two polytypes: hexagonal (2H) and rhombohedral (3R). The 2H polytype occurs as textbook-shaped particles in quartz-molybdenite veins located in the core of the deposit, while the 3R polytype occurs as disseminated, ball-shaped particles with a dull or frosted appearance along the margins of the mineralized intrusive body or central core. Each polytype exhibited metallurgical properties consistent with those reported in the literature. The 2H polytype is easily ground, kinetically “faster” floating and displays surface attributes that are amenable to higher rates of recovery. This commonly results in the production of a high-quality molybdenum concentrate under normal operating conditions at most copper concentration operations. The 3R polytype is difficult to grind, kinetically “slower” floating and displays surface attributes that are less amenable to recovery. Therefore, in deposits with higher concentrations of the 3R polytype, modifications to operating parameters may be necessary to improve the recovery of molybdenite.A preliminary investigation into the metal budget of porphyry copper and molybdenum deposits indicated a possible positive correlation between total economic metal budget and polytype content. Higher concentrations of the 3R polytype appear to be more prevalent in gold-enriched porphyries than in molybdenum-enriched porphyries. This may help explain why it is easier to obtain higher rates of recovery in molybdenum ± tungsten-rich deposits, which contain little to none of the 3R polytype. There is a potential for the metal budget of a porphyry deposit to be used as an indication of the molybdenite polytype present as well as its impact on the economics, in terms of exploration, and the processing circuit, in terms of plant design."

Jan 1, 2016

By J. Pesl, U. Kemey, F. Sauert

"The CONTOP® smelting cyclone is a water-cooled, upright, high-intensity smelting reactor. The technology for the reactor was initially developed and brought into industrial-scale operation in the area of non-ferrous metallurgy. The two largest smelting cyclones were built with a capacity of 32 tons per hour of copper concentrate mix.The newest industrial CONTOP® plant treats up to five tons per hour of zinc-bearing residues including EAF dust. The highly concentrated zinc-lead oxide produced is sold to the zinc industry. The slag fulfills the leaching criteria and is used in waterway construction. The heat transferred to the cyclone cooling system and the off-gas boiler produces steam from which power is generated in a turbine.V AI has erected a new CONTOP® demonstration plant at MEFOS, Lulea, Sweden. A zinc volatilization rate of 90% was achieved during hot commissioning with Swedish EAF dust.Treatment costs in the range of 85 to 100 EUR per ton were estimated in a feasibility study on the treatment of 73,000 and 57 ,000 tons EAF dust for a group of steelmaking mills in Southern Europe."

Jan 1, 2000

By Gabriel S. Esterhuizen

The design of support for underground excavations is a complex process in which the interaction between supports and the rock mass must be evaluated. The strength reduction method (SRM) is useful because it provides a stability factor of the supported excavation that can easily be compared between support alternatives. The method is based on numerical model analysis where the stability factor is determined by reducing the rock mass strength until collapse is indicated in the model. This paper presents the results of validation studies that were conducted using the FLAC3D stress analysis software to compare SRMcalculated stability factors to the empirically based Coal Mine Roof Rating (CMRR) and the Analysis of Roof Bolt Systems (ARBS). The objective was to determine whether the SRM, with its basis in mechanics, would predict similar outcomes as the fundamentally different ARBS and CMRR methods with their basis in empirical observations. A total of 450 different scenarios were evaluated in which the geology, horizontal stress, depth of cover, entry width, support spacing, and support length were varied. The results showed that the SRM-calculated stability factors were able to satisfactorily capture both the ?weak bed? and ?strong bed? adjustments in the CMRR. The SRM results were found to be well correlated to the ARBS stability factors for the 450 cases considered. Further analysis showed that the SRM accurately captures the effect of bolt length, depth of cover, and entry width on the overall stability of an entry.

Jan 1, 2013

By D P. Blair

The theme of this conference is blasting productivity. This article only considers the technology aspect of this theme, and in particular, the collection and analysis of experimental data. In many cases, field trials are set up to collect data on variables such as fragmentation and vibration with the aim of comparing different explosive products and/or blast designs. An important aspect of such trials is the collection of sufficient data to draw sound conclusions. In this regard, there is no doubt that the scatter in real data is the root cause of all problems of obtaining misleading results due to an insufficient number of trials. This article shows that the typical one-off trial has a high probability of producing misleading information, which could be considered to be worse than having no information at all. Assuming that sufficient data has been collected, this article also highlights the methods that can be used to make the most of that data. These methods include the application of appropriate statistics that are dependent on the nature of the scatter in the data, and the use of some of the more recent filtering and spectral approaches that can be used to reduce the noise in measured blast signals and increase the resolution of their spectral characteristics.

Nov 8, 2011

By Harold G. Moulton

IT is highly significant that engineers should seriously consider the interrelations of technology, economics, and government. It is indicative of the emergence of maladjustments and problems that perplex our thinking and frustrate our activities. Instead of a world in which scientific discoveries and their applications through engineering to the processes of wealth production are regarded as the royal road to progress, we now find science and engineering being made responsible, in no small degree, for our economic and social troubles; and the powers of government are even being invoked to stem the tidal wave of technology. Indeed, there is a deep-seated fear, manifested in the writings of some of our greatest scientists as well as in popular discussions, that science may destroy our civilization.

Jan 1, 1938

By Sara Moshfeghi, Seyyed Majdeddin Mir Mohammad Hosseini, Abolfazl Eslami

"Due to variety of current pile bearing capacity methods based on the cone penetration test (CPT), for optimum design, it is necessary to evaluate the performance of such methods in different geotechnical conditions. Geotechnical databases including piling and in-situ testing records have been recognized as useful tools for analysis, design and economical construction. In order to evaluate pile bearing capacity methods, AUT-CPT&Pile database has been compiled including 450 full scale pile load tests and CPT sounding records. This database consists of different pile types with a relatively wide range of geometries and various soil conditions. Forty three records of piles driven in sand deposits were then employed to evaluate effects of ultimate capacity interpretation criteria from load displacement diagrams. The Davisson offset limit criterion, the Brinch Hansen 80% criterion and the load at the displacement of 10% of the pile diameter were compared to estimated capacities from ten CPT based design methods currently used in practice. The Brinch Hansen 80% criterion and the load at the displacement of 10% of the pile diameter lead to reasonable results, the Brinch Hansen 80% criterion showed less scatter. For evaluating the accuracy and the precision of CPT-based methods, the results were compared to estimated capacities. Results of comparison indicate that the CPT-based methods mainly predict the pile capacity withreasonable accuracy.INTRODUCTIONAmong the different approaches of estimating the pile bearing capacity, in-situ tests, especially, the cone penetration test (CPT) are favored due to the cone similarities with piles in modes of installation as well as fast and continuous profiling. This trend is practically well established where deep foundations are to be constructed in soft to medium subsoil deposits (Eslami and Fellenius, 1997; Mayne and Niazi, 2009).Employing different design methods results in a wide range of values which complicates the selection of an appropriate one to determine the pile bearing capacity. Several studies by Briuad and Tucker (1988), Eslami and Fellenius (1997), Abu Farsakh and Titi (2004), Schneider et al. (2008) and Eslami et al. (2011) confirm disparity of different design methods predictions. Thus, for optimum design, it is necessary to evaluate and compare the performance of current methods.Geotechnical databases are known as helpful tools in research and practical applications for optimizing analysis and design and are mainly used for management and interpretation of data, evaluation of design methods, calibrating LRFD or ASD design factors, etc. Pile lateral and axial load tests are examples of databases in geotechnical engineering. A summary of several CPT and pile load test databases is presented in Table 1."

Jan 1, 2017

By S. Ianos, C. Vibert

Type and shape of large dams founded on rock depend upon the expected deformation of their foundation. Their design consequently requires the assessment of the deformability of the rock mass at large scale. Seismic refraction, laboratory tests on rock samples and empirical formulas can provide an order of magnitude of the deformation modulus, with a limited degree of reliability. Direct in-situ measurement of the deformability of a volume of rock is therefore preferred, which integrate the effect of discontinuities, such as plate loading tests, dilatometric tests, etc. The authors have been compiling results obtained by in-situ deformability tests on a number of dam sites, including the Scarabée (“Petite Sismique”) method. This last method consists in thoroughly analysing the shape of seismic wave forms transmitted through the rock mass. It has been used since now more than 40 years over a large number of dam foundations, and has proved to provide a satisfactory assessment of the static deformation modulus. After comparing the results obtained from different methods on six dam sites, the Authors conclude that their reliability closely depends upon the size of the loading device in relation to the spacing of the discontinuities. Attempts to correlate results from different types of in-situ loading tests reveal difficult, because closely depending upon local geotechnical conditions at test location. Plate jacking tests appear to be the most reliable, because involving a relatively large volume of rock. On the other hand, the Scarabée method (“Petite Sismique”) allows a rapid assessment of the deformation characteristics of the rock mass at large scale, and has been found to provide values generally in agreement with those from plate loading tests, while dilatometric or flat-jack tests were found too dependent upon local conditions. The Authors conclude that preference should be given first to the Scarabée method, which uses light equipment and is quickly performed, together with an accurate geological and geotechnical assessment for interpretation. In a second stage, Scarabée shall be complemented by adequately performed plate jacking tests in selected locations, in order to cross-check results and refine the assessment. The general accordance between the results of the two methods, which both can integrate anisotropy of rock masses, justifies this statement.

Jan 1, 2015

New technology for on-line particle size analysis of mineral slurries has opened up new applications for particle size measurement. In some cases the particle size distribution of the final concentrate is an important quality issue. This paper discusses established on-line particle size analysis technologies and presents experiences on the use of a new technique employing laser diffraction in several minerals processing operations. The main innovations in the new instrument are a simple dilution system and multiple scattering correction algorithm, which allows wide solids content variations of diluted sample in the measurement cell. Representative sample for laser measurement is produced by a simple and reliable dilution system. The applications discussed are; Blaine number measurement of Fe concentrate before pelletizing, grinding of variable batches of ore and paste thickener control.

Jan 1, 2014

By L. Yuan, A. Smith

"NIOSH’s mine fire simulation program, MFIRE, is widely accepted as a standard for assessing and predicting the impact of a fire on the mine ventilation system and the spread of fire contaminants in coal and metal/nonmetal mines, which has been used by U.S. and international companies to simulate fires for planning and response purposes. MFIRE is a dynamic, transient-state, mine ventilation network simulation program that performs normal planning calculations. It can also be used to analyze ventilation networks under thermal and mechanical influence such as changes in ventilation parameters, external influences such as changes in temperature, and internal influences such as a fire. The program output can be used to analyze the effects of these influences on the ventilation system. Since its original development by Michigan Technological University for the Bureau of Mines in the 1970s, several updates have been released over the years. In 2012, NIOSH completed a major redesign and restructuring of the program with the release of MFIRE 3.0. MFIRE’s outdated FORTRAN programming language was replaced with an object-oriented C++ language and packaged into a dynamic link library (DLL). However, the MFIRE 3.0 release made no attempt to change or improve the fire modeling algorithms inherited from its previous version, MFIRE 2.20. This paper reports on improvements that have been made to the fire modeling capabilities of MFIRE 3.0 since its release. These improvements include the addition of fire source models of the t-squared fire and heat release rate curve data file, the addition of a moving fire source for conveyor belt fire simulations, improvement of the fire location algorithm, and the identification and prediction of smoke rollback phenomena. All the improvements discussed in this paper will be termed as MFIRE 3.1 and released by NIOSH in the near future INTRODUCTION The MFIRE program, originally developed in the 1970s by the U.S. Bureau of Mines (now the Office of Mine Safety and Health Research (OMSHR) at the National Institute for Occupational Safety and Health (NIOSH)) and Michigan Technological University, has been a mainstay in modeling of the mutual influences between a fire and the mine ventilation system during an underground mine fire. Several update versions have been released over the years, including MFIRE 1.27, 1.29, 1.30, 2.0/2.01, 2.10, and 2.20. The MFIRE program logically comprises four parts: (1) a conventional network calculation, where it performs the basic network balancing without considering heat or mass transfer; (2) a temperature calculation to establish the reference temperature distribution before a non-steady state (transient-state) simulation; (3) a transient-state simulation that follows changes in ventilation step-by-step to produce a continuous description of the temperature distribution, smoke, and contaminant spread through the ventilation system during a fire event; and (4) a quasi-equilibrium simulation to predict the state of the ventilation system after a relatively long period of time (defaulted as 5 hours in MFIRE) as the fire reaches a quasi-steady state. In summary, MFIRE is a computer simulation program that performs normal ventilation network planning calculations and dynamic transient-state simulation of ventilation networks under a variety of conditions including the influence of natural ventilation, fans, fires, or any combination of these (Chang et al., 1990)."

Jan 1, 2016

By Rahul Wankhade, Sunil S. Baswankar, Aditya S. Kharatkar

Despite advances in pile design methodologies and piling techniques at site, difficulties and uncertainties still exists for design of piles particularly in coralline deposits and weak carbonate rocks. Such deposits are known to be heterogenous in nature, and occupy major stretches of earth, where piling experiences are probably very scanty. Such deposits are associated with low unit weights and usually consist of weakly cemented calcareous and carbonate soils interbedded with coral rocks containing cavities, which are completely void or filled with coral debris. Many of the studies indicate that conventional parametric relationships are may not apply to such sediments and rock formations. This paper intends to provide an appraisal of the available information that cautions against risks involved in conventional design practice and also serve as a guideline for pile design in such formations despite being a grey area of research. Contents of the paper is expected to provide a basis for the pile design and likely to serve as an eye-opener for research into this important soil-pile structure interaction problem.

Sep 1, 2022

By Alphonso Cornejo, Galen H. Clevenger

This bibliography was compiled in connection with an investigation of the Caron process for the treatment of manganese - silver ores , conducted by the T. S. Bureau of Mines in cooperation with the Netherlands East Indies Government . The object of this investigation was to develop a practicable method for treating the refractory manganese- silver ores found in these two countries . The results of the work will be published as a bulletin of the Bureau of Mines . This bibliography summarizes the available information on the subject previous to the investigative work embodied in the forthcoming bulletin, and may be useful to those metallurgists or others conducting work along this line .

Mar 1, 1923

By C. R. McClung

"Molybdenum, in the form of molybdenite, is a common byproduct of many copper mining and concentrating operations. Contrary to most copper sulfide minerals where recovery is principally liberation controlled, the recovery of molybdenite is much more complex with fully liberated particles commonly lost to tailings. It is this complexity that facilitated the necessity for a geometallurgical investigation of molybdenite from the Bingham Canyon deposit. The aim of this investigation was to determine the effect mineralogy and/or mineralogical attributes (i.e. morphology, angularity, liberation, size) have on the recovery of molybdenite in the processing circuit. A set of samples was collected from the ores and products produced by Rio Tinto Kennecott’s Copperton Concentrator. All samples were analyzed using normal polarized reflective light, Mineral Liberation Analyzer (MLA) and X-ray diffractometery (XRD) techniques. The results of this investigation revealed the presence of two distinctly different types of molybdenite, which have been identified as the two polytypes of molybdenite, i.e. hexagonal (2H) and rhombohedral (3R). The 2H polytype occurs as textbook-shaped particles in quartz-molybdenite veins that are located in the core of the Bingham Canyon deposit. The 3R polytype occurs as disseminated, “ball”-shaped particles with a dull or frosted appearance along the margins of the mineralized intrusive body or central core. Concerning their metallurgical behavior each type exhibits unique metallurgical properties that are consistent with those reported in the published literature. For instance, the 2H polytype is easily ground and kinetically “faster” floating with surface attributes that are amenable to higher rates of recovery. This commonly results in the production of a high quality molybdenum concentrate under normal operating conditions common to most copper concentration operations. In contrast, the 3R polytype is difficult to grind and kinetically “slower” floating with surface attributes that less amenable to recovery under normal operating conditions. Therefore, in deposits with higher concentrations of the 3R polytype, modifications to the normal operating parameters may be necessary to improve the recovery of molybdenum. Finally, a preliminary investigation into the metal budget of porphyry Cu and Mo deposits indicates that a positive correlation may exist between the total economic metal budget and the polytype content. For example, higher concentrations of the 3R polytype appear to be more prevalent in Au-enriched porphyries versus Mo-enriched porphyries. This observation may also serve to help explain why it is easier to obtain high rates of recovery in Mo ± W-rich deposits, which contain little to none of the 3R-polytype. Consequently, the potential for the metal budget of a porphyry deposit to be used as an indication of the molybdenite polytype present, as well as its impact on the economics (exploration) and/or on the processing circuit (plant design) could exist. In conclusion, this investigation highlights the necessity of understanding the mineralogical properties or characteristics of molybdenite and/or other economic mineral(s), as these can and will have a direct impact upon the performance and plant optimization."

Jan 1, 2016

By P. Langlois, G. Labonté, J. J. Barrett, J. Holmes

"The Voisey’s Bay mill processes a high-grade pentlandite and chalcopyrite ore in a largely pyrrhotite/troilite matrix. From 1994 to 1997, circuit development focused on making a 14% nickel concentrate. When flowsheet development resumed in 2001, the target grade was raised to 20% ni. initially triethylene tetramine and sulfite pyrrhotite depressants were used in a lime circuit, but by recycling process water and the contained thiosalts, the required nickel grade was made without depressants. construction of the mill was fast-tracked, with start-up in september 2005. ramp-up was faster than other recent nickel installations, with tonnage being limited by concentrate dewatering due to higher-thanexpected ore grades.RÉSUMÉ l’usine de traitement de Voisey’s Bay traite un minerai à teneur élevée en pentlandite et chalcopyrite dans une matrice formée surtout de pyrrhotite/troïlite. De 1994 à 1997, le développement du circuit ciblait la production d’un concentré à 14 % de nickel. lorsque le développement du schéma de traitement a été repris en 2001, la teneur cible a été élevée à 20 % de ni. initialement les déprimants triéthylènetétramine et sulfite de la pyrrhotite étaient utilisés dans un circuit à la chaux; cependant, en recyclant l’eau du procédé et les sulfosels qui y sont contenus, la teneur en nickel a été atteinte sans utilisation de déprimants. la construction de l’usine de traitement a été accélérée et elle a démarré en septembre 2005. la mise en opération a été plus rapide que pour d’autres installations récentes de nickel; le tonnage traité étant limité par le séchage du concentré en raison des teneurs de minerai plus élevées que prévu.INTRODUCTIONnickel was discovered on canada’s east coast in the vicinity of Voisey’s Bay, northern labrador, by chislett and Verbiski (Higgins, 2011) while working for Diamond Fields resources in 1993. The ovoid deposit was subsequently delineated in the winter of 1994–1995. By the end of 1995, the ovoid had been well explored, and at that time was thought to have a reserve of at least 30 million tonnes (Mt), with an average grade of 2.83% ni and 2.0% cu (naldrett, singh, Krstic, & li, 2000). Drilling to the east of the ovoid indicated the presence of significant mineralization. in June 1995, inco limited bought a 25% share in the Voisey’s Bay nickel company (VBnc), which was a subsidiary holding company set up by Diamond Fields. inco also bought 8% of Diamond Fields and negotiated the right to sell all the nickel produced from VBnc for 20 years as part of this agreement. in april 1996, inco bought Diamond Fields and acquired the remaining 75% of VBnc shares."

Jan 1, 2017

By G. S. Scott, L. D. Schmidt, J. A. KELLEY, E. L. FISH

One of the war problems with which the Bureau of Mines is concerned is to increase production of iron and steel , in which coke is one of the major factors . The output of byproduct coke for use in iron blast furnaces is insufficient and is being supplemented by coke from beehive ovens (figs . 1 , 2 , and 3) . Some difficulties that cause a reduction in iron output have been reported in the use of some of the beehive coke.6/ About 20 years have elapsed since beehive coke was made on a large scale , and many of the skilled operators of those days are no longer available . Furthermore , in many instances the quality of the coal supplied to the ovens has not been as good as formerly. The ash and sulfur contents are often abnormally high; and in other instances they vary greatly in amount, so that a nonuniform coke is produced . To assist operators to improve quality and yield of beehive coke , the Bureau of Mines equipped a truck as a field laboratory ( fig . 4 ) and sent the authors with it into the Pennsylvania beehive district . The truck contains necessary equipment for sampling and analyzing coke oven gases , measuring temperatures , screen - sizing coal, and float -and - sink testing coal . Coal specimens may be sent to the Pittsburgh laboratory for analysis . Beehive plants producing good coke were visited first to observe details of operation and to collect data on the operating process . These covered temperatures , analyses of the exit ( or trunnel) gases , and coal quality, and were to be utilized in searching for faults in plants not producing good - quality coke and to assist in improving such plants or their operation .

Dec 1, 1943