Search Documents

A study of drilling data at various stages of development of an orebody show that the semi-variogram, used for calculating the accuracy of block estimates can be ill-defined if too few data are available. The consequencesin this case are to have blocks supposedly more accurately known than is possible at the early drilling stage; such a result being potentially dangerous. However, as the amount of data increases the recalculated, semi-variograms approach the underlying semi-variogram of the deposit and the calculations made using them become more reliable and robust.

Jan 1, 1977

By Bruce D. Hanson

A computer model capable of simulating the basic production system in a variety of underground mining methods has been developed at the Twin Cities Mining Research Center. This Bureau of Mines paper describes the simulation of the basic production system at the working face, which includes drilling, blasting, mucking, and roof bolting. The model is event-oriented; that is, the status of the system is updated at the occurrence of an event. All event or activity times, including failure and repair of equipment, are treated as stochastic variables. A location dimension, in addition to the time dimension, is used, allowing the simulation of multiple location systems. To aid the user in determining the efficiency of his system, the model provides several reports. An event or activity report gives the frequency of occurrence total active time, and cumulative delay statistics for each event. An equipment report delineates the availability and utilization of all equipment. A production report provides information on various performance measures such as tons produced and holes drilled. The cost report gives the cost of various elements in the system. Operating data from an actual mining situation were used in validating the model. In addition to the description of the model, examples of simulation experiments which were performed on a room-and-pillar mine system are given. Use of the model to determine methods for improving the efficiency of the system is discussed.

Jan 1, 1974

By Anwar-ul Karim

In one of our recent papers, Cheng, Karim, Langdon, and Dom1 analyzed the creep mechanisms in a Fe-4 pct Si alloy. The experimental results of apparent ac-

Jan 1, 1970

By R. P. Townsend

It is a widely accepted "fact" that a Koepe friction hoist is generally the best solution for production hoisting when compared to a double drum hoists. This would appear to be true if one looks at the initial capital cost of just the hoist, and also if one compares the size of the motors selected for the duty. But is this the whole story? What are the longer term costs involved in the hoist's operation, and what are the relative efficiency's of the two designs? Perhaps the Koepe hoist design enjoys a better reputation than it deserves.

Jan 1, 2011

El presente texto describe las ventajas del uso del sistema de vectores aplicados en la explotación de los minerales de la mina de Atacocha. Este sistema consiste en dividir el Ore Body a explotarse, en varias partes y que al momento de hacerlo sea de forma alternada, como si se tratase de "Stopes" independientes. Entre las ventajas obtenidas por este sistema, está que el desarrollo de derrumbes se hace menos frecuente debido a que las paralizaciones -ya sea por los derrames de minerales de las cajas de Ore Bodyi -, no delimitan un detenimiento total del área de explotación, sino solo a un sector. Otra ventaja estriba en que el costo por toneladas de todos los stopes trabajados, es menor que el sistema de cuadros empleado. Asimismo, para que el sistema sea completamente efecivo, se deben conocer los límites del Ore Body, a través de los análisis y las muestras de laboratorio permanente.

Jul 20, 1957

By Francesco Chiappalone, Daniele Nebbia, Lance Waddell, Greg Colzani

As part of the 3RPORT Project, a 5-mile tunnel is being excavated underneath the three rivers of Fort Wayne using a 19-foot diameter Slurry Tunnel Boring Machine. The groundwater pressure at the tunnel axis ranges from 4.5 to 5.3 bar. The rock mass hydraulic conductivity is very high with water inflows up to 10,000gpm imposing significant challenges to the project. After excavating 1,550-feet of the TBM tunnel, major leaks between the tailskin and the segmental lining were observed, indicating the potential deterioration of the tailskin brushes and the need for inspection and eventual replacement. The first part of the paper describes the planning of the intervention, including the design of the polyurethane grouting campaign, the procedures developed for the execution and the controls established during construction to timely assess the presence of potential hazards. The second part of the paper focuses on the experience gained during execution and lesson learned to prevent future occurrences of this nature.

Jun 13, 2021

By R. Abela

Heavy mineral sands are usually beneficiated in a spiral concentrator circuit prior to separation of heavy minerals into streams of zircon, rutile and ilmenite. The performance of the spiral concentrators is heavily affected by the presence of slimes in the rougher feed. The paper quantifies the effect of slimes content and discusses the beneficial effect of spiral feed de-sliming. The net effect of inefficient slimes removal can cause significant recovery losses of the heavy minerals present in the feed.

Jan 1, 2003

By Larry F. Drolet

Charleston, SC is anything but boring. The city was founded in 1670 and has played a significant role throughout the history of the United States. Located along the coast of the Atlantic Ocean in the southeastern United States, Charleston was a vital city in America?s early existence. Charleston?s coastal location has helped the city become the fourth largest cargo port in the United States and earn the 2011 designation as the number one travel destination in the United States by the Conde Nast Traveler Magazine. Part of Charleston?s charm and beauty can be attributed to its historic structures and churches that line nearly every sidewalk, roadways that were laid out based on the width of horse carriages, great weather, southern hospitality and coastal living. Now imagine the challenges of installing new, or re-placing aging infrastructure, in this setting. Every shovel full of dirt, every stick of pipe and every roadway sub-surface has its own historic story to tell. For engineering minded individuals, Charleston?s infrastructure has almost as fascinating a history as its more visible surface structures. Charleston was among one of the first American cities to construct separate sanitary and storm water drainage infrastructure. This concept has roots dating back to the city?s founding and is a credit to the foresight of its founding fathers who understood the basic health differences between sanitary and storm water.

Jan 1, 2013

By B. W. Naugle

The Bureau of Mines investigated the changes that occur in decomposition products when coal is carbonized in a fluidized bed with steam as the fluidizing medium and the vapors are subsequently cracked without condensation in a fluidized bed of high-temperature coke. The coal used was from the High Splint bed, High Splint mine, Harlan County, Ky. Since this coal is agglomerating, it was blended with char. The integrated unit used in this investigation consisted of a 3-inch-diameter fluidized coal carbonizer, a 3.5-inch-diameter cracker containing a bed of high-temperature coke fluidized by the tar vapors and steam from the carbonizer, and gas-cleaning and product-recovery systems. The carbonizer was operated at 485° C and the cracker at 600°, 700°, and 800° C. The process variables investigated were temperature, residence time, and concentration (pound of tar vapors per pound of steam to the cracker) of tar vapors in the cracker. The total tar yields decreased as the temperature of the cracker increased, and at a constant cracker temperature of 600° C the yield of paraffins, acids, aromatics, and olefins in the distillate increased directly with the tar vapor concentration in the cracker. At 700° and 800° C only the acids and aromatics increased with increased concentration. Bases remained essentially constant regardless of the temperature and concentration. Similar results were obtained when the tar from the carbonizer was condensed prior to feeding to the cracker.

Jan 1, 1965

Tin mineralization in both eastern and western Tasmania shows a spatial correlation with middle Palaeozoic biotite granites and adamellites. The range of composition of these granitic rocks is restricted with respect to Mg, K, and Na content. Because this compositional restriction is shown by granitic rocks from other tin provinces, the concept of a genetic relationship between these granites and the associated tin mineralization is reinforced, and similar concentration mechanisms may be involved.Gold mineralization is largely restricted to eastern Tasmania and in contrast to the tin mineralization is rarely spatially associated with the middle Palaeozoic granitic rocks, although most authors have suggested a genetic correlation with hornblende and/or biotite granodiorites.Although few analyses are available, the granodiorites that are spatially associated with gold deposits exhibit similarities to granitic rocks from gold provinces elsewhere. These features suggest a possible genetic relationship between gold mineralization and the granodiorites.The composition of granitic rocks may be used as an aid to exploration in delineating areas of potential tin and gold mineralization in granite terrains.

Jan 1, 1970

By J. Kempken

Driven by customers, especially from the automotive sector, the supply of 100% prime quality has become essential. Furthermore the implication of quality costs and the yield of first class products define the steel companies' profitability and overall success significantly. The SMS group together with its subsidiary MET/Con has developed a comprehensive solution to assess the product quality over the production and processing chain. Process and production parameters originating from various data sources of the process automation are examined on their impact of quality related characteristics.Expert know how and comprehensive operational experience is translated into a quality guideline and a regulation framework as the sensitive core of the PQA solution.Once implemented, the system identifies immediately steel grade specific, deviations from ideal standard and proposes corrective actions including a final evaluation for each product at each processing step.The X-Pact® PQA (Product Quality Assessment) system is a substantial tool for root cause quality analysis and provides the required support to the production team. It will become an integral part of the corporate quality management system.

Aug 17, 2017

By L. Villa, O. Suarez, D. Arias, L. G. Corretge

The deposit comprises two vertical, lenticular bodies emplaced in the allochthonous block of a Variscan thrust. Epigenetic mineralisation occurs as replacement of carbonated volcaniclastic rocks of Cambro-Ordovician age. The dominant sulphide minerals are sphalerite and galena with minor chalcopyrite; the main non-metallic mineral is quartz and there is hydrothermal silicification, chloritisation and sericitisation. Sulphur isotope values for sphalerite and galena are heavy and reflect the fundamental relationship between delta-34S in ZnS and in PbS, suggesting isotopic equilibrium. Four sphalerite-galena pairs yield temperatures between 163 and 218 degrees C, in good agreement with the 187-207 degrees C estimated by the Ga/Ge-sphalerite geothermometer. The ore sulphide was leached by the hydrothermal solution from diagenetic pyrite in the host rocks and disseminated sphalerite and galena in Cambrian carbonates

Jun 19, 1905

By R. E. Cook

"Mineral deposits require substantial amounts of energy to transport and be processed into usable form and, as such, present a real processing challenge in that the deposits are never homogeneous and orebody compositional characteristics are all over the map. Extracting the desired mineral(s) from the deposit at sufficient profit margin, despite severe fluctuations in market price, requires process automation architecture capable of supporting an integrated enterprise solution. Such an architecture will encompasses the activities of individuals, process units, process areas, plant level activities, mine management and business planning, and accounting systems. Key to the automation process is the aspect of value generation. This article brings together the various requirements for the automation of a mining enterprise and presents the different aspects of how to obtain value across the entire mining operation.Minerals’ processing sites are historically long lived, with 20-year life-of-mine not uncommon and 75 years not unheard of. Considering that hardware technology advancements are introduced every six months, or less, it is prudent to select process automation systems that adhere to “open” industrial standards versus proprietary based systems. In the minerals processing industry, the key to survival is driving the cost of production per unit volume to the lowest possible level and provide enough profit to sustain operations. Control system architecture and business information technology are rapidly becoming important tools in the quest for productivity. Getting key dynamic business performance information at the right time to the right person or process unit is crucial to successfully achieving corporate goals. The process automation architecture selected must, therefore, be able to integrate to the various networking enterprises and business systems.The mining industry is generally known as an extractive industry that is physically oriented with respect to operations and the activities in which workers engage. Large numbers of people performing manual tasks in difficult surroundings, produce variable outputs. But times are changing – and so are industry best practices. While the nature of work still consists of activities such as ore extraction, ore movement, ore concentration, refinement and logistics, automation innovations are starting to change the nature of many of the production steps. The industry has transitioned from requiring more physical activities by workers to more information management, automated control and collaboration within the operation. Humans are good at situational intervention and nonlinear reasoning and do best when empowered with an overall production perspective. Machines and automation are good at repetitive functions, steady state operation, and managing transitions. Thus, a combination of advanced technology solutions, reliable and useful information and full human contributions are necessary to mining operations for value generation."

Jan 1, 2015

By A. Cichowicz

In this study, techniques used to design earthquake-resistant structures are applied to the deep-level mining environment. Earthquake engineers seek to identify the cause of potentially damaging resonance, and design or reinforce structures to reduce these effects. Similar techniques have been used to analyse the dynamic behaviour of the rock mass surrounding a stope in a deep South African gold mine. A three-dimensional seismic array installed in a stope at TauTona Mine (previously Western Deep Levels, East Mine) provided an opportunity to examine the evolution of the wave field close to an underground opening. A set of three-component geophones installed in a borehole above the panel revealed the development of surface waves as wave fronts reached the excavation, and an array of vertical component geophones fixed to the hangingwall provided a two-dimensional map of site effects. While the collected data do not include damaging seismic events, quantitative analysis enabled phenomena which could lead to damage, to be recognized. In the vicinity of the excavation, the energy of the seismic signal is generally transformed from high frequency to low frequency. It was found that seismic events with relatively high corner frequency (150 Hz?200 Hz) usually excite several modes of vibration (30 Hz to 110 Hz), while events with low corner frequency (30 Hz?50 Hz) do not always excite higher modes of vibration in the structure. This implies that the rock mass around the excavation is a complex medium, and should be studied using the multi-degree-of-freedom model. A strong structural effect (due to the excavation shape) was revealed as a low frequency coda wave (at 40 Hz and 60?70 Hz), well developed on the skin of the hangingwall. A strong site effect was revealed by changes in signal properties between hangingwall geophones, exhibiting strong resonances around 160 Hz and in the range 200 Hz to 300 Hz.

Jan 1, 2000

By Shaolong Chen

Feeding dry sulfide concentrate into smelting furnaces enhances process performance and reduces the energy consumption and exhaust gas flow. Direct heated rotary dryers and flash dryers have being replaced by rotary steam dryers featured by very low wear rate of the pipe heating elements and long maintenance interval. Impact of the drying processes on the environment receives more and more attention as the emission legislation tightens. In this regard, environmental factors such as SO2, CO2, dust and gas flow among rotary dryers, flash dryers and steam dryers were compared. Selection of a rotary steam dryer for copper and nickel concentrate drying would be an ideal solution to reduce the pollution of exhaust gas, as drying is achieved by indirect contact to the steam at relatively low drying temperature and as the off-gas contains almost only water vapor and air. The emissions can be significantly reduced and only small and simple off-gas handling units are needed.

Jan 1, 2006

By M. Lundström, J. Aromaa, S. Seisko

"Gold dissolution was investigated in ferric chloride media, promoted as one of the most promising alternatives for cyanide-free gold leaching. The characteristics of gold open circuit potential (OCP) and its relation to gold dissolution rate was investigated. Furthermore, the reaction mechanism of gold dissolution in ferric chloride leaching was discussed. The effect of solution variables, [Fe3+] = 0.02–1.0 M, [Cl–] = 2–5 M, T = 25–95 °C and pH = 0–1.0, on OCP and dissolution rate were studied electrochemically using rotating disk electrode (RDE) and linear polarization resistance (LPR) method with ?cyc = 1000 RPM. The investigated gold OCPs in ferric chloride solutions were found to vary between 597 and 688 mV vs. saturated calomel electrode (SCE) and gold dissolution rates between 1.2·10–5–5.0·10–4 mol s–1 m–2. Increase in temperature (25–55 °C) and ferric concentration (0.02–1.0 M) changed OCP into more positive values, while increase in chloride concentration (2–5 M) decreased it. The logarithm of gold dissolution rate was shown to increase linearly with increasing OCP at the temperature range 25–95 °C, ferric concentration range 0.02–0.5 M and chloride concentration range 2–4 M. A notable increase in the gold dissolution reaction rate was evident at T > 55 °C. INTRODUCTION Currently cyanide leaching is the predominant method used in gold production from primary raw materials (Marsden and House, 2006). However, since the Baia Mare disaster in Romania in 2000, the use of cyanide has been the subject of international concern due to the toxic nature of the chemical posing a significant health threat if exposed to the ecological entities (Hilson and Monhenius, 2006; UNEP/OCHA, 2000). Therefore, several countries e.g., Costa Rica, Czech Republic, Germany, Hungary, Turkey, many states of the USA and provinces of Argentina, have started to ban or limit cyanidation via legislation (Laitos, 2012). Thus, alternative solutions, such as thiourea, thiosulphate, oil-coal agglomerates as well as halides have been investigated in order to replace cyanide as lixiviant (Adams, 2016; Aromaa et al., 2014; Aylmore, 2005; Hilson and Monhemius, 2006; Lampinen et al., 2015). Ferric and cupric chloride leaching have been reported to have advantage over cyanidation being capable to dissolve refractory gold minerals, without pre-treatment such as pressure oxidation or roasting (Angelidis et al., 1993; Lundström et al., 2014; Marsden and House, 2006; van Meersbergen et al., 1993). According to Aylmore (2005), 4% of publications for alternative lixiviants to cyanide in gold leaching were within category oxidative chloride processes including aqua regia and acid ferric chloride leaching. Further, some patents have been granted for ferric chloride leaching of gold (Abe and Hosaka, 2010; Lundström et al., 2016)"

Jan 1, 2018

By J. D. Miller

Many factors -- political, environmental and technological -- will determine the extent to which the United States realizes the potential of its vast coal resources. Not the least of these factors is technogical development including mining, processing and transportation. With regard to processing technology, about 50% of the 800x106 tons of coal mined annually in the U.S. is processed in preparation plants. The purpose of the physical separations accomplished in these preparation plants is to remove ash (present as clays and other oxide minerals) and sulfur 'present mostly as pyrite). Coal flotation circuits for such separations are becoming more important in the processing of minus 28 mesh coal. (1,2,3) For example in the U.S. in 1960, 31 flotation plants processed 26,500 tpd; whereas in 1980, there were 80 flotation plants which processed 78,300 tpd. This corresponds to an annual growth in flotation plant capacity of 10 per year during the past two decades. Coal flotation is based on the natural or induced hydrophobicity of coal particles which are separated from hydrophilic ash and sulfur constituents by attachment to air bubbles. The coal particle/air bubble aggregates are collected in a froth phase which is created by the addition of a suitable frother such as MISC. Without exception, such separations are made in a conventional flotation cell, which, in essence, is a stirred tank reactor with a shrouded rotor to shear the air as it passes through a hollow shaft. The dispersed air bubbles (4.0 mm diameter) are stabilized by addition of the frother. Collision of the air bubbles with, and/or precipitation of the air bubbles on, the coal particles results in the formation of coal particle/air bubble aggregates which rise in the gravitational field and are collected in the froth phase developed at the top of the flotation cell. Restraints on successful separation by this conventional flotation technique are particle size and retention time. Generally it is found that effective flotation is only achieved for particle sizes between 10 and 1000 microns. Further, with respect to retention time, it is found that a nominal retention time of at least 2 minutes is required for successful separations. These facts limit the effectiveness of conventional coal flotation. Coal fines may be lost in the reject stream and disposal is frequently a problem. The retention time required for conventional flotation results in large floor space demands which limit the capacity of the plant.

Jan 1, 1981

By L. Bloomquist, C. Arnoldi

"This paper describes how Automated Mining Systems (AMS) is evolving the state-of the- art in guidance systems for autonomous underground vehicles. The techniques, tradeoffs, and lessons learned from these systems are described, including the safety regime that has been implemented.First generation autonomous guidance systems for underground vehicles relied on infrastructure for the vehicle to follow. However, there are additional costs associated with that approach.The current generation uses a pair of laser range finders as its only guidance sensors. This system uses a minimum of infrastructure, in the form of a redundant system of location referencing. Advanced steering and drive control algorithms are incorporated into this generation of system.The next generation of infrastructureless guidance systems will be based on a 3D vision sensor, which was originally developed for autonomous Mars rovers and is being adapted for underground mining use. Results of early underground field trials are presented, along with a description of this emerging technology."

Jan 1, 2004

By N Petropoulos and M J Thurley, E Righetti, M Wimmer

Fragmentation in sublevel caving (SLC) is vitally important. Both gravity flow and any downstream processes are affected. Reasonably coarse fragmentation may lead to larger draw bodies (isolated extraction zones) and hence potentially higher primary ore recovery and depressed/delayed waste rock inflow from above. Fewer flow disturbances are expected by mitigating oversize. In addition, it requires less boulder handling and reduces wear and possible hang-up problems in orepasses. To assess the present-day functionality of large-scale SLC, a multiyear, comprehensive measurement program was initiated. It covers the main elements for SLC, namely blast function, fragmentation and gravity flow. The present paper focuses on fragmentation measurements. An image acquisition system was used to document the drawpoint and the load-haul-dump (LHD) bucket for each mucking cycle. At the beginning, four buckets (about 70 t total) were sieved to validate the results of both 2D and 3D image analysis techniques. The fundamental and specific problems are discussed herein. At the moment, fragmentation of the SLC rings is evaluated using a quick rating system and a 2D fragment delineation software. The results enable a description of fragmentation and its variation during mucking but also – combined with the gravity flow measurements – conclusions on the fragmentation for different parts of the SLC ring. Possible influences on flow disturbances and ore recovery/dilution are investigated. The recent findings allow a better understanding of breakage and flow and support future process improvements.CITATION:Wimmer, M, Nordqvist, A, Righetti, E, Petropoulos, N and Thurley, M J, 2015. Analysis of rock fragmentation and its effect on gravity flow at the Kiruna sublevel caving mine, in Proceedings 11th International Symposium on Rock Fragmentation by Blasting, pp 775–792 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 24, 2015

By Jiachen Wang

China is the largest coal producing country in the world. Coal is widely distributed in China and thus the mining conditions are complex and diverse. This paper summarizes the important achievements in the last 20 years in various mining methods including the extra thick seam with large mining height top coal caving, the thick seam with large mining height and top coal caving mining, the steep seam with top coal caving and fully-mechanized mining, the thin seam automated mining, and the backfill mining. At the same time, the rapid advance in the development of mining machinery and manufacturing has also contributed to the advancement of coal mining technology and the great improvement of coal mine safety. The future direction of China?s coal mining is to further improve mine safety as to improve the coal recovery rate, promote the pillar less mining technology, develop high-efficiency backfilling technology, develop steep seam high-efficiency mining technology for seams less than 10m thick, and high recovery mining techniques for extra thick seams, improve the reliability of mining equipment, and strengthen the protection and restoration of surface environments and water resources.

Jan 1, 2014