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By David Hanson, Sean Warren, Chaparral Berry

"Coal bumps, also referred to as dynamic failure events or coal bursts (Lawson, Weakley, and Miller, 2016), continue to be a hazard in underground coal mines. While current design methods have significantly reduced the occurrence of coal bumps, they have not been completely eliminated. This paper investigates a correlation between coal compositional components, coal molecular structure, and probability of coal bumps in an effort to deepen understanding of coal behavior in an effort to reduce hazards in underground coal mines.Samples from the Penn State Office of Coal (PSOC) Department of Energy Coal Samples (DECS) were obtained for Fourier Transform Infrared Spectroscopy (FTIR) analysis using the KBr pellet method. Peaks indicative of the coal molecular structures were obtained using spectral integration software. These data, combined with published elemental data, were compared to historic bump occurrence in order to establish a possible correlation. Finally, results based on multivariate analysis of the elemental and FTIR data with bump status as the dependent variable suggest that elemental sulfur and molecular structure can be used as an indicator of bump susceptibility within the sample set considered.INTRODUCTIONThe study of coal requires consideration of multiple variables: percentages of organic and inorganic components, organic component origins, coal age, pore structure, cleat density, elemental composition, etc. Examining coal in situ increases the number of variables, such as coal depth, seam thickness, surrounding stratigraphy, and so forth. This collection of variables influences the subsequent behavior of coal simultaneously, and weighing their relative impact is a challenge for researchers. “A problem never exists in isolation; it is surrounded by other problems in space and time” (Ackoff, 1956). Having a substance such as coal that we know so much about, and yet so little, we have to ask what can be learned.An experimental study using Fourier Transform Infrared Spectroscopy (FTIR) was undertaken to determine if the chemical structure of coal contains information which may lead to a better understanding of triggers or attributes which may, in turn, lead to an increased probability of a dynamic failure event. While a full analysis of the factors driving dynamic failure are beyond the scope of this study, it is possible that a better understanding of the chemical structure of coal will lead to an increased knowledge of its inherent behavior, including its propensity to burst."

Jan 1, 2019

By B. McHenry, A. E. Wraith, P. J. Mackey

The Wallaroo smelter on the Yorke Peninsula, South Australia commenced smelting operations in 1861 treating ores from the nearby Moonta and Kadina mines. The plant expanded and modernized on several occasions and was a leader in the successful introduction of new technology to improve operations. It operated continuously until 1923 when local mines became exhausted; in the closing stages of the 19th century it was the largest copper smelter in the world outside of those in Swansea, Wales. In 1892 a small electrolytic refinery was established at Wallaroo, the first in Australia, based on principles developed by Elkington at Pembrey, Wales in 1869. The Wallaroo refinery was specifically built to recover gold and silver from copper produced by smelting gold-containing feed materials shipped from Western Australia. This first venture into electrolytic refining was replaced in 1903 by a somewhat larger refinery which, although modest in size for its time, with a capacity of about 1000 tonnes of cathode copper per year, was very productive in precious metals. Anode copper was produced by an updated version of the reverberatory-based Welsh process until 1910 when barrel-type pneumatic converters were introduced based on American practice; subsequently, anodes were cast by tapping the precious-metals rich "bottoms" portion of converter copper as produced at about one-fifth into the copper blow. The present paper describes the Wallaroo refinery, its anode supply and products, supported by initial observations on a sample of a Wallaroo cathode held in the collection of the South Australia Museum, Adelaide SA, Australia. INTRODUCTION Australia ranked 6th in the world for copper mine production in 2018, with an output of 918,000 tonnes of mined copper, after Chile, Peru, Congo, China and the USA; about 40% of Australian mined copper was smelted in the country. Interestingly, the world ranking of Australia in mined copper has, with a few variations, remained about the same for more than 100 years – of interest, it was also the 6th largest country for copper production at 21,089 tonnes in 1899. At that time, all or most of the copper was smelted in the country (Mackey, 2016). Copper was first discovered in Australia in 1842 in South Australia not far from Adelaide; additional copper discoveries in the region soon followed. At first, copper ore was shipped to Swansea, Wales for smelting (Bampton, 2003). However, in addition to the long, 150 day one-way sea passage, it seems Welsh smelters preferred higher grade of ores – these aspects and likely a mood in the new colony to be independent of Swansea (Evans, 2014) evidently encouraged local smelting at the mine sites using small, Welsh-type reverberatory furnaces fired with hardwood as fuel and operated by Welsh and Cornish migrants. The first large copper smelter in Australia commenced in 1848 at Bremer, near Callington some 60 km east of Adelaide. With larger discoveries on Yorke Peninsula, the Wallaroo copper smelter at Wallaroo Bay on the west coast of the peninsula commenced operations in 1861 (Bell & McCarthy, 2008). Thus began one of the most successful, and in its day, one of the most advanced and innovative plants in Australia if not the world. In the late 1860s, it was considered one of the largest copper smelters in the world (Bell & McCarthy, 2008)

Jan 1, 2019

By Michel Ruel

Most plants do not track how their systems perform. Optimization is the easiest way to benefit from your control systems. We suggest an approach in four phases. The first phase is to assess all equipment to determine the performances for instruments, valves, variable speed drives, and other equipment. The second phase is to remediate instrumentation problems, including the ones pertaining to valves, variable speed drives, analyzers, transmitters. When equipment is in order, loops are put back in automatic mode. If a loop oscillates, use standard default values for this type of loop. The third phase consists in validating the control strategies, properly configuring the systems (control system, programs and parameters, HMI, alarms), and then tuning the loops and control strategies. The fourth phase consists in analyzing the process and expected performances in order to optimize the control loops and control strategies. If performance is not sufficient, a decision tree will be presented to determine the right approach: advanced regulatory control, model predictive control, or fuzzy logic control. Once all steps have been completed, control performance monitoring software is used to sustain the results and pinpoint equipment or loops not performing as stated. Alarm management and rationalization could also be performed after auditing the alarm system, if needed. Examples from plants will be used to demonstrate how this step-by-step method is applied and produces results. INTRODUCTION Maximizing what you already have is the best investment to remain competitive. This article aims to show the benefits of a systematic approach using modern tools to improve plant performance. We at BBA suggest dividing the work in four phases, and a subsequent phase can begin when the previous one has progressed: Assess, Remediate, Stabilize, Optimize, or add advanced control. This approach has been successfully applied to several sites. Examples and illustrations from these plants demonstrate how this step-by-step method is applied and produces results. Under the BBA method, there are four questions to answer before proceeding to the next step. For each control strategy, you should ask the following questions: Assessment: Does it work? Remediation: Do you use it? Stabilization: Is it stable? Optimization: Does it perform? Do you need advanced control?

Jan 1, 2019

By J-N. Oyourou, R. McCrindle, C. J. S. Fourie

"Many mines in South Africa were inappropriately closed and left unattended during the last century. These old mines are potential sources of environmental pollution and may pose a health risk to local populations, since the surrounds contain elevated levels of toxic elements. Soil from the old Edendale lead mine property in Mamelodi Extension 11, east of Pretoria, which was suspected to be contaminated with lead, was analysed. The mine, which primarily extracted galena, was decommissioned in 1938. During this study, the old mine property and surrounds were screened for zinc and lead using a field-portable X-ray fluorescence (pXRF) spectrometer. The metal concentrations, which ranged from 18 to 7 300 mg/kg for zinc and from 50 to 21 000 mg/kg, for lead, were plotted together with the GPS coordinates to produce a concentration distribution map for lead and zinc. This map revealed three anomalies of unacceptably high concentrations, possibly corresponding to areas where ore had been piled or dumped to waste from the old mine. Thirty-six of the soil samples that were analysed by pXRF on site were selected and analysed in the laboratory using inductively coupled plasmaoptical emission spectrometry (ICP-OES) for verification purposes. The zinc and lead concentrations obtained from the two analytical methods were compared using linear regression analysis. Excellent correlation was obtained between the results from the two methods (r2 = 0.99 for zinc and r2 = 0.95 for lead). IntroductionEarly economic development in South Africa was based mainly on mining. However, these activities left a legacy of approximately 6 000 improperly closed mines scattered throughout the country (SAI, 2009; van Schie, 2012). Due to their proximity to settlements, these abandoned mines may pose a potential health risk to humans and an environmental hazard. Mining activities generate large amounts of waste, mostly in the form of overburden and process tailings, which often contain high concentrations of toxic elements. Bioavailable toxic elements can contaminate crops growing in the polluted area (Kala, 2010; Marwa, Meharg, and Rice, 2012) or eventually migrate and detrimentally affect the groundwater (Rösner and van Schalkwyk, 2000). Moreover, sulfides accumulated in mine waste generate acid minewater (Rösner and van Schalkwyk 2000). Unfortunately, owners of mines, closed before the promulgation of the Minerals Act more than twenty years ago (Act 50 of 1991), avoided the compulsory rehabilitation of the environment enforced by this legislation. Toxic elements, such as lead, which were confined within ores, may become exposed through mining and are therefore more easily mobilized within the environment. Elements essential to human and plant metabolism, such as zinc, when exposed by mining activities, may become hazardous due to elevated concentrations (Aslibekan and Moles, 2003; Wuana and Okiemen, 2011). Humans exposed to potentially toxic metals may experience harmful effects as discussed elsewhere (Nriagu and Pacynar, 1988; Wayne and Ming-Ho, 2005)."

Jan 1, 2019

By Mehmet Canbazoglu, Kaarlo Haavanlammi, Hannu Laitala

Cobalt is currently a critical metal because of the increasing number of electrical vehicles forecast for production. Copper and zinc are base metals that are used in many everyday applications, including vehicle production. Eti Bakir Co. Mazidagi Phosphate Plants in the Mazidagi district of Mardin, Turkey is a multi-product facility that produces cobalt, copper, and zinc, as well as fertilizers, from the roaster calcine. Roaster off gas is treated in a sulfuric acid plant (SAP) and the acid itself is utilized in fertilizer production. The comminution circuit, roaster, SAP, and calcine leaching process were developed by Outotec and integrated with the fertilizer production process implemented by Eti Bakir A.Ş. This paper describes the hydrometallurgical calcine leaching process used at the plant, with a focus on the oxidative pressure leaching of the cobalt, zinc, and copper-containing calcine. The cold and hot commissioning phases of the pressure leaching autoclave start-up are discussed together with experiences from the ramp-up period. The production processes of the copper cathode and cobalt and zinc-containing salts are also presented together with some of the plant’s operating parameters. INTRODUCTION The ETI Bakir A.S. fertilizer plant, Turkey, is located in Mardin Province near the border with Syria, (Figure 1). The leaching plant project was started in 2012. The purpose of the plant is to separate the valuable metals from the calcine produced by the pyrite roasters, which are used to produce a SO2 containing gas for the new sulfuric acid plant. Fertilizer production requires sulfuric acid, and for this reason a sulfuric acid plant was built; customer already had access to pyrite concentrate, which is used as the roaster feed. During the engineering phase of the roaster and acid plants it was noticed that the roasted calcine contained considerable amounts of valuable metals like cobalt, copper, and zinc. To recover these metals, a calcine leaching process was developed at the Outotec Research Center in Pori, Finland. The main process connections of the Mazidagi site are shown in Figure 2.

Jan 1, 2019

By L. Van Wyk, J. Fernandez, J. Suarez, L. J. Diaz, A. Uria, D. Breeuwer

"Ventilation is an essential component of any underground mine, playing a vital role in ensuring the health and safety of workers, and a mine’s continuous operation. At a time when mining companies are increasingly having to move to deeper underground operations in pursuit of high-grade ore-bodies, the search is on for more efficient ventilation systems that will allow mining to be carried out at even deeper levels whilst ensuring the protection of workers and the maximisation of productivity through temperature management and the lowering of energy costs. Mining companies today are looking for innovative ways to deliver new technologies and procedures to enhance their mine’s profitability. Energy consumption by mine ventilation systems is higher than ever due to stringent specifications of underground equipment (primarily combustion engine emissions), air quality standards and mining at deeper levels which all require more powerful ventilation systems. With energy costs associated with operating ventilation systems being a mine’s second-highest cost of production after labour, finding the optimal ventilation solution is critical to a mine’s performance. Proper fan design remains a major factor in reducing capital expenditures (CAPEX) and operational expenditures (OPEX), which means that there are compelling reasons for making use of comprehensive factory testing at full power before fans are dispatched to site to simulate the mine’s current and future design requirements, and thus verify the fan’s effectiveness in ‘real’ conditions.INTRODUCTION A primary mine fan is considered the heartbeat of the entire mine ventilation system, drawing fresh air from the surface and providing a safe environment for miners. A ventilation system’s lack of performance often leads to a reduction in acceptable air quality levels for underground working operations and can potentially have an adverse impact on production rates."

Jan 1, 2019

By C. Matthews, A. Vo

"Australia is one of the world’s leading exporters of bulk commodities and the extensive use of sampling equipment is key to the successful management of each mining operation. At the process plant, without a full understanding of the feed, product and tails, it is impossible to fully optimise the performance of the plant, such that the metallurgical balance is often open to error. At the port, a statistically correct, bias free and compliant sampling system is crucial to ensuring exported minerals are reflective of their true value and to avoid penalties. Over the last decade, as a result of the iron ore boom, there has been high demand for reliable, representative and standard compliant solids sample systems in Australia. This paper reviews several solids sampling applications at Australian mine sites, the challenges and experience gained and how the implementation of reliable representative sampling systems has provided better understanding of plant process performance, improved plant control and overall benefits to the operations.INTRODUCTION Mining is the primary contributor to the Australian economy with Australia ranking in the top 4 in economic resources for 21 primary industrial minerals in 2016 (Britt, et al., 2017). Australia is one of the world leaders in the export of the majority of its commodities including gold, copper and iron ore (Britt, et al., 2017). Therefore, a suitable and standard compliant sampling system is essential for evaluating plant performance and content verification. At the mine and at the port, the larger iron ore miners in Australia have developed stockpile models to predict the grade of their ore down to individual blocks of the stockpile. This allows the miner to create the right blend of material for sale to their customers and ensures they are not underselling their product or at risk of penalties for impurities or low grade. As an example, the average difference between the benchmark 62% Fe and low grade 58% Fe fines at the time of this report averaged US $30/tonne according to the Metal Bulletin Iron Ore Index. At a shipload of 180kt this would be a variation of US $5.4M. Whilst this is an extreme example, it highlights the economic importance of producing the correct grade product and a recognised representative sample of said product."

Jan 1, 2019

By A. Romero

"Most underground mines require heating or cooling systems to meet health and safety standards in the working areas. In regions where daily or seasonal fluctuations of environmental conditions exist, these systems tend to be over-sized and operate at low average load factors, which increase both investment and operating costs. One possible approach to reduce the temperature variations of the fresh air supplied to the mine, and so reducing the investment in large heating or cooling systems, is to use rock as a thermal regenerator or thermal storage system. Packed rock beds act as thermal inertial units, damping the atmospheric temperature oscillations to provide a more constant fresh air temperature. However, although regenerators exist in some mines, and packed bed rocks have been studied in detail in solar thermal power applications, there is a lack of tools to design new and sufficiently large storage systems of this kind. This work fills the existing gap by presenting a methodology to design and evaluate the impact on the ventilation systems of these regenerators. The method is validated using existing rock bed systems found in the literature and illustrates possible designs for small and large size regenerators in both hot and cold climates.1 INTRODUCTION “ It is quite amazing how often answers to extremely complicated problems can be obtained in this way, by using greatly simplified models of the real situation for the purpose of calculation.” Whiller, A. in private communication to J. S. Stachulak (1989). Motivation Most underground mines located in regions with extreme climatic conditions require the thermal pre-treatment of the fresh ventilation airflows, whether for heating or cooling. Heating commonly is needed in sites with sub-zero temperatures and is usually effected by direct or indirect burning of natural gas or propane. Alternatively, cooling is required in areas with hot temperatures, or in mines with high underground thermal loads where the fresh air at ambient temperature cannot provide enough refrigeration. Thus, when the ambient air conditions cannot provide by itself enough thermal power to ensure safe underground working conditions, a heating or cooling plant is required, which involves a considerable equipment and operation cost."

Jan 1, 2019

By J. L. Bellanca, L. R. Swanson

DISCLAIMER The findings and conclusions in this paper are those of the authors and do not necessarily represent the official position of the National Institute for Occupational Safety and Health, Centers for Disease Control and Prevention. Mention of any company or product does not constitute endorsement by NIOSH. ABSTRACT Proximity detection systems (PDSs) for mobile machines have the potential to decrease injuries and fatalities. Early adopters of the technology have identified some challenges, which presents an opportunity to explore and improve the integration of mobile PDSs in underground coal mines. The current study applied the task-technology fit framework to investigate the fit between mobile PDS technology and mining relative to health and safety, from the perspective of leaders at two coal mines. Quantitative results from the study show that mine leaders evaluated mobile PDS favorably for training and ease of use, system feedback, user authorization and experience, and less favorably for safety, compatibility, task completion, and reliability. Qualitative results reveal specific task, mine, and system characteristics that may have influenced leaders' evaluations. The study includes considerations for safe technology integration. INTRODUCTION Striking, pinning, and crushing accidents related to mobile machines continue to be a major concern in underground coal mining. The National Institute for Occupational Safety and Health (NIOSH) linked 22 of the 75 underground mine fatalities reported between 2011 and 2015 to power haulage [1]. The Mine Safety and Health Administration (MSHA) asserts that proximity detection systems for mobile machines (mobile PDSs) could help to prevent these types of fatal injuries [2]. Mobile PDSs use a collision avoidance technology that allows the mine to establish hazard zones and employ electromagnetic sensors to detect workers equipped with a miner-wearable component (MWC) working near these mining machines. The authors characterize a mobile PDS as an automated technology, because—in line with Lee & See’s [3] definition of automation—a mobile PDS actively “selects data, transforms information, makes decisions, or controls processes” (p. 50). When the system detects workers in the established hazard zones, it issues alerts and slows or stops the mobile machine. Even though a mobile PDS may be a viable and promising safety solution, there are still a number of questions regarding how well this automated technology will fit with mining tasks and conditions. Using a mixed-methods approach, the current study explored factors that influence the fit of mobile PDSs in the underground mining environment.

Jan 1, 2019

By J. L. Wilson

"Many modern concentrators with VSD driven SAG mills still rely on the control room operator to manually adjust the speed in reaction to increasing bearing pressure. All too often, the problem with this strategy is by the time the operator reacts with a sudden speed increase, the SAG Mill is likely already on its way to loading up. To assist the new operators, the SAG Mill at B2Gold’s Fekola Mine in Mali needed a robust control that could handle load changes and unmeasured disturbances with minimal operator intervention. With modern Distributed Control Systems (DCS) powerful enough to run advanced control, they often have Model Predictive Control (MPC) blocks built in or available as an “add-on” license, and thus MPC can be readily implemented within the modern concentrator with a relatively low added capital cost. This paper discusses an implementation of two single output MPC controllers to control the SAG Mill at Fekola. This was implemented using the existing signals and advanced control blocks available to the installed DCS.INTRODUCTION Many modern concentrators with VSD driven SAG mills still rely on the control room operator to manually adjust the speed in reaction to increasing bearing pressure. All too often, the problem with this strategy is that by the time the operator reacts with a sudden speed increase, the SAG Mill is likely already on its way to loading up. The next step the operator may take may be to cut back the feed rate, or production until the SAG is once again stable. With this sudden reaction comes an abrupt change in SAG rotational speed and power consumption that sends a surge of material down the circuit as the mill suddenly ejects more pulp. Furthermore, choosing a higher rotational speed can lead to higher than normal liner wear as the cataract overshoots the toe of the charge and impacts the liners. After start-up at B2Gold’s Fekola Gold Mine in 2017, the SAG mill was being controlled manually. The SAG rotational speed was adjusted manually by the operator in step changes depending on whether the SAG bearing pressure was increasing, decreasing or stable. During this time of manual control, the SAG fresh feed rate was also adjusted to a tonnage setpoint with a PID controller. Generally, the SAG fresh feed rate setpoint was kept at a target value, but then the feed rate was throttled back if the SAG mill or grinding circuit showed signs of overloading. The extra challenges were that the operators had limited experience and were concurrently learning how the plant operated. Also, they were also occupied with managing situations in the rest of the plant. Often their attention was drawn away from the SAG mill and during that time, the SAG Mill would load up before they could react."

Jan 1, 2019

By Rami Abousleiman, Gabriel Walton, Sankhaneel Sinha

"Although conventional coal mine designs are conservative regarding pillar strength, local failures such as roof-falls and pillar bursts still affect mine safety and operations. Previous studies have identified that discontinuous, layered roof materials have some self-supporting capacity. This research is a preliminary step towards understanding these mechanics in coal-measure rocks. Although others have considered broad conceptual models and simplified analogs for mine roof behavior, this study presents a unique numerical model that more completely represents in-situ roof conditions. The discrete element method (DEM) is utilized to conduct a parametric analysis considering a range of in-situ stress ratios, material properties, and joint networks to determine the parameters controlling the stability of single-entries modeled in two-dimensions. Model results are compared to empirical observations of roof-support effectiveness (ARBS) in the context of the coal mine roof rating (CMRR) system. Results such as immediate roof displacement, overall stability, and statistical relationships between model parameters and outcomes are presented herein. Potential practical applications of this line of research include: (1) roof-support optimization for a range of coal-measure rocks, (2) establishment of a relationship between roof stability and pillar stress, and (3) determination of which parameters are most critical to roof stability and therefore require concentrated evaluation.INTRODUCTIONRecent studies on pillar design have suggested that the assumptions utilized in traditional methods such as tributary area theory (TAT) (i.e. overburden has no self-supporting capacity, infinite pillar array, and CHILE material properties) are invalid in many geo-mining conditions (Esterhuizen, Mark, and Murphy, 2010; Frith and Reed, 2017). Although TAT is conservative with respect to pillar loading, and mine fatalities have steadily decreased since 1990, roof-falls and pillar bursts still occur and injure hundreds of miners per year (Mark, Pappas, and Barczak, 2011). Even though large-scale global mine failure has not occurred in a US coal mine since 2007, the mechanics of global and local stability as governed by the relationship between geologic parameters, mine geometry, and engineering design are still not well-constrained.Numerical methods are a highly effective tool that can be used to gain further insight into these relationships. When using such an approach, calibration to existing empirical relationships is imperative to ensure that numerical model results are realistic. In this study, we utilize the discrete element method (DEM) approach in Itasca’s Universal Distinct Element Code (UDEC v. 6.0) (Itasca, 2010).DEM accounts for explicit separation and contact of individual deformable blocks (Jing, 2003) and captures how discontinuities can affect system behavior. Discontinuous and anisotropic rockmass properties are typical features in coal-measure rock which contain various horizontal (bedding) and sub-vertical (joints) fractures depending on their depositional environment, diagenesis, and historic and current stress states."

Jan 1, 2019

By Dan Miners

"This presentation will provide an overview and understanding of Mine Safety and Health Administration (MSHA) and Ontario Regulations for Mines and Mining Plants. It includes discussions on the history and practical development of the standards and an overview of engineering best practices from a construction, maintenance and operational viewpoint. INTRODUCTION Ontario is one of the safest mining jurisdictions in the world and has some of the most comprehensive regulations for the construction, operation and maintenance of a mine. In the USA, several operators have adopted some or all of the practices prescribed by the Ontario Regulations as an internal procedure. Experience has demonstrated that these plants are indicating less unplanned downtime and fewer issues with MSHA inspectors in their hoist plants. HISTORY AND THE REGULATIONS Both Canada and the USA have had some form of laws governing the operation of mines since the late 1890s. The paths of legislation have run in reasonably parallel lines, continually improving the health and safety conditions in the mining industry. Ontario Mine Health and Safety In the 1970s the accident rates in mining were higher than any other industrial sector; this prompted a Royal Commission on the Health and Safety of Workers in Mines (the Ham Report). The recommendations of this report, published in 1976, generated several changes in the regulations regarding worker safety in mines. Following the release of the Ham report, the Occupational Health and Safety Act (OHS) was passed by the Legislature in 1978. The Act is a set of comprehensive laws governing almost all Ontario workplaces, and it replaced separate laws governing different industrial sectors. OHS is enforced by the Ministry of Labour (MOL), and this discussion will focus specifically on Ontario’s Occupational Health and Safety Act, R.R.O. 1990, Regulation 854, Mines and Mining Plants, Part X Mine Hoisting Plant (Ontario Regulations). USA Mine Health and Safety A coal mine explosion in West Virginia and medical studies on occupational disease led to the 1969 Federal Coal Mine Health and Safety Act (Coal Act). The Coal Act was the most comprehensive and stringent Federal legislation governing the mining industry to date. The Mining Enforcement and Safety Administration (MESA) was formed, following the 1973 Act, as a new departmental agency to assume the enforcement of safety and health in mines. The Federal Mine Safety and Health Act of 1977 (Mine Act) transferred enforcement responsibilities from the Department of the Interior to the Department of Labor and named the new agency the Mine Safety and Health Administration (MSHA). This agency enforces the Code of Federal Regulations (CFR), and this discussion refers to CFR Title 30 Mineral Resources, Chapter I Mine Safety and Health Administration, Department of Labor, Subchapter K—Metal and Non-metal Mine Safety and Health (MSHA)."

Jan 1, 2019

By G. A. Sutton

"At the San Manuel mine (Arizona, USA), in-situ copper leaching of a copper porphyry deposit was carried out from 1986 to 1999 during underground and open-pit mining. In 1993–1994, well¬field testing of the supergene zone, composed primarily of chrysocolla and copper-rich clay minerals, led to estimates that 52% of the acid-soluble copper (ASCu) could be recovered during in-situ leaching; however, the actual recovery from zone 6, which had the longest leach history, was approximately 42%. Comparing drillcore assay data from holes drilled before and after leaching also indicated an approximate recovery of 42%. The discrepancy between the predicted (52%) and actual (42%) recovery is probably related to several factors, including difficulty maintaining fluid saturation, channelling effects, and gypsum precipitation. ¦ KEYWORDS Copper oxides, in-situ leaching, Modelling, Porphyry, Solvent extraction and electrowinning (SXEW), Well-to-well RÉSUMÉ À la mine San Manuel (Arizona, États-Unis), on a procédé de 1986 à 1999 à la lixiviation in-situ de cuivre d’un gisement porphyre cuprifère pendant l’exploitation minière souterraine et à ciel ouvert. En 1993 et 1994, des essais effectués dans des champs de captage de la zone supergène, composée principalement de chrysocolle et de minéraux argileux cuprifères, ont abouti à des estimations selon lesquelles on peut récupérer 52 % de cuivre soluble dans l’acide (ASCu) pendant la lixiviation in-situ ; toutefois, la récupération réelle dans la zone 6, qui affiche l’histoire la plus ancienne en matière de lixiviation, était d’environ 42 %. La comparaison des données d’analyses de forage obtenues à partir de trous forés avant et après la lixiviation indiquait également une récupération approximative de 42 %. La différence entre la récupération prévue (52 %) et réelle (42 %) réside probablement dans plusieurs facteurs, notamment la difficulté à maintenir la saturation des fluides, les effets de canalisation et la précipitation du gypse. ¦ MOTS CLÉS d’un puits à l’autre, extraction par solvant et extraction électrolytique (SXEW), lixiviation in-situ, modélisation, oxydes de cuivre, porphyreINTRODUCTION in-situ copper leaching at the San Manuel mine, Arizona, USA (Figure 1), began in 1986. It was recognized that some of the copper oxide resource was not economically recoverable by conventional open-pit and heap leach methods using solvent extraction and electrowinning (SXEW) and a high stripping ratio would be required to access part of the resource. At the time, in-situ leaching was becoming popular in the uranium industry, but the approach was virtually unknown in the copper industry, especially at a large scale."

Jan 1, 2019

By Patrick Rennkamp, Wolf-Dieter Trodel, Andy Fearn

"The Jansen shafts are completed using purely mechanical excavation. This paper summarises the geology, a description of the shafts, the method used for excavation and the results achieved along with the challenges encountered and the solutions developed during the project. This experience is now being applied in the next generation machines and shaft sinking processes. This pioneering approach is changing shaft sinking in soft and medium to hard rock. INTRODUCTION The Jansen Mining project located approximately 150 km east of the city Saskatoon is the location of the BHP owned potash mine with an expected mining output of eight million tonnes annually upon completion. Mining contractors DMC Mining Services have used two Herrenknecht Shaft Boring Roadheaders (SBRs) to excavate the two blind shafts with an approximate excavation diameter of ten metres (inner diameter approximately 8.3 m) to depths of -975 and -1005 metres, respectively. The SBRs excavate the rock by a partial-face cutting method, using a transverse cutting drum mounted on a telescopic boom. The excavated rock is then conveyed away from the bench by an innovative pneumatic system and transferred into muck buckets to be hoisted to the surface. No drilling and blasting was done to keep to the BHP philosophy of using only mechanical excavation for this reference project. BHP VISION – MECHANICAL EXCAVATION BHP focused on mechanical excavation at Jansen due to the following perceived benefits: 1.No workers in the excavation chamber (shaft bottom), minimizing the exposure to traditional shaftsinking hazards associated with working in the shaft bottom. 2. Minimal damage to the rock fabric reducing the need for ground support and avoiding potential impact damage to freeze tubes located around the shaft. 3. Accurate excavation diameters with no overbreak, reducing volumes of rock to be removed and replaced with concrete lining."

Jan 1, 2019

By K. Robertson, K. A. Scalise, K. C. Kocsis, M. B. Teixeira

"Many deep and highly mechanized underground metal mines require cooling. In many cases, appropriate working conditions might be fulfilled by ventilation alone, but some require the implementation of cooling systems. The most common cooling systems are bulk air cooling and localized cooling. These systems are effective, but they use considerable amounts of electricity. Ground source heat pumps (GSHP) can supplement existing cooling and heating systems, while geothermal systems can cool the mines in their entirety if there are significant sources of geothermal energy are present. A major advantage of geothermal and GSHP systems are their renewability, which reduces the carbon footprint of the mine.INTRODUCTIONThe western United States has abundant alternative energy sources including a high potential for geothermal energy. Geothermal utilization is a viable energy alternative that many areas throughout the world have access to because high geothermal potentials are located near areas of volcanic activity such as along plate boundaries, mid-oceanic ridges, rift valleys and hot spots (IRENA, 2017). There is significant potential to use geothermal energy for many applications. With constantly evolving and innovative technologies being developed, an increasing number of geothermal applications are becoming feasible. The western United States is an ideal candidate for alternative energy applications due to the geothermal availability and the emergence of modern technology. This paper investigates the incorporation of renewable methods and the alternative energy possibilities of Barrick Goldstrike, located in northern Eureka County, NV and Rio Tinto/BHP Billiton’s Resolution Copper mine located in Superior, AZ.RENEWABLE SYSTEMSGeothermal SystemsGeothermal temperatures are typically defined as either high or low temperature systems(Shengjun, Huaixian, & Tao, 2011). The high-temperature reservoirs (>220°C / 428°F) are feasible forlarge, commercial production of electricity with dry stream and flash stream systems (Shengjun, Huaixian, & Tao, 2011). Low temperature systems, below 220°C (428°F) (Shengjun, Huaixian, & Tao, 2011), aremuch more difficult to use for energy production. Low-temperature reservoir heat can be harnessedthrough the implementation of a binary cycle plant. The working fluid for a binary cycle plant is eitherorganic (Organic Rankine Cycle (ORC)) or an ammonia-water mixture (Kalina cycle). Organic fluids andammonia-water mixtures have low boiling points that allow for the recovery of heat from low-temperaturesources (Eymel Campos Rodriguez, et al., 2013). The efficiency of the binary cycle plant varies depending upon the fluid, thus the proper selection of the fluid is critical for maximum energy output"

Jan 1, 2019

By R. A. (Dick) McIvor

"It is important to ensure that the basic mine hoist plant design fundamentals are incorporated into any new mine hoist plant project before detailed design engineering is commenced. Some of the basic design fundamentals to be considered are: hoist rope fleet and flight angles for good hoist rope coiling, hoist rope harmonic frequency study to ensure that the hoist rope does not run at full speed at a rope resonance frequency, head frame and shaft clearance diagrams to establish the optimum positions for the loading and dumping of the shaft conveyances, access in the head frame and shaft collar for hoist rope and shaft conveyance installation and removal. Failure to consider the hoist plant fundamentals before detailed engineering commences will result in extra costs for hoist plant redesign or a significant increase in operating and maintenance costs for the mine due to increased hoist plant downtime to perform tasks and a lower mine operating efficiency. INTRODUCTION The mine hoisting plant is the most critical single line component in the operation of a shaft sinking operation or a permanent installation. Bad decisions in the design and selection of the hoist plant equipment can significantly add to the operating costs and up-time in the operation of the mine. Mine hoisting plant equipment installed costs represent approximately 5 to 8 percent of the capital cost of a new mine, yet price sometimes becomes the deciding factor for procuring the hoist plant components, sometimes selecting used equipment that may compromise the design and maintainability of the mine hoist plant. Mine downtime can cost upwards of $100,000 per hour and it will not take a very long time to eat up all the so-called savings on hoist plant equipment purchases. This paper will provide guidelines for the design, selection, installation and maintenance of mine hoist plant equipment with the objective to having the right mine hoist plant with the highest operational availability and best maintainability. PRELIMINARY DESIGN INFORMATION Before any engineering commences, the following information needs to be obtained to allow the preliminary sizing of the hoist plant equipment: • Shaft depth: The shaft depth will influence the hoist rope selection based on the material and personnel loads anticipated for the mine design. The shaft depth will also influence the maximum speed of the shaft conveyances. • Annual production: The desired annual production will influence the required payload sizing with allowances for maintenance and inspections of the hoist plant equipment."

Jan 1, 2019

By M. E. Rossi

This paper discusses the use of Conditional Simulation (CS) models to provide mill feed grade profiles for different time periods. The conventional approach of classifying block estimates as ore or waste generally does not adequately represent dilution, lost ore and the anticipated grade control data, including variability of mill feed from the pit and possible stockpiles. The detailed simulation of grade control practices can be done, but at the Pre- or Feasibility stage of the project may be impractical, since drawing dig limits on multiple benches is tedious and time consuming. Using the Feasibility Grade Control (FGC) method as developed by the Centre for Computational Geostatistics (CCG, University of Alberta-Edmonton), the CS models can be processed quickly to establish dilution and lost ore, and predict daily or short-term feed to the mill. The simulated nodes can be aggregated into selective mining units with adequate representation of likely geometries to be recovered from the pit, to mimic anticipated selectivity. An example from a large copper deposit is shown. The study provides an estimated stream of tonnages and grades fed to the plant by mining periods of interest and based on a specific mine design and schedule. The resulting cash flows support the economic and financial analyses of the Feasibility Study; also leads to improving mine schedules; and aids in developing blending schemes if necessary. INTRODUCTION The conventional approach of separating mineralized material into ore or waste categories does not always include a realistic amount of dilution and ore loss. Also, often it does not provide a good estimate of the grade that will be fed to the mill. If the grade control estimates are unbiased, they will over the long run represent the long-term average of grades fed to the mill; but the anticipated variability of mill feed from the pit and stockpile sources may be misrepresented. Some references on traditional grade control implementations can be found in Chunnett (1982); Davis et al. (1989); Srivastava et al. (1992); and Nowak (1992). Alternative methods based on economic variables improved significantly on the purely grade-based control methods, see Douglas et al. (1994). Further developments involved the use of geostatistical conditional simulations (CS) and profit models, which in several cases have been successfully implemented (Aguilar and Rossi, 1996; Rossi, 1997; Deutsch et al., 2000; Norrena and Deutsch, 2002; Neufeld, 2005; Jewbali and Dimitrakopoulos, 2009). But they can be impractical, mostly due to the lack of understanding of the methodology involved; even if semi-automatic dig limit drawing is implemented, there is always a need for is tedious and time consuming checking and corrections, even if using a single profit model derived from the simulated grades.

Jan 1, 2019

"The ventilation-related risks from mines with elemental sulphur include dust explosions, spontaneous combustion with emission of heat and toxic sulphur dioxide or hydrogen sulphide gases, reactions with nitrates, corrosion, acid water, and pyrophoric reactions with naked iron or other metals. Elemental sulphur will form explosive mixtures in air at lower dust concentrations and at lower ignition temperatures than coal or sulphide dusts. Potential controls include primary ventilation circuit design, control of dust deposition and static discharges, enclosing steel surfaces, inert stone dusting, FRAS ducting, humidifying the air, alternate stench gas, self-contained self-rescuers with goggles, careful siting of underground infrastructure, controls on explosives formulations and procedures, mining method selection, controls on surface temperatures and protection of equipment, careful materials selection for ventilation seals and changes to worker clothing and training.INTRODUCTIONSulphur (“Brimstone” in biblical times) is one of the world’s most important industrial feedstocks and is used in a wide range of chemical processes and industries. Until the early 20th Century, most of the world’s production of sulphur came from ‘conventional’ underground mines in Sicily (Demetra produzioni, 2006; Bellia, 2006). This was a hazardous activity. The Frasch solution mining process replaced traditional underground mining of sulphur until the late 20th Century. Most of the world’s production of elemental sulphur is now as a by-product from sour gas produced in petroleum refineries and natural gas installations (Anon, 1993). As such, there is considerable experience in understanding and managing the hazards of elemental sulphur in chemical plants and surface transport.Whilst rare, underground mines with high elemental sulphur contents (as a gangue mineral) create an unusual range of mine design and operational issues, including many ventilation-related ones. The key hazards from elemental sulphur include: primary and secondary elemental sulphur dust explosions, fires and burning (with emission of heat and sulphur dioxide or hydrogen sulphide gas), reactions with nitrates used in explosives, corrosion of steel and other metals, generation of acid water (especially at higher water temperatures), and pyrophoric reactions with naked iron (e.g., ground support, ladderways or underground fixed plant) or other metals including silver and copper (e.g., used in electrical components and equipment)."

Jan 1, 2019

By D. Blackwell, W. R. Reed, G. Ross, S. Peters, M. Shahan

Dust collectors for roof bolting machines generally use a dry box to collect the roof bolting material. Recently, an underground mining operation converted a dry box dust collector to a wet box dust collector with a unique exception from MSHA for testing purposes. Water is routed to the roof bolter from the main water line of the continuous miner. The wet box utilizes a water spray to wet the incoming material. Testing was conducted comparing the two different collector types. Respirable dust concentrations surrounding the roof bolter with the different collection boxes were similar. The main difference in respirable dust concentrations occurred when cleaning the dust boxes. The average respirable dust concentration during cleaning of the wet box was 0.475 mg/m3, and during the cleaning of the dry box the average respirable dust concentration was 1.188 mg/m3. The silica content of the roof material was high, ranging from 28.9% to 52.7% during this study. The results from this study indicate that using the wet box as a collector reduced exposure to respirable dust up to 60%when cleaning the collector boxes. INTRODUCTION Currently, the dry vacuum dust collection system is the standard dust collector on roof bolters in underground coal mining. It has been proven to be an effective dust control to prevent roof bolter operators’ overexposure to coal mine respirable silica dust during roof bolting operations [Potts eta l, 2011 and Colinet, 2013]. The dry collection system works as follows: drill cuttings are vacuumed into the precleaner. The precleaner dumps oversized material onto the mine floor while undersized material enters the dust box via vacuum airflow produced by a blower. The cuttings entering the dust box are either deposited on the floor of the dust box or into a dust collector bag. The vacuum airflow leaves the dust box through a final filter which removes any small particles from the airflow. Figure 1 shows the internal view of two dry collection system boxes; one that does not use the dust collector bags and another that uses the dust collector bags. Dust collectors that use dust collector bags to contain material inside the dust collector box have been shown to provide better protection to roof bolter operators than dust collectors that do not use the bags [Listak and Beck 2008]. The dry collectors are very efficient at reducing respirable coal mine dust exposure from roof bolting activities. Recently, Blue Mountain Energy’s Deserado underground coal mining operation, outside Rangely, CO, made a modification to the dry collector system to convert it to a wet collector system with a unique exception from the Mine Safety and Health Administration (MSHA) for testing purposes. The wet collector system still uses a vacuum system to pull material from the vertical roof bolt hole, but incorporates a water spray nozzle located inside the dust box to wet the incoming material. The flow through the nozzle ranges from 1.9–7.6 lpm (0.5–2.0 gpm) at 0.69 MPa (100 psi). The conversion to the wet collector system removes the precleaner and the cyclones inside the dust box. The wet material (sludge) then empties through a specialized valve in the bottom of the box. The final filter is still used to prevent respirable dust from leaving the dust box through the exhaust. During operation, the wet collector dust box is opened and hosed clean after roof bolting every place. After every two entries the final filter is changed out. Figure 2 shows the inside of the wet collector box.

Jan 1, 2019

By M. Tokoglu

Accurate estimation of resources is one of the major challenges in mineral project evaluation. Contemporary mineral resource estimation practice calls for contribution from several disciplines and execution of several interdependent tasks. 3D estimation domain modelling is obviously one of the most essential components of such a substantial process which forms the basis of this research. The study constitutes a comparative analysis of four major domain modelling techniques; (i) explicit modelling, (ii) implicit modelling, (iii) indicator kriging, and (iv) conditional simulation. It involves comparison of outcomes for alternative scenarios to assess the implications of the modelling decision on resource estimates of a polymetallic massive sulfide deposit located in western Turkey. Thus, identical grade estimation method and parameters are considered to identify the discrepancies arising only from the choice of the domain modelling approach and underlying assumptions. Economic implications are demonstrated in the form of range of outcomes for the extends of the ultimate pit, ore tonnages (min:37.0 Mt, max: 46.7Mt), waste tonnages (min:201.2 Mt, max: 251.2 Mt), stripping ratios (min:5.18, max: 5.71), and total pit values (min: $1.05B, max: $1.45B). Examination of solid models as well as cross-sections revealed that major discrepancies are observed beyond outlying drillholes. Therefore, it has been proposed that assumptions regarding extrapolation distance is the main source of mentioned dissimilarities. Key words: Domain modelling, explicit modelling, implicit modelling, indicator kriging, conditional simulation INTRODUCTION Resource estimation is apparently a challenging process calling for extensive expertise and input from several sources, each of which introducing its related uncertainties. In the last decades, substantial role of quantitative analysis of several forms of risk and uncertainty in evaluating projects’ upside potential and downside risks has been realized. Studies indicated that mining companies have been severely impacted because of not meeting project expectations. As noted by Vallee (2000) “… in the first year of operation after start-up, 60% of mines surveyed had an average rate of production less than 70% of designed capacity”. Several other studies on mining projects also revealed that uncertainties related with the resource model are one of the major contributors of mentioned shortfalls. In this perspective, quantification of uncertainties associated with each component of estimation process is critical. 3D estimation domain models capturing major mineralization controls are the fundamental components of contemporary mineral resource estimation. Domain models are key guiding tools for estimation and are products of a complex process involving many unknowns and assumptions. There exists a number of 3D modelling alternatives which are distinct with respect to complexity, time and effort involved. Acknowledging potential influences on downstream mining practices and relavent economic implications, risks and uncertainties associated with 3D domain modelling are critical yet poorly studied aspects.

Jan 1, 2019