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By G. Soni

A first principle flotation model has been derived from the basic mechanisms involved in flotation. The model consists of a series of analytical equations for bubble generation, bubble-particle collision, attachment, detachment, and froth phase recovery. The model can predict flotation from both hydrodynamic and surface chemistry parameters such as bubble size, particle size, energy dissipation rate, ?-potentials, contact angles (?), etc. The model has been validated in a series of laboratory batch flotation experiments, in which mono-sized glass beads are used as feeds. The experimental results are in good agreement with model predictions both in terms of grade and recovery.

Feb 23, 2014

By M. D. Johnson

The San Andres mine, located in the western mountain region of Honduras, Central America, contains epithermal gold mineralization as disseminations, in quartz-chalcedonic veins and stockworks. Host rocks include a thick sequence of Cretaceous to Tertiary conglomerates, sandstones, rhyodacite tuffs and andesites. Mineralization is controlled by northwest and northeast striking, normal faults and fractures which dip steeply east and west. Currently, 500 STPD of 1. 93 Grams/MT gold ore is being open-pit mined from the conglomerate and andesite. The mine is at the west end of a mineralized zone that can be traced over an area of approximately 1.5 square kilometers.

Jan 1, 1993

By MAHESH SHRIWAS, CHRISTOPHER PRITCHARD

Ventilation monitoring and control in mines are becoming an integral part of day-to-day activity for maintaining health and safety of miners. The authors evaluate potential real-time monitoring solutions for detecting and reducing diesel particulatematter, mine fires, and dust in situ, and examined the state-of-the-art use of ventilation monitoring and control in underground mines for detecting and reducing air contaminants to acceptable regulatory limit. Authors review relevant documents, including research papers, trade publications, and manufacturers’ website-based information, to identify research gaps. The authors also evaluate contemporary sensors (airflow, gas, dust, silica), control system and software technologies, data transport systems, Industrial Internet of Things, ventilation network simulators, and control devices to identify potential health and safety research gaps. In this study, examples of some mines from Canada, Australia, and the USA are included where ventilation monitoring and controls have been applied. Overall, this review identifies multiple challenges and research gaps in applying mine monitoring and control systems that could be the focus of future research, offering potential improvements to miner safety and health and financial benefits.

May 12, 2020

By Kanchan Mondal, Gopi Bylapudi, Anand Bhagwat

Corrosion of steel roof support systems can cause potential premature failure of the support, thus adversely affecting the excavation stability and rock-related safety. An in-house corrosion test system was designed and developed to test full-length roof bolts for material performance based on tensile load capacity and strength under different corrosive conditions found underground. The roof bolts tested are also used to identify the possible corrosion mechanisms that influenced the bolts’ performance over time. Initially, the most commonly used bolt material in the USA, the ASTM A615 grade 60 steel roof bolts, was tested with and without stresses in a simulated underground coal mining environment for approximately 6 months, and the results are discussed. Localized corrosion forms such as crevice and pitting were mainly observed after testing. The stressed and unstressed roof bolts with and without threads that were tested in alkaline coal mine corrosive environment for 6 months passed their load-bearing capacity as per ASTM F432 test standards. From the results, it is concluded that this test protocol could be applicable to test the material performance of different roof bolt metallurgies and coatings with desired modifications to the proposed methodology for the specific underground mine environment. This paper mainly discusses the test system and protocol and shortcomings of the system and makes recommendations based on the observations and results.

By William Gleason

Despite a global slowdown in most mining sectors, Caterpillar, the world?s largest mining equipment maker continues to forge ahead with new, and improved offerings to the global mining industry. On Nov. 10, as part of its Loading and Hauling Mining Focus Session at its Tinaja Hills proving grounds south of Tucson, AZ, Caterpillar unveiled to customers and media its two latest mining products, the 994K wheel loader and 6020B hydraulic shovel. The Caterpillar 994K wheel loader builds on a nearly 25-year history of the 994 model but with one noticeable difference ? the 994K is bigger ? much bigger. Weighing in at 239,142 kg (527,218 lb) the 994 K is up to 20 percent larger and comes with up to 30 percent increase in payload capacity. This behemoth of a machine is currently being tested at Caterpillar?s Tucson Proving Grounds, Anglo Gold Ashanti?s Cripple Creek and Victor gold mine in Colorado and Taseko?s Gibraltor copper and molybdenum mine in British Columbia, Canada.

By H. G. Wickes

Virtually all fluorine consumed by the aluminum industry is as the electrolyte of the Hall-Heroult process for producing primary aluminum. A small amount of fluorspar is used but most fluorine is consumed as either aluminum fluoride or cryolite. Some fluorine- containing materials are used in secondary aluminum production, but the amount is negligible compared with primary production requirements. Any analysis of the future of the primary aluminum industry must take into account two powerful and closely related driving forces which are shaping that future. These factors are increasingly stringent restrictions on the emission of pollutants and the continuing cost-price squeeze. Nowhere do these factors combine more forcefully than in the area of fluorine consumption. We can safely assume that industry efforts to reduce fluorine consumption will be intensified and that these efforts will be fruitful. This paper will attempt to identify and quantify the factors and trends of fluorine consumption during the next decade. We will be concerned primarily with the demand for new fluorine. Sources of new fluorine will not be treated.

Jan 1, 1973

By John Newby, Mahmood Khwaja, Bernard Theron, Janice McGovern, Bernard Catalano, Michael S. Schultz

Launching a full-size pressurized-face Tunnel Boring Machine (TBM) in difficult ground conditions is always challenging. Recently, few projects have innovated the process by scaling the trenchless method of pipe jacking, and modified steel bell approach, to facilitate the launching of a full-size TBM without the need for large and deep trenches, starter/tail tunnels, or for incrementally installing supporting gear as the machine advances. This paper presents three such projects; evaluates the post-bid contractor proposed modifications; details the innovative use of pre-cast pipe segments to facilitate machine launch; and, provides an overall assessment of the benefits, challenges and lessons learned related to the modified approach.

Jun 13, 2021

By R. Gray

"Experience from Australia has identified what is referred to as non-conventional surface subsidence behaviour. This occurs under irregular surface topography, resulting in valley closure, valley floor uplift or “upsidence”, and far-field horizontal movements – even occurring beyond conventional “angle of draw” limits. This paper discusses such behaviour recently observed in Pennsylvania and focuses on the 2005 case of Duke Lake Dam in Ryerson Station State Park. In July 2005, there was a significant increase in water leakage through a number of growing cracks in the dam leading to the dam being breached to avoid an uncontrolled failure. An underground longwall mine was located approximately 900ft to the north, mining at depths of 330 – 720ft. Investigations (including a subsequent ground movement monitoring program) found a range of evidence in the vicinity suggesting that valley closure and far-field horizontal movements may have occurred resulting from the adjacent mining. The paper discusses the phenomenon of non-conventional subsidence behaviour and the Ryerson State Park case study, including an assessment of mining, geology and subsidence impacts and suggested ground behavioural mechanisms. INTRODUCTION Non-Conventional Subsidence The conventional understanding of coal mine subsidence on which most current subsidence understanding and prediction techniques are based, includes the concept of angle of draw which effectively limits the lateral extent of subsidence effects and impacts. Within this zone – above and marginally beyond the boundary of mining – downward vertical subsidence is the dominant component, together with localised horizontal movements towards the mined region, with related tilts and strains. However, more recent experience from Australia over the last two or three decades has identified what is referred to as non-conventional surface subsidence behaviour. This is found to occur in areas of irregular surface topography or variable terrain, and is characterised by phenomena such as valley closure, valley floor uplift or upsidence, and far-field horizontal movements, all of which can occur beyond the conventional angle of draw limits. NSW Department of Planning (2008) defined the conditions for both conventional and non-conventional subsidence behaviour as follows: “The conventional or general model of surface subsidence, which finds worldwide acceptance, is based on assuming the following site conditions:"

Jan 1, 2015

By Shiwei Wang, Ziwen Li, Chenhu Zhang, Peng Chen, Chengyong Wang

Accurate prediction of the partition coefficients in coal gravity separation is key to improving the preparation efficiency of coal and promoting its clean utilization. In China, the approximate formula method (AFM) has been applied to the calculation of coal gravity separation partition coefficients for decades, but its accuracy is limited. To improve the accuracy of the predicted partition coefficients, and thus the product yield of coal preparation plants, the present study proposes a modified hyperbolic tangent model to derive direct calculation formulas for the heavy medium and water medium separation partition coefficients. Four groups of coal samples were used to verify the accuracy of the direct formulas, and their predictions were compared with those of the AFM. The results showed that the partition coefficients and partition curves predicted by the direct formulas were closer to the actual values than those predicted by the AFM. Further, when the cleaned coal ash content was basically the same, the cleaned coal yield predicted by the direct formula was lower than that predicted by the AFM, and was also closer to the actual value. These results demonstrate that the direct formula produces more accurate results compared to the conventional AFM. As this formula has a reasonable theoretical basis, is simple to apply, and produces accurate results, it is expected to help improve the design and management level of coal preparation plants.

Oct 15, 2022

By Mike Hall, Tim Kelly, Mohammad Reza Jafari, Ulf Georg Gwildis

"Qatar’s capital Doha is undergoing major infrastructure improvements including a multiphase stormwater management program. Although located in an arid climate, Doha experiences flooding during rainfall events. Dewatering operations and rising groundwater levels add to the management needs. To address those needs, construction of the Musaimeer collection tunnel along Doha’s southern rim is being followed by a marine outfall tunnel connecting a pump station to a dispersion field 10 km offshore. Qatar’s geology is characterized by sabkha deposits, a series of predominantly weak and karstic rock strata that creates challenging conditions for mechanized tunneling, as highlighted by the uncontrolled flooding of a tunnel boring machine (TBM) used on the Doha Metro tunnels. Risk associated with these challenges is magnified for the outfall tunnel by drive length, sub-sea elevation, and a single access point. This paper describes the outfall exploration strategy and design decisions made in light of experience gained during the collection tunnel construction. CONTEXT – STORMWATER MANAGEMENT PROGRAM Qatar has an arid climate with an average annual precipitation of less than 100 mm. Precipitation is mostly confined to the winter months when rare, but occasionally heavy rainfall events easily lead to flooding in Doha’s metropolitan area. Its coastal location and flat topography a few meters above the sea level mean that the depth to the groundwater table is generally shallow. The karstic aquifers in the regional dolomite and limestone series contain groundwater of high salinity, which is not suitable as a potable water source. For supplying Doha’s population of more than 900,000 (2014) with potable water, the Ras Abu Fontas seawater desalination plant is operated about 10 km south of the city. This potable water production capacity is crucial for Doha’s development and – in conjunction with overirrigation and leaking sewage tanks – is also the root cause for rising groundwater tables that have been observed over the past years."

Jan 1, 2016

By B. R. Arvidson

Rare-earth elements have some unique properties that are used in many common applications, such as TV screens and lighters. In the 1970's, rare-earths began to be used in a new generation of magnetic materials that have very unique characteristics. Not only were these stronger in the sense of attraction force between a magnet and mild steel (high induction, B), the coercivity (He) is extremely high. This property makes the magnetization of the magnet body composed of a rare-earth element alloy very stable, i.e., it cannot easily be demagnetized.

Jan 1, 1998

By R. W. Utley

Over one half billion tons of coal per year is scalped, classified, deslimed, drained and rinsed, dewatered and final sized on rotary, vibrating, shaking or stationary screens. The vibrating screen is the industry work horse and performs the bulk of the screening functions in the coal preparation plant. There are two major types of brute force mechanical vibrating screens used in coal preparation plants: (1) the two-bearing one-shaft inclined screen and (2) the four-bearing two-shaft horizontal screen. Both of these types are familiar to coal producers.

Jan 1, 1966

By JIACHENG XIE, Juanli Li, Wenyong Du, Tao Cui, Mengyao Dong, Pengfei Huo

The operation of intelligent coal mining in complex geological environment is still unable to realize automation. In order to realize the autonomous cutting of fully mechanized mining equipment and improve coal production, a mining and transportation equipment dynamic advancement path planning method based on spatial kinematics coordinate deduction prediction and real-time correction prediction of coal-rock state identification of equipment cutting current index are proposed. Firstly, the spatial motion law of the mining and transportation equipment is analyzed, and the mathematical model of the spatial motion of the mining and transportation equipment is established. The relationship between the adjustment of the shearer rocker arm and the pose change of the scraper conveyor is determined, and the coordinate deduction model of the spatial advancement position of the equipment is determined, which provides a theoretical basis for the advancement path planning of the mining and transportation equipment. Then, on the basis of the mathematical model construction, combined with real geological data and equipment information, the three-dimensional dynamic planning of the advancement path of the mining and transportation equipment is carried out from the two dimensions of the horizontal advancement direction and the shearer walking direction. At the same time, the relationship between the cutting current index of shearer and the state recognition of coal-rock mass is analyzed, and the coal-rock mass state identification of cutting current and the adjustment of rocker arm model is constructed, and the real-time dynamic correction of three-dimensional path is carried out, so that the planned path can better adapt to the sudden change of real geological environment. Then, using the unity3d virtual reality technology, a simulation system for the horizontal advancement path planning of the virtual mining and transportation equipment is constructed, which simulates the real advancement operation process of the mining and transportation equipment and conducts advancement training. Finally, the dynamic advancement scheme update prediction based on the existing actual cutting but ahead of the actual cutting is realized in the virtual scene, and the optimal scheme is transmitted into the existing prediction cutting system to guide the actual physical equipment mining. The path planning method can control the coordinate position error of the advancing cutting path within 15 mm, which provides ideas for the research on the advancing path planning of fully mechanized equipment.

Nov 22, 2022

By Mike Moody

"No matter what type of ore is being extracted from a mine, mucking with front loaders can be accompanied by wet fines that cling to every surface. Once loaded into a hopper or conveyer transfer chute, viscous material can quickly build up on the walls to create bottlenecks, clogging the chute and causing expensive downtime.Clearing material from hoppers, chutes, bins and vessels can be done using manpower and tools on hand, but safety experts recommend considering a solution that prevents exposing workers to potential hazards. Operators at modern mining sites, such as the Eagle Mine, located in Western Marquette County of Michigan’s Upper Peninsula, understand that using specialized equipment reduces worker exposure, offers the safest mode of production and provides the most cost-effective lasting results.“Safety is a top priority for us,” said Ted Lakomowski, lead reliability technician at the Eagle Mine. “When we experienced clogging and downtime at the processing mill, the crew naturally swung into action to resolve it, but we immediately sought a safer long-term solution.”Stope mining for nickel and copperOwned by Lundin Mining, a globally diversified base metals mining company headquartered in Toronto, ON, Canada, the Eagle Mine is the only primary nickel mine in the United States, producing 1.5 percent of the world’s total nickel production. The first operation permitted under Michigan’s Part 632 Non-Ferrous Mineral Mining Law, it opened in 2014 and is expected to produce 163 kt (360 million lbs) of nickel, 134 kt (295 million lbs) of copper and small amounts of other metals over its estimated nine-year lifespan.The company extracts approximately 2 kt/d (2,200 stpd) from the underground nickelcopper mine using a bench-and-fill stoping process. Accessed from the surface by specialized underground trucks, the vehicles carry about 45,400-kg (100,000-lb) loads through a 1.6-km (1- mile) long and 5.4-m (18-ft) diameter ramp shaft descending into the earth at a 13 percent grade. Stoping is a bottom-up method that involves systematically blasting columns of loosened ore that is then mucked by front loaders into trucks and backfilled using cemented and uncemented rockfill."

Aug 1, 2019

By Jonathan K. Hrica, CASSANDRA L. HOEBBEL, Jennica L. Bellanca

Accidents involving powered haulage and mobile equipment such as haul trucks often account for the greatest number of fatalities in the mining industry each year. Despite previous analyses that have identified root causes and other contributing factors, there is still a need to better understand the events leading up to these types of accidents, what lessons may be learned, and what strategies can be employed to prevent fatal accidents from occurring. This study examines Naturalistic Decision Making (NDM) using the critical decision method (CDM). The CDM is a retrospective interview approach used to explore timelimited, high-stakes, decision-making. In this study the CDM is used to obtain more information about what happens prior to, during, and after a potentially fatal situation such as a near-miss event, loss of control, or minor accident involving equipment damage. Researchers captured firsthand accounts from 21 haul truck operators involved in near-miss events from mine sites of various sizes and commodities throughout the United States. These accounts provide rich and detailed narratives from the perspective of haul truck operators themselves and reveal insights into what decisions haul truck operators make, what sensory cues they perceive, and what strategies they employ during challenging and non-routine situations. Decision-related themes that emerged from the data are presented and discussed. These results, along with potential solutions offered by study participants, can help to inform future research, raise awareness about hidden hazards, and build more creative interventions and realistic training scenarios for use by the industry to address haul truck safety issues.

Feb 1, 2024

By J. Oliver, J. Cleason

"With maintenance costs rising and an increasing demand for higher production, the use of sealed spherical roller bearings can reduce maintenance costs while providing increased production uptime. The sealed spherical bearing has increased bearing life by slowing the ingress of contamination. This paper will describe how contamination and bearing wear is reduced by reviewing case histories from coal and metal mines that improved their production by decreasing downtime using sealed spherical roller bearings. INTRODUCTION The spherical roller bearing (SRB) is a robust rolling element bearing that can accommodate high radial loads, low to moderate axial loads, and misalignment with no loss in carrying capacity. (i.e. Figure 1) Because of these characteristics, it is a favorite in mining applications and many other heavy industry applications. Primary applications are the various pulleys on conveyors. Coal and hard rock mines have hundreds of miles of conveyor lines and countless head, tail, drive, and idler pulleys. Maintaining the bearings on these pulleys and replacing bearings that have failed can be a huge expense to a mine in components, labor and downtime. Ideally, the bearings are replaced when the pulley is changed out according to the maintenance cycle, about every 4 years. Reality, however, causes the bearings to be changed out every year, or sooner. These premature bearing replacements can cause production shut downs for as long as 8 hours. Conveyor pulleys have been targeted at many mines as the single biggest maintenance pain point.The primary reason for replacing conveyor bearings is internal wear from fine, solid particle and water ingress through the bearing housing seals. (i.e. Figures 2 & 3) Traditionally, the bearing is mounted in a split pillow block housing (SAF, FSAF, SDAF or SNL are typical industry styles) with only labyrinth seals (LER/LOR) for protection against the ingress of contaminants. The bearings are lubricated with grease. A common way to extend the MTBR is to purge the bearing system with large quantities of grease to flush out the contaminants. If the bearing, and thus the housing seals are not frequently purged with grease, fine solid contaminants enter the housing and bearing through the labyrinth cavities."

Jan 1, 2015

By D. S. Ramey

In-situ leaching of the oxidized copper mineral resource at the San Manuel mine has proven to be a technically and economically viable method of copper extraction. Although this leaching method has been modeled to predict future production capabilities, the expected magnitude of the ultimate recovery from any portion of the present mine is not fully understood. A closely controlled test has been designed, constructed, and is now operating to determine the rate and magnitude of copper recovery. The test, initiated in June 1992, is scheduled to operate for approximately 18 months. This paper presents an overview of the test design and current results.

Jan 1, 1993

Conventional wisdom in the mineral processing industry leads one to believe that pressure oxidation of refractory carbonaceous (preg-robbing) ores is not a practical approach to process development. Initial acid pressure oxidation testing on carbonaceous sulfide ores at the Twin Creeks Mine supported this conventional wisdom. After testing other refractory process options, including air and oxygen enriched roasting, Santa Fe Pacific Gold decided to take a second look at pressure oxidation, using conditions outside the normal range of conventional practice. A combination of very fine grinding and high operating temperature and pressure resulted in significant increases in gold extraction. This paper details the effect of operating parameters developed for Twin Creeks on gold recovery, sulfur oxidation, carbon oxidation/passivation and preg-robb through the laboratory and pilot plant investigations.

Jan 1, 1995

By M. T. Smith

In a 2,000 square mile area of Polk, Hillsborough, Hardee and Manatee Counties in Central Florida is located one of the richest known deposits of the life-giving mineral, phosphorus. Under layers of sand and clay are found millions of tons of phosphate rock, best source of this element which is necessary to all forms of life - plant, animal and human. Phosphorus is an irreplaceable ingredient in all complete plant foods, and more than 90% of Florida's vast production goes to enrich the croplands of the United States and many other areas of a hungry world. In addition to this, it has wide industrial use in the manufacture of many products - detergents, baking powder, carbonated beverages, steel, matches, munitions, glass, insecticides, dyes, water softeners and innumerable others. Not only does phosphorus make life possible for us - it also helps us to live longer and better.

Jan 1, 1962

By W. G. Willson, Y. L. Li, P. D. Rao, D. E. Walsh

The combination of high moisture and low heating value has restricted most low-rank coal (LRC) usage worldwide to mine-mouth power generation. The objective of this study was to subject two Alaska low-rank coals to hydrothermal drying to enhance their marketability in the Pacific Rim markets and to evaluate the chemical and physical properties of the dried products as a function of process conditions. Coals from Usibelli Coal Mine and the Beluga coalfield have a heating value of approximately 18.5 MJ/kg and contain about 28% moisture. Hydrothermal treatment (at 275° to 325° C) of lump coal, from the Usibelli Coal Mine and the Beluga coalfield, enhanced the heating value of the material, on an equilibrium moisture basis, from 18.5 MJ/kg to nearly 27.8 MJ/kg. The product coal, with a high heating value and only 0.2% S, is an environmentally-acceptable premium fuel; additionally, with the Hardgrove grindability index of the coal greatly improved, its value is even further enhanced. An increase in hydrothermal drying temperature promotes vesiculation of resinite. Also, ulminite reflectance increased to 0.92%, and ulminite was subjected to widespread vesiculation; this resulted in a coke-like structure indicative that the material went through the fluid stage.

Jan 1, 1993