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By Xingang Wang

Spontaneous combustion is one of the most important safety issues in the global coal industry. It is considered to be a trigger for explosions in underground mines, especially for gassy mines. This thermal event is not easily detectable in the gob and sealed area. It is also a tough job to find the most likely hot point accurately. Admittedly, determination of the propensity for spontaneous combustion before mining activity should be a necessary step in the design of a mine and ventilation plan. However, due to the complexity of the chemical and physical properties of coal, spontaneous combustion has not been fully understood. According to a proximate analysis of coal, it is believed that sulfur and volatile matter in coal are the main intrinsic factors that cause the self-heating of coal. Their oxidation at lower temperatures than that of fixed carbon to initiate coal?s self-heating should be quantified. This study aims to improve the previous mathematical model developed by the authors for studying a coal?s propensity for spontaneous combustion. It enhances the model?s ability to consider the effects of sulfur, volatile matter and moisture content in the coal ? three important factors affecting a coal?s self-heating process. Based on the law of energy conservation, heat release rates for pyrite oxidation and moisture condensation are built into the model. Finally, the simulation results in terms of time versus temperature are calibrated with adiabatic testing data extracted from the literature for pyrite oxidation and moisture condensation, respectively. From the modeling results, it is found that the higher the pyrite content the coal contains and the more moisture that condenses in an environment with high relative humidity and initial temperature, the higher the potential for spontaneous combustion.

Jan 1, 2014

By John O. Marsden

"This article is an attempt to capture a presentation given at the 2016 SME Mineral & Metallurgical Processing Division (MPD) Luncheon held on Feb. 24, 2016, in Phoenix, AZ. It was presented as a tongue-in-cheek, lighthearted view of several of the issues facing our industry, while identifying some of the challenges and opportunities available to new engineers entering the industry today.Disclaimer• What you are about to read includes personal preferences, biases and occasionally arbitrary opinions.• Some readers may have dissimilar opinions on the contents and/or the rank order of the lists.There are eight top ten lists offered in this article: (1) Industry realities (2) Things a metallurgical or mineral process engineering graduate should do (3) Books every metallurgist should have on their shelf (4) Things I wish I had known (5) Legends of metallurgy (posthumous, with highlights) (6) Things we’ve forgotten (7) Mineral processing innovations of the past 20 years and, finally, (8) The future? For some items, additional context or clarification is provided after the item, while for other items no further explanation is warranted and none is offered. Top 10 industry realities1. Metal price cycles.2. Bigger is better (except when it isn’t).3. Ore grades declining across the board of metals/commodities.4. Ores becoming more complex.5. Three-fold increase in capital costs between 2004 and 2015.6. Three-fold increase in operating costs between 2004 and 2015.7. Less capital availability/challenging financial markets.8. Environmental constraints increasing.9. Socio-political constraints increasing.10. The mine manager is always impossible to work with.As Table 1 shows, there was more than a three-fold increase in gold operating costs between 2004 and 2014. The increases for copper, iron ore and other commodities were similar."

Aug 1, 2016

By Robert A. Westman

The INRED process has been developed step by step by Boliden since 1972 at MEFOS, the Foundation for Metallurgical Research, at Lulea in Sweden. The demonstration - plant is number five in this series. The purpose of this plant, which has a nominal capacity of 60,000 tonnes per year of hot metal is to: 1) prove the process on a sufficiently large scale to provide the basis for construction of production plants, 2) test various kinds of raw materials on behalf of licensees, 3) train operators of the first production plant, 4) develop the process further for special applications.

Jan 1, 1983

In the grand scheme of things, the 9.5-t (21,000-lb) shipment of molybdenum concentrate that left Freeport-McMoRan?s Climax Mine site on May 10, 2012 was not unlike the thousands of others that have been hauled away from the site during the last century, except for the fact that this shipment marked the official rebirth of one of America?s greatest mines. For nearly two decades, 17 years to be exact, there was no production from the mine that was once the largest underground mine in the world and was so important to the Allies? effort during World War II that it was assigned the highest priority of any mine in the United States by the War Production Board. The economic recession in 1980 put an end to the mine?s success, and the Great Recession of 2008 nearly derailed the mine again. But, like the nearby town of Leadville, CO, the mine survived thanks to an investment of more than $700 million by Climax Molybdenum Co., a Freeport-McMoRan company, to bring the Climax Mine back into production.

Jan 1, 2012

By H. M. Park

Risk is a major factor in all mining activities, arising from many internal and external variables. The authors? research has resulted in a systematic method for the quantification of risk in mining projects (Park, 2012). This is the second part of a three-part series. The first part was published in the October 2013 issue of Minining Engineering magazine and can be found here at www.me.smenet.org. This paper discusses methods of assessing the overall risk associated with those variables, and presents a statistical model based on a survey of 31 experts. The third paper, to be publised at www.me.smenet.org on Oct. 14, presents an evaluation of the statistical model, using data from previous mining investment decisions in which the authors have been involved.

Oct 1, 2013

By W. B. Lambert

A common decision in openpit mining is to determine the extraction sequence of notional three-dimensional production blocks so as to maximize the net present value of the extracted orebody, while adhering to precedence and operational resource constraints. This openpit block sequencing (OPBS) problem is commonly formulated as an integer program, with binary variables representing if and when each block is extracted. In practical applications, the number of blocks can be large and the time horizon can be long; therefore, instances of this problem can be difficult to solve using the exact approach of optimization. The problem is even more challenging to solve when it includes explicit minimum operational resource constraints. Our maximum value feasible pit (MVFP) algorithm generates an initial integer feasible solution for OPBS problems, in which minimum operational resource constraints are strictly enforced. As an exact approach, we present a Tailored Lagrangian Relaxation (TLR), in which the selection of constraints to dualize is guided by information provided by the MVFP algorithm. We present results and graphics to demonstrate the utility of our techniques for instances containing up to 25,000 blocks and 10 time periods.

Jan 1, 2013

By K. C. Vories

Surface mining and reclamation has the potential to at least temporarily increase surface runoff and resultant erosion and gully development. This increase in erosion is due in part to compaction of the soil surface with heavy equipment, creation of large relatively unvegetated watersheds, and elimination of natural dendritic ephemeral drainage patterns. Methods for stabilizing gully channels which may develop prior to establishment of sufficient vegetation to control erosion are analyzed. Utilization of various sizes of riprap for channel lining, the use of riprap check dams, reinforcement of riprap check dams, and the relation- ship of type of control structure to area of watershed and resultant flow velocities are discussed.

Jan 1, 1986

By Karoly (Charles) Kocsis, Kyle A. Scalise

Understanding the climatic conditions in underground mines is necessary for efficient ventilation design, cost savings, and to ensure the health and safety of mine workers. Large volumes of ventilation and climatic data including air volume, barometric pressure, dry bulb temperature, and relative humidity were collected at active underground precious metal mines in Nevada, which allows for the determination of wet bulb temperature and other key parameters. Through the utilization of neural networks, the wet bulb temperature at the bottom of the intake shafts is predicted, while taking into account the “thermal flywheel effect” (TFE). Wet bulb temperature is one of the most important climatic parameters to model and understand because it significantly affects the work conditions and the cooling capacity of the ventilating air. The accurate prediction of the dry bulb and the wet bulb temperatures at the bottom of intake shafts is critical when assessing the climatic conditions in future underground mines and deciding onwhether a cooling system is needed to assure adequate working conditions throughout themine. By utilizing accurate predictions of wet bulb temperatures and other climatic parameters, mine personnel will be safer as reported by Bluhm et al. (2003), and a more accurate ventilation design can be achieved resulting in major cost savings for underground mines.

Mar 3, 2021

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 C. C. Clark

The National Institute for Occupational Safety and Health (NIOSH), Ground Control Engineering Branch is investigating the use of shotcrete in weak rock mass mines with the objective of reducing fatalities and injuries resulting from rock fall accidents. When shotcrete is used as part of a multi-element ground support system there is a need to know when the material has developed a threshold early compressive strength of approximately 1 MPa (145 psi) for safe re-entry of miner and machine into shotcreted mine workings. This equates to the material having developed enough strength to be self-supporting and allow for emplacement of the remaining support elements that require drilling of the shotcrete layer without degradation. NIOSH researchers have developed methods and portable test equipment to measure shotcrete strength on-site in the first six hours after application using the ASTM C 116-90 (1990) standard. These advances were demonstrated in tests on five commercially available shotcrete mixes, sprayed as dry shotcrete using the field expedient methods and equipment. The strength values from these tests allowed for real-time identification of the early strength threshold and were consistent with strengths reported using laboratory-type equipment. The findings of this NIOSH research for determining shotcrete early strength can improve mine safety by providing a method for determining initial site specific material property values to be used for design and as a means to conduct on-site quality control and monitoring during production.

Jan 1, 2010

By R. W. Leonardson

Tectonic activity in northern New Mexico during late Oligocene and early Miocene time presaged events which led to the development of molybdenite deposits at Questa. East-northeast directed crustal extension produced north-northwest striking tensional fracture systems paralleling the early Rio Grande rift. A sequence of Oligocene andesite flows and breccias is overlain by a thick early Miocene rhyolite ash-flow tuff. Eruption of the tuff initiated collapse of the Questa cauldron: the south margin of which occurs as an east-northeast striking, north-dipping structurally weak zone. Continued east-northeast post-cauldron extension permitted the high level emplacement of granite stocks with coeval rotational deformation of fault blocks composed of cauldron fill and [ ] floor. The stocks occupy north-northwest fracture zones in the south margin of the cauldron, and porphyry dikes occupy east- northeast striking faults that define the south margin. These two fracture systems have played a dominant role in localizing the intrusive porphyries and associated mineral deposits at Questa. A molybdenite-bearing breccia matrix and related stockwork mineralization generally occur within volcanic rocks. Mineral deposits are spatially related to fault zones and the upper con- tact of their source intrusives. Deposits are localized in fault zones up to several thousand feet long and 100 to 500 feet in diameter. Magmatic-hydrothermal solutions from the source aplite porphyries have produced potash metasomatic alteration which is strongly centered on the mineral and ore zones. Alteration in ore is represented by orthoclase, quartz and secondary biotite. This pattern grades into secondary biotite and propylitic zones forming successively weaker alteration assemblages away from ore. Younger phyllic and argillic assemblages are particularly widespread only where strong north-northwest extensional fracture zones cross the south cauldron margin.

Jan 1, 2013

By W. E. Bardelmeier

The high speed conveyor type self unloading bulk carrier concept has been around for about 70 years. Although the design was developed, refined and steadily improved in the Great Lakes, to date limited numbers of such vessels have emerged in the bulk ocean trades, and these have tended to concentrate within specific mineral trades. For example, North American gypsum companies have embraced conveyor self unloaders to the point where such vessels almost exclusively carry the gypsum requirements of this part of the world. One major aluminum company has developed an impressive fleet capability in self unloaders. Application of other ships tends to be fragmented through several mineral trades. A few years ago a new phenomonen began to appear on the Great Lakes. Whereas it had historically been accepted in that region that self unloaders were effective vessels for the minor bulk trades including limestone, coal, salt, gravel and sand; they had seldom been employed heavily in the big volume iron ore trades. Suddenly, however, the new generation of 60,000 ton Lakers which emerged were all designed as high speed self unloaders. The new vessels intended to trade especially in ore, or alternatively especially in coal, have somewhat different internal features, but the important point is that all are self unloaders.

Jan 1, 1979

By Richard H. Sillitoe

Gold is an important byproduct and, locally, coproduct of porphyry copper deposits, and possesses potential for discovery as the major metal in porphyry deposits in either island arcs or Cordilleran belts. Tungsten and tin occur as major components of several potentially bulk-minable porphyry deposits, as well as being byproducts from the Climax porphyry molybdenum deposit. Whereas porphyry tin systems are localized in Cordilleran back-arc settings, their tungsten counterparts appear to span a range of geotectonic settings, from Cordilleran principal arcs through back-arcs to rifts. Although silver is a common byproduct of porphyry copper deposits, it tends to be preferentially concentrated with lead and zinc on the fringes of all types of porphyry deposits and/or as late-stage superpositions; the latter situation could be of some interest in the higher parts of porphyry systems. As byproducts, rhenium, uranium, platinoids and magnetite are exploited occasionally, and rutile and the rare metals, such as tantalum and niobium, have merited consideration.

Jan 1, 1982

By A. K. Sinha

Inspite of the growing demands worldwide, thermal coal must compete in the market both in price and quality. The design and performance efficiency of coal preparation plants is thus crucial to the survival and profitability of a coal industry. While the coal recovery influences the cost of production, the quality produced by a preparation plant determines the selling price. Several coal preparation plant simulation models have been developed in recent years to help Improve the performance of coal preparation plants. A research project was recently conducted at Southern Illinois University to evaluate the practical applicability of such a model. The results of this study are presented and discussed.

Jan 1, 1986

By Jacob L. Brinkman, Catherine E. Johnson

Researchers are exploring the use of unmanned aerial vehicles (UAV) to measure concentrations of gas emissions in situations where such measurements are otherwise extremely difficult to obtain, such as NO and NO2 (NOx) emissions from surface mine blasting. Recently, countries have imposed or are planning to impose surface blasting gas pollution regulations, which creates a need for an improved understanding of UAV-based gas measuring systems. The experiments detailed in this paper were performed to determine if airflow generated by the rotors, also known as downwash, unnaturally alters concentration measurements. Downwash turbulence could create locations of varying pressure, which could affect density-based concentrations as measured by some governing entities, including the Occupational Safety and Health Administration (OSHA). 

By Zoë Dugdale, Gerald Poplin, Tim Bauerle

"Fatigue presents several challenges for the mining industry. Depending on the specific occupation, daily work or operational setup on any given mine site, mining jobs can have a fair amount of labor-intensive tasks mixed with monotonous and repetitive duties. Combined with the long working hours and shift-work schedules of mining work, the prevalence of fatigue in mine workers may seem rather unsurprising.Mining is certainly not alone in facing the challenge of addressing worker fatigue. Indeed, many of the characteristics above mirror the similarities of fatigue in other industries, such as health care, aviation and security. To the extent that fatigue in mining acts like fatigue in any other industry, then any fatigue management applications, trainings, or interventions in existence can be borrowed from other industries and applied to mining in a cookie-cutter approach. However, some have argued that mining in particular is especially susceptible to increases in the prevalence of fatigue beyond the characteristics listed above due to the multifaceted combination of factors in mining environments associated with fatigue: dim lighting; limited visual acuity; hot temperatures; loud noise; highly repetitive, sustained, and monotonous tasks; shiftwork; long work hours; long commute times due to mine site remoteness; early morning awakenings; and generally poor sleep habits (Canadian Centre for Occupational Health and Safety, 2012; Legault, 2011). Legault (2011) in particular argues that it is the combination of these factors simultaneously that can make mineworkers particularly susceptible to sleep deprivation and fatigue in comparison to other industries where these factors are often not present all together. If fatigue looks and acts different in mining, as others have argued, more research is needed to determine if, how, and why worker fatigue might need to be managed differently in mining.While the burden of fatigue on the mining population has not yet been evaluated thoroughly, methods and measures of fatigue management remain a popular point of discussion. Many commercial suppliers and consultancy groups have begun to develop technologically based fatigue monitoring systems (McMillian, 2013). Some technologies can monitor vehicle operators for indicators of wakefulness, such as percent eyelid"

Jan 3, 2018

By W. J. D. Stone

Many of the common valuable minerals have a magnetic susceptibility which is sufficiently high to render them amenable to magnetic separation. In addition,, many minerals which form the unwanted constituents of an ore can be removed by magnetic means. Magnetic separation in general has suffered seriously from, the lack of a high intensity wet separator. It is only recently that such a separator has become available to the industry. Prior to this, high intensity magnetic separation has been limited to the use of the dry techniques. Since the introduction of the Jones Wet High Intensity Magnetic Separator, extensive test work has been conducted to investigate possible applications. From the investigations conducted and the discussions that have taken place in the industry, it is apparent that the important mineral characteristic of magnetic susceptibility is not receiving the attention that it deserves. Applications for high intensity wet separation are being found in areas hitherto not considered.

Jan 1, 1963

By V

"Recent regulations, as well as a general aversion to central dust collectors within the Powder River Basin Coal user’s community, have created a need for an alternate method for eliminating airborne dust. This paper addresses the capital expenditure as well as the cost of ownership of an integrated point source air cleaning system in comparison to a central collection system. This assessment was conducted by comparing the cost to purchase and operate a central dust collection system and integrated air cleaner system on a typical multiple transfer point application. The central dust collector consists of a negative pressure blower, a series of filter bags, a collection hopper, a screw conveyor to place collected material back into the material stream, and a series of ducts to pull air and dust from individual pickup points. The point specific integrated air cleaners consists of a negative pressure blower to pull dust and air from an application point through a bag-less filter media located at the application point. The agglomerated material is then redeposited into the material stream at point of use without the need for ducting or a central material hopper. The assessment yielded a 54% reduction in capital expenditure and a 26% reduction in operating costs for the same application when using individual dust filters as opposed to a central system. In addition to the lowered cost, there are reductions in risk associated with the elimination of ductwork and the central containment enclosure for collected explosive dust. By the conclusion of this paper, the reader will have a better understanding of the quantifiable differences between a central dust collection system and a set integrated air cleaner systems. BACKGROUND Spillage has always been a problem in the bulk solids handling industry. As long as there have been conveyors, there has been spillage. Spillage is material that falls off a conveyor belt and creates a hazard in the environment around a conveyor belt."

Jan 1, 2016

By Teena Redhorse, David Tsztoo, Anthony Yu

"Since ancient times, storing and conveying water via underground water systems and tunnels has been touted for its strategic advantages. Underground cisterns and tunnels assured protection of essential fresh water supplies from man made contamination and especially from enemies who would gain an advantage by disrupting an adversary’s water supply in a siege. Modern day engineers do not usually specify tunnels for reasons of avoiding deliberate contamination or siege — however, they are just as enamored with the idea of building tunnels for water conveyances.Such was the case for the San Francisco Public Utilities Commission (SFPUC). The SFPUC provides drinking water to 2.6 million residential, commercial and industrial customers in the San Francisco Bay Area. The SFPUC’s water system includes 257 km (160 miles) of transmission pipelines and tunnels from the SFPUC’s largest reservoir, the Hetch Hetchy Reservoir inside Yosemite National Park, to San Francisco. About 129 km (80 miles) of the system consist of tunnels. A 30-km (19-mile) section of the tunnel network, called the Mountain Tunnel, was thought to be at risk of a catastrophic failure in its concrete-lined section of 18 km (11 miles). For much of the project planning process, a new replacement tunnel was presumed to be required according to the tunnel planners.Originally constructed between 1917 and 1925, the Mountain Tunnel has been in continuous service since 1925. The 30-km (19-mile) tunnel is located downstream of the Hetch Hetchy Reservoir water source in Yosemite National Park, between the Early Intake and Priest Reservoir (Fig. 1). Approximately 18 km (11 miles) of the tunnel is lined with unreinforced concrete. Though the condition of the tunnel was being monitored through water sampling and periodic inspections, there was growing concern that the tunnel lining was at risk of a partial collapse that could interrupt water delivery for up to nine months. The SFPUC was faced with a decision to construct a new bypass tunnel to replace the lined section of the Mountain Tunnel or to rehabilitate the existing tunnel."

Jan 6, 2018

By Mehmet Guney

[The Atlantis-II-Deep is a hydrothermal mineralization located along the median valley of the Red Sea at a water depth of about 2200 m. Extensive exploration of the metal-rich brine deep revealed a potentially mineable deposit on economic interest consisting of oxides, silicates and sulphides with considerable concentrations of zinc, copper, cadmium and silver. Geostatistics was applied to assess the most likely in-situ vague of the metal potential for economical exploitation. Semi-variograms were constructed to characterize the structure of the regionalized distribution of the geological parameters. Volume grades and thicknesses were determined by the kriging technique, avoiding systematically biased high or low grades, and then block .tonnages were computed. The estimation variances, distribution of errors and histograms of observed and kriged values in each grid Mock were also produced.]

Jan 1, 1983