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By Gerald H. Luttrell, Rick Q. Honaker

A coal preparation plant incorporates a variety of solid-solid separation processes that operate in relatively independent parallel circuits. Studies have shown that total plant performance can be optimized by selecting circuit cutpoints that maximize total clean coal yield irrespective of the performance of individual circuits. Although the optimum cutpoints can be determined using simulation programs, these mathematical routines require detailed washability data and empirical partition information that is not often available to plant operators. In addition, routine fluctuations in the washability characteristics of the plant feed make this approach impractical to implement in industrial facilities. As an alternative, practical optimization criteria can be developed for plant operators through a fundamental understanding of scientific principles involved in coal cleaning operations. This article provides an overview of the most important optimization criteria and presents several industrial case studies that illustrate the financial benefits of this practical approach m plant optimization.

Jan 1, 2005

By Ricardo Presnell, Erich U. Petersen, William J. Tafuri, Donald M. Hausen, Douglas N. Halbe

Large (> 100,000 oz.) sediment hosted disseminated gold (SHDG) deposits are often spatially associated with anticlines. Many SHDG deposits are within or closely associated with windows. Windows are erosional manifestations of fold culminations (4-way closed anticlines). Hydrocarbons are often trapped in fold culminations in the Canadian Rockies, and may account for degraded hydrocarbons in many SHDG deposits. In the Eastern Basin and Range Province, Mesozoic anticlines may have been large scale conduits fm gold bearing Mesozoic and Cenozoic hydrothermal fluids which became trapped and/or concentrated at the fold culminations.

Jan 1, 1990

By William Gleason

"More than 6,300 people converged on the Colorado Convention Center for the 2017 SME Annual Conference and Expo and 119th National Western Mining Conference in Denver, CO on Feb. 19-22. Many of them crammed in to hear Douglas Silver deliver the keynote address to the conference.Silver is a portfolio manager for Orion Mine Finance, a private-equity fund focused on providing funding to advanced-stage base and precious metal projects and is one of the most respected voices in the field of mineral economics. Prior to joining Orion, he served as chief executive officer and chairman of International Royalty Corp., a global mineral royalty company, which he founded in 2003 and sold in 2011.Those who were hoping that Silver would deliver at least a bit of optimism during his 90-minute presentation got what they came for from the talk titled, “When are commodity prices going to rebound?”It marked the second time Silver has presented the keynote address to SME, the first was in 2008 and was delivered during the height of mining’s super cycle (ME, June 2008). In his 2017 address, Silver looked back on the previous 10 years and the massive contraction of the global economy that resulted from the great recession that began near the end of 2008.It has been a challenging time for the mining industry. About US$1.4 trillion was lost in the global mining stocks from 2011 to Jan. 6, 2016. Major mining companies exceeded $60 billion in write downs between 2012 and 2013 and investors lost confidence in the sector, putting the global mining industry into a bear market that has taken mining equities to historic lows.However, that was then and this is now.Using numerous examples, including rising commodity prices, a steady decline in the U.S. unemployment rate, increases in discretionary income and the Dow Jones Industrial Average, which topped the 20,000 mark for the first time ever in February, Silver theorized the current down cycle is near its end and the demand for metals and other commodities will see a sharp increase by 2025. He also noted that investors are beginning to rotate back into mining equities."

Apr 1, 2017

By I. E. Odom

The physiochemical properties and industrial uses of the clay mineral montmorillonite are reviewed. Montmorillonite is the most abundant species of the smectite clay mineral group and is the predominant mineral composing bentonite deposits. The crystal structure, chemical composition, exchangeable ion type, and small crystal size are responsible for several unique properties, including a large chemically active surface area, a high cation exchange capacity, and interlamellar surfaces having unusual hydration characteristics. The type of exchangeable ion, sodium (Na), calcium (Ca), and/or magnesium (Mg), has a major influence on industrial and chemical uses of montmorillonite because of their hydration characteristics. Natural occurrences of Na mont¬morillonite in commercial quantities are geographically limited, but Ca-Mg montmorillonite deposits are known worldwide. Foundry, well drilling, pelletizing, and civil engineering constitute the major uses of montmorillonite, but the total array of uses exceeds that of any other mineral.

Jan 1, 1988

By R. A. Winters

At the operations level, productivity is a principle key to profitability. If you are competing with other mines that are paying roughly the same wage rate and the same prices for capital, materials, and energy, the only way your profit can be greater is by producing more output per unit of input. Mines with higher productivity have higher profit margins. Higher profit margins lead to greater operating cash flow, and cash flow is what distinguishes a dog from a cash cow. The turnaround in U.S. metals during the 1980s was in large part due to incredible improvements in productivity. According to statistics compiled by Kaufmann, 1991, labor productivity, measured as tonnes of primary production/manhour, increased 64% in steel, 94% in copper, 75% in lead, 143% in zinc, 132% in molybdenum, and 75% in gold. These improvements were hard won. However, with most modernization programs now complete, measuring and monitoring productivity becomes even more important as producers strive to maintain the gains they have achieved.

Jan 1, 1993

By Chester R. Harris

With the passage of the Occupational Safety and Health Act (OSHA) on December 29, 1970 and the formation and growth of the OSHA Agency it spawned, public consciousness of occupational safety was raised. It became accepted that employees had the right to "a safe and healthful workplace". With the possibility of OSHA inspections, employ ers (particularly those with large workforces) began to give serious con sideration to engineering controls, safety programs, and training in a more uniform manner than previously.

Jan 1, 1991

By John Brett

BHP Australia Coal Pty. Ltd. (BHPAC) manages and, through its parent company BHP, partly owns seven large opencut mines in the Bowen Basin of Central Queensland, Australia. In terms of developments in surface mining in Australia, the operations of BHPAC are as representative as any. The seven mines managed by BHPAC produce a combined total of about 40 Mt/a (44 million stpy) of mostly high quality coking coal. They also produce small but increasing amounts of thermal and PCI coal. Virtually all of the coal produced is sold on the export market. In 1993, Australia exported 133 Mt (146 million st) of coal. Salable production was 172 Mt (189 million st) in New South Wales and Queensland and 180 Mt (198 million st) nationwide. Mining systems Surface coal mines in Queensland can be typified as large, long-strike-length, shallow-dipping and sometimes multi-seam dragline operations. There are exceptions. Blair Athol, for instance, works a 30- to 40-m (100- to 130-ft) seam beneath shallow cover but is still a dragline operation. Moura is truly multi-seam and steeper dipping but also is still a dragline operation. Mines in the Ipswich area are small shovel-truck operations.

Jan 1, 1995

By Gu Guohua, Hu Yuehua, Zhang Qin

The flotation behavior of pyrrhotite was investigated by using ethyl xanthate as a collector. Results showed that pyrrhotite had good floatability from pH 2 to pH 11, and poor floatability when pH was >12. The flotation of pyrrhotite was dependent on pulp potential on various pH values. The potential-pH range for pyrrhotite flotation was established. Cyclic voltammeny and FTIR spectroscopic analysis showed that the major adsorption product of ethyl xanthate on pyrrhotite was dixanthogen. The intensity of FTIR signals of dixanthogen adsorption on pyrrhotite and the anode current of a pyrrhotite electrode and flotation response of pyrrhotite are correlated with pulp potentials.

Jan 1, 2005

By W. G. Pariseau

"BACKGROUND The Crandall Canyon Mine (CCM) is located in the Wasatch coal field in central Utah. Extensive longwall mining at CCM preceded a decision to recover coal left in barrier pillars on each side of a set of main entries extending far into the mine. During mining in March, 2007, a major bump occurred that led to cessation of mining in the barrier pillar on the north side of the mains and to begin mining in the south barrier pillar. Subsequent loss of ground control in August, 2007, through coal pillar bursts had tragic consequences with loss of six miners and shortly afterwards three rescue team members. An MSHA report describes the events in detail (MSHA, 2008). An important lesson to be learned from CCM is the need to select a computer program suitable for pillar design. Computer programs are engineering tools; selecting the right tool for the job is essential. In this regard, a minimum program requirement is capability for computing stress distribution within a pillar and adjacent roof and floor strata. The reason is simple: strength of rock is stress dependent; both vary from point to point in pillars and adjacent strata. Preferably, one should follow the evolution of stress as the mining plan is executed from start to finish to assure safety or to warn of a potentially hazardous situation developing as mining progresses. The approach to the problem posed by barrier pillar mining at CCM is conventional in the sense of applying well known finite element modeling techniques to analysis of a proposed mining plan. The engineering purpose is to evaluate the mining plan with respect to ground control questions including roof, floor and pillar safety. Results of previous two dimensional finite element analysis indicated pillar safety was by no means assured (1, 2, 3). Geometry of barrier pillar mining is limited in two-dimensions, for example, crosscuts are not seen in vertical cross sections. While three dimensional analyses are preferred, even moderately sized regions often lead to very large problem sizes that exceed computer capabilities. However, a recent development in finite element modeling of tabular deposits allows for whole mine analysis in three-dimensions. This technique involves a dual node – dual mesh concept. Both have been used separately in much earlier work, but are only now are used in combination. Estimation of subsidence at a kilometer scale and details of stress, strain and displacement about barrier pillars, main entries and pillars, and so on at a meter scale are possible (4). No compromise involving empirical formulas or similar guess work is required. Indeed, all calculations are based on first principles: physical laws, kinematics, and material laws. Effects of joints and in situ variability or uncertainty in strata properties, elastic moduli and strengths, may be included for greater realism. An important objective of the present study is to assess the role of three-dimensional pillar geometry in arriving at conclusions regarding barrier pillar mining versus two-dimensional results."

Jan 1, 2015

By W. X. Wang, O. Stephansson

In the mining and quarry industries, rock fragments are often transported by conveyor belt. To estimate the qualities of the rock fragments (i.e., size distribution and shape), an operator must take samples from the conveyor and manually perform a sieve analysis, which is time-consuming and tedious. Alternatively, an image-analysis system can be used to monitor the fragment quality on a fast moving conveyor belt. However, images of fragments on a fast moving belt vary to such a degree that the quality of any two successive images are not the same, and some of the images are of such poor quality that they are unrecognizable by human eyes. If poor-quality images are directly analyzed by a segmentation algorithm, the analysis will not be satisfactory. To resolve this problem, it is necessary to use an image-classification program for the automatic selection of fragment images with good quality. Because of this need, an image-classification program was developed and tested both in the laboratory and in the field Testing of the system on different types of fragments showed that the system works reasonably well.

Jan 1, 1997

The National Institute for Occupational Safety and Health (NIOSH) conducted a study to determine the effectiveness of a filtered air delivery system to reduce respirable dust exposure to roof bolter operators in underground coal mines. When performing roof bolting operations, roof bolter operators may experience exposure to high levels of respirable dust during a working shift, especially when working downwind of the continuous mining machine. While drilling and installing roof bolts, this filtered air system supplies a clean curtain of air over the roof bolter operator by means of a plenum mounted beneath the canopy. This experimentally designed air curtain, adapted for roof bolting machines used in this study, is based upon previous design prototypes, computational fluid dynamics (CFD) simulations, and trial-and-error testing. Both prototype and final designs were tested in the full-scale mining galleries at the Office of Mine Safety and Health Research (OMSHR) in Pittsburgh before being taken underground for field testing. Test results of the system in both laboratory and field studies show reductions in operator exposure to respirable dust when the operator is positioned directly under the protected zone of the canopy.

Jan 1, 2012

By James Wm. White

Computer-based mine management systems are being used in many surface mines to assign haul trucks, track equipment and manage information. Advances in digital communications allow these systems to be used in underground operations. Underground mine management systems help maximize production by providing gains in equipment and manpower use, drawpoint equalization in block caving operations, preventive maintenance and safety. Current systems use allocated or "locked" train and load-haul-dump (LHD) dispatching. Allocated dispatching rarely optimizes open pit product' on. But it offers an efficient mode of operation underground and where options are more limited. The primary objectives of underground mine management systems are to maximize production and mini¬mize contention time through allocated train, truck or LHD dispatching, traffic control, equipment monitoring and comprehensive reporting. The main components of an underground mine management system include: ? A central computer (personal computer or worksta¬tion) in a central control center. It sends instructions to train, truck or LHD drivers and allows dispatcher interaction. ? A field computer system (FCS). This consists of a touch-screen graphics console (GC) and mobile hub - on each train, truck or LHD to receive and display instructions from the central computer and accept driver input. ? A data radio network based on leaky feeder (data, voice, video) or microcell radios (data only) and advanced token-ring technology. This passes information between the central computer and the FCSs. ? Radio frequency (RF) tags mounted at boxes, weigh bridges, tips and rim tunnel main haulage ways to locate trains or LHDs (Luke, 1993). Such a management system must be in place before implementing computer-based dispatching (Vagenas, 1991) for production optimization.

Jan 1, 1997

By R. W. Hagemeyer

By way of background. it is important to keep in mind that the information presented in this paper relates specifically to synthetically produced precipitated calcium carbonate (PCC) fillers. Natural calcium carbonate fillers manufactured by grinding limestone, marble and chalk, though having similar chemical and physical analyses to PCCs, normally contribute somewhat different performance properties in paint, paper and polymer systems. Many factors have been cited and numerous theories have been proposed for the observed differences. Particle size parameters, surface chemistry and particle morphology are the items most frequently mentioned. A discussion of this subject is beyond the scope of this paper.

Jan 1, 1989

In September 2003, a test was conducted to see if a115-mm- (4.5-in.-) diam Mocap Vari-Stem blasthole plug could improve the pattern of explosives using different top stemming material. The test took place at the J.S. Faulkroad and Sonsstone quarry in McCalisterville, PA. The test consisted of a production stone blast. Half of the holes were stemmed with standard crushed stone. Two-thirds of the remaining half were stemmed with Vari-Stem plugs and crushed stone. And the remaining one-third of the second 50 percent was stemmed with Vari-Stem plugs and only drill cuttings.

Jan 1, 2004

A PDP 11/34 computer has been inter- faced to existing instrumentation in a 400 tph rod-mill/ball-mill grinding circuit and programed with a Kalman filter to estimate several unmeasured variables. A dynamic two-size- fraction model of the circuit is used to predict the complete state of the circuit including particle size distributions around the circuit, mass holdups and flowrates, the ball-mill grinding rate, water additions and cyclone parameters. Online measurements of sump level, slurry densities and product particle size are used to update the model values sequentially on a 20-second interval. This procedure results in optimal estimates of circuit variables given the relative reliability of measurements and the accuracy of the model.

Jan 1, 1983

By L. L. Probert

A three-year project focusing on the depth profiling of respirable coal mine dust particles using scanning electron microscopy coupled with energy dispersive x-ray analysis resulted in the development of statistically classified particle-behavior models. The models depict the changing silicon fraction for 5-, 7-, 9-, and 11-keV accelerating voltages, thereby giving a clear indication of the nature of various types of particles. This paper will focus on the results for respirable quartz particles that occur in underground coal mines across the U.S. The relationship between the amount of surface-available quartz and coal seam rank is well established for Pennsylvania

Jan 1, 1994

By J. W. Leonard, D. A. Newman

By using physical and chemical means to increase the bulk density of newly broken coal freed from the mine face, the potential to improve coal mine productivity is significantly enhanced. It is estimated that by increasing bulk density, greater tonnages can be placed in fixed volume scoops and shuttles cars to improve production by as much as 10% to 20%. Such improved packaging to achieve new levels of volumetric efficiency might require only small and easy to implement changes to present downstream mining operations. Opportunities exist for improving broken coal bulk density from the moment of breakage, during transport across the continuous miner or loading machine, during discharge into the haulage unit, and after placement in the haulage unit. Physical/chemical methods for broken coal compaction in mobile, fixed volume units in underground operations are discussed.

Jan 1, 1990

By W. H. Davitt

One might ask why someone like myself, involved in the determination of taxes, should be speaking at a "cost engineering" session of a national engineering society. While it is true that taxes, especially income taxes, whether they be federal, state, or local, are not usually thought of as a "cost" of doing business, it is equally true that these tax costs do reduce the distributable profits just as much, as the cost of power, supplies, or labor. Therefore, the consideration given to taxes is often as important as that given to other costs. Hopefully yea will recognize that, within certain limits, taxes can be controlled to an economic advantage. That question may then lead to another question: What does the amount of taxes have to do with me? I'm an engineer or manager; not an accountant or a lawyer. If I may take a few minutes of your time, I might be able to present in a brief discussion some interesting facts that will provide the answers to those questions. My discussion will be directed mainly to Federal taxes. However, much of it will be applicable to state and local taxes, also.

Jan 1, 1973

By A. K. Haines, M. W. Godfrey, D. M. Miller, P. C. van Aswegen

The Bacterial Oxidation [(BIOX)] process for the pre-treatment of refractory ores for gold recovery developed by Genmin, the mining division of Gencor, has been operating successfully at the Fairvew Mine since October 1986. The continuous operation of a pilot plant at Genmin Process Research has resulted in further process developmenst to improve plant operating efficiencies. These new developments, which include a higher solids content of the pulp feed to [BIOX], lower retention times, higher operating temperatures, lower power utilizaton for oxygen dispersion and reduced nutrient addition, have all been successfully implemented on the Fairvew plant. It has furthermore been confirmed that the arsenic precipitate formed in the neutralization of effluent solutions complies to the United States of America EPA standards. Contineous cyanidation pilot plant work conducted on [BIOX] product has indicated that cyanide consumption can be drastically decreased if a continuons flowsheet is implemented in preference to a batch leaching system.

Jan 1, 1992

By R. A. Metz, Isaac Vera, Hans Ruge

The El Soldado copper mineralization occurs as relatively high-grade irregular ore bodies with assay contacts and with frequent inclusions of barren rock. The sampling methods must be timely for production grade control purposes, as well as accurate and inexpensive. Sampling techniques evolved from sampling dump cars at the haulage level to sampling Scooptrams at the loading pockets. These methods were abandoned in favor of sampling production blastholes. Several sampling alternatives are discussed. These involve the selection of optimum volumes and sampling frequencies while taking into consideration geological parameters and statistical analyses of sampling data.

Jan 1, 1992