Search Documents

By Philip L. LeHoux

In recent years, much work has been done to explain the nature of the gold-carbon adsorption mechanism. The benefits of a sound theoretical basis has the obvious application to gold adsorption and elution industrial processes. Unfortunately, the lack of a clear agreement on the mechanism has provided no clear direction towards process innovation and optimization. Jones' (1989) work has gone a long way towards clarifying the specie of gold adsorbed (and thus the chemistry required to remove it). Since the development of hot caustic and cyanide elution, the kinetics have been accelerated by the application of pressure to increase elution temperatures beyond the boiling point at atmospheric pressure. However, the traditional reagent content of 15 g/L NaOH and 5-10g/L NaCN has remained largely unchanged. This is in spite of work that has shown that the presence of cyanide is not required for the elution process to take place (Adams, 1986; Adams; 1989; Jones, 1989). Adams (1989) has also compared NaOH elution rates with and without cyanide. He found improvement with the use of cyanide and a synergistic effect with the use of both. Others have found no difference in overall extraction (Jones, 1989

Jan 1, 1990

By G. A. Parkison

The sequential copper analysis method is a particularly useful technique to semi-quantitatively define the geologic, mineralogic, and metallurgical types and zonations commonly associated with porphyry-type copper deposits. The method is based on the partial dissolution behavior displayed by the prevalent copper minerals malachite, chrysocolla, chalcocite, and chalcopyrite to solutions containing sulfuric acid and sodium cyanide. Results from sequential analyses of the sample and analytical residue using sulfuric acid followed by sodium cyanide and then aqua regia solutions when compared with conventional total copper analyses can determine the amounts of leachable oxide minerals, leachable secondary sulfide minerals, and primary copper minerals, respectively. Sequential assay analytical results and interpretation are presented for copper deposits in Chile, Mexico, and the United States.

Jan 1, 1995

By S. Hoerger

Newmont has a large integrated operation in Northern Nevada with numerous mines, stockpiles, and processing facilities. There are over ninety defined metallurgical ore types and over sixty defined gold recovery process options. To take better advantage of the available synergies, a complete Nevada wide mine plan and process model along with a mixed Integer and Linear Programming optimization tool has been developed and implemented. This system is maintained and operated by a Nevada Planning Group. Standard in-house planning software tools and methods have been implemented at all mine sites. While increasing the effectiveness of planning in Nevada, these changes have allowed a significant reduction in overall Mine Engineering staff.

Jan 1, 1999

By B. K. Mishra

This paper focuses on the use of a numerical tool known as the discrete element method (DEM) to study the motion of ball charge in ball mills (14-18 ft). DEM is employed to simulate the motion of individual balls. While doing so, the effect of liner design on the grinding performance of the mill is studied. Two important factors such as the configuration of the liner and the geometry of the lifting surfaces are correlated with the overall mill performance. An attempt is made to show the effectiveness of the lifter bars in transmitting power from the mill shell to the interior of the mill with particular emphasis to large diameter mills.

Jan 1, 1992

By G. Pan

A geostatistical approach is proposed for the design of infill drilling programs. The method consists of the following four major steps: developing geological favorability models, delineating mineralization and ore envelopes, classifying resource potentials, and designing infill drilling patterns. Geological modeling develops the permissible geological zones in which infill drilling is designed. Modeling mineralization and ore envelopes establishes criteria on the potential blocks to be drilled. The blocks that are included within the ore envelopes are considered in the infill drilling. The following four types of resource potentials are used in this analysis: measured, indicated, possible and barren. Blocks in the indicated category are the top targets to be confirmed in infill drilling. Blocks of possible resources may be considered exploration targets. The algorithms involved in the analysis include indicator favorability analysis, indicator kriging and ordinary kriging. A case study on a gold deposit of the Carlin type is presented to demonstrate the methodology. The deposit was originally delineated by a sparse drilling program with about 230ft of average spacing. The infill drilling design, based on the new method, suggests a significant reduction on the number of holes from a regular-grid infill drilling pattern.

Jan 1, 1996

By Ingo Kaundinya

"INTRODUCTION Tunnels are important elements of the German federal road network which have to cope with an increasing traffic load especially of heavy goods vehicles. In order to ensure a high availability and safety level for these key infrastructures, big efforts are required by owners and operators in order to keep all infrastructures up to date. This mainly relates to current European regulations regarding tunnel safety (Directive 2004/54/EG) [1] and their national implementation, which must be fulfilled by many existing tunnels. In this context the German Federal Government spends more than 1.1 billion € for the structural and operational retrofitting of more than 120 existing road tunnels. As many of these projects have recently been finished or are still under progress, experiences and best practices could be reported. After the description of current requirements in national standards regarding structural fire protection, the paper gives an example for an upgrade of a tunnel’s fire protection by installing an additional fire protection system, which is a quite costly measure. Another possibility to fulfill current requirements regarding structural fire protection could be the numerical proof of sufficient bearing capacity of a structure. The influence of different fire loads and fire durations on the bearing capacity of typical road tunnel structures have been investigated in a research project funded by the German Federal Ministry of Transport (BMVI) and coordinated by the Federal Highway Research Institute (BASt). The results of this research project have been used to define a procedure how to investigate existing tunnels regarding structural fire protection. Finally, the research results have also been the basis for a current update of national standards for tunnel construction. REQUIREMENTS REGARDING STRUCTURAL FIRE PROTECTION The structural fire protection design of road tunnels is usually based on temperature-time curves of exposure to fire, for simplicity called ""fire curves"". The fire development after fire growth is illustrated with fire curves. Fire curves can be subdivided into a heating-up phase, a fully developed fire phase, and if applicable, into a cooling-off phase (cf. Figure 1). During the fully developed fire, the fire remains at a certain temperature level."

Jan 1, 2016

By Rahul Bhaduri

Mercury levels in Twin Creeks Vista pit ore (previously Chimney Creek, North pit ore) increased substantially since plant start-up in November 1987. Consequently, modifications were necessary to minimize industrial hygiene hazards and potential operational problems. The original plant design included mercury control measures. With progressive increases in mercury levels, the issue had to be re-addressed. Modifications to operational practice, industrial hygiene and management philosophy will be discussed. Additionally, a detailed examination of the mercury vapor suppression system currently employed at Twin Creeks will be presented.

Jan 1, 1994

By Gail Moulton

Searles Valley is located approximately 125 miles northeast of Los Angeles in the Basin and Range Province. Occupying the lowest part of the valley is Searles Dry Lake Playa, which is about 9 miles long and 7 miles wide. Three major subsurface evaporite horizons have been identified and are termed from bottom to top, the Mixed Layer, Lower Salt and Upper Salt. The evaporite beds were formed by desiccation of runoff from the eastern Sierra Nevada during Quaternary time. The saline beds are generally brine saturated with the important ions being sodium, potassium, carbonate, bicarbonate, sulfate, chloride and borate. These ions are present in the brines in various concentrations and have combined to form the minerals halite, hanksite, trona, nahcolite, burkeite, borax, thenardite, sulfohalite, glaserite and others. North American Chemical Company selectively pumps the interstitial brines to feed their chemical plants located on the western edge of Searles Lake. Minerals have been mined since 1873, beginning with borax and trona scraped from the surface. Brine processing began in 1914 with potassium chloride and borax recovery. Expansions have added sodium sulfate and soda ash to the product mix. Currently, dredging of trona ore is also taking place.

Jan 1, 1995

By James C. Gilliand

Leo-potpourri, was selected as the title to this paper for several reasons. First, it is a fascinating word--not looking like it sounds or sounding like it looks. It also allows for a great degree of flexibility in designing a presentation around it. Further, it has become popular to use this eco hyphen something pattern. We hear of eco-mania, eco-hysteria and the like. Lastly, in this era of intense environmental concern, two of the principle elements on which the integrity of our efforts must be equated are ecology and economics. Accordingly, the term "Eco-potpourris" allows me to roam at will through the great number of considerations that make up this environmental issue. Whereas only a few years ago the subject of environment and environmental control had low visibility with the public, today it competes as the focus of attention with the many other popular social issues of our time. The program content here at this meeting, for example, is liberally represented by papers dealing with one or more aspects of environmental concern. If one would look at the 1964 program, in contrast, I would expect that no more than possibly one or two papers covered this subject and even then that those papers dealt principally with the environmental aspect of occupational health. It is gratifying that the program at this meeting demonstrates a serious awareness to a broad spectrum of environmental concerns. It would be a mistake, of course, to believe that this clamor for a quality environment is a "flash in the pan" that will soon subside. The general public has been thoroughly aroused and even frightened into

Jan 1, 1972

By H. Copur

Roadheaders offer a unique capability and flexibility for the excavation of soft to medium strength rock formations, therefore, are very attractive in underground mining and tunneling operations. This paper reviews the importance, technological developments and application limits of roadheaders based on the case histories, which are compiled in a database including different roadheaders in various geological conditions. The paper also discusses the database and empirical performance prediction studies regarding instantaneous cutting rates and bit consumption rates.

Jan 1, 1998

By M. R. Yalamanchili

Recently, noequilbrium electrokinetic measurements using laser-Doppler electrophoresis were reported by Miller et al. (1992) for alkali halides and the sign of their surface charge thus determined. These results are generally as expected from simplified lattice ion hydration theory with KCI, under normal circumstances, being the most significant exception. In this regard, lattice defects (F centers and oxygen imperfections) have been found to influence the surface charge of KCI and its electrophoretic mobility. In particular, the presence of oxygen defect states in the crystal lattice has been found to be responsible for KCI's unexpected behavior. The concentration of oxygen defect states in KCI, as characterized by UV/Vis absorption, was varied in order to study their influence on the electrokinetic behavior and subsequently on the flotation response of KCl. At low oxygen contents « 60 ppm) KCI is positively charged as expected from lattice ion hydration theory. However, typically, KCI contains substantial oxygen (>300 ppm) sufficient to impart a negative surface charge which accounts for the selective flotation of KCI from NaCl by hetero-coagulation with oppositely charged alkyl amine hydrochloride collector colloids.

Jan 1, 1994

By Jean E. Tilden

An investigation of several trace elements distributed among sulfide minerals from deposits located in the southeastern United States was conducted. The deposits investigated are distributed within both the Blue Ridge Province and the Piedmont Province, which are contiguous geographic provinces. Twenty five deposits were examined;' eleven in the Blue Ridge Province and fourteen in the Piedmont Province. Figure 1 shows the locations of deposits investigated. In the deposits investigated, the mineral phases examined were pyrite, pyrrhotite, chalcopyrite, and sphalerite. These phases were chosen because of their relatively widespread occurrence, although no pyrrhotite was seen in the Piedmont Province. A total of 116 polished surfaces of ores were prepared, and mineral phases were collected from these surfaces for analysis. Samples were analyzed for cobalt, nickel, manganese, lead, tin, chromium, molybdenum, and gold. A total of 372 analyses were made. Trace elements were determined by atomic absorption spectrophotometry following standard procedures. In this study, trace elements are defined as those elements which are present in the mineral but which do not affect the chemical formula for that mineral. Lead is considered as a trace element only in ores where little or no lead sulfide could be identified as a distinct mineral phase.

Jan 1, 1972

By K. C. Shaver

The Sloan Ranch kimberlite complex is located approximately 130 km north-northwest of Denver in the Precambrian core of the northern Colorado Front Range (Figure 1). A Devonian age for the complex is suggested by the fossil assemblages in limestone xenoliths (Chronic and others, 1969), and by paleomagnetism of the kimberlite (E. E. Larson, personal communication, 1986). The presence of diamond was first reported in rocks from the Sloan diatreme by McCallum and Mabarak (1976). Prior to this time, the distinctive- appearing host rock of the Sloan diamonds had been quarried for use as terrazzo stone; examples may be seen in the floors of the airports in Cheyenne and Laramie, Wyoming. The Minerals Division of The Superior Oil Company obtained a lease on the Sloan property in 1980. During the next four years Superior built and fine-tuned a highly efficient diamond recovery facility, explored and tested the Sloan deposit, and used Sloan as a site for testing numerous exploration techniques for future use in a continuing exploration program in the Colorado-Wyoming kimberlite province. The Sloan property was ultimately determined to be sub- economic, but the lessons learned there have been very helpful in subsequent exploration efforts.

Jan 1, 1987

By Brian J. Gorva

The key objective of forming a cartel is to increase profits to members of the cartel by taking the following action: a) control output; and b) control price. However, while attempting to obtain monopoly profits the cartel members have to contend with costs associated with cartelization and such costs include the following: political costs; the cost of coordinating output and price; organizational costs (such as cheating); and administrative costs (such as the cost of attending cartel meetings). The objective of commodity exchanges is to provide an open, free market where buyers and sellers may openly complete transactions and pricing information can be immediately disseminated. These transactions include the following: a) to provide facilities for "hedging", or transferring price risk from buyers and sellers of physical commodities to "speculators" through the medium of buying and selling futures contracts, and b) taking physical delivery of metal on due dates.

Jan 1, 1983

By Robert A. Jankowski, Fred N. Kissell

Recent allegations about tampering of coal mine dust samples have led to suggestions that the coal industry needs a respirable dust compliance sampling method that is less subject to tampering. The sampler designs under consideration include fixed location monitors that could be mounted on a mining machine or located at a stationary location in the mine, and samplers that are worn, like the existing samplers. Fixed-point samplers have a design advantage, since samplers worn on the body will have size and weight limitations. On the other hand, in some cases there are respirable dust concentration gradients, which will dictate careful placement of a fixed-point sampler inlet to determine the exposure of workers. This study examined dust concentration-gradient data obtained by the Bureau of Mines and others over the last decade. As an example of spatial gradients at continuous miners, a fixed-point monitor located in front of the operators cab shows a higher dust concentration than a sampler located on the operator and reduced exposure when the sampling location is behind the operator cab. It may be necessary to use a sampling tube with a machine mounted monitor, to sample in the operators breathing zone in the cab to provide a more representative sample of the miners exposure. For face workers on longwalls or on continuous miner sections using remote control, the study shows significant dust level gradients and gradient variations between typical operator positions and mining machine locations. In addition, if fixed-point monitoring is used to monitor an area, vs the exposure of specific workers, dust control technologies currently employed to ensure reduced dust exposure such as the diversion of dust laden air away from the workers, or through the use of remote control of mining machinery may not indicate the same dust reduction obtained with current sampling techniques.

Jan 1, 1993

By T. P. Meloy

Like our wives, the comminution of brittle solids is easy to recognize but difficult to describe. However, describing it we must. Describing the fracture mechanism of brittle solids permits the eventual mathematical quantification of the results, process optimization and control strategies. This paper presents a physical model of brittle solid comminution that explains why the slope of the log-log size distribution curves have a slope of one or less in the smaller particle sizes. To develop the hypothesis, modifications of the Gaudin Meloy physical model are made. In brittle solids, comminution takes place by cracks propagating through the material. These cracks may bifurcate as they move. Cracks may terminate either on the original surface of the material, or on a secondary crack within the material formed earlier in the comminution process.

Jan 1, 1994

By V. B. Achanti, A. W. Khair

Introduction Laboratory studies were carried out at West Virginia University to investigate the rock-fragmentation mechanism of continuous miners using an automated rotary cutting simulator. The primary factors influencing the fragmentation process were found to be bit spacing, bit geometry, depth of cut and cutting-drum rotational speed. This paper presents a discussion of the effects of these parameters in achieving optimum energy consumption and minimizing dust generation during rock fragmentation. The removal of rock ridges/walls between adjacent grooves is analyzed with three hits mounted simultaneously on the cutting head, while the bit tip angle was varied from 600 to 900. Bit spacing was varied from 25.4 to 50.8 mm (1 to 2 in.) while the cutting process was assessed for varying cutting depths. Respirable dusts generated during the course of the experiments were analyzed utilizing cascade impactors. Assessment of these parameters has led to a better understanding of the cutting mechanism of continuous miners in terms of energy consumption and dust generation. A review of the literature revealed that a considerable amount of research has been carried out on rockcutting processes. Many authors agree that the mechanical cutting efficiencies of mining machines (e.g., continuous miners, shearers and road headers) are affected by a host of parameters. Some of these parameters are machine controlled, some are operator controlled, while others are uncontrollable. Efforts were focused on understanding the influence of parameters such as bit spacing, cutting depth, attack angle, bit type, drum speed, bit geometry (i.e., tip size, shape and tip angle) and rock type on the cutting process efficiency in terms of specific energy consumption and respirable dust generation (Strehig?? et al., 1975, Hanson et al., 1979, Khair et al., 1989). Roepke et al. (1976) in an attempt to study the dust and energy generated during coal cutting using point attack bits found that the dust and the specific energy consumed both decrease as the depth of cut increases. The four fundamental stages of dust generation luring rock fragmentation are identified by Zipf and Bieniawski (1989). Coal breakage by various types of wedges was assessed by Evans and Pomeroy (1966) in an extensive experimental study on British coals. Yet the industry today requires further attention and guidance to optimize the energy consumption and dust generation during the rockbreakage process. This paper attempts to give a better understanding of the influence of some of the parameters listed above and focuses on further improvement in the rock-cutting process. The specific energy consumed for different types of bits used and the respirable dust generated are analyzed in the context of the variation of a few other parameters. Laboratory investigation The experiments were performed in the Rock Mechanics Laboratories located at West Virginia University. A rock-cutting simulator designed and fabricated by Khair (1984) was utilized for this purpose. The details of this machine are available in the literature (see Khair 1984). For this study, a series of preliminary experiments was carried out to determine the optimum cutting frame advance speed. This was intended to facilitate a maximum cut depth of 31.75 mm (1.25 in.) at an advance rate of 0.525 mm/s (0.0207 ips) for all types of bits being used and various bit spacings being considered. To look into the cutting-process efficiency of a continuous miner in the laboratory, several parameters of influence are being considered. Besides the bit-geometry parameters, machine- and operator-controlled parameters, such as spacing of bits on the cutting head, the cutting head rotational speed and the total cutting depth during an experiment, are varied. At the time this paper was written, only part of the completed experiments were ana¬lyzed, and a number of experiments were still being carried out following an orthogonal fractional factorial experimental plan to assess the effect of all of the above¬mentioned parameters on the cutting efficiency in terms of energy consumption and dust generation. Three different types of tip angles, namely, 60°, 75° and 90°, and two different tip sizes, namely, diameters of 7.94 and 24.61 mm (0.313 and 0.969 in.), were used. At

Jan 1, 1999

By A. M. Wala

It is common practice in Appalachia, when extending the life of an existing mine, to acquire the adjacent reserves and extend the existing mine into it. Also, often the existing mine is renovated to accommodate the new conditions. The existing mining system and the track and belt haulage systems may be modified while the new property is integrated into the old one. All of these changes create new constraints for the mine ventilation system (M.V.S.) that require proper planning and control procedures. The authors describe and present the study that was carried out for the ventilation system of a newly expanded underground coal mine located in the Appalachian coal region. Discussed first is the process of correcting the ventilation system of the existing mine. Then, some of the stages of controlling the expanded system are discussed. Finally, numerical data for these steps are presented.

Jan 1, 1992

By J. W. III Leonard, T. E. Wilson

In addition to coalbed thickness and basic coal quality data, coal drill cores can produce design data for coal beneficiation processes. To generate design data, a coal drill core should be reduced from its original cylindrical form to a particle size distribution and composition that represents (with the possible exception of top size) a raw coal process stream. Reducing a coal core with a crushing machine rarely accomplishes this representation. This investigation employs drop-shatter impact breakage followed by dry batch tumbling in a steel cylinder rotated about its transverse axis to characterize the core in terms of first-order and zeroth-order break- age rate constants, which are indices of the propensity of the coal to degrade during handling. To reduce composition variables and conserve difficult-to-obtain coal cores, the initial drop-shatter and dry-tumbling tests were done with synthetic cores. Then, cores from three coal beds, Illinois No. 6, Upper Freeport and Pocahontas No. 5, were tested. Comparison of a crushed drill core and a drill core prepared by drop-shatter and tumbling indicated that the size distribution and size fraction composition of the drop-shattered/tumbled core more closely resembled the plant feed.

Jan 1, 2000

By Greg Beckstrom

Minnesota is a major mining state. This statement is not a dream or stretch goal but is a fact. As reported in a recent edition of Mining Engineering magazine, Minnesota ranks as the third largest state in terms revenues generated from nonfuels mineral production. The vibrancy of the mining sector in Minnesota can be attributed to several factors. The northeastern corner of the state is home to Minnesota?s iron range, one of North America?s largest deposits of iron ore. Iron ore from Minnesota is a strategic resource that has been [ ] instrumental to the nation?s development ? 90 percent of the iron used to build ships and planes during World War II came from Minnesota. Taconite pellets now produced from openpit mines on the iron range are shipped to steel mills worldwide. The growing appetite for steel in China and India has reignited once moribund mining operations throughout the iron range.

Jan 1, 2012