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By G. Castillo, J. Mortensen

"INTRODUCTION Molybdenite is typically produced as a co-product in the copper ore flotation process. At the Rio Tinto Kennecott Concentrator (RTKC) in Copperton, Utah, the molybdenite is initially floated with copper sulfides and other value minerals producing a Cu-Mo concentrate. This is then separated in the molybdenum plant by depressing copper sulfides and pyrite and floating only molybdenite. The molybdenum plant in RTKC comprises the rougher circuit and several stages of cleaning to achieve a certain grade requirement of Mo. The rougher circuit is where the first stage of separation occurs. Cu sulfides and pyrite are depressed in the rougher circuit by adding NaSH under nitrogen and in the cleaner circuit by adding NaSH under air. The depression of Cu sulfides (and pyrite) by NaSH is related to the redox activity1. It is important therefore to maintain a reducing potential in the circuit in order to achieve effective Cu-Mo separation. If the rougher circuit is under air, like RTKC’s molybdenum cleaner circuits, it is harder to maintain the target redox potential because NaSH oxidizes rapidly in the presence of air thereby increasing NaSH consumption significantly. CU-MO SEPARATION AND ROLE OF PULP POTENTIAL The collector adsorption on copper sulfide minerals is through an electrochemical mechanism2. The collector changes the surface chemistry of the Cu mineral allowing it to float. Molybdenite, or MoS2, on the other hand, floats readily in the presence of a frother as it is naturally hydrophobic. Usually, hydrocarbon oil extenders such as diesel or burner oil are added to enhance Mo recovery. In order to effectively separate Cu from Mo, the collector complex on the copper surface needs to be destabilized or desorbed using a reducing agent such as NaSH or Nokes. As long as the circuit is under highly reducing conditions, the collector remains detached from the sulfide mineral surface allowing Cu sulfide depression. Therefore, it is important to measure the oxidation-reduction potential (ORP) continually and maintain the reducing condition with addition of NaSH. For a given collector each mineral will have a characteristic potential or electrochemical window for flotation to occur3, therefore, it is necessary to reduce the potential outside of this window in order to effectively separate Cu and Fe sulfides from MoS2 minerals2. In RTKC plant, the target reducing condition is between -450 to -550 mV to effectively destabilize the collector and depress Cu and Fe minerals. Typically the dosage of NaSH used in the molybdenum plant could range from 6 to 30 gallons/min (gpm). The high dosage of NaSH could pose risk of H2S exposure. RTKC wanted to evaluate alternatives to NaSH in order to reduce its consumption and minimize risk of H2S gas generation."

Jan 1, 2016

The impact of a methane explosion on mining operations cannot be over-emphasized. The explosion is a result of rapid combustion when a methane/air mixture is ignited by an unexpected energy release, such as a mine fire, electrical arc or sparks caused by frictions or rock falls. In most cases, an ignition of methane/air mixture could result in a deflagration other than detonation. Resulting flames and overpressure induced by a methane deflagration will harm neighboring miners and local ventilation control devices.. ,It is essential that the mechanism of an explosion and associated destructiveness be fully understood. This research seeks to predict an influence region of an incident happened within a representative underground mine geometry. The most common geometric changes in an underground coal mine are bends, regulators/doors, obstacle in airways and changes in sectional area. These geometric changes could result in an attenuation of the flame and pressure wave as a result of a methane deflagration. A study of this phenomenon could enable mine planners to have better understanding of the over-pressure redistribution due to the explosion. Both numerical and experimental work has been done in this study to ascertain a better insight of this potentially devastating event. The experimental data are also used to validate the turbulence and combustion models used in this test.

Feb 23, 2014

By Harry R. Price, Jerome C. Neyer

INTRODUCTION Safety must be a primary consideration in the design and construction of tunnels. Tunnel construction has historically been considered a high-risk business. During the construction of the 14.8 kilometer (9.25) mile St. Gotthard Tunnel in the Swiss Alps in the 1870s, 310 lives were lost and another 877 workers permanently disabled. In more recent days, two tunnel construction accidents in 1971, one in Michigan and one in California, claimed the lives of 38 workers. Prior to 1971, most regulations governing safety in tunnel construction were developed by the U.S. Bureau of Mines. These included a 1941 Bulletin 439, "Some Essential Safety Factors for Tunneling" and a 1968 Bulletin 644 which updated Bulletin 439. In 1970, the United States passed the Occupational Health and Safety Act (OSHA) which became effective in early 1971. That act covered all sorts of workplace activities including Tunnels and Shafts in 29 CFR 1926.800. In 1989, a revised and renamed 29 CFR 1926.800 was issued for Underground Construction. Some of the changes introduced in this rule were the outgrowth of improvements made in the California and Michigan codes after the 1971 accidents. These new regulations are the "Rules to Live By" for tunnel construction in the United States and are generally accepted as appropriate for tunnel construction throughout the world.

Jan 1, 1995

By Thomas A. Wheeler, Robert O. Keys

The choice of the flotation reagent that suits a particular coal has become more complicated with the development of new, more efficient reagents. Frothers and conditioning reagents, in particular, have experienced a dramatic reevaluation of their role in floating various types of coals. This paper offers a better understanding of how each of the following factors contributes to the reagent selection: 1. Natural Flotability 2. Degree of Oxidation 3. Size Distribution 4. Percent Solids in Feed Slurry 5. Fluctuations in Plant Feed 6. Limitations on Froth Handling 7. Clean Coal Specifications 8. Ash Content in Feed a) discrete ashable minerals b) inherent ashable minerals 9. Water Chemistry 10. Petrographic Composition of Coal 11. Free-Swelling Index 12. Convictions of Customer The application of conditioning reagents - both promoters and emulsifiers can substantially improve the coal recovery. Some low-rank, hydrophylic coal, previously considered unfloatable can be economically recovered with the use of the proper reagent.

Jan 1, 1986

By Richard E. Deery, Reginald E. Reid

A large portion of the public lands in the United States is managed by the U.S. Department of the Interior, Bureau of Land Management (BLM). Public lands administered by the BLM comprise about 39 per cent (270 million acres) of the entire Federal surface estate or about 1/8 of the surface of the United States. Most of this land, located in the 11 Western States, including Alaska, is available for mineral exploration and development. The BLM is a multiple-use land management agency responsible for the balanced management of the public lands and their resources. The BLM's task is to ensure the balanced and sustainable development of the public lands and resources. This task translates into the management of people and their use of the public resources. As a result, the BLM manages a diverse group of programs including recreation, range lands, timber lands, fish and wildlife habitat, watershed, wilderness, scientific, cultural, and historic properties, and most importantly for this paper, energy and mineral resources. The BLM has developed several new policies with respect to mining, including policies on inspection and enforcement, financial guarantees for reclamation, and the use of cyanide. The goal of these policies is to demonstrate to the American public that mineral exploration and development can be an integral part of sustainable development on public lands in an environmentally sound manner.

Jan 1, 1991

By John M. Hird

Texas Gulf Sulphur Company's Lee Creek Mine has opened a major phosphate mining district in the Central Coastal Plains of North Carolina (Fig. 1). The ore deposit as it is now known was roughly outlined in 1961 by a Texas Gulf geologist using wire line exploration methods. Slightly uraniferous phosphate materials were detected by a slim-hole gamma ray probe run in numerous farmers' water wells penetrating the formations. A follow-up-core drilling pro- gram determined the economic ore limits to lie in the south central section of Beaufort County beneath 70 feet to 120 feet of unconsolidated sediments. The 50,000 acre deposit is known to contain over two billion tons of phosphate ore amenable to strip mining methods. A part of the deposit underlies several thousand acres of the Pamlico River estuary. The 90 million dollar capital investment plant built by Texas Gulf during 1965-66 included a strip mining operation using a 72-yard walking dragline, a three million product ton per year flotation concentrator, four fluid bed calciners, a sulphuric acid plant (acid for captive use), a phosphoric acid plant, and three solid fertilizer material plants. Shipment to domestic markets is by rail and truck and to over- seas markets by barge to a transshipment terminal at Morehead City, North Carolina. Early mining investigations were conclusive first that the phosphate ore could economically be recovered only by dry strip mining methods, and second that artesian ground waters in the formation (Castle Hayne limestone) underlying the ore would have to be controlled. This report will relate the application of ground water hydrology in depressurizing the Castle Hayne aquifer to facilitate dry strip mining at depths 130 feet below sea level at the Lee Creek Mine.

Jan 1, 1970

By Fred L. Myers

The use of finite element programs for evaluating large grinding mill shells is becoming increasingly popular. However, large scale, detailed analysis can become a burdensome task when one is required to manually prepare the necessary data to be entered into the program, while evaluating the voluminous results is even more devastating. Although available computerized finite element analyses can reduce computation time from years to months or even weeks, additional pre and post processors can reduce the time for data preparation and result evaluation to hours, while simultaneously reducing the probability of human error. Examples of the uses of these processors are presented as well as typical modeling techniques.

Jan 1, 1979

By Véronique Falmagne, Chantale Doucet, Thomas Côté

Production began in the Deep 1 zone of Goldex mine in 2017 at a depth of 1,200 m. Stope dimensions are 50 m high by 22 m wide (along strike) and the panel thickness varies between 22 to 35 m. The Deep 1 orebody is 350 m high by 400 m along strike and 200 m from hanging wall to footwall. The mining method is longhole with paste backfill with a three dimensional primary/secondary sequence advancing upwards in a typical chevron approach and retreating from hanging wall to footwall in a V-shape from a central panel. Mining at a depth of 1,200 m in massive granodiorite brings challenges related to seismicity.

Apr 26, 2022

Ventilation 'is currently used in mines to sustain human life, prevent explosions, and provide a more healthful work place. Future automated-mining systems could use ventilation techniques quite. different from today's practices. The Bureau of Mines is anticipating various methodologies for ventilating the automated mining systems which are now beginning to emerge in the mining industry. This paper examines the special ventilation requirements for automated mining systems. Topics include requirements for automated systems, current studies with blowup ventilation tubing, and ventilation of two types of highwall -ripper type mining machines.

Jan 1, 1990

By Gennaro Gerald Marino

In this paper the main subsidence- ground-structure interactions and an overview of the response of surface structures to subsidence ground movements are presented. The purpose of the paper is to augment our understanding for more effective application of available data as well as to highlight the essential site conditions in building response. The data presented general1 y applies to houses to structures up to 2-3 stories high and no more than several hundred feet in length. Superstructures of these buildings are supported by exterior (wood-frame or masonry) bearing walls with the interior floor loads carried by essentially one row of interior columns. This paper is not directed towards the response of tall buildings, steel-framed structures, or building types commonly associated with schools, churches, libraries, etc.

Jan 1, 1986

By J. L. Kohler

Control circuit failures contribute significantly to continuous miner downtime. The time required to put the machine back into production is a function of the time required to diagnose the problem, obtain parts, and make the repair; of these, the diagnostic time is often the largest. A microprocessor-based system with the ability to diagnose all of the common control circuit failures was designed, installed on a continuous miner, and tested. This paper summarizes the development of the diagnostic system, and provides examples of the system's diagnostic capabilities. Implementation issues and the hardware used for the prototype are briefly described. Finally, comments on the system's performance are presented.

Jan 1, 1993

By Yi Luo

Simulation of the multi-entry and multi-crosscut (MEMC) ventilation systems commonly employed in U .S. underground coal mines can be very tedious, due to the large number of crosscuts with stoppings to be represented in the network models. In order to reduce the amount of work needed to build the models, a common practice is to represent a number of crosscuts with one equivalent airway. However, this introduces certain errors into the simulation results. In this paper, algorithms have been proposed to simplify the ventilation networks of common MEMC systems encountered in panel development operations. The algorithms can be used to reduce a MEMC system into one airway with an equivalent resistance and to determine the airflow distributions in the system and the leakages through the stoppings.

Jan 1, 2011

By John S. Wakeman

The progress results of a pilot plant study on the effects of ball top size and other mill operating parameters are reported. Test series on taconite and quartzite crude ores using a 1.7m diameter primary mill in closed circuit with a vibrating screen indicate clear trends on the improvements of mill throughput and power consumption when using larger diameter balls. Possible effects on mill liner and ball consumption as well as future research plans are discussed.

Jan 1, 1984

By D. W. Smellie

This paper is a review of technological progress in mining geophysics during the past decade. This has been the most significant period in the history of mining geophysics. Among the already existing; techniques, instruments for ground -magnetic and electromagnetic prospecting, were developed that are more, portable and faster to operate. Induced polarization equipment came into widespread use. Airborne instruments of various types became available and were used to survey large areas. Drillhole instruments were developed and have had some use, and it is to be hoped will be used to a greater extent in the future. Two revolutionary new methods, the AFMAG and INPUT, were developed. The wisdom of attempting to cover such a broad field in a single paper might be questioned. There is the inevitable problem that each topic must be discussed very briefly. However, while papers describing individual instruments have appeared, many have yet to be described in the technical literature. The evolution of the ground magnetometer and electromagnetic instruments has not been discussed. It is only recently that a review article has appeared on airborne EM. The existence of review literature on some topics has meant that they are given less emphasis in this review than those topics inadequately covered. It will also be observed that stress is laid on "chose instruments that are generally available to the mining industry rather than those developed by individual exploration companies for their own use.

Jan 1, 1963

By H. E. Epstein, B. K. Parekh, W. M. Goldberger

Comminution is the single most expensive operation in mineral processing. It consumes about 50% of the energy required for mineral extraction (Agar, 1976). Current comminution technology is both energy-intensive and inefficient. A novel noncontact comminution process concept was developed in this study, whereby selective lib¬eration of minerals from an ore could be potentially achieved. The process involves application of electric and ultrasonic energy to liberate minerals from gangue particles. Introduction The mineral industry is a large user of energy in the US. Energy usage is increasing as the grade of ores processed decreases. It is es¬timated that comminution of ores uses about 32 000 kWh (115 trillion kJ), or 2% of the electric power produced in the US (NMAB-365, 1981). Among other minerals, ce¬ment, iron, and copper processing plants are the largest users of en¬ergy in comminution. Very little of this energy used in conventional grinding (about 1%) is used to gen¬erate new surface. The remainder is wasted (Table 1). Thus, there are substantial energy-saving and economic incentives to improve the efficiency of crushing and grinding techniques for mineral recovery. With an energy efficiency of only 1%, it would seem possible to devise methods to significantly improve comminution technology. This requires that breakage force be applied only where needed, not indiscriminately as in a conven¬tional ball mill (NMAB-365, 1981). Can apparatus and methods be de¬ veloped for large-scale commer¬cial use that allow energy to be fo¬cused at intergranular bounda¬ries? If this can be done, mono¬mineral grains would remain in¬tact and the grinding action would be selective and substantially more efficient. The novel comminution process concept described in this paper uses a combination of electric and ultrasonic energy. This energy breaks the ore and selectively lib¬erates minerals. The process has also been termed a two-stage or electroacoustical comminution process (Goldberger, Epstein, and Parekh, 1982). The mineral grain boundary is usually the weakest area in an ore. By applying electri¬cal energy to the ore, the rock frac¬tures mostly at grain boundaries. At the same time, the electric shock creates secondary hairline fractures in the ore. Additional application of ultrasonic energy to this ore provides further break¬age. The concept was proven on a molybdenum porphyry ore but needs additional study. Technical Background There have been substantial im¬provements in milling machinery and grinding operations, but rela¬tively few attempts have been made to develop alternatives to conventional impact milling. Sev¬eral methods, however, have been investigated that relate to this study. In the early 1970s there was considerable interest in a size re¬duction method known as the Snyder Process (Cavanaugh, 1972). It involved charging coarse ore into a pressure chamber, pressur¬izing with a gas, and activating a quick-opening (15 msec ) dis¬charge valve that connected the chamber to a discharge duct. This allowed solids to fluidize and ac¬celerate, subjecting the material to a variety of impulse phenomena that caused the desired size reduction. Other nonimpact means of achieving breakage and selective size reduction have been de¬scribed in technical and patent literature. Kanellopoulos and Ball (1975) considered using heat to induce thermal stress in quartz¬ite. This would cause cracking and, thus, increase grinding efficiency. The use of electrical energy to induce thermal stress was studied by the General Elec¬tric Co., in cooperation with the Montana School of Mines, under a research grant from the Anaconda

Jan 9, 1984

By Jessica M. Wempen, Dallan J. Coons, Bailey S. Simmons, Michael K. McCarter

Gate-road yield pillars are subject to increases in stress as the longwall face advances toward the pillars. Abutment loading conditions are important to gate-road layout and support design in longwall mining systems. Ground support systems are often designed based on mine experience [1,2]. Convergence monitoring is one method of ground support monitoring that can be used to infer increases in pillar stress. Convergence of a yield pillar was measured regularly over the course of six months as the longwall face approached and passed the pillar. Measurements were collected at eight locations surrounding the pillar. The convergence measurements contribute to the knowledge of when yield pillar abutment loading, caused by the encroaching longwall, is first detected. Knowing when abutment loading begins to yield the pillars can help define when standing secondary roof supports are required for head-gate entry access for specific geologic and mining conditions. 

By C. D. Taylor, A. L. Mazzella, A. L. Martikainen

In fluctuating airflow, continuous air velocity recording is the most reliable method of air velocity measurement. It allows for fast recognition of changes and the calculation of long-term averages. Also, it enables the mine operator to identify when the airflow has decreased to a point requiring action. Using ultrasonic anemometers provides an accurate option for continuous air velocity monitoring. This paper provides information about the effect of common obstructions in underground mining on air velocity readings. Stationary and moving obstructions are used to represent workers and equipment that would cause discrepancies in measured airflow. Also, it is important to know how large of a sample size is required to ensure reasonable accuracy of results. Statistical analysis is used to evaluate the required sample size. The sampling procedure is further studied by comparing two different sample rates. The results show that obstructions provide noticeable differences in air velocity measurements. Also, movement of obstructions can be recognized from changes in results. Surprisingly small sample sizes provide reliable air velocity information. Standard sample rates are found to be suitable for the underground environment.

Jan 1, 2011

By Raymond S. Shrode

Transportation is one of several important increments in the total market cost of most commodities. On a national average it has been reported that transportation accounts for about 25% of the total cost of a product at the market place. And industrial minerals are no exception. In fact, the proportionate cost frequently exceeds the 25% average. Further, it may actually determine the economic value of a deposit. Transportation may possibly be thought of as a specialized subject of concern only to a traffic manager and of only nominal interest to the mining engineer, the geologist or other technically oriented member of mineral producers' staff. However, in the industrial minerals field, interest is not commonly confined to exploration, development, production or marketing, but is in contrast an overlapping one. In a very real sense this broad area of interest in the total economics of the business is the specialty of the industrial minerals man. And transportation is a vital part of the total picture. Comments in this paper deal with rail transportation.

Jan 1, 1969

By S. S. Cook, S. E. Paulson

The US Bureau of Mines is conducting core leaching experiments with sulfuric acid on oxide copper ores from the Cyprus Casa Grande and Asarco/Freeport Santa Cruz deposit in Arizona to further the understanding of the leaching process in supergene copper ores as it relates to in situ mining. Leach solutions from atacamite mineralization contained 5 to 30 g/L (0.05 to 0.28 oz/gal) copper and few extraneous ions. Leachant from chrysocolla ores, with grades similar to the atacamite, contained 2 to 9 g/L (0.02 to 0.08 oz/ gal) copper and abundant extraneous ions. Quartz and K-feldspar had no impact on leach solution composition at any acid concentration up to 40 g/L - (0.39 oz/gal) while illite and sericite had minimal impact. Biotite, calcium-rich clay, and limonite have a significant impact on solution chemistry when there is abundant free acid in solution. High acid concentra¬tions increase acid consumption in ores with abundant biotite and limonite gangue. High acid concentrations can be used in ores with quartz, K feldspar, and sericite gangues without increasing acid consumption per unit of copper removed.

Jan 1, 1990

By Keith A. Yarborough

INTRODUCTION The National Park Service (NPS) conducted a research program from mid-1975 to early 1978 to measure alpha radiation levels in natural caves which it administers. Subsequently, a long-term management program was developed which has conducted routine monitoring of radiation levels and has computed employee exposure accumulations in certain NPS caves. The overall program: research and management; was undertaken to evaluate the possible health hazard to cave visitors, interpreters, researchers, maintenance personnel, concessions employees and other workers and to protect their health. The results of this work have been reported extensively elsewhere (see References 1 through 3, 5, 6, 9 through 13, and 14 through 26). This paper deals with the relation of radon gas and daughter produced radiation levels to the cave air flows which mobilize them. These flows are a function of interior cave and exterior ambient air temperatures and pressures and of the cave's geophysical configuration. The low-level, ionizing radiation is produced by minute concentrations of radon and thoron gases which emanate from within caves. Because of confinement, the radiation levels are often appreciably higher than in surface atmospheres. Subsequent radioactive disintegration of the gases into their ionized "daughter" products, which are particulates, permits distribution of the alpha radiation throughout a cave system. The extent and character of this distribution depends upon the particular cave and the air flows which it produces. Thus, the alpha radiation serves as a "tracer" to describe the flows. The flow analysis is divided into two parts: 1) A qualitative description with respect to the two basic geophysical cave types over both long-term (annual) and short-term (diurnal to weekly) periods. 2) A quantitative description of the unsteady, uniform and non-uniform, one-dimensional, incompressible motions for both influent and effluent air flow situations in both basic geophysical cave types. A part of the qualitative description presents "Special Measurement" data: Tsivoglou [vs.] Kusnetz working levels, Tsivoglou individual daughter levels and free ion concentrations, radon gas concentrations, and equilibrium ratios. A great deal of important work has been carried out by Mr. Bobby C. Carson, Cave Radiation Technician at Mammoth Cave National Park, Kentucky. He reports these findings later in this conference (Ref. 6). Some of his results have been used here to establish the cave air flow analysis. Other National Park Service personnel have made measurements at others of the caves for which data are reported here. All of this work and cooperation has been vital to the success of this research program. It is very much appreciated. THEORETICAL FLOW DESCRIPTION Previously reported research (See Ref's. 20, 21, 23 and 25) has established the qualitative relationship between the alpha radiation in caves and their natural air flows. The radiation serves as a representation of these air flows. Changes in radiation with time represent changes in the main forces which produce the air flows. The quantitative data have substantiated that [all caves in which the primary cause of air flow is due to temperature produced gravity (density) gradients and also having minimal man-made disturbances, experience seasonal variations in airborne alpha radiation. The radiation levels increase in summer but decrease in winter], based upon seasonal air movements through each cave system which occur naturally. Two general types of physical cave configurations which control the air flows have been identified as: 1. Those which go up into a hillside or mountainside: Type I ("Upside-down" = USD). 2. Those which go down into the earth; Type II ("Right-side-up" = RSU). These act to control the air flows seasonally. The summer increase in Type I caves is due to increased air flows, whereas in Type II caves it results from stagnation or reduced air flows. This seeming paradox is explained by the physics of the air flow regime in each cave type and has been detailed elsewhere [Ref's. (20), (22) through (25)]. It[ i] true, in general, that air flow decreases airborne radiation in the [immediate vicinity] in which it occurs. Any paradox results from subsequent distribution throughout the case as to [ how] the air moves through a cave [system] with respect to time and space. Exceptions to the cave air flow "rule" are: 1. Caves in which pressure gradients and pressure fluctuations [predominate] in producing the air flows. 2. Caves in which man-made effects and management practices are superimposed on the natural air flow regime. Man-made disturbances which can alter the natural cave air flows are tunnels, elevator shafts, bore holes, sealed and closed portals, etc. If these are not properly sealed, the natural air flows which they change will totally alter the distribution and seasonal variations of the alpha radiation levels. These exceptions may act separately or in combination.

Jan 1, 1981