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By James K. Hallenburg

Geophysical borehole logging is a valuable and inexpensive tool for coal deposit evaluation, development, and production. In addition to the usual determinations of depth and seam thickness, geophysical borehole logs can effectively and accurately determine the coal ash, moisture, and heat contents in situ. Location and evaluation of the partings can be done quickly and accurately. Overburden character determination, such as roof competence, dewatering parameters, ripability, trace element content of the coal and overburden, and sulfur content can be done with existing tools and techniques. The quality of such determinations depends upon the quality of planning and calibration.

Jan 1, 1984

By M. S. Riyazulla

The Hutti greenstone belt comprising predominantly of low-potassium tholeitic basalt has undergone regional metamorphism of a transition zone between greenchist to amphibolite facies. The important mineral constituents of the volcanic suite are amphibole and plagioclase which appear to be the product of regional metamorphism. These minerals have been recognized as the main indicators of metamorphic temperature and pressure. With a view to understand the P-T conditions of metamorphism of the belt, electron microprobe studies were carried out on amphibole and plagioclase and the chemical data was used to decipher the metamorphic conditions. The results obtained indicated a metamorphic temperature of about 6000 c and pressure of 5 kbs. for the Hutti greenstone belt.

Jan 1, 1996

By William C. Peters

The frustration encountered by exploration crews in connection with land acquisition could be graphed to show a correlation with the natural law that everything tends to become more so. Figure I shows a rather common, situation. The combinations of ingredients are almost limitless and the resulting brew is often poisonous to an exploration man. A single step, that of taking a series of deep soil samples is often delayed until some sense can be made from "floating" unpatented claims which are obscure in orientation as well as position, placer claims overlapping lode claims, location posts with empty Prince Albert cans, and claims with no apparent assessment work for ten years. Add to this some patented claims with¬out monuments, a state or federal withdrawal area which may or may not invalidate pre-existing claims, a loosely defined tunnel site, and some ranchers who understandably resent the separation of surface rights from mineral rights. The picture is familiar to exploration men. One approach to such problems is to ignore them until someone voices an objection -- but then an even more chaotic situation is likely to develop. Another practice is to stake new claims to cover all ground that is "open" at first glance and then find out if there are conflicts so that the new claims can be adjusted accordingly.

Jan 1, 1970

By Richard A. Thomas, Liming Yuan, James H. Rowland III, DAVOOD BAHRAMI

To reduce the number of injuries resulting from fires on mobile, diesel-powered mine equipment, it is crucial to promptly suppress a fire once it is detected. The focus of this research was to determine the effectiveness of fire suppression agents. Large-scale tests were conducted using five different fire suppression systems based on: dry chemical, wet chemical, dual agent (dry and wet chemical), carbon dioxide, and water mist. Suppression nozzles were placed around the diesel engine where diesel fuel, engine motor oil, and hydraulic circulating oil spray fires were ignited. The results of this study can help mining companies and manufacturers by providing scientifically based data on the capabilities of the different fire suppression systems.

Feb 1, 2024

By Josiah Pohl, Christopher Utter, Kyle Everly, Akshay Chowdu

Battery Electric Vehicles offer increased energy efficiency for open-pit load & haul operations at a potentially lower overall carbon cost. Electrifying a mine’s fleet, however, presents a unique set of operational challenges. In this study, we explore the effects of electrification on productivity at real operations using a Discrete Event Simulator. The model can simulate multiple shifts, a mixed fleet of diesel and electric trucks, charging and refueling stations, trolley systems, and accurate shovel-truck loading cycles. This study helps determine the trade-offs of adopting electric fleets and how they interact with the layout of today's mines.

Jun 25, 2023

By F. J. Sotillo

Mineral processing requires good classification of particles to attain an adequate separation of minerals. This is of utmost importance in the case of sulfide minerals. An ideal classification is obtained when particles are separated at a given mesh, which is fixed according to the characteristics of each sulfide ore. Under these ideal conditions, particles coarser than the mesh of separation are recovered in the underflow, whereas particles finer than the mesh of separation are recovered in the overflow. This paper presents the results of pilot plant tests that were performed on Ag-Pb-Zn and on Ag-Au Peruvian sulfide ores using a Density Separator, and the comparison of these results with those obtained using hydrocyclones, under similar operating conditions. The results show that the ratio of circulating load is reduced by 50% by using a Density Separator with respect to that obtained by using hydrocyclones. Moreover, the effect of the improvement in the separation efficiency obtained by using the Density Separator on the kinetics of flotation is also shown. Silver recovery of the Ag-Pb-Zn ore increased by 18% whereas gold grade in the concentrate of the Ag-Au ore is doubled.

Jan 1, 1998

By L. Yuan, J. H. Rowland, R. A. Thomas

"Hydrogen (H2) gas released during battery charging can result in cross-interference for carbon monoxide (CO) sensors used for early fire detection and compromise the integrity of the mine atmospheric monitoring system (AMS). In this study, a series of laboratory-scale and full-scale experiments were conducted to evaluate the responses of different CO sensors to H2 gas. In the laboratory-scale experiments, constant H2 concentrations in the airflow, from 100 to 500 ppm, pass through sensors. While in the full-scale experiments, increasing H2 concentrations generated as a byproduct from charging the batteries at the battery charging station rise to the sensors under different ventilation scenarios. The H2 concentrations at the CO sensor location were measured using H2 sensors and were correlated with the CO sensor response. The effects of ventilation and sensor location on the CO sensors responses were also analyzed. The results of this study can help mining companies to select appropriate CO sensors and improve the deployment of these sensors to ensure the safeguard of underground miners. INTRODUCTION As many types of battery-powered mining equipment such as scoops and shield haulers are used in underground mining operations, charging stations are required to charge the equipment batteries. These batteries are of lead acid chemistry. A safety issue exists with the battery charging stations as all lead acid batteries produce flammable H2 gas during the normal charging process. Overcharging or excessive heat can quickly cause batteries to produce even more H2. If H2 is not appropriately diluted or dispersed, it builds up, and the risk of fire and explosion increases. Mine Safety and Health Administration (MSHA) regulation (30 CFR Part 75.340) requires that battery charging stations should be housed in noncombustible structures or be equipped with a fire suppression system. When a fire suppression system is used, the battery charging stations must be ventilated with intake air that is directed into a return air course or ventilated with intake air that is monitored for CO or smoke using an AMS. The monitoring of intake air ventilating battery charging stations should be done with sensors that are not affected by H2."

Jan 1, 2018

By J. M. Wempen

As development in underground coal mines progresses away from the critical components of the ventilation system, including the main fans and ventilation shafts, resistance is markedly increased. This results in higher pressure and flow requirements from the main fan(s) to maintain adequate face ventilation, which often requires that the primary ventilation system is upgraded with additional shafts and surface fans. The use of booster fans underground is a potentially practical alternative. This study presents simulations of the use of booster fans in two underground ventilation scenarios, one longwall and one room and pillar. The booster fan effects on the power requirements of the ventilation systems are evaluated.

Jan 1, 2011

By D. Nutakor

Rock joint stiffness is not only a poorly known parameter, but also has no established laboratory measurement procedure. This paper presents methods used to determine the normal and shear stiffnesses of healed joints filled with vapor-altered minerals obtained from the Yucca Mountain site in Nevada. Results show that these joints behave linearly up to 85% of their loading history and are stiff with strengths very close to the strength of the intact rock. Factors that might have contributed to the linear behavior of these joints are discussed and areas requiring further investigation are provided. Joint normal stiffness ranges from 7.16 to 64.77 GPa/mm with an average value of 26.93 GPa/mm, while joint shear stiffness averages 11.41 GPa/mm and ranges from 3.09 to 28.41 GPa/mm. Young?s modulus of the vapor-altered joint infilling was calculated from the stiffness of the healed joint. Young?s modulus of the vapor-altered joint filling material averages 7.89 GPa and ranges from 2.15 to 19.43 GPa. Given the pervasive presence of such altered rock, usually in the form of sub-spheroidal 3-D pockets, this property should be of value in any numerical modeling attempting to describe the mechanical behavior of these tuff formations at the level of detail where inclusions might be a factor.

Jan 1, 2008

By Joel L. Morrison

The preparation of coal-water slurry fuel (CWSF) has the potential to be a commercially viable technology for the coal industry. The technology base required to prepare stable CWSF using grinding circuits has been developed over the past decade and is now being applied to the preparation of CWSF from wet coal fines which are generated during coal beneficiation. When preparing CWSF, the optimum CWSF formulation must be determined to ensure that the fuel will be stable while having acceptable atomization and combustion properties, and the production run must be monitored closely to ensure that the CWSF quality is maintained. This paper describes the CWSF formulation process, CWSF preparation circuits, and some of typical problems encountered in, and solutions to, the transportation and storage of CWSF.

Jan 1, 1993

By Jr. Smith

Borates have been mined in the desert areas of California and Nevada for more than 100 years. To about 1890, playa surface mining provided the chief sources of boron minerals. Underground mining of colemanite and later of borax and kernite was predominate until about twenty years ago. Open pit mining of the large deposits of borax and kernite near Boron, California has been most significant for the past twenty years. Mining of colemanite in the Ryan, California area, near Death Valley, began in 1907. Following the discovery of the large deposits in the Boron area (about 1957), mining in the Death Valley area became nearly nonexistent. Only small tonnages were mined for special uses. Little mining was done in the Boraxo area near Ryan. The first claim was made in about 1915 In 1960 the area became the property of the Kern County Land Company, which was acquired by Tenneco Oil Company in 1967. In 1976 the various borate properties and claims in this region were acquired by American Borate Corporation. The open pit mine is now approximately 400 feet (121.9 m) deep, 3000 feet (914.4 m) long and 1000 feet (304.8 m) wide. The borates in the Boraxo pit consist primarily of three minerals. These are about 50% coiemanite (C2B6O11' 5H2O), about 40% probertite (NaCaB5O9.5H2O), and 10% ulexite (NaCaBcO9.8H2O). The colemanite, along with boric acid and high-grade coiemanite ore from Turkey provide the only sodium-free borates for production of textile grade fiberglas. When heated to its decomposition temperature, colemanite decrepitates to a fine powder. This provides the basis for the concentration process. The gangue minerals in this deposit are primarily calcite and clays, including bentonite. The ore body has a very low arsenic content.which is a desirable feature. Test work had been done with samples prior to the results discussed herein. This paper will discuss results of test work which were the basis for erection of a plant, and the subsequent plant operations.

Jan 1, 1978

By S. Underwood

The tracer gas method of conducting ventilation surveys is a means of determining air quantity in underground mines with knowledge of the concentration of the tracer in the atmosphere and the flow rate at which the tracer is being released. The technique is useful in inaccessible areas of underground mines and areas where traditional point measurement of velocity is not practical. Sulfur hexafluoride (SF6) is the industry standard tracer(Kennedy 1987) used in underground mines because it is safe, stable, and not naturally occurring in the mine environment. The implementation of a second tracer will increase the versatility of the tracer gas technique allowing for simultaneous releases for the study of interrelated ventilation circuits, and for conducting multiple experiments in less time. This paper will detail the selection of perfluoromethylcyclohexane (PMCH) as a novel tracer with sensitivity, physical properties, and analysis characteristics similar to SF6. Methods for the release of liquid PMCH into underground mines will be recommended, and the vulnerabilities of sample loss due to condensation of vapor PMCH will be explored. Finally, the benefits and implications of using PMCH as a second tracer will be discussed.

Jan 1, 2012

By T. Hollenberg, N. Nolten

The mining industry is one of the major energy consumers in Namibia. Energy costs increase the operating costs of Namibian mines, in particular, the processing plants, and result in an overall increase of production costs. A substantial part of the energy used is directly imported from South Africa. The cost of energy has been increasing rapidly in the past few years and will most likely continue to do so in the future. In 2015, the average wholesale price for energy from national power utility NamPower was US$87/MWh after rising more than 12 percent annually in the two previous years. At peak times, which are early in the morning and late in the evening, imported-energy prices are extremely high and have to be factored into the electricity tariffs. This problem is expected to intensify due to a projected 4 percent annual increase in energy demand. A major target of the Namibian mines, therefore, is to consider possible ways to address energy-saving challenges and to investigate possibilities for the mines to generate electricity internally during peak times. This is in alignment with the mines’ strategic plans and objectives to reduce total energy consumption and costs from both national and foreign electricity suppliers. In this paper, we explore addressing some of the key energy consumption and optimization challenges through process energy reuse and solar energy production to decrease demand for imported energy through a case study carried out in cooperation with Skorpion Zinc Mine and Refinery.

Jan 1, 2018

By A. Bruynesteyn

Many papers 'have been publihed on the role of the bacterium.Thiobacillus ferrooxidans in the oxidation of reduced sulfur compounds, and years of research have established the following environmental factors, which influence biological oxidation. 1. Oxygen is required for the oxidation of reduced sulfur compounds to the sulfate form. Sufficient oxygen. is available from the air, consequently, it is of importance to get the air to the bacteria. 2. The bacteria are active in the pH range 1.4 3.5. Maximum activity occurs at pH 2..0 - 2.8. 3. -In order to allow the bacterial populations to expand, certain essential nutrients must be available. Nitrogen has to be supplied for the production of body protein, and ammonia is the source most readily accepted by the bacteria. Carbon dioxide is the only utilizable source of carbon and the small amounts available in air are the primary source of this element. Small amounts of phosphate, manganese,, potassium,. calcium. and magnesium are also required. These trace minerals are available from the water and host rock in sufficient quantities. 4. Water is required as a carrier for the oxygen carbon dioxide and other nutrients, as-well as a solvent for the metallic sulfates produced. The bacteria are motile and the water allows the bacterial populations to spread:: bacterial activity ceases if the equilibrium relative humidity drops below 100%. 5.-optimum bacterial activity occurs at temperatures of 34 - 35°.C (93 -.95° F). All activity ceases above 45° C. At lower temperatures, activity its dramatically decreased, but there is still a significant amount at 10 - 11° C.- Thiobacillus ferruoxidans has been isolated from a mine with a year round temperature of 3° C. 6. Unpublished results from our laboratory show that biological leach ore oxidation takes place during the rest periods at the same rate as during the wet leaching periods providing there is a film of moisture remaining around the particles. Optimum conditions can be readily achieved in the laboratory, but application of our laboratory knowledge to commercial leaching dumps is riot as simple. Attempts to achieve improved environmental conditions for the bacteria in leaching dumps would require substantial capital investment and careful planning of leaching operations. This paper

Jan 1, 1972

By L. A. Baker

The presence of goethite in a hematite ore has been shown to strongly affect the time of heating to the firing temperature. The investigation of spalling of single pellets and of packed beds has enabled free water and goethite spalling to be identified as separate phenomena. In addition, it has been shown that even for an 18 inch deep bed of green balls the free water and goethite drying periods can be considered separately. Based on this observation, a method of predicting production rate and hood temperature profile is presented. The method required knowledge of the ore goethite content, ore grind and the green pellet bulk density. Laboratory results were found to be in good agreement with actual plant practice and have led to improved process performance.

Jan 1, 1972

By Lok W. Home

HISTORICAL DEVELOPMENT At the beginning of the 1970 more than 90% of pro¬duction drilling in open-pit mining was obtained with the use of rotary drills. At the same time, the use of rotary drills underground was virtually nonexistent. Several progressive mines began questioning whether efficient rotary drilling could not be adapted to under¬ground applications. In the late 60s and early 70s at¬tempts to use rotary drilling were made by Inco, Ltd. and Meramac Mining, utilizing drill units designed as a combination of small diameter raise drills and rotary drills. These initial attempts were unsuccessful primarily due to the immobility of the equipment and low degree of dependability. At the same time, experiments con¬ducted by Inco and Meramac using large diameter in¬the-hole percussion drills produced immediate encourag¬ing results. The first serious attempt at utilizing rotary drilling underground was made by Texasgulf in 1971 at Kidd Creek mine in Canada. An experimental stope 15 m wide, 36 m long, and 30 m deep was drilled using 200-mm diam rotary drilled holes. The machine used was a Robbins' Model 11 D. The Model 11D is a rotary drill designed to drill drain and utility holes under¬ground. The results of this test revealed that large diameter blasthole stoping was feasible. The indications were that the major areas of concern-fragmentation and pillar damage-could be controlled and a new low-cost stoping method resulted. At this point Texasgulf and Robbins entered into a cost-sharing agreement to develop a rotary drilling unit specifically for this stoping method. Drilling of the trial stope required pouring a concrete pad at each drill hole plus anchoring the derrick to the pad by means of rock¬bolts. Utilization expressed in terms of drilling time to available time was less than 20%. It was obvious that the required unit had to be mobile, setup time had to be minimized, and rod handling had to be improved. The first attempt at an underground production-type rotary drill consisted of mounting the basic 11D on an air-powered Eimco 600 Series crawler. The crawler was equipped with four screw-type leveling jacks operated by an impact wrench; rod rack facilities for 60 m of 1.2-m long, 170-mm diam rods; a rod handling facility consisting of an air-lift swing boom and a pipe loader which automatically positioned the rod under the float¬ing drive box; a turnbuckle anchor system requiring in¬stallation of four rockbolts in the drill drift floor and placing turnbuckles from the rockbolts to the corners of the drill; and trailing power units containing the electrics and hydraulics required to operate the drilling unit. Operation of this unit revealed a vast improvement in drilling time but some problem areas remained. The anchoring system required secondary drilling and proved difficult to adapt to the localized irregular floor surface and the trailing power unit was difficult to maneuver and was causing unnecessary maintenance costs. Addi¬tional improvements resulted in the standard 11MD rotary blasthole drill. DESCRIPTION OF UNIT This standard model consists of the drill and the power unit integrally mounted on an air-powered crawler chassis (Fig. 1). The rod-handling and leveling¬jack systems are similar to those used on the prototype Texasgulf unit and remained relatively the same. The anchoring system has been replaced by the roof jack, initially screw type but now hydraulically actuated. The anchoring system is necessary as the drill exerts more thrust than the weight of the unit. During operation it is found that the two front jacks adequately anchor the machine. The complete unit's operational dimensions are: height, 3.2 m; width, 2.1 m; and length, 4.2 m requiring a 3.5- x 3-m drill drift. The derrick is pivot mounted and raised and lowered by a hydraulic cylinder reducing the transport height to 2.5 m. The derrick is also turnbuckle mounted to allow dip angle drilling from vertical to 0.52 rad (30°) off vertical. The drill derrick can be mounted to allow dip axis to be parallel or perpendicu¬lar to the long axis of the unit. The standard rods are 1.2 m in length and are contained in racks of 10 which can be removed for transportation. Drilling torque is produced by a 56-kW (75-hp) electric motor driving a double vane pump which in turn drives a Robbins high torque gear-type hydraulic mo¬tor. In addition to the hydraulic motor, the machine drive system has a 3.9:1 planetary gear reducer. This results in six speeds with the following minimum and maximum range: Maximum rpm 112 Torque 3725.5 J (380 kg m) Minimum rpm 10 Torque 14 706.0 J (1500 kg m) Drilling thrust is provided by two bootstrap cylin¬ders pressurized by a variable volume pump. This sys¬tem can produce from 0 to 267 231.2 N thrust in either direction. Bailing air (approximately 17 m3/min at 382.2 to 490.3 kPa) is introduced through a rotary swivel pass¬ing directly through the center of the drive system to keep efficiency and losses to a minimum. Hole annulus is also kept to a minimum by using 170-mm rod when drilling a 200-mm hole. A small amount of water is added to the air for dust suppression. The machine has to be supplied with air, water, and electrical power. It does not appear feasible to provide an integral air power supply with the rotary drill such as is done with open-pit rotary drills. Air is required and installed during the primary development of the drill drift. The machine can be adapted to drill hole diameters from 170 to 228 mm for blasthole operations. The drill string consists of the rotary bit, crossover stabilizer, roller stabilizers, and standard rods. The operator controls speed and thrust pressure from an operating console which can be mounted in a conve¬nient position. Mount Isa has made an adaption to the operating console to permit remote collaring of drill holes in an uncleared floor.

Jan 1, 1982

By Klaus Rieker

"Since the mid-19th century the River Emscher in the German Ruhr District has been used for disposing of wastewater. In the early 1990s, it was decided to replace the existing open wastewater system with a sewer system and to restore the River Emscher to its natural state. The major Emscher conversion project is divided into a large number of individual schemes, with construction phase 30 being the largest. By applying the pipe jacking method, interlinking tunnels with section lengths in excess of 1,100 m are constructed. USAGE OF THE EMSCHER OVER TIME The 85-km long river Emscher flows right through the Ruhr District. It has its source to the east of Dortmund and flows into the river Rhine near Dinslaken (Figure 1).The Emscher has been used to dispose of wastewater since industrialization began about 200 years ago. Intensive coal mining over the years led to considerable subsidence causing stagnant sewer areas which in turn led to typhus and other deceases. Thus in 1899, the Emschergenossenschaft was founded to create an efficient interceptor system for a catchment area of 865 km² through lining, raising and Emschergenossenschaft decided to free the waterways of the Emscher system from sewage and to improve them in ecological terms by 2020. A budget of 4.5 billion euros was earmarked for this purpose.The construction of sewer conduits began in order to no longer transfer the wastewater into the Emscher. The currently ongoing construction of the “Emscher Interceptor” - the main sewer - represents the heart of the Emscher conversion project. The interceptor will run along the river over a length of 51 km. Three pumping stations are required to confine the sewer’s depth to elevations between 15 and a maximum of 40 m below the surface. Since early 2012, the Emscher has been free from wastewater east of the Dortmund-Deusen clarification plant. There are two further clarification plants situated along the Emscher, which treat the still contaminated river water down-stream. Once the Emscher Interceptor is in operation, they will receive wastewater solely from the tunnel system."

Jan 1, 2016

Despite the current economic downturn that is now decimating iron ore production, Minnesota?s mining operators remain optimistic about the long-term prospects for the industry. Reflecting this optimism, the development of several new mining projects continues in the state. The future of mining in Minnesota was the featured topic at the combined 82nd Annual Minnesota Section of SME Meeting and 70th Annual University of Minnesota Mining Symposium. More than 500 mining industry professionals, including engineers, executives, mining managers and equipment suppliers from the around the world, attended the meeting, which was held April 14 and 15, 2009, in Duluth, MN. The combined meeting featured a keynote session with three distinguished speakers plus a panel discussion by representatives from several of Minnesota?s taconite producers. The keynote speakers were Curtis Clark, president and chief operating officer, Behr Dolbear, who gave a presentation on the ?State of the Mining Industry.? Phil Newman, chief operating officer, CRU Strategies, spoke about challenges facing the mining industry and James A. Skurla, acting director, Bureau of Business and Economic Research, Labovitz School of Business and Economics, University of Minnesota Duluth, discussed the importance of mining to northeastern Minnesota?s economy. The taconite producers panel discussion included Jonathan Holmes, vice president and operations manager, ArcelorMittal; Ed Latendresse, vice president and general manger, Hibbing Taconite; John Tuomi, vice president operations services, United Taconite and Mike Mliner, vice president and general manager, Northshore Mining. The mangers provided updates on their respective operation The meeting included concurrent technical papers sessions on mining, processing, environmental and nonferrous mining. The sessions included technical papers that provided information on the status of a number of new mining projects in the state. The conference also offered a SME short course titled ?The basics of iron mining.? A tradeshow that featured about 100 companies and organizations offering products and services to Minnesota?s mining industry ran in conjunction to the conference. It was estimated that more than 900 people, including conference registrants and special invited guests of the vendors, attended the tradeshow opening reception. This was the largest trade show in many years. The Minnesota Section of SME also held its annual business meeting during the conference.

Jan 1, 2009

By Robert H. Oliver

Flowsheet flexibility in new 750 TPH coal cleaning plant provides three unusual capabilities. Two compartment drum coarse H.M. washer can be adapted to provide two stage separation. Coarse section of plant can be operated without fine section when washing surface mined coal. Fine section can operate with flotation cells bypassed if strip coal oxidation kills the froth. Plant can be fed by belt from bulk storage, front end loader from storage piles and truck from the mines. Raw coal and each of four washed products can be fed by belts to three separate loading points on two separate railroads.

Jan 1, 1979

By G. L. Simmons.

Many large. low-grade (refractory) sulfide gold resources exist in Nevada and other parts of the world that are not amenable to concentration by conventional flotation practice, Over the past several years Santa Fe Pacific Gold (SFPG) has investigated flotation process options to economically treat low-grade refractory resources of this type at Lone Tree and Twin Creeks. Conventional flotation technology applied to the original high-grade gold resources at Lone Tree and Twin Creeks was initially unsuccessful. Review and analysis of auriferous (gold-bearing) iron sulfide mineralogical characteristics and flotation chemistry provided a fundamental understanding that led to the development of a new flotation process that SFPG refers to as N2TEC. This paper discusses the development of this technology and compares N2 TEC results with conventional flotation practice.

Jan 1, 1997