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By V. de Macedo Torres

There are technical and commercial limitations on using high fluorine copper concentrates in industrial copper smelters. The presence of more than 1000 ppm of fluorine in copper concentrates affects the sulfuric acid units generally integrated to copper smelters, and penalties are normally applied to high fluorine concentrate prices. Several process alternatives to this issue were studied at CVRD Technology Center (SUTEC): modifications on conventional sulfuric acid plants to use high fluorine concentrates, removal of fluorine containing minerals in flotation using depressants, selective leaching of fluorine minerals and sulfuric leach of copper concentrates. Finally, a hydrometallurgical process of removing fluorine was developed by SUTEC.

Jan 1, 1997

The Virginia Center for Coal and Energy Research has been developing models of wireless signal propagation in underground coal mines since 2007. The current mine propagation modeling software, named COMMS, is able to locate potential broadcast points for underground wireless mesh systems and estimate their coverage. COMMS utilizes programmed routines to calculate necessary values to both quantitatively and qualitatively solve and analyze predicted coverage areas. The program approximates the spatial relationships that are encountered, such as ventilation regulators, belts and other obstructions. Using this model for propagation allows the optimal communications node locations to be calculated, by using lessons learned from current installations and experience with the new technology. In addition, the optimization can be calculated by checking all possible combinations of broadcast locations. This paper compares these optimization calculation methods. The ability to solve a mine?s communication network provides a pre-installation mine network design map, creates coverage maps of the mine and allows planning for future communication activities

Jan 1, 2011

By R. Shields

"Hard rock mines move large volumes of material. But the conveyors essential to this movement suffer lots of problems, including carryback, spillage, dust, and belt wander. Many of these issues are created at the transfer points where the belts are loaded. This presentation will start with an overview of the latest transfer point systems that incorporate safety and serviceability by design. It will then report on recent projects. One project is the Conveyor B Transfer at the Coeur Rochester silver mine near Lovelock, Nevada. Here performance was improved with the installation of belt support cradles, engineered chute walls with external wear liner, and a compact dust collector. A second project is the improvement of belt support idlers and skirtboard sealing in a long loading zone of a conveyor under the concentrator at an Arizona copper mine. THE IMPORTANCE OF TRANSFER POINTS Conveyors are essential in mine material handling. Their performance will often make the difference in mine productivity and profitability. A key to conveyor performance are the transfer points where the conveyor belt is loaded and discharges. At these transfer points, many of the problems encountered with the conveyor system are created. The problems that arise at the transfer stations include off-center and segregated loading, mistracking, blockages and plugging. And there are a variety of problems originating with fugitive material—cargo released in the form of carryback, spillage, or airborne dust—that are created or exacerbated in the transfer points. These fugitive materials turn into other conveyor-related problems, including shortened component life, unplanned outages for conveyor maintenance, unexpectedly high labor costs for maintenance and cleanup, worker health and safety problems, and issues with community relations. As estimate attributed to the U.S. Mine Safety and Health Administration (MSHA) notes that 85 percent of conveyor maintenance is a result of fugitive material at conveyor transfer points. TECHNOLOGIES TO IMPROVE TRANSFER POINTS A number of techniques to improve the performance of conveyor transfer points have been developed. They include: • Absorbing impact, to prevent damage to belt, belt support systems, and conveyor structure, and reduce spillage caused by the impact energy arising from long material drops or large lumps of material loaded onto the receiving belt. • Stabilizing the belt line, to eliminate sag that allows spillage and encourages material entrapment that can damage the belt. • Protecting the skirtboard seals, by sheltering the sealing strips from the mass of cargo pushing material toward the edges of the belt. • Using self-adjusting, multiple-barrier edge seals, to keep material on the belt by providing long-lived seal efficiency with minimum maintenance requirements. • Controlling and centering the belt’s path, to eliminate belt wander and the spillage and damage it can cause. • Allowing dust to settle, through the incorporation of chutework that provides expanded stilling zone and the use of dust curtains at the points where the belt enters and exits the transfer. • Adding supplemental dust control systems, through the installation of systems for passive dust gathering, water-based dust suppression, and/or active dust collection."

Jan 1, 2017

By Ulf B. Andersson, Christina Dahnér-Lindkvist, Bruno Figueiredo, Jessa Vatcher, Jonny Sjöberg, Joel Andersson

Hydraulic fracturing to precondition the rock mass in high seismic risk environments has great potential. Unfortunately, there are many unanswered questions about how to best implement a hydraulic fracturing program at individual mine sites, and even how to best use our engineering tools to evaluate these plans. To give the hydraulic fracturing field tests at LKAB’s Kiirunavaara Mine the best chance of success, fully-coupled, discontinuum numerical modelling Itasca’s 3DEC code was used together with statistical simulations of the fracture network. For modelling purposes, it was assumed that hydraulic fracturing successfully reduces seismic risk through 1) the creation of hydraulic fractures along a plane at each injection site, and 2) activation of existing discontinuities. A variety of scenarios for the mine were evaluated, which focused on site specific uncertainties (such as the spacing of the pre-existing discontinuities) and practical solutions (such as the hydraulic fracture spacing, selection of injection medium, and hydraulic fracture site location relative to production). The discrete fracture network (DFN) realizations were developed using available statistical data for discontinuities near where hydraulic fracturing was planned.

Apr 26, 2022

By Xinyang Wang

It is believed that sulfur and volatile matter contents in coals are the main intrinsic properties to cause the self-heating of coal. Their oxidation at lower temperatures than that of fixed carbon to initiate coal's self-heating should be quantified. This study is aimed to improve the previous mathematical model developed by the authors for studying the coal's propensity for spontaneous combustion. It enhances the model's ability to consider the effects of sulfur, volatile matter and moisture contents in the coal - three important factors affecting the coal's self-heating process. Sulfur exists in coal primarily in the form of pyrite which will be oxidized rapidly under suitable conditions. Volatile matters, higher in low rank coals, are more easily to be oxidized. Heat of water condensation provides initial energy for low temperature oxidation. Heat release rates for pyrite oxidation and moisture condensation are built in the model. Finally, the simulation results in terms of time versus temperature on pyrite oxidation and moisture condensation are validated with the adiabatic testing data respectively.

Jan 1, 2013

By Ajit Godbole, Ping Chang, Ramakrishna Morla, Purushotham Tukkaraja, Shivakumar Karekal

This paper presents the optimum auxiliary fan(s) location to control air recirculation in dead-end workings where dieselpowered vehicles operate. Investigations were conducted with various secondary fan locations from the dead-end crosscut with varying the intake air quantities using a 30 m3/ s capacity twin 75 kW auxiliary fan and 45 m3/ s capacity twin 110 kW auxiliary fan to control air recirculation and DPM. The results showed that if the drive intake airflow rate matches the fan capacity, air recirculation will occur even when the fan is located 10 m away from the crosscut entry. Results also showed that if the intake drive air quantity was greater than or equal to 150% of fan capacity, no recirculation was observed when the twin 75 kW fan location was at least 5 m and the twin 110 kW fan location was at least 10 m away from the dead-end crosscut access.

Oct 18, 2022

By R. B. Berg

Montana sapphires were first discovered in alluvial deposits in the Helena area in 1865 and subsequently were discovered in other alluvial deposits in southwestern Montana and also in a lamprophyre dike at Yogo in central Montana. From about 1900 until the late 1930?s, when synthetic sapphire began to come into widespread industrial use, Montana sapphire mines produced large quantities mainly for watch bearings with lesser production for the gemstone market. The Yogo deposit is now mined for the gemstone market and two of the alluvial deposits are mined to produce sapphires for the fee-sieving of sapphire-bearing gravel and for the direct sale of gemstones. The generally pale-colored sapphires from the alluvial deposits in southwestern Montana are heated to enhance their colors whereas the generally blue sapphires from the Yogo deposit require no treatment. Markets for sapphires from both the alluvial deposits and the Yogo deposit are strong. In spite of reported historic production in excess of 70 tonnes, mineable resources appear to remain at most major deposits. Also abundant untested lamprophyre dikes in central Montana may host sapphires similar to those at the Yogo deposit.

Jan 1, 2009

By Don Stevens

The Denali Prospect (147° 08' 20" W, 63° 08' 50" N) is located on the south flank of the Alaska Range in the Clearwater Mountains in south central Alaska. (See Figure 1). The mineralization was discovered in 1963 and surface explora¬tion began the following summer. Surface trenching and diamond drilling were used to locate and sample the mineralized zones. In 1969, an adit totalling approximately 1400 feet was completed. In 1970, a -15% grade decline approximately 1800 feet long was completed. Further diamond drilling was done along with both underground programs. Although much work remains to be done to properly evaluate the prospect, results from all the work to date are quite encouraging. This paper will consider the geology of the prospect and the surrounding area, some- aspects of the geochemistry of the sulfides, and the origin of the sulfide deposits. This paper includes data from this writer's Ph. D. dissertation, "Geology and Geochemistry of the Denali Prospect, Clearwater Mountains Alaska" from the University of Alaska and subsequent work.

Jan 1, 1972

By Randall J. Essex

The Construction Institute of the American Society of Civil Engineers recently published the second edition of a 1997 publication on geotechnical baseline reports. The new publication, called Geotechnical Baseline Reports for Construction, Suggested Guidelines, represents a 2-year effort that adds three new chapters to the original publication, as well as capturing practitioner commentary through two industry workshop sessions. The paper will overview the contents of the new publication, particularly the three new chapters.

Jan 1, 2008

By Katzer R. Klimpel, J. Sewell

Dr. Roussey Roussev The use of chemical additives on grinding is of significant importance considering the high energy consumption of grinding processes. My research indicates that the dispersant approach explains the effects, in this particular case of wet grinding. Further, the dispersant approach combined with torque measurements give the possibility of clarifying the mechanisms involved when using grinding aids. I find the conclusions derived from the data obtained to be correct and useful for grinding. In general, I agree with the explanations. However, I would like to discuss several additional points that I consider to be important, and in the same time to mention some of my own results from investigations similar to those presented in the study under discussion. The "bed volume concept" and the change of slurry viscosity explain adequately the data plotted on fig. 3, in conjunction with Figs. 1 and 2. However, the significant increase of the average torque in the case of 83% solid with XFS-4272 introduces the necessity of establishing the optimum of percent solid when dispersant is used. For example, the optimum percent of solid for different materials varies. One of the reasons is the material's mass density. On the other hand, it is necessary to determine the concentration of the chemical used. Because of this, it would be interesting to know how the cited concentration was selected. The supportive discussion and verification by Dr. Roussev, with results similar to that of the paper, is appreciated. I will try to answer the additional questions he has raised. To begin with, the mill was fitted with six lifters of approximately one-quarter inch height. There has been extensive lab and plant level work to understand downstream influences of using dispersants like XFS-4272*. In sulfide ore processing, which is the area in which most industrial scale testing has been performed with this approach, neutral to positive influences have been observed. For example, positive effects (e.g., increased recovery) have been noticed in flotation operations involving ores that have a tendency to produce excessive slimes upon grinding. (1) Also, the use of a dispersant has been shown to demonstrate a positive influence on classification by improving the sharpness of separation and preventing a decrease in d50 value that usually accompanies increasing flow rates to classifiers.(2) The biggest potential downstream problem is in thickening, which at the dosages involved, has not been a problem in plant scale usage. The commercial price of dispersants like XFS-4272 is quite variable depending on source, concentration, etc, but a typical cost of XFS-4272 to achieve a 10% increase in throughput in industrial mills has been between 20 and 35- US per ton of feed ore (1981).

Jan 12, 1982

By Steve Kral

The mining industry is no stranger to hard times. Throughout its history, the industry has faced the ups and downs of commodity prices, difficult-to-mine-and-process ore bodies, labor issues and other problems. Throughout it all, though, the mining industry continues to provide the materials needed for society —even in the face of attacks by those who seek to cripple the industry or have it go away. The reason the mining industry survives, of course, is that mankind requires the products the industry produces. And, in recent decades, the industry has developed new technologies and improved on existing ones to produce those products in environmentally sound ways. At the same time, the economic benefits have been enormous to communities throughout the world where mining takes place.

Jan 1, 2002

By Todd Minoski, Matthew McElhinney, Mark Morris, Mark Mazzella, Joseph Bright, Morgan Sears, Craig Compton

To promote the safety and health of U.S. mineworkers, researchers with the National Institute for Occupational Safety and Health (NIOSH) are currently involved in gathering additional field data from the nation’s underground coal mines. The purpose of this field study was to monitor ground movement and changes in pressure during mining where conditions include a thick parting in the coal seam. To accomplish this, three arrays of field instrumentation were installed in the wraparound bleeder of a room-and-pillar panel at the Maple Eagle mine located in southern West Virginia. Borehole pressure cells (BPCs) were used to monitor the change in pressure in pillars located adjacent to the gob. Roof extensometers were installed to measure roof sag at various horizons in the immediate roof, while rib extensometers were installed to measure displacement of the in-seam parting as mining progressed. Additionally, visual observations and manual measurements were taken during subsequent site visits. The repeatability of results, important from a scientific perspective, was accomplished by successfully obtaining field measurements from two nearly identical instrumentation sites. The data collected indicated that the front abutment extent at the edge of the panel was approximately 200 ft, corresponding to a distance of 9– 10 times the square root of the depth. Yielding of the slabbed pillar began when the pillar line was approximately 290 ft outby the instrumentation sites. This was followed by load shedding onto the abutments and the measurement of small amounts of roof sag in the No. 1 entry. Instrumentation data, as presented in this paper, can be used to better understand stress redistribution, pillar performance, and roof/rib displacements. Additionally, this data is suitable for assisting in the calibration of numerical models. Insight gained from applying these models can be used to make better engineering-based judgments for conditions that could potentially be encountered in the future.

Jul 1, 2023

By L. C. de Kooker, K. Esmaeili, I. Musonda, M. Ferentinou

A numerical investigation of the effect of pore pressure regime on the safety factor and the critical failure mechanism is presented for fly ash storage facility. Pore pressures’ measurements from standpipe piezometers and pore pressure estimated from seepage analysis are used to compare the factor of safety for a fly ash slope. This was applied for considering static and seismic scenarios. A probabilistic approach was applied to account for the uncertainties resulting from the limited data available and support a qualitative risk assessment evaluation. Slope stability analysis is conducted in two and three dimensions, adopting the limit equilibrium analysis approach, and also a finite element seepage analysis, to assess the stability of the slope. The two-dimensional cross-sections were extruded to three-dimensional models to estimate the factor of safety and associated shear failure. The results from the performed analysis suggest an increase in safety factor values of 5%.

Mar 27, 2024

By Cody Giroux, Homer Scurlock, Michel Wasag

Silica and Crystalline Quartz exposure continues to be a serious health threat to nearly 2 million workers in the United States, including more than 100,000 working in high risk jobs such as abrasive blasting, foundry work, stonecutting, rock drilling, quarry work, mining and tunneling. The primary focus of this study is to identify the best methodology to reduce particulate-laden air and limit/eliminate exposure to respirable dust with silica/crystalline quartz during tunneling operations. This study focuses on two de-dusting systems employed on similar tunnel construction projects. The first project is the Coxwell Bypass Tunnel located in Toronto, Ontario Canada. The second project is the Westerly Storage Tunnel located in Cleveland, Ohio. The Toronto project is utilizing a wet de-dusting system. The Cleveland project is using a dry de-dusting system. The objective is to determine which system provides the best protection and suitability to capture, remove and ultimately reduce respirable concentrations of silica/ crystalline quartz to safety and healthy levels in underground tunneling activities.

Jun 13, 2021

By H. Savasci, G. Yarim, J. S. Chung

As part of ongoing deep-ocean mining research, hydraulic transport systems as well as status of deep-ocean mining systems are reviewed in the aspects of manganese nodules and crusts from 8006,000-m depth. The emphasis of the investigation of hydraulic transport is placed on the shape effect of particles on the pressure gradients and flowrates. Series of tests are being conducted to study the lift characteristics of a 2-phasevertically upward hydraulic transport of 2 types of small solid particles in a PVC pipe of 1-in (2.54 cm) diameter: irregular-shaped silica sands and equivalent spherical glass beads. Pressure drops and mass as well asvolumetric flow rates were measured by electromagnetic(EM) flowmeter and mass flowmeter. The particle sizes used are 8-10 mesh. The results in turbulent flow range of 101045Re show that pressure gradients or friction factors are smaller for the spherical beads than the sands. The larger the concentration of the particles are, the larger the pressure gradients become. The larger the particle concentration is, the less the effect of particle shape on pressure gradients becomes. The shape effect is greater for the minimum particle transport velocities than for the settling velocities.

Jan 1, 1999

By R. D. H. Bedd

GEOLOGICAL NOTES The area under discussion is situated approximately 150 m north of Loraine No. 3 shaft at ± 1500 m below surface. The block being mined extends from about halfway between 50 and 52 levels to just below 48 level (see Fig. 1). The EB reefs form the lower portion of the EB zone of the Elsburg series and in the 81 line area the various conglomerate bands show the best development. Up to 18 separate reef bands are developed and the distance from the bottom conglomerate band to the top is ± 26 m. The thickness of the quartzite which forms the middling between the various reef bands varies from 0.1 to 2 m. The strike is roughly north-¬south. The reef bands are payable individually. However, owing to the steepness of the reefs and their close prox¬imity, conventional mining would prove very difficult. The nonpayable reef bands all carry varying amounts of gold and the whole area is a massive payable reef body approximately 26 m wide and 60 m high at 300 to 400 m on strike. The major structure of the area consists of a north¬-south trending syncline. The western flank of the syncline has a steep easterly dip, in places approaching the vertical. This flank cuts out against the overlying rocks of the EA zone. The latter forms a noncon¬formity with the underlying EB zone. The eastern flank of the syncline dips to the west at an average dip of 0.17 rad (10°). The 0.1 rad (6°) north-plunging syncline was sub¬jected to severe faulting. The most important are the Nos. 4 and 10 faults, both of which have a roughly north-south strike. The No. 4 fault dips to the west at an angle of 1.04 rad (60°) with a downthrow of approximately 150 m to the west. The dip of the No. 10 fault is 0.69 to 0.81 rad (40° to 50°) west, with the western block having moved 150 m updip relative to the eastern block. The EB reefs are being mined by the sublevel stoping method down from the sub-outcrop position to the cutoff against the No. 4 fault. On the downthrow side of the No. 10 fault, that is just above the 54 level, two reef bands are payable and will be mined conven¬tionally. ROCK MECHANICS From the section in Fig. 1, it can be seen that the area under consideration is surrounded by stoped-out areas. This will naturally change the stress distribution extensively. The only way to calculate the stress field for such a geometry is to use the finite element method. It was established that this method worked for the present geometry and so the method was applied to predict the stress behavior of the final geometry. From the results, it appeared that the effect of the old stopes was to destress the area. There are, however, some areas-such as the 50 and 48 north footwall haulages-which will require continuous attention. In these two footwall haulages, deterioration can take place due to tensile stress which

Jan 1, 1982

By B. J. Vorster

Introduction The South African Iron and Steel Co. Ltd., in Sishen, operates a large iron ore mine in the Cape Province of the Republic of South Africa. The mine is about 600 km (370 miles) west of Johannesburg. Its annual capacity is 100 Mt (110 million st) of ore and waste. Present production is 60 Mt/a (66 million stpy). The mine operates continuously six days a week. Primary equipment includes 55 154 t (170 st) Wabco and Unit Rig trucks and 14 P&H shovels. During 1979, a feasibility study into the application of a trolley assist system was launched. This was due to the escalation in diesel fuel costs and the appeal by the South African government to reduce the use of fossil fuels. Tests and economic evaluations proved the system technically feasible. The estimated discounted cash flow return exceeded 50%. Diesel fuel consumption would be reduced by 120 ML (31.7 million gal) in the next 10 years. The construction of 7.7 km (4.8 miles) of line and the conversion of 66 154 t (170 st) trucks were completed in March 1982. System description The conventional 154 t (170 st) diesel electric rear-dump haul-truck is equipped with two direct current wheelmotors in the rear axle. They drive the rear wheels through planetary gearboxes. A 1.2-MV (1600-hp) diesel engine and an alternator is used to power the wheelmotors. The trolley assist system consists of an overhead power line, a current collector mounted on the truck, and add-on control equipment where external electric power is routed by way of the current collector to the motorized wheels. The diesel engine is used to propel the truck on level sections. On inclines, the wheel-motors of the truck are coupled by way of a current collector to the externally generated electrical power supply for propulsion. The diesel engine, having lower output than the wheelmotors, limits the truck performance. Previously, maximum output was required from an engine on inclines. By supplying the wheelmotors from a virtually unlimited outside electric energy source, the truck performance is enhanced to the extent that speed is increased by 46% and fuel consumption reduced by 75%. System design The unique operational requirements of this mine rendered the already proven trolley pole system useless. Minimum loss in truck mobility and flexibility was required. Overhead lines and substations were required to be relatively light and portable. This enables fast repositioning of a line with no loss in material. These unique specifications set the base for the design of the Sishen system. Steel I-beams, 203 x 203 mm x 52 kg/m (8 x 8 in. x 35 lb per ft) with lengths varying from 8.3 to 11.3 m (27 to 37 ft), mounted on base plates about 4 x 2.6 m (13 x 8.6 ft) were used as masts. The masts were erected at about 50 m (165 ft) and the base plates covered with about 12 t (13 st) of iron ore to keep them absolutely stable. Results from the pilot installations indicated that using single cantilever cross arms for insulator and overhead conductor suspension was not practical. The tension in the overhead varied too much with temperature changes, causing too much sag in the lines. There had to be a positive and negative conductor. It was decided to suspend each polarity on an independent cantilever and keep the conductors under constant tension by weights acting through a two-to-one pulley tensioning arrangement. For each overhead conductor, a standard 160-mm (6.5-sq in.) grooved copper railway conductor was used. To obtain the necessary current carrying capacity, two of these conductors are used in parallel per pole. Insulators are rated at 4 kV and are of the composite type. An 11-kV three-phase line, supported by the pantograph line masts on the opposite side of the dc line, feeds the rectifier stations. The rectifier stations consist of an 11-kV to 860-V, three-phase 1.46 MVA transformer and a three-phase diode bridge rectifier. The output voltage is 1200 V do earthed through a current limiting resistance network so that the line po-

Jan 4, 1986

By S. Dixon

The Phelps Dodge - PD/PERI Heap2D Model is a phenomenological stockpile leaching model that has been used to investigate the best operating practices for leaching chalcocite. The model was used to investigate the interrelationships of raffinate application rate, aeration rate, raffinate iron grade, acid cures, lift height, crush size, bulk density, air injection spacing and raffinate drip emitter spacing.

Jan 1, 2006

By K. Terhaar, K. Prisbrey

The objective was to determine operating protocols for a lead and silver column flotation cleaner, being considered for installation at Sunshine Mining & Refining Co.’s Kellogg mill in Northern Idaho. In this column, tetrahedrite and galena were floated, and pyrite and other gangue minerals, including siderite and silica, were depressed. The procedure was to develop a dynamic simulation using a linear transfer function approach. The transfer function related cause and effect variables such as the influence of collector and depressant dosages on recovery and grades. Bench-scale flotation tests followed by pilot column testing provided the data used to develop a linear transfer function. The transfer function was derived using a spreadsheet. This model was applied to simulate how the flotation column could be made to respond to disturbances in feedgrade. The results were that xanthate, zinc sulfate, and sodium cyanide were found to be suitable controls for grade and recovery. Simulations showed the best sequence of manipulations of these reagents, and these sequences were useful for future operator training. The conclusion was that linear transfer functions were able to simulate lead and silver recovery, develop scenarios for operator training, and provide a foundation for future on-line control.

Jan 1, 1999

By W. D. Hausel

Archean supracrustal rocks of the South Pass greenstone belt of western Wyoming have been the State's most prolific source of gold and iron ore. Actual gold production statistics are incomplete, but as much as 400 to 500 thousand ounces may have been mined with some silver and tungsten as a by-product. Iron ore was also mined from the greenstone belt for 22 years, and production totaled more than 90 million tons. Immediately south of the exposed greenstone belt in the Oregon Buttes area, Tertiary boulder conglomerate, which has been eroded from the granite-greenstone terrain, may contain a gold resource of 28.5 million ounces (Love and others, 1978). The amount of gold placered from stream alluvium derived from these Tertiary conglomerates is unknown.

Jan 1, 1986