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By R. Bhaskar

The control of quartz levels in the respirable dust requires an approach different from that used to control respirable coal dust. The unique physical properties of quartz have to be utilized when developing quartz dust control systems. Also, techniques that modify the surface properties of quartz dust so that conventional dust control measures are effective should be explored. For instance, the wetting characteristics of quartz can be modified so that the capture efficiency of the quartz dust can be improved. Foam sprays assist in modifying surface wetting characteristics. This paper summarizes the results of a study that was conducted in an operating mine to evaluate the effectiveness of a compressed air foam spray system installed under the boom of a continuous miner and directed so as to cover the pan and the gathering arm. The objectives of the study were to evaluate the effect of the foam underboom sprays on (1) the respirable dust concentration in the ambient air, (2) the quartz concentration in the respirable dust. The engineering design of the foam generation and delivery system is described in the paper, followed by a description of the mine and the dust sampling strategy. The data were analyzed to study the effect of foam on respirable dust and quartz concentrations at the miner cab, face return and the intake. The results of the data analyses and costs are presented in the paper.

Jan 1, 1991

By Jingzhi Liu, Xueping Hu, Huai Wang, Simin Yang, Baoqiang Yu, Deguang Zhan

In this study, response surface methodology (RSM) and Box-Behnken design to improve copper extraction from refractory copper oxide ore were investigated. Based on single factor tests, quadratic polynomial equation to describe the relationship between influencing factors (particle size, leaching temperature, sulfuric acid concentration, leaching time) and copper leaching rate could be obtained by RSM. The optimum parameters determined by the model are as follows: particle size 64.60% − 74 μm, leaching temperature 74.15 °C, sulfuric acid concentration 0.49 mol/L, and leaching time 140.85 min. Under these conditions, experimental copper leaching rate of 85.12% could be achieved, which was very close to the predicted maximum value (85.34%) by the model, indicating the quadratic polynomial model was accurate and reliable. Copper leaching rate increased approximately by five percentage points comparing to the result of single factor tests. This study indicates that response surface methodology is an effective method to optimize experiment conditions and achieve an ideal experiment result.

Aug 17, 2022

By A. B. Cecala

Two recent Bureau studies evaluated workers' dust exposures in automated pallet loading processes. The first study involved a Bureau designed dust control system using a push-pull ventilation technique. The unit was shown to reduce workers' dust exposures by 76% during pallet loading at a ground silica operation. A hydraulic lift table was used to automate the bag stacking process; this kept the loading height constant throughout the entire pallet loading cycle. The second study evaluated different commercial automated pallet loading systems. These systems automatically stack the bags onto pallets, shrink wrap the pallets, and deliver the pallets to a fork lift pickup location. Results from a ground silica evaluation site indicated respirable dust samples taken were below the Threshold Limit Value (TLV) as established by the Mine Safety and Health Administration (MSHA).

Jan 1, 1990

By D. Donison

The practice of blasthole mining is typically applied in competent ground conditions, primarily because of the open stope dimensions. At Magma Copper -Superior Mine, a field pilot project was completed examining a variation of blasthole mining in poor ground conditions. The results were very encouraging not only from a technical viewpoint, but also productivity viewpoints. This paper describes the pilot project and the resulting implications.

Jan 1, 1994

By Steven E. Paulson

In situ mining is emerging as a potential alternative to conventional surf ace and underground mining techniques. A major factor in determining recoveries by in situ mining is the proportion of ore minerals that can be contacted and solubilized by the leach solutions. To provide basic information on the processes occurring during in situ leaching, particularly at the microscopic scale, the Bureau of Mines has developed a geologic characterization research program. This includes laboratory experiments using leaching apparatus that can accommodate whole core samples. Whole core experiments result in higher leach solution-ore mineral contact ratios than packed column experiments, and also allow for the assessment of permeability changes taking place as the result of mineral dissolution, precipitation, and clay swelling within the flow channels in the rock. A nonreactive, reusable reaction cell has been designed and tested. The leaching apparatus can be used for constant-pressure or constant-flow experiments and allows for the control of flow rate, pressure, and temperature during the experiments, thus permitting studies on a wide variety of ore samples. Details of the experimental apparatus and design are presented, as well as preliminary results from the first series of experiments on an oxide copper ore from the Casa Grande, AZ, area.

Jan 1, 1987

By Ing. E. h. Martin Herrenknecht, Werner Burger

In recent years, there has been a dramatic increase in the number of machine driven soft ground tunnelling projects. This increase is largely due to the technological development of slurry and EPB Shield systems. A new generation of soft ground tunnelling machines, markedly different from those of five years ago, now overcomes ground conditions that until now were too costly and impractical to undertake. The paper reviews the latest soft ground tunnelling machine developments in material transport, guidance and control, seismic surveying, soil conditioning, settlement control, cutting tool applications and variable mode operating systems. Specific projects where this technology has been applied will be highlighted.

Jan 1, 1999

By C. E. Capes

The spherical agglomeration process provides an attractive method for the cleaning and recovery of fine coals in the form of compact oil-bonded pellets. In treating a washery effluent containing 50% minus 20 micron material by this technique, the slurry was first mixed under vigorous agitation with oil to deash and dewater the fine coal. The flocculated coal pulp was then formed into larger agglomerates on a modified balling disc. The operation of a semi-pilot scale process is described and an analysis of some of the operating and system variables is given. A semi-theoretical expression to predict the final agglomerate size under various conditions is derived and compared with the experimental data. Coal producers are faced with a growing requirement to clean and recover fine mesh coals. Greater mechanization of the extractive and preparation processes has resulted in finer-sized products containing larger quantities of associated foreign matter and preparation plant effluents contain quantities of fine coals which are potentially valuable. These losses will probably increase with the expansion of production and will require the development of effective disposal and utilization processes under pressure of the lack of adequate disposal areas, the enforcement of air and stream pollution laws, and the economic need to obtain the maximum yield of salable product(1)

Jan 1, 1970

By Shingo Morimoto, Toru Sasaki, Masato Shinji

"1. INTRODUCTIONTunnel face stability is one of the most important consideration in New Austrian Tunneling Method. In general, if all of the material properties of ground can be obtained through the field investigations, the tunnel face behavior can be predicted using numerical simulation prior to tunnel construction. However, estimating the safety of a tunnel face is difficult, especially in cases where the ground is very weak such as in an urban area.In this study, numerical analyses of tunnel excavation in very weak ground conditions, such as a low cohesion and low internal friction angle, were carried out. The relationship between the average shear strain distribution on the tunnel face and the overburden was analyzed. This relationship estimates the shear strain of the tunnel face relative to the critical shear strain obtained by the ground properties. The critical shear strain was defined as an allowable value for the maximum shear strain. We proposed the allowable overburden as tunnel face stability index (TFI) that satisfies the critical shear strain criterion of ground. Finally, a design chart of the allowable overburden for various cohesion values and friction angles of ground was created. This chart is useful in the preliminary tunnel design stage to judge the necessity of additional counter measures against normal tunnel support design.2. WEAK GROUND MODELING AND ANALYSIS PROCEDURE2.1 Setting material propertiesWith reference to a past study1), the material properties were adopted on the basis of material properties in the standard worst rock classification case called “DII”2) for standard support pattern of weak ground in Japan. The typical material properties for “DII” are listed in Table 1. In addition, Fig.1 shows the distribution of the representative weak ground according to cohesion and internal friction angle. When the internal friction angle is relatively high and the cohesion is weak, the ground is categorized as sandy ground. Furthermore, when the internal friction angle is low and the cohesion is strong, the ground is categorized as clayey ground."

Jan 1, 2016

By K. Bunney

A high-pressure laboratory elution rig was commissioned to simulate industrial Zadra and AARL elution conditions for the stripping of gold, silver and mercury from loaded activated carbon. It was found that cyanide was essential for the efficient elution of both mercury and silver, while gold was found to elute most effectively in hot, low-ionic strength solutions. Therefore, the standard AARL-type elution, which implements a cyanide soak and water elution, results in a lower recovery of mercury and silver from the carbon. No single set of conditions was found whereby gold, silver and mercury can all be effectively eluted in a single step. However, sequential elution conditions can efficiently recover all metals and provide a potential approach for separating these metals.

Jan 1, 2010

By Michael Murphy, Gamal Rashed, Brent Slaker

Many underground stone mines in the United States operate on multiple mining levels. The effects of interburden thickness, pillar offset between mining levels at various depths of cover, and in situ stress conditions are poorly understood. Pillar offset is the degree to which pillars are not columnized or stacked. In this study, calibrated numerical models are used to examine limestone pillar stability in these conditions. Also, the critical interburden thickness required to minimize the interaction between mining levels is explored. The model results show that there is interaction between numerous factors that control the stability of stone pillars in multiple-level conditions. The highest degree of local pillar instability occurs when pillar overlap ranges between 10 and 70 percent. The highest degree of stability occurs when pillars are stacked.

Jan 1, 2023

By J. K. Grunig

A process consisting of leach, continuous countercurrent decantation, resin-in-column ion exchange, evaporative crystallization of beryllium sulfate, and decomposition of the sulfate was developed for Spor Mountain, Utah, ores. The process is metallurgically sound, has a minimum of process steps, and is applicable to a wide variety of beryllium ores. The most novel aspect of the process is a resin system of ion exchange which is highly selective for beryllium and which rejects substantially all impurities except for minor amounts of aluminum, magnesium, fluorine, and sulfate in addition to beryllium. The oxide from sulfate decomposition meets specifications of potential users.

Jan 1, 1982

By George C. Hawley

Historically, mica usage has been low because of limited availability; as a by-product of many small processors, who have lacked motivation for extensive R & D. The discovery of a 30 million ton deposit of 85-90% pure phlogopite, when existing markets are only 300,000 tonnes annually, forced the search for large volume new markets. Increasing costs of energy, petrochemicals, plastics and glass fibers, and environmental constraints on asbestos usage, have led to new opportunities for mica as a reinforcing filler. Extensive research and developments; in beneficiating, processing and treating mica, has been necessary to satisfy these new markets.

Jan 1, 1981

By R. Mattos, E. Calcina, G. Quispe, S. S. Kanchibotla

During blasting, rock breaks and moves but standard grade control practices do not adjust ore waste boundaries to cater for blast movement. Rock movement resulting from blasts can result in mischaracterization of grade boundaries resulting in ore loss and dilution. Ore loss takes place when ore is mischaracterized as waste and sent to waste dumps, and dilution occurs when waste is mischaracterized as ore and sent for processing. Las Bambas operations of MMG Peru, realized the economic impact of blast movement on ore loss and dilution and adjust ore boundaries using limited blast movement measurements. This is a step in the right direction but has limitations for everyday application. This paper discusses the advantages of disadvantages of current blast monitoring techniques and introduces an operational tool to estimate polygon movements for different blast designs and confinement conditions. Blast movement estimates from this new tool have been compared against the estimates from the current tools for several production blasts and the results were quite promising.

Mar 2, 2022

By C. K. Blankenship

The competitive forces now driving the electric utility industry and the constraints of regulation at all levels are changing the way we will all do business now and into the next century. Utilities are using every technological tool at their disposal to find optimum solutions to challenges in every aspect of operations. In fuel planning and procurement, these tools include models that predict which dispatch line-up will comply with environmental regulations at minimum cost. This paper presents how those tools are being used for Duquesne Light Company.

Jan 1, 1995

By Jr. Flynn

The filtration process has long been utilized in the mining industry and typically associated with processes where clear solutions are required. One definition of filtration states that it is utilized to affect a more complete separation of liquid and solid phases than is possible with settling alone. The development of Diatomaceous Earth filter aids has added a new dimension to filtration technology in the mining industry. It makes possible the filtration of slimes with almost perfect clarity, and at rates that become economical.

Jan 1, 1980

By Utku Gumus, Ertan Bostanci, Hanifi Copur, Ahmet Rüfai Bilgin, Ugur Altay

"Field observations on replacements of 12-inch constant cross-section double disc cutters in Tuzla Wastewater Tunnel excavated by an EPB TBM with 3.151 mm excavation diameter excavating hard rock are summarized. Cutter life is correlated to rock’s uniaxial compressive strength and Cerchar abrasivity index, and TBM operational parameters. Number of cutter replacements, average cutter replacement rates and types of cutter damages are summarized. The relationships between cutter life and rock properties and TBM operational parameters are analyzed by single variable regression method. Detailed analysis between chainages 1+200 and 1+982 km indicates that average cutter consumption rate is 35.7 m3/replacement (4.6 m/replacement). Cerchar abrasivity index and uniaxial compressive strength does not indicate any meaningful relationship with cutter life. Penetration per revolution and field specific energy might be used for predicting lives of constant cross-section double disc cutters. However, additional data is required to generalize the findings of this study. INTRODUCTION Cutter life / replacement and/or consumption rates in terms of cutter cost and replacement time loses is one of the most important parameters affecting excavation performance of mechanical excavators, especially of TBMs used very widely and equipped with usually disc cutters. Predicting cutter cost is a very important task in especially feasibility stage of tunneling projects. Basic parameters affecting cutter life can be classified into 3 general groups as geological and geotechnical, excavation machine (TBM) related, and operational parameters (Bilgin et al., 2013). The geological and geotechnical parameters are the most dominant ones among them. The machine related parameters should be arranged in accordance with the expected geological and geotechnical conditions for the best TBM excavation performance and minimum cost."

Jan 1, 2016

By G. D. Hood

The U.S. Bureau of Mines investigated rapid froth flotation through more efficient bubble-particle collisions that improved the overall flotation kinetics. An in-line static mixer efficiently mixed the bubbles, water, and ore, selectively attaching these bubbles to the hydrophobic mineral's surface. As the mixture entered the flotation chamber, the hydrophobic mineral was already attached to the bubbles and was quickly floated away from the remaining ore pulp. The rapid flotation system was evaluated for beneficiation with a western porphyry copper ore containing 0.67 pct copper, and a phosphate-bearing amine flotation tailings sample containing 9.5 pct P2O5 in a quartz matrix. Over 88 pct of the copper was recovered from the ore in a rougher concentrate containing 5.9 pct copper at a rate 7 times faster than conventional flotation. Sixty percent of the quartz in the phosphate-bearing sample was floated at a rate 4 times faster than conventional flotation. The unfloated product retained 80 pct of the phosphate in a l6.9-pct P2O5 concentrate.

Jan 1, 1993

By George L. Atwood

The Monsanto Company's Henry Mine is located 17 miles northeast of Soda Springs, in the southeast corner of Idaho. Ore being mined is phosphate rock which lies in the Permian Phosphoria formation. The ore is the raw material for Monsanto's three furnace elemental "P" plant near Soda Springs. The finished product from the furnaces is elemental phosphorus which is subsequently used in the manufacture of detergents, food preservatives, fire retardants and other consumer items. Mining is by open pit methods using 0-9 crawler tractors to rip and push-load rubber tired scrapers in stripping and mining operations. The equipment spread consists of six D-9G crawler tractors, four Caterpillar 6578 scrapers, eight Euclid S-24 scrapers, one Reich T750 drill and one Caterpillar No. 16 patrol plus various support equipment. Stripping is performed on a 12-month basis, two shifts per day. Mining is performed mainly in the summer months on a one shift basis. The hauling season begins May 15 and ends November 1 due to freezing weather and snow conditions. Annual production is 1,000,000 tons of phosphate rock and 2,500,000 to 3,000,000 yards of stripping. Stripping, mining and hauling is performed for Monsanto by Dravo-Soda Springs, a mining contractor. Dravo-Soda Springs owns, operates and maintains all equipment used in stripping, mining and hauling. The contractor is paid for stripping by the bank yard and for ore mined and hauled on a tonnage basis. The Monsanto elemental phosphorus plant began production in 1952 with ore being trucked to the plant from the Ballard Mine. Haulage was over public roads in 15, 24-ton semitrucks. A private haul road was constructed from the Ballard Mine to the Monsanto Plant in 1958 and 1959 to accommodate trucks with two twenty-yard trailers. This 11/ mile road was first used in the 1959 hauling season. In 1965, five new Kenworth tractors with two, 'forty yard trailers were introduced into the haulage system. These units carried 120 ton payloads and were used until

Jan 1, 1972

By M. Misra

It is estimated that the volume of low -level and intermediate level contaminants present in the soil at different DOE sites is of the order of several million cubic feet. The existing remediation scheme is containerization followed by burial in Land Disposal Facilities (LDF's) which is economically unattractive warranting the need to develop alternate remediation routes. One such route is the physical separation based volume reduction approach to removing a MINIMUM AMOUNT OF CLEAN SOIL with the radioactive particles, reducing the amount of material that requires disposal. The purpose of this study was to evaluate and test the feasibility of using physical beneficiation techniques for removal of contaminants from soil. The performance criterion was to recover at least 80% of the activity in 20% or less of the original contaminated soil volume. Four different radioactively contaminated (primarily uranium and plutonium) soils from DoE sites namely LANL, INEL, Fernald Plant 1 Storage Pad (ID-B) and Mound soils were tested using gravity, magnetic, gravo-magnetic, hydrocyclonic and flotation devices. The paper is divided into the two sections. The first section presents the overview of the Heavy Metals in Contaminated Soil Treatability Project conducted at the University of Nevada, Reno (UNR) describing the salient features of a state-of-the art Soil Washing Laboratory and the technology equipments used in the test program. The second section describes the soil characterization and typical volume reduction results obtained from the UNR tests. Among the physical separation processes, only flotation processes passed the performance criterion. For the LANL and INEL soils where the contamination was contained in coarse particle size, it was possible to recover more than 80% of the activity in less than 10-20% of the original volume of the soil thus rendering 80-90% of the soil "clean". For Fernald and Mound soils where contamination was of colloidal nature, flotation based processes showed encouraging results and are recommended for further studies.

Jan 1, 1995

By A. B. Cecala

The Bureau of Mines performed a study to determine optimal locations for longwall face methane monitoring equipment. Longwall face ignitions continue to be a concern to the U.S. coal mining industry. Gains in ignition control technology have been somewhat negated by advances in longwall productivity. More reliable, heavy-duty longwall face systems generate higher production rates and increase methane liberation rates. These rates will likely continue to rise in the future as further coal production increases occur. Efforts will continue in the areas of methane drainage, methane containment, and methane dilution. In addition, more effective face methane monitoring is needed. As technology continues toward automated longwall panels, the importance of monitoring for methane at the shearer becomes even more significant. Since the primary face ignition source is the shearer mining machine, the Bureau ran tests to determine the best location to take methane readings on the shearer. This information, in conjunction with data obtained from field studies, provides a knowledge base for selecting optimum face methane monitoring locations.

Jan 1, 1993