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By W. Z. Choi

A model describing size reduction and mineral liberation during grinding has been extended to include multiple classes of composite particles. The majority of the model parameters have been directly determined using computerized image processing equipment to analyze the products from batch grinding tests. A coarse-grained sphalerite ore from Tennessee, representing a nearly ideal binary mixture of sphalerite and dolomite, has been used to experimentally validate the model for the case of dry, batch grinding. In all cases, excellent agreement has been observed between the model predictions and the experimental results.

Jan 1, 1986

By R. B. Lawrie

Diesel powered underground mining equipment is presently the most productive, safest and efficient equipment used in underground mining operations. The widespread application of this equipment to underground mining is restricted, however, largely because of the difficulty of controlling the diesel engine exhaust emissions. This paper briefly examines control devices currently available for underground application, and also discusses the theory and mechanics of controlling diesel missions with particulate traps and filters.

Jan 1, 1985

By A. B. Cecala

Over the past decade, a substantial effort has been made to improve the air quality inside enclosed cabs of both underground and surface mobile mining equipment to reduce respirable dust exposures to the equipment operators. As part of this effort, the National Institute for Occupational Safety and Health, (NIOSH) completed a comprehensive laboratory study which determined the significant factors for cab filtration and pressurization systems. From this information, a major underground mining equipment manufacturer designed a filtration and pressurization system which was incorporated into the enclosed cabs of its equipment. A long-term evaluation was performed on the effectiveness of this filtration and pressurization system to improve the air quality in the enclosed cabs of two different pieces of equipment, being a face drill and a roof-bolter machine, at an underground limestone mine. This long-term evaluation demonstrated a significant reduction in dust levels comparing outside to inside cab respirable dust concentrations. During this evaluation, a modification to remove one of the filters on the roof-bolter machine simplified the design without sacrificing the system?s efficiency. Testing using particle count instruments performed during non-production time periods on both pieces of equipment indicated Protection Factors greater than 100 when comparing respirable-sized dust particles inside the enclosed cab relative to outside.

Jan 1, 2012

By John C. LaScola, Gerald L. Finfinger, Michael A. Trevits

Methane gas is an ever-present problem facing the underground coal mining industry. Mine operators are mandated by law to maintain safe concentrations of methane gas within the mine environment. Ventilation is the method of choice used by all mine operators to reduce gas concentrations. When gas emissions are such that ventilation alone cannot control the gas, methane drainage methods must be applied. In the 1970’s, there was a concern that unprecedented gas emissions would be experienced as mine operators began new developments in the deep and gassy Blue Creek and Pocahontas No. 3 Coalbeds. Such concern was well founded as significant gas volumes are being emitted as these mining operations mature. In 1971, the U.S. Bureau of Mines began to tabulate and track the change in mine emissions. These data were extracted from the underground coal mine quarterly air quality-quantity inspections performed by the Mine Safety and Health Administration. At that time, approximately 6560 Mm3/d (231.7 MMcfd) of gas were emitted from 430 underground coal mines. It was determined however, that the mines emitting less than 2832 m3/d (100 Mcfd) contributed only 2.1 percent of the total daily gas flow. In 1988, underground coal mines emitted 8350 Mm3/d (294.9 MMcfd) from 487 mines. This report evaluates the changing nature of U.S. mine gas emissions over the last 18 years.

Jan 1, 1991

By Yu. A. Polozov, V. A. Lagunov, O. Yu. Lushinkova, Yu. I. Svirskiy, Eh. Ya. Kipko, Roy A. Williams

Hydrodynamic investigations in exploratory boreholes and grouting holes are conducted for the purpose of obtain¬ing information about the hydraulic properties of the hydrostratigraphic section to be intersected by the proposed underground workings. The information obtained from the investigations provides the basis for calculating the hydrau¬lic coefficients of fractured permeable rock, the dimensions of the anticipated grout isolation curtain(s) around the un¬derground workings, the number and location of grouting holes, the injection pressure modes, and also the volume(s) of grout that will be required (Anon., 1976, 1978). The following data on each aquifer are obtained from the investigations conducted in monitoring and grouting bore¬holes and the analysis of the results: 1) the top of each hydrostratigraphic unit, 2) the thickness of each unit, 3) the ground water fluid potential distribution in each unit, 4) the coefficient of permeability, 5) the piezoconductivity, 6) the fracture porosity, 7) the geometry of the fractures in the rock, 8) the elasticity-compressibility coefficient of the fractured rock, 9) the chemical composition of the ground water, 10) the direction of flow of the ground water, and 11) the expected inflow rate of water into the shaft, drift or tunnel. STG uses its DAU-3M type flowmeter to conduct in¬vestigations of directions of flow in vertical, inclined and horizontal drillholes. The DAU-6 instrument is used to de¬termine the direction of flow of ground water in each frac¬ture or fractured aquifer. Various singular and double DAU type packers are used for pumping and for injection studies (tests) and for flowmeter investigations. Normally the instruments enumerated above permit in¬vestigations to be conducted in each separate aquifer with¬out reinforcing the holes with casings. On the basis of these investigative data, both the hydraulic properties of unfractured rock and the hydraulic properties of the fractured rock are estimated. Dual porosity rocks require special attention because they tend to segregate the grout. 3.1 FLOWMETER INVESTIGATIONS IN BOREHOLES The STG flowmetric methodology is based on the mea¬surement of the ground water flow rate through the borehole by hydrostratigraphic interval after the disturbance of the hydrostatic equilibrium in the "hole-aquifer system" (after pumping or injecting). The relationship of the head changes to the discharge into or from a particular hydrostratigraphic unit obtained during the tests serve as the basis for calcu¬lating the hydraulic properties. Flowmetric investigations facilitate the determination of the number of aquifers, their depths, their thickness, the hydraulic properties of the fractured rock and the magnitude and direction of the flow of ground water. 3.1.1 FLOWMETER HARDWARE STG conducts flowmetric investigations in boreholes using its DAU-3M-108, DAU-3M-73, DAU-3M-57 and DAU-3M-44 instruments.' They have respective external diameters of 108, 73, 57 and 44 mm. The type of flowmeter selected for use depends on the borehole geometry and the technological scheme for carrying out the investigations. Boreholes with a drilling diameter of 76-93 mm are inves¬tigated with the DAU-3M-73 flowmeter; boreholes drilled by bits with a diameter of 112 mm and more are investi¬gated using the DAU-3M-108 flowmeter. The DAU-3M¬108 and DAU-3M-57 instruments are used for flowmetric investigations with a packer. 3.1.1.1 The Downhole Sensor The sensor design of the DAU-3M-73 hole flowmeter is shown in Fig. 2. The design of the DAU-3M-108 instru¬ment is similar to the design of the DAU-3M-73 instrument. The frame of the flowmeter sensor shown in Fig. 2 consists of a casing, an upper and lower centering mount and two rings to which the guiding rods are attached. The upper rods are built into the connector bushing; the lower rods are built into the coupling sleeve. The borehole cable is attached using a half-coupling, a packing ring and a constriction nut. Thus, the frame of the flowmeter sensor is made so that the free passage of water to the impeller is facilitated along with the necessary rigidity. The primary moving component of the flowmeter is the double-bladed impeller, which rotates on cobalt-tungsten pivots and agate thrust bearings. Special extended air cham¬bers protect the supports of the impeller from the action of the borehole fluid which may contain fibrous and abrasive particles. The air located in the chambers shields the sup¬ports from direct contact with the borehole fluid when the sensor operates in a borehole. The hollow casing of the impeller serves the function of a lower cap. The upper cap is attached to the casing using a threaded connector; it is affixed also with a lock-nut. An adjusting screw with a

Jan 1, 1993

By M. P. Evans, Rainer Kahrger

During the last decade or so great advances were made in the solvent extraction, electro winning technologies. They, combined with heap leaching, made it viable to exploit large, relatively low grade oxide copper deposits. The El Abra mine is a good example for such a deposit. Situated in Northern Chile at an elevation of about 4000m (14000 feet), 70 krn north of Calama, the El Abra deposit has been known for many years. In the early 1990's Codelco decided to sell a major holding in the deposit to international mining companies. After lengthy negotiations Cyprus Minerals finalized in June 1994 the purchase of 51% of the deposit with Codelco retaining the balance. lance. Already in 1993 Cyprus and the engineer on the project, began discussions with international materials handling companies with regards to the materials handling system required for the project. These early discussions were considered critical for this fast track project. Immediately after the notice to proceed with the project, several companies were invited to submit competitive conceptual proposals for that portion of the material handling system which was to transport crushed and treated ore from the plant to the leach pad and build the leaching heaps at a rate of up to 150 000 tons per day. A supplier was selected. Additional studies were made for the conveyor system from the mine to the fine crushing plant. Due to the extremely rugged terrain and high altitude at the mine, a decision was made to locate the plant and the leaching operations 15 km east of the mine at an elevation of 3400m. In July 1994 the supplier started the conceptual engineering with a design team at the engineer's San Francisco office. The undertaking was unique in the sense that the supplier's engineering team was integrated into the project for the duration of the conceptual engineering. The open and continuous communication greatly contributed to the success of the design work.

Jan 1, 1996

By Kendall Y. Keuhey

The Mercur Mine, developed and operated by Getty Mining Company, is designed to process 3,000 tons/day of gold ore from the historical Mercur Hill mining district. The mill process involves crushing, grinding, and cyanide carbon in leach for recovery of gold ores ranging from 0.08 to 0.10 oz/ton. During the mining of normal grade ore, a substantial tonnage of material containing 0.02 to 0.05 oz/ton is mined and would be available for heap leaching. Also, Getty Mining is developing methods to test and prepare lower grade material for heap leaching by rejecting a course rock fraction from the grinding circuit SAG mill. This lower grade fraction is suitable for heap leaching, and its removal will upgrade the regular mill feed. Other test methods are directed toward leaching techniques on some 4.0 million tons of tailings that resulted from roasting and/or cyanide leaching Mercur ores in the early 1900s. The natural carbons associated with the Mercur deposits require special treatment to reduce their gold adsorption effects when leached with cyanide.

Jan 1, 1983

By A. Jahedsaravani, M. Massinaei, M. H. Marhaban, N. Mehrshad, M. I. Saripan

"It is well known that froth visual features reflect the operating conditions of the flotation process, so that being able to accurately obtain the froth properties is the most significant criteria to optimize and control this process. Froth segmentation is a useful procedure that can determine the bubble size distribution. Several algorithms have been proposed in this field, but marker-based watershed transform shows the best performance. In spite of this fact, the algorithm suffers from oversegmentation in cases when the flotation froth includes large bubbles along with small ones. In the paper, the marker-based watershed method is modified to prevent oversegmentation of large bubbles. The developed algorithm is validated using some froth images captured at different operating conditions, so the results indicate that the method can segment the mixture of big and small bubbles effectively.IntroductionFroth flotation is a widely used process for separating valuable from gangue minerals. Effective control of flotation circuits has a dramatic effect on overall performance of a mineral processing plant. In most flotation plants, process operators monitor the froth surface visually and make adjustments to process parameters based on their interpretation of the surface appearance and their idea of the appearance of an ideal froth. However, due to natural complexity of the flotation process, achieving optimal control is often not possible for human operators.In recent years, attempts have been made to control the flotation circuits using machine vision systems (Moolman et al., 1995; 1996a,b; Bartolacci et al., 2006; Kaartinen et al., 2006; Vanegas and Holtham, 2008; Aldrich et al., 2010). The froth bubble size distribution is the most significant control variable that reflects the operating conditions in a flotation machine. To date, a number of approaches have been proposed for bubble size measurement from froth images, including segmentation (Sadr-kazemi and Cilliers, 1997; Wang et al., 2003; Mehrshad and Massinaei, 2011), texture spectrum (Nguyen and Thornton, 1995), wavelet (Liu et al., 2005), an improved texture spectrum approach, a method based on binary images (Lin et al., 2008) and, finally, using interfacial morphological information (Yang et al., 2009)."

Jan 1, 2015

By Jianliang Li, Xi Peng, Guorong Lu

This paper describes a wind tunnel modelling study on airflow and pollutant concentration in a large open pit mine located in southern China. A 1:1000 scale model of the surface mine was fabricated and placed in a wind tunnel. Airflow velocity in the test section of the wind tunnel can be continuously adjusted from 0.3 m/s to 6.0 m/s. In this study, both the present pit condition and the projected final pit condition were modelled. Airflow direction and velocity profiles were obtained. The impact of wind direction and velocity on airflow was also studied. The pollutant concentration distribution in the open pit was simulated using smoke, and a distribution profile was obtained. Respirable dust concentrations at the mine site were measured, then its concentrations at the projected final pit condition were estimated using the obtained pollutant concentration distribution profile. Under normal meteorological conditions, it is expected that the respirable dust concentration for the final pit should not exceed the government standard. Key Words: wind tunnel modelling, open pit, surface mining, scale model, mine ventilation, airflow profile, point source.

Jan 1, 1993

By Harry G. Hedgepeth

Exploration of the Big Island trona beds by Stauffer Chemical Company started early in 1959. During the intervening time, Stauffer Chemical Company of Wyoming has developed a Large trona mine in this southwestern Wyoming area and has increased the over-all production of soda ash from natural sources by nearly one-half million tons per year. The trona, which is a hydrated sodium bicarbonate mineral, lies some 800 feet into the sedimentary rocks of the Green River formation. Present production is approximately 850,000 tons per year being extracted by means of a room-and-pillar mining system. Conventional coal mining equipment is used with some modification to accommodate local conditions. The mined and crushed ore is hoisted to the surface and processed in an on-site refinery. Refined soda ash is shipped to widely separated locations in covered hopper railraod cars. Construction in progress at Stauffer's plant will double the present capacity.

Jan 1, 1966

By S. K. Sharma, ANKUSH GALAV, G. S. P. Singh

Providing a suitable protective water barrier pillar (PWBP) is common to reduce inundation hazards in underground coal mines. The imperative factors influencing its performance include the water head acting on the pillar, cover depth, pillar width, strength properties, and permeability characteristics. The mechanical failure of such pillar is a stress-controlled phenomenon, whereas the hydraulic failure is a strain-based phenomenon. A finite-difference numerical modeling approach was developed to study the hydro-mechanical coupled behavior of protective water barrier pillars. The mechanical stability was evaluated in terms of the percentage of failed (ZoF) and intact zones. The influence of the strain-controlled weakening on the permeability of the flow medium was studied through the coupling of the mechanical and hydraulic effects. The coupled steady-state model was used to estimate the outflow rate and its hydraulic stability. The adequacy of the protective pillar was also investigated by assessing mechanical stability and capability to resist hydraulic pressure against the maximum expected water head. A seepage rate-based classification system has also been proposed to evaluate the seepage potential and assess the hydraulic stability. The model has been validated for two case studies at the cover depth of 136–189.5 m and the existing pillar width of 16–42 m against the water head of 25–141 m.

Aug 18, 2022

By C. H. Grant

The Dew Chemical Company has been engaged in explosives research since 1953. The incentive for this research was based on the desire to find additional markets and uses for magnesium metal of which Dow is a heavy producer. The thermodynamic calculations for explosives incorporating light metals indicate energies approximately twice that of non-metallized explosives currently being used. Early in 1960, we acquired additional patent rights from independent inventors and decided to set up a development station at Virginia, Minnesota, to conduct a commercial testing and market evaluation program with this new product. The actual manufacturing of the explosive was to take place in the bore holes. Due to the complexities involved in controlling the manufacture of the explosive in the bore hole, performance was sometimes in doubt. Furthermore, our experience indicated that the metallized explosive systems could not be evaluated by the standard laboratory methods then being used, and it was necessary for us to look for more suitable research methods. Tests were conducted on several known methods for explosive evaluation. The most promising were the Navy underwater method for energy evaluation, and a modified Livingston crater method intended to compare explosive performance in rock. After shooting over two thousand charges of eight to 60 pounds under water and in taconites and granites with many types of explosives, we have developed a metallized explosive which is now being manufactured at a pilot plant in Virginia, Minnesota, and is being evaluated commercially.

Jan 1, 1963

By Elif Emil-Kaya

Samarium (Sm), as one of the rare earth elements (REEs), has gained significant attention in the production of samarium- cobalt (SmCo) magnets due to their high corrosion and oxidation resistance, as well as their high-temperature stability. SmCo magnets find applications in various industries, including but not limited to national defense, aerospace, military and medical equipment. Sm and Co have been classified as critical metals due to their economic importance and supply risk. Recovering Sm from SmCo magnets is an effective method to ensure a stable supply. The present study investigates an integrated hydrometallurgical treatment and combustion process for the preparation of rare earth oxide (Sm2O3 ) powders from SmCo. Initially, SmCo powders are exposed to nitric acid, and the resulting slurry is selectively oxidized at 250 °C to obtain Sm(NO3)3 , Co2O3 and Fe2O3 . Subsequently, the selectively oxidized powders are leached with water to extract Sm. Sm2O3 powders are produced from the obtained leaching solution using an energy- and time-efficient solution combustion process. Finally, the optimal conditions for the production of Sm2O3 are identified, and the produced powder is characterized through X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM) analysis.

Nov 1, 2024

By Myron W. Mellor

Our efforts at McNally, to find a better way to mechanically separate particles from liquid in a slurry have led to the development of two new centrifuges. The first unit utilizes a slotted opening screen as the filter media and retains all plus 200 Mesh and most of the 200 by 300 Mesh particles. The second unit is a solid bowl centrifuge with a novel method of removing the solids and delivers an effluent containing as little as 300 PPM solids in suspension. The first unit was designed to separate particles in the range of about 1 MM x 0 or smaller top size from the liquid slurry and produce solids having low surface moisture content, and a liquid concentrate containing a low percentage of solids. A prototype of this unit has been in the field undergoing tests for over two years. A few of these test results are shown in Tables I & 11. Testing has been mostly limited to the field of coal, how- ever this does not mean that the machine would accept only coal slurries. The machine has produced a dewatered product having as low as 5.5% surface moisture, and an effluent containing as low as 1.4% solids and handled slurries containing from 15 to 50% solids by weight.

Jan 1, 1975

By Daryl R. Tweeton

The Bureau of Mines measured the geochemical changes as H2S04 was used for in situ uranium leaching by Rocky Mountain Energy Company near Casper, Wyoming. Cores and ground water were analyzed before leaching. Water samples were taken from observation wells located between injection and production wells as the leach solution was brought up to full strength in several steps. Measurements were made of pH, Eh, temperature, conductivity, total dissolved solids, dissolved oxygen, HC03, U, V, Na, K, Ca, Mg, SO4, C1, Mo, Mn, Fe, Al, Si, F, P, As, and Se. The data were gathered to assist in geochemical modeling of leaching and to study the potential environmental effects of acid leaching. Environmental considerations appear favorable. For example, the concentration of Se, a toxic element often found in uranium deposits, stayed below the EPA standard for drinking water.

Jan 1, 1979

By K. V. Raj, C. A. Berry, A. T. Weakley, A. L. Miller, P. R. Griffiths, D. A. Parks

Diesel particulate matter (DPM) has been classified as a carcinogen to humans by the International Agency for Research on Cancer. DPM exposure is therefore regulated by the U.S. Mine Safety and Health Administration (MSHA). The current monitoring process takes days or weeks for exposure levels to be known, and a real-time monitoring device is needed. It is believed that infrared spectroscopy has potential for use in a real-time, field-portable device. This paper presents a method for measuring organic carbon (OC) and elemental carbon (EC) in DPM for a broad range of OC/EC ratios. 

A comparison of gold, platinum and sulfide ion selective electrodes was made in this investigation for determination of Eh in solutions containing sulfide ions as a model system. The comparison was made in terms of the accuracy of the measured response, response time, pH dependence, and reproducibility of measurement. In addition, the sensitivity of each electrode towards changes in sulfide ion concentration was measured in terms of the change in measured Eh per decade change in concentration of sulfide ions. On the basis of a detailed investigation of the electrode processes occurring at the surface of gold and platinum electrodes, it was postulated that within the pH range investigated these electrodes respond to changes in the hydrosulfide ion, HS-, concentration in solution. In comparison, the sulfide ion selective electrode is known to respond to changes in the sulfide ion, S-, activity in solution. Although the potentials measured with gold and platinum electrodes were mixed potentials, pretreatment procedures can be used to obtain a signal suitable for process control. For control of sulfide ions in flotation pulps, the use of a gold electrode pretreated at 1.0 V with respect to a standard hydrogen electrode is recommended.

Jan 1, 1990

By Leland L. Mink

Open-pit mining is sometimes conducted in areas where the artesian pressures contained in aquifers underlying the pit's floor are great enough to cause floor heave. In order to reduce this pressure several methods are commonly used. One of these methods is a pressure relief well or depressurization wick. The wick consists of a borehole which is filled with gravel and cased at the surface. The wick is allowed to flow freely, thus reducing pressure near its location. The spacing and depth of these wicks can be determined by a simple analytical and graphical technique which considers the weight of material overlying the aquifer and the artesian force within the aquifer. An example of the technique using data from a Colombian coal mine is presented.

Jan 1, 1986

By Henry B. Estabrooks

As was the case with many other mining companies, the management of Tennessee Copper Company' viewed with some interest reports in various trade and technical journals of the successful use of ammonium nitrate-fuel oil mixtures as an explosive in coal stripping., construction, open pit mining and finally in underground salt mines. The apparently simple transition from the "interested" stage to a point where in excess of 80% of the ex¬plosives used is ammonium nitrate may be of interest. The Tennessee Copper Company operates five mines in the "Copper Basin" of Polk County which lies on the extreme southeast corner of Tennessee. The ore is a massive sulfide principally pyrrhotite and pyrite with some tough lime silicates as gangue while the walls are greywacke interbedded with schist. Average total production is 28,000 tons per 5-day week and an average of 422 feet of development per week. Development work consists of 8'x 8?, 6?x 7?, 5'x 7? and 4'x 6? drifts driven with drifter drills using 1-5/8" carbide detachable bits and 5'x 5' raises driven with stopers using 1-5/8" bits.

Jan 1, 1962

By David E. Thompson, Andrew F. McKown, Herbert H. Einstein, Amr S. Azzouz

INTRODUCTION Design of supports for underground chambers in rock has undergone considerable development. This becomes evident when comparing support dimensions of subway station caverns built in the U.S. over the past fifteen years. The Porter Square Station cavern, which is a part of the Massachusetts Bay Transportation Authority (MBTA) Red Line extension, is the latest in this series. It is approximately 168 m (550 ft) long, 21 m (70 ft) wide, and 14 m (45 ft) high, and has a permanent support of light steel ribs imbedded in a 0.4 m nominal (15 in) shotcrete lining. An extensive construction control instrumentation program made it possible to evaluate the performance of the cavern and its support. This evaluation, which is presented in this paper, was the objective of a research project sponsored by the Urban Mass Transportation Administration (UMTA) and jointly conducted by Haley and Aldrich, and MIT. The actually used design procedure was compared with other approaches, notably procedures based on Finite Element analyses and empirical rock mass classification methods. Support dimensions predicted with all these approaches were compared to the actual support and its performance.

Jan 1, 1983