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By L. M. English

A basic model was developed to help assess methane control needs for the longwall mining of coal in gassy areas. Rather than depending on reservoir and rock mechanical theories, it uses an empirically determined gas emission rate as an input, and it operates on the assumption that, within a specific region and zone, gas emissions will be relatively equivalent for uniform incremental volumes of gob created by mining. The computer program divides longwall panels into segments, keeps track of the face advance and generates emission rates and volumes for both the entire panel and for individual zones within the panel by summing values for all undermined segments. This model can aid in the determina¬tion of the number, size and location of vertical wells or other methane-control applications that are needed for gob gas control.

Jan 1, 2000

By J. A. Herbst, Z. Rogovin, Lo. Y. C., K. Rajamani

Knowledge of the amount of time material spends in a continuous mill in a closed grinding circuit is essential for circuit performance analysis and scale-up design. A convenient method for acquiring this information involves the use of pulse tracers in residence time distribution (RTD) experiments. In typical grinding circuit experiments, RTD measurements are done by injecting a pulse tracer into the mill inlet and detecting it in the circuit exit. In this article, an easy mathematical method for calculating mean residence time and the degree of mixing of material in a mill present in a closed grinding circuit is developed. There are no restrictions on the location of the tracer injection or detection points with this method. Any convenient location in the circuit can be chosen without affecting the residence time distribution measured. The analysis of impulse response data obtained from several commercial grinding circuits using this method is presented.

Jan 1, 1988

By D. V. Ramani, M. M. Kissel, M. T. Ityokumbul

Experiments were carried out to determine the efficacy of bubble column flocculation. An acid-base neutralization method was used to determine the mixing time in a 0.064- by 1.5-m bubble column equipped with a Mottporous sparger. The mixing times decreased as the tracer injection point approached the gas sparger. Preliminary flocculation experiments on two clay samples were carried out. The effects of frother addition and airflow rate are presented and discussed.

Jan 1, 2000

By V. P. Petrov, V. S. Znamensky

There are a great number of asbestos deposits in the USSR, and some are quite large. The main deposits of chrysotile asbestos are shown in Fig. 1. The Bazhenovo deposit, which is located in the Sverdlovsk region, is the largest and has been mined since 1889. Systematic studies of asbestos deposits were begun from the very be- ginning of Soviet government and are most often connected with the names K.E. Tarasov, P.M. Tatarinov, B.J. Merenkov, N.D. Sobolev, F.V. Syromjatnikov, V.N. Lodochnikov, V.P. Petrov, V.P. Eremeev, L.A. Sokolova, V.R. Artemov, and V.F. Dybkov. Investigations by these people and others helped the USSR be one of the most important producers of asbestos in the world. In this chapter, the main asbestos deposits of the USSR are explained in a general outline from the point of view of their genesis, common features, and differences that must be taken into account for forecasting, exploration, and the mining of asbestos. All chrysotile asbestos deposits of the USSR were formed from magnesium rock as a result of comparatively low grade temperature, hydrothermal alteration, and free crystallization of fibrous chrysotile in open cavities that served as catalysts. Chrysotile, a widely distributed rock-forming mineral, is not in general an important mineral for industry as it is a long fibrous and main vein variety. However, it must serve for geologists as an important prospecting criteria. And, the geologist should search for the mineral not only in places of possible chrysotile generation, but in places where asbestos may be crystallized in its long fibers. The Soviet geologists distinguish chrysotile asbestos deposits in two groups: (1) ultrabasic rocks and (2) sedimentary dolomite terranes, taking into account how the maternal rock was affected by hydrothermal solutions. The largest deposits are related to ultrabasite. In dolomite, the largest deposits are small and their asbestos contains almost no iron, which makes it a better filler for insulating plastics. There are a few types of asbestos deposits within the limits of the ultrabasic group, the largest being a Bazhenovo type to which the deposits of the Urals are attributed. This Bazhenovo asbestos is characterized by the most complete zonality of disposition for various kinds of asbestization. These types of deposits are, for the most part, the only ones presently working in the USSR. The Bazhenovo deposit is connected to the gabbro-peridotite intrusive belt that is about 180 km long and is broken into a number of fault blocks as shown in Fig. 2. Granitoid veins of intruded rocks are found along the deepest faults, and were sources of hydrothermal solutions that affected the maternal rock. The nearest granitoid vein, ultrabasite, is substituted by listwanite that consists of quartz, talc, carbonate, and some other essentially talcous rock. The next zone of hydrothermal alteration is composed of serpentine. The boundry between serpentinite and unaltered ultrabasite is as irregular, diffuse, and rough as the boundaries between all other zones. Nearer the vein of granitic rock, ultrabasite is entirely serpentinized into massif serpentinization that penetrates through cracks and fissures. There is an unaltered ultrabasite space between fissures, and the biggest block is preserved unaltered in the central part of the massif. The Soviet geologists call this ultrabasic sopka. Preservation of the unchanged blocks is of great importance for deposit formation as volume changes are impossible during the process of asbestization and serpentinization. It may be confidently said that asbestization in Bazhenovo type deposits is possible only when alteration of ultrabasite has not completely occurred. Under conditions of massif volume, a very big mass of substance must be carried out of the ultrabasite for the progressive stage of serpentinization. However, in the regressive stage,

Jan 1, 1986

By Persio de Souza Santos, Ayres Ferrelra Morgado

In this work, a sample (of about 100kg) of an ore considered as smectitic, not yet industrialized, from Lages-SC-Brazil, was tested for evaluation of its industrial applications. First, we characterize them by XRD, DTA, FRX, and CEC analysis. After this, the smectitic clay was changed to sodium form by treatment with sodium carbonate. Then, the homoionic sodium clay was tested for iron ore pelletizing agent, as binder of foundry sands, and drilling mud with good results.

Jan 1, 1998

By Thomas B. Borak, Keith J. Schiager, Janet A. Johnson

INTRODUCTION Several major factors introduce uncertainties into the assessment of radon progeny exposure to miners using time-weighted average radon progeny concentrations: uncertainty in the measurement of radon progeny concentrations in specific areas, assignment of an individual miner's time to those areas, variation in radon progeny concentration between measurements and potential human errors involved in calculating concentrations and handling data. The currently available grab-sampling methods for determining working level were analyzed to determine the magnitude of the uncertainty due to each of these factors. For all measurement methods studied, the variation in the airborne concentration with time in operational areas of a mine is the dominant factor in the uncertainty in determining annual radon progeny exposures for individual miners. Uncertainties relating to accuracy of the method and precision of measurement were found to contribute a significantly greater portion of the total uncertainty than human errors. Under normal conditions, if the technicians performing the measurements are conscientious and well trained, human error contributes little to the total uncertainty of the radon progeny exposure determination. The primary goal of radiation monitoring is the reduction of radiation exposure to the lowest reasonably achievable level below regulatory limits. Monitoring personnel in mines should be trained not only to obtain accurate estimates of miner radiation exposures but also to recognize and, when possible, to implement correction of situations which result in unnecessarily high radon progeny exposures. ESTIMATION OF UNCERTAINTY DUE TO HUMAN ERRORS Human errors affecting the assignment of annual radon progeny exposure to individual miners can be placed in two categories: those related to the measurement of radon progeny concentration in specific mine areas and those related to estimation of occupancy time for individual miners and transcribing data to permanent records. The former are specific for the measurement method used; the latter are common to all methods. Errors in Determination of Working Level All systems for determining radon progeny concentration require measurement of several parameters, which include volume of air sampled, count rate and decay time. These quantities and appropriate constants are used in a basic equation, specific to the system, which estimates working level. An unintentional random mistake in measurement of any one of these parameters or in the selection of proper constants will contribute to the uncertainty in the determination of working level. In our analysis of human error we separated each measurement method into a sequence of independent operations, with each step subject to operator error. For each operation we estimated the probability of occurrence and the consequence of errors to obtain a resulting uncertainty. Certain types of errors result in specific consequences. For example, we assumed that an error of 5 seconds in timing of a 5-minute sample results in a fractional error of 1/60 (1.7%). Other types of errors can result in a range of uncertainty. Transposing digits read from a scaler can produce errors ranging from near zero to approximately 60%. In these cases we calculated the statistical variance for the distribution of errors. We assigned the square root of the variance divided by the mean as the consequence factor for that type of error. This is essentially the same as a coefficient of variation. The product of the probability of occurrence and the consequence factor is the fractional uncertainty in the measurement due to that particular error. The total uncertainty due to human errors is calculated by taking the square root of the sum of the squares of the uncertainties generated by all manual operations. Uncertainties Due to Human Error for the Kusnetz Method One of the techniques most commonly used to estimate working level in U.S. uranium mines is the Kusnetz method. A generalized way to express the equation used to compute WL by this method is: WL = (Net Alpha Counts)/(V)(ST)(CT)(E)(K) where: V = sample flow rate in liters/min ST = sampling time in min CT = counting time in minutes E = absolute counting efficiency K = Kusnetz conversion factor (dis/min-L per WL), as a function of decay time in minutes. The example of human error analysis presented here is based on the Kusnetz procedure having a timing sequence of 5 minutes sampling time, 40 minute decay time, 2 minute counting time. During the sampling procedure a stop watch is used to determine the timing interval. We assume that it is common to make small timing errors of a few seconds, but larger timing errors occur infrequently. Errors greater than 30 seconds are considered to be essentially non-existent since we assume that the

Jan 1, 1981

By M. J. McPherson, P. Mousset-Jones, G. Danko

Ventilation and refrigeration fortune climate modification contributes significantly to the operating costs of a deep hot mine. Mine climate simulation programs can he used to minimize the impact of these costs. There are several computer codes available to assist in this work. Whichever simulation program is used, it is the mine ventilation engineer who must supply the input data. This paper raises and answers the following question, namely, what accuracy is required of the basic input parameters, in order for a certain precision to he obtained in the predicted air temperatures? In the first part of the paper a new approach is described to estimate the dry and wet bulb temperature of the airflow, either in a dry or wet roadway. The calculation procedure allows an arbitrary temperature change with time, using Duhamel's superposition solution. Matrix-vector representation is applied to simplify the computational structure. In the second part of the paper the sensitivities of the dry and wet bulb air temperatures are analyzed, to the changes of the rock thernrophysical properties, the heat transfer coefficient, and the wetness factor.

Jan 1, 1987

By Ronald J. Allain

Water soluble polymers play an important role in many industries. The mining industry is dependent on these materials to help accomplish many solid-liquid (water) separations. Mechanical devices alone are not capable of achieving the degree of separation needed. Mechanical and chemical separations act in concert to accomplish the necessary separation. The history of the use of water soluble polymers has gone through several evolutionary phases and I believe we are facing another of these phases. At first, various natural products were common - starches, gums, and various polysaccharides. These were replaced by the synthetic polymers based on copolymerization of various vinylmonomers mainly in conjunction with acrylamide. The use of these polymers and their needs continues to grow. This paper will cover a brief overview followed by a look at the future of water soluble polymers. A focus will be on applications of water soluble polymers in the mining industry.

Jan 1, 1994

By Angelus S. C. Owili-Eger

The protection of groundwater resources is a growing issue on both the legislative front and within the private sector. At present, the legislative push is to establish within the Environmental Protection Agency a comprehensive research, development, and demonstration program relating to groundwater contamination and resources. It is evident that certain aspects of such legislation will be directed at the mining industry. Consequently, the mining industry must position itself to address the issues and concerns from a backdrop of facts and knowledge by developing an integrated hydrogeochemical model of the mining environment.

Jan 1, 1989

By A. Afrouz, F. P. Hassani

The types of bulkhead that contain backfill in stopes under various pressures and mining conditions are outlined. Conventionally adopted theoretical and empirical techniques were integrated in the design and construction of each type of bulkhead utilized underground. Methods to monitor the performance of bulkheads are discussed.

Jan 1, 1993

By E. J. McGuire, E. W. Brickle

INTRODUCTION Several recent technological improvements - largely by the convey-or industry - have increased the importance of inclined shaft construction for developing mines where ore deposits are relatively shallow. With these newer systems, long conveyor haulages are economically feasible, allowing mine owners to justify the expense of the inclined shaft or slope. What this actually means is that they can now take advantage of the versatility this construction offers. For example, haulage capacity can be changed by conveyor additions or replacements; equipment can be trammed to and from the surface quickly without costly breakdown and re-assembly; and a walkway is available for workers in the event of an emergency. Now, another innovation may accelerate this type of construction, the use of tunnel boring machines or "Mechanical Moles" to dig the slopes. While conventional. drill and blast methods have been used previously to build inclined shafts, the tunnel boring machine technique offers greater production rates, higher safety and a better, much cleaner bore. McGuire Shaft & Tunnel Corporation of Ft. Smith, Arkansas recently started such a slope project - the first ever bid by a contractor based on the use of a "Mechanical Mole".

Jan 1, 1997

By B. C. B. Pretorius

A heat load analysis of the very hot sub-shaft area of Loraine gold mine situated near Welkom, South Africa, showed. that the heat that needed to be removed to give acceptable wet-bulb temperatures at the working faces could not be done by the normal ventilation air alone, but would have to be complemented with extensive refrigeration. The paper outlines the considerations in selecting the cooling system adopted for this shaft.

Jan 1, 1980

By R. Houot, C. Leschevin, G. Gillet

In mineral processing, conventional magnetic separators are equipped with traditional magnetic circuits (magnetic iron yoke with copper coils or iron-clad solenoid) that develop magnetic fields of less than 2 T'. For minerals of low magnetic susceptibility, use of these circuits has many disadvantages. Only a separator with a superconducting magnet can contribute to solving the problems and produce a high magnetic field. This paper presents and describes a magnetic separator having a superconducting magnet with integrated closed circuit for helium liquefaction. The system generator and maintenance are simplified by extensive automation realized by a versatile program- mable autocontrol unit. A comparative study if the results on concentration and purification of different raw materials with the new and with conventional separators is described.

Jan 1, 1987

By Irwin R. Higgins, Richard S. Dennis

Acid recovery employs ion exchange resin as an adsorption media for the separation of inorganic acids from mixtures of acids and their metallic salts. This technology has been used to treat spent pickling and plating liquors to recover acid for reuse in the bath and to reduce waste acid neutralization costs. Acid recovery can also be used for electrolyte treatment to facilitate valuable metal recovery and to improve product quality. Conventional fixed bed ion exchange (I-X) systems are impractical for acid recovery because of complex control design and large resin inventories needed to process strong acid concentrations. TETRA'S CCIX™ continuous I-X contactor has been used successfully in a simple, continuous operating mode to separate acid from its salt. Efficient separation is enhanced by refluxing which allows acid to be produced as a salt-free product at nearly its original strength. Continuous treatment also recovers heat to the bath and improves metal quality due to consistent acid quality.

Jan 1, 1995

By Lynn B. Hales, Randy A. Ynchausti

There is a large economic driving force associated with improving metallurgical performance in mineral processing plants using process control. Because of this and other benefits, control systems of the future will develop towards more sophisticated user friendly computer based systems that use powerful software analysis and control techniques. Auto-tuning, adaptive control and process models will gain expanded use because of their transparent availability to the system designer. Control of individual unit operations will be optimized and coordinated through expert systems that monitor economic conditions and management directives and direct operations accordingly. Plant areas, considered cost centers for years, will be integrated into plant-wide control systems for economic control and optimization. New control hardware, process sensors, control strategies and software development tools will be presented, as well as an overview of the economics driving the continued development of advanced process control systems.

Jan 1, 1993

By John E. Urosek, Herman Schade

In March, 1988, a fire occurred in a large underground coal mine. Coal Mine Safety and Health of the Mine Safety and Health Administration was immediately notified of the situation. They requested the assistance of the Pittsburgh Health Technology Center (PHTC) to provide monitoring and analysis of the mine atmosphere in and around the fire area to insure the safety of the miners escaping from the mine and for the miners involved in extinguishing the fire. The capability to provide this type assistance is maintained by the PHTC Offices located at 4800 Forbes Avenue, Pittsburgh, Pennsylvania. The equipment used is maintained field ready and can be mobilized almost immediately. This paper will discuss the response to this recent major mine fire.

Jan 1, 1989

By M. S. Klima, M. Fofana

The use of a laboratory-scale magnetic fluid-based separator for coal separations was examined. A Frantz laboratory magnetic separator was modified by fabricating new pole pieces of the appropriate geometry to provide the proper magnetic field gradients. Two separation chambers, which were constructed of Plexiglas, were designed to fit between the pole pieces. A commercially available, water-based, ferromagnetic fluid was used as the separating medium. The separating density was changed by varying the current intensity of the electromagnet coil. Both batch and continuous separations were made using 0.59 x 0.50-mm and 0.18 x 0. 15-mm coal. The results are compared to those obtained using organic liquids.

Jan 1, 1998

By Carlos A. Jaramillo, Seng Hing Ngu

"The Murum Hydroelectric Project is a 944-MW development consisting of a 145 meter high RCC dam, two 2660 meter long, 9 meter excavated diameter upper pressure tunnels, surge shafts, two 950 meter long 7 even meter OD penstock tunnels and a surface powerhouse. The project is located in the eastern section of the State of Sarawak, Malaysia, about 200 kilometer from Bintulu, in the Rajang Fold-Thrust Belt, an Upper Cretaceous to Upper Eocene fold and thrust belt that extends under most of Sarawak. The Belaga Formation consists of a thick sequence of deep marine sediments currently appearing as steeply dipping strata of thin to thick bedded, fine to medium grained sandstone interbedded with argillaceous rocks, resulting on a “Flysch” type geologic environment. The project pressure tunnels were excavated perpendicularly to these strata resulting on frequent change on rock conditions and behavior, and required rock support. This paper describes the characterization of the rock mass, design of rock support, and incidents during construction. Particularly interesting were convergence issues in Tunnel 1 resulting from Tunnel 2 excavation. INTRODUCTION The Murum Hydroelectric Project is located in the eastern section of the State of Sarawak, Malaysia, about 200 kilometers from Bintulu, and upstream of the Bakun Hydroelectric Project. The project consists of a 145 meter high RCC dam, a 50 meter high intake tower, two nine meter OD and 2660 meter long upper pressure tunnels, two nine meter OD and 175 meter long vertical shafts, two 25 meter diameter and 80 meter deep surge tanks, two seven meter OD and 950 meter long penstock tunnels and four seven meter OD and 50 meter long branch tunnels, two 8 meter diameter to 3.4 meter diameter and 1400 meter long penstocks installed within the shafts, penstock tunnels and branch tunnels ending in a powerhouse with 944 MW installed capacity. LAYOUT OF THE WATERWAY TUNNELS The two waterways tunnels are basically parallel as shown in Figure 1, with each tunnel supplying water to two units in the powerhouse. The tunnels start separated 25 meters center to center, but 250 meter from the intake the separation increases to 35 meters. The tunnels are lined with reinforced concrete until they reach the surge shafts and steel lined from there to the powerhouse. The tunnel profile is shown in Figure 2."

Jan 1, 2016

By Leo J. Laughlin

In recent years, heavy mining applications have put an increasing demand on conveyor pulleys. This has resulted in the increased usage of turbine pulleys. The designs of these pulleys are often based upon the failures seen in the conventional welded designs, overlooking the interaction of pulley-shaft system components as the profile of the disc is modified. This paper will focus on the development of balanced design philosophy using case studies of turbine pulleys in heavy mining applications, evaluated with FEA.

Jan 1, 2002

By D. Leppert

Mr. Garrett brings up several interesting points with respect to the proposed API specification for "nontreated bentonite." However, although not explicitly stated, these specifications are being written based strictly on bentonites from the Wyoming/South Dakota area. Other sodium bentonites may be suitable for use as drill mud but will be unacceptable since the specifications are designed for Wyoming bentonites. Regardless of the API's intent that its specifications are intended only as guidelines, they are generally adhered to on an international basis and, for practical purposes, might as well be chiseled in stone. Estes (1986) notes that the quality of bentonite available from Wyoming producers has steadily declined since the early 1960's. The plastic viscosity: yield point (PV:YP) ratio was included in the current API 13A specification primarily to prevent excessive polymer treatment of lower quality bentonite to make drill mud. However, with development of polymers designed to control YP, this specification cannot ensure that only high-quality bentonites are used for drill mud. Nor will the new specifications for untreated bentonites. Other sodium bentonites are available. Bentonite produced in southeast Oregon demonstrates superior performance characteristics without addition of polymer or other chemicals. However, the exceptionally high purity of these deposits leads to a relatively high YP:PV ratio since the naturally high YP probably results from the higher purity and smaller particle size of this bentonite (Rath. 1986 and personal communication). These bentonite; typically have a smectite component exceeding 90% (Rath, 1985), compared with 70% to 75% smectite for typical Wyoming bentonites, as determined by X- ray diffraction and tests for colloid content. As evident from the accompanying table, the untreated Oregon bentonite has excellent rheological properties, though different from Wyoming bentonites due to the high purity. Additionally, this bentonite reacts well with polymers typically used in the oil industry, making it eminently suitable for use in a low-solids mud system. The extremely low grit content, less that 0.5% on a 75 mm (200-mesh) wet sieve, greatly exceeds the standards set for Wyoming bentonite. Optimum rheological properties are obtained at a higher moisture content than Wyoming bentonites. At 10% moisture, API 13A maximum, the clay is overdried, again reflecting the high smectite content. In summary, the specifications proposed by the API Task Group will ensure that only Wyoming producers can supply "nontreated bentonite to the oilfield since specifications are

Jan 1, 1990