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By P. L. Dunn, G. T. Adel, E. B. Cruz

Automatic control of fine-coal cleaning circuits has traditionally been limited by a lack of adequate sensors. Although several nuclear-based analyzers are available, none have seen widespread acceptance. In this investigation, image analysis is used for the on-line determination of ash contents in fine-coal slurries. The ash content of a flotation tailings stream is correlated to the mean gray level of the slurry. Based on a 90% prediction interval, an analysis of sensor performance indicates an accuracy of 73[±] 4% ash over a range of from 65% to 90% ash. While the results are comparable, the video-based system costs only a fraction of what a nuclear-based analyzer costs. The sensor is now installed at the Middle Fork preparation plant, which is owned by Pittston Coal Co.

Jan 1, 1999

By Eddy J. Jacques

When the automatic control of a ventilation process is considered, and supervising expert systems need to be designed, an important problem to address is: what will be the optimal set points of the regulators that should meet a certain number of independently formulated requirements, distributed over a ventilation network? The set of these requirements, expressed in terms of air flow quantities or differential pressures in certain airways, need not be consistent. Their number is not limited by the number of available regulators, nor by their nature, i.e. passive or active. Moreover, they may be subject to upper or lower limit values. The method described here addresses this problem and tries to provide a tool that should allow to calculate the set points of all the regulators as a global and optimal solution with respect to this set of distributed requirements. The pure mathematical developments in this paper are kept as short as possible in order to allow more room for the description of a relevant example.

Jan 1, 1991

By J. M. Mutmansky, B. Kolonja

A PC-based simulation model using the software packages SIMAN and CINEMA was developed to simulate and animate truck-shovel operations. The model is capable of simulating one mathematical dispatching strategy using linear and dynamic programming and six heuristic dispatching strategies. Data were collected from an actual operating mine through time studies and analysis of historical records. Statistical analyses were performed, and appropriate theoretical distributions were fitted for various time events in the truck-shovel cycle. The model was then applied to study overall impact of these dispatching strategies on constrained and unconstrained mine productivity. The simulation/animation model developed in this study seems to be an efficient planning tool for choosing optimal fleets and finding an optimal dispatching strategy to produce an equilibrium between the quality and quantity of production.

Jan 1, 1995

By P. Somasundaran

Flotation of oxide minerals is controlled by a number of factors, such as surface potential and solubility of the mineral, concentration and type of various inorganics, properties of the collector, pH, ionic strength and temperature. The role these factors play depends on the mechanisms of adsorption of the collector inorganics or polymer additives. The major mechanisms include electrostatic interactions, chemical adsorption, chain-chain interaction between adsorbed collector species and modifications of the surface by inorganics. In real systems, flotation is, however, markedly affected by various other processes, including aging of the minerals, surface precipitation of the collector on the mineral and associative interactions between various collector species leading to highly surface active, for example, ionomolecular complexes. These effects are reviewed here with selected examples.

Jan 1, 1999

By Gerrit V. R. Goodman, Edward F. Divers, Charles D. Taylor

Future mining systems will possess the ability to cut from crosscut to crosscut where advances could exceed 30.5 m (100ft). However, limitations arise when ventilating such mining systems. In deep advance mining, there will be no workers at the face to manually advance ventilation tubing or curtain. Additionally, traditional methods provide no means for maintaining face ventilation after the miner backs out. Problems such as these have suggested the need for innovative ventilation methods compatible with deep advance mining systems. The Bureau of Mines is currently considering a number of innovative ventilation schemes. One such method is the use of a jet fan to ventilate a deep cut. A jet fan is simply a freestanding fan using little or no ducting to direct the ventilation flow. Previous testing in large metal-nonmetal mine entries showed that jet fans provided adequate face ventilation for deep advances in large headings. Current testing will determine the application of jet fans in ventilating smaller coal mine entries. Another approach considered compatible with deep advance mining will use either exhausting or blowing tubing that can be remotely extended from crosscut to crosscut. During the mining cycle, such a device would extend automatically as the miner sumps into the face. The Bureau of Mines is considering several different operating designs using this tubing.

Jan 1, 1991

By L. Lichty, R Bhappu, R. Rowan, G. Ramadorai

Treatment of refractory gold ores containing arsenic have always presented a major problem in their processing to recover the contained precious metal values. The major difficulties are concerned with lower recoveries, production of hazardous fumes, effluents and residues. Because of'these arsenic related problems, many otherwise economically attractive precious metal deposits and dumps all over the world are not exploited. In recent years, treatment processee for refractory gold ores and concentrates have been explored and a few commercial operations employing roasting or pressure leaching have resulted. Roasting has limitations due to environmental constraints related to off gases. Pressure leaching involving high temperatures (180% to 200%) and pressures (400 psi) is accompanied by high capital and operating costs. An alternate route to roasting for treating pyrite and arsenopyrite ores and concentrates ia the "lime-oxygen hydromet" process carried out at a moderate temperature (100%) and pressure (100 psi). A simplified process for treating such arsenic containing ores and concentrates utilizing low temperature and pressure oxidation is presented. This low cost treatment with compressed air and lime renders arsenic as an inert component in the residue, meeting all the requirements of the EPA Toxicity Test. The precious metal values are then extracted from the autoclaved residue by standard cyanidation. This paper discusses this new development.

Jan 1, 1990

By Chris J. Conway, Bruce W. Atkinson, Graeme J. Jameson

The flotation of coal in the fie and coarse particle size ranges presents particular problems. Fine or ultra-fine coal less than 100 microns presents a challenge to conventional flotation machines because the rate of capture of the coal particles can be very low, so longer residence times are needed. Also, conventional mechanical cells are not normally designed with froth properties in mind. Froth drainage may be inadequate, leading to excessive entrainment of ash. The upper limit of flotation of coal is normally put at about 500 um (30 mesh). It appears that, in mechanical cells, coarser particles tend to be torn away from bubbles in the turbulent environment created by the impeller. In this paper, results are presented from plant trials of a high-intensity flotation column of novel design, namely the Jameson cell. Extensive trials have been conducted on coal slurries with a top size of around 1 mm. Size-by size analysis shows that it is possible to achieve high yields of low ash product over the whole particle size range.

Jan 1, 1995

By S. Kelebek, G. W. Smith

Four samples of galena, each prepared differently, dry ground chalcopvrite and real gar have shown various quantities of liberated sulfur corresponding up to nine equivalent monolavers on their surfaces as determined by the solvent extraction/UV analysis of sulfur using ethanol. The pretreatment of a dry ground galena sample with acidified ammonium chloride or neutral, saturated sodium chloride solutions rendered the mineral readily floatable. The collectorless floatabilities of galena pretreated with the former solution and of drv ground chalcopvrite have been evaluated in reference to the natural floatability of sulfur using the critical surface tension of floatability approach with aqueous methanol solutions. It is shown that the amount of sulfur- on these samples can be correlated with their flotation rate, which was found to he first order within the critical surface tension range. The larger the concentration of surface sulfur, the faster the sulfide mineral floats, thus, the greater its flotation rate constant.

Jan 1, 1990

By Kalyan Saikia

An integrated statistical-geostatistical modelling of gold exploration data of Gurahar Pahar prospect of Mahakoshal greenstone belt in Central India has been attempted. Statistical modelling of gold accumulation and width reveal a positively skewed 2-parameter lognormal distribution fit with an estimate of mean gold as 0.84 gram/tonne. Geostatistical modelling provided a spherical semi-variogram function fit with mean kriged estimate and mean kriging variance of gold as 0.76 gram/tonne and 0.23 (gram/tonne)2 -respectively. Ore inventory and grade-tonnage relationships for a selected part provided an estimate of 3,36,000 tomes of ore with an average gold of 0.76 gram/tonne at 0.5 gram/tonne cutoff grade.

Jan 1, 2002

By W. R. Reed

NIOSH continues to conduct respirable dust control research for surface mine blasthole drilling operations. Research areas have included testing variables (shroud leakage area, drill deck cross-sectional area, shroud height, collector-to-bailing airflow ratio, etc.) that have the most impact on respirable dust control, development of a dust collector inlet hood, development of a dust collector dump point shroud, and testing of a small diameter water separating sub. This paper summarizes the results of the aforementioned research that has been completed. Additionally, past dust control research for drilling operations of both underground and surface mines completed by the U.S. Bureau of Mines, created in 1910 and incorporated into NIOSH in 1997, is reviewed.

Jan 1, 2008

By F. L. Wilke

The prototype of an expert system, designed to assist layout planning of face operations, is presented. By specific combination of knowledge-based and conventional EDP techniques it has been possible to extend the known Kepner-Tregoe method up to the determination of mature layout solutions in difficult planning cases. It has been proven that the presented strategy - which can be applied to any kind of problem with similar structure - is apt to provide efficient EDP support for handling complex mining problems. Such support goes far beyond the purely numeric evaluation of envisaged alternatives.

Jan 1, 1989

By John T. Bartlett

During the last decade, the increasing price of gold has renewed interest in the various metallurgical techniques for recovering precious metals. Much of the recent technology advance has been aimed at low grade deposits resulting in more complex processes and the necessity of tighter economic control. These factors along with more stringent environmental constraints have made it necessary to optimize each process to minimize energy and raw material consumption and reduce waste discharge. In most cases, detailed process analysis is required to detect inefficiencies and provide alternative solutions for process improvement. Also during this same period, the computer has become widely accepted and computerized mathematical modeling has been applied to an increasingly broader range of problems. Microcomputer based process modeling and simulation systems are routinely used to analyze and improve communition, hydrometallurgical, and pyrometallurgical processes for the recovery of precious metals.

Jan 1, 1987

By P. D. Nora, M. G. Ranade

A statistically designed pot grate-kiln test program was conducted to determine the agglomeration process variables necessary for increasing the low temperature disintegration resistance (LTD) and reducibility (R40) of magnetite-based Empire acid pellets. The ASTM tumble index and compression strength were to be maintained at an acceptable level. Six process variables - bentonite addition level, preheat time and temperature, firing time and temperature, and cooling rate - were investigated within the constraints of the Empire plant. The bentonite addition level and firing temperature had the largest effect on pellet properties. The results of this program were verified during a plant trial. The target firing temperature at the Empire plant has been decreased for increasing the LTD and R40 of commercially produced Empire pellets.

Jan 1, 1987

By M. Galetakis

The difficulties that rise during the evaluation of multiple-layer lignite deposits come from the deposit structure (alternating lignite layers with intercalated material of varying thickness), as well as from the limitations of the applied selective mining. Thin layers of lignite and interbedded waste layers are grouped under specified assumptions regarding thickness and ash content, to form the exploitable blocks. However, in practice the decision for excavating a block is made under subjective constraints of different importance or by using uncertain data. Advances in Fuzzy Inference Systems (FIS) have provided a new approach to the evaluation of multiple-layer lignite deposits. FIS have the ability to handle imprecise or incomplete or linguistically ambiguous information and to incorporate them into decision-making processes. In the developed FIS (Mamdani type) new linguistic variables, concerning with working conditions, operators? experience and production were involved. The FIS was used for the estimation of quality characteristics and reserves of the exploitable lignite produced from Southern Field mine, Ptolemais (Greece).

Jan 1, 2005

By J. E. Murphy, Y. Topkaya, R. E. Johnson, B. R. Palmer, D. K. Dysinger, R. B. Bhappu, A. E. Clark

The U.S. Bureau of Mines utilized a central composite experimental design to investigate leaching kinetics of pure chalcopyrite in the sulfuric acid-oxygen system. The six factors studied were oxygen pressures of 150, 300 and 450 PSI, leach temperatures of 35O, 65O, and 95O C, oxygen-to-chalcopyrite mass ratios of 0.5, 1.0 and 1.5, leach times of 8, 16 and 24 hours, initial acid strengths of 0.6, 1.2 and 1.8 g H,SO,/g chalcopyrite and pyrite to chalcopyrite mass ratios of 0, 1, and 2. Chemical analysis and oxygen consumption measurements indicatedthat leaching occurs through three consecutive reactions. Temperature was the primary determinant of leach rate and solution acidity was the primary determinant of oxygen consumption, sulfur oxidation, and activation energy.

Jan 1, 1993

By David Brown, Glen Hall, Ken DeVos, Frank Barone

Dredging and Flooding was completed on the Falconbridge Limited "New Tailings Area" in the period from 1996 through 1998, as part of their site closure measures. Part of the decision making process and closure planning was water quality prediction, including oxidation and diffusion modelling. The purpose of this modeling was to define the potential water quality that would result during and after dredging. A significant body of research on the geochemistry and oxidation kinetics of this site had been compiled. The results of the modeling provide practical insight on the potential water quality that may be expected. Water quality in the pond has steadily improved since flooding was completed with the exception of short term peaks during spring runoff. Aquatic vegetation is appearing through natural recovery and transplanting of local species, and colonies of minnows are now observed in the ponds.

Jan 1, 2000

By B. C. Paul, R. Q. Honaker, M. Huang

Froth flotation is now, the most commonly used method for cleaning fine-coal fractions in coal-preparation plants. Past research and industrial practice have demonstrated that froth flotation achieves excellent separation efficiencies for fine coals having only a small fraction of middling particles. However, the efficiency of froth flotation decreases sharply as the concentration of middling particles increases. This is due to the flotation of high-ash particles that have a small amount of hydrophobic coal present at the surface. Because gravity-based processes are much more efficient for the treatment of middlings, the application of centrifugal washing for fine-coal cleaning was studied with an emphasis on the primary cleaning of fine-circuit feed. Results are shown of a parametric study that used a semibatch Falcon centrifugal concentrator. The results of the study revealed that separation performance is a function of particle size, bowl geometry, feed solids content and feed rate.

Jan 1, 1996

By R. J. Sweigard, R. V. Ramani

Three case studies were undertaken to investigate the role of land use potential evaluation in reclamation planning and to determine the impact of regional differences on final land use plans. The three surface mines studied were representative of operations in the Appalachian, Interior, and Northern Great Plains provinces. The scope of the investigations included a survey of regional characteristics, a detailed investigation of the mining operations and site conditions, and an assessment of local land use planning activities in the area of the mines. Special attention was given to key factors that presently determine the use of reclaimed land. Also, for each case study, the postmining land use potential was evaluated using site planning principles. Specifically, the environmental, economic, and social impacts of several potential postmining land use plans were considered.

Jan 1, 1987

By Xintan Chang

A computer software package, named CFIRE, for the general ventilation network analysis and fire control, mine fire and/or coal spontaneous combustion, has been developed at Xian Mining Institute in China. It is a multipurpose package with adequate capacities of ventilation map drawing, ventilation network analysis, gob fire simulation, steady state ventilation simulation and transient state ventilation simulation. It was written in a user-friendly style, driven by menus, facilitated by on-screen messages and supported by the allowance of user interferences. CFIRE has used up-to-date research findings focussing on the practical needs of coal mines. This paper discusses briefly also the relevant theoretical principles on which this package has been perceived.

Jan 1, 1989

By Eugene F. Casey, William H. Hansmire, J. Ghaboussi, Randall L. Lentell, Harvey W. Parker

INTRODUCTION Construction of a major intercepting sewer in Brooklyn, New York involved tunneling in soil over several subway lines. In two instances the clearance between the subway and sewer was sufficiently close that concern was raised about the influence of the new construction. Prior to each critical crossing, analytical studies were performed which characterized the tunneling influence. It was demonstrated that with adjustments in construction procedures the crossings could be made without affecting the integrity of the subway linings. A comprehensive program of instrumentation and full-time monitoring was undertaken to ensure that any unforeseen adverse developments during crossing would be recognized. The successful crossings were subsequently made with minimal influence. Reported herein are the special construction conditions for the two crossings, the analytical simulation of behavior, and the results of monitoring on the subway linings. SEWER TUNNEL CONSTRUCTION AND EXISTING SUBWAYS The Red Hook Intercepting Sewer is a 2600 m (8600 ft) long tunnel which is part of a major water pollution control project in New York City. For clarity of nomenclature, the sewer is termed a 'tunnel' while the rapid transit structures are termed 'subways'. For routine construction, the tunnel was mined by hand with a 3.2 m (10 ft-5 in.)

Jan 1, 1981