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By H. Tutu

The legacy of gold mining operations continues to affect water quality in the Witwatersrand Basin in South Africa. The acid mine drainage (AMD) emanating from the tailings dumps liberates heavy metals from the ore minerals. The objective of this study was to characterise the geochemical processes that are important in understanding chemical evolution of polluted water in the study area. Analytical results for water samples collected in the catchment of the study area generally showed elevated concentrations of heavy metals in the vicinity of tailings dumps and mining operations and a decrease in the distal. Dams and wetlands, despite their proximity to the tailings dumps, recorded low concentrations of heavy metals and other pollutants. The characterisation of AMD was summarised in a conceptual model in which plots of redox potential versus pH and electrical conductivity versus pH were identified as the most important sub-models that captured the gross physical-chemical characteristics of polluted water and its interaction with the environment.

Jan 1, 2006

By Andrew Mackenzie, Paul Rantala

Data is now appearing in literature that indicates many current paste fill systems in Canada suffer from plugged lines and severe wear rates. Both of these conditions suggest: design problems with the pipe distribution system, backfill composed of poorly graded material and/or possibly poor operator practices. Problems that can be prevented in the design stage, but still may be readily solvable with current technology. However, if left untreated will lead to an increasing frequency of down time. The compatibility of the distribution system with the paste fill rheology is fundamental and essential for the reliable delivery of fill. Either many mine operators are not familiar enough with the technology to provide a critical review that could foresee problems down the road, prior to construction and or North American designers are not clarifying their designs to their customers. The objective of this paper is to highlight key concepts to mine operators with the purpose of better enabling a critical review of contractor's/consultant's designs. There is a great deal of understanding about the rheology of backfill over a range of pulp densities from hydraulic slurry to dense to paste. However, outside of deep mines (especially in South Africa) neither hydraulic or dense fill distribution systems have suffered the problems of paste fill. Paste fill is fundamentally different from hydraulic fill principally in its transportation characteristics. These differences have a direct impact on the design of the distribution system. By understanding the practical implications of these differences the operator can play a more active role in their design while better appreciating how to best operate their own system.

Jan 1, 2001

By I. H. Keith

INTRODUCTION The following papers describe the extraction of nickel in the form of ferronickel from the Dominican laterites. The Falconbridge process was developed initially in the Falconbridge Metallurgical Laboratories and subsequently in several successive stages of pilot plant operation in the Dominican Republic. In the course of this work we came to believe that there is advantage in piloting on site. Mining, metallurgical and geo-political considerations all have major impact and that belief has been borne out by commercial plant experience. Lateritic nickel ores differ substantially, even within the same orebody, in their amenability to extraction methods. The Falconbridge process takes account of the heterogeneous nature of the deposit. Three years of geological field exploration led to ten years of process development after it was realised that the then known metallurgical processes would not give economical extraction from the Dominican ores. In addition to establishing the viability of a novel pyrometallurgical approach, it was necessary to verify design parameters for a very considerable scale-up to prototype commercial operation. The plant was eventually constructed within the original estimates of time and cost. Unique features contributing to the technical and commercial success of the project are described. Additionally, some bold extrapolation based on pilot plant work, eventually proved to be quite conservative. The mine is not a conventional open pit operation, but is perhaps better characterised as an earth moving job. Novel application of mobile equipment led to great flexibility in the mine, where operation of several mining fronts is essential to maintaining uniformity of ore feed to the plant. The practical aspects of almost total acceptance of the oversize run-of-mine material through a high-capacity unit,

Jan 1, 1979

By E. J. Meets, C. F. Meyer

Bord and pillar mining at shallow depth (400 m approx. maximum) is widely used in South African coal mines. One of the problems encountered in extracting coal in this manner is the ventilation of advancing bord and pillar headings. The traditional ventilation methods of force, exhaust and overlap (force/exhaust) are reasonably effective but tend to be both cost and labour intensive. Ducting often restricts the available free area of roadways thus impeding the transport of coal and other materials inbye the coal production section. Due to the above facts, ductless fans are currently being used to minimize the amount of ducting required in advancing sections. Two different types of fans are used, namely, vortex fans and the so-called `jet' fans. Vortex fans were developed from the fan blade design used for vertical take-off aircraft. The fans have the capability of delivering air over distances of about 30 m in the underground situation without any ducting attached to it. Jet fans are standard axial flow fans fitted with outlet reduction pieces which increase the velocity pressure at the discharge to such an extent that the air delivery distance is improved to almost match that of vortex fans. The paper describes some applications of both these fan types in advancing bord and pillar sections.

Jan 1, 1993

By Edwin A. Harre, John J. Mortvedt

Plants obtain nutrients from both air and soil. They absorb carbon dioxide mainly from the air, although some carbon dioxide may be dissolved in soil water which is absorbed by plant roots. Carbon dioxide, a gaseous form of carbon and oxygen, supplies the carbon which usually makes up 50% or more of plant structure. Growing plants use water more than any other biological substance. Plant nutrients dissolve in soil water and enter the plant via root absorption. Water is then given off into the air as the plant breathes or transpires. Water also supplies hydrogen and oxygen to plants. Plant roots absorb nutrient cations or anions by contact exchange with soil clay particles. Inorganic or mineral nutrients essential to plants are supplied through the soil. Inorganic or mineral composition of plants usually is less than 5% of their weight. In most crop-growing areas, much of this nutrition is inadequately supplied from soil reserves and must be provided by fertilizers. The role of the fertilizer industry is to provide economical, efficient, good quality fertilizers to improve or maintain soil productivity for optimum crop production. The essential plant nutrients other than carbon, hydrogen, and oxygen which often must be added to soils or plants are categorized as primary nutrients (nitrogen, phosphorus, and potassium), secondary nutrients (calcium, magnesium, and sulfur), and micronutrients (boron, chlorine, copper iron, manganese, molybdenum, and zinc). These classifications are based on quantity of nutrients utilized by plants and do not imply their function or degree of necessity. One point of major significance to the fertilizer industry is that not all fertilizer minerals contain the plant nutrients in a chemical form available to the plant. A product which may be considered a fertilizer mineral may require substantial processing or treatment before it becomes useful as a nutrient source or fertilizer.

Jan 1, 1994

By Steven J. Page, Robert A. Jankowski, John A. Organiscak

Quartz dust is one of the most significant ongoing health concerns in coal mining today. Since initial verification of this health risk in coal mines by the Mine Safety and Health Administration (MSHA) during the early 1980’s, the Bureau of Mines has conducted numerous studies in underground mines to identify the sources of quartz dust and its fundamental characteristics. The most significant underground quartz dust source was found to be the continuous miner excavating rock. The percentage of quartz was also found to be higher in the smaller size fractions of the dust when significant amounts of rock was mined by the continuous miner. Furthermore, the quartz content in the continuous miner return remained fairly consistent at greater distances from the face. Another important factor speculated to affect quartz dust generation and its size characteristics is the morphology of the quartz bearing rock. The quartz content of dust between mines had notable differences with respect to the differences between kaolinite content in the dust. Low kaolinite content was associated with higher quartz content and increased size segregation of quartz into smaller dust particles, indicating that the free silica bonding matrix in the rock is most likely another factor responsible for quartz dust produced through mechanical comminution.

Jan 1, 1991

By D. G. Bosse

Equipment choices for ultrafine grinding encompass several different types of dry and wet size-reduction devices These need to be put into functional perspective for systematic analysis of capabilities and limitations versus processing requirements of the materials to be satisfactorily ground Particle strengths plus maximum and average sizes are the primary variables controlling grinding action requirements and equipment options for efficient processing These are fairly well understood and provide the starting point for decisions Particle space requirements under dynamic processing conditions vary with particle shapes and size-distributions by as much as 30X This additional major variable IS not widely appreciated and does need adequate description to provide a firm basis for selecting processing compositions and procedures

Jan 1, 1983

By A. K. Ghose, S. Chakraborti

The research work outlined in this paper examines the utility of index tests for evaluating the strength of coal, both in the laboratory and in-situ. For routine evaluation of strength and deformation properties of coal seams, as inputs for design in stability analysis and equipment selection, the index tests are cost-effective and also make less demand on time and manpower. Four index tests, namely Protodyakonov Index, Cone Indenter Index, the Point Load Strength Index and Schmidt Rebound Hammer, were evaluated for 13 coal samples and correlated to fundamental strength and deformation properties such as uniaxial compressive strength, Brazilian tensile strength and modulus of elasticity of the same coal stratum. The index tests, barring Point Load Index, showed relatively low percentage scatter compared to the fundamental strength and show marked advantages for routine estimation of coal seam strength.

Jan 1, 1986

By Malcolm J. McPherson, Daniel J. Brunner

This paper describes an experiment conducted to investigate the law of airflow on a mechanized longwall coal face. Background to the Square Law relating frictional pressure drop and airflow is presented and deviations from this Law are discussed. The procedures used to investigate the Law of Airflow for the longwall are described and the results are presented. The results verify the Square Law relationship for airflow along a mechanized longwall face.

Jan 1, 1987

By S. E. Clay, P. R. Taylor

A physical model for the diffusion and flow of gases through porous solids, which accounts for the random nature of individual gas molecules moving through a solid of definite structure, has been formulated. The model was solved using' the Monte-Carlo technique. It was then used to evaluate specific constants related to the dusty gas model and to describe the gas-porous solid diffusion phenomena. Experimental results were used to validate the stochastic model.

Jan 1, 1988

By S. J. Parkin, P. Shead

Extraction of coal at Harworth Colliery is undertaken in the Deep Soft seam at roughly 1000m depth where the strata temperature is 42 "C. Production employs the longwall retreating method using high powered mechanised methods to extract coal at a rate of approximately 40,000 tonnes per week from a single face. This paper describes the climatic conditions encountered on a typical district , 6's district, where the initial ventilation set-up was as a typical U-type district which was antitropally ventilated. Under this initial set-up climatic conditions in the intake typically exceeded 30 "C effective whilst in the face area and in the return airway effective temperatures in excess of 32 "C and 33 "C were common . The paper then proceeds to describe the methods employed to attempt to improve the climatic conditions on the district, especially with regard to the coal face and return airways and describes in detail the effects of reversing the district airflow direction, employing homotropal ventilation, on the climatic conditions. The results of this reversal have been dramatic and have resulted in a substantial improvement in the climatic conditions experienced , however problems have been encountered with the control of methane gas since the changeover. The final part of the paper describes the results of computer simulations to analyse the effect of various ventilation designs on the predicted climate for future production districts in order to de- fine a district layout which will produce acceptable climatic conditions in the working zone without the need to use refrigeration techniques and which will improve methane gas control .

Jan 1, 1997

By R. V. Huff

An in-situ leaching technology was developed for copper oxide minerals at the Van Dyke deposit at Miami, Arizona. This paper discusses the process developed and the activities that occurred. Specifically, the activities of well installation, deposit data acquisition, leach testing and equipment development are reviewed. Installation and operation of the test facility are described.

Jan 1, 1988

By K. Verghese, H. M. Lee, R. P. Gardner, K. Boateng

Results of work on the development of a phenomenological model for the continuous flotation process wing short-lived radioactive tracer techniques for determining model parameters is reported. A model that incorporates a flotation first-order rate constant and a residence time distribution based on the cross-flow finite-stage (CFFS) model has been derived and investigated. The short-lived radioactive tracer techniques and the nonlinear search methods necessary to extract the model parameters have been developed. The conditions under which all the model parameters can be extracted from a single radiotracer experiment are detailed and illustrated. A micro- computer-based unique data logging system has been designed, assembled, and implemented for collecting the necessary transient radiotracer data. Results are reported for a continuous laboratory flotation process for the two systems, mica ore and coal.

Jan 1, 1987

By James L. Crowe

Electric-power-generating plants fired by fossil fuels are faced with increasingly stringent requirements for control of sulfur emissions. Several approaches for limiting these emissions, or for operating such facilities in an environmentally acceptable manner, are being pursued. Some of the approaches are based on the use of naturally occurring carbonate rocks or of materials derived from them. This paper discusses primarily the carbonate-rock-based processes being developed for control of sulfur dioxide emissions from fossil-fueled electric-power-generating plants. It includes a discussion of the role of carbonate rock materials in removal of sulfur dioxide from stack gases after combustion, capture of gaseous SO2 during the combustion process, and removal of sulfur from fuel prior to complete combustion. Materials derived from carbon- ate rocks are generally used in processes which convert the sulfur to a throwaway product, but there are also proposed processes in which the sulfur is converted to a useful product and the absorbent is regenerated for reuse.

Jan 1, 1974

By F. Palmay, R. D. Gwilym, P. Eng

INTRODUCTION As the experience in Canada indicates, it is becoming more and more common to evaluate major mining projects, especially those relating to uranium, with respect to their environmental effects. As part of this evaluation public hearings are becoming the rule rather than the exception. In this area the 1970's and presumably the 1980's can be characterized as the age of "Environmental Assessments" or "Environmental Impact Statements" which form the basis of these hearings. These documents tend to require significant amounts of research, data collection and effort in their preparation, and tend to be closely scrutinized by the hearing body and by groups in opposition to the project. This opposition is becoming more organized and sophisticated. The assessment or impact document, together with the evidence supporting it during the hearings can: (a) mean the difference between a lengthy and hence costly hearing and a smoother, shorter and less expensive one, (b) result in requirements for extensive modification at the expense of the proponent to his project, (c) result in the proponent being required to carry out extensive studies, research or monitoring programs, and (d) conceivably may in certain situations result in the project actually being turned down. Therefore, while on the one hand it is important to have available technical answers to concerns relating to uranium, its associated and perceived hazards, it is getting more and more important to be able to present these answers in both a written and oral format in such a way as to meet the criticism and concerns of the opposition, be they citizens in general or special interest groups including environmental lobbyists. JURISDICTION From a Canadian perspective, the first legal question to be answered is which level of government has jurisdiction over uranium mines in general and specifically over aspects relating to the environmental effects, including the health and safety aspects, of uranium mines and

Jan 1, 1980

By T. C. Rao, N. Suresh, M. Vanangamudi

Experiments have been conducted on a 76¬mm water-only cyclone treating cowl below 2 mm size having different proportion of -0.075 mm fines. The effect of cone angle of the cyclone (compound cone) has been analyzed on water split, separation of -0.075 mm fines, separation of coarse solids, and on separation behavior of individual size ructions of the feed. It has been noted from the results that there exists a linear relationship between the flow rate of water in the feed and flow rate of water reporting to overflow stream. This relationship is independent of the cone angle and, with changes in the fines content in the feed, only the intercept of the straight varies, keeping the slope constant. Further, it has also been found that the percentage of fines below 0.075 mm reporting to the overflow is directly proportional to the percentage of feed wafer reporting to the overflow. This relationship is found to be independent of the cone angle and the fines in the feed. The performance of the water-only cyclone has been analyzed by plotting partition curves for different experimental conditions. In addition to this, the Rosin-Rammler equation has been fitted to the partition curves of the hulk feed and individual size-fractions. Tile analysis of the results has revealed that the specific gravity of separation increases with increase in the cone angle of the cyclone while it decreases with increase in percent fines present in the feed. Mathematical relationships have been developed to relate the variation in SG50 with cone angle and percent fines in the feed.

Jan 1, 1990

By Wai Wu, C. Haycocks

The majority of Appalachian coal deposits lie in a multi-seam environment. Historically, the decision to extract a particular seam has been based on ease of access, ownership and economics rather than ground control considerations. As mining progresses and seams are being mined out, it is increasingly common to find working and abandoned mines in close vertical proximity to each other. Such contiguous operations can produce both positive and negative ground control situations in neighboring seams. These ground control problems, defined as interaction problems, are frequently reported, and their severity can range from minor roof problems that may require no additional support to complete loss of a large section of coal reserves (Stemple, 1955; Peng & Chandra, 1980; Haycocks & Karmis, 1983; Su et al, 1984). As a consequence, interaction problems are of growing concern to the Appalachian underground coal industry. Although interaction problems in multi-seam mining have been recognized for many years and many investigations have been conducted to study the problems, the ground control principles involved in their development are only partially understood. Previous research has identified four interaction mechanisms: pillar load transfer, innerburden shearing, arching effects and upper seam subsidence (Haycocks et al, 1982; Haycocks & Karmis, 1983). Pillar load transfer mechanisms and innerburden shearing have been successfuly used to explain interaction phenomena associated with undermining operations, while arching and subsidence have been used to assess problems during overmining. In addition, interaction-controlling factors such as cover, innerburden and seam thicknesses, extraction percentages on both seams, time delay between operations on two seams, and characteristics of innerburden rock have been identified and utilized in evaluation of interaction effects (Haycocks & Karmis, 1983; Webster et a1.,1984). As an example, Figure 1 shows the relation of innerburden layering and thickness to interaction on the lower seam. The combination of such theoretical work and the analysis of case study information has made it possible to determine, with a certain degree of confidence, the interaction damage in undermining conditions. The results of such an approach have been sufficiently successful and complete to be incorporated into a software package to assist field engineers in estimating potential interaction effects when undermining a previously mined upper seam (Grenoble et al, 1984; Grenoble & Haycocks, 1985; Grenoble et al, 1985). Although the conventional finite element and photoelastic modeling techniques have been

Jan 1, 1986

By Gary S. Brierley, Tracy J. Lyman

INTRODUCTION Geotechnical engineers play a major role in tunnel design primarily because tunnels are constructed entirely within the ground. In general, this role can be divided into two major tasks: subsurface investigations and project design. Under subsurface investigations, it is necessary for the geotechnical engineer to accurately describe the ground in which the project will be built. Under project design, it is necessary for the geotechnical engineer to work together with other members of the design team to make certain that the tunnel fulfills its intended purpose at least cost. Given in the paper are the authors' opinions about what constitutes an adequate scope of services for these two tasks on a tunneling project. SUBSURFACE INVESTIGATIONS o Background Study All subsurface exploration programs for tunnels begin with a thorough investigation of background information about the proposed site. Such background information includes geologic, reports topographic maps, aerial photography, and case history reports of other nearby tunnels. Once completed, it is necessary to study the background information so that the proper scope and magnitude of subsurface exploration work is performed in a manner that provides maximum input to a knowledge of those intact and rock mass properties that are important for an understanding of the entire ground mass. The blind application of field and laboratory techniques, no matter how sophisticated, is wasteful and potentially

Jan 1, 1989

By A. Unal, R. L. Grayson

The use of radio frequency identification (RFID) technology to solve informational needs in isolated and restricted underground mining environments are reviewed, and the specifications of some of the past and currently available systems are presented. The advantages and disadvantages of using various frequencies, system configurations and specific components, including their construction standards and capability, are also discussed. The remaining challenges to the more widespread use of RFID systems for personnel and vehicle tracking are identified, and recommendations concerning the operating environment capabilities are detailed. Finally, the ultimate requirements for maintaining system integrity during and following a coal mine emergency are discussed.

Jan 1, 1999

By Robert L. Bonomi

One of the major operating costs for any labor-intensive operation is that of its employees' wage and benefits package. Today's packages are extremely complex, with multiple pay rates for different grades and shifts, intricate bonus criteria, and expansive benefit packages that include all sorts of medical, dental, pension and other costs that can be "hidden" from direct examination and consideration. The problems of estimating the total cost of such a package to a company becomes even more acute at negotiation time, when pressure from both sides to settle intensify and changes to package offers come rapidly. A comprehensive system is needed that can evaluate these costs and perform sensitivity analyses, on the various components of an agreement so as to aid in the solving of major labor deadlocks, productivity problems, and cost impacts created by those agreements.

Jan 1, 1982