Search Documents

By Y. J. Wang

The use of controlled recirculation began in the early 1930s. Although this method has been applied in many mines since then, a generalized comprehensive network analysis is still lacking. This paper presents a unique approach in which the ventilation network with a controlled district recirculation is divided into two subsystems: a main subsystem and a recirculation subsystem. The subsystems are analyzed individually, and the results and their relationships are then integrated into discussions of the total ventilation system. The analysis of the recirculation subsystem is facilitated by introducing a nondimensional parameter (A), which represents the ratio of the air quantity for the working face to that for the subsystem. As a result, far and regulator pressures and air power for various recirculation arrangements can be effectively expressed as a function of and the subsystem air quantity. Numerical examples are included.

Jan 1, 1997

By F. H. Mertens

The concentrators of Gecamines are fed by a great variety of ores and produce different types of oxide and sulfide concentrates. It is therefore important to translate the performances of each circuit in terns of dollars in order to reach cost optimization in each mine to product line. A new system has been recently implemented for achieving this objective. Technical data and expenses are collected, allocated and analysed on mainframe applications. On the other hand, optimization and simulations are carried out on microcomputers which are linked with the mainframe files. Various kinds of auditing reports can be produced, including those leading to investments and cash-flow pattern which are

Jan 1, 1991

By S. Helgen, C. Byrns, A. Davis

The 4000 acre historic Robinson Mining District outside Ely, Nevada hosts a continuum of oxidelsulfide waste rock dumps of different ages. In an effort to develop a paradigm to explain past, existing, and future conditions at the site profiles of oxygen, pH, temperature, and specific conductivity were collected from various waste rock dumps using a hand-driven soil gas probe and a down-hole sampling device. The resulting data are useful in interpreting the fate and manner of pyrite oxidation within the dumps and in identifying waste rock dumps that may require remedial measures compared to those that require only minimal action prior to closure.

Jan 1, 2000

By K. G. Sutterer

The prevalent use of coal combustion byproducts in engineering applications has been with Class C and Class F fly ash as admixtures in structural concrete. But, the use of fly ash and bottom ash byproducts from modern desulfurization processes is receiving increased attention. The University of Kentucky has been conducting research into civil- and mining-engineering applications of these products. The studies have included extensive investigation of the geomechanical behavior of the materials and the effect of mineralogy on this behavior. These studies indicate important mineralogical considerations in the selection of materials for a specific application and highlight the importance of quality control before and during usage on specific projects.

Jan 1, 1997

By K. A. Heasley

The objective of this paper is to back analyze the August 6th, 2007, collapse at the Crandall Canyon Mine in Utah, in order to better understand the geometric and geomechanical factors that contributed to that collapse. In this work, the LaModel boundary-element program, along with the best available information, is used for the back analysis. To initiate the analysis, a six-step base model of the mining in the Main West area was developed. This base model included a step for each of the critical stages in the mining of this area. Next, calibrated values for the critical input parameters, rock mass stiffness, gob stiffness and coal strength, were developed and optimized based on the best available information. Finally, the model was used to simulate the final mining scenario. As a result of this back analysis, a number of conclusions can be made concerning the mine design and the August 6th collapse: 1) overall, the area was primed for a massive pillar collapse because of the large area of equal-size pillars, 2) the abutment stress from the active retreat sections and the adjacent longwall panels were significant contributors to the collapse and 3) from the modeling alone, it is not clear exactly what triggered the August collapse, although the active mining is a reasonable assumption.

Jan 1, 2010

By Evans U. Jegbefume

A plane strain two-dimensional finite element model employing the method of negative reaction loading has been used to model roof collapse and subsidence resulting from the underground gasification of coal in regions of soft overburden such as that found in Texas. The model included dry zones of rock around the cavity. Roof collapse was included by considering the final state of stress in the elements and removing those that had undergone tensile failure. The two-dimensional plane strain model was extended to include thermal loading and thermal softening of the roof rock. Roof collapse initiation and growth of the cavity were modelled by examining the portion of the rock immediately above the cavity under thermal and hydrostatic load. The model was extended to include linear creep using the method of incremental strains. The overburden was modelled as a generalized Kelvin material.

Jan 1, 1982

By R. A. * Russell, J. R. * Brooks, E. J. Griffith

In 1967, a major impoundment to contain phosphate tailings was built near Columbia, TN. Precise records were maintained on the behavior of the impoundment throughout its 20-year active life. The volume of the impoundment was determined. The DNT (dry net tons) of solids added to the impoundment were continuously measured. The rise of the mud line in the impoundment was measured monthly. The density of the settled strata was determined, as required to understand the behavior of the settled tailings. And experiments were per formed to increase the settled density of the clays. The impoundment is currently being retired and stabilized. It covers more than 400 acres and the settled muds are almost 200 ft thick. The clays have been sufficiently solidified with electroendosmosis to support the growth of cypress trees. More than three milllion trees are being planted.

Jan 1, 1992

By J. M. Scharer, Bruce E. Halbert, Lysane Bouduc, Douglas B. Chambers, Jennifer L. Kirkaldy, Carol M. Pettit

Io contrast to acid mine drainage (AMD), neutral mine drainage (NMD) has not yet received widespread attention. Metal and sulphate concentrations can be elevated and of concern in neutral drainage from waste rock and tailings. In the present paper, metal release in high ionic strength mine drainage at neutral pH is evaluated at several mine sites. Specific factors including oxidation rates, buffering capacity, and hydrology are also addressed and their effect on the production of contaminated NMD from mine wastes is evaluated. Case studies are presented involving current seepage water quality and predictive geochemical modelling to illustrate the possible time frame and magnitude of the contamination.

Jan 1, 2000

By R. Bruce Tippin

The silicates represent the largest and most common group of minerals on earth. Yet in spite of the chemical similarities, numerous mineral processing plants worldwide are operating successfully to yield varied commercial products for numerous uses. The silicates that are commercially produced in the United States by flotation include quartz, feldspar, mica, spodumene, talc, kaolin, and wollastonite. The operation of several plants and the conditions affecting mineral separation by flotation are described. Because the process is usually dictated by the desired market, specifications for the most common products are provided. Potash is a basic fertilizer component, along with phosphate and nitrogen. Potash is typically produced from underground evaporite beds or recovered from natural brine solutions. Flotation of potash is unique in that it is processed in a saturated salt solution. The potash flotation process is outlined and several commercial operations are described.

Jan 1, 1999

By R. D. Deister

The Buick concentrator represents state-of-the-art technology in automated digital process control operation utilizing a centralized computer. The process control strategies implemented at Buick are no longer new to the industry, but the successful application of these developments is still rather unique in North America. Productivity improvements, determined to be a direct result of the process control developments, are the primary topics of this paper. Emphasis is placed on metallurgical benefits including both lead and zinc recoveries; lead concentrate grade; and reductions realized in reagent consumptions, operating costs, and personnel. A detailed description of the concentrator, along with a history of the process control development and a more in-depth discussion of the control strategies implemented at Buick can be found in the references. (The Buick flowsheet is depicted in Fig. 1).

Jan 1, 1987

By K. Hanumantha Rao, P. K. Sharma

A pure strain of Paenibacillus polymyxa and mineral- adapted strains are used to bring about surface chemical changes on pyrite and chalcopyrite and, thus, theirflotation. Paenibacillus polymyxa was adapted by repeated subculturing in the presence of pyrite and chalcopyrite. The surface chemical changes of bacteria due to adaptation and of minerals after their interaction with bacterial cultures are evaluated by electrokinetic and infrared spectroscopy and are discussed with reference to their flotation responses. Interaction of bacterial cells, bacterial metabolites and whole bacterial cultures affected the Hallirnondflotation behavior of the sulfide minerals. The Xanthate flotation results show that pyrite, but not chalcopyrite, is depressed when the tests are carried out after interaction with chalcopyrite-adapted Paenibacillus polymyxa. This investigation demonstrated that the surface chemical properties of bacteria can be manipulated successfully to achieve the desired effects in the flotation process.

Jan 1, 2000

By Paul D. Chamberlin

The evolution of heap and dump leaching has followed the development of agglomeration, materials of construction for leach pads and ponds, solution distribution systems, testing techniques, and state regulations. They are now mature processes. Possible future directions and developments are discussed. In situ leaching of precious metals is waiting to be commercialized. Regulators are reluctant to allow the use of cyanide because of the potential for excursions and operators are reluctant because of the potential for lawsuits. Developments in alternative lixiviants are needed before in situ leaching is accepted.

Jan 1, 1989

By S. K. Kawatra, T. C. Eisele

Although column flotation is known to be more effective than conventional flotation for cleaning fine coal, little attention has been paid to the considerable sulfur removal potential of this process. Whereas conventional flotation can only with difficulty remove pyritic sulfur from coal, flotation columns can make this separation readily due to their greater selectivity. This project has used a modified flotation column to remove pyrite from fine coal. This column has been shown to be capable of removing 70 to 85 percent of the pyritic sulfur from coal while recovering 80 to 85 percent of the total calorific value. However, the remaining pyrite is too finely disseminated to be readily removed by physical means. Currently, experimentation is in progress using bacterially-catalyzed dissolution of pyrite in acid solution to remove ultrafine pyrite and aid in the removal of coarser pyrite inclusions.

Jan 1, 1988

The implementation of NAFTA in January 1994 was expected to have small but beneficial effects on the Mexican economy, mostly through increased investments. Mexico's mining industry was especially likely to benefit, as mineral investment funds would be diverted to the now safer Mexico and away from similarly endowed but more risky Latin American mineral economies. The results during the past two years have shown that it is government and macroeconomic factors that influence investment flows, rather than the fine tuning of trade flows through so called 'free-trade" agreements.

Jan 1, 1997

By G. D. Trump, F. L. Stanley

Spirals have become one of the most popular methods for treating fine coal. Unfortunately, spirals tend to produce an undesirably high specific gravity cut point and often misplace significant amounts of coal and/or rock. In the present study, a process-engineering tool known as linear circuit analysis was used to identify problems with traditional spiral circuits and to suggest alternative configurations. These analyses indicate that a modified rougher-cleaner circuit incorporating a middlings recycle stream offers the best option for improving performance while maintaining a reasonable circulating load. In light of this finding, a full-scale test circuit was installed and evaluated at an existing preparation plant. Data obtained from the plant tests indicate that the new spiral circuit can simultaneously reduce the cut point and improve separation efficiency. Preliminary economic analysis show that the new circuit provides an attractive payback on capital investment.

Jan 1, 1999

By W. Robert Rose, Randall Pyper, Carlos Mirabal, Jaime Eguivar

In 1984, work was started to determine the viability of heap leaching silver-containing waste dumps from Cerro Rico near Potosi - Bolivia, at an elevation of 4300 meters (14 100 it.). The result today is an unusual heap leach utilizing fine crushing, grinding, and agglomeration to process 1000 tonnes per day of ore containing 200 g/tonne silver. The unique metallurgical, economic, and political factors will be discussed which led to the decision to build a heap leach rather than a conventional agitation leach plant. Capital and operating costs will be given along with some of the uncommon process design and equipment problems encountered while developing the operation.

Jan 1, 1990

By Natesa Jayaraman, Jon C. Volkwein, Edward D. Thimons

The Bureau of Mines has studied the impact of shuttle car movement on face ventilation. Real-time measurements of air velocity, methane gas, and respirable dust were recorded and compared with a time study of face shuttle car movement. Work was conducted in a blowing face ventilation section where a scrubber-equipped mining machine operated. Air velocities decreased by an average of 35% as the shuttle car entered the face, restricting air flow, and increased by an average of 35% as the shuttle car pulled away from the face, drawing with it additional air. Return air methane levels follow the face air flow volumes, decreasing as air volume increases. The surge of air created as the shuttle car leaves the face helps to dilute methane. Respirable dust levels, however, were found to increase as the air flow increased and decreased the scrubber capture efficiency.

Jan 1, 1989

By Salama

In the conventional approach, the separator feed incremental masses are assumed to be concentrated at the midpoints of the density or size intervals and subjected to a model partition function. The resulting separation predictions would change if the locations of the incremental masses were changed. As a result. the predicted results depend on the choice of locations where the feed incremental masses are concentrated in the density or size intervals. A technique that utilizes the cumulative-mass-distribution of the circuit feed and the derivative of the partition (separation) function relative to density or size variables is proposed. The proposed technique eliminates the dependency of the predictions on choice of where the feed incremental masses are concentrated within the density or size intervals. Since the proposed technique is based on the cumulative masses at the upper limits of the density or size intervals, the technique produces a single prediction whereas the existing techniques produce predictions that depend on where the incremental masses are concentrated. In fact, it has been demonstrated that the existing conventional technique, in which the incremental masses are concentrated at the midpoints of the density or size intervals, is a first-order approximation of the technique proposed.

Jan 1, 2002

The advantages of quantitative environmental risk assessment techniques over the more commonly used qualitative approach is widely accepted. One important parameter related to the level of risk is the extent and geographic spread of pollutants. Geographic Information Systems (GIS) provide a powerful and highly flexible tool that increases the sophistication of the risk assessment methodology. Through spatial representation, the estimated risk becomes more comprehensive, thus facilitating the decision making process. In addition, valuable qualitative information can be incorporated into the risk assessment procedure with the help of GIS. This paper illustrates a methodology for quantifying risks posed to human health, by exposure to contaminated land, in a manner, which gives a measure of the uncertainty in the assessment and preserves the spatial distribution of the risks. The case study utilised to illustrate the methodology is a large industrial area around a number of decommissioned minerals production and processing sites with known high heavy metal loads at Lavrio, Greece. The spatial distribution of Pb concentration in soils was derived from 425 soil samples collected over a total area of 120 km2. Indicator kriging was used to quantify the spatial distribution of the risk and related uncertainty and the results displayed in map form using GIS.

Jan 1, 2003

By S. P. Banerjee

Injection of inert gases to combat mine fires has been practiced in various parts of the world for a long time. Of late, nitrogen has become the preferred inert gas for control of mine fires and safe salvage of longwall equipment as compared to carbon dioxide or fuel gases produced from burning of fuel. In India, carbon dioxide has been used for fire fighting in a number of mines during the 1960s and 1970s. More recently inert gas produced from burning of fuel oil in surface plants has been used in controlling the atmosphere in fire areas in two mines. In yet other cases, liquid nitrogen has either been poured directly into fire areas in liquid form or injected in gaseous form to keep the fire in check. Nitrogen produced in liquid form in an oxygen plant is more costly than nitrogen produced from PSA (pressure swing adsorption) based plants. A PSA-based plant has been installed in one of the Indian mines in 1986 and more are in the offing. This paper reviews the application of various inert gases in Indian mines and discusses the likely trend of inert gas application in Indian mines in the future.

Jan 1, 1987