Search Documents

By John F. Papp

Chromite is used both as a metallic and nonmetallic mineral. Chromite ore is used as the source of chromium by the metals industry and is used, without chemical alteration, in the refractory and foundry industries. Chromite ore is also the source of chromium for the chemical industry. On average worldwide far more chromite ore is used by the metallurgical industry than by any other industry. Thus, although the primary purpose of this chapter is to describe the nonmetallic uses of chromite, the metallurgical uses must also be discussed in order to provide a complete description of this commodity.

Jan 1, 1994

By James R. Aggson, Verne E. Hooker

GENERAL CONSIDERATIONS The design of a mine or any underground opening in rock is similar to the design of any other structure, such as a building or a bridge, in one important way. This similarity lies in the fact that the stability of the structure is a function of the loads that will be applied during the structure's expected lifetime. In the case of an underground opening, the applied load is the product of the existing in situ stress field and the concentration of this field that is produced by the extraction of a load¬bearing material. Thus, a knowledge of the in situ stress field is considered a basic requirement in the design process and essential to the eventual stability of the underground structure (Duvall, 1976; Obert, 1972; Merrill and Peterson, 1961; Dahl and von Schonfeldt, 1976; Hedley and Wilson, 1975). The in situ stress field can be used along with the physical properties of the rock masses involved, the ge¬ometry of the various rock types, the geometry of the openings involved, and a failure criterion to evaluate structural stability of a planned mine by theoretical or numerical techniques. This same information can be used to investigate ground control problems in existing mines. In situ rock stress determinations can be separated into three categories: the determination of applied stress, also called the absolute or field stress; the deter¬mination of concentrations of the field stress near open¬ ings; and the determination of changes in rock stress as load-bearing material is removed. The applied stress field is more difficult to determine than are stress changes. Various instruments and techniques have been developed to determine applied rock stress and stress changes in rock. ABSOLUTE OR FIELD STRESSES Theoretical Considerations In the absence of actual measurements, it is often assumed that at any point, the vertical stress is equal to the weight of the overlying material. [ ] where S„ is vertical stress, S is average weight density of overburden rock, and h is depth from the surface. This is normally consistent with actual experience. The horizontal stresses are assumed to be equal and related to the vertical stress through the Poisson effect. [] where Sh is horizontal stress, S„ is vertical stress, and v is Poisson's ratio. The derivation of Eq. 2 is dependent on lateral con¬finement of the rock mass. An increasing amount of information is rapidly becoming available which indi¬cates that the in situ stress field at a particular location cannot simply be assumed to be a gravity-induced stress distribution in which the secondary principal stresses in the horizontal plane are due to confinement and Pois¬son's effect. Rather they can be a complex function of gravity loading, regional stresses, structural features, ex¬cavation geometries, and variations in surface and/or possibly basement rock topography. Furthermore, the underground principal stress dis¬tribution is not necessarily vertical and horizontal as is often assumed. The deviation of the three-dimensional stress distribution from vertical and horizontal can be due to a combination of both topographic (Hooker, Bickel, and Aggson, 1972) and structural features.

Jan 1, 1982

By Gregory A. Hope, Kym Watling, Matthew I. Jeffrey, Ronald Woods

Surface enhanced Raman Spectroscopy carried out in real time has been applied to identify surface species formed during gold leaching in chloride and thiosulfate media. Chloride ion is adsorbed prior to the gold dissolution potential, but its coverage is significantly diminished at the beginning of leaching. A gold chloride band is again observed when dissolution is rapid, together with bands characteristic of AuC14- ions in solution. With thiosulfate, a thin gold sulfide layer is formed slowly in the potential region where leaching occurs. At higher potentials, thiosulfate is oxidized to sulfur and sulfate, both products being identified by Raman spectroscopy.

Jan 1, 2005

By Kenneth F. Lane

In most industries it is normal commercial policy to try to gear production to the market. In times of scarcity output is pushed to its maximum and in times of glut output is reduced. Because of the effects of supply and demand, these times correspond to times of high and low prices respectively so the policy results in maximising long run total profits. Stockpiling is often an integral part of the policy. Stocks are accumulated during depressed market conditions and sold off when demand revives. This further increases the long run total profits. However, such policies cause violent fluctuations in short term profitability and impose severe financial strains. Indeed planning and implementing the policies are a central management concern which is often critical to the success of the industry. The mining industry is no exception and, for many raw materials, trying to balance supply with demand is an international problem. Stockpiling and restricted production agreements are common elements of policy. But very little attention has been paid to the one additional control which is unique to the mining industry, namely, the cut off grade. This neglect is apparent at all levels from individual mines to national economies.

Jan 1, 1979

By Boshou Bian

Air quantity is the primary parameter governing the working condition of a mine fan. In order to improve the fan performance and efficiency, reduce its energy consumption, and guarantee mine safety, it is very important to obtain an accurate value. However, generally speaking, the fan ducting or drift on surface is very short in distance and contains sharp bends. The air quantity of the mine is so concentrated in this way that the air velocity becomes very high, and the airflow, either in the fan drift before the fan impeller or at the downstream diffuser, is very turbulent. Therefore, no anemometer is satisfactory because there is too much difference between the measured value and the actual value of air quantity at the mine fan.

Jan 1, 1989

By J. A. Ryder

Compressed air is a relatively inefficient yet very convenient vehicle for transmitting mechanical energy. It is inefficient when compared to, say, hydraulic or electric energy systems since compressor and pneumatic machine efficiencies are quite low (in the range 20-65%) and reticulation losses can be quite high unless adequate pipe diameters are used to minimize friction drops. It is convenient in that capital and maintenance costs of pipes and machines are exceptionally low, the equipment is flexible and lightweight, the technological level is simple, the form of the energy supply is intrinsic- ally safe, and as an additional minor but psychologically important benefit, it provides a ready source of cooling and air supply for emergency use in deep hot mines. It is for these reasons that compressed air is a premier source of energy for many forms of underground equipment, in particular hand or rig-mounted rockdrills, some forms of rock- handling equipment, and a host of minor applications including agitators, small-lift pumps and temporary f am installations. In a typical S. African deep-level gold or platinum mine, compressed air generation accounts for 15% of the total mine electrical energy bill - more than is used for hoisting. In these mines it is not uncommon for over 100 km of underground compressed air piping to be installed, primarily to supply handheld rockdrills.

Jan 1, 1979

By Bruce A. Brown

Construction aggregate is the most important nonmetallic-mineral commodity in quantity and value that is produced in Wisconsin. Crushed stone is produced from the Precambrian crystalline rocks and the Ordovician and Silurian carbonates, and sand and gravel is extracted from Quaternary glacial deposits. Dimension stone is quarried from both the Precambrian crystalline rocks and Paleozoic carbonate rocks. Other nonmetallic minerals include industrial sand, lime, roofing granules, terrazzo aggregate, and peat.

Jan 1, 1999

By A. R. Laplante

In this paper, the performance of the Knelson Concentrator and of the batch and continuous Falcon Concentrators are compared. The units are based on different operating principles, and perform quite differently. The Knelson yields very high free gold recoveries over a wide size range of both the recovered and rejected species. It is less effective in recovering very fine (<15 μm) or very flaky gold, as encountered in flotation feeds, concentrates or tails. It is the preferred unit for gold recovery from grinding circuits. The batch Falcon is effective in the fine range, typically less than 37 μm for gold. Its recovery zone is quickly saturated when there is significant heavies in the feed. It works best as a pre-concentration unit, or when sulphide content is low. The continuous Falcon is a versatile unit which is capable of recovering fine heavies (density down to 5 g/cm 3), especially from coarser gangue.

Jan 1, 1993

By F. L. Wilke

A model is presented to minimize the winning costs per shift within the different sections of a potassium mine by liner programming and to simulate the other areas to get all costs in order to comp re different production strategies. he model is based on a a given total layout of the underground mining which is considered to be fix during the planning period. Room-and-pillar mining is assumed to be used. Potassium extraction is done by drilling and blasting. Transportation of the raw material to sectional crushers is done by scoop-trams where it is crushed to coarse-grains which allow further transportation by conveyor belts to the hoisting shaft or to a bunker. When production is stopped, the continuously working factory is supplied by means of this bunker. Starting from a desired composition of the raw material the model has to keep the given total. demand of raw material per shift, to minimize the winning costs, to keep the capacity constraints of the equipment and to determine the planned output of production of the sections per shift. Costs of the areas which follow the extractions are added to extraction costs in order to allow a comparision of costs of several alternatives of production. Optimization in extraction and assignment of scoop-trams to sections is done by linear programming. The other areas of the mine are treated by simulation. The model output is a schedule of the calculated costs broken down into costs of processes, equipment, and kinds of costs. This proceeding enables to compare different ways of production.

Jan 1, 1979

By Juan P. Camus

One of the most important decisions in mine development is the selection of the mining method. Open pit or underground methods are selected depending on the shape of the deposit, and its position with respect to the surface. When the decision is not clear or evident, then the common rule is to compare underground and open pit projects to choose the one which yields the maximum return. However, in some circumstances&apos; the best alternative is to start-up the operation with an open pit until a point where mine operating costs make more convenient to employ an underground method. In this case, the final pit limit is not directly related with commodity prices and its position is a funtion of capital and operating costs associated with both methods. The goal of this paper is a mans of establishing the proper ultimate pit considering a potential underground mine. The methodology is quite simple and can be implemented to work with a variety of available routines for pit optimization, such as Lerchs-Grossmann, floating cone, network flow and the Lemieux moving cone optimizing algorithm, which is the tool used by the author.

Jan 1, 1992

By William S. Butcher

Research and development of tunneling technology is rapidly taking its rightful place as an important ingredient in the Nation&apos;s research and development strategy. The state of technology in tunneling is very important to the Federal Government. Through its support, both direct and indirect, of a wide range of public works, our government, using the taxpayer&apos;s money, is the biggest buyer of tunnels. So that this money is spent wisely and efficiently, it is important that potential developments in tunneling technology that promise lower cost tunnels be pursued, if the cost of reaching the goals is commensurate with the prospective benefits. For too many years, the Federal Government&apos;s activities in the tunneling technology field were fragmented. Recently, specific coordination efforts have been initiated. It may surprise some to realize that the total Federal expenditure on excavation technology research and development, which is largely devoted to underground excavation, is growing by leaps and bounds. In fiscal year 1971 alone, approximately $19 million were expended by Federal agencies. This current fiscal year (FY 1972) that amount will increase to $24 million. It would appear that next year we will exceed the 1972 expenditure by 52 percent to bring the total FY 1973 expenditure up to $36 million. As most of this money is devoted to underground excavation, it is clear that the Federal Government

Jan 1, 1997

By John Rushton

Surface mining, from ore extraction to processing, requires many types of equipment to obtain the final product. Mine equipment often includes shovels, drills and haul trucks. Ore processing equipment, including plants, mills and concentrators, are also part of surface mining operations. Surface mining operations emphasize production. Production is where the bills are paid and fortunes are made. However, there must be support to keep the equipment operational. To most production people, equipment maintenance is a necessary evil. Maintenance is not glamorous work. It is often neglected when praise is being passed around. It is easy to recognize higher production, greater capacities, faster cycle times or more loads hauled. But who cares if an engine is replaced in 12 hours instead of 48? The answer is, everyone should - from the hourly miner to the mine manager. Surface mining equipment needs constant maintenance work. It must be lubricated, components replaced, electrical problems repaired and other problems addressed. Repair work for any surface equipment takes time away from production. It costs money. Maintenance costs cannot be avoided. However, they can be minimized. Minewide communication should include operations cooperating with maintenance. Traditionally, operations resist surrendering equipment to maintenance if it can continue to produce. The rationale is, every load that can be hauled today is money in the bank. If the unit is taken down, the money is lost. This thinking is prevalent in many surface mining areas, including the mill. "Not on my shift," the operator thinks. "Let the next crew worry about it. The problem with this thinking is in probability and statistics. The longer equipment goes without maintenance work, the higher the probability of equipment failure. When the failure does occur, it is certain to cause the equipment to remain down longer than if the maintenance department had been allowed to take it down. Many mining operations have closed early in their lives because of poor maintenance practices. This has become the industry standard because substandard levels of performance are acceptable. Management believes it gets five to six hours of work from maintenance people during an eight-hour shift. Actually, the industry average is less than two hours of work per shift. Real productivity levels of less than one hour are not unusual. There are few exceptions. However, a daily work schedule (DWS) will increase productivity at many properties by 50% to 100%. A 200% improvement is not unusual. The DWS will work. Maintenance people are among the most intelligent and motivated people on the property. They deserve the chance to be productive. [ ] In preparing a DWS, management needs to understand two productivity principles - the productivity spread and the real maintenance workday.

Jan 1, 1997

By J. Pang, S. Chander, A. Briceno

The mechanism of sulfur oxidation in pyrite is a function of the rate and driving force for oxidation. New evidence is presented to show that, at moderate potentials, a sulfur-rich hydrophobic layer is formed. Under ordinary conditions, the sulfur layer is covered with a layer of iron oxides, hydroxides, sulfate or oxy-sulfide ions. Pyrite is hydrophilic under these conditions. In the presence of iron-chelating agents or iron sequestering ions, an iron layer might not form. Under these conditions, the sulfur layer is exposed, and the pyrite might become hydrophobic. Stronger oxidizing conditions decompose the sulfur layer, thereby making the surface hydrophilic.

Jan 1, 1994

By D. W. Fuerstenau, G. S. Sudhir, P. C. Kapur

Quartz-limestone feed mixtures were ground in a laboratory-size, choke-fed, high- pressure roll mill. As compared to individually ground minerals, the harder component (quartz) in the product mixture is coarser, and the softer component (limestone) is finer. An energy split index is introduced for quantifying the disproportionate split of the mill energy between the feed constituents. This index is incorporated into a grinding kinetic model for simulation of the product size distributions of the mineral components as a function of energy input to the mill. The self-similar character of the size distributions is analyzed and an energy-size reduction relationship for the roll mill is highlighted.

Jan 1, 1992

By G. Y. Li, D. Farahmand

The dilemma of a numerical analyst not only concerns the problem of modelling the non-linear behaviour of intact rock, but also the non- linearity contributed by structural discontinuities. In this light, it is the intention of this paper to examine some aspects of the non-homogenity and structural discontinuities of rock and incorporate this behaviour into boundary element numerical solution. Non-homogeneous material is considered piecewise, thus homogeneous and is modelled by using sub-regions. The Mohr- Coulomb failure criterion is employed to model the non-linear behaviour of the major discontinuities. A computer program is developed based on the procedure for combining the direct boundary element method and the displacement discontinuity method. A linear element type is employed in the formulation of numerical solution. The computer program is used to study the stress distribution in a gold mine.

Jan 1, 1986

By Melvin A. Jennings

Even though the title of this paper is quite long, the ideas presented herein are very simple. In fact, it occurs to me to be somewhat humble about coming before such a distinguished group with such a simple presentation. However, the application of these ideas has proven useful in at least two copper flotation plants. The purpose in presenting this paper is to inspire some interest in the great stores of data chat the Mining Industry often accumulates without making any attempt at analysis. Unfortunately, many milling engineers rely rather heavily on percent recovery as a strict measure of a concentrator&apos;s relative performance. The fallacy of this reasoning is not difficult to see since, by definition, percent recovery is a function of feed assay, tails; and concentrate grade. If copper tailing is constant, and it very nearly is for a strictly sulfide copper ore, percent recovery must fluctuate almost directly to the feed assay. The point that I wish to make here is that it is very seldom justified to compare the percent recovery figure from one period of time to another without considering the difference in feed assay. The problem of comparing results is even further complicated when the ores are of mixed oxide and sulfide mineralogy.

Jan 1, 1978

An atomic force microscopy (AFM) has been applied to study the adsorption of potassium amyl xanthate (PAX) and potassium ethyl xanthate (KEX) on arsenopyrite surface in solutions. AFM images show that the collectors adsorb on arsenopyrite surface in patches at pH 6. Increasing the chemical dosage will increase the adsorption density of the patches on mineral surface. The increased probe-arsenopyrite adhesion measured in PAX solutions at pH 6 is attributed to the adsorption of the patches, suggesting the hydrophobic nature of the patches, which is likely the oily dixanthogen. It is also found that arsenopyrite is reactive in water in the presence of air. At a high pH with the addition of Ca(OH)2 the adsorption of collectors on arsenopyrite is greatly retarded or depressed because the mineral surface is coated by a lot of precipitates, which is hydrophilic in nature as shown by the measured strong repulsive probe-arsenopyrite detachment force. The findings confirm that the flotation behavior of arsenopyrite in xanthate solutions is very similar to that of pyrite.

Feb 27, 2013

By Thomas E. Browne

The Electric Power Research Institute Energy Supply Program is developing coal supply forecasts. By coal supply forecasts I mean the future relationships between coal price and production levels. A representative supply curve is shown in Figure l. It will make the rest of my presentation clearer if at this point I give you some background about EPRI and the Energy Supply Program. EPRI is funded by the nation&apos;s electric utility industry to develop new technologies for the production and conservation of electricity. Most of the research is conducted by outside contractors. We participate in joint projects with the Department of Energy and other organizations. The Energy Supply Program is one of three "economic" programs. The other two are Energy Demand and Conservation, and Systems. The Systems Program&apos;s main function is to provide the means to integrate the output of the other two Programs. The primary function of the "economic" programs is to provide information pertaining to future energy prices, availability, requirements, etc. to the EPRI personnel planning R&D programs. A secondary role that is becoming more and more important is providing information of direct use to the electric utility industry. I should note that the results of all EPRI&apos;s contract work are available to the general public. A "Coal Supply Analysis System" is being developed for EPRI by Charles River Associates. To the extent possible it will draw upon existing work, but much additional work needs to be done in the area of coal supply economics.

Jan 1, 1977

By Michael J. Taylor

Introduction A prime goal in the design and operation of uranium milling waste or tailing disposal systems is to mitigate adverse effects of tailing liquid on the adjacent groundwater. Adverse effects are often defined as modifying the groundwater quality in such a manner as to have detrimental health effects on downstream users. To accomplish this goal, the following three types of systems are employed with regard to the seepage and groundwater aspects of waste disposal: Type I Systems Seepage is allowed to occur unabated from the tailing disposal facility. Detrimental radionuclides and chemical elements are prevented from causing adverse downstream effects by natural purification actions in the subgrade geologic materials and the near zone groundwater. Monitoring is required to assure the predicted natural purification is occurring. The consequences of seepage loss is minimal since the m be predicted with current investigation and analytical techniques and can be evaluated as to effectiveness during operations. Type II Systems Seepage is partially retained in a waste impoundment or leakage from a designed retention system is anticipated. Natural purification is relied on for controlling migration of detrimental radionuclides or chemical elements, or contingency planning is employed to collect and return the tailing liquid to the impoundment. Installation efforts and concern for escape of tailing liquid are greater than for Type I systems, but extra precautions to preclude all seepage are not implemented. Monitoring is required to detect leakage and/or assure the natural purification of escaping tailing fluid. The consequence for accidential excusions are moderate, and will be excessive only if massive system failure occurs. Type III Systems Seepage is totally restricted by a costly system constructed and operated with extra care. Natural

Jan 1, 1980

By R. A. Wharton, Z. Yang, R. W. Smith

The electrokinetic and flotation behavior of the green alga Chlorella vulgaris was studied in the absence and presence of Pb(II), Al(III) and flotation collectors. It was found that the presence of Al(III) is necessary for good flotation of the organism, whether or not Pb(II) is present, when dodecylammonium chloride or sodium dodecylsulfate is used as collector. Best flotation using dodecylamine is at about pH 8, and best flotation when using sodium dodecylsulfate is at about pH 4. It appears because of the small size of the organisms that the Al(III) is necessary for flocculation to enhance bubble-cell contact and C. vulgaris removal from water. When N-dodecyl-2-aminopropionic acid is used as collector, good flotation occurs at about pH 4 without the addition of Al(III).

Jan 1, 1992