Search Documents

By Felix Schmid

ABSTRACT Lateritic bauxite deposits of economic size and grade in Sierra Leone occur on granulites of the Kasila series. The high grade trihydrate ores of Mokanji are exploited by SIEROMCO since 1964. Remaining reserves are small (2 million tons) and operation moved over to the Gondama deposits of similar grade. Port Loko bauxite reserves are estimated at 100 million tons and are of relatively lower grade. It is planned to treat this ore locally into alumina. Guinea's bauxite reserves exceed those of any other nation. They occur as hard lateritic bauxite covers on plateaus of the Pre-Cambrian sedimentary formations and on doleritic intrusions. The genesis is still controversial. The Sangaredi mine has produced high grade ore for the last 10 years. Friguia exploits a relatively lower grade ore at a rate of about 2 million tpy to be treated in their local alumina plant. Kindia ore is mined at a yearly rate of 2,5 million tons since 1974. Untouched reserves at Ayékoyé and Tougué/Dabola are estimated at 6,000 million tons.

Jan 1, 1984

By M. Stephen Enders

The Little Rocky Mountains host epithermal gold-silver bearing vein and stockwork deposits in a syenite intrusive complex. Pegasus Gold Ltd. is currently mining the oxidized deposits by open-pit methods and recovering gold and silver by heap-leach processes. A geologic program has been designed to effectively determine the basic ore characteristics; 1)mineralization; 2)oxidation; 3)structural setting; 4)lithology; 5)alteration; and ultimately, 6)the leachability of the ore. Geologic mapping, sampling, drilling, assaying, and testing are routinely used in exploration, development, production control, mine planning, and ore reserve estimations. Timely and accurate assay results are essential for the program's success.

Jan 1, 1983

By David R. Kalasky

One of the primary areas of computer application in mine ventilation has been the analysis of mine ventilation networks. A variety of network analyzers that are aimed toward the solution of flows in a given network has been developed. These programs typically use the Hardy Cross or other iterative algorithm for solution of any network, even those that are complex. The computer software has become more efficient and sophisticated over time and has thus been widely adopted for ventilation network analysis. One of the shortcomings of these programs is that they have been developed with the idea of analyzing the ventilation requirements at a single point in the lifetime of a mine. This provides the ventilation engineer with an important tool for analysis but falls somewhat short of providing a convenient means to economically com- pare alternative methods for ventilating a mine. The program described in this paper provides such a tool. The principal concepts that were necessary for the completion of a computer program that analyzes ventilation alternatives is the capability of efficiently determining the ventilation requirements at a variety of times during the lifetime of the ventilation system and some method of analyzing the costs of the alternatives on a realistic comparative basis. To accomplish this task, the authors began using Penn State's mine ventilation simulator designated as PSU/MVS, Didyk et al. (1977a, 1977b) and added the necessary additional software to accommodate the need for multi-period, time-dependent analysis of the net- work. The software was then tested on a coal mine ventilation problem with a 23-year life. The problem points out the value of such a program for ventilation analysis.

Jan 1, 1986

By Elmer R. Drevdahl

During the last few years there has been a rapid increase in the development of the community or junior college throughout the United States, Some factors behind this development include the need for more college facilities to service the growing number of high school graduates, the desire of the public to provide some post high school education at reasonable costs, and the need to provide post high school educational opportunities not now provided by most of the universities and colleges. Many of the new community colleges provide at least three educational services including local opportunity to provide the first two years of a four year college program, two year technical-vocational programs of a terminal nature, and adult educational opportunities. The community college has the advantage of not being saddled with years of academic tradition which prevent it from changing to suit the educational needs of the community It serves. The flexibility of the community college in developing new programs, particularly in the technical areas, is going to provide industry with many of the badly needed technicians it is now unable to secure.

Jan 1, 1965

By Leons Kovisars

Two-thirds of the world copper produced in 1979 incurred cash costs between $0.35 and $0.89 per lb, averaging $0.62 per lb. North American costs are higher at $0.48, $0.88, and $0.68 per lb, respectively. Variable cash costs are $0.20, $0.58, and $0.39 per lb for the world; $0.29, $0.63, and $0.46 per lb for North America. Cash costs are relevant for comparing existing operations and evaluating market pricing during periods of excess supply. Analysis of full costs of production (cash costs plus income taxes, profit, and non-cash items) becomes relevant in evaluating the incentive price required to develop new production plants. In mid-1979 this cost (incentive price) was about $1.10 per lb; it is expected to approach $2.00 per lb by 1985.

Jan 1, 1979

By Joseph A. Whitchurch

The N20 to N25 Tunnel (basic) segment was the second tunnel contract awarded for construction by The PB/MK Team. This project embodied 3.9 km (2.4 miles) of tunnel and was located within the northwest quadrant of the 86.9 km (54 mile) long main collider ring. The contract required the excavation and initial support of a 54.3 m (178 vlf) deep ventilation shaft, a connecting horseshoe shaped Adit and TBM starter tunnel and 3,865 m (12,680 If) long main collider tunnel with a 4.3 m (14 ft) minimum finished diameter. This paper discusses the construction methods, equipment utilized and the production achieved in the construction of the ventilation shaft, connecting adits and the main collider tunnel.

Jan 1, 1995

By Norbert Patzelt, Johann Knecht

Future ore reserves of major gold producers in North America and elsewhere will consist of refractory gold ores. About 60 % of the current U.S. gold production is mined in Nevada. Several of the large gold operations in this state indicate that 40 to 90 % of their future ore feeds will contain refractory gold. To com­pound problems, average head grades for refractory U.S. gold ores had fallen from 8 - 9 g/mt to about 4 g/mt by 1991. In Latin America, 52 % of the gold operations will require milling for optimal recovery. Deeper reserves are, like in North America, refractory. Therefore a special treatment process is needed in order to allow for the gold ore to be leached downstream in a conven­tional cyanidation process for a high gold recovery. There are several options available for this oxidation process like treat­ment of the gold bearing ore in pressure oxidation, in a biooxi­dation or in a roasting plant depending on the reason for the refractoriness. If organic carbonaceous matters and sulfides are the prima­ry reasons for the refractoriness, whole ore roasting is a pre­ferred method for the treatment of this type of ore. Since dry ore is to feed to the roaster, a dry grinding mill is advantageous. For the dry grinding system, the moisture content and the ore char­acteristic is of importance. Those parameters decide the mode of the grinding system. For autoclave systems common wet grind­ing systems can be applied. This paper deals with technical aspects for dry grinding plants and gives an outlook on and pos­sibilities for new grinding systems.

Jan 1, 1996

By Eberhard Stolarski, Michael Tacke

When the oxidized surface gold deposits are mined out, the underlying refractory gold ores become the challenge of treat­ment systems. The size and value ofrefractory gold ore reserves are a function of recovery efficiency and operating cost. The start-up of LURGI's gold roasters at NEWMONT's Carlin site has established whole ore gold roasters as a key to high gold recoveries. The ores from several deposits of the Carlin trend are roast­ed utilizing LURGI / NEWMONT technology, which has achieved gold recoveries approaching 95%. This is in dramatic contrast to the traditional perception that roasting is limited to gold recoveries in the mid 80's. Extensive investigation in pilot scale is required to achieve stable high gold recoveries for most variables in the ore body. The key question for all pilot tests is the classic question of (ROM) run of mine ore roasting or concentrate roasting. All variables are dominated by the leaching/ recovery char­acteristics of the natural ores. The degree ofrecovery improve­ment by roasting / calcining establishes the frame of the eco­nomical conditions. The full range of flexibility is required for the design of the plant to allow for ore variations in heat values, combustible con­tents, agglomeration behavior and off-gas composition. The variables in the ore body influence, therefore, the price of the plant proportionally to its flexibility. Concentrates are usually fairly stable in composition, com­bustion behavior, heat values and particle size since they are a product of the very selective flotation process. Flotation is not the successful process step when the tailings remain high in refractory gold contents.

Jan 1, 1996

By G. S. Dobby

Particle collection is considered to occur by particle collision with the bubble followed by the particle sliding over the bubble during which attachment may occur. Collision is quantified by a collision efficiency, EC. The existing model for EC is extended by including particle inertia. Attachment is quantified by an attachment efficiency, EA calculated as the fraction of particles which reside on the bubble for a time greater than the induction time. These calculations use recent data on the liquid velocity distribution over the upper half of rigid spheres. Collection efficiency, EK is given by EK = EC ? EA. Detachment is not considered. The mode is examined and shown to agree with much experimental data. For example the maximum observed in recovery vs particle size (d) can be explained as E increases with increasing d , while EA decreases. The decrease in selectivity at fine sizes is in accord with the model result that for dp < 5µm, EA ? 100% (i.e. EK ? EC) almost regardless of induction time. A decrease in bubble size does increase EK but does not improve selectivity. A high particle density (> 5g/cm3) is shown to cause a sharp peak in recovery vs size and a decreased maximum size of floatability. Finally, the possible effects of bubble and particle concentration are explored.

Jan 1, 1985

By Joaquin Marti, Peter A. Cundall

This paper reports on some recent work in which several schemes were developed to model jointed rock under high stress, with particular reference to the phenomenon of "block motion" observed during dynamic loading of underground structures. Three approaches were made, corresponding to an increasing relative importance of internal block deformations as compared to rigid block movements. The first one uses distinct element method and assumes internally rigid blocks, which can break, repeatedly, whenever an empirical crack criterion is met. In the second approach each block is allowed three degrees of freedom to deform internally. The third approach, still in the development stage, permits arbitrary deformation of all blocks, which are internally decomposed into finite-difference zones and automatically rezoned during slip to preserve the calculation accuracy on joints. The last two schemes allow arbitrary constitutive relations for the intact rock, and all three schemes permit the geometrical arrangement of joints to be arbitrarily complex, in contrast to normal Lagrange, finite-difference programs, which are unsuited to model discontinua.

Jan 1, 1979

By Richard R. Klimpel

The author was the banquet speaker at the 48th Annual MPD meeting, sponsored by the SME Colorado Minerals Processing Section, May 14-16, 1998, in Colorado Springs, CO. Here are his remarks. It has been an exciting experience to have spent 34 years involved with the process of generating patented technology eventually leading to commercialization. In today&apos;s terminology, this process is called technology transfer. I have had the unusual experience of being involved doing basic research as an inventor while also being responsible for managing new product development and commercialization. In addition, I worked for 31 years before my retirement for a large research-oriented company, The Dow Chemical Co. In 1995, the company spent more than $1 billion dollars on research and development. The last three years of my career have been spent working with a research-oriented university, The University of Florida. And I have worked as a consultant helping several companies to optimize their products and processes. It is on this cumulative experience base that the preparation of this article is based.

Jan 1, 1998

By John G. Whellock

Over the last decade new constraints have emerged in the metallurgical industry which challenge the very basis of design and construction of smelters and refineries. The hackneyed designs of the past will not now serve the revised objectives of: - minimal cost of ownership - improved productivity - reduced energy consumption - greater flexibility in feed or product - minimized recycle loops and by-products - more stringent environmental control The impact of these constraints has been channeled constructively into process intensification - exemplified at the large scale by the introduction of flash smelting technology and at the smaller scale by the application of rotary process vessels and converters for augmented heat and mass transfer. The design of successful process plants depends on the understanding of the unit operations and their interactions which is the discipline of systems engineering. With the advent of increased process intensification the importance of a systems approach to process design and implementation becomes paramount. This paper describes the systems approach with specific reference to medium scale projects in the primary and secondary metallurgical industry.

Jan 1, 1985

By William H. Dresher

World trade has increased significantly during the last quarter century. However, a new rational for protectionism is emerging which argues for the restriction of trade as a means of preserving and protecting the environment. Fearing lower environmental standards in the Third World, environmentalists are calling for new trade barriers between the developed countries and the developing countries to combat what they see as "eco-dumping." The "greening" of protectionism and the merging of environmental standards into international trade agreements could fundamentally change the world trading system as well as seriously impact the availability of raw materials to provide for the needs of the peoples in both the developing and the developed worlds. This discussion will deal with the agreements and regulations that promise to influence the trans boundary shipment and recycling of scrap metals and wastes containing metals and their projected impact on world trade and metal prices. Emphasis will be placed on the Base1 Convention, whose restrictions concerning trans boundary shipment of scrap metal and metal-containing wastes for recycling took effect on December 31, 1997.

Jan 1, 1998

By Hamid Maleki

A geotechnical monitoring program has been implemented at Energy West Mining Company for enhancing site-specific evaluation of longwall stress conditions. This program consists of underground measurements at five locations in two neighboring mining districts located in the Hiawatha and Blind Canyon Coal Seams under moderate to deep cover. Within the last five years, additional measurements, including data on recorded seismic events and face conditions, have been incorporated into the data collection program together with detailed geologic mapping of longwall gateroads. In conjunction with the measurement program, the authors have completed detailed boundary-element stress analyses of the mine plans. Models have been calibrated using the data from in-mine instrumentations and then routinely used for evaluation of mine plans at depths approaching 2,600-ft. The work has improved our understanding of load transfer, seismicity and yield pillar performance. It has identified areas of potential increased stress levels at certain longwall face positions and provided guidance to measures that could be considered to mitigate the potential for these increased stress levels.

Jan 1, 2009

By Vernon R. Degner

The past two decades has seen the application of the mechanical flotation machine, originally developed primarily for metal1iferous ore beneficiation, increasingly applied to cleaning coal in the 28x0 T. Mesh size range. Internal cell hydrodynamic studies of mechanical flotation machines of all sizes, as well as computer aided modeling studies of flotation kinetics has, within the last five years, established a basis for optimizing coal flotation circuit design and machine operation, and has a1 so pointed a way toward improvements in mechanical flotation machine design for the future. Consideration of the trend toward increased fines produced by current mining techniques, as well as the environmental need for a progressively cleaner product, lends support to basing the design of the mechanical coal flotation machine of the future on finer feed; below 100 microns in size. Future types of mechanical flotation machines, which may satisfy the fine coal cleaning requirements for a significant improvement in product grade while maintaining the combustible recovery levels of current technology, are discussed.

Jan 1, 1988

By Richard C. Smith, Steven H. Brown

Commercial scale in-situ leach uranium facilities (i.e., solution mining) have operated since late 1975, and have begun to appear in increasing numbers in the last few years. Solution mining involves the pumping of ground water, fortified with oxidizing and complexing agents, into an ore body, leaching and solubilizing the uranium in-situ, and then pumping the solutions to the surface where they are fed to a mill. Milling is by conventional means, involving ion exchange, precipitation, calcining and packaging processes. This paper presents an overview of the solution mining process, and discusses an empirical method that has been used to determine the radon gas release rate in Bq (curies) per year for the overall operation of the facility including wellfields, milling processes and waste storage reservoirs. In addition to radon generation on the surface from radium decay, it has been determined that the major component of radon release is associated with the dynamic generation of radon from solutions returning from underground. Process parameters impacting this evaluation and the mathematical expressions developed are discussed. The preliminary data accrued is presented.

Jan 1, 1981

By Mark A. Alspaugh, E. A. “Bud” Viren

The driving force behind most advances in technology is need. In the early 1980s, underground coal miners in the USA wanted to build longer conveyors to handle larger capacities but continue to use fabric reinforced belting with mechanical fasteners. Conveyors with intermediate drives were certainly the answer but achieving reliable designs required a significant learning curve. Basic design methodologies had to evolve including advanced simulation of starting and stopping along with complex control techniques and logic. Some components also evolved as specific performance requirements changed Today, in addition to underground mining, the technology has been used extensively in the tunneling industry where the need is for control of belt tensions to negotiate tight horizontal curves. Even though intermediate drives are not used extensively on the surface yet, the lessons learned will find their way to long overland surface conveyance where smaller components are more available and reliable, and often with less capital cost. This paper will document the evolution of intermediate drive technology over the last 30 years and will show examples of its current use.

Jan 1, 2004

By Bruce F. Bohor

Silica sand has been mined in Illinois from the St. Peter Sandstone since the turn of the century, especially in the area around Ottawa on the Illinois River in the north-central part of the state. Production of this sand, consumed mainly by the glass and foundry industries but also sought after for many other uses, has grown with the economy, and last year&apos;s output in Illinois exceeded 4,000,000 tons. Such an important commodity was given the early attention of the Illinois State Geological Survey, and a very complete report was issued in 1928, authored by J. E. Lamar. The mining and processing of the sand has changed very little during the intervening 40 years, so that much of Lamar&apos;s data and descriptions are applicable today. More recently, the stratigraphy of the St. Peter Sandstone in north-central Illinois has become better known from the work of Willman and Payne (1942). The present authors have borrowed generously from Lamar&apos;s publication, and we wish to acknowledge the contribution of both of these studies to our work.

Jan 1, 1969

By Greg Joachims

Composition of salt in the Permian Flowerpot Shale in northwest Oklahoma suggests that the salt in this formation was deposited in the early phase of solar evaporation. Brine produced through natural dissolution of the subsurface salt has netted very pure brines, with relatively low concentrations of magnesium salts that should result from late-stage precipitation of salt deposits from sea water. Over the last 100 years, extensive studies of sea- water evaporites, in relation to brine density, have been a topic of discussion. The development of evaporation models has facilitated the increased production and purity of solar salt (salt produced through evaporation of brine by the sun&apos;s energy). Conversely, this information can be utilized to gain an understanding of how rock-salt formations were precipitated from sea water by analyzing the elemental constituents of the rock salt and of the resulting brine. By evaluation of well-documented, phase-curve tables of sea-water evaporation, a basic theory can be formulated on how the Flowerpot salt unit was formed.

Jan 1, 1999

By Edward F. Fries

Computerized, real -time monitoring had its beginning in the U.S. coal industry in the early 1970&apos;s. Over the last 10 years, developments in technology have made systems available that are capable of monitoring and controlling many mine parameters that can increase safety and production. However, situations currently exist where computerized monitoring systems are not being utilized to their fullest capability. They produce reams of printed output that are not sorted in a useful format, and human operators are not able to react fast enough in emergency situations tn tile large amount of information that the systems generate. A solution is the application of an expert system as the interface with real-time monitoring. An expert system would use an extensive knowledge base and human-type reasoning ability to make decisions on optimum strategies. Expert systems have been applied successfully to problems in other industries, and could provide significant benefits to mine information management systems. The use of an expert system with real-time mine monitoring is discussed in this paper.

Jan 1, 1986