Search Documents

By E. T. Pecina

Bioleaching is a viable option for the processing of auriargentiferous refractory ores with high arsenic content. The application of mesophilic (A. ferrooxidans and ?L. ferrooxidans?) and thermophilic bacteria of the genus Sulfolobus (S. solfataricus and S. acidocaldarius) as oxidant treatment before the cyanidation of an industrial arsenical pyrite concentrate is presented. The results show that extraction of gold and silver increases due to bio-oxidation caused by mesophilic bacteria and results in a maximum gold recovery of 68%. In all strains studied, biooxidation resulted in an average silver recovery of 50%. The results showed that all evaluated strains were sensitive to solids content (5 to 20%) and average particle size (75 and 38 µm) of the concentrate.

Jan 1, 2010

By D. J. Hutchinson, S. Nickson

Cable bolts are used as a means of rock support around underground excavations in many mines across Canada and around the world. A substantial body of research on cable bolting was conducted at a number of Canadian universities and mines from the mid-1980s through the 1990s. Since then, research into selected areas of cable bolting practice has continued in Canada. The research has focussed on cable bolt instrumentation and on the inclusion of cable bolts in empirical stope design techniques. A review of cable bolting practice is now warranted at many mines. It has been five years since the completion of the previous substantial body of Canadian academic research and the associated advancement in understanding of cable bolt design, implementation and verification practice. Attempts were made at that time to transfer the new design procedures and performance assessment technologies to mine-site personnel. In some cases, this was effective, and ground control personnel continue to improve on their cable bolting practice at each specific mine site. However, at other sites, experienced people have moved on, and the new, less experienced personnel do not have access to the training or technical resources required to improve their understanding of the subject. In other cases, the technology was not transferred effectively to practitioners, with the result that substantial improvements can be made to the cable bolting practice at those mines. Guidelines for auditing cable bolting practice are provided in this paper. The guidelines include a discussion of the objectives of the audit, suggestions for audit procedure and a summary of the possible outcomes of a cable bolt audit. The objectives of an audit might include assessing the reasons for unexpected cable bolt failures, evaluating the quality of the installation procedures, quantifying the efficiency of the cable bolt system and assessing training requirements and procedures. A cable bolt audit should include consideration of all aspects of the cable bolting cycle, including the design, implementation and verification phases of the operation. At the end of the audit, a ranking should be assigned to the components of the cycle. The ranking system can then be used to identify items that require immediate attention, others that could be improved and others that are adequate. Following completion of a cable bolt audit, increased confidence in the support system and its application is generally, found, along with the potential for cost savings in many cases.

Jan 1, 2002

By T. W. Lloyd

Accurately predicting coal seam discontinuities is an important part of modern underground coal mining. Conventional methods of coal exploration sometimes fail to identify rapid variations that may seriously impact mining and quality. Radio Imaging Method (RIM), a geophysical approach to mapping longwall panels, has been developed where electromagnetic signals are transmitted and received though the coal block. The amount of signal loss for a given distance, when compared to the coal seam characteristics, identifies anomalous areas. A comparison of RIM predictions with actual geologic conditions encountered during longwall mining demonstrates the accuracy and usefulness of the data.

Jan 1, 1986

By Andrew T. MacKenzie, Paul A. Rantala

Predictive pastefill rheology (flow characteristic), models have long challenged pastefill practitioners. While the methodology and practicality of recipe formulation is attainable in most locals, the remaining challenge has been to devise a predictive mathematical or empirical model of paste flow characteristics. Flow phenomenon can now be assigned mathematical and physical basis. The authors herein disclose physical and mathematical methods that demonstrate how operators could proceed when designing reliable pastefill systems. Knowledge presented will allow users flexibility in adjusting flow-rates. Laboratory data shows stiff pastefill delivery design can be derived through mathematical relationships of particle size, material characteristics and pipe diameter.

Jan 1, 2001

By Norman A. Nadel

Those of us who have directed our efforts toward the construction of tunnels have long maintained that tunnel construction is more closely an art than it is a science. We have spent time underground with hard-bitten, tobacco chewing shift bosses and superintendents who have made seat-of-the-pants decisions at the face which have been based upon their long experience underground coupled with uncanny intuition. The courage and skill of these men in the performance of their art is legendary. Without question, they have constituted the backbone of the tunnel construction industry. But just as John Henry, the steel driving man, despite his stout heart and dedication to his task, was supplanted by the steam drill, I fear that our tunnel stiff, at least as we have known him, will become an endangered if not extinct species. The reason for this is clearly that tunnel construction is slowly but inexorably making the transition from being an art into being a science, and more and more its performance is requiring the services of scientists as opposed to artists. The tunneling art has been undergoing change for many years, and yet until recently the changes have not been basic. We have improved the way we do the same old things. For example, John Henry would be flabbergasted if he saw the rock drills we use today. He would not have engaged in the legendary drilling contest with one of our modern drills, He would have simply conceded defeat.

Jan 1, 1970

By Ted D. Johnson

INTRODUCTION The tailing dam is part of the SOHIO L-Bar Uranium Mine and Mill located about 70.8 kilometers (44 miles) west of Albuquerque in northwestern New Mexico. The dam location is shown on Figure 1. The tailing dam is one of the last upstream method dams permitted in the industry. Design and construction aspects of the project, as well as operation and maintenance considerations, are reviewed herein. Since initial construction, SOHIO Western Mining Company and Woodward-Clyde Consultants have developed several modifications and improvements in the dam's operating and monitoring procedures. This work has been done in coordination with the New Mexico State Engineer's Office and in accordance with recommendations in a report done for the Corps of Engineer's Phase I Dam Inspection Report. Modifications and improvements described should be of particular interest to owners and operators of other tailing dams utilizing the upstream method of deposition. The tailing facility was designed for a 10-year life to provide an ultimate storage capacity of 6 1/2 billion kilograms (7 1/2 million short tons) in an area of about 180 acres. A plan view of the tailing dam is shown on Figure 2. The tailing consists of approximately 75% sand size material and 25% fines (material passing the No. 200 sieve). The tailing dam includes a small earth starter dam with raises of the dam accomplished using tailing deposited by upstream method techniques. The starter dam is a homogeneous embankment about 610 meters (2000 feet) long, a maximum height of 12 meters (40 feet) and 2 1/2:1 (horizontal to vertical) upstream and downstream slopes. The starter dam contains an internal drainage system which includes a near vertical chimney drain connected to horizontal finger drains. A typical section through the maximum height of the starter dam is shown on Figure 3. A small confining dam, approximately 1.6 meters (5 feet) high, is constructed beyond the limits

Jan 1, 1980

By M. H. Al-Dabbagh

In this paper, the authors outline the deficiencies of PERT/CPM as a method for scheduling complex projects such as mine development. In particular, PERT/CPM networks cannot accommodate logical nodes (events) or stochastic branches (activities). The Graphical Evaluation and Review Technique (GERT), developed by Pritsker and. co-workers, is introduced as an alternative to PERT/CPM that overcomes many of the deficiencies of the latter and enables a more realistic analysis of complex projects that are subject to significant uncertainties. A brief overview of GERT network structures and network analysis is given and a PC implementation of the method is described. The technique is illustrated by application to the development of an open-pit gold mine in Saudi Arabia.

Jan 1, 2002

By Z. Kokesz

The following paper presents the results of geostatistical studies of the selected hard-coal deposits in Poland. Geostatistical methods were applied mainly to the characterization of variability structure of the coal seams thicknesses as well as sulphur and ash contents in the coals. Results imply that the accuracy of coal reserves estimations can be improved if kriging method is applied. Kriging allows predicting more precisely the values of such parameters as thickness and sulphuring content.

Jan 1, 1993

By C. H. Grant

On the Mesabi Range, Ammonium Nitrate is used for blasting a variety of materials having widely varying blasting characteristics. The materials vary from hard, dense, magnetic taconite, which requires heavy blasting, through relatively soft, earthy, direct shipping ores, which require only light blasting to facilitate shovel operation. In view of the fact that materials gradational between these two end members are encountered in large tonnages, it is evident that a wide range of blasting situations face the mine operators on the Mesabi Range. In April of 1956, at Cleveland-Cliff s Hawkins Mine near Nashwauk, Minnesota, a fertilizer grade of Ammonium Nitrate prills was first used as a blasting agent. This first attempt was made without the addition of any carbonaceous material and even though it did go off, the force was not sufficient to produce the required results. Fuel oil was then added In the amount of one gallon for each 80 pounds of Ammonium Nitrate, with the oil and Ammonium Nitrate being added to the hole simultaneously. This blast was successful. Since then most of the mining companies have used Ammonium Nitrate, experimenting with various ratios of oil and fertilizer, mixing these ingredients either before or during loading of the holes. Since the additional of fuel oil to the Ammonium Bitrate before loading produces a more uniform saturation, most companies have adopted the method of pouring the fuel oil directly into the Ammonium Nitrate bags and then pouring the mixture into each hole. The ratio of 3- ½ quarts of fuel oil to each 80 pound bag of Ammonium Nitpate prills is now being used.

Jan 1, 1958

By D. Robert Weir

The pioneers in pressure hydrometallurgy have provided a solid foundation during the past four decades. The pressure techniques are now capable of being used to push back the frontiers in the winning of metals. Pressure hydrometallurgy has been used to meet the objectives of extracting metals; purifying metal solutions, recovering metals; and rendering waste streams acceptable for disposal to waste repositories and the environment. Some examples of each of these functions are briefly reviewed. The applicability of pressure techniques to the recovery of precious metals is discussed.

Jan 1, 1985

The Peruvian mining industry has seen an explosion of foreign investment since President Albert? Fujimori's government was first elected in 1990. Since then, Peru has taken some large steps toward recovery, making it the envy of most other developing countries. A measure of political stability was gained in 1992 when Shining Path leader Abimael Guzman was captured. In addition, the country has taken on a huge privatization program, rewritten its foreign investment laws and has reined in its annual inflation rate from 1,700% in 1990 to about 8% by late 1997. Small wonder then that attendance at the XXIII Peruvian Institute of Mining Engineers conference reached a record level, many of whom are employed by some of the world's largest mining companies. About 2,700 mining industry professionals from all over the world attended the week-long event, held in late September in Arequipa. That was an increase from 1995s 1,600 attendees, that meeting also held in Arequipa.

Jan 1, 1998

By Robert J. Timko, R. Lincoln Derick

The Bureau of Mines evaluated the integrity of escapeways in a three entry underground coal mine. A center conveyor belt entry (secondary escapeway), was flanked by an intake (primary escapeway) and a return entry. Diesel equipment was used throughout the mine for material and personnel haulage. A carbon monoxide monitoring system, tied to a data recording computer on the surface, was deployed throughout the belt entry and at selected sites in the intake and return entries. Previously, the company had a fire of unknown origin in another mine, which prompted an interest in the performance of their escapeways. An initial, qua1itative evaluation was performed by burning approximately 14 kg of coal at the mouth of the intake entry. The first test was followed by a similar burn at the mouth of the belt entry. These initial trials showed a high quantity of leakage between entries. In several follow-up evaluations, simulated fires, using a tracer gas, were set in the intake and belt entries. Tracer gas concentrations were obtained in all entries at four different underground locations. The results of these tests showed that permanent stoppings could not guarantee isolated, contaminant-free escapeways.

Jan 1, 1989

By D. Morin, J. Villeneuve, S. Foucher

The development of new processes has to follow "best practice" rules in order to be technically and economically as efficient as possible. However, innovations, new process routes and new rules are continuously emerging to minimize financial risk and maximize environmental compliance. Process simulation, which offers a complete overview of the flowsheet, makes it possible to cope with this new challenge-minimizing waste production and water consumption. Furthermore, simulation provides an estimate, at the early stage, of the cost of alternative technical routes. Four examples involving biotechnological circuits are presented, both at the design and commissioning stages.

Jan 1, 2000

By Deborah A. Kramer

Although beryllium was initially discovered in 1797, it was not until 1916 that the first significant quantity of beryllium metal ingot was produced in the United States. Before 1940, most of the small quantity of beryllium metal used in the United States was supplied by Germany. Beryllium was not used in its metallic form; it was used as an alloying addition to other metals, mainly copper and nickel. World consumption of beryllium at that time was estimated to be a few hundred kilograms annually. Because of increased tensions in Europe before World War II, imports of metal from Germany ceased in 1940, and domestic production was required to meet the needs of the military. As a result, by 1946, the United States became the principal supplier of beryllium products for the world, a condition that prevails today. Because of beryllium's high strength, light weight, and high thermal conductivity, it has been used in a large number of industrial and defense applications as a metal, alloy, and oxide. The United States is the only country other than China and the former USSR currently producing beryllium products from beryllium ores and concentrates. Bertrandite, mined in Utah, is the principal ore source of domestically produced products. Imported ore, mainly from Brazil, supplements domestic ore supplies. Production and consumption data for the United States is shown in [Figs. 1 and 2]. Production data for 1969-1979 is withheld to avoid disclosing company proprietary data.

Jan 1, 1994

By Maria S. Adusumilli, A. Bhaskara Rao

ABSTRACT The presence of gold in lateritic crusts over mafic and ultramafic volcanogenic complexes in / and greenstohe belts, has called the attention in several parts of Brazil and also in Australia. Recent studies reveal the variety of structures and mineralogy of such crusts, and their importance in correlation with host(bed) rock types, as exploration guides, specially for greenstone belt metallogeny. The expected nature of growth of plates and/or nuggets in such crusts is under detailed study, and is considered as possibly due to dissolution and reprecipitation phenomenae of disseminated-fine-low grade ore in the host rock, in this investigation, laterite geochemistry, though incipiently discussed todate, is of fundamental importance and significance. Lateritic gold can be classified texturally as: dusty and diffused, fine, thin platy, taDular, and nuggets. Such gold is pure, and is often restricted to nodular (pisoliths, ooliths, concretions) forms or the matrix, that constitute the crusts or lateritised gravel beds which have an essentially goetnitic nature. Further this gold is recovered directly by mining the crusts or the adjoining placers with the metal derived from them. The thickness and extension of laterite crust zones is extremely variable depending oh the paleoclimatic conditions, and is conditioned to the favourable lithology and its structural expression. However, the "growth" of gold in these laterites will be conductive , without doubt, to several small scale mining activities, specially in the developing countries and regions limited to latitudes 309N and 309S.

Jan 1, 1987

By Frank F. Aplan

Froth flotation has been used to improve the recovery of fine coal, for minimizing the sulfur and ash content of clean coal and for the removal of fine coal from recycled or discharged backwater from coal preparation plants. Though froth flotation and allied processes for ores date from the turn of the century, with the first U.S. commercial application in 1911, coal flotation has been introduced into U.S. practice much more slowly. The first European coal flotation plant was started in 1920, and by 1933 Europe had 60 operating plants while the United States had only one plant, newly commissioned. Over the years there has been a steady increase in coal flotation so that today one-third of the 345 U.S. plants employ the process. This report traces U.S. coal flotation practice and technological improvements from early laboratory experiments in 1915 up to today's extensive use of the process.

Jan 1, 1999

By R. Asamoah, K. B. Owusu, G. Abaka-Wood, W. Skinner

The hostile nature of industrial autogenous (AG)/semi-autogenous (SAG) mill operation necessitates the need for robust and reliable online measurements. Mill slurry density is regarded as a critical variable and requires a suitable range for grinding efficiency. In this work, mill acoustic sensing of five different slurry densities (50, 60, 70, 80 and 90 wt.% solids) was investigated using a laboratory-based AG/SAG mill. The results showed that slurry density of 70-80 wt.% solids gave the highest mass of -75μm particles and similar acoustic intensity. The mill acoustical level increased continuously coupled with energy reduction as a function of increasing slurry density, an indication of potential realtime measurement.

Mar 2, 2022

By Peter M. Fozzard

A review is made of the actual costs of recent foreign mineral exploration programmes in third world countries. Target identification leading to the selection of areas, or macro-targets, must follow a well planned and defined series of steps. Suggestions are made with respect to this inter-active project development work. Potential revenues in the broad sense will always determine the overall economics of exploration but clear objective philosophy, good planning and adequate financing are essential for exploration success. Considerable opportunities exist for making important foreign mineral discoveries and broad selected suggestions are made for the identification of exploration areas in relation to high-grade and precious metal mineralization.

Jan 1, 1984

By Jean E. Kiel, Rob Dorey, Dirk J. A. van Zyl

1.1 INTRODUCTION This chapter seeks to provide an overview of important factors involved in the implementation of heap leach technology as a vehicle for gold extraction from its ores. Toward this end, brief discussions of the various elements important to this process are presented here. Topics covered in this chapter include a brief history of the process; basic chemical reactions responsible for the process ; characteristics of ores amenable to heap leaching; location of the greatest concentration of heap leach projects in the U.S.; heap leach components, methods, regulatory/permitting considerations; and economic considerations. Most of these subjects are treated at much greater length in subsequent chapters. Thus, this chapter serves as a summary for those which follow, in addition to providing the reader with a feeling for those topics which may be of most immediate interest. 1.1.1 History of the Process Modern Day Precious metal heap leaching technology has developed over the past decade, although the principles of heap leaching per se, as well as those of gold extraction through cyanidation have a long history (see discussion below). However, it is in the past 10 years that heap leaching has developed into an efficient method of treating oxidized gold and silver ores. It has proven to be both an efficient way to extract precious metals from small, shallow deposits, as well as an attractive way to treat large, low- grade, disseminated deposits. Heap leaching has several advantages compared to conventional milling (i .e., crushing, grinding, and agitation leaching). In general, these advantages include simplicity, lower capital and operating costs, shorter start-up times, and less intensive environmental regulatory concerns. A possible disadvantage of currently existing heap leach technology is a potentially lower percentage of metal extraction being obtained from the ore than would be the case with conventional milling (Potter, 1981; Hiskey, 1985; and Thorstad, 1987) The actual principle of heap leaching has a long history as inferred previously. For example, mines in Hungary recycled copper-bearing solutions through waste heaps in the mid-sixteenth century (Hiskey, 1985), and Spanish miners percolated acid solutions through large heaps of oxide copper ore on the banks of the Rio Tinto around 1752. By 1900, leaching operations were employing such techniques as leach/rest cycles to maximize copper recovery (Taylor and Whelan, 1942; Thorstad, 1987). Copper dump leaching is currently

Jan 1, 1988

By C. N. Bensley, S. K. Nicol

The major developments in fine coal processing in Australia are reviewed. Emphasis is placed on the approaches taken by various Australian coal producers to improve the recovery of the coarse size fractions (minus 0.5 plus 0.25mm) and upgrade the selectivity of flotation at ultrafine sizes (minus 0.075mm). The effects on fine coal preparation of flotation circuit changes, the influence of physical and chemical variables on coarse coal flotation and the impact of spiral concentrators and column flotation, are discussed. Reference is also made to the development of oil agglomeration technology for the treatment of fine coal refuse and some of the factors which have led to its current demise.

Jan 1, 1988