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By V. K. Gupta

The experimental results of some wet batch and continuous grinding experiments carried out in a 40 x 40 cm grate discharge ball mill have been analyzed for the variation of the grinding rate parameters, Si, with various operating conditions using a linearized population balance model. The wet grinding tests were carried out under conditions which were very similar to those encountered in the actual practice in plant operation. Well distributed -4 and -20 mesh feeds of two complex pyritic ores were used. The volume-percent solids in the pulp ranged from 30-40, the particle load from 5-8 kg, and the solids feed rate from 70-1 10 kg/hr.

Jan 1, 1981

By S. Chander

Neutralization of acidity by addition of alkaline materials is a commonly used method to treat acid mine drainage. However, this procedure requires large amounts of reagents based on acid-base accounting. The potential use of organic additives in preventing or ameliorating acid mine drainage was investigated in this research. The tests were conducted in weathering columns using refuse samples from a coal cleaning plant. Both cationic and anionic compounds were tested. For a comparison, tests were made in the presence of limestone and lime. The results show that some of the reagents substantially retarded the rate of oxidation whereas others even enhanced it. The suppression of the rate of pyrite oxidation was ascribed to surface chelation. Formation of surface compounds prevented the pyrite particles from further oxidation. Such a treatment required only small quantities of reagents since the reaction was confined to the surface.

Jan 1, 1992

By S. Kelebek, S. O. Fekete

The flotation process developed at Falconbridge laboratories utilizes sulphur dioxide and diethylenetriamine (DETA) reagent combination in the depression of pyrrhotite to allow its separation from pentlandite and chalcopyrite. DETA by itself has failed to produce flotation selectivity with samples from plant and pilot plant streams which showed relatively high redox potentials. However, DETA was found to function effectively on laboratory-generated samples under certain conditions. The results of poor depression are in keeping with thermodynamic calculations which indicate that in the presence of sufficient xanthate and DETA, the formation of ferric dihydroxy xanthate and dixanthogen is possible under oxidizing conditions. The use of sulphur dioxide alone has also resulted in a rather poor depression of pyrrhotite. However, the combined use of these reagents has resulted in an efficient and consistent separation of pyrhotite from pentlandite and chalcopyrite. Various aspects of this selective flotation system are presented along with a discussion on possible operating mechanisms.

Jan 1, 1995

By D. W. Scott, D. G. Minnes

Introduction Ontario's diverse industrial mineral resource base includes structural minerals such as sand and gravel, crushed stone, building stone, clay, shale, limestone, and dolostone. These resources are used to produce aggregates, brick, metallurgical stone, fillers, cement, lime, and other construction materials. The majority of the operations are in deposits of Palezoic and Quaternary age in southern Ontario, close to the major markets. Province-wide, there were more than 140 Mt (154 million st) of aggregates produced in 1985. About 115 Mt (128 million st) of that was produced in southern Ontario with the rest being largely from Crown land in northern Ontario. Structural industrial minerals account for more than 80% of the value of total industrial mineral production. The remaining 20% is accounted for by the nonstructural minerals, such as salt, which is produced in the southwestern part of the province. A host of other nonstructural industrial minerals are known. Production, though, is currently restricted to calcite, gypsum, quartz, talc, nepheline syenite, and byproduct metallurgical sulfur products (Fig. 1). Major production is close to the large markets of urbanized southern Ontario and the northeastern and northcentral US. With an abundant variety of industrial mineral resources and the large population within 650 km (400 miles) of most deposits, the market offers great potential. Ontario's nine million people accounted for about 35% of Canada's entire $476.3 billion gross domestic product in 1985. This equates to about one-third of the nation's buying power being within a 200-km (125-mile) radius of Toronto. This major concentration of industrial and economic activity has resulted in a well-developed industrial minerals industry that fulfills most of the structural industrial minerals demand in Ontario. Nonstructural industrial minerals are similarly well placed to compete in this high demand area. Although Ontario manufacturers still import some of these materials, Ontario products are achieving significant market share. And, they serve the needs of neighboring provinces and states. Present production and trends Ontario has traditionally produced significant amounts of industrial minerals. This produc¬tion had a value of $956 million in 1984 (Table 1). Structural materials production in 1985 and 1986 approached or exceeded levels not seen since the early 1970s. Many new products have been developed using these raw materials. The industry is becoming concentrated in the hands of several large companies, mainly four large cement com-

Jan 12, 1987

By Stanislaw Wasilewski, Zdzislaw Krzystanek

Ventilation process in deep mines features relatively low efficiency. Commonly used passive control by means of regulators and flow throttling leads to remarkable energy losses that could be lower if effective monitoring and remote control of main fan operating point were implemented. In the paper, some results of investigation carried out in Polish coal mines to evaluate real energy losses in ventilation process are described. Different methods for main fans performance monitoring and control are considered and compared especially those using fan drive speed control to minimize power consumption. On the other hand some criteria for power evaluation are analysed and algorithms for optimum location of controllers in ventilation network are considered. The results of investigation are being implemented in the first system for monitoring and control of main fan operating point in Miechowice colliery.

Jan 1, 1995

By Ihsan Berk Tulu, Ted Klemetti, Deniz Tuncay

"The Analysis of Retreat Mining Pillar Stability (ARMPS) program was developed by the National Institute for Occupational Safety and Health (NIOSH) to help the U.S. coal mining industry to design safe retreat room and pillar panels. ARMPS calculates the magnitude of the in-situ and mining-induced loads by using geometrical computations and empirical rules. In particular, the program uses the “abutment angle” concept in calculating the magnitude of the abutment load on pillars adjacent to a gob.In this paper, stress measurements from U.S. and Australian mines with different overburden geologies with varying hard rock percentages were back analyzed. The results of the analyses indicated that for depths less than 650 ft, the ARMPS empirical derivation of a 21° abutment angle was supported by the case histories; however, at depths greater than 650 ft, the abutment angle was found to be significantly less than 21°. In this paper, a new equation employing the panel width to overburden depth ratio is constructed for the calculation of accurate abutment angles for deeper mining cases.The new abutment angle equation was tested using both ARMPS2010 and LaModel for the entire case history database of ARMPS2010. The new abutment angle equation to estimate the magnitude of the mining-induced loads used together with the LaModel program was found to give good classification accuracies compared to ARMPS2010 for deep cover cases.INTRODUCTIONIn the early 1990s, the Analysis of Longwall Pillar Stability (ALPS) was introduced by Mark (1990) as a chain pillar design software and was generally accepted and used by the U.S. coal mining industry. Following the success of ALPS, the National Institute for Occupational Safety and Health (NIOSH) developed the Analysis of Retreat Mining Pillar Stability (ARMPS) program for designing retreat mining pillars using a similar approach as ALPS (Mark and Chase, 1997). The Australian mining industry also recognized the success of ALPS, and Colwell, Frith, and Mark (1999) calibrated the program to Australian conditions. The ALPS and ARMPS programs draw their strengths from the large databases that are used to calibrate them (Mark, 2009). However, following the Crandall Canyon Mine collapse in 2007, NIOSH had to reconsider the pillar design criteria used in deep-cover retreat mining (Mark, 2010). The ARMPS overburden load prediction algorithm was improved to more accurately predict the loading of narrow panels with high overburden depths by implementing the pressure arch concept, and this new version is called ARMPS2010."

Jan 1, 2019

By H. Rush Spedden

A process has been developed and piloted to reject copper, lead, iron, phosphorus, bismuth, antimony, elemental sulfur, and insol from molybdenite concentrate without decomposing the contained molybdenite and rhenium. The impure concentrate is first heated with concentrated sulfuric acid at 260 to 290°C for 1 hour. This bake not only oxidizes the contaminating sulfides, but also activates the concentrate for later rejection of insol by flotation. Two stages of leaching follow the sulfation step. The first is an acidified water leach which extracts the oxidized copper, iron, and phosphorous; the second leach rejects the lead, bismuth, and antimony into a warm concentrated solution of sodium chloride. Final upgrading is achieved by conventional froth flotation. The chemistry of the process as well as results obtained from its implementation in a 5,000 lb/day pilot plant are presented.

Jan 1, 1971

By Luke Erickson

San Francisco Public Utilities Commission is planning to replace 5 miles of pipeline under San Francisco Bay. The tunnel will be constructed using an Earth Pressure Balance (EPB) TBM and will be the first TBM-driven tunnel under the Bay. The alignment passes under environmentally sensitive habitats, through interbedded layers of sands and clays, and through a buried bedrock ridge. This paper discusses the geotechnical characterization and anticipated tunneling conditions and presents the analysis of various construction methods that resulted in the selection of an EPB TBM. Considerations related to tunneling with an EPB TBM are described in detail, including ground conditioners, TBM cutterhead wear, muck control, and squeezing ground.

Jan 1, 2008

By Gerald M. Ellis

ntroduction As the gold mining industry continues to develop in the Dominican Republic and Haiti, more deposits will undoubtedly be discovered that will be amenable to development. The Pueblo Viejo gold mine is currently in operation in the Dominican Republic. It has become an important component of that country's economy. Pueblo Viejo output is important to the government as a foreign currency earner. It is also said to be among the world's more successful gold mines. But, while Pueblo Viejo is successful, no other major gold discoveries have been made in recent years. Therefore, alluvial deposits of gold have caught the attention of geologists on the Island of Hispaniola. In the past four years, exploration and investigation of alluvial deposits have been initiated in both the Dominican Republic and Haiti. This type of activity is expected to continue over the next few years. Alluvial gold mining is rudimentary gold washing, done mostly by farmers. It is an old tradition, dating back at least 100 years, and is done by small, independent, or community farming villages in the mountains and plains of the Dominican Republic. Investigations in the DR Recently, alluvial gold investigations have been undertaken in well known locations of the Dominican Republic. One is in the Villa Altagracia area. Here, the terraces and gravels of the Haina River basin were examined, test-pitted, and assayed by Minera Altagracia, a local Dominican mining group. Results led to a new investigation by the state-owned Rosario Dominicana (RD), the company that mines the gold at Pueblo Viejo. Rosario tested areas previously investigated by Minera Altagracia. RD could not define the type of concentration that could justify an industrial-scale type of exploitation. The Haina River placers are located in the flats and valleys of Central Dominican Republic. They are classified as small-scale type of operations where local cooperatives can do the traditional gold washing. It is not now considered a dredgable project for a mining company. The next alluvial gold investigation was undertaken by the Dominican Department of Mines and others in an area of some 700 km2 (270 sq miles) in the northeast near Miches. Farmers have been washing gold in streams and excavating pits in various areas, particularly La Mina and have made a living. Government geologists panned several hundred streams and river tributaries. They also washed material from deep excavations. The results, however, were negative insofar as locating alluvial gold concentrations suitable for large-scale or industrial-scale exploitation. The most favorable locations were the terraces along the Jayán and Cuarón Rivers in the area of Miches. But the grade od concentration is poor. Actually, only traces of gold were found in these

Jan 8, 1986

By Patrick M. James

Many in mining believe that the industry is slipping behind in public image, in public mineral education and, particularly, in mining's basic right to do business. It is critical to turn things around - to change the rules of the game soon - before mining loses any chance of recovery. In the industry's experience, there is a technique of project development and operation that can help gain ground on public opinion. Only recently has this technique had a name, and that is sustainable development. What is sustainable development? Sustainable development is broadly accepted and supported by the international business community. And significant thought and work has been devoted to the subject. Research into the topic was initially confusing because the definitions of sustainable development are written in terms the writer, and his or her constituency understands. To some, it refers to environmental protection. To others, it is about social responsibility. And to the developer, it is about economic benefit. Slowly a theme emerged from the research that seemed to be part of all the definitions. That theme has three parts. First, the development, whatever or wherever it is, must contribute economic value to the developer and the stakeholders of the development. Stakeholders in this context include employees, neighbors, residents of the surrounding area, citizens of the country, suppliers and all others affected by the development. Next, sustainable development must contribute environmental value. This means that at a very minimum it must be neutral and not cause irreparable damage. And last, and what is new for miners and most other businessmen, it must contribute real social value to the stakeholders. How to use the concept? With that three-part theme as a working definition, the mining industry must find ways to use that “the challenge is for an individual company to translate what sustainable development means for them. There is no one model..." Donald W. Gentry is president and chief executive officer of Polymet Mining and former professor emeritus of mining engineering at Colorado School of Mines. He added: "While simple to state, the concept is anything but simple to implement. Present trends indicate ... one wins the sustainable development argument by staking out the high ground early..." In other words, start using sustainable development principles at the beginning of the project. New ways of doing business The mining industry's challenge is to implement sus¬tainable development universally around the world. Paternalism as a way of doing business is dead and a new model of doing business is emerging. All types of businesses are learning to deal with the stakeholders of new developments. Mining cannot be an exception to these trends. To understand how the international mining business came to sustainable development, it is useful to look back a few years. For many North American mining engineers, there were few opportunities for foreign assignments from the 1960s to the 1980s. American companies had been asked to leave many of the Latin American countries. Africa was going through a continent-wide upheaval. The Soviet Union and China had Eastern Eu-

Jan 1, 2000

By Carson Sharp Beltch

The determination of aqueous cyanide is accomplished by either detection in the sample as collected or by removal of the cyanide of the collected sample, followed by detection. The direct determination of the cyanide content of a solution can only be used in the simplest of systems, since many interferences can result in errors. Thus the most widely used method for total cyanide determination involve the reflux distillation of the sample using heat, acid and vacuum or air flow. The basic theory underlying this analytical approach is that by reducing the pH, the quality of molecular hydrogen cyanide will be in- creased and can be removed from the solution by elevating the temperature. The hydrogen cyanide is then collected in a caustic solution and analyzed. The general approach of removing the cyanide from the sample by distillation represented a major advance in this area of analytical chemistry. It enabled the determination of cyanide in many additional types of samples. When it became apparent that the tightly bonded cyanide complexes were not being detected by this approach, many methods fox complex ion destruction were proposed. These methods usually involved low pH adjustment with oxidizing mineral acids, coupled with the catalytic decomposition of the tightly hound complexes. All off the complexes except the strongest could he broken by these methods. The catalytic reflux distillation step has been found to have some negative aspects, since many materials that can be distilled with hydrogen cyanide will interfere with the color development step and result in a false positive reading.

Jan 1, 1981

By Howard J. Handewith

Long used in mine development in England, Europe and Russia, roadheaders are growing in size, features, productivity and application. Beginning with the basics, this paper covers the economic and the technical aspects of the new roadheaders in both mine production and development. The author explains how to choose and integrate roadheaders into ongoing operations as another step in the inexorable march from labor to capital intensive mining. Innovations now on the drawing boards are covered that are the challenge of the future.

Jan 1, 1983

By K. A. Natarajan, Namita Deo

Strains of Bacillus polymyxa, preadapted and grown in the presence of corundum, were found to be capable of the efficient separation of hematite from alumina. Results of tests performed using binary hematite-corundum and ternary he- matite-quartz-corundum mixtures in the presence of cells and metabolic products separated from the adapted bacterial culture indicated that more than 99% of the hematite could be efficiently separated through selective flocculation after desliming. It was found that alumina-specific bioproteins and other nonproteinaceous compounds were secreted by bacterial cells after adaptation to the mineral. The utility of this bioprocessing is demonstrated in the removal of iron from bauxite ores through selective

Jan 1, 2000

By Jasinder S. Jaspal, Bradley J. Bourquin

Introduction Operation is underway at the Dutch Creek No. 1 mine of the first US longwall panel to be mined under the cooperative agreement between the US Bu¬reau of Mines and Mid-Continent Resources. The 244-m (800-ft) wide longwall face is part of a multilift longwall demonstration. A 3-m (10-ft) top slice is being extracted from the 8.5-m (28-ft) coal seam. This occurs in an area of the property where the Coal Basin A and Coal Basin B beds have come together to form one seam. This face, longest ever operated in the US, is being worked on an advancing longwall system. During the first months of its operation, this longwall face has been very productive and safe. Mid-Continent Resources operates two coal mines in the Coal Basin, located in the White River National Forest near Carbondale, CO. The Colorado Fuel and Iron Co. originally opened this property in 1895, and conducted a small mining operation for 10 years on the north rim of the basin and then abruptly shut down. Mid-Continent began operations in 1956, after the Coal Basin fields had lain idle for about 60 years. Operations commenced at the outcrop of the Coal Basin B bed situated at the 3-km (10,000-ft) elevation. At this time, coal was produced from Coal Basin A and Coal Basin B seams in the area. Since 1981, operations have been centralized at two mines, the Dutch Creek No. 1 and the Dutch Creek No. 2, both located in the center of the basin. Since 1981, Mid-Continent has shifted its emphasis to longwall mining as the primary method of production, and each of these mines is equipped with state-of-the-art longwalls using shields as the method of roof support. A 4-km (13,000-ft) long twin-bore rock tunnel is being driven at a lower elevation of 2.4 km (8,000 ft) to intersect the coal seams at depth, as they dip 12° in a westerly direction. This tunnel will enable the company to reduce costs by replacing trucks with conveyor belt haulage (Fig. 1). Mid-Continent began longwall operations in May 1976 with the US's first modern, mechanized advancing longwall face, using chocks. In August 1978, a second advancing longwall face was started. Results from two faces showed that the mining system could be used effectively to manage the difficult conditions encountered in both the Dutch Creek No. 1 and the L. S. Wood No. 3 mines. Unfortunately, low productivity and high costs plagued the company's advancing faces. The problems resulted principally from major equipment failures, poorly designed chocks and face conveyors, and the lack of an efficient, cost effective system for building packwalls. Flushing of rock between chocks and roof control were also major problems. In Sept. 1979, Mid-Continent and the US Bureau of Mines entered into a cooperative agreement to demonstrate the feasibility of mining thick coal seams using the multilift longwall mining method. Two lifts are to be used to mine the 8.5-m (28-ft) thick coal seam in Dutch Creek No. 1 mine. The Bureau provided mining equipment for 180 m (600 ft) of longwall face. This included the shields, face conveyor and drive units, shearing machines, panel belt, and stageloader. As a result of previous experience in advancing longwall mining, Mid-Continent purchased an additional 60 m (200 ft) of face, including roof supports and an additional face conveyor. Design The Dutch Creek No. 1 is a slope mine located on the flank of a plunging anticlinal structure that

Jan 1, 1984

By Andy B. Wallace

Veins in the Pyramid district of northwestern Nevada occur along steep fractures in Oligocene and Miocene quartz latite tuffs. The vein mineralization is zoned from a central enargite-pyrite zone outward through a complex polymetallic intermediate zone and an outer zone of galena and pyrite. Wall rock alteration includes advanced argillic and sericitic envelopes along veins superimposed on district-wide propylitization. The ore distribution and alteration patterns were probably produced by an increase in pH, a decrease in sulfur fugacity, along with cooling of the migrating hydrothermal fluid.

Jan 1, 1978

By W. R. Hibbard

Emerging from discussions of U.S. energy policy: from the Project Independence Blueprint; from President Ford's statements to Congress; and from several independent appraisals of the situation; there is a clear objective to achieve an appropriate balance of supply and demand in the near term future (1) by developing more efficient ways of using energy and (2) by extending domestic sources of energy. More specifically, the strategy for achieving this goal has three parts (1) Conservation of energy through greater efficiencies in automobiles, appliances, lighting, heating, and industrial processes. (2) Increased domestic production of oil and gas through new sources such as the outer continental shelf and new efficiencies such as tertiary recovery. (3) Substitution of coal and uranium for oil and gas in utility power plants and industrial heating. The goal of energy research and development is to help achieve these goals and to help minimize the economic, environmental and social impact of our shift from imported energy to domestic sources. The focus of this paper is the implications of the expanded use of coal, and the research and development which may help achieve the above goals in so far as coal is concerned.

Jan 1, 1975

By J. C. Cawley

Improvements in today's maintenance practices are mandatory as more complex and productive machines evolve in the mining industry. By keeping machine reliability high through improved maintenance procedures, overall mining costs can be reduced. The Bureau of Mines is investigating diagnostic maintenance systems for underground mining machinery. A hydraulic expert diagnostic system and an electric motor predictive diagnostic system have been designed and installed on a Joy 16CM continuous miner. An electrical diagnostic system has been designed and installed on a Joy 14CM continuous miner. Each system is functionally described and the relative merits of expert diagnostic systems versus algorithmic diagnostic systems are discussed.

Jan 1, 1992

Despite limited discussion, Chemistry of Flotation is a good text and reference 1985 by M. C. Fuerstenau, J. D. Miller, and M. C. Kuhn Society of Mining Engineers Caller No. D Littleton, CO 80127 Softcover, $23.50 (member), $18.50 (student member), $28.50 (list) Review by Richard R. Klimpel Chemistry in Flotation, as stated by the authors, is intended as a textbook for students as well as a reference book for practicing flotation engineers. It covers subject matter related to surface phenomena; collectors and collector salts; natural floatability; the flotation of sulfide minerals, insoluble oxide and silicate minerals, semisoluble salts, and soluble salts; and slime coatings. There are no discussions in the book on practical plant implications of flotation chemistry, such as the influence of rate, particle size effects, dosage, flotation equipment, and methods of chemical addition. The book itself is small (only 177 pages), and, as published, is in an easy-to-handle soft cover. Once one accepts the intent of the authors, this book really does represent a very concise and convenient summary of the chemistry of flotation. It is, however, far from complete in its discussion of concepts and implications of data. Very often in the presentation, key prior knowledge (or at least subject matter awareness) not given in the book, is assumed. Thus, depending on one's familiarity with the specific subject matter, some sections can be easily followed while others could be tough going. Some of the discussion is so brief and terse on important subjects that unless the reader already realizes the meaning of the presentation, the conclusions to be drawn are not always clear. Therefore, if one is not expecting a self-contained primer on flotation chemistry, this book is very useful. To this end, the book is recommended to practitioners of flotation chemistry. The presentation of data in figures and tables is good. It helps considerably in the book achieving its conciseness. The authors certainly are qualified and knowledgeable in the subject matter - apparent in the style of presentation. In summary, this reviewer thoroughly enjoyed this book and will use it as a concise review of flotation chemistry. Richard R. Klimpel, member SME, is a scientist with Dow Chemical Co., Discovery Development, 1776 Building, M. E. Pruitt Research Center, Midland, MI 48640. International Symposium on Blast Furnace Ironmaking, 1985, The Indian Institute of Metals, The Tata Iron and Steel Co., Ltd., Jamshedpur 831007, India, 282 pp., papercover, no price given - Papers from this symposium held in Jamshedpur, India, include the following: determination of coal and coke quality; feed to blast furnaces; burden quality and blast furnace performance; operation of blast furnaces on charcoal; review of cast house slag granulation systems; developments in blast furnace engineering and control; process improvements in blast furnace ironmaking; coal injection into the blast furnace; and coke from stamp charged coal. Advances in Materials Technology for the Process Industries, 1985, edited by H.A. Huskins, National Association of Corrosion Engineers, P.O. Box 218340, Houston, TX 77218, 273 pp., softcover, $20-This book is the proceedings of a meeting held in Atlanta, GA in October 1984. It describes innovations in metallurgy, ceramics, glass, composites, and polymeric materials that impact the integrity and economics of operating systems. It covers biotechnical developments, improvements in membrane systems, or beneficiation processes, as well as developments in electrochemical controls, testing procedures, and surveillance techniques. A Reference Guide to Mining Legislation in Canada, 1985, by B. Barton, B. Roulston, and N. Strantz, The Canadian Institute of Resources Law, Room 430, Bio Sciences Building, The University of Calgary, Calgary, Alberta, Canada T2N 1N4, 120 pp., bound, $US28- This guide provides a ready means of finding how the different jurisdictions in Canada regulate mineral activity. It covers the rights required for exploration, development, and production of mineral metallics and industrial minerals. It does not cover placer mining, petroleum and natural gas, bituminuous sands, coal, or structural materials. Dictionary of Geological Terms, 1985, edited by Robert L. Bates and Julia A. Jackson, The American Geological Institute, 4220 King St., Alexandria, VA 22302, papercover, $7.95 plus $1 for postage - This third edition is for geoscience students, teachers, and rockhounds. It defines the core vocabulary of earth sciences, contains 8000 revised definitions, and includes 1000 new terms. It adds recent terms in plate tectonics, hydrology, and permafrost studies. Accurate definitions are given without technical jargon, cross-references are included, and commonly used abbreviations are provided. Processing and Utilization of High Sulfur Coals, 1985, edited by Yosry A. Attia, Elsevier Science Publishing Co. Inc., 52 Vanderbilt Ave., New York, NY 10017, 787 pp., bound, $142.50-These proceedings comprise the majority of the papers presented at the First International conference. Investigators there reported the latest discoveries, developments in commercial practice, and state-of-the-art reviews of scientific principles and applications of various technologies for handling, processing, and use of high sulfur coals. Sessions were held on: characterization of sulfur in coals; environmental problems and impact of high sulfur on coal use; selective mining and blending; coal desulfurization by physical and chemical cleaning techniques; handling of coal fines; sulfur capture during coal combustion; biological desulfurization of coal; and new applications for high sulfur coal. The Economics of Magnesium Metal, 1985, Roskill Information Services Ltd., 2 Clapham Road, London SW9 OJA England, 129 pp., 71 tables, appendices, bound, $750-Despite setbacks in some major magnesium markets in 1985, Roskill's latest forecast for the last half of this decade is for a 4% to 6% annual growth rate in demand. Growth for magnesium metal is expected in the motor industry for use as a possible substitute for aluminum. Some magnesium producers are altering their marketing strategies to cultivate this market. This study also includes a review of the worldwide magnesium industry, its end uses and consumption, and international trade and price trends.

Jan 7, 1986

By C. Flores, R. Y. Wan, M. C. Fuerstenau, T. S. Jordan

Most oxidized manganiferous silver ores contain manganese associated with silver and are not amenable to conventional silver extraction methods, including direct standard cyanidation techniques. However, it is known that dissolution of the manganese might yield a suitable material from which silver can be recovered by conventional methods. In the segregation process, which involves heating the ore with a small quantity of salt and with a source of reducing agent to 680°C - 800°C, the silver is volatilized, migrates and is reduced to metallic silver particles. Conventional cyanide leaching is applied to the resulting calcine. Laboratory investigations have been conducted on a manganiferous silver ore analyzing 0.02 % Cu, 0.09 % Pb, 0.33 % Zn, 12.55 % Mn and 187 g/ton Ag to study the influence of roasting temperature and time, quantity of salt and quantity of coke on silver extraction by the application of segregation roasting followed by cyanidation. Cyanide leaching tests were carried out at room temperature on the segregated calcines produced by using an alkaline cyanide solution containing 2.0 lb/ton of NaCN at pH 11 for 72 hours. The results indicated that 97.8 % of silver extraction can be attained at 850°C, with 2.0 % salt, 1.0 % Coke and 30 minutes of roasting time.

Jan 1, 1993

By C. Patrick, T. Combs

The purpose of this paper is to provide a method for analyzing the sequencing of mining production processes and predicting the effects of any planned changes. Included is a description of the development and utilization of a project-scheduling simulation that combines analytical scheduling with stochastic-activity durations. The simulation is demonstrated in two realistic examples: a longwall face-to-face transfer sequence and the effect of varying advance rates on longwall development sections. Statistical data that can provide a basis for more informed production decisions are generated in the form of project activity/path criticality and project-duration distributions. In both examples, a quantitative risk assessment, regarding subjective decisions in underground production sequencing, is presented.

Jan 1, 1996