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By John C. Brower

Bolivia is nor a major gold producer but has produced continuously since pre Inca times. Production reached a peak in 1964 of about 4,000,000 grams and is currently about 1,000,000 grams. Production is mainly from the Tipuani River valley north of La Paz and is derived from Pleistocene basin fill: the Cangalli conglomerate and overlying terraces. Abandoned Pleistocene lake terraces south of La Paz in the Oruro area are another source of gold whose potential have not been realized. In both the Tipuani and Oruro areas, primitive hand methods are the principal means of production, with the exception of a single modern dredge. In spite of a long history of production, probably very little of the gold potential has been mined.

Jan 1, 1979

By K. Chandrasekaran

Carbon-in-leach (CIL) is conventionally used in gold processing operations when preg robbing components are present in the ore. The CIL process is becoming attractive even in other situations when preg robbing is not a factor. This article discusses the situations in which the CIL circuit can be applied. The results of leach-carbon-in-pulp (CIP) and CIL circuits at Newmont Gold's Mill No. 2, No. 4 and No. 5 are presented for comparison: Mill No. 4 was initially designed for a throughput of 4.1 kt/d (4500 stpd). It is presently operating at an average throughput of 6.6 kt/d (7300 stpd) without significant changes to the original design. The design considerations of the Mill No. 4 CIL circuit are discussed. The design of any processing facility represents a series of decisions. The final design options should ultimately be resolved based on economic as well as technical considerations. Every design decision represents some sort of compromise. From the designer's view point, these decisions are made with the conviction that the final product represents the most prudent long-term expenditure. The design throughput rate is a decision reflecting a maximum return for the capital and operating costs that the plant will incur over the life of the mineral resource. The result is a plant that is not operator proof or maintenance free because it would be too costly to build. At some point, the incremental increase in the level of capital expenditure would not adequately compensate for the lower

Jan 1, 1991

By Jon A. Hummer, Aleksandar D. Bugarski, Shawn Vanderslice, Teresa Barone

A study was conducted to examine the potential of diesel emissions control strategies based on retrofitting existing power packages with exhaust aftertreatment devices and repowering with advanced power packages. The retrofit systems, a diesel oxidation catalyst (DOC) and diesel particulate filter (DPF), were evaluated individually using a US EPA tier 2 (ter 2) engine operated under four steady-state conditions and one transient cycle. The DOC effectively curtailed emissions of CO, and to some extent organic carbon (OC), elemental carbon (EC), and aerosol number concentration. The DPF system offered substantially higher reductions in OC and EC mass and aerosol number concentrations. Both, the DOC and DPF achieved reductions in the aforementioned emissions without adversely affecting emissions of NO2 and nano-sized aerosols. The strategy of repowering with an advanced system was examined using a US EPA tier 4 final (tier 4f) engine equipped with a cooled exhaust gas recirculation system and diesel exhaust fluid-based selective catalytic reduction system, but not with a DPF system. The tier 4f engine contributed substantially less than the tier 2 engine to the EC and OC mass, aerosol number, and CO, NO, and NO2 concentrations. The tier 4f engine was very effective in reducing aerosol mass, NO, and NO2 concentrations, but it was not equally effective in reducing aerosol number concentrations. The implementation of viable exhaust after treatment systems and advanced diesel power packages could be instrumental to the underground mining industry to secure a clean, economical, and dependable source of power for mobile equipment.

By John A. Brooks

The description of a phosphate flotation operation is repeat information for many people, except for variations in flow sheets. This paper is written to show the variations in flows, and to give enough. of the overall flows to allow anyone not familiar with the operation to be able to formulate a fair idea of the operations.

Jan 1, 1962

By Alten F. Grandt

Surface mining consists of the removal of the geologic strata overlying the coal seam usually with large electric shovels, draglines or bucket wheels. The method produces more or less parallel ridges or peaks of cast overburden, usually called "spoil banks". The mined lands vary widely in their inherent characteristics to produce a vegetative cover and thus can be put to a wide variety of uses. Use is the key to economic and social benefits. Physical and Chemical Characteristics of Soil Material of Surface Mined Lands after surface mining operations, the soil material is a heterogeneous mass whose physical and chemical properties are dominated by the character of the geologic strata overlying the coal. These strata are highly variable in thickness and character. They may include the surface soil, loess, glacial till, sands, shales, slates, limestone and sandstone rock. The method of mining with the several types of mining equipment will also affect the resultant mined area.

Jan 1, 1968

By Ray E. Harris

New developments have occurred in Wyoming's industrial minerals industry since the 32nd Forum on the Geology of Industrial Minerals in Laramie, Wyoming in 1996. The soda ash trona and bentonite industries have experienced overall growth. Gypsum and limestone production have remained constant, but have the potential for dramatic growth. The mining of zeolite ceased in 1997. The struggling dimension stone industry has increased production, but development has lagged behind the schedule predicted in 1996. The construction of a container glass plant and associated production of glass raw materials, as predicted in 1996 and imminent in 1998, is now on hold due to unforeseen market factors. Increases in railroad and highway construction have, and will, greatly increase the production of construction aggregate for local uses. An iron carbide industry, not foreseen in 1996, is in the planning stages.

Jan 1, 2001

By Richard A. Thomas, Liming Yuan, Lihong Zhou, James H. Rowland

Hydrogen (H2) gas released during battery charging can result in cross-interference for carbon monoxide (CO) sensors used for early fire detection and compromise the integrity of the mine atmospheric monitoring system (AMS). In this study, a series of laboratory-scale and full-scale experiments were conducted to evaluate the responses of different CO sensors to H2 gas. In the laboratory-scale experiments, constant H2 concentrations in the airflow, from 100 to 500 ppm, pass through sensors. While in the full-scale experiments, increasing H2 concentrations generated as a byproduct from charging the batteries at the battery charging station rise to the sensors under different ventilation scenarios. The H2 concentrations at the CO sensor location were measured using H2 sensors and were correlated with the CO sensor response. The effects of ventilation and sensor location on the CO sensors responses were also analyzed. The results of this study can help mining companies to select appropriate CO sensors and improve the deployment of these sensors to ensure the safeguard of underground miners.

By H. M. Woodrooffe

In the U.S.S.R. three of the world's major-known phosphate deposits are located. These have an estimated reserve of 2,600 million short tons of contained phosphorus. The best known lies in the "Khibiny Massif', an alkalaic rock formation some 600 square miles in area with mountain peaks rising to an altitude of 3300 ft above the surrounding terrain. Location and Climate The Khibiny Massif lies north of the Arctic Circle in the Kola Penin-sula, 100 miles south southeast of Murmansk, at a latitude of 67° 30' north and a longitude of 35° 30' east. It is serviced by rail from Murmansk and Leningrad (900 rail miles south). Figure 1. The phosphate operations are centered about the two cities of Apatity and Kirovsk. The former has a population of 35,000 and is on the Leningrad¬Murmansk railway. Kirovsk, 15 miles to the east, is now a city of 85,000. The region is at the limit of the tree line with most of the ground cover typical tundra. The mean annual temperature is -4°C and, in a normal year, precipitation occurs on 240 days. Because the temperature does not exceed freezing for 300 days each year, virtually all of the precipitation is snow. The two towns are nestled between mountains and, because of the weather, extensive avalanche control systems incorporating major engineering construction have been introduced to divert snow slides away from the populated areas. General Kirovsk was first settled in 1923 and the apatite occurrences were recognized shortly after. In 1933, the first concentrator for the recovery of the mineral was completed, producing in its first year of operation 170,000 tons of concentrate. With the growth and demand for phosphate in the U.S.S.R., a second concentrator was erected at Apatity. It calve on stream in 1963. Because of the severe climate, in the early days mining was limited to 85 days per year. With the introduction of new techniques and improved mining methods, the season has been extended to 115 days.

Jan 1, 1972

By Yi Zheng

Under normal circumstances, methane released along a longwall face represents only 10%-20% of the total me- thane emitted from the entire longwall panel. However, there might be a sudden surge of methane at the face which may cause a potential problem because the friction from shearer cutting, support movement, and scraper conveyor dragging can be ready ignition sources. Therefore, to predict the distribution of methane will be critical to prevent possible explosions. In this paper, methane dispersion patterns along a lognwall face are simulated under normal and abnormal conditions. With the simulation of methane released from the face, around shearer drum, and from the broken coal on the conveyor, places with possible high methane content can be identified by different phases of working process and shearer positions. Local ventilation measures are evaluated so precautionary measures can be planned ahead.

Jan 1, 2012

Compagnie Minière Espérance mines a primary gold orebody in an openpit. The ore is processed through crushing, primary gravity concentration, grinding and secondary gravity separation, generating tailings with remaining fine gold. Analysis of the material in the pond has indicated a residual gold grade sufficient to justify a chemical treatment process to recover the gold. However, direct cyanidation would require a prohibitively large installation for the site, which is located in a remote rainforest environment. It was decided to test the feasibility of preconcentration using flotation. As lab tests proved up the technical feasibility of the flotation process, an on-site pilot operation was carried out to assess the continuous circuit performances, define the best configuration and obtain enough data for industrial circuit sizing. Data collected during the pilot campaign was used for calibrating a process simulator built with the USIM? PAC software. The simulator validated the feasibility of upgrading the existing plant, including the reprocessing of tailings to obtain an acceptable fine gold recovery from a small amount of concentrate.

Jan 1, 2010

By Peter Werner

Technological advances in mine equipment and milling processes have enabled mining companies to exploit ever lower grades of ore. The result has been larger disturbances, greater volumes of waste, a complex web of infrastructure, and an overall trend toward mega projects that can extend over several square kilometers. This explosive growth in a mining operation’s disturbance footprint provokes an obvious question: What is it going to cost to reclaim all of this? At face value, this can be an enormous financial liability for a company, but since the timing of reclamation may be years in the future for many operations, these costs can be heavily discounted, thereby limiting the burden on the corporate balance sheet. Nonetheless, mining companies are eager to remove these liabilities as quickly as possible; conversely, regulators want assurance reclamation will, in fact, occur. How might one bridge these competing interests? Navigating the practical and financial requirements of a post-closure landscape requires foresight, judgement and assumptions; however, companies that do not adequately plan for these future expenditures when there is no offsetting income stream will likely face some difficult decisions. Simple risk analysis tools and utilizing the time value of money can help bring some clarity to this end-of-mine life phase.

Dec 1, 2025

By Rex T. Ellington

The fluidized bed is an effective method for investigating retorting phenomena and possibly a commercial means of retorting oil shale. Both were examined by Sinclair Oil Corp. (now part of Atlantic Richfield Co.) in the period 1.965 to 1968. The results of the work show that presence of an oxidizing environment during retorting results in loss of oil yield which indicates that vapor phase oil burns in preference to combustion of coke on spent shale. This has implications for several types of retorts. Correlation of the results of this work with that of other investigators shows that the partial pressure of retorting products in contact with oil shale during retorting has an effect on yield. Consideration of hardware indicates that there are several possibilities for commercial embodiment. As a companion to shaft-type retorts the fluidized bed could have good potential. Realistic assessment of costs suggests that further development may have to await commercialization of another process. The existence of a plant in which to test prototype size would markedly reduce such development costs. Results Preliminary development work with the apparatus was carried out using a fluidized bed of sand, as explained later, with the entire system brought up to temperature and flows stabilized. The shale was injected rapidly in a slug (batch) which had small mass compared to that of the high temperature system to make the reaction approach isothermality with reasonable approximation of instantaneous preheating. Typically, the temperature in the center of the bed dropped from 900°F to 600°F one minute after batch addition. It returned to 750' within three minutes and 900° within seven minutes. Obviously, the bed was quenched but it recovered rapidly. Average bed temperatures of 700' to 1020°F were examined to compare the effect of temperature with published results. Yields In the 700°F range were only 10 to 15%, of Fischer Assay (FA). Above about 950'F, oil yields decreased and gas yields increased. Nitrogen was used first as the fluidizing gas to provide a chemically inert medium. Incept for an insignificant dip at 895"F, Figure 1, oil yield was not affected by retorting temperature in the 800° to 900' range as long as residence time was adequate (16 minutes). At 925°F, the oil yield was some 103% FA. With further increase in temperature, the yield decreased to 86% FA at 1015°F. There is no increase in carbon on spent shale, the lost oil goes to Increased gas make.

Jan 1, 1972

By M. P. Meehan

The purpose of this paper is to present the key elements in a system; study of the electrical system for a timing and/or tilling operation. The ability of an electrical system to function in a reliable fashion at its proper levels is essential for an operation to be successful. A system study consists of a load study for determining the capability of the electrical network to provide power to the various loads and a short circuit study for determining the capability of the electrical protective equipment to properly protect against fault conditions. The sequence of events in a system study is data acquisition, determining the electrical parameters and analyzing the ability of the system to meet these requirements. If the system is small, herd calculations will be the manner in which the study will be conducted; if it is large then commuters will be used. A load study has as its objectives the determination of the capability and reliability of the source of power, transformers and conductors to satisfactorily deliver power to the loads at an acceptable voltage level. The Information required is a single line diagram showing the source, transformers, conductors and loads.

Jan 1, 1980

By Toru Nakao

Fujiwara Quarry had been operated by the "Glory-hole Benchcut" mining system. But because it became difficult to meet the expanding demand by this system, "Central- shaft MCP" mining system was introduced in 1979. This MCP is equipped with a hydraulic walking system manufactured for the first time in Japan. Nowadays "Central-shaft" mining is the common method at limestone quarry in Japan. In this method crushing facilities are usually installed at the bottom of the shaft. But at this quarry, MCP was adopted and installed on the quarry surface. Many MCPs are operated in foreign countries, but in Japan few examples exist. Normally, Japanese limestone deposits lie in high mountains, which is obviously inconvenient for MCP to walk in and around the quarry. This difficulty, however, was overcome at this quarry, and MCP has been operated satisfactorily and efficiently for about 2 years after it was installed. In order to overcome the difficulty, in "Cen¬tral-shaft MCP" mining system, two mining methods are employed, the one is "SLICE-DOWN" mining method, and the other is "BLOCK-CUT" mining method.

Jan 1, 1982

By Danny W. Hagood

High methane liberation and mining depth were two major factors which prompted the development of a high- capacity face ventilation system at Jim Walter Re- sources, Inc., No. 4 Mine. No. 4 Mine, one of four deep shaft mines presently under development, is located approximately 50 miles southwest of Birmingham, near Brookwood, Alabama (Figure 1). The coal seams under development are located in the Warrior Coal Field and include both the Blue Creek and Mary Lee Seams, Depth of cover averages 2000 ft. (610 m) with an average total mining height of 8 ft. C2.4 m). [ ] It is generally accepted that the methane content of a particular coal increases as the overburden depth is increased [l] ; experience to date has shown that the gas condition of the No. 4 Mine is no exception to the rule. To further compound the problem, the over- burden depth, coupled with the relatively soft nature of the Blue Creek coal, has resulted in an initial layout based upon 150 x 150 ft (45.7 x 45.7 m) centers. Considering the above-mentioned mining conditions, the means and the effectiveness of the face ventilation system becomes paramount where productivity is concerned.

Jan 1, 1980

By W. L. Price

The intelligent selection of wire cloth and perforated plate for screening surfaces seems a rather confusing subject to the newcomer in aggregate processing. The proper application of various screening surfaces is a complicated one and one could consider himself an expert only after many years of working with all applications. However, part of the subject matter could be simplified considerably for, the average screen user. In this paper an attempt will be made to do this, by presenting some comparative specification data along with cost figures Unfortunately, it is impossible in the limited scope of this paper to give actual service comparison records between different cloths or cloth and plate. Anyone who has considered making actual service comparisons for competing screening media is well aware of the almost insurmountable problems Their solution would form the basis for a separate paper on that subject alone. Therefore, this paper will be limited to comparative data up to the point of installation.

Jan 1, 1961

By J. H. Rowland, R. A. Thomas, III, C. D. Litton

Atmospheric monitoring systems (AMS) are required when using air from conveyor belt entries to ventilate working sections in U.S. underground coal mines. AMS technology has the potential to increase fire safety mine-wide, but research is needed to determine the detection and response times for fires of a variety of combustible materials. To evaluate the potential of an AMS for fire detection in other areas of a coal mine, a series of full-scale fire experiments were conducted to determine detection and response times from fires of different combustible materials that are found in U.S. underground coal mines, including high- and low-volatility coals, conveyor belts, brattice materials, different types of wood, diesel fuel, and a foam sealant. These experiments were conducted in the Safety Research Coal Mine (SRCM) of the U.S. National Institute for Occupational Safety and Health (NIOSH) located in Pittsburgh, PA, using a commercially available AMS that is typical of current technology. The results showed that through proper selection of sensors and their locations, a mine-wide AMS can provide sufficient early fire warning times and improve the health and safety of miners.

Jan 1, 2016

By Charles E. Mongan

The problem of roof control in the coal-mining industry is of major importance inasmuch as 65 percent of all coal-mine fatalities result from falls of roof, face, or ribs. The Health and Safety Research and Testing Center of the Federal Bureau of Mines at Pittsburgh, Pa., is engaged in several programs directed toward increasing safety in coal mining. The Roof Control Research Group has 4 programs aimed at reducing roof fall accidents. One of these programs is the use of sonic techniques to explore mine roof strata.

Jan 1, 1961

By L. R. Duncan, W. H. McCracken

Magnesium is the eighth most abundant element in the earth's crust and the third most plentiful element in seawater. It is found in more than sixty minerals and in brines and seawater as a magnesium salt. One of the more important magnesium minerals is magnesium carbonate, MgCO3, with a theoretical maximum magnesia, MgO, content of 47.6%; this carbonate form represents the world's largest source of magnesia. The next most used sources for magnesia are magnesia-rich brines and seawater, where it occurs as magnesium sulfate and magnesium chloride. Other commercially important magnesium-bearing minerals are dolomite, CaMg(CO3)2, which serves the aggregate industry as well as the chemical industry; brucite, Mg(OH)2, which is used in the production of both caustic and sintered magnesia; olivine, ([MgFe]2-SiO2), which serves the refractory and heat storage industries; talc, (H2Mg3(SiO3)4), which serves several industries as a filler and as an ingredient in cosmetics; and serpentine, (H4Mg3SiO9). All these minerals are of commercial value because of the desirable characteristics given to them by magnesia and by its placement in the crystal structure. These minerals are the starting raw materials for a wide range of products. These include the production of magnesium metal, and several grades of magnesia used for the production of both sintered magnesia for refractory manufacture and lighter fired caustic magnesia, the latter is used in fluxes, fillers, insulation, cements, decolorants, fertilizers, chemicals, in the treatment of waste water including pH control, and in the removal of sulfur compounds from exhaust stacks. Magnesite is one of several major minerals possessing a dual character, i.e., non-metallic industrial mineral because of its principal end use as a calcined/dead burned raw material in non-metallic end products and magnesium metal. A large percentage of the magnesia used to produce magnesium metal comes from seawater1 brines. The total primary metal production worldwide is about 350 ktpy. This report reviews magnesite solely as an industrial non- metallic raw material. Magnesite for most refractory purposes must have a content of sintered magnesia above 85%, with a preference for those sources that have the potential for 90 to 98% magnesia values. Dolomite, used in large tonnages because of its physical properties in the construction industry, also has a use in the chemical and the refractory industry. In its calcined form, dolomite is used as a slag addition in the making of steel, and it is used in a high-purity calcine to precipitate magnesium hydroxide from brines or seawater. The precipitated magnesium hydroxide is intermediate for the production of deadburned clinker for refractories and the production of magnesium metal. In many cases the high-purity magnesium hydroxide obtained by precipitation with calcined dolomite, or in some cases limestone, has supplanted much of the world's production of magnesia from the natural mineral magnesite. This is especially true of the United States and in major industrialized areas of Europe and Japan. The best known of the minerals directly and widely exploited for its magnesia content is magnesite (MgCO3), one of the calcite group of rhombohedra1 carbonates, which includes calcite (CaCO3), siderite (Fe2CO3), and rhodocrosite (MnCO3), among others. The members of this group enter into a wide range of substitutional solid solutions when the positive ions have similar radii. The radii of magnesium and iron ions are within 6% of each other; hence magnesite and siderite form a complete series, of which the mineral breunnerite (ferroan magnesite) is a well known end member. The radii of calcium ion is 36% larger than that of magnesium ion and only limited substitution exists at each end of the MgC03-CaCO3 series. Dolomite is not a member of the calcite group, but it occurs when calcium and magnesium ions alternate in equal number in an ordered structure among carbonate ions. The result of this relationship is that calcite and dolomite are commonly found intermixed with magnesite. They occur, commonly, as identifiable crystal entities, which can be separated to a varying degree from the magnesite by benefication techniques. Magnesite, when pure, contains 47.8% MgO and 52.2% CO,. The pure mineral is found occasionally as transparent crystals resembling calcite. Magnesite principally contains variable amounts of the carbonates, oxides, and the silicates of iron, calcium, manganese, and aluminum. Although the genesis of natural magnesite deposits can be complex, it is distinguished in nature in two distinct physical forms, namely crystalline, (with a wide range of visible crystal sizes) and cryptocrystalline, sometimes referred to as amorphous, where the crystal size is not detectable to the eye and will range from 1 to 10 pm. The two types not only differ in crystal structure but in the sizes of the deposits and in modes of formations. The crystalline form has a Mohs hardness of 3.5 to 4.0. The color range is from white to black with shades of yellow, blue, red, or gray. The color is not a significant indicator of purity but in a given deposit an experienced person can often roughly grade the magnesite by observing color and crystallinity. Macrocrystalline deposits occur in relatively few, but generally large, deposits on the order of several million tons. The ore shows a marble-like crystal structure and belongs to the sedimentary or metasomatic groups of origin. The cryptocrystalline variety of magnesite frequently occurs in many small deposits, although there are exceptions. Cryptocrystalline magnesite is typically massive with no cleavage and is sometimes descriptively called bone magnesite. The fracture is usually conchoidal, with a hardness of 3.5 to 5.0. The color is mainly white, but it can have tints of yellow, orange, or buff. Accessory silaceous minerals such as serpentine, quartz, or chalcedony are usually present. Calcium minerals are normally absent or in low concentration, this contrasting with the macrocrystalline form where calcium minerals are almost invariably present and some- times in high concentration. The specific gravity of cryptocrystalline magnesite ranges between 2.90 and 3.00, whereas the value of pure crystalline magnesite is 3.02. In actuality, the normal specific

Jan 1, 1994

By Ron F. Schritt

Over the many years since the development of the steam powered shovel, various powering and control techniques have been employed for the various shovel functions. While volumes have been published on this subject, this paper will be limited to a very brief discus-sion of one of the latest of these and its application to a unique machine. The evaluation of the subject machine is far beyond the scope of this discussion, which will be limited to the techniques and equipment employed, and the considerations involved in their choice. The basic requirements for any power and associated control system for any power shovel function have remained relatively un-changed over the years. To the extent possible, such an equipment grouping must be: Easy to install during fabrication Easy to maintain and repair by available personnel Life cycle cost competitive Adequately reliable Adequately responsive And as may be expected these factors are arranged in various orders of priority by different manufacturers and users. All the various time honored approaches have to some extent fulfilled these require-ments but were discarded or fell into disuse when more effective approaches were developed. The latest in this long line of develop-ments and perhaps the most promising is that of electro-hydraulic controls and hydraulic drive.

Jan 1, 1977