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By James W. Collins

The bucketwheel stacker/reclaimer is suited for a variety of bulk material handling systems, especially those operating with stockpiles in excess of 30,000 tons. The bucketwheel stacker/reclaimer, although relatively new in the United States (first introduced here in 1964), has been successfully used in European countries since the early 1940's. Basically the machine is the outgrowth of the bucketwheel earth excavator and the traveling tripper boom type stacker. Since their introduction here they have achieved wide acceptance, especially with coal fired power plants. (Figures 1, 2, and 3.) The stacker reclaimer has been utilized in barge and ship loading/unloading facilities, and in the material handling systems for steel mills, where it has been used to stack and reclaim iron ore at rates up to 6000 tph stacking and 4000 tph reclaiming. They have also been employed at mine mouth power plants for the handling and storing of the plant fuel supply and to help balance the mining rate with the fuel consumption rate.

Jan 1, 1973

By Simón Díaz‑Quezada, Ernesto Arancibia, HUMBERTO ESTAY, Tomás Vargas

In situ leaching (ISL) is an attractive technique that enables copper recovery from copper oxide ores that are either low-grade or located at depths too great to be economically exploited through conventional methods. At present, in situ leaching (ISL) has been applied to intact copper oxide ores, in particular, those which (i) present a good natural permeability and (ii) do not require preconditioning. Many copper oxide ores present low natural permeability. These are located above the water table and need preconditioning for the ISL application. The present work shows an economic assessment of the application of ISL to this type of copper ores. The preconditioning technique considered here involves the application of partial mining by sublevel stoping by removing a small fraction of the ore. This technique results in forming an ore bed with good permeability and good solution collection at the stope base. The economic assessment of this approach suggests that it can be implemented with positive net present values to copper oxide ores located at depths in the 100–300 m range, with copper grades above 0.4%. The maximum acid consumption values are below 52.5 kg/t, with blasting procedures designed to produce an ore bed with an average particle size below 6″. The breakdown of operational costs indicates that the mining cost is still very high, accounting for up to 60% of the total operating costs. Therefore, optimizing mining procedures is still necessary for improving the economic outlook of this approach and thus expanding the application field of ISL.

Feb 4, 2023

By John H. Lichtblau

There are three parties to the oil imports controversy: the domestic oil producers, whose side has just been ably summarized by Mr. Jameson; the oil importers; and the public. Domestic producers and importers are both motivated by economic self-interests, that is by their natural and legitimate desire for profit maximization, in their respective positions. Thus, domestic producers, rightly, regard every barrel of imported crude oil (with the exception of some specialty crudes) as a displacement of a barrel of their own crude. Hence, the lower the import Level the better they like it. Conversely, U .S. refiners whose plants are located at the seaboard or at certain inland waterways generally welcome a higher level of imports because refiner profits are based primarily on the spread between the crude oil price and the refined products price, since crude oil represents by far the refiner?s largest cost factor. The relatively low cost of foreign oil means therefore higher profits to those refiners able to process such oil, This applies particularly to integrated companies whose own domestic oil production is insufficient, to meet their refinery requirements but who have developed ample low-cost foreign oil supplies.

Jan 1, 1962

By Paul C. Miclea, Robert E. Murphy

The behavior of fire and airflows in a confined tunnel differ significantly from more familiar fire situations outside, due to the buoyant effect which tends to create a layer of hot smoke and gases flowing away from the fire near the crown of the tunnel, while air supporting combustion moves toward the fire beneath the smoke layer. A subway emergency ventilation system is designed to force air to flow through the tunnel, shifting the balance of heated air in the direction of the forced flow and avoiding the "back-layering" of hot gases and fumes. This paper presents a computer program, called the "Subway Environment Simulation" (SES), which can be used to predict airflows created by the emergency ventilation system. It utilizes the latest state-of-the-art analytical treatment of fires in enclosed spaces, including observations from mine fires and gas explosions. The program allows designers to reduce construction cost by identifying unnecessary ventilation shafts and by verifying fan capacities. In addition, the program allows the designers and operators to determine safe evacuation routes, in case of a train fire, by predicting the occurrence of back-layering. It can be used to determine when the ventilation system can control the direction of smoke movement to provide a clear and safe path for evacuating people and facilitate fire fighting operations.

Jan 1, 1989

By R. N. Chakravorty, R. J. Kolada

Introduction Spontaneous combustion in coal mining is recognized as a major hazard in terms of safety and economics. A survey by Olaf (1979) revealed that 80% of coal mine fires were caused by spontaneous combustion. Modern mining methods demand a high capital investment. Closure of a working face may then result in a huge loss. Even a short production interruption can prove expensive. Spontaneous combustion may also produce lethal amounts of carbon monoxide, thus posing a serious threat to the health and safety of underground miners. The worldwide recession in the early 1980s resulted in a number of mine closures and production cutbacks. So large stockpiles at mine sites were common. Experience has shown that stockpile fires are difficult to extinguish. Critical factors influencing spontaneous combustion There is no simple method of predicting whether a particular mining method applied to a specific coal seam will result in spontaneous combustion. Under favorable conditions of heat accumulation, spontaneous combustion can occur with any type of coal. It is known that subbituminous coals are more susceptible compared to low volatility bituminous coals, and that a high ratio of exinite increases the risk. However, the inherent moisture content of the coal and the exposed surface area may be more significant. Actual mining and ventilation conditions also strongly influence susceptibility. In practice, the experience gained with the mining method applied to a particular type of coal seam must be carefully evaluated with respect to the factors responsible for spontaneous combustion. Feng, Chakravorty, and Cochrane (1973) summarized the critical factors influencing spontaneous combustion in coal mines (Table 1). Prevention methods and strategies Mine layout is the most important factor preventing spontaneous heating. Working districts should be designed so that a particular section can be isolated on short notice without affecting production in others. Sites for preparatory seals should be identified and marked during planning. With coal seams that are highly susceptible to spontaneous combustion, the retreat method of working is preferred. This is because the gob is not subjected to a large difference in ventilation pressure. Coal pillars should be designed to resist excessive crush. The panel system of working is preferred, particularly for mining coals susceptible to spontaneous combustion. The size of each panel is calculated based on the incubation period and the rate of extraction. Controlling air leakage is also important for controlling spontaneous combustion. This is usually achieved by minimizing ventilation pressure difference, proper siting of doors, and avoiding unnecessary stopping and starting of fans. Air leakage is also reduced by sealant coating, injection of cements in cracks and crevices, and by maintaining good gateside packs. Application of inhibitors to control spontaneous combustion met with limited success. Chamberlain and Hall (1973) concluded that borate solution or Montan powder sprayed in the gob area or infused into a low rank coal would reduce the possibility of spontaneous combustion. Early detection of heating Significant research is being conducted worldwide to develop methods for early detection of heating. Monitoring combustion products during the early stage of heating is the most suitable method for detecting spontaneous combustion. The major gaseous products resulting from low temperature oxidation of coal are carbon dioxide, carbon monoxide, and water vapor. In mining operations, carbon dioxide monitoring is considered unsuitable because there are sources other than spontaneous heating from which this gas may originate. Carbon monoxide, however, is a more specific product of combustion during low temperature oxidation of coal. Over the years,

Jan 10, 1988

By M. J. Meulendyke

Within the mineral processing Industry. a range of grinding conditions exists which include semi-autogenous grinding (SAG), rod milling. and conventional ball milling. Each of these mill environments presents a unique environment for grinding media, requiring the application of specific physical and chemical properties for optimum grinding media performance. The environments are characterized by varying degrees and combinations of abrasive, corrosive, and impact wear. An extensive test program has been conducted to determine the extent wear rates vary between these different applications. Test results are related to production results, ball size, and mill operating conditions.

Jan 1, 1989

By C. C. Hatch

As part of a general project to simulate a concentrator, the Brenda Mines Limited secondary crushing plant, located near Peachland, B. C., was sampled during the summer and winter of 1975 to develop a digital crushing plant simulator specific to the Brenda operation. The purpose of this simulator was to study the influence of manipulable process variables on important responses and to permit study of alternative circuit configurations if desired. This paper describes the simulation methodology employed and presents the results of a computer study of the secondary crushing plant (1).

Jan 1, 1979

By Herman L. Bauer

The Robinson Mining District near Ely, Nevada, is one of the major porphyry copper districts in the world. Within the district is an east-trending zone of altered porphyry, metamorphosed sedimentary rocks, and sulphide mineralization surrounded by Paleozoic limestone, dolomite, shale and sandstone, Tertiary volcanics, and Quaternary alluvium. Six major disseminated ore deposits have been exploited in this eight-mile zone. About 20% of the district production has come from disseminated ore in metamorphosed sedimentary rocks found adjacent to altered quartz-monzonite porphyry. The following brief statements summarize the inter-relationship of porphyry, alteration, metamorphism, and mineralization: 1. Disseminated copper ore does not occur in unaltered porphyry or in unmetamorphosed sedimentary rocks 2. Sedimentary rocks have been only weakly metamorphosed where intruded, by unaltered porphyry. 3. Intensely metamorphosed sedimentary rocks are found only adjacent to, altered porphyry. 4. Many hydrothermal minerals are common to both altered porphyry and adjacent metamorphosed sediments. 5. Disseminated ore is found in altered porphyry and adjacent meta¬morphosed sedimentary rocks. 6. In general, there is a direct correlation between grade of ore in porphyry and copper content in the adjacent rocks. 7. Chemical changes in the altered porphyry facies and metamorphosed rock facies appear to be related:

Jan 1, 1963

By A. R. Wilde

The Muruntau gold deposit is situated in the Kyzyl Kum Desert of Uzbekistan. It is currently being mined in the world's largest open pit gold mine with production believed to be of the order of two million ounces per annum. The open pit measures about 3.5 by 2.5 km and extends to a depth of 350m. The gold ore resource in the Muruntau deposit, including production, is about 170 million ounces of gold (Anonymous, 1996). This paper presents a summary of the deposit geology and its regional geological setting. Information used in this paper has been generated from observations made on two visits to the mine and its environs, and a review of the Russian-and English-language literature.

Jan 1, 1999

By Klaus Grebe

Recent investigations by Mannesmann Research have shown that disintegration of sinter with widely varying quality levels is subject to a much more complex set of influences than was previously assumed. It was confirmed that disintegration at temperatures between 300 and 600 °C is triggered by the degradation of hematite. The specific tendency of hematite to disintegrate is, however, not constant: sinters containing the same amount of hematite can show widely differing disintegration tendencies depending upon structural homogeneity, porosity and gangue quantity. Especially sinters with heterogeneous structures transmit stress to the hematite phase and this favours disintegration. Another factor is the brittleness of the glassy silicate phase, which can be influenced even by small modifications of minor gangue constituents.

Jan 1, 1981

By Syd S. Peng, C. Y. Chen

Introduction The Surface Mining Control and Reclamation Act was passed in 1977 to put an end to the uneven environmental standards and enforcement established by various coal mining states in the US. One year after passage, the Secretary of Interior was directed to promulgate permanent program regulations implementing Title V provisions of the Act. These regulations were to form the basis for state regulatory programs under the Act and to allow states to assume primary regulatory responsibility. To implement the underground mining provision of the Act, the Secretary is directed in section 516(a) of the Act to promulgate rules. But they must take into consideration the differences between surface and underground coal mining. The regulations developed by the Secretary in 1979, with respect to subsidence control, included: • a subsidence control plan as part of the permitting process; • substantive provisions establishing performance standards for subsidence control; and • provisions providing for the prohibition of mining under perennial streams, impoundments larger than 24.6 dam3 (20 acre ft), and certain public facilities and urban areas. Industry challenged the Secretary's regulations implementing the subsidence control provisions. The litigation was consolidated with all other challenges to the permanent program regulations. (Permanent Surface Mining Regulation Litigation, Civil Action No. 79-1144; D. D.C., May 16, 1980.) In two opinions dealing with the multitude of issues raised by both industry and environmental groups, the US District Court of the District of Columbia ruled against industry. It upheld the promulgated subsidence control provisions. The US Court of Appeals stayed the appeals pending the agency's review and revision of its regulations. The regulatory reform was conducted in accordance with the order from the Secretary of Interior and the President in 1981. As a result, the subsidence control regulation was revised, reproposed, and finalized in June 1983 (Federal Register). This regulation, along with others, was again challenged by environmental groups and industry. On Oct. 1, 1984, the court, after finding the Secretary's reading of the Act reasonable, upheld the 1983 subsidence regulation except for one section. On Feb. 21, 1985, in accordance with the court's ruling, the Office of Surface Mining (OSM) suspended a portion of 30 CFR 817.121 (c)(2) concerning the damage correction requirement for structures or facilities and reproposed it on July 8, 1985 (Federal Register). In conjunction with a request for public comments, OSM now also seeks comments on the omission from the 1983 rule of the requirement in the 1979 rule regarding a presubsidence survey and monitoring of damage to structures. Technical issues related to subsidence regulations The subsidence regulations of June 1, 1983, consist mainly of two parts: a subsidence control plan as part of the permitting process; and substantive provisions establishing performance standards. The latter also includes provisions for prohibiting mining under certain areas. Under subsidence control plan section 784.20, minimum require-

Jan 2, 1986

By S. K. Kawatra, S. J. Ripke

Bentonite clay is used as a binder for iron ore concentrate pelletization. Bentonites are sensitive to cations such as calcium, magnesium, sodium, and potassium that are known to be dissolved in the moisture remaining in the iron ore concentrate. These cations affect the ability of bentonite to absorb water, as measured by the plate water absorbance (PWA) test. This paper addresses the relationships between plant water chemistry and pellet strength for a wide PWA range of bentonites. Experiments were conducted to determine the effect of concentrate moisture solute chemistry and bentonite PWA value on the wet knock and wet and dry compressive strengths of iron ore pellets. Experiments used seven different types of bentonite that had PWA values ranging from 564 to 1033. Flushing plant concentrate with distilled water to remove the dissolved cations resulted in increased pellet strengths, to a widely varying degree, for each bentonite tested; wet knock values increased an average of 92% and dry compressive strength increased an average of 46%. In addition, pellet strengths were not found to be directly related to the ability of bentonite to absorb distilled water, measured by the PWA test.

Jan 1, 2002

By Enrique Fernández

INTRODUCTION The high speed rail link between Madrid and Asturias, in the North of Spain, has encountered in the Cantabrian range the biggest challenge of the whole line, a very deep tunnel, 25 km long through a foreseen difficult geology. This tunnel was divided in the following four lots for construction: ¦Lot 1: Pola de Gordón- Folledo. L=10,7 km ¦Lot 2: Folledo-Viadangos. L=4,166 m ¦Lot 3: Viadangos- Los Pontones. East tube. L=10,4 km ¦Lot 4: Viadangos- Los Pontones. West tube. L=10,4 km. Dragados S.A. leading a JV was contracted to design and built the Lot 2 on the captioned Pajares High Speed Railway Tunnel. The Lot 2, comprising the middle third section of the 25 km long tunnel has an additional challenge: the construction of one access from the surface to allow it own construction. Feasibility reports and preliminary design do not foresee the use of TBM due to the risk of squeezing ground at the deepest area of the tunnel. On the other hand, conventional NATM excavation of the twin tunnels and ancillary works, including access shafts were against the expected construction schedule by the client, due to the poor ground foresee at the early stage.

By D. L. Passmore

The development of microcomputer software that provides an analysis of pit-specific accident and production data for the mining industry is seen as a vital component in a total loss-control system. The Mine Injury Reporting System (MIRS) allows users to access accident and production data prepared by the Health and Safety Technology Center of the Mine Safety and Health Administration of the United States Department of Labor for any particular state and to generate a simple, yet informative, report.

Jan 1, 1988

By William F. Brandom

INTRODUCTION Cross, et al. (1974), produced a retrospective study of standard setting for underground miners. This report had two distinct components; i) criteria of importance for the protection of the miners, and ii) economic considerations for standard setting. The methods for setting radiation safety standards reviewed were: dose calculations and consensus methods; epidemiology; pathology; bioassay; animal experiments; sputum cytology; chromosome aberrations; and, the Mantel-Bryan Model. By looking back, the authors intended to enable officials to look ahead in making future decisions based on reasonable conclusions. Now it may be time to consider underground miners' protection from another perspective: are there miners who may be especially susceptible to toxic environments?; and if so, are there any biomedical assays that might be indicative of exceptional sensitivities to toxic substances? The human population is genetically very heterogeneous. The data of Saccomanno, et al. (1973), reveal great variability in individual response to radon daughter exposure and only a small portion of the miner population subject to toxic inhalants develop squamous cell metaplasia (Saccomanno, et al., 1970). The majority of the miner population is either not susceptible or is resistant to the toxic agents. This information suggests the existence of a small subpopulation with increased sensitivity or reduced resistance and underscores the need for indicators from biomedical assays that might prove of value for the detection of such individuals. The heightened awareness of the contribution of pollutants in the environment for the potential induction of mutations and carcinogenesis lead to a profusion of short-term bioassays to circumvent the high cost and time-consuming large toxicity animal studies. Over 100 bioassays across taxa from microbes to man are at various stages of use or development (Hollstein, et al., 1979). Less than a dozen tests currently offer early promise for application to[ in vivo] effect studies of man. Many are still in early development, lack the sensitivity needed for a retrospective or prospective study at current permissible exposures, are impractical to conduct in the field, or are not cost effective. The purpose of this paper is to review some of the bioassays that may now, or in the near term, prove applicable for the detection of individual underground miners with increased susceptibility to toxic agents. Throughout this statement, it is assumed that any single test may give false negatives or false positives and, therefore, a tier of tests should be investigated. The possible tests are in various stages of development; some tests better proven than others with a firmer data base and, therefore, with greater probability of usefulness. Some of the less proven assays are not ruled out if they have practical or theoretical promise as indicators. Table I summarizes the assays critiqued for their potential to monitor the effects of [in vivo] exposure to genotoxic substances. POTENTIAL INDICATORS OF HIGHLY SENSITIVE MINERS Assays of Body Fluids It is desirable to have data on the agent(s) to which subjects are exposed when humans are monitored by biomedical effects. Obviously, to varying intensity, the underground mining environments are monitored for radon daughters and it is recognized that the miners are also exposed to other pollutants, most notably, uranium ore dust and diesel fumes. Further testing for the metabolites of the pollutants can be done on body fluid, urine. [High Performance Liquid Chromatography (HPLC)]: This is a very sensitive method for the detection of mutagenic metabolites in urine. The urine is treated with the enzyme sulfatase and beta-glucuronidase to permit identification of substances that are made nonmutagenic by conjugation as glucuronides. The sample is then passed through an XAD-2 resin column and the absorbed organic molecules eluted with acetone. The sample is then split and evaporated to 1 ml and used for direct chemical analysis using HPLC. One drawback to the test is the inability to measure cumulative exposure, but multiple samples can be obtained and comparison to baseline (control) and exposure samples can reveal qualitative differences as a consequence of exposure to mutagens. [The Ames/Salmonella Microbiological Assay]: The Ames/Salmonella microbiological mutagen test is the most extensively used short-term bioassay, with over 2,600 chemicals having undergone testing by this method (Hollstein, et al., 1979). The method, thoroughly worked out and tested for 10 years, consists of taking the second split urine sample from the HPLC preparation, evaporating to dryness and dissolving in dimethylsulfoxide (DMSO). The sample is then applied directly to

Jan 1, 1981

By Thomas S. Mackey

The industrial types, sources, and quantities of USA tin residues are identified and the methods of treatment reviewed. The effect of a lower tin price, due to a current major world surplus of tin metal, is mentioned and covered in some detail. The names and locations of over 100 USA firms recovering tin residues are listed. Current smelting and refining charges are included to convert the residues into tin metal and alloy. The impact of the suspension of the LME daily tin price since October 24, 1985 to date, and the failure of the International Tin Council to support the Buffer Stock Manager are reported with comments.

Jan 1, 1986

Impala Platinum?s No.16 Shaft mine is currently under construction and is expected to reach full production of 256 500 tons per month by 2014. Mining will start at 1 260 m below surface with a maximum mining depth of 1 535 m where virgin rock temperatures of 56.6°C will be experienced. As a result of depth, high virgin rock temperature and narrow reef mining, an expected total of 31.5 MW[R] of air cooling capacity will be required to achieve acceptable underground conditions. This will be achieved by cooling mine intake air in a single dedicated air cooling installation located on surface. The compact installation includes air cooling spray chamber, refrigeration machines, condenser cooling towers, evaporator and condenser water reticulation as well as all electrical and control systems. Construction and commissioning of the first phase of this air cooling installation has recently been completed on a turn-key contract basis.

Jan 1, 2009

By C. Babbitt, J. O’Green, N. I. Jayaraman

In many mines, dust-laden air from an entry being driven by a continuous miner will contaminate the intake air to the roof bolter operator and other downwind personnel. Through a US Bureau of Mines (USBM) contract, Foster-Miller Inc. has evaluated several control techniques to reduce the respirable dust exposures of downwind personnel. One fan and tubing technique consisted of bypassing the miner-generated dust directly to the section return. The results of the evaluation of this technique revealed that reductions in dust concentrations of 90% or more can be achieved at downwind roof bolter locations. A second method was to clean the dusty air from the upwind continuous miner by using a dust collector. The cleaned air was then supplied to the bolter through collapsible tubing. An underground evaluation showed reductions of 82% to 96% when the dust collector was operating. A third method was to reduce the quantity of dust contributed by the miner to the return airstream. A water-powered scrubber was installed over the throat area of the continuous miner. More than 1.18 m3/s (2500 cfm) of dusty air moved through five tubes with dust collection efficiency exceeding 75%. Underground evaluation results showed that return dust concentrations were reduced by about 60%. This paper discusses the ventilation and dust control techniques used for personnel downwind of the continuous miner.

Jan 1, 1987

By N. J. Keys

This paper concerns the development and application of a high throughput multi-stream photometric sorting machine developed for the South African gold mines. It is now believed that this sorter and its progeny may be found suitable for a large proportion of all possible sorting applications. A laser light source and sensitive photomultiplier are employed in a scanning system to detect light reflected from the surfaces of rocks passing through the sorting zone. Electronic circuitry then analyzes the photomultiplier signal, which represents the varying intensity of the reflected light, and produces control signals to actuate the appropriate valves of an array of air blast rejection devices to remove from the feed certain particles selected by the analyzing process. Typical throughput per machine ranges from 50 tons/hour for a-2 ½? + 1 ¼? feed to 200 tons/hour for -6" +2 ¾ " material.

Jan 1, 1974

By R. J. Smith

Hornestake's Mclaughlin Mine is the first commercial application of pressure oxidation pretreatment of gold prior to cyanidation. Inherent to the autoclave process are several liquid/solid separations. Flocculant consumption represents a significant portion of the consumable reagent costs at McLaughlan. This paper focuses on the efforts of the Operating, Metallurgy and Engineering groups to improve thickener operation and minimize flocculant consumption. An operating philosophy incorporating feed solids control, increasing flocculant dilution water and minimizing flocculant solution shear has resulted in a reduction in 1986 flocculant costs of $0.054/t ($0.06 st) versus 1985 costs. Additional changes are projected to result in a further cost reduction of $0.20/t ($0.22/.st) in 1987.

Jan 1, 1988