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By L. Tondo, W. Lim

The high pressure grinding rolls (HPGR) is a relatively new technology which offers the potential benefits in energy savings, circuit simplicity and improved product characteristics in minerals processing applications. Over 300 machines are now operating world-wide, but most of these are used for grinding cement clinker, and relatively few are used in conventional mineral processing. One of the rea- sons for its current limited use in the minerals processing industry is that design, scale-up and flowsheet assessment procedures are seen to be relatively immature and untested. This has reduced confidence in the potential application of the technology. To help rectify this situation an industry funded research project was undertaken, one of whose aims was to develop and prove a mathematical model of the HPGR and a scale-up procedure. Data were collected from tests using laboratory, pilot and in one case a full scale unit (2.2m diameter). A range of feed types were tested including quartz, limestone, kimberlite, bauxite, iron ore and gold ore. These data were then used to develop models of the size reduction performance, power draw, throughput and operating gap for a wide range of pressures, feed sizes, and roll speeds. This paper describes the models that have been initially developed and illustrates their accuracy using some of these data.

Jan 1, 1998

By M. A. Marticorena, R. Stratton-Crawley, C. I. Basilio

Diethylenetriamine (DETA) is a selective depressant for nickeliferous pyrrhotite during pentlandite flotation. Laboratory flotation tests conducted on ore and process samples showed that pyrrhotite rejection is greatly improved by small additions of DETA; however, the effectiveness of this depressant is most noticeable when the mineral sample is oxidized. LIMS and XPS analyses conducted on flotation products and pyrrhotite specimens showed that the difficulty in pyrrhotite rejection arises from inadvertent activation of the mineral by heavy metal ions, such as Ni2+, cu2+ and Ag+, that are present in the process water. In the presence of DETA, however, the mineral is deactivated under oxidizing conditions. The deactivation mechanism may involve oxidation of the activation products, which are likely in the form of heavy metal sulfides, followed by solubilization by DETA. FTIR spectra of pyrrhotite electrodes contacted with DETA showed no trace of the reagent on the surface, substantiating the view that its role is one of complexing agent that enhances the dissolution of activation products under oxidizing conditions. FTIR spectra of pyrrhotite contacted with amyl xanthate solutions showed that both dixanthogen and iron xanthate are formed on the surface, the latter becoming more predominant at higher potentials. In the presence of DETA, however, only a small amount of xanthate is adsorbed on the mineral at potentials (Eh) approximately 200 mV higher than the case without DETA.

Jan 1, 1995

By Victor F. Hollister

This section includes examples of discoveries of Kuroko- and Anyoz-type massive sulfides, and shale-hosted, zinc-lead deposits, and describes exploration models for each group of case histories. Exploration or empirical models can differ from genetic models, because ore guides and controls are emphasized in exploration models. Genetic models may form the scientific basis for exploration or prospecting models, although factors that are important to the localization of ore are stressed in exploration models. The paper by Sato (abstracted herein) on Kuroko deposits can be used as a general exploration guide for that type of deposit. It is clear, however, that no unambiguous stratigraphic control for Kuroko-type ore is given in the Sato paper. The paper by MacIntyre (an excerpt herein) describing Gataga, Midway, and Windy Craggy includes most of the elements of the shale-hosted and Anyox models. Although more recent work by the Geological Survey of Canada has modified the Windy Craggy stratigraphy, the Anyox model as applied to Windy Craggy is well described in the MacIntyre (1983) paper. Discoveries of ophiolite-, Ducktown-, volcanic-associated Ni- Cu-, and Besshi-type deposits are not included in this section. Conformable massive sulfide deposits are generally assumed to be syngenetic. Sulfides in the crosscutting feeder zones, however, are classed as epigenetic. Therefore, volcanogenic massive sulfides can contain both a syngenetic and an epigenetic component. Vital to the development of the epigenetic component is a heat source that propels the convection cycle that forms both components. In all massive sulfide discoveries described in this section, it is assumed that a volcanic magma fueled the hydrothermal fluids.

Jan 1, 1991

By John P. Dunford, Lewis A. Martin

Researchers from the Spokane Research Laboratory, National Institute for Occupational Safety and Health, in cooperation with engineers from the Department of Mining and Geological Engineering, Montana Tech, Butte, MT, conducted tests to evaluate the tensile strength, fiber count, and adhesion of shotcrete applied to panels at the Chief Joseph Mine, a research and training facility operated by Montana Tech. The tests were conducted in the mine ramp 45 m (150 ft) inward from the access portal at a 15.25-m- (50-ft) long test area divided into five 3-m- (10-ft) long sections. The shotcrete was applied with an Aliva 240.5 machine fitted with a predampener. Different amounts of fiber were entrained for each panel. Background data for the tests were obtained from earlier tests in Nevada, where the typical amount of fiber in the shotcrete is 6.54 kg/m3 (11 lb/yd3). All shotcrete was applied to a minimum thickness of 76 mm (3 in). Cylindrical cores were drilled at the wall-rock interface, and adhesion was tested after 28 days of curing. The goal of this research is to reduce the need to install multiple supports at the advancing face by creating a safer mining system that limits the time miners are exposed to unprotected roof.

Jan 1, 2005

By Greg Barfoot, Kurt Keskimaki

The Henderson Mine is located approximately 50 miles west of Denver, Colorado. A project is underway to replace the existing rail system which transports molybdenum ore 15 miles from the mine to the mill using three flight conveyor system. The first conveyor is a 1 mile, high lift conveyor which transports the ore from an underground crushing station to the end of the existing rail tunnel. The second conveyor is 10 miles in length and utilizes the existing rail tunnel to transport the ore from the mine, which is on the east side of the Continental Divide, to the mill located on the west side. The third conveyor takes ore from the tunnel portal to the mill through a series of 7 horizontal curves and inclines up to 15 degrees. The project applies advanced conveyor design to tackle the installation of the system in an operating mine and achieve the highest possible level of reliability. This paper outlines the design process for this system, discusses the options which were evaluated and how the current design evolved.

Jan 1, 1998

By Charles A. III Cravotta

Streamflow and water-quality data for the northern part of Swatara Creek, which drains a 112-km2 area in the Southern Anthracite Field of east-central Pennsylvania, indicate iron, copper, and lead, and to a lesser extent manganese and zinc, are transported with suspended particles during stormflow conditions. During stormflow conditions, concentrations of these constituents typically peak prior to peak stream stage as a result of scour and transport of streambed deposits. In contrast, sulfate is transported mostly as a dissolved ion. Concentrations of sulfate, specific conductance, and pH are inversely related to streamflow, indicating dilution and acidification during stormflow. This effect is attributed to the mixing of poorly buffered stream water having pH 6.0-6.5 with weakly acidic storm runoff having pH 4.0-4.5 and low dissolved solids.

Jan 1, 2000

By S. S. Peng, Luo. Y.

In a shearer longwall mining operation, the longwall hits are responsible for breaking into and chipping the broken coal blocks away from the coal face. However, underground observations found that the bits being used were working under various degrees of wear. This wear can be reduced by using better-designed longwall bits and by properly selecting shearer operating parameters. A computer program was developed to simulate the performance of the longwall bits. The information required by the program are the shape of the bit head, the installation of the bits on the drum and the operation parameters. Through the simulations, the main factors affecting the bit-wearing process are identified. Suggestions are also made for improving the design of the longwall bits.

Jan 1, 1998

By B. Denby

Recent advances in virtual reality (VR) have resulted in major opportunities for improving the safety training of mine workers, supervisors and managers. VR has the potential to expose mine personnel to hazardous situations in a safe, highly visual and interactive manner. Customized simulations of mine layouts, dynamic operations and mine environment can be set up, and mine personnel can be allowed to move around the virtual mine, making decisions at key points. The consequences of both correct and incorrect decisions can be immediately fed back to the trainee.

Jan 1, 2000

By S. Majumder

The longwall face supports are provided to prevent the caving of the immediate roof at the working face. The thickmess of the immediate roof may be obtained from the working height and the average bulking factor. A strong bed, capable of withstanding maximum bending moment among the beds within the above roof, can be identified. The load on the strong bed may be obtained by finding out the overlying beds that will rest on the former during sagging. The limiting span, L, for this unsupported loaded bed, as a beam with built-in ends, can be calculated. The support density required at the supported span (face to goaf edge), a, during the first fall, is now estimated with a view to have a safety factor 2 at the face end, when bending failure occurs at the barrier end. However, the above value is inadequate to provide necessary safety margin against bending failure at the face end, during the subsequent cavings as cantilever, for L/a less than 20.6. d For the latter case a separate expression is derived.

Jan 1, 1986

By Jorge Gutierrez C.

CODELCO-CHILE, the world's largest copper producer, began an integrated study of the informatics situation in the corporation at the end of 1980. As a result, a five years strategic Systems Plan was elaborated and approved by top Corporate management. Main points in this plan were: a systems architecture with information integration to the top level management; a higher degree of information technology in the production areas, an optional systems development resources utilization and a high profitability of the plan itself. During the study phase a series of theoretical definitions were fixed and used as a basis for the plan's design. A "common systems" approach was chosen as the development strategy instead of corporate systems or separate divisional efforts. Top management should be highly involved in the revisions of the plan, as well as qualified users should be chosen as project managers. The systems architecture should grant the information integration to the corporate level, in order to support an integrated planning and administration environment for the corporation. A total of 15 projects were defined, involving 570,000 man-hours and shifting the development efforts towards the production and production services areas. The paper presents a critical evaluation of the whole process, showing its good and bad aspects and a positive global balance. It also points some suggestions and hints to any corporation who wishes to get involved in a similar experience.

Jan 1, 1989

By Michael J. Sapko, Robert A. Cortese

A flame powered trigger device has been developed to explosively activate suppression barriers to quench gas and coal dust explosions. The important feature of the device is a silicon solar panel, which collects 0.3 p to 1.1 D wavelength radiation from the developing explosion, and generates electrical energy to initiate a detonator, which in turn causes the rapid explosive release of an extinguishing agent into the advancing flame front. Solar panels that are rated to produce 20 w of electrical power when exposed to the sun light are producing about 200 w when exposed to full-scale dust explosion propagating in the U.S. Bureau of Mines' Lake Lynn Experimental Mine. The solar panel is electrically isolated from the detonator by a pressure sensitive switch until the arrival of the precursor pressure pulse, which always precedes a deflagration. This combination of pressure arming and flame powered photo generator prevents false barrier activation and requires no external power supply.

Jan 1, 1991

By S. K. Kawatra, T. C. Eisele

Pyrite depression is of great interest in sulfide mineral flotation, where pyrite is a common gangue mineral. Since the floatability of pyrite is a function of the pH and a variety of other chemical factors, pH control is a critical part of sulfide flotation circuits. A wide variety of pyrite-depressing chemicals have been studied and used in sulfide- mineral processing, with considerable success. However, there are certain applications where there are still no satisfactory pyrite depressants, and even when suitable depressants are available, there is always a need for less-expensive reagents. Microorganisms, such as the bacteria Thiobacillus ferrooxidans, are known to depress pyrite flotation. However, the dependence of the depression on the type of organism or on suspension pH is still being determined. In this study, the relative effectiveness of various microorganisms, and the effect of pH, has been examined. Screening tests using microflotation showed that every microorganism tested was capable of depressing naturally hydrophobic pyrite at acidic pH. Larger-scale experiments with two of the screened organisms and two different pyrites showed that microorganisms are very effective depressants at acid pH, but are largely ineffective at neutral and alkaline pH where the pyrite surface is not naturally hydrophobic.

Jan 1, 1994

The development of economical and effective treatment processes for solid and aqueous waste is a critical issue facing the mining industry today. Cyanide, nitrates and acid rock drainage are environmentally sensitive effluents that require treatment or containment for acceptable disposal. In situ biotreatment processes are an emerging technology (Thayer) for cyanide oxidation, denitrification, sulfide mineral alteration and metal re- mineralization. Biological cyanide oxidation is competitive with chemical treatment processes (peroxide, alkaline chlorination) for process solutions, spent ore and tailings detoxification. Microbial denitrification treats mine waste contaminated with nitrates from blasting, processing or nitrification of the host rock. Bio-alteration of sulfide minerals and metal re-mineralization may present the most cost-effective and environmentally acceptable method of dealing with sulfide tailings and leachate solutions. Field test programs for cyanide bio-degradation and denitrification of spent ore and process solutions were designed and run at two mines. Although the treatment bacteria and the application processes are similar, each waste presented site-specific problems for adapting the biotreatment processes. Some of the site problems include climate, ore geochemistxy, field bacteria production, waste microbiology and application engineering. This paper compares treatment design and results for cyanide oxidation and denitrification in heap detox treatments.

Jan 1, 1992

By Terry Ritzel

Predictive maintenance technologies include vibration analysis, tribology, infrared thermography, ultrasonic detection and electrical measurements. These technologies have been applied to large electric mining shovels at the Cyprus Sierrita Mine outside of Tucson, AZ. The predictive maintenance program was initiated on the P&H models 2300 and 4100 electric shovels during August 1996. Results of these technologies have shown the potential for improving electric min- ing shovel availability and minimizing maintenance costs. Predictive technologies provide the tools to assess machinery condition. Availability is enhanced by the condition-based planning of component replacement. Maintenance costs are minimized by focusing resources through condition-based prioritization.

Jan 1, 1997

By R. C. Oberth, C. F. Lee, E. M. Taylor

INTRODUCTION Underground siting of nuclear power stations is drawing increasing attention in various parts of the world. Scandinavian countries took the early lead in this field because of their experience in the design and construction of underground hydroelectric stations and industrial plants, and because they have near-surface rock formations which are ideally suited for hosting large underground caverns. The world's first underground nuclear facilities were built in Norway (Halden) and Sweden (Agesta) and were commissioned in 1959 and 1963 respectively. Figure 1 summarizes the main features of these and two other small-scale European facilities. (1-4) American utilities and regulators are also for a variety of reasons assessing the benefits and penalties of underground siting. A recent study by Sandia Laboratories (contracted by the Nuclear Regulatory Commission (NRC) focussed on identifying potential safety benefits of underground siting. (5) Although the study concluded that underground plants would have improved containment for some accidents, as well as better external protection, NRC, in assessing the overall benefits and penalties, decided not to impose mandatory underground siting for nuclear stations. In June 1976, the California Legislature enacted a law which directed the California Energy Commission (CEC) to examine the issues concerned with underground siting of

Jan 1, 1979

By P. C. Cochrane, I. S. Clelland, S. H. E. Phillips

Geological and hydrological conditions in the strata overlying the Salado Formation vary considerably in the Carlsbad, NM, area. The first four shafts sunk at International Minerals and Chemical Corp. (IMC) property have been located in competent and essentially dry conditions, while other shafts on adjacent properties have had such adverse conditions that ground freezing has been chosen as the water and ground control technique for shaft sinking. At the location of the IMC No. 5 shaft there has been extensive erosion and salt dissolution in the Rustler Formation, leading to collapse of some zones of the strata. Both ground freezing and pregrouting were considered as alternative methods of stabilizing the extremely poor ground conditions and controlling the potentially very heavy water inflows. It was decided that pregrouting the shaft was feasible and would offer substantial cost and time saving over a ground freezing technique. This paper describes the pregrouting techniques used and illustrates the requirement for flexibility in a grouting program so that it can be modified to reflect any new or additional information obtained during the progress of the grouting.

Jan 1, 1987

By B. K. Baird, P. C. Satchwell

The application of cutoffs during and after pit optimization is examined for a lower-grade multimetallic copper deposit. Pit optimization requires calculation of the net revenue associated with each mining block. The calculation incorporates parameters such as metal prices, grades and expected recoveries, mining and processing costs, smelting and refining charges, and penalty element and royalty charges. Sensitivity analysis during pit optimization reveals which parameters have significant effects on the total contained resource tonnage and total contained nondiscounted revenue in the optimized pit. The cumulative effects of changing several of the more-significant parameters are investigated The application of a copper cutoff grade to a block inside the optimized pit could result in the less-than-optimal extraction of the resource. A block with a copper grade below the applied cutoff could be economic due to the presence of other metals. Conversely, a higher-copper-grade block may be subeconomic. Also discussed are the merits of applying a copper-grade cutoff, an "equivalent-grade" cutoff and a dollar-per-ton cutoff to blocks inside the optimum nit.

Jan 1, 2002

By Juan Eduardo Barrera

SUNNARY AND CONCLUSIONS Argentina presents to the foreign and local investors a mineral wealth that is largely unexplored, untested, underdeveloped and therefore incompletely evaluated. In view of the above, the new administration of President Raul Alfonsin through its Department of nines has designed and implemented a strategy ( Plan de Expansión Ninera P.E.M.), whose main objective aims at improving the "investment climate" in the sector. It is the Government's basic intention to apply the Mining Promotion Law with responsibility but with generosity to encourage the attraction of investment (local and foreign) to the sector. The establishment of a Data Bank system to evaluate possible new potential ore mining developments will help to connect the owners of potential projects with investors outside the sector. Argentina has an interesting gold ore potential. Estimated reserves of individual projects already known amount to almost 300 tonnes of gold for potential production. The government strongly believes and present information indicates that more systematic exploration has to be undertaken in the Jurassic areas that almost cover the whole of Patagonia. Two recent gold discoveries (Angela in the Chubut province, and Cerro Vanguardia in Santa Cruz province) indicate the potential of this area.

Jan 1, 1988

By R. L. Grayson

In 1995, the United States Congress abolished the Bureau of Mines in the US Department of Interior. But Congress preserved the safety and health research functions being performed at the Pittsburgh and Spokane Research Centers. These functions were transitionally housed in the US Department of Energy before permanently merging with the National Institute for Occupational Safety and Health (NIOSH), Department of Health and Human Services, in October 1996. Since the rnerger of the former Bureau of Mines with NIOSH, there has been an active evaluation of ongoing research activities, significant interaction with stakeholders, and the development of a process leading to "data-informed" priority setting. This paper reviews the current surveillance information concerning the level of injury and disease from mining work and discusses how research priorities are evolving to improve the contribution of research to the prevention of injury and disease.

Jan 1, 2000

By S. J. R. Lowrie, J. S. Edwards, A. D. Jones

A small scale model has been constructed to simulate air and gas flows on a full scale retreat longwall coal face. Scaling relationships were derived to define how the main aerodynamic properties of the full scale could be preserved in the small scale model. These scaling requirements include: a minimum value for the Reynolds number for the flow on the face in order to maintain turbulent flow with a constant non-dimensionalised coefficient of turbulent dispersion; a constant Richardson number to maintain similitude for the formation of layers of buoyant gas; scaling of the permeability of the waste so as to obtain the same proportion of seepage flow through the waste; pressure gradients due to the ventilation and to the density difference (between the air and the gas layer) were kept in proportion; and in the waste, the relative contributions of inertial dispersion and molecular diffusion were approximately in proportion. The complementary roles of computational fluid dynamics (CFD) and aerodynamic scale models for simulating mine ventilation are discussed. The physical model is described and an example presented of simulations of the effect of changes in mining condition on the effectiveness of gas control in retreat longwall coal faces.

Jan 1, 1995