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By J. S. Anderson

Size reduction models of cone and impact crushers have been developed using Whiten's generic computational structure for the description of crushers. They incorporate a laboratory single particle breakage test and the t-family of curves to describe the breakage behaviour of the feed ore. A quantitative model of 7-foot cone crushers has been developed, based on surveys of Svedala (Kobe) and Nordberg machines. Survey data on a Canica vertical shaft impact machine have been used to validate the impact crusher model. Given the crusher operating conditions, such as tonnage, feed size, set and liner condition, or rotor speed and radius, plus breakage information on the feed, the models provide good predictions of product size distribution, and appear to be robust over a wide range of conditions. They are incorporated in commercially available computer simulation packages.

Jan 1, 1998

By M. Noaparast, F. Woodcock, A. R. Laplante

A novel methodology for estimating gold recoveries in gravity-separation circuits is presented. The methodology makes use of a population-balance model. The model represents gold liberation, breakage and classification behavior and applies preconcentration and recovery performance curves to gravity-recoverable gold. The derivation of the necessary parameters is explained and demonstrated using data from an actual gravity circuit and from a projected application. The methodology makes it possible to estimate the performance of a gravity circuit having a large gold circulating load and a relatively-low unit recovery (e.g., a jig) or having a high recovery on a bleed of the circulating load (e.g., a Knelson Concentrator).

Jan 1, 1996

By N. Rajmohan, K. T. Jacob

Presented is a thermodynamic feasibility analysis of extracting base metal chlorides from low-grade, multi-metallic oxide ores using CaC[1]2 as a chlorinating agent in the presence of SO2 and O2. The oxides react to form corresponding chlorides, while CaC[1]2 is converted to CaSO4. The Ellingham diagram is used for comparing the standard Gibbs' free energy change for the sulfation-chlorination reaction of a large number of oxides. Except for alumina, silica and chromia, most of the other metal oxides will be converted to their respective chlorides. The volatile chlorides can be condensed, and the chlorides present in the condensed state can be leached. A process is proposed that uses a nontoxic chlorinating agent and gives an efficient separation of the metallic values from the gangue.

Jan 1, 1993

By J. C. Franklin

The U.S. Department of the Interior, Bureau of Mines, has developed a data acquisition system to continuously monitor radon, working level, absolute pressure, temperature, relative humidity, and air velocity. Data have been taken in intake and exhaust drifts, working stopes, and sealed-off areas of positive and negative ventilated uranium mines. Radon emanation rates, ranging from 1.7- to 12.2 x 2 10-l4 Ci/cm /sec were determined in four mines. The ratios of short duration, primary fan shutdown time to radon normalization time were 1 to 2 and 1 to 4, respectively, for-negatively and positively ventilated mines. Blasting and slushing caused radon increases of 160 and 67 percent, respectively.

Jan 1, 1980

By E. J. McGuire, E. W. Brickle

INTRODUCTION Several recent technological improvements - largely by the convey-or industry - have increased the importance of inclined shaft construction for developing mines where ore deposits are relatively shallow. With these newer systems, long conveyor haulages are economically feasible, allowing mine owners to justify the expense of the inclined shaft or slope. What this actually means is that they can now take advantage of the versatility this construction offers. For example, haulage capacity can be changed by conveyor additions or replacements; equipment can be trammed to and from the surface quickly without costly breakdown and re-assembly; and a walkway is available for workers in the event of an emergency. Now, another innovation may accelerate this type of construction, the use of tunnel boring machines or "Mechanical Moles" to dig the slopes. While conventional. drill and blast methods have been used previously to build inclined shafts, the tunnel boring machine technique offers greater production rates, higher safety and a better, much cleaner bore. McGuire Shaft & Tunnel Corporation of Ft. Smith, Arkansas recently started such a slope project - the first ever bid by a contractor based on the use of a "Mechanical Mole".

Jan 1, 1997

By M. Josick Comarmond, Paul L. Brown, Greg P. Timms, A. Ian M. Ritchie, John W. Bennett

Geochemical kinetic models have only become available in recent years and their utilisation in the prediction of effluent chemistry from sulfidic waste rock piles is even more recent. The models used to date, however, have incorporated some questionable assumptions. This paper shows how geochemical, mineralogical and physical field data have been coupled to remove some ill-founded assumptions in the construction of a geochemical kinetic model. Further, the paper discusses a comparison between the observed effluent chemistry from a waste rock dump at the Rum Jungle copper/uranium mine in northern Australia with model predictions. In general, there is good agreement between the two, although an anomalous result is discussed.

Jan 1, 2000

By Donald P. Spitzer, Peter V. Avotins

The flow properties of thickener underflow slurries can be characterized by their rheological parameters. Most of these slurries exhibit Bingham plastic behavior, characterized by a yield stress, to, and a Bingham viscosity, nB. Red mud is generated as a leach residue in the Bayer process. The use of new Bayer process flocculants which contain hydroxamate functional groups leads to muds which are qua1itatively considerably more fluid than muds generated with conventional polyacrylates or acrylatefamide copolymers. A variety of rheological tests confirm lower yield stresses and less extended floc structures with the new flocculants, at the same solids levels. Conversely, under given viscosity restraints, the new polymers make it possible to operate at higher solids levels, which offers major benefits in processing red muds.

Jan 1, 1992

By Robert C. Freas

Genesis 1:28 "And God blessed them and God said he fruitful and multiply and replenish the earth and subdue it and have dominion over it." Genesis 2:15 "And the Lord God made man and put him in the garden to dress it and keep it." Depending on one's perspective, these two verses from the Book of Genesis either complement one another or are in conflict. I believe that they are complementary. What they imply is that where there is privilege, there is responsibility. Privilege comes from the fact that the Lord created the heavens and the earth and he placed man on the earth to have dominion over it. The responsibility that accrues to us comes when the Lord also said that we are accountable for how we handle that which he has given us. The very nature of our responsibilities in resource utilization or, more appropriately, resource management, has changed over time as the nation's needs and priorities have changed. Thus, I have attempted to examine, from a historical perspective, how natural resource policy has evolved, where we are now and what may lie ahead.

Jan 1, 1995

By Zhu Mingshan, Wu Jiang, Xu Yingqin

A mathematical model to simulate spontaneous combustion of coal in goaf was developed. Under the condition of two-dimensional flaw of air through a bed of uniform mixture of coal, gob, stone etc., the model simulates the temperature rise in the air-and-particle system associated with Arrhenius particle surface reaction. The model is developed as a set of coupled non-linear partial differential equations, which include (1)mass conservation equation for oxygen, (2)energy conservation equation for gas, (3)energy conservation for solid, and (4)velocity equation for gas, that are solved numerically. An elaborate parametric analysis is made of effect of leakage air flux and position of source and sink, parameters relating to the coal accumulating character and the kinetic properties of coal on the tendency to spontaneously combust. In addition, the dynamic process of temperature rise within goaf under several conditions is displayed with picture drawn by computer.

Jan 1, 1991

By Bruce T. Stanley

Though most porphyry-molybdenum deposits lend themselves to various reserve estimating techniques, still there must exist the constant effort to not merely obtain an estimate but rather to obtain the best estimate. To answer the challenge of a complete ore reserve estimation, one must attack the problem with the purpose of obtaining the results closest to reality. What we wish to determine is simple: metric tons (short tons), grade, and kilograms (pounds) of molybdenum contained. In order to effectively accomplish this task, further consideration must be given to the ease of using the information obtained and its inherent reliability. The only known method for ore reserve estimation that supplies the needed results along with its distribution and a measure of confidence provided by sound mathematical backup is geostatistics. The following review is an example of geostatistical application of an ore reserve estimate at the AMAX Henderson mine demonstrating technique, viability, and usefulness of results.

Jan 1, 1979

By K. V. S. Sastry

Pelletization, sintering, and pressure compaction are the most common methods used to agglomerate ore concentrates. Over the last 20 years agglomeration has grown enormously in popularity and has become a standard unit operation in the nonferrous, cement, fertilizer, and ceramic industries. However, it is in the processing of iron ores and the preparation of blast furnace feed that agglomeration is used most and its application has grown fastest (Ball, et al., 1973; and Sastry, 1977). This chapter deals with an account of the current practices and future trends in the application of computers relative to an overview of the process design and engineering considerations of the unit operation of agglomeration.

Jan 1, 1979

By J. R. Diehl, R. W. Lai, R. W. Hammack, S. U. M. Khan

Cyclic voltammetry (CV), flotation response, evolved-gas analysis (EGA), and X-ray photoelectron spectroscopy (XPS) were employed to evaluate the major differences in the surface property and surface reactivity of a selected coal pyrite and a mineral pyrite. Surface properties of pyrite were evaluated in terms of flotation response in the presence of both an anionic fluorosurfactant and sodium hydrosulfide. The charge transfer adsorption and oxidation potential of sodium hydrosulfide were evaluated using cyclic voltammetry. Drastic differences in the flotation response have been observed between the coal pyrite and the mineral pyrite. Significant differences in the cyclic voltammograms at pyrite surfaces of these two sources were also observed. Measurements by XPS and EGA were used to determine the oxidation products and the rate of oxidation of the coal-pyrite and the mineral-pyrite surfaces.

Jan 1, 1991

By Lee W. Abramson, James E. Crawley

Caltrans is studying alignments for a 160-kilometer-long high speed ground transportation system from Los Angeles to Bakersfield across the Tehachapi Mountains. This link is needed to connect southern California with San Francisco by a short passenger rail service. None presently exists. The system will require tunnels and viaducts along the route with sections crossing two major active fault zones. High speed ground transportation technologies are being evaluated for achieving rail speeds of between 200 and 480 kilometers per hour. This paper presents the technical requirements for tunnels along the alternative routes being considered for the project.

Jan 1, 1995

By N. R. Sainath

This paper discusses a laboratory investigation that studied the microscale flow characteristics of copper ores and the variation in flow behavior resulting from flow of leach solution. Fractures in 40- and 100-mm-diam (1.5- and 4-in.-diam) cores were first mapped by visual inspection. The permeability of cores to water-stressed in a triaxial stress field representative of in situ conditions - was estimated. The samples were then exposed to 20g/L (2.7 oz/gal) sulfuric acid and the experiment was repeated. The porosity and the rate of recovery of copper from the specimen during leaching were also studied. The measured permeability of unleached samples with no visible fractures ranged from 10-16 to 10-19 m2 and it increased as leaching progressed. The porosity increased significantly with leaching, while the rate of copper recovery decreased.

Jan 1, 1994

By D. Leppert

Large deposits of natural zeolites may provide cost-effective alternatives for treatment of soil and water contaminated ) with heavy metals and radionuclides. Research on the Bikini atoll demonstrated that addition of clinoptilolite to the soil significantly reduces cesium uptake by plants. Re- search on the potential use of zeolites in soils at Bunker Hill, ID indicated only minor benefits at very high contamination levels vs. US Bureau of Mines (USBM) work on the use of zeolites for treatment of mine waste waters emphasized problems with natural waters that previous studies have not addressed. High levels of competing calcium in natural waters significantly decrease the effectiveness of zeolites for heavy metal sorption and may limit the usefulness in these applications.

Jan 1, 1991

By Michael D. Balen

The plate-glass windows in the bus were cracked and mud-coated. Nevertheless, they afforded an excellent view of the many head-on collisions we narrowly avoided along the route from the Magadan airport to town. Apparently the driver thought the left side of the road was smoother than the right side, for he drove in the wrong lane at all possible times, even in the face of oncoming traffic. As far as we could tell, neither side of the road was any better than the other. Either way, we had to hang on just to stay in our seats. We careened past trucks and pedestrians, nearly always in the face of impending disaster. When the bus finally pulled into the parking lot of the Okean Hotel in Magadan, we had to thank the driver, not only for safely delivering his passengers, but also for the lasting first impression he gave us of the Russian Far East.

Jan 1, 1995

By David J. Herzog

There are two steps in evaluating potential mine waste impacts on ground and surface waters. Characterize the mine waste (characterization methodologies) and assess potential impacts (assessment strategies). One or both may be required for mine permitting, operation and closure. The first step is to characterize the waste. Determine if it has the potential to release chemical constituents or acid rock drainage to the environment. If no potential exists for release to the environment, the evaluation process is complete. A monitoring plan is then established. If the potential exists for release of chemical constituents or acid rock drainage to the environment, a strategy to evaluate potential impacts must be implemented. Strategies discussed here to evaluate potential impacts were developed during investigations at precious metal and base metal mines in Nevada. Water resources in Nevada consist mostly of ground water. So the strategies discussed focus on potential impacts to ground water. However, several of these strategies also apply to assessing potential impacts to surface water. Implementing these strategies has helped determine the potential for impact and has been successful in permitting mine expansion as well as allowing continued operation and obtaining mine closure at several mine sites in Nevada. These strategies were carried out in accordance with Nevada Division of Environmental Protection (NDEP) regulations and through the National Environmental Policy Act (NEPA)

Jan 1, 1995

By Robert A. Hains, William P. Balaz, K. Payne

Ceramics are usually used to line chutes, pipes, dust collectors, separators, cyclones or bins where abrasive or corrosive material is moving. Improvements in ceramic manufacturing methods and quality, use of other abrasion resistant materials in combination with Alumina ceramic, improved adhesives and installation methods allow the use of Alumina ceramic tile in applications with impact. This paper discusses the criteria to determine if ceramics can provide a cost effective alternative to other liners for abrasive material handling applications, design parameters for liner systems, system costs, and case histories. The goal will be to provide a practical guide for improving the performance of existing ceramic lined systems or determining if ceramics is a cost effective solution for your abrasive material handling applications.

Jan 1, 1996

By W. D. Monaghan, G. L. Mowrey, C. W. Ganoe

In addition to developing various types of coal-interface detection systems, the US Bureau of Mines is actively involved in developing a coal rib-thickness monitoring system for high wall mining applications. One particular system that shows promise uses a ground-penetrating radar system to detect the coal-air boundaries of coal ribs. Based on preliminary laboratory and field tests, results indicate that this method can be applied successfully in highwall mines to maintain a constant rib thickness. The coal seam should be relatively clean in the vicinity of the antenna (e.g., have minimal partings or dirt bands) for best results.

Jan 1, 1996

By Gülhan Özbayoglu, Yusuf Ziya Akgök

The effect of cooling rate on the flotation behaviour of copper slags of flash smelter plant in Samsun was investigated. Fresh molten slag was solidified in laboratory scale in three different ways. All the samples were characterized by chemical and mineralogical analyses. The chemical analyses showed that samples prepared from fresh slag had 0.9 to 1 % Cu with 40 % Fe and 30 to 32 % SO2. Old pit slag samples contained between 1 to 3% copper. Microphotographs showed that rapidly cooled slags showed fine size distributions, e.g. the copper grains in granulated slag had sizes in 1-2 microns. On the other hand, the size of copper grains in slowly cooled slags increased above 40 microns. Flotation tests carried out by using potassium amyl xanthate and Flotanol-C showed that slowly cooled slag reduced the copper losses in the tailing and improved the grade of concentrate. Under the light of laboratory investigation, the pit dimensions of Samsun Plant have been modified which resulted in a pronounced improvement of the grade and recovery of concentrate produced at Samsun slag flotation circuit.

Jan 1, 1995