Search Documents

By Ying Lu, Jeffrey C. Johnson, Chen-Luh Lin, Jan D. Miller, Sindhoora Puvvada

The amount of energy used to break rock is of interest in mine-to-mill operations to minimize energy consumption during blasting at the mine site and comminution at the processing plant. In this research, a direct energy measurement was made using high-velocity impact to cause breakage of long granite cores, and to study the energy dissipation along the entire bar length. The results show the formation of three zones of damage — fragmentation, fracture and elastic — that have been characterized in 3D using X-ray tomography. The fragmentation zone of the granite bars was studied in detail to describe the particle size distribution and the particle shape characteristics. The experimental energy dissipation in the fragmentation zone was found to be in close agreement with the expected energy calculated from the Bond work index (BWI) equation [1] when the anisotropic granite particles in the fragmentation zone are defined by length rather than by sieve size. The results increase our understanding of rock breakage and energy consumption and may find future applications in mine-to-mill operations.

By Robert E. Goodwin

There are four main requirements which must be considered when selecting a wire rope for the best serviceability. A proper choice is made by correctly estimating the relative importance of each of these requirements and selecting s rope which has those qualities best suited to withstand the combination of destructive forces expected under continued service. A wire rope should possess: 1. Strength sufficient to support the maximum load expected and with s proper safety factor. 2. Ability to withstand bending and to resist bending fatigue without failure of the wires. 3. Ability to withstand surface abuse such so abrasive wear, pounding, and wire scrubbing. 4. Ability to withstand abuse such as crushing and distortion.

Jan 1, 1968

By L. M. Chan, D. H. Carlson, J. H. Johnson

This paper discusses laboratory evaluation of a tailpipe emissions measurement apparatus (EMA) developed by Michigan Technological University (MTU) under contract to the Bureau of Mines. The apparatus dilutes diesel exhaust and measures the concentrations of diesel particulate matter (DPM), CO, C02, NO and NO2 at known dilution ratios. The EMA was evaluated by side-by-side comparison of its measurements with those by laboratory grade instruments. During the preliminary laboratory evaluation concentrations of DPM, CO and CO2 were measured. The concentrations of CO and CO2 measured by the EMA were usually within ±14 pct of laboratory-measured values for CO and ±20 pct for CO2. EMA DPM concentrations correlated well (r = 0.96) with the laboratory values, but were 29 pct lower on average. The CO and C02 differences were observed to be related to the method of calculating the EMAs' dilution ratio and the difference in DPM concentrations is attributed to thermophoretic and/or condensation losses related to the EMA's unheated sample probe. Preliminery analysis of data obtained with a heated sampling probe and modifications in the sampling procedures have indicated reduced variability in DPM and in the calculated dilution ratios.

Jan 1, 1991

By P. Somasundaran, S. Venkatachalam, N. K. Khosla, K. Khosla

Froth flotation of alumina particles was studied by employing and hydrogen gas bubbles. The effect of current density was studied over a range of 0.1 to1.6 kA/m2. Compared to hydrogen, the use of oxygen bubbles at any given gas evolution rate resulted in a higher flotation recovery. The existence of an optimum current density, for each given particle size was indicated. Flotation at higher current densities resulted in better flotation kinetics, while flotation at lower current densities resulted in better Spas utilization.

Jan 1, 1996

By R. B. Inturi, R. G. Reddy

Solid-state reduction of roast Movat chromite ore with carbon was carried out as a function of the C/FeO ratio at temperatures ranging from 800°C to 900°C. The reduction was studied using thermogravimetric analysis (TGA). A two¬stage mechanism consisting of the reduction of FeO with carbon monoxide and the regeneration of CO by the oxida¬tion of carbon with CO2 was proposed. The rate-controlling step is the carbon oxidation reaction. A kinetic equation, that of random nucleation, was proposed. The activation energy for the reduction was determined to be 55,800 J/mole and is compared to those activation energies determined for other chromite ores.

Jan 1, 2000

By Suresh K. Bhatt

Appalachian coalfields have been the predominant source of quality coals since the inception of commercial mining in the United States. In a broad sense, Appalachian coalfields can be considered those east of the Mississippi River, representing about 55% of total US coal production. In this special feature on Appalachia in MINING ENGINEERING, emphasis is given to the four coal-producing states of Pennsylvania, West Virginia, Virginia and (eastern) Kentucky. These four states produce more than 90% of the coal from the total Appalachian region, or about 40% of the total US coal production. Historically, Appalachia has been the principal source of coal for domestic industries and for export. There have been numerous fluctuations in the Appalachian coal industry during the past 20 years. Appalachia was affected by cyclical and structural changes in various industries, particularly the US steel industry, and changing world coal markets. It was also the region of more mine worker labor stoppages than other parts of the country. In general, the factors that affected Appalachian coal production over time are identical to those that determined changes in coal production nationally.

Jan 1, 1995

By D. C. Willett

INTRODUCTION The Symposium on the Development of Underground Space, held in Seattle, Washington, from October 1 through 3, 1980, was organized by the "Deep Space" subcommittee of the ASCE's Underground Research Technology Council. The primary objective of the symposium was the exploration of the interfaces between the investigation, design and construction of large underground facilities in "deep space" which, for the purposes of the committee, has been defined as starting at 100m below ground surface. The meeting focussed primarily on tunnels, caverns and shafts in hard rock; the meeting format comprised a number of brief presentations concerned with the technical aspects of investigation, design and construction, followed by an open discussion, and concluded with the assembly of recommendations regarding the interface problem by the symposium participants. The principal considerations brought out during the symposium, and a general review of the conclusions, are briefly presented in the following paragraphs. INVESTIGATION The sessions dealing with "Investigation" were chaired by Dr. H. Pratt. Presentations were made by Dr. D.C. Banks, Dr. W.A. Hustrulid and Dr. Pratt. The extent of the interface of the investigation phase with the other (design and construction) phases of an underground facility will depend in large measure upon the nature of the facility; at one end of the spectrum, the investigation must be in continuous and closely coupled relationship with the design of a radwaste facility. At the other end of the spectrum, for (say) a small mining operation, the interface is largely associated with the initial development, with only minor on-going involvement.

Jan 1, 1981

By L. J. Lindsay

Kaiser Resources Ltd. operates a coal mining complex in Southeastern British Columbia. A large surface mine, a conventional underground mine, and an innovative hydraulic underground mine are presently in operation. The products of these mines are fed to the Elkview plant. This coal has to be prepared to 9. 5% ash and 6'o total moisture for export from the port of Roberts Bank near Vancouver, British Columbia to Japan at a rate of 4. 5 Mltpy. The moisture requirement for the coal product was recently increased to 8. 0% total moisture. The entire operation has been described in various publications (1), (2), (3). Details of the venture will not be repeated in this paper. In this paper we hope to describe the modifications made to the original coal preparation plant in order to satisfy market requirements for quality and quantity of coal.

Jan 1, 1974

By B. T. Darnton

Gravity concentration at the Pegasus Gold Montana Tunnels Mine was initiated in late June, 1991 with the commissioning of a coarse gold scalping circuit that processes a small portion of the ball mill circulating load. The primary objective for the circuit was to reduce the risk of gold particles advancing to flotation that are too coarse to float. The secondary objective was to enhance overall gold recovery and payable gold ounces in a cost effective manner. The gravity circuit has proven itself to be a major success. The above mentioned goals have been achieved, and they have been maintained at record throughput rates that are 30% higher than when the circuit was commissioned. A number of modifications and improvements were made over the last three years which allowed the gravity circuit to keep pace with the higher tonnage, these are discussed in detail in the body of this paper. The overall approach to gravity concentration at Montana Tunnels has always been to optimize production rather than maximize the gold ounces produced. This philosophy has now yielded a circuit expansion and relocation project which will allow for an estimated 50% increase in gravity gold production, while reducing the overall unit costs of production significantly. This paper will review historical gravity circuit performance, improvements, and the current relocation and expansion project.

Jan 1, 1995

By Robert C. Bates

Background is given on the various equations used to describe diffusion and convective flow of radon in porous media. Bureau-developed equations for modeling diffusion and Darcy flow through multilayered porous media are described briefly, and examples of their use are given. Analysis results discussed include: The transient effect of pressure changes in different length models, time dependent flux changes in multi-layered models, and radon flux through pinholes in sealants

Jan 1, 1980

By Leon Y. Sadler

Equations which predict the unsteady-state response of the continuous froth flotation cell to changes in operating conditions are necessary for the rational design of an automatic flotation cell control system. Unfortunately application of automatic control to froth flotation separation equipment has lagged behind application to other types of separation equipment (for example distillation columns, absorbers, liquid-liquid extractors, etc). This may be due partly to the unavailability of suitable mathematical models for predicting the dynamics of continuous mechanical froth flotation cell. This paper presents the results of a comparison of four dynamic flotation models (in transfer function form) using the same set of unsteady-state continuous flotation data. One of the transfer functions tested has been presented previously in the literature (1), another (2) has been accepted for publication, and two are given here for the first time. In addition, data are presented which confirm earlier findings that the mixing in the rotor-stator type cell is nearly perfect. The specific purposes of this paper are to: (1) provide the automatic control systems designer with several alternative dynamic mathematical models of the continuous mechanical froth flotation cell (2) give some idea of the relative a¬bility of each model to predict unsteady-state behavior by fitting each model to the same set of experimental stimulus-response flotation data and (3) provide more insight into the macro-mechanisms prevailing in the continuous mechanical flotation cell. The dynamic models which are presented and tested here all relate the time variation of the concentration of a given floatable mineral in the tailings to a time-dependent disturbance in the same floatable mineral concentration in the feed to the flotation cell.

Jan 1, 1972

By Robert P. Bell, John T. Waggoner

The Metropolitan Water District of Southern California is designing new outlet facilities for Lake Mathews, including a junction shaft, connecting tunnels, and an ear-shore outlet tower. Since Lake Mathews must remain operational during construction, groundwater inflow potential is a concern. This paper describes the challenges and methods used to investigate rock mass and groundwater conditions at an operational reservoir, where offshore and onshore geotechnical exploration was performed. Several investigative and analytical methods were used to characterize rock mass and groundwater conditions, including rock coring, downhole geophysical and video surveys, hydraulic conductivity testing, automated groundwater level monitoring, and laboratory testing.

Jan 1, 1999

By John D. Grothe

Laboratory experiment as a basis of commercial plant design has been the subject of much analysis and thought and on which a large number of articles and papers have been published. We would be forced to choose between an unduly brief exposition if we wanted to cover it completely, or no exposition at all. We must therefore concentrate upon the essentials without ignoring at the same time too many of the qualifying factors which, by the choice of what we want to examine, may become side issues. In doing so, we do not imply that these side issues are therefore any the less important. In every case, what is said here applies with almost equal force to the pilot plant which may be necessary as it does to the commercial plant. In discussing a recent paper by Derek C. Shelton on the Santa. Barbara Mill in Chihuahua at a meeting of the Inst. of Mining & Metallurgy (London), D. J. Ottley said on the matter of relating laboratory results and small scale tests to full scale plant results that he would like' to draw the attention of members to the great difficulty of scaling up mineral dressing plants and processes. He felt that this was an important yet neglected subject which merited considerable fundamental scientific attention from mineral dressers and plant design engineers in particular. How much of this fundamental scientific attention has, as a matter of fact, been accorded to the subject, mainly by our sister profession, Chemical Engineering. The close similarity to chemical engineering problems that we meet, particularly in hydrometallurgical operations, suggests that Chemical Engineering publications offer a rich source of information and discussions of methods useful to us. We have only to think of pressure leaching, ion exchange, liquid-liquid extraction, precipitation and so on, all problems in chemical engineering unit processes or of the new Freeport Sulphur Nickel plant in Cuba or the Sherritt Gordon plant and many others.

Jan 1, 1960

By Dale C. Matthews

Pressure oxidation of refractory gold ores is becoming more popular in our environmentally sensitive society. This paper will discuss some specific process problems and solutions involved with starting up and operating an autoclave circuit.

Jan 1, 1991

By L. L. Newman, K. D. Ferguson

Traditional methods for mine waste management produces two waste streams and the construction of separate disposal facilities. Tailings impoundment design is usually controlled by physical stability problems. Alternatively. the waste rock offers high stability characteristics but hydraulic properties that create ideal conditions for oxidation. The problem of oxidation is significantly reduced for tailings due to a fine texture that augments water saturation. This paper introduces concepts for the co-disposal of tailings with waste rock and evaluates the physical behaviour of an integrated waste system. 'he potential benefits of co-disposal are shown for a typical mine such as Equity Silver.

Jan 1, 2000

By J. W. Walkiewicz

The U.S. Bureau of Mines has conducted studies using microwave energy to stress-crack iron ores. In a microwave chamber which simulates a continuous throughput operation, the Bond grindability of a taconite sample was improved by 13 pct at a bulk temperature of 197? C. To further improve the economics of microwave fracturing, higher powers up to 16 kW were used to rapidly heat samples to relatively low temperatures in a continuous belt-fed applicator. A significant enhancement of grindability was obtained with a minus 1.9-cm taconite rod mill feed. At a sample temperature of 130? C, the grindability was improved a maximum of 26.1 pct over the non-microwaved sample.

Jan 1, 1993

By E. H. Cho

Pittsburgh #8 coal cleaned by the conventional froth flotation was oxidized in a 2-liter Parr Stirred Top Bench Reactor. The oxidation time was varied up to 5 hours; the temperature, from 150 to 225°C, the oxygen pressure, from 15 to 500 psi; and coal dosage, from 15 to 60 grams in 600 ml of distilled water. The oxidation of coal was evaluated by measuring total acidic group formed on the coal surface as well as by measuring the adsorption of calcium ion from a solution under standard conditions. It was found that the oxidation increased with increasing oxygen pressure without much leveling-off effect. However, the oxidation of coal increased sharply from 150°C to 175°C and then tended to level off above 175°C. The adsorption of calcium was reached more than 3% on the coal oxidized under favorable conditions. The adsorption of calcium on coal increased sharply with increasing equilibrium pH. The BTU loss was sensitive to oxidation temperature. This study concludes that the optimum oxidation of coal should be conducted at high oxygen pressures around (e.g. 500 psi) 170°C for 3 hours. This study also concludes that the oxidation in an autoclave is far superior to that in a fluidized bed in terms of calcium adsorption, BTU loss and reaction time.

Jan 1, 1994

By G. G. O. O. Uwadiale

Because mineral matter is finely distributed within the matrix, Nigerian Labia coal is nonresponsive to conventional processing techniques. However, testing has shown that Lafia coal can be upgraded by selective oil agglormation. The optimum oil concentration was found to be 10 mL of paraffin per 25 g of coal. A product containing 6% ash and 1.9% sulfur was obtained with a yield of 90%. Optimum results were achieved with a grinding; time of from 2.5 and 3 hrs, which produced a 98% -400 mesh product. However, further grinding wars found to be deleterious to the process. Also, high pH adversely affected concentrate yields. Utilizing kerosene as a bridging liquid, a product containing 4% ash and 0.33% sulfur was achieved at a natural pH of 6.3 with a yield of 85%. At pH 9 and 10, a product containing 4.5% ash was achieved with a yield of >90%.

Jan 1, 1997

By Frank F. Aplan

Introduction Gravity concentration may be defined as that process where particles of mixed sizes, shapes, and specific gravities are separated from each other by the force of gravity or by centrifugal force. The nature of the process is such that size and shape classification are an inherent part of the process in addition to separation on the basis of specific gravity from whence the process got its name. Mother nature has long practiced this form of mineral concentration by concentrating such heavy and relatively indestructible minerals as gold, platinum, cassiterite, ilmenite, zircon, and diamonds in placer or beach sand deposits. Once freed of their host granitic or other rock through natural weathering processes, these minerals are then subjected to stream or wave action producing a natural classification and concentration of the heavy minerals. Gravity concentration dates back to antiquity and was certainly the first ore concentration process used when selective mining and hand sorting would no longer suffice to produce the quality of concentrate desired. Forerunners of the present day sluice box and panning techniques were undoubtedly used by the ancient Egyptians on the upper Nile to separate gold from stream gravel. By the second century BC the extraction of gold from veins in quartz was well detailed by Agatharchides, but there is evidence that gold was brought into Egypt from the south as early as the XI1 Dynasty (~1900 BC).1 Most assuredly gravity concentration devices were used during the later Bronze Age to separate the heavier tin and copper minerals from their lighter gangue minerals. The Athenians used an elementary form of Rowing film concentration at their lead-silver mines at Laurium,2 and elementary jigging using wicker baskets was also probably developed at this time. Agricola's famous treatise De Re Metallica3 demonstrates that by the 16th century gravity concentration technology was well advanced and a large number of devices had been developed. Chinese

Jan 1, 1985

By Elif Emil-Kaya, Bernd Friedrich, Merve Papakci

Samarium (Sm), one of the rare earth elements (REEs), and cobalt (Co) are used in the production of SmCo permanent magnets, which have excellent temperature stability, corrosion resistance and oxidation resistance. Of the two types of SmCo magnets, one contains a high amount of iron, approximately 15.2 percent. This paper focuses on the recycling of iron (Fe)-bearing SmCo. In this study, an oxidative leaching process with nitric acid was developed to eliminate iron through in situ hydrolysis and to dissolve REEs and Co. The influence of experimental conditions on the formation of an amorphous iron compound through the hydrolysis of Fe3+ in a nitric acid environment was thoroughly examined based on a Taguchi orthogonal array. The optimal parameters for oxidative leaching were determined to be an acid concentration of 3 mol/L, a solid-to-liquid ratio of 1/10, and a process temperature of 60 °C.

Jul 1, 2024