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By P. Jonsén

Understanding mill charge motion is important. In the charge, the centre of gravity is shifted from the rotational centre of the mill system, and its motion is induced by rotation of the mill, while at the same time the charge creates a torque into the mill system. Breakage of ore particles and wear of liners/ball media are closely linked to the motion. To study these phenomena in a physically correct manner, numerical models for different parts of the mill system are needed. Validations of such models are scarce, because of the difficulty to measure in a tumbling mill. Experimental measurements in a lab mill were done for diverse load cases: varying feed materials, mill fillings, mill speeds and pulp liquids. The mill is set up to directly measure the charge-induced torque. The accuracy is good with relative uncertainty smaller than ±2% for relevant load cases. A full three dimensional numerical model of the whole mill is used to predict induced torque. Agreement between predicted and measured torque at steady-state is good. In addition, the model can accurately predict the mill start-up behavior for torque and mill power. This proves that the model is physically correct, and can be used for full-scale mills.

Feb 27, 2013

By D. L. Lampshire

Biological leaching using native heterotrophic bacteria was studied by the U.S. Bureau of Mines as a means of extracting manganese from a domestic low-grade wad ore. Column heap leaching simulation techniques were employed using molasses as the nutrient source for the bacteria. These column studies were designed to investigate the effects of molasses medium flow rate, concentration, and replacement interval on the extent and rate of manganese extraction. .Results showed that flow rates between 0.41 and 8.1 L/min/m2 had little impact on manganese extraction. The total amount of molasses used did have a direct effect on the extent and rate of manganese extraction. Manganese extractions over 90-pct were obtained in 12 weeks of bioleaching with 2-week medium replacement cycles.

Jan 1, 1993

By Andrew B. Pervis

With the ever increasing demand for Finer powders by industry there has been a continuing effort by air classifier manufacturers to improve and offer machinery capable of producing these fine powders. Common to these classifiers is the use of a multivaned rotor through which passes all of the air used to transport the particles to be classified. Rotor revolutions per minute and the amount of air passing through the rotor are the main variables in determining the particle sizes which will be able to pass through the spinning rotor. A simplified equation derived by setting the air drag force carrying a particle through the rotor equal to the centrifugal force due to the spinning rotor's action on the entering air and particle is: Diameter of Particle = [ ] Where K is a function of air viscosity, particle configuration, rotor and blade configuration; RPM is rotor revolutions per minute; M3/sec. is air quantity passing through the openings between the rotor blades.

Jan 1, 1983

By F. G. Miller

Over the past 30 years, the coal industry has been continually striving to perfect methods for cleaning fine coal to acceptable ash and sulfur contents while maintaining maximum product yield. The flotation process has been part of this effort and its importance is expected to grow as new utilization technology demands finer and purer coal products. The work outlined in this paper is part of a larger effort aimed at development of new and improved flotation systems for removing sulfur and ash from as-mined coal as well as for producing super-clean coal for future markets. The concepts and data presented are now serving as a basis for designing fine-coal circuits in which improved efficiency is obtained by optimum use of flotation.

Jan 1, 1986

By F. Lincoln & B. Rodier, G. Poniatowski, N. Kawashima, T. J. White, J. H. Kyle, G. F. Eaton

The history of Australia is a narrative of the discovery and development of its mineral wealth. The gold strike at Ballarat, Victoria, in 1851 transformed the colony by triggering the first great influx of migrants to Australia, and the development of subsequent mineral discoveries lead to a vast resource industry. However, beneficiation of base and precious metal ores carried with it an environmental penalty, not addressed until the last quarter of this century. In particular, the extensive deposits of gold, silver, lead, copper and zinc reside in sulphurous ores which often contain arsenic, antimony and mercury as significant contaminants that are released as unwanted by-products during smelting and refining. Until recently, these toxic concentrates were discharged to the atmosphere or receiving waters, collected in tailings ponds close to the smelters, or dumped at sea. Although such procedures . were acceptable in the past, more stringent environmental controls have required a re-examination of these practices and encouraged intensive efforts to develop enduring solutions to the disposal of these wastes. From this research has emerged a promising new generic technology called Xtaltite (pronounced crystal-tight). In this approach, geochemical principles are employed, first, to reduce the toxicity of heavy metals to low levels, and second, to identify and engineer suitable repositories for the permanent disposal of the consolidated waste form. In this paper, we emphasise the application of Xtaltite to the disposal of arsenious smelter fumes derived from gold winning. The principles ofXtaltite will be described and its technical and economic performance compared with conventional technolo­gies.

Jan 1, 1995

By R. S. Farinato

Thionocarbamate flotation reagents have enjoyed a niche position in the recovery of copper sulfides and activated sphalerites since their introduction in the mid 1950's (Harris, 1954). Thionocarbamates containing an allyl group (-CH2- CH=CH2), introduced recently Lewellyn, 1985; Nagaraj, 1988; Avotins, 1991), are used commercially as collectors for copper sulfides and activated sphalerite. Laboratory flotation tests and plant usage have demonstrated that allyl-containing thionocarbamate collectors exhibit certain unique properties that distinguish them from the corresponding dialkyl thionocarbamates. Spectroscopic (FTIR, XPS) and wettability studies of N-allyl iso-butyl thionocarbamate (AIBTC) and its saturated analog N-propyl iso-butyl thionocarbamate (NPIBTC) adsorbed on copper at pH 9 were performed in order to investigate whether there were any fundamental reasons for these differences. Flotation tests were carried out on chalcocite, copper ore and an activated sphalerite.

Jan 1, 1993

By K. V. Raj, VASU GANGRADE

Airflow in large-opening stone mines is largely dependent on the natural ventilation due to the large cross- section area of the opening. The openings of such stone mines are typically twice or thrice the size of typical underground coal or metal/nonmetal mines. Due to the influence of natural ventilation, air velocities as well as the static pressure drop in the mines are low. Mines rely on auxiliary fans to ventilate active faces to reduce contaminant exposure to mine workers. The National Institute for Occupational Safety and Health (NIOSH) is conducting research on ventilation of large-opening stone mines to reduce worker exposure to dust and other contaminants such as diesel particulate matter (DPM). In order to reduce worker exposure to dust and DPM, an understanding of the airflow pattern due to auxiliary fans in the mine is needed. Under this research, NIOSH researchers are exploring the computational fluid dynamics (CFD) modeling to understand the airflow behavior in large-opening mines. In this paper, the team is presenting the results from three-dimensional CFD modeling of airflow in a large-opening stone mine and investigating the effect of a fan placement with the movement of trucks.

Feb 1, 2025

By Josef J. Schwegel

The first vertical shaft lime kiln operating according to the parallel-flow regenerative principle was developed and built in the nineteen-fifties by Schmid-Hofer in Austria. Upon proving this concept of calcining or "burning" limestone to be very energy efficient for the production of good quality lime, Maerz Ofenbau AG of Zurich, Switzerland was in 1965 licensed for the design detailing and construction of these kilns. The first regenerative shaft type lime kiln outside of Austria was built in 1966 and through close co-operation with customers and their operating personnel, the advanced technical developments of today's kiln designs were accomplished. At present approximately 190 kilns of this type in capacities ranging from 60 to 700 short tons per day have been built or are under construction throughout the world in highly industrialized as well as less developed countries.

Jan 1, 1981

By J. Frostiak

The Campbell gold operation of Placer Dome Inc. produces an arsenopyrite-sulphide concentrate which must be treated either by roasting, biooxidation or by pressure oxidation to obtain high gold recoveries. Pressure oxidation is a proven process and has the inherent advantage of meeting the stringent environmental regulations in the province of Ontario. A comparison of biooxidation and pressure oxidation was completed early in 1990 and the latter was selected by Placer Dome as the preferred process for replacement of the roasters. The commercial plant design was based on technology supplied by Sherritt Gordon and in July of 1991, the existing roaster operation was shut down and a new pressure oxidation plant was commissioned. The following summary describes the start up of the new facility and presents typical operating data.

Jan 1, 1992

By R. W. Fedors, S. T. Green, F. T. Dodge, D. B. Walter

Spatial and temporal temperature variations in a high-level radioactive waste repository drift can give rise to moisture transport within the drift. Knowledge of this moisture transport may be important to assessing the potential for corrosion of all metallic components in the drift. The model presented here shows one approach to simulating evaporation, transport, and condensation of water in large underground openings using a framework based on computational fluid dynamics. Simulation results that explicitly model water and latent heat transport are presented.

Jan 1, 2004

By K. J. Stanaway

Environmental pressures on waste disposal are forcing pigment producers to use higher content TiO2 feedstocks with lower levels of trace elements. Despite this, 50% of the worlds TiO2 comes from ilmenite concentrates with only 37 -54 % TiO2 An industry growth rate of 25 % in the next ten years combined with trends to diminishing resources and lower grades for rutile (95 % TiO2) and leucoxenized ilmenite (55 to 90% TiO2) mean that unless new discoveries are made soon, the industry will become even more reliant on ilmenite. A hypothetical ideal feedstock is presented and strategies to obtain it are suggested. Reasons for some of the mineral specifications are given.

Jan 1, 1994

By Jon C. Jenkins

In order to plan the most efficient mine installation, a company should take advantage of all available information and tools. One of the first factors of a coal reserve that needs to be determined as accurately as possible is the quality of coal the mine will have access to during the life of the installation. With the aid of many types of well logs and computor analysis, we are investigating several methods of log correlation to determine such data as moisture, ash, sulphur, and BTU on an in place basis. It may be possible to determine this data more accurately in this manner than by using diamond drill cores for analysis and thus allow for a more profitable mine installation. The production of an underground mine is based on many factors, two of these being roof control and line water, where present either in the roof or coal seam. Using many of the same logs obtained from reserve and active mine areas, we have attempted to determine roof and floor characteristics such as strength, lithology, and moisture properties. Using data obtained from this program, we will make comments on possible length of bolt to be used, possible mining width, and pillar size as they would pertain to these reserves and active mine areas.

Jan 1, 1969

By J. C. Agarwal

A significant portion of the, coal mined by U. S. Steel is beneficiated to upgrade the quality of the resultant coke to meet blast-furnace requirements. Primarily because of degradation from modern mechanized mining methods, a considerable quantity of the coal to be beneficiated is in the 1/4-inch by 100-mesh size range. In the cleaning plants, this coal is usually cleaned on concentrating tables and then mechanically dewatered in solid-bowl centrifuges to 9 to 14 percent water. At some plants, to further decrease the amount of water shipped with coal, and to improve the coking characteristics of the coal at its destination, mechanical dewatering is followed by thermal drying. At U. S. Steel's-Alpheus preparation plant at Gary, West Virginia, approximately 50 percent of the total coal produced is in this fine size range, and two fluidized-bed dryers are used for the thermal drying step. The two fluidized-bed dryers are 14 feet in diameter and were designed by the Dorr-Oliver Company. Although the original design called for a rate of drying equivalent to 37 tons, of moisture per hour, presently they are removing twice that amount. This paper describes, the major problems encountered' in operating these dryers at the present, high capacities and how they were overcome.

Jan 1, 1963

By H. V. S. Tingley

My topic today is future trends in compensation for the mining industry. I seldom get the chance to speak about a subject of such immediate interest to an audience, so I would like to make the most of this opportunity by telling you that everybody in this room will become rich beyond his wildest dreams in the next few years. I would like to open my talk that way, but in compensation, like everything else, there is a great gap between dreams and reality. Back to reality. When we talk about compensation, we?d better define our terms because the compensation is really an umbrella for five basic types of payment made to management personnel. Slide 1 identifies these elements of compensation.

Jan 1, 1980

By John B. Squyres

The purpose of this paper is to describe certain features of the uranium deposits of the South San Juan Basin, and to suggest a mode of origin for the deposits which is consistent with the data. A series of photographs is included at the end of the paper to illustrate the nature of the ore bodies. Since the general geology of the Grants Region is well described in the literature, it will be only briefly reviewed, and the time will be spent instead on the morphology, spatial relations, and geochemistry of the ore deposits. Part of this material is original, but data and ideas have been taken from a variety of sources, including the literature and the personnel of the USGS, the AEC, and many of the operating companies of the South San Juan Basin. I gratefully acknowledge these sources. The accuracy of the data and the conclusions presented here are my own responsibility, however.

Jan 1, 1974

By R. Gunda

Due to the rapidly increasing production rates and deepening of mine working areas, there is a drastic rise in the number of thermal issues to be addressed for maintaining a safe mine environment. As high temperatures and humidity in underground mines could affect the health and performance of workers, and ultimately the production rate, it is necessary to provide a properly controlled safe environment. The backfilling of stopes in metal, non-metal mines results in different thermo-physical properties for the hanging, side and foot walls, modeling of which is not provided by any existing mine climate simulation software. This paper presents the modeling of such a single stope using the MULTIFLUX (MF) software, developed at the University of Nevada, Reno. A special case is presented in this paper, where a case study from the Homestake mine in the US with a drift and ramp connected to a stope with high Virgin Rock Temperature (VRT) and various spot heat sources is modeled in MULTIFLUX and CLIMSIM, and the results are compared against each other. Another case is presented in which the stope of the previous case is modeled with walls, each having a different set of thermo-physical properties. These results are compared with the former results to analyze the effect of anisotropic properties.

Jan 1, 2011

By Miguel N. Herrera, Abbas H. Mirza, Fiona M. Doyle

The standard test methods used to determine the pyrite content of coal and mineral wastes, and their propensity to release acidic drainage, are critically reviewed. In addition to analysis of total sulfur by combustion, test methods using selective oxidation of pyrite by HNO3 and H2O2 are available. The oxidation kinetics of pyrite vary appreciably from sample to sample, and it is difficult to ascertain whether complete dissolution has occurred in heterogeneous materials. The reliability, reproducibility and suitability of different standard test methods were studied, using well characterized ore and coal pyrite samples. The kinetics of pyrite dissolution were also investigated. The results are discussed in terms of the fundamental chemical and physical characteristics of each sample, and the implications for waste characterization are considered.

Jan 1, 1992

By James S. Falcone

Soluble sodium silicate materials have well known applications in flotation for desliming, selective depression and corrosion control. Recent advances in the understanding of the complex polymeric nature of silicate solutions using NMR spectroscopy, combined with our studies of the effects of polymeric silicate anions on metal ion activities in solution, oxide mineral surface charges and surfactant adsorption on clays are related to beneficiation processes. The results of these studies indicate the sodium silicates can be used to cause a solution chemistry and particle surface charge characteristics favorable to enhanced effectiveness in typical ore beneficiation systems.

Jan 1, 1981

By D. Bessinger, J. Nell

The electrical conductivity of rutile was optimised as a function of time, temperature and gas composition. These optimised conditions were used to treat rutile/zircon feed prep concentrate samples from a South African heavy minerals producer, prior to electrostatic separation. Enhanced separation between rutile and zircon was obtained when compared to untreated samples. Samples treated in a hydrogen atmosphere and cooled in nitrogen showed the best separation when passed through a high tension electrostatic separator using conditions of high sample temperature and high relative humidity.

Jan 1, 2005

By A. Cordonnier, Ch. Obry, R. Evrard

In spite of the large annual expenditures and the vast field of activity covered, it cannot be said that many new grinding machines have actually come to light and modified the existing market for more than half a century. Manufacturers have mainly made advances in increasing machine sizes, efficiency and reliability, and in machine automation. The relatively recent emergence of roller presses is the only exception to this homogenisation of machine ranges. The development of roller presses in pregrinding has shown the advantages of compression grinding over the ball mill from the power consumption point of view. But classical roller presses still have maintenance problems due to the high grinding pressure. The FCB Research Centre has carried out much work in this field and in particular has studied the advantages of this process in pregrinding and integral grinding. These researches lead to the development of two new compression grinding machines. The first one, HOROMILL®, presented for the first time on the 8th European symposium on comminution at Stockholm, finds its application in the field of fine to very fine grinding in dry process. The second one, RHODAX®, presented at INTERMAT in Paris, covers the field of secondary and tertiary crushing and the first stage of grinding for most of the minerals in dry or wet process. Its high reduction factor permits to do with only one machine the work realised today with two or three crushing/milling stages. These two complementary machines offer a wide range of combination summarised on [Figure 1].

Jan 1, 1995