Search Documents

By Dennis C. Martin

Construction of the Cerro Colorado on-off leach pad in northern Chile required about 3 Mm2 (32.3 million sq ft) of fill over an area of about 600,000 m2 (6.5 million sq ft) in irregular terrain with relief of up to 40 m (130 ft). Earthwork construction was completed in about six months using mine waste, placed in 4 to 6 m (13 to 20 ft) lifts with mine haul trucks. The lift thickness was reduced and the compactive effort increased in the upper 10 m (33 ft). This was done to develop a mat for additional resistance to possible differential settlements due to the modest density of the fill and dynamic (earthquake) conditions. A single 2-mm (80-mil) high-density polyethylene (HDPE) liner was used below the leach pads. This was protected from the loading and unloading equipment by bedding and cover systems. It consisted of screened sand, gravel and silt as the bedding and cover layers and a heel of screened gravel and primary crushed low-grade ore.

Jan 1, 1995

By D. Tao

More than 80 million metric tons of fly ash is produced annually in the U.S. as coal combustion by-product. Fly ash can be converted to value-added products if unburned carbon is reduced to less than 2.5%. However, most of fly ash is currently landfilled as waste due to lack of efficient purification technologies to separate unburned carbon from fly ash. A rotary triboelectrostatic separator has been developed and patented recently at the University of Kentucky with unique features. Several fly ash samples have been used to understand the effects of major process parameters on the separation performance. The results show that compared to existing triboelectrostatic separators, the rotary triboelectrostatic separator has significant advantages in particle charging efficiency, solids throughput, separation efficiency, applicable particle size range. Key words: Coal, Combustion Waste; Fly Ash; Particle charging; Separation.

Jan 1, 2008

By Waldo Valderrama, Luis Magne, Paola Grandela

The effect of liner shape on power consumption was studied in a small laboratory mill under various operating conditions. It was found that the angle subtended between the lifter front face and the face in contact with the mill case has the most significant influence. The increasing height of lifter reduced power consumption, whereas the lifter spacing did not show any influence. The effect of height is less relevant at lower front angles. Highest power consumption is achieved with a 45" front angle. A comparison of cylinders and balls under identical conditions gives higher power consumption for ball charges. The data does suggest that, for maximum power draw, slip in the outer layers of the charge and the early recirculation of energy to the mill case should be avoided. Both factors prevent an efficient energy transfer to the mill charge.

Jan 1, 1995

By W. D. Hall, M. Norris, J. R. Henke

Dewatering wells producing iron-rich water experience rapid declines in yield and drawdown due to the formation of ferric (Fe3+) hydroxide deposits in well screens, pump intakes and riser pipes. Precipitation is caused by a combination of dewatering-promoted iron oxidation and iron oxidizing bacteria. Physical and chemical well rehabilitation techniques, as well as alternative well-construction and well development techniques, were evaluated in this study. The addition of acid downhole feed systems to dewatering wells that are prone to iron encrustation can, in many cases, prolong their operational lives up to 500% that of unacidified wells.

Jan 1, 1992

By K. Hanumantha Rao, K. S. E. Forssberg

The limestone deposit of Gâsgruvan, Sweden contains around 89.2 per cent of calcite. Conventional and column flotation studies have been carried out using sodium oleate and modified fatty acid collectors in the presence of sodium silicate modifier. The effects of collector and silicate concentrations, and particle size on the flotation response of calcite have been investigated. The results have been discussed in comparision to the performance of conventional and column flotation cells. The feed size is found to be a significant factor to achieve a high grade calcite concentrate either by conventional or by column flotation. The loss of selectivity at fine particle sizes is examined using a modified DLVO theory.

Jan 1, 1995

By W. M. Hart, Q. H. Shen, J. S. Chen, S. S. Peng

The automatic data-acquisition systems that are now available can continuously monitor and record changes in leg pressure and changes in advancing ram stroke in every shield. These systems can record shearer position at any moment during a mining operation. The data obtained can be used to improve production and maintenance management and can be used to provide better roof control at the longwall face. Research now being conducted jointly by West Virginia University and Cyprus Amax Coal Co. is aimed at developing a longwall-management system (LMS) for mine operators. The LMS software package, which works in the Microsoft Windows NT environment, performs data interpretation and analysis, production management, maintenance management and ground-control management for longwall mining.

Jan 1, 1997

By Paul M. Godlewski, Gerry Millar, Harvey W. Parker

Recently, over 70 railroad tunnels in the western USA have been enlarged and rehabilitated "live track," utilizing modern excavation and lining methods, in most cases to clear the larger double-stack container cars. This paper presents the general conditions of the tunnels and the technical aspects and costs of the rehabilitation of approximately 40 kilometers of tunnels, which range in length from a few hundred meters to 13 kilometers. Concrete-lined tunnels were rehabilitated by grouting and rock bolting, while unlined or timber-supported tunnels were relined with shotcrete and rock bolts. High output lining methods were required because of limited track time. Enlargement has been accomplished primarily by carving notches out of the concrete linings with a roadheader, or occasionally with saws. Unlined tunnels were enlarged by drill-and-blast or roadheader excavation.

Jan 1, 1991

By F. F. Aplan, V. Choudhry

This investigation is an exploratory study to evaluate a large number of potential pyrite depressants for use during coal flotation. Subsequently, the more promising reagents can be evaluated in detail. Several reagent categories (such as alkalis, lime, oxidizing agents, reducing agents, specific inorganic ions and dispersants) that were found to be effective pyrite depressants are discussed here. Other pyrite depressants will be discussed in Parts II and III.

Jan 1, 1993

By Lisa Shevenell

Three pits at the Getchell Mine contained water during a hiatus in mining activity (1968-1983). For this period, expected concentrations of As, C1, SO4 and TDS resulting solely 16om evaporative concentration were computed. Computed values are 1.6 to 2.3 times greater than those measured in local groundwaters. However, computed values fix As, SO4 and TDS are lower than measured values in the pit lakes. In some cases, the computed values are only 8% of the measured pit lake values, indicating a major control on water quality via water-rock interactions. In contrast, computed C1 values exceed measured pit lake concentrations.

Jan 1, 2000

By L. C. Atkinson, E. A. Azrag, T. M. Hanna

The results of using a simple analytical solution and a relatively complex numerical model to estimate ground water inflow to an open pit mine are compared. The analytical solution assumes lateral, radial flow to a fully penetrating pit in an idealized confined aquifer, whereas the numerical model simulates fully three-dimensional flow to a partially penetrating pit from a water table aquifer. The latter is a more realistic simulation of the problem, but the former method is significantly easier to use. Comparison of the results obtained with the two methods for some typical hydrogeologic conditions encountered in mining yields ratios between them in the range of 0.2 to 0.6. These values can be used as a coefficient in the Pit Flow analytical solution to produce reasonable estimates of in-flow even when there are significant differences from the idealized conditions implicit in its application.

Jan 1, 1995

By J. C. Stankus, J. J. McCaffrey, S. Guo, S. S. Peng

An innovative concept in longwall tailgate support is discussed. This new concept utilizes a high-capacity roof-truss system to replace conventional wooden cribs. The first field test was conducted at the Bailey Mine and was very successful. Similar tests were installed in other mines and seams. An extensive instrumentation plan was designed and implemented in the truss test area. The test data demonstrated that the dynamic roof-truss system effectively controls the various abutment pressures caused by longwall mining. Thus, a stable tailgate entry is maintained

Jan 1, 1997

By Robert Irvine

Exploration activity for diamonds in Canada has recently experienced a dramatic increase. Disclosure of a diamond discovery exhibiting features of a potentially economic deposit contained in a kimberlite pipe in the Lac de Gras area of Canada's Northwest Territories has sparked substantial interest in-Canada and abroad and has triggered the largest staking rush in terms of area in the history of Canadian exploration. In this paper, we report on the nature and extent of current exploration activity in Canada for diamonds (with special attention to Arctic regions), the results of this activity to date, and the context in terms of current world markets for diamonds.

Jan 1, 1995

By T. Tamagawa, S. H. Tabaian, I. Iwasaki, N. X. Fu, M. Kobayashi

A gaseous chlorination process for the hydrometallurgical treatment of a chalcopyrite concentrate was investigated. The overall process is visualized to consist of low-temperature chlorination -selective oxidation, followed by aqueous chloride leaching and SX-EW for producing electrolytic copper, elemental sulfur and ferric oxide. In this article, the chlorination phase of the process is described. Initially, the chlorination behavior of chalcopyrite concentrate micropellets was investigated using a small batch-type fluidized bed reactor. The optimum conditions thereby established were used in continuous chlorination tests. The chlorinated products thus prepared were used in the selective oxidation phase of the investigation.

Jan 1, 2000

The problems of toxic, noxious, and explo¬sive atmospheres caused by gases and dusts are certain special environmental considerations in underground mining. Some other problems unique to underground mining are design of stable structures in the strata and their support, lighting the workings, and control of noise in confined spaces. These affect the health and safety of the workmen and deserve critical analyses. Some of the most important environmental parameters of underground mining are summarized in Table 1. The list is not exhaustive but illustrates the scope of environmental planning in underground mining. This chapter will discuss the use of computers and computer models in mine atmospheric environmental planning.

Jan 1, 1979

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 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 D. Edward, C. Clarkson, B. A. Firth

The presence of misplaced ultrafine particles decreases the separation efficiency of unit operations used in coal preparation. Although the classification of fine coal was considered to be adequate for the needs of the coal industry during the 1970s and 1980s, it is apparent that further improvements in the yield/ash/moisture relationship achieved by coal preparation plants will require increased efficiency in this size-separation step. This paper describes the capability of current and developing techniques to address the problems that need to be overcome.

Jan 1, 1998

By G. P. Dvoichenkova, E. A. Trofimova, M. V. Zaskevich, V. A. Chanturiya

The paper presents theoretical and practical aspects of directed adjustment of physicochemical properties (pH,Eh) and ion composition of recycle and mine water by electrochemical treatment. Treatment is run in the conditioners of diaphragm-type with production of alkaline catholyte of pH value up to 12 and acidic anolyte of pH up to 2. In process of water electrolysis the directed motion of Mg2+ and Ca2+ ions is observed from anode volume to cathode one, were they precipitate as hydroxides and carbonates; it leads to decrease of salt content in anolyte and catholyte. The anolyte has been concentrating anions, it is being saturated with oxygen, which reaches 20-35 mg/L. The results of experimental and industrial testing of electrochemical technique for mine and recycle water in flotation of diamond-containing and sulphide-scheelite, hematite, phosporite, apatite-nephelite, bauxite ores indicated the increase of recovery up to 2-1 5% and grade up to 0,5-2%, concurrent with decrease of reagent consumption from 15 to 50 %. Modules of industrial conditioners of different type capacity have been developed.

Jan 1, 1995

By P. K. Davis, B. Gharib

The results of a previous basic study of the flow and design characteristics of hydrocyclones demonstrated that a recovery as high as 99% with a product rating* of 0.95 can be achieved on a batch+ basis with a single, water-only cyclone if it is configured properly. The next logical step was to demonstrate continuous processing of gob for the efficient recovery of coal by means of a laboratory-size demonstration system. A project to design and construct such a single-¬cyclone system was sponsored by the US Department of Energy, which also sponsored the initial study. A recovery of 93% with a product rating of 0.89 was demonstrated. The system design and the data taken are discussed.

Jan 1, 1990

By M. S. Klima, M. Fofana

The use of a laboratory-scale magnetic fluid-based separator for coal separations was examined. A Frantz laboratory magnetic separator was modified by fabricating new pole pieces of the appropriate geometry to provide the proper magnetic field gradients. Two separation chambers, which were constructed of Plexiglas, were designed to fit between the pole pieces. A commercially available, water-based, ferromagnetic fluid was used as the separating medium. The separating density was changed by varying the current intensity of the electromagnet coil. Both batch and continuous separations were made using 0.59 x 0.50-mm and 0.18 x 0. 15-mm coal. The results are compared to those obtained using organic liquids.

Jan 1, 1998