Search Documents

By J. G. Groppo

A series of performance studies have been conducted using counter-current column flotation to recover a marketable clean coal product from existing preparation plant fine waste streams. The test work was conducted at several preparation plant sites in Kentucky and Virginia and utilized a 0.15m (6 in.) I.D. column that was 5.79m (19 ft.) high. The refuse streams tested included both thickener feed and classifying cyclone overflow with a typical size distribution of 100 mesh X O. The percent solids of the column flotation feed varied from 1.5 to 15% while the ash content ranged from 30-60%. The concentrates produced contained 2-10% ash with BTU recoveries of nearly 90% using 0.12-1.25 kg/ton (0.25-2.5 lbs/ton) fuel oil and 0.12 kg/ton (0.25 lb/ton) MIBC. These results were consistent with or better than results obtained in preliminary laboratory scale column flotation evaluation. Test results from 7 different seams are discussed as well as scale-up relationships utilized to design a full scale installation presently in operation.

Jan 1, 1990

By Edwards R

Greater efficiency of capture of minus 6 mm to fine micron size particles of free gold is achieved with the Knelson Concentrator. The development, principles of operation and recent innovations relating to this enhanced gravity concentrating device are described by the inventor, followed by a description of application and consequent economic benefits in low grade alluvial gold deposits by a large scale user of Knelson Concentrators in the Northern Territory of Australia.

Jan 1, 1990

By L. M. Cenegy

The formation of scale is common in gold ore processing plants. A working definition of scale, applicable to the various scaling conditions found in gold ore processing plants, would be: "a hard, tightly adhering deposit formed in place by the precipitation of calcium-bearing mineral compounds from water". The most common scale found in gold processing plants is calcium carbonate (CaCO3) although calcium sulfate (CaSO4) is occasionally a problem.

Jan 1, 1990

By M. C. Roberts

The material composition of product is defined as the quantity of metal used per unit of product manufactured during a year. This ratio measures the efficiency of converting a ray material into final products. The material composition of product has shown steady and persistent declines over time for most metals and materials. This tendency demonstrates the continued improvements in manufacturing technology, resulting from substitutions of other materials and improvements in production efficiency. The purpose of this paper is to study trends in the material composition of product to reveal the impact of advanced materials on the use of traditional metals.

Jan 1, 1990

By N. Arbiter

The theoretical analysis of tumbling mill energetics and performance has largely neglected mill dimensionality, and, in particular, the importance of the length/diameter ratio. This is in spite of the fact that practice varies substantially in this area: geographically, for semi-autogenous and autogenous mills, as between North America and South Africa/Scandinavia; historically, for overflow ball mills, for which the L/D ratio has increased significantly from the earliest small mills to/the largest mills currently. The present study is concerned primarily with the influence of the L/D ratio on the design and operation of overflow ball mills; on the occurrence of the overload phenomenon; and on the limits, if any, it may impose on mill capacities because of critical pulp axial velocity limits. It will be shown that the shape face or is of major importance in this area; and that its adjustment to the extent that this is practical should remove the diameter limitations previously postulated for this mill type.

Jan 1, 1990

By B. K. Cantrell

A miner working in an underground coal mine with diesel equipment is exposed to a wide array of pollutants from the diesel exhaust. These include CO, CO2, NO, NO2, SO2, diesel-exhaust aerosol, and a variety of hydrocarbon compounds. A quantitative definition of the health risk resulting from these exposures remains elusive, but during the past several years, progress has been made in defining the problem. Results from epidemiological studies by Garshick, et al. (1988); animal inhalation studies by Mauderly, et al. (1986); Iwai, et al. (1986); and Brightwell, et al. (1986); and in vitro studies by Lewtas, et al. (1986), have provided sufficient data for the National Institute of Occupational Safety and Health (NIOSH) to recommend that "whole diesel exhaust be regarded as a 'potential occupational carcinogen,' as defined in the Cancer Policy of the Occupational Safety and Health Administration," NIOSH (1988). NIOSH further stated that "though the excess risk of cancer in diesel-exhaust-exposed workers has not been quantitatively estimated, it is logical to assume that reduction in exposure to diesel exhaust in the workplace would reduce the excess risk."

Jan 1, 1990

By George Hope, Edward H. Smith

In late 1989, LAC Minerals purchased 65% of Bond International Gold and as a result became controlling shareholder of the El Indio Mine through Bond and San Jose. El Indio is a world class, complex sulphide gold deposit located in the hydrothermal alteration belt of the Andes mountains in the 4th Region of Chile. The mine is located in the high Andes about 185 km east of La Serena at an elevation of 4000 meters. The 1450 workers at El Indio live in the mine camp at 3200 m and on days off are bussed to La Serena. The El Indio mine was started in 1979 by St. Joe Minerals Corp., bought by Bond in 1987 and subsequently by LAC in 1989. The mine has produced 2.7 million oz. of gold, 9. 5 million oz. of silver and 170,000 t of copper since start of operation. The mill is currently operating at a rate of 2850 t/d and producing a copper/gold concentrate which is roasted to produce a copper/gold calcine and high quality, saleable crude As203• A small proportion of the precious metals are also produced as bullion from the leach circuit. Total production during 1989 was 224,197 ounces of gold, 1,309,342 ounces of silver and 26,968 tonnes of copper. The average cash cost of production for the period was U.S. $96 per ounce of gold, net of by-product credits. The average realized price was $5.30 per ounce of silver and $1.14 per pound of copper.

Jan 1, 1990

By Hustwick I

New Zealand Steel Mining Limited operates two independent sand mining operations on the West Coast of the North Island of New Zealand. (Fig. 1)Waikato North Head 30km south of Auckland supplies ironsand concentrate as the raw feed for New Zealand Steel's works at Glenbrook, and Taharoa 70km further south, exports ironsand concentrate to Japan. Taharoa uses two sets of six low pressure Warman centrifugal pumps in series to load bulk ore carriers 3km off shore through two underwater pipelines.Waikato North Head delivers the ironsand to Glenbrook l8kms through a 200mm ID buried pipeline using two stages of high pressure positive displacement (HPPD) pumping.A high level of operating and maintenance expertise has been developed since commissioning the two systems which are proving to be reliable, efficient and of minimal impact environmentally.

Jan 1, 1990

By S. K. Bhatt

This paper reviews major developments in continuous haulage technology for underground coal mines. Haulage systems, both in use and development, are investigated through a comprehensive literature search and visits to mines and manufacturers. The systems include flexible conveyor train, mobile conveyor, multiple-unit continuous haulage, extensible, and belt turning systems. Strengths and weaknesses of the systems are assessed in light of their operating under remote control and their application to the computer-assisted continuous mining machine being developed by the U.S. Bureau of mines. Through mining scenarios, candidate haulage systems are conceptualized to be consistent with the capabilities of the mining machine.

Jan 1, 1990

By R. Bhaskar

An airborne dust cloud is an ensemble of particles of varied size, density, shape and states of aggregation. An understanding and quantifying of the dispersion and deposition of the dust generated in mines is essential to the development of measures for reducing worker exposure to dust. In coal mining, the major portion of the dust is generated during the cutting of coal using either a shearer or a continuous miner. The major phenomenon affecting ambient concentration is the deposition of dust. Particle deposition may take place due to the effect of gravitational, inertial, electrostatic, and thermal forces, and mechanisms such as Brownian and eddy diffusion, and inertial impaction. The three major mechanisms of deposition in turbulent flow in mines are diffusion (Brownian and eddy), sedimentation and inertial impaction. The mechanisms determining particle deposition are size dependent.

Jan 1, 1990

By R. H. Lien

The Bureau of Mines, U. S. Department of the Interior, is investigating chemical and biological decontamination of complex wastewaters such as tailings pond water containing 280 ppm CN and 5 ppm Se as well as significant concentrations of arsenic, copper, iron, silver, and zinc. The most effective chemical procedure involves cyanide oxidation using hydrogen peroxide or sodium hypochlorite followed by selenium reduction using ferrous hydroxide. The effluent contains <l ppm CN and 20 ppb Se; concentrations of other major contaminants meet EPA drinking water standards. Preliminary research indicates that biological cyanide oxidation is possible even in highly alkaline solutions (pH 10.5) containing high cyanide concentrations; indigenous bacteria destroyed 85 pet of the cyanide. Exploratory research shows that other bacteria removed up to 79 pet of the selenium from chemically oxidized, low-cyanide water. These promising results may lead to a final processing scheme that involves a combination of chemical and biological techniques.

Jan 1, 1990

By R. A. Haney

The Mine Safety and Health Administration (MSHA) has conducted studies both in coal and noncoal mines to evaluate methods for sampling and separating diesel particulates from mineral dust aerosols. The agency is investigating size separation techniques to distinguish between diesel particulate and respirable coal mine dust. Additionally, ashing techniques have been used to distinguish diesel particulate from mineral dust in metal and nonmetal mines. As part of these studies, personal exposures to diesel particulate for various mining occupations have been measured. This paper describes the measurement techniques and summarizes the exposure levels for various underground mining operations.

Jan 1, 1990

By DAVID C LAURENCE

The richer, shallower sapphire deposits of the New England region of New South Wales which have been traditionally mined by the small miner are almost worked out. Larger mining and exploration companies are replacing the small miner and exploring for the primary source of sapphire or lower grade alluvial deposits.Although in recent years considerable exploration effort has been directed at locating the primary source, commercial exploitation of sapphire is still restricted to the working of alluvial deposits.If the Australian industry is to compete against Asian and African producers it must use cost effective exploration, mining, processing and marketing methods.

Jan 1, 1990

By R. E. Krauss

The McLaughlin Mine is a world class epithermal gold deposit located in the coastal thrust fault of Northern California, U.S.A. Homestake adopted a proactive strategy in the permitting of the Mine. Extensive environmental base line studies were undertaken. Engineering and process alternatives were evaluated for environmental impact along with other factors. A unique pressure oxidation process was selected. Screening studies were conducted as a basis for the selection of waste rock and tailings disposal sites. Project engineering and permitting were fast tracked. Construction required eighteen months and the first gold bar was poured in Parch of 1985, six years after the initial discovery. Project facilities are designed and operated so as to minimize environmental impacts. A comprehensive monitering program demonstrates permit compliance. Reclamation of the site is ongoing throughout the Mine?s twenty year life. Non-mined lands are managed to maximize wildlife habitat value.

Jan 1, 1990

By R. W. Waytulonis

New exhaust control techniques and devices may be necessary to meet future diesel particulate matter emission standards in underground coal mines. This paper reviews conventional work practices and devices used to control diesel exhaust emissions, and new techniques being tested by the Bureau of Mines. Discussions will center on important work practices and on the function and efficiency of exhaust after-treatment devices. An industry/government cooperative research project to develop and test an exhaust after-treatment system for part 36 equipment is also discussed.

Jan 1, 1990

By N. B. Aughenbaugh

Compacted clays are used as permeability barriers in many mineral engineering projects such as heap leaching, containment ponds, tailings disposal and earth dams. Source materials used for clay liners include a wide variety of sand, silt and clay admixtures that exhibit dramatically different engineering properties when densified. The permeability and plastic properties of fine-grained soils are reviewed with respect to the state of compaction as the water content varies. Be-cause they are weak in tension, compacted clays are susceptible to cracking when subjected to differential flexural movements. Designs of compacted clay liners must include an evaluation of their flexibility which is the ability of a fine-grain soil to bend plastically without cracking. This paper will also discuss the importance of flexibility with respect to soil types, compaction effort, failure mechanism and testing evaluation to the performance of clay liners in preventing seepage of pollutants from a containment site.

Jan 1, 1990

By William H. Pailes, Vincent Castronova, Daniel Lewis, Norman L. Lapp, George Goodman

"INTRODCJCTIONAlveolar macrophages are free lung cells located on the surface of small airways and alveoli. These phagocytes play an important role in the protection of the lung against airborne bacteria and particles.1 However, hyperactivation of pulmonary phagocytes can lead to excessive secretion of enzymes and reactive oxygen species which could result in lung injury, emphysema, or fibrosis.2,3 Analysis of bronchoalveolar lavage effluents for cell types and cellular activity has yielded information concerning the etiology of various pneumoconioses. For example, emphysema associated with inhalation of coal dust or cigarette smoke has been related to enhanced secretion of reactive oxygen species from alveolar macrophages.4-7 In contrast, hypoactivation of alveolar macrophages has been associated with inhalation of diesel particulates"" and has been related to increased susceptibility to pulmonary infection. s Inhalation of cotton dust has been associated with dramatic increases in lavagable polymorphonuclear leukocytes9 while pulmonary sarcoidosis and silicosis have been related with high numbers of lymphocytes in lavage effluentsl0,11The objective of the present study was to obtain lavage effluents from 8 control subjects, 8 healthy power plant workers exposed to fly ash, 1 healthy coal miner, and 1 rock driller with acute silicosis. These effluents were analyzed for total numbers of alveolar macrophages, lymphocytes and neutrophils and for secretory activity of alveolar macrophages. Data were then analyzed to determine what response patterns were characteristic for given dust exposures.METHODSSelection of SubjectsThe 8 control subjectS were all adult males from the area of Morgantown, WV. Two subjects among the controls had smoked cigarettes for approximately three pack-years and had stopped more than ten years ago. The 8 power plant :workers were all healthy adult male employees of a power facility in Hatfield, PA, approximately thirty miles from Morgantown. One of the power plant personnel was a comparable ex-smoker. The remaining subjects were all lifelong non-smokers. The coal miner was a healthy non-smoking male from Morgantown, WV. The rock driller was a patient under treatment with corticosteroids for acute silicosis. He had shown considerable clinical improvement with this treatment but still manifested significant radiologic and pulmonary functional abnonnalities at the time of lavage. The mean age of the 8 control subjects was 36 years (range: 31 to 49 years); the mean age of the remaining subjects studied was 38 years (range: 29 to 53 years)."

Jan 1, 1990

By Bodo Peinemann

For more than 35 years Lurgi has been providing its fluid bed roasters on a world­wide basis. The current total annual capaci­ty of the 250 Lurgi roasters approaches 26 million mt of sulphide minerals, including gold-bearing flotation pyrite concentrates. While the stationary fluid bed has been uti­lized for roasting exclusively, Lurgi has now commercially introduced its Circulating Fluid Bed (CFB) technology for gold roasting in a successful effort to maximize gold re­covery.

Jan 1, 1990

By Gordon T. Austin

The combined value of production of natural abrasives, which includes tripoli, special silica stone, garnet, staurolite, and emery, increased about 9% in 1988. In the case of emery, the increase was due to an increase in unit value of the material produced. The increase in the value of garnet and staurolite production was simply the result of an increase in the quantity of materials produced. However, special silica stone experienced both an increase in unit value and quantity produced. The nonmetallic manufactured abrasives industry, which includes only silicon carbide and fused aluminum oxide in the reported statistics, enjoyed the best production year since 1981 in terms of total quantity produced. Production increased 22% in quantity and 16% in value com-pared with those of 1987.

Jan 1, 1990

By K. Wood, R. McIvor, P. Blythe, M. Lavallee

A new analytical approach for characterizing and improving the performance of ball milling is presented. Individual ball mill circuit design and operating variables can be related to overall circuit performance through two distinct parameters for classification and breakage. The ball mill circuit functional performance equation is presented.Total mill x Classification x Test specific x Grinding power draw system efficiency grinding rate rate ratio= Production rate of new product size materialExamples from industrial plants and applications in the research and development field are discussed.

Jan 1, 1990