Search Documents

By D Craw, D Wilson, D Chappell

Gold is extracted by cyanidation of a sulphide-rich concentrate at Macraes mine, and after cyanidation, the concentrate is discharged to tailings impoundments. The concentrate tailings were discharged to a dedicated concentrate impoundment from 1989 to 1993, afterwhich they were blended with the flotation tailings. Since mid-1998, concentrate tailings have been redirected to the dedicated concentrate impoundment. The concentrate tailings contain up to 1 ppm gold, and will be reprocessed in the future. However, it is a regulatory requirement that a contingency plan be in place to rehabilitate the concentrate tailings should the mine operation cease for any reason. Initial predictions suggested that the sulphide-rich tailings would oxidise and acidify, creating a potential long term environmental problem. Investigations of the state of the tailings after 4 years show that these predictions were overly conservative. Only minor oxidation has occurred in the upper 2 metres of the tailings where the pH has locally dropped from 10 (discharge condition) to between 7 and 8. Below 2 metres, the tailings are essentially unchanged from their deposition state. The low rate of change in the tailings is due to their very low permeability which in turn is a consequence of the fine grain size (ca. 15 ¦m). Dewatering is extremely slow, and incursion of oxygenated water is negligible. Calculations suggest that water movement over 30 m will take at least 100 years and possibly 1000 years. The contingency plan is to capitalise on the very low permeability and keep the tailings from drying with a semipermeable cap. A layer of limestone will be added to the top of the tailings, beneath the cap, to enhance alkalinity of any percolating water. If acidification does occur, contrary to expectations, any acid produced will be neutralised by underlying calcite-bearing schist, schist in the concentrate impoundment wall, and the flotation tailings immediately downstream. In addition, dilution by alkaline ground and surface waters would further ameliorate any acidic discharge.

Jan 1, 1998

By Roshan B. Bhappu

This is the Centennial year of AIME and many of us reading this issue of ' will be getting ready to attend the Centennial Celebration in New York from February 26 through March 4. The officers of the Division sincerely hope that a large number of our members will attend the fine technical sessions and social functions arranged for this really big meeting. The year 1971 will be a crucial one for MBD. This SME Division is a working group organized "to furnish a medium of cooperation among those interested in the basic unit processes and unit operations of minerals beneficiation; and to promote the advancement of this branch of mineral technology through meetings for professional intercourse, and to stimulate the preparation, reading discussion and circulation of papers connected therewith." No one can deny the worthiness of these objectives or minimize the efforts that Division officers and members have made to attain them. Much has been done over the past several years to achieve a smooth-running and effective MBD organization. However, there is still room for improvement and much more needs to be done in order to provide the best possible services for the membership and the profession.

Jan 1, 1971

By C. W. Davis

This report follows the same general scheme as did its predecessors; it begins with a dissertation on some phase of ore-testing, continues with results of investigations of ore-treatment methods and of metallurgically important analytical processes, and concludes with an exposition of tests made by established methods on typical ores selected as representative of certain mining districts. One of the first things that is done after an ore has been received is to look at it under the microscope. Microscopic examination serves as an important complement to chemical analysis in interpreting the percentage composition in terms of minerals. If it has been found difficult to treat an ore, the reasons for this action and indicated methods to overcome the difficulties may be ascertained by testing with a microscope. For example, failures in selective flotation have been traced to intimate mineral association and changes in mineral surfaces through incipient oxidation. The importance of surface stains or tarnishes and the presence of adhering slime particles have been found to be responsible for the difficulty experienced in the treatment of certain gold ores.

Jan 1, 1938

By C. W. Davis

This report follows the same general scheme as did its predecessors; it begins with a dissertation on some phase of ore-testing, continues with results of investigations of ore-treatment methods and of metallurgically important analytical processes, and concludes with an exposition of tests made by established methods on typical ores selected as representative of certain mining districts. One of the first things that is done after an ore has been received is to look at it under the microscope. Microscopic examination serves as an important complement to chemical analysis in interpreting the percentage composition in terms of minerals. If it has been found difficult to treat an ore, the reasons for this action and indicated methods to overcome the difficulties may be ascertainedd by testing with a microscope. For example, failures in selective flotation have been traced to intimate mineral association and changes in mineral surfaces through incipient oxidation. The importance of surface stains or tarnishes and the presence of adhering slime particles have been found to be responsible for the difficulty experienced in the treatment of certain gold ores.

Jan 1, 1938

By George A. Savanick

An experimental hydraulic jetting device intended to operate in a 16-in-diam borehole was designed, fabricated, and used to cut coal and simulated coal samples. This device consisted of two 0.107-in-diam nozzles that rotated in a plane perpendicuIar to a 50-inch length of high-pressure tubing. Experi¬ments were also conducted with stationary jets issuing from a single 0.142-in-diam nozzle. Numerous experiments were performed using systematic variations of jet parameters coupled with assessments of cutting rates. These Bureau of Mines tests showed that when operated at 4,000 psi pressure and a 40-gpm flow rate (1) the device can fragment coal up to a distance of 8 feet from the nozzle, (2) 4,000-psi jets cut more effectively than lower pressure jets with the same nozzle diameter, (3) stationary jets do not cut as effectively as moving jets, (4) interkerf breaking occurs when the kerf spacing is less than 2 inches, and (5) if the kerfs are spaced <1/2 inch, the jet is deflected and thereby reduces cutting effectiveness.

Jan 1, 1975

By S. Mundike

A scraper-based block cave method has been successfully applied to extract the Lower orebody at Nchanga since the 1950s. Since inception, scraper drifts and service ways have been supported using steel arch sets fabricated to a specific design from high strength manganese steel To reduce costs and to improve productivity, trials commenced in 2002 using fibre reinforced shotcrete as an alternative support method. One of the areas, the 2420 8E 1C trial drift, was subjected to abutment loading for several months prior to undercutting and cave mining. Shotcrete installed exhibited minor cracking shortly after application but very little deterioration thereafter. Following the success of the trial, the application of fibre-reinforced shotcrete was extended to other drifts. This paper describes the application of fibre-reinforced shotcreteat Nchanga and outlines design and quality assurance methods employed.

Jan 1, 2005

By Deming Wang, R. A. Overfelt

"This paper presents a computer-aided heat transfer simulation method to predict the thermal characteristics of an alloy sample in a special furnace for directional solidification. A two-dimensional transient heat transfer by conduction combined with radiation is developed to calculate the energy exchange between a directional solidification furnace and the sample. Finite difference equations with control volumes are used to calculate the transient heat transfer. A special boundary control volume is used to combine heat conduction and radiation in the transient heat transfer. Heat radiation effects on the surfaces of the special control volumes with a changeable view factor during directional solidification processing are also represented. The simulation results are verified by measurable experimental data. Using the computer simulation model, many thermal properties of the directional solidified castings can be obtained, such as temperature distribution, solidification velocity, the shapes and positions of the liquid/solid interface and thermal gradient at the interfaces. These are very important to analyze microstructure of casting alloys, avoid casting defects and control casting quality. 1 IntroductionIn directional solidification (DS) processing of castings, the temperature distribution, the interface between liquid and solid zone, thermal gradient in the mushy (pasty) zone and solidification rates are very important factors to analyze the microstructure and the casting quality. These variables affect the orientation and size of dendrites, shapes of grains, solute segregation and deleterious casting defects, such as microporosity, freckles and segregation channels. In order to avoid the casting defects, the temperature distribution and thermal gradients of castings during directional solidification must be strictly controlled. However, the structure of furnaces used for directional solidification is often complex. Heat transfer and temperature distribution within a casting not only depend on furnace temperature but also on the thermal properties of the casting alloy, crucibles, retorts etc. A more accurate heat transfer analysis."

Jan 1, 2001

By AIME AIME

EVERYONE enjoyed the coal meeting and found it profitable. At least your correspondent did, and those to whom he talked. Close to a hundred were there. The Coronado proved an excellent headquarters hotel, though it is two miles or more from the business district of St. Louis; its Crystal Room was suitable for the technical sessions; its Lounge adequate for registration and informal chats; its Club Caprice made an artistic setting for the informal banquet; and its Coal Hole in the basement presumably served other needs-unfortunately we passed up an invitation to find out, and never got another. To be sure, the first day of the meeting (Monday, Oct. 28) was a drizzly one, but that only served to keep people inside where they belonged. Believe it or not, the first technical session was only five minutes late in getting tinder way, with H. N. Eavenson&apos;s words of welcome. M. M. Leighton then took over the conduct of the meeting, and invited Eugene McAuliffe to read his paper on how much coal the railroads are likely to use in the future. E. G. Bailey then presented some written discussion; among other things he wondered about the success of stokers on locomotives, and whether or not the burning of coal in locomotives could not he made a cleaner operation. Mr. McAuliffe pointed out that railroads are built to haul coal rather than to burn it. Maximum firebox efficiency is often subordinated to the traffic situation. Powdered-coal firing has not been a success because of limited firebox space. Stokers have resulted in economies indirectly, because large locomotives cannot he hand-fired and stokers thus make them possible. Nowadays it is not so important to do away with smoke, cinders, and soot, because most trains are sealed up and air-conditioned.

Jan 1, 1935

By L. D. Patts, G. H. Schnakenberg

Achieving substantial reductions in the exposure of underground miners to diesel particulate matter in a number of metal and nonmetal mines in the U.S. depends on the ability of the industry to widely implement advanced diesel emissions control technologies, primarily diesel particulate filter (DPF) systems. Recent field studies showed that diesel particulate filter systems with Cordierite and silicon carbide ceramic filter elements are capable of reducing concentrations of diesel particulate matter and elemental carbon by more than 70 and 90 percent, respectively. But those studies and several other attempts to implement DPF systems in underground mines revealed a number of relatively unique technical and operational challenges that are limiting industry-wide implementation of this technology. This paper provides detailed analysis of some of those challenges and short overviews of several projects launched by NIOSH Pittsburgh Research Laboratory in an attempt to provide the underground mining industry with more adequate DPF systems. These systems employ advanced technologies to overcome the most pronounced challenge, the regeneration of DPF elements installed on mining engines that generate relatively low exhaust temperature. This paper presents essential findings obtained through a long-term evaluation of DPF system with diesel fuel burner technology installed on a heavy-duty load-haul dump vehicle in an underground metal mine. In addition, the essential results of the laboratory evaluation of a popular on-highway DPF system which was adapted and optimized for underground mining applications will be summarized in this paper.

By C. H. Elder

An analysis of the geologic structure of an area of Buchanan County, Va., was made by the Bureau of Mines using imagery from an airborne AN/APQ-97 side-looking radar system to evaluate that mapping technique for delineating structural features that may cause mining problems. Side-looking airborne radar (SLAR) was found to be a useful remote sensing tool for geologic structural analysis, Fault and joint systems identified by lineaments and linear patterns in the imagery were verified by surface and in-mine observations. Little Paw Paw fault was extended 10 miles by SLAR lineament analysis. A 22-mile fault, here named the Bishop-Bradshaw Creek fault, was mapped by lineament analysis and verified by observation of the fault on the Bishop Coal Co. mine map and on offset patterns of commercial gas production along the fault and surface observation of lineament along the fault. Three major super-imposed joint sets and several fault or fractured zones were identified by SLAR lineament analysis, showing more complex structure than earlier mapping indicated. SLAR imagery accurately delineated structural features that are known to affect gas migration and accumulation and that weaken the rock forming the immediate roof to mine workings, causing mining problems and potentially hazardous environment in the mines.

Jan 1, 1974

By R. F. Hochstein, A. J. Neale, B. C. Flintoff

"Process control technology holds very significant potential benefits for many mineral and coal processing plants. The impact can be expected in terms of performance improvements (e.g. increased throughput, better quality control, higher availability), through reduced operating costs (e.g. lower reagent consumptions, manpower reductions) and in the form of intangibles (e.g. reduced vulnerability to manpower turnover, increased productivity in the user group). However, the installation of a process control system will represent considerable capital expenditure and will generate an operating cost. No management team would approve the funding for such a project without some reasonable measure(s) of the profitability of a proposed system. This paper describes a methodology for addressing the justification problem. Of particular interest is the approach to quantifying performance improvements, frequently found to be the predominant benefit of process control.INTROPUCTIONProcess control has become widely recognized as an essential component of any processing operation. It has direct impact on productivity, process efficiency and product marketability. The reported pay backs associated with successful installations underscore this observation. As a consequence, many operators who have little in the way of process automation are looking to initiate control projects, while those who currently enjoy some level of automation are looking to upgrade existing control systems (= process + instrumentation + hardware + software + operators + support). While the emphasis here would appear to be on retrofit process control projects, new plants, or those currently in the design stage, will usually find themselves in one of these categories shortly after startup 1."

Jan 1, 1990

Historically, mine ventilation practices as it was referred to then and which was enforced by legislation of those days, focused primarily on the conditions in the working place and little attention given to actual exposures of workers to contaminants in the working environments. With the advent of the Leon Commission of Inquiry into Safety and Health in the South African Mining industry in 1994, findings in the report indicated that more attention should be given to occupational health of workers. The upshot of this report resulted in the promulgation of the new Mine Health and Safety Act (MHSA) with certain sections of it devoted to all the aspects of occupational medicine and occupational hygiene. This paper describes the present situation with regards to statistics on occupational hygiene performance and compensation paid out to persons who have contracted occupational diseases, as well as the way forward in terms of legislation implemented in September 2002 on the chronic and acute issues affecting the mining industry in SA.

Jan 1, 2003

By Frank B. Fulkerson

Aluminum production in the Pacific Northwest has a new potential for expansion and increased stability of operation. This new potential results from greater availability of power; lower freight rates on alumina and aluminum; good market prospects for the metal, including western aluminum market expansion following a decline in defense requirements in the 1950&apos;s; and possibility of developing bauxite deposits in the Pacific Basin as well as other mineral resources. INTRODUCTION This is a report of a special study by the Bureau of Mines of the primary aluminum industry of the Pacific Northwest. It outlines developments relative to the United States as a whole.

Jan 1, 1962

By Benjamin Smith Lyman

THE importance of topography to geology is so commonly underrated as to deserve to be pointed out again and again. The relation of topography to the different branches of geology may be seen best by a glance at them all. Geology is well understood to consist of the observation of facts about rocks as materials of the earth (geognosy ), and the explanation of those facts (geogeny). The facts to observe are: I. GEOMETRICAL, as (1) structure, including the dip and strike at different points, the size, shape, and position of basins and saddles; (2) vertical section, that is, the thickness of rock groups and of their parts ; (3) horizontal or geographical position. II. PHYSICAL, such as texture, whether sedimentary or crystalline ; and, if crystalline, whether granitic, porphyritic, amygdaloidal, globular, or concretionary; whether compact or granular; coarse or fine; pervious or impervious; hard or soft; firm or tender; with cleavage or without; massive or thin; the microscopic structure; also whether magnetic or not; soluble or insoluble; fusible or infusible; and the constituent minerals. III. CHEMICAL, that is, the composition of the rocks and of their minerals and their affinities. IV. PALÆONTOLOGICAL, as what kind of fossils are in the rocks,

Jan 1, 1873

By T. N. Rushton

Rate minima are encountered in the reduction of magnetite with hydrogen. In a certain temperature zone, the reaction rate decreases with rise in temperature. This is inexplicable by classical kinetic theories; neither is a transition in reduction mechanism suitable for interpreting the observed behavior, This anomaly can be fully explained by hypothesizing two species of chemisorbed hydrogen with different adsorption coefficients and activation energies for adsorption. Competition between two energetic states of adsorption occurs with temperature rise, with the low energy state predominating below the anomalous temperature zone and the high energy state above it. The presence of two possible adsorption sites appears to be characteristic for oxidic adsorbents.

Jan 1, 1968

By 1980, the U.S. mining community had reached a broad consensus regarding coal pillar design. The pillar load could be estimated from tributary area theory, and the pillar strength from empirical formulas and laboratory coal strength testing. Then the growth of longwall mining required new thinking. Recently, powerful design methods have emerged from analysis of large data bases of real-world pillar successes and failures. These include the Analysis of Retreat Mining Pillar Stability (ARMPS), the Analysis of Longwall Pillar Stability (ALPS), the Mark-Bieniawski rectangular pillar strength formula, and guidelines for preventing massive pillar collapses. Sophisticated numerical models have also helped transform the pillar design landscape. In the process, our understanding of pillar mechanics has been greatly enriched.

Jan 1, 1999

By Harold B. Ewoldt

The Appalachian Ores Co., Sweetsprings, W. Va. was a small but persistent producer of manganese ore for several years prior to 1942. Most of the ore mined was hard, nodular psilomelane, with some pyrolusite and, wad, occurring in clay. The Bureau of Mines started an investigation of the area in January 1942 and completed the work in May 1942. Twenty-four churn-drill holes were bored, aggregating 2,084 feet. A total of 420 feet of test pits was sunk on selected drill holes to check the churn-drill sampling. Twelve drifts and crosscuts aggregating 139 feet were driven from the bottom of test pits to investigate concentrations of manganese nodules. Three hundred sixty-six churn-drill samples and 102 other samples were sent to Bureau laboratories for analyses. Beneficiation tests were conducted in the Burp.au of Mines laboratory in Rolla, Mo. Results of testing 10 samples indicated that approximately 80 percent of the material in crude ore could be discarded by log washing. Gravity tests indicated &apos;that 55 percent of the total manganese in the crude ore was recoverable as a gravity concentrate averaging 34.6 percent manganese.

Jan 1, 1949

By L. Dudley Stamp

In my last report on Petroleum in Burma and India1, details were given of production and development up to 1932. It was pointed nut, that the only statements available for Burma were those published officially by&apos; the Government of India in the Annual Review of the Mineral Production of India (Records of the Geological Survey of India), which are issued about 10 or 11 months after the close of the year. Operations in Burma are almost entirely in the hands of three companies—the Burmah Oil Co., the British Burmah Petroleum Co. (with its subsidiary, the Rangoon Oil Co.) and the Indo-Burma Petroleum Co.—and these companies preserve a policy of secrecy, so that details are not available of new wells, depth, wells abandoned, or of other figures, except in so far as the Government considers it advisable to publish the information in its possession. GeneRal Developments in 1933-1934 As predicted in 1933, there have been no spectacular developments and no new fields have been discovered. Nor are there any new indications of a likelihood of fresh discoveries. The policy of extremely careful exploitation. has been continued and intensified; production is being maintained at an almost steady level and can be so maintained for many years to come—indeed, it is the policy of the leading company to permit refinery and local market requirements to dictate the production required. Contrary to experience in practically every other part of the world, India has shown a slightly decreased demand for petroleum products—especially kerosene, but also for gasoline. The increased use of electricity would explain the lower demand for kerosene, but the falling off in the demand for gasolinc can only be attributed, according to the Chairman of the Burmah Oil Co., to the depression and to the incidence of heavy taxation. In India (including Burma) as a whole, production was 305,018,751 Imperial gallons in 1931 (8,714,822 U. S. barrels); 308,606,031 Imp. gal. in 1932; 306,009,022 in 1933 and is estimated at 308,000,000 in 1934.

Jan 1, 1935

By Michael J. Jorgensen, Anoop Polsani, Khurram S. Khan

Riveting operations in aircraft manufacturing involves the use of power tools for manually drilling holes for the rivets, power drills for the setting of the holes for the rivets, as well as rivet guns to drive and set the rivets. To close the rivet, the rivet is driven against a metallic bar commonly called a “bucking bar”. The bucking bars are typically held firmly to increase the quality of the riveting, as well as keep the bucking bar from “dancing” against the metal piece being riveted. Thus, employees in aircraft manufacturing involved in riveting are exposed to hand-arm vibration from several sources, and epidemiological evidence suggests that vibration-related musculoskeletal disorders are associated with long term exposure to riveting tasks in the aircraft manufacturing of aircraft.1,2 Recently, tungsten technology has been introduced into aircraft manufacturing for bucking bars, which are heavier than traditional steel bucking bars of the same size. Rivet guns with tungsten pistons instead of steel pistons have also recently been introduced with the objective of reducing vibration exposure to the riveter. The objective of this study was to assess vibration characteristics of steel and tungsten bucking bars and rivet guns to identify the combination that simultaneously reduced the combined exposure to both the “riveter” and “bucker”. Methods Vibration (10g tri-axial accelerometer, Biometrics S2-10G-MF Series 2) was measured from eight experienced employees using seven different rivet guns on size 6 rivets, with the same person bucking for all subjects. Vibration was also measured on two different bucking bars for these same eight subjects, with the same person driving the rivets using the various rivet guns. The rivet guns consisted of three E4 steel piston guns with different RPMs (Guns A-E4, B-E4, C-E4), an E4 vibration dampened rivet gun (Gun D-E4D), an E3 steel piston rivet gun (Gun E-E3) and an E3 and E4 tungsten piston rivet guns (Guns F-E3T and G-E4T). The bucking bars were made of 90% tungsten (1694g) and cold-rolled steel (843g), and were the same shape and size. A two-way repeated measures analysis of variance was performed on the vibration (mean frequency weighted resultant acceleration) on both the rivet gun side and the bucking bar side, and mean rankings were used to assess the vibration simultaneously for the rivet gun and bucking bars to investigate which combinations provided the lowest vibration exposure. Results Frequency weighted resultant acceleration was significantly lower on the E3 tungsten (F-E3T) rivet gun than the E4 steel piston (B-E4) and the E4 tungsten piston (G-E4T) rivet guns (Figure 1). When measuring vibration on the bucking bar, the E4 (A-E4) steel piston rivet gun resulted in lower vibration on the bucking bars than the E4 tungsten piston (G-E4T) and E4 vibration dampened (D-E4D) rivet guns (Figure 2). Additionally, use of tungsten bucking bars resulted in a 35% decrease in resultant frequency weighted acceleration than when using steel bucking bars.

Jan 6, 2006

By James Noll, Sam Janisko

Underground miners are exposed to some of the highest levels of diesel particulate matter (DPM) in the United States. Therefore, it is important to monitor the exposure of miners to DPM, but it can be difficult because of the complex composition of DPM and the number of interferences. Currently, elemental carbon (EC) is used as a surrogate because it makes up a significant fraction of the DPM and is not affected by interferences. Standard measurement methods for EC can be time consuming and only record end of shift results. In this research, a laser absorption technique that enables one to measure EC concentration in near real time was shown to be a beneficial tool. The real time data showed that the fresh air being drawn into a stone mine was not properly reaching the working area and needed to be redirected to decrease DPM concentrations. The real time data also provided a more accurate efficiency ofan environmental cab compared to just using the standard method by detecting the opening of the cab&apos;s window and door. The EC optical monitor was also worn by researchers in a mine to show how it can give not only the average concentration for the shift but also reveal when and where a miner is exposed to DPM. Keywords: Laser absorption, diesel, elemental carbon, mining, exposure