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By David G. Almond

"Economies of scale and the variable characteristics of many large ore deposits have resulted in grinding installations having large SAG mills fitted with variable speed drives. Problems associated with effective operation of this equipment has created the need for better operator knowledge of mill load behavior and the need for new instrumentation capable of providing accurate information about load movement and composition. This paper discusses two performance enhancing instruments available to address these needs.INTRODUCTIONThe economic demands of new mining projects has resulted in increased equipment sizes and this is particularly evident in milling where there are now many SAG mills operating in the range of 28’ – 40’ diameter with installed powers of 8 – 22 MW. These mills are designed to process very high capacities of ore daily2 and the variable characteristics of many of the deposits mined results in the need to vary the mill speed during processing to cater for the changes in ore hardness. Mill speed changes often result in operational problems associated with high-energy impacts striking the mill liners reducing energy efficiency as well as degrading the grinding media through breakage, accelerating liner wear and in extreme cases even breaking liners. These operational problems have given rise to the need to have instruments aimed at providing operators with accurate information in real time about the load composition and movement within SAG mills.The original concepts for operating SAG mills were derived from past experience of operation of conventional fixed speed ball mills. However, the relatively stable conditions that applies with fixed speed and constant ball charge in ball mills supports theoretical approaches to the grinding process based on energy calculations such as Bond’s Work Index concept. Later a set of parameters Si and Bij were used for describing load kinetics, but all of these methods neglect the details of load movement and how the energy is actually used inside of the mill. It is now commonly accepted as a basic rule that SAG mills grind by impact whilst ball mills grind by attrition and consequently SAG mills are designed and operated to generate a large amount of impacts by the cataracting load without paying sufficient attention to where these impacts are actually occurring. Many mills are operated on the basis that as long as the mill is consuming the expected power there is little attention given to the class of bodies using this energy and this often results in the inefficient use of energy."

Jan 1, 2005

By C. Legote

"This paper investigates the conditions leading to the indefinite termination of production in four critical primary panels at an underground coal mining operation, the observed shortcomings in the mining approach, and the proposed strategy to mine through the affected panels. Initial assessment of the abandoned panel conditions indicated time-dependent strata failure,(i.e. bolted roof failure overrunning intersections), which occurred from mere minutes to up to four weeks post-production, with and without prior warning of failure. This prompted the constant re-supporting of back areas, which raised safety and productivity concerns. Investigation of the initial mining conditions revealed that the failures were due to a critical combination of factors, the chief of which was isolated horizontal stress. Other factors that were initially overlooked by the mine (i.e. influence of hydraulic stress, misinterpretation of borehole data), resulted in the conditions being described as abnormal. Remedial actions were determined, and in so doing, a new strategic approach was formulated to thoroughly address all failure concerns. The four panels were explicitly planned to serve as the main intake and return airways for the recently commissioned secondary ventilation shaft, as well as providing access to millions of tons in proven coal reserves. It is thus imperative to mine the panels. A feasibility study showed that the proposed strategy set for implementation would be financially viable. Paper written as project work carried out in partial fulfilment for BEng(Mining Engineering) degree"

Jan 1, 2015

By Steve Kral

When the price of gold cracked the US$9.60/g(US$300/oz) mark last year, the gold-mining industry began to crank up again. This followed several years of gold prices that had languished in the mid-200s. Existing mines increased production and mines that had lain dormant for many years were getting second looks. The United States still produces a large amount of gold. But not much of the new production is coming from that country. Instead, strict environmental regulations still have companies wary of trying to invest the millions needed to start a new mine or expand existing ones. And after years of studies and negotiations between legislators, environmental interests and the mining industry, the United States still has not crafted a new mining law.

Jan 1, 2003

By A. Rajan

"Drawing upon the experiences of a gold extraction plant startup in the Southern Pacific, this paper will describe the importance of the commissioning phases to the project outcomes to achieve early target production despite an overall time compression to attain full plant production. Some of the highlights of the paper include: impact of roles played by the Owner’s construction and operations representatives during project commissioning, the formation of a capable and competent “Mod Squad,” availability of trained operating personnel, control over work priorities and the scope of work needed to bring the plant to safe initial operations. The commissioning team comprised subject matter experts skilled in process technology supported by “generalists” thoroughly conversant in overall plant operations. The merits of a structured team approach to brainstorm and resolve commissioning challenges as opposed to direction from individual subject matter experts is discussed. IntroductionStartup or commissioning is a unique period in the life of a project. Each stage of a project-exploration, feasibility, design, construction, commissioning, initial operations and continuing operations-requires special talents, know-how, and practices. Each stage makes particular demands of the people involved. Initial operations are no exception.Having experienced the 1997 startup phases of oxide and sulfide facilities for a gold extraction plant at a remote island in the Southern Pacific, I can attest to the many challenges and rewards. Commissioning for both facilities was extremely successful and brought the entire project on line well ahead of the targeted completion dates. Using this specific project as an example, this paper will highlight some of the key features of project commissioning. In this paper, the term “pre-commissioning” denotes all activities that lead to mechanical completion; “commissioning” occurs when feed is introduced; and “initial operations” are defined as the duration when operations accepts the system/facility and takes over."

Jan 1, 2000

By E. E. Buban

A self-contained breathing apparatus has been developed to provide complete respiratory protection for a miner in an irrespirable atmosphere. The apparatus has the desired features of comfort, reliability, maintainability, and quick-donning capability. The apparatus is packaged in a moistureproof envelope and is protected in a shock absorbing, fiberglass resin carrying case. The apparatus is a small, lightweight, one-time-use device that can be readily worn on a miner's belt, requires no maintenance and is designed to have a shelf life of five years and a carrying life of three years. It is deployed to the use position in a period of 15 to 30 seconds. Man tests conducted in-house and at the National Institute of Occupational Safety and Health (NIOSH) testing laboratories established that this unit meets all performance requirements listed in the Code of Federal Regulations, Title 30, Part 11, Subchapter B, Subpart H (CFR 30, Part 11) for respiratory protective devices. The unit, which has received joint approval (TC-13F-37) on a prototype basis from the Mining Enforcement and Safety Administration (MESA) and NIOSH has: (1) Ten-minute service life under escape conditions. (2) Thirty-minute service life when the wearer is at rest. (3) Peak-to-peak breathing resistance of less than our inches water column height. (4) Inspired gas temperature of less than 135°F. (5) Breathing gas contents greater than 19.5 volume per cent of oxygen and less than 2.5 per cent carbon dioxin. (6) A weight (complete in carrying case) of 2.75 lbs. (7) A carrying case size of 6-1/2"x 5-1/8"x 3-1/8".

Jan 1, 1974

By I. Liebman

Two triggered barrier systems and several extinguishing agents were tested against coal dust explosion propagating in the main entry of the Bureau of Mines Experimental Mine at Bruceton, Pa. One system used a high-pressure cylinder to propel the extinguishant; the second system used pressurized nitro-gas or Halon 1301 (CF3Br) in a low-pressure system to power the disperser. The relative efficiencies of the extinguishants were determined by compar¬ing calculated concentrations of the extinguishant clouds present in the mine during suppressing of the explosions. Results showed the following trend of increasing effectiveness: Purple-K (KHC03)<water<hybrids consisting of foam or water combined with Halon 1301<Halon alone. On a weight basis, water was two to three times as efficient as Purple-K, whereas the hybrids and Halon alone were only marginally superior to water. Maximum efficiency of an extinguishant is attained by high rates of discharge from the barrier and by minimizing the time interval between onset of discharge and flame arrival to that necessary for discharge. Both the high- and low-pressure barrier systems were demonstrated to be capable of suppressing coal dust explosions; however, because of the potential hazard of the former, the low-pressure system is considered to be the most attractive prototype.

Jan 1, 1979

By M. S. Fleming

The objective was to evaluate central lubrication systems for potential use on underground mining equipment. Previous use on continuous mining equipment resulted in poor system performance because of improper selection of lubricants, component failures, and an inconsistent delivery of lubricant to the bearings. The principles and operational characteristics of systems are reviewed and evaluated, and it was concluded that systems are available which can provide reliable central lubrication if properly applied, installed, and maintained. The procedures for applying a system to a continuous miner are discussed. Investigation revealed the lack of significant information on lubrication-related equipment failures and injuries related to maintenance and repair operations, the lack of significant failure rate data for central lubrication system components, and the lack of performance standards for central lubrication systems and components. To continue the development of systems for underground mining equipment it is recommended that a data bank on failures and reliability for equipment with and without central lubrication systems be created, and standardized specifications and performance criteria be developed for central lubrication systems and components which will be used on underground mining equipment.

Jan 1, 1979

By Edgardo Orderique

El presente texto describe el modelo de desarrollo del proyecto minero Antapaccay, de forma que cada etapa en el proceso de determinación de reservas, sea rigurosamente evaluada y estimada. La secuencia comprende el programa de taladros exploratorios, explicación geológica y mineralógica del yacimiento, interpretación y modelamiento geológico, modelamiento de leyes, definición de parámetros de optimización del pit, generación del pit final, planeamiento estratégico de fases de minado y secuencia anual del mismo, siguiendo el objetivo de maximización del NPV. Asímismo, se explican los aspectos de medio ambiente y relaciones comunitarias.

Sep 9, 2007

By Loren R. Anderson

Traditionally, an evaluation of the safety of slopes has been based on computing a safety factor against failure. In computing the safety factor, the geometry of the slope, the soil parameters and the pore pressures are treated as deterministic quantities even though they are known to be random variables. A pseudo-three-dimensional probabilistic slope stability model has been developed that treats shear strength as a random variable. The model uses the probability of a slope failure as an assessment of slope reliability. The model can accommodate zoned embankments of soil in which the strength is described by the Mohr-Coulomb strength envelope. Autocorrelation functions are used to describe the spatial correlation of the strength parameters, c and tan ø. Model error can also be included in the analysis. The model has been applied to an existing tailings dam and to several hypothetical examples. These examples are presented to illustrate the influence of the choice of the soil strength variability parameters on the probability of failure. The results show that the critical failure surface based on the minimum safety factor is not necessarily the failure surface that will yield the maximum probability of failure. The analysis of the tailings dam shows that variance reduction can be large and that the model error is the dominant source of uncertainty for the embankment analyzed.

Jan 1, 1982

By A M. Sherwood

The Otago and Southland lignite deposits represent by far the largest known fossil energy resources in New Zealand. Despite their size they have remained virtually untouched since exploration in the 1970s and 1980s defined their extent. In total there is an estimated 10.9 billion tonnes of lignite in 13 defined fields in Otago and Southland. Much of the exploration work only targeted seams at shallow depth and it is highly probable that there are further resources at depth in the fields that have been explored to date. &nbsp; L&amp;M Lignite Limited (L&amp;M) holds exploration permits over a number of lignite deposits and is currently engaged in pre-feasibility studies to investigate the potential of the lignites for gasification. L&amp;M is focussing its studies on the Hawkdun and Ashers-Waituna deposits. Coal quality in these deposits, particularly Ashers-Waituna, is highly suitable for gasification. In total the two deposits contain 1647 Mt of potentially recoverable lignite. L&amp;M has engaged a variety of consultants to progress this project. The Hawkdun and Ashers-Waituna deposit databases have been re-evaluated and the resources remodelled. Further drilling has been carried out and the coal quality database has been expanded. The baseline project is to develop a mine to feed a plant that will produce liquids, specifically low-sulphur diesel and naptha, using the Fischer-Tropsch process. The project anticipates a staged development of 10 000 barrel per day units, each requiring mining at the rate of 12 700 tonnes of lignite per day. The production of other products including ammonia-urea, methanol, hydrogen and electric power is also under study.

Jan 1, 2005

By Kazuo Magata, Hirohiko Fujita, Masazumi Tashiro, Yoshiaki Sato, Yoshio Shinoda

The Shinkansen of the Japanese National Railways (JNR) presently in operation between Tokyo and Hakata, approximately 1,000 km, was constructed at three stages: between Tokyo and Shin-Osaka opening in 1964, Shin-Osaka and Okayama in 1972 and Okayama and Hakata in 1975. Works on the extension of 400 km from Okayama to Hakata were launched in March 1970. As construction of the undersea Shin-Kanmon Tunnel on the extension was the toughest task, requiring many, many months, the work was undertaken earlier than any other works on the extension. It was brought to its completion in June 1974 at the cost of about 22, 000 million yen. The Shin-Kanmon Tunnel is the third undersea tunnel constructed to connect the main island of Honshu and Kyushu across the Kanmon Straits. (Table 1)

Jan 1, 1976

By G. R. Hopkins

"Refiners are generally considered solely as fuel producers, but actually they also comprise a group one of the largest consumers of fuel. For example, during the year 1929 the refineries-burned 51,544,000 barrels of oil as fuel, or the equivalent of over 5 per cent of the crude oil processed in that year. In addition enough other fuels - coal, natural gas, refinery or still gas, and petroleum coke - were utilized to raise the total fuel consumption based on B. t. u. equivalent to more than 10 per cent of the heat value in the total crude oil run to stills. Refineries utilize fuel chiefly as the heat-forming element distillation, but also under-boilers in the formation of steam used in refining, for the heating of buildings, and in the generation of electricity.In the early days of refining, the problem of fuel utilization and fuel economy was of scant importance to the refiners. Margins of profit were comparatively high and the major portion of the operatros1 attention was directed toward increasing their throughput. However, the keen competition that has prevailed in the refining industry over the past five years or more has taught the refiners that their expenses, one of the largest items of which is the cost of fuel, must be curtailed. Thus in 1925 the refiners used an average of 829,000 B. t. u. to refine a barrel of crude oil, wheras by 1929 this average had been reduced to 639,000 B. t. u., a decline of 23 per cent (see fig. 1)Since 1925 oil has ranked first as a refinery fuel (see fig. 2). The use of natural gas increased during 1926 and 1927 but declined in 1928 and 1929. On the other hand, the use of refinery gas has grown rapidly in importance. Coal has shown a steady decline in use at refineries since 1925. Petroleum coke has never supplied more than a very small fraction of the total fuel requirements, although there has been a steady increase in its use."

Sep 1, 1930

By V. A. Melezhik, P. K. Skufin, L. P. Nilsson

these factors into account. Theoretical and

Aug 1, 1994

By Fieldner. A. C.

"In preparing this paper, an attempt was made to obtain results of plant-scale carbonization tests on washed and unwashed coal tram to same mine. A letter. in which the following questions were asked, was sent to some 50 coke-oven superintendents and others who might be interested:“What is the influence of washing coal on:(1) The chemical and physical properties of coke, as for example, the size, the amount of breeze, the fracture, strength, cell-structure, etc.(2) The quantity and quality of gas and by-products.(3) The capacity of the ovens.(4) The composition of the coal..""Your general opinion, as well as any specific data or results of testa, on this important subject will be greatly appreciated.""Of the 45 replies received, 24 stated that they had never used washed coal; 11 had used washed coal but had no comparative data on similar coals washed and unwashed; 7 answered some of the questions based on their general experience; and 3 gave some test data on Pittsburgh bed coal from western Pennsylvania. In none of the three tests did the washed coal come from the same mine as the unwashed. The washed coals in the three tests were from the same washery - one of modern construction in which the operations are under careful technical control in order to give a uniform product containing a minimum of surface moisture. The unwashed coals which were previously used in these plants were from different nearby mines in the same coal bed, and were supplied by the same company. Obviously, no sweeping or finale conclusions can be drawn from these few tests on coal from a single washery. Therefore, the writer vas obliged to consult the literature, coal-carbonization and coal-washing engineers, and other authorities to supplement the fragmentary information gleaned from the questionnaires in order to present a picture of chat gas engineers may expect from the use of washed coal in a carbonizing plant."

May 1, 1930

By M. Ge

Pattison Mine is a small sandstone mine located in Iowa. The sandstones produced by the mine are not common construction and aggregate materials. The stones are used to produce a special type of sand for hydraulic fracturing, a critical technique for recovering tight gas and shale gas. These sandstones are very different from the minerals and rocks which have been studied extensively in mining. On the one hand, they are brittle as characterized by an unusually high friction angle, up to 69°, and steeply curved failure envelopes. On the other hand, they are friable, possessing extremely low, and in most cases zero cohesion. The scarcity of the ground control techniques for this particular mining environment has created many difficulties for the mine operators. In order to resolve these problems, a research program was set up by the mine and Missouri University of Science and Technology. This paper discusses the preliminary results of this investigation.

Jan 1, 2012

By A B. Phillips

This paper details the approach adopted to upgrade the current metallurgical facilities at both the Driefontein and Kloof Gold Mines in the Republic of South Africa. Goldfields Ltd operates eight metallurgical plants within South Africa of which three have recently been upgraded to replace the older technology previously installed, with modern equipment. This upgrade was undertaken with a view to improving extraction efficiencies and to reduce operating costs. The upgrade was undertaken in a phased approach with the first phase focused on the replacement of the filtration/zinc precipitation processes with modern pumpcell carbon-in-pulp technology. Included in this upgrade phase was the installation of an automated hands-free electrowinning cell, which represents the first commercial application of its kind in the industry. The second phase of the upgrade entailed replacement of the multiple comminution stages previously installed with large SAG and SAG/Ball mill combinations. Due to the rapid return on these projects, a fast-track approach was adopted which necessitated the purchase of available good conditioned second-hand mills from both within South Africa as well as in Australia. Goldfields Ltd is a large mining house with gold mining operations in South Africa, Australia and Ghana. A well advanced PGM exploration project is underway in Finland- Arctic Platinum.

Jan 1, 2003

By Floyd G. Anderson

A study was made of the effectiveness of dust-control methods being employed in connection with continuous-mining operations. Airborne dust exposures of workmen and dust loadings of return air were determined for six types of continuous-mining machines. The conditions required for control of dust exposure are summarized and include ventilation of the working face by an exhaust system. Return-air dust loadings ranging up to 13 pounds per hour are reported.

Jan 1, 1963

By J. O. Marsden

Parts I and II in this series of papers presented the chemistry of medium-temperature pressure leaching of copper sulfide concentrates and reviewed the metallurgical development of a process to effectively recover copper using medium-temperature pressure leaching and direct electrowinning (DEW). Key features of the process were the use of superfine grinding of the concentrate (to a P98 of 12 to 15 µm and P80 of 6 to 7 µm), pressure leaching at 160ºC and 1,380 kPa (200 psi) oxygen overpressure, DEW to produce LME Grade A cathode, recycling of the lean electrolyte to the pressure leaching step and treatment of a lean electrolyte bleed by solution extraction (SX). Recycling of the lean electrolyte provided all of the acid required to effectively dissolve copper and convert approximately 65% to 70% of the sulfide sulfur to elemental sulfur, resulting in an ?acid-autogenous? process referred to as the ?MT-DEW-SX? process. This paper (Part III) discusses the steps taken to develop and complete a large-scale demonstration of the process at Bagdad, Arizona, in 2005.

Jan 1, 2007

By Greenwood J. N

This is the fourth paper in the series on Australian w,ar materials and the work was undertaken as part of the programme for producing hard carbides. It had been intended to determine the influence of tantalum and columbium&apos; carbides in mixtures with tungsten carbide. Owing to other, urgent developments, it has not been possible to proceed with that programme.1. THE PROCESSING OF A TANTALITE ORE(a) The OreThe minerals in which tantalum and columbium most commonly occur are tantalite and columbite. These two minerals are the end members of an isomorphous series of tantalates and columbates of iron and manganese, but in nature the series grade into each other.Some of the best deposits of tantalum and columbium ores in the world occur in the north-west of Australia. Until recently tantalite low in columbium was the only mine~al in demand but discoveries of extended uses for columbium, e.g., addition of ferro-columbium to high chromium I steels inhibits intergranular corrosion (weld decay), have created a demand for columbite low in tantalum as weB. Both of these types of&apos; ore occur in the Pilbara district in Western Australia and most of the ore mined is exported to America after a preliminary grinding and concentration by gravity.A sample from the Bynoe Harbour locality, west of Darwin, was used in this investigation. It consisted of coarse lumps of tantalite with quartz in minor amounts. Cassiterite w.as also present. A recent investigation!l) gave the analysis as:

Jan 1, 1943

By Frederick H. Raab

A power-line proximity-warning (PLPW) system must have a high probability of detection (alarm activation at a specific distance), low probability of false alarm, and minimal set-up and maintenance. Tests of electric-field sensors have not demonstrated a dependable alarm distance. Alternative sensing methods such as microwave radar, optical radar, and sonar can meet the requirements by direct measurement of the range from the boom to the power line. Suitable microwave techniques include RF pulse, chirp FM/CW, and baseband pulse. Baseband-pulse radar has adequate range capability and does not require expensive microwave components. The radar cross section of a power-transmission cable is adequate for its detection optical-radar systems based upon LEDs and photodiodes are inexpensive, but can achieve only marginal performance in this application because of their limited modulation bandwidth. Since laser diodes and cryogenically cooled photosensors must be used to achieve the desired range resolution, the cost of an optical-radar system is greater than that of a microwave radar system. Sonar systems are feasible, but are not as precise and cost at least as much as baseband-pulse-radar systems. The performance of both optical-radar and sonar systems is degraded by dirt, necessitating the inclusion of a "windshield wiper.&apos; Baseband radar appears well suited to the PLPW application. The cost of a baseband-pulse radar PLPW system is expected to be comparable to that of an electric-field PLPW system. Development and testing of an experimental model are therefore recommended.

Jan 1, 1982