Search Documents

By E. T. Sugar

English China Clays, the world's largest producer of China Clay, has its main production capacity in the South-West of England, where a complex of pits, refining plants, dryers and ports covers an area of approximately 100 square kilometres. The possibility of a computerised information network was first considered in 1980. The system was required to provide information at the central level and also at local plant level to improve co-ordination and control. Immediate access by any authorised user, and flexibility of interrogation were important aims. A small micro-based prototype system was implemented in 1981, and later that year development of the mainframe system commenced. This latter system will provide at least one terminal in every works location and will allow inter-communication of laboratory test data as well as detailed stock levels and production data. An integrated system for order processing will allow stock levels to be monitored in relation to anticipated requirements. The system has been developed by the Data Processing Department using the IDMS database package running on an ICL ME29 mainframe. It was decided to use microcomputers as terminals, which although more complicated because of protocol emulation allows stand-alone applications to be run on the same equipment. Those applications concerning Production Planning are outlined in the paper. Communication on the network is by synchronous transmission over dedicated lines. All data is stored on the central database with terminals accessing it in a star configuration. The system is currently partially implemented with 30 available screens at 18 separate worksites.

Jan 1, 1986

By Uday Kumar

This paper presents details of an availability study for a fleet of diesel engine operated load-haul-dump (LHD) machines used in a Swedish mine. For the purpose of this study, the LHD machines have been considered as a system comprised of many subsystems like engine, brake, transmission, etc., in series. As availability is dependent on both the reliability and maintainability characteristics of the system, together with reliability, the concepts of maintainability are also discussed. The need for exploring the data for the presence of any structure, which is very common in repairable system data sets, is emphasized with suitable examples. Simple graphical techniques are used for verifying the independent and identically distributed (IID) assumption for the data set. The error introduced due to the use of the exponential distribution in place of more appropriate distributions in estimation of availability and reliability characteristics is analysed.

Jan 1, 1989

By N. D. Jagger

In order to maximize the benefits obtained from flocculating agents when used as settling aids in high rate and conventional thickeners, it is often necessary to dilute the thickener feed prior to flocculant addition. In some cases, no flocculation at all is possible unless dilution water is used. The most common method of diluting thickener feed has been to recirculate some of the thickener overflow by means of a centrifugal pumping system. This represents a significant capital and operating cost. Supaflo Technologies of Australia has developed and patented an internal recirculation method known as Auto Dilution (or "Autodil") which is based on the principle that an hydraulic head differential exists between the inside and outside of the feedwell because of the higher S. G. of the pulp inside the feedwell, By installing non-return ports in the feedwell wall at the appropriate level, supernatant solution flows into the feedwell at a calculated rate and dilutes the feed without any need for external recirculation of overflow.

Jan 1, 1993

By Robert L. Virta

An asbestos substitute is any material that replaces asbestos in a commercial product. There are many asbestos substitutes, each with its own unique physical and chemical properties. Substitutes can be inorganic or organic, fibrous or nonfibrous, and natural or synthetic. They also can be used as a direct substitute for asbestos or as a replacement product. Probably in no other field is the diversity of substitute materials so great. The concept of asbestos substitutes is not new. The first major effort to develop asbestos substitutes was undertaken by the federal government. The United States has always been dependent on foreign sources for strategic-grade asbestos, and during World War II, the government was concerned that these supplies would be cut off. Strategic-grade asbestos was critical in many electrical and thermal insulation applications (electrical insulation, battery plate separators, flame-proof boards, insulation for rocket components, etc.). A reliable supply of nonstrategic-grade asbestos also was required for general civilian and military applications, such as in brakes, clutches, and construction materials. The government not only initiated a major search for deposits containing strategic-grade asbestos, it also funded research on synthesizing asbestos in the laboratory and developing products that did not contain strategic- grade asbestos. These efforts, as well as those conducted by the private sector, generally were unsuccessful. In the late 1960s and early 1970s, a second major effort to develop asbestos substitutes began because the general public was concerned about the health threat posed by the release of asbestos fibers during the manufacture, use, repair, and disposal of asbestos-containing products. Strict regulations covering the mining and manufacturing sector already had been enacted because of the issue of occupational exposure. The issue then became environmental exposures. Environmental regulations were enacted, and through time they became more strict. The combination of increasingly strict environmental regulation, maturing of some asbestos markets, and liability issues prompted many manufacturers to discontinue asbestos product lines or search for asbestos substitutes. As a result, asbestos usage dramatically declined from the 1970s to the present (Table 1).

Jan 1, 1994

By Mark W. Cadwallader

Heap leach mining requires liners in order to contain leaching solutions for both economic and environmental incentives. The use of HDPE geomembrane liners for heap leaching is discussed in this paper. Comparison is made to clay liners, with inclusion of economic considerations. Several heap leach projects incorporating geomembranes are discussed.

Jan 1, 1987

By George H. K. Schenck

INTRODUCTION Boom-type miners mechanize the cutting and loading of a solid face of rock having a compressive strength as high as 124 MPa (18,000 psi). These machines differ from continuous miners in that they can cut much harder rock for any given cutter-motor power. In addi¬tion, a boom miner is more flexible, selectively cutting any cross-sectional configuration from circular to square arched faces, 1.57-rad (90°) turns, and mixed faces. The basic operational concept of these machines, utilizing a rotary cutterhead mounted on a slewing boom, gained importance in Europe during the 1960s, where, due to their specialized use in roadway development in coal mines, they were called roadheaders. Along with continuous miners, boom miners share the ability to fully mechanize the cutting and loading of rock, while eliminating the need for explosives and the shattering and overbreaking of roof and rib rock that is normal with conventional mining methods. The machines are crawler-mounted and most have a gathering-arm load¬ing system that, moves the cut rock onto an internal chain conveyor, subsequently discharging the rock into a transport device such as a shuttle car or a bridge conveyor. Light- to medium-weight boom miners are cutting softer rocks and minerals successfully, including coal, shale, rock salt, potash, phosphate, weak sandstones (e.g., those associated with uranium ore), and other softer ores such as iron. Heavy third-generation ma¬chines have extended rock cutting to much harder ores such as borate, oil shale, and almost all rock associated with coal seams, except for the harder sandstones and limestones. The mention herein of specific manufacturers, brand names, or models is made by way of example only and does not constitute endorsement by the author or The Pennsylvania State University. All costs cited herein are in 1977 US dollars. TYPES OF BOOM MINERS All boom miners utilize drag bits fixed on a rotary cutterhead that is powered by an electric motor mounted in the slewing and elevating cutter boom. The cutter¬head is either a ripping or a milling type, and the machines have evolved through three generations (Boldt, 1977). As shown in Fig. 1, only one boom miner cur¬rently produced can use both ripping and milling cutter¬heads on one machine. Table 1 lists boom-miner models built in large num¬bers and/or successfully used or marketed in North America. Table I excludes machines of which only a few have been produced and none sold in North America, such as those manufactured by Demag, Eick¬hoff, Paurat, and Thyssen-Rheinstahl. The only Ameri¬can boom miners are the F-16 and Super ROC¬MINER"', manufactured by AEC, Inc., State College, PA. Machine Generations Three generations of boom miners can be distin¬guished according to their times of introduction, their rock-cutting abilities, and their weight classifications. Fig. 2 illustrates typical best-practice production rates possible from boom miners for selected cutter-motor power sizes (other power figures can be interpolated). Productivity is related directly to the energy applied to the cutterhead and indirectly to machine weight; higher

Jan 1, 1982

By James P. Connell

HISTORICAL BACKGROUND The American Concrete Institute defines shotcrete as "mortar or concrete conveyed through a hose and pneumatically projected at high velocity onto a surface." This definition thus includes what is traditionally known as gunite, which is a pneumatically applied mortar. In mining practice, the term shotcrete is restricted to pneumatically applied concrete, and this differentiation will be used in this chapter. In 1914, following the invention of the mortar gun in 1907, then chief engineer of the US Bureau of Mines (USBM) George Rice developed the gunite process for underground test work at the USBM facility at Bruceton, PA. After World War I, gunite was used extensively in American mines and was also utilized for underground civil works such as the San Jacinto tunnel in California. The greatest development was in Europe where, as early as 1911, gunite was successfully used as an overlay for deteriorated tunnel linings. In 1951, the Swiss firm Aliva developed a pneumatic gun capable of handling coarse aggregate, thus making possible the first use of shotcrete at the Maggia hydropower development. Initially, shotcrete was used to reduce manpower requirements for forming and placing conventional concrete. However, by 1954 Sonderegger was reporting that the structural advantages of shotcrete were derived from its flexibility and from the fact that it could be applied almost immediately after the opening had been made. The incorporation of wire mesh into the shotcrete led to the new Austrian tunnel method or NATM. The use of shotcrete in American mines has been implemented more recently. This delay seems to be due to previously unsuccessful experiences with gunite as a structural material and to the US reliance on wood or steel supports in main-line haulageways. The long experience with the apparently more substantial rigid supports led mine operators to be reluctant to accept the new and seemingly unrealistic lighter shotcrete support. APPLICATION REQUIREMENTS Shotcrete is a relatively new material for use in underground support systems. Consequently, experienced miners are not always available who are capable of applying the material effectively. Shotcrete, particularly in the small cross sections typical of mine shafts or haulageways, is applied in cramped quarters under less than ideal conditions. Adequate lighting should be made available. The surface should be clean and free of running or dripping water. It may be necessary to collect flowing water in plastic pipes or water collection devices. Any dry cement dust from previous shotcrete applications should be washed from the surface in order to assure a good bond. The US Bureau of Reclamation (USBR) while shooting test panels at the Cunningham tunnel in 1974, found that experienced shotcrete operators were able to obtain up to three times greater compressive strengths than were obtained by unskilled operators using the same equipment and shotcrete mix. ENVIRONMENTAL AND SAFETY REQUIREMENTS Since sodium and potassium hydroxide, as well as other moderately toxic compounds, are often contained in shotcrete (particularly where accelerators are used), safety precautions must be taken to prevent skin and respiratory irritation. Nozzlemen and helpers are required to wear gloves, protective clothing, and ventilation hoods with a filtered air supply. Respirators approved by USBM, equipped with chemical filters that will not pass the caustic mists, may be permitted in lieu of hoods if goggles or safety glasses are worn. Protective ointments are available to reduce skin irritation. All air and shotcrete feed hoses should be equipped with safety-type couplings and secured with safety chains at each coupling to prevent whipping in the event of a hose or coupling failure. Some environmental effects can take place down-stream from the development face being supported. The accelerator compounds, as well as the portland cement used in the shotcrete, will be found in the rebound material which falls to the invert of the heading. Since these compounds may be leached from the rebound material and carried by the drainage system, it may be necessary to install neutralizing or other water treatment facilities. Investigations may find that the final reaction with other compounds being leached from the mining operations may result in a more or less environmentally acceptable end product. USES OF SHOTCRETE General Uses Shotcrete, as a combination of cement, aggregate, and accelerator, is utilized for underground openings such as shafts, adits, haulageways, and service chambers for the following general purposes : (1) primary sup¬port; (2) final lining; (3) protective covering for excavated surfaces that are altered when exposed to air (the protective covering may be of a temporary or final nature); (4) protective covering for steel or wooden supports, rockbolts and rockbolt plates, heads, nuts, and other mats, including wire fabric, used to prevent rock-falls; and (5) as a lagging material in place of timber, steel, or concrete between steel or wooden supports. These applications can be grouped into three general use categories: shotcrete used as a rock sealant, shotcrete used as a safety measure, and shotcrete used as a structural support. Use as a Rock Sealant Thin applications of shotcrete can reduce or prevent slaking of shales or other rocks that are altered when exposed to the wetting and drying cycles created by mine ventilation circuits. While shotcrete may be effective in preventing such rock alteration, at the present time it is not as economical or efficient as other commercial sealants. However, if the sealant property can be incorporated into the structural support capability, the added contribution is usually helpful. Thin applications are not usually sufficient if the alteration of the

Jan 1, 1982

By Jerry Peterson

Mine maintenance planning, scheduling and daily workflow communications are crucial elements for enhancing overall efficiency and reducing costs. Equally important, it helps identify time periods that equipment will be unavailable so conflicts with production demands are avoided. The current CMMS Kennecott Energy Corporation (KEC) utilizes does not perform these functions in an effective manner. A solution to this problem was to develop an intuitive web-based maintenance planning, scheduling and work flow system call E-MESA. This paper will discuss the E-MESA'S system structure and advantages and disadvantages of using the web based E-MESA solution to perform the maintenance functions described above.

Jan 1, 2002

By Charles D. Litton

Introduction The successful performance of a mine-wide fire detection system depends upon its ability to detect the presence of a fire rapidly and reliably. It should be sufficiently rapid so that there remains enough time to either safely evacuate a mine or successfully extinguish and control the fire or both. It should be reliable so that false alarms are minimized without sacrificing sensitivity or time response. Systems should also be durable enough to withstand the mine environment over long periods of time while maintaining a high degree of re1iability. Maintenance and calibration of the system should be simp1 e and not require the expenditure of excessive time and manpower to keep it operational. Sensitivity, reliability, and durability of mine fire sensors and their electronic support systems have been the subject of significant Bureau research within recent years. The bulk of this type of information, along with the reports from which the remainder of this paper is derived, can be found in the Bibliography. It suffices to say that there exist commercially available systems for use in mines. This paper addresses a strategy for the use of such sensors and systems. Many factors influence the design of a mine-wide fire detection system, such as the potential sources and modes of ignition, the types of combustibles involved and the quantities avai1able for fire growth and flame spread. Mine air ventilation influences the growth and spread of a fire and also serves to transport the products-of-combustion to other areas of a mine remote from the fire. Fire sensor alarm thresholds place limits on the sizes of fires that can be detected. The time to respond to a detected fire, either in terms of evacuation or control and extinguishment, place additional time constraints on the design of fire detection systems. These factors interact with each other, often in complex ways, and it is the definition and understanding of these factors and their interactions that hold the key to the design of adequate and re1iable fire detection systems. Our level of understanding of the problem has increased dramatically within recent years and it is the intent of this paper to discuss the progress that has been made and how the information can best be used to improve the level of fire detection in underground mines.

Jan 1, 1986

By Robert L. Bates

The natural separation of one element or compound from others in the earth's crust is a rare geological phenomenon; accumulation of large quantities of a separated substance forms mineral deposits of value. Although igneous and metamorphic processes are effective at times, by far the most significant fractionation is sedimentary. High-silica sandstone, high-purity limestone and dolomite, salt, and anhydrite-gypsum occur in very large deposits and are termed first-order fractionates. The marine diatomite of California, the trona of Wyoming, and the kaolin of Georgia and South Carolina are in deposits of comparable purity but smaller size, and are designated second-order fractionates. The paper considers the various processes and environments in which such industrially valuable deposits were formed.

Jan 1, 1972

By Francis R. McAllister

SYSTEM ENGINEERING Years ago, while attending Harvard's Advanced Management Program, Professor Robert Hayes introduced our class to the, then not-so-familiar, concept of systems engineering. First assignment-dinner at The Benihana of Tokyo Restaurant! Delighted, but a bit mystified with the assignment; we had dinner at Benihana. Back in class, Professor Hayes inquired about the assignment and persuaded us; that Rocky Aoki's business formula for Benihana was not necessarily Japanese cuisine, but rather the systematic way in which he moves more people-if you will, processes more people through his restaurants than his competition, by systematically linking all restaurant functions. For instance, the bar is a holding area in which patrons ideally wait no more, or no less, than 20 minutes. When seated, your table, which accommodates eight, is filled with eight even if you are a party of two. The Japanese chef is also the entertainment, and when, at the end, he cleans the grill, you are being subtly prompted that dinner is over. The bill accompanies ice cream, systematically delivered shortly thereafter. You are expected to pay promptly and depart, as there are eight more, mostly unacquainted, people who have waited 20 minutes in the bar, and who are assembled ready to be seated at your table. For me-this was electrifying. I understood the concept, concluded it was very powerful and felt prepared to conquer whatever, by means of its application. That was years ago and I can safely say I have yet to fully realize on the euphoria of that moment. Why? Well, I simply conclude: • The concept of systems engineering is simple and not revolutionary, but The application of systems engineering is far from simple and is revolutionary.

Jan 1, 2004

By Meliton M. Garcia, Satya Harpalani

The volume of gases produced in major and trace amounts as a result of detonation of explosives in an underground mine was determined. The volumes of major gases (CO, CO2, NO and N02) were measured immediately following detonation, during the mucking operation, and following the removal of muck. Tests to identify and quantify the gases produced in trace amounts were performed following the detonation only. The composition of the gases produced varied significantly depending on the composition of the explosive/blasting agent. An average of 95% of the gases produced were found in the test chamber immediately following the detonation, while 2% was found in the chamber following the removal of the muck. Several compounds were identified in trace amounts. Of particular interest was the detection of benzene, toluene, butenes, ethyl benzene and naphthalene since exposure to some of these compounds, even in trace amounts, could present a serious health hazard.

Jan 1, 1987

By I. Chatterjee, M. Misra

The principle of microwave drying of fine coal is based on the selective absorption of microwaves by water. Coal is a poor absorber of microwaves. As a result, water can be removed from fine coal by selectively heating water molecules. One of the difficult problems during microwave heating is the exact determination of temperature in the core of the materials. The electromagnetic energy absorption in coal/water mixtures during microwave drying is controlled by several factors including the dielectric properties of the constituents. In this paper, electromagnetic and thermal models of coal are presented that can predict the energy absorption and temperature distribution during microwave drying.

Jan 1, 1992

By J. M. Scharer, Bruce E. Halbert, Lysane Bouduc, Douglas B. Chambers, Jennifer L. Kirkaldy, Carol M. Pettit

Io contrast to acid mine drainage (AMD), neutral mine drainage (NMD) has not yet received widespread attention. Metal and sulphate concentrations can be elevated and of concern in neutral drainage from waste rock and tailings. In the present paper, metal release in high ionic strength mine drainage at neutral pH is evaluated at several mine sites. Specific factors including oxidation rates, buffering capacity, and hydrology are also addressed and their effect on the production of contaminated NMD from mine wastes is evaluated. Case studies are presented involving current seepage water quality and predictive geochemical modelling to illustrate the possible time frame and magnitude of the contamination.

Jan 1, 2000

By Peter W. Scott

Feldspars have major uses in glass manufacture and in ceramic products. About 6 million metric tons (6.6 million short tons) are used annually. Feldspars are desirable because of their high aluminum and alkali contents. Na feldspars are favored for glass, while K feldspar is often preferred in the pottery and tile industries. Economic deposits occur in a variety of geological environments. Most are in granites or granite-like bodies, pegmatites being a common source worldwide. Alkali granites, particularly those some- times called alaskites, are mined directly as a source of feldspar and associated minerals. Some other igneous bodies, such as aplites, rhyolites, and partly altered granites (for example china stone) provide alternative feldspar-rich products. Nepheline syenites and phonolites are other sources of feldspar and contain higher amounts of alkalis. Feldspar-rich (arkosic) sediments derived from the weathering of pegmatites and granites are widely extracted and processed for use in ceramics. The present study reviewed the various sources of feldspars throughout the world. Data on the quality of products has been taken from literature, and samples have been obtained from a large number of producers. The mineralogy and chemistry of the samples has been determined and, as far as possible, have been related to the geology of the source area. Feldspar products show a wide range of chemical and mineralogical compositions. Some are pure Na feldspar (albite), others are made up entirely of K feldspar (microline and orthoclase), but many are mixtures of Na and K feldspars. Significant quantities of quartz are often present, and many products contain mica and kaolinite. Fe203 con- tents are very low, typically less than 0.1 percent. Detailed mineralogical studies show that four groups of products can be recognized on the basis of feldspar mineralogy. These are albite, albite with microcline, microcline with orthoclase, and orthoclase with albite. Products containing microcline and orthoclase together are mostly sedimentary in origin. Those with albite only, or albite with microcline have a pegmatitic or granite origin. Those containing orthoclase as the dominant K feldspar are derived from aplites or rhyolites. There does not appear to be any relationship between the feldspar mineralogy and the quartz content. Peraluminous S- type granites and pelite-dominated high-grade metamorphic rocks, in which there is a significant volatile component, are likely to be the most important feldspar sources. Partial kaolinization of feldspar-containing rocks often improves minability, decreases crushing costs, reduces iron content, and increases the K2O/Na2O ratio.

Jan 1, 2001

By T. R. C. Aston

Extensive undersea coal reserves, identified in the offshore portion of the Sydney coalfield, Nova Scotia, have resulted in the implementation of a multi-year research program to develop site specific guidelines for the undersea longwall mining operations. At present, uncertainty exists regarding the applicability of the current undersea mining guidelines. Preliminary studies have revealed four potential schemes for monitoring seafloor longwall subsidence profiles: seasurface, subsea, geophysics, and direct monitoring. However, further work has indicated that the use of marine geophysical techniques may be the most effective method of identifying and evaluating seafloor subsidence profiles by comparing pre- and post-mining seafloor topographies.

Jan 1, 1990

By B. Moudgil, Hassen El-Shall

Particle shape and size distributions are among the most important parameters that affect the filtration efficiency of phosphogypsum in wet- process phosphoric acid production. Cost-effective enhancement in filtration rate is desired by phosphoric acid producers for higher plant capacity and lower operating costs. In this regard, numerous research efforts have been carried out in different laboratories as well as in pilot and plant testing. Nevertheless, changes in phosphogypsum crystal shape and size distribution deserve special attention. In this study, the results obtained in the presence of Crysmod and Hiflo-S5 surfactants are discussed. The influence of such additives on crystal morphology and size distribution are studied under different sulfate contents (supersaturation). The obtained data are correlated with process efficiency parameters such as filtration rate, digestion of rock, and recovery of phosphate values. Up to 60% increase in filtration rate is obtained. In addition, an increase in digestion efficiency and P205 recovery is achieved due to addition of surface active agents. The observed beneficial effects are explained in the light of the changes induced in crystal habit, size, and size distribution.

Jan 1, 1999

By T. Malterer, R. Adams

Peat has unique physical, chemical and biological properties. These include high porosity and water retention, high absorption and adsorption properties, and high buffering capacity. In addition, peat is a rich medium for microorganism activity. Peat has traditionally been used for horticultural purposes. However, in recent years, peat is increasingly being used for waste- treatment purposes. This paper reviews North American literature on the use of peat for waste-treatment applications. The literature indicated that peat has potential for use in the treatment of municipal and on-site effluents, for the removal of low concentrations of heavy metals and for the adsorption of liquid and gaseous hydrocarbon pollutants.

Jan 1, 1997

By Steve Garcia

GEORGE WEINMAN: Our next speaker is Steve Garcia, operations vice president and general manager of mining at IMC-Agrico, Florida. Steve was born in Lakeland, Florida, to an IMC mining family. He has 17 years with IMC-Agrico and Freeport companies, including assignments in North Carolina, Nevada, Arkansas, and Indonesia. His work within the industry includes technical and operating positions including chief metallurgist, drying superintendent, and mines operations manager at Pane Creek. Other experiences include design of a grassroots phosphate facility in North Carolina; construction and start-up of a gold facility near Elko, Nevada; work in the Blytheville, Arkansas, ammonia urea facility; and three years managing engineering, construction, and support services in Irian Jaya, Indonesia. Steve's presentation is "Evaluation and Standardization of Multiple Slurry Pumping Systems."

Jan 1, 1998

By J. Mark Richardson

Modern mining operations are increasingly affected by complex economic factors. Broad and rapid fluctuations in metal prices, rising operating costs, socio-political trends and the inherent technical difficulties encountered in most operations, all can combine to quickly change once-profitable ventures into money-losing propositions. Accurate knowledge of metal inventories during all phases of an operation has become essential to wise management decision-making. This paper reviews key elements of metallurgical accounting: sampling theory, measurement technology and computerized data adjustment. Application of current technology to the reconciliation of a hypothetical operation is discussed.

Jan 1, 1991