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By Joseph M. Keane

Introduction The English word "sedimentation" is derived from the Latin verb "sedere" meaning to sink down. As a mineral processing unit operation, sedimenta¬tion has been defined as the separation of a suspension into a supernatant clear fluid and rather dense slurry containing a higher concentration of solid (Brown, G.G. 1960). Sedimen¬tation has been historically subdivided into thickening, which has the primary purpose of increasing the solids content of one of the thickener prod¬ucts relative to the feed stream, and clarification, which has the primary purpose of removing solids from the feed stream to produce a product essentially free from particu¬late matter. There is no absolutely precise distinction between these subdivisions and in certain applica¬tions, both objectives can be accom¬plished. Major Design Factors The capacity of conventional metal¬lurgical sedimentation devices is a function of slurry throughput and its attendant settling rate. Important factors, recognized by early investigators (Taggart, 1972), which influence the settling rate of a given metallur¬gical slurry include: Feed dilution or solids-liquid weight ratio Size and shape of the particulate solids Specific gravity differential between the solids and liquid phases Presence of electrolytes and/or flocculants Pulp viscosity Slurry temperature In addition to the foregoing histor¬ical factors, recent investigators have noted (Pearse, M.J., 1977) that other parameters which may have an influence upon settling rate and, thereby, thickener performance include: Method of flocculant application Particle size distribution Particulate wetting characteristics Feeding arrangements Rake speed and type Existence of convection currents Wind disturbance Evaporation All of the above factors should be examined and the effect upon thick¬ener performance brought about by manipulating the factor over the expected operating range should be determined if performance optimization is desired.

Jan 1, 1986

By T. B. Whitmoyer, J. E. Sneckenberger, M. A. Jerabek, C. F. Stanley

The measurement of acoustic impedance at frequencies up to 6,400 Hz has been proposed as a diagnostic tool to yield more detailed information about lung condition. A three generation branching system of plastic Y-tubes has been constructed. The impedance of the branched system is measured by an impedance tube using the two-microphone technique. The impedance spectrum is used to calculate the reflection coefficient spectrum, which is converted to an impulse response by an inverse FFT. The area function is extracted from the impulse response by the Ware-Aki algorithm. Measurements of acoustic impedance of the branched system were made for several different end conditions of the eight terminal outlets. The outlets were either blocked with modeling clay, plastic packing material, or aluminum blocks or were unblocked. Six measurements were made of each configuration. In general, the more outlets blocked, the larger the shift to the right of the impedance magnitude peaks for frequencies above 3000 Hz. The impedance magnitude peaks for the plastic packing material were shifted in frequency to the right relative to the peaks of the other system terminations. The impedance magnitude peaks for the clay and aluminum system terminations were significantly different in magnitude but not shifted in frequency. The area functions at the end of the branched system were significantly different (a > 99%) for most of the end conditions. Area functions for the modeled branched lung systems between the end of the impedance tube and the termination outlets of the branched system were similar but distinctively different for the various end conditions. These results indicate that the two-microphone technique can sense small changes in the terminating end conditions of a rigid system of branched tubes and thus may sense impedance changes due to lung disease in the conducting airways. Keywords: acoustic impedance, lung model, area function.

Jan 1, 1991

By H. Ziock, J. Ruby, A. A. Johnson

Power generation systems that promote energy security and environmental benefits are highly desired and pursued by a number of government and industry programs. Gasification of coal, other fossil fuels, or biomass has the technical promise of high efficiency and low or zero emission. Gasification for the purpose of electrical power generation has been researched, developed and demonstrated over the last 20 years, but for many reasons is not viewed as economically competitive. This paper describes a coal-based gasification technology well suited to mid and long-term goals of secure, environmentally clean energy. The technology should be adaptable for use with other carbon-based fuels including biomass and a full range of fossil fuels. The new zero emission gasification process is sponsored by ZECA Corporation, a continuation of the Zero Emission Coal Alliance (ZECA). ZECA has completed process design and engineering to assess the viability of a concept originated at Los Alamos National Laboratory, and the creation of a business plan to define paths for advancing the technology toward a near-term goal pilot plant. The zero emission carbon (ZEC) technology includes hydrogasification, the production of hydrogen and the carbonation of lime with CO2. For the power generation base case, the hydrogen is used in high temperature coal compatible fuel cells to produce electricity and the carbonate is calcined to produce a pure stream of CO2for sequestration. This paper provides the status of work with the ZEC technology and the availability of crucial equipment, materials and required testing. Discussions are presented for future actions to accelerate the technology assessment, testing and demonstration of a ZEC plant. Brief remarks are provided on complementary projects dealing withCO2separation and gasification costs.

Jan 1, 2004

By T. P. Meloy

In the last decade increased and prolonged interest has been displayed in the use: of tunneling or rapid excavation to solve many of the urban and industrial problems confronting our society. There has been talk and action on the interurban rapid transit systems for major cities, and even preliminary designs for a Boston to Washington interurban transit system. Much of this interest stems from the search to the solution of our increasingly complex urban problems, where the surface area must be given over more and more to the inhabitants, and the subsurface for transit, utility and other services. While tunneling is not a panacea to urban ills it holds a real solution to many existing problems. There is also, among the tunneling experts, a growing confidence that technical problems of rapid tunneling can be solved. To solve these problems, R & D money must be invested. If it is to be money invested either by private industry or governments, there must be significant returns on the investment to justify the research and development need to bring about the breakthrough that will make tunneling a major contribution to the solution of urban problems. To make these economic studies more extensive and more accurate tunneling demand figures were needed. To this end, the Organization of Economic Cooperation & Development - OCED - included in its Conference on Tunneling a section on tunneling demand. As a result of the conference the organization for Economic Cooperation and Development issued a report entitled "The Advisory Conference on Tunneling - Report on Tunneling Demand 1960-1980. " This report was presented at the OCED Conference on Rapid Excavation, held at Washington, D.C. To obtain the data in the Report, questionnaires were sent to the OCED countries and 18 replies were received from Australia, Austria, Belgium, Canada, Denmark, France, Germany, Ireland, Italy, Japan, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland, United Kingdom, and the United States. While it is true, that data were missing, that sometimes the definitions were confused, and that several countries provided no cost estimates at all, in general, this report contains the most comprehensive gathering of data that ever existed in the field. All data in the OECD report is expressed in terms of meters or cubic meters, and costs are in U.S. dollars.

Jan 1, 1970

By M. A. Reyes, L. Yan

"Heat and humidity buildup within refuge alternatives (RAs) may expose occupants to physiological hazards such as heat stress. Mine Safety and Health Administration (MSHA) regulations require RAs in underground coal mines to provide a life-sustaining environment for miners trapped underground when escape is impossible. RAs are required to sustain life for 96 hours while maintaining an apparent temperature (AT) below 95°F (35°C). NIOSH tested a 10-person tent-type RA, a 23-person tent-type RA, and a 6-person metal-type RA in NIOSH underground coal mine facilities to investigate the thermal environment over a 96-hour period. The test results showed that mine air and mine strata temperatures surrounding an RA occupied by simulated miners increased over the 96-hour test period. The test results suggest that RA manufacturers should consider this increase in temperatures when calculating and evaluating RA components during surface and laboratory tests. The findings can equip stakeholders with additional considerations for calculating heat and humidity temperature profiles for RAs not tested in situ. INTRODUCTION RAs are designed to provide a life-sustaining environment for miners who cannot escape after a mine disaster. One of the major considerations for integrating RAs in mine environments is the thermal environment inside the RA and the impact that the surrounding mine conditions have on the temperature and humidity buildup. Previous research has observed that the metabolic heat of the occupants and the heat released by the CO2 scrubbing systems will cause the RA interior air temperature to increase. In addition to the increase in temperature, an occupant’s respiration and perspiration, as well as the chemical reaction of the scrubbing chemicals with CO2, will contribute to an increase in humidity within the RA. The resulting internal thermal conditions, if not controlled, can subject miners to conditions that can lead to heat exhaustion, heat stroke, or even death depending on the duration and magnitude of exposure. Apparent temperature (AT) is a temperature-humidity metric for the perceived temperature caused by the combined effects of air temperature, relative humidity (RH), and wind speed. It is used to assess the perception of indoor temperatures when workplaces are not sufficiently heated, cooled, or insulated to provide comfortable or healthy conditions. Mine Safety and Health Administration (MSHA) regulations require that RAs must be designed to ensure that the internal AT does not exceed 95°F (35°C) when the RA is fully occupied."

Jan 1, 2018

By Warren E. Fife

This paper will discuss the application of a continuous miner using a fixed drum milling type cutting head for the underground mining of hard rock and salt ores. Continuous mining machines of the ripper chain cutting head, oscillating milling cutting head and boring arm designs have been used in rock and salt applications with various degrees of success. The large boring arm miners have been successful in potash, trona and salt, but they have not been successful in mining rock materials like iron ore. The main method used in underground mining rock materials is the conventional drilling and blasting the ore from the solid. This is particularly true for the harder, more abrasive copper and iron bearing ores. The softer salt based ores of potash, trona and rock salt can use several underground mining methods depending on seam conditions. Several of these methods use underground coal mining equipment that has been extensively redesigned to adapt it for use in mining noncoal materials. Conventional mining methods employ the use of a universal cutting machine to undercut or topcut the ore body before face drilling and blasting takes place to produce a smooth parting of the ore. The boring arm continuous miner is widely used in underground mining of potash and trona ores. It produces a tunnel with a smooth semicircular contour which results in good rib and roof stability. The ripper chain continuous miner is also widely used in mining the salt based ores of potash, trona and rock salt. They are used more frequently in Europe than in the United States and Canada. Some reasons for using the mechanical mining machines as opposed to the conventional drilling and blasting techniques for mining hard rock ore bodies are the resulting improved rib and roof control, facilitates selective mining of the ore body, and requires less man-

Jan 1, 1974

By G. Brofas

Mt Giona situated in the floristic hot-spot of southern-central Greece has an especially rich flora that counts more than 1000 native vascular plant taxa (species and subspecies) and an important plant endemism that is estimated to be about 10% of the native flora. The danger of population reduction of rare and endemic plant species and the opportunity to use rare native species in rehabilitation projects are two different aspects of rehabilitation planning in Mt Giona. In this study, an inventory of rare and endemic species of the area, their classification into IUCN threatened categories and an estimation of their habitats vulnerability are provided. The results emphasize the necessity to develop a monitoring program to analyze population viability of certain threatened plant species. The creation of artificial micro-reserves on calcareous spoils derived from bauxite mining for the conservation of water-stress tolerant rare and endemic plants is also proposed. An inventory of the species that have colonized the mining spoils was also undertaken. Twelve of them are endemics. Seven native species, because of their biological and ecological features, were selected for rehabilitation purposes of disturbed areas by mining activities. Seed germination, aspects of their reproductive biology and seedling emergence after sowing in pots under field conditions were studied. The seed germination study in the laboratory led to the identification of the optimum germination conditions and the creation of germination protocol for each species. Seedling emergence depends on the sowing season and the mulching. The use of the above species is recommended for rehabilitation purposes. The creation of artificial micro-reserves on calcareous spoils derived from bauxite mining for the conservation of water-stress tolerant rare and endemic plants is also proposed.

Jan 1, 2007

By Stefan Norgaard

In today's modern gold mining industry in Australia, and the world, more and more companies are recognising the competi­tive advantages gained by implementing an effective training program for operations (processing plant) personnel. Plant operators, or process technicians, are unique amongst all other gold mine employees. They are at work in shifts cov­ering 24 hours a day and their actions can have a profound effect on the operation's economic performance. To a large degree, the minute to minute decisions and actions of an operator can deter­mine whether gold is extracted to bullion in the goldroom or is discharged into the tailings dam. Experience has suggested that most small to medium sized gold operations in Australia, and even some large ones, have not implemented an effective training program. This is not attrib­uted to deliberate negligence or "anti" attitudes against training, moreover mill superintendents and metallurgy managers are technical people not oriented to human resource techniques. Usually the demands of designing, constructing and commis­sioning a gold plant overshadow the need for training in the first instance, In fact some well designed plants treating friendly oxide friable ore have little need for a dynamic well trained oper­ating staff. However, many plants do require a thinking team to optimise production and changing ore conditions towards the end of a mine's life can expose poor competence levels at large expense. Few managers will argue that training is a necessity and results in a win-win situation. The operators win by increased job skills, job satisfaction, clear career development and possibly better pay conditions. Trained personnel usually reciprocate with increased effmt and work ethic. The company wins also by having a thinking team which will maximise gold production and reduce operating costs.

Jan 1, 1998

By Scott W. Beckman, Leslie C. Thompson, Joseph A. Kizis

Heap leaching of ore with cyanide is a common and economical means of extracting precious metals (gold and silver) from mined ore. The use of cyanide, and the heap leach process, can seriously impact the environment. In the worst case, catastrophic failure of containment structures can release toxic levels of cyanide into receiving bodies of water, resulting in toxicity to ecological communities and contamination of public water supplies. Furthermore, cyanide degradation products such as nitrates can also impact local streams, lakes, and aquifers. Even if cyanide can be removed, the crushed residual ore may generate acid solutions that can release toxic heavy metals into the environment. Pintail Systems, Inc. (Pintail) of Aurora, CO, in conjunction with technology partners Science Applications International Corporation (SAIC) and Fairmile Gold Corporation (Fairmile), have developed a microbially-based precious metal lixiviant that can be used as an alternative to cyanide. The microbial process, called BioLix, is Pintail's second-generation biotechnology product for the recovery of precious metals from ore. The BioLix process is based on the enzymatic induction of organic lixiviant compounds using proprietary inducing agents and microorganisms. The process operates at near neutral pH and ambient temperatures using non-pathogenic microorganisms and food-grade chemicals. Precious metal extraction is also enhanced through the employment of microorganisms that facilitate mineral-solution reactions such as surfactant generation (improved wettability), and oxidation of gangue minerals that expose mineral surfaces to leaching. In order to demonstrate the effectiveness of the BioLix process, results from laboratory bench-scale experiments and a column study are presented. In addition, new applications for this enabling technology are discussed and include re-leaching of spent ore heaps, in situ leaching, and cyanide replacement for heap leaching.

Jan 1, 2000

This paper reviews the technical advice available to support companies in the delivery of social aspects of sustainable development. It will draw on diverse experience from the sparsely populated plains of the Central African Republic, one of the poorest countries in the world, to the densely populated villages of the Carpathian Mountains in Slovakia. It will review basic requirements for the consideration of social issues, as well as guidance on international best practice. It will review: the legal basis; coverage; consideration of alternatives; scope; inclusive decision-making; indicator development; impact monitoring and evaluation. The paper will discuss the breadth and depth of social issues for consideration, including the realms of responsibility of a company in terms of social development in different operating environments. The extractive industries invest substantial amounts of money which typically dwarfs local development, health or education budgets. Capacity building for local authorities is not directly the role of the company, but when understood as a strategy for risk management, it can play a vital part of sustainable development that benefits the local community and reduces the risk of social problems impacting profits. The paper will argue that social impact assessment is most effective when the outcomes are in line with a company?s principles and support core business practices. It is important that social impact assessment is viewed as an integral part of project decision-making and moves away from mistrusted PR and unsustainable philanthropy toward partnership, which finds suitable and appropriate solutions delivering ?win-win? outcomes. While development should not be seen as a direct company objective, engaging with development actors to better understand the operating context can ensure that social investment complements existing initiatives. The paper will also present different mechanisms for engaging with local actors, as well as developing successful social programmes.

Jan 1, 2007

By David R. Reid, Lawrence W. Talbot

INTRODUCTION In the mining industry, timing in land acquisitions can be of the essence. In order to secure promising lands, deals are often negoti- ated quickly and evidenced by letters of intent containing what the parties feel are the essential terms of the deal. In some cases, a company is willing to acquire land only if it can lock up a number of promising properties, and so a "non-binding" letter of intent is used to formalize the essential terms, while leaving the company without legal liability. Later, the letters of intent will be sent to a lawyer to prepare a formal acquisition agreement. Many times, how- ever, especially in a land acquisition rush, another company will attempt to better the deal prior to the execution of that formal agreement, and the first company will be forced to rely on the initial letter of intent, only to find out to its chagrin that it has no deal In other cases, the company holding the desired property is another mining company, and the negotiation of an option or joint venture is the only way the first company can acquire an interest in the desired land. In order to make its offer more attractive, it may have to reveal confidential or proprietary information about the property or the surrounding lands. Here, too, letters of intent are often used to formalize the essential points of the agreement. Once again, however, prior to the execution of a formal joint venture agreement, the transaction may collapse and the letter of intent prove to be only that. In this paper, the authors examine the dangers associated with the use of letters of intent and the specific provisions courts look for to find a binding contract, and consider how to increase the

Jan 1, 1988

By James Stewart

"THAT WHICH WE CANNOT SEE" INTRODUCTION Often it has been stated that the greatest of all fears is fear itself - fear created only by that which we cannot see or by that which we fail to understand. The elimination or minimization of fear can best be accomplished by a thorough understanding of the underlying causes of the fear. As related to the mining industry the omnipresent fear is the dread of acquiring cancer through accumulated exposure to "that which we cannot see" - radioactivity. The understanding of the resulting exposure effects can best be obtained through acquisition of authentic data and the subsequent analysis of the same by a group of highly qualified specialists. I may point out that the nuclear industry and its source, uranium mining, greatly surpass any other industries in the degree of public awareness as to its potential environmental effects. Public out-cry has always influenced major decisions relating to how industries conduct their operations and much of their effort has resulted in many changes. The issues of health and safety in the mining industry have created considerable public concern, but intense concern to those of us directly involved within the industry. Increasing concern regarding the effect of human activity on the quality of the outer environment of air, land, and water has developed within the past two decades. There is now a growing concern about the health and safety of persons at work in their inner environment, of their working-places in industry. Hearings and investigations conducted in Canada by three appointed "Royal Commissions" have all confirmed that this concern is well justified when focused on the health and safety of workers in our mines. REGULATORY CONTROL OF URANIUM MINING OPERATIONS In Canada, the ownership of mineral resources and the control of their extraction, except for uranium, is vested under the "British North America Act" in the provinces. In all provinces the statutory basis for health and safety provisions in the mining industry can be found in the provincial "Mining Acts" with each province assuming the responsibility to produce its own "Mining Act". In particular, all of the Mining Acts in Canada place upon the management of a mine the responsibility to ensure that provincial provisions are met. The "Federal Register" and mining companies parallel this arrangement in the United States. Equivalent legal

Jan 1, 1981

By Dirk Bleazard

Barrick Goldstrike Mines is improving the reliability of mining and processing equipment through the use of failure analysis and condition monitoring activities. Program results include an increase in equipment capacity and an overall reduction in operating costs. Identifying equipment failure modes and developing associated capital asset management practices can minimize failure consequences. Successful programs have included alterations to management practices, equipment modifications, and/or the implementation of condition monitoring programs. By controlling or minimizing the effects of incipient equipment failures, corrective actions can be taken earlier in the failure cycle. This results in an associated reduction to repair costs and equipment down time. Mining companies invest in their capital assets to provide the capacity necessary to meet operational needs. Over time, functional failures occur that reduce this productive capacity. Diagnostic technologies now exist that allow the condition of equipment to be monitored. Early response to this information minimizes the effects of functional failures and restores equipment re- liability. Reliability is a performance indicator of overall equipment condition. It is most often expressed in terms of mean time between failures. When the established objectives of a capital asset management program include the maximization of this failure interval, trailing indicators, such as availability and operating cost improve. The probability of equipment failure is influenced by engineering design and operating conditions. The performance level resulting from this operating environment is expressed as "inherent reliability." Without maintenance intervention, equipment will ultimately fail to perform its intended function and become less reliable. Therefore, maintenance must be managed as the supplier of reliable operational capacity. Maintenance can only supply equipment performance that approaches the level of inherent reliability. Actually achieving inherent reliability requires that all maintenance decisions are made at the economically optimal time. Enhancing performance levels beyond inherent reliability can only be achieved by altering operating conditions or practices or through physical equipment modifications. An evolution in maintenance management philosophy has been under way since the beginning of the industrial revolution. As equipment has become more sophisticated, so have maintenance practices. At the beginning of the industrial age, equipment tended to be over designed and slow moving. The first maintenance philosophy was one of reactive maintenance. Maintenance intervals were dictated by the operational status of the equipment. As a result, production interruptions were common and capacity needs were met through an investment in redundant capital assets.

Jan 1, 1998

By C. Timothy Shaw

Traditionally, only the large mining companies have maintained specialist departments in such areas as Rock Mechanics, Ventilation and Safety. To the small companies this has been a luxury that they could ill afford. Any work required by such companies in these areas, more complex than could be handled by the existing staff, was done by consultants. This situation is changing though and there is a need arising for many specialist departments. These changes are partly being brought about by the effects of inflation as the ever increasing costs are causing more and more operators to increase the size of their operations in search of economies of scale. In addition though the plethora of new laws and regulations are creating a need for many more specialists in all areas of mining in order to ensure compliance. The abovementioned factors, added to the existing Pattern of mines endeavoring to improve the working environment for their labor force, both for reasons of practical labor relations and also due to further legislative pressures, have thus created a climate where, in the near future, departments such as Rock Mechanics, Safety, Ventilation, Environmental Engineering and Subsidence Control will be commonplace in mining companies. It will no longer be practical to function without such services. Many mining companies already maintain such departments and this has particularly been true of the big mining groups of South Africa. From the experience gained by many of these large companies with specialist departments, it is clear that the maintenance of a cadre of experienced, competent professionals in such a department has not always been easy. It would seem from the experience gained that one can generalise and state that graduate mining engineers tend not to view specilisation as an optimum direction for their career development. It is of course true that many professionals, especially those with higher than a bachelors degree, do view these areas as valid career options, but even here experience shows that wastage is high. The time therefore seems to be ripe to take a look at this area in some detail to see whether reasons for the problems can be isolated. Working from that some suggestions can be made as to directions in which improvements might be made. If the challenge of the demands of the new regulations are to be met then such improvements must be made.

Jan 1, 1980

By R. C. Emmett

Gravity sedimentation is one of the most widely used unit operations in mineral processing and hydrometallurgy. Properly selected and operated sedimentation equipment can provide probably the most economical means of concentrating solids or clarifying solutions. Because of the variety of different approaches possible, including the use of modern flocculants, it is easy to overlook the optimum approach in selecting equipment. The different types of sedimentation systems that can be used in the minerals field and the sizing methods that are currently employed will be discussed here. Sedimentation applications usually fall into two areas, clarification or thickening. While the two operations are basically similar, the difference in emphasis (a well-clarified overflow as opposed to a highly concentrated underflow) results in significant differences in testing, equipment design, and operation. Clarifiers may be merely simple settling vessels with no special features, other than ample volume to provide the detention time needed for suspended solids to settle out of the feed slurry. Or, they can be designed to employ elaborate solids-contact techniques utilizing coagulants or flocculants to achieve more rapid clarification through the growth of particle agglomerates. Thickeners also are available in a wide variety of designs, with the main differences concentrated in the design of the raking mechanism. Thickeners operating in series (continuous countercurrent decantation or CCD) are used to recover valuable solution or purify the insoluble solids. Tray thickeners are used for recovering fine particulate solids such as alumina seed, but in other applications have been supplanted largely by unit thickeners or inclined plate units. Thickeners and clarifiers sometimes are used for storage of either solids or overflow liquor, or employed as precipitating reactors, such as in desilication applications. The use of flocculants and coagulants is much more common in modern processing plants, primarily due to the reduction in capital costs rendered possible through the use of these reagents. The terms flocculant and coagulant are often used interchangeably; generally, it is understood that flocculants refer to organic, high molecular weight synthetic or natural polymers which are useful in flocculating most suspended solids, but generally are ineffective on colloidal suspensions. Coagulants refer to chemicals such as those commonly used in water treatment, alum, ferric salts, lime, etc., which are usually far more effective on colloidal solids but cannot achieve the degree of agglomeration that is possible with the polymers. In some cases, both coagulants and flocculants are used in order to achieve optimum results.

Jan 1, 1986

By Silvia Misk, Cristina Araújo, João Felipe Costa, Roberto Rolo

Linear estimation methods are widely used for resource evaluation. Among the existing linear estimation methods, ordinary Kriging (OK) was accepted as the best estimator to determine the average ore grade of each block. However, OK is inadequate for modeling small blocks in relation to data spacing, resulting in over-smoothed models. In this study, the results of the recoverable resource from the short-term model are compared to estimated models generated by the traditional method, i.e., OK, and non-linear methods. The conclusion is that non-linear methods improve the accuracy and precision of the long-term model when compared to the model generated by OK.

Jun 25, 2023

By D. A. Fenton

The reliability of large diameter, high horsepower ball mill is paramount when large production and minimum downtime is required. The 17 ft. x 56 ft. double compartment ball mill at St. Lawrence Cement Company has the first gearless drive built in North America and has the world's largest hydrodynamic bearings currently built and running. The machine has seen three years operation and has met its specifications. The mill was designed by Aerofall Mills Limited and the gearless drive built and designed by the Canadian General Electric Company. This paper discusses the operation of the first North American installation of a gearless drive ball mill from the mechanical, electrical and process aspects.

Jan 1, 1977

By Ralph W. Barbaro

This paper presents a cyclic queueing model which evaluates the productivity of a shovel-truck materials haulage system. For a cyclic queueing problem with exponentially distributed service times, a cyclic queueing model provides exact solutions in a fraction of the time that simulation takes to produce an approximate solution. The model is applied to an example problem, and the results are validated with simulation. Simulation is used to show that the assumptions of exponentially distributed service times and steady-state are not serious problems. A cyclic queueing model can be used to quickly obtain an accurate assessment of the productivity of a shovel-truck system.

Jan 1, 1986

By J. Driscoll

After 30 years of success, Newmont Gold Company has temporarily ceased production from the original Carlin Pit. In late 1993, the Carlin East Decline was driven and an extensive underground exploration program was started. Today, Newmont Gold produces refractory ore from the Carlin East underground at the rate of 700 t/d (770 stpd) for an annual production of over 100,000 ounces. Over 70 underground miners enjoy the estimated 6-year mine life at Carlin East. About 70% of the ore at Carlin East is mined by mechanized longhole stoping with delayed cemented backfill. The remaining ore is mined by underhand drift and cemented fill methods.

Jan 1, 1997

By Albert H. Fay

The gypsum industry makes significant contribution to the wealth of our nation. This non-metallic mineral ranks in the highest order with America's most precious resources. Evidence of this is borne out by the fact that gypsum is a vitally necessary element in the building, industrial and agricultural industries. In 1967, the United States consumed 14 million tons of this valuable ore. Of .this amount 69% was required by the building industry for the manufacture of building materials. An additional 21% was directed to the industrial market, for the manufacture of Portland Cement and for other industrial uses. The remaining 10% was used for agricultural purposes.

Jan 1, 1969