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By William S. Eaton

Managing a mine or mineral processing operation in today's environment presents many unique challenges to mining companies. In recent years, headlines around the world have publicized major incidents such as those associated with the Marcopper Mine in the Philippines, the cyanide release in Guyana from the Omai gold mine and numerous other mishaps associated with mining. These notable upsets were due to engineered system failures, either during normal operations or as a result of uncontrollable events. There fore, many mining firms are attempting to assess their overall risks and establish some priority for expenditure of limited operational and environmental budgets. Failure of an engineered component can have dire operational consequences that affect profitability until repair or replacement can be completed. In addition, there may be significant environmental consequences associated with the engineered system failure. This, too, may affect profitability for an extended time or even the viability of an operation. An engineered risk assessment (ERA) can support a mining company's efforts to cost effectively manage environmental risks associated with the operation of its facilities. The ERA approach also provides information about the current condition of engineered systems. This ERA approach provides a systematic review of the risks of an engineered system failure and the possible associated environmental consequences at mining company facilities. This approach has been successfully applied to many industries and types of engineered systems (Barneich et al, 1996; Whitman, 1984; Power and Tomkins, 1974; Keeney, Nair, and Kulkarni, 1979). This approach evaluates all mining and mineral processing facilities located at a single site and compares them with similar facilities located at multiple mine sites. The ERA approach has been applied to a mining, milling, smelting, leaching and refining operations. These assessments can be part of a comprehensive environmental program to aid in the recognition and cost effective management of the potential environmental risks associated with the operation of facilities. ERA results support plan-

Jan 1, 1997

By Mark A. Anderson

INTRODUCTION The accomplishment of a well engineered design, and the realization of efficient plant operation cannot be achieved without weaving a web of safety consciousness from the beginning of the project. When the plant becomes operational, and throughout its life, responsibility safety will rest with the client or operator. Recognition of this understanding does not reduce the importance of the engineering and construction contractor's role, but merely puts the responsibility where it belongs. A project which has had little or no operator input during the early stages of design is almost certain to have serious work place safety, health, and environmental problems in spite of the fact that all MSHA and OSHA design requirements were met and the engineering was performed using accepted practices. DEFINITIONS The author has a personal preference in safety definitions that begins and ends with simplicity. If the safety criteria, program, and rules are confusing or complex, the results will soon become obvious. Confusing and complex are the key elements in the avoidance of responsibility and if punitive is added to the list, a brew exists which breeds accidents, illness, and poor performance. A safely designed and operated plant is one that a worker can journey to each day; leaving that person and his or her family with the above average expectation that the person will return healthy, emotionally intact, and hopefully a little wealthier. If the objective or results of a planned or existing safety program don't fit the definition. then the reader is probably contemplating a very sophisticated

Jan 1, 1986

By James M. Williams, Michael E. Zellars, Arthur J. Roth

INTRODUCTION Our present estimates of world P205 consumption for all uses show an average annual growth rate of approximately 1.9% per year. The estimated 1985 consumption of 41.5 million tonnes of P205 is predicted to increase to 57.1 million tonnes of P205 by the year 2005, which represents a growth from 157.7 million tonnes in 1985 to 217 million tonnes of phosphate rock in 2005. The present situation of oversupply and extremely weak phosphate product prices is, however, expected to continue in the short term and a normal supply/demand balance may not be achieved until after 1990. The growth in P205 demand, in conjunction with the higher cost of replacing low cost mines as they are depleted, will place economic pressure on world farm economies through the increased cost of phosphate fertilizers. The availability of rock supply is not the challenge; rather, it is the economics of new rock supply. This economic challenge of providing new rock supply is by no means limited to the United States. Even in centrally controlled economies, the cost of rock from domestic mines of marginal quality and economic viability, coupled with burdensome infra¬structure requirements, may result in tonnage additions at very high cost. Although government subsidies to offset higher production cost is a factor in some countries, world production in the next 20 years will be directed, if not governed, by economic factors. Established infrastructure, good quality reserves, and existing operations will provide a competitive advantage for new prod¬uction. It is our opinion that the current world supply structure will remain relatively stable through 2005, in that most of the traditional suppliers will retain supply roles. U.S. rock production, although it is not expected to grow beyond the present level, will still be a major contributor to world supply. Although dramatic changes within mining, fertilizer production and farm economics may appear disruptive, the current supply scenario will, in general, continue with the major issue being production economics. WORLD DEMAND Demand for P205 by region in the world has been estimated using projections of population, crops and yield, arable land, economic and other data as a basis for future demand projec¬tions by Blue-Johnson and Associates, our col¬laborators on a recent multi-client study. Non-fertilizer P205 demands were estimated in the same general manner. These estimates of future demand are based on an assumption of reasonable world political and economic stabil¬ity, debt repayment requirements maintained at workable levels, and resolution of problems in the agricultural economy to a point where normal supply/demand forces can interact freely to provide a basis for continued P205 supply. The results of these studies indicated an average growth rate of 1.9% per year through the year 2005. This growth could be as low as 1.5% per year, or as high as 2.5% per year. It is our opinion that the estimated rate of 1.9% per year is most probable. This moderate growth rate considers both the major economic constraints facing the world agricultural industry today and the general problem of affordability of fertilizers and other crop inputs. WORLD SUPPLY There are adequately defined world reserves of phosphate rock today to provide supply well into the future, even at much higher levels of demand than presently projected. Using the U.S. Bureau of Mines estimates, which are based on stringent criteria for definition of reserves, the present world reserves base is approximately 35 billion tonnes. Identified resources raise the potential for production by orders of magnitude. Potential resources based on geological trends, and including offshore deposits, would again result in orders of magnitude increases in rock resources. Morocco leads the world in reserves base with approxi¬mately 21 billion tonnes. The U.S. is second, followed by the Republic of South Africa and Russia. These four countries control about 87%

Jan 1, 1986

A joint research effort by Newmont Gold and Du Pont, working with Kurtis Mooney, of Tri-Combined Resources has developed a new ore-sample bag made of "Tyvek," a spunbonded olefin. "The goal was to find a bag with the best trade-off between efficient draining of moisture, minimal fines loss and compatibility with the conveyor drying process we were developing for our new assay lab," Charles Bucknam, analytical development coordinator for Newmont Metallurgical Services states. None of the available polypropylene, cotton or canvas bags had the needed combination of properties. "Our original tests in 1987 on the plastic bags we had been using showed an average loss of 5.4% of mud sticking to the bags when they were emptied into drying pans. Part of the sample was still in the bag as a residual." Tests on bags of "Tyvek" showed low residuals when the samples were dried in the bags before they were emptied, but about 3% of the fines were lost through the seams. Mooney recommended a new bag design, with fold-over seams.

Jan 1, 1990

By Hans von Michaelis

It is appropriate that this opening session of HAZPAC '91 and Randol Gold Forum CAIRNS '91 should address the question of what the two industries can learn from each other. The panel is made up of members with experience in both industry. Several are experts on managing both hazardous waste and the mine/mineral processing environment. There is a marked difference in the regulatory needs with respect to treating and disposing of mining and mineral processing wastes, and "hazardous" or industrial waste materials. The topic of this paper is on the things that the two industries have in common: Many of the processes and technologies that are being used or are currently being developed for treatment of hazardous waste are the same or similar to the processes that have been used for decades or k,nger in the mineral processing industry. Hazardous waste treatment and remediation of contaminated solid and/or groundwater is a relatively new industry. Many of the practitioners in this new industry are relatively inexperienced in most of the "new" technologies that are being applied or developed.

Jan 1, 1991

By F. -U. Schneider, F. Wellenkamp

Based on previous investigations of ultrafine comminution in planetary ball mills, a new centrifugal mill has been developed which permits similar high stress conditions. Because this new type of mill is equipped with an immobile chamber, devices for measuring energy, for cooling the milling vessel, as well as, in continuous operation, for material feed and discharge can be more easily attached than to planetary ball mills. Observations of particle behaviour have shown that, in the case of dry grinding, most of the material is found on the mill walls even after short grinding times. Due to the fact that energy dissipation takes place mainly in the zone near the wall, a grinding system which reduces the amount of ball filling required is at an advantage.

Jan 1, 1995

By J. A. Arias

The oxidation kinetics of pyrite and refractory gold concentrates in acidified ferrous sulfate solutions in the presence of oxygen-sulfur dioxide gas mixtures has been studied. The effect of temperature, pulp density and gas composition were determined. The optimum oxidation rate was obtained at 80°C and 2 percent sulfur dioxide in the gas mixture. The oxidation of the sulfide minerals is attributed to the presence of ferric ions, which are continuously regenerated by the gas mixture. The objective of this study is to find a new hydrometallurgical method to render sulfidic refractory gold ores amenable to cyanization.

Jan 1, 1993

By R. J. Piniazkiewicz

Talc orebodies are mined in Asia, Australia, Europe, North America, and South America. Operators in North America must be efficient quality suppliers to thrive in a talc market in which many overseas suppliers have advantages such as lower hourly wages, shorter distances to ports, and less government regulation and intervention. Continuous improvement through teamwork and innovation is needed in the following areas to thrive amidst worldwide competition: 1) Maximization of the in-place value of ore. 2) Research and development to yield new processes and products. 3) Safe productivity. 4) Involvement in legislative processes. 5) Wellness programs to lower health care costs.

Jan 1, 1993

By Im C. J.

The addition of coal preparation plants changed the coal industry during the past. Now it is time co once again improve the quality and types of coal products coming from future coal preparation plants to meet the changing needs of our society. Clean Coal Technology, along with federal support provided, is forcing our industry to provide cleaner coal products for industrial applications. Liquid fuels from coal is just one of many new products from a coal preparation plant that has a ready market in the transportation sector. UCC Research Corporation is developing these new liquid coal products and this paper will describe the progress and the new slate of coal products to be provided from future preparation plants.

Jan 1, 1989

By J. N. Carras, N. W. Bainbridge

In order to further the understanding of spontaneous heating of longwall goafs a numerical model was developed, based on conservation principles applied to the transport of heat, water vapour and oxygen across the god Advective air flow into the goaf is caused by the differential air pressures across the god The air velocity field within the goaf area was computed using Darcy's law. The boundary and initial conditions concern air pressure, temperature and relative humidity. The oxidation rates and heat generation rates of the goaf materials required for the simulation were obtained from laboratory measurements. The main outputs of the model are temperature, oxygen and water contour maps, the rate of air leakage into the go4 velocity field and pressure distribution across the god. The model while still in its development stage, is able to simulate a heterogenous goafs constructed from different materials with different thermal and mass flow properties. Validation of the model by comparing its output with measurements from within goafs is required before the model can be used with confidence in a predictive sense.

Jan 1, 1995

By R. Wisniewski, S. Schafrik

Every underground coal mine in the United States must deploy and operate a wireless communication and electronic tracking system. This paper addresses the reliability and availability of an installed tracking system and the communications infrastructure that supports it. This paper assumes that the tracking system uses the communication system to perform its operation. A particular interest is the requirements for the systems to operate continuously without failure after a mine disaster for 24 hours, and the requirements in the MINER Act for the tracking systems to be “functional, reliable and calculated to be serviceable” and the communications systems “redundancy.” These requirements imply a certain reliability and availability. This paper describes a quantitative way to assess these systems requirements, using tools that are available to and commonly used by the reliability, maintainability and availability community.

Jan 1, 2014

By E. J. Rogans, W. N. Cartner

Carbon technology has largely superseded filtration plants as the more acceptable gold recovery technology. This has, over the last two decades, provided a tremendous driving force for the development of new equipment. One of the main focus areas of this technological development is the development of effi­cient interstage screening systems. Several variations of exter­nal and internal screens are available, with the more recent shift away from air cleaned units to mechanically swept units. This paper discusses the development of one such mechanically swept interstage screen and how the development led to the suc­cessful implementation of a carousel type of CIP operation. The first generation Pump-cell emerged as a consequence of the success achieved with the mechanically swept NKM screen, The idea was to modify the screen to incorporate the functions of pumping, screening and agitation in a single drive unit, the screen generating sufficient lift for interstage slurry flow so that all contactors would be at the same level. This sys­tem was further incorporated as a high intensity modular CIP contactor, i.e. low slurry residence times combined with high carbon concentrations. A discussion on the kinetic gold adsorp­tion theory and its manipulation in the design of the pump-cell concept is discussed in a paper published in a previous Randol Conference< 1), Testwork carried out at Vaal Reefs proved the concept of the Pump-cell on a pilot plant scale<2), which resulted in the building in 1990 of the first large Pump-cell plant at West Witwatersrand Gold Mine designed to treat 340m3 of pulp per hour and , even though the plant operated successfully with respect to gold recovery performance, a few problems were experienced with the basic engineering design(3),

Jan 1, 1996

By Fathi Habashi

Precipitation of a metal from an aqueous solution of its salts by another metal is known as cementation, because the precipitated metal is usually cemented on the added metal. This phenomena was once described by the alchemists as "transmutation," when they dipped a piece of iron in a solution of copper sulfate and the iron was coated with a layer of metallic copper. The process can be predicted in terms of electrode potentials. The metal with the more positive (oxidation) potential, as given in Table 13-1 of the electromotive series, will pass into solution and displace a metal with a less positive potential.

Jan 1, 1970

By V. C. Rogers, K. K. Nielson

INTRODUCTION An evaluation of the radiological health risks from uranium mining and milling requires the determination of several key parameters. As shown in Figure 1, the first step is the estimation of the radioactive source term. The radionuclides in the ore consist of the 238U decay series nuclides shown in Figure 2, the 235U series nuclides, and 40K. The 238U decay series isotopes dominate the source term, with the 235U series isotopes causing less concern and 40K remaining at background levels. [ ] Specifically, the risks from uranium mining and milling are mainly associated with 230Th, 226Ra, 222Rn, and its short-lived daughters. These radioisotopes are mainly alpha-particle emitters; hence, some dispersion mechanism is necessary to bring them into intimate contact with man so that they can be inhaled or ingested For water pathways, the leaching of the isotopes from [ ] the solid ore or tailings provides a measure of the amount of contaminant initially available to the environment. For the air pathway, dust-creation mechanisms such as blasting, crushing or general resuspension processes dominate for 226Ra and 230Th. However, 222Rn, being a chemically inert gas generated from the decay of 226Ra, can migrate through the ore, overburden and tailings over considerable distances. As shown in Figure 1, the next step in the pathway to man is environmental dilution and delay. For the water transport mechanism, the delay in the isotopes reaching an accessible water supply may be considerable (several thousand years or more), but for airborne nuclides the dispersion in the atmosphere is rapid and constitutes the main mitigating factor. Considerable ventilation is provided in underground mines to dilute and remove radon and its daughters in order to keep their concentrations low and thereby minimize their inhalation by miners. The rate of uptake by both the workers and the general public is often difficult to ascertain. It involves breathing rates, rates of water consumption and other poorly-defined parameters. The final steps are the risk estimators used to predict doses and cancer rates from the inhaled radon daughters and ingested or inhaled radium. Many

Jan 1, 1981

By W. Ghyoot, J. Boonstra, H. Dijkman, C. Buisman, M. Picavet

Paques and Umicore have demonstrated the feasibility of biological treatment of the highly complex Hoboken wastewaters in a1 m3/h pilot plant at Umicore Precious Metals, Hoboken, Belgium. In the first step arsenic was precipitated from copper smelter effluent as As2S3using biogenic produced H2S. Other metals such as copper, lead and cadmium were also removed as MeS to concentrations well below the discharge levels. Subsequently, sulfate and nitrate were removed to low concentrations (<300 mg/l and < 5 mg/l respectively) in high rate engineered bioreactors. Sulfide produced in the sulfate reduction process was recycled to step 1 for metals precipitation. Selenite/selenate was partly removed in the sulfide precipitation step, whereas the excess was biologically reduced and removed as selenium to concentrations <0.2 mg/l.

Jan 1, 2003

By J. C. Watts

Ball mill grinding circuit control has received increasing emphasis in the past few years due to such factors as declining ore grades, increasing production costs, and advances in analytical devices and minicomputer technology. Since ball mill circuits have been a traditional bottleneck in mineral processing plant throughput, control systems often improve through- put without requiring additional processing equipment. In addition, much of the variability of the grinding product size and consistency is often removed, allowing better process operation downstream. Among the problems which arise in designing and implementing a process control strategy for ball mill circuits are circuit constraints imposed by processing equipment and local management, proper instrument selection, installation and maintenance, and use of calculated or inferred variables for process measurements. This paper discusses these problems and attempts to identify valid approaches to their solution.

Jan 1, 1979

By John K. Kellis, Fazley Azhar

Advancements in AC drive technology offer conveyor designers a viable drive alternative for conveyor systems which require accurate load sharing as well as multiple drive systems. Recently developed AC drives have the ability to accurately control the output torque of AC motor. These AC drives, compared to current DC drives, offer superior performance characteristics while enjoying the benefits of an AC motor. Conveyor applications and case studies incorporating this AC drive technology are presented for review.

Jan 1, 1998

By Glenn A. Shirey, Robert D. Stoessner, S. Gopalakrishnan

Under a contract awarded by the U.S. DOE-PETC, the Pennsylvania Electric Company and New York. State Electric and Gas Corporation are conducting a test program to evaluate and optimize the performance of a two-inch air-sparged. hydrocyclone (ASH) for cleaning fine coal. The test program is being conducted at the Homer City EPRI Coal Quality Development Center, utilizing Upper Freeport coal classified to minus 0.15 mm as the process feed material. A matrix of experiments has been conducted to establish the influence of significant design and operating variables (including overflow and underflow orifices, inlet slurry pressure, airflow rate, and reagent dosage) on the production of deep cleaned coal. Performance of the ASH is being compared to conventional froth flotation, utilizing advanced techniques and selected flotation reagents. This paper focuses on work completed to-date to optimize the performance of the air-sparged hydrocyclone for cleaning fine coal. INTRODUCTION The Pennsylvania Electric Company (Penelec) and New York State Electric and Gas Corporation (NYSEG) have been evaluating advanced fine coal cleaning processes for the production of compliance grade coal (1.2 pounds S02/million Btu). Laboratory bench-scale froth flotation results were compared with results of advanced flotation processes as performed by various organizations, utilizing the same coal feed. Among the processes evaluated, the air-sparged hydrocyclone (ASH) - developed by Dr. Jan Miller at the University of Utah - was considered to offer the best potential for retrofitting into an existing coal preparation facility because of the increased capacity per unit volume. The ASH has been shown to process over 100 times the throughput of conventional froth flotation cells. In May of 1988, Penelec/NYSEG was awarded a contract from the Department of Energy&apos;s Pittsburgh Energy and Technology Center (DOE-PETC) to optimize the performance of a five cm (two inch) ASH for producing compliance grade coal from raw classified minus 0.150 mm (1.00 mesh) Upper Freeport coal, and to compare its performance with conventional froth flotation utilizing advanced techniques and selected flotation reagents. The test work is being conducted at EPRI&apos;s Coal Quality Development Center (CQDC) in Homer City, Pennsylvania, utilizing a circuit processing 0.10 to 0.25 tons of coal per hour. Other members of the Penelec/NYSEG contract team include the University of Utah, Advanced Processing Technologies, Inc., Davy Dravo, Kaiser Engineers, Ebasco Services, and Management and Technical Systems. ASH DESCRIPTION AND OPERATION The ASH-2 System is a five cm ID (actually 4.76 cm) air-sparged hydrocyclone manufactured by Advanced Processing Technologies, Inc., under license from the University of Utah, for the purpose of research, evaluation and development. A schematic drawing of the air-sparged hydrocyclone is presented in Figure 1. Basically the air-sparged hydrocyclone consists of two concentric right-vertical tubes, a conventional cyclone header at the top, and a froth pedestal at the bottom. The inner tube is a porous tube through which air is sparged radially. The outer nonporous tube simply serves as an air jacket to provide for even distribution of air through the porous inner tube. The slurry is fed tangentially through the conventional cyclone header to develop a swirl flow in the radial direction. Air is sparged through the jacketed, inner porous tube wall and is sheared into small bubbles by the swirl flow. Hydrophobic particles in the slurry collide with these bubbles and, after attachment, are transported radially into a froth phase which forms on the cyclone axis. The froth phase is stabilized and constrained by the froth pedestal, thus moving towards the vortex finder of the cyclone header and discharged as an overflow product. Hydrophilic particles generally remain centrifuged in the slurry phase and are discharged as an underflow product through the annulus created by the froth pedestal.

Jan 1, 1989

By L. A. Hansen, D. L. Buffington, G. H. Beckwith

This paper reviews geotechnical engineering considerations in heap leach pad design, discusses design philosophy and provides design procedures. A brief discussion of surface water hydrology ground- water protection and other design considerations are also presented. Special emphasis is placed on projects in the arid and semiarid regions of the Western United States where annual evaporation exceeds rainfall, and where good foundation conditions are usually present.

Jan 1, 1987

By David Field, David Powell, Richard Hulsen

The Mission Valley Light Rail will loop through San Diego State University (SDSU)and to minimize the impact of construction most of the works will be underground. The project will require construction of a 330-m long (1080-ft), 11.24-m wide (36.9-ft),single twin track tunnel through Stadium Conglomerate, a poorly cemented dense sandy gravel with cobbles. Key technical issues are discussed including the ground conditions and predicted ground response, the use of sequential excavation methods to control deformations and specific construction concerns such as instrumentation and monitoring. Management of the construction process to minimize risk is particularly important in this environment and the strategy selected to control the works is also considered.

Jan 1, 2001