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By J. V. Byrnark, R. W. von Bitter

The Hibbing Taconite Co. concentrator flowsheet, which is noted for its simplicity, uses single- stage autogenous grinding coupled with two stages of magnetic separation and two stages of size classification to produce a magnetite concentrate. This paper discusses the pilot-plant development of single-stage grinding, the commercial mill grinding performance, and mill liner development. Process innovation discussion includes process control computer implementation, size classification improvements, mill speed changes, magnetic separator improvements, and quality control innovations.

Jan 1, 1987

By M. Moats

Copper electrowinning operations have dramatically improved their ability to produce high quality copper at low costs over the past several decades. Even so, some fundamental knowledge is still lacking that could allow operations to run even more efficiently. For example, a rule of thumb exists that estimates a current efficiency loss of 2-3% per gram per liter of iron in the electrolyte. While several laboratory studies have been performed that demonstrate this rule of thumb is likely true, no definitive relationship exists. In this paper, the first steps in developing a definitive relationship are presented. The effective diffusivity of ferric ions in synthetic copper electrowinning solutions was measured using chronoamperometry and the Cottrell equation. The effective diffusivity of ferric ion was determined as a function of electrolyte concentration and temperature. Synthetic electrolytes were then used in laboratory-scaled copper electrowinning experiments, where relationships between current efficiency and solution composition were found to exist under stagnant conditions. Key words: Copper electrowinning, Current efficiency, Chronoamperometry, Ferric ions

Jan 1, 2009

By Richard S. Ghent, Daniel G. Warnock

JOHN HAMRIC: Our next speakers are Richard Ghent, manager of environmental health and safety for CF Industries, Hardee Phosphate Complex, in Wauchula, Florida. Richard has 20 years' experience with environmental health and safety affairs. He has a bachelor of science degree from the University of South Carolina. With him is Daniel Warnock, who is supervisor of safety and training also at the Hardee Phosphate Complex. Daniel's experience is in safety programs and electrical training. Their presentation is "Regulations Versus Management Practice." RICHARD GHENT: Written procedures give structure to safety programs. At their best, they are brief and understandable to facility personnel and clearly identify roles and responsibilities. At worst, they attempt to recite the entire regulation they are intended to address. Some regulations, such as OHSA's Hazard Communication Standard, require employers to develop, implement, and maintain a written program. As written programs and procedures are developed, some basic questions arise: Is the program designed to achieve compliance with regulatory requirements or does management expect the program to go beyond compliance to some higher level of performance? Management may have difficulty in measuring and communicating performance expectations in safety. A facility with 4 million safe work hours does not suddenly become unsafe the day their safety record is broken. Generally, management expects safety programs to meet regulatory requirements and to protect the employer from enforcement actions and fines from regulatory agencies. Management also expects that safety programs will result in a safer work environment with fewer incidents, accidents, and near misses. But it is difficult to know when a safety program has succeeded. If the program is expected to go beyond compliance, what other standards should be included (e.g., ANSI standards, company management practices, lessons learned from inspections and audits, recommendations from safety committees, etc.) in the

Jan 1, 1998

By R. J. Lee

Asbestos analysis is conceptually simple. The objective, in most environmental analyses, is to determine the number of asbestos fibers per unit area or volume in a sample. The sample may be a consumer product, an ambient air sample, or a water sample. This determination is complicated by several factors: (1) sample collection and preparation, (2) counting techniques, and (3) operational definitions of asbestos in use. Three different definitions have been used in the study of environmental samples and are summarized in Table 1. The analytical procedure and detail required in the analysis vary with the definition of asbestos. Accordingly, this may be the only type of environmental analysis where the definition of a substance dictates the choice of analytical methods, and the rigor demanded of the analysis. Lead, arsenic, or beryllium are sub- stances having a constant definition and the method of analysis chosen depends on the concentration and precision required. However, the meaning of the term asbestos fiber is dependent on the eye of the beholder. Macroscopically, asbestos has certain physical properties that make it highly useful. Rockforming minerals do not display similar characteristics. Now, the question arises as to how three definitions of asbestos came into being. This is a result of two factors: (1) the definition of asbestos on any scale intrinsically involves the morphology or shape of the material, and (2) the advent of the transmission electron microscope permits detection of asbestos fibers and other mineral fragments in a size range where the physical properties of asbestos such as tensile strength, flexibility, or thermal resistance are difficult, if not impossible, to measure. There is a good deal of controversy about which definition is most appropriate for regulatory purposes because of a lack of appropriate health effects data (Cooper, 1978). Most differences of opinion center on the questions surrounding the following: 11 Morphology-Is a 3:l aspect ratio an appropriate medical or physical lower limit for the definition of an asbestos fiber? 2) Length-Are asbestos fibers shorter than some arbitrary length (5 pm) as hazardous as longer fibers? 3) Mineralogy-Is the mineralogical distinction between asbestos and nonasbestos minerals medically significant? While these questions are directly resolvable only with the biological and health effects data, ultimately such data reflects the ability of analytical procedures to fully characterize the materials used in health effects studies on animal models, and to monitor the exposure to particulates with different physical attributes in the workplace or community (Cooper, 1978). The following sections outline the analytical problems involved in distinguishing the asbestos and nonasbestos varieties of the same mineral; the analytical procedures available for identifying asbestos and measuring its concentration in environmental samples; the ability of these methods to distinguish asbestos fibers from nonasbestos particles; and their precision and reproducibility. Finally, we suggest some future directions in terms of definition and procedure that would greatly improve the quality of such analyses. ASBESTOS VS. NONASBESTOS Asbestos that is mined commercially belongs to two mineral families; amphibole and serpentine (Zoltai, 1978, Wylie, and Steel, 1978). The

Jan 1, 1986

By L. Xu, R. Bhaskar

While a NIOSH accepted procedure exists for determination of quartz in the respirable dust samples from coal mines, no specific procedure has been defined for quartz determination in bulk samples. In this study, the effect of particle size on the estimation of quartz using the infrared technique was evaluated. Several laboratory tests were performed to determine the dependence of the infrared absorbance peak height on the different sizes of quartz particles. The significant dependence observed between quartz particle size and the measured peak height indicates the potential for erroneous interpretation of the quartz in bulk samples depending on how the samples are prepared. A procedure to reduce the effect of size in the determination of the quartz content is suggested.

Jan 1, 1994

By R. V. Ramani, R. Srikanth, R. Zhao

A two-part study was conducted to understand the factors affecting respirable dust generation potential or dustiness of coal seams. In the first part, the data from three prior comprehensive laboratory studies was analyzed to establish quantitative relationships between respirable dust generation potential and coal characteristics. This analysis indicates that respirable dust generation rate is positively correlated with Hardgrove Grindability Index (HGI), fuel ratio (fixed carbodvolatile matter), Vitrinke Reflectance (VR), and Level of Organic Metamorphism (LOM). In the second part, specially-designed single breakage experiments were conducted to determine the primary dust generation potential of 17 coal samples obtained from four continuous miner sections, three longwall sections, and the Penn State Coal Data Bank. The single breakage study indicates that primary dust generation rate is positively correlated with fixed carbon content, fuel ratio (fixed carbon/volatile matter), VR, and LOM. Since VR and LOM are strongly influenced by the process of coalification, differences in respirable dust generation rates in different coal seams may be explained by the thermal metamorphism of sedimentary organic matter during subsurface burial.

Jan 1, 1995

By E. Fidler

A recent headline in the Wall Street Journal declared, "trendy management schemes very often fail." Many of the management techniques addressed in the accompanying article are associated with quality management including reengineering, benchmarking, total quality management, and employee empowerment. The article made the point that executives, employees, and customers who are involved in such programs rate the effectiveness of these programs very low, and the programs often fail. Yet, we all know of companies that have made significant advances in their operations using these same quality management practices. Why do a few succeed while many fail? History has shown that the companies that successfully carry out quality management programs have two things in common: 1) Strong leadership committed to the success of the program. 2) A comprehensive plan for carrying out and maintaining the program. Stated another way -the reason many companies fail is the lack of committed leaders and inadequate planning. It is ironic that the title of the Wall Street Journal article is "The Best Laid Plans."

Jan 1, 1994

By D. Olsen

The paper discusses the legislative and practical approach adopted to problems of management of environment in relation to coal mining in a very sensitive area of the south coast of New South Wales. The environmental problems are complicated in this area due to multiple and very often conflicting land usages. The environmental approach in relation to water quality maintenance, noise control and air quality is discussed and methods adopted meet stringent requirements. Requirements of New South Wales Regulations on Environmental Impact Statements (EIS) are described.

Jan 1, 1988

By E. L. Reed

This paper addresses the state and federal permit- ting requirements and regulatory constraints associated with the development of new "grass roots" surface coal mines in the Western United States. Since a major portion of new coal development in the West will be on federally leased coal in Wyoming, my comments are directed towards that geographical area. This will give the reader some insight into the current regulatory framework within which western mining companies must operate-i.e., the major applicable state and federal laws and regulations, the more important state and federal regulatory agencies, and the major construction and operating permits that are required. Before discussing the impact of the regulations on our business, I would like to tell you something of my company and then briefly discuss Exxon's forecast of the long range outlook for coal. Carter Mining is an Won affiliated surface coal mining company. Exxon became interested in the coal business in the mid 1960's with the recognition of the future need for alternative fuel sources. Since that time, it has acquired coal reserves located in Wyoming, Montana, North Dakota, Arkansas, Texas, Illinois and West Virginia. Carter's first surface mine, the Rawhide Mine, located north of Gillette, Wyoming began production in August, 1977. Our second surface mine, Caballo, located just south of Gillette, began operating last October. We have a third block of federally leased coal just east of Gillette. By 1985 we anticipate Carter's western surface mines will be producing at an annual rate of 30 million tons, subject, of course, to successful market development efforts and regulatory considerations. Rawhide will ultimately have a permitted capacity of 24 MM tons per year. The coal at Rawhide is in two seams; one 80 feet in thickness and the other 20 feet (including a 6 to 10 foot parting). A large shovel is used to remove the overburden, and a similar shovel and dragline are used to mine the coal. Caballo has a 75 foot seam; otherwise it is similar in design and operation to the Rawhide Mine.

Jan 1, 1979

By Yoshiaki Numata

It is a matter of importance to use the lower alkyl monoethers of propylene glycol (polyPGME) as a frother in sulfide mineral flotation, for their compounds are highly soluble in water and are surface active frothers to some extent. The purpose of this study is to clarify fundamental roles of frothers in sulfide mineral flotation by investigating the effects of polyPGME on the floatability of galena with xanthate and adsorption property those ethers at the liquid/air interface. Fundamental investigation on the flotation of sulfide minerals using o,o-dialkyl dithiophosphates has been carried out through galena floatability tests in the following two cases:(l)single use of dithiophosphate for sulfide mineral collection and (2) joint use of dithiophosphates for its collection.

Jan 1, 1991

By Daniel W. H. Su

The ability to predict the effects of longwall mining on topography and surface structures is important for any coal company in making permit applications and anticipating potential mining problems. The sophisticated finite element model described and evaluated in this paper is based upon five years of underground and surface observations and evolutionary development of modeling techniques and attributes. The model provides a very powerful tool to address subsidence and other ground control questions. The model can be used to calculate post-mining stress and strain conditions at any horizon between the mine and the ground surface. This holds the promise of assisting in the prediction of mining-related hydrological effects.

Jan 1, 1986

By Roger C. Wilmoth

The most common method of treating mine drainage to prevent water pollution consists of neutralization and aeration. This process removes the acidity, iron, aluminum, and some other heavy metals, but does not render a water suitable for domestic or industrial use because of the high dissolved solids, hardness, and sulfate in the treated water. The Environmental Protection Agency (EPA), has been sponsoring and conducting research since 1966 on the use of reverse osmosis (R.O.) for the treatment of mine drainage. This process has been found to be highly effective in the removal of nearly all the dissolved solids. In addition, since R.O. is a concentrating process, potentials for recovery of valuable heavy metals are possible. This paper is a review of the state-of-the-art on the treatment of mine drainage by reverse osmosis.

Jan 1, 1972

By D. Hong, K. N. Han

The leaching behavior of rhenium in ammonium iodide solutions with iodine as oxidant was studied. Experiments were carried out in an autoclave to investigate the effects of stirring speed, temperature, solution pH, and iodine and iodide concentrations on the dissolution of rhenium. It was found that a high temperature and a high solution pH were essential for the efficient leaching of rhenium. The dissolution rate was found to be dependent upon the concentration of iodine and iodide. It was concluded that the dissolution of rhenium under the conditions studied was controlled by the mass transfer of iodine with an apparent activation energy of 15.8 kJ/mole.

Jan 1, 1999

By M. Cambridge

The design process must anticipate all construction and operational conditions and make an allowance for all eventualities. Prevention of failure during operational life, and in some cases post abandonment, requires that a risk assessment is undertaken during the design stage which defines not only the factors of safety to be used but the criteria for the structure during its operating life. These operating criteria should clearly identify the at-risk structures and the inspection and monitoring routines required to ensure compliance with the design objectives. On a mine site, it is the role of mine management to ensure that the operating rules be applied throughout the mine life and that a system of inspection and monitoring procedures be instigated. Where the risks are significant, high-level auditing by an independent engineer will also be required. Within the inspection and auditing framework, the designer needs to incorporate instrumentation to enable the operators and management to confirm that the facility meets the requirements of safety, stability and environmental compliance whilst continuing to meet its operational function. This paper reviews the use of inspection and monitoring to prevent failure and provides, in summary, examples of where monitoring has been undertaken and prevented failure. A tabulated review of legislation, regulations and technical guidance generated as a result of previous failures or untoward events is provided.

Jan 1, 2005

By A. Haile, A. Poole

During 2001-2002, the Granny Smith Mine of Western Australia undertook the development of a planned circular failure. Excavation took place in an interim pit wall that intersected the transported sediments, lake clays, and palaeo channel sands that overlay the deposit. The purpose of the study was to refine feasibility level slope parameters used for the initial design of the Wallaby pit, with the intent of increasing the overall slope when excavating the ultimate pit limits. During excavation, the geological and hydrogeological characteristics were studied in detail and data was collected using area-specific instrumentation and monitoring. Failure occurred in mid February 2002, at which time a detailed survey of the excavated slope using laser technology was conducted to provide geometric information suitable for back analysis of the material shear strength. The slope failure and associated information was analysed by geotechnical consultants. The revised shear strength and hydrogeological parameters were then applied to design the final pit walls. The slope redesign provided a cost saving of approximately seven hundred thousand US dollars. Design, slope formation, back analysis, the geology of the clay units, the hydrological environment, planned infrastructure, management and safety issues, and the on-going slope performance of the final slope are discussed.

Jan 1, 2004

By David M. Miller, Pramod C. Thakur, Larry D. Taylor

The most common technique used to suppress respirable coal dust in air is that of spraying with fine water particles. The water droplets are typically much larger than respirable dust particles and they collect dust particles mainly by interception. Dust collection efficiencies can be improved by reducing the droplet size and in- creasing the droplet velocity. This is typically done by reducing the surface tension of water and increasing the water pressure. Dust collection efficiency can be further improved by in- creasing the electrical attraction between the water and dust particles through electrostatic charging. A technique developed by Conoco accomplishes both surface tension reduction and electrostatic charging by discharging weak solutions of surfactants in water at high pressures, 13.8 to 27.6 MPa (2000 to 4000 psi) in an intrinsically safe manner. The paper de- scribes the process and presents related dust suppression data.

Jan 1, 1986

By J. R. Allan

Loki Gold Corporation of Vancouver, B.C. is developing the Brewery Creek Mine, an open pit heap leach gold mine, 55 km East of Dawson City in Yukon, Canada. Mineable reserves are 17.1 million tonnes of ore grading 1.45 grams/tonne, containing 24.8 tonnes (797 000 oz) of gold. Ore processing will employ a cyanide heap leach using run of mine ore. Permitting this mine has drawn significant attention because the heap leach technology, while proven in other jurisdictions, has not been used in Yukon. Engineering design of the heap leach was similar to that for heaps in more temperate climates, with the added issues of permafrost and cold weather operations. Solution balance with seasonal placement of ore and year -round leaching requires very large pond capacity for spring thaw conditions.

Jan 1, 1996

De Beers? Finsch diamond mine began operation in the 1960s as a surface project using the latest technology available. During the 1990s, the operation, located about 160 km (100 miles) west of Kimberley, South Africa, began its move as an underground mine. The earlier stages (Blocks 1, 2 and 3) of underground work at Finsch used open stope mining methods, also using the latest in technology. The mine began developing Block 4 in 2004. How-ever, studies on this level showed that block caving was a more efficient mining method than open stoping. It was during those studies that De Beers determined that Block 4 would be a good candidate for testing Sandvik?s automated truck haulage technology.

Jan 1, 2008

By A. W. Hamilton

If you don't know a gauss from a grasshopper, you may be better off than you, think, particularly if you're an ore dressing engineer charged with the responsibility of selecting magnetic equipment for minerals separation and beneficiation. Gauss is a unit of measure for a magnetic field. It indicates the number of imaginary lines of force per square centimeter or per square inch radiating from a magnet. In discussing the strength characteristics of a magnet, we have come to speak of a magnetic field of 800 gauss, for example, meaning 800 lines of force per square centimeter. Gauss became the standard for selecting drum type separators many years ago under an arbitrary set of circumstances. The standard has continued to this day even though magnetics applications engineers have long considered it inadequate. The configurations of the older gauss meter were such that the most accurate and convenient readings on a drum type separator could be made at distances greater than one inch. So, an arbitrary distance of two inches was established and that two inches became the standard. Since then, it has become commonplace to specify magnetic strengths for drum separators according to average gauss readings at two inches; for example 500 gauss average at two inches, 750 gauss average at two inches and so on, even though gauss readings at two inches have much less to do with the separating and beneficiating function of a given application than was formerly believed. The standard was adopted as a means of gauging the strengths of electromagnetic drum type separators, for they were the only ones around at the time. These machines were usually designed with no magnetic considerations other than that the material to be separated should be agitated vigorously and the magnetic fields should be deep and strong. Drums built this way performed well enough, so it seemed logical to measure their magnetic strengths. Hence, gauss at two inches. Now, new improvements in magnetic techniques have made average gauss measurements at 2 inches positively obsolete.

Jan 1, 1971

By C. L. Jiang

The role of iron ions (Fe2+ and Fe3+) in the flotation of both ore-and coal-pyrite with ethyl xanthate was comparatively investigated. The complete/partial depression of ore-and coal-pyrite in neutral to weakly alkaline solution is due to the formation of ferric dihydroxy ethyl xanthate between xanthate and the oxidation products of pyrite, ferric and ferrous ions. With xanthate as collector, coal-pyrite was found to be nonfloatable above pH6. In the presence of iron ions and between pH6-9.5, the flotation of ore-pyrite was significantly depressed. Ferrous ions have a stronger effect on pyrite flotation than ferric ions in neutral to weakly alkaline solutions.

Jan 1, 1996