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By Chester R. Harris

With the passage of the Occupational Safety and Health Act (OSHA) on December 29, 1970 and the formation and growth of the OSHA Agency it spawned, public consciousness of occupational safety was raised. It became accepted that employees had the right to "a safe and healthful workplace". With the possibility of OSHA inspections, employ ers (particularly those with large workforces) began to give serious con sideration to engineering controls, safety programs, and training in a more uniform manner than previously.

Jan 1, 1991

By Mark W. Springett

The sampling of precious metal deposits entails inherent problems due to the low mineral abundances, high mineral specific gravities, skewed grade distributions and wide ranges of mineral particle sizes. Sampling practices and precautions are discussed with particular attention to each of the tripartite stages of sampling - sample acquisition, sample preparation and sample assaying. Practical examples of approaches to the sampling problem are given and some examples of significant sources of error are provided from gold and silver deposits in North America.

Jan 1, 1992

By Charles A. Ramsey, Kathleen S. Smith, Philip L. Hageman

We developed a statistically based strategy for sampling the surficial material of mine-waste dumps for use in screening and prioritizing historic dumps on abandoned mine lands. This sampling strategy entails the collection of a representative composite sample from individual dumps and allows for regional or watershed-based assessments. One 30-inment dump-composite sample collected using this sampling strategy contains as much information, relative to average value, as 30 individual grab samples at 1/30 of the analytical cost.

Jan 1, 2000

By Donald W. Gentry

This article introduces mine planning as a complex process based on the quantitative and qualitative assessment of a myriad of independent and inter-or co- dependent variables. The interdependent variables of particular interest in this paper are those associated with mine planning activities that impact metallurgical processing plant performance and costs. These variables are identified and examples are provided to substantiate the argument that the magnitude and sensitivity of these variables must be formally assessed and analyzed to determine their potential impact on overall economics.

Jan 1, 1991

By Gary L. Simmons

Aqueous pressure oxidation at low temperature, although desirable from a process engineering and operations point of view, presents unique problems when temperatures approach 160°C (320°F). In developing the pressure oxidation process for the Lone Tree Mine, elemental sulfur formation and agglomeration with pyrite proved to be a problem. This paper discusses some of the unique mineralogical and chemical characteristics of the Lone Tree sulfide deposit that make it amenable to low temperature pressure oxidation. Problems encountered during pilot plant operation and their solutions are also discussed.

Jan 1, 1993

By John W. Greene

For the past two years, Tenneco Minerals Company has been evaluating a refractory, pyritic, carbonaceous gold deposit, Results from agitated biological oxidation reactor tests show the gold extraction was increased from 15 to 90 percent using microbial oxidation, Also, no preg robbing occurred after complete microbial oxidation. Three column biological oxidation tests were then initiated on minus 1/2 inch ore. Biological oxidation was discontinued in two of the three tests, These columns then were leached with cyanide. The maximum gold recovery was 62 percent. No preg robbing was observed,

Jan 1, 1990

By Kenneth N. Han, Xinghui Meng

The leaching of gold and silver from various ores in ammoniacal solutions conta1mng various oxidants has been investigated. The samples tested included elemental gold, sulfidic as well as carbonaceous refractory ores, and tellurides. When pure elemental gold powders were used, the maximum amount of gold dissolved under the conditions studied was 16.3 ppm, 42.4 ppm, 82.0 ppm, and 152.2 ppm, respectively, at 140°C, 160° C, 180° C, and 200°C. Five different refractory ore samples were also tested. The recoveries of gold and silver from these refractory ores were typically 92% and 95%, respectively.

Jan 1, 1992

By Gus Van Weert, Roy van Lier

It has been demonstrated for two totally different silver bearing and cyanide refactory concentrates that the formation of silver jarosite can be prevented through the addition of iodide to the autoclave feed. A molar ratio of r/ Ag+ of no more than 1 was sufficient to raise silver extractions in a subsequent cyanide leach from 4% after autoclaving without iodide addition to 98% for the sulpho-salt concentrate and from 15% to 97% for the pyritic acanthite concentrate. Flowsheet proposals will be discussed to prevent loss of the iodide additive. The use of chloride instead of iodide will also be reviewed.

Jan 1, 2000

By Kurt Zeidler, Vojtech Gall

London Underground Limited are currently constructing an extension of the Jubilee Line. The approximately 16-km long Jubilee Line Extension Project connects the existing Green Park Underground Station with the Canary Wharf area and Greenwich. Being a part of the project, the London Bridge Station (Contract 104) was built using a combination of the New Austrian Tunneling Method (NATM) with Compensation Grouting. NATM was successfully applied in softground and urban areas under restrictive requirements regarding settlement limitation. Information on the flexibility of the method and the influence of Compensation Grouting on ground and tunnels are given.

Jan 1, 1997

By A. R. Zambrano

Equations for Power Draw, Capacity, and Work Input for predicting the performance of industrial grinding mills are derived based on torque measurements obtained in a laboratory instrumented mill. These derivations are based on mechanical principles and on the first order kinetics of the grinding process. Rittinger's, Kick's and Bond's laws express Work Input as Work Index, W;, times a Particle Size Function. These laws are only particular cases of more general expressions having the Particle Size Function raised to an exponent, the Work Exponent We. Case studies illustrate the excellent prediction of the W;-We models, compared to the three mentioned laws.

Jan 1, 2001

By K. E. Brown, T. D. Murphy

At Monterey Coal's No. 1 Mine in central Illinois, it became necessary to predict if the sulfur content of individual trainloads of coal would exceed a contract sulfur maximum. Using geostatistics and Monte Carlo-type simulations, a forecasting procedure was developed to meet this need. The developed procedure predicts the monthly, mean sulfur content of the coal shipped and the probability of individual shipments exceeding the contract limit. During the first five months of using this procedure, the forecasted, monthly mean sulfur value was within 0.03% of actual. This represents a significant improvement over the inverse-distance, gridding-based, forecasting used previously.

Jan 1, 1994

By C. R. Jenkins, G. S. Taylor

Three sedimentation ponds had their performance evaluated before and after installation of modifications. Each pond had a floating baffle installed, two had siphon outlets, and one had a floating outlet device. Baffles inhibited short circuiting, and the outlet devices retarded flow following a rainfall event and drained the pond, creating a large storage volume to maximize detention time. Total suspended solids and settleable solids tests were measured on samples of influent and effluent to evaluate pond performance. Particle size analyses were conducted on samples containing measurable amounts of solids. Performance improved in each pond, with baffles providing the major improvement.

Jan 1, 1987

By M. M. Ragin, B. J. Scheiner

The US Bureau of Mines (USBM) has been investigating the use of polyethylene oxide (PEO) as a flocculant for a variety of mineral wastes. As part of this investigation, the hydrodynamics of the flocculation process were studied. It was determined that to obtain optimum dewatering results, the factors of energy input into the stirrer, polymer concentration, and polymer dosage must be considered. It was found that at a given polymer concentration, there were an optimum stirrer speed and polymer dosage. With excess PEO, the amount of water removed in the trommel decreased, but no evidence for steric stabilization was observed.

Jan 1, 1987

By I. Iwasaki, J. N. Orlich

The effect of slurry rheology and ball coating characteristics on the abrasive wear of grinding media and the rate of grinding were studied using -10 mesh quartzite in laboratory marked ball wear tests. Pulp viscosity was found to be closely related with both the thickness and physical characteristics of the coating affecting abrasive wear. The packing density of particles at the ball surface was the primary determinant of wear while the grinding rate was more dependent on viscosity and thus the ball coating thickness. The optimum grinding rate was achieved when the coating thickness was about twice the largest particle size.

Jan 1, 1988

By Anthony J. Stewart, Jim W. Rosteck

This paper will discuss some of the equipment used to construct the middle segment of the MetroWest Water Supply Tunnel. The $252 million, seven-year project located in Framingham, Massachusetts consisted of two hard rock TBM drives worked from a single shaft. The 24,407-foot long west heading was constructed at the same time as the 35,006-foot long east heading. Also included was raise bore construction of four, 30-inch diameter steel lined riser shafts, one 12-foot finish and one 10-footfinish shaft as well as two major valve chambers. The main shaft was 400-feet deep and 32-foot diameter.

Jan 1, 2001

By Richard J. Frechette

Very few facilities containing hydraulically deposited tailings have been completely reclaimed and capped at this time. Design of a closure cap for a tailings impoundment has relied heavily on consolidation theory in order to achieve a cap that maintains sur­face drainage. Obtaining data for the consolidation evaluation can be difficult and costly. The author reviews the performance of two tailings impoundment closure caps that have been suc­cessfully installed and presents the experience gained from these projects with an emphasis on the ability to optimize cap design through post-operational monitoring prior to initiating cap con­struction. Using the optimization approach, a significant earth­work quantities reduction may be realized for the ultimate cap.

Jan 1, 1998

By F. G. Rinker

World demand for metallized iron continues to increase, keeping pace with steelmaking requirements for lower-cost hot metal. Virgin iron ore and in-plant oxide fines can be reduced to direct reduced iron (DRI) and hot-briquetted iron (HBI). Maumee Research & Engineering Inc. (MR&E) developed an improved coal-based process for the cost-effective production of either DRI or HBI. Starting with dry compaction, the process combines the latest technology for material preparation, rotary hearth furnace construction and environmental control. Coarse iron ore fines are blended with pulverized nonmetallurgical coal to produce a highly metallized (>90%) product. This paper presents production and installation cost data based on operating and under-construction iron oxide reduction facilities.

Jan 1, 2002

By A. J. Hudson, M. R. Yenchek

Faulty insulators on mine trolley/track haulageways may allow leakage of currents into the mine roof, which may ultimately result in the combustion of the roof material. The National Institute for Occupa¬tional Safety and Health (NIOSH), Pittsburgh Research Laboratory (PRL), devised a passive means to detect overheating insulators on di¬rect current systems. The detector consists of a spring- loaded car¬tridge that ejects a reflective streamer of white Teflon tape when subjected to elevated temperatures. The cartridge assembly can easily be installed over the outer metallic shell of an existing trolley line insu¬lator. If an insulator overheats due to ground leakage currents, the vis¬ible streamer alerts mine personnel traveling on the haulageway.

Jan 1, 2000

By A. S. Malicsi, M. D. Baker, I. Iwasaki

Fine grinding may he required for- some coals to remove sulfur and ash or to prepare coal-water slurry. Fine grinding leads to increased hall wear and its effect on the surface properties of the ground coal becomes of concern. Marked hall wear - tests were performed to study the effects of oxygen, pH, the soluble species of coal, and the addition of pyrrhotite on hall wear. The synergistic action of coal and oxygen greatly enhanced the corrosion of mild steel halls during grinding. Elec.trochemica1 measurements on a mild steel electrode in coal slurries and SEM observations of grinding hall surfaces were carried out to explore the corrosive wear mechanism.

Jan 1, 1991

By Bruce Cavender

Production managers look to innovative practices and equipment to reduce operating costs and improve efficiency. These innovations apply to both technical and social aspects of production operations and may be high-tech or low- tech in nature. They may be based on the implementation of a few large-scale "breakthrough projects or numerous small-scale activities, depending on the availability of capital funding and the company's past experience. Successful managers systematically identify innovative opportunities that capitalize on their organization's expertise. They quantify the associated benefits and risks and then manage the implementation of selected innovations to minimize cost and uncertainty. They monitor the results of the innovation after it has been implemented and adjust operating and managerial practices as necessary to maximize the innovation's benefit.

Jan 1, 1998