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By JoAnn Silverstein, Eric A. Marchand

Competition between Thiobacillus ferrooxidans and non-iron-oxidizing heterotrophic bacteria was induced by the addition of glucose to a co-culture of T. ferrooxidans and A. acidophilum in an oxygen-limited environment. Iron oxidation was inhibited as dissolved oxygen was used preferentially for glucose metabolism. Furthermore, as the water became anoxic, glucose was consumed along with the oxidized iron species (Fe3+) during iron respiration resulting in a pH increase from 2.0 to 4.0. Results suggest that biologically mediated acidification of drainage water can be reversed by dispersion of an easy to degrade, soluble, and inexpensive carbon source such as glucose into the subsurface.

Jan 1, 2000

By Frederick Schwarz

At the El Realito project, Sonora, Mexico, the Luz del Oro joint venture has recently inferred a geologic resource of 400 to 800 kt of 2.5 glt gold potentially present in gossans, breccias, and veins. El Realito, under investigation for a dump leach, open pit operation, is located in the Sun Antonio Mining District where gold and silver veins and gold placers have been exploited since Spanish colonial times.

Jan 1, 1990

By L. M. Bigler, J. L. Dobra

With the passage of Mexico's Mining Law in 1992, the tax treaty with the US in the same year, and the passage of the North American Free Trade Agreement, gold mining for non-Mexican mining companies in Mexico has changed dramatically. The statutory changes have created an opportunity for non-Mexican precious metals' producers to own 100% of a Mexican gold concession. This paper examines the financial feasibility of a hypothetical gold mine and processing plant in Mexico. The analysis includes the operational consequences of the recent weakness of the peso, as well as tax and employment issues.

Jan 1, 1996

By N. T. Rempe

The underground voids that result from mining provide opportunities for deep geologic waste disposal (DGWD). Such disposal could solve many environmental problems. DGWD takes careful planning, technology transfer and true partnership between waste generators and mine/repository operators. The US government is now planning on using specially mined excavations to dispose of radiotoxic and mixed waste. Using the experience gained from the domestic projects that are now in preparation and from foreign repositories that are now in operation, US mines can claim their rightful share of the growing market for DGWD.

Jan 1, 1998

A number of factors affecting the properties of cemented aggregate fill (CAF), particularly its strength development have been studied through a series of laboratory investigations carried out at the Western Australian School of Mines in the Western Australia in recent years. The outcomes of these investigations indicate that apart from cement dosage, aggregate particle size distribution, aggregate quality, additional fine materials, water salinity, admixture dosage and sample scaling all contribute significantly to the development of cemented aggregate fill strength.

Jan 1, 2001

By Janice M. Zinck, W. F. Griffith

Four different high density sludge-type processes, Cominco HDS, Geco HDS, Tetra HDS Process and the Staged- neutralization process were studied for their effectiveness in treating a low strength Zn-Fe rich acidic drainage solution. Each proms was run continuously for at least two weeks after obtaining steady state conditions. The final effluent quality, lime consumption, sludge density, settleability, filterability, viscosity, neutralization potential, metal leachability, operating and capital costs were measured and evaluated for each process.

Jan 1, 2000

By K. S. Shivakumar, R. Bhima Rao, M. R. Patil

Liberation size can be estimated using various techniques such as grain counting, frequency curves, X-ray intensity and the mesh of grind. The present investigation deals with the estimation of the liberation size of graphite flake contained in a schistose ore from Shivaganga, India. It was observed that the flakes are liberated at from 75 to 150µm. The rougher flotation concentrate obtained after grinding the run-of-mine ore for 5 min contained 54% fixed carbon. This represented the first stage of liberation. After regrinding to <90 µm in the presence of sodium silicate and guar gum, a cleaner concentrate containing 82% fixed carbon was obtained.

Jan 1, 1998

By D. Malhotra

Gold and silver ores are generally leached in weak cyanide solutions for recovery of precious metals. However, pretreatment of refractory ores requires flotation to concentrate the precious- metal minerals. Also, flotation is a common concentration technique for recovering precious metals as byproducts in sulfide-mineral flotation circuits. The present paper reviews current plant practice and future challenges for precious metal recovery.

Jan 1, 1999

By Frank F. Roxborough

The paper presents a brief account of the principal findings and an assessment of the practical value of a substantial international research effort into the mechanical excavation of rock that has been in progress over the past 30 years. This assessment together with an appreciation of the emerging trends in mechanical excavation suggests what are likely to be profitable lines of future inquiry.

Jan 1, 1985

By Ronald J. Doll, John Elkin, M. P. Evans

The application of "Alignment Free” right angle shaft mounted drive systems offers improved reliability and reduced costs for surface and underground belt convey- ors. Comparisons to conventional approaches will cover installation, operating, maintenance, and spares inventory cost savings. Various options for belt acceleration and load control on fixed and variable length (booster) belt conveyors will be reviewed for operating performance, reliability, and total cost. Lastly, a case study of a successfully operating installation will be highlighted.

Jan 1, 1996

By N. N. Clark, C. M. Atkinson

Pachuca tanks are used widely in the mineral industry for leaching and mixing operations. An analysis has been presented previously to predict circulation of homogenous slurry in Pachuca tanks with full height draft tubes. However, settling of solids causes deviation from the homogenous case. Circulation of settling slurry in a Pachuca tank is modeled and shown to be a function of settling velocity, solids fraction, solid and liquid density, air flew rate, and tank dimensions. The pressure balance is shown to be very sensitive to these parameters, especially at low slurry velocities. Equations for predicting the air requirements in Pachuca tanks containing settling solids are presented.

Jan 1, 1988

By J. S. Lewis

Beneficiation and physical and chemical processing of non-terrestrial materials will borrow strongly from terrestrial experience but will also involve the necessity of handling literally unEarthly feedstocks, reagents and environmental conditions. The present state of scientific and engineering understanding of the processing of non-terrestrial minerals, gases and hydrocarbons is reviewed, with the production of rocket propellants, life-support fluids, structural metals and refractories as the goal.

Jan 1, 1994

By Shaoxian Song, Shouci Lu, Jingyon Gou, Pan Yiuwen

The calculated potential energies of interaction between hydrophobic particle of three minerals (rhodochrosite, quartz and talc) and air bubble show that the energy of hydrophobic interaction is the dominant factor for their attachment. An attachment rate equation, integrating particle -bubble collision and adhesion by introducing a "capture efficiency", has been put forward. It was found that the hydrophobic particle-bubble aggregates can not be disconnected in the bulk zone of flotation cell, whereas in the impeller zone the breakup may occur, particularly for the coarser particles captured by bubble. Finally, the flotation rate constant was estimated theoretically and verified by experiments.

Jan 1, 1995

By M. C. Manderson

While the United States has been the world&apos;s largest volume producer and marketer of phosphatic fertilizers for many years, it has recently suffered heavy losses for a variety of reasons. While improved economic performance is expected, it is still at least a year or two away. But when recovery does manifest itself, it will likely yield only mediocre profits, due in part to the fact that about 50 percent of output is export-dependent. Therefore, there appears to be limited likelihood that profits will be adequate to justify the further outlay of large amounts of capital for expansion.

Jan 1, 1986

By James R. Arnold, Timothy D. Arnold

The mathematical rigor of the collegiate engineering experience prepares an engineer well for the technical aspects of his or her career. However, as that engineer progresses in the industry, how well does he or she do as a manager? The exacting, detailed, and complete problem-solving process that engineers are trained to use sometimes conflicts with the nimble, rapid decision-making process required in the dynamic world of business. This paper discusses the topic of "engineers as managers.”It will investigate the personality traits of engineers relative to the traits of successful managers, and provide specific details about how well engineers have done in the field of management.

Jan 1, 2001

By J. W. Leonard, D. A. Newman

By using physical and chemical means to increase the bulk density of newly broken coal freed from the mine face, the potential to improve coal mine productivity is significantly enhanced. It is estimated that by increasing bulk density, greater tonnages can be placed in fixed volume scoops and shuttles cars to improve production by as much as 10% to 20%. Such improved packaging to achieve new levels of volumetric efficiency might require only small and easy to implement changes to present downstream mining operations. Opportunities exist for improving broken coal bulk density from the moment of breakage, during transport across the continuous miner or loading machine, during discharge into the haulage unit, and after placement in the haulage unit. Physical/chemical methods for broken coal compaction in mobile, fixed volume units in underground operations are discussed.

Jan 1, 1990

By William E. Hole

The sand and gravel industry provides an enormous quantity of materials vital to the maintenance of low-cost construction. There has been little effort to conserve this valuable natural resource. In fact, existing regulations which affect sand and gravel operations act more to waste these materials than to conserve them. Another factor affecting the industry is new legislation requiring the reclamation of worked-out pits. Although such legislation creates many administrative headaches for a sand and gravel operator, there exists the possibility through such legislation of gaining some conservation measures that could be helpful to the industry.

Jan 1, 1974

By D. Papacharalampos

A combination of decision- theoretic and knowledge-based methods can be used to classify rock-types from satellite data both efficiently and accurately. An expert system utilizes knowledge-based rules, as a field geologist does, to produce results that make geological sense. Our expert system (GEMS), first processes background information from preexisting knowledge and develops a plan, then classifies individual pixels, and finally generalizes the results using geological rules and plots a map. The system is implemented on a microcomputer and is inexpensive enough to be a part of the standard equipment of any geologist who prepares reconnaissance maps.

Jan 1, 1986

By William J. Gregg

Mechanical testing results on oriented Devonian gas shale core throughout the Appalachian basin show a preferred fracture direction perpendicular to bedding. The preferred direction is generally parallel to the Allegheny Front, but is only coincidentally parallel with in-situ stresses in some areas of the basin. The strength of the preferred orientation of induced fractures decreases with distance from the Front. It is suggested that strain related to Paleozoic deformation is responsible for this mechanical fabric and thus the direction of induced fractures in laboratory tests may not be of use as indicators of in-situ stress orientations as previously suggested.

Jan 1, 1986

By Michael D. Zuber

This paper discusses the use of a coalbed methane simulator that has been modified to account for the removal of grid blocks as a function of time to estimate gas emission and production for a variety of mine-associated problems. The specialized features of the simulator are presented. Example applications illustrate the models&apos; use in estimating methane emission rates during mine roadway development, and estimation of longwall panel degasification by horizontal boreholes.

Jan 1, 1997