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By A. C. Noble

Ore reserves are often less than 30% of the geologic resource estimates initially prepared by exploration geologists. Differences of this magnitude can lead to serious problems in the early valuation of properties when the geologic resource estimates are interpreted to represent ore reserves but are later found to be misleading and gross overstatements of the actual ore tonnages. The geologist can avoid such difficulties by considering the implications of mining, metallurgical recovery and economics early in the project and by using appropriate qualifiers in the resource statement. Examples using typical deposit characteristics are used to demonstrate how the cutoff grade, stripping ratio, dilution, mining extraction and metallurgical recovery affect ore reserve estimations.

Jan 1, 1994

By P. Zhang

The Crago “Double Float” process is widely used in upgrading phosphate ore. This process is inefficient, as it floats about 30-40% of the sands in the flotation feed twice and requires a deoiling step. This paper summarizes several research projects on improving phosphate flotation. The University of Utah investigated a new flotation chemistry for efficient flotation of phosphate in a single step. The Florida Institute of Phosphate Research developed several single-collector, all-anionic flotation flowsheets using various sizing schemes. In addition, Eriez invented the HydroFloat separator, which demonstrated great potential for processing coarse flotation feed in one step.

Jan 1, 2004

By Mayank Srivastava, Satya Harpalani

Production of methane is an inevitable consequence of mining coal. Although the number of mines practicing recovery of methane prior to, or during, coal mining is increasing, ventilation air methane (VAM) is still a significant source of methane addition in to atmosphere. Recent studies have shown that there are ways to recover the VAM energy, while simultaneously reducing the methane emission in to atmosphere. This paper discusses a case study, currently underway, to develop a technique to quantify the VAM emission from a mine. It also presents the different VAM utilization techniques and the suitability of one for the mine being studied. Finally, the paper summarizes the research issues that require further investigation.

Jan 1, 2005

By Hanguang Wu, V. Izaxon, Sukumar Bandopadhyay

This paper presents an analysis of the heat transfer process between the mine ventilation air and the frozen rockmass. The heat transfer model takes into account not only by the mutual change in air and rockmass temperatures, but also by the phase change of ice-water- ice. Based on the analysis presented here it is concluded that the mine thermal regime can be regulated by having the air enter the mine through mined-out excavations or development airways.

Jan 1, 1995

By Gopalan Ramadorai

This paper presents a review of halogen solvents used in the processing of precious metals. Reagents of widely varying chemical structures, such as chlorine gas, calcium and sodium hypochlorite, chlorine dioxide, iodine and bromine have been used for precious metal extraction. None of these chemicals are a replacement for cyanide: however, each of these chemicals present an opportunity for use in processing a specific type of ore. The ore and chemical must be matched to each other for success. Recovery of metal from the leach solutions also offers challenges.

Jan 1, 1994

By R. J. Gochin, G. D. Schena

Mineral processing options and technical innovations should be financially assessed. Indeed technical feasibility alone does not offer an adequate process selection criterion. An appraisal by the use of engineering economics principles leads to a more efficient evaluation and selection of feasible mineral processing solutions. Financial consequences of different options synthesised by profitability indices allow better decision making. Selected examples derived from real world problems are used to illustrate the potential of engineering-economics methods applied to mineral processing.

Jan 1, 1995

By Greg Barfoot, Alex Harrison

Conveyors with multiple drive pulleys of the same diameter and wrap, driven by identical motors through gearboxes of the same ratio, consume different powers. The fundamental issues related to this problem hinge around the drive pulley co- efficient of friction and the intermediate tension. Some basic design concepts will be presented with reference to validity and applicability. The paper will describe some experimental results obtained from multiple drive conveyors in which the drives are spatially separated. The dynamics of tripper drive and linear booster drive systems are overviewed with reference t

Jan 1, 1993

By I. J. Jansen, C. L. Hooks

Successful soil construction involves prepa¬ration of an adequate base, selection of high quality soil ma¬terials, and placement of those materials by means which will establish a continuous macropore network and modest to low soil strength. Where such has been accomplished, experi¬ments reveal row crop productivity on reclaimed land which is very competitive with that on undisturbed land. Inferior productivity and sensitivity to drought stress are experienced where the soils are excessively compacted during construc¬tion. Some deep tillage practices have been quite successful in improving the compacted soils, but it is preferable to avoid compaction as the soil materials are handled.

Jan 1, 1987

By Allen V. Reicks

This paper reviews the impact of the idler set on the performance of belt conveyors. Idler rolls as part of the load support system and their interaction with the conveyor system will be discussed. in particular, the rotating performance of the individual idler roll concentrating on the rotating resistance and life of the bearing and seal design are addressed in detail. A basis for the development of performance specifications for use in conveyor design that takes advantage of the idler manufacturers design and manufacturing expertise is discussed.

Jan 1, 2008

By J. R. Palmes

Flocculation of coal fines with varying degrees of wettability was studied under well defined hydrodynamic conditions. In this study, three coal samples were tested with three different flocculant types. The results revealed that flocculation depends strongly on both the coal surface properties and the type of flocculant used. A hydrophobic flocculant was found to be effective for hydrophobic and slightly oxidized coal, a semihydrophobic flocculant was found to flocculate, to different extents, all of the samples except the oxidized cool, and polyacrylimide flocculated all of the coals, which is a clear indication of its insensitivity towards coal wettability.

Jan 1, 1994

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 R. W. Reisinger

An historic underground copper mine in Wyoming is discharging neutral but copper-laden water into a pristine creek. The EPA-deferred site qualifies for reclamation by the Wyoming Abandoned Mine Land (AML) program. The cleanup goal is to restore the discharge so that the creek can eventually support a trout fishery. Hydrological and geochemical investigations underground have suggested two sources of mine water: one clean and the other containing copper. Results of bench-and pilot-scale tests support the viability of using low-cost passive treatment techniques to reduce copper concentrations in the near-freezing mine discharge.

Jan 1, 2000

By Timothy P. Smirnoff, Anthony Stirbys, Amanda Elioff

The construction of the continuing expansion of the Los Angeles Metro System has required the construction of eight new station structures. One contractor proposed, as a construction alternative for the support of excavation of the Hollywood/Vine Station, the use of soil-mix walls instead of the conventional soldier piles and wood lagging. Soldier piles and shotcrete or wood lagging support systems had been generally used on the other sub-way station excavations constructed to date throughout the system. Immediately east of that station and in almost exactly the same geology, the Hollywood/Western Station was being excavated at the same time using a conventional support system. This paper com-pares the performance of these two support systems in the alluvial soils of the Los Angeles Basin.

Jan 1, 1997

By Jerry R. McGaha, Joseph A. Dos Santos

The favorable economics of conveyor based haulage, especially in moving large volumes. has long been acknowledged. This has given impetus to significant developments over the last two decades in conveying systems and equipment. Such developments have resulted in improved equipment and system reliability, versatility and mobility. The present writing presents conveyor systems and their variations. Long overland conveyors of various profile and plan layout are considered along with various typical support systems. This includes discussion of horizontally curving, two-way and booster driven conveyors. High Angle Conveyors-[HACs] are reviewed, citing in-pit as well as plant application. Finally, several important advances in idler and in pulley design are presented.

Jan 1, 1989

By J. C. Stankus, S. S. Peng

Many coal seams are associated with soft floor strata. During mine development, if coal pillars are not properly designed, floor heave occurs and causes interruption of coal production. In the severe cases, the section or mine is abandoned. One method for controlling floor heave is floor bolting. This paper describes the demonstration of flour bolting methods in a West Virginia, info coal mine. Three methods were used: vertical full resin bolting, floor truss bolting and floor truss bolting pins a floor slot at the center of the entry. The design of each method and the experimental results are discussed.

Jan 1, 1995

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 Donald A. Dahlstrom, Soumitro Nagpal, Timothy Oolman

Bacterial oxidation of a pyrite/ arsenopyritic gold-ore concentrate was carried out with continuous flow operation in 14 liter (1.4x10-2 m3) mechanically agitated reactors. 02 and C02 uptakes were determined at varying residence times. Bacterial concentrations were measured using a protein assay. A sharp optimum in biooxidation rates was observed with increasing steady-state residence times. Growth of the bacteria and biooxidation of the mineral were both shown to be strongly dependent on dissolved 02 levels in the liquor.

Jan 1, 1990

By R. Sripriya, Ch. V. G. K. Murty, N. D. Rao, P. V. T. Rao, A. Ramu

Studies were carried out to improve the performance of hydrocyclones at Tata Steel's chrome ore beneficiation plant in Sukinda, India. The optimal cut point of the hydrocyclones was determined in the laboratory using a stub cyclone. In the tests, the operating and design variables, including spigot diameter, density of feed slurry and inlet pressure, were varied. Subsequently, plant trials were carried out, and attempts were made to develop a model of the hydrocyclone using the Rao, Lynch and Plitt model. The cyclone efficiency was represented by the parti¬tion curve, and the performance was evaluated mathematically from a reduced efficiency curve, represented by the equation:

Jan 1, 2000

By Karl-Heinz Bruemmer, Karl Wollers

1- Importance of Shafts for the Exploration and Extraction of Coal Deposits Coal mining in the Federal Republic of Germany is carried out in a depth between 800 and 1200 m below sea level (Fig. 1). The shortest connections underground in a mine and up to the surface are vertical shafts. Such shafts assume, with ventilation, manriding and the winding of material, the most important functions for the maintenance of mining operations. In the German coal mining industry, a difference is made between the main shafts providing a direct access from the surface to the deposits, and the so-called "blindshafts" which serve as a connection between two or several haulage levels underground. [ ]

Jan 1, 1976

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