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By R. L. Grayson

Compliance standards for respirable dust, which are reduced because of high quartz concentrations, have become an industry-wide problem. Research on the physical and chemical character of quartz-classified particles in respirable coalmine dusts indicates that they mine exist in intermixed layers or may be coated by clay or coal material. The relative amount of intermixing varies with the coal seam being mined. If most of the quartz particles of a mine dust are "pure," then the dust may have a high fibrogenic risk potential because of truly free silica and the compliance standard should be lowered. If, however, the quartz is locked inside another material matrix or coated, a reduced compliance standard may not be appropriate.

Jan 1, 1992

By P. J. Bethell

This paper reviews current fine coal cleaning circuitry, including water washing cyclones, tabling and froth flotation. It goes on to examine possible future beneficiation based on emerging technologies. Circuits considered include those incorporating spirals, fine heavy medium cycloning, hydrosizers and column flotation.

Jan 1, 1988

By W. Keilich

A methodology of subsidence prediction using the Distinct Element code UDEC has been developed as an alternative for subsidence modelling in the Southern Coalfield, New South Wales, Australia. The models have been validated by comparison with empirical results and observed caving behaviour. At this stage, modelling capability is limited to flat lying terrain. It is planned to apply the methodology to areas of high topographical relief to investigate the mechanics of valley closure.

Jan 1, 2006

By Dennis L. Boley, Francesco Gallavresi, Donald A. Bruce

The authors describe novel aspects of ground reinforcement and treatment as related to soft ground excavation for tunnels throughout the world. Insitu reinforcement for cut slopes (soil nailing), as underpinning (reticulated micropiles), and as direct tunnel support (infilaggi) is introduced. Ground treatment focuses on new aspects of permeation grouting (by the tube'a manchette system), and on jet grouting-a very powerful and positive new technique. Recent developments in equipment, materials, methods and instrumentation are reviewed, with special reference to major tunnelling projects in Italy and Singapore.

Jan 1, 1987

By Ellis G. Goree, George A. Simmons, Andrew B. Pervis

The pneumatic classifiers are widely used for fine dry powders separation These classifiers can be used for either the removal of fines from coarse feeds or the removal of coarse particles from ultrafine feed To optimize the operation of pneumatic classifiers, a thorough understanding of the impact of operational parameters on the efficiency of classification is essential This paper describes the design features and effects of operational parameters followed by illustrations of pneumatic classifiers usage in two case studies

Jan 1, 1983

By T. A. Jones

The Kelsey Centrifugal Jig is an enhanced gravity concentrator capable of separating fine minerals and/or minerals with relatively small differences in specific gravity. Since the first commercial installation at the Renison Bell tin mine in Australia, development and improvement in hardware has continued, including the introduction of the high-capacity J1800model Kelsey Jig. The Kelsey Centrifugal Jig is widely applicable to fine mineral recovery duties, with key application areas including mineral sands, tin, gold and nickel. Other areas of application include: iron ore, base metals, chromite, PGMs, soil remediation and scheelite. The latest developments on the Kelsey Jig are discussed together with a review of recent installations involving: • Fine gold / sulphide recovery from leach tailings • Magnesium mineral removal from nickel sulphide concentrates • High-grade zircon recovery from plant tailings

Jan 1, 2004

By M. Galetakis, C. Roumpos

A sustainable coal industry needs to achieve a number objectives concerning mainly with superior utilisation of deposits and improved environmental performance. Modern quality control systems, which are greatly based on the on-line analysers, play an important role in achieving sustainability targets. This paper discusses the testing and application of on-line ash analysers installed in the Ptolemais and Megalopolis lignite mines in Greece and examines the possibility of using this type of analyser to control blending and homogenisation operations. The effect of the accuracy of on-line analyser to control process, when used for the characterization of low rank coals with complex and variable composition, such as greek lignites, is examined.

Jan 1, 2005

By Boris M. Vorobjev

The paper in question discusses a wide range of topics related to computerized coal mine monitoring systems starting with the history of development and application of computerized monitoring coal mine systems and finishing with modern trends in the design and updating of such systems. The paper focuses exclusively on methodological and technical aspects of computer-based coal mine monitoring systems and their applicability in both surface and underground coal mining operations.

Jan 1, 1989

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 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 L. G. Austin

The use of crushed power station slags, both natural and coated, as granules for roof shingles shows some promise. Test shingles weathered for some years showed rust spotting and granule deterioration as serious problems. Chemical analysis on a particle-by-particle basis using a scanning electron microscope-energy dispersive spectroscopy system showed the wide variability of chemical composition of the granules within a given sample. Analysis of particles acting as sources of spotting within the weathered samples showed high iron contents but no rules could he developed for predicting the long-term stability of different compositions.

Jan 1, 1990

By Alain A. Sonntag

This paper presents the most recent developments in KREBS technology directed towards treating higher throughputs, increasing efficiencies and providing further improvement in SX technology with a new concept: the submerged launder. Industrial plants built in the last past few years and using these improvements are described.

Jan 1, 1989

By D. I. Phillips, P. J. Bethell

This paper focuses on the -1/2 mm cleaning at Elk Run Coal. The original circuitry incorporated desliming cyclones. Problems with slimes entrainment in the cyclone underflow (froth cell feed) resulted in poor froth cell selectivity. Laboratory test work led to the installation of high frequency desliming screens. Consequently, great improvement in cell performance was brought about by enhanced desliming with the ability to use split flotation. The modifications resulted in significant improvement in total plant performance and overall yield while maintaining clean coal quality.

Jan 1, 1987

By Zhou Aimin, Xie Benxian, Song Chongkai, He Zhexiang, Zhang Changqing

Concrete pump is commonly used to transport paste and high-density backfill over relatively long horizontal distances. However, since the investment in concrete-pump and its operating cost are quite high, the application of paste backfill is limited in China. For seeking an alternative paste backfill technology, squeezed-transport technique and equipment has been developed. The new technology has been adopted at Tonglushan Copper Mine of Daye Nonferrous Metals Corp for overcoming a difficulty of long-distance transportation of high-density cemented tailings fill. It proved to be an alternative paste backfill method with simple backfill system, saving investment and low operating costs.

Jan 1, 2001

By J. E. Chilton

Methanometers with catalytic heat- of-combustion sensors used in coal mines today will read low for flammable gases when oxygen (0,) concentrations are low or when methane (CH,) concentrations are greater than 10%. Thus, these methanometers may not be reliable during operations such as fire fighting or recovery of sealed mines. The U.S. Bureau of Mines developed a total flammable gas detector (TFGD) to measure CH, at concentrations up to 100% and to measure flammable gases in low 0, concentrations. This paper describes the operation and construction of the TFGD and discusses measurements of flammable mine gases obtained from a mine in western Pennsylvania.

Jan 1, 1992

The authors give a corrected form of the Korobov algorithm of optimal open pit determination and describe a method of optimising the mining sequence within a preliminary pit design. A method of automatically including roadways is also given.

Jan 1, 1992

By Tuncel M. Yegulalp

In this paper we revisit the well known "Ultimate Pit Limit Problem" and suggest an alternative approach for fast and efficient solution. We follow the approach originally proposed by Johnson and Barnes (1988), but utilize the "Excess Scaling Algorithm" in solving the equivalent maximum flow problem. This algorithm provides significant increases in speed and reduction in memory requirements over the well known Labeling Algorithm of Ford and Fulkerson (1956), enabling one to solve large problems with relatively small computers. We present results of a series: of benchmark tests using this approach against the well known Lerchs Grossman algorithm as well as a brief description of the new algorithm.

Jan 1, 1992

By Kenneth N. Han, Yichang Guan

The dissolution behavior of metals from Au/Ag/Cu-alloys has been studied using rotating disc electrodes in solutions containing acids, cyanide, and ammonia. Electrochemical methods as well as leaching tests were adopted in this study. The results showed that there was no galvanic effect on the dissolution of metals from homogeneous alloys. In aerated cyanide solutions, the dissolution of gold, silver, and copper from their alloys was partly controlled by surface chemical reaction, but largely by mass transfer. On the other hand, the galvanic coupling effect played a very important role in heterogeneous alloy systems.

Jan 1, 1995

By V. Saltas

In the present work, dielectric spectroscopy experiments were conducted on bentonite samples collected from Milos Island, in order to study their electrokinetic behavior in correlation with water content and mild heat treatment. Low-frequency dielectric spectroscopy has proved to be a power tool in the study of the electrical behavior of clay-water systems, because polarization and relaxation processes typically affect response at frequencies below 100 kHz. Therefore, dielectric and conductivity measurements in the frequency range of 10mHz to 1MHz were carried out by means of a high-resolution broadband spectrometer on bentonite samples, at various levels of hydration. The evolution of dielectric response was also examined after annealing of the samples. Experimental data were computer fitted with the empirical Havrilliak?Negami dielectric relaxation function on which a conductivity term was superimposed. The evaluated parameters of the fitting function are shown to be strongly affected by the water content of the measured samples.

Jan 1, 2006

By R. Sawyer, M. Sadler, M. Holdworth

Greens Creek is a high grade Ag/Au/Pb/Zn deposit located in southeast Alaska. Maximizing the Net Smelter Return revenue from the fine grained mineralization is a dynamic process given changes in metal prices, smelting terms, ore grades and flotation characteristics. This paper discusses the evolving concentrate production strategy, and how it is affected by such factors as ore and concentrate specifications and by market conditions. Also described is the development of an on-line computer program that provides the mill operators with real time NSR data and a means for optimizing Net Smelter Return.

Jan 1, 2002