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By D. R. East

Recent experiences within certain sectors of the international mining industry suggest an underestimation of the environmental risk associated with the design of mine waste management facilities. These experiences show that the technical and managerial challenge of responsible mine waste management is not always fully appreciated. Unfortunately, the image of the mining industry's environmental performance is negatively impacted by a relatively few number of failures. This negative view overrides the many positive contributions made by the majority of mining companies. The fact that these failures continue to occur to this day in both developed and developing countries is indeed remarkable, and indicates a degree of risk-taking approaching unacceptable levels. The design requirements for tailing storage facilities are, in many cases, more demanding than those of conventional water dams, because seepage of fluids which contain dissolved metals may pose a greater threat than the mere loss of water.

Jan 1, 1999

By José Luis Lee Moreno

This paper presents a preliminary phase of a study being conducted by the Department of Geochemistry of the Consejo de Recursos Naturales No Renovables in the vicinity of the Pachuca-Real del Monte Mining District. This district is located in central Mexico, about 100 km northeast of Mexico City. It has been in operation for the past 450 years and has produced about 38 million kg of silver and about 190 thousand kg of gold. At the present it is being worked by the state owned mining company of Real del Monte and Pachuca. The rocks of the area consist mainly of Tertiary volcanics, ranging in age from early Oligocene to late Pliocene. Ore bodies are recognized as epithermal, vein type fracture fillings. The main ore minerals are argentite and acanthite normally accompanied by base metal sulphides, Gold is present in small amounts as native gold and in other minerals. Orientation geochemical studies performed on soil and rocks over known veins in the district, showed zinc to be the best indicator. Lead and silver anomalies are restricted to the immediate vicinity of the veins, mercury shows the mineralized structures only when the "C" horizon is sampled, while antimony gave erratic values. The El Chico area is about 10 km north of the Pachuca-Real del Monte district and covers approximately 400 sq km. Geological evidence indicated the possibility of an extension of the Pachuca ore bodies in this area. Results obtained from soil and rock samples from El Chico, showed several anomalous area. Detailed investigations proved these anomalies to be related to faults and fractures which in several cases have been found to be mineralized. Drilling is planned with preliminary results expected by late 1974.

Jan 1, 1974

By J. R. Johanson

In recent years the procedures for functionally designing bulk storage bins and hoppers have evolved from qualitative guess and try methods to a quantative method based on theory and tests of the bulk solid to be stored. This quantative method, developed and implemented by Dr.'s A. W. Jenike and J. R. Johanson as with any new design, must prove its effectiveness and validity in the actual operation of the finished equipment. How accurate are the theoretical predictions? Is it possible to extrapolate from bench size tests on a small ample of the bulk solid to the full scale bin design? Can the theoretical designs be economically translated into working hardware? In this paper the answers to these questions are discussed in light of actual bin operations.

Jan 1, 1968

By Louis I. Briggs

Evaporite rocks, salts of the more soluble ions in seawater, are deposited when seawater becomes concentrated by excess evaporation in marginal basins having restricted circulation with the open sea. The simple conceptual model of an evaporite basin (Figure 1) has a single inlet connecting the basin to the open ocean, the restriction to open circulation being caused by a bar or reef near the mouth of the inlet. As the oceanic water flows from the inlet into the basin it tends to form a thin layer of brine that spreads out over the surface of the basin brine, and as it does so, the salt concentration In the surface layer gradually increases owing to continued evaporation of the water. When the solubility products of the salts in the surface layer are exceeded, the salts precipitate and settle to the bottom of the basin, The order of precipitation follows their order of least solubility. Normally the carbonates separate first, followed by the sulfates and chlorides and the more complex double salts. In nature there is considerable overlap in their ranges of precipitation. The water flow in the basin, also shown schematically in Figure 1, diverges from the inlet essentially perpendicular to the lines of' equal salinity in the surface brine. The distribution of salts deposited in such a model will parallel the isosalinity lines, being arcuate and concave toward the inlet (1)

Jan 1, 1967

By R. H. Lambeth

Disposal of mine tailings in "waters of the United States" is presently prohibited even though case studies indicate that the practice may be environmentally viable. To simulate disposal in the natural environment, nine containers of tailings and sediment were instrumented and placed on the ocean floor near Juneau, AK as were ninety-six biosample containers. Pore water concentrations of five metals were determined, and biota populations were characterized for both materials. After 500 days of exposure there were no statistical macro scale differences between tailings and sediment biota populations or Cu, Pb, and Zn pore water concentrations. Tailings released slightly more Fe than sediment, but sediment released significantly more Mn than tailings. Disposal of mine tailings in marine waters may be environmentally safe.

Jan 1, 1998

By Z. Zhang, R. G. Reddy

The viscosities of industrial lead slags of varying compositions were measured as a junction of temperature using a Brookfield viscometer. Based on the experimental data obtained from this study and based on other investigations reported in the literature, an expression was developed to correlate the viscosities of industrial lead silicate slags as a function of composition and temperature. The effect of each individual slag component on the variation of the slag viscosity is identified. The composition dependency of lead silicate slag viscosity is discussed. The calculated results using this viscosity expression are in good agreement with the measured data. Key words: Viscosity, Lead silicate slags

Jan 1, 2003

By Frédéric Flament, Daniel Hodouin, Claude Bazin

A control strategy is proposed to meet the following specifications of flotation control: minimize the variations of concentrate and tails grades and recovery while limiting the amplitude of variations of the manipulated variables. The strategy consists of determining future control actions which optimize a performance criterion over a limited time horizon. The desired dynamic behaviour of the controlled flotation plant is specified using reference models. The strategy is tested on a 2-computer plant simulator working in an environment which emulates the industrial conditions.

Jan 1, 1993

Acid mine drainage is still a common problem in the northern Appalachian high sulfur coal region despite mining and reclamation practices applied to control it. Mining companies must treat water with alkali to raise pH and precipitate metals in order to discharge the water into receiving streams. Common chemicals used to treat drainage are limestone, hydrated lime, soda ash briquettes, caustic soda, and ammonia. Each chemical has advantages or disadvantages under specific conditions. A simple spreadsheet program was developed to evaluate costs of treating acid mine drainage across several specified water quality parameters and time horizons. Caustic soda and soda ash were shown to be cost effective for treating low flows and low acidity over short time periods. However, as quantity of water increased, quality decreased, and time horizon increased, the ammonia and hydrated lime systems were found to be much cheaper than caustic soda.

Jan 1, 1991

By L. Darkwah

The use of explosives in coal mining inevitably results in oversize, midsize and undersize (fines) products due to fragmentation. The oversize can be broken into smaller sizes by further processing. However, the undersize have a negative affect on the efficiency of a mining operation. Therefore, limiting the amount of fines can be economically crucial. This paper concerns investigations aimed at reducing fines generation in coal mining. Inherent fractures were identified as one of sources of fines generation. This paper is centered on establishing a relationship between the fracture occurrence, the explosive properties and the blast outputs, which are evaluated in terms of the fines generated.

Jan 1, 1998

By E. Alaphia Wright

An accepted approach to open pit mining sequence planning is one of computer aided planning where: the planner works out his mining sequences by trial and error using interactive graphics; This approach gives results that could in- variably be improved given more time for the planning exercise. Increased emphasis on interactive planning reveals a need for simple formalized procedures for improving mining sequence planning practices. This paper discusses a case study in which Dynamic Programming (DP) is used in mining sequence planning. It is shown that DP can be applied to identify various intermediate, pit boundaries. These are then arranged in descending order of economic values and their material contents analysed with respect to tonnages, grades, production requirements, and equipment capacities. Those increments which best satisfy defined conditions are selected and the others discarded. The mining sequence is thus built up as a chain of best- economic valued mining increments satisfying given production requirements and constraints.

Jan 1, 1989

By Joyce A. Ober

Strontium occurs commonly in nature, averaging 0.034% of all igneous rock; however, only two minerals, celestite and strontianite, contain strontium in sufficient quantities to make its recovery practical, and these minerals are found in sedimentary rocks. Of the two, only celestite has been found to occur in deposits of sufficient size to make development of mining facilities currently attractive. Celestite, the most common strontium mineral, consists primarily of strontium sulfate (SrSO,). Strontianite, the second most common mineral, consists primarily of strontium carbonate (Sr CO3). Strontianite would be the more useful of the two common minerals because strontium is used most commonly in the carbonate form, but few deposits have been discovered that are suitable for development. The physical properties of strontium ores are listed in [Table 1].

Jan 1, 1994

By F. W. Petersen

In the precious metal industry, activated carbon is used extensively for the recovery of gold and silver from cyanide solutions, particularly from slimy pulps and unclarified solutions. However, carbon can easily become fouled by inert particles in the pulp, thus decreasing the activity or gold loading of the carbon. This paper attempts to quantify the distribution of fine inert particles in activated carbon. Furthermore, a possible mechanism for the intrusion of fines will be postulated. Precipitated silica and ground silica sand were used to simulate pulp conditions and their loadings on activated carbon were determined by ashing. The kinetics of intrusion of fines into the pores of carbon were relatively fast, and were dependent on the concentration in the pulp. Results indicated that particle size of the solids and zeta potential of the fines influenced the loading of inert species on carbon. Scanning electron microscopy and secondary ion mass spectrometry showed a decrease in solids concentration to the centre of the carbon particle.

Jan 1, 1995

By Yannis Faitakis, Brenda M. Wright, Gail Powley, Mark Hamblin, Randy B. Paine

A major problem in the ore extraction process is the high degree of variation in the mix of materials that make up the mined ore. The mix of materials makes it extremely difficult to characterize and predict the behavior of the ore when it is processed. The Quality Production Database (QPD) tool was successfully used in order to predict and transfer information regarding the quality characteristics of the ore being delivered to the extraction and hydrotransport unit operators. This paper describes the use of QPD in the prediction of various ore characteristics at the Syncrude Canada Ltd. processing facility.

Jan 1, 2000

By Winfield G. Wright, Philip L. Verplanck, Douglas B. Yager, Dana J. Bove, M. Alisa Mast

The upper Animas River watershed is affected by metal-rich drainage from abandoned mines and by natural weathering of mineralized bedrock. To investigate the importance of natural metal sources, surface waters were sampled in a minimally mined but intensely altered area of the watershed. Water chemistry was strongly controlled by the degree of bedrock alteration. Propylitically altered rocks, which contain calcite, produced neutral waters with low metal concentrations, whereas quartz-sericite-pyrite alteration was characterized by acid-sulfate type waters with high metal concentrations. A mass-balance approach was used to estimate natural metal sources, which accounted for 56-905 of the dissolved metal load discharging from the study area

Jan 1, 2000

By Lijun Xu, Ragula Bhaskar

The transport of dust particles from a turbulent air stream on to the surface of a mine entry is mainly due to the effect of diffusion, sedimentation and inertial impaction. While the literature in aerosol science contains many references on particle deposition, most studies apply to smooth surfaces in small, short tubes. The deposition data from those experiments may not be applicable to deposition in mine airways that have large areas of rough surfaces and extend several thousand meters. This paper describes the mechanisms of mine dust transportation and deposition, specifically, by estimating the turbulent deposition velocity for coal dust in mine airways. Data from in-mine experiments on ambient dust concentration and dust deposition along a straight entry were used. A statistical model for dimensionless turbulent deposition velocity was developed, and compared with the models developed by other researchers. The model shows that the distance from the dust source is an important factor in the turbulent deposition of mine dust.

Jan 1, 1995

By J. W. Craven, M. Katom, K. M. McCaffery

At Ok Tedi, ore type and SAG feed size distribution vary widely and frequently. This makes control of the SAG mills by application of the power/pressure relationship difficult. Power logic has traditionally been conservative due to power spikes associated with rapid size-distribution changes. A new expert system was installed in early 2000. The system incorporates multiple state fuzzy logic to deal with frequent and radical ore type and size variations, along with monitoring of motor temperatures. A short-term power spike no longer warrants immediate radical action. This has resulted in increased mill throughput and improved circuit stability. Key words: SAG mills, Mill control, Fuzzy logic

Jan 1, 2003

By Ian H. Clark

A series of numerical experiments were performed in order to elucidate the stress distribution, fracture strength and mineral liberation potential in single specimens of rock during crushing. Fracture strength was shown to reduce under eccentric loading conditions. Similarly, the presence of inclusions, both hard and soft, reduced the fracture strength. The predicted crack paths indicate that mineral liberation is unlikely to be preferential.

Jan 1, 1992

By Alex Harrison, Steve Kasper

Various countries around the world have testing and manufacturing standards in place for steel cord belting. These standards are very comprehensive in what they allow the end user to specify, however, their practical significance in terms of belt life is more difficult to quantify. Such testing standards will be briefly reviewed in this paper in relation to the implication for end user expectancy. Since there is no US standard of manufacture, the end user is left with writing their own specifications. In addition, such standards do not address the effect on belt life of manufacturing faults, such as cord plane buckles, or lateral cord movement. Some new technology used to test steel cord belting will be described as an aid to both manufacturer and end user. Specific end user related issues addressed on this paper are: Tracking and belt quality Cord plane irregularities and performance Cord size and belt life Cord fatigue and testing

Jan 1, 1993

By Francis W. Brown, Philip R. Hunt, Douglas N. Halbe

Refractory arsenopyrite ore from Western Mining Corporation's Lancefield deposit in Western Australia is treated by fluosolids roasting of a flotation concentrate followed by cyanidation of calcine and flotation tailings. The project development is reviewed from original testwork through circuit design, operating experience, and subsequent expansion.

Jan 1, 1990

By W. P. Diamond, A. C. Smith, J. A. Organiscak, T. P. Mucho

The U.S. Bureau of Mines examined bleederless ventilation practices to evaluate their use as a spontaneous combustion control measure in U. S. coal mines. Results indicate that restricting airflow into mined-out areas (bleederless ventilation) is recognized worldwide as a spontaneous combustion control measure. However, ventilation practices commonly used to limit airflow to mined-out areas are not easily applicable to United States mining conditions, systems, experience and regulations. The types of bleederless ventilation systems used throughout the world and the spontaneous combustion risks associated with these systems are discussed. Primary design considerations for bleederless ventilation consist of the interaction of ventilation practices, methane drainage, ground control, seal construction and mine monitoring. Technological improvements needed for U.S. application of bleededess ventilation are also discussed.

Jan 1, 1995