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By G. B. Misra

Though installations of main mine fans vary widely, the commonest installation is of a surface exhaust fan connected to an upcast shaft some distance below its collar by a horizontal fan drift bending sharply. downwards near its junction with the shaft. The junction of the fan drift with the shaft often causes considerable shock pressure loss if not properly designed. In one of the major coal mines in India circulating 180 m3/s of air through the mine a pressure drop of 229 Pa out of the total fan pressure of 568 Pa occurred at this junction while in a smaller gold mine circulating 9.4 m3/s it was 147 Pa out of a fan-drift pressure of 382 Pa. With larger mines circulating larger volumes of air, ill designed fan drifts can lead to considerable wastage of the power of ventilation. Shock loss at the junction of fan drifts with exhaust shafts depends on (1) the angle of deflection of the bend, (2) sharpness of the corners (both inner and outer) at the junction, (3) the degree of contraction of the flow-stream which depends on the cross- sectional area ratio of the shaft and the fan drift as well as the amount of leakage through the shaft collar. It must be noted here that the friction pressure loss in the bend is negligible compared to the shock pressure loss.

Jan 1, 1980

By D. Robert Weir, Roman M. G. S. Berezowsky

Pressure oxidation can virtually always render refractory auriferous sulphidic ores and concentrates amenable to cyanidation. Its effectiveness as a pretreatment of refractory gold feedstocks is reflected by the successful startup and operation, over the past four years, of four commercial plants. At least three more are scheduled to come on stream during the next three years. Over the past eight years, a variety of ores and concentrates have been subjected to integrated miniplant testing and process demonstration by Sherritt, and data derived from these studies have been used in the design and construction of several of the commercial facilities. Some factors affecting the selection of pressure oxidation in gold recovery processing are discussed.

Jan 1, 1989

By Numan Elmas

Barite deposits located in Dinek and surrounding region have important economic features with their large reserve capacity for Turkey. The objective of this study is to elucidate geological and depositional characteristics in terms of. site investigation and chemical analysis. In order to do this, geological area of about 300 km2 was examined and detailed geological map was constructed. It was observed that Barite mineralization in these deposits was occurred in carbonate and pelitic rocks of Lower Cambrian-Lower Ordovician. Deposits were exposed to advanced diagenesis regional metamorphism and tectonics that rotated and deformed the barites; therefore, barites shows secondary veins, brecciate and fracturing structure. Even though, a few light isotope values of barites may suggest hydrothermal and exhalative sedimentary characteristics or possible mixing with magmatic fluids, generally heavy isotope values indicate that the sulfate ions were supplied from coeval seawater and, many of sedimentary features and petrological, geochemical characters support dominantly sedimentary origin.

Jan 1, 2005

By F. Duan, W. G. Pariseau, C. S. Schmuck

Three dimensional comparisons between calculated and measured displacements in the hanging wall of a rock mechanics study region at the Homestake Mine show correlation coefficients of 0.7 or higher. Two and three dimensional back analysis of the data lead to different scale factors for determining rock mass strengths and moduli from laboratory values and seemingly to different rock mass properties. A simple analytic model suggests that indeed not only are there two independent scale factors, one for strength and one for moduli, but that there is a logical relationship between the scale factors obtained from two and three dimensional back analyses of the same mine measurements. The three dimensional modeling procedure implemented in the finite element code UTAH3 thus seems to have a realistic potential for investigating underground hardrock mine questions not amenable to two dimensional analysis.

Jan 1, 1987

By P. E. Snoek, R. L. Gandhi, C. S. Miller

Slurry operations are an integral part of mineral processing. There is therefore reason to consider using slurry pipelines for long distance mineral transportation. This paper reviews the current state-of-the art of such systems and, in particular, the design factors which must be addressed. It also discusses the selection of major components such as pipe, pumps, valves and storage facilities. Finally, the major steps required to determine the economic feasibility of a slurry system are listed and the major advantages and disadvantages of slurry pipelines compared with other forms of land transport are summarized. SLURRY PIPELINES: GENERAL OVERVIEW Minerals Transported Long distance slurry pipelines have been successfully used for transporting coal, iron concentrate, copper concentrate, limestone and phosphate. Additionally, several tailings disposal pipelines of considerable size and length have been built, but these generally are not categorized as long distance commercial mineral transportation systems. Table 1 lists selected examples of commercial slurry pipelines.

Jan 1, 1986

By H. Sis, S. Chander

The pressure filtration behaviors of dispersed and flocculated alumnae slurries at high percent solids were investigated with the objective of determining the effect of surfactant type and concentration on slurry properties. A high-purity alumina powder was used as a model solid. Dispersion of the alumina was controlled by pH and by surfactants that are known to act as electric and steric stabilizers. The effects of both ionic and nonionic sutfactants were investigated. Surface charge measurements of the slurries were carried out by an electrokinetic sonic amplitude (ESA) method to better understand the mechanisms. The effect of surfactant type and concentration on the kinetics of pressure filtration and cake properties are discussed.

Jan 1, 2000

By R. Hogg, M. Polat, S. Chander

A fresh dust generator was designed and built in order to study the agglomeration behavior and other characteristics of freshly generated airborne dust. The size distribution of the freshly generated quartz airborne dust produced by the generator was measured both directly in air and after dispersion in water. It was observed that same dust particles had an apparently coarser size distribution in air than in water, suggesting possible agglomeration of the dust particles. It was also observed that the size distribution obtained by a cascade impactor was very similar to the liquid dispersed size distribution, implying deagglomeration by the impactor. The agglomeration was confirmed by microscopic observations of particles in air and those collected on a microscope slide. The extent of agglomeration played a decisive role on the fraction of the dust actually becoming airborne. It was also found that contamination of the airborne dust by the rolls of the crusher was almost twice as much as that of the product.

Jan 1, 1991

By André Vervoort, Jef Caers

Compound lognormal distributions serve as new generalized distribution laws for analyzing and estimating ore value distributions or related properties such as the average ore grade. These models are an alternative to the well known lognormal distribution. They are the translation of general geological constraints on the genesis of the deposit cumulated in suitable statistical properties. In this paper a maximum likelihood framework is established for estimating the parameters of such laws or parameter functions thereof. It is shown that under certain conditions maximum likelihood estimation is accurate and efficient in estimating the mean value even when relatively few samples are available. The method is based on a numerical maximization of the likelihood function of these models given the data. Confidence limits on these estimates are set up using resampling techniques such as the bootstrap. By this a complete methodology is presented for inference on ore grade distributions such as is shown in an example of gold data from the Merriespruit mine (South Africa) and the diamond size distribution of the Bougban deposit (Guinea).

Jan 1, 1996

By Mustafa Kumral

The study area is located in the Alpine-Himalayan zone in Turkey. Geologically, this is a very complicated region, and the rock units generally are divided into two groups as either allochthonous and autochthonous. Tectono-stratigraphically, the units are Paleozoic quartzite, black limestone, arkosic sandstone, interlaminated radiolarite and Triassic limestone, thick Jurassic limestone, detritic limestone with alternating Eocene Nummulites beds and cream-green marl, Miocene siltstone, and ophiolite. Trachyte, trachyandesite, feldspathoidal trachyandesite porphyry, tuff, and pumice formed by volcanism during the Plio-Quaternary also are present. Recent alluvium and slope detritus locally cover all the other rock units. A number of sulfur outcrops occur in the area. Among them are outcrops at Keciborlu, Yelliyatak Hill, Buyuk, and Kucuk Kukurt Dere. The most important sulfur deposits are found in volcanic tuff and siltstone-marl, and they include highly organic material. Sulfur may accumulate around recent gas diffusions and also as massive formations. The information about local geology and sulfur isotopes shows that the sulfur originated From the crust and probably comes from organic-rich Paleozoic and Triassic units. The sulfur did not move between Triassic and Pliocene time. However. Plio-Quaternary volcanism did cause movement of the sulfur, and this was followed by formation of the secondary sulfur due to post-tectonic thermal activities and the mixing of other surface waters.

Jan 1, 1999

By I. Tsolas

Sustainable development is becoming increasingly more important for the mining industry and therefore mining companies should be able to measure their progress towards sustainability. Greek Public Power Corporation (PPC) S.A. is a company which produces lignite in open cast mines in Western Macedonia and in Peloponnesos. The present paper uses operational data kindly offered by PPC S.A. to derive sustainability indicators by means of Data Envelopment Analysis for three large scale lignite open cast mines of PPC (i.e. Main Field, Kardia Field and South Field mines). It also examines three environmental parameters related to the contribution of these mines to sustainable development; namely, the annually produced volume of waste masses, the annually produced quantity of ash from the lignite combustion and the annual volume of pumped water. The calculated sustainability indicators were keeping constantly better during the last years of the different periods for each one of mines studied here, showing that the mines met their goals from both economic and environmental aspects during the last years of their operational periods studied. The contribution of open cast lignite mines studied here to sustainable development can be monitored by the derived indicators analyzing annual mine operational data. The derived indicators can serve as tools to detect where improvements can be made, though another potential use of these indicators can also be during the preparation of feasibility studies or environmental impact studies using necessary benchmarking data.

Jan 1, 2007

By George A. Desborough, Stephen J. Sutley, Reinhard W. Leinz, Paul H. Briggs

The mode of occurrence of metals in mine wastes is investigated using sequential extractions. Metals are extracted from some or all of seven operationally-defined phases: water-soluble, ion-exchangeable, carbonate, amorphous Fe-oxide, crystalline Fe-oxide, sulfide, and silicate. The quantity of metals extracted from each phase varies with particle size. The presence of jarosite (potassium end-member formula, KFe3[SO4]2[OH]6) influences the selection of the procedure for extracting the crystalline Fe-oxide phase. Anglesite (PbSO4) and cerussite (PbCO3) are extracted as several phases. Extraction results can be explained only in part by X-ray diffraction (XRD) mineralogy because of lack of specificity of the extraction procedures, relatively high XRD detection limits, and the presence of 40% XRD-amorphous matter in each waste. The increasing chemical strength of the sequentially applied methods provides a basis for judging metal availability, water-soluble metals being most available and silicate-bound metals being least available.

Jan 1, 2000

By David J. Kruse

Although it may be perfectly acceptable to neglect the belt's elastic behavior for many conveyor designs, this can lead to disastrous consequences for others. So how can a designer know in advance if a dynamic analysis is required? Unfortunately, in many cases it is impossible to foresee or predict dynamic problems prior to performing the actual analysis. However, a basic understanding of the principles of conveyor dynamics, as well as knowledge regarding common problem areas, can significantly help the designer make more educated decisions during the initial design stage. This paper will demonstrate how static calculations alone can incorrectly represent the true behavior of the conveyor system. It will also discuss the importance of correctly sizing and locating the take-up system to provide the most economical conveyor design. The use of capstans will also be discussed followed by two examples demonstrating their proper operation.

Jan 1, 2002

By L. M. English, Y. J. Wang

When plotted as head vs. volume, fan curves start high and decrease with increasing volume, while mine head curves start low and rise with increasing volume. Their intersection is the system operating point. However, as every ventilation instructor knows, the fact that head loss is a negative number (debit) and fan head is an energy addition (credit) is often a stumbling block to student or audience comprehension since the curves seem to reflect the opposite. It is possible to use the intuitively correct curves- pressure losses as negative values and energy additions as positive values - and still obtain the correct operating point. Adding the two curves produces a third curve that intersects the x-axis at the operating point, the point at which the fan energy input exactly matches air circulation energy loss. Using this technique also makes it easier to account for outside influences on the system, such as natural ventilating pressure. With the standard approach, it is quite easy to add or subtract such influences to the wrong curve. This approach can be extended to the graphical solution of any series/parallel ventilation network. The results are the same, and the approach is logically consistent and less confusing.

Jan 1, 1999

By J. E. House

Creative ideas and endeavors require imaginative and positive responses, if they are to be reduced to practices. This lecture will define the plurastic roles of various technical disciplines which were important in the development of the LIX reagents. Specific personalities, facts, and events will be used to trace the development from an idea, to the exciting acceptance and practice of the technology. An objective analysis of the entire LIX reagent development, spanning twenty-five years experience of the author, will be given, these will be used as a basis for critical examination of how the various technical disciplines could improve their effectiveness in advancing future technologies.

Jan 1, 1990

By J. Willison

Over the past decade, the coal mining industry has faced the difficult task of remaining profitable in the midst of declining market prices. Historically, the industry has been quite capable of meeting this challenge by various means. As total costs to mine and market coal continue to increase, new methods of tackling the problem must be implemented. Studies have shown that although many options exist to influence both inby and outby costs, the greatest potential remains in addressing costs at the coal face. Mining operations can positively effect a change in their profitability by either reducing costs, or by increasing production to in turn lower their net cost per man-hour. Original equipment manufacturers can play a key role in both options through the introduction of new technology that permits higher extraction rates, as well as other advantages leading to lower cost coal. A leading advancement over the past 30 – 40 year period has been the advent of progressively higher voltages to operate the mining equipment. This advance enables higher power transmission for a given cable size, operation at lower amperages resulting in less voltage fluctuation, and reduced heat on the cable and electrical components.

Jan 1, 2003

By Stanley M. Miller

Analysis of discontinuous rock masses for engineering design purposes requires information about fracture characteristics. For such studies, fractures or other elements of the rock fabric (bedding, foliation, etc.) should be considered in a statistical manner because they generally have high frequencies of occurrence and are discontinuous over the design area. A practical design procedure includes defining structural domains as those areas which contain fractures with similar orientation patterns. Within a structural domain, the statistical distributions of fracture set characteristics (spacing, fracture density, dip, dip direction, etc.) may be computed from mapped data and then used to quantitatively describe the rock fabric. These distributions can then be randomly sampled (using Monte Carlo techniques) to simulate the rock fabric and to help define potential failure surfaces along fractures. 1 The prediction of failure geometries is an essential part of stability analyses used in designing rock slopes or underground openings. In current probabilistic design procedures, Monte Carlo techniques that rely upon the iterative generation and analysis of deterministic instability models do not incorporate spatial aspects of the random variation in fracture set characteristics, 1,2 but consider the characteristics to be spatially independent.

Jan 1, 1979

By Yanmin Wang, Eric Forssberg

This paper presents recent experimental results in wet ultra-fine grinding and classification of industrial minerals carbonates and kaolin clays using a stirred ball mill and a high performance centrifuge. The studies have been focused on the effect of beads (size, density and load) on the grinding efficiency. The use of chemical additives for the control of slurry rheology in the stirred ball milling is presented. The role of pre-crushing with a high-pressure roller mill on subsequent ultra-fine grinding is discussed for energy saving and size reduction. The use of a disc-stack nozzle centrifuge for ultra-fine classification duties at high solids contents is presented.

Jan 1, 1998

By P. R. Shivdasan, R. D. Hagni

Cathodoluminescence microscopy (CLM) is uniquely applicable to the study of carbonatite-related fluorspar ore deposits. The mineralogy of the carbonatites, sodic and potassic fenites, marbles, quartzites and fluorite ores are readily determined and characterized. Calcite, dolomite, apatite and fluorite were deposited dominantly under high-temperature conditions, and they exhibit strong cathodoluminescence (CL). At the Okorusu, Namibia, carbonatite complex and fluorspar mines, three types of carbonatites have been recognized by field mapping and laboratory CLM. The main carbonatite intrusion is fine grained and consists mainly of calcite. A later phase of pegmatitic carbonatite consists of calcite, magnetite, Fe-rich pyroxene, apatite and pyrochlore. Pyroxene carbonatites were recognized mainly through their study by CLM.

Jan 1, 2002

By Y. C. Kim, I. S. Roditis, P. K. Medhi

The strongly skewed grade distributions and the need to estimate the local recoverable reserves in a selective mining environment are the two problems that ordinary kriging (OK) cannot easily handle. With the recent introduction of the non- parametric, distribution-free technique of indicator kriging (IK), the above problems can be solved. This paper describes the result of performance evaluation of IK in an open-pit gold-silver deposit. For performance evaluation, the predictions of local recoverable reserves using IK were compared with the actual reserves based on blasthole information. The IK estimator, although a bit optimistic (or overestimating), performed very well in predicting the total recoverable ounces of gold from each panel on a test bench. The OK estimator was also used to try to predict local recoverable reserves, by treating each panel as either waste or ore, depending on the panel's average grade. Under this criterion, OK was found to be quite biased and pessimistic (or underestimating).

Jan 1, 1988

By Solomon S. Katz

As more and more computer software is written for geological mapping applications, the users of the software are discovering the problems of transferring data between the programs, maintaining correct data and integrating maps produced last week with those produced today. One way to deal with these situations is by using a geographic information system (GIs). Last September the USGS and National Academy of Science held a 5-day GIs symposium on integrating technology and geoscience applications (USGS, 1988). It was followed in October by GEOTECH '88 (Peters and Krajewski 1989) which had a session exclusively for GIs applications in the Geo-Sciences. Editorials in Geobyte (Leonard, 1986, 1988) suggested that geographic information systems will be the next major computer programs to be adopted by the mineral industries. As far- back is 1985, the Computer Oriented Geological Society (COGS) printed An Introduction to GIs in their newsletter (Katz, 1985). About 20 years ago, a revolutionary idea occurred in the world of business data processing. It was the idea that all related data be stored in a standard format, in a single place and that all related computer application programs would use the same data.

Jan 1, 1989