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By S. Marx

More than twenty years ago Sasol, ISCOR, and some parastatals played a major role in ensuring that South Africa had sufficient technical skills. When the economy became tight and business and government were pressurized to decrease costs, the first budgets that were reduced were the training budgets. It seemed to be too expensive and too time-consuming to train apprentices. According to Stacey2, this is a major strategic issue facing the mining industry in South Africa. Two factors added to the shortage of skills challenge: ? Skills erosion and job losses ? Artisans ? currently the economy produces 5 000 but the need is 12 500 ? Level of mechanization in South Africa less than 10 per cent ? Average age of operators and artisans is 50 ? Greater awareness of occupational health effects of hand-held drilling. ? Workplace challenges ? The impact of HIV/AIDS and other employee wellness issues ? Changes and challenges in workplace environment i.e. the mining industry.

Jan 1, 2012

By G. W. Jones

Gas analysis is of great practical value to the combustion engineer as a guide in the proper deli and operation of power and heating plants. The automotive industry, however, has made little use of gas analysis in the design and construction of engines. Tests4 made by the Bureau of Mines have shorn that for the average motor vehicle approximately 30 per cent of the heat value of the gasoline passes out in the exhaust as incomplete-combustion products. The tendency at present is to pay more attention to ease and flexibility of operation than to efficiency of combustion. However, neither condition can be fully realized except where each cylinder gets a mixture of the same composition - that is, when certain cylinders do not "load up" with gas at the expense of the others. When this occurs, due to some of the cylinders having too rich a mixture while in others it is too lean, it is impossible to get efficient combustion from the fuel used. Gas analysis enables the engineer to determine the quality of the mixture fed to the different cylinders with a high degree of precision. Briefly, the method consists in making an analysis of the exhaust gas from each cylinder while the engine is in operation.

Jan 1, 1924

By A. M. Starfield

The study of strain waves in rock over the past decade has, for the most part, been an investigation related, but not applied, to rock blasting; the design of rock blasts has proceeded on a basis that is independent of strain wave research. This duality is reflected in the paper by Dr. Clark.1 While the greater part of the paper is devoted to a discussion of spherical waves in elastic and visco-elastic media, it is in an entirely unrelated section, the section on scaling and cratering, that the practical approach to rock blasting is found. Work done by the U. S. Bureau of Mines, as described in the paper by Duvall, Atchison, and Fogelson,2 has established a correlation between crater dimensions and the peak compressive strain in the rock. Strain wave measurements have thus been used to compare explosives but have not, as yet, been applied to the planning of a production round once an explosive has been selected. The optimum burden, for instance, is still determined either by experience, empirical formulae (e.g. that of Langefors 3), or a cratering experiment and the theory that has been developed around that proposed by Livingston.4 Even then there is some ambiguity in applying deductions from short, concentrated explosive charges to the long charges often used in practice (although Bauer 5 reports doing this with considerable success) and wave theory has until recently thrown no light on this problem, being confined, with only a few exceptions, to spherical charges. The hesitation in applying strain wave theory has probably been due to two questions that have not been answered satisfactorily: just how important is the strain wave in rock breakage, and if it is important, under what conditions will the wave break rock? This paper is an attempt to answer the first question, to avoid the second question by an admittedly oversimplified assumption, and then to investigate the implications of this assumption for blasting with long cylindrical charges.

Jan 1, 1967

By O. Bergmann, R. E. Lueders, R. R. Ellefson, H. M. Brennecke, D. S. Davies

A new hydrometallurgical process has been developed to recover copper from sulfide ores. Copper is leached in a staged reactor system utilizing nitric and sulfuric acids at 105OC. Iron is removed from the pregnant liquor as a jarosite, and cathode copper is electrowon directly from the purified pregnant liquor. The spent electrolyte is recycled. Nitrogen oxides evolved from the leach are reconverted to nitric acid and are also recycled. Sulfur is rejected as So, jarosite, and gypsum. The process is highly versatile and can recover precious metals, molybdenum, and zinc when these elements are present. Continuous, integrated, semi-pilot plant operations using chalcopyrite ores demonstrated 99% copper leaching and production of cathode grade copper. Economic evaluation shows that the process is competitive with pyrometallurgical and other hydrometallurgical processes.

Jan 1, 1982

By R. S. Austin

One-third of the world's and most US kaolin is produced from Late Cretaceous and Early Tertiary sedimentary strata in Georgia and South Carolina. The kaolin is part of a belt extending to Arkansas of aluminous lateritic deposits, including bauxite. Original sediments were profoundly altered by chemical weathering during Early Tertiary time. Mining exploits those uncommon deposits where extreme leaching and chemical recombination have produced a clay of nearly pure mineral kaolinite. Properly selected and refined, kaolin is an important pigment, filler, extender and chemical compound in the paper, paint, plastics, ceramics and catalyst industries.

Jan 1, 1998

By A. S. Yue

It was deemed desirable to obtain an understanding of the vacuum desulfurization process. McKechnie1 has reported that the sulfur content of nickel- and cobalt-base alloys is reduced in vacuo. Keverian and Taylor2 have observed that vacuum melting causes desulfurization of iron-carbon-silicon alloys. Garnyk and samarin3 have desulfurized transformer steel by vacuum treatment. Experiments were conducted in order to investigate the desulfurization of liquid iron under reduced pressures, and to establish the effect of some alloying elements, and various crucible materials. A vacuum-induction furnace of 50-lb capacity was used. The charge was Armco iron. Silicon was added as 90 pct ferrosilicon, carbon as electrode graphite, and aluminum as high-purity aluminum metal. Magnesia and silica crucibles were used, their inside diameters were 5 1/2 and 5 3/8 in., respectively. The temperature was measured with an optical pyrometer and it was held at 1600 1 15°C. Samples were withdrawn with quartz tubes of 6 mm ID, without disturbing the furnace atmosphere. Pressures were measured with an alphatron gage. The experimental results are shown in Fig. 1. They indicate that: 1) Sulfur can be removed from liquid iron alloys by vacuum treatment; 2) The desulfurization is enhanced by the presence of silicon, carbon, and aluminum, all these elements increase the activity of sulfur dissolved in liquid iron;4 3) The pronounced effect of silicon indicates that probably a volatile silicon sulfide is formed, Alcock and Richardson5 have observed a similar phenomenon; 4) The same rate of desulfurization was obtained when the metal was contained in either magnesia or silica crucibles. Dr. J. Keverian has contributed many discussions and recommendations. M. S. Sutliff has helped in conducting the heats. The permission of General Electric Co. for this publication is gratefully acknowledged.

Jan 1, 1960

This paper carries on from an earlier paper 'Cemented fill practice and research at Mount Isa' and reports further on the laboratory programme at Mount Isa to develop a cheap cem- ented fill using Company waste products. The practical economic significance of availability of cheap cementing agents is re- viewed, with the various alternative approaches available The basic approach adopted within this paper is that use of reactive pozzolans such as ground slags to replace a proportion of the Portland cement in the fill can make mining methods employing cemented fill more economic- ally competitive with other mining methods.

Jan 1, 1973

By Keith Heasley

In many practical situation where the LaModel program in used to analyze the mechanical response and failure of the mining environment, there are very few actual field measurement from the site available for deriving the appropriate input parameters. For coping with this typical lack of field data, this paper presents some recommended calibration techniques derived from on an in-depth understanding of the laminated model formulation and from many years of experience applying LaModel to practical situations. For each of the critical input parameters (rock mass stiffness, gob stiffness and coal strength) in LaModel, a specific calibration technique is recommended and presented along with the justification for the technique and some appropriate derivations/equations for assistance. It is hoped that this frank discussion of recommended calibration techniques can help novice LaModel user develop better models and can initiate a discussion among rock mechanics experts on how to improve upon the presented techniques.

Jan 1, 2008

By Mark W. Cadwallader

Heap leach mining requires liners in order to contain leaching solutions for both economic and environmental incentives. The use of HDPE geomembrane liners for heap leaching is discussed in this paper. Comparison is made to clay liners, with inclusion of economic considerations. Several heap leach projects incorporating geomembranes are discussed.

Jan 1, 1987

By Bruce A. Kennedy, Richard M. Stewart

Slope stability has now become a practical tool in the design and operation of open pits. The selection of slope angles is a critical decision that can have far-reaching effects on the accumulated cash flow and the overall profitability of a mining project. Slope failures can now be dealt with in a number of ways. Two methods - the total removal and the partial unloading of a failing zone-have been practiced for many years. However, with the refinement of monitoring techniques, open pits can now learn to live with a slide and even turn a potential loss into a gain. There are various techniques, such as presplit blasting, drainage systems, and artificial stabilization, which can be applied immediately in an existing open pit to improve the stability of the pit slopes. The technology of slope stability will play an important part in the future mining of low grade, previously marginal orebodies, which will have to be exploited if the mineral needs of the world are to be met.

Jan 1, 1971

Air pollution control regulation$ already implemented or being considered for implementation require substantial investment of capital to remove the sulfur oxides from copper, lead, and zinc smelter gases. There will be an attendant increase in production costs and possibly an associated increase in the price of these metals to the consumer. The total investment and any resultant metal price increase will depend upon the control regulations that ultimately will be adopted by the individual States. Controversy has arisen between the metals industry and governmental control agencies regarding the status of stack gas desulfurization technology and the ability of industry to control sulfur oxide emissions to the degree proposed by some of the more stringent regulations currently under consideration. This paper evaluates the problems involved in achieving various degrees of control over smelter sulfur oxide emissions and the technology available to accomplish the task of assuring clean air. The estimated cost of compliance is reviewed for the copper, zinc, and lead industries, but principal at tent ion is given to the copper situation.

Jan 1, 1971

By R. K. Collings

"This paper summarizes research that was done at the Mines Branch, Ottawa, to evaluate samples of phosphogypsum for gypsum products manufacture. The samples were from phosphate fertilizer facilities at: Port Maitland, Ontario ; Valleyfield, Quebec; and Fort Saskatchewan and Redwater, Alberta. All samples were wet-screened, washed, filtered and calcined in a laboratory kettle at atmospheric pressure. Tests were also made at higher pressures in a small autoclave. The gypsum and resulting hemi-hydrate, being acidic, were treated before, during and after calcining with various bases. The hemi-hydrate products were checked for time of set, compressive strength and bond to gypsum wallboard paper. The results of this study indicate that phosphogypsum from each of the sources investigated has potential as a substitute for mined gypsum in gypsum products manufacture. Pilot-scale testing is recommended to confirm that the product would be satisfactory for the manufacture of plaster products on a commercial basis."

Jan 1, 1972

By Earl Bardwell

IN his paper entitled, Development of Hindered-Settling Apparatus, Dr. Richards has related the history of the development of the hindered-settling classifier and given illustrations of the several types of this apparatus which lie has designed.1 An earlier paper,2 Close Sizing Before Jigging, shows the nature of the hindered-settling phenomenon and the results which it produces. In the first-mentioned paper Dr. Richards describes the method of getting hindered settling and shows the relation that the constriction bears to the classifier. The question of proper ratios between the area of the sorting column and the area of the constriction opening Dr. Richards leaves open, aside from certain statements as to the ratios which have been found to give good results in practice. While working with a hindered-settling classifier of the type now in use at the Boston & Montana Reduction Plant of the Anaconda Copper Mining Co. a number of interesting facts were brought out which have thrown considerable light on the question of proper ratio between the area of the sorting column and the area of the constriction and which will be made the subject of this paper. Free and Hindered Settling. -If a, mineral particle be dropped into a vessel containing still water, the particle will sink in accordance with the laws of free settling in water, which are as follows: 1. Of two grains having the same specific gravity but differing in size, the larger will settle in still water at the greater velocity. 2. Of two grains having the same size but differing in specific gravity, the heavier grain will settle at the greater velocity.

Jan 8, 1913

By M Rimes

This paper describes a technique to predict achievable head grades and likely variances from target grade for the Shovelanna Iron Ore Project, in the Pilbara region of Western Australia. The block model from which the production schedule is produced was created from a wide spaced drilling program and was classified as an Inferred Resource under the JORC Code. Ideally, production schedules and target grades would be determined using a combination of Proved and Probable reserves. However sometimes it is necessary to consider the requirements of potential off-take parties who have specific grade tolerances. A technique is needed to simulate mining sequences and grade variations early in the planning process, using an æexplorationÆ block model rather than the normal æminingÆ block model. Marketing contracts require examination whether the target grade {Fe, P, SiO2, Al2O3 can be kept constant, or must be revised during the life of the mine. A model (written in ExcelÖ using Visual Basic macros) develops a feasible, close to optimal, mine plan from block model data. Cut-off grades for minable ore are chosen. The model evaluates ore tonnage, grade and stripping ratio against depth. Outputs at this stage include plots of slices through the orebody, at nominated x, y and z coordinates, showing ore grade, waste, drill hole locations and topography. The model then searches for a feasible satisfactory mine plan. The initial grade target is the average for the identified ore blocks. The available block list (ABL) at any time is the set of ore blocks, any one of which can be mined without removing any other ore block. The entire initial ABL has an unacceptably large ætotal grade stressÆ, defined as [(Grade-Target)/Tolerance]2, summed over the four relevant minerals {Fe, P, SiO2, Al2O3}. The model trims the ABL, removing the block most harming the total stress. Trimming is repeated until the total grade stress reduces to an acceptable level. The trimmed ABL defines the first mine campaign. Removing the trimmed block set, a second ABL is exposed, which is again trimmed and mined. The process is automatic: a few seconds computation provides a complete mine plan. Re-running the model with adjusted grade limits quickly shows whether a uniform target can be achieved or whether the target must be modified during the mine life.

Jan 1, 2007

By M. Sahoo, P. Burke, Y. Fasoyinu, J. P. Thomson

The effects of grain refinement, mold temperature and chemical composition on the hot tearing resistance of aluminum alloys 535.0 and 206.0 has been studied by pouring constrained rod castings in metal molds. In addition, two prototype components that could be used in automotive applications were also poured from both alloys by gravity tilt-pour and low pressure permanent mold casting processes. This paper summarizes the results and issues encountered during the casting trials. It was shown that grain refinement and mold temperature ::::: 400°C reduced, and sometimes eliminated hot tear cracks in both alloys. The two prototype engineering components could be cast successfully from both alloys in metal molds. The metallurgical issues related to molten metal treatment and processing temperatures were well controlled. However, issues related to the control of hot tearing, casting and mold design must be addressed in future studies to guarantee the production of defect free castings.

Jan 1, 2006

By Robert W. Freedman

In the Bureau of Mines study, a filter with a 20-by 20-inch-square cross section was inserted into the exhaust ducting of a 4-stroke-cycle, 90-hp diesel engine, and the efficiency of removal of total particulate was measured gravimetrically as a function of time. Removal efficiencies were close to 90 pct during the main portion of several extended runs employing several combinations of filter beds. Variations in engine load had little effect on collection efficiency. Particle size as measured by a Bureau-developed online instrument centered on 0.07 m based on number count. Removal efficiency increased rather sharply for both larger and smaller particles.

Jan 1, 1979

By F. C. Townsend

Centrifugal modeling was used to evaluate reclamation schemes of; (a) flocculants, (b) sand/clay mixes, (c) flocculants/sand addition and (d) capping with sand or sand/clay mix. Results suggest the hierarchy of effectiveness is: (d) capping, (b) s/c mixes, (c) flocculants/sand addition and (a) flocculants. Comparisions between currently used large strain consolidation computer programs reveal no difference between piecewise linear or finite strain calculations. Correlations between numerical and centrifugal model predictions reveal excellent agreement on magnitudes; however, rate predictions require improvement in laboratory input data and centrifugal scaling relationships.

Jan 1, 1987

By A. J. Getz

The paper reviews the status of the major precious metals projects in Australia, Papua New Guinea, Indonesia, the Philippines, and New Zealand. The projects may be at the stage of exploration, development, operation, or expansion. The paper covers project location, reserves, method of resource exploitation, anticipated production, and other unique conditions.

Jan 1, 1990

pAbad, Leopoldo F., Min, Engr,, Div. of Mines, Bureau of Science Manila, P. 1. '23 Abadilla, Quirico A,, Geol., Lago Pet. Corp Box 172, Maracaibo, Venezuela, '20 Abbey, Robert Graham, The W. W. Sly Mfg, Co Train Ave., Cleveland, Ohio. '21 Abbott, A. N., Mines Supt., Mazapil Copper Co., Ltd Concepcion del Oro, Mexico, '28 Abbott, Clarence E., Mgr., Mines & Quarries, Tenn, Coal, Iron & R. R, Co,, 1242 Brown Marx Bldg,, Birmingham, Ala. '04]

Jan 1, 1928

By T. S. McGahey

The southeastern region of the United States has long been a major market area for coarse and medium particle size natural ground calcium carbonate fillers. The primary market for calcium carbonate in the southeast traditionally has been as fillers in building materials such as carpeting, joint cement and roof shingles. In these applications the economic value of the calcium carbonate in the final product is weighted more toward lessening the cost of the final product, as opposed to contributing any desirable physical characteristics. For example, in carpet backing applications the calcium carbonate filler does little more from a physical standpoint than add weight and body to the backing adhesive. The important factor in the use of calcium carbonate in carpet backing is that it can be used at high loading levels to replace the more expensive latex binder, thus lessening the cost of the final product. It is estimated that calcium carbonate producers in the southeast sell in excess of 200,000 tons (181,436,000 kg) annually for use in latex compounds for carpet backing applications.

Jan 1, 1986