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By L. J. Erck

H EAVY-MEDIA separation continues to be the favored process for concentrating the coarser fractions by elimination of undesirable tailing and middling fractions. The first vessel used for heavy-media separation was the closed-top cone. Further developments then led to the Akins spiral separator which fulfilled the requirements for improving metallurgica1 separation as well as gaining mechanical advantages. During the last season there has been a substantial influx of separator designs for further improvements of metallurgical separation based on the heavy- media method as well as attempting to garner further mechanical advantages with reduction in power consumption to boot. The newest of these designs was the Hardinge counter-current separator which was introduced into the field last spring in two plants. Both Hardinge separators proved satisfactory in operation and substantiat-

Jan 1, 1950

The liquid products of low-temperature carbonisation of coal are of variable composition, very much influenced by the rank and type of coal, and process parameters. In general the tar contains a high proportion of phenols and a low proportion of bases. The neutral oil is more analogous to a thermally cracked petroleum oil than to a high temperature tar. Present practice and possible future trends in the production of chemicals and liquid fuels from low temperature tar are reviewed in the light of recent work on the detailed composition of the tar The phenols and aromatics will probably continue to be of most value, with the bases a useful source of spec- ialty products. However the high aliphatic content of the neutral oil (particularly 1-olefins and n-paraffins) is bound to receive more attention for chemicals as well as for liquid Fuels.

Jan 1, 1969

Coal mining safety and health legislation is more than typical of safety legislation which has been born of adversity. Indeed, in the main it has been the child of disaster. Requirements which now appear obvious were indeed only occasioned by either social injustice or more commonly by great disasters. Even then changes were often made only after months or years of deliberation by committees. Early mining legislation in New South Wales benefited from the experience in Great Britain. The pioneers of our industry were miners from there and brought with them the basic British legislation, so we started with knowledge gained the hard way. A review of accidents statistics provides a measure of the effectiveness of mine safety legislation, but unfortunately rules cannot control human nature. Miners, managers and inspectors must work as a team to make mines safe and new legislation in New South Wales is planned to this end.

Jan 1, 1975

By J. B. Hiskey, W. J. Schlitt, W. G. Pitt

Aqueous SO2 (sulfurous acid) is an interesting chemical compound. It functions as a reagent in various hydrometallurgical systems, but also represents an undesirable constituent in gyro- and hydrometallurgical effluent solutions. When present in such streams, SO2 can be oxidized to the more stable sulfate form to avoid exsolution of SO2 as a source of fugitive emissions and to simplify standard water treatment plant operation. This study provides information on the stoichiometry, kinetics, and mechanism of SO2 oxidation using oxygen and an iron salt catalyst with solutions containing 0.05-20 g/L (0.002-0.7 oz per gal) SO2. The effects of iron salt concentration, oxygen pressure, temperature, degree of agitation, and pH on SO2 oxidation are also described.

Jan 1, 1984

By J. -M. Chautru

A geostatistical simulation of a typical mining site for polymetallic nodules in the North Pacific Ocean is presented. This is the first stage in the design of an industrial mining system. Two variables which have a major effect on the orebody's economic potential are considered, namely: the maximum slope of the ground inside a mining block of 50 x 100 m; and the average quantity of nodules on the same support. Two geostatistical problems have emerged in this study. The first is due to the lack of a change of support model for the maximum of a variable. A provisional solution, considering an experimentally accessible 'equivalent' support, is proposed. The second is due to a non-linear link between the two variables. To be able to take this into account in the simulation, we propose a new method based on the decomposition: X = E(X/Y) + Residue (X). Satisfactory results were obtained with this approach.

Jan 1, 1987

By D. F. Coolbaugh

Asia, the largest and most populous continent, has had little political influence on world affairs until very recently. The picture is rapidly changing. Although the cultures of various Asian countries differ widely, today they are united in their desire to industrialize. This desire is the key for expansion of Asian mineral production. The following discussion deals primarily with the situation in the south and southeast Asian countries -India, Pakistan, Burma, Thailand, Cambodia, Laos, South Vietnam, Malaya, and Indonesia.

Jan 10, 1960

By S. Saklar, i. Bayraktar

The effect of the feed size distribution on the kinetic parameters in pyrite flotation was studied. The kinetic parameters of the particular sizes were determined as a function of whether other particle sizes were present. From the data, a relation between the pyrite flotation rate and the particle size distributions was obtained. It was shown that the flotation rate constant (k) is a function of the size modulus (dt) of the Gates-Gaudin-Schuhmann distribution, and its variation may be expressed as k = a • exp(b . d,) for either individual size fractions or composite feed. Parameters a and b are dependent on the particle size distribution of the feed. Specifically, parameter a increases linearly as the distribution becomes coarser. The above relationship was also tested under conditions in which the collector (KAX) dosage was varied from 130 to 278 g/t. It was shown that the established relation was not dependent on the collector dosage.

Jan 1, 2002

Table B-1. Summary of respirable coal mine dust samples collected under 30 CFR 90 by MSHA inspectors for underground occupations, 1988-92* [ ]

Jan 1, 1997

By J. P. Barbosa, R. V. V. Araújo, R. B. E. Trindade

Bromide stabilizes the auric or aurous ion by forming a stable complex in acidic aqueous solution. The oxidizing agent normally used for the process is bromine, which is a corrosive liquid with high vapour pressure. This is, in fact, the main reason why it has not found acceptance yet as an industrial oxidant for gold. Ferric ion with hydrogen peroxide and/or sodium hypochlorite have already proved to be effective oxidants for the dissolution of gold from a rotating disc in a bromide-containing aqueous solution. In the present work, preliminary tests with four selected ore samples were tested to evaluate the dissolution of gold with the same system already tested with the rotating disc (Br-/Fe3+/H2o2/NaCIO). Compared to the conventional cyanidation, results were superior in one instance only. The major obstacle seems to be the maintenance of a suitable potential to allow the complex formation. However, the studied system may be interesting, is in some situations it may yield better results than conventional cyanidation; therefore, further investigation seems to be worth doing.

Jan 1, 1995

By Henry Engelmann

ORes are generally found in the mines mixed with more or less base matter, which renders their treatment by smelting or milling unnecessarily costly. They have to be sorted. Those of a higher grade remain often mixed with substances which might, with hardly a loss of metal and at small expense, be removed by dressing machinery, and a concentrated and purified ore thus obtained, which would bring a far higher price, because it can be reduced by cheaper methods, and, at any rate, at less expense, besides affording a saving of transportation, which in our territories is often an item of no small magnitude. The ores of a lower grade have often to be

The relevance of borehole and bore core evaluation to the design of underground coal mines is illustrated by considering the technical parameters of colliery design and the information from which they are constructed. The nature of this information is described, together with some methods for its storage, processing and presentation. Geophysical exploration techniques are compared as information sources. It is concluded that borehole and bore core evaluation is relevant and necessary for colliery design, but that optimum results will be obtained if drilling can be combined with geophysical techniques. Because of the inherent uncertainties in prediction of mining conditions the necessity of obtaining as much information as practicable from drilling evaluation is also stressed.

Jan 1, 1977

By Bernard Amadei, Richard E. Goodman

A medium is anisotropic if its properties vary with direction. This is the general characteristic of many rocks, for example, schists, slates, gneisses, phyllites and other metamorphic rocks. Bedded and regularly jointed rocks also display anisotropic behavior. This paper is concerned with the influence of rock anisotropy on in-situ stress measurements. It is limited to stress measurements by overcoring techniques for which strains and displacements are recorded either on the walls of a pilot hole at the end of one or several boreholes or within instrumented solid or hollow inclusions perfectly bonded to the surface of the pilot hole. The rock is described as homogeneous, continuous, anisotropic and linearly elastic. The following questions are answered with special emphasis on rocks that can be classed as transversely isotropic or orthotropic: the number of independent measurements obtainable in a single borehole; the number of boreholes required to determine the in-situ stress field; the influence of rock anisotropy on these numbers; the influence of the anisotropy type and the error involved by neglecting rock anisotropy.

Jan 1, 1982

By Bob de Raadt

For a long time industrial underwater blasting has stood in need of a calculation method, for the determination of shockwave-proof as well as shockwave-effective charge distances to objects in water. After a brief discussion of the physical background of the shockwave mechanism in water, the author discusses an empirical theoretical computing method based on the "Bubble boundary" concept. The practical application of this model is finally shown in an account of a few underwater blasting operations in which charge weights of c.1-1000 kg were involved.

Jan 1, 1980

By Ben F. Dickerson

Mineral exploration programs have often experienced mismanagement in the decision-making process, and these errors have consequently resulted in stockholder losses. Unfortunately, the events leading to these errors are little known and rarely studied, since managers aren't prone to publicizing their mistakes. However, a bit of magnified hindsight may serve to identify some of the problems. It is interesting to note that there does not seem to be a generally agreed-upon definition of the role and function of exploration management. Several articles have addressed this subject, written by both academic and industry exploration personnel. Two apparent thought trends can be observed: First, the theoreticians insist that modern scientific management principles can be directly applied, without modification, to mineral exploration. However, when one searches for the rules, the proponents rapidly retreat behind the computers and talk learnedly of management information systems and game theory.

Jan 6, 1978

By P. C. Thakur

In gassy coal mines, some methane drainage is essential for mine safety, but the ratio of total methane drained to total methane produced by the mine can vary from 10 to 70 percent. The volume of methane not captured is diluted by ventilation air and vented to the atmosphere. Since captured methane can be processed and sold, it makes sense to maximize methane drainage from coal mines. This paper describes ventilation and methane drainage schemes to achieve these goals.

Jan 1, 2003

By A. D. Davis, C. J. Webb, F. W. Beaver

The proposed National Underground Science Laboratory will be housed in the former Homestake Gold Mine at Lead, South Dakota. Uses will include underground neutrino experiments that must be shielded by several thousand feet of rock, as well as ground-water research in fracture-flow environments, and investigation of the microbiology of extreme environments. The Homestake Mine has about 300 miles of underground workings. Seepage of ground water into the mine openings is approximately 500 gallons per minute. Average annual precipitation in the northern Black Hills is approximately 28 inches per year. The majority of this becomes surface-water runoff or evapotranspiration, with little ground-water recharge because of the low permeability of the Precambrian rocks in the area. Dewatering of the workings over the 125 years of operation of the mine has influenced the subsurface hydrology of the 8,000-footdeep mine.

Jan 1, 2003

Marcie A. Greenberg RMCMI PRESIDENT 1995-1996 on behalf of the RMCMI Board of Directors and Officers of The Rocky Mountain Coal Mining Institute cordially invites you and your family to attend the 92nd Regular Meeting and Convention to be held June 30 thru July 2, 1996 Durango, Colorado

Jan 1, 1995

By Henry Engelmann

ORES are generally found in the mines mixed with more or less base matter, which renders their treatment by smelting or milling unnecessarily costly. They have to be sorted. Those of a higher grade remain often mixed with substances which might, with hardly a loss of metal and at small expense, be removed by dressing machinery, and a concentrated and purified ore thus obtained, which would bring a far higher price, because it can be reduced by cheaper methods, and, at any rate, at less expense, besides affording a saving of transportation, which in our territories is often an item of no small magnitude. The ores of a lower grade have often to be

Jan 1, 1874

By Robert G. Moorhead

Fine-coal screening can be one of the most critical operations in a modern coal-cleaning plant. The yield and quality of clean coal produced in fine-coal circuits is controlled as much by how efficiently 0.15 mm (100 mesh) particles are sized as on the performance traits of the fine-coal cleaning device itself. In addition, the increased interest in effective fine-coal sizing operations indicates that many operators have also discovered its importance in affecting the quality and yield of clean coal produced in fine-coal circuits. This paper describes the three most prevalently used fine-coal screening technologies and discusses their sizing mechanism, performance, and application.

Jan 1, 1988

By P. H. Thornton

MaNY intermediate phases are solid solutions which have a solute-solubility range greater than 3 at. pct. These phases, which are generally very strong and often have simple crystal structures, are usually extremely brittle so that specimens of simple shape cannot be produced by the usual mechanical-deformation techniques. Furthermore, single crystals of reasonably uniform composition are difficult to grow by the Bridgman technique because the phases generally form by a peritectic reaction, which causes pronounced segregation. In this note, a technique is described for the preparation of thin-rod specimens of brittle intermediate phases, which may be used for physical-property studies such as resistivity changes' and for the conversion of such rods into single crystals. The method has been used for the preparation of rod single crystals of the phases and Ingots, of about 100 g weight and 11 mm diam, were made by melting together the appropriate amounts of high-purity materials (usually 99.999 pct) in sealed

Jan 1, 1967