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By J. W. Harshbarger, E. L. Montgomery

The region of metallic ore deposits in northern Chile, southern Peru, western Bolivia, and northwestern Argentina occurs in arid zones at altitudes as high as 6 km (19,700 ft). Because surface water supplies are meager, new mines require unexploited sources of water. Prolific ground water aquifers occur in salar basins in this region of the Andean Highlands. Exploration water wells have been constructed and aquifer characteristics have been tested in eight salar basins. Results indicate ground water quality is good. Aquifer transmissivity and storage computed from results of pumping tests indicate maximum capacities of more than 170 L/sec (2700 gpm) for individual production water wells. Results of investigations conducted by the authors demonstrate that ground water reservoirs in the Andean Highlands comprise a source of large quantities of water for the mineral industry.

Jan 1, 1986

By R. E. Ray, J. W. Stevenson, J. A. Berry

Conventional concrete block plastered with a cementitious coating is the most common material used in the construction of permanent stoppings to direct airflow in underground mines in the US. All mines experience various degrees of strata convergence depending on depth of overburden, geological conditions, and type of roof support employed. Strata convergence will cause cracks and joint openings in masonry stoppings, resulting insignificant air leakage losses. Where strata convergence is severe, complete structural failure of the stopping can ultimately occur. Reconstruction of damaged or destroyed stoppings adds expensive overhead to mining operations, and even greater expenses are incurred from the additional fan horsepower required to overcome leakage losses. Ideally, a stopping should maintain high resistance to airflow while yielding to strata convergence. By properly incorporating a polyisocyanurate rigid foam material within the masonry block structure, stopping service life can be increased in mines experiencing strata convergence problems such as floor heave, roof loading, and lateral rib movement.

Jan 1, 1986

By A. S. Malicsi, I. Iwasaki

The removal of hydrophobic coatings of flotation collectors from iron ores becomes of interest when a duplex flotation process is considered for upgrading, when a pelletizing process is considered for a concentrate floated with a fatty acid or a soap collector, or when a disposal of froth products from cationic silica flotation is of environmental concern. Ozone can oxidize organic compounds rapidly, thereby removing the hydrophobic coatings of flotation collectors. Ozone is widely used for treating and purifying drinking water, waste water treatment, and for chemicals processing (Murphy and Orr, 1975; Rice et al., 1980). Its uses in metallurgical operations, however, are very sparse (Allegrini et al., 1970; Chernobrov and Rozinoyer, 1975; Ishii et al., 1970; Iwasaki and Malicsi, 1985; Matsubara et al., 1978). Yet, its high reactivity and the absence of potentially hazardous byproducts become of interest in destroying flotation reagents adsorbed on mineral surfaces or remaining in mill water for recycle or for discharge. Duplex Flotation A duplex flotation process, as applied to oxidized iron ores, would involve a fatty acid flotation of iron minerals followed by an amine flotation of the siliceous gangue from the rougher iron concentrate. Such a process has been used in the Florida phosphate fields. Fatty acid coatings cannot be removed as readily with a simple acid or alkali treatment from iron oxide surfaces as from Florida phosphates. A combination of reagents, such as lime and quebracho, lime and alkali phosphate, or sulfuric acid and oxalic acid, has therefore been proposed. In a previous article (Iwasaki et al., 1967) , the use of activated carbon was found to be effective in removing fatty acid coatings both in the duplex flotation and the pelletizing processes. The use of ozone offers another approach to the removal of fatty acid coatings from iron oxide surfaces. To investigate the possible application of the duplex flotation process, a specularite ore from Michigan analyzing 36.5% iron was used. A 600-g (1.3-1b) sample was ground in a laboratory rod mill together with 250 g/t (0.5 lb per st) of sodium silicate to -150 µm (-100 mesh). This was transferred to a Fagergren laboratory flotation cell, and deslimed four times at 20 µm (quartz equivalent). The deslimed pulp was transferred to a laboratory conditioner, diluted to 40% solids, and conditioned with 250 g/t (0.5 lb per st) of soda ash and 250 g/t (0.5 lb per st) of oleic acid. The conditioned pulp was then transferred back to the Fagergren cell, floated until barren of froth, and the rougher froth product was returned to the cell and cleaned. The results are presented in Table 1. The cleaner concentrate at this point analyzed 45.3% Fe. The cleaner concentrate coated with fatty acid was transferred to a 2-L (0.53-gal) beaker. While the pulp was agitated with a glass T-stirrer, ozone was bubbled into the agitated pulp for 15 minutes at a rate of 10 mg/min (0.00035 oz per min) ozone (250 g/t or 0.5 lb per st 03 feed). It was observed that the pulp ceased to froth after about 10 minutes. The amine flotation of siliceous gangue from the ozonated pulp was carried out first by conditioning with a dextrin, a commonly used starch depressant for iron oxides. This was followed by flotation with a stage addition of an ether amine at increments of 100 g/t (0.2 lb per st). Three stages were required to float the siliceous gangue to near completion. The three froth products were combined and cleaned twice. When the cationic flotation Rougher, Cleaner 1 and Cleaner 2 cell products were combined, an iron concentrate analyzing 64.5% iron was obtained at an overall iron recovery of 72.8%. Pelletizing Fatty acid flotation concentrates have been pelletized successfully in northern Michigan mills. But at other locations, fatty acid coatings on iron flotation concentrates proved so undesirable in agglomeration that other methods of concentration had to be sought. For example, a sinter mix containing iron ore concentrates upgraded by fatty acid flotation resulted in decreased productivity. This occurred because the micropellets of particles with the hydrophobic coating are less tolerant of moisture. Thus, the bed permeability is lost (Beebe, 1965). The agglomeration of concentrates obtained by the fatty acid flotation alone, and the hydrophobic coatings destroyed by ozonation or by the duplex flotation process, is not expected to cause any difficulty since the surfaces of the concentrates would be hydrophilic. Removal of the fatty acid coating with activated carbon, indicated by the loss of floatability, was shown to restore the decrepitation temperature of wet balls during drying cycle (Iwasaki et al., 1967). Disposal of Cationic Silica Flotation Froths Recent demands of iron blast furnaces place the silica content of the magnetic taconite pellets at about 5%. Conventional process for magnetic taconite involving fine grinding and magnetic separation often produces magnetic concentrates analyzing in excess of 5% silica. This is due to the presence of the middling grains of siliceous gangue and magnetite. Cationic silica flotation of magnetic taconite concentrates (DeVaney, 1949) may be used to reduce the silica content. But the amine coating on siliceous gangue becomes of environmental concern when the flotation tailings are discarded in tailing ponds.

Jan 1, 1986

By L. W. Saperstein, J. C. Mills, L. B. Phelps

Selective placement of toxic mine spoil has been advocated as a means of reducing environ¬mental pollution at the source. However, methods of burial to control environmental damage are not well understood. Using the finite element method, this paper investigates the burial of toxic material within low permeability packages below the water table. The effects of differing package and spoil permeabilities, anisotropy, and infiltration are modeled to provide information about their effect on the flow system. Projections can then be made that will assist in the design of the toxic spoil package to limit the amount of ground water flowing through them.

Jan 1, 1986

By F. F. Aplan, E. C. Dowling, R. R. Klimpel

Numerous flotation models have been proposed in the literature. Thirteen of these have been applied to batch flotation data and evaluated with respect to one another using statistical techniques. Flotation tests were carried out on samples of a US porphyry copper ore (Pinto Valley, AZ). The ore was tested using various collector and frother systems to produce different time-recovery profiles. These were used to calculate flotation rate and ultimate recovery parameters for each model. The models were then evaluated statistically to determine the overall fit of the calculated to the observed data and to test the range of significance of the parameters in each model.

Jan 1, 1986

By E. E. Bauer

Technical data describing the critical points for selection of the proper hammer and of the boom and power pack for mounting on mobile gyratory crusher installations are presented. Charts describing typical rocks with breakability indexes for hammer selection are included. Comparative data of representative available hammers along with criteria for evaluating hammer selection are also presented. Factors affecting the selection of the boom and the power pack, as well as optional features for ease of operation and improved safety are described.

Jan 1, 1986

By S. E. Clay, G. P. Martins, P. R. Taylor

A grain model for gas-solid reactions in cylindrical pellets is formulated and solved numerically. The numerical solution demonstrates when it is safe to assume either a thin disk or a long cylinder geometry, and when the more general two dimensional geometry must be used. The numerical solution also demonstrates the solution of a two-dimensional moving boundary problem (i.e., when the reaction is diffusion controlled and the ratio of the height to diameter dictates two dimensions).

Jan 1, 1986

By A. D. S. Gillies

The effectiveness of coal mine face ventilation and the ability of airflow to maintain satisfactory methane and respirable dust levels in the working face area has been studied through the use of scale modeling techniques and underground testing procedures. In particular, consideration has been given to examination of the effects of operation of a high airflow, machine mounted dust scrubber unit on face air patterns. Results obtained through a cooperative study with the Peabody Coal Co. demonstrate that new mining cycles can be considered that increase production efficiency while maintaining satisfactory ventilation conditions.

Jan 1, 1986

By I. Iwasaki, K. A. Smith

A chlorination process for treating metal sulfide flotation concentrates is described. The process involves low temperature chlorination combined with sulfur chloride conversion and selective oxidation to produce nonferrous metal chlorides, elemental sulfur, and ferric oxide in a three-stage fluidized bed reactor. The nonferrous metal chlorides may then be water leached, separated, purified, and electrolyzed to recover copper and nickel metals and to regenerate chlorine for recycling.

Jan 1, 1986

By Y. J. Wang

A graphical technique by which the operating points for a two-fan ventilation system can be represented as the intersection of the modified fan curves is described. In constructing the diagram, the air quantities associated with the fans are considered to be independent variables and used as the axes of a rectangular coordinate system. The diagram may include, in addition to the modified fan curves, contour lines for resistances, pressures, and air powers. Procedures for drawing the diagram are discussed and illustrated with an example of the ventilation system.

Jan 1, 1986

By V. Rajaram

The oil shales located in the Appalachian Basin cover an eight-state area of the eastern US and are referred to as Devonian (black) shales. These shales have been exploited for their gas potential for several years. The Institute of Gas Technology (IGT) has conducted research since 1972 on the production of shale oil from the Devonian shales. This resulted in the development of the HYTORT process. This process demonstrated that the yield from the Eastern oil shales can be greater than the value indicated by the Fischer assay method. IGT estimates that 67 Gm3 (423 billion bbl) of oil could be recovered by HYTORT processing of surface minable eastern US shales. Recently, American Syncrude Corp. and Southern Pacific Petroleum NL have proposed oil shale projects in Kentucky. This paper will describe the surface mining and retorting techniques that have been studied for exploitation of the Devonian shales, and enumerate the problems that have to be overcome before commercial production can be realized.

Jan 1, 1986

By B. J. Steblay

Roof bolts are the primary means of supplemental support in coal mines and are widely used in other mines. Presently, post installation loads are measured infrequently on only about 10% of the bolts by using standard torque wrenches that limit accuracy to about ± 30%. Because mine roof bolts are long, slender, non-uniformly sized, roughly forged, placed in a difficult environment, and subject to severe bending on installation, researchers have been unable to use ultrasonic reflection techniques to measure strain. A complete measurement system has now been assembled by the US Bureau of Mines, Denver Research Center. Obstacles such as bolt preparation, transducer mounting, reliable reflection, and calibration have been dealt with. The seemingly simple concept of measuring the time of flight of an ultrasonic pulse to a reflector is actually complex due to the need to measure to 0.0025 mm (0.0001 in.) accuracy, the sensitivity of velocity to temperature, and stress, and the stability required to make measurements over several years.

Jan 1, 1986

By R. W. Marrs

Kimberlite contains a unique assemblage of minerals and exhibits a characteristic pattern of spectral reflectance in the visible and near-infrared wavelength region. This spectral pattern is readily discerned in well exposed kimberlite outcrops, but becomes increasingly difficult to identify when outcrops are partially covered by vegetation or soils derived from nonkimberlitic materials. Detection of poorly exposed kimberlite diatremes is possible using multispectral imaging techniques where spectral bands are chosen to optimize contrast between the kimberlitic soils, nonkimberlitic soils, and vegetation. Careful processing of the multispectral data is essential to separate the spectral signature of kimberlite from the signatures of other components of the scene.

Jan 1, 1986

By H. Soto, I. Iwasaki

Primary amines are strong collectors of apatite and they can selectively float sedimentary phosphates from calcareous ores. However, secondary and tertiary amines and trimethyl ammonium salts are ineffective. Kerosene reduces the collector requirements became hydrocarbon is co-adsorbed along with the amine on the mineral surface. The heats of reaction of aminium ions with such anions as phosphate, carbonate, and sulfate were measured in a microcalorimeter. They are discmsed in terms of the solubility of the precipitates formed and their relationship with the adsorption mechanism of primary amines on phosphate minerab. Experimental evidence supports a view that primary amines are adsorbed through chemical interaction between the aminium and phosphate ions at the mineral surface.

Jan 1, 1986

By R. S. Schechter, T. R. Guilinger, P. Bobeck, J. G. Price, L. W. Lake

This paper presents the results of an experimental study on the rate of uranium and molybdenum extraction from a flow reactor. Specific variables tested are fluid throughput and flow rate, lixiviant cation, and injected pH and carbonate concentration. The ore tested was from the Felder mine in southern Texas. It contained substantial quantities of marcasite and molybdenum disulfide that competed with the uranium ore for oxidant. Flow studies showed the oxidation of molybdenum disulfide under field conditions is mass transfer controlled, whereas the uranium oxidation is limited by surface reaction rate. The rate of uranium oxidation decreased with decreasing pH. The total carbonate levels, on the other hand, were unimportant. Ammonium carbonate appears to greatly decrease, if not completely halt, the reaction of marcasite with the oxygen. This effect was not found using either sodium or potassium carbonate.

Jan 1, 1986

By A. Sainato, E. Baker, J. Cervik

In Europe, water infusion is used widely to reduce generation of respirable dust during mining. Its use in the US is limited to a few plow operations in the deeper parts of the Pocahontas No. 3 Coalbed. The technology for infusing water into retreating longwalls is described and results of a recent Bureau test in the Lower Sunnyside Coalbed demonstrated dust reductions ranging from 47% to 64%. Because water infusion increases moisture content of the coalbed, face air velocities in excess of 2.5 m/s (500 fpm) are possible, further diluting dust levels before dust entrainment occurs. An economic analysis shows a 23% reduction in operating costs when coal production is increased by changing from unidirectional to bidirectional mining with water infusion.

Jan 1, 1986

By I. Iwasaki, K. A. Nataratjan

In a previous paper, ozone was shown to remove residual xanthates in flotation pulp solutions as well as to destroy the xanthate coating on bulk copper-nickel sulfide concentrates before differential flotation (Iwasaki and Malicsi, 1985). The oxidation and decom- position mechanisms of xanthate solutions in the presence of commonly used oxidants such as oxygen, chlorine, hypochlorite, bromine, iodine, and hydrogen peroxide at different pH levels have been reported in the past (Rao, 1971). Most of these studies have been restricted to xanthate solutions of pH less than 10. Very few references are available on xanthate decomposition in highly alkaline (pH > 12) solutions (Jones and Woodcock, 1983; Philipp and Fichte, 1960; Tipman and Leja, 1975). No systematic study of xanthate oxidation by ozone has been reported, although its use in flotation has been recognized of late (Allegrini et al., IWO; Ishii et al., 1970; Matsubara et al., 1978). To improve the efficiency of ozone use in flotation, it is essential to understand the mechanisms involved in the decomposition of xanthates with ozone, more specifically, to establish the stoichiometry and decomposition rate. In the present work, a preliminary attempt was made to investigate the effect of pH on xanthate decomposition, and probable mechanisms of xanthate oxidation with ozone.

Jan 1, 1986

By M. J. Hart, E. C. McDowell

There are no formulas that guarantee success when obtaining zoning approval for mineral aggregate mining. Local land use decisions often represent the most controversial issues faced by a community. Public awareness, concern, willingness to get involved, sensitivity to the environment and, probably most important, fear of change only begin to describe the atmosphere in which local land use decisions are made. The public hearing process is quasi judicial, adversarial, and unfortunately, not designed for resolution of disputes. It is not difficult to see the need for an alternative to present methods. Hopefully, some day there will be a process that will do away with or at least minimize unnecessary, unproductive, and unmanageable community conflicts.

Jan 1, 1986

By E. M. Frizzell

Introduction In 1956, the first mobile crusher was installed in a limestone quarry in Hover, Germany. These early mobile crushers solved the problem of wet and soft ground conditions that did not permit the use of haulage trucks due to the high cost of building and maintaining the haulage roads. Quarry operators also wanted to take advantage of continuous belt conveyor haulage systems and the resulting cost savings. European mines, particularly the coalfields, are in soft materials that allow use of bucket wheel excavators and their following continuous haulage system of belt conveyors. Quarry operators, with this background knowledge of belt conveyors in mining, easily accepted the conveyor concept, once in-pit mobile crushing solved the problem of size reduction of mine-run-rock required for conveyor application. Four years after the initial mobile crusher installation, the first report published on the subject appeared in the December 1960 issue of Mining Engineer (Kochanowsky, 1960). With this early background and basis for direction, mobile in-pit crushing and conveying have increased to more than 74 installations. The capacity, type of crusher, and material being processed appear in Table 1. These data in Table 1 indicate that experience to data has been heavily influenced by limestone installations of less than 1 kt/h (1102 stph). Most of these installations were directly fed by a mine face excavator because of the limestone quarry ground conditions. Crusher Configurations Crushers systems developed to date have varying mobility capabilities. These range from fully mobile units that are used continuously in this mode to fixed, permanently located in-pit crushers. The following terms are presented to help distinguish the range of mobility within the configurations of "mobile" crusher systems planned or now in use. Mobile Crusher The crusher works at the mine face, is directly fed by an excavator, and moves in unison with the excavator on its own transport mechanism as the mining progresses. An example is the unit delivered in 1976 to Yamama Cement Co. in Reyadh, Saudi Arabia.

Jan 1, 1986

By S. Inaba, K. Taguchi, T. Uenaka, I. Mizuguchi, K. Umeji, H. Isako

At Kobe Steel Ltd., various improvements in pellet quality have been carried out since beginning lime-fluxed pellet production. Especially, dolomite-fluxed pellets, developed in 1975, have superior high temperature properties. With this improvement, successful BF performance has been achieved. But, in order to achieve more successful BF performance, improvements of physical properties such as the shape factor, reposed angle, and the bulk density are desired. Now, crushed pellets have been developed for the improvement of those characters. The test operation with these new pellets in Kakogawa No. 2 BF was carried out with successful results. This report describes the development of crushed pellets and their use in BF.

Jan 1, 1986