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By R. A. Pyper

Laboratory leaching experiments were conducted to ascertain the effectiveness of acidic solutions of thiourea, CS(NH2)2, for dissolving gold from finely disseminated gold ores. The ore tested was from the Chipmunk orebody of the Northumberland mining district in Nye County, Nevada, USA. Extractions of up to 90 percent were attained from the ore. Extraction was shown to be dependent on thiourea concentration, ferric sulfate oxidant concentration, acid concentration, and leaching time. Optimum conditions were an ambient temperature leach near pH 1.0 utilizing 100-200 kg/t thiourea and 50 kg/t ferric sulfate for 8 to 24 hours.

Jan 1, 1981

By Wesley W. Eckles

Microcomputer technology has begun to revolutionize petroleum engineering. Petroleum engineers' use of relatively inexpensive personal computers (PC's) is likely to continue expanding rapidly. Since 1982 SPE's Microcomputer Applications Committee has developed a Society-wide users group, a bi-monthly newsletter (MICROCOMP NEWS), an SPE Short Course, a hardware and software distribution program, and a world wide electronic network (SPE NET). The purpose of this paper is to share SPE's experience in creating a dynamic program for meeting the individual member's need in the application of microcomputers to petroleum engineering. My hope is that this will encourage other engineering and scientific organizations to provide similar programs for their members.

Jan 1, 1985

By J. B. Knaebel

I have been asked to discuss the "Development of the Twin Buttes Mine for Production." This property, which is a large low-grade open pit copper mine about 25 miles south of Tucson, Arizona, was recently brought into production by The Anaconda Company under a long-term lease agreement with the Banner Mining Company. Since the scope of this paper is limited to the subject broadly indicated by its title I will confine discussion of historical, environmental and other general matters to a brief summary sufficient, I hope, to establish a background of those conditions which influenced our approach to the technical and economic problems that faced us at Twin Buttes. The paper deals primarily with our studies and activities related to the solution of these problems and with the resulting engineering and business decisions that were taken - decisions which culminated last September in the initial commercial operation of another major open pit copper producer unique and interesting in several respects.

Jan 1, 1970

By O. Tranbarger

In aging tunnels, wall and roof deterioration can eventually result in defects that must be detected and repaired to maintain safe structural conditions. In investigating tunnel defect conditions, a specialized FM radar system was developed with a programmable VHF and UHF operating sweep range for optimizing the penetration and measurement capabilities. The new FM radar technology was tested in two aging brick-lined tunnels in New York City. Test results showed that FM radar signals could penetrate eight courses of water-saturated brick and that the original steel liner outside the tunnel walls was intact.

Jan 1, 1985

By Y. B. He

The effect of the overflow to underflow (O/U) flowrate ratio of a dense medium cyclone on its performance is tested utilizing a 6" dense medium cyclone and density tracers. The results show that the O/U flowrate ratio is clearly correlated with the separation cut point D50, the separation efficiency Ep, the density differential 0, and short circuiting of the cyclone. Within certain limits, a higher O/U ratio results in a better separation efficiency, a higher D50 and an increased density differential. A lower O/U ratio, on the other hand, reduces the cut point shift and density differential. The phenomenon of short circuiting to the underflow, which is especially significant for fine particles, is directly connected with an excessively low O/U ratio.

Jan 1, 1992

By S. P. Chong, Peter V. Avotins

The iron and steel industry continues to operate at depressed production levels due to the low level of demand for steel and foundry products. Crude steel production in the Western world dropped by 13.7% from 459.3 Gt (506 billion st) in 1981 to 396.4 Gt (437 billion st). The reduction was particularly severe in North America where the industry suffered a loss of 37.3% from 123.6 to 77.5 Gt (136 to 85 billion st). This reduced level of production severely affected iron ore and agglomerates output. Substantial curtailment was made in both sintering and pelletizing plants to meet reduced demand. The pressure on these plant operators shifted from quantity to quality. With energy cost becoming an ever increasing part of production costs, conservation was a major area of emphasis. Iron Making Sinter has continued to be the favored burden for blast furnaces overseas. As hot metal production declined and excess sintering capacity developed, many of the overseas operators that have been using pellets found it advantageous on hot metal production cost to increase the ratio of sinter at the expense of pellets. This was the case despite the depressed price level of pellets in the world market. In North America where pellets have been the predominant burden material-mainly because it is necessary to pelletize the fine grain iron ores available domestically-there was also increased interest in sinter usage. Bethlehem Steel Corporation's 13.6-m (44.5-ft) furnace at Sparrows Point experimented with a burden with more than 70% of sinter during the second half of the year and indicated some favorable results as compared to its previous 50% super flux sinter and 50% acid pellet burden. The blast furnace operators continued to press for improved burden quality. In addition to the emphasis on the importance of burden chemistry and quality, uniformity, much emphasis was placed on improving reducibilitiy and high temperature metallurgical qualities. These burden properties were recognized to hold further promise in reducing fuels rates. Sintering With reduced consumption caused by the cutback in hot metal production, many sinter plants sat idle while others operated at greatly reduced rates. The deemphasis on production in many plants allowed them to experiment with various means to reduce operating costs. The most notable action was the introduction of low cost South American pellet feed fines into the sinter ore mix. These feed fines, which are finer than 150 µm (100 mesh) ore, were previously thought to be too fine for sintering. However, when the full production rate is not required the use of up to 40% in the ore mix was reported to be successful with the aid of burnt lime and adequate premixing and granulation of the sinter mix before sintering. The emphasis on quality and tighter cost control also has resulted in a further breakthrough in sintering technology. It was recognized that good feed preparation-including selection of compatible ores, good blending, good pseudo-particle formation, additive size control increased bed depth, and closed control of the sintering bed heat pattern-could allow the production of high quality sinters with much lower heat input and FeO level. Bed depth of more than 600 mm (23.6 in.) was practiced in a number of operations. Total heat input of better than 1.3 GJ/t (290,300 kcal per st) has been achieved. Kawasaki Steel's Chiba Works has also achieved a 5.3% SiO2 in the sinter with good quality. The low heat input approach allowed production

Jan 5, 1983

By C. L. Pillar

In the capitalistic system the success of a mining enterprise is measured by the rate of return on the investment and the speed by which its redemption is achieved. Exploration in search of ore deposits often results in the emergence of the lean orebody which does not meet basic company requisites. At this point a decision must be made whether to place the orebody into production or postpone production pending more favourable market conditions. The wisdom of this decision, borne out by future results, demonstrates the quality of a company's management and is instrumental in the degree of financial success it achieves. The project feasibility report must show a rate of return on the capital invested that is attractive to the company, plus its full redemption in the desired period of time, in order to bring the property into production on a sound economic basis. Mining companies have demonstrated their ability to bring the profitability of a marginal property from a point that says "no go" to a point of "go" by substantial reduction of expenditure without adversely affecting production rate or cost. Here is where the real challenge exists for today's mining engineers and plant designers; they will have to develop better ideas and concepts: ideas that will still allow maximum production at reduced capital expenditure, This is the sound way marginal orebodies can be brought into production without inflationary increases in the price of their product.

Jan 1, 1969

By E. D. Goddard, D. S. Murphy

Acid resistance, zeta potential and ESCA (electron spectroscopy. for chemical analysis) experiments were performed on emperador marble and four calcium carbonate samples (onyx calcite, travertine calcite, Iceland spar calcite and aragonite). Six fluorine-containing reagents were used to treat the surfaces of these materials: magnesium hexafluorosilicate, zinc hexafluorosilicate, sodium fluoride, zinc fluoride, strontium fluoride and stannous fluoride. The acid resistance of treated samples proved to be much higher than that of their untreated equivalents. The isoelectric point of treated samples approaches the isoelectric point of fluorite. Also, the fluorine content, as measured by ESCA, of a marble surface treated with magnesium hexafluorosilicate is much higher than that of an untreated sample. The binding energy off of fluorine and calcium the treated marble is consistent with the formation of calcium fluoride.

Jan 1, 1994

By Kenneth J. Reid, Marian S. Stachowicz

A preliminary evaluation of a new in-stream particle size analyzer has been carried out using materials obtained from a taconite plant in Northern Minnesota. Results are reported for bench scale, pilot scale and full scale tests, the latter being carried out in a taconite plant concentrator. The unit employs a novel scanning laser microscopy principle and details of the equipment configuration and operating principles are presented and discussed. Data acquisition is via an eight channel digital electronic system and particle counts are collected on the basis of reflected light pulse time intervals which are a direct measure of particle size. Output is available as an eight point individual or cumulative size distribution or as computed averages. The practical aspects of sample point location and flow requirements for reproducible results are outlined and discussed.

Jan 1, 1990

By Margaret Armstrong, Chris Roth

One advantage of kriging is that it provides both an estimate of the block or point grade, and an indication of the local precision via the kriging variance. If one assumes that the estimation errors are normally distributed, then confidence intervals for the grades can be calculated. But in mining, grades are rarely normally distributed; in general, they are skew. This is particularly true for precious metals. In this paper we study confidence intervals for variables with non-normal distributions. Using a non linear geostatistical technique, the grades are transformed into their normally distributed equivalents. Confidence intervals are obtained for these normal variables, and back transformed to give the corresponding confidence intervals for the grades, for either points or blocks. This approach is applied to gold data from the Witwatersrand basin in South Africa.

Jan 1, 1996

By Stanislaw Wasilewski, Zdzislaw Krzystanek

Ventilation process in deep mines features relatively low efficiency. Commonly used passive control by means of regulators and flow throttling leads to remarkable energy losses that could be lower if effective monitoring and remote control of main fan operating point were implemented. In the paper, some results of investigation carried out in Polish coal mines to evaluate real energy losses in ventilation process are described. Different methods for main fans performance monitoring and control are considered and compared especially those using fan drive speed control to minimize power consumption. On the other hand some criteria for power evaluation are analysed and algorithms for optimum location of controllers in ventilation network are considered. The results of investigation are being implemented in the first system for monitoring and control of main fan operating point in Miechowice colliery.

Jan 1, 1995

By T. W. Healy, M. S. Moignard

The use of electrokinetic or zeta-potential phenomena in studies of the properties of mineral sulphides has increased greatly over recent years. This review aims to examine and discuss the body of literature on the subject of electrokinetic properties of sulphides in a comprehensive and critical manner. Although the review covers the period from 1925 to 1975, it is only in the past ten years that researchers have been fully aware of the implications and problems of chemical reactions, notably oxidation and precipitation reactions, on the surface properties of sulphide minerals. These papers are discussed in more detail than the earlier publications. A table containing a list of determinations of iso-electric- points and points-of-zero-charge of mineral sulphides, and the methods employed in obtaining these results, is presented.

Jan 1, 1976

By J. Köppel, K. Kovári, Ch. Amstad

INTRODUCTION The measurement of displacements in soil or rock in the vicinity of underground openings provide valuable information for a better understanding of the behaviour of the structure. On the basis of systematic observations conclusions can be drawn concerning - safety of the opening in the various stages of excavation - effectiveness of the support measures - nature of the rock pressure to be expected - influence of the construction of the opening on neighbouring structures (settlements of foundations, underpassing other tunnels etc.) - comparison of theoretical predictions with the actual structural behaviour (1). Today there are several types of suitable instruments available that can be employed at reasonable costs for such investigations (2). The most important ones are the multiple point borehole extensometer, the inclinometer and the multiple point borehole deflectometer. As is well-known, the extensometer only measures the displacement component in the borehole axis, while the inclinometer and the deflectometer provide monitoring of rock mass movements normal to the borehole axis. In the following a new instrument is described, which has been given the name Extenso-Deflectometer ISETH. In this single piece of equipment certain features of the above-mentioned three types of borehole instruments are incorporated. it enables the measurement of all three components of the displacement vector at consecutive points along the borehole, the axis of which may have any direction in space. This device is portable like the inclinometer. A simplified version

Jan 1, 1979

By N. P. Titkov

This paper presents the results of laboratory and pilot plant investigations for the development of efficient methods of beneficiating hematite ores from the Krivoi Rog, Kursk Magnetic Anomoly, Olenogorsk, and other localities. The tests included gravity, magnetic (in a high intensity field), flota¬tion, and magnetizing roasting methods. It was possible to develop efficient beneficiation methods depending on the mineral composition of the ore and degree of dissemination of ore and gangue minerals. The paper shows the relationship between the iron silicate and quartz content of the ore and the technologic indices of the various beneficiation methods. Some of the conclusions based on these investigations and the technical and economic computations related to the cost of one ton of pig iron produced from concentrates obtained by the various beneficiation methods are: 1. If the hematite ore is not disseminated uniformly, it is expedient to use a combined gravity and flotation process. Ore particles up to 50 am. in size are beneficiated by gravity (heavy suspension, jigging, and others) and yield a lump concentrate. The middlings from this process are recrushed and floated; 2. Finely disseminated hematite ores, containing small quantities (less than 5 percent) of iron silicates, are most effectively beneficiated by flotation. Anionic (sulphate soap, tall oil emulsion with various foam depressors) as well as cationic collectors may be used. Depending on the mineral and chemical composition of the ore, it is possible to obtain concentrates containing up to 65 percent iron with an extraction up to 94 percent; 3. Finely disseminated, mixed hematite-magnetite ores may be beneficiated by flotation or a magnetic separation-flotation process; 4. Finely disseminated hematite ores, containing large quantities of iron silicates and earthy hematite ores are most efficiently beneficiated by the magnetizing roasting method. This method will yield concentrates containing up to 68 percent iron with extractions up to 90 percent. Although beneficiation by the magnetizing roasting process is costly, it will nonetheless, when employed on this type of ore, yield the least expensive pig iron.

Jan 1, 1960

By Frank C. Appleyard

As the environmental movement gained force during the past few years, it was inevitable that attention would be focused on surface mining, and we have seen this method of extracting minerals from the ground come under heavy attack by conservation groups, the press and television, legislators at all levels of government,, and the public at large. It is difficult, and in some situations, perhaps impossible, to measure either the need for, or the results of, land reclamation in absolute terms. Therefore, much of the criticism of surface mining has been based upon subjective analysis rather than hard data, with the result that discussion of the subject often includes a fair amount of emotional response. To be fair, this reaction is not limited to just our critics; even we hard headed engineers sometimes respond in the same way, an observation with which you may agree when I finish this talk. This leads to the thought that whether you are for it, or against it, land reclamation in many respects is a state of mind. That is, our reaction to it can vary considerably, depending on how far we have thought it through. And think it through we must, because the pressures being brought to bear need to be met with positive actions if the problem is to be brought under control, and in the next few minutes I would like to discuss from a management point of view some ideas which might aid in this thinking process. It would be a mistake, I believe, to think that the current energy crisis will suddenly bring the environmental movement to a stop, and therefore, we can relax and go back to running our busi¬ness the way we used to. This is not realistic; on the contrary the energy crisis is focusing attention on the limitations of our natural resources as nothing else could, and with respect to land

Jan 1, 1974

By Peter J. Huck, Yoginder P. Chugh, M. Jennings

INTRODUCTION Large areas of the United States coal reserves have been undermined by room-and-pillar mining over the past century. These abandoned mines generally cause subsidence of the ground surface many decades after mining. Reports from England (1) where there is a longer history of room-and-pillar mining indicate that mines abandoned two centuries ago may still be causing subsidence, and causing surface destruction to urban areas or farm lands that have been developed in the interim. The devastation wrought by subsidence, both in terms of property loss and societal disruption is enormous. The authors discuss here the methods by which subsidence in abandoned mines may be controlled. Two distinctly different subsidence control technologies have been developed in the U.S. for abandoned coal mines. These are referred to as (1) Point Sup- port methods, and (2) Areal Backfilling. As the names imply, point support methods are used to protect individual structures, or even individual foundation elements of structures, whereas areas backfilling techniques may be applied to protect entire neighborhoods or urban districts hundreds of acres in extent. Both point support methods and areal backfilling have specific sub-categories of techniques that may be applied under different conditions as appropriate. POINT SUPPORT METHODS Point support methods are characteristically employed by civil engineers chartered with the design of a new structure or the protection of an existing structure. The subsidence control measures are only a part of a larger project, the safety of which must be assured to a degree of near certainty. The costs of point support methods involve a large number of bore-holes and the use of expensive materials in relatively small quantities. There exist several dozen point support methods, which operate either to support the underground cavities, controlling subsidence, or to isolate the structure from the effects of subsidence if it should occur. The latter methods usually involve deep foundations through the mine opening supporting the structure on the underlying strata. Our concern will be with the former method to support underground cavities to prevent subsidence. Gravel Columns and Associated Methods Gravel columns may be placed in the mine opening using the methods shown in [Figure 1]. Boreholes are drilled through the mine strata, and gravel poured down the borehole to form a pile on the mine floor. When the tip of the pile contacts the mine roof, it is rodded down to spread the pile, and permit additional gravel to be placed. The objective is to place as much gravel as possible in the mine opening, and to achieve firm contact with the mine roof. The gravel pile acts to reduce subsidence by three mechanisms. The filling of a significant fraction of the open mine volume reduces the amount of potential subsidence simply by killing open volume within the mine. In effect, the extraction ratio has been reduced by introducing the volume of gravel. The toe of the gravel pile abuts against nearby pillars, providing lateral support and protection against pillar deterioration. In effect, the height of the pillars has been slightly reduced by burying their lower portions. Finally, some direct support is provided to the roof strata, reducing the roof span and enhancing stability. The gravel column method may be used in a variety of applications, and with materials other than gravel. For example, gravel columns may be placed in a close line around the perimeter of the building to form a continuous gravel wall. The interior of the site may then be completely filled with sand, slurry or other material. Alternatively, a lean concrete may be used in place of gravel, so that the piles achieve significant structural capacity. The grout column, shown in [Figure 2], begins with the installation of a conventional gravel column which is placed around a grout pipe that extends through the borehole into the mine opening. When the gravel column is in place, portland cement grout is injected in stages. At each stage, sufficient grout is injected to fill the interstices in the gravel to build a column perhaps two meters in diameter and a meter tall. The group pipe is then raised one meter, and after the previously injected grout has set, the next stage of grout is injected. The process builds a column of grouted gravel to the

Jan 1, 1982

By N. Arbiter

During the first four decades of flotation practice, close to 200 machine designs were patented, although only about a score were ever used commercially. By the end of that period, the rigors of use had resulted in obsolescence of most pneumatic cells, with a few mechanical cells dominating the field. After World War II, newer designs began to appear but most were modifications in varying degrees of older designs with special features added. Of the dozen or so most recent developments, almost all are pneumatic, relying on compressed air instead of impellers for motive power, although in several cases pumps supplement compressors. Table 1 lists a few of the more fully documented new cells, with their significant characteristics, along with similar characteristics of a widely used mechanical cell. New designs in general are emphasizing: bubble size control; in several cases, methods for delivering feed directly to the froth; methods for introducing and dispersing air through nozzles, eductors, packed beds, or permeable walls; and variable cell volumes, relative to capacities, ranging from very small, with less than a second of retention time, to the largest, with retention times of over 20 min. An important question is the extent to which any of the newer designs are based on locating weaknesses in current mechanical cell designs and then using these as a starting point for innovations. In the present study, the key subprocesses which must take place in a cell are outlined; mechanical cells are analyzed to establish where weaknesses may exist; and then alternative subprocesses are considered which could effect improvements. COMPONENTS FOR CELL DESIGN It is assumed that mineral surface chemistry has been modified as necessary to provide optimum potential floatability. While the cell process may affect this to a degree, cell design is primarily concerned with actualizing the existing potential floatability. The cell design problem is to provide more effectively for the following: 1) Dispersion of air to obtain an optimum bubble size distribution at an optimum ratio of air volume to feed volume. 2) A hydraulic environment which permits most effective contact of potentially floatable particles with bubbles: [Table I - Cell Comparisons* Cell Type Mechanical Column Deister Miller ASH No. of units Multiple Single Single Single Retention time min.10/20 17/27 3.8 ca. is Capacities mt/m3s 0.022/0.066 0.066/0.20 0.11 10.4 st/ft3d 1/3 0.3//0.9 m5.0 469 Air hold-up % 15/20 20 n.a. 50/80 Air escape velocity m/s 0.015/0.0200.020/0.025 n.a. n.a. ft/m 3/4 4/5 n.a. n.a. * References: Mechanical (Harris, 1976,1985), (Bassarear, 1985); Column (Travis, et al. 1987); Deister (Zipperian and Christophersen, 1985); ASH (Air-Sparged Hydrocyclone) (Miller 1989).]

Jan 1, 1989

By A. K. Ghose, S. Chakraborti

The research work outlined in this paper examines the utility of index tests for evaluating the strength of coal, both in the laboratory and in-situ. For routine evaluation of strength and deformation properties of coal seams, as inputs for design in stability analysis and equipment selection, the index tests are cost-effective and also make less demand on time and manpower. Four index tests, namely Protodyakonov Index, Cone Indenter Index, the Point Load Strength Index and Schmidt Rebound Hammer, were evaluated for 13 coal samples and correlated to fundamental strength and deformation properties such as uniaxial compressive strength, Brazilian tensile strength and modulus of elasticity of the same coal stratum. The index tests, barring Point Load Index, showed relatively low percentage scatter compared to the fundamental strength and show marked advantages for routine estimation of coal seam strength.

Jan 1, 1986

By Y. J. Wang

The concept of subsystem characteristic curves for multiple-fan ventilation networks is presented through the construction of characteristic curves for two-fan, series-parallel networks. By considering fans as the individual network branches, the multiple-fan network is viewed as consisting of two components: any one fan branch, which is called the reference fan branch, and its associated subsystem. Thus, F subsystems can be designated for the network with F fan branches. Each subsystem contains one or more fan branches. The subsystem characteristic curve is the pressure-vs.-quantity curve of the subsystem. As illustrated in the example networks, the subsystem characteristic curve is not a strictly increasing curve and does not pass through the origin. The intersection of the characteristic curves for the subsystem and the reference fan branch represents an operating point. Multiple intersections therefore represent multiple operating points.

Jan 1, 1994

By Gilmore R. Tostengard

The advent of inexpensive computers has opened vast opportunities for improved planning and control of capital projects. The mining and mineral processing industries have welcomed the opportunity, and new and improved quantitative management techniques have abounded. This chapter will discuss commonly used computer applications for economic justification of the project, preparation of the cost estimate, planning the work schedule, monitoring work progress, and control of costs and productivity. Finally, there is a review of the degree to which the industry uses these applications. Our experience suggests that while we in the industry have been quick to adopt the new techniques, the quality of our input data has not always kept pace. During the next decade, our push should be toward improving the quality of the basic data and assumptions so that we can fully benefit from the sophisticated techniques. The GIGO (garbage in, garbage out) principle is a wellworn cliche, but it is especially valid here. One of the keys to getting good input is commitment. Unless the managers who are to use or benefit from the system are committed to it, the effort will fail. They must be com- mitted to the underlying principles of planning and control sufficiently to expend their time and resources on them; planning should be especially given emphasis. They can't be too busy to plan.

Jan 1, 1979