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By CORNELIUS STEPHANUS LODEWYK SCHUTTE, WIEHAN ADRIAAN PELSER, JEAN HERMAN VAN LAAR, MICHAEL DAVID HARMSE

Rising electricity costs in South Africa have resulted in a need for optimized compressed-air networks in the mining environment. As a result, the financial benefit of air receivers needs to be reconsidered along with the economic dispatch strategy. This study investigates the use of an evolutionary algorithm in the mining industry to determine the potential financial benefit for various-sized air receivers, as well as their dispatch strategy. A genetic algorithm was selected due to the improved solution reliability and accuracy compared to other optimization techniques. This study indicates that a genetic algorithm can be used to determine the optimal dispatch of compressed air in the deep-level mining industry. Further, this study indicates that air receivers are financially viable in the mining industry and can be used to reduce operating costs, improving profitability.

Dec 1, 2022

By Ahmed A. El-Saie

To reduce the problem of overbreak and its associated added costs, a new technique is proposed to make a slot around the tunnel profile in hard rock. The Finite Element Method was used to investigate the effect of the slot on the stress field and deflection of the tunnel core. Beam theory was also applied to calculate the stresses and deflections of a slotted tunnel for several different slot depths.

Jan 1, 1981

By L. Stas

The authors have been interested in stress measurements in the rock mass for a long time. This paper describes the development of new apparatus for stress measurements in a rock mass. The principle of stress measurement by this device is based on the relief method as applied on the conical shaped surface of the bottom of a borehole. The design started based on the experience of K. Sugawara and Y. Obara who have been using the compact conical borehole over-coring system (CCBO). The conical shape of the strain gauge probe CCBO makes the fixation of the probe in borehole easy and, also, makes the measurement of stress in independent directions possible. The principle of the measuring method, the preparation of the borehole, the design of the probe for continuous measurement of stress during the course of overcoring are described. Also, a simplified version of the probe for long term monitoring of stress variations in the rock mass by means of the inserted body method and the initial laboratory results and in-situ testing of the development sample are described. Additionally, testing was done regarding the possible glues in relationship to the creep effect for this case.

Jan 1, 2006

Fine coal is substantially more costly to process than coarse coal because of technical difficulties associated with separating fine particles and removing process water from both clean coal and refuse. Therefore, companies are often forced to discard coal fines to waste impoundments. According to a recent report published by National Research Council, the U.S. coal industry is discarding 70-90 million tons of coal fines annually to 713 active impoundments, most of which are located in Central Appalachia. On October 11, 2000, a 72-acre impoundment near Inez, Kentucky, accidentally released 250 million gallons of coal slurry into nearby underground mines, creeks, rivers, and schoolyards, thereby creating serious environ-mental concerns. Fortunately, recent advances in separation technologies make it possible to recover fine coal more efficiently from existing coal preparation plants and from waste streams previously discarded to impoundments. The availability of these new technologies allows companies to increase profitability and minimize environmental risks, which are conducive for achieving sustainable mining.

Jan 1, 2003

By L. R. Hossner

Chemical and physical properties of surface soils and overburden materials must be evaluated prior to strip mining activities. This information can be used to assess whether subsurface overburden can be equal in quality to the existing surface soils, especially when these soils are classed as prime farm lands. In Texas, materials from the Carrizo, Calvert Bluff, Simsboro, and Hooper Formations overlie the lignite. The Carrizo Formation consists of thick clean sands with poor water and nutrient retention capabilities. These materials are least suited for placement of the surface of reclaimed land. The oxidized, medium textured overburden from the Calvert Bluff and Simsboro Formations possess adequate water and nutrient properties and are better suited for sustained plant growth. Non-oxidized Calvert Bluff and Hooper sediments generally have acceptable properties for reclamation. However, caution must be exercised in vegetating these materials since they may contain acid forming sulfide minerals.

Jan 1, 1982

By Larry A. Lien

Membrane technology has been available for about 30 years, but has been used very sparingly within the general mining industry. However, recent developments in polymer chemistry, spiral wound element construction, pretreatment equipment and element cleaning techniques have improved the reliability and robustness of membrane based systems. These improvements have expanded the potential to use this "new" technology to enhance critical recoveries of gold and silver in heap leaching operations or in the extraction circuit. Another opportunity for the mining industry will be to use membrane technology in new processes like controlling organic acids or ammonium thiosul­fate to enhance gold and silver extraction during leaching opera­tions. Finally, the most common use for membrane technology is for the control of mining water balance and acid mine drainage issues. Polymeric membranes, specifically thin-film composites, have been developed that will purify, fractionate or concentrate gold or silver. Recent applications have been developed for spi­ral wound modules that operate across the pH spectrum from 0 to 14. Systems using membranes have been constructed that operated on feed streams from 200° C to 3000 centipoise. Most recently, membrane based systems have been pilot tested suc­cessfully to purify solvents, like LIX. Opportunities exist to apply membrane technology to concen­trate gold and silver cyanide solutions with thin-film composite Reverse Osmosis (RO) membranes at elevated pH values above 10. Incorporating membrane technology could allow one to increase production without incurring additional expansion of the gold extraction side of the process. Furthermore, free cyanide is not rejected by the Reverse Osmosis membranes, but other inorganic salts are rejected 98+%, thereby, allowing an essentially ion free, except for the free cyanide, to be recirculat­ed back to the heap leach operation for enhanced extraction.

Jan 1, 1998

By W. H. Jay, F. Lawson, D. F. A. Koch

Ion exchange resins may in the future displace activated carbon in gold plants where cyanidation is practiced. Recently patented technology based on interpenetrated polyurethane polymers shows that these new materials offer significantly improved loading kinetics over both activated carbon and commercially available ion exchange resins. These polymers are not restricted either in particle size or in density and therefore offer the gold industry the potential for a further technological advancement.

Jan 1, 1995

By Daniel Saramak, Agnieszka Saramak

A big issue in crushing and grinding operations in raw materials handling is high energy consumption and low breakage effectiveness. According to the Legendre [7], only 10% of energy input is directly consumed on the feed material breakage, while the remaining portion is dissipated in the form of heat and noise [8]. In the industry of limestone powder production, the grinding operations constitute integral part of technological circuits, and the energy consumption in operations of industrial comminution consume as high as 2% of world energy [14]. High-pressure grinding is the technology with proved energy benefits both in ore processing circuits and in limestone grinding. The promising results concerned mostly the achieved energy savings and good results of material breakage were achieved and demonstrated in numerous investigations [1,3,12]. However, it appears that a proper selection of operational parameters of the press devise, determination the feed material characteristics and adjustment of process course san be of a key-significance in improving an effectiveness the HPGR operation. Operational parameters of devices and process course should be verified towards the characteristics of the feed material, which mainly applies to the particle size and shape of the feed material and its moisture, and also mineralization in case of ores [2,4,9]. There are various investigations concerning an impact of the operational pressing force on comminution results which mostly refer to the determination of energy consumption and crushing ratio [5,6,10,13]. Investigations on the moisture content are less common, however their results suggest that, in general, the HPGR feed with higher moisture shows the tendency to higher comminution intensity, while the energy consumption increases together with increasing of feed material moisture. Investigations on olivine sand feed [11] showed that crushing ratio decreases for higher moisture, especially when the material is crushed at higher pressing force. HPGR devices, however, shouldn’t be regarded as a unique and perfect solution for comminution of each type of material. But they indeed may bring technological and economic benefits, comparing to conventional crushing and grinding machines, resulting in more favourable breakage of material particles and lower consumption of energy per unit mass of processed feed material.

Feb 1, 2025

By S. D. F. Rocha, A. L. A. SANTOS, E. M. A. BECHELENI, F. P. C. Silvas

Hydrometallurgical processes are needed to extract nickel (Ni) when it is disseminated in mineral matrix. High-pressure acid leaching (HPAL) and atmospheric acid leaching (AAL) are alternatives, and AAL has the advantage of requiring mild temperatures and pressure. Reducing-reagent tests improved the extraction of metals for the specific limiting portion of the ore. Low dosage of sodium thiosulfate presented better selectivity and safer operating conditions, allowing metal extractions of 50–62 percent at 95 °C. However, the low extraction rate obtained for Ni and the similar levels of impurities — magnesium (Mg), manganese (Mn), cobalt (Co) and iron (Fe) — extracted may represent economical and technological challenges in the downstream process.

By Huaiyu Liu, Shan Liu, Dashang Chang, Maixi Lu, Yaqun He, Yali Kuang

The expert system for coal preparation plant design mainly solves the crux--separation flowsheet design and optimization of product structure. There are twelve basic flowsheets available in the system which are representative of financial plants. The system can select better flowsheets automatically according to the property of feed and scale of plant. Then, it can choose the best flowsheet and product model from the better flowsheets through analysis and optimum calculation. The expert system is made up in Turbo Pascal 6.0 and consists of three sub-systems: Lump and grain coal system, coal slimes processing system, and raw coal system. Several representation methods, such as production rule, procedure, and object-oriented programming, are used to express the expert's knowledge in the system. To decide the optimum product structure, Zangwill's method is used to make an advance product model. The expert system has the performance of interpretation strategy, by 'tracer" technology and pre-arrangement text, and of learning new expert's knowledge.

Jan 1, 1996

By C. R. Tatman

Failure to achieve the planned production rate at new mines and mine expansions has a major adverse impact on a project's economics. A study of 60 steeply dipping tabular deposit-type underground mines showed that 35% of the mines did not achieve their production goals. An empirical formula based on the geometry of the deposit and expressed as a rate factor is applicable to select a production rate for this type of deposit. The formula is: Annual production rate = Rate factor x Rate multiplier. The appropriate rate multiplier for each category of deposit thickness and the associated risk can be used to select an appropriate production rate.

Jan 1, 2002

By Peter Zhang, I. BERK TULU, Morgan M. Sears, Heather Dougherty, Ted Klemetti, DYKE MARK VAN, Gabriel S. Esterhuizen

Ground falls in longwall gateroad entries remain a concern in modern longwall operations. The gateroads are subject to changing horizontal and vertical ground stress induced by longwall extraction. These stress changes can result in failure of the strata around an entry leading to large deformations of the entry roof, floor and ribs. The gateroad support systems are required to control the failed strata while maintaining safe access to the longwall face and unimpeded ventilation. This paper presents research conducted to better understand the stability issues in gateroad excavations and to develop procedures for evaluating support and layout alternatives for longwall gateroads. Using the results of a field-monitoring program and numerical model analysis of case histories, a conceptual model of gateroad support needs was developed. The conceptual model formed the basis for developing a set of equations that can be used to estimate likely roof sag and support loading for given roof geology and longwall-induced loading conditions. The developed equations were used to compare predicted gateroad stability to field study results, showing satisfactory agreement. The calculation procedures are used to demonstrate their application in assessing support alternatives at a case study mine. It is concluded that the developed analysis procedures provide realistic assessments of likely ground stability and can be used to evaluate alternative gateroad support systems at operating longwall mines.

By S. D. Bechtel

Bechtel Civil and Minerals, Inc., one of the Bechtel group of companies, is a large engineering and construction firm that services the mining industry, among others. The firm's head, S. D. Bechtel Jr., comments on how his E&C company is dealing with the recessionary economy. First, he offered a historical perspective. About a half century ago-in the middle of the Great Depression-W. A. Bechtel and several business partners drew up a fixed price bid to build the Hoover Dam. At that moment in history, the W. A. Bechtel Co. was a modest success, but the times were troubled and uncertain. Money was scarce and a lot of contractors across the country were one project ahead of bankruptcy. The bid for Hoover was a make-or-break proposition for Bechtel, and it turned out successfully. The Hoover Dam was a no-frills operation in an isolated and harsh environment. There was plenty of hard work, long hours, and not many amenities. Controlling costs was critical. Everyone knew what had to be done, and why and what the consequences were. Today's Challenge Bechtel is now a bigger, more complex organization whose management views the current economic recession as a challenge to be met in much the same way W. A. Bechtel met the challenge of the Hoover Dam: by pulling together with a sense of purpose and direction. In many respects, Bechtel's situation today has a number of parallels to that which faced my grandfather. The company is eminently successful, but times are tough and there are plenty of signs that they could get tougher. My grandfather bet on the Hoover Dam to insure the future health of his company and I think we can work together again in that same tradition, make some tough decisions together, and the company's future can be just as promising. The first and most important requirement is to make certain that everyone understands the situation. The Bechtel group of companies are in an excellent financial position now. Its workload hit an alltime high in 1982 and it is well positioned in its principal markets. But the next two years may be critical for the company. Traditionally, Bechtel's work load lags behind general developments in the economy. Although many of its clients continue to suffer serious business difficulties, Bechtel is only beginning to feel the impact. The worldwide market for basic metals remains soft; relatively low prices and abundant supplies of oil and gas have flattened the petroleum market and made once promising synfuels projects economically unattractive; utility clients are still caught in the vise between overregulation and escalating costs. And persistently high, long-term interest rates have made capital investments expensive and difficult to justify. The company maintained a healthy workload through 1982. In some areas it has had little new work and consequently has been forced to lay off some staff as projects have been canceled or concluded. In other areas new work has tided the company over and more people have been hired. But new work bookings have fallen off, creating some uncertainty for the near future. 1983 requirements are clear, although seemingly contradictory. Belt tightening and cost reduction are necessary for Bechtel to remain healthy and competitive, enabling it to handle a possible further downturn with a minimum of turmoil and dislocation. At the same time, we need to allocate resources and funds in areas that will keep us positioned for the turn-around marketplace.

Jan 2, 1983

By Ramon S. Pizarro, W. Joseph Schlitt

Introduction Trying to synthesize innovations occurring in gold processing is not simple. At present, this technology is exploding, brought about by the high price of gold. This price has compelled the mining industry, as a matter of survival, to produce gold. The frantic search for gold deposits continues, from glacial areas to tropical jungles. The search has been fruitful. New exploration techniques have helped to locate deposits. Some are amenable to conventional processing techniques. Others are in unusual settings that challenge the ingenuity of extractive metallurgists. Ore deposits containing traces of invisible gold, refractory mineralization, and impurities and deleterious materials that previously defied treatment are now being profitably processed. Metallurgists have developed various processing methods and equipment for gold ore treatment that reflect differences in ore characteristics, grade, mineralogy, reserves, topography, climate, and location. These processes can be categorized as: • For nonrefractory or readily leachable gold ores - vat leaching, heap leaching, and agitation leaching. • For ores containing free gold - gravity concentration methods, followed by mercury amalgamation, and • For refractory gold ores - flotation, roasting, pressure oxidation, followed by cyanidation leaching. In actual practice, a combination of these processes may be required. This is because gold mineralization, although usually simple, may be associated with other mineral species or with clays that make the ore difficult to treat. Furthermore, after the gold has been solubilized to form a cyanide complex, one of two important processes must be applied to recover the gold. These ore zinc cementation (Merrill-Crow process) and Carbon adsorption, desorption, and electrowinning. New techniques for leaching and recovery are also advancing. These will become the bases for the next generation of gold processing plants. Nonrefractory Gold Ores Nonrefractory ores with readily leachable gold are among the .easiest to treat. Even so, non-refractory ores from epithermal deposits are likely to contain too much clay. When these ores are damp, they may clog the screens and cone crushers. Depending on the type of process, scrubbing the crushed ore is very effective in overcoming clay problems. After dewatering, the slimes enter the cyanidation process and the thickener overflow is stripped of gold values and recycled. Semiautogenous (SAG) mills are also gaining popularity due to lower capital costs and ability to treat wet, sticky ores. If properly sized, the secondary crushing and screening plants, together with a secondary ball mill, can be eliminated. When the ore is of such a low grade that it can not support fine grinding, vat or heap 'teaching may be applicable. These systems are being actively applied in the US and elsewhere. Rapid construction and low capital costs are important features of these plants. Vat leaching is ideally suited for fast leaching ores and small tonnage deposits located in areas with harsh winters or wet tropical climates. For effective vat leaching, the ore is crushed to less than 25 mm (1 in.), agglomerated with lime or cement to control fines, and leached with sodium cyanide solution (upflow or downflow). The degree of size reduction is a tradeoff between increased costs of comminution and improved gold recovery from smaller particles. However, the size of material

Jan 11, 1984

By S. A. Tims

INTRODUCTION The Falconbridge mine ore body extends about 1.6 km (1 mile) in length and the deepest developed ore is on the 6050 level below surface. The ore zone varies in width from a few inches to over 30 m (100 ft) and the average width is 4.9 m (16 ft). Access levels are driven in the ore at 53.3-m (175-ft) intervals. The principal method of mining is overhand longitudinal cut-¬and-fill. Prior to 1962 timber square-set stoping as a secondary extraction method was used for about 15% of the total production. Undercut-and-fill was intro¬duced at Falconbridge in 1962 as a potential replace¬ment for the square-set method in heavy ground. The undercut-and-fill method was developed by Inco in the 1950s, its principal application being to transverse pillar mining. Falconbridge made modifications to this method. A feature of the mine is the No. 1 flat fault which dips 0.79 rad (45°) towards the northeast. The main characteristic of the fault is the presence of large swells of ore directly under the plane of the fault. The ground under the fault area is highly fractured and associated with massive sulfides. In the past, the ore under the fault was recovered, with difficulty, by either tight cut¬and-fill or square-set stoping. In the 1970s these meth¬ods were supplanted to a large degree by the under-cut-¬and-fill method. An advantage of the current undercut-and-fill method which uses cemented fill compared to the cut-and-fill and square-set methods is the reduction of dilution due to better control of the walls. At Falconbridge mine, it is estimated that the grade of ore produced by undercut¬and-fill is improved by approximately 10% over other methods. Where undercut-and-fill is used in very weak ground, a much greater improvement in grade can be expected. Table I shows mining production for 1974. The undercut-and-fill method was first used at Falconbridge during 1962. The first longitudinal stope was prepared for undercutting by laying down laminated beams the length of the stope and installing a lagging mat floor on top of the beams. Unconsolidated tailings fill was poured on top of the mat floor. As the cut ad¬vanced under the floor, heavy posts were placed under the laminated beams at 1.8-m (6-ft) intervals. During 1966, a radical change was made to the method when tailings fill, consolidated with portland cement, replaced the unconsolidated fill. This development eliminated the laminated beams and heavy mat floor and greatly im¬proved the stability of the stope. This system, with minor variations, is currently used at Falconbridge mine. APPLICATION The undercut-and-fill method is used to mine in¬competent ground, sills or floor pillars under mined-out levels, or a block of ore isolated between levels. It is occasionally used to advantage in sequencing produc¬tion from various mining blocks. This is done by mining a block of ore cut-and-fill method and at the same time mining the ore block directly underneath by the under¬cut-and-fill method. The undercut-and-fill mill holes at Falconbridge are either boreholes, stripped timbered raises, or steel mill holes. Boreholes and rock raises tend to slough in heavy and broken ground which increases dilution when sloughing exceeds the ore width outline and also in¬creases the difficulty of moving down to start the new cut. For example, in one installation, a 1.2-m (4-ft) diam borehole sloughed to a size of 3.7 x 5.5 m (12 x 18 ft). The undercut-and-fill method usually requires a mill hole extending from the level below the ore to the top horizon of the ore block. The customary methods of providing a mill hole are: 1) A borehole is driven from level to level through the ore block and a chute installed on the bottom level (Fig. 1). 2) An existing raise is used as a mill hole. If the raise is timbered, a steel mill hole is installed inside the timber and tailings fill poured around the steel mill hole (Fig. 1). 3) An existing steel mill hole, situated at one end of a mined-out stope, is used as the mill hole for an ad¬jacent undercut-and-fill ore block. The mill hole posi¬tion is determined when planning the mining sequence of the first stope (Fig. 2).

Jan 1, 1982

By William H. Meadows

This information describes the ventilating and methane gas testing procedures utilized during the raising of a mine shaft using a Robbins 81-R drill. An overview of the raise boring process is presented to illustrate the ventilating and gas testing procedures. A mine shaft project, 4.88 m (16 ft) in diameter and approximately 457.2 m (1500 ft) in length, will be the focal point of the presentation, with reference to similar projects for additional comments on variations in procedure.

Jan 1, 1980

By Ian Corrans, Gary Johnson, John Angove

The Activox™ process is a new method for the pre­treatment of refractory gold ore concentrates prior to cyanidation. The process has been developed in Western Australia, and relies on a combination of fine grinding and pressure oxidation to achieve the destruction of sulphide minerals and the liberation of encapsulated gold. The process operates under much more moderate conditions than those that would typically be used for conventional pressure oxidation of similar concentrates. This results in significantly lower capital and operating costs being achievable.

Jan 1, 1993

By C. E. Jordan

The fundamental properties of the Bureau of Mines patented dielectric separator were studied to provide insight regarding its design and operating characteristics. Force equations for mineral particles were derived and evaluated experimentally. High dielectric mineral recovery was proportional to the calculated effective dielectric force volume that surrounded each drum electrode wire. Electrode spacing was the most sensitive design parameter, requiring less than 0.4-cm electrode spacing for a good separation. Operating characteristics and ore characteristics were investigated. With a dielectric constant difference as small as 2, good separations were made on a laboratory scale at energy consumption below 12 kw?h/mt.

Jan 1, 1985

By E. M. Frizzell

In an effort to economically and efficiently enhance the erosion control aspects of present surface coal mine reclamation practices, the US Bureau of Mines has recently completed a two-phase research program wherein irrigation strategies and equipment developed under the first phase were field tested on three surface coal mine sites. The fundamental basis for the use of irrigation as a reclamation tool is to provide the plant moisture requirements as a supplement to prevailing natural precipitation, and thereby support the natural growth of drought-hardy native vegetation. Portable solid-set irrigation equipment and several irrigation strategies were tested on large 6-ha (15-acre) sites in Montana, Wyoming, and New Mexico. Results of these tests will be presented which include daily irrigations, precipitation levels, soil moistures, climatic data, and density cover and biomass of the native plants.

Jan 1, 1987

By M. Dosemeci, M. McCawley, J. McLaughlin, Z. Wu, F. Hearl, W. Blot, K. Peng

Proposals have been made by two organizations, the International Standards Organization (150) and the American Conference of Governmental Industrial Hygienists (ACGIH) for a revised respirable dust criteria and criteria for thoracic and inspirable dust. These criteria yield different results than criteria based on lung deposition patterns in assessing the hazards due to dust exposure. Since these differences are a function of the size distribution of the dust an analysis of dust size distributions from various mining operations was performed to determine the amount of difference that could occur. The dust size distributions available for this analysis were taken from U.S. coal mines and from Chinese metal mines. The mass of mechanically generated dust that will deposit in the alveoli was found to be in direct proportion to the ISO/ACGIH criteria estimates in the mines studied. Therefore, respirable dust estimates for substances such as coal and silica are not a problem. Estimates of exposure to diesel exhaust in these mines, however, were not always in the same proportion to the estimated alveolar deposition. Also, concern with an excess of bronchitis among miners may not be adequately addressed by the use of samplers conforming to the ISO and ACGIH criteria. The cascade impactors used to acquire the data for this analysis require four to eight substrates per sampler. For daily dust exposure assessment this method is cumbersome and time consuming. Therefore, two new samplers have been designed to meet the need for determination of deposited dust mass. These samplers follow the lung deposition curve rather than the penetration curves proposed by the ACGIH and ISO and require analysis of only two substrates per sample.

Jan 1, 1992