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By A. W. Khair

This paper presents an analysis of the dynamics of bit wear on the productivity of the continuous miners. Two field surveys have been carried out. The first survey was to assess the impact of bit wear on productivity and production cost. The second survey was to study the wear characteristics of the cutting tool (i.e. magnitude, forms, and mechanisms of bit wear). Primary factors affecting bit wear is identified and laboratory experiments were carried out to study the effects of some of these primary factors on wear in detail. Results indicate that bit wear has a significant effect on the productivity of the continuous miners. Furthermore under the severe geologic conditions (i.e. cutting rock partings and roof and floor rocks) bit wear not only hampers the productivity, but also increases the production cost due to a higher number of bit consumption. This study also indicated that bit wear accelerates beyond 20% of the conical height loss which corresponds to 7% of the weight loss. This increase rate of wear is an indicative of higher abrasion between bit body and cutting material, resulting in a dustier environment.

Jan 1, 1993

By Jacob Carr, Bruce Whisner, Adam Smith, Jingcheng Li

Electromagnetic-based proximity detection systems (PDSs) are utilized on mining machinery to protect workers from being pinned or struck. These systems generate magnetic fields covering the space around a machine, and a miner-wearable component (MWC) detects the field. The PDS determines the distance of miners relative to the machine based on the detected magnetic flux density in the magnetic field. This information is used to establish warning and shutdown zones around the machine. Maintaining a stable magnetic field is essential for system accuracy. However, components used to generate magnetic fields can be influenced by temperature changes. Depending on ventilation conditions and seasonal alternation, a PDS can be subject to significant temperature fluctuation. To better understand and quantify this phenomenon, researchers from the National Institute for Occupational Safety and Health (NIOSH) developed an experimental apparatus to study the influence of temperature on magnetic field generator circuits used in PDSs. Results from the study show that the electric current through a generator can be influenced by both ambient and internal temperatures, modifying the magnetic field that is produced. These findings show that temperature can significantly influence the ability of PDSs, used in underground coal mines, to accurately determine a worker’s position in relation to mining machine.

By K. Hanumantha Rao, A. Javadi Nooshabadi

"Formation of hydrogen peroxide (H2O2), an oxidizing agent stronger than oxygen, by chalcopyrite (CuFeS2), which is a copper iron sulfide mineral, during grinding, was investigated. It was observed that chalcopyrite generated H2O2 in pulp liquid during wet grinding and also in the solids when placed in water immediately after dry grinding. The generation of H2O2 during either wet or dry grinding was thought to be due to a reaction between chalcopyrite and water where the mineral surface is catalytically active in producing •OH free radicals by breaking down the water molecule. The effect of pH in the grinding medium or in the water in which solids are added immediately after dry grinding showed that the lower the pH value, the higher the H2O2 generation. When chalcopyrite and pyrite are mixed in different proportions, the formation of H2O2 was seen to increase with increasing pyrite fraction in the mixed composition. The results of H2O2 formation in pulp liquid of chalcopyrite and together with pyrite at different experimental conditions have been explained by Eh-pH diagrams of these minerals. This study highlights the necessity of revisiting the electrochemical and/or galvanic interaction mechanisms between the chalcopyrite and pyrite in terms of their flotation behavior.IntroductionHydrogen peroxide causes nonselective oxidation of sulfide minerals if present in pulp liquid. Oxidation of sulfide minerals takes place when they are exposed to atmosphere and during the grinding process when the particle size is reduced for flotation. The oxidation of chalcopyrite leads to iron dissolution from the particle surface and from a metal-deficient, sulfur-rich surface (Fairthorne et al., 1997). Other studies report the formation of iron hydroxide on the surface with the metal ion dislodged on the surface (Buckley and Woods, 1984; Chander, 1991). The chemical reactions for the oxidation of chalcopyrite in alkaline and in acidic solutions with the addition of oxidants, such as oxygen or hydrogen peroxide, are shown in Eqs. (1) and (2), respectively (Shi and Fornasiero, 2010)."

Jan 1, 2015

By N. Edmonson

Introduction An examination of statistics for the world phosphate fertilizer industry since 1980 reveals that there is an increasing tendency for fertilizer-manufacturing activity to concentrate in the areas of phosphate-rock mining. The economic justification for this resource-oriented strategy is clear. The choice between shipping phosphate rock, a comparatively low-value product, and shipping a more valuable finished fertilizer product will always, as long as cost considerations control the decision, be resolved in favor of the latter. The historical existence of substantial phosphate fertilizer-manufacturing capacity, which is oriented toward fertilizer-consuming activities and dependent on imported phosphate rock, shows that narrow cost considerations have not always determined the industry's location. One is entitled to ask what conditions have changed to precipitate the observed relocations, and how permanent are these changes. These questions are the subject of this investigation. Recent trends in world phosphate trade Since 1980, the changing pattern of world trade in phosphate materials reflects an increased interest in manufacturing phosphate fertilizer in rock-producing areas. This is shown by the decline in the total tonnage of phosphate rock being traded worldwide compared to world consumption of phosphate fertilizers (Fig. 1). This relative decline has continued since 1984, which is a longer period of time than could be explained by temporary cyclical market factors. Other evidence corroborates this conclusion. The world's phosphate-rock production is relatively concentrated geographically. In 1992, the top ten producing countries accounted for 92% of world production. Figure 2 shows that the share of world fertilizer production in the top ten rock producers has increased. Yet, further evidence of the direction of trade changes can be had by looking at the pattern of the world's sulfur trade. The first step in the manufacture of any of the widely used phosphate fertilizer products is the acidulation of phosphate rock with sulfuric acid. In most instances, phosphate fertilizer producers have found it economical to produce their own sulfuric acid by burning elemental sulfur, and such operations account for over 60% of all sulfur consumption in the world. 1 Therefore, a concentration of phosphate fertilizer production in rock-producing countries should produce a similar concentration of sulfur imports in the same countries. Figure 3 suggests that there has been a tendency since 1989 for sulfur exports to go increasingly to the rockproducing countries. World phosphate-location strategy is not limited to the alternatives of shipping rock and shipping finished fertilizers. A third alternative consists of producing phosphoric acid, the principal phosphate fertilizer intermediate, at the rock deposit, and then exporting it to market-oriented ammonium phosphate plants. This arrangement offers the importing country the advantages of shipping a more concentrated product while retaining the economic multiplier benefits of a domestic high-analysis fertilizer industry. India, and several other countries, imports merchant-grade phosphoric acid to use as input for the domestic value-added fertilizer industries. For various reasons, the trade in phosphoric acid has never quite lived up to the promise suggested by the foregoing discussion. Figure 4 shows no growth in this trade in the last ten years, either in absolute terms or in relation to the world's consumption of phosphoric acid. Most of the decline in the trade in phosphorous in rock form has been replaced with trade in finished fertilizers. The trade in superphosphoric acid was a growth activity in the late 1970s with the growth in US exports to the USSR, and this trade survived the Carter-era embargoes of US-Soviet trade. However, no additional sizable markets for superphosphoric acid developed, and other suppliers sought out the Soviet market. The problem with superphosphoric acid is that the cost of its incremental concentration is as great as the savings from shipping the more concentrated product. The Soviet market was a special case. The political breakup of the Soviet Union disrupted the superphosphoric acid trade after 1991 and led to a shutdown of the US export capacity.

Jan 1, 1996

By S. D. Michaelson

Open pits and quarries are the major sources of all "hard rock" tonnage mined today. Normally, ore is fractured from the pit face by blasting and then truck-hauled to a primary crusher where processing begins; over- burden (or waste) is generally truck-hauled from the pit to dump areas. Truck haulage of blasted ore and overburden accounts for some 25 to 50 percent of total mining costs in a typical open pit and commonly is the largest single cost factor. Obviously then, cost reduction efforts should properly focus on improving existing haulage systems and developing new breakthrough techniques for material transport. Continuous flow systems for large tonnages ordinarily will result in a lower cost than batch systems such as truck or rail haulage. Continuous flow with pipelines for liquids and slurries, or conveyors for medium to coarse dry materials (in the -8 in. range) are the accepted economic answers for bulk materials handling over reasonable distances.

Jan 1, 1968

By Lee S. Richardson

Silicon is usually considered to be a useful metallic alloying element. To be more truthful, it is not a metal at all, but a semiconductor, whose electrical resistance (when pure) is high and decreases with temperature. We will join the metallurgists, at least for this paper, and refer to it as a metal. In its commercially available form, silicon is metallic in appearance, brittle, with a density of 2.33, less than that of aluminum. Silicon dioxide or quartz has a high heat of formation, which not only makes the metal a useful reductant for other materials, but also makes it difficult to reduce from its ore. The melting point is 1412°C, slightly less than steel, but substantially higher than aluminum or cast iron. The alloys of silicon with iron, usually called ferrosilicons, have some unique advantages. The melting points of most alloys are substantially below those of iron or silicon (Fig. 1). The two major compounds formed (FeSi and FeSi2) help somewhat in the reduction of silicon by their energies of formation, but the influence of these phases on the mechanical properties is more important. Four major groups of alloys are made -- silicon metal (>95% silicon), 75-85% ferrosilicon, 50% ferrosilicon, and silvery pig iron (12-22% silicon). The alloys between 50 and 65% silicon and between 25 and 40% silicon are normally avoided because of structural instabilities, presumably of the two compounds, leading to disintegration of the alloys on cooling.

Jan 1, 1974

By J. Herbst, C. C. Harris, G. Poling

The modern flotation machine is the result of decades of adaptation to a changing environment. In response to falling ore grades, and rising demands, tonnages, and costs, attempts are now underway to expand machine capacity by about an order of magnitude, while at the same time maintaining metallurgical performance and if possible reducing power requirements per unit throughput. Empiricism and rule-of-thumb have guided flotation machine design and scale-up, and a current need is for the development of a fundamental understanding of the subject. Design features of current and some obsolete machines are discussed in an attempt to outline those principles of flotation machine design which are known, and to delineate topics needing investigation. Attempts are made to distinguish between essential machine features required by the physics of the process, those features resulting from speculative theories on the flotation mechanisms, and features which are essentially styling variations. Topics discussed include: flotation mechanisms; tank and impeller/ stator design and dimensions; impeller speed; aeration; power consumption; particle suspension and dispersion; capacity; correlation of design parameters and operating variables; scale-up and scale- down; materials flow; problems in machine design. Design details and operating data for several current machine families are provided in Appendices.

Jan 1, 1976

By N. Sheikh

In galena flotation, lead ethyl xanthate, Pb(EtX)2, is precipitated and is physically adsorbed in the form of multilayers on the chemically adsorbed first layer of Pb(EtX). 1,2) The solid particles are coated with layers of Pb(EtX)2 in heterogeneous manner over surface areas possessing both anodic and cathodic character (3,4) It is anticipated that the mode of formation of Pb(EtX)2 and the number of ions present, together with stable or unstable by-product species, have great influence on the surface characteristics of galena. The information obtained from a study of these parameters may have important practical applications in flotation. Lead ethyl xanthate is sparingly soluble in water. The metal and xanthate ions released to the aqueous solution during its dissolution undergo various types of reactions depending upon the pH values of the system. Extensive work (5,6) has been carried out to elucidate the mechanism involved in acid decomposition of xanthate ions. Different decomposition paths (7,8) have been proposed for the hydrolytic decomposition of xanthate in neutral and alkaline solutions, The concentrations of lead ions vary due to a number of chemical reactions, regulated by the pH and the temperature of the bulk phase. The hydrophobic character of Pb(EtX)2 may change with the nature of chemical reactions. Some of the numerous by-product species in solution may adsorb on the solid and change the properties of surface film either favourably or adversely. The flotation performance of galena, therefore, may depend to a considerable extent on the physical and chemical stabil¬ity of Pb(EtX)2 layers. Since little work has been reported in literature dealing with the stability of Pb(EtX)2 and its correlation with the flotation of galena, attempts have been made In this study to evaluate the behaviour of freshly formed Pb(EtX)2 in aqueous systems at various pH values.

Jan 1, 1971

By George M. Meisel

This paper is devoted to a discussion of the factors governing design of concentrators for large grinding circuits. Emphasis is placed on the manner in which use of ever larger grinding mills has affected the size of grinding bays, service cranes, gear reducers and electric motors, and the selection of ancillary equipment for cushioning of the starting load of large mills. Information is presented on the effect of using large grinding mills on the capital and operating costs of concentrators, e. g. : (Fig. 1) ? Benefits in lower cost of mills, drives and materials handling equipment, plant space, power, grinding media, operating labor and maintenance, and in ease of instrumentation and automation. ? Penalties in distribution of materials from the grinding mills to multiple lines of equipment which have not been developed to commensurately large sizes, and higher cost of ancillary equipment.

Jan 1, 1968

By Gunter Fauth

The setting of tasks for the process control of coal cleaning, and in this connection the requirements for instrumentation can be classified into the following three fields: - Monitoring the operation of individual units, or process steps, - Control of units or process steps, - Control of the entire coal cleaning process with the intention of optimizing the operation and the profitability of the process. Instrumentation is affected by the type of cleaning processes. For introduction Figure 1 shows the simplified flow sheet of coal preparation which is usual in the German Ruhr District and in which desirable places for the measurement of ash, moisture and sulfur content are marked. The preparation plant is supplied with run-of-mine coal from the shaft via a homogenization facility. In a first step of primary classifying the raw feed coal is screened at about 10 mm. The raw coarse coal ( = 10 mm) is sorted by jig washers or heavy-medium separators. the raw fine coal (< 10 mm) at first is pneumatically sized at about 0.5 to 0.75 mm. The fines, the aspirated dust, are a finished partial product which will be added to the final metallurgical or steam coal. The material 10 to 0.75 mm subsequently is sorted in fine coal jigs and dewatered in centrifuges. The sludge obtained with the wet cleaning processes is dewatered in thickeners and fed to the flotation. Concentrate and tailings are dewatered by filters or bowl centrifuges and by chamber filter presses or belt filter presses, respectively. The partial products coarse coal, fine coal, flotation concentrate, aspirated dust, and middlings are blended to result in the sellable products metallurgical and steam coal.

Jan 1, 1984

By D. A. Norrgran, J. A. Wernham

Introduction In view of the continuing depletion of natural resources, requirements for energy conservation, plant optimization and hazardous waste management, and environmental consciousness, recycling and secondary recovery of materials are being developed with increasing interest Many secondary recovery processes are being developed that apply mineral processing technology. Gravity separation, magnetic separation and flotation have all emerged as explicit methods for recovering residual values from various process streams and hazardous constituents from waste streams. Recently, a technique for concentrating metallics has been successfully reintroduced. The concept of the alternating magnetic field eddy-current separator was developed over a century ago using rudimentary electromagnets (Patent 400317 issued to Thomas Edison on March 26, 1889). Widespread acceptance was, however, hindered by high costs, marginal results and poor economic incentives for secondary recovery. With the recent increased interest in secondary recovery and the development of high-energy rare earth permanent magnets, the eddy-current separator has now gained prominent acceptance. The separation forces imparted by an eddy current separator are the function of the magnetic field intensity and the alternating frequency of the magnetic field. The evolution of permanent magnets has provided a cost effective alternative for the generation of high-intensity magnetic fields. High-energy rare earth permanent magnets have substantially reduced the capital and operating costs over the electromagnetic circuits employed in antecedent eddy-current separators. Specifically, in recent years, the strength of permanent magnets has increased several fold with neodymium-boron-iron rare earth magnets now providing an energy product of 35 million gauss-oersted. Figure 1 shows the evolution in the strength of permanent magnets. The development of these rare earth magnets has led to the design of circuits possessing a magnetic force an order of magnitude greater than that of conventional permanent magnetic circuits. The eddy-current separator has been successfully applied in several metal sorting and recovery operations. Most common is the sorting of metal from shredded automobile scrap and municipal waste. With the advent of high-frequency, high-intensity magnetic fields, the separator has advanced to the point where it has direct application in the beneficiation of fine sized metals. Relatively fine sized (-1/4 in.) metal bearing slags and spent foundry casting sands as well as precious metal hearing electronic scrap demonstrate excellent metallurgical response to the eddy-current separator, and applications have progressed to finer materials and more selective separations. Theory Electrical currents are induced in all conductors when exposed to an alternating magnetic field. The induced current generates a magnetic field in the conductor that opposes that of the alternating magnetic field. Figure 2, is a schematic illustration of generated eddy currents. In this particular example, the alternating magnetic field is produced by a series of permanent magnets mounted on the circumference of a rotor. The permanent magnets have alternating polarity. As the rotor revolves, an alternating magnetic field is produced, and the rate of revolution determines the frequency of the alternating magnetic field. When a conductor, such as a metallic disc in the illustration, is placed in the alternating magnetic field, a closed loop current flow occurs. The current loop in the conductor produces a magnetic field that is a mirror image of the alternating magnetic field. At any point in time, the induced magnetic field in the conductor directly opposes the alternating magnetic field. This opposition of magnetic fields produces an instantaneous repulsion in the conductor. The conductor is consequently repelled from the rotor. The alternating magnetic field has no effect on nonmetallic materials as they pass through the magnetic field and discharge the rotor in a natural trajectory. [ ]

Jan 1, 1992

By A. G. Mayton, D. H. Ambrose, C. C. Jobes, N. K. Kittusamy

In a systematic study, the National Institute for Occupational Safety and Health (NIOSH) evaluated seat designs in low- and mid-seam shuttle cars during production operations at two underground coal mines in southern West Virginia. The purpose was to support, with additional data, earlier findings that NIOSH ergonomic seat designs (featuring viscoelastic foam padding and lower-back support) may help reduce health risks to operators of coal mine shuttle cars. Eight shuttle car operators evaluated seven seat designs (one already in use in each vehicle and five NIOSH designs) relative to perceived and measured whole-body vibration (WBV) exposure (including vehicle jarring/jolting) and discomfort. Operators’ perceptions using a visual analog scale (VAS) and questionnaire ratings were compared with International Standards Organization (ISO) 2631-1:1985 fatigue-decreased proficiency (FDP) limits and measured WBV levels on low- and mid-seam shuttle cars. Objective and subjective data results indicated that NIOSH seat designs (with added adjustability, lower-back support and improved seat padding) performed better to reduce vehicle jarring/jolting levels and that shuttle car operators favored them over existing seat designs. The NIOSH low- and mid-seam shuttle car seats showed 45 to 77 percent better performance in FDP and 9 to 60 percent better performance overall in operators’ ratings. Considering the VAS results for low- and mid-seam shuttle cars under no-load conditions, operators rated the level of jarring/jolting 18 to 89 percent lower with the NIOSH seats. Reductions in measured vehicle jarring/jolting were 19 to 46 percent for the three-directional vector sum accelerations relative to the existing seats on the low- and mid-seam shuttle cars. Questionnaire responses indicated that operators for both shuttle car models rated NIOSH seat designs as more comfortable overall. Vehicle operators most frequently suggested adding armrests to improve the seats on the mid-seam shuttle car. A suggested improvement for the low-seam shuttle car was to make the seat a better fit for the operator compartment, which would enhance clearance between the operator and vehicle controls and allow for better seat adjustment and operator visibility.

Jan 1, 2009

By E. D. Attanasi, M. W. Bultman, J. H. DeYoung

The 1987 recovery in the US mining industry permitted modest increases in exploration expenditures that year (Fig. 1). Favorable market conditions apparently allowed the gains to be sus¬tained in 1988. There was great uncer¬tainty early in the year as to whether world and US economic growth would be a casualty of the October 1987 worldwide stock market crash. By nearly all measures, the performance of the US minerals industry was strong¬. A weak US dollar and the strong growth of worldwide capital spending resulted in in¬creased US exports of con¬sumer and producer durable items as well as strong domes¬tic demand for metals. In fact, 1988 US steel industry exports reached levels not attained since the mid-1970s. It was re¬ported that steel industry labor productivity is now roughly twice the 1981 level. Among metals with signifi¬cant average nominal price increases in 1988 over 1987 levels were copper (43%), alu¬minum (52%0), and zinc (44%). Even though domestic copper production has grown since 1984 by 30% in mining and 24% in refining, em¬ployment in mining and milling is 4% below the 1984 level. Domestic unit costs are reported in the range of $1.10 to $1.33/kg (50 to 60 cents per lb). The US base metals industry is proba¬bly in its best cash position in many years. However, there has not been a large increase in exploration expendi¬tures. This is due mostly to the percep¬tion that worldwide capacity can easily be increased. Industry reports do show that "low cost" copper producers have been buying reserves from weaker com¬panies. The 1987 Society of Economic Ge¬ologists (SEG) survey of exploration activity indicated that 95 cents out of every exploration dollar spent by US and Canadian firms was for base and precious metals (Economic Geology, January 1989). Press reports, though, make it clear that most of that spending was targeted for precious metals. US claim staking data (Fig. 2) rein¬forces this suspicion. The apparent lag in new claim filings in Alaska and phe¬nomenal growth in filings in the lower 48 states suggests that exploration is directed at relatively low risk targets. In the conterminous 48, more than 40% of the new claims were made in Nevada, indicating an emphasis on gold (although even Nevada had some base metals exploration). Even with a price decline during 1988, the difference between the gold price and average global "cash" production cost of $7.30/g ($227 per oz) still leaves room for an attractive return (Northern Miner, 1988). Exploration plans and results Metals Economics Group (Halifax) indicated in its 1988 exploration survey that exploration expenditures by US and South African firms would be at about 1987 levels. It also reported that Canadian and Australian firms were ex¬pected to reduce their exploration spend¬ing significantly. Firms in both coun¬tries were caught in changes in tax laws. In Canada, the Mining Ex¬ploration Depletion Allow¬ance (MEDA) once permitted generous tax write-offs to in¬dividuals investing in miner¬als exploration. It was to be replaced in January 1989 with the Canadian Exploration In¬centives Program (CEIP). Although structured and ad¬ministered differently than MEDA, CEIP can provide an equivalent or possibly greater financial incentive for min¬eral exploration, for junior mining companies. In 1987, it is estimated that junior com¬panies accounted for two¬-thirds of the off-property (or grass roots) exploration ex¬penditures in Canada. Australia will revoke the tax exemption for gold in 1990. Australian operators, therfore, were expected to concentrate efforts on speeding up pro¬duction during 1988 and 1989. In 1988, Chile and Mali announced special efforts to attract gold explora¬tion by foreign companies. The Cana¬dian government continues to express concern about the write-off (and drawdown) of base metal reserves. Falconbridge did announce a new initiative to identify additional base metal reserves in the Sudbury district. Discoveries Gold deposits dominated discoveries

Jan 1, 1989

By Y. Guan

The adsorption of zinc species onto silica in ammonical solutions has been studied. Adsorption isotherms reveal that increasing adsorption occurs as the solution pH is made more alkaline. Fr-IR spectroscopy revealed that the adsorbed species is a zinc ammine complex.

Jan 1, 1993

By C. J. Konya, A. Konya

"Presplitting is a form of blasting that when executed properly will create a smooth wall that will minimize secondary conditioning. In recent years, presplitting has become a popular technique to be used in both the mining and construction industry, however, presplitting fails on many occasions because of ‘geologic conditions’. This is typically because of improper explosive loads consisting of overloading and underloading blastholes. In this paper the authors introduce new factors such as a presplit factor which varies for different rock types, selection criteria for the spacing of presplits, the optimization of explosive load, as well as prediction methods for the environmental affects for the technique of Precision Presplitting. BACKGROUND Methods of controlled blasting in which a smooth, stable wall could be blasted have been an important consideration since blasting in mining and construction has begun. How can one use an explosive, with its massive energy and power, to break a non-homogenous rock without causing backbreak, poor walls, or deviations in the wall over large distances? The blasting industry has known for a long time that blasting ‘high benches’ would result in better walls and less backbreak. However, this was not a sufficiently controlled technique for critical projects, such as the Niagara Power Plant. This was one of the main challenges Hercules Powder faced when they began the project. In order to achieve this, they used a new tool in the explosive engineer’s toolkit, presplitting. The presplitting done on the Niagara Power Project utilized 1 ½” x 8” (38mm x 203mm) 40% gelatin dynamite in 2 ½” (63.5) diameter boreholes. This was done on multiple levels with benches between 12 feet to 52 feet (3.6m to 15.8m) with a total powder factor of 0.75 pounds/cubic yard (0.45 kg/m3). The spacing on these holes ranged between 18 inches to 24 inches (0.46m to 0.61m), center to center (Langfors & Kihlstrom, 1973). The strange aspect of this project was that this “lightly loaded” closely spaced row was fired before the production blast, yet this project produced some of the best walls seen at that time directly from blasting. In today’s blasting industry, presplitting is a more common way to produce smooth, stable high-walls for both the construction and the mining industry. Today, explosive loads for traditional presplitting is generally measured in pounds per foot (kilograms per meter) and typically ranges from 0.30 lb. /ft. to 0.5 lb. /ft. (0.45 kg/m to 0.75 kg/m). MECHANICS OF PRESPLITTING When analyzing a blasting process like the Niagara Project, many wonder how did that work when normally confining a charge would cause cratering and increased backbreak. Since then, presplitting mechanics have been studied extensively. It has been shown in many models that presplitting is not achieve through the collision of shockwave, but by gas pressure in the boreholes. In addition to models and finite element simulations, this has been proven full scale using Pyrodex, a propellant, to create a presplit plane with no shock wave present (Konya, Dean Barrett, & Smith Jr, Presplitting Granite Using Pyrodex, A Propellant, 1986)."

Jan 1, 2017

By N. T. Rempe

The underground voids that result from mining provide opportunities for deep geologic waste disposal (DGWD). Such disposal could solve many environmental problems. DGWD takes careful planning, technology transfer and true partnership between waste generators and mine/repository operators. The US government is now planning on using specially mined excavations to dispose of radiotoxic and mixed waste. Using the experience gained from the domestic projects that are now in preparation and from foreign repositories that are now in operation, US mines can claim their rightful share of the growing market for DGWD.

Jan 1, 1997

By III Feeley

Coal is the nation&apos;s most abundant fossil energy resource and serves as the primary fuel for the U.S. electric-power industry. However, its continued and expanded use is often challenged by the nature and amount of its associated impurities, such as mineral matter, sulfur, and trace elements. The moderate- to high-sulfur content of many U.S. coals is of particular concern today as potentially more stringent regulations requiring further reductions in sulfur dioxide emissions are being considered. The most prevalent method currently employed to control SO2 emissions from coal-burning facilities is post-combustion flue-gas desulfurization. However, physical coal cleaning (a.k.a. beneficiation, preparation) methods can also be effective in removing sulfur and ash impurities from coal prior to combustion. In a typical physical cleaning operation, raw coal is crushed to about 50-mm (2-inch) topsize, and then screened into coarse, intermediate, and fine size fractions. Crushing liberates some of the ash-forming minerals, including the portion of inorganic sulfur (pyritic) not chemically bound to the coal matrix. The percentage of impurities liberated generally increases as the coal particle size is reduced. Coarse- and intermediate-sized coal particles are typically subjected to specific gravity-based cleaning methods, while fine-sized (less than 0.5-mm) coal particles are beneficiated using froth flotation, a technique based on surface property differences. Greater cleaning potential exists at finer sizes because of increased liberation of impurities, but this potential is not fully realized because of inefficiencies associated with fine particle separation using state-of-the-art coal cleaning technologies.

Jan 1, 1990

By Charles L. Kimbell

The year 1988 for the minerals indus¬try was one of favorable worldwide economic conditions for continued, rationally constrained growth. There was continued improvement in relations between market economy nations and the Soviet Union and China. The "shooting war" between Iran and Iraq ended. Soviet troops withdrew from Afghanistan. And conditions were generally favorable for economic growth in developed market economy countries. These favorable conditions were darkened only somewhat by the continuing foreign debt crises discernible in some major mineral producing developing market economy countries. However, there were situations developing that became major headlines in the late spring - situations that may have pronounced effects in 1989. The most significant event is the muddled situation in China. There is a good chance of worsening international relations and consequent restraint of development projects that could prove beneficial to China and her international partners. Of only slightly lesser evident significance was the death of Ruhollah Khomeini in Iran. This could lead to a variety of paths for the new Iranian leaders. Continued outbreaks of ethnic unrest in the Soviet Union clearly presented problems to the Gorbachev regime. This unrest has raised questions of how far the doctrines of "glasnost" and "peristroika" would be extended, including extensions into the minerals field. Another area of unrest is Panama with its tainted election and the Western Hemisphere&apos;s obvious dissatisfaction with the Noreiga regime. While not a direct threat to any major mineral industry enterprise, the political situation certainly presents a potential threat to the Panama Canal. That threat would have considerable impact on world

Jan 1, 1989

By Zygmunt Sadowski

Problems encountered in barite flotation from various waste materials such as spent drilling muds are likely to be closely connected with the effect of chemical additives and metal ions present either added or present as contaminants, on the flotation. Fuerstenau and Palmer (1976) have studied in detail the adsorption of multivalent cations onto oxide and silicate minerals. It was observed that the adsorption of a multivalent metal species exhibits a sharp pH dependence which is related to the formation of hydroxy complexes of the metal ions in solution. Investigations on the recovery of barite from tailings ponds and mining wastes (Sullivan and Lamot, 1981) have shown that such barite materials can contain large quantities of carbonate and silicate minerals (including clay minerals). Also iron oxide slimes can be present. From these substances cations such as Ca2+, Mg2+, Fe2+ and A13+ can potentially dissolve and be present in the aqueous phase accompanying the various minerals. These ions and their hydrolysis products can have a substantial effect on any subsequent flotation scheme. The present study investigates the effect of the noted ions on both the stability and electrokinetic behavior of barite suspensions.

Jan 1, 1986

In addition to capital and operating costs, the accurate estimation of ore reserves is a key component to the successful outcome of any feasibility study. In recent years, there have been many project failures caused by the improper estimation of ore reserves. The accurate estimation of an ore reserve relies heavily on an understanding of the geology and the underlying assumptions unique to the estimation techniques being used. These assumptions are reviewed, and the shortcomings of the estimation techniques and their possible impact on a given project&apos;s economics are discussed. The latest developments in geostatistics in overcoming existing reserve-estimation problems are presented.

Jan 1, 1998