Search Documents

By P. Henderson, M. E. Morris, W. A. Johnson, F. D’Alessandro, D. Wilton

"The objective of this research is to develop and apply computer models to evaluate the potential lightning impacts on underground coal-mining. These models can then be utilised to assist in the design of effective controls. This project will provide a significantly improved level of knowledge and control over current lightning abatement techniques. The findings may also be applied to open cut and coal preparation situations. Computer modelling identified that by isolating cased boreholes from underground conductive media such as roof mesh, and placing spacings between roof mesh the risk of an ignition can be reduced by more than a factor of ten. These controls should be applied in conjunction with minimising the potential for a flammable atmosphere to exist underground and ensuring that there is no transmission medium for the lightning to reach the atmosphere. INTRODUCTION The objective of this research was to develop and apply computer models to evaluate the potential lightning impacts on underground coal-mining. These models could then be utilised to assist in the design of effective controls. If successful this project would provide a significantly improved level of knowledge and control over current lightning abatement techniques. The direct potential for harm from lightning has long been recognised for the surface facilities of coal mines. However recent events at Blakefield South in NSW on January 5 2011 (DTI, 2011) and at Sago mine in the USA in 2006 (MSHA, 2007) have suggested that there is potential for lightning to cause significant damage to the underground workings of a coal mine. A very detailed analysis carried out by as part of the MSHA investigation into the SAGO disaster by Sandia Laboratories identified at least ten other incidents over the past thirteen years where lightning had probably caused the ignition of a sealed goaf area of a mine (SANDIA, 2011). In addition there is a long history of lightning related incidents in South African coal mines (Geldenhuys, 1985). Fortunately in those cases no lives were lost. The event at Blakefield South has suggested that there may be the potential for ignition to occur in an active longwall goaf. The potential for a lightning strike to ignite a flammable atmosphere in an underground coal mine has been demonstrated from the past experience both here and overseas. It requires three things: • Lightning • A mechanism to convey the lightning underground to the flammable atmosphere • A flammable atmosphere."

Jan 1, 2016

By R. J. Sterrett

To the average mine operator, the implementation of environmental regulations are viewed as a drain on the profitability of the mine. Since the birth of environmental awareness in the late 1960's, which led to the passage of the National Environmental Policy Act (NEPA) in 1969, and through the publicity brought about by the discovery of Love Canal in 1978, the public are clamoring for increased environmental protection. It should be emphasized that the concern regarding the issues of the handling and disposal of nuclear and toxic wastes is not limited to a few overzealous environmental advocates. Toxic waste issues have "grass roots" interest and support. A reflection of this support has been the passage of key pieces of federal legislation. . Of particular interest are the following acts: Clean Water, Toxic Substances Control, Surface Mine Land Reclamation, the Resource Conservation and Recovery Act (RCRA) and the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA). The last act is often referred to as "Superfund". Both RCRA and CERCLA have been re-authorized and amended, and in their re-authorization they have been substantially strengthened. Of the last two pieces of legislation, RCRA is the most powerful in that it governs the handling of hazardous wastes from "birth to grave". CERCLA was established to cleanup abandoned waste sites which are threatening human health or the environment. These cleanups can be undertaken by the government and then billed back to the previous owners or to the disposers at the sites.

Jan 1, 1988

By H. F. Ghezzi

The indirect method of drying coal fines is applied to filter cakes which ordinarily contain 22 to 30% moisture and are not readily transportable. The "Thermal Dryer", which operates on the mass transfer principle, has found wide use in coal preparation plants. The thermal dryer is penalized in operation by the necessity of adding coarse coal to the wet fines before entering the dryer body in order to produce a permeable bed, and thus enable hot gases to uniformly contact the wet mass. The ratio of coarse coal to fines varies from 2:1 to as much as 4:1, depending on the average particle size, moisture, and ash content of the fines.

Jan 1, 1985

By Malcolm Scoble

This contribution examines the motivation and prospects for mining companies to become Learning Organizations and integrate Lifelong Learning into their culture. Mining Schools have a potentially central role to play in developing Learning systems for access by industry. Reference is made to initiatives to develop a system that is based on collaboration between UBC, Edumine and the Canadian Institute of Mining, Metallurgy and Petroleum. Recent experiences with this model are reviewed.

Jan 1, 2005

By Parris A. Lyew-Ayee

This paper is the first preliminary report on the bauxites and terra rossas of the Caribbean. It concentrates on the islands of the Greater Antilles, and for reference purposes the Yucatan Penin- sula is included. At this point, observations made in Jamaica, Haiti, and the Dominican Republic are compared with reported information on Puerto Rico, the Bahamas, Cuba, the Cayman Islands, and the Yucatan Peninsula with regard to occurrence, as well as physical, chemical, and mineralogical composition. From this, an attempt is made at classifying the types of bauxites in the Caribbean, indicating the best reserves estimates, and the process ability of these bauxites. Some suggestions are also provided to fuel the controversy over the likely source material(s) or origin of the Caribbean bauxites.

Jan 1, 1984

By J. A. Finch, B. J. Huls

Accurate level detection is required to make full use of level in optimizing control strategies for flotation columns. Techniques based on pressure and electrical conductivity are compared. Pressure and conductivity profiles give good agreement on level. Level calculated from single and multiple pressure values became more accurate using, in order, one, two and three sensor locations. The level estimate remained in error, however, because, unlike the collection zone, froth zone bulk density varies with height. A conductivity probe continually updating the conductance profile is a practical method of obtaining an accurate level.

Jan 1, 1990

By G. S. Dobby

High-intensity wet magnetic separators have been successfully introduced into the mineral processing field over the past ten to fifteen years, due largely to rapid advancements in magnet design. Wet magnetic separation, until recent years, was applied solely to the concentration of minerals of high magnetic susceptibility, such as magnetite, at relatively coarse sizes. Now, however, high-intensity separators are capable of treating weakly paramagnetic minerals and have extended the range of treatable particle size down to about one micrometre(1,2). . One of the more recent-high-intensity separators developed is the Kolm¬Marston Marston type high-gradient magnetic separator (HGMS) (3,4) It consists basically of an iron-clad solenoid surrounding a matrix material - a fine, ferromagnetic steel wool or expanded metal lath. A schematic diagram of the device is shown in Figure 1. Large, highly localized, pertebations of the magnetic field are created by the ferromagnetic matrix. It is these field gradients that are instrumental in developing large magnetic forces which act on the mineral particles. Operation of the separator is simple. Slurried sample is fed through the matrix and, depending upon the mineral parameters of particle size and magnetic susceptibility and. the operating parameters of flow rate, field strength and feed weight, some particles will be attracted to and adhere to the magnetized matrix, while the others will flow through the matrix. The separation is completed by later removing the background magnetic field and flushing the captured mineral particles into a separate container. The process can also be applied on a continuous basis (S).

Jan 1, 1977

Operation of a pilot-scale Floatex density separator was studied using a pyrite concentrate slurry feed. Experimental measurements were further utilized in parameterization of a hindered settling simulation model. The model incorporates particle slip velocity calculation and also a separation efficiency function, adjusted to describe the feed material characteristics. The model was used to compute the overflow and underflow compositions when both fluidization bed pressure and teeter water flow rates were varied. In addition, prediction accuracy and the model validity were evaluated. The simulations gave good results when the teeter interstitial velocities were moderate enough to avoid excessive turbulence in the fluidization. Prediction of the cumulative overflow and underflow size distributions in most experiments yielded essentially less than 10% relative error between the sample data and the estimated value of the 50% passing sizes.

Jan 1, 2011

By Jacques L. Mauboussin

The EUROPEAN ORGANIZATION for NUCLEAR RESEARCH (CERN) has undertaken the construction of a LARGE ELECTRON POSITRON COLLIDER (LEP), near GENEVA (Switzerland). The facility includes the main 27 km long tunnelled ring, 18 shafts, 20 experimental caverns and many auxiliary galleries. Roughly 800 000 cu.m were excavated in the molasse at 50-140 m depths, using roadheaders for caverns and auxiliary tunnels and 3 WIRTH, 4.5 m diameter, fullface TBMs for the main circular tunnel. Each TBM performs 25-30 m/day. Provisory lining behind them uses either precast concrete elements or shotcrete. Works a e being carried out by a joint-venture of European contractors led by FOUGEROLLE (France).

Jan 1, 1987

By David Wilburn

Recycled materials are increasingly being used in road construction to supplement natural aggregate derived from crushed stone, sand, and gravel. An understanding of the amount of substitution that is taking place, its economics, and factors affecting the level of substitution is useful in estimating the potential for recycling and in assessing the total supply of aggregate. While U.S. consumption of recycled aggregates from crushed concrete is estimated to have increased 160 percent between 1994 and 1996; it comprised less than 5 percent of total aggregates consumed in 1995. Construction waste supply is regional, and is determined by infrastructure decay and replacement rates. Aggregate recycling rates are greater in urban areas where infrastructure is being replaced, natural aggregate resources are limited, disposal costs are high, or strict environmental regulations prevent disposal. Recycling is expected to increase as construction contractors attempt to save on transportation, disposal, and new material costs. Aggregate producers include recycled material as an option to consumers in order to prolong the life of their reserves and improve their range of products. Recycled aggregates can be a supplement for natural aggregates in selected applications, but their use should be evaluated locally based upon relative cost, quality, and market factors Because aggregate recycling is often affected by local and regional transportation systems, disposal and tipping fees, resource supply, the market for specific products, and municipal support, costs for three representative fixed site operations of different sizes were modeled. Under study conditions, all were found to be profitable, but highly dependent upon local tipping fees and market prices, which can differ significantly by location. Smaller operations were found to have different operational dynamics, often requiring creative marketing or incentives to maintain profitability.

Jan 1, 2001

By Kevin Fitzpatrick, Carmen Scalise, Patrick Jensen

"The Metropolitan Water Reclamation District of Greater Chicago (MWRDGC) owns and operates the Tunnel and Reservoir Plan (TARP) system which was adopted in 1972. TARP is a network of 110 miles of deep tunnels and ultimately 3 large reservoirs to combat waterway pollution and flooding within a 350 square mile area served by combined sewers. The original TARP concept included additional tunnels to convey CSOs from the largest storms to the reservoirs. With the initial TARP tunnels complete and the reservoirs nearing completion, MWRDGC commissioned hydraulic and hydrologic modeling studies to analyze the benefits of additional conveyance tunnels. These updated studies optimized the configuration of additional tunnels considering integration with potential future local sewer system upgrades. The alternatives considered several routes of 25, 30, and 35 foot diameter tunnels, ranging from 10 to 18 miles. Alternatives were analyzed based on projected reductions to basement flooding compared to the relative costs. TUNNEL AND RESERVOIR PLAN After World War II the Chicagoland area underwent rapid growth and development. With the Metropolitan Water Reclamation District of Greater Chicago's (MWRDGC) service area becoming increasingly impervious, the flat Chicago landscape was increasingly at risk of significant flooding. In the mid and late 1950's, Chicago experienced multiple extreme storm events that had significant impacts on the city and generated the momentum necessary to initiate what would ultimately become one of the world's largest civil works undertakings. In 1957 a Flood Control Coordinating Committee was formed, consisting of representatives of the MWRDGC, Illinois Department of Public Works, Cook County, and the city of Chicago, to review various plans and develop recommendations for a course of action. With more than 50 alternative concepts being identified, the Tunnel and Reservoir Plan (TARP), which itself is a composite of various alternatives, was adopted the by the Metropolitan Water Reclamation District of Greater Chicago (MWRDGC) in 1972. The need to adopt a long term plan was further influenced by the Clean Water Act, which was enacted only 8 days prior."

Jan 1, 2016

By Pelin Altinkaya, Maria Leikola, Jussi Liipo, Mika Haapalainen, MARI LUNDSTROM, Eero Kolehmainen

Chloride leaching has many advantages compared with other alternative processes to cyanidation because it has increased metal solubility, improved redox behavior and high leaching rate properties. Also, chlorination is a nontoxic and environmentally friendly process, which is sought by the mining and metallurgy industry. In addition to these advantages, chloride is an effective reagent for the dissolving of metals from refractory ores and process residues that have trace amounts of valuable metals waiting to be valorized. 

By Thomas E. Howard

Engineers today face a tremendous challenge. Growing population and rising standards of living all over the world are creating unprecedented and accelerating demands on and for all kinds of technology. At the same time, the public is becoming more and more conscious of--and concerned with--the impact of technology on human welfare. The growing controversy over the Supersonic Transport is a case in point, It is clear that the modern engineer must expect to spend a growing share of his time considering this dilemma and evaluating the tools that are available to him, not only with respect to their adequacy for the job at hand but also their capability for meeting the increasingly demanding--and, in many cases, conflicting--requirements of the future. This meeting seems a particularly appropriate place to speculate about the future of mining technology. The summary of the state-of-the-art in surface mining contained in the papers scheduled for the International Conference, together with the recently published Surface Mining volume, constitute not only a major contribution to the technical literature but also form an impressive record of technologic progress. That record, and the advanced technology displayed in the exhibits, and to be discussed in the SME technical sessions demonstrate engineering achievement in which the mining community can justly take pride.

Jan 1, 1968

By Dan Nilsson

Open pit mining is the strong sector of the American mining industry. In the middle of the 60's. 17-18% of the ore in metal mines was mined with underground methods. From the middle of the 60's to 1980 the production in open pit metallic mines increased from about 400 to close to 600 million short tons while at the same time the underground mine production decreased a little, from about 90 to about 80 million tons. Less than 15% of the ore prodction now come from underground mines. Large amounts of waste rock were also handled in the open pits. In the middle of the 60's about 600 milion tons were handled, in 1980 1,200 million tons were moved. This means that the average stripping ratio increased from about 1.5 to over 2.0 tons of waste rock per ton of ore, figure 1.

Jan 1, 1983

By Carl C. Martin

The treatment of ores in preparation for fatty acid flotation is characterized by a wide divergence in methods, and attempts to define "common practice", even for the same type of mineral, are usually of little value because of the numerous exceptions. Such factors as desliming, pulp density, pulp temperatures, and reagents for conditioning are successfully employed under conditions representing almost extreme opposites. More precise control of variables is necessary than with sulphydric flotation processes It appears likely that variations result from independent development of a process from the multitude of variables that characterize fatty acid flotation and the ores of non-metallic minerals. Consequently, a symposium is a suitable way of presenting a summary of pretreatment methods for fatty acid flotation processes, together with froth control practices, as they exist today.

Jan 1, 1959

By Tzou-Shin Ueng

Rock reinforcement of rock anchors and rock bolts are commonly used for the support of large rock caverns. The rocks at the location of most large underground openings are usually under very high initial stresses prior to excavation. Hence, the stress redistribution caused by excavation will induce considerable rebound deformations of rocks surrounding the caverns. Since the pressures exerted by the reinforcement are generally far below the initial rock stresses, the reinforcement will be stretched along with the rock deformations, and the stresses in the reinforcement increase accordingly. It is not uncommon for the stress in the reinforcement to reach the yield strength, and in some cases the reinforcement may even have failed. Therefore, the increase of stresses caused by the rebound deformations of rocks should be taken into account in addition to the force required to stabilize the caverns. It was found that the measured stress increases of the prestressed tendons after installation were in good agreement with those computed based on the measured rock deformations between surface and the anchoring point of the reinforcement. The rebound rock deformations and the stress increases in the reinforcement can be estimated based on the results of the finite element analysis and experiences in previous field measurements incorporated with considerations of the geologic conditions, rock properties, rock reinforcement and construction procedures.

Jan 1, 1986

By James E. Lawver

At the present time, the Florida phosphate industry is experiencing one of the worst marked slumps in its one hundred year history. Recent agriculture over-production has caused low grain prices such that the net income of U.S. farmers is expected to drop to its lowest level since the 1932 depression. The farmers' low income, along with high interest rates that preclude them from borrowing to purchase fertilizer, make the immediate U.S. phosphate market outlook bleek at best. The export outlook is also pessimistic due to world recession and the U.S. dollar's high exchange rate. In June, 26% of the phosphate industry's workers were laid off for an indefinite period of time. Despite the immediate painful slump, the long-term outlook for the industry looks good. Florida has enormous reserves and will continue to produce a third of the world's phosphate supply simply by making changes in the present system of mining, beneficiation, waste disposal and land reclamation.

Jan 1, 1983

By Z. Man, X. Zhu, Y. Xian, Y. Tao

"Fine coal separation has been always concerned. The froth flotation is not efficient in desulfurization because of the low rate of sulfide liberation from raw coal, the natural hydrophobicity caused by sulfur concentration on the surface of sulfide, and the presence of large amounts of middling feed. An efficient centrifugal gravity separator was employed to separate for Shandong –0.5mm high sulphur coal, the partition curve of centrifugal separator was obtained with conclusion that the Ecart probable error value of the separator is 0.095, the imperfection I value is 0.128. Finally, comparing with the coal flotation using progressive release method, the result shows that the effect of the desulfurization with centrifugal gravity force field based on density difference between coal and minerals are much better than that of the floatation which operates based on the difference in surface properties. It provides a efficient technical way for fine coal separation. INTRODUCTION Coal plays the most important role in the energy consumption in China. Although natural gas, wind energy, nuclear power has made great progress in recent years, but the share of coal in the final energy consumption accounts for 70-80%, which is determined by energy storage of China. Under the requirement of environmental protection, the clean utilization of coal resources becomes more and more important, and the need has already been identified. Coal washing and processing plays an important role in the process of high-efficiency and clean utilization of coal. For the separation of fine coal, flotation is a traditional method for effective separation and has been used in large scale industrial applications in coal preparation plant. However, for the separation of difficult-to float coal, especially fine oxidized coal and low–rank coal with hydrophilic surface, flotation is usually inefficient [1-3]. Although many pretreatment methods have been adopted, including grinding, microwave pretreatment, new flotation reagents, the problem of efficient separation has not been completely resolved [4-6]. Thus, an enhanced gravity separation method using particle density difference rather than hydrophobic difference was proposed for the separation of fine coal. Many research results have proved that this is a practical and effective method of sorting. R.Q. Honaker used Falcon C10 concentrator, Knelson centrifugal separator and spiral separator to clean the fine coal with size of 600*210 µm and 210*37µm, the effects of different operating parameters on the separation index was discussed. The results show that the separation density of Falcon can reach 1.6, and the Ep value can reach 0.1-0.15. This paper revealed that for the separation of fine coal with high sulfur content or fine grained content. Falcon has high separation efficiency with low cost. Separation results present in another paper showed that the desulfurization efficiency of inorganic sulfur was better than that of flotation [7-8]."

Jan 1, 2017

By A. Noble

"Linear circuit analysis (LCA) is a fundamental tool that may be used to evaluate, design and improve the performance of mineral separation. The traditional LCA methodology provides a comparative evaluation of circuit designs purely from the unit interconnections. The quantitative approach uses the analytical circuit solution to evaluate the slope of the circuit’s partition curve at the midpoint. Since the partition slope is often associated with a separation’s general selectivity, this numeric value is used to compare and rank alternative configurations. Unfortunately, the partition curve slope only reflects the separation potential of middling material. By itself, this value does not account for the relatively high unit dollar value of pure material or the gains and losses in mass yield associated with alternative circuit configurations. Realizing the value in the LCA methodology, but respecting the limitations of the partition slope valuation, the authors have derived two new performance indicators that quantitatively address pure particle misplacement (the Partition Moment of Inertia) and circuit mass yield (the Yield Score). Together, these parameters provide a better indication of separation economics in typical mineral and coal separation systems. Since the two parameters provide independent information on circuit selectivity and circuit yield, a Pareto efficiency, multi-objective function selection approach is proposed for preliminary circuit selection.IntroductionOver the past 30 years, numerous scientific and industrial studies have proposed various mineral processing circuit design methodologies that attempt to optimize the allocation of separation resources within the processing plant. Over this period, the methodologies have undergone various transitions, including the increased inclusion of process models and computationally intensive algorithms, as well as a general shift from a purely technical solution (Lauder and McKee, 1986) to partially economic solutions (Abu-Ali and Sabour, 2003; Cisternas et al., 2014). Today, circuit design is largely driven by flowsheet simulation; however, no consistent design methodology is used across the industry.One intriguing approach for circuit evaluation is linear circuit analysis (Meloy, 1983a). This method evaluates the separation potential of the circuit solely considering the unit configuration and stream interconnections. No preliminary data other than the basic circuit configuration is required to use the approach."

Jan 1, 2015

By B. T. Stanley

The basic geological data, derived from boreholes, exploratory test pits, drivages, and mine development, include information on parameters such as ore thicknesses, grades, depths below surface, structural attitudes of beds, rock types, and lithology of beds overlying and underlying the deposit. These data are usually supplemented by analytical information obtained from more detailed chemical, physical, and structural investigations of the various horizons. Even then, the relatively small number of sample points in the ore body and the sparsity of the sample volume make it necessary that the available information be interpolated between sample points and extrapolated into areas beyond the limits of the sample points. Such interpolation and extrapolation are usually done by making suitable assumptions about the parameter's continuity in the ore body and by building a suitable mathematical model. The mathematical model provides the values for chosen parameters at the nodes of superimposed conceptual grids of any desired dimensions such as a grid cell equal to the size of a mining block or any other criterion. This network of values, for any parameter, can then be used for mine planning, designing, and controlling functions. Additionally, these data can also be used to calculate ore reserve and quality in total and/or for any required block. Figs. 1 and 2 broadly illustrate the scope of work that may be involved in a geological ore-body modeling study for a coal deposit. Figs. 3 through 6 describe the scope of a commercially avail- able computerized system (MEDSYSTEM of MINTEC, Inc.) for creating drill-hole data base, mineral inventories, and for planning coal and uranium projects. The application of MEDSYSTEM to calculate reserves and to long-range planning in steeply pitching coal deposits is described in subsection 3.4, Chapter 4.

Jan 1, 1979