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By L. Prosser, A. Iannacchione, G. Esterhuizen

The potential for roof falls in underground mines remains a clear and present danger for mine workers. An investigation of ground conditions in nearly 50% of the nation’s underground stone mines found that the state of roof stability is primarily determined in a limited and subjective manner. These large opening mines, with roof heights typically of 7 m or more, make physical observation difficult. Although some mines use monitoring techniques to gain additional information on roof stability, this practice is usually short-term and localized to address ground conditions in a particular section or part of the mine. A methodology to assess the risk for a roof fall is proposed in a preliminary fashion based on engineering judgment acquired from extensive underground stone mine experience and examination of related literature. The proposed method utilizes an observational technique to identify the risk of roof falls in three categories. Case study scenarios provide a realistic picture of model implementation. Providing the mine level decision maker with an accurate assessment tool to ascertain the level of risk related to ground conditions is expected to reduce mine worker injuries and fatalities. Moreover, the presences of danger can be overcome with a clear picture of quantified ground conditions.

Jan 1, 2006

By D. Lelinski, R. Bokotko, J. D. Miller, J. Hupka

Air-sparged hydrocyclone (ASH) flotation is a new, promising technology, and, since its conception, numerous applications have been successfully tested. Nevertheless, research and development efforts have continued to improve the technology with respect to operating conditions and design considerations. Results, from experimental studies on bubble generation in the ASH system are presented in this paper. Bubble size distributions generated during ASH operation were determined using a high-speed photographic technique. The influence of many factors, including surfactant concentration, water flow rate, and porous-tube pore size have been studied. Test results indicate that these process variables have a profound effect on the bubble size distribution. With an increase in surfactant concentration or water flow rate (shear field), the bubble size distributions become narrower and shift toward smaller average bubble diameters. However, the influence of pore size is more complicated. Depending on the experimental conditions, the average bubble size was found to range from about 100 to 300 µm in diameter.

Jan 1, 1997

By Hassan El-Shall, Rosana M. Macedo Borges, Ponisseril Somasundaran, Regis Stana, José Renato B. Lima, Patrick Zhang

The phosphate fertilizer industry is a large activity in Brazil because the soil has a phosphorous deficiency. The phosphoric acid that is produced is extensively used in the production of fertilizer. It is produced by reacting phosphate carbonaceous rock with sulfuric acid, generating phosphogypsum as a by-product. In 1991, there were about 29 million tons of phosphogypsum stored in Brazil. This has increased to an estimated 280 million tons in 2001. While the phosphogypsum is used in the cement industry and also in agriculture, the quantity used is much less than the production rate, and the stockpiles are still increasing. The radioactivity of this waste may not allow its continued use as a construction material and some other uses. However, Brazilian phosphogypsum contains a smaller quantity of radioactive materials than is reported for phosphate rocks from other countries. One important reason is the geological origin of the Brazilian apatite. All the large deposits being currently mined are igneous, not sedimentary, as is the majority of the phosphate rock produced around the world. An extensive study is being conducted to characterize the phosphogypsum generated in two production facilities in Sao Paulo state to develop safe uses for this waste and determine the environmental impact caused by the present method of phosphogypsum disposal.

Jan 1, 2002

Various computer packages are now available for balancing data obtained from complex concentration plants. It is well established that the filtered data generated by these programs are statistically better than the raw data. However the degree of improvement as well as the accuracy of the estimated variables depend strongly on the propagation of measurement errors through the estimation algorithm. Therefore, for the subsequent use of the filtered data, their confidence intervals are as important as the data themselves. Variance of filtered variables have been derived in a very general way for any arbitrary flowsheet and when data originate from various sources such as flowrates, chemical assays, particle size distributions and pulp percentages of solids. The theoretical formulae are incorporated in the BILMAT package for mass balance calculation and illustrated on various flowsheets involving grinding, classification and flotation. The validity of the proposed method is discussed by a comparison to a Monte Carlo approach, for a simple processing circuit.

Jan 1, 1986

By Michael J. Sapko, Robert A. Cortese

A flame powered trigger device has been developed to explosively activate suppression barriers to quench gas and coal dust explosions. The important feature of the device is a silicon solar panel, which collects 0.3 p to 1.1 D wavelength radiation from the developing explosion, and generates electrical energy to initiate a detonator, which in turn causes the rapid explosive release of an extinguishing agent into the advancing flame front. Solar panels that are rated to produce 20 w of electrical power when exposed to the sun light are producing about 200 w when exposed to full-scale dust explosion propagating in the U.S. Bureau of Mines' Lake Lynn Experimental Mine. The solar panel is electrically isolated from the detonator by a pressure sensitive switch until the arrival of the precursor pressure pulse, which always precedes a deflagration. This combination of pressure arming and flame powered photo generator prevents false barrier activation and requires no external power supply.

Jan 1, 1991

By W. J. Miles

At the beginning of the 20th century, barite was a mineral of minor importance in the United States. Its primary use was to extend lead oxide in white paint. Barite also added the special qualities of hiding power and flatness to paint. Because white lead sometimes turns black or yellow and barite does not, ground barite became a pigment on its own merit. Barium chloride was added to bricks before fi ring to stop efflorescence when exposed to weather. Barium carbonate or nitrate added luster and brilliance to glass. Barium chemicals were added to refining sugar, enameling iron, making oilcloths and paper collars, and in the manufacture of paper, artificial ivory, rubber and lithopone. Lithopone became a major paint ingredient in the 1920s; its use lasted until the 1950s, peaking at 150 kt (165,000 st) of barite in 1937 and 1947 for the manufacture of lithopone. Later in the 20th century, titanium dioxide replaced lead oxide, barite and zinc oxide in the coatings industry. In the 21st century, barite is used as a filler, extender or weighting agent in products such as paints, plastics and rubber. Some specific uses include its use in brake and clutch pads for automobiles, automobile paint primer for metal protection and gloss, to add weight to rubber mud flaps on trucks and to add weight to the cement jacket around petroleum pipelines under water. In the metals casting industry, barite is part of mold release compounds. Because barite significantly blocks X-ray and gamma ray emissions, it is used as aggregate in high density concrete for radiation shielding around X-ray units in hospitals, nuclear power plants and university nuclear research facilities. Ultra-pure barite consumed as liquid is used as a contrast medium in medical X-ray examinations. Barite is the raw material for barium chemicals, such as barium carbonate, which is an ingredient in faceplate glass in the cathode-ray tubes of televisions and computer monitors. In the 21st century, barite industrial uses accounts for an estimated 78 kt/a (86,000 stpy) in the United States.

Jan 1, 2009

By R. Gong, R. Bhaskar

[Full-scale laboratory experiments were performed to evaluate the effect of ventilation and water spray pressure on the potential dust capture efficiency of a ventilation system comprised of blowing ventilation and an underboon scrubber. The tests were performed for a 1.52-m (5-ft) roof height and 2.36 m-3/s (5000 cfm) blowing ventilation volume, and a 2.44-m (8-ft) roof height and 4.72 m3/s (10.000 cfm) blowing ventilation volume at three face positions of the miner. The scrubber suction rate was varied for the tests to study the effect of scrubber flow rate on capture efficiency. The airflow patterns and scrubber efficiency were determined by performing tracer gas tests. Tracer gas was released through a manifold placed in front of the rotating miner drum. The gas was sampled in a grid fashion using a real-time multi-point gas sampling system. The capture efficiency of the scrubber was evaluated based an the peak gas concentration of the gas laden air drawn through the scrubber and the amount of gas passing, through the scrubber as a fraction of the gas released at the face. The data were analyzed to yield scrubber peak concentrations, potential exposures at various operator locations and the gas removal percentage (GRP). The underboom scrubber appears to work best in the end sump position, relative to the start sump and start slab positions. The capture efficiency scrubber was higher for 2.44-m (8-ft) roof heights compared to 1.52-m (5-ft) roof heights. The data also showed that the scrubber air discharged behind the mining machine may be drawn into the face area by the action of the blowing ventilation system, resulting in recirculation.]

Jan 1, 1994

By R. Bruce Thorndycraft

This paper will describe several modifications to design of con­ventional oxide gold heap leaching. They are targeted at reduc­ing costs and simplifying heap operations. These modifications were conceptualized during consulting work on over 90 differ­ent heap leaches. In 1995, a unique opportunity arose to imme­diately apply all of these design concepts to the permitting and construction of a new facility at the American Girl Mine in southeastern California. American Girl Mine has operated since 1987. In April 1995, the mine faced a situation with grave consequences for cash flow. Approval for mining of a new ore zone, Oro Cruz, had just been granted, after lengthy delays by California regula­tors. All existing pad space would be filled by October. Only 6 months were available, and new pad siting and design were still undecided. Permitting of a new pad had not begun. Options were quickly reviewed. A strong criteria for pad site selection and design was ease of permitting. There was also a strong desire to install a system that would achieve better met­allurgical recovery and reduced operating costs, compared to previous heaps at this mine. One site offered the best chance for rapid permitting. It was the site of the original 1987-90 heap leach. This already dis­turbed ground contained 1.6 million tons of heaped ore. The old heap had just completed detoxification and was about to be signed off as a Group C waste, ready for reclamation. Instead of recontouring and revegetating the old heap, which the reclamation plan anticipated, we offered BLM and the County something even better. We proposed to off-load much of the detoxed old heap, and reuse the space. The off-loaded material would be back-filled into the original open pit, imme­diately adjacent. While the footprint of the proposed new pad was much larger, the reuse of disturbed ground, and backfilling of the open pit, had very strong appeal to the regulators. Our permitting strategy included the technical design of the proposed new facility. Many of the new design details also appealed to the regulators, particularly the "zero active ponds" concept.

Jan 1, 1996

By K. C. Carriere

INTRODUCTION The purpose of this paper is to introduce the reader to basic control strategies for solid/liquid separation in mineral processing and to indicate some of the implementation difficulties to be encountered, without becoming overly involved in details of process, equipment or software. It is assumed that the reader has some familiarity with control systems and with dewatering processes, since exploration of these topics would require considerably more length. The paper is organized into three parts: first a general discussion on the need for control of dewatering processes and of the general criteria involved, next a more detailed elaboration on control strategies for the various unit operations, and finally a case study showing a specific approach towards such a project. Motivation & Objectives The justification for implementing any control system in an industrial plant is to improve operations and thereby to increase profitability. Without this motivation, the system will likely be perceived as unnecessary and will decline into disuse, an expensive and troublesome monument to someone's ill-conceived ideas. However, when a control strategy is correctly conceived, implemented and integrated into operations, it can provide significant advantages in operating ease and efficiency, and a handsome return on investment. In general terms, the objectives in establishing a control system are: • stabilization of process disturbances maintenance of product quality • maximization of throughput • dearer definition of process • protection of personnel and equipment A successful control strategy must address at least some of the above criteria. However, the most important requirement is a commitment on the part of plant personnel and management to start up, operate and maintain the system, and to upgrade it to reflect current process status and operational philosophy. Process Applications In this paper, control strategies will be explored for the most common methods of dewatering of mineral pulps. These unit operations include: drying, centrifuging, filtering and sedimentation. While the first three are important, they do not tend to be as complex as sedimentation, and thus will not be as exhaustively treated. Sedimentation is very widely applied, not

Jan 1, 1986

By C. James, J. Siefke, D. Shumway

The Mojave Desert is a particularly fragile ecosystem that faces several significant impacts. These include rapid housing development, overdrafted water supplies, and loss of wildlife habitat as a result of mining, industrial activity and urban sprawl. Over the past three years, a diverse group of educators, natural resource managers and business leaders has been assembled under the auspices of a local college to provide unique natural resource education opportunities for the region. By leveraging the collective experience of these present generation natural resource professionals, the Mojave Sustainability Project hopes to provide the next generation of professionals with that knowledge and those technical skills upon which tomorrow’s community can rely. This paper is a case study of how partnerships between academia, government, industry and the community can serve to address the regional social, environmental, and economic needs of today, while investing in the development of those professionals who will balance these needs tomorrow.

Jan 1, 2005

By VIVEK KASHYAP, PATRICK TAYLOR

Zinc ferrite is the major phase component present in zinc refinery residue (ZRR) and electric arc furnace dust (EAFD). Up to 71 percent zinc ferrite has been reported to be present in ZRR, and in most studies zinc ferrite has been deemed the major phase in EAFD. In 2010, the global annual production of EAFD was 3.7 Mt, with 15.20 kg of EAFD generated per ton of recycled steel [1]. The generations of ZRR and EAFD have been growing over time, requiring a greener approach for the reutilization and extraction of valuable elements. ZRR can be a potential source of zinc, as its zinc content is as high as 30 percent [2,3]. The presence of zinc ferrite makes the extraction of zinc difficult because zinc ferrite is refractory to leaching, and direct leaching is inefficient. The Waelz process is currently employed to extract zinc from EAFD and other metallurgical wastes. The Waelz process operates in the temperature range of 1,100 to 1,500 °C and uses coke as reductant. This study explores a carbon-free and relatively low-temperature process for the selective extraction of zinc from pure zinc ferrite.

This paper presents the development of a knowledge based integrated decision support system (E.X.I.S) for the extractive industries to provide information concerning the environmental impact of extractive operations on land quality, surface and ground waters, and the best solutions for the rehabilitation/revegetation of the waste disposal areas to the relevant target groups (extractive industries, regional authorities, national authorities, research institutes, public). GIS was integrated with the decision-making models for the rehabilitation and revegetation of mine spoil. The system design involves several steps including site selection ? mine type identification ? waste identification ? selection of rehabilitation (revegetation or other methods). The knowledge based model consists of two integral parts: the model base, in which the input data are processed and classified using special fuzzy algorithms and criteria and the knowledge model, which hosts the various decision algorithms concerning evaluation of vegetation covers, selection of trees and plant species, selection of rehabilitation and revegetation schemes and also economic analysis for each option. The system input will include parameters on site characteristics (climate, topography, geology, hydrology etc), waste type and properties (physical-geotechnical and geochemical data) as well as environmental parameters of the existing waste disposal area. Based on the values of the above parameters and the characteristics of the rehabilitation technologies developed worldwide, the system, using IF-THEN rules will define a list of appropriate techniques for the rehabilitation of the examined waste. Then, the model will involve the application of multi-criteria analysis (MCA), i.e. a structured system for ranking alternatives and making selections and decisions. Each technique shall be judged based on its behavior into four fields, i.e. financial, social, technical and environmental criteria. In turn these fields will be analyzed into a lower level of evaluation criteria.

Jan 1, 2006

By Jasper D. Ward

The Indiana Limestone Company has developed an insulated, thin and comparatively light-weight pane 1 suitable for use as a spandrel panel in a curtain wall. The panel is about four inches thick and is composed of limestone backed with insulation. The inner surface of the insulation is protected with asbestos-cement board or a metal pan, depending on the type of insulation, building-code requirements and appearance (if the surface is left exposed). The limestone is cut to the size of the spandrel openings and the insulation and backup is applied in the mill ready to be shipped and in- stalled in the wall grid, A mortarless and waterproof joint with the metal frame components is achieved through the use of neoprene, thiokol, and caulking, The limestone is "dirt-proofed" (waterproofed) in the mill to slow down discoloration. The panel weighs more than some presently used materials. However, ILCO's architects and engineers have found that curtain wall systems capable of withstanding imposed wind loads are made up of sections large enough to carry this extra load of stone with little or no modification to the size of the metal frame. Limestone, a traditionally sound material, can be used in this new way without losing any of its natural qualities of dimensional stability, resistance to fire, and permanence.

Jan 1, 1959

By R. C. Babcock

Exploration for mineral deposits in the western United States is increasing annually, and the data generated by this effort are increasingly complex, diverse, and abundant. It is obvious that to make full use of this data base, which is both private and public, the technology of the computer must be involved. To lay out the framework for discussion of the particular uses of computers in all steps of exploration, this chapter will discuss the various approaches to the reconnaissance program which might be considered, the types of data to be acquired, the interpretation of these data, and the generation of recommendations based on this interpretation. Where possible, some of those areas where computer technology is now used will be pointed out. The discussion will cover the extent to which the computer is now utilized in those areas or where it should be brought into the program to aid in these activities. However, this chapter will not present an exhaustive evaluation of this technology, but will stress the exploration job and its requirements, so that subsequent discussion of the technology itself can be placed in perspective.

Jan 1, 1979

The Barrick Zaldivar mine is an openpit, heap-leach copper mine in Region II of northern Chile at an elevation of 3,300 m (10,826 ft), approximately 1,400 km (870 miles) north of Santiago and 175 km (109 miles) southeast of the port city of Antofagasta. In 2006, Zaldívar produced 307 million lbs of copper, with reserves estimated at 5.7 billion lbs. The mine uses conventional methods of openpit mining: Pure cathode copper is produced by three stages of crushing and stacking the ore, followed by heap leaching and bacterial activity to extract copper from the ore into solution. A solvent extraction and electrowinning process then removes the copper from solution and produces the cathode copper. A flotation plant also recovers copper contained in the fine fraction of the crushed ore. In 2006, an existing A-frame structure that covered copper ore from the mine?s secondary crushing operation was damaged beyond repair. The material delivery configuration of this original structure had the conveyor carrying incoming ore directly over the low roof to drop ore into the building at its peak, and ore trickling from the sides of the conveyor had accumulated on the roof, overloading it. A better solution had to be found, and fast: First, the Chilean Commission does not permit uncovered piles of this type since the extremely fine material leads to serious pollution problems. Second, Barrick Zaldivar is very concerned about worker safety, and the amount of dust created by the uncovered pile was not acceptable. Finally, some amount of copper was lost in the dust generated by the winds of the Andes. The major issues faced by Barrick Zaldivar in designing a new structure included:

Jan 1, 2009

By W. C. Hellyer

In an autogenous grinding circuit in which feed at approximately nine inches top size is reduced to a size suitable for subsequent processing, the build- up of a "critical size" fraction in the media causes problems. A "critical size" fraction has been defined as, "media too small to effect reduction by impact grinding of ore coarser than a quarter of an inch and too large to be broken by the largest size of media in the charge. 9, (1) The buildup of a "critical size" fraction reduces the capacity of the mill, increases the grinding power requirements per ton of finished product, and generally produces a finer grind than is desired. It is general practice to overcome this problem by the addition of large diameter steel balls to the grinding charge. This has certain disadvantages, such as; (i) an increase in mill liner wear; (ii) wear on the steel balls, and; (iii) some loss in flexibility in grinding circuit operations resulting from difficulties in removing the steel balls by means other than by grinding out.

Jan 1, 1970

By Felicia F. Peng, Wenguang Wang

The purpose of this research work is to predict the dust concentration distributions of different particle sizes on longwall faces. This Is necessary because the dust sources must be identified before dust control techniques can be recommended and applied correctly. The dust concentration data at longwall faces were determined by using Real-time aerosol monitors (RAM-1) and gravimetric monitors. However, these field data cannot explain the nature or the mechanisms of dust flow phenomenon on longwall face. Therefore, a mathematical model Is developed taking Into account the characteristics of airflow, the natures of dust generation and particles, the mechanisms of dust transport and deposition as well as the multiple dust sources on the longwall faces. In this paper, the identification of respirable dust sources on the longwall faces are determined. The dust particle size distributions In various longwall faces are analyzed and classified. The comparison analyses of field data and model predictions are presented. Specifically, the general trends of dust concentration on the longwall faces obtained at different positions and at various conditions are discussed.

Jan 1, 1991

By Richard C. Smith, Steven H. Brown

Commercial scale in-situ leach uranium facilities (i.e., solution mining) have operated since late 1975, and have begun to appear in increasing numbers in the last few years. Solution mining involves the pumping of ground water, fortified with oxidizing and complexing agents, into an ore body, leaching and solubilizing the uranium in-situ, and then pumping the solutions to the surface where they are fed to a mill. Milling is by conventional means, involving ion exchange, precipitation, calcining and packaging processes. This paper presents an overview of the solution mining process, and discusses an empirical method that has been used to determine the radon gas release rate in Bq (curies) per year for the overall operation of the facility including wellfields, milling processes and waste storage reservoirs. In addition to radon generation on the surface from radium decay, it has been determined that the major component of radon release is associated with the dynamic generation of radon from solutions returning from underground. Process parameters impacting this evaluation and the mathematical expressions developed are discussed. The preliminary data accrued is presented.

Jan 1, 1981

By Jerry C. Tien

Mining in China dates back at least 4,000 years. Today, with no less than 103,000 metal/nonmetal mines and between 40,000 to 80,000 coal mines, China’s mining industry is undoubtedly the largest in the world. Despite improvements in recent decades, seemingly endless mining accidents continue to make the news. Official coal mining deaths were 6,702 in 2003, and 6,027 miners died in 2004; actual figures may be much higher. Added to these were the 2,699 deaths in the metal and nonmetal industries. Most of these accidents were due to CH4 (methane gas) explosions and fires as a result of inadequate mine ventilation de-sign or practices. A good portion of these accidents occur in small, privately run and often technically illegal mines. During the past 10 years, the Chinese government has attempted to crack down on small and often technically illegal mines without much success. The number of accidents and associated fatalities has not significantly reduced. However, there appears to be a new urgency in China’s efforts to step up mine safety in the country. After its worst reported mine disaster in more than a half century, the government quickly paid reparations to families, suspended high-level officials in charge and announced additonal reforms. One of those was the elevation of the central government’s work safety office to cabinet-level status. There has been increased transparency in reporting and investigation of mine accidents and disasters in recent years. There has also been an increase in public criticism by labor leaders concerning the neglect of mine workersafety.1 This article examines the causes of China’s many mining accidents, current legal and enforcement structures, respective mining health and safety related laws and regulations, recent mining industry developments and the latest effort to curtail small mining operations.

Jan 1, 2005

By Sotiris Psomas, Colin M. Eddie

"Steel Fibre Reinforced Concrete (SFRC) Segmental Tunnel Linings have successfully been used for over 20 years in the UK and have been adopted in a number of high profile projects such as High Speed 1, Crossrail, Thames Tideway, as well as High Speed 2. Tunnel linings and especially SFRC design are not covered in the Eurocodes. This shortage of SFRC tunnel design rules seems to be partially addressed by several international publications. However, in the UK, the ‘design-assisted by testing’ (DAT) approach has also been adopted. The Paper discusses the UK’s best design practice and focuses on the DAT methodology as applied in the case of the 6.9km (4.3miles), 7.8m (25.6 feet) ID Lining for the £635million Lee Tunnel Project. The design approach, the full scale testing at the Building Research Establishment (BRE), and the construction innovations are presented. This experience will be transferred to the £4billion Thames Tideway Tunnel.INTRODUCTIONSteel Fibre Reinforced Concrete (SFRC) has been used for Tunnel segments for more than 20 years. The first application of SFRC in the UK was for the Heathrow Baggage tunnel (1994). Since then significant size tunnels have been designed and constructed, such as the Jubilee Line (1999) High Speed 1 (CTRL, 2006), Crossrail (2014), Lee Tunnel (2014) and the scheduled 25km Thames Tideway (‘Super Sewer’) and High Speed 2 rail tunnels. However one the main obstacles in achieving streamlined design and improving efficiency are the lack of appropriate design guidelines for SFRC tunnel segments. This issue will – to some extent – be addressed by a number of current documents on tunnel FRC design either being produced by BSi (PAS8810, expected 2016), ACI (544.R) and ITAtech (Design Guideline PCFRC, 2015) in an effort to advance the design of SFRC and take into consideration the recent developments in Steel and Macro-Synthetic FRC technology."

Jan 1, 2016