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By Y. Q. Lu

Efficient flotation of fine phosphate minerals from a deslimed waste phosphate stream (-74 microns) has been achieved by both bench-scale flotation and by flotation with a 2-inch air-sparged hydrocyclone (ASH) unit. A sample was collected from the waste phosphate slime stream at the SF Phosphate Limited Operations near Vernal, Utah, for flotation experiments at University of Utah laboratories. The collector used was a mixture of fatty acid, petroleum sulfonate and kerosene. Bench-scale flotation test results show that the minus 15-micron particles have a significant adverse effect on phosphate flotation. When the minus 15-micron material was removed by a classifying hydrocyclone, improved flotation recovery and concentrate grade were realized. A bench-scale flotation recovery of 86 % with a concentrate grade of 16% P2O5 was obtained from classified waste slime (74 x 15 microns) feed material containing 11.3% P2O5 In contrast, a 90% P2O5 recovery was achieved with a concentrate grade of 16-18% P2O5 by single-stage ASH flotation. With a second stage of ASH flotation, a concentrate containing 23% P2O5 was realized at an overall recovery of 75%. These results indicate that the industrial application of ASH flotation technology for phosphate recovery from waste slimes is promising.

Jan 1, 1995

By Roy A. Koski

This paper describes variations in feed characteristics, preparation techniques, response to induration and product quality in pelletizing magnetite concentrates, earthy hematite ore fines, and specular hematite concentrates in grate kiln systems. The Cleveland-Cliffs Iron Company manages plants processing these various materials on the Marquette Iron Range in northern Michigan. The operations include the Humboldt Mining Company, Marquette Iron Mining Company, Empire Iron Mining Company and the Pioneer Pellet Plant. The combined output of the operations is approximately 9,000,000 long tons per year. The Humboldt Mining Company, owned by Ford Motor Company and Cliffs, produces pellets from a specular hematite concentrate. The Empire operation, which processes magnetite ore, is owned by Inland Steel Company, McLouth Steel Corporation, International Harvester and Cliffs. The Pioneer operation, which processes earthy hematite ores, is a joint venture of Republic Steel Corporation, McLouth Steel Corporation, Bethlehem Steel Corporation and Cliffs. The Marquette Iron Mining Company, owned by hones and Laughlin Steel Corporation, International Harvester, Wheeling-Pittsburgh Steel Corporation and Cliffs, produces pellets from specular hematite concentrate at the Republic Mine and Eagle Mills Pellet Plant. With the exception of the Eagle Mills plant, the operations employ the grate-kiln pelletizing system. Descriptions of the Empire, Pioneer and Republic operations, which have a combined capacity of 7,200,000 tons per year, are given in the paper.

Jan 1, 1969

By V. Svalbonas

The process of grinding mill quality assurance brings with it associated truths and myths. When the mill quality assurance process took its first great steps forward in the late 1970s and early 1980s, they were in response to the conditions existing, in our industry, at those times. In the late 1990s, we are faced with different conditions, and problems, and need fresh solutions. Yet the system developed for the early 1980s has produced no new approaches for the late 1990s, becoming instead more hardened and entrenched. This lack of development and actual resistance to research is now costing the industry significant amounts of money in late start-ups and useless scrap loss.

Jan 1, 1999

By H. R. Butler, J. F. Church, A. T. MacGibbon

Introduction Inco is the major North American nickel producer. Initially based in Sudbury, Ontario, its past exploration activity was directed toward finding new nickel deposits. New nickel sulfide discoveries outside Sudbury have included Thompson, Manitoba; Shebandowan, Ontario; and Widgiemooltha in Western Australia as well as a host of nickel laterite deposits. The company is currently diversifying into other commodities, including gold. Inco's exploration department participated in uranium discoveries in Saskatchewan and chromite discoveries at Tiebaghi in New Caledonia. In addition, it found new gold deposits at Lupin, Northwest Territories; Crixas, Brazil; Hoyle Township, Ontario; and Casa Berardi in Quebec. Crixas and Casa Berardi are currently being evaluated by underground exploration. Figure 1 shows some Canadian Shield gold locations where Inco is or was an active participant. Base metal developments Base metal exploration in shield areas has been greatly eased by applying scientific studies. Archean nickel sulfide deposits have been found using komatiitic-flow models (Fardon, 1971). Volcanogenic massive sulfide model has been applied to copper-zinc deposits (Sangster and Scott, 1976). Such deposits were subsequently seen developing on the sea floor through black smokers (Spiess, MacDonald, and Atwater, 1980). Sedimentary processes were recognized early as important in ore formation, particularly in the southern hemisphere (King, 1976). And many ore deposits are now regarded as a simple part of the geological column (Stanton, 1960 and 1972). Petrographic work on alteration patterns in and around ore bodies was used to develop standard porphyry copper models (Lowell and Guilbert, 1970). Epithermal models for precious metals followed. Stratigraphic zonation patterns have been formulated for base metal deposits, including keel facies, ore facies, and cap or distal facies. Gold developments The work on base metal deposits naturally spilled over into precious metal exploration when the gold price was allowed to float on world money markets. Early work on elements associated with gold deposits, especially arsenic, tellurium, selenium, and mercury, pioneered more detailed geochemical work (Bagby and Berger, 1985; and Groves, Ho, and Houstoun, 1984). Geochemical patterns have been recognized around microfine gold deposits. And the study of gold precipitation patterns in modern geothermal systems has helped understand gold deposition. In the late 1960s and early 1970s, it was noticed that numerous Archean banded iron formations contained anomalous gold values. From this and other observations, the syngenetic exhalite gold model has developed. Gold deposits also occur along shears in some plutons such as the Belmoral mine in Quebec. This indicates the importance of epigenetic processes in ore formation. Shield ore settings Initial studies recognized that the major gold camps in the Canadian Shield were mostly in greenstone belts and found along "breaks," especially zones of faulting and sedimentation. Gill (1948) wrote, "Only recently, as a result of detailed mapping, has the importance of major schist zones such as the Larder Lake, Cadillac, Porcupine Creek, and Destor Breaks been recognized. These zones of persistent adjustment mark broad belts favorable for ore occurrence." The importance of shearing in ore location and regional greenstone stratigraphic position close to late sedimentary packages was clearly understood. And structural models have been further developed for some Canadian ore deposits (Hubert, Trudel, and Gelinas, 1984). In the Beardmore-Geraldton camp of northwest Ontario, the importance was soon recognized of fold noses in banded iron formation, as localizers for gold ore. This importance had also been recognized in Western Australia,

Jan 2, 1987

By Thomas D. Henderson, Wayne R. Hopkins, Arthur Lynch

Brought on stream in 1975, the 10,000-tpd copper oxide processing plant of Anamax Mining Co. at Twin Buttes, Ariz., is now at design capacity. Based on acid agitation leaching, solvent ion exchange, and electrowinning, the Anamax plant bridges an ore to metal gap by producing mine site copper cathodes from lime-bearing oxidized feed. Until recently, such material was considered submarginal because copper recovery was uneconomic using conventional methods. The new Twin Buttes oxide plant, the largest of its kind in North America, is one stage in the expansion of Anamax, a joint venture owned equally by The Anaconda Co. and Amax Inc. Other phases include an accelerated stripping program in the pit, an expansion of the sulfide concentrator from 32,000 to 40,000 tpd, and construction of a 57 MW diesel generating station for the oxide plant. Once the basic oxide flowsheet had been selected, Anamax awarded a contract to a joint venture of Arthur G. McKee and Co.' (Western Knapp Engineering Div.) and Davy Powergas' (a member of the Davy International group). The contract covered process design, engi¬neering, procurement, and construction. The property, identified by Banner Mining Co. in the 1950s and developed by Anaconda, was put into production in 1965 as an open pit mine equipped with a 32,000-tpd sulfide flotation concentrator. The Twin Buttes mine has since become one of the largest earth¬moving operations in the world, excavating some 10 tons of waste per ton of ore. At the original sulfide mill feed rate, the mining fleet moved 375,000 tpd of material (225,000 tpd alluvium and 150,000 tpd of rock). The most significant copper mineral in the ore body is chalcopyrite, which is scattered in pockets of weak mineralization. Cap oxidation has progressed to depths of several hundred feet, principally as chryso¬colla. Present estimates place minable reserves at 347 million tons of sulfide ore grading 0.6% copper and 55 million tons of oxide ore grading 0.9% recoverable copper from 1.25% total copper. The nonre¬coverable fraction is composed of native copper and insoluble copper oxides and sulfides. The oxide ore has been partially stripped, and 25 million tons having a copper content greater than 0.6% have been stockpiled. The stripping of oxide ore to expose sulfides will continue for several years. The copper oxide studies launched by Banner Mining in the 1950s were continued by Anaconda. Process routes investigated included: acid leaching; cyanide leaching; segregation roasting; chlorination, oxidation, and reduction; flotation in combination with leaching; cal¬cite flotation plus leaching; copper oxide flotation; and sulfidization flotation. By late 1968 test work favored a low temperature roast followed by an ammonia-ammonium carbonate leach of the ore. During this period, acid leaching had been discounted because of excessive con¬sumption of expensive acid by the high limestone ore matrix. Restric¬tive SO2 emission controls in 1971 suggested an increase in acid production and availability at a lower cost. Research then switched to acid leaching, resulting in development of the present flowsheet. Mechanically agitated leaching in a cascaded series of tanks was selected in preference to vat leaching after piloting a stirred-tank system. Preliminary testing of vat leaching indicated that inter-vat solution clarification problems could be caused by gas evolution from leaching of high limestone ore. Lack of research time for resolution of this problem, plus success of the pilot agitation system, dictated the final flowsheet selection. In 1973 Anamax decided to proceed with agitation acid leaching to produce liquor for a solvent ion exchange (SIX) and electrowinning (EW) installation. At that time, such systems were proving their eco¬nomic viability, and they allowed direct recovery of high quality cath odes while bypassing the smelting and refining of lower grade cement copper precipitates. The Anamax oxide plant processes a grade of about 1% recovera¬ble copper from stockpiled sources and new mine production. Unit operations include size reduction, agitation leaching, countercurrent decantation washing of residue, pH adjustment of solution, clarifica¬tion, solvent ion exchange, and electrowinning of copper, with a mini¬mum of environmental impact. The feed to the primary crushers is composed of: 1) -10-in. stockpiled oxide ore, which has passed through the mine crusher and has been grade-segregated to allow blending for a consistent feed material. 2) -4-ft ROM oxide ore stockpiled in the early mining operation. 3) -10-in. ore currently being mined. Ore is delivered in 100-ton mine trucks to a dump pocket, where an apron feeder transfers the ore to an inclined 6-in. fixed grizzly. The grizzly oversize passes through a 48 x 60-in. primary jaw crusher, where it is reduced to -6 in. The fixed grizzly undersize and the crusher product are conveyed to a 4-in. vibrating grizzly. Oversize from this grizzly reports to a 7-ft Standard cone crusher, where it is reduced to -1 in. The crusher product and the vibrating grizzly undersize are conveyed to two 8 x 20-ft double-deck vibrating screens that operate in closed circuit with two 7-ft short head cone crushers. Screen undersize (-1/2 in.) is delivered to a covered conical fine ore stockpile with a designed live capacity of 15,000 st. Beneath the stockpile are ten Pioche belt feeders feeding two conveyor belts that supply the milling circuits. Each group of five feeders has two variable speed and three fixed speed drives. Grinding to 95% -48 mesh is done in two parallel lines, each consisting of an 111/1 x 18S -ft rod mill and a 12' x 30-ft ball mill in open circuit. Water is added to maintain a pulp density of 72% solids in the mills. Further water additions are made to the ball mill discharge sumps to create a 60% solids slurry for transfer to the leaching reactors. The nominal grinding rate is 440 tph solids. A splitter box on the product from the mills separates the incoming slurry into two streams, one for the leaching reactors and the other for the pH adjustment reactors. This split is determined by the lime content of the feed material and the pH of solution entering the pH adjustment reactors. Five 30-ft diam by 31-ft high mechanically agitated, rubber-lined leach tanks are arranged in cascade, with gravity transfer from one to another by enclosed launders. Concentrated sulfuric acid (93.2%) from storage is added to the pulp principally at the first leach tank, and the reacted slurry leaving the cascade after a 5-hr residence time at 50% solids is pumped to countercurrent decantation (CCD) wash thickeners.' At this point, most of the soluble copper has been leached from the ore. Up to 250 lb of sulfuric acid is consumed per ton of ore, the acid being supplied in tank cars from a nearby smelter. Leached slurry at 50% solids is washed countercurrently with return raffinate from the SIX plant in a series of four Doff-Oliver center caisson, 400-ft diam thickeners. Solids advance from thickeners No. I through No. 4 to the tailings dam. SIX raffinate advances from thickener No. 4 to thickener No. l, where a pregnant solution overflows to pH adjustment. To optimize solvent extraction, the pH of the pregnant solution from CCD thickener No. I is adjusted from 1.5 to 2.5 by adding unreacted ground slurry (split from the grinding circuit) to the preg¬nant overflow of No. I CCD thickener. The resulting slurry is retained for 45 min in three mechanically agitated leach tanks. CO, generated during leach and pH adjustment is ducted to a demister, where entrained acid droplets are removed. The cleaned CO, and the No. 4 CCD underflow are the only effluents from the plant. The underflow of No. 4 thickener mixes with tailings from the sulfide concentrator and is neutralized. Slurry exits the pH adjustment vessels at about 10% solids and

Jan 1, 1985

By Mehmet Bugdayci, Onuralp Yücel, Yeliz Demiray Cucurachi, Ahmet Turan

The production of strontium (Sr) metal from its oxide via an aluminothermic process under 1–5 mbar pressure was examined in this study. SrO of 99%purity by weight was used in the experiments. The effects of stoichiometry and the duration of the process on the efficiency ratio of the metallic strontium were examined. The effects of functional additives (BaO, CaO, CaC2) were also examined. Characterization was carried out using X-ray diffraction spectrometry (XRD), atomic absorption spectrometry (AAS) and flame photometry techniques. The highest Sr efficiency ratio obtained was 96.89% in the experiment conducted at 1250 °C with 300% Al stoichiometry and 300% BaO stoichiometry.

Aug 7, 2020

By S. Odell

The Bureau of Land Management (BLM) has constructed two biochemical reactor systems (BCRs) to treat mining influenced water from the Forest Queen Mine near Silverton, CO. The bioreactors coupled with a natural wetland provide treatment to the Forest Queen Mine drainage. The central objective of this paper is to review the performance of the bioreactors and wetland treatment system. The bioreactors have been in operation for nine years and along with the natural wetland are still removing a high percentage of the influent metals.

Jan 1, 2010

By A. K. Bakshi

Slurry rheology affects autogenous grinding performance by changing the rock's breakage characteristics. In this study pilot scale batch autogenous grinding was carried out to observe the effect of viscosity on the breakage characteristics of the rocks (the media), and on the overall specific energy consumption. Clay/fines content, and temperature of the initial charge, were varied to alter the viscosity of the slurry. Results showed that at higher slurry viscosity, rocks became more difficult to break, resulting in an overall increase in the specific energy consumption of the mill. Also, it was observed that viscosity had a significant effect on the amount of critical size material present in the grinding circuit, where the critical size material is the material which is too large to be effectively ground in the mill, and too fine to act as grinding media.

Jan 1, 1996

By O. A. Velasquez, A. R. Kumar

"Continuous miners are often equipped with a flooded-bed dust scrubber to clean the air from close to an active underground coal mining face. However, its impingement screen is prone to clogging due to an accumulation of dust, thereby lowering the scrubber’s efficiency and potentially exposing the mine workers to higher levels of dust. Fans can compensate for the increased resistance by varying their operating parameters, but the scrubber screen needs significant maintenance which leads to downtime. The authors have proposed a suitably sized Vortecone as an alternative to the conventional flooded-bed dust scrubber system. Water is used as the filter medium, which is replaced and recycled continuously. Preliminary CFD investigations of Vortecone scrubbers have indicated higher cleaning efficacies, especially in the respirable range. This paper presents the results including the flow characteristics and capture efficacies of a full-scale Vortecone. Multi-phase flows, including free-surface modeling and particle tracking methods, have been adopted. ACKNOWLEDGEMENT The authors acknowledge the National Institute for Occupational Safety and Health (NIOSH) for funding this research project. This research is being developed with the support of a NIOSH Grant 200-2014-59922- ‘Coal Mine Dust Mitigation through Novel Scrubber Development and Numerical Modeling’. The views expressed in this paper are those of the authors and do not necessarily reflect those of NIOSH. This project is aimed at designing novel and efficient scrubbing systems for underground mining operations. The authors acknowledge Dr. Thomas Novak of the Department of Mining Engineering, the University of Kentucky for his support and encouragement. The authors also thank Dr. Sunil Vytala, CFD engineer at Cradle CFD for his invaluable inputs to the numerical models.INTRODUCTION Continuous miners are the main production machines deployed in room and pillar mining operations. These miners extract coal by the shearing action of the wethead cutting drums. Strategically placed water sprays on the drum not only cool the bits extending their useful service life, they also suppress the dust at the point of generation itself. A flooded-bed dust-scrubber (Campbell, et al. 1983) is usually integrated onto the continuous miner to arrest dust from close to the active face. These fan-powered scrubbers have an impingement screen flooded with water, which also serves as the filter element. A demister downstream of the screen removes the excess water from the air cleaned. These conventional scrubbers have been found to be very effective in alleviation of respirable dust levels underground (Chao and De-sheng 2000) (Colinet, Reed and Potts 2013). However, the inefficiencies of the flooded-bed dust scrubbers arise out of their internal components. Depending on the mining conditions, the screen may be clogged by the accumulation of the trapped dust particles. The resistance of the scrubber system is increased reducing the airflow. The flooded-bed dust-scrubber system would, therefore, require frequent maintenance of the screen and the demister (Listak 2010). Since any maintenance needs to be carried out under supported roof, this leads to loss of availability of the equipment as well. In addition to this, the continuous miner operators could be exposed to elevated levels of dust when satisfactory airflow at the face is not achieved."

Jan 1, 2018

By M. A. Bouchat

The Kipushi deposit, where the Prince Leopold Mine has been installed, belongs to Union Miniere du Haut-Katanga and is located in the Belgian Congo, 20 miles SW of Elisabethville, at the vicinity of the Northern Rodhesian Border. The deposit is of the hydrothermal metasomatic vein-type; mineralisation took place, through the limestone of the, lower Kundelungu. This is a special fea¬ture of the deposit, compared to the other copper deposits of the neighbourhood, both in the. Belgian Congo and in Rhodesia. Actually, the primary mineralisation of these other deposits; is directly related to the stratigraphic systems: schistous dolomitic in the Belgian Congo and Roan in Rhodesia. Both facies are older than the Kundelungu and separated from this formation by a tectonic cataclysm. The valuable elements occuring at Kipushi are principally copper; and zinc. The deposit also contains smaller quantities of lead, precious metals and other elements including germanium.

Jan 1, 1960

By J. E. Lawver, R. J. Haskin, A. Nussbaum, E. A. Laurila, W. J. Bronkala, D. M. Hopstock, J. H. Brophy, M. Wada, E. J. Tenpas, R. W. Salmi

Electrostatic separation is the selective sorting of solid species by means of utilizing forces acting on charged or polarized bodies in an electric field. Separation is effected by adjusting the electric and coacting forces, such as gravity or centrifugal force, and the time forces act on the particles, such that different species will have different trajectories at some predetermined time. Separations made in air are called electrostatic separation even though there is always some flow of current. Separations made using corona discharge devices are often called high tension separations. Separations made in liquids are termed separation by dielectrophesis if motion is due to polariza¬tion effects in nonuniform electric fields and termed electrophoresis if motion is due to free charge on species in an electric field. There are no industrial applications of mineral concentration by electropho¬resis or dielectrophesis; thus this section is limited to concentration in air. Typical Industrial Separations Typical applications of electrostatic separation are: 1) Beneficiation of ores, such as the concentration of the minerals ilmenite, rutile, zircon, apatite, asbestos, hematite, and many others. 2) Purification of foods, such as the removal of trash and rodent excrement from cereal seeds. 3) Sorting of reusable wastes, such as separating insulation from copper wire shreds. 4) Electrostatic sizing, namely, the sorting of solid particles ac¬cording to their size or shape. Table I is a partial list of industrial separations made by electrostat¬ics. The various types of electrostatic separators and the feasibility of commercial separations are most easily understood by reviewing pertinent basic electrostatic theory and the selected electrical proper¬ties of solids prior to describing the equipment and application. This is the sequence of presentation used in this section. Electrostatic Units One of the greatest sources of confusion and error is due to the multitude of units used in electrostatic literature. The system of units used throughout this section is the rationalized MKS, often called Systéme International (SI) units. In this system the mechanical units are the meter, kilogram, and the serond. The unit of force is the newton (N). This system is completed by the addition of the unit of charge, the coulomb (C). The fourth dimension, viz., the coulomb. could also be considered to be the ampere, since one ampere is the flow in a conductor of one coulomb per second. A more complete definition of the coulomb is given in Chap. 4, p. 6-11. The derived

Jan 1, 1985

By AMIT SHARMA, BIBHUTI BHUSAN MANDAL

Operators of mining vehicles are exposed to high levels of whole-body vibration (WBV) and are therefore at risk of developing vibration-related health disorders. For implementing an effective control strategy, it is imperative to locate the source(s) of vibration, and the specific changes that might occur to the vibration signals during its transmission through the seats to the recipient human body. With this objective, Seat Effective Amplitude Transmissibility (SEAT) values of seat modules used in dumpers (n = 10) and other heavy earth-moving machines (n = 11) were evaluated in an iron ore mine. Vibration was measured simultaneously on the seat and on the cabin floor beneath the seat using tri-axial and uni-axial accelerometers. The study aims at determining the quality of seat modules of the transport and non-transport vehicles from the perspective of their natural resonance frequencies and capability of any such seat in reducing harmful vibration. The highest acceleration values were observed in the z-axis for all the dumpers. SEATrms values ranged from 78 to 133% and SEATvdv values ranged from 72 to 130% for the dumpers. For other HEMMs, SEATrms values ranged from 55 to 125% and SEATvdv values ranged from 56 to 123%. Mechanical vibration contains multiple frequency components. To understand the changes taking place to the different signals at these frequencies, 1/3 octave band analysis was carried out for the signals recorded both on the seat and the floor. There was significant attenuation (38 to 57%) at 4 Hz for three Dumper seats, whereas they resonated in the range of 1.6–2.5 Hz. The transmissibility(%) in the resonating frequencies ranged from 108 to 156%. Resonance frequencies for the remaining seven dumpers ranged from 3 to 8 Hz. The spine has been reported to resonate at 4 Hz, whereas resonance at 1.6 Hz has little significance to human beings in regard to WBV of a seated person. Hence, the characteristic resonant frequency of 4 Hz of seats as observed in the present study has the potential of causing adverse impacts on spinal health. Evaluation of SEAT factors and resonance characteristics of seats are therefore recommended to be examined while selecting a mining vehicle for regular deployment in mines.

Mar 12, 2021

By J. A. Meech

An analysis of screen design options on the operating efficiency of secondary crushing plants has been conducted using a dynamic computer model. The model allows for the simulation of a wide variety of crushing circuits and can be run on either a microcomputer (IBM PC/XT) or a large time-sharing mainframe computer. Size reduction and separation characteristics of crushers and screens are based on standard manufacturer design and performance data. Input/output routines are available in tabular, alarm or strip chart recorder modes to facilitate operation of the program. A number of alternate circuit designs are compared to show the influence of surge capacity, screen size and area, screen deck location, and closed side crusher settings on the operation of a 10,000 ton per day plant. The program is currently in use at Queen's University to teach plant operations and control. It has potential to be a valuable tool for operator training.

Jan 1, 1985

By S. Dixon

The Phelps Dodge - PD/PERI Heap2D Model is a phenomenological stockpile leaching model that has been used to investigate the best operating practices for leaching chalcocite. The model was used to investigate the interrelationships of raffinate application rate, aeration rate, raffinate iron grade, acid cures, lift height, crush size, bulk density, air injection spacing and raffinate drip emitter spacing.

Jan 1, 2006

By Chinmay Shingote, Robert Visintainer, Renjie Ke, Jaikrishnan R. Kadambi, John Furlan

Hydrocyclone separators are widely used in various industrial applications in the oil and mining industries to sort, classify, and separate solid particles or liquid droplets within liquid suspensions, which are considered to be multiphase systems. Numerous valuable studies have been conducted in recent years to investigate the flow fields inside hydrocyclones. However, much of the information regarding the performance of cyclones in the literature has limitations and much of it cannot be considered as completely applicable to most real-world applications; many of the studies investigated the flow fields within extremely simplified hydraulic designs that are not representative of the complex geometries or large sizes which are typical in industry. Therefore, in this study, the two-phase flow system inside the actual hydraulic geometry of a milling circuit hydrocyclone is explored with the aid of both computational and experimental techniques (particle image velocimetry (PIV)). More specifically, the flow field with an air core has been investigated. In addition, the air-liquid two phases flow in a hydrocyclone might cause some challenges on both the computational and experimental sides. Two turbulence models are utilized in the numerical calculations: the Reynolds stress model and large eddy simulation. The computational studies are mainly focused on the local flow behavior and the prediction of the dimensions and shape of the air core. Different section planes of hydrocyclone are selected as planes of interest and divided into several fields of view (FOV) for PIV measurements. Two-dimensional experimental velocity vector maps are obtained in each of the fields of view. The computational results are validated globally using pressure and flow rate readings at the boundaries and locally by comparison to the PIV velocity vector maps and profiles.

By Yi Luo, Jian Yang, Hua Jiang

Surface subsidence events induced by underground longwall coal-mining operations can cause various disturbances to surface structures, ranging from integrity and stability to functionality problems. Highway bridges, as a kind of special road construction that can only tolerate smaller movements and deformations than road pavements, are particularly susceptible to severe influence caused by subsidence-induced ground movements and deformations. However, based on accurate subsidence prediction and correct influence assessments, efficient and effective mitigation and remediation measures can be designed and implemented to ensure the continuous service of bridges, safety of travelers, and smooth mining operations. In this paper, based on the predicted final and dynamic surface movements and deformations, the techniques to assess subsidence influence on the integrity, stability and functionality of bridge structures (such as decks, beams and abutments) are presented. A number of mitigation measures to protect bridge structures are recommended, along with an actual application case.

By Yi Luo, Jianwei Cheng, Mingming Li, Lei Xiao

Concealed thermal events in longwall gobs present safety hazards for underground coal miners and can significantly interrupt mining production. The probable causes for such thermal events range from coal oxidation at slightly above ambient temperature to smoldering fires due to spontaneous combustion of the broken coal left in the gobs. Locating such “hot spots” is the key step for planning and implementing mitigation measures to bring such thermal events under control. If a mine section, or even an entire mine, has to be sealed, understanding the status of the sealed mine atmosphere is important for the decisions guiding subsequent actions. The gas composition data obtained through the tube bundle mine atmospheric monitoring system is firsthand information of great value. Fire ratios proposed by various researchers and derived from gas composition data are useful in determining the fire status and even approximating the source locations (Timko and Derick, 2006). However, the applicability of each of these ratios under particular conditions should be carefully evaluated. The use of properly combined fire ratios can enhance the certainty of analysis. The explosibility of a sealed mine atmosphere deserves primary concern for safety reasons during seal construction, idle time and reopening of the sealed area.Mine atmospheric monitoring data from a longwall mine with flame fire have been analyzed. Efforts have been made to identify the possible causes, locations and statuses of these events using the obtained gas data, as well as other ventilation, geological and mining parameters. The effect of injected inert gas to control the events has also been quantified. The explosibility of the sealed atmosphere has been determined using two methods.

Jan 1, 2012

By D. H. McCain

Through a unique partnership between the Colorado Mine Safety and Training Program (CMSTP), the Colorado Rock Products Association (CRPA) and the Higher Education and Advanced Technology (HEAT) Center, a video packed, dazzling CD-ROM training program was developed for new miners entering the aggregate industry. Why this product was developed, and why the aggregate industry, will be discussed along with the challenges faced throughout the project. Cooperation from every one involved including MSHA made this the product of which all other training materials in the mining industry will be measured against in the 21st Century. This product's versatility and wide application makes it a tool that is as critical to a mine's success as any earth moving machine. Developed with both state and federal grant moneys allows this product to be affordable to small operators and independent contractors. The quality of this two CD-ROM set rivals any commercially made CD-ROM training.

Jan 1, 2001

By A. Jahedsaravani, M. Massinaei, M. H. Marhaban, N. Mehrshad, M. I. Saripan

"It is well known that froth visual features reflect the operating conditions of the flotation process, so that being able to accurately obtain the froth properties is the most significant criteria to optimize and control this process. Froth segmentation is a useful procedure that can determine the bubble size distribution. Several algorithms have been proposed in this field, but marker-based watershed transform shows the best performance. In spite of this fact, the algorithm suffers from oversegmentation in cases when the flotation froth includes large bubbles along with small ones. In the paper, the marker-based watershed method is modified to prevent oversegmentation of large bubbles. The developed algorithm is validated using some froth images captured at different operating conditions, so the results indicate that the method can segment the mixture of big and small bubbles effectively.IntroductionFroth flotation is a widely used process for separating valuable from gangue minerals. Effective control of flotation circuits has a dramatic effect on overall performance of a mineral processing plant. In most flotation plants, process operators monitor the froth surface visually and make adjustments to process parameters based on their interpretation of the surface appearance and their idea of the appearance of an ideal froth. However, due to natural complexity of the flotation process, achieving optimal control is often not possible for human operators.In recent years, attempts have been made to control the flotation circuits using machine vision systems (Moolman et al., 1995; 1996a,b; Bartolacci et al., 2006; Kaartinen et al., 2006; Vanegas and Holtham, 2008; Aldrich et al., 2010). The froth bubble size distribution is the most significant control variable that reflects the operating conditions in a flotation machine. To date, a number of approaches have been proposed for bubble size measurement from froth images, including segmentation (Sadr-kazemi and Cilliers, 1997; Wang et al., 2003; Mehrshad and Massinaei, 2011), texture spectrum (Nguyen and Thornton, 1995), wavelet (Liu et al., 2005), an improved texture spectrum approach, a method based on binary images (Lin et al., 2008) and, finally, using interfacial morphological information (Yang et al., 2009)."

Jan 1, 2015

By Jeramy B. Decker, Paul H. Madsen

"During the excavation of the north bound tunnel of the Devil’s Slide Tunnel project, deformation (convergence) was measured after passing through Fault Zone B. The tunnel convergence was not symmetrical, but was larger on the left side of the profile. It was determined that a shear zone nearly parallel with the tunnel drive was contributing to the uneven deformation. This paper will discuss how it was determined that the shear zone existed and how multi-point borehole Extensometers (MPBX) were used to verify that a significant amount of the deformation was occurring due to movement along the shear zone as the excavation was advanced. In addition, performance of the shotcrete liner in the area of the convergence will be examined. Finally, the paper will consider the means and methods that were utilized to ultimately control and stabilize the deformation. INTRODUCTION The Devil’s Slide Tunnel Project consisted of excavating two 1,250 meter tunnels each with a profile of 80 m2 utilizing the New Austrian Tunneling Method (NATM) or otherwise known as the Sequential Excavation Method (SEM). The tunnels are part of the California Coastal Highway south of Pacifica, CA, a suburb of San Francisco. The tunnels were opened to traffic in March of 2013. Geological Setting The tunnels run north-south through the San Pedro Mountain ridge, which is part of the Santa Cruz Mountains. The tunnel lies within the San Andreas Fault system and is 7.2 km west of the surface trace of the San Andreas Fault and 2.8 km east of the surface trace of the San Gregorio Fault. The 10 km strip between these two faults is referred to as the La Honda structural and terrain block (Decker et al. 2010; Amini et al. 2005; Earth Mechanics Inc. 2003). Locally, the tunnel passes through three blocks representing different geological conditions: South Block, Central Block, and North Block (Figure 1) (Decker et al. 2010; HNTB Corporation et al. 2005). The South Block consists of Mesozoic aged granodiorite and quartz diorite. The South Block also contains many local shear zones and a low angle thrust fault (Fault A). The South Block ends at Fault B, which is the southern border of the Central Block."

Jan 1, 2016