Search Documents

Recovery of Pentlandite and Chalcopyrite from Tailings by Bi-Cyclone Powerful Flotation Column

Sep 13, 2010

By A. M. Dale, J. Standeven, B. Evanoff

We encountered several areas of methodologic uncertainty during development of a data collection method for use with vibrating hand tools in metal assembly. A local manufacturer sought our assistance designing a data collection method for evaluating and predicting risks of upper extremity disorders associated with use of vibrating hand tools. Current methods of vibration measurement are described in ISO 5349 [2]. However, the complexity of measuring vibration along with other exposures such as force and posture has limited the number of workplace-based studies of upper extremity disorders that have included direct measurements of vibration. Data from this preliminary study was used to look at two issues: a comparison of vibration values between production and non-production workers when performing the same task, and a comparison of worker ratings of vibration comfort to direct measurement of tool vibration. Methods Eight experienced production workers used each of six metal fastening tools to install fasteners. Vibration was collected by 3 tri-axial accelerometers, one attached to the tool handle following ISO 5349 recommended locations, one attached to the hand dorsum on the 3rd knuckle and one to the thumb side of the wrist. Data sampling rate was 10,000 samples/second. Hand grip and feed forces were obtained using a Novel pressure sensing mat on the palm. Each trial consisted of installing 10 fasteners per tool for each of the 6 tools. The test set-up placed the wrist in the position typically used by the operator during production. Each worker documented subjective comfort and effort ratings on a seven point scale following each series of fastener installations. One series of testing was completed by three non-production workers inexperienced in fastener installation to simulate use of alternative employees for data gathering. Vibration data for each trial were acquired, digitized, and stored using Lab View. The X, Y, & Z axes were used to calculate the vector sum response for each tri-axial accelerometer. The tool data were digitally filtered following ISO recommendations. Calculated data consisted of the mean RMS over the tool’s on- time, the starting and breaking peak impulses, and the peak of the frequency response. Results Production workers (n=8) were right hand dominant males with a mean age of 55 years and normal hand strength (mean right grip = 106 lbs). Non-production workers (n=3) had similar characteristics. We found large and statistically meaningful differences in hand force during tool use between production and non-production workers (mean production workers = 9.77 lbs, mean non-production workers = 43.30 lbs, p = 0.0001). Vibration values obtained from the hand also showed a statistically meaningful difference (mean in production workers = 0.67 Gs, mean in non-production workers = 1.48Gs, p = 0.0014, figure 1). Experienced worker ratings of comfort during tool use demonstrated a moderate correlation with measured vibration (r=0.63). Worker ratings trended with direct recordings from the tool handle as shown in figure 2.

Jan 6, 2006

By S. P. Singh

The purpose of the cut is to provide a free face to which the remainder of a development or breasting round can break. The results of field testing in drifts and at a quarry face were used as a basis for a description of the rock breakage and flushing mechanism in the cut. It was concluded that the important features of a cut design are proper hole spacing, sufficient relief volume, drilling accuracy and relief holes slightly longer than the planned length of the round. The void space provided by the relief holes should be about 15% of the cut volume, with more required in weak, highly fissured rocks. The importance of drilling accuracy increases with round length, an error being magnified by the small blasthole spacing. The first hole pulls only about 20% of the round length, 4-6 holes having to be fired before the cut is pulled close to its design depth. The first four blastholes should be fired with a minimum inter-hole delay of 100 ms to provide progressive relief of burden and avoid the superimposition of ground vibrations. The earliest-firing charge should be closest to the relief area and act laterally, while the first of the vertically-fired charges to be detonated should be the uppermost. Problems during cut-pulling include sympathetic detonation, dynamic pressure desensitisation, charge disruption and freezing of the cut

Dec 1, 1995

By S. Ersayin

In 1998, the Concentrator Modeling Center was established within the Coleraine Minerals Research Lab, Coleraine, Minnesota, to develop models for simulation of iron ore processing plants, and to assist plant operators in improving performance of their aging plants. The short-term objective was to develop necessary models for reliable simulation using conventional techniques, while the long-term objective was set as liberation-based modeling and simulation of these plants. The short-term objective was achieved in 2002 after the development of models for magnetic separators, hydro-separators and fine screens. A project funded by the U.S. Department of Energy was carried out to demonstrate the capability in improving iron ore processing at the Minorca plant. As a result of this study, a 10% improvement in throughput at the plant was obtained, and simulation became a desired tool for plant operators. A significant step in the long-term objective was reached in 2005 with the development of a liberation model. This was followed by incorporation of models capable of processing liberation data into the software. By early 2007, the Concentrator Modeling Center had the capability of performing liberation-based simulation of entire plants.

Jan 1, 2009

By Klaus Stoss, Bernd Braun

The sinking and lining of a large mine shaft with 8.0 m i.d. and 1,133 m total depth is described in detail. The ground freezing method was applied to safely sink the shaft through unstable, waterbearing strata. Following a brief introduction to the geological and hydrological conditions and the owner's shaft requirements, is the general technical concept to sink and line the shaft. Particular emphasis is put on the lining system which has to provide stability and absolute watertightness for the lifetime of the shaft, even though mining takes place in its immediate proximity. Machinery and equipment used to execute the work are mentioned and commented. Furthermore, the excavation and lining of the large filling stations using rock anchors and shotcrete are described. Details on performance rates are given.

Jan 1, 1983

By Denis Thibodeau

his paper describes a study of an altered mining extraction and the resulting Rockmass response at VALE?s Creighton Mine. Typically, the deep mining zones have strict stope extraction guidelines to ensure safety and productivity; however, these guidelines offer low flexibility or few options for stope sequencing. The 402 O. B. being in a good rock mass, at moderate depth and stress regime at Creighton, offered an opportunity to drive a more flexible mining sequence with stopes and a pillar. A three-phased approach was used to mitigate risk of the mining plan: 1- Numerical modelling to fully anticipate rock mass response to the proposed mining sequences. 2- In situ seismic monitoring to collect stress and seismic activity data. 3- Analysis of the in situ data to correlate to the modelling results. The creation and the extraction of a pillar in the 402 O. B. was successfully completed. The recorded seismic activity agrees well with the numerical modelling since most of the seismic activity is localised in the hangingwall where the deviatoric stress corresponds to an early damage process. The moderate levels of deviatoric stress cause localised failure with low level of seismic activity.

May 1, 2013

By Patrick J. Cain

The fatigue-failure characteristics under high-frequency (10 KHz) cyclic loading were determined for a marble, granite, and quartzite. The rock speci-mens were cyclicly loaded (using a high-power piezoelectric sonic transducer) at a constant strain amplitude generated by forming a longitudinal standing stress (strain) wave in the cylindrical test specimen. The number of load cycles required to fail each rock type at a given strain amplitude was deter-mined. The fatigue fractures were tensile in nature and the fracture load amplitudes were as low as 30 pct of the static tensile strength. Also the internal heating of the rock caused by the material damping (internal friction) was measured. The damping and internal heat generation in the specimens was analyzed to show that nearly all of the power input can be accounted for as a change in enthalpy in the specimen. Using these results the thermal strain in the rock was calculated to evaluate its contribution to fatigue failure. The thermal strain was found to range up to 30 pct of the dynamic strain amplitude depending on the load amplitude and the number of load cycles. The specific energy required for failure was determined and possible applications of the high-frequency fatigue fragmentation process are discussed.

Jan 1, 1975

An Integrated Study of Bubble-Particle Attachment Mechanisms

Sep 13, 2010

By R. J. Matetic

The Bureau of Mines, as part of a program to improve mine planning and development, is currently investigating the effects of pillar load transfer, which can impact mining operations wi.thin a multiple-seam configuration. At two mine sites where such ground interactions were present, the Bureau performed a complete geological analysis and installed and monitored instrumentation to gather pertinent data on rock mechanics. Overburden depth varied dramatically in the vicinity of the study area and reached a maximum at the study site; innerburden thick-ness was less than a pillar width (40 to 4S ft); heaving was experienced in both mines where sandstone and/or shale floor units were observed; overlays of the mine layouts show pillars were not totally superpositioned; a maximum of S in of roof to floor convergence was measured; and pressure readings indicated pillar core loading only and increased to a maximum of 7,000 psig over instrument setting pressure.

Jan 1, 1987

Blast vibration analysis under relatively near-field conditions has been carried out in a narrow-vein underground operation. The objective was to characterize the vibration signal (particle acceleration and velocity) from carefully controlled stope blasts. The limitations of such analysis in deriving design guidelines for reducing dilution has been elucidated. It has been shown that identification of each individual hole with specific explosive types can yield explosive-specific predictive equations for particle velocity. This has been coupled with measurement of actual overbreak to arrive at a limiting vibration level to generate a realistic design tool for controlling dilution in narrow-vein mines.

Jan 1, 2003

By Christophe Bragard

The Los Angeles Metro Eastside Extension light rail project included a 1.5 mile underground segment, which consisted of twin 18'?10" ID tunnels, bored with two EPB-TBMs. One of the major project challenges after the completion of the bored tunnels was the excavation of six cross passages within alluvial geology below the water table and with low ground cover. Sequential excavation methods were employed and this paper details the design, ground treatment, support measures, and construction methods used to mine these cross passages beneath the congested urban streets of the City of Los Angeles.

Jan 1, 2008

By B. D. H. Knights

In November 2009 Mintek installed the FloatStar? advanced flotation stabilization system on Vale's Cauê iron ore beneficiation plant in Brazil. In September 2010 the system was upgraded to include flotation optimization. The circuit consisted of two parallel cleaner circuits producing final concentrate. The tailings from the cleaner section passed through a scavenger circuit. Large, well-instrumented feed sumps played an important role in circuit stability, presenting a good opportunity for advanced control. Previously the plant was controlled using distributed control system (DCS) level control only. The flotation circuit processes roughly 30kt/day. The FloatStar system provided advanced control of the flotation circuit as well as of the sumps feeding the circuit. The system underwent a lengthy trial to assess the benefit that it provided. Two data sets were analysed, showing performance under advanced stabilization and optimization respectively. Several validation and consistency criteria were employed to ensure the quality of the analysis. Iron recovery and iron tailings grade were used to measure system performance. The analysis showed that the system increased recovery by up to 2.7%. In addition, the system decreased the iron tailings grade by between 1.2% (from 23.5% to 22.3%) and 4.3% (from 31.3% to 27.0%) during different test campaigns. The analysis also showed that the entire FloatStar stabilization system was active for 72.7% of the time from first activation to the end of the first data set (approximately 200 days). From the analysis it was concluded that under similar conditions for 'ON' and 'OFF' tests, the system provides a clear benefit. It was also found that over the longer term, the system continues to provide a benefit. This finding suggests that the results were not simply due to a short-term advantage. The size of the data set, as well as the magnitude of the recovery improvements, lends considerable confidence to these results. Therefore, it can be concluded that the FloatStar control system provides substantial benefit to operations at this site.

Jan 1, 2012

By W. L. Jacobsen, T. L. Dyer

Cortez Gold Mines completed a feasibility study for a new openpit gold mine in north central Nevada. The production schedule calls for a peak in material movement. This schedule is based on current operational efficiencies and equipment parameters observed at the company’s existing openpit operation. To mitigate risks of over/under predicting production, simulation modeling was used to validate the loading and haulage requirements during the peak production period. The advantage of simulation is the ability to provide a realistic model of a mining operation based on scheduled and unscheduled random events during the period under analysis.

Jan 1, 2007

By I. Dimitrov, S. R. McCutcheon

"Industrial-grade limestone is found in both the Lower Silurian La Vieille Formation and Upper Silurian LaPlante Formation of the Chaleurs Group in northern New Brunswick. Currently, between 150 000 and 200 000 tonnes of limestone are produced per year from the proximal facies of the LaPlante Formation at the Sormany quarry of Elmtree Resources Ltd., located west of Bathurst.The proximal facies of the LaPlante Formation was deposited on the margins of tectonically uplifted Ordovician terranes. This facies comprises stromatoporoidal-algal bindstone intercalated with wackestone, packstone, and floatstone in variable proportions. The distal facies comprises calcareous shale and minor limestone deposited deeper offshore.Folding and faulting related to Middle Devonian Acadian tectonism have caused an increase in the apparent thickness of the limestone sequences, especially adjacent to the regional Rocky Brook-Millstream fault. Structural and stratigraphic observations indicate that some of the limestone bodies in the area have been tectonically displaced from their site of deposition.A variety of prospecting techniques was used to locate new limestone resources, including geological mapping, airborne and ground electromagnetic surveys, and satellite remote sensing. Clastic rock units above and below the LaPlante Formation have distinctive properties that help to trace the intervening limestone along strike. Because of water-saturated glacial cover, thick vegetation, and the small size of targets, airborne geophysical methods did not prove effective in delineating limestone beds, but aeromagnetic surveys helped map the underlying clastic unit. The remote-sensing data and especially high-resolution digital elevation models helped in identification of karst topography related to limestone."

Jan 1, 2007

By B. J. Moore

The Bureau of Mines has estimated helium resources of the United States at 727 billion cubic feet as of January 1, 1979. These resources are divided into four categories in decreasing degrees of assurance of their existence: (1) Helium in storage and in measured natural gas reserves, 185 billion cubic feet; (2) helium in indicated natural gas resources, 150 billion cubic feet; (3) helium In hypothetical natural gas resources, 186 billion cubic feet; and (4) helium in speculative natural gas resources that makes up the remaining 206 billion cubic feet. The identified helium reserves, which are made up of that in measured and indicated natural gas categories, are further divided into depleting, non- depleting, and stored classifications. The depleting resources are those that are associated with natural gasfields that are, or will be, produced for the natural gas they contain. All of the helium in undiscovered natural gas resources are included in this classification. These depleting resources comprise 600 billion cubic feet of the total resource base. The nondepleting helium resources are estimted tototal 88 billion cubic feet. There is 39 billion cubic feet of helium in storage in Cliffside gasfield near Amarillo, Tex.

Jan 1, 1980

By R. C. Courtney, D. J. Forrester

Modern advances have led to sweep and multibeam bathymetric surveying techniques that yield three-dimensional images of the sea floor and have also produced high-powered personal computers with which to control the data and analyse the results. At Sydney, in Nova Scotia, the topography of the sea floor over the longwall workings was observed before and after mining with a precision echo-sounder in 1987-89, with sweep bathymetry in 1993 and with multibeam bathymetry in 1994-95. The results of the latter programme produced what was probably the first observation of a complete three-dimensional subsidence trough over a longwall panel 2 500 m x 168 m. The subsidence has been quantified to a sufficient degree of accuracy to allow simple trend analysis, which has shown that the pattern and shape of movements are similar to those found elsewhere but with significantly smaller maximum subsidence. A prediction model has been calibrated

Jun 19, 1905

By A. W. Schlechten, W. J. Kroll

As this paper is written, the only method for the commercial production of lithium metal is by the fusion electrolysis of LiC1-KC1 mixtures, as first proposed by Gunkz.2 The details of the industrial process have not been made public hut Osborg8 stated that an efficiency of more than 90 pct is obtained with a lithium metal recovery above 95 pct and that the metal is 99.5 pct pure. Pletenev9 gave a power consumption of 66 kw-hr per kilogram of lithium metal produced with a salt consumption of 9 kg of LiCl and 0.4 kg of KCI. Pletenev's figures indicate a somewhat lower recovery than that given by Osborg. In a recent report on' German lithium plants, Motock7 gives figures that are also less favorable than those reported by Osborg. At the German plants the lithium recovery in electrolysis was only 83.4 pct, with a power consumption of 140 kw-hr per kilogram of lithium. The metal averaged only 97 pct pure, with sodium and potassium as the chief impurities. The presence of SO2, SO3, SiO2, Ba, Ca, and appreciable amounts of Na and Fe2O3 were especially disturbing in the electrolysis, and it was necessary to run the cell for some time to eliminate most of these impurities and condition the bath. It may be noted here that most of these impurities do not interfere with a thermal reduction process. These facts show that the present method of producing lithium is fairly efficient and would suggest that other methods could not compete. However, fusion electrolysis has certain drawbacks, such as the necessity of supplying costly, low-voltage direct current and of collecting and processing the anodic chlorine if it is not to be wasted. An even greater disadvantage is that lithium chloride must be used for an electrolyte. It is one of the most expensive salts of lithium, since it cannot be produced in anhydrous form by precipitation from aqueous solution, as is done with LiF or Li2CO3. The reduction of lithium by a vacuum process similar to the ferrosilicon method for the production of magnesium would have certain advantages. Small units such as Pidgeon retorts, would give flexibility of production to meet demand, and a small plant would require moderate capital outlay. There is a possibility of using idle Government-owned magnesium plants for such purposes. The raw materials needed for vacuum thermal reduction would not have to be extremely pure, Director, with respect to the iron and calcium Content. This paper describes a series of experiments to determine the effectiveness of various agents for the reduction of lithium compounds. The investigation is part of a program of vacuum metallurgy con-

Jan 1, 1949

By Richard Morland

Some simple and fundamental objectives To challenge and inspire our people to embrace safety as a value ?A stand for safety as a value ?A stand for our people ?A stand by our people ?Prevent harm to our people ?Eliminate suffering for individuals, families, friends, colleagues

May 1, 2010

By J. T. Bartlett

Life-of-mine process simulation is an interdisciplinary effort and a useful means of thoroughly evaluating mining and minerals projects. Communication between geologists, mine planners, miners, metallurgists, and managers not only benefits each discipline but facilitates design of an efficient operation and allows for accurate forecasting of productions and cash flow. By focusing on the key areas: geology; mine design; waste dumps; stockpiles; metallurgy; weather data; tailings disposal; using contours, block models, mine plans, process flowsheets, design criteria, operating and control strategies, maintenance schedules, and operating costs to perform detailed daily simulation from start-up to shut-down; a comprehensive understanding for all disciplines is achieved. Construction of a METSIM model that includes all test work and project data from drill holes through net present value calculations brings the pieces together to achieve optimum process design, minimize operating problems and eliminate the term ?black box? from project meetings and discussions.

Feb 27, 2013

By D. Getzlaf

"Oilfield cementing has been utilized in the industry since the turn of the century. Originally, wells were shallow and criteria for well integrity were somewhat limited. Since that time, wells have stretched the envelope in depth, temperature, and pressure. Environmental regulations have also become more stringent, thus, the importance of hydraulic isolation between permeable zones, and between these zones and surface has become more and more important.Initially, oilfield cements were comprised predominantly of construction cement and very limited additives. As time progressed, additives were incorporated to control pumping time or placement time and little effort was placed on optimizing actual components within the cement chemistry. This paper presents issues and concerns created by adding just one new component to the fundamental chemistry of an oilfield cement."

Jan 1, 2004