Search Documents

Gold, silver and palladium may be separated from the other base metals and sulphur contained in copper sulphide precipitates derived from the Sherritt-Gordon nickel process using a process involving an oxidation roast, a reduction roast and a Cu(II)/acetonitrile leach. Sulphur is removed as SO, in an oxidation roast and the hot calcine is reduced with carbon, or with carbon plus cuprous chloride. The resulting product contains metallic copper which is readily dissolved with cupric ions in aqueous acetonitrile solution. Copper powder is recovered by thermal disproportionation. The residue contains the bulk of the iron and precious metals and may be treated by a number of methods, including direct cyanidation or melting with suitable fluxes. Melting the residue will produce a copper alloy containing the precious metals and remove the iron as a slag. The alloy can be recycled to the copper leaching stage or sent for toll refining depending on the precious metal content. Impurities from the leaching circuit are controlled by a bleed circuit which in one approach utilizes the SO, from the calciner to produce Chevreul's salt and separates copper from the soluble cobalt and nickel. Alternatively, the bleed may be directed back to the main refinery copper boil stage or oxydrolysis stage.

Jan 1, 1982

By R. W. Stahl

Burning coal-mine refuse banks were surveyed in 15 States. The following characteristics were tabulated for 495 hanks: County; name, population, and distance of nearest town; size and status of bank; status and stage of fire; and topography. Ways of controlling fires were reviewed, the compacting and sealing method proving most satisfactory. Means for preventing refuse-bank fires by proper construction of banks are described.

Jan 1, 1964

By J. Hadjigeorgiou, T. R. Stacey

This paper introduces the Quantified Value-created Process (QVP), a decision-making process for use in mine design and operation. The implementation of the QVP is founded on a ten-step rock engineering design process and a ten-step strategic planning process. The potential of this approach is demonstrated by examples of value created as a result of good research, design, and planning. The QVP is divided into two parts, namely, a ‘planning the process’ section and an ‘implementing the process’ section, and can be considered to be an extension of the risk approach. All costs, direct and indirect, associated with a significant mining decision (design, operational, investment) must be quantified in advance of committing to that decision, to determine the value that will be created in the short, medium, and long terms. Ethical values, associated with health, safety, the environment, public perception, and social aspects, may be difficult to quantify in economic terms, but must nevertheless also be considered. In contrast with a traditional risk approach, the QVP will identify the upside, and allow executives to make more informed strategic decisions. In this context it is essential to actively engage upper management in the decision process.

Feb 2, 2022

By Jiulong Cheng

Underground coal mining causes overburden deformation and failure, one major form of which is bed separation in the overburden. Surface subsidence can be controlled by injecting grout into the bed separations. For a long time, the grouting results of bed separation can not be validated. This is the problem in the application of this technique. This paper analyzes the conditions leading to bed separation, develops mathematical models for seismic wave fields generated before and after bed separation, and bed separations grouted with different materials, and computes the seismic wave field characteristics using the finite difference method. The results show that the existence of bed separation causes changes in the characteristics of seismic wave field, and that different grouting materials generate different seismic wave field characteristics. Intact strata, bed separation, and bed separation filled with air or water all display distinctive seismic wave field in amplitude and frequency spectra. After mining, the original location that provides strong seismic reflection wave no long exists. It is replaced by a weak and syncline-shaped reflection wave. The area, where the seam wave disappears, is larger than that of the mined area. The location, where a bed separation occurs, generates a set of reflection waves stronger than the normal one. The energy of the reflection waves varies with the materials filling the separations. Bed separations filled with air generate stronger reflection waves than those filled with water. The major frequencies for those filled with air are lower than those filled with water. Therefore, it is possible to determine the property of filling materials by analyzing and comparing the amplitude and frequency spectra of the reflection waves. Case studies of application of seismic method for exploring bed separations and grouting were analyzed. The results show that it is feasible to use seismic technique for exploring bed separations and grouting.

Jan 1, 2006

By Valentin Choquenaha Bombilla, Oscar Alvarez Muiloz

"Tintaya’s basic production line is copper concentrate, which has an important gold content. The process used is flotation; the objective of the metallurgical department is to obtain the best results in the copper recovery without neglecting the gold, using very specific reagents. Copper recoveries are considered high, nevertheless every day emphasis is placed upon increasing those recoveries. Regarding gold, optimum recoveries could not be achieved with flotation; and implementation of a gravity circuit was considered.According to microscopy studies, the coarse and very fine grains of gold in native form are lost to tails. The native gold due to its high specific gravity is concentrated at the underflow of the cyclone, remaining in the circulating load of the circuit. It reaches three times the concentration compared to the head grade entering the ball mills. This re-circulation generates very fine and laminated gold particles inside the ball mill, passing to the classification stage making a short circuit to the overflow of the cyclone.The very coarse gold particles as well as the thick flakes of gold do not react favorably to the conventional flotation process; thus studies that have included gravity separation have been conducted to increase the gold recovery. Part of the research included concentrating tables, jigs, and Knelson Concentrators. The Knelson Concentrator proved to be the best selection in terms of metallurgical performance and recoveries considering the throughput and operation conditions of the Tintaya Plant.The gravity concentration circuit with the Knelson Concentrator was commissioned in BHP Tintaya in October 1998, as per the flowsheet shown later on. Presently the global gold production surpasses any estimated expectations.Present efforts are directed towards showing the evaluation and optimization of the different parameters that govern the performance of the Knelson concentrator, as well as illustrating the difficulties and successes throughout the operating period.In the first year of operation 200 tons of gold concentrate have been produced with an average concentrate grade of 320 gramdton, having paid back in full the cost of the automated KC-XD- 48 Knelson Concentrator, the peripheral equipment, and the cost of the installation."

Jan 1, 2002

By H. Soto, J. Jara, F. Nava

"A combination of oxidation and precipitation was used to eliminate cyanide from gold milling effluents. Preliminary laboratory work developed with both synthetic cyanide solutions and with industrial effluents indicated that ozone can easily destroy free cyanide and weakly complexed cyanide (i.e. copper and zinc cyanide). In this case the reaction is quite fast and seems to be controlled by the mass transfer of ozone to the solution. Experimental results indicate that free cyanide and weak-acid dissociable cyanide in mill effluents can be reduced to less than 1 ppm. However, the iron-cyanide complexes proved to be quite resilient to destruction with ozone and they remained in the solution even after most of the free and weakly complexed cyanide was destroyed with ozone. These results were confirmed in a pilot trial developed at the Sphinx plant in northern Quebec.To deal with the problem presented by the presence of the iron complexes two different approaches were studied: use of a combination ozone-ultraviolet light oxidation, and the precipitation of iron-ferrocyanide complexes in the residual solution after ozonation. This last method proved quite promising since reduced the total cyanide levels of industrial solutions assaying as much as 250 ppm to less than 1 ppm of total cyanide. Control of the · pH of the solution was the key to obtain the precipitation of the iron complexes. The use of iron to precipitate cyanide complexes has the advantage of being less expensive and less toxic than copper (used by the Inco process)."

Jan 1, 1992

By S. H. Ash

For several years considerable activity has been devoted to economic and social factors affecting California metal-mining operations as they relate to accidents and their cost. The reason for this intense interest is that accidents cost this industry annually over $1100,000 in industrial insurance premiums for mines insured by insurance carriers only; during 1924-32, inclusive, they amounted to $3,616,9115. There are several reasons for this high cost, the most important of w rich are the consistently .high frequency and severity rates of injuries occurring in the industry. Coordination of effort, appreciation of a mutual problem, and widespread education are essential if accidents and their cost are to be reduced.

Jan 1, 1935

By Helen D. Robinson

The seawalls that surround Ellis Island were constructed in the early 1900s and now show varying degrees of deterioration. An innovative approach to the structural repair of the seawalls was developed, which consisted of the use of micropiles for stabilization of vertical and horizontal seawall movements. The micropiles were installed through the existing seawalls and penetrated through a thick overburden, consisting of soft alluvial deposits and relatively hard glacial till, and were bonded into Manhattan Schist. Drilling of the micropiles often encountered timber and other obstructions. The selection of micropiles for stabilization of the seawalls offered significant advantages over other foundation systems and over alternative soil improvement techniques. They allowed drilling through a variety of materials without the need for significant retooling or changes to the drilling procedure. This reduced the impact of foundation construction on the sensitive historical landscape and structures, and prevented the need for significant foundation work from the water side of the seawalls. In addition, micropiles offered relatively high installation rates and flexibility to adapt to the varying conditions along the seawalls.

Jan 1, 2008

By Z. Q. Zhou

It is the first worke in design of pile foundation to determine the carring capacity of single pile, and a static loading on site is considered to be the lost derect and reliable way. All values P and settlements S induced can be plotted as a broken-line. Since soil is a kind of elasto-plastic and cohesive material, the increasing of settlements is generally greater than that of loads. Different value Pu nay be given by different tester on his P-S diagram, because of erroys in the test and complicated, characteristics of soil. The analytical method of exponential equation shown in this paper derives a specified solution. After using an exponential curve to regress values of loads P and corresponding settlements S from on-site test, coeficients A and B of exponential equation can be obtained. With this curve an ultimate carrying capacity of single pile can be determined. The resistant forces of pile shaft and pile tip can also be defined by the tangent of the calculated knee point, as it is called (tangent method). At last, an example is given to show how the ultimate carrying capacity of f 500mm bored pile is obtained with this method for a project in Kunming.

Jan 1, 2010

By J. C. Edwards, C. C. Hwang

In ventilated tunnel fires, smoke and hot combustion products may form a layer near the ceiling and flow in the direction opposite to the ventilation stream. The existence of this reverse stratified flow has an important bearing on fire fighting and evacuation of underground mine roadways, tunnels and building corridors. In the present study, conducted by the National Institute for Occupational Safety and Health, a CFD program (fire dynamics simulator) based on large eddy simulations (LES) is used to model floor-level fires in a ventilated tunnel. Specifically, the critical ventilation velocity that is just sufficient to prevent the formation of a reverse stratified layer is simulated for two tunnels of different size. The computer code is verified by checking the computed velocity profile against experimental measurements. The CFD results show the leveling-off of the critical ventilation velocity as the heat release rate surpasses a certain value. At this critical ventilation, the ceiling temperature above the fire reaches a maximum for both tunnels. The velocity leveling-off can be explained from this observation. An extended correlation of Newman (Combust. Flame 57 (1984) 33) is applied to the temperature profiles obtained by CFD. At the critical ventilation, temperature stratification exists downstream from the fire. The computed critical ventilation velocity shows fair agreement with available experimental data taken from both horizontal and inclined fire tunnels. The CFD simulations indicate that the Froude modeling is an approximation for tunnel fires. The Froude-scaling law does not apply to two geometrically similar fire tunnels. The CFD results are compared with two simple theories of critical ventilation by Kennedy et al. (ASHRAE Trans. Res. 102(2) (1996) 40) and Kunsch

By Colin C. West

On August 7, 1986, Barge 45, while being towed near the mouth of the Niagara River, was swept downstream and pinned against one of the central piers of the Peace Bridge. The barge rested against the pier with 125 feet overlying the Canadian border and 50 feet overlying the American border. The tug boat which was towing the barge was lost further downstream. Fortunately, the crew escaped and were rescued with no loss of life. There was serious concern about the potential erosion effects of the river currents on the foundation of the bridge pier as caused by the flow concentrations around the barge structure. Due to the time of year, with the approaching Fall and associated worsening weather conditions, it was imperative that the barge be removed as soon as possible. Donjon Marine of New Jersey, the United States Navy's Atlantic Zone Contractor, was called on to retrieve the barge. By this time the original owner had abandoned the wreck.

Jan 1, 1987

Case I- Timber Pile Test- 4 pages describe the pile driving record, the pile load test and the boring log. Case II- 24 inch square prestressed concrete pile-5 pages give details about the pile driving, the boring log, the pile driving record, and the pile load test. Case III- 12 inch square prestressed concrete pile- 5 pages describe the compilation of SPT blow counts for the whole project, the pile driving record, the pile load test and the detailed boring logs. The 70 foot long pile was driven by a Vulcan 08 pile hammer. Case IV- 12 BP 53 Steel H pile- 3 pages give the pile load test, the pile driving record and the nearest boring log. The 64 foot long pile has its tip at elevation 908 ft. and the ground is at elevation 972 ft. The contractor augered to elevation 959 ft. before driving the pile with a Conmaco 08 single acting pile hammer. The hammer had an 8000 pound ram, a rated energy of 26,000 ft-1b., and a 7 1/2 inch thick asbestos cushion. Dynamic measurements were made during driving of the test pile and measured a hammer energy equal to 12,500 foot-pounds.

Jan 1, 1988

By Harri J. Lehto, Marja I. Oja

"The purpose of grinding circuits is to produce a particle size distribution that has as much as possible the wanted particle size class. In practise, however, the production of the wanted size class is not at all as simple as it sounds. In the case of industrial minerals for example the end user may give very tight specifications for the particle size distribution and for the chemical composition of the product. This leads in many cases to a very demanding grinding process, if we want to reach and maintain these specifications. In other words, the required size distribution is not necessary the best possible for the chemical composition.Screen models aim to predict the size distribution and flow of the products when a feed size distribution, feed tonnage, and grade efficiency curve are known. The approach used in this study was to select the most suitable empirical model for classification. Suitability of the existing models has been evaluated and accuracy compared. The tests showed that best grade efficiency model was the Rosin-Rammler model.The performance of a screen was evaluated in order to minimize the amount of fine material in the screen overflow. The experiments were carried out using Derrick single-deck screen, first alone with recycling and then in the closed circuit with a rod mill using two different scales. The separate screen tests showed the expected behaviour of the grade efficiency curves. In the pilot tests the Leonard screen efficiencies stayed almost constant. This suggests that the screen works better in a milling circuit. However the loading of the screen turned the product of the mill coarser that helped screening. The grade efficiencies obtained from the pilot tests had the same general shape. The regression analysis of the pilot test runs did not give an acceptable correlation for the parameters. This suggests that pilot tests cannot be directly used to scale or to optimise industrial milling circuits. However they can be used to predict the trends of behaviour of an industrial circuit."

Jan 1, 2003

By Kevin G. Stricklin

Introduction Continuous monitoring techniques have been used in the US and abroad for many years. A continuous miner has a monitor that measures methane and automatically gives a warning if the methane exceeds 1%. It deenergizes the continuous mining machine automatically at a maximum concentration of 2%. Main fans are also continually monitored to ensure operation. Alarms may also be given at a remote location should a fan slow or stop. The systems being developed can continuously monitor various gases and equipment throughout the mine and transmit pertinent data to a surface monitoring station. At this station, conditions throughout the mine can be monitored and, in some instances, controlled. These are known as Mine Wide Monitoring Systems (MWMS). History The use of environmental monitoring systems began in 1976 when a federal court approved the petition of modification to use belt air at the face. The first mine to receive a modification did install a system to supplement existing safeguards. Later, the Mine Safety and Health Administration (MSHA) and the US Bureau of Mines (USBM) conducted tests dealing with the use of belt air. Findings from these tests are being used to set guidelines as requirements of a petition. These requirements include: • Velocity of air has to be 0.25 to 1.5 m/sec (50 to 300 fpm); • Monitors will be installed at each belt drive and tailpiece and at intervals not to exceed 610 m (2000 ft); and • An alarm level of 10 ppm, above the ambient level is appropriate. The early uses of environmental monitoring could only be used outby the last open crosscut. That may be a reason for an initial slow growth of these systems. In June 1982, MSHA began evaluating systems that could be used in returns to ensure that monitoring systems being used in areas where permissible equipment is required does not of itself pose an explosion hazard. This is known as the Mine Wide Monitoring Systems Evaluations and Sensor Classification program. The evaluations and classifications granted are based on electric currents and voltages. Use of mine wide monitoring systems The environmental aspect of MWMS in today's coal industry deals with carbon monoxide (CO), methane (CH4), and air velocity. Just as all mines are different and encounter different problems, the MWMS are diverse and can be used to provide necessary data in all areas of coal mines. Mine operators in an ultragassy seam, for example, may be concerned with monitoring methane, while a mine that used diesel equipment may want to continuously monitor for diesel contaminants. In a mine with roof fall problems, airflow monitors may be helpful as an indication of whether the air is flowing in its normal course and at its normal volume. Today's MWMS can monitor any or all of these parameters. Most systems can be expanded as mining needs require. For example, a mine is now being monitored for methane and five years from now CO monitoring would help increase safety. It may be possible to use the same system by adding additional equipment. In the US, 30 environmental monitoring systems were installed from May 1985 through May 1986. In 1984 and 1985, there were 38 and 44 environmental monitoring systems in operation, respectively. Due to mine closings, 11 of these are no longer in use. However, the number of mines using environmental monitoring systems increased to 63. Use of these systems are not limited to any geographic area or

Jan 9, 1987

The Detachment of Coarse, Composite Particles from Bubbles

Sep 13, 2010

By L. A. Panek, F. D. Wang, M. C. Sun

A method of stability analysis of underground opening by the limiting equilibrium approach is presented. The Coulomb shear failure criterion is employed to find possible fracture surfaces and to evaluate the shear strengths along them. The normal stresses required for the calculation of shear strength, and the shear stresses for the calculation of total shear force along the fracture surfaces, are obtained by the finite-element method of plane-strain analysis. The factor of safety against Coulomb shear failure is calculated as the ratio of the shear strength to the shear force along a fracture surface, similar to the practice in slope stability analysis. Four shapes of openings are analyzed, with three ratios of horizontal lithostatic stress and four coefficients of internal friction. The critical fracture surfaces found by this method of analysis are consistent with the arching of roofs and slabbing of ribs commonly observed.

Jan 1, 1972

By Ron J. Elliott, Dylan Wedgewood

A series of five signature holes were blasted at the Highvale Mine and the resultant seismic data was analyzed to make recommendations on how best to address neighbour complaints regarding blast vibrations. From an analysis of peak vibration levels measured at the closest neighbour for blasting during 2016, it was determined that the blast vibration intensity varied between 1.4 to 4.3 mm/sec (0.06-0.17 ins./sec.), well below the level of concern for the onset of minor damage to residential structures, however, the frequency of the blast vibrations was between 2.2 and 9.7 Hz, which is within the range of the natural resonant frequency for a single story home. This was determined to be the cause of the neighbour complaints, as the home would be responding to the blast vibrations.

Jan 1, 2018

By Wayne Trudel, Eric Saderhold, Lloyd McEvers, Lori Clarke, Charles Lynn Bolin, Leroy Schutz

Editor’s note: This is the second part of a two-part series on how mine geologists added about 141t (4.53 million oz) at Newmont Mining’s gold operations in Nevada during 2003. Part one (ME, July2004, pp. 19-26) showed how cross-functional teamwork among mine geologists, engineers, metallurgists and operators added $65 million in revenues at Newmont’s Gold Quarry Mine. Part two deals with how this same cross-functional team added about 25.8 t (830,000 oz) of gold reserves and two years of life at the company’s LoneTree Mine. This was done through improved reconciliation methods, pit optimization designs and updated geotechnical parameters. Part two also discusses how Newmont’s Nevada mine personnel added about 62.2 t (2 million oz) of gold reserves at its Twin Creeks Mine, extending the mine’s life by several years. The Lone Tree Mine is a sediment-hosted, micron gold deposit. It is dominantly situated in the Golconda thrust footwall. The north-south trending Wayne Zone fault controls the highest-grade ores and

Jan 1, 2004

By Donald P. Tuchman, Robert P. Vinson, Steven J. Page, Linda J. McWilliams, Gerald J. Joy, Steven E. Mischler, Jon C. Volkwein

The National Institute for Occupational Safety and Health (NIOSH), through an informal partnership with industry, labor, and the Mine Safety and Health Administration, has developed and tested a new type of instrument known as the personal dust monitor (PDM). The dust monitor is an integral part of the cap lamp that a miner normally carries to work and provides continuous information about the amount of respirable coal mine dust in the breathing zone of that individual. Testing was conducted on 25 prototype instruments in the laboratory to verify the instruments’ accuracy as received from the manufacturer and after a period of underground use. The laboratory testing verified previous work; there is a 95% confidence that the individual PDM measurements were within ±25% of reference measurements. In-mine testing determined the precision, durability, and miner acceptance. Data from the mines showed a field precision of 0.078% relative standard deviation for the PDM and 0.052% for the recognized standard—the coal mine dust personal sampler unit. The PDM had about 90% availability for collecting valid information in over 8,000 hr of underground use. Anecdotal comments by miners indicated that they found the PDM more convenient to wear for sampling than currently used instruments because of the integration of the sampler into the normally worn cap lamp. The means of the instruments’ pre- and postmine accuracy verification test values were statistically equivalent. Additional data were collected to measure the equivalency of the PDM to the U.K. Mining Research Establishment sampler, as required by U.S. law. However, analysis of the data was more complex than originally anticipated because the variance with increasing concentration required use of a more sophisticated statistical model. Explanation of and results from this work will be the subject of a second publication. Under the broad range of test conditions covered in this work, the PDM functioned as well as the current sampler in terms of availability for use, accuracy, precision, and miner acceptance.

Jan 1, 2006

By Lawrence M. Gochioco

The interpretation of coal seismic data requires a certain precision and accuracy to make the results more reliable. The signature of the seismic wavelet provides a host of valuable geologic information. Subtle features and anomalies, not easily observed in conventional black and white seismic sections, are enhanced through color attribute displays in terms of frequency, amplitude and phase. Coal seam anomalies like sandstone washouts produce a distinct pattern in frequency and amplitude displays due to the change in the net acoustic impedance contrast. Faults produce frequency and amplitude variations due to interference within the Fresnel zone that straddles the fault. The magnitude of displacement is estimated by studying the effects of faults on reflection amplitudes and frequency from computer-generated models.

Jan 1, 1989