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By W Valery, A Jankovic

The ball mill in closed circuit with hydrocyclones is an industry standard, and well known methodologies exist for equipment sizing, selection and design. However, the potential to improve the capacity of ball mill circuits by replacing cyclones with screens has been recognised for many years and recently has been successfully realised, thanks to developments in fine screening technology. Proper methodology for equipment sizing and selection is required to capitalise on this opportunity, but there is currently insufficient information and few guidelines available on how to design such a circuit. This paper discusses the differences between ball mill circuits closed with cyclones and with screens. A methodology is described for equipment sizing and selection for a circuit closed with screens, and the laboratory testing requirements are described for low grade base metal ores and magnetite ores. An economic evaluation is also presented for a case study demonstrating the potential benefits of closing a ball mill circuit with screens.CITATION:Jankovic, A and Valery, W, 2013. Energy efficient ball mill circuit - Equipment sizing considerations, in Proceedings MetPlant 2013 , pp 285-295 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 15, 2013

By Yvone Franco Crosato

The dense population of Hong Kong requires the construction of tall buildings in reclaimed areas or perched on the slopes of the many hills. The large loads to be supported are carried by deep foundations. Many of those are bored piles, to rock, of diameters up to the 3.0 m. of today.

Jan 1, 2000

By . Jaime G Tapia Aguirre

La Unidad Minera Rosaura del Grupo Glencore fue considerada la mina subterránea más segura del país durante los años 2005, 2006 y 2007. Sin embargo, cuando el Grupo Glencore adquirió la concesión de Rosaura, el panorama minero era de una mina marginal, de bajas leyes. Por esta razón, el único metodo a ejecutar para hacer de Rosaura una mina rentable era el de utilizar un método masivo. Em ese semtido, el presente texto señala la operación de mina cone el análisis y conocimiento de causa raíz en la prevención de caída de roca.

Sep 12, 2011

Two concentrates from Palabora, in South Africa, containing 0.056-0.068% undesirable Cu and 0.8 or 2.2% Ti, were chlorinated with air:chlorine ratios of 10:1, 15:1 and 20:1 at temperatures between 1 200 and 1 329 K. The resulting volatile chlorides were condensed and the solutions analysed for Cu, Fe and Ti. Recovery of Cu was less than 25% at low temperatures and short reaction times, but at 1 258 K almost all Cu was removed from the magnetite at all ratios of chlorine to air. At higher temperatures, the increased carrying over of iron as FeCl3 could be minimised by decreasing the partial pressure of chlorine. No titanium was detected in the volatile products and the percentage of Cu recovered was independent of Ti concentration in the concentrates, though as a function of Cl2 vol%, more Cu was recovered at 1 200 K from the low-Ti than from the high-Ti concentrate. In a fluidised-bed reactor, Cu recovery was 58-90% and iron carry-over less than 10 ppm

Jun 21, 1905

By Osvaldo A. Bascur

Connectivity between mining and metallurgical process operations and their business systems has become a reality. Expanded use of plant information on the desktop is a standard tool for revenue improvement, cost reduction, and adherence to production constraints. The industrial component desktop support access to information for continuous improvement and innovation by staff personnel and engineers. Collaboration between groups enables the implementation of an overall process effectiveness index based on losses due to equipment availability, production recovery and quality rate. In this sense, the paper point out three cases studies of large integrated power stations.

May 25, 1998

By Moi Arzamendi, Jose Ramirez, Kenneth Kniss, Sunil Arora, James Gingery

Construction of a new approach embankment for a railroad bridge over a river in Southern California required placing up to 12 ft of fill over soft to medium stiff silts and clays along an approximate 1,500-ft long stretch. The embankment, situated within a narrow railroad right-of-way between an existing live track and existing buildings, would have been susceptible to excessive settlement that could damage existing buildings and numerous underground utilities if regular weight soil fill had been placed over the unimproved ground. To limit total and differential static settlements to tolerable levels, a design was developed using a combination of mechanically stabilized earth wall with lightweight cellular concrete fill and rigid inclusions ground improvement. This paper describes the design of the ground improvement system, construction methods used, and challenges of working next to live railroad traffic. Ground improvement quality control and assurance measures, and verification of performance by settlement monitoring are also addressed. INTRODUCTION AND BACKGROUND The 0.9-mile San Diego River Double Track (SDRDT) project is located on the Los Angeles-San Diego- San Luis Obispo (LOSSAN) Corridor in San Diego, California. The project includes the replacement of the existing 900-ft long single track railroad bridge over the San Diego River with twin double track structures. Construction of the project is phased and closely coordinated with the associated Mid-Coast light rail project (San Diego Trolley Blue Line Extension). The new bridge is a 7-span, twin steel, through girder structure supported by six cast-in-place reinforced concrete pier caps and two abutments. The large diameter cast-in-drilled-hole (CIDH) foundations are up to 9 ft in diameter, with upper portions encased in a 1.5-in.-thick permanent steel casing. The north abutment approach embankment includes a mechanically stabilized earth (MSE) retaining wall up to approximately 10 ft high and 1,520 ft long. This paper focuses on the design and construction of the north approach embankment. The project site is characterized by challenging geotechnical and seismic conditions. The site contains liquefiable soils interbedded with soft cohesive soils, underlain by competent layers of sand/gravel/cobble and other sedimentary formations. Static settlement of the new railroad, crossing utilities and adjacent buildings was a primary design concern for the north approach embankment.

Jan 1, 2018

By Kyoosang Yoo

The report presents the results corresponding to the analysis of a lining system for tunnels in soil and soft rock in creep-active ground. The purpose of the analysis is to evaluate the performance of a lining at each construction stage. The steps include: 1. Accurate representation of the initial undisturbed state of stress 2. Excavation, 3. Lining installation 4. Injection of mortar and its curing, and 5. Short-, medium- and long-term creep behaviour in the surrounding soil/rock. The response of a prototype tunnel is simulated using the computational finite element framework MSC.marc2008.

Jan 1, 2010

By James P. Rider, Charles D. Taylor, Edward D. Thimons

Research was conducted to investigate how ventilation of a mining face is affected when scrubber flow is greater or less than intake flow. Tests were conducted in a full-scale surface test gallery built to simulate a mining entry with a continuous mining ma- chine at the face. Methane gas was released at constant flow at the mining face. Gas measurements taken at six locations near the face were used to evaluate how well the face was being ventilated. Increasing scrubber flow resulted in lower methane levels even when scrubber flow was much greater than intake flow.

By B. P. Sereda

The properties, characteristics and phase structure of chamotte refractories produced with the usage of mullitecorund chamotte and caoline have been given. The comparison of new refractory C-45 obtained by us and refractory C-43 produced by traditional method has done. The physical-chemical properties of refractories is reviewed. The visual porosity, density and pore characteristics of given refractories was calculated. It is established that C-45 has the less gas permeability then C-45 that gives melting units more stability. The petrographical microstructures of refractories have been done. The main phase structures and their influence on refractories properties have been observed. It is established that refractories with mullitecorund chamotte adition has more advantages then refractories gained by traditional method and can be applied to melting units.

Jan 1, 2010

By J. M. Riley

This report summarizes Bureau of Mines experiments in purifying sulfate leach liquors, which were prepared from low-tenor beryl concentrates by modifying the Degussa process. The leach liquor was prepared from a beryl concentrate containing 2.7 percent BeO by (1) sintering the beryl concentrate with limestone in a rotary kiln at about 1,150° C. and by (2) treating the sinter first with sulfuric acid and then with water to form and extract beryllium sulfate. About 80 percent of the beryllium was dissolved. The resulting leach liquor contained 2.4 grams of BeO, 20 grams of Al203, and 6 grams of Fe203 per liter. The laboratory solution contained much more aluminum and iron than a solution derived from treating 10 percent BeO concentrate, which is the standard raw material used by industry. Tests were made to determine the behavior of the solution toward alum purification and limestone neutralization both of which were employed industrially in conventional Degussa procedure.

Jan 1, 1962

By Q. J. Browne, M. A. Miller

Silver Bell produces about 22,000T of fine copper annually from low-grade chalcocite and oxidized copper ore that is recovered by sulfuric acid leaching and SX-EW processing. The current mineable reserves are 146 million short tons averaging 0.39% Cu, at a 0.15% cutoff. Silver Bell utilizes two types of mining methods to develop the low-grade reserves: (1) a conventional blast, load and haul method for run-of-mine leach ore, and (2) rubblization of material on the margins of existing pits. Rubble leach ore is blasted, terraced with a bulldozer, and leached in place. Mining and/or rubble leaching is currently active in four separate pits. Laramide-age intrusive rocks host porphyry copper mineralization at Silver Bell. Quartz monzonite porphyry dikes and stocks, mafic-poor equigranular granite (alaskite), and sub-volcanic dacite porphyry are the predominant host rocks. Most of the ore currently mined comes from near-horizontal enrichment zones containing veinlets and disseminated grains of pyrite and chalcopyrite rimmed by chalcocite. Conversion from a milling operation to a leach only operation allowed for a much lower cutoff grade than was historically used at Silver Bell. Mine geologists were able to increase copper resources by drilling exploration targets that were previously interpreted to provide lower-grade mineralization below cutoff-grade for milling. Geologic parameters that effect the distribution of rubble and mineable leach ore include: ore grade and thickness, variable alteration styles in intrusive host rocks that affect fragmentation during blasting, acid consuming carbonate wallrocks (reactive skarn) which influence leach solution pH, solution flow paths and drainage, presence of leachable oxide mineralization in non-reactive skarn, and depth to hypogene mineralization which is currently uneconomic. Geologic parameters are used to predict rubble bench limits, vary blast hole spacing for consistent fragmentation, and correct errors in mineral zone classification based solely on blast hole assays. An expansion-drilling program has identified approximately 150 million tons of new leachable copper resources with an average grade of 0.35% Cu.

Jan 1, 2002

By B. Tiryaki

Longwall shearers usually suffer from excessive pick and pickholder consumptions and severe wear of the back plate of the clearance ring section of shearer drums. In practice, most of the drums were seen to be withdrawn from the face due to the abovementioned problems, while vane picks and their holders were intact due to the improper lacing design of the clearance ring picks. However, few underground investigations and their results on the effect of lacing arrangement of clearance picks on the service life of shearer drums have been published. Nevertheless, the pick consumption characteristics of shearer drums were not investigated in detail, since these are fewer pick consumptions with shearers when compared to roadheaders. This paper is concerned with the comprehensive in situ trials on the effect of lacing of clearance ring picks on the lifespan of shearer drums, and the pick consumption characteristics of longwall shearers at Cayirhan Coal Mine in Turkey. The lifespan of shearer drums employed with shearers in this mine increased 70 per cent, while the consumption rate of clearance ring picks decreased threefold through using an alternative lacing for clearance picks, indicating the significance of utilizing proper design techniques for clearance ring picks for the service life of shearer drums. Statistical analyses carried out, using the raw pick consumption data, implied that the clearance ring picks experienced much higher loads than vane picks, revealing that special attention must be paid to designing clearance ring picks. An average maximum consumption value of 41 was determined for clearance ring picks, with corner-cutting picks having the most replacements, while it was 35 for vane picks, on three-day based pick replacements.

Jan 1, 2004

By M. Mostert

Mining companies sponsor a range of non-core, corporate social responsibility projects to adhere to social and labour plans and environmental management prerequisites that form part of a mining licence application. Some companies go above and beyond such projects, sponsoring initiatives that generate renewable energy through solar power, wind energy, natural gas, etc. The challenge for these companies is to choose between a variety of projects to ensure maximum value, especially in times when the economic climate might be less favourable for such projects. The focus of this research was to analyse the concept of sustainability as it exists today, and to apply that to the triple bottom line accounting method in an attempt to quantify the sustainability of a project. Research was done on the methane burn-off project at Sibanye Gold?s Beatrix Mine to establish how such projects are planned and financed, and what impact they have on the triple bottom line of a company. The financial bottom line is, by definition, one that executives understand. This paper also proposes a quantitative method for defining the social and environmental bottom lines as well. By considering the financial, social, and environmental values, the study attempts to determine a monetary value for a sustainable renewable energy project. This monetary value can be compared to similar values obtained for other sustainable renewable energy projects under consideration. The research suggests that monetary value alone is not enough to base a sustainable decision on, and qualitative measures are suggested for use in conjunction with quantitative methods. The selection method proposed should assist the board of a mining company to choose the most sustainable option and the project that will add the greatest value to the company across all three bottom lines. It will also provide increased justification for such renewable energy projects, even in periods of harsh or uncertain economic climates.

Jan 1, 2014

By Christopher J. Bise

INTRODUCTION Traditionally, the purpose of mine ventilation has been defined as diluting, rendering harmless, and sweeping away hazardous gases which may accumulate in the mine workings. In addition, the ventilation sys- tem must keep the mine air as close as possible to the composition of the outside air in order to provide a healthy environment for mineworkers and to prolong the useful life of mine equipment. When plans are being developed for opening a new mine, sound engineering dictates that a calculated estimate be made of both the maximum air quantity requirement and the accept- able mine pressure (head) loss related to the under- ground layout and projections. For efficient mine ventilation, the two problem areas that demand constant attention are (1) the control of fugitive air (through short circuiting or leakage) and (2) the provision of ample airway capacity. Fugitive air is that quantity of air which enters the mine but short-circuits the mine ventilation system through improperly constructed stoppings, doors, overcasts, etc.; it represents an investment in power consumption (to move the air by the fan) while providing little, if any, return on the investment. Typically, efficient mines are those that can deliver 50% of the air handled by their fans to the working faces. Paying close attention to a new mine's ventilation system at the outset can provide numerous benefits during the later stages of mine development. It has often been noted that the main cause of trouble in many mine ventilation systems can be found within a radius of 2500 ft from the fan installation. Ample airway capacity is essential to maintain the mine's head loss within manageable limits. Similar to an industrial ventilation setting, the mine's headings are the ductwork for the handling of air. The difference between normal industrial ventilation and mine ventilation is apparent when more capacity is needed; a plant can install new or larger ductwork, but it is difficult for a mine to install new entries or enlarge existing entries. Air velocities are usually maintained under 800 fpm to limit the stirring up of dust in the intakes. With this in mind, it is usually simple to estimate the number of entries required in the ventilation system. The problem that often arises, though, is when the system's capacity is overestimated and the required head loss to achieve the desired quantity is excessive. Experience has shown that problems are often encountered when the mine's condition requires much more than three inches of water gage to ventilate the mine on a day-to-day basis. Thus, if proper attention is not paid to these parameters in the preplanning and initial development of a new mine, it may take an extremely high water gage to achieve the ultimate quantity. This chapter will not delve deeply into the theory of mine ventilation; many other books have been writ- ten on that subject. Instead, the following sections will point out the important considerations that should take place before the development of a mine ventilation system, as they relate to normal industry practice. FUNDAMENTALS OF AIRFLOW Volume Versus Water Gage The common method of measuring ventilation pressure is in terms of inches of water gage (wg); one inch of water corresponds to a pressure of 5.2 psf (pounds per square foot). Further, airflow follows a square-law relationship between volumes and pressures where, as shown in the previous section, a doubling of quantity requires a quadrupling of pressure. Table 1 shows how heads and quantities are related. Using Table 1, it is readily apparent that, for the same mining conditions, an increase in pressure from one inch wg to three inches wg results in only 34,640 cfm when the initial quantity is 20,000 cfm. Pressure Losses Pressure losses in mine ventilation systems are caused by friction between the heading walls and the air stream and by shock losses due to abrupt changes of the air stream caused by obstructions. The common pressure-loss formula for mine ventilation is: [ ] where H is the pressure loss in inches of water gage, K is the coefficient of friction, L is the length of the airway in feet, 0 is the airway perimeter in feet, V is the air velocity in feet per minute, and A is the cross-sectional area of the airway in square feet. Table 2 lists the US Bureau of Mines schedule of friction factors (K) for mine airways. Recent research indicates that the values of K are slightly less for coal mines than those presented in the USBM Schedule, and Table 3 should be consulted in this instance. It should be

Jan 1, 1986

The Rate Variable Batch Test (RVBT) - A Research Method of Characterising Ore Floatability

Sep 13, 2010

By B. R. Reddy, Y. V. Swamy, B. V. R. Murthy, H. S. Ray

The Ni oxide was reduced with a CO-CO2-N2 gas mixture and the effects were observed of process variables such as roasting temperature, time and CO partial pressure. Extraction of over 90% of Ni was achieved by ammoniacal leaching of ore that had been reduced for 1 h at 760 degrees C under a gas mixture with a volumetric CO/(CO+CO2) ratio of 0.57. The kinetic data were found to conform to the Ginstling-Brounstein equation. The applicability of this model was confirmed by evaluating the apparent activation energy with the use of independently constructed differential and integral plots, which showed an excellent match

Dec 1, 1995

By J. C. Martin

Equations for three-phase, three-dimensional, compressible flow (including capillarity) are reduced to two-dimensional relations by a partial integration. This reduction allows three-dimensional flow problems to be treated with mathematics for only two spatial dimensions. The results can be used to formulate flow equations for two-dimensional reservoir simulators in which the effects of capillarity and fluid segregation in the third dimension are represented. Such reservoir simulators would retain many of the aduantages of two-dimensional simulators while simulating three-dimensional effects. The principal restriction of the method is that the thickness of the reservoir should be small, compared to the distance across the reservoir. INTRODUCTION In recent years, computers have been used to calculate the performances of many reservoirs. Most of the detailed calculations, however, are based on finite difference solutions of the flow equations, and present day computers are seldom able to handle a sufficient number of cells to produce entirely satisfactory solutions, even for reservoirs represented by two-dimensional arrays of cells. The situation becomes much worse when one wishes to approximate the reservoir by a three-dimensional array. A great saving in computation or a more detailed solution can be obtained for many reservoirs by using the partial integration of the equations of flow presented in this paper. The integration reduces the three-dimensional equations to two-dimensional relations; and, for studies of two-dimensional flows in vertical cross-sections, the equations are reduced to one-dimensional relations. Most reservoir performance calculations currently are based on one- or two-dimensional flow re1ations.l-3 In some cases flow in the third dimension is approximated by assuming a particular type of vertical saturation distribution, such as gravity segregation.l.2. The relations developed in this paper approach those for segregated flow as the capillary pressures approach zero, and they approach those for uniformly distributed saturations as the capillary pressures are increased. For this analysis, the ratio of the reservoir's thickness to the maximum distance across it must be small. The capillary pressures between the oil and water should also be small compared to the maximum pressure difference in the reservoir. This requirement is met by most reservoirs. It is assumed that the capillary-pressure curves are well defined, whether or not hysteresis effects are included. Also, the reservoir must have sufficient vertical permeability to allow the fluids to segregate. The results presented here provide a firm theoretical foundation to Coats' et aL5 assumption of vertical equilibrium and extend the relations to three-phase flow. Coats' assumption of vertical equilibrium, which he verified by calculations and experiment, is developed here mathematically from basic flow equations. DISCUSSION SATURATION AND PRESSURE DISTRIBUTIONS Appendix A presents a mathematical analysis of fluid flow in reservoirs where the ratio of thickness to maximum distance across the reservoir is small. The results indicate: (1) that the fluids along any line perpendicular to such a reservoir's upper surface are in static capillary equilibrium (vertical equilibrium); (2) that, to a first approximation, the fluid pressures and properties are functions of only areal position in the reservoir and time; and (3) that hydrostatic pressure gradients exist along any line perpendicular to the reservoir's upper surface. The results might be expected after studying several physical considerations. First, no flow is allowed normal to the upper and lower reservoir boundaries, which are relatively close together.

Jan 1, 1969

By A. M. Keenan, R. H. Carpenter

Geologic faults have always been a plague to the mining industry, and have often reduced a mining venture from a profitable to a marginal operation, and even at times have forced companies to liquidation or bankruptcy. The use of geology as an economic tool in coal mining is not generally recognized, particularly in coal deposits which are horizontal or essentially flat-lying, in which faulting might not be prevalent. However in pitching coal seams, the existence of faults is considered an inherent challenge, as the inclination of the seam or seams per se, is a product of geologic disturbance. The problems of faults are a constant challenge to the management of the Thompson Creek Coal and Coke Corp. in their operations in Pitkin County, Colorado, where high grade medium volatile coking coal is mined. The background for this paper has been provided by the experiences of these operations, in overcoming the effects of faults in mining, and resolving the fault structures. The properties of the Thompson Creek Coal and Coke Corp. are located in central Colorado, 13 miles southwest of Carbondale, Colorado, a tow] on the main highway between Glenwood Springs and Aspen, Fig. 1. The elevation at the mine portals is approximately 8000 feet: there is a relief of some 2.000 feet to the adjacent ridges rising away from the [nine portals. 'The entire present production of these properties totaling 180.000 tons of clean coal per year is trucked to the railhead at Carbondale, Colorado, from whence it is shipped to the Geneva Steel Plant at Provo, Utah. The properties were initially opened in September 1952. A total of 125 men are currently employed with the production conting from the Number 1 and 3 Mines, and development workings of the Number 2 and 5 Mines respectively. While the No. 2 Vine was opened in 1953 prior to No, 3 Mine, the encountering of faults without sufficient development work accomplished to sustain production, necessitated the diversion of manpower to the other [nines for economic considerations. GEOLOGY '1-he productive coal seams occur in the Mesaverde formation of Late Cretaceous age which outcrop along the eastern edge of the Piance Creek Basin from the Grand Hogback, a part of the southwestern flank of the White River Uplift north of Glenwood Springs, southward through the 'Thompson Creek area and the

Jan 1, 1961

By Panagiota Tsolis-Katagas, Basilios Tsikouras, Tassos A. Grammatikopoulos, C. Katagas

"Mineralogical techniques including microscopic methods, reflected and transmitted light microscopy, Cathodoluminescence (CL) and Scanning Electron Microscopy equipped with an Energy Dispersive Spectrometer (SEM-EDS), are useful in determining the quality of industrial minerals. They are essential for studying ores and metallurgical products including the evaluation of physical characteristics of the mineral, paragenetic relationships, associations with possible deleterious contaminants (e.g., sulphides), spatial distribution within the ore zones and liberation characteristics. The methods are inexpensive, and provide quick identification and distinction among the industrial minerals and the gangue minerals in a section. Additionally, SEM is necessary to reveal complex textural sequences and 3-D measurements of minerals and quick semi-quantitative analysis.Common analytical methods include Electron Microprobe Analyses (EMPA) and Whole Rock Analysis (WRA) (commonly with XRF and ICP) for major and trace elements. The EMPA analyses of industrial minerals provide information on the purity of the analyzed grains as opposed to the bulk chemical analyses that may be misleading due to contamination by other associated common “gangue” minerals. These techniques have been implemented for the case studies of wollastonite, V-magnetite and muscovite. Therefore, these methods can provide extremely useful information and lead to the implementation of a successful pilot-testing programme.MINERALOGICAL EVALUATION OF DEPOSITSDespite their considerable and increasing economic importance, industrial mineral deposits have traditionally been neglected by economic geologists, and are only rarely the subject of the detailed analysis widely lavished on metallic mineralization. Moreover, in that they generally represent concentrations of “normal” rock-forming minerals, albeit commonly with particular textural and/or geochemical features, they have tended to fall between the mainstream of petrogenetic studies and mineral deposit research (Grammatikopoulos 1999). For many industrial minerals, little attention has been paid to the factors responsible for their local concentration as large and high-grade bodies. This comparative neglect has particularly been the case for minerals such as talc and wollastonite, widespread in metamorphic rocks, in which they are reasonably interpreted as components of assemblages derived, respectively, from pelitic sediments, ultramafic igneous rocks and siliceous limestones."

Jan 1, 2003

By Jackson R. Pressley, Bruce Vandenberg

The knowledge of how and when your explosives go off can help you make intelligent decisions regarding future application of explosives thus removing some of the black magic associated with blasting. The net result will be intelligently set-up shots with timing, explosive charges, and placement more accurately done. Lower operational costs can be achieved when the correct combinations are applied.

Jan 1, 1992