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By J E. Everett

When ore is being selected from a regularised block model, a common procedure is to accept as ore any block whose iron content exceeds a cut-off value, and whose content in each contaminant analyte is below an appropriate cut-off value. This method defines a quadrant within the multidimensional analyte space, such that any block lying within the quadrant is accepted as ore and any block lying outside the quadrant is rejected as waste. The cut-off levels can be adjusted to maximise ore tonnage at a target grade (or analyte vector). When the method is applied to a project comprising multiple pits with systematically differing grades, it is found that ore tonnage at target grade is maximised if different cut-off quadrants are used for the different pits. This is apparently illogical, because it implies that an ore block from one pit may be accepted as ore, but an identical block from another pit is rejected as waste, even when ore from both pits is to be blended into the same product and there are no production cost differences between the pits. The paradox is an example of the ætheory of the second bestÆ: if there are multiple conditions for optimality and one condition is broken, then obeying the other conditions may not be the best policy. The problem lies with the quadrant cut-off method, which is shown to be inconsistent even for selecting ore from a single pit. A criterion that is inconsistent cannot be optimal. It is shown that a linear composite cut-off function provides maximum ore tonnage, and that a single composite cut-off criterion is consistent and optimal over multiple pits. Further, it is shown that a composite cut-off function not only maximises ore tonnage at a specified composition, but also can be used to select ore so as to maximise project value, if marginal costs and values are available.CITATION:Everett, J E, 2013. Selection of ore from multiple pits, in Proceedings Iron Ore 2013 , pp 185-192 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 12, 2013

By Samuel F. Rodrigues, Clodualdo Aranas Jr., Fulvio Siciliano

The application of thermo-mechanical control processing (TMCP) in hot rolling of steels has become a common routine since the last 60 years. The understanding of the physical metallurgy behind TMCP played a major role in the early developments. Physical and numerical simulation works are performed firstly to derive the fundamental metallurgical knowledge and secondly to conceive existing TMCP practices. In this paper, a summary TMCP techniques is presented. The occurrence of dynamic transformation of ferrite in the austenite region is shown by means of synchrotron light diffraction methods. This phase transformation mechanism is taken into consideration and its effects on TMCP are proposed in an exploratory way.

Oct 1, 2019

By R. A. Lowe

Smectite is a common impurity in the kaolins of Georgia. This impurity is harmful to the low-shear rheology of kaolin slurries in concentrations as low as a few weight percent. The deleterious effect of smectite on the low-shear rheology is due to the swelling of the mineral. Montmorillonite containing clays were treated to precipitate a compact brucite layer {Mg(OH)2} in the interlayer region of the expandable layer silicate mineral. This treatment forms a hydroxy-Mg-montmorillonite with characteristics similar to chlorite. This treatment effectively reduces the swelling capacity of the mineral and improves the rheological properties of kaolin slurries contaminated with smectite impurities.

Jan 1, 1999

By J. Bertisen, G. Davis

Previous analyses of small samples of mining projects have found that feasibility studies tend to well under-estimate the actual capital costs of the project. Our review of 63 mining and smelting projects completed over 4 decades confirms that as-built capital costs are, on average, 25% higher than as estimated at the bankable feasibility study stage. There appears to be little attenuation over time of this bias in capital cost estimation, at first appearing to reflect an absence of learning on the part of the consulting engineer. We instead argue that this persistence of bias is intentional, driven by a scarcity of project financing and the need to inflate the project economics in a bid to secure financing. Around this intentional bias is a considerable amount of scatter. Roughly half of all projects’ as-built capita costs fall outside of the expected ±15% of the feasibility study capital cost estimate, even after allowing for intentional estimation bias. Cost overruns of 100% or more happen in roughly 1 out of 13 projects. The data reveal that a shifted lognormal probability distribution should be used when modeling mining project capital costs in a Monte Carlo analysis.

Jan 1, 2007

By Travis Watts, Chris Prater, G. T. Lineberry

Moving overburden at minimal cost is becoming increasingly important to coal mining companies throughout the U.S. The coal market is currently doing well, with an average spot coal price for Central Appalachia product (12,500 Btu, 1.2 SO2) standing at $62.00 for the week ending November 11, 2005, so it is at this time that companies stand to achieve healthy rates of return on their investments. Cast blasting is one method of blasting used effectively by some surface mining operations. This method allows most of the overburden to be removed and placed (cast) directly in the spoil pile by the use of explosive energy. With the proper design of a cast blast, a high percentage of overburden material can be directed into piles without the use of earthmoving equipment, hence increasing production and lowering the cost associated with overburden removal.

Jan 1, 2006

By S. S. Ibrahim

The left behind material after the combusion of fossel fuel in some power stations in Cairo; weighing tens of tons every years, was investigated. The material called "Fly Ashes" containing 7.5% Ni, 10.0% V and 9.50% Cr; could be considered as a promising source of such valiable elements. As well as the small grain size (050 70 "m) of the material, and besides the complexity of their formation history, hydrometallurgical methods appeared to be the effective technique to deal with. Yet, preconcentration is possible by means of magnetic and gravity separation methods. The end product is assaying 16.60% Ni and 20.2S!; V with weight recovery of about 60.15%.

Jan 1, 1995

By M. A. Qianjie

The problems of coalmine safety in china remain unsolved for decades. Starting with the description on safety status quo of coalmine in china, different existing analysis and measures discussed for the safety problem solution of coalmine china. With the consideration of system thought in mind, the author present with a unique systematic reason analysis method on such actuality--individual analysis and general analysis--each for its particular purpose. Upon such cause analysis, construction of the safety system is made clear and, solutions for such problems provided.

Jan 1, 2006

By Peter N. Gabby

A mineral survey of 8,300 acres of the 24,980-acre Burnt Creek Wilderness Study Area (ID 45-12), was conducted by the U.S. Bureau of Mines in 1985 at the request of the Bureau of Land Management. The study area is located in Custer County, ID, 90 miles northwest of Idaho Falls. No mines, claims, or prospects are in the study area. The northern half of the study area and adjacent lands to the north, northeast, and east are or were recently under oil and gas lease, Basalt and latite-andesite of the Challis Volcanics predominate in the study area. Several hundred feet east of the study area is a quarry in talus of Mississippian-age limestone that was used for sized 100-pound rock fill in the Old Dry Creek Reservoir dam. Two samples, one taken at the quarry and the other at a limestone outcrop on East Fork Burnt Creek, have CaC03 content in the range of 90 to 95 percent, and is suitable as the limestone component of Portland cement, However, limestone outside the study area could supply foreseeable demand. Lead- silver mineralization has been observed in Paleozoic carbonate rocks elsewhere in the Lost River Range, but these rocks do not occur in the study area.

Jan 1, 1986

By Raymond L. Lowrie

Deregulation, as authorized by the Energy Policy Act of 1992 (PL102-486) allows free-market competition in the electric-utility industry. As the act unfolds, though, uncertainties abound about the type, degree and direction of impacts throughout the affected economy — from fuel suppliers to electricity generators and from power distributors to energy consumers. Instead of having a familiar base of captive customers and electricity prices fixed by negotiation with state public utility commissions, utility companies are preparing for open, free-market competition. They are looking at all areas, including fuel supply, to cut costs to remain competitive. Humorous anecdotes are told about utility companies shunning insiders for senior executive positions. Instead, they are opting for people from the telephone or other industries with deregulation experience. And there are light-hearted stories about a trend away from traditional electric-company names, such as the name of a city or state followed by Edison or Power and Light, to space-age names, such as Ameren, Entergy, Illinova or Unicom. No one wants to be left behind or be perceived to be left behind.

Jan 1, 1996

By William Kranz

THE increased service demands on some of the products of the National Malleable Castings Co. prompted it about eight years ago to investigate the electric furnace, both in America and in Europe. The process bad' already been sufficiently developed in Europe to lead us to believe that the electric furnace would most nearly meet our requirements. After further investigation and consultation with the highest authorities on the subject, we decided upon the Heroult type as the simplest and most practicable. In 1910, we built a furnace of this type, of 300 lb. capacity, for experimental purposes, and although it was crudely constructed the quality of the material we were able to make justified the installation of a 6-ton Heroult furnace in 1912. This furnace has three electrodes, 17 in. in diameter, uses three-phase, 60-cycle current, and is equipped with Thury regulators, which give us good regulation and a uniform load on the line even when cold melting. The power factor of the furnace is 94 per cent. Since July, 1912, the furnace has been in continuous operation, producing up to the present time, over 20,000 tons of both carbon and alloy steels of varying analyses and of exceptional quality. Both cold-and hot-metal charges have been used, with a power consumption of about 150 kw-hr. per ton in the case of hot-metal charges and from 500 to 600 kw-hr. per ton in the case of cold charges. The electric energy consumed varies according to the final analysis of the steel and the amount of refining required. Too much cannot be said about the refining possibilities of the electric furnace, for no other method of steel manufacture can compete with the electric in this respect.

Jan 5, 1915

By W. M. Jr. Aubrey, R. L. Stone

INTRODUCTION Most metallic minerals and some industrial minerals have a relatively high specific gravity and most have at one time or another been concentrated by gravity methods. The principles of gravity concentration are straightforward, well documented and easy to understand, but in practice there are many pitfalls that await the engineer in the development of an integrated flowsheet. Gravity concentration equipment has a long history of use and there is a great diversity available. The equipment is capable of treating material over a broad size range, only falling off in efficiency in the very fine sizes. Gravity concentration is also inexpensive, generally free of environmental problems, and commercial equipment can process large tonnages of ore with a minimum of capital cost. As might be expected of an efficient and low cost process, the bulk of the tonnage quickly and inexpensively. Another obvious application is treating mineral deposits such as hematite and manganese ores that are sufficiently liberated after a minimum of crushing to allow production of a coarse concentrate that will meet market specifications. Except for hand picking and mechanical sorting, there is no competing process on coarse size material. Conversely, it is sometimes obvious that gravity concentration does not warrant consideration. Examples are ores that require very fine grinding to attain liberation, for ores where the minerals of interest have a gravity similar to the gangue, and ores that are strongly magnetic. Actually a mineral processing engineer may not know if gravity is the best way to concentrate an ore, but he should have little difficulty recognizing when gravity concentration deserves consideration based upon specific gravity differences and liberation gravity concentration has wide use. size. His challenge then is to At times its selection as the identify and test the applicable primary concentration process is processes, to develop a obvious. Low grade placer deposits metallurgical balance and flowsheet of tin, gold and beach sands usually for the best process, to estimate are only profitable because gravity production rate over the life of concentration is able to throw away the deposit and to make equipment

Jan 1, 1986

Longwall mining is a commonly used method of coal extraction that involves the complete removal of large, rectangular panels of coal. Longwall mining causes the immediate seam roof to break and fall into the void created by mining. The convergence of the surrounding strata towards the mining void causes subsidence on the surface. The subsidence magnitude is related not only to the mining depth, the topography, the geological features and the overburden materials, but also to the sequence of the strata overlying a coal seam. In additional to the vertical subsidence which is evident at the surface, there are also horizontal movements inwards toward the centre of the void, which cause the surface to tilt, bend, stretch and com-press. This paper presents a parametric investigation of the influence of the overburden stratigraphy to surface deformations due to longwall mining using 2D finite element models. Models simulate rock movement by applying equivalent edge load to the open roof.

Jan 1, 2008

By Georg Petersen

El presente artículo describe la actividad petrolera realizada durante el año 1962. En 1863 el Gobierno del Perú derogó al Ing. A. E. Prentice el estudio de las posibilidades petroleras de Piura y Tumbes, a través de la perforación del primer pozo de petróleo en Zorritos a través de herramientas imperfectas. Ante tal éxito, en 1864 Lama y Rudens gestionaron que se constituya en Nueva York la "Compañía Peruana de Petróleo". Posteriormente, doce compañías petroleras han desarrolado trabajos de exploración y nueve se encuentran en estado de producción. En este plano tenemos a Belcom Petroleum Corporation Perú, Cerro de Pasco Company, Empresa Petrolera Fiscal, Compañía peruana de Petróleo "El Oriente", International Petroleum Company, Mobil Oil Company, Mobil Oil Company of Perú, Compañía de petróleo Ganso Azul, Peruvian, entre otros.

Jul 1, 1963

By Georg Petersen

El presente artículo describe la actividad petrolera realizada durante el año 1962. En 1863 el Gobierno del Perú derogó al Ing. A. E. Prentice el estudio de las posibilidades petroleras de Piura y Tumbes, a través de la perforación del primer pozo de petróleo en Zorritos a través de herramientas imperfectas. Ante tal éxito, en 1864 Lama y Rudens gestionaron que se constituya en Nueva York la "Compañía Peruana de Petróleo". Posteriormente, doce compañías petroleras han desarrolado trabajos de exploración y nueve se encuentran en estado de producción. En este plano tenemos a Belcom Petroleum Corporation Perú, Cerro de Pasco Company, Empresa Petrolera Fiscal, Compañía peruana de Petróleo "El Oriente", International Petroleum Company, Mobil Oil Company, Mobil Oil Company of Perú, Compañía de petróleo Ganso Azul, Peruvian, entre otros.

Jul 1, 1963

By Dale A. Sketchley

The objective of Quality Assurance and Quality Control programs on advanced exploration projects is to ensure that data from sampling, assaying, and recording of geological observations are of high integrity for the purpose of obtaining reliable mineral resource and reserve estimates. National Instrument 43-101 Standards of Disclosure for Mineral Projects states that all scientific and technical reports must be prepared and certified by a Qualified Person in accordance with professional and industry standards following Mineral Exploration Best Practices Guidelines and Definitions, and Guidelines of the CIM Standards on Mineral Resources and Reserves. Additional information is given in Companion Policy 43-101CP and Technical Report Form 43-101F1. Although the Qualified Person must discuss and describe the Sampling Method and Approach; Sample Preparation, Analyses, and Security; and Data Verification; there is little specific information in the guidelines on Quality Assurance and Quality Control programs. Examples from the Oyu Tolgoi Cu-Au Project are given for optimizing sampling protocols, following proper sample preparation procedures, safeguarding sample shipments through chain of custody, ensuring quality of assaying with Round Robin monitoring programs, verifying transcribed data, and validating data with check assays to ensure high integrity for resource and reserve estimation. Oyu Tolgoi, also known as Turquoise Hill, is in the South Gobi desert, Mongolia, about 550 km south of the capital city of Ulaanbaatar, and 875 km northwest of Beijing, China. The project covers a major copper-gold system, which consists of the South West, South, Central, and Far North deposits, comprising high sulphidation and porphyry mineralization with oxide, supergene, and hypogene ore types. Exploration is done by multiple diamond drill rigs, and samples are prepared on-site and shipped to laboratories in Mongolia, Canada, and Australia for further preparation and analysis.

May 1, 2003

By Bo Zhou

During secondary aluminum recovery, complex aluminum scraps are melted and refined often in a rotary melting furnace and the aluminum metal has to pass through a molten salt layer and melt down in a bottom aluminum bath. Previous experimental study and industrial observations have indicated that salt shell formation and re-melting on the metal solids in the early stage plays a critical role in the overall melting process of the scrap. In the present paper, mathematical models are developed to simulate the process of salt shell formation and its re-melting, as well as aluminum melting in the molten melt. Influence of the salt layer properties, the residence time of the metal particles in the salt layer, the particle size, the temperature of bulk melt were investigated. Reasonable agreement with the measurement data was reached. The developed melting model will be used to construct a population balance model of the scrap melting behavior for a rotary melting furnace, taking into account the distributed characteristics of the scrap. Finally, an overall process model based on Computational Fluid Dynamics (CFD) for the rotary furnace will be constructed, coupling with the population balance model for the scrap melting.

Jan 1, 2003

By Plato Malozemoff

Our young, technically oriented people today are entranced by the space program, by physics that unlocks the secrets of nature, by electronics, and by other new technologies. The mining industry seems to be their last choice. Enrollment in mining schools is dropping and so is the interest of our great universities in mining curricula. The image of the mining industry appears to be one of being conservative, nonprogressive, resistant to change, and lacking in excitement and challenge. I submit that this public image is wrong. While the initial development of mines is usually slow and seemingly plodding, the problem of solving the imponderables of nature-the ore emplacement, its structure and physical characteristics, its response to recovery processes, and its probable ultimate profitability-is stimulating to the most acute and searching of minds and requires careful application of a combination of many technologies. The paths to obtaining the desired results must be within the bounds of reasonable expenditures in the early stage of development when risks are still high, and this financial discipline is a further stimulus to the imaginative search for the right answers.

Jan 6, 1968

By J. M. Menacho, J. M. Reyes

"Batch and continuous regrind tests were conducted in 3 kW and 15 kW tower mill units, respectively. Single particle size classes of a chilean copper sulphide concentrate were employed in the batch tests, while a fraction of the plant stream was deviated to the continuous unit operated under different conditions.Results are interpreted in terms of the simplified grinding kinetic model energy-based and conveniently adapted to this application. Based on the above figures plus some industrial data supplied by MPSI Inc., a scale-up relationship was developed for the apparent specific rate of breakage siE, as a function of the net power draw P, i.e.siE = siE text (P/P test) 0.089This equation fit very well the available data at the three scales and its application to regrind 4400 t/day of rougher copper concentrate from 70% below 325 Tyler mesh to 95% below same mesh, involves around 30% energy-saving compared to standard ball mill for same grinding task.INTRODUCTIONImpact and abrasion-attrition breakage are two extreme mechanisms present in any grinding system in a proportion defined by specific design and operating conditions. Impact breakage is generally efficient for coarse grinding, while abrasion-attrition is adequate to produce fine particles. Efficiency of conventional tumbling mills decreases as fineness of the product increases, even though distribution of applied stresses is always much stronger than internal force distribution in the particles. On the other hand.in a vertically stirred ball mill like the tower mill, distribution of applied stresses and particle strengths are in the same order of magnitude, making possible nearly ideal abrasion conditions (1).Tower mill configuration includes a cylindrical body vertically mounted and provided with a central screw with flights to produce circulation of balls moved up through the inner region to return down by the external space. Fresh material can be fed into the top , center or bottom in order to assure appropriate agitation of suspended particles. Size reduction and evacuation rates should compensate settling of coarse particles to avoid sanding of the screw. Detailed description of the tower mill and its operation have been given elsewhere (2),(3)."

Jan 1, 1989

By J. M. (Mac) Beggs

With New Zealand?s ratification of the United Nations Convention on the Law of the Sea in 1996, the government of the day increased work on developing an oceans strategy to help create a governance framework for the country?s extensive existing and potential maritime territories. This project took a new direction in 2001 with the establishment of an ad hoc committee of 6 Ministers, and their appointment of a Ministerial Advisory Committee (on which the senior author served) to consult with the public, identify widely held values and inform the development of a Vision for subsequent policy development. The current second stage of the policy development process involves a working group of officials from the relevant agencies completing a stock-take of existing laws and regulations to identify overlaps and gaps that should be addressed in the third and final stage. The public consultation process revealed, as might be expected, a wide range of perspectives but a solid consensus in favour of a coherent, and balanced, framework to enable the realization of economic benefits of ocean development so long as appropriate environmental standards (broadly expressed in terms of sustainability) are not compromised.

Jan 1, 2002

By R. o. Cretier, L. A. Cisternas, A. López-Valdivieso, F. Valdes, E. Gálvez, G. Gahona

The size of the particle plays an important role in the flotation of minerals. Comminution allows the release of valuable species and their subsequent recovery. Then, the degree of concentration and recovery will depend on the size of the particle. In this work, we investigated the flotation of coarse particles (-850 +150 μm) of copper ores when using the fluidized-bed separator (HydroFloat® cell) and compared it with the process of conventional flotation with medium size particle (-150 μm) (Metso cell) using seawater. The collector concentration was the main variable studied in terms of copper recovery. The results show that the flotation of coarse particles is feasible using seawater without frother

Jan 1, 2020