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By Steve Kral

In a lagging economy where profits are tight, businesses cut costs. No revelation there. The mining industry, though, has always looked for ways to reduce production costs — no matter the state of the economy or commodity prices. The fact is, when planning a new mine or the expansion of an existing one, mining companies gamble that commodity prices will be reasonably high when a project comes onstream. It takes millions of dollars and several years to bring a mine into operation. And a lot can happen economically between the time management gives the go-ahead for a new project and its completion.

Jan 1, 2002

By J. M. Wempen

Booster fans, large underground fans, can increase the volumetric efficiency of ventilation systems by helping to balance the pressure and quantity distribution throughout a mine, reducing leakage and reducing the total power requirement. However, in ventilation systems that use booster fans there is a potential for system recirculation, the leakage of return air to intake air, and also for localized recirculation near the fan through the bulkhead and airlock doors. Air that is recirculated locally decreases the system efficiency because the quantity of air flow through the fan increases without increasing the airflow throughout the system. To understand the detailed flow characteristics of a ventilation system with a booster fan, two-dimensional computational fluid dynamics (CFD) models were developed using the software Ansys-FLUENT. Though two-dimensional models do not represent the full complexity of the flow dynamics, they do provide a good representation of the flow characteristics and they allow for a qualitative analysis of how the flow dynamics are affected by the system characteristics. The CFD models were used to evaluate how the number of booster fans, the booster fan placement, the location and geometry of the fan installation and the construction of the airlock system affect the flow characteristics and the localized efficiency of the ventilation system.

Feb 27, 2013

By T. J. Lynch

A new class of polymeric dispersants for industrial minerals has been synthesized and evaluated. Currently available dispersants give initial low viscosities at high mineral loadings, however slurry viscosities can rapidly double or triple on standing over the first several days. The new dispersants give low initial viscosities that are more stable and maintain a lower viscosity for at least one month. The new dispersants are made possible by controlling the polymer molecular weight distributions during their manufacture such that essentially all of the dispersant is adsorbed onto the mineral surface, preventing depletion flocculation.

Jan 1, 2012

By A. M. Radigan, W. G. Prast

M.S. Azun The authors' paper did not explain the facts and reasons why state companies are established and what their role is in international industrial mineral trading. Also, I do not agree with the conclusion implying that the main goal for state companies is to capitilize natural resources. Almost all state companies are founded by certain laws and their activities are arranged by state regulations. Their only aim is to operate mineral deposits for their people and to protect the rights of the people. Although some ore deposits, such as nonstrategic or small, may be exploited by privately owned companies, the state has the right to control the operation and production. Activities of state companies may or may not be widened because of the character of the deposits and the importance of the mineral market involved. For some countries, although governments may occasionally change hands, the policy of the mineral trading system is not affected by this change. There is no doubt that any government desires to make more earnings to increase GNP, when it is involved in operating and trading mines. It wants to produce and sell the finished products, instead of unprocessed ones, if possible. When it is known that some mineral deposits are relatively rare, such as Turkish boron deposits, the government can nationalize the mines to control production and affect the market. If there is an abundance of a certain mineral in the market, the government can cut production and set a floor price, such as Canadian potash. Also, when production of a specific mineral is unique, such as Turkish chromite, the price of such mineral may be set by correspondant government. One may add that if some governments with their state companies produce a certain mineral in a larger amount, they may decide to establish a cartel to protect their production and price. These are the facts followed by government-owned state companies and partially government-owned companies. The reason being charge of many deposits by the state companies is always the same: "protect" the mineral rights of the people.

Jan 2, 1984

By D. F. Machuca-Mory

A change of support model consists of a procedure to change a stationary histogram at a small data scale to represent a larger scale; typically a distribution of sample drill-hole data is changed to represent a chosen selective mining unit (SMU) scale. Most grade variables average arithmetically. Thus, the mean stays the same for different scales, and the variance changes according to well-established theory using average variogram values. The longstanding challenge has been to predict how the shape of the histogram changes. The discrete gaussian model is widely used because it appears reasonable and introduces few artifacts; there are no artificial minimum/maximum values and the target mean and variance are reproduced exactly. The resulting distribution shape, however, is strongly dependent on a multivariate gaussian distribution. The authors generalize the approach by taking advantage of a property of the isofactorial model, which allows one to specify where the random function falls on the spectrum between a low-entropy mosaic model and a maximum-entropy diffusion model. A measure of dissemination (MD) is computed using a ratio of the madogram and the variogram. The change of support algorithm is developed that uses a variable measure of dissemination (VMD) that is easily calculated and fit to data from the deposit. The resulting VMD change of support model is very flexible to represent different mineralization styles encountered in practice; global predictions of recoverable reserves are more accurate and decision-making is improved. A number of real examples are shown to demonstrate the approach.

Jan 1, 2008

By R. W. Carn, D. Vincent

Environmental Considerations With significant increases in bulk coal movements through terminals, operators are under constant social and political pressure to reduce or remove environmental pollution problems incidental to their operations. To meet these requirements, both equipment manufacturers and terminal designers are endeavoring to design equipment and systems with stringent environmental controls. The most challenging environmental problems facing coal terminal designers and developers are terminal siting restrictions, dust control, and noise abatement. Terminal Siting Finding a suitable site can be a difficult problem because of public concern over coal dust or the impact of a terminal on the surrounding community or natural habitat of the area. Often the only suitable flat land available for terminal development is on a tidal estuary or salt water marsh with great environmental value. In many cases a period of four to six years of full environmental and social assessment has been needed. A recent example of such difficulties is the expansion at Roberts Bank, British Columbia, where environmental impact assessment studies and their public review took almost six years from initial expansion applications until the time of approval. Dust Control Modern coal terminal dust control techniques usually consist of water sprays at strategic locations to suppress dust. The application points include rail car or barge dumper, main conveyor transfers, perimeter sprays around stockpiles, stacker/reclaimer, ship-loader transfers, and loading spout. The water sprays may include a chemical wetting agent or surfactant to reduce the water requirement and increase effectiveness. Recently there have been advances with development of effective micro foam agglomerating agents. In these systems, a micro foam with very small bubble sizes is sprayed into the coal stream. The foam fills the interstices between coal particles and wets the coal fines. These systems have proven to be very effective and usually one application before stockpiling and one upon reclaiming will markedly reduce the coal dusting. Stockpile perimeter sprays can be operated either manually or at the sophisticated terminal, actuated by a computerized control system that senses key environmental conditions such as humidity, precipitation, and wind velocity. Most modern terminals collect the drainage from the stockpile area, remove the solids in settling basins, then recirculate the water to reduce water requirements and effluents from the site. Dusting of long-term storage stockpiles can be reduced by spraying the piles with chemical resin or latex binding compounds to seal the surface. These compounds also can minimize erosion of the pile by rainfall. Dust collection with air evacuation systems and cyclone or wet scrubbers can be used at key areas such as rail car dumpers, main conveyor transfers, and ship-loader spouts. The trend in dust control is away from dust collection since most dust collectors are high maintenance items requiring good operator supervision and servicing. Coal handling conveyors are usually open and uncovered. However, in areas requiring special attention they may be covered or even completely enclosed. Dust generation from terminal roads is often a significant amount of the total dust emitted from a terminal. To reduce this dusting, roadways where traffic is heavy can be paved or sprayed by water trucks. Speed limits can be enforced and use of tracked mobile equipment for stockpile handling rather than rubber-tired loaders is encouraged by authorities. Noise Abatement Terminals located close to residential areas are often faced with noise control problems. Noise can be one of the most difficult environmental problems to solve. Usually, use of electrically-powered equipment is encouraged to reduce noise levels. Rail car dumper houses can be totally enclosed to reduce both dust and noise emissions. Diesel locomotives can be fitted with special muffling devices. Green belts of trees surrounding a terminal or the ap-

Jan 7, 1983

By J. A. Botín

NPV is a static measure of project value which does not discriminate between levels of internal and external risk in project valuation. Due to current investment project?s characteristics, a much more complex model is needed: one that includes the value of flexibility and the different risk levels associated with variables subject to uncertainty (price, costs, exchange rates, grade and tonnage of the deposits, cut off grade, among many others). Few of these variables present any correlation or can be treated uniformly. In this context, Real Option Valuation (ROV) arose more than a decade ago, as a mainly theoretical model with the potential for simultaneous calculation of the risk associated with such variables. This paper reviews the literature regarding the application of Real Options Valuation in mining, noting the prior focus on external risks, and presents a case study where ROV is applied to quantify risk associated to mine planning.

Jan 1, 2012

By Z. H. Zhou

It is difficult to remove cadmium from raw indium using only electrolytic refining because their standard potentials are similar. In this paper, physical and chemical methods were used to remove Cd from raw indium. Indium metal is vacuum refined for two hours at 400°C with a vacuum pressure of 20 Pa. In this process, 99.70% of the Cd can be removed. The removal rate of Cd reaches 90% to 95% when indium is further smelted for 10 minutes in a 20% glycerin solution of KI and I2 at 180°C. When pre-indium is electrolytic refined in an In2(SO4)3-H2SO4 system, in which the indium content is 80 to 100 g/L, the pH is 2.0-3.0 and the current density is 80 to 100 A/m2, the contents of the impurities decrease and the purity of the indium product reaches 99.99%.

Jan 1, 2007

By Jim Owens

The methodology of quarrying changed significantly in the Indiana limestone industry in the 60 years between Sept. 11, 1941 and Sept. 11, 2001. The former was the date of the Pentagon groundbreaking ceremony, while the latter was when the building was damaged by American Airlines Flight 77. So too, though to a lesser degree, did the machinery and methods used to fabricate the stone. The rededication ceremony on Sept. 11, 2002 marked the end of the Phoenix Project, as the rebuilding effort was named. The story of this remarkable project illustrates what the American construction(and Indiana limestone) industry can accomplish when working toward a common goal.

Jan 1, 2005

By S. Rupprecht

"This article addresses the prevalence of poor public reporting practices of coal exploration results, coal resources and coal reserves in southern Africa. Currently, the reporting of coal tonnage without supporting coal qualities or saleable tonnes and quality is a poor reporting practice that occurs far too often. Not all coal is equal — therefore it is extremely important that investors or potential investors are provided with the full details of both run-of-mine (ROM) and saleable coal tonnage, their associated qualities and other material and relevant information.Competent or qualified persons should note that publicly reported information should be sufficient to enable an informed reader to make a reasonable and balanced assessment of the significance of the information provided. “Companies are encouraged to provide information in their public reports, which is as comprehensive as possible (CRIRSCO, 2013).” However, too often this isn’t the case, and material matters are either not reported or inadequately disclosed.According to the South African National Standard (SANS) 10320:2014 draft document, “tonnage and coal quality that will be available for sale, either in the raw ROM state (raw saleable) at a specified moisture content, or after beneficiation of the ROM coal by processing operations to produce materials at specified qualities, size ranges and moisture contents. The assessments must demonstrate that at the time of reporting, the marketing of the products is reasonably justified. The basis of the predicted practical product yield to achieve the saleable coal reserve must be stated. The moisture basis of reporting shall be stated.” An example as to why coal qualities are so important to the public, the requirements of South Africa’s electric public utility (Eskom) power stations are detailed in the followint paragraphs. The Kendal power station, commissioned in 1988, operates at a calorific value (CV) range of 19 to 20 MJ/ kg, an ash content between 29 and 34 percent and volatiles between 20 to 21 percent. Other power stations, such as Kriel or Hendrina, may require different qualities, such as a CV range of 22 to 23 MJ/kg, an ash content between 20 and 28 percent and volatiles between 22 to 23 percent. Thus, in terms of domestic saleable coal, it is not just about reporting the coal qualities but also informing the investor as to which power station the coal is intended to be sold as “boilers are designed to burn particular qualities of coal” and “it is not always possible to transfer coal between stations because of different quality requirements at each station (Chetty, 2010).” Sulfur content is another important quality with the ideal coal content having a quality of less than 1 percent sulfur."

Jul 1, 2019

By A. Noble

The design of separation circuits can be a complex, labor-intensive and costly process. While the engineer?s experience along with extensive data sets and simulation are crucial tools for determining the final solution, a more fundamental approach is suitable to compare preliminary options and reduce the number of potential alternatives. In light of this need, the authors have developed the Circuit Analysis Reduction Tool (CART?). This software package relies on the fundamental principles of linear circuit analysis; however, the solution methodology has been streamlined to automatically incorporate stream splitting and unique separation performance for each unit. The resulting tool allows preliminary analysis of circuit designs without the need of detailed feed characterization. In addition to the basic analytical approach, this paper supports the veracity of the methodology with several simulated examples for various separation models.

Feb 27, 2013

By M. J. Blattman

Upon completion of an underground mine design, the planning engineer is faced with a surprisingly complex problem, “What development and mining sequence should be implemented so as to maximize the return on investment?” The problem relates to the scheduling of development headings to access stope production areas in such a way that the most money is made as quickly as possible for as long as possible. The total dollar value of the stopes, the average grade, the total tonnage, nor even the profit margin do not accurately give an indication of the “proper” mining sequence on their own. This paper will outline a method being developed by the author that can create a sequence of events that maximizes the net present value (NPV) of a given development and production design using information already being generated during the design process.

Jan 1, 2003

The Pogo Mine, near Delta Junction, Alaska is a new 2500 STPD gold operation. The control system of the mine and milling operations are a hybrid of DCS (Distributed Control System) control and PLC (Programming Logic Controller) control. A DeltaV DCS system serves as the main control and operation platform while the PLCs operate a multitude of vendor specific packages. The communication backbone of the DCS system is a hybrid of star and ring fiber optic topology, which provides reliability and flexibility. The communication between the DCS and PLCs is typically facilitated by serial communication. This communication insures the integrity of the whole control system.

Jan 1, 2008

By M. Karmis, C. Haycocks

The evolution of longwall mining is briefly traced from its inception in England in the 1620's. In the beginning this method recovered 90% of coal with roof closure controlled by packs and walls. Mechanization began with kerf cutting, crude face conveyors, and improved face support. Full face mining was accompanied by the introduction of self- advancing hydraulic supports. U. S. longwalls evolved a retreating system to recover blocks of coal outlined by room and pillar panels. Computer control combined with the most modern technology have greatly increased productivity. Past trends are used to predict future technological directions.

Feb 24, 1997

By J. V. Ghelarducci, M. A. Sharpe, D. G. Chedgy

This article presents a novel design, called the Climax, High Capacity Processor (HCP), for pre-combustion cleaning of coal. This design is particularly suitable for the plant capacities of 400 ~ 660 TPH. The HCP is different from the conventional designs with an equivalent throughput in three major aspects: 1) the use of one large capacity HM cyclone to separate coarse and intermediate raw coal in a single circuit; 2) the elimination of the conventional secondary magnetics recovery system by use of the high efficiency Climax, magnetic separators; 3) the use of "single line" piping with a minimum requirement of ancillary devices. In comparison with conventional designs with similar capacity, the HCP plant costs much less in capital investment, operation and maintenance.

Feb 24, 1997

By H. Verakis, M. J. Sapko

The Pittsburgh Research Laboratory (PRL)1 of the National Institute for Occupational Safety and Health (NIOSH) in collaboration with the Mine Safety and Health Administration (MSHA) Technical Support Center has devised a prototype hand-held instrument which can provide a direct assessment of the potential explosibility of a coal and rock dust mixture. Current Federal regulations require that rock dust be applied in all underground areas of a coal mine to mitigate the propagation of a coal dust explosion. To determine compliance with the Federal regulation, mine inspectors collect dust samples from sections of underground coal mines for an MSHA laboratory analysis of incombustible content. However, the laboratory analysis may not be completed for more than a week or two, during which time the mine area from which samples are taken may be inadequately protected. The operation of the Coal Dust Explosibility Meter (CDEM) is based on the difference in optical reflectance between light rock dust and dark coal dust. For a given coal volatility, the optical reflectance of such mixtures is relatively constant at the limit of explosibility, independent of the coal dust particle size. The CDEM is not intended to replace the current MSHA laboratory analysis of coal mine dust samples for incombustible content, but to serve as a supplemental device for enhancing mine safety through improved rock dusting practices.

Jan 1, 2006

By D. McBride

Representative samples are required from process streams in order to accurately measure chemical and physical characteristics. This information can then be used by process operators and metallurgists to evaluate the process and effect control actions for the operation. The capture and presentation of representative samples can be critical to measuring values, such as elemental analysis and particle size, with on-line or near-stream analyzers. A comprehensive multi-physics model has been developed and used to better understand the effects of slurry flow and particle segregation under certain operating parameters. An algebraic slip model coupled with a free surface algorithm is used to track motion and position of particles and phases within a specified geometry.

Jan 1, 2009

By M. D. Lackey

The "Art" of Big Hole Drilling has been in a continual state of evolution at the Nevada Test Site since the start of underground testing in 1961. Emplacement holes for nuclear devices are still being drilled by the rotary drilling process, but almost all the hardware and systems have undergone many changes during the intervening years. The current design of bits, cutters, and other big hole drilling hardware results from contributions of manufacturers and Test Site personnel. The dual string, air lift, reverse circulation system was developed at the Test Site. Necessity was really the Mother of this invention, but this circulation system is worthy of consideration under almost any condition. Drill rigs for Big Hole drilling are usually adaptations of large Oil Well drill rigs with minor modifications required to handle the big bits and drilling assemblies. Steel remains the favorite shaft lining material, but a lot of thought is being given to concrete linings, especially precast concrete.

Jan 1, 1983

By P. A. Hagerty

Biological treatment of metals-impacted water using sulfate reduction is a viable means of treatment that has been applied in pilot and full scale at numerous projects. One of the fundamental challenges with this type of treatment is the selection of an appropriate substrate to support the sulfate reduction process long-term. The substrate degradation products provide a carbon source and an electron donor for metabolism by sulfate-reducing bacteria and consequently organic characteristics are critical; however, the physical attributes of the substrate are equally critical to an efficient and optimized substrate mix. This paper explores the affect of particle size (a.k.a. grain size) of several substrate mixes on the treatment efficiency of sulfate reducing treatment systems. Substrate selection can be separated into two phases of evaluation, the primary selection phase and the secondary optimization phase. The primary selection phase considers such fundamental attributes as source availability, economics, bioavailability and longevity. These fundamental activities are conducted in order to identify potential candidate ingredients of the substrate mix which are regionally available, economically viable and consistent with the biogeochemical aspects of the project. Recent work has been conducted in the development of testing protocol for organic substrates to quantify bioavailability (Martinez Hernandez et al. 2010, Place et al. 2006) as part of the primary selection phase. Once the substrate ingredients have been selected based on the primary criteria, the mixture of these ingredients is then developed based on an optimization process, including consideration of the substrate ingredient?s particle size distribution.

Jan 1, 2011

By L. Xinghua

Limonite is a general term for a group of amorphous iron oxide and iron hydroxide materials. It is considered as one of the very refractory iron ore types due to its wide variation in chemical composition, iron content, moisture content and easily sliming in the course of comminution. Iron grade of test sample is 25.48%, the iron minerals are mainly limonite; and the gangue minerals consist of quartz and feldspar in majority, secondarily silicate minerals. In this test work, high intensity magnetic separation (HIMS)-cationic reverse flotation and magnetic roasting-low intensity magnetic separation (LIMS) tests were conducted on limonite ore. The test results show that the concentrate with iron grade of 50.97% and recovery of 68.50% can be obtained by HIMS-cationic reverse flotation technique; while using magnetic roasting-LIMS technique, the better concentrate indexes of iron grade of 60.36% and recovery of 89.71% are achieved, and the iron grade of tailing is only 4.42%. Therefore, the magnetic roasting-LIMS technique is a better suitable method for beneficiation of low-grade limonite ore. Keywords: Low-grade limonite; Mineralogy; HIMS; Cationic reverse flotation; Magnetic roasting; LIMS

Feb 27, 2013