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By M. Kumral

Raw material fed into a processing or refining plant is required to be uniform in composition for several reasons. When the mined ore is highly variable in quality the only way to ensure consistency is to homogenize the ore prior to the process. The problem is more complicated in the case of multiple ore sources. The idea behind the research is that theoretical blending ratios can serve not only to meet predefined specific criteria but also to reduce grade fluctuations of variables under consideration. In this paper, the problem is formulated as a quadratic programming problem, whose objective function is in quadratic form and constraints are linear. A case study was conducted on a data set from an iron orebody to demonstrate the technique. The objective was to minimize the blend variability in terms of each variable (in this study, iron, silica, alumina and lime) grade of ores extracted in three different production faces. The stockpile capacity, lower and upper limits of each variable satisfying operational requirements and non-negativity were constrained to the model. A modified simplex method developed by Wolfe was used for solving the blending and homogenization problem. The promising results can be used as apart of the stacking and reclaiming design. Keywords: blending and homogenization problem, quadratic programming, Wolfe method.

Jan 1, 2005

By L. R. C. Cairncross

In this study, the general case of semi-batch precipitation of nickel hydroxide, Ni(OH)2, is modelled. In practical terms, this precipitation may occur at high ionic strengths, and therefore the model for solution chemistry requires a thermodynamic model that is applicable for these non-ideal systems. The activity coefficient model used is the ELEC-NRTL. The simulation of the solution chemistry is performed using AspenPlusTM, which is a steady-state process simulation program. This allows for rigorous evaluation of the solution speciation, and hence the degree of supersaturation which dictates the precipitation kinetics. The solution chemistry provides the basis for predicting the formation of solids. The model consists of a solution chemistry part and a solids formation part. The inputs to the model include the initial concentrations of the streams entering the reactor, kinetic parameters for the precipitation processes, and a particle size distribution obtained from experiments. The solids formation part of the model employs the method of moments for the evaluation of the population balance. The population balance accounts for total particle number, and the formation and increase in size of particles across the entire particle size range. This balance requires kinetic parameters for the processes of nucleation, growth and agglomeration. Using optimization routines inherent in AspenPlusTM, parameters for the rate of nucleation, growth and agglomeration may be extracted from experimental particle size distributions. These are then used in the model to extrapolate to other conditions. Once an understanding of the kinetics of the precipitation processes is gained, the model provides a predictive tool for optimization of these kinetics, in order to increase the overall particle size and therefore improve solid-liquid separation. The work is deemed to be significant as it sheds some light on solids formation processes involved in precipitation?including nucleation, growth and aggregation?and develops a predictive modelling tool applicable to solutions of high ionic strength. We argue that this dewatering of suspensions is affected significantly by particle size distribution and surface properties of the solids formed by precipitation. This modelling tool should facilitate the design of solids formation processes where downstream dewatering is enhanced.

Jan 1, 1997

By Lawrence P. Goldfarb

This paper presents the results of the geotechnical investigation for the repair of the Fashion Island Boulevard Bridge, Bridge No. 350160, in San Mateo, California. The concrete, precast girder bridge suffered considerable damage during the Loma Prieta earthquake. The existing 36-inch, precast, prestressed concrete piles cracked and spalled at their tops. Based on analyses performed by Biggs Cardosa Associates, structural engineers, the piles did not have sufficient strength and ductility to resist the dead plus seismic loads specified in the Caltrans "Bridge Design Specifications". Additional support for the bridge was needed and the repair strategy consisted of installing large diameter pipe piles at the existing bent and abutment locations. This paper describes the geotechnical engineering analysis and design decisions for the large diameter pile design.

Jan 1, 1993

Provide improved permanent stoppings designed specifically for use in mines with large cross-sectional entries. Approach The large entry sizes in many mines, such as oil shale, salt, and limestone, make the conventional stopping construction techniques used in smaller opening mines unacceptable. The Bureau of Mines and Colorado Mining Association jointly sponsored a contract to design and test new or modified stopping concepts for these mines. The most promising concepts were then tested in an oil-shale mine having 30-foot-high by 55-foot-wide mine entry openings. All stopping designs tested were evaluated in terms of cost, air tightness, and resistance to blast damage.

Jan 1, 1987

By M. K. G. Vermaak

There are practical indications that flotation recovery of palladium bismuth tellurides is poor. This work tested whether this can be caused by a lack of interaction of the collector with the telluride. Impedance measurements, voltammetry and Raman spectroscopy were performed to determine the interaction of dithiocarbonate collectors (KEX) with Pd-Bi-Te. Impedance measurements showed lower capacitance values in solutions containing KEX, indicating the formation of a continuous surface layer. Anodic and cathodic polarization diagrams show the mixed potential to be higher than the reversible potential of the xanthate-dixanthogen equilibrium reaction; hence the formation of dixanthogen on the surface is possible. Electrochemically controlled in situ Raman spectroscopy did indicate the presence of bulk diethyl dixanthogen on the surface. Raman spectroscopy has confirmed the co-presence of xanthate with dixanthogen, indicating that xanthate retains its molecular integrity when it adsorbs on the surface of the Pd-Bi-Te. As a result, the mineral surface is expected to be hydrophobic and alack of collector interaction with the mineral is not the reason for the low PGM recoveries experienced. Keywords: Raman spectroscopy; Pd-Bi-Te; ethyl xanthate; platinum flotation; Great Dyke; Pd-bearing bismutho-tellurides and moncheite.

Jan 1, 2004

The more than 40,000 mining industry professionals that are expected to attend the National Mining Association’s(NMA) MINExpo International2000 trade show and conference will be treated to the exhibition’s largest display ever. The exhibit is expected to cover more than 60,385 m2(650,000 sq ft) and feature more than 1,300 exhibitors. The event is set for Oct. 9-12, 2000 at the Las Vegas Convention Center in Las Vegas, NV. Richard L. Lawson, NMA’s president and chief executive officer, said, “MINExpo 2000 will showcase everything that mining is proudest of. This is the largest premier mining exposition in the world.” MINExpo is held every four years.

Jan 1, 2000

By Kray Luxbacher

Three-dimensional time-lapse velocity tomograms were generated to image stress redistribution around a longwall panel to produce a better understanding of the mechanisms that lead to ground failure. Mining-induced microseismic events provided passive sources for the three-dimensional velocity tomography. Surface-mounted geophones monitored microseismic activity for 18 days. Most similar studies have utilized active sources including longwall shearers, controlled explosions, and hammer blows. These active sources generally require a person to initiate and measure the location and time of the source, and are not conducive to continuous monitoring. This method utilizes mining induced microseismic events as passive sources and lends itself well to continuous monitoring. Two event location methods were compared in order to move toward quantification of tomographic results in terms of ground conditions. Additionally, LAMODEL was utilized to determine the expected stress distribution around the longwall panel and compare these images to the velocity tomograms. Eighteen tomograms were generated, one per day, and high velocity regions in the set of tomograms generated from the initial location algorithm correlated with abutment stress redistribution predicted by numerical modeling. This research is significant as it has the potential to improve safety in underground mines and is the only example of long term passive velocity tomography implementation for the purpose of inferring stress redistribution around an area of active mining. Though still immature, this technology has the potential to allow mine personnel to image areas of active mining on a regular basis and detect areas with anomalous velocity distributions indicating potential safety hazards.

Jan 1, 2007

By W. S. Weldon, R. M. G. Machunter

The use of spiral separators for the beneficiation of fine coal typically in the size range - 2+0.lmm is now well established process technology. Developments during the mid 1980's resulted in the production of cost effective, efficient large diameter coal spiral separators. Recent developments and research have been geared to optimise metallurgical performance, materials handling and equipment geometry of large diameter coal spiral separators.

Feb 24, 1997

By F. Sawyerr

A bubble population balance model is proposed for the prediction of Sauter mean bubble diameters in mechanical flotation cells. In the model, the flotation cell is treated as two separate, statistically homogeneous zones?the impeller zone, and the bulk tank zone. Balance functions for the rates of bubble breakage, coalescence, recirculation and inlet-outlet events are proposed based on classical chemical engineering research in two- and three-phase fluid mixing systems. An initial simulation of the population balance model shows trends in bubble size distributions comparable to measured distributions in industrial mechanical flotation cells.

Jan 1, 1998

The main orebody of the Bodangora mine is a metalliferous quartz reef within a major fault plane in the strongly folded and faulted volcanic rocks of the Ordovician-Silurian Oakdale Formation. The similarity of the type of mineralization to that of other pyrometasomatic deposits in this area suggests that the mineralizing fluids originated in the nearby Wuuluman Granite.The associated Mitchell's Creek West or Dick's reef is discussed briefly.

Jan 1, 1970

By Walter Valery, Peter Radziszewski

"The NewCrest Cadia operation boasts the largest SAG mill commissioned last June 1998. A request was made to shed some more light on possible SAG mill charge behaviour. Three different software were used to simulate SAG mill charge behaviour:Mishra/Rajamanis MillSoft DEM charge motion program, Radziszewskis agglomerated DEM charge motion program and Powell/Nuricks MillTraj outer trajectories program. The contexts simulated are: 20/30 % charge volume, 65/75/85 % critical speed using the Hi-Lo lifter configuration specified for the mill as well as a Hi-Lo 60 degre lifter face configuration. Further, lifter interval was also studied to determine the effect on power draft. Power predictions are compared with those obtained during the commissioning period.INTRODUCTIONThe NewCrest Cadia operation is located outside of Orange, New South Wales, Australia. With proven reserves of 190 million tonnes at a grade of 0.75 g/t Au, the mill was designed to process 17 Mtpa (2065 tph) of ore with an 86% copper and 73% gold recovery. The grinding circuit (Fig. 1, Table I) boasts the largest SAG mill (Fig. 2) and was commissioned last June 1998."

Jan 1, 1999

The safety of mining operations is significantly influenced by the in situ stress fields in which the mining excavations are created. From the point of view of planning of mining operations, the in situ stress field is a most important input parameter for valid modelling of excavations. Many in situ stress measurements have been carried out for mining and civil engineering projects in southern Africa over the past 30 to 40 years. A database of in situ stress measurement results and observations has been compiled. This paper presents results extracted from the database which are considered to be of particular interest to mining areas in South Africa. The database will permit the estimation of likely stress conditions in new areas of mining, provide a basis for evaluation of results from future in situ stress measurement programmes, provide a basis for comparison of observed behaviour with expected behaviour, and provide a source of data on which realistic design and layout analyses can be based. The information contained in the database indicates that horizontal to vertical stress ratios in the Carletonville, Klerksdorp and Rustenburg areas are significantly higher than the value of 0,5which is commonly used in mine layout planning.

Jan 1, 1998

By J. Nell

An overview is given of the matte melting process used for the beneficiation of South African platinum group metal (PGM) ores. Most producers use six-electrode furnaces to melt the concentrate and Pierce Smith converters to oxidize excess iron sulphide from the furnace matte. Concentrates from two reef types (the so-called Merensky and UG-2 reefs) dominate the feedstock supply. Concentrate from the Merensky Reef is low in chromium and does not pose significant melting problems. Concentrates from the UG-2reef contain much higher levels of chromium, which results in the formation of chromium-rich spinels during melting. This is attributed to the low solubility of chromium in furnace slag under typical operating conditions (an oxygen partial pressure of 10-8?10-9bar at temperatures of 1550°C to 1600°C). During the converting process, care is needed to avoid excessively oxidizing conditions, which result in cobalt, nickel and copper losses to the slag. High nickel losses result in the formation of Fe2NiO4 (trevorite), which often forms solid solutions with FeCr2O4and Fe3O4. In future, the main challenge in the processing of South African PGM ores will be to cope with ever-increasing levels of chromium in the concentrate. A short-term solution to the problem would be to melt the concentrate under slightly reducing conditions to promote the formation of CrO, which is more soluble in the slag than Cr2O3.A longer-term solution to the problem would be to abandon the current matte-smelting process in favour of an alloy-based process, which would offer total flexibility with respect to the amount of chromium that can be tolerated in the feed. Keywords: Merensky, UG-2, furnace, slag, matte, converting, spinel, chromium

Jan 1, 2004

By Alexander J. Verstraeten

Work started on the building of the Amsterdam Concert Hall in 1880 by driving over 2000 wooden piles of 13 m on which foundation-beams out of wood and brickwork were made. During construction the design was changed. This was due to the latest German developments, requiring double walls instead of single, so that the space in between could be used for ventilation and heating. Therefore the pile load, originally designed at approximately 100 kN, increased even to 170 kN for some piles, causing settlements and unacceptable cracks in the brickwork. Settlements of up to 18 cm were measured. In 1985/1986 around 400 vibration-free Tubex-displacement-piles were installed under the Concert Hall, with a shaft of 0355 mm, a pile shoe of 0560 mm and a pile length of approximately 18 m. After these Tubex piles had been installed they took over the complete weight of the whole building, thus eliminating further settlements and damage. 95% of all the construction activities took place while the concerts went on. The chosen solution also made it possible to create a new basement under the Concert Hall as an extension for dressing-rooms etc.

Jan 1, 1987

By Flor De Cock

The paper reflects part of the work from the European Regional Technical Committee on Piles (ERTC3) during its mandate between 1994 and 1999, and, in particular, describes the find­ings from an International Seminar held in 1997 in Brussels on European practice for design­ing axially loaded piles. The seminar included contributions from 17 European countries, each of which provided a synopsis of their respective national design approaches. This paper pays particular attention to the design methods based on laboratory and in-situ test data for both bored and displacement piles.

Jan 1, 2002

The notes from which this paper has been prepared were set down at the time of the author's departure from Australia in 1935. Mr. Frank Forman, Government Geologist of Western Australia, who has very kindly read the paper in manuscript, affirms that the views here set forth are now accepted by most geologists. Thus, Forman's recent presidential address before the Royal Society of Western Australia (1937) mentions sediments in the Kalgoorlie Series "including banded jaspers and jaspilites."While it may, therefore, be superfluous to belabour the question further at this time, Mr. Forman has encouraged the author to publish this paper as a summary or both past and present views.To those specially interested in the subject of the paper, a study of pertinent Plates attached to Western Australian Geological Survey Bulletin No. 71, 1917, is suggested.The type of rock which is variously called "jasper bar," jaspilite, or "ferruginous quartzite" is familiar to all mining men who have worked in the West Australian goldfields.In its typical form it is a "striped" rock consisting of alternate layers of white or pinkish silica with red to brown bands of iron-bearing silica.In the course of geological work in many parts of Western Australia I studied exposures of jasper bar and was repeatedly impressed with the similarity of much of the material to the sedimentary "banded iron formation" of Canada. It was, therefore, a surprise to learn that the jasper bars were not generally regarded in Australia as sedimentary horizons. It is true that Honman offered convincing evidence of the sedimentary origin of the jaspers...

Jan 1, 1939

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 A. Swanson

The Australian coal industry has been subdued in recent years and only a few new plants have been constructed, but the drive for greater efficiency has seen continued technological developments. The paper lists the new plants and major upgrades, plus summarizes technical developments in the areas of dense medium processing, fine coal treatment, froth flotation, dewatering and on-line analysers.

Jan 1, 2001

By M. J. Sapko

The design requirements for mine ventilation seals have undergone a radical transformation in recent years, and these revisions have greatly increased the cost of the seal designs and their construction. For example, in the past two years, new federal regulations have increased the minimum design requirement to withstand explosion pressures from 138 kPa (20 psig) to 345 kPa (50 psig) or 827 kPa (120 psig), depending on whether the sealed mine volume is monitored continuously or not. Moreover, there is still a possibility that under certain conditions (such as detonations) even higher pressure requirements may be necessary. The ability of a monolithic, stand-alone mine seal to reliably withstand the full range of current and future pressures is becoming increasingly difficult and expensive. In an effort to develop a practical alternative, the West Virginia Office of Miners? Health Safety and Training (WVOMHST) and the National Institute for Occupational Safety and Health (NIOSH) have collaborated in a research effort to develop a practical, economic, and safe mine sealing technique that can enable mines seals to meet the full range of new explosion pressure design requirements. The basic idea is to use a barrier of common mine gob and rubble in combination with a conventional mine seal so that the pressure resulting from a gas explosion is reflected, absorbed, and attenuated, so the pressure on the ventilation seal is reduced. This paper discusses some concepts and preliminary test results for a ?Passive Mine Blast Attenuator? (PMBA) that can provide a useful alternative to increasingly larger and stronger stand-alone mine seals. Numerical models and full-scale experiments conducted at the NIOSH Lake Lynn Laboratory Experimental Mine (LLEM) show that the use of a PMBA can signficantly reduce the blast pressure and impulse on conventional ventilation seals. DISCLAIMER: This information is distributed solely for the purpose of pre-dissemination peer review under applicable information quality guidelines. It has not been formally disseminated by the National Institute for Occupational Safety and Health (NIOSH). It does not represent and should not be construed to represent any agency determination or policy.

Jan 1, 2009

By P. A. Plunkert, D. E. Morse, L. McCartan, J. F. Papp

The mineral sector is a fundamental part of the U.S. economy. It contributes to the real gross domestic product (GDP) at several stages —basic (mining), intermediate processing, manufacturing of finished goods and construction. The real GDP increased by 3.5 percent from 2004 to 2005. The nominal GDP was $12.5 trillion at the end of 2005. Housing starts were up by more than 5 percent for the year, and the unemployment rate decreased to 5.1 percent in 2005 from 5.5 percent in 2004. The prime interest rate increased from 5.25 percent at the beginning of the year to 7.25 percent at the end of the year. The value of minerals mined in the United States in 2005 rose significantly because of increased unit prices for some metals —particularly molybdenum — and significantly increased production for some industrial minerals, mainly cement, construction sand and gravel, and crushed stone.

Jan 1, 2006