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By B. J. Sauer

Variable frequency drives (VFD’s), or adjustable frequency controls (AFC’s) as they are more precisely identified, have been available to the mining industry for over 20 years. However, in recent years as the push to cut production costs has become ever so crucial, AFC usage has become more widespread. This paper seeks to provide professionals in mineral processing plant design and operation with an introduction to AFC’s, insight as to why AFC control for AC induction motors can be advantageous, and specification and design considerations.

Jan 1, 2002

By Charles E. Whieldon

The importance of producing more oil from known petroleum reserves has placed increased emphasis on the application of secondary-recovery methods. Recently published reports3 4/ describe the results of waterflooding in Roane and Pleasants Counties, W. Va. (see fig. 1.) This report describes the Barron Kidd Oil Co.?s Santee waterflood project, Maxton sand, Burton field, Church district, Wetzel County, W. Va. (See fig. 2.) The Federal Bureau of Mines hopes that these reports will stimulate interest in improved waterflooding techniques, thereby discouraging premature abandonment of oil leases.

Jan 1, 1961

By F. W. Bowdish

A theoretical and experimental laboratory study has shown that the rate of breaking of oversized particles in a ball mill is proportional to 1) the concentration of such particles, and 2) the area of the balls, provided that the balls are larger than a certain size relative to the particles. If all undersized material were removed as formed, the rate of breaking would be almost independent of the quantity in the mill. Rate equations are given which are similar to those for zero, first, and second order reactions. Deviations of small balls from the equation for a second order phenomena are quantified by a factor called "nipping efficiency." Some data are correlated by a dimension-less equation, which is used to estimate nipping efficiencies from data not in the correlation. The investigation described here was undertaken after a literature survey revealed that little was known concerning the mechanism of breaking of particles within a ball mill and the effect of this mechanism upon grinding rates. One paper, by Roberts1 , offered a theory concerning the mechanism of breaking, and a rate equation for the breaking of particles larger than some size to particles smaller than that size. That paper provided the starting point for a theoretical and experimental investigation of grinding under carefully controlled conditions. THEORETICAL CONSIDERATIONS In his paper on the probability theory of ball mill grinding, Roberts theorized that "... a given expenditure of power leads either to a certain number of point to point blows per bp-hr or to a certain distance of line contact per hp-hr ..." He assumed that the balls touch each other during each blow or during moving contact. Then he said that a volume of pulp, dependent upon the size being considered, would be covered per minute within which all oversized particles would be crushed to particles smaller than that size. Naturally, the higher the concentration of oversized particles in the pulp, the higher the rate of which they would be broken. From this reasoning Roberts obtained the differential equation -dC/dt = k hp/ton C (1) where k is a constant for any size of particle, density of particle, and moisture content of pulp. C is the percentage of oversize in the material to be ground, t is the time, and hp/ton is the power input per ton of material in the mill. He then integrated the equation to log Co/Ct = k/2.3 hp/ton t , where Co and Ct are the percentage of oversize at time zero and t respectively. By always using the same quantity of material in a mill and assuming that it required constant power to run the mill, he was able to combine the horsepower per ton factor with the other constants to give an equation for a first order rate.

Jan 1, 1961

By J. W. Joubert, R. C. W. Webber-Youngman, M. D. Budeba

"SynopsisCost estimation for surface coal mines is a critical practice that affects both profitability and competitiveness. New mines require these costs to be estimated using available information before a project begins. The competitive advantage of a new mine depends on it being both efficient and cost-effective. Low-cost producing mines have a higher chance of survival in a low-price environment than do high-cost producers. The competitiveness and profitability of a coal mine is based on the costs of production and the supply position on the cost curve. There is no single method of cost estimation, and the available methods consider only one or a few variables, leaving out multiple variables that could significantly affect the estimation of mine costs. Mining companies are thus searching extensively for a method that will increase accuracy in the estimation and evaluation of mining projectsThis paper highlights the shortcomings of the available approaches and proposes a data envelopment analysis method to develop a frontier for effective surface coal mines, and the use of a parametric method for modelling the costs and productivity of new mines to ensure effective competitiveness. The models will extend the capability of estimation and the accuracy of estimates using the efficient decision-making units, by considering the optimal mine-specific and external variables affecting costs.IntroductionCoal contributes 25% of the world’s primary energy needs, after fuel oil, which contributes 35%. The world energy demand, estimated over the period 1990 to 2030, is expanding at a cumulative annual growth rate (CAGR) of 1.7% (Schernikau, 2010, p. 14). This emphasizes the need for enhancing the production of existing mines, as well as opening new mines in order to increase the supply of coal."

Jan 1, 2015

Published experimental data on thermodynamic behaviour of cobalt-containing slags have been reviewed and used in validating a recently developed thermodynamic model. The results from the exercise show that the model provides a reasonably good description of behaviour of cobalt in multi-component slag systems. The models for cobalt containing slags, matte and oxide solid solution phases were incorporated into CSIRO?s multi-phase equilibrium (MPE) package, which was used to calculate the equilibrium distribution of cobalt between matte and slag phases under various conditions. The results agreed well with the experimental data. Furthermore, the good agreement between the calculation and the plant data indicates that the operating conditions of industrial smelting and converting processes are close to equilibrium. Two diagrams showing the effects of slag chemistry and SO2and O2partial pressures on the distribution of cobalt between phases were generated for conditions similar to smelting and converting processes. These diagrams provide some useful guidelines for developing new strategies to improve cobalt recovery.

Jan 1, 2004

CENTRAL mine ore consists mainly of galena and marmatite in a siliceous and rhodonitic gangue, the average assay values being approximately 11.5 oz. per ton Ag, 14.5% Pb, 14.5% Zn, 1.3% Ox Pb, 0.3% Ox Zn.Owing to the 1923 fire in the underground workings, much of the ore now being mined has been subjected to a certain amount of oxidation, as shown by the oxidised values above.This factor is of great importance from a flotation point of view, as a sulphide surface which has been subjected to the influence of oxidation is not as amenable to flotation concentration as a fresh sulphide surface. The importance of this factor is increased when a differential flotation is to be made, and, as in the case of Central mine ore, the sulphide, which is to be floated first, has been oxidised...

Jan 1, 1931

Prediction of fragmentation by blasting is most commonly based on theassumption that a single distribution of pre-existing discontinuities is present within a blasted rock volume and that the underlying mechanism of failure is tensile failure. It is assumed that the tensile stress field created by a blast initiates and extends radial cracks around the blastholes. Interaction between radial cracks from different blastholes and the free surface creates rock fragments. In reality, fragmentation of the rock occurs due to two mechanisms.One is related to the compressive-shear failure of the rock (mainly rock matrix) close to the blastholes, while the second mechanism is the previously mentioned tensile failure of the rock mass. The secondmechanism of failure occurs in the form of extension of the larger cracks in the region beyond the crushed rock, and this type of fragmentation occurs after the crushing phase. In the case of hard rock or blasting where the extent of crushing is minimal, the currently used prediction methods give a reasonably good result. However, there are many blasting conditions where the amount of rock crushing is significant. In the case where fragmentation of the given rock volume occurs dueto two different mechanisms, modeling of the rock fragmentation with a single distribution function is not appropriate. To model the fragment size distribution generated by two different mechanisms, it is necessary to use a two-component fragment size distribution function and a scaling parameter that will determine the proportion of the fragmented volume created by each mechanism. The purpose of this paper is to present results of blast fragmentation modeling based on two mechanisms of failure. The two-component model (TCM) utilises experimentally determined parameters from small scale blasting and parameters of the Kuz-Ram model, for more accurate prediction of the complete rock fragment size distribution curve. The methodology is such that it is possible to predict complete fragment size distribution, including fines, of ROM product for a future mine, at the feasibility phase of mine design.

Jan 1, 1999

By P. K. Hofmeyr

Base Metal (Cu, Ni, Mo, Zn, Co etc.) analysis traditionally has been very slow in conventional analytical laboratories which can lead to additional costs being incurred in waiting time of drill rigs or mining excessively off-reef. Recent developments in the automation of analytical laboratories now allow for very rapid turn-around times for base metal analytical data which can help reduce such costs as well as reduce the unit costs of the analyses themselves. 2.0 CONVENTIONAL ANALYTICAL LABORATORY PRACTICE Conventional analytical laboratories are necessarily are very manual. Sample preparation is slow and laborious, samples are moved from stage to stage manually and, typically, all samples are processed in batches so a sample which is the first to be, say, milled has to wait for the complete milling of the batch before it advances to the next stage eg. mixed with wax prior to pelletising for XRF analysis. Inevitably this results in long sample data turn-around times for laboratories handling large numbers of samples. Manual sample preparation can only be accelerated by increasing staff which increases costs and can lead to additional errors being introduced. Cleaning of sample preparation equipment, eg. crushers and mills, between samples is essential to avoid cross-contamination between samples and this is slow and labour-intensive. In manual sample preparation the correct sample numbers staying with the samples is totally dependent on the efficiency of laboratory operators. It is extremely difficult to detect when errors have occurred due to the switching of sample numbers during the sample preparation stages. Running duplicates and QC samples at best is only partially successful in detecting when sample number switching errors have occurred. Errors of this nature and cross-contamination problems due to incomplete cleaning of sample preparation equipment tend to occur when laboratories are working at pressure due to high sample numbers and when supervisors are not present during 24/7 laboratory operations which is often required on plant process control laboratories. These problems are common to all conventional analytical laboratories and their magnitude is dependent on the level of control and efficiency of QC systems practised by individual laboratories. The disadvantages of conventional manual analytical laboratories can be summarized as follows:- 1. Labour-intensive which is costly especially when multiple shifts have to be used during 24/7 operations.

Jan 1, 2005

China has made great progress in thick coal seam mining, commonly characterized by longwall top-coal caving mining and single-pass longwall mining with a large cutting height. At present, the maximum mining thickness of longwall top-coal caving reaches 20 m while that of single-pass longwall mining approaches 8.8 m. The top-coal caving–related technologies have significantly improved the mining efficiency of thick coal seams and have also made a great contribution to the centralized underground mining of coal. Thus, the number of underground coal mines is greatly reduced in China. However, due to the increase of the mining height and the changes in mining operations, the overburden movement caused by the mining of thick coal seams is more intense, and the influence scope is larger, which brings a series of new problems on ground control of longwall faces. In order to enhance ground control and improve the mining efficiency of thick coal seams

Jul 28, 2020

By George J. Karcas, Raimo Kuusisto, Pertti Pekkala

Ongoing Outokumpu development in Solvent Extraction and Electrowinning Technology, involving all aspects of process chemistry, equipment and control, extends over a period of close to 30 years. The development in SX started with molybdenum and rhenium, continued with zinc, manganese, cobalt and nickel and is now focusing on copper. The OutoCompact VSF? SX concept, which has been recently introduced, is a honed version of earlier VSF? technology. The Outokumpu VSF? ("Vertical Smooth Flow") SX package includes the DOP ("Dispersion Overflow Pump") units, the Spirok Mixers, the OutoCompact Settlers including their DDG ("Dispersion Depletor Gate") fences and tank farm equipment such as the LOS ("Loaded Organic Scrubbing") tank as well as the CEP ("Copper Electrolyte Purifying") tank. Although the VSF? SX package can be implemented according to several optional lay-outs, the so-called Track version has lately been introduced to the advantage of new plants. The new OutoCompact SX technology decreases the footprint of future VSF? plants. The lay-out, including plant size flexibility, have further been improved by Outokumpu?s new OutoReverse settler technology. Two of several SX plants currently under construction rely on reverse settlers in order to maximize their performance. The Outokumpu EW technology includes process know-how as well as proprietary equipment. The copper EW package consists of permanent stainless steel cathodes based on wax-less technology and lead anodes utilising polymer concrete cells with the double contact bus bar system and ventilation hoods fitted for efficient mist control. The lifting of cell hoods, as well as cathode washing, is done by the cathode pulling crane. Proper electrolyte flows and matching current density further ensure high productivity of LME grade copper cathodes.

Jan 1, 2005

The only economically significant deposit of dolomite in New Zealand is at Mount Burnett, in north-west Nelson. The dolomite, associated with marbles and schists, is complexly deformed, and is of Paleozoic age.A very large quantity is present, although the recoverable amount is to some extent limited by the difficult terrain.Physically the quality of the dolomite is excellent. It is a tough, durable, fine grained rock. Chemically it is a little more variable. The range and frequency o~ the more important impurities are illustrated by hlstograms, as is the "dolomite factor"-a measure of the amount of the mineral dolomite in the rock. lbe dolomite factor averages 84 per cent, the remainder of the rock consisting largely of calcite. Quarrying, milling, production, and uses are described. In 1966 production reached 13,250 tons.

Jan 1, 1969

Demonstration of Solid-Liquid Separations Using Recycled Supernatant that Contains Temperature-Responsive Polymer The effective use of recycled supernatant that contains temperature-responsive flocculant is demonstrated for solid-liquid separations. The recyclability of poly(N-isopropylacrylamide) (PNIPAM) of several different molecular weights and a 15 per cent negatively charged derivative are compared. Batch settling tests of a-alumina suspensions are first conducted at 50¦C, with a subsequent 25¦C period, after which the supernatant is harvested and used to flocculate subsequent suspensions. Using this procedure consecutive separations are obtained with the repeated recycling of uncharged PNIPAM containing supernatant. Batch settling tests indicate that hindered settling rates increase with molecular weight of PNIPAM. Adsorption studies indicate that strong adsorption of PNIPAM onto alumina occurs with PNIPAM at 50¦C and that significant desorption occurs after cooling at 25¦C. However, the extent of desorption decreases with molecular weight resulting in low amounts of PNIPAM for recycling and poor settling behaviour when high molecular weight PNIPAM is recycled. Little recyclability was evident using the negatively charged PNIPAM. On the basis of these findings a recycling-thickener apparatus that uses low molecular weight uncharged PNIPAM is proposed.

Sep 13, 2010

By LaMar G. Evans

The rapid determination of uranium in ores by radiometric means was investigated by the Bureau of Mines. Among the various procedures and schemes tested, two showed most promise. They were the ratio scheme developed in the Bureau's Tucson, Ariz., laboratory and the equilibrium method developed by the Canadian Department of Mines and Technical Surveys. The ratio method is a simple, empirical procedure for classifying the state of equilibrium in ores by measuring their radioactivity by means of a Geiger-Muller counter under three different conditions, using filters. The principal merit of the method is in providing a clue as to the reliability of equivalent uranium determinations.

Jan 1, 1958

Separation of Iron Particles from Banded Haematite Quartzite (BHQ) Ore by Selective Magnetic Coating The separation of fine iron particles from banded hematite quartzite (BHQ) has been studied using selective magnetic coating. The BHQ ore assays as 38.9 per cent Fe, 42.5 per cent SiO2 and 1.0 per cent Al2O3. Mineralogically, the ore contains hematite and quartz as the major mineral phases where as goethite and magnetite is present in minor entities. Natural magnetite of very fine size and oleate-magnetite in colloidal form, prepared synthetically in the laboratory are used as the coating material on the surface of hematite particles. The selective coatings of oleate-magnetite on BHQ surfaces followed by magnetic separation studies have indicated that, it is possible to achieve 62.3 per cent Fe with 8.5 per cent SiO2 at 85.4 per cent iron recovery. The recovery of iron values is found to be superior in comparison to the conventional magnetic separation techniques. The selectivity of coating for enhancing the magnetic response of iron particles is achieved by controlling the surface properties of the particle via electrokinetic potential adjustment by controling pH and addition of oleate-magnetite. In the separation process, the effects of pH, magnetic intensity and addition of oleate-magnetite are studied to achieve the maximum grade and recovery of iron values. The optimum separation is observed at pH of 7.5, oleate-magnetite concentration of 0.25 ml/g of BHQ ore and a magnetic intensity of around 0.8 Tesla. The X-ray diffraction (XRD), Infra-red spectroscopy (IR) and UV-visible spectroscopic studies strongly suggest preferential coating of magnetite on hematite surfaces. Scanning electron microscopy (SEM) studies have brought out the semi-quantitative features of BHQ ore. The recovery of iron values from a lean grade ore such as BHQ is carried out looking into the future needs of this ore in India for iron and steel making.

Sep 13, 2010

By J. Geertsma, F. de Klerk

During the hydraulic fracturing treatment of an oil or gas well the liquid pressure in the borehole is increased until tensile stress in the surrounding rock exceeds tensile strength. Once a tensile fracture is initiated, it is penetrated by liquid from the borehole and fracture propagation under continuous hydraulic action takes place. The fracturing liquid carries a propping agent to ensure a highly permeable flow channel after pressure release. Field results range from failure to obtain increased production to outstanding success. In all cases, however, it unfortunately remains uncertain whether the values chosen for the operational parameters, such as injection rate, pumping time and fluid viscosity, were in fact the ideal ones. Though experience provides a lead, a more satisfactory way to predict results would seem to be to subject the fracture propagation process to a theoretical analysis that (1) makes the maximum use of the relevant physical information and (2) so simplifies the resulting calculations that the field engineer gets practical data that he can handle comfortably. We are attempting here to do this in connection with the prediction of fracture width and areal extent before pressure release. What remains of the fracture afterwards depends on the distribution of the propping agent between the fracture walls, and that is a separate story. Idealization of the Problem To keep the problem tractable, a number of simplify- ing assumptions have had to be made: 1. The formation is homogeneous and isotropic as regards those of its properties that influence the fracture-propagation process. 2. The deformations of the formation during fracture propagation can be derived from linear elastic stress-strain relations. 3. The fracturing fluid behaves like a purely viscous liquid; i.e., any peculiar flow behavior due to the addition of gelling agents or other additives is neglected. Moreover, the effect of the propping agent distribution on the distribution of fluid viscosity in the fracture is not taken into account. 4. Fluid flow in the fracture is everywhere laminar. 5. Simple geometric fracture-extension patterns are assumed — either radially symmetrical propagation from a point source (Fig. 1A) or rectilinear propagation originating from a line source (Fig. 1B). In the first case the periphery of the fracture is circular, in the second case it is rectangular. 6. A rectilinear propagation mode can be accomplished only by injection over a large perforated interval, thus forming a line source. Such a rectilinear fracture must therefore be located in the vertical plane. A circular propagation mode might be expected from injection through a narrow band of perforations. This forms a point source. Because gravity effects are excluded from our considerations, the fracture propagation plane may in this case assume any angle with respect to the wellbore as far as the

Jan 1, 1970

By Simon D. Handelsman

?Artisanalmining ?Application of human energy (e.g. pick & shovel) directly to produce minerals ?majority no technical skills and lack adequate working tools ?Small-scale mining ?Application of modern technology for limited scale mineral production Significance of ArtisanalMining ?15 million people in artisanaland small scale gold mining ?55 developing countries ?Use of mercury damages health of 100 million people

May 1, 2006

By E. D. Calvert

The objective of this research was to examine variations in melting and forging practice for four titanium-base alloys and to determine their effect on the resultant product. Of particular interest was the evaluation of the skull-casting technique. The data should serve as a guide to producers and consumers of titanium products. Physical properties of four titanium-base alloys in ingot form and in sheet form were evaluated and correlated, where possible, with variations in the melting and casting procedure. Consumable-electrode melting was used throughout, but arc current and furnace backfill pressure were varied, and ingots were formed both by melting directly into a water-cooled copper mold and by skull melting followed by pouring into a graphite mold. Alloying metal additions for the alloys tested were (1) 8 percent manganese, (2) 6 percent aluminum and 4 percent vanadium, (3) 6 percent molybdenum and 2 percent aluminum, and (4) 16 percent vanadium and 2.8 percent aluminum.

Jan 1, 1962

By Robb L. Swenson

Construction of foundations for the Skyway Segment of the San Francisco Oakland Bay Bridge required innovative techniques due to the mass of the structures being inserted and the unique subsurface of the Bay. Twenty of the pier structures required large sheet pile cofferdams. Eight other foundations were installed in open water without cofferdams at the deeper part of the Bay. This narrative will present the initial planning, as well as the stages of installation, for each type of foundation. The first section will discuss foundation constructability modifications made during the initial planning phases of the project. Considerable effort was expended by Caltrans, the owner, T.Y. Lin the designer, and KFM (Kiewit/FCI/Manson) the contractor in modifying the design to assure that required tolerance would be maintained during the installation of the foundations. The final section will describe the steps required for installation including: initial access dredging, installation of cofferdams, preparation required to install the footing boxes, footing box installation, foundation support pile installation, and pile to box connections.

Jan 1, 2013

By G. J. Hearn

between particles in the classifying region is then

Apr 1, 1995

By G Mark, K L. Blake, G de Jong, J F. Rotherham, N D. Adshead

Magnetite deposits with distinctive ¦ actinolite ¦ apatite-bearing gangue and spatially-extensive sodic-calcic wall rock alteration occur in both Proterozoic metamorphic terrains and Mesozoic-Tertiary magmatic arcs. Examples from both settings constitute significant sources of iron ore (egKiruna, Sweden; El Romeral, Chile) and some host major Cu-Au deposits that have a local association with K-silicate alteration (eg Cloncurry district, NW Queensland; Copiapo district, Chile). A growing body of evidence points to a hydrothermal origin for these systems involving high temperature, low S oxidised fluids. The Cloncurry magnetite-Cu-Au deposits are products of the local structurally channelised influx of a specialised high salinity ore fluid into larger-scale alteration systems developed during pluton emplacement at greater depths than those associated with subvolcanic (porphyry) Cu-Au deposits. The geological characteristics of deposits in magmatic arcs are consistent with a similar mode of origin albeit in rather different tectonic settings.

Jan 1, 1995