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By W. A. Te Riele

The National Institute for Metallurgy was the venue for a one-day colloquium on 'The Chemistry of Processes for the Recovery of Gold on Activated Carbon'. Organized by the South African Chemical Institute (Southern Transvaal Section) in collaboration with the National Institute for Metallurgy (NIM) and the South African Institute of Mining and Metallurgy, the colloquium attracted tremendous interest from the mining industry. Some 300 metallurgists, engineers, and chemists were brought up to date on advances in this technology made by scientists of NIM and the Anglo American Research Laboratories (AARL).

Jan 1, 1980

By K. P. Gupta, P. A. Beck, N. S. Rajan

By determining the a phase boundaries in the following ternary systems: V-Fe-Si (at 1175oC), V-Co-Si (at 1175°C), V-Ni-Si (at 1175oC), Cr-Mn-Si (at 1000°C), Cr-Co-Si (at 1175°C), Cr-Ni-Si (at 1175°C), V-Fe-A1 (at 1175°C) and Cr-Co-A1 (at 1175°C), it was found that Si exerts a stabilizing effect on these a phases, while A1 tends to destabilize them. Si atoms in solid solution occupy sites D in the a structure, The co/ao ratio increases with increasing Si-, Mn- or Fe-content. The volume of the unit cell decreases with increasing Si-content. THE stabilization of certain metal silicides (the Nowotny phases) by the addition of relatively small

Jan 1, 1961

By Michael P. Richardson

INTRODUCTION This paper is intended to be a summation of the state-of-the-art i n draw theory and draw- point spacing. Knowledge of this very important factor in the successful design and operation of a block caving mine is scarce and nonconclusive. It is hoped that the presentation of this paper will stimulate interest and discussion which will lead to a stronger understanding of these a1 1 important factors. Please note that block caving as used here- in refers to block, panel, and mass caving systems in general, not just to the specific system of block caving where discrete blocks of ore are prepared and caved as a unit. DRAW THEORY The knowledge of draw theory as related to the practice of block caving mines is, unfortunately, very limited. In recent years much work in draw theory has been done in respect to sublevel caving systems and an understanding of draw mechanics relating to sublevel caving seems to be emerging. This work is certainly helpful to those of us interested in block caving but the question of "what goes on up above" still hounds us since we are more interested in the region of draw which begins just above the area where sublevel caving interest ends. Herein is presented a brief summary of draw theory with an attempt to look at the factors which can help our understanding of the area of draw influence in block caving mines. Nature of Gravity Flow An understanding of the flow of granular material (rock, sand, grain, or prill as examples) is the first step toward understanding block caving draw. If we take a supported column of granular material and allow gravity flow through an aperture at the bottom of the column, an ellipsoidal shaped zone of disturbance of the in-place material will form and grow with extraction of material through the aperture. The volume of this zone of disturbance or loosening is about 15 times the volume of material extracted at any given time (Kvapil, 1980). Figure 1 shows the development over time of the zone of disturbance. The ellipsoid of disturbance represents a future ellipsoid of extraction which will equate to the volume of materia1 extracted by that future time. Extraction involves the movement of the particles located vertically over the drawhole directly downward while material outside this direct vertical volume moves radially inward and down toward the drawpoint as shown in Figure 2a. Figure 2b shows the result of this motion on originally horizontal strata within the ore column. Increased draw increases the eccentricity of the ellipsoidal volume or, in other words, the ratio of the height over the width of the disturbed area increases as ore is withdrawn from the column (Kvapil , 1980). This becomes important to block caving since eventually a vertical cylinder of draw will be approximated as this ratio increases without bounds. Figure 3 shows this result. The width of this draw cylinder is a critical dimension for the determination of draw point spacing in relationship to block caving mine design. McCormick (1968) for one, felt that within this cylinder of draw, mass flow would take place. This is the

Jan 1, 1981

Jan 1, 1967

By F. W. Jr. Sperr

THE byproduct coke oven is the most important artificial source of fuels for metals melting. Its products are solid, liquid, and gaseous in form. The amount of coke and primary byproducts obtained per ton of coal varies with the nature of the coal. The following represents the results obtained in many plants: Metallurgical coke (over 3/4 in.) 69 per cent. of coal Domestic coke (1/2 to 3/4 in.) 2 per cent. of coal Breeze (under 1/2 in.) 4 per cent. of coal Surplus gas, cubic feet per net ton 6600 Gas for heating ovens, cubic feet per net ton 4400 Tar, gallons per net ton 9 Ammonium sulfate, pounds per net ton 25 Benzols, gallons per net ton 4 All of these products, except ammonium sulfate, have important fuel value. Part or all of the metallurgical coke may be crushed or screened to furnish additional domestic coke. If producer gas is used, there will be a surplus of 11,000 cu. ft. of coke-oven gas per net ton of coal. The use of coke in the metallurgical industries has been retarded by the mental attitude of writers who disregard the dependence of coke quality on the conditions of its manufacture. Terms like "byproduct coke,"' "beehive coke," "48-hour coke," and "72-hour coke" are only generally descriptive and tell nothing of the coke quality. For example, one writer1 stated that in brass-foundry practice, Connellsville coke is considered much superior to byproduct coke on account of the high sulfur content of the latter. Another2 says, "At equal prices for hard Connellsville coke and for byproduct coke at the foundry door, the hard coke is unquestionably cheaper. It will melt more metal per ton than the byproduct coke and requires less labor, as the byproduct coke is less dense and burns faster, thus requiring more frequent firing." A little study of the conditions under which coke is manufactured will show the error in mak-

Jan 10, 1920

"Acid resistant brick lined autoclaves and related vessels are utilized in pressure oxidation for the recovery of gold, copper, and other metals. The combination of the corrosion resistant membrane, acid resistant brick, mortar and steel shell is a composite system that requires a sophisticated stress analysis. In order to obtain meaningful results both the model and physical properties of the materials must be carefully selected. Evaluation of the calculated results requires an understanding of both the failure mechanisms of ceramics and experience with the performance of existing lining systems.INTRODUCTIONAcid brick lining systems are used in pressure oxidation autoclaves and related vessels to provide thermal and mechanical protection for corrosion resistant membranes that are applied directly to the interior of the vessel shell. The acid brick and mortar must be resistant to the process conditions and must provide a mechanically reliable structure.The construction of lined vessels incorporates a wide range of materials that can include the carbon steel vessel, austenitic weld overlay, lead lining, organic membrane, ceramic brick, mortars and other alloy components. The physical properties of the materials can vary by orders of magnitude and when combined in the construction of the lined vessel create a complex composite structure. The materials may be bonded together or act independently of each other. Stresses are induced into the lined vessel include pressure, thermal expansion, chemical expansion and mechanical loads.The complexity of these systems makes it is very difficult to account for all of the variables in the structural analysis of lined vessels. Historically calculations were simplified and designers primarily relied on experience with previous applications.The greatly improved tools for Finite Element Analysis (FEA) available today allow for detailed calculation of the stresses imposed on the vessel shell and lining. Koning & Lauzon (2004) presented a paper on design fundamentals including a discussion on the application of FEA methods at Pressure Hydrometallurgy 2004 in Banff. When a designer carefully constructs a model and selects the correct materials properties for the calculations, meaningful and useful results can be achieved."

Jan 1, 2012

By M. E. Rossi

Reconciliation of long-term block model reserves and mine production frequently shows significant discrepancies. This reconciliation can be done comparing the long-term block model reserves against a grade control model (generally, a model based on blast holes or production data). in this paper called an FI factor for tonnages, grade, and ounces; and also it should be done comparing the grade control model to the mill feed (or loaded to heaps) tonnages, grades and ounces (called an F2 factor). The long-term model usually contains blocks with dimensions larger than the size of the selective mining unit (SMU) of the operation. The smoothing effect of an estimator such as kriging will generally result in a grade-tonnage curve that does not match the grade-tonnage curve of the SMU's to be recovered. This problem is partly to blame for the reconciliation discrepancies found. In addition, in-pit perfect selection is impossible. and therefore the grade-tonnage predictions based on blast holes also need to be assessed, considering both unplanned dilution and the errors of estimation of the grade control model. This paper will focus on using conditional simulations to assess the uncertainty of the predicted grade-tonnage curve in terms of minable reserves, and in the framework of long-term mine planning. Quantifying the uncertainty in no uncertain terms is done in conjunction with a popular pit optimizer, which will yield not one, but several possible minable reserves, and therefore a range of possible minable tonnages and grades per pit shell or scheduled phase. This is a step further from the usual sensitivity analyses that are performed for deposit evaluation or development planning. Specifically, this approach takes into account the volume-variance relationship, the selectivity of the mining operation, planned and unplanned dilution. and carries the local uncertainty implicit in grade estimation into the mine design and mine planning phases. The motivation for the approach is discussed through an example, as well as a description of the procedures and steps involved.

Jan 1, 1998

By H. H. Lowry

Science attracts the attention and interest of an individual or an industry in general only in proportion to the apparent direct application to its immediate welfare or benefit. Engineering accomplishments, as aphlied science, therefore receive more recognition than the scientific discoveries on which they are based. Even self-evident truth needs endless repetition before recognition: engineering as applied science cannot advance beyond the science on which it is founded. Scientific research, and discovery, is sometimes forced by the limitations recognized by those active in its development for the use of society and industry and sometimes results from an apparently superficially illogical curiosity about natural phenomena. Research has received inadequate support except in industries born in the laboratory, the chemical and electrical industries, from which many lessons might well be drawn by their elder associates. The rapid growth of these industries has been largely due to close cooperation of scientists and engineers. Most rapid advance is made when the research worker and the engineer keep in close touch with each other's ideas and problems. Many of the developments of modern industry are based on discoveries buried for years in scientific journals because the "time was not ripe" at their discovery. The situation with regard to utilization of coal is quite the oppositre. The fundamental facts in regard to the scientific aspects of the problem of developing the energy from coal are scarcely known. The engineer, without much scientific cooperation, has accomplished much in increasing the number of kilowatt-hours per pound of coal from 0.31 in 1919 to 0.69 in 1934, in increasing the 1000 gross ton-miles of freight hauled from 12.2 to 16.4 per ton of coal in the same period, in fuel economy in production of coke, and in developing the production of motor fuel in Germany and England by hydrogenation of coal. This lack of scientific research on the utilization of our most important natural resource, coal, has been due undoubtedly in large part to the reluctance of investigators to study the interrelationships involved in the complicated processes in which coal is used. These complexities are made

Jan 1, 1936

By Gunnar Thaning, Borje Bjorkvall

At LKAB Central Division for Metallurgical Research at Malmberget, Sweden, fired pellets are examined in respect to mechanical and reduction properties. The paper deals with descriptions of the test methods. It also involves the rationale for the choice of these tests. Their correlation to the blast furnace operation will be examined. The mechanical tests used are the ISO-tumbler test and the cold compression strength test. Concerning the metallurgical properties, experiments have shown that some superbasic pellets in particular have different disintegration properties in different temperature ranges. Pellets which have favorable reduction properties when tested under isothermal reduction at high temperature may disintegrate to a large extent under low temperature reduction. This is also valid for some types of acid pellets. Consequently, it was found to be necessary to determine the reduction strength both at high and low temperatures. In the low temperature range, the disintegration is measured by tumbling the pellets in soft reducing conditions at 600°C in a modified Linder test equipment. The high temperature reduction strength is determined under load in the Burghardt-Grebe equipment. However, in order to get more information of the high temperature strength, LKAB intends to introduce a softening test. The tendency of high temperature disintegration will also turn up in the swelling test. The swelling properties are examined according to a procedure developed at LKAB. In this test the pellets are subjected to free swelling without mutual contact. The reducibility of the pellets is recorded in the swelling test.

Jan 1, 1974

By Arthur Phillips

DURING the past few years considerable interest has been shown in the study of fiber, and its effect, in wrought metals. Fiber has recently been defined as a "condition of parallelism of important lines or details in the structure. "1 Briefly stated, two distinct types of fiber are commonly encountered. One results from the alignment in the direction of working of constituents, more or less segregated, such as slag, oxides, carbides and dendritic formations. The second, and least understood, type is produced by working the metal below the recrystallization temperature in such a way as to develop a parallelism of the grains. This condition is readily recognized by the pronounced elongation of the grains in the direction of working. Under certain deformational treatments the grain fragments produced by cold working tend to orient in certain definite directions with respect to the axis of extension. Furthermore, even in metals that have been annealed after cold working preferred orientations may be present. It is perhaps logical to assume that such marked parallelism of structural elements would be manifested by directional properties in the metal. As a matter of fact, tests on many kinds of materials have shown differences in varying degrees. In recognition of this condition, propel design, for many purposes, places the fiber axis in such a way as to present the direction of maximum strength to the greatest applied stress.

Jan 1, 1931

By B. E. Burakov, S. D. Lupal, O. A. R. Thalhammer, B. Saini-Eidukat

Electric-pulse disintegration is a mineral separation technique that liberates all mineral grains from any igneous or metamorphic rock irrespective of its lithology or grain-size distribution. The normal mechanical crushing of whole-rock samples is replaced by the rending effect of an explosion, produced by applying an electric current from a high-voltage power source. A voltage greater than the 100 kV necessary for the electrical breakdown of rock samples is achieved by using capacitors charged in parallel, but discharged in series. The sample sits in a water bath and the rapid distribution of electric pulses leads to an explosion which occurs preferentially along grain boundaries of the sample. Individual, undamaged mineral grains can be recovered in their original shape and form regardless of grain size. Examples are given of the liberation and concentration of important accessory minerals from different rock types. The examples show the recovery of diamond from two types of non-kimberlitic host rock in Popigai and Kumdykol in Kazakhstan and platinum group minerals associated with chromitites from the Konjdor intrusion and sulphides from intrusions in the Kola Peninsula in Russia

Apr 1, 1995

By Emil O. Frind, David W. Blowes, K. Ulrich Mayer

The multicomponent reactive transport model MIN3P can be used to simulate the evolution of pore water, pore gas, and the mineralogical composition in mine waste environments. The model is formulated for variably-saturated conditions, considers transport of dissolved and gaseous species, and describes geochemical reactions based on a partial equilibrium formulation. Reaction processes included are complexation, oxidation-reduction, ion-exchange, mineral dissolution-precipitation and gas exsolution- dissolution reactions. An example application, describing the generation of acid mine drainage and subsequent reactive transport for a ID-vertical profile in a tailings impoundment near Elliot Lake, Ontario, is provided.

Jan 1, 2000

By Germán Ruíz H

"El estudio describe la aplicación de la estadística como método analítico en la industria minera. En este sentido, para determinar cualquier cantidad es necesario primero conocer la variabilidad de ella, dado que si sus valores varían marcadamente es difícil que se llegue a un valor promedio de confianza. Por ende, para tener confianza en un promedio calculado, este debe basarse en un determinado número de lectura y así hacer una determinación previa. Solo elevando al cuadrado las desviaciones de las lecturas simples con respecto al promedio de dichas lecturas, la variabilidad es positiva. De forma, que aunque las lecturas sean menores que el promedio encontrado, este siempre será positivo, descartando la posibilidad que las desviaciones negativas cancelen las positivas, y estas pueden ser sumadas a pesar de sus signos."

Aug 20, 1965

By Robert H. Merrill

Several investigators have obtained solutions for the concentration of stress around circular, ovaloidal, elliptical, and rectangular holes in an elastic, isotropic, semiinfinite plate subjected to uniaxial and biaxial stress. These solutions are used to evaluate the changes in stress around openings immediately under the undercut normally used in conventional block caving operations. The evaluations are based on the assumption that a horizontal undercut removes most of the vertical component of a biaxial stress field. The location and magnitude of the significant changes in stress concentration around the opening are computed. Conditions under which the assumptions used in the evaluations may or may not be consistent with conditions around block caving mines are discussed, and examples of preferred opening shapes for a biaxial (hydrostatic) stress field are shown. This report is a summary of one phase of an investigation to establish design methods for the size and shape of mine openings used in block caving mining methods .

Jan 1, 1962

Jan 1, 1917

By Arthur Tauber, Horst Kedesdy

FERRITES are sintered metallic oxides of the spinel structure type1 and belong to the class of soft ferromagnetic materials. Similar to a ceramic, they can be formed and fired to a dense body, exhibiting a high electrical volume resistivity ranging from 102to 107 ohm-cm as compared with 10-6 ohm-cm for some of the metallic magnetic materials. This high resistivity, with resulting low eddy current losses, finds special application at high frequencies. The dispersive susceptibility of ferrites at microwave frequencies has also led to many applications in this field. Ferrites are used in low frequency applications where high resistivity with high permeability is desirable. During the last few years ferrites exhibiting rectangular hysteresis loops have been developed for computer and magnetic memory systems. The general formula for ferrites is MeFe2O4 where Me is a divalent metal ion such as Ni, Zn, Mg, Mn, Cu, Cd, and Fe. Only two of these ferrites are nonferromagnetic, namely, those with Zn and Cd. Solid solutions can be formed between different ferrites, and it is of interest to note that solid solutions of a ferromagnetic ferrite with a nonferromagnetic ferrite yield much better magnetic materials than the basic ferrite body. In general, it can be said that the solid solution formation between ferrites has widened the field of ferrite synthesis and has led to methods of preparing materials with a large variety of magnetic properties. During the last two decades the synthesis of ferromagnetic oxides has been the object of extensive research, but commercial production has been started only within the last ten years. Along with more fundamental studies, there remains the never- ending task of developing ways to realize the optimum characteristics of materials in large-scale production. Ordinarily, to produce a ferrite material it is necessary for the constituent oxides to be mixed intimately, pressed, and then fired at temperatures above 1000°C. Ferrite Synthesis: Formation of a basic ferrite by solid state reaction from Fe2O3 and a monoxide such as NiO, under normal atmospheric conditions, is governed by a progressive diffusion of cations between adjacent particles of the constituents. Firing temperature, furnace atmosphere, and cooling can vary the magnetic properties, however. If, for example, a dioxide, a sesquioxide, or an oxide of the Me3O4 type is substituted for the monoxide, the reaction mechanism becomes more complex and extremely dependent on atmospheric conditions and firing cycles. For this reason reproduction often

Jan 1, 1958

By J. A. Kitchener, J. P. Anfruns

Measurements have been made of the rate of capture of single particles of strongly hydrophobic, surface-methylated, quartz, of sizes ranging from 12 to 40 µm diam., by single rising bubbles of diam. 0.5 to 1.1mm. The results agree closely with the theoretically calculated hydrodynamic collision rates, indicating that, in this system, every collision results in capture and retention of a particle.

Jan 1, 1976

PT Freeport's Mine in Irian Jaya, Indonesia uses a number of 500m long vertical ore passes to transfer ore from the open pit to the mill. The current tonnages moved are in the order of 125 ktpd and this will be increasing to 240 ktpd. This amount of falling rock generates high pressures in the ore bins, when ore feed is terminated the pressure is no longer constrained resulting in back blasting of materials and air up the ore passes. Three methods were tested to try and eliminate or reduce this problem; recirculation of the entrained air, widening of the orepasses and relieving the pressure of the back blast. The final method proved to be the most effective in the short term. As a long term solution the orepasses are currently undergoing widening.

Jan 1, 1998

By H. Kose

In this research, a model quarry with an annual production capacity of 1 000 000 tonnes has been studied for both pit and hillside quarry cases with constant overall slope angle and variable bench slope angle, considering road grades of 8 per cent and 10 per cent. First, technical requirements have been determined and then the effect of production parameters, such as hole diameter, type of quarrying (pit or hillside) and road grade, on the cost has been investigated to determine bench height. Based on the results, it has been concluded that hole diameter has to be kept large in both pit and hillside quarrying to reduce drilling unit costs. In addition, in order to take advantage of gravity and reduce transportation cost, it has been suggested that bench height and road grade have to be kept high and low respectively in the case of hillside quarrying (downhill transportation) while, in the case of pit quarrying (uphill transportation), bench height and road grade have to be kept low and high respectively, in order to transport the blasted material to a lower height and distance, to save energy, thus decreasing the transport cost. Keywords: Quarry, pit, hillside, road grade, bench height

Jan 1, 2005

By Graeme Heyes, Warren J. Bruckard, Michael A. Somerville

"Over the past few years CSIRO Minerals has been conducting research aimed at developing a continuous copper converting process to replace the traditional two-stage batch process that is currently used to produce blister copper. Sirosmelt type reactors and calcium-ferrite (lime-based) slags have been used rather than the conventional iron silicate slags. The research work has now been extended to focus on the development of a single-stage continuous copper making process (so-called direct copper converting) in which copper concentrates are converted to low-sulfur blister copper in a single step, that is the smelting and converting steps occur in one continuous stage.One feature of the direct copper converting process is that copper losses to the slag phase can be high, meaning the slag produced needs to be treated to recover the copper value. The feasibility of the whole copper making process will most likely depend on the efficiency and cost effectiveness of the copper recovery stage. Flotation has been identified as the most economical option to recover the copper from direct copper converting slags where it has been estimated that a copper recovery from the slag of above 90% is required to make the overall single stage copper making process economically feasible.A limited series of laboratory batch flotation tests was conducted on a suite of calcium-ferrite-based slags made in laboratory smelting trials. Copper sulfide concentrates from MIM were used as feed-stocks. The objectives of this work were to develop a robust flotation process to maximise the copper recovery and iron rejection from slags made in the process, and to establish operating conditions for future continuous flotation pilot plant trials.The slags treated included a reduced low copper slag, an oxidised high copper slag composite, and a very reduced low copper self-pulverising slag. The copper content of the slags varied from 2.9% to 14% Cu and the CaO/Fe ratio varied between 0.30 and 0.54. In general, the higher the copper content the more oxidised the slag. The copper was present as metallic copper, oxide copper and copper-calcium ferrite phases with the phase mix related to smelting conditions. The slags were crushed, ground, wet-screened at 355 or 210 µm to remove coarse metallic particles of copper, and floated at natural pH (about pH 11) using reagents and conditions appropriate for the selective recovery of the copper phases. Reagent additions were typically 200 g/t KEX and 500 g/t Na2S.9H2O and the grind size was generally a P80 of about 40 µm."

Jan 1, 2003