Search Documents

By L. A. Abichequer

ROM grade variability is one of the most important factors influencing plant product recovery. Due to the influence of grade variability on mine profits, it is deemed important to guarantee a proper homogenization of the ore through a well-planned blending and homogenization pile system from which the ore is reclaimed at an acceptable grade fluctuation. This study tests geostatistical simulation efficiency in predicting in situ grade variability. The methodology is illustrated using a data-set from a large phosphate mine in central Brazil. Additionally, real data obtained at the mine site during January and February 2007 were used to derive the actual grades of each pile formed during this period. Each pile was formed by a selection of blocks within a dig line and these lines mined along the year 2007 were also made available. Given the real grades, it was possible to reconciliate and validate the results predicted by the proposed methodology. The main outcome of this study is the opportunity to check the geostatistical simulation as a tool to quantify the variability of the homogenization system.

Jan 1, 2009

By J. O. Marsden

The copper industry is cyclical with the price determined by market forces (i.e. the balance between supply and demand for the metal.) The period of each cycle typically varies between 6 to 9 years. These cycles drive decision making for exploration, new project and mine development, mine closures, process improvement, research and development, and technological innovation. The gold industry is fundamentally different from copper in that supply and demand do not, alone, determine metal price and many other factors play a key role, including global and regional financial conditions, political stability, and the global future economic outlook. However, the gold price experiences trends and longer term cycles that similarly drive business decision making. This paper examines developments in the copper industry that have occurred over the past few price cycles (approximately 20 years) and explores how the lessons learned can be applied to gold extraction. A number of specific examples and opportunities are discussed in detail, including; technology development and innovation, cost control and business improvement, material characterization, comminution equipment, biological heap leaching, and concentrate pressure leaching.

Jan 1, 2009

By U. Atici, R. Comakli

"Understanding rock properties is of vital importance in mining and civil engineering. Rock properties are generally determined through laboratory tests, which require a large number of uniformly shaped samples and technicians who use indirect methods to determine rock properties. The texture coefficient (TC), which represents various textural parameters including the size, shape, orientation, and relative proportions of grains and the matrix, is an efficient means for indirectly evaluating the mechanical behaviour of rocks. In this study, 12 different rocks (ten granites, one diorite, and one gabbro) were collected and their engineering properties. including specific gravity, porosity, P- and S-wave velocities, Schmidt rebound hardness, uniaxial compressive strength, and elasticity modulus, were investigated. Relationships between TC and these measured properties were assessed. Statistically significant (at the 95% confidence level) correlations were found between the TC and compressive strength, elasticity modulus, sound velocity (both compression and shear waves for dry and saturated samples), but no significant correlation was found with Schmidt rebound hardness. The results suggest that it is possible to use the relationships between TC and the mechanical properties of rocks in rock classification. IntroductionIn every aspect of rock engineering, knowing rock properties is essential for determining and predicting the behaviour of rocks and rock masses. Mechanical properties of rocks are important parameters in mining, geology, and engineering, and they are affected by textural characteristics such as grain size, grain shape, cement type, degree of cementation, mineral content, and the ratio of the grain area to the matrix area. The effects of textural properties on the physical and mechanical properties of rocks have been investigated for a long time, and previous studies revealed close relationships between single parameters related to rock texture and mechanical properties of rocks (Akesson et al. 2001; Gunsallus and Kulhawy 1984; Merriam, Rieke, and Kim, 1970: Onodera and Kumara 1980; Prikryl 2006; Ulusay, Tureli, and Bider, 1994; Tugrul and Zarif 1998). Rock properties are usually determined using mechanical tests, which require uniformly shaped and relatively large samples. However, it is not always possible to obtain such samples. Furthermore, rocks with similar textural and structural properties may exhibit different mechanical behaviour. Howarth and Rowlands (1987) developed a texture coefficient (TC) that expresses all the main textural parameters of a rock in a single dimensionless quantity based primarily on statistical assessment. The TC makes it possible to understand the effects of a rock’s textural properties on its mechanical properties using thin sections instead of large, uniform samples. Ersoy and Waller (1995) investigated the relationship between strength and TC for limestone, sandstone, and siltstone; they also examined the effect of rock properties and TC on drilling performance. Ozturk, Nasuf, and Bilgin (2004) explored the relationship between rock quality and TC by evaluating the uniaxial compressive strength (UCS) values of limestone, basaltic andesite, and tuff. Gupta and Sharma (2012) evaluated TCs as well as the petrophysical and mechanical properties of quartzite from the lower and higher Himalayas and found a strong relationship between TC and UCS. Similarly, Ozcelik, Bayram, and Yasitli (2013) investigated the relationship between TC and various parameters in marble by applying the statistical analyses developed by Ozturk, Nasuf, and Kahraman (2014)."

Jan 1, 2019

By G. A. Wiebols, N. G. W. Cook, N. C. Joughin

Introductory remarks Dr N. G. W. Cook: This paper was published in your Journal in May of this year and you will, therefore, have had the opportunity of reading it over the past six months. I can state that experience has shown that the paper is substantially correct, but a number of questions have to be answered. The first question, Mr President, that I would be happy to answer, is how is it that one is able to cut hard, abrasive quartzite with a strength some six times greater than that of good concrete? The essence of the answer is that there is a tremendous difference between abrasion, or scratching, and cutting, or chipping. For example, it is well known that a diamond will scratch or abrade almost anything. It is also relatively easy to chip, crack or crush a diamond. As a demonstration I have here an ordinary bench grinder, and with the bench grinder I also have a piece of tool steel. The wheel on this bench grinder is a silicon carbide wheel, which is an extremely hard material, and the tool steel is much softer. In rock-cutting we use tungsten carbide for cutting the quartzite. The quartzite and the tool steel have roughly the same hardness. You can sharpen tungsten carbide with a silicon carbide wheel. In fact, this is done. It won't surprise any of you, therefore, when I show you that tool steel can be sharpened with silicon carbide. Now, what I propose to do is to change the configuration of this experiment and use the soft tool steel to cut silicon carbide, and if I can do that, I think you will agree that I have gone some way to being able to cut quartzite, which is about as hard as tool steel, with tungsten carbide, which is harder than quartzite. Let me do this. (Demonstrates.) That, I think, is a very clear demonstration of how it is possible, with a metal, to cut an extremely hard and brittle material. What, essentially, is the difference that we have here? In the first case, I held the tool with a relatively low force against the hard silicon carbide wheel. This generated a relatively low average stress, which was insufficient to fracture the carbide wheel. Nevertheless the protuberances on the silicon carbide wheel indented the tool steel and abraded it at a multiplicity of points, and quickly reduced the section of the tool steel that I held against the wheel. By changing the configuration and clamping my tool steel in a firm post, against the silicon carbide wheel, I changed these conditions very extensively. I now had a high force. I had to exert a considerable moment on that lever. The tool was anchored so that it could sustain these high forces, and they generated high stresses, which were adquate to fracture the silicon carbide. Now, what about wear? It so happens that, in these two experiments I have just done, the power I was using was about the same-a small fraction of a horse power.

May 1, 1968

By H. E. Bartlett

This paper deals with the sampling and mass measurement for ore delivered from a shaft to a processing plant and the contribution of the data from these measurements to the metal balances from shaft deliveries to final metal production. Accurate measurement of the grade and tonnage of run-of-mine ore is important for four main reasons; ? It enables the measurement of the production from different profit centres to within statistically determined confidence limits for daily, monthly, or annual averages. The profit centres could be individual shafts within a mining complex or ore treated on a toll basis ? The monthly production at shaft head is compared to the grades and tonnage determined from underground sampling and mass measurement in terms of a shaft call factor ? The sum of the production from the shafts is the input to concentrators. This input is a major part of the total input into a complex with concentrators, smelters, and refineries. In terms of the Codes of Practice for Metal Accounting the inputs are compared to outputs and inventory changes to assess the efficiencies and unaccounted losses or gains at the various stages in the flow of metal from source to market ? On a daily or daily moving average basis, the grades and tons from shafts are monitored and compared against these quantities from underground measurements. This acts as a control on off-reef mining, dilution, and other factors underground. Accurate measurement of grade of ore at the shaft head has been a challenge because of the large particle size. The conventional wisdom has been that ore can be sampled accurately only after it has been milled to give a slurry that is sampled as feed to a flotation process. However, when the ore fed to a flotation plant comes from multiple sources each source has to be sampled separately. So, relying on the grades determined using the sampling of concentrator input with cross-stream slurry samplers is not an option for determining the grade from an individual shaft. Impala has developed a system for sampling and weighing run-of-mine ore from multiple shafts. The system involves sampling the inputs to the plants using cross-belt (hammer) samplers and weighing the deliveries using in-motion railway weighing systems. Many samples are taken. Individually they have a high variance but, as a consequence of the averaging effect of large numbers and as shown by statistical analysis, the mean results are fit for the purposes of daily grade control for shafts and for monthly accounting of production from individual shafts. In the metal accounting systems at Impala, the measurement of input, including ore and toll-treated material is compared to the output in the form of final metal and tailings losses, as well as any inventory change that takes place, in order to determine a final metal balance from mill feed to product. The calculated inventory is compared to that measured, and the difference, or unaccounted- for metal, is then reported as a percentage of input. The balances obtained over several years yields balances for platinum that are below 1% imbalanced. Keywords metal balancing, platinum mines, AMIRA codes of practice, metal accounting, sampling, run-of-mine ore, statistical analysis.

Jan 1, 2014

By N. Hamlef

In this study, the effects of heat treatment on phase formation and surface morphology of the Cr-Pt coated system are investigated using X-ray diffraction and electron microscopy techniques. The CrPt andCr4Pt (Cr3Pt - A15 type) phases were formed after heat treatment of the coated samples. Heat treating at 1000°C renders a distinct island coating morphology that is non-continuous in nature. A diffusional model is proposed for this coated system with regards to the surface morphology formation after heat treatment.

Jan 1, 2014

By C. J. Van Niekerk

When gold plant residues are cycloned for producing a coarse product for backfilling the gold and uranium values are upgraded in the backfill product. Gravity concentration, wet high intensity magnetic separation and froth flotation were investigated as first-stage recovery processes to recover these economic values from backfill prior to placement underground. This paper addresses the recovery of values from flotation concentrates and also details the economic feasibility of a treatment route including flotation, followed by roasting of flotation concentrate to liberate gold entrapped in pyrite and reverse gold leaching of the calcine so produced.

Jan 1, 1988

By John Freer

Over 200 delegates attended the SAIMM Colloquium on Flotation, which was held at Mintek on 22nd September, 1983. In introducing the programme, the Chairman of the Technical Programme Committee, Mr Eugene Fivaz, said that an attempt had been made to strike a balance between theoretical and practical papers, which he hoped would provide something for everyone. He wished to record in advance the thanks of the Institute to S.A. Cyanamid for sponsoring the lunch, and to Bateman Equipment Limited for the cocktail party to be held at the end of the day's proceedings.

Jan 1, 1983

Professor Miklos Salamon, Research Adviser to the Chamber of Mines of South Africa, has won the Rock Mechanics Award for 1983 of the American Institute of Mining, Metallurgical and Petroleum Engineers 'for applications of analysis to many varied practical mine design problems’. Mintek reports Report M119 A versatile computer programme for data capture in multi-element analysis by a sequential X-ray spectrometer. Report M120 South African costs of equipment for the metallurgical industry (1983). Report M125 Commissioning of an automated microphotometer used in spark-source mass spectrometry.

Jan 1, 1984

By A. N. Brown

Professor D. G. Krige, of the Department of Mining Engineering of the University of the Witwatersrand, received the degree of Doctor of Engineering (honoris causa) from the University of Pretoria at the Autumn Graduation Ceremony in April 1981. He was honoured an outstanding engineer for his world-renowned pioneering work in the field of statistical methods of ore valuation, or geostatistics as it has become known. Metalliferous Ore Deposits A short course on the 'Evolution of Metalliferous Ore Deposits' will be held at Rhodes University, Grahamstown, from 8th to 13th February, 1982.

Jan 1, 1981

Minutes of the Annual General Meeting held at the St. Helena Club on Wednesday, 27th July, 1977, at 7.30 p.m. Book review Advances in extractive metallurgy, 1977. Proceedings of the third symposium organised by the Institution of Mining and Metallurgy held from 18-20th April 1977. London, the Institution of Mining and Metallurgy, 1977. 244 pp. £18,50. Coal preparation A meeting of the Organising Committee of the Eighth International Coal Preparation Congress took place in Moscow on 24th and 25th May, 1977.

Jan 1, 1978

By D. Menne

A comminution model and a quick laboratory milling test procedure are presented. These allow the determination of milling parameters for the - optimization of ball size and pulp density in operating mills estimation of the performance of new feed stocks in an existing mill - estimation of the expected milling performance for a new project. Information on the estimation of the size of mills to deliver specified amounts of comminution energy, and amount of expected ball, rod, and liner wear to allow cost estimates for new projects, is also included.

Jan 1, 1983

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 B. R. Broekman, J. P. W. Bennie, P. D. K. Robinson, R. P. Viljoen

The theme of the Congress was 'Resources and Technology', the intention being to highlight those basic technical aspects in the disciplines of geology, mining, extractive metallurgy, and metals technology that are required for successful mineral-based operations. The technical programme covered a fairly broad field, as is appropriate for the CMMI Congress, and was generally considered to be of a high professional standard; informative and, with the exception of some minor hitches, well-run. Parallel sessions were held in the four disciplines. All were well attended, and despite tight presentation schedules, certain valuable discussions developed.

Jan 1, 1994

By C. T. Connor, O&apos

The 10th Annual UCT -US Minerals Processing Symposium was held at the Van Riebeeck Hotel at Gordon's Bay from 31 July to 2 August 1991. The conference was attended by 133 delegates representing a broad cross-section of the mining and metallurgical industry in South Africa. For the first time the Symposium, which was celebrating its 10th anniversary, was extended to two days. A cal for papers was announced and the organizers were inundated with responses resulting in a very full technical programme which consisted of 29 oral and 15 poster presentations.

Jan 1, 1991

By C. Pohlandt

A literature survey of methods suitable for the determination of cyanides in process streams and effluents is presented. Of the large number of methods published, 92 are examined in detail, emphasis being placed on the selectivity of the methods, i.e. the extent to which they enable one to distinguish between ionic cyanide and metal-cyanide complexes. Methods designed for the determination of 'total cyanide' (i.e. ionic cyanide as well as coordinated cyanide) are evaluated critically. Other aspects of the methods are also considered, such as sensitivity, accuracy, speed, and freedom from interferences.

Jan 1, 1983

By L. Woollacott, R. P. King

This paper presents data collected from full-scale plants in order to verify the predictions of a new simulator of CIP or CL operations. Good agreement was found between the experimental data and the simulator predictions. The simulator is able to predict the effects of many of the complex operating phenomena in GIP and CL plants that previous simulation techniques could not describe. This is illustrated by predictions of how factors, such as the manner of carbon transfer, concurrent leaching, and gold loading on eluted carbon, can affect the performance of an adsorption plant.

Jan 1, 1990

By M. D. Prendergast

Research into the ferrous metallurgy of Rhodesian Iron Age societies M. D. PRENDERGAST (Visitor) Iron-working was a widespread economic activity in Iron Age Rhodesia, and merits historical and metallurgical investigation. However, the research done so far has been incidental and poorly disseminated. This paper reviews the available evidence and the ways in which it can be interpreted by archaeologists and historical metallurgists. Particular attention is paid to smelting techniques and current metallurgical research, and brief suggestions are made for future research. v074n06p254.pdf

Jan 1, 1974

By L. H. W. Walker

As part of an overall design of a computer based mining managerial system, the geological and mineral estates management disciplines find themselves centrally placed in terms of producing fundamental data both before and during the mining operation. Computerisation of all aspects of these fields of endeavour has come to be seen as essential for complete integration with other mining orientated disciplines. Release 1 .l. of the Anglo American system of mineral estates management has been tested and is in the process of being implemented at several Anglo American Gold Division mines.

Jan 1, 1987

By P. Jordan

The practice of ilmenite smelting in electric arc furnaces has been researched and published over the last few decades. An issue that has not been addressed is the understanding of the properties of ilmenite smelting reductants, and linking these properties to the subsequent smelting behaviour in the furnace. The reduction mechanism of ilmenite smelting is not fully understood, but it is believed that the Boudouard reaction plays a role. This paper investigates the behaviour of a number of reductants when reacted with CO2 at different temperatures. Keywords Boudouard reaction, carbon reactivity, reductants, ilmenite smelting.

Jan 1, 2011