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By A. Cichowicz

The objective of this work is to quantify the effect of the rock mass surrounding a stope or a tunnel on the seismic signal so that the rockburst damage on the excavation can be derived. It has been shown that the transfer function of rock mass surrounding an excavation can be modelled using a damped oscillator. The method of estimating the transfer function is extended in this paper. The parameters of a damped oscillator are estimated using inversion techniques and the transfer function is modelled as a time-varying system. The technique is tested on data acquired at three different sites in two deep gold mines. Employment of a modal model of the transfer function was suitable in two cases. Application of this technique is essential to track the time variation of the natural frequency during ground motion caused by a seismic event.

Jan 1, 1999

By F. H. Abd EL-Rahiem

A selective dispersion process is presented and the work carried out to find optimum process conditions to minimise the colouring material in ground calcium carbonate (GCC) is described. The feed material is the overflow product from a hydrocyclone which results from using a Denver Attritioning machine with semi-autogenous grinding for one hour and a 1:1 ore/water ratio. By using sodium silicate (SS), with pH 9 and pulp density 5%, the iron content (as colouring impurities) is decreased from 0.21% in the original concentrate to 0.12% in the final concentrate. The degree of whiteness reached is improved to 85% from 63% in the original material. However, by using hexametaphosphate (SHMP) at pH 10 at the same pulp density, the iron content decreased to about 0.073% and hence the whiteness degree increased to about 96%.

Jan 1, 2004

By J van Rooyen, S. Archer, M. Fox

The use of dilute sulphur dioxide (SO2) gas mixtures for the oxidation/precipitation of manganese has been explored widely in recent years. The technical merit of the concept is well proven and implementation of the technology on commercial scale is imminent. This paper reviews the technology of manganese removal by means of dilute SO2 gas mixtures and highlights some of the challenges associated with its implementation on industrial scale. A brief review of the technology is presented; the review considers both the mechanism and chemistry of manganese oxidation/precipitation with dilute SO2 gas mixtures. The impact of variables such as temperature, pH and SO2 concentrations on the manganese removal process is assessed. Challenges associated with implementation of the technology on industrial scale are discussed. Gas dispersion is highlighted as a critical design consideration.

Jan 1, 2007

By R. H. O?Connor, B. N. Soutar

The paper reviews the introduction 01mechanical shaft drilling into the sinking 01shafts in the Gold Fields Group. A comparison is made between the operating costs 01the drilling rig and those of conventional hand-held machines, and it is concluded that, despite certain disadvantages, mechanical drilling is preferable.

Jan 1, 1988

Statistics is essentially a study of variability, the use of some suitable mathematical model representative of such variability, and the application of this inferred pattern of behaviour to practical problems. Probability theory is the mathematical structure devised for providing models for chance happenings. Perhaps the simplest example of a chance happening is the result obtained in tossing a coin. Although the result of a single toss can never be predicted with certainty, there is no reason why in repeated tosses the expectancy of heads and tails should not be equal. In such a case the outcomes of the experiment are said to be equally likely, so that the probability of obtaining heads (or tails) is 1 in 2, that is, 0,5. This simple probability .model refers to a 'mathematical' or 'unbiased' coin. Whether such probabilities are meaningful for actual coins tossed in any particular way is a matter for experience to determine. Probability models have also provided the basis for representing observed variability in cases where the actual under- lying probabilities are only partly known or defy analysis. A typical example of the latter case is the variability observed in the values obtained from gold or other ore samples. The interacting natural forces which gave rise to this variability are obviously very complex and are unlikely ever to be unravelled completely. In spite of this, probability theory and the more recent geostatistical theories have provided us with models which can represent this variability on a reasonable basis. Applied statistics and geostatistics must therefore never be accepted as exact mathematical sciences. Furthermore, a basic and essential concept is that in the type of applications covered in these notes, no model must ever be accepted as necessarily the final and exact answer to the problem; thus, any model must prove and continue to prove its appropriateness in practice, preferably by follow-up comparisons.

Jan 1, 1981

By R. G. Koelmans

In 2001 Platinum overtook gold in foreign revenue earnings for South Africa. The export sales from platinum group metals amounted to R29.3 billion as opposed to gold export sales of R28.6billion1. Organizations must undertake new ventures to replace old, worn-out and obsolete assets with new ones. These assets could be a building, a new product or process, a new mine, or anything that can help the organization to achieve its objective. These ventures are projects by their nature. When a project is pronounced a success, the judgement is usually based on some factual evidence, although not every one uses the same data. From the literature, it is obvious that there is a lack of consensus and objectivity as to what constitutes a successful project. The purpose of this paper is to address the following questions: ?What constitutes a successful project? ? How does one measure project success? ?How can one work toward project success? This paper addresses the requirements for project success of three of the primary stakeholders of a project, namely the business or client, the employees as far as the project team is concerned, and the local community. Indicators are developed into a work breakdown structure (WBS)-like chart to demonstrate success indicators. These indices take cognisance of all the constituents required for project success. The indicators are further developed to take cognisance of the requirements of the local communities. These indices are then weighted to arrive at a total score for the respective stakeholders. Using these WBS models, the success and performance of a project can be evaluated. This score is considered an objective measure of project success. Projects are evaluated more consistently across different projects and the project manager is provided with a management tool that can assist him/her in ensuring greater project success. The shortcoming of this approach is that the weights of the different indices have been estimated at this stage. Research will have to be conducted to more accurately reflect the weights assigned to the indices.

Jan 1, 2004

By H. W. Read

Sustained growth in demand for platinum group metals has resulted in an unfettered increase in new projects undertaken by the platinum producers. These projects are outsourced to various degrees. The argument of this paper is that both the client?s project manager and the consultant?s project manager are essential elements in the successful execution of a project. Their roles are not only different but also complementary, and are defined in the paper. Data gained from considerable experience in the South African corporate mining environment underpins the opinions expressed in the paper. Furthermore, an extensive literary search was undertaken to determine trends in related industries outside the South African context. Throughout the argument it is emphasized that project philosophy emanates from a systems view and must be treated as an overarching whole. The elements of project management become meaningless unless they are connected to one another and integrated into a cohesive unit. Advancing the knowledge field of project management is of critical importance to mining investors. There is no doubt that a key determinant of the sustainability of mining business is closely related to the efficiency of all-inclusive project management. From pre-investment and feasibility studies, implementation and execution, to ramping-up to full production, scientific project management has a critical role to play. Guidelines for the pursuance of this ideal are proposed. The introduction contextualizes the subject matter in an overview of the evolution of mine management in South Africa and abroad. Then, brief insight is given into the philosophy of project management. This exposition is confined to the predispositions, presuppositions and defining characteristics of project management. The core of the paper looks at the roles of the client?s project manager in relation to the consultant?s project manager. This section is underpinned by practical experience gained by the author on numerous mining projects. A view is taken of the future of project management in the mining industry. The conclusion summarizes the argument and aligns project management trends in the mining industry.

Jan 1, 2004

By N. A. Smith, R. J. Fowell, J. L. Hislam

Abstract: Data are presented from two sites in southeast England, where problems were encountered in tunnelling through ground containing flint. In response to the difficulties, substantial laboratory testing programmes were initiated to determine the strength of the flints.It is shown that the strength varies very considerably, even within a single flint particle and that the practice of estimating unconfined compressive strength by a single multiplier applied to the point load strength index (Is(50)) may give misleading results. The preparation of UCS specimens for testing was found to be very difficult and it is recommended that tunnel machine capacity is assessed relative to Is(50). Résumé: Des données sont presentées sur deux sites dans le sud-ouest de l’Angleterre,où le perçage d’un tunnel dans un sol contenant du silex a posé des problémes. En consequences de ces difficultés, des programmes substatiels de recherché en laboratoire ont été initiés afin de déterminer la resistance des silex. Il est demontré que la resistance varie considérablement, même au sein d’une particule de silex, et que la pratique de estimation de la résistance en compression non confinée, (UCS) par le biais d’un simple coefficient appliqué au ‘point load strength index (Is50)’ pourrait donner des resultants trompeurs. La préparation de specimens UCS destinés aux tests s’est avérée trés difficile et il est recommandé que la capacité de la machine de perçage de tunnels soit calculée relativement au Is50. Zusammenfassung: Daten von zwei Standorten in Südosten von England, wo Probleme beim Tunnelbau durch feuersteinhaltigen Grund antraffen, sind angegeben. Wegen diesen Schwierigkeiten wurden Laboratoriumsforschungsprogramme eingeleitet, um die Festigkeit von Feuersteinen zu bestimmen. Es wurde gefunden, dass die Festigkeit sehr unterschiedlich war, selbst bei einzelnen Feuersteinstücken, und dass die Praxis, die unbegrenzte Kompressionsfestigkeit (uKf) auf Grund eines einzigen Multiplikationsfaktors vom Punktladefestigkeitsindex (Is50) abzuschätzen, zu irreführenden Resultaten führt. Die Vorbereitung der uKf Prüfstücke war sehr schwierig und es wird vorgeschlagen, dass die Kapazität der Tunnelbaumaschine in Abhang der Is50 bestimmt wird.

Jan 1, 2003

By J. Ungar, F. X. McGarvey

The selectivity of ion-exchange sites varies with the matrix of the polymer, the nature of the site. and the method of application. The effect of these variables on the recovery of uranium is examined. with particular attention to vinyl pyridine and to symmetrical and asymmetrical quaternary ammonium sites. The effect, on the loading. of high concentrations of chlorides in the liquors is discussed. and other components of the liquors that may cause fouling of the resin are also considered. The discussion is supported by the results of tests conducted on various types of resins. The economics of the process is discussed briefly.

Jan 1, 1981

By J. Ungar, F. X. McGarvey

The selectivity of ion-exchange sites varies with the matrix of the polymer, the nature of the site. and the method of application. The effect of these variables on the recovery of uranium is examined. with particular attention to vinyl pyridine and to symmetrical and asymmetrical quaternary ammonium sites. The effect, on the loading. of high concentrations of chlorides in the liquors is discussed. and other components of the liquors that may cause fouling of the resin are also considered. The discussion is supported by the results of tests conducted on various types of resins. The economics of the process is discussed briefly.

Jan 1, 1981

By H. D. Mtegha

The Southern African Development Community (SADC) aims to harmonize mineral policies and regulatory regimes in the minerals sector. This paper provides a review of the progress made towards harmonization of mineral regimes in the region. It singles out only the mining fiscal environment, as this is normally one of the key issues of interest to potential investors as well as the host state. Indications are that the region is slowly progressing towards a more harmonized approach, and there is evidence that the ?race to the bottom? has been prevented, which is the basis for an integrated mineral sector that the region aspires to.

Jan 1, 2011

By D. J. Hallbom

A new graphical method termed the ?Design Curve Diagram? (DCD) has been developed to analyse non-Newtonian pipe flow data by relating the plastic Karman number to the plastic Reynolds number. Since the plastic Karman number is directly proportional to the pressure loss gradient and the plastic Reynolds number is directly proportional to the velocity, the DCD is essentially a non-dimensional pipe flow curve. This makes the DCD conceptually easier than the commonly used Hedström-Moody diagram. While, the DCD was developed for the analysis of yield plastic fluids (e.g., Bingham plastics), it is equally applicable to Newtonian fluids.

Jan 1, 2007

By Siyabonga Malevu

Chemical Initiatives? Umbogintwini plant is the production facility of Chemical Initiatives? business. Umbogintwini?s J Plant manufactures sulphuric acid. The plant was designed and built by Simon Carves, and was commissioned in 1974. The plant was designed to produce 500 tons/day of Sulphuric acid (H2SO4) at maximum rates. The Sulphuric acid manufacturing is through the famous contact process whereby liquid Sulphur is injected through dried air in a burner operating at 1000 °C to form sulphur dioxide (10.5% SO2). The SO2 gas is then cooled in waste heat boiler no. 1 before being fed to a four pass converter which provides 99.5% SO2 conversion to sulphur trioxide (SO3). The SO3 gas is the absorbed by 98.5% H2SO4 through the inter-pass & final tower to make more concentrated acid and dilute it with water back to 98.5% H2SO4 in acid pump tanks and dispatched to storage tanks. The manufactured Sulphuric acid is supplied to a variety of industrial manufacturing customers includes Pulp & Paper industry, Mining industry, Chemical manufacturing industry etc.

Jan 1, 2009

By M. U. Ozbay

The stability of pillars is analysed on the assumption that pillars shed load in a stable manner if the slope the strata load-deformation relation is steeper than that of pillars in the post-peak regime. Concepts of local stiffness, mine structural stiffness, and critical stiffness are discussed. Procedures are described for the determination of strata stiffness for various pillar layouts by use of the available boundary-element computer programs. The postpeak stiffness of pillars is assessed from the available data relating to the post-peak load-deformation relationship and width-to-height ratio. Stability analyses are carried out by the contrasting of strata stiffness with post-peak pillar stiffness. It is shown that the strata stiffness becomes unacceptably small for a stable yield-pillar layout when the span exceeds about 5 times the depth. The strata stiffness is found to increase, thereby increasing the stability, as the span-to-depth ratio, number of pillars, and percentage extraction are decreased. It is also found that the stability in a yield pillar becomes difficult to achieve when al the pillars in a layout are in the descending part their post-peak load-deformation curve

Jan 1, 1989

The kinetics of cyanide loss were found to be first order under any given set of conditions, allowing rate constants to be easily determined. At room temperature and in the absence of activated carbon, some cyanide is lost by hydrolysis to hydrogen cyanide, but this does not occur to any significant extent at pH values higher than about 10. A higher rate of hydrolysis occurs when air agitation is used. When activated carbon is present, an additional carbon-catalysed oxidation reaction is responsible for a fairly high loss of cyanide. The evidence indicates a reaction mechanism that consumes oxygen and produces cyanate ion. Some of the cyanate thus produced decomposes to form a mixture of ammonia, carbonate, and urea, depending on the solution conditions. Additional cyanide is lost as a result of the adsorption of sodium cyanide by the activated carbon. At high temperatures, an additional hydrolysis reaction, which involves the formation of ammonium formate as an intermediate, occurs an/j is responsible for. a high loss of cyanide, leading ultimately to the formation of ammonia, hydrogen, and carbon dioxide. The presence of activated carbon has no effect on the rate of this reaction.

Jan 1, 1990

By D. Moradkhani, S. M. Javad Koleini, M. Abdollahy, F. Soltani

"The objective of the study was to determine the type and distribution of rare earth elements (REEs) in the phosphate flotation concentrate from the Esfordi flotation plant in central Iran, in order to understand their leaching behaviour. Samples of the concentrate were prepared and analysed using XRF, XRD, ICP, and EMPA. The Ce, Nd, La, and Y contents were 5608, 2227, 1959, and 679.7 mg/kg, respectively. The main REEbearing minerals in the concentrate are fluorapatite, monazite, and xenotime. Apatite is the chief mineral of the concentrate and the ratio of apatite to monazite is greater than 60. From EMPA analysis, monazite contains a much higher proportion of REEs than apatite, but more than 50% of the REE content of the concentrate is in apatite, as this is the main mineral constituent of the concentrate. During the leaching of REEs in the phosphoric acid production process, more than 99% of the total rare earth values report to the large amounts of phosphogypsum (CaSO4·2H2O) formed during the dissolution reaction. Accordingly, two process options are suggested for treating the Esfordi concentrate. In the first option, the concentrate is treated with 98% H2SO4 at 200–300°C. After digestion and water leaching, phosphorus and REEs are precipitated out of solution. In the second option, the concentrate is treated in a pre-leach stage. The process residue from the pre-leach stage is then subjected to acid digestion at elevated temperature for phosphoric acid production.IntroductionThe rare earth elements (REEs) comprise a set of 17 chemical elements in the periodic table, specifically the 15 lanthanides plus scandium and yttrium. REEs and alloys that contain them are used in devices such as computer memory, rechargeable batteries, cell phones, catalytic converters, magnets, fluorescent lighting, and many more (Krishnamurthy and Gupta, 2004). China supplies about 94% of the REE demand, with the remaining 6% coming from Russia and Estonia, the USA, India, Malaysia, and Brazil (Zhanheng, 2011). Increased industrial development in China has prompted the Chinese government to limit annual export quotas to approximately 35 kt of rare earth oxides (REOs), while non-Chinese annual demand is expected to reach 80 kt by the year 2015. This constriction of supply is being met by the development of many new rare earth mining projects, each of which has its own unique mining and processing challenges (Jordens, Cheng, and Waters, 2013). One of these projects is the Esfordi phosphate project, which is located in Yazd Province in central Iran. The concentrate from the Esfordi flotation plant contains 1.2–1.5% REEs."

Jan 1, 2017

By Wm. Bleloch

SYNOPSIS The feasibility of rejection of nitrogen from stack gas by recycling of top-gas with cold-blast 95 to 98 per cent oxygen is assessed. It is concluded that nitrogen could be removed to a level below 3 per cent of the stack-gas using recycled cleaned cold top-gas and 95 to 98 per cent oxygen produced by a single-column air separation plant with liquid-air reflux instead of liquid nigroten reflux. The partial pressure of carbon monoxide in the stack-gas could be doubled without top pressure and the deposition of carbon and reduction of iron oxides by the stack gas could be markedly increased. It is concluded that rate of stock descent could be doubled compared with present-day practice and an iron make of 4400 kg/m 2 of hearth area/hour may be attainable with a working volume of 129 m2/m hearth diameter by this method. Oxygen consumption is estimated at possibly 280 m2 (0.4 t)/t iron made and carbon consumption at possibly 280 kg/t iron. Power consumption for oxygen including auxiliaries is estimated at 304 kWH/t 100 per cent oxygen as 95 to 98 per cent gas. The air separation cycle due to Schuftan is discussed in some detail, and the components of a 1 600 metric ton/day separation plant are briefly discussed. The paper is a theoretical essay.

By A. Kijko, C. W. Funk

Methods for the analysis of seismic hazards in mines are reviewed as illustrations of the techniques that are being used in some South African mines. The classical parameters that describe a hazard are the seismic activity rate, ?, the Gutenberg-Richter value, b, and, occasionally, the maximum regional magnitude, mmax The activity rate is calculated readily owing to the inherent simplicity of its definition. The evaluation method presented for the Gutenberg-Richter b value takes into account the presence of mmax Three statistical procedures are described for the assessment of mmax which the maximum observed magnitude, Xmax a crucial role. Often, the configuration of mine seismic networks is changed, or the networks are improved, which inevitably gives rise to changes in the completeness of the seismic catalogues. The routine analysis of seismic hazards must account for these time dependent changes. A method for the evaluation of hazards is reviewed that accommodates varying levels of quality in the catalogues. Finally, the concept of the volume of ground motion (VGM) is presented. This is a technique that allows for most aspects of seismic hazards in mines. The advantage of the VGM is that a hazard can be described by one physically significant value: the volume of rock (cumulated over a time period) in which the ground motion exceeds some critical particle velocity. Data from the gold mining region in South Africa known as the Far West Rand is used in a demonstration of the discussed methods of hazard analysis.

Jan 1, 1994

By S. M. Bradshaw

In order to assess the requirements for online matching when using a transverse electric field (E-field) applicator to treat mineral ores continuously, the effect of varying load properties on matching has been investigated by simulation. The effective permittivity of the ore to be treated is expected to show variation on both short (< 1 s ) and long (minutes) time scales. By modelling the ore as a series of slices with alternating effective permittivity values, it was shown that permittivity variations on the scale of the expected particle size are attenuated significantly and matching is not required. For variations in permittivity on the length scale of the free-space wavelength, variations in reflected power are at most within ±10% of the mean. This is not considered operationally significant, as extreme permittivity variation over this length scale is unlikely, given the expected distribution of ore particle sizes to be treated. At typical ore transport speeds through the applicator, these variations occur on a time scale an order of magnitude shorter than the response time of typical industrial online matching equipment. This implies that online matching is neither required nor possible for short time scale variation. Long-term variations in dielectric properties can be adequately compensated for by current matching technologies. It is concluded that the transverse E-field applicator is robust to changes in the dielectric properties of crushed ores within the expected range of their variation.

Jan 1, 2012

A dual rate kinetic model consisting of differential equations is used to describe the kinetics of the adsorption of gold cyanide on activated carbon. The partial differential equation describing the material balance in the liquid phase is written for the special case of a fixed bed system. It is shown that an isotherm for the case of a closed system is required to yield accurate simulations of the equilibrium in a column of activated carbon. Whereas the equilibrium loading of gold cyanide is influenced by the free access of oxygen to the system, the traditional open batch stirred tank experiments, which are used to estimate parameters for the calculation of breakthrough curves for organic solutes, cannot be used here. The program solves this model at incremental heights in the column at a specific future point in time. Runge-Kutta and backwards- difference methods are used in the numerical solution. A Von Neumann method is used to show that the solution is stable. Kinetic parameters can be estimated either from batch experiments or from short column runs. In the latter method the column should not be long enough to contain the concentration wavefront for the system of interest. Results obtained from bench scale continuous column experiments were used to verify the computer model. Pure gold solutions as well as real leach liquor were used in both short column and countercurrent moving bed experiments.

Jan 1, 1987