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By I. J. A. Brackley

An investigation of the slope stability of a pit and failures of spoil dumps, carried out at Silicon Smelters quartz mine, Pietersburg, South Africa, is described. The major geological feature of the mine is the intensely foliated schist in the footwall, with exceptionally Iow strengths upon extensive discontinuities, and the similarly unusual strength properties of the dumped schist spoil. The selection of slope angles for the pit is described, and a proposal for the stabilization of the failing spoil dump by segregated dumping is explained.

Jan 1, 1985

By M. Rudman, L. Pullum, L. J. W. Graham

Centrifugal pumps are the workhorse of hydraulic conveying systems but their performance is derated when viscous non-Newtonian fluids, such as pastes and/or coarse solids are present. The reduced performance for purely viscous Newtonian fluids may be calculated using techniques such as the Hydraulic Institute method, but similar deration for non-Newtonian fluids is not so easy to apply. As part of the AMIRA P599 project investigating high concentration suspension pumping, centrifugal pump tests were systematically conducted on a wide range of non-Newtonian coarse particle suspensions. Suspension sup to 38% v/v of coarse particles with mean diameters in the range of 1.1 < d50< 3.4 mm suspended in carrier fluids with dynamic yield stresses of 0 < t?< 17.2 Pa and shear thinning indices in the range 0.35 < n< 0.79 were examined. Techniques such as the Hydraulic Institute de-ration method require a characteristic shear rate to be assigned before application with a non-Newtonian fluid, and a method based on pump geometry, fluid rheology and flow rate is proposed. This method predicts the dramatic characteristic reduction in head at low flow rates that is often observed and explains why larger pumps are relatively insensitive to this form of head deration. Head deration due to the presence of coarse particles in non-Newtonian carrier fluids is seen to follow similar trends to that of Newtonian suspensions and often dominates the total deration procedure.

Jan 1, 2007

By E. J. Magri

Consideration is given to the problem of the estimation, from limited data, of the likely grade and tonnage for a new mining property that is to be exploited by the selective mining of two metals that have substantial contributions to make to the total revenue. In particular, the case of a new gold and uranium mine in South Africa is analysed as follows. (I) The applicability of the underlying lognormal bivariate model for different support (i.e. ore unit) sizes is examined. (2) The necessary parameters for the bivariate lognormal models for different block sizes are estimated from abundant chipsampling data from a section of the Hartebeestfontein Gold Mine using alternative approaches, and the results are compared. (3) A method is given for obtaining the necessary parameters for a tonnage-grade relationship relative to a joint pay limit from the very limited information likely to be available at the end of the exploration stage of a gold mine, and the results are compared with those obtained from the large volume of data available from a minedout area.

Jan 1, 1982

By B. Geelhoed

Gy&apos;s formula for the variance of the fundamental sampling error (FSE) is based on a model that assumes independent selections of particles. A generalization of this model, which can theoretically lead to more realistic representation of actual sampling processes, was, for the first time, experimentally verified by repeated sampling from a well-mixed batch consisting of particles of zirconium silicate of two different sizes. The predictions for the sampling variance made in Gy?s theory and in the more general model were compared with the experimentally observed sampling variance. During the experiment performed here, the variance prediction made in the theory of Gy ranges from 0.96 × 10?7(g2/g2) to 0.95 × 10?7(g2/g2), which is approximately a factor 60 lower than the experimentally observed variance (5.76 × 10?6(g2/g2)). The difference between the Gy prediction and the experimentally observed variance cannot be fully explained by the uncertainty in the experimentally obtained variance due to the finite number of degrees of freedom. Therefore, the difference is likely to be a significant effect. This shows that, under the experimental conditions, Gy?s formula for the variance of the FSE probably undervalues the sampling variance, unless an empirical correction factor for grouping and segregation is applied in the theory of Gy. The new theory resulted in a variance prediction of 6.00 × 10?6(g2/g2), which is much closer to the observed variance than the Gy prediction. This indicates that the generalization of Gy?s theory offers an outlook for providing a better variance prediction than the Gy predictor in the case of dependencies between particle selections. The results are discussed. Keywords: sampling, variance, parameter for the dependent selection of particles, Gy, experiment.

Jan 1, 2009

By E. J. Magri

This paper describes a geostatistical study of the relative merits of diamond-saw sampling and conventional chip sampling, using results from experimental work carried out on Randfontein Estates Gold Mine and Western Areas Gold Mine. The diamond-saw sampling procedure is described, and it is concluded that this is a very efficient operation and leads to good-quality sampling that is clearly an improvement over conventional chip sampling. The study principally involved the computation of the errors of estimation of the mea gold value of mining panels for the two sampling methods, revealing that, in the normal production environment, the diamond-saw sampling method is a significant improvement over conventional chip sampling, as evidenced by the reduced estimation errors achieved. The question of optimum sample spacing is discussed, and it is concluded that the required spacing for chip sampling needs to be smaller than for the diamond-saw method.

Jan 1, 1986

By P. J. Barton, N. F. Peverett

A brief review of the development and ultimate design of the Model 16 Photometric Sorter is given, including the differences between it and its predecessor, the Model 13, which is currently in operation at Doornfontein. A description of the West Driefontein sorting plant is given, together with the rationale of its design. The installation programme for the sorters is described, and current operating and maintenance procedures are discussed. Operating results are tabulated and compared with the original test results. Operating costs are also discussed.

Jan 1, 1980

By M. J. King, A. Weissenberger, W. G. Davenport

Keywords: Pyrometallurgy, sulphuric acid, sulphur dioxide The raw material for sulphuric acid manufacture is clean SO2 gas. It comes from (i) burning molten by-product sulphur; (ii) roasting or smelting metal sulphide concentrates, and (iii) decomposing contaminated organic chemical process sulphuric acid catalyst. Efficient gas cleaning is required for metallurgical and contaminated acid decomposition gases, especially the former. Sulphuric acid is made from SO2 gas by (i) oxidizing the SO2(g) to SO3(g) in contact with supported liquid-phase catalyst then (ii) reacting the resulting SO3(g) with the water component of 98.5 mass% H2SO4, 1.5 mass% H2O acid. This paper discusses the reasons for these process steps and indicates how acidmaking can be controlled and optimized. Special emphasis is placed on SO2(g) oxidation efficiency and how it is influenced by feed gas composition, feed gas temperature, catalyst composition, catalyst bed pressure, number of catalyst beds, and double versus single contact acidmaking. In addition, a review of various other treatment methods for SO2-bearing gases is provided. A brief description of each process is included along with commentary on their technical and economic applicability for use at metallurgical facilities.

Jan 1, 2006

By A. F. Spinks, S. P. Nicholls

"The Lower Orebody at Chingola Division of Nchanga Consolidated Copper Mines, Limited, is a stratified orebody that is mined by a continuous caving system. The accurate determination of the developed and semi-developed ore reserves has always been difficult. The new system proposed in 1971 is designed to update and, as new informa¬tion becomes available, to account for the depletion of, the reserves.There are three main inputs to the system. These are borehole data, survey data and extractions data. The borehole data are input to a geological borehole master file system, which holds every recorded detail of a borehole in an easily extractable form. These data can be extracted for ore reserve calculations or for contour mapping of orebodies and rock types. The grades for use in the ore reserve calculations are extracted from the relevant boreholes.The survey data are information on the position of the blocks and drifts, taken from plans, and information on the scraper drift and trough drive positions taken from sections. The information is extracted from the plans and sections using a D Mac pencil follower. The ore reserve is calculated from the survey data and the borehole data.Data on extractions are taken from scraper operators&apos; logs, tramming records, skips hoisted records and accepted mill tonnages and grades. Using these data, the mill tonnages are reconciled back to the drifts, to deplete the current ore reserves.As new workings are brought into operation and further evaluation holes are drilled, the relevant data are input and the new developed ore reserve is calculated."

Jan 1, 2014

John Keith Elers Douglas recently retired from active participation in the activities of the South African Institute of Mining and Metallurgy after over forty years of diligent and valuable service to the Institute. This account of his contributions to the mineral industry and associated organizations is presented as a tribute to all his hard work and dedication. Mineral processing The Fourteenth International Mineral Processing Congress, sponsored by the Canadian Institute of Mining and Metallurgy, is to be held in Toronto from 22nd to 27th October, 1982. The theme of the meeting is &apos;Worldwide industrial application of mineral technology&apos;.

Jan 1, 1981

By S. A. Ziebold

There is often a need to increase capacity through existing mist eliminator installations without significant tower modifications. Often there is not enough extra space outside existing vessels unless more expensive changes can be justified. Also, plant downtime must be considered. The challenge in retrofitting is to overcome velocity limitations inherent in the design while at the same time extend performance capability. The solution most often is to create new ways to add extra filter area while remaining constrained to the existing space. This strategy, however, can dangerously backfire if basic design principles are not followed. Mist eliminator design is a complex integration of many conflicting performance parameters. Often the objective is to increase scrubbing capacity while maximizing collection efficiency and service life and minimizing operating pressure drop (energy cost), particle regeneration (re-entrainment) and overall maintenance costs. Results of plant retrofitting using mesh pads, impaction fibre beds and diffusion fibre beds are presented based on actual plant projects. Often the retrofit project can be more effective by increasing the scope and combining other new plant equipment with the upgrade such as new tower components. In some cases, the type of mist eliminators can be upgraded from impaction type (velocity dependent) to Brownian diffusion type (velocity independent) if additional downstream protection or reduced emissions are desirable, especially at turndown rates. Trade-offs between different fibre bed types and styles are discussed as they relate to performance and maintenance.

Jan 1, 2007

1. Book review • World mineral statistics 1974 to 1978. Production: Exports: Imports. London, H.M.S.O., Institute of Geological Sciences, 1980. (Reviewer: R. P. King) This edition is the third in a regular series prepared by the Institute of Geological Sciences. It is a useful compilation of statistics on the production, export, and import of fifty-eight different mineral commodities. Each mineral is listed by country, and a table is provided for the annual production, the annual imports, and the annual exports for each commodity included. However, some commodities are treated in considerably more detail; for example, aluminium and bauxite have tables under the following headings: Production of Bauxite, Production of Alumina, Production of Primary Aluminium, Exports of Bauxite, Alumina and Aluminium, Imports of Bauxite, Alumina and Aluminium. The information presented is the latest official information available from primary sources; the compilers have not relied on data from secondary compilations. This publication will be of considerable assistance to all who are concerned with the trading of mineral commodities and their production.

Jan 1, 1981

By N. K. Singh

The calculation of resource volumes for large mineral sands deposits is the process of systematically compiling all known data in order to define the volume of ore contained and its intrinsic economic value. Traditionally, this process has been highly speculative in nature, as the variability of the layer thickness, even between closely spaced, boreholes can be highly variable. The issue of horizon continuity is of critical importance in mine modelling and resource definition. Accurate volume estimates are difficult to derive from drilling data alone, as the borehole spacing of an economically viable drilling programme is often greater than the spatial frequency of the variations in profile thickness. The limitations associated with this inferential approach to resource estimation can be mitigated through the use of newly developed ground penetrating radar (GPR) methods, thereby maximizing orebody optimization by reducing contamination and orebody loss. The use of GPR in the mining industry has historically been limited to shallow, high-resolution applications, such as the location of voids in limestone or the mapping of paleo channels for alluvial gold and diamonds (Francke and Yelf, 2003). These limitations have not been technology based, but rather market based, as the vast majority of GPR systems were originally designed for civil engineering applications. A new generation of GPR technology, designed specifically for maximum penetration in sand environments, is now being developed. This technology has been trialled extensively at the Richards Bay Minerals heavy mineral sand deposit in South Africa with optimistic results. The clay base of the mineral sands has been imaged to some 120 metres. Further equipment refinements are expected to yield even deeper profiling and higher resolution. The resolution offered by this technology is unique, allowing individual depositional sequences to be imaged and modelled in three dimensions. This paper will discuss the advances in GPR technology relevant to the mineral sands industry, as well as methods to optimize and integrate GPR data into existing mine models. Also addressed will be approaches to three-dimensional modelling of high-resolution GPR data and subsequent volume estimations.

Jan 1, 2007

Spiral concentrators are compact, cost-effective and generally efficient gravity concentration separators for a wide range of applications (for example: coal, beach sands, iron ore, chromite and tantalite). Large mineral processing plants consist of thousands of spiral concentrators resulting in large plant footprints (capital intensive) and the adjustment of splitters is time consuming, impractical and is in many cases neglected?high capacity (HC) spiral concentrators aim to address these shortcomings. As a result Exxaro Namakwa Sands is currently investigating high capacity spiral technology for the spiral circuit upgrade at the primary concentrator plants (PCPs). This article summarizes the rougher spiral performance evaluation that was conducted on different types of spiral concentrators (the traditional MG4 spiral concentrator and the high capacity (HC) spiral concentrator) under different feed conditions. In addition, the effect of slimes on the spiral concentrator performance was also investigated. Slimes rheology was linked to the poor concentrator performance at the higher slimes concentrations. The test campaign shows a sacrifice in recovery under design-feed conditions can be expected when using high capacity spiral concentrators in the rougher stage when compared to traditional spiral technology currently in use. Both spiral concentrators show a detrimental impact of slimes on the performance, but the high capacity spiral concentrator is more sensitive to the higher slimes conditions.

Jan 1, 2010

By D. F. Malan, J. A. L. Napier

A number of shallow coal or hard rock mines employ pillar mining systems as a strategy for roof failure control. In certain platinum mine layouts, pillars are designed to ‘crush’ in a stable manner as they become loaded in the panel back area. The correct sizing of pillars demands some knowledge of the pillar strength and the overall layout stress distribution. It is particularly important to understand the impact of the layout geometry on the effective regional ‘stiffness’ of the rock mass around each pillar. An important design strategy is to model relatively detailed layout configurations which include a precise representation of the local pillar layout geometry and to analyse multiple mining scenarios and extraction sequences to select optimal pillar sizes and barrier pillar spacing. Although computational solution techniques are now impressive in terms of run time efficiency, a major difficulty is often encountered in assigning suitable material properties to the pillars and in devising an effective material description of the layered rock strata overlying the mine excavations. This paper outlines an efficient numerical strategy that can be used to assess large-scale pillar layout performance while retaining the ability to modify individual pillar constitutive behaviour. The proposed method is applied to selected layouts to compare estimated average pillar stress values against values determined by detailed modelling and against observed behaviour.

May 3, 2023

By A. Chryss, L. Pullum

Shear-thickening suspensions abound throughout the hydraulic conveying industry; at least this is the perception of many engineers running plants where hydraulic conveying is commonplace. In reality, shear thickening behaviour is limited, in the main, to high concentrations of fine particles, including colloidal and biological suspensions, at moderate to high shear rates. In the authors? experience most cases of shear-thickening behaviour have been either simple ?coarse? particle interactions, poor instrumentation techniques, or both. In some cases these were obviously heterogeneous flows, while in others flows that were homogenous, or were thought to be homogenous. Examples, which illustrate this erroneous perception are given. However, the trend towards pastes and complex suspensions that use high concentration carrier fluids means that the underlying slurries for many of these flows may now be truly shear-thickening. Unfortunately, suspensions that might exhibit shear thickening also invariably exhibit slip, or wall-particle depletion. These separate phenomena are difficult to resolve experimentally and many observations of apparent shear-thickening behaviour are in fact obscured or convoluted by slip effects. A method is presented whereby the true flow properties of these high concentration suspensions, and hence accurate prediction of pipeline flows, can be made using a parallel plate rheometer.

Jan 1, 2007

Foamed cement packs offer a viable alternative to conventional timber or other forms of packs for permanent underground support. These packs comprise steel mesh and hoop containment with an outer bag for the grout; woven, laminated polypropylene fabric being ideal for the purpose. The grout is supplied in 25kg bags and fed into a purpose ? designed foam placer machine which delivers the foamed grout directly to the packs from 60 metre long delivery hose. Foamed cement grout as a fill material offers attractive properties for support packs, in summary these are: Variable Grout Strength Grout strength is controlled by the grout density being delivered from the placer machine. This can be changed by the machine settings. Strength Development Fast rate of strength development is possible so that support is available quickly. Pack yield The foamed grouts are compressible so that yielding of the grout pack can be achieved without loss of support. Rate of Filling Three sizes of placer machine are available, these use one, two, or three 25kg bags per minute of grout, pack filling time is therefore a matter of minutes, a typical 0.75m diameter pack x 1.2m high taking some 17 minutes to fill. Tests in a 1000 tonne press have confirmed that the above characteristics can be achieved with foamed cement packs at acceptable cost. This will be illustrated in the paper with experience to date.

Jan 1, 2008

By F. J. J. Blaauw

This paper discusses a bold venture into the use of interactive computer graphics technology as the foundation of an overall integrated mining managerial system. The wide range of applications that can be addressed through the use of this technology is highlighted, and some discussion of the major facts of this project, which is still in its early stages, is provided.

Jan 1, 1987

By B. M. Munyungano

Rössing Uranium Mine operates a recovery circuit with continuous ion exchange followed by solvent extraction. Serious organic degradation problems were encountered during 1985/6, 2000 and 2005 in the solvent extraction plant. The preferential loss of the tertiary amine extractant was observed during the above-mentioned period. Previous investigations revealed that the tertiary amine was breaking down to nitrosamine, which cannot take part in the exchange reaction with U3O8. A reduction in the redox potential of the solvent extraction plant feed to below 500 mV halted this preferential loss. A lot of effort has been made to try and understand the actual mechanism for nitrosamine formation. Current understanding for the degradation is that formation is due to high nitrates on the strip side of the circuit emanating from nitrates from the precipitation process using ammonia. It is the current belief that pH lower than 3.7 on the strip side results in loading of nitrates onto the solvent. If oxidizing conditions prevail on the extraction side of the solvent extraction circuit, the tertiary alamine will then degrade into nitrosamine. This phenomenon is yet to be established and verified. It has, however, been established that the above process is brought about the following conditions ?High redox potential greater than 550 mV predominately caused by a high Fe3+/Fe2+ratio (4:1) ?Perception that if Fe2+<0.5 g/lit will contribute to high redox ?High concentrations of NO-3 in the conc eluate (feed to SX)/ammonium sulphate (NO-3> 4 g/l based on historic values) ?Presence of Mo as a catalyst ?Tests also have proved that the presence of nitrous acid in a concentration of 1 g/lat 550 mV leads to formation of nitrosamines from alamine.

Jan 1, 2007

By P. R. Mothemela

The objective of the investigation is to optimize the truck and shovel operations for pre-stripping at New Vaal Colliery by introducing campaign mining. The aim of campaign mining is to improve the efficiency of the loading, hauling, dumping, and maintenance operations which are critical to the success of truck and shovel operations. The current loading (single-sided loading method), hauling, and dumping operations at New Vaal Colliery were found to be inefficient. Time studies were used as a major indicator to highlight the inefficiency of the truck and shovel operations, and it is recommended that an improved loading configuration, hauling, and dumping operations be implemented by using campaign mining. It is also recommended that a service truck be used to maintain the pre-stripping fleet in order to reduce travelling times to the main workshop. As expected, the improved operating conditions will lead to an increase in pre-stripping production.

Jan 1, 2013

A knowledge of the steady-state mass and energy requirements of a particular process is essential to a determination of the economic feasibility of that process. A predictive simulation technique can be of great value in this respect. A versatile computer program based on a fundamental thermodynamic approach has been developed for the prediction of process requirements. The equilibrium composition of a multiphase system is determined by the technique of free energy minimization. Energy-balance calculations are performed using the appropriate thermodynamic data for the chemical species present in the composite materials used. All models for the process units under consideration are written in modular form, the output being calculated from the input and the specified operating conditions. The computer program is written in such a way that it can be used easily by anyone familiar with the processes involved, even though he may have no previous experience with a program of this type. The program is structured so as to facilitate the varying of one parameter without any alteration to the others, thus simplifying the investigation of the effects of any parameters considered to be important. The program has the advantage of being able to compare existing and new processes on the same basis, namely from the ores to the molten metal.

Jan 1, 1987