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By J. C. R. van Schoor

In this study the applicability of a batch press to predict the energy consumption and particle size distributions for medium-pressure roller presses was investigated. The relationships between energy consumption, feed size and product size are discussed with reference to Hukki?s interpretation of Bond?s and Rittinger?s laws, as well as the particle size parameter used. It was found that the comminution laws have limited utility for the characterization of the performance of the medium-pressure roller crushers or the batch press used, and also depend on the particle size distribution indicator used. It was also found that the batch press is not a suitable simulator for medium-pressure roller mills as it was notable to predict the energy requirements, or to predict the size distributions that would be obtained for the ores evaluated.

Jan 1, 2012

By J. C. van Dyk, F. B. Waanders, J. Brand, C. A. Strydom

"Underground coal gasification (UCG) is a fast-emerging, in situ mining technology that provides access to low-cost energy through the utilization of coal reserves that are currently not technically or economically exploitable by conventional mining methods.Groundwater monitoring for conventional coal mining in South Africa is well established, with SANS, ASTM, and ISO standards for the specific environment, location, and purposes. South Africa’s groundwater is a critical resource that provides environmental benefits and contributes to the well-being of the citizens and economic growth. Groundwater supplies the drinking water needs of large portions of the population, and in some rural areas it represents the only source of water for domestic use. Implementation of, and adherence to, groundwater monitoring standards are thus non-negotiable.The groundwater quality management mission, according to the Department of Water and Sanitation in South Africa, is set in the context of the water resources mission and reads as follows:‘To manage groundwater quality in an integrated and sustainable manner within the context of the NationalWater Resource Strategy and thereby to provide anadequate level of protection to groundwater resources and secure the supply of water of acceptable quality.’ (SABS, 2016).In this paper we propose fit-for-purpose groundwater monitoring standards for a commercial UCG operation. It is important to proactively prevent or minimize potential impacts on groundwater through long-term protection and monitoring plans. Scope of study / standard proposal The purpose of this paper is to set out a National Standard Proposal to emphasize groundwater monitoring as one of the five strategies of the ‘Policy and Strategy for Groundwater Quality Management in South Africa’ (Department of Water Affairs and Forestry, 2000) and to align it with the National Water Act, Act no. 36 of 1998 (Republic of South Africa, 1998).The focus of this standard is directed solely towards groundwater monitoring during underground coal gasification (UCG). Groundwater in this context refers to water as sampled from dedicated monitoring wells around the targeted site, which will include the shallow aquifer referred to as groundwater, and water flow at the level of the underground gasifier, referred to as ‘coal water’."

Oct 1, 2018

By V. Matou?ek

The paper addresses pipe flows of aqueous medium-sand slurries at velocities lower than the deposition-limit velocity. Laboratory test results including measurements of particle concentration distributions are used in order to describe a flow with a (pseudo-) linear concentration gradient above a stationary bed. Particle dispersion within the flow is evaluated and a stratification-ratio equation is formulated, estimating a portion of contact load in the flow. The formula is incorporated in the proposed predictive model for the hydraulic gradient for a medium-sand flow above a stationary bed.

Jan 1, 2007

By F. Bourgouin

Thirty-one years ago, African leaders met in Lagos for the drafting of the Lagos Plan of Action for the Economic Development of Africa, 1980?2000. The main objective of the plan was to increase Africa?s self-sufficiency and in this regard, the plan had a section pertaining specifically to redressing the ills of an unproductive mining and minerals industry and harnessing its potential for socio-economic development. However, if we look at the nature of this sector on the continent today, its characteristics resemble the diagnosis of the sector given in the plan back in 1980: lack of information on endowments of minerals; lack of value added in the sector; low development and use of those endowments that are not of interest to transnational corporations (TNCs); and most importantly, low contribution to socio-economic development. The primary consequence of the lack of visible benefits to African states, despite growth and development of the sector in terms of increased mining activity led by Foreign Direct Investment is that countries with mining industries are characterized by dysfunctional internal processes. Improvements in governance, monitored with indices such as those set out in the Extractive Industries Transparency Initiative, the Millennium Development Goals, and other such ?good governance? agendas, are being asserted. However, before we prescribe the introduction of initiatives or guidelines based upon highly subjective norms which we believe to fit this diagnosis, it is necessary to review how it is that we got to this situation that we are in today. How is it that, 31 years after the Lagos Plan of Action, we have not seen any major changes in the role the industry can play in socio-economic development, despite the vast increase in mining activity on the continent?

Jan 1, 2011

By D. A. Vetter

A novel mathematical model is presented which describes the behaviour of beds of particles, of uniform size and shape but different densities, during autogenous separations. The approach used in the formulation of the dispersion model is a phenomenological one based on a statistical view, which leads to a diffusion-like representation of the autogenous-separation process. Although the model currently considers only density-related phenomena, it accounts quantitatively not only for the density-segregation aspects of the process but for the interactions between the particles. Quantitative predictions of the dispersion model are compared with the results obtained in tests using a specially constructed experimental batch jig, and it is shown that the model provides an adequate quantitative description of the process for particles of uniform size and shape. It is pointed out that, for the description of more complicated autogenous separations, a more rigorous formulation of the particle drag and density-segregation terms will have to be incorporated into the dispersion model. Nonetheless it is concluded that the model as presented in this paper provides not only a novel insight into the mechanisms of autogenous separations but a means by which to analyse similar systems.

Jan 1, 1987

By B. S. Xakalashe, M. I. Khama, Q. G. Reynolds

The carbonaceous reduction of manganese ore is an energy-intensive process that releases large amounts of pollutant gases. In an attempt to circumvent the greenhouse gas emissions, this research investigates hydrogen as an alternative reductant. The reduction of manganese ore with hydrogen results in the structural changes in the intermediate products, which might limit the diffusion of the reactant gases through the pores. Computational fluid dynamics (CFD) models capture the structural changes and predict the rate controlling mechanism and this is key in designing the prereduction reactors. The current work uses CFD models to predict the degree of reduction in a shaft furnace under hydrogen reducing conditions. Manganese ore is described as a collection of scalar and tensor fields such as thermal conductivity of the porous medium, density, and viscous resistance. The results indicate that advection contributes significantly towards the overall transport of hydrogen to the reaction sites. Porosity of the final product was found to be higher than porosity of the raw material.

Mar 4, 2025

One of the most critical and complicated steps in mine design is a suitable mining method selection based upon geological, geotechnical, geographical and economical parameters. Since there are many factors involved in mining method selection, the decision-making process is very difficult. In this paper, the Analytical Hierarchy Process, with 13 criteria, is used to develop a suitable mining method for the Golbini No. 8 deposit in Jajarm (Iran). Six alternatives (conventional cut and fill, mechanized cut and fill, shrinkage stoping, sublevel stoping, bench mining, and stull stoping) are evaluated. The studies show that the suitable mining method for this deposit in the present situation is the conventional cut and fill method.

Jan 1, 2008

The influence of Harold Hotelling?s work in the field of mineral economics is both unusual and outstanding. In the 66 years since its development, theory surrounding the economics of exhaustible resources has only been significantly researched since the early 1970s. At that time a wave of research into the economics of exhaustible resources arose from the threat of global resource scarcity and continued into the late 1990s. Current East Asian and global demand for natural resources as well as mineral and metal commodities, has stimulated interest in the optimal and sustainable exploitation of exhaustible resources to the point that the subject is worthy of review. Hotelling?s theory and the assumptions that he made in establishing a model for the optimal exploitation of mineral resources at the industry level and at the level of the individual mine owner, are examined. He showed that the rate of increase inexhaustible resource prices should be equivalent to the market rate of interest and that in a market with rising prices the rate of extraction should be constant. In markets where demand is stable optimal exploitation requires that the rate of extraction should decline over time, while in a monopoly market he showed that the rate of extraction is retarded. In addition, the effects of cumulative production on costs and prices, the uncertainty associated with estimates of the resource stock, the impact of exploration and issues of intergenerational equity are examined. An analysis of the optimal price path, extraction costs and mineral rents at an industry level is presented as a model. An analysis of the rates of production and optimal benefits at the individual mine level including total, average and marginal costs on the optimal rate of production, is considered. Optimal extraction rates for a mine with a clearly defined concave positive cost equation vary according to the position on the marginal cost curve. The influence of discount rates and the size of the ore reserves on the rates of mineral extraction are also examined and could define the frontier of usefulness for the ?economics of exhaustible resources?.

Jan 1, 2007

By W van Drunick, S Naik

To date, Anglo Research has carried out several projects, based on the techniques developed in the AMIRA P9 (AMIRA International Limited), to develop comminution and flotation models for several Anglo Base Metals and, to a lesser degree, Anglo Platinum flotation plants. Plant optimization is thus achieved through steady-state sampling, model-fitting and simulation using the JK SimMet and JK SimFloat software packages. The surveys can vary depending on the needs of the plant/client. The survey can therefore include as little as a single piece of equipment, an entire milling/flotation circuit, or a complete circuit from primary comminution to final flotation concentrate (i.e. the ?integrated survey?). The presence of the AR team on-site usually precipitates in face-value observations that can lead to initial improvements. This stems from the knowledge-sharing on best practice that exists in parallel with the surveys. Numerous (reasonable) changes can then be simulated, thus indicating the optimization step most likely to result in the best efficiency improvements. The simulations can include changes in the flowsheet, ore characteristics, mill loads, grinding media size, change in grind, flotation residence time, air hold-up and several more. Plant surveys can result in process changes that provide the plant with either: higher plant tonnage, improved plant grind, additional flotation recovery and/or improved product grade. The additional benefit of performing an integrated plant survey is that the effects of an optimization change in the comminution circuit can be simulated using the flotation model. This paper describes a number of case studies where individual and integrated plant surveys were conducted by AR for Anglo Base Metals.

Jan 1, 2007

By C. Musingwini

The South African platinum mining industry is using a number of different mining methods, including variations of the same method, to extract the narrow reef tabular platinum deposits of the Bushveld Complex. These mining methods fall into three broad categories, namely conventional, mechanised and hybrid mining. A question sometimes asked in the industry is whether mechanized mining methods are more efficient than conventional mining methods. An objective answer requires the methods to be evaluated against multiple criteria simultaneously, whereby each criterion has a relative degree of importance in the overall decision. The most efficient method is the one that scores highest on each criterion. However, some of the criteria can be conflicting, such as by increasing dilution the shaft head grade decreases. The analytic hierarchy process (AHP) methodology was selected for the study because it is used to solve problems of this nature. A survey was carried out to determine the relative importance of each efficiency criterion by drawing on the knowledge and experience of mine technical services and project management practitioners in the industry. Efficiency data for four different mining methods drawn from the Egerton (2004) study were used as a case study. The conventional mining method ranked as the most efficient mining method from the four methods considered. The exercise indicates potential for the AHP to be used in the South African platinum mining industry as a tool for selecting optimal layout designs, conduct regular evaluation of the performance of production shafts, or objectively evaluate line managers for promotion. The work described in this paper is part of the methodology used in a current PhD research study at the University of the Witwatersrand. Keywords: Analytic hierarchy process (AHP); multiple criteria decision analysis (MCDA); decision-making; conventional mining, hybrid mining, mechanized mining.

Jan 1, 2008

By E. G. Galvez, E. Mate, L. A. Cisternas, C. Cruz, L. Cortés, M. E. Osorio

Designing and optimising flotation circuits are critical for mineral beneficiation plants, and therefore several procedures have been published. The modelling of flotation circuits with the objective of design and optimisation is problematic in that different approaches are used for the modelling of flotation units and regrinding units. Usually, regrinding models are based on particles characterised by their size, while flotation models are based on species characterised by fast and slow classes. The relationship between particle size and liberation can be used, but it requires laboratory studies that are time-consuming and costs are high. It is therefore not surprising that few studies on flotation circuit design and optimisation include flotation units and regrinding units simultaneously. In this paper, it is proposed to model the regrinding stage using species characterised by fine-slow, medium-fast, and coarse-slow flotation species. In deep, the regrinding model is derived from a population balance approach based on flotation species. The fraction of these species at the feed and product of the grinding unit is determined by flotation tests. Then, based on these data, the model parameters can be determined by a regression estimation procedure. A local ore was used to validate the model. Keywords: Modelling, flotation circuit, grinding circuit, process design

Jan 1, 2020

By R. A. Govender, A. Mudau

"Rockbursts continue to be a major contributor to mine accidents and cause of damage to mine excavations, particularly at great depth. The problem of rockbursts has also escalated in civil engineering tunnels driven at depth, due to high levels of in situ stress at such depths. Attempts have been made in the past to mitigate the impact of rockbursts, with rock support remaining the ultimate method for providing stability in rockbursting environments. However, records show that, on many occasions, conventional support elements such as rockbolts, wire mesh, shotcrete, and lacing fail to withstand severe rockburst events.Recently, a support method termed ‘sacrificial’ support was proposed as a potential additional method to prevent rockburst damage, based on observations made after rockburst events in a mine. The philosophy behind a sacrificial support system is that, under dynamic loading conditions, support in the form of a liner must fail; leaving behind, undamaged, what was previously supported rock mass. The sacrificial support concept reported herein is applicable in situations where the source (i.e. seismic event) of the rockburst is located remote from where rockburst damage is likely to occur.Spalling tests based on the split Hopkinson pressure bar (SHPB) technique were conducted to study some aspects of dynamic rock fracturing in tension at high strain rates and the role a sacrificial layer plays in combating dynamic rock failure. A single Hopkinson pressure bar, with a long cylindrical intact rock specimen attached at the bar free end, was impacted by a striker on the opposite free end in order to generate a dynamic stress pulse responsible for spall failure upon reflection from the specimen free end. Different liners and liner combinations were then introduced at the specimen free end as support. Such a simple, yet robust, experimental set-up allowed the potential benefits and failure mechanisms associated with sacrificial support under dynamic loading to be demonstrated and compared with ‘sacrificial support’ behaviour observed in real rockburst events in a mine. Analysis of the results revealed that varying liner thickness and mechanical impedance between rock and support liner play a significant role in limiting rockburst damage."

Jan 1, 2016

By T. Feroze, B. Genc

"Blind headings in room and pillar coal mines are a major source of methane and coal dust. Most methane and coal dust explosions therefore occur in the blind headings. The primary cause of these explosions is the disruption of the local ventilation system. Line brattice (LB) ventilation systems are used to ventilate blind headings by directing air from the last through road (LTR) into the heading. The amount of air available to ventilate the face of the empty heading depends on the heading dimension, settings of the LB, and velocity of air in the LTR. LBs are commonly installed by underground supervisory staff based on work experience, which may result in ineffective ventilation. The correct installationof LBs remains a challenge. In this study, a validated computational fluid dynamics (CFD) model has been used to analyse the effect of the LB ventilation system variables on the air flow rates close to the face of the empty heading. Full-scale three-dimensional models with various heading heights, heading depths, LB settings, and LTR velocities were simulated. The air flow rates and patterns at various locations inside the heading were analysed. A comparative study was carried out to quantify the effect of each of these system variables on the flow rates close to the face of the heading. Based on the findings, a user-friendly numerical model was formulated that can be used to estimate the flow rate close to the face of an empty heading for different practical settings of the system variables. This model can help the supervisory staff to swiftly implement the ventilation plan according to the regulations and the mine standards. The model can also serve as part of the curriculum for educating future mining engineers."

Jan 1, 2017

By T. Feroze, B. Genc

"Blind headings in room and pillar coal mines are a major source of methane and coal dust. Most methane and coal dust explosions therefore occur in the blind headings. The primary cause of these explosions is the disruption of the local ventilation system. Line brattice (LB) ventilation systems are used to ventilate blind headings by directing air from the last through road (LTR) into the heading. The amount of air available to ventilate the face of the empty heading depends on the heading dimension, settings of the LB, and velocity of air in the LTR. LBs are commonly installed by underground supervisory staff based on work experience, which may result in ineffective ventilation. The correct installation of LBs remains a challenge.In this study, a validated computational fluid dynamics (CFD) model has been used to analyse the effect of the LB ventilation system variables on the air flow rates close to the face of the empty heading. Full-scale three-dimensional models with various heading heights, heading depths, LB settings, and LTR velocities were simulated. The air flow rates and patterns at various locations inside the heading were analysed. A comparative study was carried out to quantify the effect of each of these system variables on the flow rates close to the face of the heading. Based on the findings, a user-friendly numerical model was formulated that can be used to estimate the flow rate close to the face of an empty heading for different practical settings of the system variables. This model can help the supervisory staff to swiftly implement the ventilation plan according to the regulations and the mine standards. The model can also serve as part of the curriculum for educating future mining engineers."

Jan 1, 2017

By H. Vuthaluru, O. Kavianipour, C. -Z. Li, N. Suresh, D. Sahu

The paper describes a CFD model developed for 76mm Dense Medium Cyclone (DMC) using Ansys Fluent Software to gain insights into the separation of particles according to their size and density. The simulation used in this paper includes the Reynolds stress model to predict the turbulence inside the cyclone body. An Eulerian-Eulerian multiphase CFD model was applied to model a number of physical aspects such as the separation of coal particles and the segregation of magnetite media solids. The experimental results generated in a laboratory scale DMC were used for the validation purpose and the predicted results of CFD have been validated for the flow splits of water, magnetite and coal. The simulation results obtained from the Eulerian-Eulerian multiphase model revealed that the prediction agreed with experimental results, and matched reasonably well in terms of the mass flow rates of water, magnetite and coal. Furthermore, the partition curve of the DMC when mapped for the separation of - 3.0+0.50 mm size also showed to be in agreement with the experimentally obtained curves. The gravity of cut (SG50), also predicted by the Eulerian-Eulerain multiphase CFD model, was found to be in the vicinity of observed experimental value of SG50. Keywords: Dense medium cyclone, Eulerian-Eulerain multi-phase modelling, computational fluid dynamics, cut gravity (SG50)

Jan 1, 2020

By J. W. Oberholzer

The use of computers in the South African coal mining industry has increased during the 1980s. Applications at mine level commenced in the financial and personnel areas of payroll systems, mine accounting procedures and staff record keeping. More use is made now on mines of technical programs for purposes such as mine planning and mine survey calculations. The Coal Mining Laboratory of the Chamber of Mines Research Organization has provided, for a number of years, a service to Chamber member collieries in regard to the application of technical computer programs. Programs presently in use for simulating production procedures and conveyor belt transport systems are described. In addition, reference is made to the collection, storage and analysis of data concerning the performance of continuous miners over a period of eight years. More recently a computer program for the simulation of the cutting action of continuous miner cutting drums has been developed. The use of this program to assist with drum design is explained. The fact that many requests to make use of the programs are received from collieries is an indication of their acceptance by industry. Their interest in running the programs themselves on their own desktop computers has led to the need to convert the software for microcomputers.

Jan 1, 1987

By T. Oberthür

The Great Dyke of Zimbabwe constitutes the world&apos;s second largest reserve of platinum group elements (PGE) after the Bushveld Complex in neighbouring South Africa. Within the Great Dyke, economic concentrations of PGE are restricted to sulphide disseminations of the Main Sulphide Zone (MSZ), which are currently mined at the Ngezi, Unki, and Mimosa mines. Near-surface oxidized MSZ ores have a large potential. Their total resources are in the range of 160-250 Mt; however, all previous attempts to extract the PGE from this ore type have proved uneconomic due to low PGE recoveries (<< 50 per cent) achieved by conventional metallurgical methods. Within the ores of pristine, sulphide-bearing MSZ, the PGE are bimodally distributed. Platinum occurs mainly in the form of discrete platinum group mineral (PGM) grains (mainly bismuthotellurides, sulphides, and arsenides), whereas approximately 80 per cent of the Pd (and some Rh) is hosted in pentlandite. Within the oxidized MSZ ores, the PGE are polymodally distributed. Whereas the arsenide- and sulphide-PGMs that make up approximately 25 per cent of the original Pt content of the ore largely remain stable (relict PGMs), the remaining PGMs are disintegrated. The base metal sulphides are destroyed, partly releasing their base metal and PGE contents, and are replaced by iron oxides or hydroxides. Unspecified amounts of the PGE are redistributed and either form secondary PGMs, are found in chemically and mineralogically ill-defined (Pt/Pd) -oxides or hydroxides, or in iron-hydroxides, Mn-Co-hydroxides, and in secondary silicates. The problematic processing of oxidized MSZ ores is attributable to their complex nature and polymodal distribution of the PGE, prohibiting a significant upgrading of the ores by conventional metallurgical methods. Therefore, only bulk leaching methods are viable for ore treatment, and novel metallurgical methods have to be developed for the processing of these ores. Our ongoing work aims at locating the PGE in their mineralogical form in order to understand the mineralogical balance of the PGE in the ores and thereby facilitate the evaluation of metallurgical options for their recovery. A short overview on options and recent advances regarding the recovery of the PGE from oxidized ores is given.

Jan 1, 2013

One of the key issues facing gold producers is the management of cyanide and the implementation of the International Cyanide Management Code. Many operations now use cyanide destruction processes to ensure that the material being discharged to the tailings dam is compliant with regulatory requirements and the International Cyanide Management Code. One of the problems for operations is the quantification of both cyanide species and their reaction products throughout the leach and destruction circuits. Therefore methods have been developed utilizing high performance liquid chromatography (HPLC) to measure free cyanide, cyanide complexes of metals such as copper and iron, and other species formed from reactions in leaching and cyanide destruction, including cyanate, thiocyanate, and sulphur species (eg. sulphite, thiosulphate and sulphate). This enables a complete mass balance for cyanide and sulphur in both leaching and cyanide destruction. This paper outlines the methodology which has been developed and discusses the application of these methods in the fundamental research currently being conducted on the impact of sulphide minerals in cyanidation and cyanide destruction chemistry.

Jan 1, 2009

By T. T. Matuludi

Kleinkopje Colliery has five Wemco drums that were installed and commissioned in 1978. Over the years, there have been remarkable changes in mining and geological conditions at the colliery. First, an increase in the percentage of fines was recorded, which resulted in an uneven split or an imbalance in silo levels between material feeding the cyclone (-12 mm) and Wemco drum (+12 mm) sections respectively. This problem was solved by doing modifications around the banana screens to allow finer material to the drums. The imbalance challenge was then followed by spontaneous combustion that takes place in situ and results in low product yield. The results obtained from efficiency tests indicate that although there is a limit in the percentage of -6 mm material in the feed, Wemco drums are still very efficient and applicable to the current mining conditions. These results also suggest that it is essential to lower the throughput when the drums are treating low yielding coal.

Jan 1, 2010

By R. Ajalloian, L. Karimzadeh

This paper describes the engineering properties of Givi dam foundation. Givi dam will be built across the Givi River on the andesitic rocks (Karaj formation) in Ardabil province (northeast of Iran). Geotechnical investigations including drilling, pumping tests, sampling for laboratory testing and discontinuity survey. Physical and mechanical properties of andesitic rocks such as density, water absorption, porosity, uniaxial compressive strength, triaxial compressive strength, durability and direct shear tests are evaluated in this paper. Discontinuity data are process for the determination of dominant sets and for the rock mass characterization in terms of classification systems ( RMR, Q and RSR ). Correlations between these three classifications are discussed. Le barrage doit être construit sur la rivi_re givi qui cou_e sur les andesites (formation de Karaj)dans la province d_ Ardebile situee_ a Nord- Ouest de l_ _Iran. Les études géophsique commesondage, Pompage. Et échantillonnage afin de verifier les discontinutés out éte_ effectuées. Lesproprietés physique et méchanique des roches andesifique ont éte_ verifieés. Les informations concernaüt aux discontinuitiés afin de montrer leur principale direction ont éte_ verifieés, les proprietés des roches dans leurs ensemble ont éte_ etudieés. Les divers classifications(RMR,Q,RSR ) ont éte_ comparés et analyseés. Dieses Schreiben ist zur Erklaerung der Ingenieureigenschaften ueber Baugrund des Givi Deiches.Dieser Deich soll im Givi fluss auf Andesitgesteine (Karaj formation) gebaut werden. Der platzdes Deiches legit im Ardebil Provinz nordwestlich von Iran. Geotechnische Untersuchungen Sind:Bohrungen, pumpen Versuche, Probenentnahme fuer Laborversuche, BrechbarkeitBestimmungen, physikalische und mechanische Eigenschaften der Andesitgesteine wurde hierausgewertet, wie Z.B.: Wasserleitfahigkeit, Porositaet, Scherfestigketswiderstand, Informationenueber Brechbarkeiten der Gesteine wurde gesamelt, und die meisten Brechbarkeiten bestimdamitman die Gesteine besser klassifizieren kann. In Endefekt wrid die Resultate verschiedeneKlassifizierung wie RMR, Q, und RSR besser geachtet und zusammen vergliechen.

Jan 1, 2003