Search Documents

By P. M. Vercruijsse

Dredging is an industry in constant transformation. It has changed tremendously in the last decades. The traditional dredging activity, like construction and maintaining ports and harbours, desilting of drainage and irrigation channels, keeping reservoirs at depths and removing sediments from waterways, is still of importance. However, it is surpassed by other applications of dredging technology. Reclamation is an important example, where large amounts of sand are dredged, transported over large distances and used to make new land for industrial, housing, airport and other infrastructural purposes. Beach nourishment and other protective measurements should be mentioned here as well. Other applications like offshore winning of oil and gas, environmental clean-up, mining of interesting minerals like gold, diamonds, titanium and tin as well as aggregates from inland and offshore deposits are of importance. For all of these dredging applications equipment is required, and with changing circumstances and constraints, the design and use altered significantly. Larger dredging depths and increasing capacities require an impressive scale-up of equipment and tools. A demand for higher accuracy and selectivity set the requirement for a higher level of automation and control in combination with a well trained crew. Operations under more difficult circumstances and with other soil characteristics necessitated the development of new dredging components and systems. A sound basis for all developments was and still is a better understanding of the various dredging processes. This paper will highlight some eye-catching developments in the dredging industry. It will focus on issues in the field of hydraulic transport such as ever increasing capacity and dredging depth, as well as the pumping of large size materials.

Jan 1, 2007

By K. Richardson

Although the De Beers group has a long history of placer mining on land, the group only became actively involved in deep water marine diamond exploration and mining in1983 with the formation of De Beers Marine. Full-scale commercial mining commenced around 1991. Since then, the group marine mining capability has grown into a formidable fleet of 8 large deep water (>70 m) mining vessels, as well as other special purpose geo-survey platforms. Marine diamond production by the group is expected to be just short of 1 million carats in 2006. DeBeers operates across the entire value-chain spectrum from geology and geo-survey, through sampling to mining, and finally ore processing into high value concentrate. Supporting these operations involves significant service activities such as maintenance, security, logistics and environmental management. Specific challenges exist in terms of developing or acquiring appropriate technology for marine mining. These challenges have resulted in DeBeers operating extensive in-house R&D and projects departments, as well as drawing extensively from technology partners. An array of computational and test facilities are also available to support R&D and projects activities. Hydro transport in various guises is key to the current approaches to marine mining and ore processing. Use is made of airlift and centrifugal pumping for hydraulic hoisting of very coarse gravel, while splitters, launders, dewatering, elutriators, jet-pumps, centrifugal pumps, dense medium circuits, pipeline systems, and instrumentation for coarse abrasive particles are used extensively in the ore processing plant.

Jan 1, 2007

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

A decision by joint-venture partners Anglo American, Gencor, and the Industrial Development Corporation to proceed with the expansion of the Columbus Stainless Steel plant in Middelburg will contribute significantly towards the economic growth that South Africa needs so desperately. The expanded facility, expected to come on-line in 1995, will be the largest single-plant producer of stainless steel in the world, and the company will rank sixth overall in world production.

Jan 1, 1993

By T. Feroze, B. Genc

"The ventilation of underground coal mines plays an important role in minimizing the risk of methane and coal dust explosions. The ability of ventilation, with the use of line brattices (LBs), to remove methane and coal dust in empty headings is dependent on the amount of air leaving the LB and entering the heading. The quantity of this air depends on the associated system variables, namely heading dimensions, settings of the LB, and velocity of air in the last through road (LTR). However, the exact effect of these system variables on the flow rate at the exit of the LB in an empty heading is not known. The installation of LBs in South African coal mines is generally carried out based on experience. This can result in overor under-ventilation and may increase the cost of providing ventilation or cause accidents, respectively. In this paper, using computational fluid dynamics (CFD), the air flow rate at the exit of the LB in an empty heading was estimated using full-scale three-dimensional models. The CFD model used was validated using experimental results Firstly, the settings of these three system variables were varied, the flow rates at the exit of the LB were measured, and finally the results were used to calculate the effect of each system variable. The outcome is a mathematical formula that can be used to estimate air flow rate at the exit of the LB in empty headings for any practical scenario.This paper will help the coal mining sector in South Africa by providing estimation models based on scientific reasoning for the installation of LBs, and will also serve academia as part of the curriculum towards educating future mining engineers."

Jan 1, 2016

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

By D. G. Almond

Low-grade, complex mineral deposits have resulted in the need for complicated large-throughput processing plants delivering increased productivity, reliability, and utilization, together with reducing operational costs. Complex mineralogy has resulted in complicated process flow sheets designed to recover minerals as efficiently as possible. In addition, the remote location of many minerals¬-processing plants, continuously rising energy costs, and fierce competition pose significant challenges to the modern mine, compounded by a global scarcity of qualified and experienced operational personnel. Over the last decade the Internet and automation technologies have undergone major advancements. Automation technologies, solutions, and concepts that existed, but were considered risky or unreliable prior to the year 2000, have now gained acceptance and matured. Furthermore, new technologies and different collaboration schemes have appeared, offering innovative solutions to the mining industry to address many of the challenges described. These advancements in reliable remote systems that access technology through the Internet provide significant opportunity to support mining operations, enhance process performance, provide engineering services, and proactively anticipate and execute maintenance services. This paper references a global survey of automation trends in the mining industry and the potential for an intelligent collaborative environment using automation technologies to exploit opportunities in operating the plant of the future, increasing effectiveness, and reducing operational costs. A variety of possibilities are described, including asset management solutions, remote access capabilities, performance monitoring solutions, advanced process control technologies, and the formation of an intelligent collaborative environment. A real example where this technology is used to support the operation and maintenance at a cement plant in Egypt is given to underpin the concepts described in this paper.

Jan 1, 2013

By Z. Song

Real-time monitoring makes it possible to detect any disturbance occurring in production, while decision instruments can efficiently assist decision-makers to optimize production, reduce iterative workload, obtain better solutions, and preview possible results. Technologies for the above already exist and have been proven in the process industry, i.e. refining and smelting. Optimization is also essential for profitable and stable mining production. Real-time monitoring has already taken hold in mining operations, especially in surface mining, while optimization techniques have also been widely used in underground mining, particularly for planning and scheduling. This review is limited to the hard-rock mining production of metallic ores such as gold and copper. It reviews optimization techniques developed for mine planning and scheduling, and communication technologies suitable for underground applications. It also presents control features for individual operation units, and discusses the technical viability of a mining production real-time optimization (MPRTO) system for underground mines, with possible benefits and challenges. Operational disturbances always occur in mine production. An MPRTO system can be useful to maintain operational effectiveness and efficiency by allowing quick changes to short-term plans. This paper briefly describes the MPRTO system, including the input, output, and basic algorithms. The technical prerequisites for the system specified here are already available. Further studies that are required to improve the system are discussed. Keywords real-time optimization, underground mining, production, operation.

Dec 1, 2013

By D. F. Malan, L. Scheepers

Seismic risk in the deep gold mines of South Africa has been studied for many decades. A clear understanding of the effect of geotechnical conditions on the seismic hazard nevertheless remains elusive. Certain reef types seem to be associated with a higher risk of rockbursts. The stability and deformation behaviour of excavations on the different reef horizons are affected by the rock types and the varying strength properties. The seismic response to mining is therefore also expected to differ according to the geotechnical conditions. As a case study of this behaviour, the seismicity at Mponeng mine was investigated. On the VCR (Ventersdorp Contact Reef) horizon, two areas can be delineated. On the eastern side of the mine, the footwall is shale, and on the western side it is a strong brittle quartzite. More large-magnitude events occur in the area with the shale footwall than the area with the quartzite footwall. Moment tensor analyses indicated that the majority of the large-magnitude events are not related to geological structures, but are face-related, implying that shear failure of intact rock is occurring ahead of the mining front. Preliminary modelling indicated that the closure volume for the shale footwall may be higher than that for the quartzite footwall, providing a possible explanation for the observed difference in seismic response.

Mar 2, 2022

By J. Yianatos, P. Vallejos

In the last decades, the exponential increase in the cells’ volume resulted in significant advantages such as investment costs, footprint and energy savings. However, in larger size cells, despite the increased diameter/height ratio, new constraints arose related to the need for decreasing the larger froth transport distances to enhance the froth recovery. Thus, the use of froth crowders and internal launders became compulsory to maintain the froth transport distances but decreasing the ratio between gas and collected mineral flowrates. Consequently, the bubble load will increase until reaching a critical bubble surface coverage. In this paper, the concentrate carrying capacity (tph/m2) is described in terms of the bubble surface coverage (bubble loading) at the pulp-froth interface and the froth recovery (froth transport) and is evaluated as a function of the cells’ volume and operating variables. A sensitivity analysis, based on industrial operating and design conditions, such as superficial gas rate, particles size, froth crosssectional area and cells’ volume, was developed for evaluating the metallurgical performance of cells from 100 to 630 m3. Results show that limiting carrying capacity can arise for the whole range of cells’ volume, depending on critical operating conditions, particularly in first rougher cells and cleaning stages of industrial flotation circuits. The increase in cells’ volume consistently increases the bubble loading (bubble surface coverage) under all conditions, approaching the limiting conditions more rapidly in the case of cells without internal launders. Otherwise, the limiting condition was achieved when the particle size DPS decreased from 50 to 20 (μm) and for superficial gas rates significantly less or larger than 1 (cm/s). The use of internal launders allows for increasing the range of the operating conditions needed to reach a certain carrying capacity. Keywords: Bubble carrying capacity, flotation cells, bubble surface coverage, cells’ volume

Jan 1, 2020

By M. L. Mahlatji

Mechanical alloying of an equiatomic mixture of crystalline Ti and Pt elemental powders in a high-energy ball mill formed an amorphous alloy by solid-state reactions. Mechanical alloying was carried out in an argon atmosphere at a rotation speed of 1200 r/min and a 20:1 ball-to-powder weight ratio, for time intervals of 4 to 40 hours. At an intermediate stage of mechanical alloying, scanning electron microscopy showed the formation of characteristic layered structures of inhomogeneous composition within the powder particles. X-ray diffraction analysis showed the gradual disappearance of crystalline Bragg peaks and the emergence of broad amorphous maxima as milling progressed. The amorphization process was completed after 8?12 hours. The amorphous state of the product indicated that temperatures during processing did not exceed the crystallization temperature of the alloy.

Jan 1, 2014

By J. E. Chilton

No regular monitoring of methane is required in areas of gassy coal mines outby the mining face. Methane ignitions that have occurred in mine outby areas indicate the need to provide better protection to workers. Handheld methane monitors are now used by some miners to make periodic measurements of methane at the working face. The IYONI II gas detector which is incorporated into a miner’s cap lamp and worn on a miner’s helmet can continuously provide an alarm signal whenever methane levels exceed a set level. Tests were conducted to evaluate the performance characteristics of this methane detector by measuring response times with methane gas supplied through a calibration fixture or adaptor. Other response time tests were performed with the detector in an environmental test box. Performance was also evaluated in a full scale test gallery where face methane emission and underground ventilation were simulated. Procedures for calibration by response time measurement of the IYONI II detector have been developed. In limited testing, the IYONI II detector was found to reliably detect the presence of 1 percent by volume methane.

Jan 1, 2003

The key functions of project evaluation are to assess potential profitability and to develop an effective operational design. For mining projects, design aspects include mining methodology, ore treatment methodology and production rates. All of these characteristics impact on project economics and overall value. Resource models, which form the ultimate basis of project evaluation, typically consist of tonnes above cut-off, grade above cut-off and the spatial distribution (connectivity) of tonnes/grade above cut-off, for one or more variables. Dilution, ore loss and metallurgical recovery are all modifying factors applied to the resource model during evaluation and determination of profitability. A key issue is: how is the value determined? In addition to traditional combination of in situ tonnes/grade, the following merit serious consideration: the concentration of deleterious elements, throughput rates, mining/processing costs and - importantly - metallurgical recovery. Geometallurgy is an emerging field targeted at integrating these issues by identifying either direct measures or proxies for throughput (hardness, grindability), recovery (liberation, mineral shape/texture, etc) and concentrate quality from easily collected macro-, meso- and microscopic data. These 'geometallurgical variables' drive project costs and revenues in a fundamental way. For geometallurgical characterisation to have a real impact on business design, it must enable improved mine planning. When creating spatial estimates for such variables, it is preferable to find proxies that can be measured as close to the intact rock mass as possible. However, spatial estimation of proxies for geometallurgical properties and responses is complex and requires special consideration. Unlike grades, both proxies and absolute measures of geometallurgical variables are not necessarily linear or additive and therefore require very careful geostatistical consideration. In some cases, models must predict extreme values of geometallurgical attributes rather than averages. Incorrect characterisation of metallurgical recovery/throughput can (and has) led to misspecification of the scale of projects, and thus can be seriously value destructive. Aspects of geometallurgy have long been important in iron, bauxite, manganese and coal deposits and are increasingly on the radar for base and precious metal miners. However, as more metallurgically complex deposits are developed and mining of large-scale, low-grade deposits becomes more commonplace, the importance of characterising the metallurgical response in order to generate properly optimised projects will rapidly increase. It is possible that in many `traditional' (ie grades and tonnes) reserve models, the variables that drive the project are missing!

Jan 1, 2007

By A. Ndibalema

Blasting is one of the primary functions in any mining operation. Despite the fact that it generally constitutes between 30% to 40% of the mining cost, blasting also affects the cost-effectiveness of down steam activities such as load and haul, safety, tyre life for haul trucks, crushing and milling. Over the past three decades, significant progress has been made in the development of new technology in an attempt to reduce costs and increase efficiencies and productivities of blasting activities. Mine to mill project concepts have paved the way for such developments. Other advancements have included sophisticated computer modelling technologies for blast design and performance analysis. There are many factors that affect the cost of blasting. These can be divided into two categories; controllable and uncontrollable. The latter includes costs related to depreciation, exchange rates and government legislation with the former category including contractor versus owner blasting costs, efficiency and productivity issues and product quality. Controllable factors have one common denominator which can determine their outcome; direct site management influence. Excavator digging rates and final floor conditions give a good measure of blasting performance, and alternatively cost effectiveness. This paper is aimed at benchmarking against a blast optimisation database, understanding the relationship between costs and identifying opportunities for improvement. Understanding the cost drivers allowed a typical cost model to be developed for the current mining operation at Geita and this was used to drive continuous improvement with emphasis on closing the information loop.

Jan 1, 2008

By C. Chibwe, M. Tadie

Copper electrowinning models are useful for prediction of process performance, optimisation and improved understanding of complex phenomena such as current distribution without the expense of physical experiments. Recently, finite element models such as those generated in COMSOL Multiphysics have been developed for the electrowinning process. The predictive capacity of these models is improved by incorporating physical and chemical phenomena. Since physicochemical properties of electrolytes can have a significant effect on the quality of copper produced, this work was conducted to investigate the effect of such properties on electrodeposition at varying levels of copper, sulphuric acid concentration, iron concentration and temperature, in the presence of a smoothing agent. Tests were conducted at conditions similar to those for industrial copper electrowinning. Mathematical correlations were developed for the following properties; density, conductivity and diffusivity which were compared to existing models in literature and thereafter applied in a COMSOL generated model. The model predicts, current distribution at the cathode surface, deposit thickness (morphology), concentration of species within the cell and current efficiency. Current distribution output shows the impact of several phenomena on the deposit generated including the relationship between increasing copper concentration and current density and lack of influence of acid concentration on this property. Keywords: Electrowinning, physicochemical properties, electrolyte composition, modelling

Jan 1, 2020

By J. Hadjigeorgiou, Y. Potvin

In a benchmarking paper published in the SAIMM Journal, Potvin and Hadjigeorgiou (2008) reviewed ground control strategies to manage large deformations in underground hard rock mines. Significant differences were identified in the design and acceptable tolerance between civil and mining engineering practice for squeezing ground conditions. Variations were also noted in ground support strategies between Australian and Canadian mines. In this paper we review progress in design methodology and ground support practice since 2008, including the availability of more effective deformation monitoring, new design tools, greater access to yielding ground support elements, and better installation practices. An improved understanding of technical and practical issues associated with squeezing conditions has led to the development of ground support guidelines for a range of squeezing ground conditions in hard rock mines.

Jul 5, 2023

By S. Özgen

In this study, the possibility of beneficiation of chromite tailings in the Uckopru/Fethiye-Turkey region by a combination of hydrocyclone and multigravity separator (MGS) was investigated. The two significant operational parameters of hydrocyclone, which were diameter of the apex and diameter of the vortex, and the three significant operational parameters of the MGS, which were drum speed, tilt angle, and wash water, were varied and the results were evaluated with the central composite rotatable design. In order to produce a chromite concentrate by hydrocyclone and MGS, mathematical model equations were derived by computer simulation programming, applying the least-squares method using Minitab 15. Second-order response functions were produced for the grade and recovery of chromite concentrates.

Jan 1, 2012

By E. L. Thyse, P. Bepswa

The Western Cape Mineral Processing Facility (WCMPF) is a collaborative educational initiative between the Department of Process Engineering at the University of Stellenbosch and the Chemical Engineering Departments at the University of Cape Town and the Cape Peninsula University of Technology. The primary objective of the WCMPF is to facilitate the education, development and graduation of suitably qualified engineering graduates and diplomats for the mining and mineral processing industries. In recent years the WCMPF has embarked on a number of initiatives aimed at improving the quality of mineral processing education which include, more importantly the introduction of novel ?end to end? or ?integrated? practicals. The practicals are developed around a specific mineral theme or route, which more than often includes the development of several new pilot plant practicals demonstrating key unit operations or processes in the selected mineral theme or route. The most recent mineral processing pilot plant practical programme is developed around the beneficiation of heavy mineral sands. The programme consist of the following developed pilotplant practicals: the online electrostatic separation of free flowing mineral sands using a Roche Mining Carrara high tension roll separator incorporating a Blue Cube Systems MQi in-line mineral quantifier; the production of titania-rich slag and pig iron from the smelting of ilmenite and anthracite in a 60 kW direct current (DC) plasma arc furnace as well as the mineralogical characterization of the feed and products; the continuous closed-circuit ball milling and screen classification of titania-rich slag. This paper illustrates the important role of a well-designed heavy mineral sands beneficiation pilot plant practical programme in facilitating the education and development of suitably qualified personnel for the mining and mineral process industries.

Jan 1, 2007

By M. H. Tyeb, C. Banerjee, A. K. Majumder

The primary requirement from a hydrocyclone is the classification of the feed solid particles. Particle classification occurs inside a hydrocyclone by virtue of the relative radial distribution of the suspended particles, based on their size and specific gravity. The particle classification behaviour in a hydrocyclone is experimentally studied in this paper. The phenomenological features of the air core at different feed solid concentrations and the distribution of the solid concentrations in the hydrocyclone are also analysed by the theoretical study of flow features in a steady Rankine vortex. Semi-empirical models for predicting the hydrocyclone performance in terms of flow split ratio, and cut size have been developed using the background knowledge of convoluted hydrodynamics. In addition, to validate the classification performance of a smaller diameter hydrocyclone, the potential of the present model is extended for envisaging the same for larger diameter hydrocyclones. A comparison between the model predicted values and the measurement data shows a good match. Keywords: Hydrocyclone, classification, Rankine-vortex, air core, modelling

Jan 1, 2020

By L. M. Tavares, T. M. Campos, P. M. Faria, R. M. Carvalho

Recent advances in mechanistic ball mill modelling are expected to allow for more accurate predictions that overcome the well-known limitations of phenomenological approaches, including their inability to predict the effect of liner geometry and their wear, in grinding. Although able to describe continuous operation, the UFRJ model of ball mills has only been validated in the past in mills that operate in batch mode, either in laboratory or pilot scale. The present work demonstrates the application of the mechanistic UFRJ ball mill model to predict fine grinding of iron ore in a pelletising plant in Brazil, the first application of such a mechanistic modelling in continuous mode. It shows that the model provides accurate descriptions of flows after iterations in a closed-circuit with hydrocyclones. Keywords: Ball mill, iron ore, grinding, modelling, particle breakage

Jan 1, 2020