Showing papers in "Journal of The South African Institute of Mining and Metallurgy in 2019"

State-of-the-art of standing supports for gob-side entry retaining technology in China

Abstract: Gob-side entry retaining technology (GERT) is a popular layout of the roadway in many modern coal mines due to its outstanding advantages in high production yield ratio and enabling the ‘Y’ shape ventilation configuration. During the past two decades, various standing supports, as the critical component of GERT, have been proposed and implemented. However, few systematic investigations have been conducted. This paper starts with a concise introduction of the movement of the strata overlying the standing support when the whole service period of retained gob-side entry is considered. A recently proposed new classification of standing supports based on the cross-section is then described. To obtain an in-depth comparison of each standing support, the advantages and drawbacks are investigated based on the installment procedure, economic benefits, and mechanical behaviour. Furthermore, recommendations for further research topics have been identified, such as the development of novel hybrid composite structures either in terms of the backfilling materials or the confining material. These backfill materials include coal rejects concrete, geopolymer concrete, high water-content slurry, and other environmentally friendly materials made of industry by-products. Emerging materials, including fibre-reinforced polymer (FRP) composites, high-strength steel, geosynthetic material, and combinations of these materials, should be considered. The key purpose of this review is to offer solutions for the development of easyto-construct, cost-effective, and environmental friendly standing support for GERT.

An evaluation framework for virtual reality safety training systems in the South African mining industry

Abstract: Mining companies strive to increase and maintain production, while simultaneously remaining competitive in the global economy. Furthermore, they must ensure workers’ safety and maintain good safety records. The use of virtual reality (VR) facilitates the development of tools and systems for various purposes that can improve knowledge and understanding of the work environment. VR is a rapidly growing technology that uses the ever-increasing power of computing to simulate real-world and imaginary environments and situations with a high degree of realism and interaction. The availability of 3D modelling tools and simulation programming engines that work effectively with a mid-range desktop PC and standard 3D graphics card, make VR technology viable and attractive for mainstream training applications. The design, development, and implementation of interactive VR training systems is proposed as an innovative approach to augment safety training. However, in order to assess the impact of such VR training systems it is of particular importance to determine the effectiveness of the design of such systems. This article proposes an evaluation framework for this vital purpose. This framework comprises criteria to assess VR training systems, specifically relating to usability, instructional design, VR systems design, and mining industry context-specific aspects. Although the framework was developed as an evaluation tool to assess effectiveness of the design of such systems, it can equally well be used as a set of design principles to inform the design of VR training systems for mining.

Mapping hydrothermal minerals using remotely sensed reflectance spectroscopy data from Landsat

Abstract: exploration and exploitation of mineral resources to sustain their economic growth. Usually, the traditional mineral exploration techniques require enormous finances, prolonged time, and tremendous manpower, particularly in areas that are not easily reachable (Maduaka, 2014). Furthermore, mineral exploration required state-of-the-art techniques and expertise along with geological, geochemical, and geophysical datasets, which may not be easily available or may be lacking where access is problematic (Kaiser et al., 2002; Bemis et al., 2014). Modern remote sensing technology has proved to be one of the highly efficient and robust techniques used for mineral exploration. The use of remote sensing satellite images for geological mapping and mineral exploration usually involves studying the physicochemical properties of rocks and weathering soils, such as mineralogy, landforms, geochemical signatures, and the spatiall distribution of lineaments (Bhattacharya et al., 2012). A fundamental principle of mineral exploration is that it is quite possible that undiscovered deposits will be located in the close vicinity of discovered ones. For example, if mining is taking place in a particulat area, then similar minerals will be more likely found nearer to the discovered deposit, and as the distance increases, the likelihood of new discoveries will decrease. In that situation, before drilling exploratory boreholes at new locations, remote sensing can be used effectively to identify regions with higher chances of mineralization, mainly through multior hyperspectral remote sensing images (Gholami, Moradzadeh, and Yousef, 2012; Ciampalini et al., 2013). The use of reflectance spectroscopic information derived from remote sensing data allows effective localization of mineral exploration and reduces the cost and time spent on fieldwork for geological, geophysical, and geochemical studies (Short and Lowman Jr, 1973; Tedesco, 2012; Marjoribanks, 2010). Several remote sensing studies for mineral exploration and lithological mapping have been done in arid and semi-arid regions. In areas with good geological exposure, satellites in orbit are capable of acquiring spectral reflectance data directly from rock or/and soils (Sabins, 1999; Di Tommaso and Rubinstein, 2007; Zhang et al., 2007; Pour and Hashim, 2012; Mahboob, Iqbal, and Atif, 2015). Mapping hydrothermal minerals using remotely sensed reflectance spectroscopy data from Landsat

Development of a blast-induced vibration prediction model using an artificial neural network

Abstract: for fragmentation of coal and overburden. If the explosive energy is not fully utilized it causes blast-induced ground vibration, which may damage nearby structures. Ground vibration is expressed as peak particle velocity (PPV). During different stages of mine planning and operation, it is necessary to use a ground vibration prediction model for blasthole design. Selection of the modelling technique is crucial. Mathematical and statistical modelling techniques have limited application because of the lack of explicit knowledge about the complex mine blasting system. Vogiatzi (2002) highlighted the problem of multicollinearity in case of statistical modeling techniques. Mutalib et al. (2013) stated that mathematical models are unable to capture the nonlinear relationship between several blasting-related parameters due to the complexity of the model input data. However, the difficulty involved in modelling complex blast vibration problems can be removed by adopting an alternative soft computing modelling approach. One of the soft computing techniques is the artificial neural network (ANN). Ragam and Nimaje (2018) developed an ANN model for predicting PPV using six input variables. Kosti et al. (2013) stated that the conventional predictors fail to provide acceptable prediction accuracy. They showed that a neural network model with four mine blast parameters as input could make significantly more accurate on-site predictions. Sayadi et al., (2013), using a database from Teheran Cement Company limestone mines, found that a neural network resulted in maximum accuracy and minimum error. Khandelwal and Singh (2009) developed an ANN model using 150 data records from an Indian coal mine with site-specific rock characteristics and geomining setting. Khandewal and Singh (2007) built a ground vibration prediction model for a magnesite mine using four prediction variables with 20 data records. Kamali and Ataei (2010) predicted PPV in the structure of the Karoun III power plant and dam using an ANN. El Hafiz et al. (2010) evaluated ground vibration predictors using data from a single-station seismograph at a limestone quarry in Egypt. ANN prediction models have been built for one Indian coal mine and one limestone mine. Using the findings of these initial studies, it is essential to enhance the application of ANN in various mines in different Indian coal mining Development of a blast-induced vibration prediction model using an artificial neural network

Changes in subsidence-field surface movement in shallow-seam coal mining

Abstract: (China National Coal Association, 2018), making it the largest coal producer in the world, accounting for almost half of total world coal production. Coal production and distribution play a vital role in the energy industry of China. However, entire overlying strata, from coal seam to surface, are disturbed as a result of long-term, high-intensity and large-scale mining, causing surface subsidence. This results in groundwater loss, surface desertification, vegetation loss, and mud-rock flows. These issues have become topics of common concern throughout society. According to related research results (Liu 2008), the area of surface subsidence caused by coal mining in China has reached about 600 000 ha, some 0.2 ha (and up to 0.42 ha) of surface subsidence for every 10 000 t of coal produced. Surface subsidence disasters not only damage buildings, water conservancy, transportation infrastructure, and farmland, but also cause adverse effects on individual and community lifestyles, environmental hygiene, and economic development. Deterioration of the ecological environment in mining areas has a long history and is very harmful (Lu, 2015). Surface subsidence is an extremely important control index for underground excavations. Many experts and scholars have devoted resources to the research and remediation of damage caused by coal mining from the surveying, numerical simulation, mathematical, mechanical, geological, and mining engineering points of view. These studies have revealed general laws of mining subsidence (Hu, 2012). The most prominent characteristic of these is that surface subsidence has an obvious time-dependency, and may continue for several months, or even years, from the start to the end of surface movements. Since the 1970s, with the wide application of computer methods, numerical simulation has been increasingly applied in the calculation of mining subsidence and the analysis of subsidence mechanisms, and many experts and scholars have undertaken research in this field, such as Dahl and Choi (1981). The West German scholar Kratzsch (1974) summarized methods of predicting coal mining subsidence in his book ’Mining Damage and Protection’. Ma and Yang (2001) researched the spatial and temporal effects of rock movement using the discrete element method. Cui and Deng (2017) carried out a real-time displacement analysis of surface movement and deformation for the main section of a coal mine, and studied mining subsidence utilizing a rheological model. Surface subsidence continually changes during the exploitation of a mining face; Changes in subsidence-field surface movement in shallow-seam coal mining

An audit of environmental impact assessments for mining projects in Kenya

Abstract: The aim of the audit was to determine whether the mining project environmental impact assessments (EIAs) in Kenya are undertaken according to international best practice. A sample of 50 EIA reports for the 2007–2016 period was evaluated using 18 criteria in the Environmental Law Alliance Worldwide (ELAW) guidelines. The findings showed that only two criteria were considered ‘excellent’ according to the ELAW guidelines, namely baseline environmental assessment and prediction of physical impacts. Six criteria were found to be ‘satisfactory’, including prediction of social impacts, analysis of alternative options, and impact mitigation. The reports were quite weak in terms of: consideration of all phases in the mining cycle, environmental regulatory framework, prediction of biological impacts, stakeholder consultation and engagement, integration of human right issues, and integration of climate change and cost-benefit analysis. It is therefore recommended that the Kenyan National Environment Management Authority (NEMA) should consider tightening the EIA terms and conditions in the approval of statutory terms of reference (ToR) for full-scale mining EIAs to ensure improved performance of EIA as a tool for environmental protection.

Evaluation of shaft locations in underground mines: Fuzzy multi-objective optimization by ratio analysis with fuzzy cognitive map weights

Abstract: The determination of the location of production and ventilation shafts is one of the most important issues in underground mines from both a technical and an economic viewpoint. This study introduces an integrated approach using fuzzy cognitive map (FCM) and fuzzy multi-objective optimization by ratio analysis (FMOORA) to evaluate several candidate shaft locations and consequently increase ore production from underground mines. The FCM based on a hybrid learning algorithm was applied to analyse interactions and internal relationships between criteria and to find complex causal relationships between different factors. After importing the weights resulting from the FCM into the FMOORA, shaft alternatives were evaluated and prioritized. An iron ore case example was evaluated by the integrated approach. Results of the integrated approach were validated by the results obtained from fuzzy-TOPSIS and on-site evaluations by mining experts.

Developing a 3D mineral texture quantification method of drill core for geometallurgy

Abstract: CITATION: Voigt, M.J. et al. 2019. Developing a 3D mineral texture quantification method of drill core for geometallurgy. Journal of the Southern African Institute of Mining and Metallurgy, 119(4):347-353. doi:10.17159/2411-9717/590/2019

Recycling pre-oxidized chromite fines in the oxidative sintered pellet production process

Abstract: is well-known for its corrosion resistance, which is mainly due to the inclusion of chromium (Cr) (ICDA, 2013). Stainless steel is mostly produced from recycled scrap and ferrochrome (FeCr), a relatively crude alloy of Cr and iron (Fe). FeCr is predominantly produced by the carbothermic reduction of chromite, a mineral belonging to the spinel group characterized by the unit formula [(Mg,Fe2+)(Al,Cr,Fe3+)2O4] (Haggerty, 1991; Paktunc and Cabri, 1995; Tathavakar, Antony, and Jha, 2005). Although Cr can occur in 82 different minerals, chromite is the only source of new Cr units that can be exploited in commercial volumes (Motzer and Engineers, 2004). Approximately 95% of mined chromite is used in the production of various FeCr grades, of which high-carbon and charge grade FeCr are the most common (ICDA, 2013). Beukes et al., (2017) recently presented a review of FeCr production processes. According to this review, FeCr is principally produced in (i) conventional open/semi-closed submerged arc furnaces (SAFs) that are mainly fed with lumpy (typically 6–150 mm) chromite ore, fluxes. and reductants, (ii) closed SAFs that are fed with oxidative sintered chromite pellets, as well as lumpy reductants and fluxes, (iii) closed SAFs fed with prereduced chromite pellets, as well as lumpy reductants and fluxes, and (iv) closed direct current (DC) arc furnaces fed with fine (typically 6 mm) chromite ore, fluxes, and reductants. Of particular interest for the present paper is the oxidative sintered pellet process, which is commercially known as the Outotec steel belt sintering process (Outotec, 2017). Various authors have previously described the oxidative sintered pellet production process (Riekkola-Vanhanen, 1999; Beukes, Dawson, and van Zyl, 2010; Basson and Daavittila, 2013). Chromite fines (typically 1mm) are wet milled together with a small percentage of a carbonaceous material that serves as an energy source during sintering. The grain size specification that must be obtained during milling is typically a d80 of 74 μm (80% passing size of 74 μm). Ceramic filters are used to dewater the milled slurry to a moisture content of below 9%. A fine clay binder (usually refined bentonite) is then mixed into the moist filter cake with a high-intensity mixer, and the moist mixture is pelletized in a pelletizing drum. The newly formed pellets are screened on a roller screen. Oversized pellets are broken down and recycled, together with undersized pellets. This leads to fairly homogeneously sized green (uncured) pellets with an average diameter of approximately 12 mm. The green pellets are then layered on a Recycling pre-oxidized chromite fines in the oxidative sintered pellet production process

Evaluation of the physico-mechanical properties of plutonic rocks based on texture coefficient

Abstract: rock properties is essential for determining and predicting the behaviour of rocks and rock masses. Mechanical properties of rocks are important parameters in mining, geology, and engineering, and they are affected by textural characteristics such as grain size, grain shape, cement type, degree of cementation, mineral content, and the ratio of the grain area to the matrix area. The effects of textural properties on the physical and mechanical properties of rocks have been investigated for a long time, and previous studies revealed close relationships between single parameters related to rock texture and mechanical properties of rocks (Akesson et al. 2001; Gunsallus and Kulhawy 1984; Merriam, Rieke, and Kim, 1970: Onodera and Kumara 1980; Prikryl 2006; Ulusay, Tureli, and Bider, 1994; Tugrul and Zarif 1998). Rock properties are usually determined using mechanical tests, which require uniformly shaped and relatively large samples. However, it is not always possible to obtain such samples. Furthermore, rocks with similar textural and structural properties may exhibit different mechanical behaviour. Howarth and Rowlands (1987) developed a texture coefficient (TC) that expresses all the main textural parameters of a rock in a single dimensionless quantity based primarily on statistical assessment. The TC makes it possible to understand the effects of a rock’s textural properties on its mechanical properties using thin sections instead of large, uniform samples. Ersoy and Waller (1995) investigated the relationship between strength and TC for limestone, sandstone, and siltstone; they also examined the effect of rock properties and TC on drilling performance. Ozturk, Nasuf, and Bilgin (2004) explored the relationship between rock quality and TC by evaluating the uniaxial compressive strength (UCS) values of limestone, basaltic andesite, and tuff. Gupta and Sharma (2012) evaluated TCs as well as the petrophysical and mechanical properties of quartzite from the lower and higher Himalayas and found a strong relationship between TC and UCS. Similarly, Ozcelik, Bayram, and Yasitli (2013) investigated the relationship between TC and various parameters in marble by applying the statistical analyses developed by Ozturk, Nasuf, and Kahraman (2014). As indicated by the aforementioned studies, the relationships between a rock’s textural and mechanical properties have been extensively investigated for sandstone, siltstone, and limestone. In contrast, little consideration has been given to these relationships in plutonic rocks. Plutonic rocks incorporate an extensive variety of rock types, thereby complicating their mineralogy, Evaluation of the physico-mechanical properties of plutonic rocks based on texture coefficient

Optimization of conditions for the preparation of activated carbon from olive stones for application in gold recovery

Abstract: The purpose of this study is to prepare a new activated carbon from olive stones for use in gold recovery by carbon-in-leach (CIL) and carbon-in-pulp (CIP). The preparation method chosen was physical activation using steam. The effect of four process parameters: the residence time for carbonization, the activation temperature, the residence time for activation, and steam flow, were studied by the mean of response surface method (RSM) in order to optimize the yield, iodine index, and attrition characteristics. These two last responses were used as primary indicators of gold recovery capacity and mechanical strength. The results obtained show that optimal activated carbon can be prepared under the following conditions: a carbonization time of 157 minutes, activation at 921°C for 53 minutes, and a water vapour flow of 0.18 mL/min. This optimum carbon has an iodine value greater than 1100 mg/g and an attrition index in the order of 0.74%. These values reflect the quality of the precursor (olive stones) as a raw material for the development of an effective new activated carbon for the gold mining industry.

The use of unmanned aircraft system technology for highwall mapping at Isibonelo Colliery, South Africa

Abstract: understanding of the structure of any mineral deposit. Several mapping methods may be applied depending on the available exposure/outcrop and nature of the orebody; for example, coal deposits typically suboutcrop only, therefore an opencut highwall provides the best exposure for mapping the geology. Mapped information, when incorporated into a resource model (generated from exploration borehole data), improves the understanding of the orebody or coal seam. This research paper focused on the use of unmanned aircraft system (UAS) technology for pit highwall mapping to generate data for updating geological models and avail the latest information to mine planning to improve the short-term plans. The Isibonelo Colliery’s geological model is updated annually and is termed a resource geological model, from which the mining model is built. This research was motivated by the absence of a short-term geological model that could be used for short-term mine planning. Short-term models are built by mine geologists, when they take the latest release of the resource geological model and add in data as it becomes available from progressive mining. The data includes surveyed highwall seam-roof and/or seam-floor contacts, faults, dykes, blast-hole data, grade control hole data, and any other measurements deemed necessary for modelling. Highwall mapping with a survey total station is standard practice at Isibonelo Colliery. Recent technological advances have made new digital photogrammetry techniques available for mapping, with a camera being carried by a UAS which does highwall mapping. The process of short-term geological modelling allows for the incorporation of small-scale features, such as seam rolls and previously unidentified faults, which may not be obvious from broadly spaced exploration drill-hole data.

Slag carry-over and the production of clean steel

Abstract: For effective steel refining in the ladle (secondary steelmaking) the amount of steelmaking slag that is transferred from primary steelmaking must be limited, because the steelmaking slag contains iron oxide, manganese oxide, and phosphorus oxide. Adverse effects of slag carry-over include increased consumption of deoxidizers, phosphorus pick-up by the steel, and increased ladle refractory wear. Infrared imaging at longer wavelengths is an effective non-contact method to detect slag in the tapping stream. Various devices are used to shut off the tapping stream rapidly. These include slag darts, pneumatic slag stoppers, and slide gates for steelmaking converters, and eccentric bottom tapping for electric arc furnaces.

Upgrading of raw vanadium titanomagnetite concentrate

Abstract: In view of the continuous depletion of titanium, rutile, and ilmenite mineral deposits, the search for cost-effective practices for titanium production using vanadium titanomagnetite as raw material has become increasingly important. In this study, vanadium titanomagnetite concentrate obtained from the Panzhihua area in China was upgraded via fine grinding followed by magnetic separation to produce high-quality vanadium titanomagnetite concentrate. The potential utilization of this concentrate was investigated. Mineral liberation analysis and electron microprobe analysis were used to investigate the deportment of the impurities and major minerals. Experimental results showed that magnetic separation increased the Fe grade by 4% compared with the raw concentrate, while the total content of Al2O3, SiO2, MgO, and CaO impurities decreased from 12.35% to 7.73%. Process mineralogy studies confirmed that the proportion of titanomagnetite in the high-quality vanadium titanomagnetite concentrate increased to 95.84%. Spinel and sphene were enclosed in the titanomagnetite particles at the nanometre scale, which would make them practically impossible to remove through mineral processing techniques.

South Africa's options for mine-impacted water re-use: A review

Abstract: currently rated as one of the 30 driest countries in the world, with an average rainfall of 490 mm/a, approximately half of the global average. As an indicator of the degree of regional variability in South Africa’s water supply, it has been shown that 70% of all runoff is from approximately 20% of the land area. Regardless of the water scarcity faced in South Africa, our water conservation track record is poor, with an average consumption of 280 L/d per person, almost 60% more than the global average of 175 L/d per person. Around 40% of this allocation is utilized in watering lawns and gardens (Zhuwakinyu, 2017). The South African government predicts water demand to outstrip supply as early as 2025. On an international scale, the situation appears just as dire, with the United Nations High Level Panel on Water (HLPW) expecting a 40% water shortfall by 2030, which may affect up to 1.8 billion people based on current water demand trajectories (Zhuwakinyu, 2017). Currently, South Africa is experiencing the worst drought since 1904, which has triggered severe water shortages, negatively affecting agricultural output in all sectors (News24, 2016). The potential exists for nation-wide ‘water-shedding’ initiatives, similar to the electrical load-shedding programme initiated by Eskom, being implemented for homes and businesses in the near future if the situation continues to decline. Currently, water restrictions are in place country-wide with the Western Cape being the worst affected province. In 2016, eight of the nine provinces, with the exception of Gauteng, were declared drought disaster areas. The country’s total water supply is currently estimated at 14.6 km3/a, of which surface water is the main source. The current demand is estimated to be between 15 km3/a and 16 km3/a, and it is expected that South Africa will experience a 17% water supply and demand gap by 2030 (Webb, 2015; News24, 2016; Zhuwakinyu, 2017). The UN World Water Development Report (2017) argues that improved wastewater management could facilitate the achievement of the UN’s 2030 Sustainable Development Goals (SDGs). SDG-6 specifically has a target to reduce the proportion of untreated wastewater by half by 2030. while sustainably increasing water recycling and safe re-use (WWAP, 2017). The report also suggests that wastewater which is traditionally discarded could be treated to provide a non-potable water resource for use in agriculture and energy production. According to the Water 2017 Report, more than 50 countries South Africa’s options for mineimpacted water re-use: A review

Prediction of gas holdup in a column flotation cell using computational fluid dynamics (CFD)

Abstract: Computational fluid dynamics (CFD) was applied to predict the average gas holdup and the axial gas holdup variation in a 13.5 m high cylindrical column 0.91 m diameter. The column was operating in batch mode. A Eulerian-Eulerian multiphase approach with appropriate interphase momentum exchange terms was applied to simulate the gas-liquid flow inside the column. Turbulence in the continuous phase was modelled using the k-epsilon realizable turbulence model. The predicted average gas holdup values were in good agreement with experimental data. The axial gas holdup prediction was generally good for the middle and top parts of the column, but was over-predicted for the bottom part of the column. Bubble velocity profiles were observed in which the axial velocity of the air bubbles decreased with height in the column. This may be related to the upward increase in gas holdup in the column. Simulations were also conducted to compare the gas holdup predicted with the universal, the Schiller-Naumann, and the Morsi-Alexander drag models. The gas holdup predictions for the three drag models were not significantly different.

The state of mine closure in South Africa - what the numbers say

Abstract: The consequences of ineffective mine closure in South Africa are evident from the number of abandoned mines and operations on extended care-and-maintenance, the on-selling of mines to less well-resourced companies to close, and increasing illegal mining activities. However, the data to substantiate these observations and provide insight into the underlying issues has not been available. Through the Promotion of Access to Information Act, a list of mine closure certificates applied for between 2011 and 2016 and a list of certificates granted over the same period for all nine regions of South Africa was obtained. From the analysis of this data, we show that the mine closure system as implemented in South Africa is largely ineffective. Although closure certificates are being granted, these are for prospecting sites and small-scale mines, which have a relatively small environmental impact. No large mines of any environmental significance were relinquished over the period under review, with very few applying for closure certificates. Furthermore, the issuing of closure certificates varies significantly between regional offices, with the success rate for applications being generally low and issuing of certificates taking an extended period.

Investigation of microcrack formation in vanadium-titanium magnetite using different crushing processes

Abstract: Characteristics of microcracks in vanadium-titanium magnetite crushed by high pressure grinding roll (HPGR) and conventional jaw crusher (JC) were investigated. In crushing by both HPGR and JC, stress cracks, intragranular cracks, and cleavage cracks were developed. Stress cracking was the initial stage and fundamental basis of fracture. The intragranular cracking could accelerate the comminution process and thus increase the content of fine particles in the crushed products. Cleavage cracking could enhance the liberation of valuable minerals and gangue minerals. Narrow size fraction samples were prepared and characterized by optical microscopy, scanning electron microscopy (SEM), the Brunauer, Emmett, and Teller (BET) method, mineral liberation analyser (MLA), and Bond ball mill. The specific surface area and pore volume of the HPGR products were found to be significantly higher than for JC products due to the presence of abundant microcracks and a higher fraction of fine particles. Compared to the JC products, the HPGR products showed a better degree of liberation and lower Bond ball mill work index (BWI), although the difference gradually decreased with increasing fineness of grind. The application of HPGR not only reduces the energy consumption in the subsequent grinding process, but also optimizes the separation of vanadium-titanium magnetite and improves the TiO2 recovery in ilmenite.

Investigation of flow regime transition in a column flotation cell using CFD

Abstract: CITATION: Mwandawande, I. et al. 2019. Investigation of flow regime transition in a column flotation cell using CFD. Journal of the Southern African Institute of Mining and Metallurgy, 119(2):173-186. doi:10.17159/2411-9717/2019/v119n2a10

Diamond exploration and mining in southern Africa: Some thoughts on past, current and possible future trends

Abstract: boasts a history of 150 years of discovery and mining, forming the cornerstone of development of the core, modern economies at the southern tip of Africa. Since the discovery, in the 1860s and 1870s, of the secondary diamond placers and primary diamond-bearing kimberlite deposits in the central interior of the then Cape Colony and Orange Free State, southern Africa has endured as the pre-eminent diamondproducing region in the world. Notwithstanding periodic competition from significant new discoveries in other parts of the globe and the paucity of recent, new discoveries in the region, its ranking is unlikely to change in the short to medium term. In a geological context the region contains the Kaapvaal-Zimbabwe and Angola-Kasai cratons, identified in terms of Clifford’s rule as areas inherently prospective for diamonds, being underlain by portions of the Earth’s crust that are tectonically stable and older than 1.5 billion years (Clifford, 1992). Although the Democratic Republic of Congo (DRC) would, in a geographic context, be considered to be part of Central Africa, for the purposes of this review it is included in southern Africa since northeast Angola and the adjacent parts of the DRC form part of the same geological terrane and diamond production from both countries needs to be considered together. Historical and current diamond production from the northeastern parts of the DRC around Kisangani is not considered to be significant and its inclusion in the overall numbers for the DRC does not materially affect the overall picture presented here. Hence, in this review, the countries considered are South Africa, Zimbabwe, Namibia, Angola, the DRC, Lesotho, Botswana, and eSwatini (previously Swaziland), the first five of which each has a history of diamond production stretching back more than 100 years, and in the case of South Africa, 150 years (Table I).

Theoretical, practical, and economic difficulties in sampling for trace constituents

Abstract: The heterogeneity of trace constituents in lots to be sampled for the determination of their contents has been the object of extensive work by many authors in the past. The scope of this paper is to focus attention on the works done by Gy1–3, Ingamells4–7 and Pitard4, 8–11. Links between the works of these authors are investigated, and an up-to-date strategy to resolve sampling difficulties is suggested. The challenge is to provide adequate, realistic sample and sub-sample mass at all sampling and sub-sampling stages, all the way to the balance room at the assaying laboratory. More often than not, meeting theory of sampling (TOS) basic requirements to keep the variance of the fundamental sampling error (FSE) within reasonable limits are beyond economic reach, or at least in appearance. Therefore, when these difficulties are ignored for practical reasons, awareness becomes the only tool at our disposal to show the possible consequences. Such awareness must be properly managed, which is the primary objective of this paper. For the unaware reader, TOS refers to Gy’s work combined with compatible and positive contributions made by others. TOS is a dynamic knowledge that should be complemented by existing and future contributions, which is the mission of WCSB in many ways.

Improving the separation efficiency of Southern African haematite from slimes through selective flocculation coupled with magnetic separation

Abstract: With depleting reserves of high-grade iron ores in South Africa, the local minerals processing industry is increasingly paying attention to fine tailings material as a potential resource for the future. A significant proportion of these tailings consists of slimes, i.e. material finer than 38 μm. Upgrading of slimes by physical separation techniques is usually constrained by low efficiency at such fine sizes. Selective flocculation has the potential of overcoming these constraints to a degree. This paper reports on a study that investigated that potential by coupling selective flocculation with magnetic separation to improve separation efficiencies. The coupled process achieved an improvement in the grade of the magnetic concentrate from 52.3% to 59.2% Fe at much the same Fe recovery. This constitutes an improvement in separation efficiency from about 40% to 57%. These results were achieved under laboratory conditions, confirming the positive indications found in the literature, and give an indication that similar results may be possible at an industrial scale.

The use of 3D ground penetrating radar to mitigate the risk associated with falls of ground in Bushveld Complex platinum mines

Abstract: Some of the recent advances in ground penetrating radar (GPR) technology are discussed in this paper; in particular the move to, and potential value addition offered by, the 3D approach to surveying over the more conventional 2D approach. Case studies at two platinum mines in the Bushveld Complex are used to stress the fact that the niche role for GPR is that of immediate hangingwall assessment, aimed at identifying geological features that could potentially result in falls of ground (FOGs). The paper also highlights the obstacles that still need to be overcome to enable GPR to become a routine tool in local mining operations, and recommendations are offered on how to address these obstacles through ongoing research efforts.

Hydrothermal preparation of biochar from spent coffee grounds, and its application for the removal of cadmium from coal tailings leachate

Abstract: Spent coffee grounds were transformed into biochar using a hydrothermal method. Some of the biochar product was pre-treated through surfactant impregnation with sodium dodecyl sulphate (SDS) to enhance its adsorption capacity. The non-treated(NT) and pre-treated(PT) biochars were characterized using FTIR spectroscopy and SEM-EDS analyses, which revealed that the products had the potential for adsorption of heavy metals from solution and confirmed the successful impregnation of biochar with SDS surfactant. The two adsorbents were then used for the removal of cadmium from solution and the adsorption behavior and capacity determined through adsorption isotherm, kinetic, and thermodynamic studies. It was found that the cadmium was adsorbed in several concentric layers on the surface of the adsorbents through a chemisorption mechanism. The PT biochar was identified as a superior adsorbent, with a capacity of qe = 10.67 mg/g compared to the NT biochar with qe = 4.82 mg/g. The adsorption of cadmium onto the PT biochar was further determined to be spontaneous and endothermic. It was therefore concluded that the PT biochar shows potential as an adsorbent and could be considered for implementation in the treatment of metal-polluted effluents.

Monte Carlo simulation of uncertain parameters to evaluate the evacuation process in an underground mine fire emergency

Abstract: In the process of designing a fire safety system for underground mines, computer fire models can be used to analyse and estimate the consequences of fire scenarios for the evacuation process and the safety of mineworkers. The models need to be fed with data, some of which is stochastic in nature. Recent literature addresses the need for a computationally effective methodology for introducing uncertainties in the input parameters of fire and evacuation models to improve safety in underground mines. This research paper presents the results obtained from a methodology that implements Monte Carlo simulation, which follows the normal distribution of the fire load and the pre-movement time uncertainty to generate multiple scenarios that are simulated in a 3D model to show the propagation of combustion products through the mine ventilation network. These results are then used to estimate the fractional effective dose (FED) of fire combustion products in workers, and the available safe egress time (ASET) and required safe egress time (RSET), which can highlight the safety issues in the evacuation process. To demonstrate the model, a case study of the SASAR.N. Macedonia lead-zinc mine was used in which 50 variations of scenarios were simulated. The results from the simulations are analysed and potentially harmful fire scenarios highlighted. In addition to being able to identify potentially dangerous fire scenarios, the model can also help in the process of conducting fire risk assessment and in improving the evacuation system in the case of an underground mine fire.

Monitoring the performance of DMS circuits using RhoVol technology

Abstract: applied beneficiation technique for the density separation of valuable products from crushed ores. The industrial applications of dense medium separation have been summarized and reviewed by various authors (Scott and Napier-Munn, 2000; Bosman, 2014; NapierMunn, 2018). Dense medium cyclones (DMCs) are widely used in the coal and diamond industries to produce clean coal or to preconcentrate kimberlitic ores, respectively. Cyclone performance (separation density monitoring) techniques are varied. In the mineral industry. Density tracer tests (NapierMunn, 1985, 2014; Davis, Wood, and Lyman, 1985) without mineral material, are widely used, although their accuracy in predicting operating cut-points becomes limited once mineral material is introduced. More recently, radio frequency tracers have been also used for the determination of cyclone efficiency (Partition Enterprises, 2017). Density fractionation (the sink-and-float process) is a traditional practice used throughout mineral processing laboratories to ascertain the efficiency of density-based separators. It has also been used as a yield predictor in the coal and iron ore industries, where the density profile of the crushed runof-mine (ROM) ore is correlated with the plant yield. Densimetric evaluation methods have historically used heavy liquids, tetrabromoethane (TBE) of various densities. but these liquids carry health and environmental risks (Wills, 1987). More recently, non-toxic lithium heteropolytungstates (LST) have been used, where the desired densities are achieved by maintaining the solutions at specific temperatures (Koroznikova et al., 2007). Although sink-float densimetric analyses give a useful indication of cyclone performance, their practicalities in providing information to effect timeous plant-control and optimization are often limited. Long delays (up to 12 weeks) between sample collection and availability of results are not uncommon (Ndlovu, 2015). Furthermore, the repeatability of data can often be poor due to the inconsistent nature of its operation, since sinkfloat analysis is a manual process and very dependent on the dexterity and experience of the operator. The RhoVol process begins by accurately measuring the mass of each particle, followed by a 3D reconstruction of its volume using images from multiple cameras (Forbes, Voigt, and Bodika, 2003; Forbes et al., 2006). The Monitoring the performance of DMS circuits using RhoVol technology