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By K. Isaac, S. O. Bada

This research focuses on the co-firing of discard coal with refuse-derived fuel (RDF) to utilize this abundant resource in South Africa for energy generation and reduce the volume of waste disposed of at landfills. The potential of a coal with a high ash content (> 40%), which is a grade used in some power stations in South Africa, and its combustion compatibility with two different RDFs in terms of emission reductions has been established. Gaseous emissions and ash residues from the combustion and cocombustion of the coal, two different RDFs and coal/RDF blends of different proportion were analysed. One of the RDF samples contained mostly paper (PB) and the other mostly plastic (PL). Co-combustion ash from the discard coal and RDFs showed a decrease in chloride and alkali metal contents as the coal ratio in the blend increased. The slagging propensity of the co-fired blends was found to be very low, while the propensity for fouling decreased from high to medium for all the blends with < 75% RDF. Cocombustion of RDF with coal showed a decrease in SO2 emissions from 387 ppm (discard coal) to 50 ppm for the sample containing 25% coal discard plus 75% PL. A 15% PL to 85% coal blend also reduced NOx emissions from 145 ppm (100% PL) to 88 ppm. The lowest CO2 emission observed was 6000 ppm for the blend of 85% discard coal plus 15% PB. It was established that the most favourable fuel blend that can produce the lowest sulphur emissions if used for power generation is the 25% coal discard plus 75% PL sample.

Aug 2, 2022

By B. P. von der Heyden, T. Blenkinsop, A. Mamuse

Zimbabwe hosts a varied array of coloured gemstones. With the exception of emerald deposits and several world-class pegmatites, few of the gemstone occurrences have received detailed attention from the scientific or mineral exploration communities. In the present contribution we summarize the status of knowledge of the gemstone deposits and occurrences in Zimbabwe, paying particular attention to the geological settings in which they were formed. Synthesis of this regional geological approach reveals that there may be significant exploration potential for further gemstone occurrences, particularly in the extensive pegmatite fields and in Al-enriched orogenic belts that have undergone greenschist to granulite facies metamorphism. Further socio-economic and developmental initiatives will aid in optimizing the value generation from this important sub-sector.

Feb 12, 2024

By C. Bester, G. M. Rohde

A major challenge in the mining sector is the responsible management and efficient storage of mine residue. Over recent years numerous tailings dams have experienced unintended spills and failures, with severe consequences for the mining industry, the environment, local communities, and the regional economy. The fourth industrial revolution (4IR) is impacting society due to increased interconnectivity, processing speed, and automated technologies. This paper explores whether 4IR technologies have the potential to mitigate risks associated with tailings dams. Experts in the field of tailings dam operational management were surveyed to determine their view on the risks associated with tailings dams and the potential of 4IR technologies to mitigate these risks. The survey found that a majority of experts believe that certain 4IR technologies have the potential to reduce the risks associated with tailings dam failures.

May 27, 2025

By A. McQuillan, N. Bar

Geotechnical models developed during the planning stages of open pit mines are three-dimensional so as to capture the spatial variation in lithological, structural, hydrogeological, and geomechanical conditions. Geological models that describe the lithological and structural (faulting and folding) characteristics of a deposit are always 3D. Likewise, boreholes and piezometers used to develop geomechanical properties and groundwater models are drilled at spatial offsets across the deposit to understand the lateral and vertical characteristics. Yet when geotechnical analysis is completed, often the three-dimensional geological, hydrogeological, and structural models as well as geometrically complex 3D mine designs for optimizing economic mineral recovery and overburden removal are simplified to two-dimensional sections. In this paper we demonstrate that this simplification can lead to the wrong failure mechanism being identified, analysed, and/or a conservative factor of safety being calculated and hence an over-estimation of slope stability. Through case studies we show how three-dimensional analysis methods are more suited to rock slopes, particularly those with anisotropic material strength, when singularities such as geological faults are present, and nonlinear slope geometry. When the same slopes are analysed in two dimensions, the failure mechanism calculated is often fundamentally incorrect. The case studies further reveal that the factor of safety calculated in three dimensions is not always higher than the two-dimensional factor of safety.

Feb 6, 2023

By S. Sinha, S. Ganguly

"In an opencast mine explosives are used for fragmentation of rock. Inefficient use of explosive energy in an opencast operation produces excessive ground vibration, which is measured by peak particle velocity (PPV). To mitigate ground vibration, it is essential to develop a model to predict PPV. At present empirical models are used. These models are based on only a few input variables, hence they fail to take into account the effects of the myriad factors that cause ground vibration. Due to lack of explicit knowledge about the complex mine blasting system the scope of application of mathematical and statistical modeling techniques is limited. The artificial neural network (ANN) technique is a learning algorithm that can remove some of these limitations and can be applied to predict PPV. In this paper an ANN model is developed for prediction of blast vibration using 248 data records collected from three coal mines with diverse geomining conditions. The correlation coefficient between measured PPV and model output was found to be 0.96 and the average error percentage 11.85. The ANN model output was compared with the output of three empirical models that are widely used for prediction of PPV. The correlation coefficient between the PPV predicted by an empirical model and measured PPV data was 0.63 and the relative error percentage 38.47. This result demonstrates the superiority of the ANN model compared to empirical blast models. By using site-specific structural discontinuities as input the model performance can be further improved. Sensitivity analysis and 3D plotting were used to gain further knowledge about blast-induced ground vibration. IntroductionIn an opencast coal mine explosives are used 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."

Feb 1, 2019

By G. de Tomi, G. C. Teodoro, E. Rodovalho, T. M. El Hajj, J. A. S. Tenório

The selection of an underground mining method stems from a multivariate analysis that considers geomechanical, geological, economic, and operational parameters. Even after identifying the most compatible method, there is no assurance that the mining company will achieve the best performance. The geological complexity of some deposits requires adaptations of methods described in the literature to obtain more selectivity and reduce mining waste. There are some studies on geometry of underground structures, but a methodology that describes an adaptation of a room-and-pillar mining method for ore bodies with down-dip varying from 20° to 25° is novel. The present work aimed to reduce dilution by adapting the traditional room-and-pillar mining method (TRP) to inclined ore bodies. This new method is entitled short-hole room-and-pillar (SHRP). The equations that measure the dilution are defined according to the geometry of stopes and openings. The results comprise comparative analyses of the operational and planned dilutions to measure the performance of the SHRP method. The average operating dilution of the SHRP method was more than five times lower than the planned dilution according to the TRP method. Low operational dilution indicates high selectivity of the method and its potential to reduce underground mining tailings.

Sep 9, 2024

By R. Trammell, O. Eterigho-Ikelegbe, S. O. Bada

In response to the enormous amounts of coal discard generated during coal mining and preparation, the development of an efficient and sustainable strategic use of this resource is essential. Furthermore, the rising urban population over the next decades is confronted with the depletion of quality raw materials for building components. To this end, this study reports new information on the morphology, water absorption, and flexural strength properties of ceramic composites produced from three different coal discards and polysiloxane pre-ceramic polymer (PCP) resin. In addition, test results relating to the continuous operating temperature, chemical resistance, and efflorescence potential of the composites are presented. The results show that the water absorption and flexural strength of the coal composites, up to 1.94% and 36.46 MPa respectively, exceed the requirements for ceramic and clay roof tiles. The continuous operating temperature of composites is found to be more thermally stable than conventional roofing tiles (concrete and ceramic) between ambient temperature and 600°C. In addition, the excellent chemical resistance of the composites (94.43%−99.98%) compared to conventional roofing tiles (67.82%−99.97%) eliminates the need for additional external coatings. The interesting results documented so far suggest that this technique could be used to produce low-temperature application building products such as bricks, panels, roofing tiles, etc. This new recycling technique offers an excellent opportunity to eliminate enormous volumes of coal discard and to advance the circular economy in the coal industry.

Aug 2, 2022

By R. Minnitt, C. Morgan, D. Fourie

The problems associated with outliers and their adverse effects on resource estimation in deep level South African gold mines are presented, and solutions suggested in available literature are reviewed. Traditional Witwatersrand type outlier capping uses the 99th percentile grade as the upper limit, a somewhat blunt approach. The occurrence of high and low grade areas in mining operations and the estimation of resources using geostatistical techniques require that the assumption of stationarity be upheld. Honouring the stationarity of data requires that mining areas be subdivided into appropriately sized and spaced domains. In order to overcome high-grade conditionally biased block estimates, the overly strong influence of extreme grades is mitigated by using naturally occurring grade sub-domains, by identifying outliers within the grade sub-domains, allocating relevant capping limits, and weighting them in a post-estimation process to. Rather than applying a capping value across a domain it applies a maximum cap based on the extreme value and its range of influence; the method also ensures that relevant capping occurs even in lower grade sub-domains. The proposed method for capping outliers recognises that metal contained in high grade chip samples should not be over-capped, and based on the grade of surrounding samples. The post-processing method of capping outliers does not interfere with the kriging equations. The method is simple, elegant, and can be easily applied. An advantage is that the output from the kriging process is not overwritten, allowing for comparison between original kriging results and post-processing results.

Sep 1, 2021

By I. Druce, C. Li, T. Qu, J. Dong, W. Y. Xinchao, V. Nkuna

CITIC Heavy Industries has a large installed base of grinding equipment throughout Africa in different configurations, including high-pressure grinding rollers with ball mill and semi-autogenous ball crusher. The total installed power of CITIC’s mills exceeds 430 MW. In this paper, we compare several typical grinding circuits of copper in Africa with about 15 kt/d throughput based on ore properties, process selection, equipment sizing, and key equipment capital and operating costs. Actual operating performance is also introduced. The comparison for the following mine sites provides a general reference for the selection of copper grinding circuits with this approximate throughput: Kamoa-Kakula Copper Mine with high-pressure grinding rollers with ball mill circuit, and Deziwa and Sicomine Copper-Cobalt Mines with semi-autogenous ball crusher circuits

Jan 1, 2023

By C. Banff, E. C. F. Hamman, J. Venter

Open pit slope stability analyses for large scale instabilities are often carried out using limit equilibrium, finite element or finite difference computer programs. All of these require empirical estimates of rock mass shear strength when calibrated values are not available, which is a common occurrence. A common method of estimating rock mass shear strength is the Hoek-Brown failure criterion, which often over- or underestimates rock mass shear strength when used in limit equilibrium or elastic linearly plastic slope stability analyses, resulting in published alternative estimates for the coefficients of the Hoek-Brown failure criterion. This paper investigates the differences between limit equilibrium and elastic linearly plastic slope stability analysis based on the Hoek-Brown failure criterion. The investigation consisted of a comparison of 3840 RS2 finite element analysis models completed with strain softening, and 216 Slide2 limit equilibrium models. The models were used to evaluate a methodology to determine equivalent limit equilibrium and elastic linearly plastic shear strength parameters that provide the same stable slope angles and instability back break distances as the more representative strain softening stress analysis methods. This paper presents the methodology and compiles the results into design charts and equations for equivalent limit equilibrium Mohr-Coulomb shear strength parameters, that simplify calibration against actual case studies. The results compare well with older empirical shear strength estimates, however, a detailed calibration of the results against case studies will need to be carried out. The analysis also did not consider pore pressure effects; this is left for future publication.

Sep 1, 2025

By R. Altındag, D. Akbay

The point load index is a simple, fast, and inexpensive method for determining rock strength and can be applied both in the field and in the laboratory. There are, however, some disadvantages and limitations to the method, and the test results can be affected by the person carrying out the test, the rock characteristics, or the test device. In this study we describe an investigation into how the point load index value is affected by the shape of the conical platens used in the test. Point load index tests were carried out using different devices fitted with conical platens of different spherical radii, and on a modified device which circumvented the limitations/disadvantages. It was seen that the point load index value increased as the platen radius increased, as expected. In the case of testing using non-standard conical platens, an equation is proposed to normalize the point load index value with respect to the standard spherical radius value.

Nov 1, 2021

By D. F. Malan

This paper provides an overview of the concepts of citations and journal impact factors, and the implications of these metrics for the Journal of the Southern African Institute of Mining and Metallurgy (JSAIMM). Two key research literature databases publish journal impact factors; namely, Web of Science and Scopus. Different equations are used to calculate journal impact factors and care should be exercised when comparing different journals. The JSAIMM has a low impact factor compared with some of the more prestigious journals. It nevertheless compares well with journals serving other mining sectors, such as the Canadian CIM Journal. The problems associated with journal impact factors are discussed. These include questionable editorial practices, the negative impact of this concept on good research, and the problem of a few highly cited papers distorting the journal impact factor. As a consequence, there is growing resistance to the use of journal impact factors to measure research excellence. The San Francisco Declaration on Research Assessment is a global movement striving for an alternative assessment of research quality. As a recommendation, the Editorial Board of the JSAIMM should adopt a pragmatic approach and not alter good journal policies simply to increase the journal impact factor. The focus should remain on publishing excellent quality papers. Marketing of the Journal, the quality of the published papers, and its open access policy should be used to counter the perception that journals with high impact factors are better options in which to publish good research material.

Sep 1, 2022

By S. M. H. Haddad, M. Saghaeian, R. Hejazi, V. Sheikhzadeha, A. H. Baladastian, A. Dehghani Ahmadabadi

Sulfide impurities in iron ore concentrates play an important role in designing pelletising and steel making plants. Therefore attempts are made to keep the sulfur content of the final concentrate produced by the plants as low as possible. Generally, in the beneficiation process of iron ore concentrate, the removal of sulfur is performed through magnetic separation systems, followed by reverse flotation. The sulfide content of the iron ore concentrates originated from two main sources, including pyrite and pyrrhotite. In this research, in order to compare the floating capability of these two types of sulfide minerals, two iron ore concentrates with different sulfide constituents, pyrite or pyrrhotite, were selected. Reverse flotation tests were done separately on these samples under similar conditions. Process parameters considered for the tests included pH (2, 4, 6, 8 and 10), collector consumption (150, 200, 250, 300 and 350 g/t) and frother consumption (40, 50, 60, 70 and 80 g/t). Potassium Amyl Xanthate (PAX) and Methyl Isobutyl Carbinol (MIBC) were the collector and frother used in the tests, respectively. For modelling and optimising process parameters, the Central Composite Design (CCD) method was applied to the test results. Empirical coded equations were obtained for responses involving weight recovery, Fe recovery, Fe grade and S grade. Finally, comparison of test results revealed that the elimination recovery of pyrite sulfides was far greater than pyrrhotite sulfides, and it was possible to remove 84% sulfur content of the pyrite sample compared to minus 30% for the pyrrhotite sample. Keywords: Reverse flotation, pyrite and pyrrhotite, sulfur removal, iron ore concentrate, beneficiation plant

Jan 1, 2020

By P. R. Jochens

South Africa depends to a considerable measure on the exploitation of mineral reserves and the processing of these minerals. One of the prime requirements for the mining and metallurgical industry to continue in this vital role is access to sufficient energy in a suitable form. Hence, four important questions are discussed: Does South Africa have sufficient energy for the processing of its minerals and metals! Will the cost of energy allow South Africa&apos;s minerals and metals to compete on world markets? Can mining and metallurgical processes become more energy-efficiency Can mining and metallurgical processes be adapted to the various forms of energy that may have to be utilized in the future? It is concluded that about 26 per cent of the extractable reserves of coal would be required in the mining and processing of 50 per cent of South Africa&apos;s reserves of gold, platinum-group metals, copper, iron, ferrochromium, and ferromanganese. However, the reducing agents required exceed the extractable reserves but not the total estimates of mineable in situ resources of metallurgical coal and anthracitic coal. Even under the severe constraint that coal could become virtually the sole source of energy, only about three-quarters of the extractable reserves of coal would have been consumed by the year 2025. The reasonably assured resources of uranium metal that can be recovered at less than $80 per kilogram are considerable and, at current conversion efficiencies to electricity, are equivalent to one-fifth of the extractable reserves of coal. The rate of exportation of energy in the form of U30. was about five times that of coal in 1978. It is pointed out that the price of energy has a direct effect on the competitiveness of metals, and, although constituting only a small proportion of the selling price of precious metals, it represents a significant proportion of the selling price of copper and metals recovered from oxide ores. The scope for the conservation of energy appears to be greater in the extraction and conversion of primary energy-carriers to electrical energy than in other mining or metallurgical fields. Provided that alternative sources of energy can be converted to electrical energy, they can be applied to the mining and metallurgical industries. The decision as to which type of energy should be used in specific mining and metallurgical situations is complicated, and is likely to be subjected to closer scrutiny than in the past. The hope is expressed that the tentative conclusions reached will give rise to more-quantitative analyses from those qualified to undertake such an exercise. Inevitably, the questions asked at the outset give rise to more questions, and the more interesting ones are posed in the context of each conclusion.

Jan 1, 1980

By T. Bhambhani, E. Arinaitwe

Solvay has developed several novel reagent innovations to improve separations in sulfide ore flotation and address major industry challenges. These innovations include: a) carbon management strategies to reduce the deleterious impact of organic carbon on flotation circuits; b) new collectors for heavily tarnished or oxidized Cu-Au ores; and c) a functionalized depressant for minimizing penalty elements in metal concentrates. Owing to their unique chemistries, these innovations exhibit a wide spectrum of rather unique properties that are quite in contrast to the traditionally used reagents. The chemistry, attributes, application, and advantages of these innovations are discussed in this paper based on laboratory, pilot, and plant results and observations for various ores

Jan 1, 2023

By Matthew D. Viergutz

MECS? HRS technology has reliably recovered intermediate pressure steam from sulphuric acid plants for more than 20 years. This steam can either generate electricity or replace steam produced by an existing fuel-fired boiler. As worldwide greenhouse gas emissions continue to rise, industries are looking for novel and cost effective solutions to reduce pollution, particularly carbon dioxide, from their plants. Waste heat recovery technologies such as HRS offer new and existing plants the opportunity to maximize energy efficiency while reducing their reliance on energy supply from external sources. This paper offers a unique look at energy recovery in sulphuric acid plants and how recent innovations in MECS? Heat Recovery System technology make HRS more financially viable ? and more green - than ever.

Jan 1, 2009

By Matthew D. Viergutz

MECS? HRS technology has reliably recovered intermediate pressure steam from sulphuric acid plants for more than 20 years. This steam can either generate electricity or replace steam produced by an existing fuel-fired boiler. As worldwide greenhouse gas emissions continue to rise, industries are looking for novel and cost effective solutions to reduce pollution, particularly carbon dioxide, from their plants. Waste heat recovery technologies such as HRS offer new and existing plants the opportunity to maximize energy efficiency while reducing their reliance on energy supply from external sources. This paper offers a unique look at energy recovery in sulphuric acid plants and how recent innovations in MECS? Heat Recovery System technology make HRS more financially viable ? and more green - than ever.

Jan 1, 2009

By Y. R. Murthy, S. Angadi, A. K. Bhatnagar, S. K. Tripathy, L. O. Filippov

Dolomite is an essential raw material for the refractory industry, a flux in the iron and steel industry and also for the extraction of magnesium metal. Generally, particle size reduction, screening and classification are used for the preparation of the high-grade sized material for different applications, whereas low-grade fine fractions are not utilised. These fines or low-grade overburdens are dumped at the mine site for future utilisation, which creates environmental issues along with inadequate space management. In the present investigation, a detailed study was carried out to decrease the silica content of the low-grade dolomite fines from Gomardih , India, containing 28.6% CaO and 20.1% MgO along with 8.3% silica. Different process flow sheet options were evaluated with a combination of dry classifier, wet classifier, gravity concentrators as well as flotation. Different process variables were assessed along with mineralogical characterisation to optimise the process for efficient rejection of siliceous gangue minerals. Results indicated that dolomite, calcite and quartz are the major mineral phases present in the ore along with other minor minerals. It was concluded that two-stage flotation was an effective process for the reduction of silica up to below 1% after grinding to a particle size below 212 μm. A process flow sheet with a combination of gravitation air classifier and flotation can produce a concentrate with silica content below 4.5%. Keywords: Dolomite, flux, dry classification, flotation, characterisation, beneficiation

Jan 1, 2020

By R. Dehghan, M. Zarei, A. Tohry, S. C. Chelgani

Typical depressants for selective reverse flotation of iron oxides from complex silicates do not generally show high levels of efficiency. Therefore, as a hot topic, there are several ongoing investigations in this area. The main aim of this paper is exploring the potential of using humic acid (HA) as a depressant in reverse cationic flotation of hematite from complex silicates. For such a process, the wettability and flotation behaviour of pure minerals (hematite and silicates) was investigated at pH 10 in the presence of HA and cationic collector. Adsorption mechanism of HA on these minerals was measured by zeta-potential and FTIR. Results of flotation tests showed that at the lower concentrations of HA, selective separation of silicates from hematite is beneficial, where the floatability of amphibole was higher than pyroxene. A higher separation efficiency of hematite through reverse flotation was observed in the presence of amphibole, in comparison with the presence of pyroxene. Wettability studies showed that HA has a significant effect on reducing the hydrophobicity of treated minerals with the collector. The adsorption, ZPC and FTIR test results indicated that HA was adsorbed on both silicates and hematite. However, the absorption intensity onto hematite was much higher than silicates. It was found that the adsorption mechanism of HA on hematite takes place through both strong H-bonding and ligand exchange. Keywords: Reverse cationic flotation, humic acid, iron oxide, complex silicates, surface adsorption

Jan 1, 2020

By T. Nyakudarika

The Unki Platinum Mines concentrator, employing an MF2 circuit configuration which includes fully-autogenous primary milling of run-of-mine (ROM) ore, was commissioned in November 2010. The project was Anglo American Platinum?s first PGM concentrator in Zimbabwe and would form a significant contribution to the group?s platinum production. The project financials demonstrated that the project was operating-cost sensitive. After reviewing the metallurgical testwork, mineralogical examinations, and the history of similar operations, it became apparent that the Unki ore characteristics rendered it amenable to autogenous milling. The primary ball mill, structurally designed for 30 per cent steel load, could be operated at the required initial phase throughput with fully-autogenous primary milling, realizing savings in both power requirements and grinding media consumption. The original mill sizing had been done with fully-autogenous milling in mind, but allowing for flexibility and mitigation in case of varied mining fragmentation. Since attaining steady state, target grinds have been achieved. This paper looks at the Unki ore characterization programme, design considerations, and the operational and control philosophy for a successful comminution circuit, and discusses the design to produce a flexible, low opex, mitigated comminution and overall MF2 flowsheet that is easily expanded in line with the potential for optimum exploitation of the orebody.

Jan 1, 2012