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By J. Bal, V. D. Dao, W. Li

"SynopsisThis study proposes a methodology for evaluating the risk of coal bumps in multiple-seam longwall mining. Both the stress field and the total energy release (TER) during retreat were evaluated in the specified case involving multiple-seam mining using the LaModel program. The results of numerical simulations indicated that both the peak vertical stresses on the panel edges and the peak TERs in the outby longwalls increased significantly as the horizontal offsets were reduced from 60 m to zero. With the comprehensive consideration of the stress field and TERs, a conservative offset of 60 m was ultimately adopted when developing the gateroads of the lower panel in the field. The field measurements indicated that coal bumps were avoided completely by employing the proposed design, and the maximum roof-to-floor and rib-to-rib convergences of the tailgate during retreat were only 360 mm and 576 mm, respectively.IntroductionCoal bumps – sudden, violent bursts of coal – pose a serious threat to the safe excavation of coal. Their occurrence depends on the properties of the surrounding rocks, stress field, and dynamic disturbance. The complexity of the mechanism of coal bumps is further enhanced in multiple-seam mining due to seam interaction. Multiple-seam mining is most frequently found in the coalfields in eastern China, such as Xuzhou, Xinwen, Zaozhuang, and Huainan. In the past, due to issues of availability, economics, and ignorance of the potential risk in multipleseam mining, coal seams in such conditions were mined without proper planning to account for seam interaction. Fortunately, studies published over the past three decades have raised awareness of the problems associated with multiple-seam mining, and indicated that the ground control issues induced by multiple-seam mining can be avoided and/or minimized with proper planning.A number of technical studies pertaining to the design of multiple-seam mines have been published. These studies can be divided into two groups based on their methodologies of design: empirical (Chekan and Listak, 1993; Haycocks and Zhou, 1990, Matetic et al.; 1987a, 1987b) and numerical approaches (Li et al., 2000; Maleki, 2007; Mark, 2007; Peng, 2007; Zipf, 2005). The majority of the extant studies on the interaction mechanisms in multiple-seam mining have focused on the load transfer during operation, resulting in the proposal of the pressure bulb theory (Forrest et al., 1987; Haycocks and Karmis, 1983; Peng, 2008; Peng and Chandra, 1980) and pressure arch theory (Holland, 1973; Oram and Ponder, 1997) to guide multiple-seam mine design. However, neither, of these theories can be used to evaluate the potential for coal bumps."

Jan 1, 2015

By M. S. Shishvan, J. Sattarvand, R. S. H. Meij

Navigating miners during an evacuation using a smart evacuation technology can significantly decrease the evacuation time of an underground mine in case of an emergency. This paper presents a mathematical programming model to calculate the most efficient escape path for each miner as a critical component of the smart evacuation technology. In this model, the total evacuation distance of the crew is minimised and scenarios with blocked pathways, and stamina categories for the miners are simulated. It was found that all the tested scenarios are technically feasible. Using the feature that filters out blocked pathways has no downsides, as safer routes are calculated, and there is no penalty in the computation time. The paper also discusses the social and technical issues that need to be overcome before the algorithm can be implemented as an actual escape solution.

Sep 1, 2021

By I. Mitov, A. Stoilova, D. Krastev, B. Yordanov

We present three technological scenarios for the recovery of valuable components from gangue, stored in the tailings dam at Kremikovtzi metallurgical plant in Bulgaria, into marketable iron-containing pellets. In the first approach the iron concentrate was recovered through a two-stage flotation process, desliming, and magnetic separation. In the second proposed process, the iron concentrate was subjected to four sequential stages of magnetic separation coupled with selective magnetic flocculation. The third route entails the not very common practice of magnetizing roasting, followed by selective magnetic flocculation, desliming, and magnetic separation. The iron concentrate was pelletized in a laboratoryscale pelletizer. Each technology has been assessed with regard to the mass yield of iron concentrate, the iron recovery. and the iron, lead, and zinc content in order to identify the most effective route.

May 1, 2021

By C. Steyn, J. D. le Roux

A dynamic model is used to represent the single-stage closed grinding mill circuit at Mogalakwena North Concentrator. The circuit consists of a ball mill closed by a hydrocyclone. The circuit is modelled according to a semi-mechanistic non-linear dynamic model available in literature. An algebraic routine is used to fit model parameters to steady-state process data. Preliminary validation results against dynamic data indicate that the model is capable of capturing the main dynamic trends of the plant. Since classical system identification techniques proved insufficient to produce accurate models; the non-linear model can be used as a reliable source for model-predictive controller design. Keywords: Grinding, modelling, process control, parameter estimation

Jan 1, 2020

By K. E. H. K. Ishak, S. R. M. Zan

Cement production requires significant energy, and entails high costs and CO2 emissions. This is because the clinker requires very fine grinding. Grinding aids can improve production and fineness and decrease energy consumption by reducing the agglomeration of particles and protecting the balls and liners in the mill. In this study we compare the effects of three different grinding aids on clinker grinding using a ball mill. A commercial grinding additive, triethanolamine (TEA), and two industrial grinding aids (GAA079 and GAA088) were compared by ball milling tests, with additions of 0.05, 0.25, 0.50 and 1.00 wt%. The industrial grinding aids were characterized using gas chromatography-mass spectrometry (GC-MS). Particle size and morphological analyses were performed using SEM and XRD. The best results were obtained with 0.25% GAA088, which has a higher active component of diethanolamine isopropanolamine (DEIPA) than TEA. The unique combination of TEA and DEIPA in GAA088 enhances grinding efficiency and significantly improves the particle size distribution compared to TEA alone.. The grinding aids produced smooth rounded particles, which have a smaller specific surface area, enhancing the quality of the cement. XRD showed no significant structural distortion with or without grinding aids, and it was also found that the grinding aids helped decrease ball coating during grinding. The use of grinding aids can significantly improve clinker production and fineness while decreasing energy consumption, which can help reduce the costs and CO2 emissions associated with cement production.

Sep 6, 2023

By M. G. Maruma, L. A. Mampuru

"Mill liner wear is a major cost item in the mining industry and there is continuous research to prolong the life of the liners. Over the years it has become apparent that even though high-chromium white cast irons are highly efficient as abrasion-resistant materials, a combination of wear resistance and fracture strength remains difficult to achieve. Increasing the hardness of the high-chrome white cast iron (HCWCI), which improves the resistance to abrasion wear, is often accompanied by a deterioration in fracture strength. Operational conditions inside the mill require that the liner should be made of highly wear-resistant material with some fracture strength. Vanadium additions ranging from 0.2 to 3 wt% were made to HCWCI in an attempt to refine the microstructure. It was found that an increase in vanadium content promotes grain refinement. A content of 1.5-3 wt% gave the best results as measured by the maximum breaking strength.IntroductionOver the years it has become apparent that even though high-chromium white cast irons are highly efficient abrasion-resistant material, a combination of excellent wear resistance and fracture strength remains difficult to achieve. The exceptional wear resistance of highchromium white cast iron (HCWCI) is attributed to hard chromium carbides embedded in an austenitic/martensitic/pearlitic matrix. When the chromium contents exceed 12 wt%, interconnected MC3-type carbides of conventional cast irons are replaced by rodshaped and isolated M7C3 carbides (Powell, 1980), leading to an improvement in the impact toughness, ductility and fatigue resistance. However, the main M7C3 carbides in HCWCI are hard and brittle and can provide an easy path for crack propagation. This limits the applications of HCWCI, particularly in severe impact conditions. Most operations involving HCWCI are in crushing and grinding and the life of a part/liner is limited by its wear resistance. However, improving the wear resistance of HWCI comes at the cost of a significant reduction in fracture strength. Concerns about premature failure of HCWCI mill liners in the mining industries prompted a study to improve the wear resistance and mechanical properties of HCWCI."

Jan 1, 2016

By K. C. Corin, M. S. Manono

The mining and mineral concentration of Cu-Ni-PGM sulfide ores in South Africa occurs in semiarid regions. The scarcity and availability of water resources in these regions has become one of the biggest challenges facing mineral concentrators.S Owing to this challenge, concentrators have to find ways through which they can manage and control their water usage. Recycling and re-use of process water in mineral concentrators has therefore become common practice. This practice is beneficial in that it reduces reliance on municipal water, harnesses compliance to stringent environmental regulations on water usage, and it also offers a better response to the Sustainable Development Goals. This could however be somewhat concerning to the operator as recirculated water often has higher concentrations of ions compared to fresh or potable water. The unintended change in the process water quality may potentially affect critical aspects of flotation such as the stability of the froth. This has led to the need to find those process water ions that have the greatest impact on froth stability. Thus, this paper investigates the effect of various ions common in process water of a typical Cu-Ni-PGM concentrator on froth stability. Bubble size, water recoveries, foam height, and dynamic froth stability in both twophase and three-phase flotation systems are used as proxies for froth stability. Findings of this study are deemed crucial towards the development of a process water management protocol in sulfidic Cu-Ni- PGM ore concentrators. Keywords: Bubble diameter, electrolytes, flotation, froth stability, water quality

Jan 1, 2020

By E. K. Mutinda, D. K. Maina, R. M. Kasomo, B. O. Alunda

Assessment of blast fragment size distribution is critical in mining operations because it is the initial step towards mineral extraction. Different empirical models and techniques are available for predicting and investigating the consequences of blasting, one of which is the Kuznetsov Cunningham-Ouchterlony (KCO) model. In this paper we summarize the advances in the empirical models from inception until now, and explore the improvements that have been made so far with particular emphasis is on the most recent KCO model. Utilization of the model and the errors that arise between expected and the actual outcomes are analysed. The results indicate that the KCO model remains useful for predicting the blast fragmentation at limestone mine sites, despite the availability of other advanced prediction models. It is also a valuable instrument for pre-surveying the impact of varying certain parameters of a blast plan.

Mar 1, 2021

By K. Wu, X. Yuan, R. Du, C. Chao

"Lump coals are currently employed to replace part of coke in the COREX melter-gasifier for ironmaking. In order to optimize the process, the pyrolysis kinetics of Datong coal used in the COREX process was studied. A sectioning method is proposed to overcome certain shortcomings of traditional methods for studying the pyrolysis of coal. Based on the sectioning method and the characteristics of the coal pyrolysis process, the temperature range was divided into three intervals. In the first, the adsorbed gas and water of crystallization were removed; in the second, the coal was transformed into semi-coke; and finally, the semi-coke was further coked. Three models of reaction were then established to study the different stages of the pyrolysis process: an interfacial chemical reaction model, a random pore model, and internal diffusion with shrinking volume. The results showed that the experimental data fitted the models well, with all correlation coefficients (r2) exceeding 0.97. Finally, the mechanisms of reaction and kinetic parameters for each temperature range were derived, which laid a necessary foundation for optimizing the usage of non-coking coal in the COREX process. IntroductionIn view of environmental concerns and the shortage of good-quality coking coal, the COREX process was designed as a new ironmaking technology, attracting wide attention (Fang et al., 2005). In this process, lump coal and a small quantity of coke are directly charged into the melter-gasifier, where a high-quality reducing gas is generated for the reduction of the iron ore (Kumar et al., 2009). In contrast to the conventional blast furnace (BF) process, non-coking lump coal is used as the reducing agent and as the energy source, and the iron charge consists of lump ore and/or pellets, which results in the elimination of the coke oven and sintering plant as well as a decrease in investment (Kumar et al., 2009; Liu et al., 2012).Although the COREX process has made great progress, in current production practice the energy consumption greatly exceeds that of the BF, and it requires a certain amount of coke to maintain permeability of the semi-coke bed (Wang et al., 2008). In addition, the process consumes a lot of good-quality lump ore and lump coal. The pyrolysis of coal is the first step in most coal conversion processes, such as carbonization, gasification, and combustion (Aboyade et al., 2013). The reaction behaviour of lump coals in the COREX melter-gasifier is crucial, as it determines energy utilization and gas composition, as well as the metallurgical properties and particle size of the semi-coke produced (Prachethan et al., 2011; Zhang et al., 2014). In order to optimize the process and improve its competitiveness, the pyrolysis kinetics of Datong coal used in Baosteel’s COREX C-3000 facility was studied."

Jan 1, 2016

By R. L. Setsepu, S. O. Bada, J. Abdulsalam

The utilization of biomass as a solid fuel for co-firing has received great attention from boiler manufacturers as a clean coal technology (CCT) option. This research aimed to produce biocoal pellets, as a clean energy fuel, using hydrochar from trees planted to rehabilitate acid mine drainage (AMD) water and fine coal discards. The hydrochar was synthesized by hydrothermal carbonization of Searsia lancea harvested from AMD-contaminated land at a temperature of 280°C and a residence time of 90 minutes. It was blended with discard coal (–1 mm) at ratios of 25% and 50% hydrochar to produce different forms of solid pelletized biocoal (BC). The physicochemical and mechanical properties of each of the biocoal pellet blends were determined. The 100% hydrochar had the highest calorific value of 29.99 MJ/kg, while the raw discard coal had a calorific value of 16.73 MJ/kg. The ash content decreased from 42% in the discard coal to 25% in the blend of 50% coal and 50% hydrochar biocoal pellets. Biocoal pellets comprising 25% hydrochar and 75% discard coal (BC25 HC/75 COAL) displayed the best mechanical properties (compressive strength 3.06 MPa) of all the fuels, but the physicochemical properties were inferior to the BC50 HC/50 COAL pellets. This research has demonstrated that hydrochar synthesized from a tree species planted for hydraulic control of AMD has the capability to act as a binder for improving the mechanical properties and energy characteristics of fine discard coal.

Dec 1, 2021

By M. Seerane, R. Machaka, P. Ndlangamandla

"Metal injection moulding (MIM) is a near-net-shaping powder metallurgy technique suitable for the cost-effective mass production of small and complex components. In this paper, the effects of the metal powder particle size on the final properties of 17-4 PH stainless steel are reported. Three different particle sizes (d50 33.0, 7.91 and 4.04 µm) were used to prepare the injectable MIM feedstocks using a CSIR-developed wax-based binder system at a fixed solids loading of 60 vol.%. The distribution slope parameter and the rheological flow index behaviour were used to predict the flowability of the feedstocks. The effects of the particle size on MIM products were established. The results are discussed in terms of the subsequent microstructural and mechanical properties of MIM 17-4 PH stainless steel against the established MPIF Standard 35. IntroductionMetal injection moulding (MIM) is a near-netshape manufacturing process established as an alternative to produce complex small-tomedium shaped components that were previously fabricated by conventional methods at higher costs (Attia and Alcock, 2011; Todd and Sidambe, 2013).Although recent advances in micromanufacturing (mainly machining and electrodeposition-based) have enabled the fabrication of complex micro-size geometries directly into miniaturized parts, these processes are generally neither routine nor easily accessible at present (Attia and Alcock, 2011).Typically, the MIM process consists of four steps: mixing, injection moulding, debinding and sintering. Mixing involves blending of the desired metal powder composition with carefully selected multicomponent organic binders at the right proportion. This mixture, which is called feedstock, is then injected into a mould of a required shape to form a ‘green part’. Debinding is the removal of the binders by chemical, thermal, or catalytic means while maintaining the shape of the part. Finally, the debound part is sintered to a full or near-full density part (Sotomayor, Varez and Levenfeld, 2010). The MIM process is essentially a combination of plastic injection moulding with conventional powder metallurgy technologies."

Jan 1, 2016

By J. C. Barry, J. H. van Laar, P. L. Crouse, H. Bissett, I. J. van der Walt

"Plasma-assisted spheroidisation of metal powders offers several technical advantages with respect to both the ease of materials handling and powder-metallurgical item manufacturing. Advantages include improved flowability, increased powder packing density, elimination of internal component cavities and fractures, changes in morphology resulting in decreased friction between particles and contamination during pneumatic transport and enhanced particle purity. In this empirical study, spherical iron particles were produced using a microwave plasma operating at atmospheric pressure and characterized using optical microscopy and SEM techniques. Iron powders were fed into the system at fixed operating conditions, resulting in particles with spherical structures. The theoretical estimate of the time required for melting to occur is 1.6 ms, an order of magnitude smaller than the actual residence time. IntroductionParticle design and functionalization has become an increasingly popular aspect of materials synthesis and powder-metallurgical item manufacturing. One such technique involves the spheroidisation and densification of feed materials, typically in the form of chemical powders with wide particle size distributions. The major benefits of powder spheroidisation include improved powder flowability, increased powder packing density and powder purity, reductions in internal voids and defects, as well as the ability to manipulate the particles surface morphologies (Boulos, 2004). Thermal plasma processing has the potential for scale-up and for producing industrial quantities of spheroidised powder.Thermal plasma technologies offer a wide spectrum of material synthesis and treatment options, amongst others the synthesis and spheroidisation of nano-sized ceramic and metal particles (Kumar and Selvarajan, 2006). The spheroidisation process occurs within the plasma discharge via in-flight heating and melting of the powder feed material, given high enough plasma temperatures (Fridman, 2008, p. 495). Surface tension in the molten droplets results in spherical, or nearly, spherical, powder particles being formed upon exiting the plasma discharge where the droplet undergoes rapid cooling and freezes. Quite often, the bulk density of these spherical particles is higher than that of the starting material (Boulos, Fauchais and Pfender, 2013, p. 42). The different plasma spheroidisation techniques reported include radio frequency (RF) induction thermal plasmas (Jiang and Boulos, 2006; Karoly and Szepvolgyi, 2005; Yuming, Junjie and Yanwei, 2013), nontransferred direct current (DC) thermal plasmas (Chaturvedi et al., 2014; Kumar and Selvarajan, 2008; Suresh, Selvarajan and Vijay., 2008) and microwave-assisted plasma processing methods (Chen, Gleiman and Phillips, 2001; Vanamu et al., 2004; Weigle et al., 2004)"

Jan 1, 2016

By K. Barani, F. Moradpouri, M. Godarzi

A sampling campaign carried out on the lead flotation circuit at Lakan lead-zinc processing plant demonstrated that the Pb recovery was only about 68-69%. Characterization of the Pb flotation tailing showed that 61.4% of the Pb is in the –37 μm size fraction, which is difficult to recover by flotation. Batch flotation experiments were carried out on a plant sample of the lead flotation feed and high-intensity conditioning (HIC) was used to improve flotation recovery. The results showed that increasing the collector conditioning time from 1 to 3 minutes significantly increases the Pb recovery from 42.5% to 57.3%. Further increases in conditioning time to 5 to 7 minutes decreased the Pb recovery. With a collector conditioning time of more than 3 minutes, due to the surface cleaning effect, increasing collector and frother dosage improved the flotation selectivity and recovery, even at higher collector dosages. The Pb recovery increased from 69.1% to 79.8% with increasing impeller speed from 600 to 1250 r/min. HIC increases the flotation kinetics and greatly improves the flotation recovery and concentrate grade.

Apr 2, 2022

By R. Kumar, N. R. Mandre

"The beneficiation of iron ore slimes by selective flocculation was studied. Polyacrylamide (PAM) and guar gum were used as flocculant, along with sodium hexametaphosphate (SHMP) as a dispersant. The samples collected were initially subjected for chemical and mineralogical studies. The mineralogical studies indicated the presence of haematite and goethite as the principal iron-bearing minerals, with quartz and kaolinite as gangue minerals. The selective flocculation tests showed that the Fe grade can be enhanced from 58.24% to 64.60% Fe at a recovery of 66.33% using polyacrylamide as the flocculant. A Fe grade of 63.20% at a recovery of 68.04% was obtained using guar gum as flocculant. The efficacy of the studies was analysed using a separation index, which indicated that the higher separation index was obtained with the tests employing polyacrylamide as the flocculant. IntroductionIndia is endowed with huge reserves of highgrade iron ore and is one of the prominent producers in the world. As the high-grade iron ores have been exhaustively mined, it has become imperative to use low-grade iron ores, fines, and slimes to meet the growing demand. Also, generation of fines and slimes during mining and processing contributes to loss of minerals to the extent of 30% of the total value (Mandre and Panigrahi, 1997). These fines/slimes are often discarded as waste into tailing ponds, containing considerable amounts of iron. Therefore beneficiation of tailings/slimes has become necessary for optimal utilization of the resources.In recent years, interest in recovery of valuable minerals from low-grade ores, slimes, and tailings has increased worldwide. These activities are initiated not only to recover minerals but also to address various environmental issues associated with fine particle treatment. The literature reveals that several technologies have been employed in this regard, including flotation, advanced gravity separation, and high-intensity magnetic separation. However, these processes are found to be ineffective for fine particle treatment due to lower collision probability in flotation, decreased gravitational effect in gravity separation, and reduced drag force in magnetic separation, among other factors (Batisteli and Peres, 2008; Das et al., 2007; Dworzanowski, 2012; Rocha, Caneado, and Peres, 2010). Therefore, it is in this regard that selective flocculation has gained importance in treating slimes in recent years."

Jan 1, 2017

By V. Jokovic

Hydrocyclones are the most commonly used classifiers in the mining industry. The reason for this is their low operating cost and a small footprint. Data from plant trials where screens replaced hydrocyclones indicated that lower bypass of fines and sharper separation could improve breakage rates, with a positive effect on flotation circuit performance throughput. Despite the importance of classification, hydrocyclones have not received as much attention as more expensive comminution units, and their technological progress has been incremental. Noticeable water split (Rf) reductions of a semi-inverted hydrocyclone have been reported in the past. According to theory, the hydrocyclone with reduced Rf will improve classification of fines. A classification study using semi-inverted hydrocyclones was conducted to determine if a hydrocyclone could be operated in a way that would minimise misclassified fines. The classification performance of a semi-inverted hydrocyclone will be presented in this paper and other potential applications will be discussed. Keywords: Semi-inverted hydrocyclone, water split, misclassification of fines

Jan 1, 2020

By M. A. El-Sayed

"Double oxide films (bifilms) are significant defects in light alloy castings that occur when, during melt handling, the oxidized surface of the melt is folded over onto itself and then entrained into the liquid metal, encapsulating a portion of the local atmosphere. These defects create crevices in the final castings and have been shown to decrease tensile and fatigue properties, and also to increase their scatter, making casting properties unreproducible and unreliable. This paper reports on two different experiments performed to study the behaviour of such defects in Al alloys. In the first experiment and as a proxy for a bifilm, air bubbles were held in an Al-5Mg alloy melt for varying periods of time before the melt was allowed to solidify. The composition of the gas content of the bubbles was subsequently analysed using mass spectrometry to ascertain how it changed with time. In the other experiment the influence of the age of bifilms on the mechanical properties of Al-5Mg castings was assessed by holding castings in the liquid state for different times before solidification, followed by mechanical property testing and SEM and EDX studies of the fracture surfaces of tensile test bars. This research could provide a better understanding of the behaviour of double oxide film defects, and may lead to the development of new techniques by which these defects could be eliminated, or at least deactivated, in light alloy castings. Introduction One of the major structural defects affecting the reproducibility of mechanical properties of aluminium castings is the double oxide film defect (El-Sayed and Essa, 2017; El-Sayed and Ghazy, 2017). This type of defect is usually created as a result of poor filling system design. Owing to the very high reactivity of liquid Al-Mg alloy with oxygen in the air, the surface of the liquid metal can be considered to be permanently coated with an oxide film (Weigel and Fromm, 1990). As a consequence of surface turbulence, the oxidized metal surface can become folded over onto itself, but not fused, and then submerged into the bulk liquid, with a portion of the mould atmosphere being entrapped within it (Campbell, 2003; Al- Sayed, 2016; El-Sayed, Hassanin, and Essa, 2016)."

Nov 1, 2018

By J. D. Zhou, F. Yang, X. G. Bi

"In this investigation, the phosphorus distribution ratios in the CaF2 system and B2O3 system dephosphorization slags for high-phosphorus hot metal pretreatment were measured by an indirect method under laboratory conditions. Firstly, the phosphorus distribution ratio between liquid slag and solid iron was measured, and then the phosphorus distribution ratio between liquid slag and hot metal was calculated. Phosphorus capacity was calculated in terms of the composition and optical basicity of the slag. Dephosphorization slag was also studied by scanning electron microscopy, energy dispersive analysis, and X-ray diffraction analysis. The experimental results show that the phosphorus capacity of the B2O3 slag system is much greater than that of the CaF2 system. It is demonstrated thatB2O3 can completely replace CaF2 as fluxing agent for high-phosphorus hot metal pretreatment. With CaF2 as fluxing agent, the phosphorus capacity increases with increasing CaO content in the slag, but the phosphorus distribution ratio decreases. B2O3, when used as fluxing agent, can react with high melting point phases such as 2CaO·SiO2 and 3CaO·P2O5 in the slag to form new phases with low melting points such as 11CaO·B2O3.4SiO2, 2CaO·B2O3.SiO2, and Ca9.93(P5.84B0.16O24) (B0.67O1.79), thereby acting as a fluxing agent. When the ratio of w(B2O3)/w(CaO) is 0.16, the phosphorus distribution ratio reaches its maximum value, that is, the dephosphorization ability of the slag is at its maximum. IntroductionAs international iron ore prices continue to rise, the development of China's steel industry is facing a lot of pressure. Against this background, development and utilization of domestic high-phosphorus iron ore resources is particularly important. When highphosphorus iron ore is used in ironmaking, the phosphorus content in the hot metal can reach 0.35% or more, and the hot metal must be pretreated. For hot metal with 0.08–0.10% dissolved phosphorus, the traditional hot metal dephosphorization pretreatment technologies are relatively mature. However, when using these methods to dephosphorize hot metal containing 0.35% P or more, the amount of dephosphorization slag can reach 100–150 kg per ton of hot metal. Furthermore, the traditional dephosphorization methods require the addition of large amounts of CaF2 as fluxing agent, and this results in high fluoride levels in the dephosphorization slag. The fluorine in the slag can partially dissolve in water and thereby causes high fluoride concentration in the water and soil. Once the fluoride is absorbed by humans or animals, it can result in toxic effects on the central nervous system and myocardium. In addition, fluoride can accumulate in the environment, and thereby pose a health risk to animals and humans through the food chain (Li, 2007; Liu, Wang, and Dong, 2011, Diao, 2013). The objective of this research is to replace CaF2 with B2O3 as fluxing agent while achieving the expected goals of hot metal pretreatment."

Jan 1, 2016

By T. Matlou, S. Myendeki, V. Midzi, T. Zulu, H. Mabotja, T. Mulabisana, B. S. Zulu, L. Hlatshwayo, T. Makhateng

The Council for Geoscience (CGS) performed a macroseismic investigation following the occurrence of an earthquake in the Boksburg area on 11 June 2023. The event had a magnitude of ML 4.4 and a focal mechanism that showed the event as having strike-slip motion along a northwest-southeast oriented fault. The event resulted in aftershocks, some of which occurred away from the causative fault in the east in an area without a mapped fault. However, the cluster of past events in that area suggests that there is an active fault. Due to the size of the main earthquake, a macroseismic survey was conducted to determine its impact on the community in the region. Analysis of observed data obtained from questionnaires resulted in the creation of 153 intensity data points. Their distribution showed high intensity values close to the earthquake source area. However, the investigation highlighted a number of anomalies, such as the higher than expected intensity values observed far from the event epicentre. It could be that these anomalies are caused by site conditions, for example, amplification of ground motion due to thick soil layers.

Jan 12, 2025

By N. Duda, P. Śliwiński, P. Stefaniak, B. Jachnik

Ventilation and air-conditioning are some of the most energy-consuming processes in deep underground mining. Additionally, the energy consumption of these processes systematically increases along with the expansion of the mine. Therefore, proper energy efficiency assessment and consumption forecasts of these systems are particularly important in modern mines for ongoing tracking and planning of the likely costs. In the article, a short-term prediction model for surface air–conditioning stations is described. This model takes into account dependencies that were identified, based on the data from the supervisory control and data acquisition (SCADA) systems. These dependencies between the response value and the external conditions are then incorporated into the model. This way, for example, the ambient temperature or the total number of specific days of the week (with sometimes significantly lower or higher than the weekly average energy consumption levels) are included. Taking into account these dependencies, and e.g. forecasted average monthly temperatures allow us to include the seasonality of energy consumption in the presented model. In the article, a sample energy efficiency analysis of the A/C system based on an example of the KGHM Polish Copper Polkowice-Sieroszowice mine is performed. The results of the solution proposed in the article are then evaluated, and compared to the currently functioning, more basic forecasting methods. However, given the general nature of the dependencies used in the model, similar solutions could be used in other case studies.

Sep 1, 2021

By M. Bryson, G. Marap, M. Ntlhane, M. D. Hlahane

This study investigated flotation of phosphate from a low-medium grade 8-12% P2O5, 65-73% SiO2 sedimentary phosphate ore from Kropz Elandsfontein (herein referred to as Elandsfontein) in South Africa. Quantitative evaluation of minerals by scanning electron microscopy (QEMSCAN) was used to determine apatite grain size distribution, liberation and mineral association in the F2 horizon sample. The mineralogy indicated that apatite was liberated and for the Elandsfontein plant to operate at the design throughput, the flotation feed has to be milled to a coarse grind ranging between 300 μm and 425 μm. Reverse flotation process routes using varying reagent dosages, and flotation feed top sizes that could possibly yield a final product of 31% P2O5,10% SiO2 at a reasonable +70% P2O5 recovery were investigated. Based on the results, a split circuit of coarse (-300+212μm) flotation and fine (-212+20μm) flotation, was mostly preferred as compared to treating the whole ore. A final combined concentrate of 31% P2O5 and 10% SiO2 with P2O5 recovery of 84% could be produced from the reverse split circuit. The robustness of reverse flotation for both coarse and fine fractions was further investigated. Reverse flotation of the fines fraction was found to be robust and produced a final product of 31% P2O5. It was however more challenging to achieve the required product grade and recoveries on the coarser fraction (-425+212μm), suggesting that reverse circuit was not adequately robust at fractions coarser than 300μm. Keywords: Phosphate, sedimentary, reverse flotation, particle size

Jan 1, 2020