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By P. G. Toledo, R. I. Jeldres, G. R. Quezada

Chile is the main producer of copper in the world and lately the mining industry has suffered challenges due to the lack of water in the north of the country, along with the new policies of not using fresh water for the industry. This has prompted the use of seawater as an alternative source for mining. Several studies have been driven due to this new scenario, which have shown that seawater can be beneficial, if certain ions are removed from the process. This is the Mg that generates precipitates at high pH, that have been shown to make mining operations difficult. In particular, thickening operations are impaired by the presence of Mg ions, where aggregate formation and sedimentation decreases substantially. Our studies suggest the competence of the precipitates in adhering to the polyacrylamide (HPAM) flocculant and not towards the surface of the quartz minerals. This motivates the present work to use molecular dynamics to study the adsorption of a HPAM molecule on quartz surfaces and the surfaces formed by Mg precipitates. The surfaces are immersed in a saline solution or seawater that includes the HPAM molecule. Results are obtained by measure the adsorption frequency and duration. We obtained that the HPAM molecules are preferably absorbed on the surfaces of magnesium hydroxide. This gives us a good agreement with what is observed experimentally and strengthens the premise of the competition of hydroxide with the flocculant. Keywords: Molecular dynamics, adsorption, tailing flocculation, magnesium removal

Jan 1, 2020

By A. Navarra, A. Quelopana

The mine production scheduling problem (MPSP) has been studied since the 1960s, and remains an active area of computational research. In extending the concepts of the MPSP, the automated mine may now be regarded as a hierarchical intelligent agent in which the bottom layer consists of distributed robotic equipment, while strategic functionality occupies the higher layers. Here we present a disambiguation of artificial intelligence, machine learning, computational optimization, and automation within the mining context. Specifically, the Q-learning algorithm has been adapted to generate the initial solutions for a high-performing strategic mine planning algorithm, originally developed by Lamghari, Dimitrakopoulos and Ferland, based on the variable neighbourhood descent (VND) metaheuristic. The hierarchical intelligent agent is presented as an integrative conceptual platform, defining the interaction between our new Q-learning adaptation and Lamghari’s VND, and potentially other hierarchically controlled components of an artificially intelligent mine, having various degrees of automation. Sample computations involving Q-learning and VND are presented.

Dec 1, 2021

By P. T. L. Koh, M. P. Schwarz

A series of parametric studies were carried out for a flotation cell using computational fluid dynamic (CFD) modelling to determine the local response of hydrodynamic performance measures to change in operating conditions. As an example, an Outotec cell was used to carry out the response analysis. The hydrodynamics of the flotation cell has been previously investigated by laboratory measurements presented by Schwarz et al (2019), and a CFD model of the cell was developed and validated using these measurement data (Schwarz et al., 2019). In this work, parametric studies have been performed by modelling the flotation cell at different stirring speeds and gas flowrates, varying above and below standard conditions. Predictions of void fraction, bubble size, bubble surface area flux and particle–bubble collision rate are presented showing the effects of increasing and decreasing stirring speed and gas flowrate around the base case. Generally, the total gas holdup in the flotation cell was found to increase with increasing gas flowrate. The bubble diameter was found to decrease with increasing stirring speed and increase with increasing gas flowrate. The collision rate increased with both stirring speed and gas flowrate. The parametric results show that there is a correlation between the bubble surface area flux Sb which is affected by stirring speed and gas flowrate, and the particle–bubble collision rate. With the collision rate as an indication of flotation collection, it is also possible to show that cell performance can improve more by increasing stirring speed than by increasing gas flowrate in a situation where everything else remains constant. The CFD results can form the basis for a Response Surface Method (RSM) analysis which can then be used for automated optimization of cell performance. Keywords: Flotation kinetics, computational fluid dynamics, bubble surface area flux, particle-bubble collision rate

Jan 1, 2020

By S. Mohanta, B. C. Melkap

"SynopsisDry beneficiation of coal by air dense medium fluidized bed is an emerging trend. It is widely believed that the particle size of the medium has a significant effect on the separation efficiency. This investigation demonstrates that medium particle size has a major effect on separation efficiency. Experimental results show that different size fractions of the same feed respond differently to the same size fraction of medium solids. Furthermore, a particular size fraction of feed coal responds differently with different size fractions of medium solids. The Ep values and overall metallurgical performance parameters, obtained from experimental results, clearly indicate the superior performance of an air dense medium fluidized bed separator when using –150+106 µm magnetite powder as the fluidizing medium. These observations reinforce the importance of sizing the medium particle size for the air dense medium fluidized bed.IntroductionIn an air dense medium fluidized bed (ADMFB), a fluidizing bed of a particular density is created by suspending solid particles in an upward air flow. A feed containing coal particles of different densities is introduced into this fluidizing bed. The particles with relative density less than the bed density float on the top of the bed, while particles denser than the bed density sink through it. Since there is a general correlation between ash content and density of coal particles, it is possible to remove ash-forming impurities from a raw coal to the required level by regulating the density of the fluidizing bed. Recently, the ADMFB process has received significant attention world-wide for its specific advantages of low operating cost and less restrictive for small capacities (Luo and Chen, 2001; Houwelingen and de Jong, 2004; Dwari and Hanumantha Rao, 2007; Sahu et al., 2009; Mohanta et al., 2012). This process is not recognized as a well-established industrial practice because of the availability of efficient wet processing technology. However, with the revival of interest in dry beneficiation of coal in general, and ADMFB in particular, there is a concerted effort to improve the efficiency of the ADMFB process, and successive improvements have made the process a competitive and viable option for beneficiating coal."

Jan 1, 2015

By John Taylor

?Introduction to Black Mountain ?Historical metal accounting practice ?Metal accounting audit ?Feed measurement ?Sample precision ?Concentrate measurment ?Current metal accounting practice ?Further refinements to the metal accounting practice

Jan 1, 2005

By M. Steyn

This article captures the intrinsic differences of thermal coal products, their utilization and their substitution characteristics. South Africa produces approximately 245 million tonnes of coal annually. Eskom consumes 46% (approximately 112 million tonnes), 26% (approximately 65 million tonnes) is exported, and SASOL Synthetic Fuels consumes 18% (approximately 44 million tonnes) and a further 9% (approximately 22 million tonnes) is consumed by domestic users in various different industries. Marketing theory contributes significantly to understanding the importance of technical product and quality appreciation and comprehension, encompassing elements of price, distribution, and promotion. Coal product specification is determined by the inherent geology of a resource and the number of complex actions to market the product to a specific consuming market. Sampling, analyses, beneficiation application, and an array of parameters contribute to matching thermal coal products to the value-in-use it provides to the different markets and its consuming industries. Coal producer shave come under increased scrutiny since South Africa has been experiencing electricity shortages since early 2008. General misunderstandings were declared on public forums and in the media by both legislators and the South African public since a perception developed that South African coal producers are exporting coal that could be utilized by Eskom.

Jan 1, 2010

By D. Francois-Bongarcon

The ?Poisson effect? is defined and characterized. It takes place even when the material to sample is not liberated. Gy, Pitard, Ingamells, and others, including the author, recommend that a minimum average number of particles of mineral of interest characterize the recommended sample size. How many? Recommended numbers range from 6 to 40 particles depending on authors, corresponding to standard deviations of 41% to 16%. Some guidelines are proposed, and the often alleged ?double-Poisson? effect is examined.

Jan 1, 2009

By H. D. Mtegha

Mining is important to the economies of both Tanzania and Namibia. Recently, both nations revised their national mineral policies to ensure future economic benefit. The main difference in the mineral policy-formulation processes followed by the two countries is identified as the degree and timing of stakeholder involvement during the articulation process. In the case of Namibia, the stakeholders were involved from the start in identifying issues and in suggesting policy solutions. In contrast, the Tanzanian process involved stakeholders after a framework had been developed by a task team. The Tanzanian emphasis was on attracting foreign investment into a traditionally state enterprise system of mineral investment and development. One can argue that the policies developed met the initial requirements, and both are, therefore successful, despite the different processes of policy formulation that were used. However, several fundamental questions arise as a result of the two approaches. This paper attempts to answer these questions by providing a comparison of the processes used for developing and formulating the mineral policies of Tanzania and Namibia. It concludes that the Namibian consultative process is perhaps more sustainable in the long-term because of its wider public support. Time will tell which of these policy-formulation processes provides a basis for sustainable economic growth for developing mineral economies.

Jan 1, 2010

Orebody modelling and reserve estimation are now subject to sophisticated procedures, but folded stratiform and stratabound deposits present particular problems in transforming coordinates of samples and blocks into their correct relative positions prior to deformation. In this paper an approach is taken whereby a geologically interpreted reference plane is used as a control. The study area is the Rio Tinto Minera copper mine near Santiago de Compostela, Spain. The transformation procedure on the 'unfolded' state is described, its limitations assessed and advantages considered.

Jan 1, 1987

While some of the practical details of ilmenite smelting are not well documented, there is a substantial body of literature on the principles of ilmenite smelting, and the behaviour of solidified titania slag. This information is summarized, focusing on the basic reactions, departure from equilibrium, the behaviour of impurities, and reactions of solidified slag. The emphasis is on the South African operations.

Jan 1, 2007

Nowadays, fully encapsulated rockbolts have become a key element in the design of ground control systems. The main reason is that they offer high axial resistance to bed separation. In this research, the load transfer capacity of a fully grouted bolt is evaluated analytically in an elastoplastic rock mass condition. The research considered the effect of bolt end-plate on load transfer capacity. Bolt and surrounding materials were assumed to be elastic and elastoplastic materials respectively. The load transfer mechanism of a fully grouted bolt is a function of parameters such as bolt length, shear stiffness of interfaces, in situ stress, presence of face-plate and distance along the bolt. These factors were analytically evaluated. Finally, the load along the bolt was predicted in different surrounding rock mass characteristics.

Jan 1, 2011

It is well known that the ability to influence project value reduces significantly as planning progresses and decisions regarding project parameters are made. However, at the prefeasibility stage in particular, where one of the main aims should be to evaluate a wide range of options in order to select the best for more detailed further study, there is often a reluctance to spend the time and money needed to do this rigorously. This paper demonstrates, by a number of case study examples, how significant increases in value may be obtained by fully evaluating the combinations of alternatives for various project design parameters, including (though not limited to) mining methods, haulage methods, mining rates, processing methods and rates, sequencing of mining, and cut-off grades, with changes and upgrades over time where applicable. The additional value unlocked is typically orders of magnitude greater than the additional cost of the more comprehensive study. The dangers of misuse of simplistic sensitivity analyses and failure to identify how strategies might change in response to changes in external factors are also illustrated, and the importance of selecting the best `grade descriptor' is discussed.

Jan 1, 2007

By K. M. Banks

The hot ductility of in situ melted tensile specimens of micro-alloyed steels having C contents in the range 0.12?0.17% (mass %) have been examined over the 700?1000°C temperature range. An improved testing method for simulating the continuous casting process was used, which takes into account both primary and secondary cooling conditions. Increasing the N content to electric arc furnace levels (0.01% N) was found to cause a serious deterioration in ductility. V-N steel gave better ductility than Nb-containing steels due to less precipitation. From a cracking perspective, low- N steels are generally recommended but, when not feasible, a combination of Nb and V gives even better ductility. However, to be sure of avoiding transverse cracking in higher N steels a small addition of Ti is required. This resulted in a decrease in the fraction of fine particles and in accord with this better ductility. Transverse cracking of industrial slabs was then avoided.

Jan 1, 2011

By N. A. Chapman

The effect of using conventional crushing and HPGR in combination with dry or wet milling was investigated using a base metal sulphide (sphalerite), and a PGM (platinum group minerals) ore in order to determine how these different processes affect the flotation performance. In the case of sphalerite, irrespective of the crushing procedure (HPGR or conventional), dry milling resulted in the highest grades and recoveries of zinc. Conversely, in the case of PGMs, a similar treatment produced the poorest results. The results were investigated further by comparing the relative effects of factors such as percentage liberation, particle size, and surface properties of the samples produced by the different milling procedures as well as the concentrates and tailings obtained from the flotation tests.

Jan 1, 2013

By B. M. Kunar

It is well known that job-related hazards and individual factors influence occupational injuries. However, research involving coalminers has been limited. This case-control study assessed the relationships of job-related hazards and individual/life style factors with injuries among underground coal miners. It compared 245 cases with at least one injury during the previous two-year period with 245 matched controls with no injury. The data were gathered via personal interview and analysed using the conditional logistic model. The significant risk factors were materials handling (adjusted OR 5.15), poor environmental/working conditions (2.63), geological/strata control-related hazards (2.35), lack of formal education (3.00), sleep disorders (1.86), alcohol consumption (2.32), disease (2.23), having a large family (5.40), and risk-taking behaviour (9.40). Machine-related hazards, sleep disorders and alcohol consumption primarily affected workers aged less than 45 years; whereas, environment/working condition-related hazards, presence of disease, smoking, risk-taking behaviour and large family size were more likely among workers aged 45 or over. Keywords: Occupational injuries, sleep disorders, job hazards, alcohol, coal miners

Jan 1, 2010

By J. Manchisi

Laboratory investigations were conducted to establish the feasibility of bioleaching a mixed copper oxide/sulphide rougher concentrate from Nchanga Mine on the Zambian Copperbelt. The objective was to determine the kinetics and extent of copper extraction for this material. Batch experiments were conducted under different solution conditions in stirred tank bioreactors. The progress of (bio)leaching was monitored through measurements of soluble ferrous and ferric iron, copper, pH, and redox potentials, while bacterial activity was monitored online through 02 and C02 gas utilization rates. About 20 per cent copper was solubilized within 2 hours in all cases of non-oxidative (abiotic), oxidative (abiotic), and bioleaching experiments. This was attributed to the dissolution of mainly copper oxides. Subsequently, bioleaching experiments resulted in an overall copper extraction of 93 per cent, with up to 8 g.L-1 copper after six leaching days, compared to 58 per cent copper extraction in the abiotic oxidative acid leaching experiments. However, there was little effect of time (i.e. poor dissolution kinetics) on copper recovery for abiotic non-oxidative acid leaching of the material. Hence, the rate of sulphide leaching increased due to the activity of bacteria. Thus, the material is potentially bioleachable under mesophilic conditions. However, more exhaustive test work needs to be conducted to establish the effect of bioleaching variables and heat requirement.

Jan 1, 2012

By L. A. Jagger

The world?s second largest producer of platinum, Impala Platinum Ltd, approved two new twin shaft projects at the end of September 2004, Nos. 16 and 20 Shafts. Both shaft projects are stand-alone entities and are being sunk from surface. Previously Impala had embarked on a strategy of extending the life of its third generation shafts by means declines. No. 16 Shaft is the first of a new fourth generation shaft complex, while No. 20 Shaft is the last of the third generation type shafts in the so-called shallow to intermediate mining zone. This paper details the basic designs of each project and covers the initial implementation. Although both projects are twin shaft systems, the access methods from the shafts to the reef horizon differ. Initiatives implemented to speed up the projects are also briefly covered.

Jan 1, 2006

Mixed integer programming (MIP) has been used for optimizing production schedules of mines since the 1960s and is recognized a shaving significant potential for optimizing production scheduling problems for both surface and underground mining. The major problem in long-term production scheduling for underground orebodies generally relate to the large number of variables needed to formulate a MIP model, which makes it too complex to solve. As the number of variables in the model increase, solution times are known to increase at an exponential rate. In many instances the more extensive use of MIP models has been limited due to excessive solution times.

Jan 1, 2010

By J Cahill, M Lee

Leinster Nickel Operations, located in Western Australia, consists of an underground and three open pit mines in relatively adverse ground conditions. This paper reviews our ground control practices in the open pits, covering aspects of ground support, wall control and monitoring. These methods have been effective in allowing mining operations to continue beneath unstable slopes. In particular, the use of Groundprobe?s Slope Stability Radar has enabled the Harmony Open Pit to safely operate for months following indication of failure from traditional methods. This case study highlights the benefits of investing in appropriate slope stability monitoring systems.

Jan 1, 2006

By F. T. Cawood

This article offers a personal and independent view on the threats to the sustainability of the South African minerals industry. It argues that if the six identified threats of insufficient spending on research and development, general standard of education, nationalization, inadequate infrastructure, Aids prevalence and labour inefficiency are not acted upon as a matter of urgency, the future of the mining industry, along with its important contribution to the economy, is at risk.

Jan 1, 2011