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By M. Cuba

Geostatistical modelling aims at providing unbiased estimates of the grades of elements of economic interest in mining operations, and assessing the associated uncertainty in these resources and reserves. Conventional practice consists of using the data as error-free values and performing the typical steps of data analysis - domaining, semivariogram analysis, and estimation/simulation. However, in many mature deposits, information comes from different drilling campaigns that were sometimes completed decades ago, when little or no quality assurance and quality control (QA/AC) procedures were available. Although this legacy data may have significant sampling errors, it provides valuable information and should be combined with more recent data that has been subject to strict QA/QC procedures. In this paper we show that ignoring the errors associated with sample data considerably underestimates the uncertainty (and consequently the economic risk) associated with a mining project. We also provide a methodology to combine data with different sampling errors, thus preserving the relevant global and local statistics. The method consists of constructing consistent simulated sets of values at the sample locations, in order to reproduce the error of each drilling campaign and the spatial correlation of the grades. It is based on a Gibbs sampler, where at every sample location, the actual sample value (with error) is removed and a conditional distribution is calculated from simulated values at nearby sample locations. A value is drawn from that distribution and kept only if it satisfies some statistical requirements-specifically, the global relative error and local means and variances must be reproduced. All sample locations are visited and simulated sample values are generated iteratively, until the required statistics are satisfactorily attained over all sample locations. This generates one realization of possible sample values, respecting the fact that the actual samples are known to carry an error given by the global relative error. Multiple realizations of simulated sample values can be obtained by repeating the procedure. At the end of this procedure, at every sample location a set of simulated sample values is available that accounts for the imprecision of the information. Furthermore, within each realization, the simulated sample values are consistent with each other, reproducing the spatial continuity and local statistics. These simulated sets of sample values can then be used as input to conventional simulation on a full grid to assess the uncertainty in the final resources over large volumes. The methodology is presented and demonstrated using a synthetic data-set for clarity.

Jan 1, 2012

By A. M. Bauristhene

Ti-64, which accounts for more than 50% of the worldwide titanium tonnage, has found commercial importance in industries requiring components with high specific strength and resistance to corrosion. Investment casting is the preferred production method due to the difficult machinability of the alloy. This study was aimed at investigating the mechanism and the extent of alpha case formation on Ti-64 components cast using the investment casting method with YFSZ (yttria fully-stabilized zirconia) shell moulds after vacuum induction melting. The extent of the reaction between the mould hot face and the molten metal has been studied by varying parameters such as soaking temperature and mould hot face composition, and examining their effects on the reaction with the mould. An increase in the soaking temperature had an effect on the alpha case, both in appearance and hardness, but had no effect on contamination levels by carbon, oxygen, and nitrogen. The depth of alpha case increased with soaking temperature, increasing from 35 µm to 161 µm with an increase in temperature from 1200°C to 1400°C. The micro-hardness profiles provided insight into the effect of the alpha case on the mechanical properties of the Ti-64 alloy by displaying hardness values of 1000 HV0.1 and above, but could not be solely utilized to determine the alpha case penetration depth due to microstructural differences in the unaffected Ti-64, in particular the martensitic microstructure that formed with a fast cooling rate from a higher temperature. Levels of expected contaminants such as Zr, Y, 0, and C were low. The addition of the colloidal zirconia binder affected the interfacial reactions. YFSZ proved to be a thermodynamically stable refractory material, with the alpha case possibly forming as a result of segregation.

Jan 1, 2013

By I. Y. Motovilov, S. A. Telkov, M. B. Barmenshinova, Z. S. Abisheva

As a rule, removing waste rock at the beginning of the process improves the conditions for the flotation of minerals, and also reduces the operating costs of crushing, grinding and flotation. Lead-zinc ores in the Shalkiya deposit of the Republic of Kazakhstan are classified as difficult for enrichment, but taking into account their significant reserves, they are one of the main potential ores for the production of lead and zinc. Under industrial conditions, for processing ores of the Shalkiya deposit, a selective flotation concentration scheme with the production of lead and zinc concentrates is recommended. However, according to the recommended scheme, it is not possible to obtain high-quality concentrates of lead and zinc, with high metal recovery. The paper presents the results of studies of preliminary gravitational enrichment of lead-zinc ore in the Shalkiya deposit. Based on the fractional analysis for the particle size range of -40+8 mm, Henri- Reingard enrichment curves were constructed, separation density (2730 kg /m3) was established to isolate the light fraction with the lowest possible lead and zinc content, and gravity enrichment indices (0.7-0.71) were determined. It was found out that when using gravitational enrichment of the original large-sized ore in the Shalkiya deposit, tails are released at the beginning of the technological process with a yield of up to 20% with the extraction of silica up to 30%, calcite up to 11% and carbonaceous matter up to 12%. As a result of the studies, it was found that the beneficiation of crushed lump ore could be conducted in heavy suspensions. One of the positive aspects of the use of gravitational enrichment is the reduction of energy costs for grinding the heavy fraction, which was experimentally proved in this article. Keywords: Lead-zinc ores, Shalkiya deposit, fractional analysis, gravitational enrichment, floating fraction, sunken fraction, separation density

Jan 1, 2020

By K. Naidoo, M. Pelser, J. Hagemann, K. C. Sole

The copper tankhouse at Rustenburg Base Metals Refinery is an essential component of the Anglo American Platinum value chain. The tankhouse uses starter-sheet technology that was adopted in the 1980s, so dependence on manually intensive labour and overall operational excellence has a significant impact on process performance. An efficient, stable, and sustainable electrowinning process contributes to minimising energy consumption and reducing operational costs, and enables improved product quality and increased throughput. Historic performance of this tankhouse has often been suboptimum over prolonged periods. An in-depth operational review of performance from 2018–2024 was carried out to understand challenges, risks, and high-impact factors that contribute to poor performance. Implementation of adherence to fundamental operational basics identified from global best practice, such as the frequency and quality of cell cleaning and maintenance, preventing backlogged harvesting or maintenance, preserving cell-top furniture conditions and integrity of electrodes, preventing short circuits and poor current distribution, and maintaining a high level of operational discipline, has since contributed to an era of exceptional performance. Root-cause analysis fault trees pertaining to poor current efficiency and high scrap rate are summarised. Current efficiency has significantly improved since 2021, now consistently exceeding 88%. The copper scrap rate, previously believed to be limited to a minimum of 4%, achieved a historic monthly low record of 2.06% in 2023. Chemical and physical quality has considerably improved, and cathodes exhibit minimal morphological defects.

Jun 27, 2025

By Z. Leng

"After detonation of the explosive, the final blast-induced damage area around the blast-hole falls into three categories, namely crushed zone, fractured zone, and elastic deformation zone. This paper presents a modified model to calculate the size of crushed zone around a blast-hole in drill-and-blast, with the hoop compressive stress and cavity expansion effect taken into account. The material in the crushed zone was assumed to be a granular medium without cohesion, but with internal friction. On this basis, the formula for crushing zone radius was derived. The proposed approach was verified with tests reported in the literature and the simulated results from SPH-FEM coupled models. A full statistical analysis was also carried out, and the predicted values were found to be in better agreement with the test results compared with other models. A sensitivity analysis of the modified model showed that the size of the blast-induced damage area is mainly affected by the following factors: rock mass properties, in situ stress, and borehole pressure. In particular, the roles of borehole pressure and in situ stress are discussed. Finally, suggestions are made on how the size of the crushing zones can be decreased. IntroductionOver the past decades, drill-and-blast has become the most commonly used technology in rock excavation. It is well known that in rock mass fragmentation with explosives, the annular rocks around the blast-hole are converted into fines. The formation of these fines consumes a significant part of the energy of the detonation, which in general is ignored in the determination of the efficiency of detonation (Glatolenkov and Ivanov, 1992; Furtney et al., 2012). Many studies show that only 20–30% of the total explosive energy is effectively used in fragmenting the rock, and up to 50% of the energy generated by conventional charges is wasted in overcrushing of the crushed zone and the inner part of the fractured zone (Ouchterlony et al., 2004; Sanchidrian et al., 2007). How to control the crushed zone to enhance the effective utilization of explosive energy, reducing the unit explosive consumption and the engineering cost, is therefore of great significance."

Jan 1, 2016

By C. G. Goncalves

The Gautrain rapid rail link project is currently Africa?s largest infrastructure project connecting South Africa?s major airport (OR Tambo), Johannesburg and Pretoria. Phase one is planned for completion in time for the 2010 FIFA Soccer World Cup and involves 80 km of track and 15 km of underground tunnels. The key shaft sinking blasting issues revolve around maximising advance and improving blasting cycles to meet the tight deadlines as well as environmental control which, in some cases takes place only 15m from the city infrastructure. To achieve success, DetNet South Africa supplied a range of electronic detonator systems to cater for the different blasting applications involved (tunnels, portals, shafts and viaduct foundations). One such product, QuickShot, was used for the first time in a major civil engineering project and has been used in most of the shaft sinking blasts to date. The QuickShot system combines pre-programmed electronic detonators with special on-bench components that enable the user to quickly and easily design the firing sequence solely by using the order of connections. This precludes the user from having to deal in absolute delay times. The connecting system enables benches to be hooked-up speedily by multiple users who have differing levels of experience. This paper provides details of how, after 33 months, the system has been embraced by the project by aiding in maximised advances, improved cycle times and meeting the required environmental constraints.

Jan 1, 2009

By Dick Minnitt

Large-scale variability in process plants and process control can be identified and controlled through disaggregating the overall variability in a process stream. Conventional statistics and Statistical Process Control (SPC) fail to address the concept of stream heterogeneity, therefore fail to identify and distinguish between the various sources of variability in a process stream. A modified set of 445 data from a process plant is used as an example to explain the benefits of variography in process control. Large-scale variability, usually in the form of product composition cycles and chemical cyclic variations may be manifest throughout a sampling system or a process plant, but this type of variability is most easily discernable in one-dimensional process streams. The Moving Average is a powerful tool for identifying large and small scale variability and cyclical behaviour in process streams, while the variogram is a custom built tool that allows the components of variability to be identified and resolved. The positions in the variogram at which the different variance can be read and the nomenclature of these types of variability is described. The transfer of variances converted to standard deviations to the Control Charts, allows an operator to appreciate the appropriateness of Upper and Lower control and specification limits. The overall contribution of the various sources of variability is represented in a pie diagram.

Jan 1, 2007

Careful monitoring of the position of the cave front is essential for well-managed block cave mining. Seismic monitoring systems yield 3-D information about the location of fracturing ahead of the cave. However, because the a seismic gap between cave surface and seismogenic zone is of unknown extent, the cluster of micro-seismicity can only yield an upper bound for the cave height. The large velocity contrast between the fractured rock in the aseismic gap and the broken loose material within the cave can be used by an inversion procedure to find a few simple geometric parameters (such as height of the top of the cave) if a simple 3-D shape?for example a paraboloid?is assumed for the cave. Ray-tracing must be used as the large velocity contrasts cause seismic waves to bend around the cave, but the inversion takes the form of a minimization problem in only a few dimensions and so the computational time is feasible. This technique has been successfully tested on realistic synthetic data.

Jan 1, 2007

By R. S. Sarracino, M. J. Louw, S. M. Vather

Two detonation models, IDeX for ideal VOD and CPeX for non-ideal VOD, were used to predict the velocities of detonation (VOD) of five explosives: ANFO, a bulk emulsion, and three repumpable emulsions (R100 Gold, R100 Diamond, and R105). The theoretical VODs were compared with the in-hole VODs of the explosives, and the predicted and actual values were found to be within experimental error for ANFO and the bulk emulsion. The results were not consistent for the repumpable emulsions. The discrepancies can be explained as being due to variations in mining and loading practices. The results show that the detonation models can be effective tools in predicting the behaviour of explosives in different diameters and rock confinements, provided that the user is aware of the factors that can affect the optimal usage of explosives and equipment.

Jan 1, 1993

By E. J. Y., G. J. McLachlan, E. Amini, Koha

Inferring individual component flotation rates from recovery-time data of ore complexes is important in optimising and designing minerals processing plants. However, existing two-component first-order flotation models are computationally intensive to solve using conventional non-linear least squares regression. In this paper, a Convolutional Neural Network (CNN) is used to approximate the inverse function which predicts the two-component first-order model parameters using recovery-time data. This paper compares the accuracy and computation speed of the proposed CNN against traditional non-linear least squares regression on 1 million generated data based on a known two-component firstorder kinetic model. It is shown that using a CNN is possible to approximate the inverse function for the non-invertible two-component model with recovery-time as an input matrix for convolution operations. The CNN method is 450 times faster to compute than the Trust-Region (TR) non-linear least squares regression algorithm. However, the CNN model is less accurate compared to the TR algorithm overall. Keywords: Flotation kinetics, convolutional neural network, inverse problem, modelling and simulations

Jan 1, 2020

By T. Moodleya, I. Govender

Despite the widespread use of DEM to simulate particle processes, comparatively little work has been done to evaluate its accuracy. One of the reasons is a lack of available measurement techniques that can capture dynamic information at the momentum transfer timescale which is lower than 10-6 s - typical of the kinetics occurring within the drum. This work makes use of Positron Emission Particle Tracking (PEPT), an in-situ method capable of measuring 3D kinematic data at 1000 frames per second. PEPT measurements are performed using 3 mm and 5 mm mono-size glass beads in a 300 mm diameter rotating drum at critical speeds that are relevant to industry. We undertake systematic ‘tuning’ of DEM with a view to optimising the agreement between experiment and simulation. To ensure an equitable comparison scale, both the DEM and PEPT data are coarse grained within representative volume elements. This work seeks to validate DEM predictions against experimentally derived PEPT kinematic measurements. Keywords: PEPT, nuclear imaging, DEM, Tumbling Mills

Jan 1, 2020

By Y. Wang

Arsenic-bearing acidic effluent from hydrometallurgical processes contains many harmful metal ions and must be appropriately treated before discharge. In the present study, arsenic, copper, zinc, aluminum, and magnesium were co-precipitated by means of the Fenton reaction. The precipitates obtained under different conditions were investigated to determine their stability. The results indicate that pH value and hydrogen peroxide (H2O2) dosage have significant effects on the removal of various elements. Arsenic, copper, zinc, and aluminum (but not magnesium) can be removed at pH 5–6 and anH2O2/As mole ratio of 2 at ambient temperature. The precipitates were mainly amorphous and granular with particle size in the micrometre range. The arsenic concentration in leachate from the toxicity characteristic leaching test was 3.6 mg/L, which proves that the precipitates are effective in fixing arsenic.

Aug 3, 2023

By J. A. Batista-Rodríguez, F. J. López-Saucedo

A new methodology is proposed for the preliminary assessment of coal blend quality, which combines gamma-ray spectrometry and magnetic susceptibility measurements. This methodology does not replacethe conventional methods of assessing coal quality, but can help to control the quality of the coal blending process, as well as reduce the amount of proximate analysis required and the determinations of calorific value and total sulphur. The methodology includes five steps. First, both geophysical measurements aremade with handheld equipment. The samples with magnetic susceptibility ≤ 1 × 10-3 SI are then separated. From these samples, those with total gamma intensity ≤ 20 nGy/h are separated. These samples have a higher calorific value and lower ash and moisture content. To separate the samples of better quality and with lower total sulphur content, in step four the samples with total gamma intensity > 20 nGy/h are separated from those with magnetic susceptibility ≤ 1 × 10-3 SI. This last group includes samplesthat will cause less total sulphur-related environmental pollution. In the final step, the quality of both radioactive sample groups is corroborated from the calorific value measurement and ash, moisture, andtotal sulphur contents in at least 10% of all coal blend samples from both groups. In this study, more than1000 samples were analysed with this new methodology, and the results are remarkably similar to the ASTM classification of the Sabinas Basin coals.

Apr 2, 2022

By P. J. Le Roux

"Mining companies are under constant pressure to reduce their cost structures to sustain profitability. In mines using an open stoping mining method, dilution often has a significant effect on profitability. At Target mine in South Africa, dilution in some open stopes was found to exceed 10%, falls of ground being a major contributor to the problem. This dilution can reduce the recovered grade from 5.5 to 4.5 g/t, resulting in a potential loss of about R21 million per month based on a gold price of R240 000 per kilogram. In addition to the cost of dilution, the cost of damage to, or loss of, trackless equipment as a direct result of falls of ground in open stopes is significant. Other associated costs include transport, hoisting, secondary blasting, milling, and plant treatment of waste material. Stable open stopes are essential in order to reduce falls of ground. Back-analyses of stope instability at Target mine have indicated that conventional rock mass failure criteria are unsuitable for stope design. An alternative strain-based criterion has been developed, and has proved to be very successful, allowing the stability of open stopes to be calculated reliably. Since its implementation in 2010, dilution and equipment damage have decreased markedly, creating value for the mine. IntroductionMines that make use of an open stoping mining method aim to extract only the ore, leaving the waste behind. Many orebodies have well-defined boundaries between the ore and the waste rock. In such orebodies, the introduction of waste into the ore due to overbreak dilutes the grade. In massive disseminated orebodies, dilution is less problematic. Overblasting, falls of ground, or other causes may result in dilution. A study undertaken in Canada (Pakalnis et al., 1995) found that approximately 51% of all underground metal mines utilized open stoping mining methods and, from surveys conducted at these mines, open stoping operations experienced dilutions of up to 20%, and occasionally more. Dilution of this magnitude has a significant economic impact on any mining venture. Research carried out in Australia by Capes (2009) came to the same conclusion."

Jan 1, 2017

By X. Chen, G. Wang, D. Wan

Computational fluid dynamics have been applied for detailed modelling of particle-bubble collisions. The most accurate approach in the previous work is using the point particle method to treat particles and bubbles. Nevertheless, the sizes of particles and bubbles are generally bigger than the Kolmogorov scale in the high turbulence of the flotation environment, which makes the point particle method inappropriate. This paper describes particle-resolved direct numerical simulation on the collisions between particles (denoted as heavy particles) and bubbles (denoted as light particles) in a homogeneous isotropic turbulent flow field, and a comparison with the point particle method.. A largescale stochastic forcing scheme was implemented within the mesoscopic multiple-relaxation-time LBM approach to maintain turbulence intensity at targetted levels. Both kinematic and dynamic collision kernels were evaluated to study the correlation of total collision events and turbulent kinetic energy (TKE) dissipation rate. The results show that collisions between particles increase with the TKE dissipation rate as radial relative velocities between particles increase with it. In the particle-resolved simulations, the dynamic collision kernels were found to not match with the kinematic collision kernels as in the point particle method. Quantitatively, they were approximately 4 to 10 times smaller than the corresponding dynamic collision kernels. Therefore, it is not reasonable to estimate the kinematic collision kernel in particle-resolved simulations as its rationales are not valid. However, the collision behaviour can still be accounted for by means of the dynamic collision kernel since it is obtained from the direct statistical analysis of the collision events. Keywords: Lattice Boltzmann Method; particle-resolved simulation; multiphase flow; collisions

Jan 1, 2020

By J. Petersen, T. Moyo, J. Dinga

The leaching of chalcopyrite in ferric sulfate media is notorious for its slow and inhibited kinetics. Different methods have been proposed to improve the kinetics, including the use of organic compounds as additives to the leaching media. In this study, the enhancing effect of methanol, ethanol, 1-propanol, and 2-propanol on the leaching of chalcopyrite in aerated acid ferric sulfate solutions using different reactor systems was investigated. The results revealed a clear improvement of copper dissolution by methanol and 1-propanol relative to tests with no additives under similar conditions. Operating a continuous-flow mini-column reactor yields surprisingly good results, potentially related to the maintaining of a consistent leaching micro-environment on the mineral surface. Scanning electron microscopy studies showed that the alcohols result in the removal of surface deposits formed during the anodic dissolution, potentially thus facilitating improved cathodic reduction of the ferric ion to drive the anodic dissolution.

Jan 1, 2023

By A. Y. Senchenkoa, Y. V. Kulikov

The relationships revealed between ore hardness and specific energy consumed by crushing and grinding are described in the paper. A comparison of key technical and economical parameters of SAG and HPGR circuits is made, based on testing of several ore types for greenfield projects. The comparison of results make it possible to estimate efficiency of the technologies application, depending on ore hardness and taking into account potential risks for a circuit under design. Keywords: Comminution circuits, SAG, HPGR, test results

Jan 1, 2020

By V. K. Risinggård, M. Sparta

We report on the development of a finite-element method model for a pilot furnace for the production of manganese alloys. The model is a multiphysics model that addresses material flow, electrical conditions, heat transfer, and physical and chemical transformations. It is capable of studying both quasi-steady and transient states in time-dependent simulations. The model includes common charge materials and fluxes and can simulate production of both ferromanganese and silicomanganese alloys with acid and basic slags, as well as changing charge compositions. The model output provides access to the material distribution in the furnace during furnace runs, temperature profiles, current paths, energy balances, and alloy and slag production rates and compositions.

Apr 16, 2024

By D. F. Malan, T. E. Oates

A recent experimental pillar extraction project at a UG2 bord-and-pillar mine presented a unique opportunity to compile a new pillar database. Currently, the South African hard rock bordand- pillar mines are designed using the Hedley and Grant formula with a modified K-value. This empirically derived formula was developed for uranium mines in the Elliot Lake district of Canada. The use of this formula for the design of pillars in South Africa is questionable. Very few pillar failures have nevertheless been observed and its current calibrations for the various reef types are possibly too conservative. A new UG2 pillar database of 66 pillars, of which seven are classified as failed, was compiled by the authors. This enabled a revised ‘first-order’ calibration of the K-value for the Hedley and Grant formula. The new estimated value for the UG2 is K = 75 MPa. This gives a pillar strength that is more conservative than the PlatMine formula. This work should nevertheless be considered as only a preliminary calibration as the database was small. Further work is also required to determine whether the exponents in the formula for the width and height parameters are appropriate for UG2 pillars.

May 3, 2023

By A. Tosun

"The size distribution of the muckpile formed as a result of open pit blasting operations has a considerable effect on the efficiency of loading, hauling, and crushing. Various researchers have developed specialized computer software that uses image analysis methods for determining the size distribution of the muckpile. However, these methods have some limitations. One of the most important of these limitations is that the very fine fragments in the muckpile cannot be used in the size distribution calculation. In this study, 18 test blasts in total were carried out in two limestone quarries belonging to Batiçim Corp. in Izmir, Turkey. A new model was developed in order to ensure that very fine fragments are used in the size distribution calculation. The size distributions of the test blasts were calculated by both the Wipfrag computer program and the new model. Correlations were established between the muckpile size distributions determined by both methods and the parameters determining the efficiency of the loader. IntroductionThe size distribution of the muckpile formed as a result of open pit blasting operations has a considerable effect on the efficiency of loading, hauling, and crushing. Various researchers have established certain correlations for predicting the efficiency of the operations according to the muckpile size distribution so that production can be carried out economically (Tunstall and Bearman, 1997; Nielsen and Kristiansen, 1996; Workman and Eloranta, 2004; Michaud and Blanchet, 1996; Frimpong, Kabongo, and Davies, 1996; Osanloo and Hekmat, 2005; Molotilov et al., 2010). In these studies, the 50% passing size (X50) is generally used. These methods rely on the correct measurement of the size distribution of the muckpile formed by the blast. The most reliable measurement method would be to subject the entire muckpile to a sieve analysis, but this is obviously impracticable. Therefore, computational method based on image analysis have been developed. These include IPACS (Dahlhielm, 1996), Tucips (Havermann and Vogt, 1996), Fragscan (Schleifer and Tessier, 1996), Cias (Downs and Kettunen, 1996), GoldSize (Kleine annd Cameron, 1996), Wipfrag (Maerz, Palangio, and Franklin, 1996), Split Desktop (Kemeny, 1994), PowerSieve (Chung and Noy, 1996), and Fragalyst (Raina et al., 2002). In these methods, the size limits of the fragments forming the material are determined by image analysis on photographs of the muckpile. However, the computer software has some limitations. It does not take into account the third dimension of the muckpile, nor the size distribution of very fine fragments. In particular, the fragment size ranges below 2.5 to 3 cm cannot be determined, and therefore these cannot be included in the muckpile size distribution. However, the muckpile formed by a bench blast contains a wide range of particle sizes (Tosun et al., 2015)."

Oct 1, 2018