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By D. Harbottle, D. Rhodes, T. F. Jones, S. R. Biggs

Multiphase process design and optimization often depends upon the rheological properties of sludges and slurries. In practice the task of determining these important properties is usually carried out by removing small samples from a process line or process unit and performing tests with proprietary bench-top analysers near to site or at a remote laboratory. Sampling will remain an important procedure in industrial processes, but there is also a strong case for augmenting the routine information obtained using an in situ sensor, as suggested below. ?Sampling protocols can result in extensive turnaround periods from sample collection to the generation of results. The delay can have an effect on a variety of factors such as product quality, process operability and efficiency. ?Sampling of toxic or radioactive material can prove an even greater challenge to minimize human involvement. ?Removal often changes the rheology of a specimen, and might lead to incorrect conclusions being drawn about the condition of a sludge. ?Sludge and slurry in a containment suffers a gravitational gradient, so that a removed sample should be paired with its location, particularly in the vertical dimension.

Jan 1, 2007

By G. T. G. Emere

With the assistance and encouragement of Mr B.C. Alberts, the Institute's immediate Past President and Iscor's Senior General Manager: Mining, the Committee of the Johannesburg Branch recently organized a two day excursion for members to the northern Transvaal. The itinerary included visits to the Grootegeluk colliery, the Matimba power-generation utility, and the Thabazimbi iron-ore mine.

Jan 1, 1989

Mixed integer programming (MIP) has been used for optimizing production schedules of mines since the 1960s. The major problem in the long-term production scheduling for an entire orebody is that the number of integer variables needed to formulate an MIP model is too large to solve the formulation. This number may reach well over one hundred thousand. To overcome this difficulty, this paper presents two new algorithms to reduce the size of the problem. These algorithms assign an earliest and latest possible start date for each machine placement, eliminating the integer variables that correspond to machine placement before its early start date and after its late start date. A case study based on Kiruna Mine, the second largest underground mine in the world, is summarized in the paper. It shows substantial improvement in the solution time required using the new algorithms. This increased efficiency in the solution time of the MIP model allows it to be applied to Kiruna Mine, with the potential to increase substantially the net present value (NPV) of the project.

Jan 1, 2008

By D. S. van Vuuren

Industrial production of titanium occurs via the batch-wise reduction of titanium tetrachloride (TiCl4) with a reducing metal, being magnesium in the Kroll process, or sodium in the Hunter process. In the search for low cost titanium, the CSIR is developing a continuous process to produce titanium powder directly via metallothermic reduction of TiCl4 in molten salt, dubbed the CSIR-Ti process. The move to a continuous process has been attempted by a number of organizations, but was until now always met with failure, due in no small part to challenges inherent in the process chemistry. The reaction between TiCl4 and the reducing metal can occur directly, when TiCl4 or any titanium sub-chlorides present, comes into contact with suspended or dissolved reducing metal. The reaction can also occur indirectly, without any physical contact between the reacting species, via an electronically mediated mechanism. The reaction mechanism via electronic mediation can cause TiCl4 to react at the outlet of the feed port, rapidly causing blockages of the TiCl4 feed line. The electrical conductivity of the metal reactor can also cause the electronically mediated reaction to favour the formation of titanium sponge on the reactor walls and internals, rather than titanium powder. Various methods were investigated to overcome the problem of blockages in the TiCl4 feed line, e.g. mechanical removal, sonic velocities, dilution of the TiCl4 and the use of ceramic feed lines. This article discusses problems experienced with the continuous feeding of reagents, and various methods attempted are shown and discussed. Information is also given on the morphology, chemical composition and suitability of the final titanium powder for powder metallurgical application as presently produced by the CSIR-Ti process. Keywords Titanium dioxide, titanium nitride, carbo-thermic reduction, ilmenite, slag, tunnel kiln, residence time.

Jan 1, 2011

By M. J. Little

Potgietersrust Platinums Ltd is Anglo Platinum?s only open pit operation and annually extracts 57 million tonnes of rock from 2 open pits. Over the past 3 years ~220 km of exploration drilling has been done, ~1000 km of rock face have been exposed for face mapping and over 7000 laboratory and field tests have been conducted. This has produced large amounts of geotechnical data to be utilised for feasibility studies, initial slope design and ongoing slope optimisation. It was necessary therefore to develop geotechnical databases to manage the vast amounts of data collected. SABLE and MineMapper 3D databases were created for logging and mapping respectively, with rock testing data incorporated into both. A pit inspections database was developed in MS Access and the existing groundwater and slope monitoring database was improved. The databases were linked to AutoCAD and Datamine to ensure that the latest geotechnical data is used for planning, draughting and modelling. The use of geotechnical databases ensures that no data is lost, standards are maintained and analysis can be easily performed. This increases the confidence of the analysis and allows the geotechnical engineers to optimise slope designs and blast designs on a regular basis. This reduces the risk of slope failure thus making the open pits more economical and safe.

Jan 1, 2006

By F. Hees, A. H. Bracken, L. I. Boshoff

"Biological cementation of the Mandena heavy mineral sand deposit in Madagascar was causing difficulty in dredge mining and hence in planning and control of production rates. An investigation was initiated to better evaluate the geotechnical properties of the orebody by defining the distribution and geotechnical properties of the cemented strata, in order to generate a site-specific geotechnical model for the deposit. The geotechnical characterization was developed by an integrated approach using several ground investigation techniques such as piezocone (CPTu) testing, geotechnical drilling, standard penetration testing (SPT), as well as laboratory testing. The final outcomes of the investigation included a 3D geotechnical model showing the distribution and extent of the cemented areas, as well as the typical geotechnical parameter ranges associated with each of the defined geotechnical units. The interpretations developed were incorporated into the mine and production planning to ultimately optimize operational planning and control.IntroductionQIT Madagascar Minerals (QMM) is a heavy mineral sand mining operation at Mandena, near Fort Dauphin in Madagascar. During the final planning and commissioning stages of the project, the need to fully characterize the unusual geotechnical conditions was identified and a geotechnical investigation became necessary.Nature of the problemDuring the commissioning phase it was found that mining production was being hampered by biologically cemented/indurated layers encountered within the sands. Closer inspection of the indurated horizons in the dredging face revealed that these layers contain a high loading of bacteria and fungi. It appears that the bacteria produce an extracellular (outside the cell) polysaccharide (i.e. sugar and carbon salts), which form a gelling biofilm to trap nutrients. There are a number of different bacteria. The fungi, on the other hand, produce a network of fibrous strands that bind the sand grains together. Thus both bacteria and fungi probably contribute to the ‘apparent cohesive’ strength or binding of the indurated sand (Lynn, 2008)."

Jan 1, 2017

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 P. A. Roberts

A modified in situ leaching method for extracting gold from oxidized gold ores using a non cyanide lixiviant is proposed. A non cyanide lixiviant is suggested because of the obvious concerns posed by injecting cyanide bearing solutions into the subsurface. Oxidized gold ores are the initial focus because earlier research on the use of sodium thiosulphate as a lixiviant under anaerobic conditions indicated that the presence of pyrite led to rapid thiosulphate breakdown. A reconnaissance research programme, involving ore characterization and hydrometallurgical testwork on samples from four Australian ore deposits and preliminary reactive transport modelling studies was carried out. This work showed that lixiviant-oxidant combinations of sodium thiosulphate and ferric EDTA, and iodide and iodine are both capable of extracting high percentages of accessible gold from the selected samples under anaerobic conditions. The ore characterization and reactive transport studies, suggested that both physical and chemical methods of permeability enhancement may be required to lift bulk permeability and the availability of gold for dissolution to sufficiently high levels to obtain adequate gold recoveries. Physical permeability enhancement could be achieved by blasting and/or hydraulic fracturing of the ore. Assuming that such methods prove to be both necessary and economically viable, the mining method would no longer be regarded as simple in situ leaching. Therefore, the term ?in place leaching? has been adopted for the proposed gold extraction system

Jan 1, 2009

By R. Weideman, K. du Preez

Biological sulfate reduction has become a successful treatment alternative for acid mine drainage and Mintek is developing biological processes for treatment of highsulfate mine waters. Treatment of these high-sulfate waters is achieved by sulfatereducing bacteria that reduce sulfate to produce sulfide as a product, in the form of H2S and HS− at neutral pH. This introduces the opportunity to apply treated effluents from biological treatment processes for the recovery of metals, such as copper, from metallurgical waste streams. This study models the kinetics of copper sulfide precipitation from a complex bioleach liquor. The results indicated a rapid rate of reaction and the formation of covellite, suggesting the potential to use biogenic sulfide to recover copper as a metal sulfide product.

Jan 1, 2023

By H. Rosen

The pump is the heart of most industrial and mining plants, providing the energy to separate valuable minerals from process feed. The actual effect of the pump, both in terms of production costs and overall process efficiency, is often assumed or misunderstood by engineers due to insufficient pump performance data. Pump performance can be understood and corrected, where required, through continuous performance monitoring, leading to dramatic improvements in both pump life cycle costs and system efficiencies. The performance of every pumping application is subject to variation and the main contributing factors are as follows: ?Unavoidable deviations from pump supplier curves ?Pump wear ?Pump curve derating factors for slurry pumping ?System curve variation ?Deviation from basic principles of centrifugal pump operation. These are discussed in detail through case studies and the author?s personal experiences. This paper shows ways to minimize the effect of these variations, thereby reducing performance loss and preventing damage to the pump. The paper discusses the benefits of efficient pump operation, the requirements of pump performance monitoring, and its practical application to pump operation in the slurry and water environments. The cost of remedial actions is explored and compared against the savings in both power and plant reliability, resulting in a reduced life cycle cost of the pump.

Jan 1, 2010

By K. C. Corin, M. Tadie, N. Ndamase

Fresh water conservation efforts and strict environmental regulations have forced the mining industry to reduce freshwater consumption and effluent discharge. This is achieved by recycling process water back to mining processes. The performance of flotation circuits depends on the pulp chemistry. When process water is recycled to flotation cells, organic and inorganic species that have accumulated over time alter the pulp chemistry. The presence of accumulating ionic species such as SO4 2- and S2O3 2- has been found to hinder the adsorption of collector ions onto mineral surfaces. Sulphide minerals are semi-conductors; electrochemical reactions take place on their surfaces. The adsorption of collectors onto mineral surfaces takes place via electrochemical reactions. This study, therefore, aims to investigate how the presence of accumulating ionic species at varying ionic strengths affects the adsorption of sodium ethyl xanthate onto chalcopyrite from an electrochemical perspective. Synthetic plant water comprised of single salts with varying ionic strengths was used. Rest potential measurements were conducted to investigate collector-mineral interactions in the presence of these ionic species. Microflotation tests were performed to determine whether the presence of these ionic species affects mineral floatability. Higher chalcopyrite recoveries were achieved in the presence of SO4 2- than in the presence of S2O3 2-. Rest potential measurements were found to successfully predict microflotation performance in the presence of the ions of interest. Keywords: Flotation water quality, electrochemical adsorption; xanthate collectors

Jan 1, 2020

By F. Samimi Namin

One of the main tasks in exploitation of mines is to select a method suitable for the deposits, specific features including geometric, geo-mechanical and geological features. The purpose of selecting a mining method at this stage is to choose one or more method(s) having the most coordination with the deposit?s conditions and external factors, including the allocated budget and local technology for detailed feasibility studies. Several methods have been developed in the past to evaluate suitable mining methods for an ore deposit, based on its physical characteristics. These approaches can be classified into three groups: (1) profile and checklist methods, (2) numerical ranking (scoring) methods, and (3) decision-making models. Most of these methods have shortcomings. Considering the fact that most of the specifications of mineral deposits, such as dip and depth, are linguistic variables, absoluteness of the explaining parameters by previous methods can be mentioned as the most important disadvantage of these methods. This paper discusses the Fuzzy technique for order performance by similarity to ideal solution (Fuzzy TOPSIS) to determine the mining method. The fuzzy decision making (FDM) software tool is employed to develop a Fuzzy TOPSIS based model. Application of this model with various values (crisp, linguistic and fuzzy) of the deposit eliminated the existing disadvantages of other methods. Two empirical illustrations demonstrate the effectiveness and feasibility of the evaluation procedure. These show that the proposed model performs better than its alternatives. Keywords: mining method selection, fuzzy TOPSIS, decision making, mining engineering, linguistic variables.

Jan 1, 2008

By B. Talbot

How this simple plant generates a large revenue stream. The concept behind the Tailings Scavenging Plant (TSP) is simple: it is a non-complicated modular plant which is designed to be more stable than upstream plants. This, plus the use of ?high energy?, enables the plant to recover any metal missed by the upstream operation. Impala Platinum?Mineral process started pilot plant exercises in June 2003. The pilot plant ran for one year before the capital for the full-scale plant was approved. This year was used to motivate, design and cost a full-scale plant. The metal produced during the pilot and feasibility study enabled this part of the project to run at a small profit. The scale-up to full-scale was relatively simple as the pilot plant had a capacity of 180 m3/hrand the full-scale plant was designed for a capacity of 550 m3/h. The design for the full scale plant was completed in May 2003, with ground breaking taking place on 19 May 2003. The construction phase of the project went well with the commissioning of the first two modules taking place on 22 October 2003. The remaining two modules were commissioned two weeks later. The plant was at full capacity by the 20 November 2003. A review of the plants performance for the first 5 production months is as follows: the plant has required only a few minor modifications and additions, it has run well in excess of 95%availability with no major wear apparent. In addition to this, the plant has produced 3 times the metal forecast.

Jan 1, 2004

The vast majority of the roughly 100 million rock anchors installed in mines in the USA each year use resin cartridges1. About 4.5 million of these bolts are installed using a mechanical shell in addition to the resin to create an active (pre-tensioned) bolt. Over 1 million of the bolts are passive cable bolts and typically have an effective grout length of 1.2 m, regardless of the cable length, which could be as long as 6 m. The successful performance of the resin grouted bolts depends on several parameters, including the annular gap between the bolt and hole wall, which should be relatively small, ideally from 3 mm to 5 mm. This requirement, combined with the high viscosity of the resin, produces a high back-pressure that can cause the bolt being installed to buckle or not be installed to standard. It is this back-pressure that limits the effective grout length with passive cable bolts and causes the mechanically anchored bolt failures (typically called ?spinners? where the mechanical shell does not anchor). This creates potentially unsafe conditions and wastes time and money. A purpose, built rig was used to mimic underground installations and record the back-pressures during full scale applications in the laboratory. This information was used, and is still being used, to reduce the failures and sub-standard installations by producing improved designs. In addition, a flow model was calibrated that can act qualitatively to estimate the back-pressures and can be used as a crude screening process before full scale prototypes are built and tested. To date, the results obtained have been used to stop the use of a mechanical shell due to the proven higher rate of failures. A new, improved mechanical shell is being field tested and another system is underdevelopment. The use of the rig is therefore ongoing to develop improved mechanical anchor systems. It is too early for real data; however, anecdotal evidence seems to indicate that significant improvements can and will be made.

Jan 1, 2011

By C. O. Aksoy, G. G. U. Aksoy, A. Fisne, I. Alagoz, E. Kaya

Coal produced in underground mines is transported to the surface by means of conveyor belts throughout long roadways. The combustion of belts puts a large number of employees at great risk. Underground collieries differ from other underground mines -due to the combustible nature of the product. The most prevalent cause of belt fires in underground coal mine is spontaneous combustion due to oxidation of the coal, which also enables the conveyor belt to burn over time. In 2014, a belt fire in an underground coal mine in Manisa-Soma, Turkey caused 301 fatalities. A study has been conducted on this accident for approximately 3 years, consisting of combustion tests in a purpose-built research gallery, comparison of the test results with mine records of the accident, and CFD modelling of the mine environment. The intensity of the fire was sufficient to redirect the air flow underground, causin large amounts of toxic gases to fill almost the entire mine in approximately 15 minutes. It is recommended that CFD analysis be used in planning emergency action strategies in underground mines.

Dec 13, 2023

Mill relining is a major contributor to overall plant downtime. Reducing the number of mill liner pieces removed from and replaced in the mill has a direct impact on the overall reline time and in turn, mill availability. To improve the mill availability of Ridgeway Operations' 32 foot SAG mill, a number of initiatives were implemented in terms of liner design. These included the conversion of the shell from 40 to 30 rows, reducing the number of pieces from 80 to 60 each shell reline and reducing the number of pieces from 48 to 32 per feed end reline. In addition, modifications were made to the discharge end of the mill to extend the life of the outer pulp lifter and discharge cone, thereby reducing the frequency of change out. The standard radial outer pulp lifter was converted to an angled design. The discharge cone was converted to the BullnoseTM design supplied by Bradken. This paper discusses the design changes made and the expected benefits to the Ridgeway Operations in terms of mill availability improvements.

Jan 1, 2007

Grains are subject to contamination by mycotoxins which are metabolic by-products of various fungi. The fungal infestations produce local concentrations of the mycotoxins thousands of times higher than the average. These facts make the sampling of the grain for assessment of the mean mycotoxin levels potentially very difficult. In the context of sampling theory, this morphology of the infestations creates a very high distributional and intrinsic heterogeneity of the grain shipment. The distributions of mycotoxin concentrations in seaborne shipments that exist at loading and the number and intensity of infestations that develop under shipping conditions are unknown. All grain shipments carry spores that may give rise to mycotoxin-producing colonies; moisture and temperature determine the final extent of the problem. This paper develops the value of the sampling constant with respect to intrinsic heterogeneity based on data on observed Ochratoxin A (OTA) concentrations in individual wheat kernels. A useful relationship between the distribution of mycotoxin concentrations on a kernel to kernel basis and the distribution of concentration over subsamples is developed.

Jan 1, 2009

The Skorpion process comprises three processing steps-atmospheric leaching in sulfuric acid, zinc solvent extraction and electrowinning to produce special high grade zinc. The major mode of impurity transfer was attributed to crud runs in the solvent extraction circuit. Crud may be described as a heterogeneous, partly inorganic, partly organic mass of material which accumulates predominantly at the interface between organic and aqueous solutions. The paper describes the root causes of the crud formation in the solvent extraction circuit and optimization strategies which are being followed to prevent impurity excursions in electrowinning. Keywords: zinc oxide, solvent extraction, crud formation, colloidal silica.

Jan 1, 2007

By D. Van Dyk

Horizontal rotating mills are being used all over the world in different mineral and power generation industries. David Brown South Africa, with over 140 years of experience in gear manufacture and design, has been supplying these industries with innovative designs at exceptional quality. The gearing systems associated with these industries are challenged daily with operating conditions that are not always fully understood. Failures are therefore experienced, over time in the industry, which cannot always be fully explained. David Brown South Africa has developed a gear monitoring system, the Intelligent Gearing System, in association with Transmission Dynamics (UK), in order to monitor and analyse these operating conditions in real time. The system has been designed on the principles of Six Sigma, incorporating Design for Six Sigma. The purpose with this system design is to monitor the operating conditions on the pinion, record the information and analyse the data in relation to the rate of fatigue damage to the girth gear and pinion. This is done in real time and unattended. The output from the Intelligent Gearing System can be fed back into the operating system of the mill user, in order to display an alarm for operating conditions exceeding the design criteria as well as information on the rate of fatigue damage due to these operating conditions. When the mill operating and the effect on the fatigue life of the mill gearing components, conditions are better understood, mill users can forecast critical spare holding levels with an increased accuracy. The Intelligent Gearing System also allows early actions to remove reasons for system overloads.

Jan 1, 2006

By J. Engelbrecht

Understanding the deportment of minerals in size fractions has already led to improvements in the flow sheets for platinum minerals beneficiation. There are, however, more potential changes in the flow sheets that may improve the recovery of platinum group metals or reduce the costs of beneficiation before refining. Based on known technology of pre-concentration, milling, gravity concentration, flotation, and magnetic separation a number of potential alterations or additions can be considered and motivated based on the mineral deportment in size fractions.

Jan 1, 2012