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By C. F. Vos, J. D. Miller, J. C. Davidtz

"This work presents the potential for improving the flotation recovery of slow-floating sulphide minerals with the use of starvation dosages of a normal dodecyl (n-C12) trithiocarbonate (TTC) co-collector, together with a sodium isobutyl xanthate (SiBX) and dithiophosphate (DTP) collector mixture.At potentials below –150 mV (SHE), addition of nC12-TTC with SiBX improves the hydrophobicity of pyrrhotite, yielding captive bubble contact angles greater than those measured for SiBX or nC12-TTC alone, suggesting a low potential synergistic effect. This synergistic effect is further studied using Fourier transform infrared (FTIR) spectroscopy, the results indicating an increase in the surface concentration of the collector species when in a mixture. Thus, nC12-TTC with SiBX may act as an immobile surface anchor to which SiBX/SiBX2 molecules bond, increasing the localized concentration of collector species.Bench-scale flotation tests using mixtures of SiBX/DTP/nC12-TTC on a platinum group element (PGE)-bearing ore from the Bushveld Complex in South Africa confirm an improved metallurgical performance at very low substitutions (approx. 5 molar per cent) of SiBX. The improved recoveries for PGE, Cu, and Ni are correlated with improvements in the flotation kinetics of their slow-floating components. IntroductionShort-chain (less than C6) xanthates are very effective for the bulk flotation of sulphides (Fuerstenau, 1982), and early work (Leja, 1968; Gaudin, 1957; Plaksin and Bessonov, 1957; Taggart, Giudice, and Ziehl, 1934) indicated that the presence of oxygen in flotation slurries is necessary for the oxidation of the xanthate collector at the sulphide mineral surface to induce hydrophobicity. Fundamental research into the chemistry and adsorption mechanisms of xanthates over the years (Finkelstein and Poling, 1977; Woods, 1976; Winter and Woods, 1973) has revealed that for iron-bearing sulphide minerals, adsorption occurs predominantly through a charge transfer process. Oxidation of the adsorbed collector to the corresponding dimer takes place if the mixed potential of the system is greater than the reversible potential for dimer formation. In oxygenated slurries the rate of adsorption and oxidation of the collector depends greatly on the substrate surfaces. For chalcopyrite (Guler et al., 2005; Leppinen, 1990; Roos, Celis, and Sudrassono, 1990) and pentlandite (Hodgson and Agar, 1989) a two-step interaction with xanthate is proposed in which the chemisorbed xanthate is further oxidized to the dimer. The initial interaction of xanthate with pyrrhotite is through physisorption where xanthate physisorbs onto positive surface sites followed by oxidation to dixanthogen (Khan and Kellebek, 2004; Bozkurt, Xu, and Finch., 1998). This process is, however, slow and increased reaction time is needed to improve flotation recovery (Buswell and Nicol, 2002)."

Oct 1, 2018

With the increased variability of today's large-scale mining operations, consistent flotation performance is important to improving and sustaining overall recovery through the circuit. The Newcrest Telfer Mine has implemented advanced process control technology to obtain stable level operation and consistent mass pull in the copper rougher and scavenger flotation circuits. The final result has been an overall reduction in variability, which impacts on both copper and gold recovery. This paper describes the methodology and implementation of the improvements in control at the Newcrest Telfer Mine as being an essential part of the business for minerals processing.

Jan 1, 2007

By M. M. Oosterveld

Diamonds are mined from ancient raised beach deposits in southern Namibia where complex geological controls have resulted in patchy diamond distribution, largely related to irregularities (trapsites) in the bedrock. The distribution of the number of diamonds per sample is a discrete, reverse- J shape distribution which can be characterized by two parameters. These parameters have been transformed into a Beta and Theta Contribution which can be interpreted as reflecting the 'quantity' and 'quality' of the trapsites. The relationship of statistical parameters, obtained during the sampling of an ore deposit, to the geology of the deposit is an important element of ore reserve estimation. The large-scale regional trends in the contributions have been explained in terms of the geology.

Jan 1, 1987

By Timo Niitti, Antti Rinne, Janne Turunen, Klaus Schommarz, Sami Grönstrand

This paper captures the essential steps employed in developing Outotec?s new FloatForceTM mechanism. The development of a flotation mechanism essentially revolves around the efficient transfer of installed power, or capital cost, to optimum flotation performance. Optimum flotation performance will be achieved if a balance between metallurgical results, operating and capital costs is maintained. The development of the FloatForceTM mechanism was done by careful evaluation of each of these three areas. This paper focuses on how experience, CFD and laboratory equipment, pilot and plant tests are used to test and evaluate a new flotation mechanism. Validated variables include mixing profile, power draw and local air hold-up. Metallurgical and mechanical design considerations are not covered in this paper. Besides using the FloatForceTM mechanism in new flotation equipment, the FloatForceTM mechanism can be used in existing flotation cell installations, thus enabling improvements in the mixing profiles, solids suspension and metallurgical performance of operating flotation circuits. Results of several tests carried out in existing plant operations are presented.

Jan 1, 2007

By R. P. King

A class of gravity separation unit operations in ore-dressing relies for its operation on the production of a stratified bed. Heavier material gravitates downwards, and separation is achieved by splitting the ore horizontally, with the recovery of a dense stream and a lighter stream. The important ore-dressing unit operations that fall in this class are the jig, the Reichert cone and the pinched sluice. A new quantitative model based on Mayer's potential theory is developed here. This model is developed completely for the simple case of binary mono-size particulate materials, but the extension to units operating with feed material distributed over particle size and density is discussed in principle. The model can be used to predict the performance of these units and is very suitable for simulation. The model is tested successfully against experimental data obtained from a batch jig and a Reichert cone.

Jan 1, 1987

By J. T. Nel

The Kroll process is the traditional method of producing zirconium metal by reduction of zirconium tetrachloride with magnesium metal. This paper discusses the production of zirconium metal in a plasma reactor. Anhydrous low-hafnium ZrCl4 and Mg metal were fed continuously to a 30 kW non-transfer plasma reactor at a rate of 0.31 kg.h-1. Due to losses in the system the recovery of crude product was 77.5 %. After purification to remove unreacted feed material and MgCl2 by leaching, >98 % pure zirconium metal powder was obtained. The overall recovery of purified Zr was 74 %. The conversion efficiency of the process was 95 %.

Jan 1, 2012

By Luis Rudolphy, Pekka Tähkiö

"Flotation plant design, construction and start-up can be challenging tasks, because multiple factors and disciplines have to be combined in an efficient manner, in order to execute a project that meets the technical, financial and timeframe expectations. Key considerations that need to be addressed when designing a flotation plant are process requirements, equipment integrability, automation, and up- and downstream processes/designs. Furthermore, several other lifecycle factors need to be considered, such as servicing and maintainability, operational costs, future expansions and decommissioning, among others. To address these challenges, Outotec has developed a new approach to designing flotation plants that targets eliminating most of the inherent risks that can be found in these types of projects. The new Outotec® plant is a fully modular approach in which the above-mentioned challenges have been taken into consideration in the design phase. As a result, the cPlant concept can give several benefits for new and experienced companies involved in the minerals processing business, such as lower risk investments, fast and cost-efficient flotation plant delivery, faster ramp-up period, easy plant expansions, fully automated processes and operation and maintenance ease. As well, dismantling and transportation of the cPlant to a new location is easy and fast, hence the new cPlant concept makes possible to exploit small, short-lifespan ore deposits and also retreat old tailings ponds that might contain valuable minerals and where the ore quantities are limited. Furthermore, cPlant is easily implemented for brownfields and temporary expansions during bigger expansions."

Jan 1, 2015

By S. Moodley

In the chloride process for TiO2 pigment production, various titania feedstocks (i.e. rutile, synthetic rutile, slag, and upgraded titania slag (UGS)) are chlorinated in a fluidized bed reactor with petroleum coke at temperatures between 1000°C and 1100ºC to yield gaseous metal chlorides. Although feedstock preference is largely based on TiO2 content, feedstock physical properties (i.e. density, sphericity, size distribution, and porosity) differ; these differences will affect fluidization behaviour and can inadvertently affect conversion efficiency. For example, a high carryover from the reactor reduces particle residence time and decreases conversion rates. Owing to dwindling rutile reserves in the world, most chloride producers are forced to feed blends of feedstocks to their chlorinators; and so it becomes important to understand whether blends have an effect on the hydrodynamic properties of the bed. This paper describes the physical characterization of different feeds and the determination of the elutriation constants for slag, rutile, synthetic rutile, and a blend (i.e. 50 wt% rutile, 50 wt% slag).A common feature of the tests was that particles finer than 75 µm tended more than any other size to be elutriated. The tested rutile, classified as a Geldart Group B material, had the lowest carryover, whereas the slags had the highest. Interestingly, the elutriation constant ([ki]) of the blend is lower than those of either of its individual components.

Jan 1, 2012

By B. B. Tati

The project report is based on vacation work done by the writer at the Khutala Colliery during December/January 2009?2010. The purpose of this report is to explain and describe the design process in a multi-seam mine design for coal extraction at the Khutala Colliery. The multi-seam design will focus on the No. 2 and No. 4 seams as these are the seams that are currently being mined by underground methods at Khutala Colliery. The seam thicknesses and the parting thickness between the seams provide suitable conditions for designing a multi-seam mine design. An investigation into the pillar design aspects is carried out followed by a numerical modelling analysis of various scenarios. This analysis validates the first principles approach provided by multi-seam design guidelines. The design results from the analysis of the selected pillar design indicate sufficient parting for primitive conditions between seams, thus illuminating the need for superimposing in-panel pillars. This multi-seam mine design confirms the potential for the extraction of coal in a new panel. The design indicates that significant amounts of power station coal are present and suitable for extraction by room and pillar mining methods. The panel block indicates 401 625 tonnes of ROM coal. This block has a life of panel that will be mined just over a 4-month period. This 4-month period is assumed to mined at a production rate of 48 000 tonnes per month. The total capital cost required for the new panel is R48 281 127.05. Keywords Multi-seam mining, panel design, ventilation flow, superimposition.

Jan 1, 2011

By E. A. Brinkmann

A kinetic model framework for single particle kinetics in combined diffusion and adsorption processes is presented. The framework applies to the general case in which both diffusion and the adsorption reaction play important roles in determining the overall rate in processes where the migrating species can both adsorb and accumulate. The technique, which should be applicable to a wide range of reaction mechanisms, consists of an iterative integration procedure for the coupled diffusion and reaction equations. The case of a reversible linear adsorption reaction rate is developed. In order to verify the technique as a legitimate method of model development, an analytical solution for the identical case is derived and compared to the numerical solution. Excellent agreement exists between the two solutions.

Jan 1, 1987

By Y. C. Kim

The estimation of local recoverable reserves using the widely spaced exploration drill hole information in an open-pit mine is probably one of the most difficult tasks in ore reserve estimation. The difficulty of this problem is magnified if the grade distribution is highly skewed, such as in a gold deposit. This paper describes the results of performance comparison of three different kriging techniques in an open-pit gold - silver deposit. The three different kriging techniques compared in their local recoverable reserve estimation capabilities are: (1) lognormal kriging, (2) indicator kriging, and (3) probability kriging. For performance comparison, the predictions are compared with the actual recoverable reserves determined from blast hole information. Based on the results from one test bench, both indicator and probability kriging performed better than lognormal kriging, perhaps owing to samples not being truly lognormal. Between indicator and probability kriging, probability kriging results were definitely superior to indicator kriging results.

Jan 1, 1987

By SAIMM SAIMM

To the members of The South African Institute of Mining and Metallurgy We have audited the annual financial statements of The South African Institute of Mining and Metallurgy set out on pages 575 to 586 for the year ended 30 June 2005. These financial statements are the responsibility of the Institute?s Council. Our responsibility is to express an opinion on these financial statements based on our audit. Scope We have conducted our audit in accordance with International Standards on Auditing. Those standards require that we plan and perform the audit to obtain reasonable assurance about whether the financial statements are free of material misstatement. An audit includes: examining, on a test basis, evidence supporting the amounts and disclosures in the financial statements, assessing the accounting principles used and significant estimates made by management, and evaluating the overall financial statement presentation. We believe that our audit provides a reasonable basis for our opinion. Audit opinion In our opinion, the financial statements fairly present, in all material respects, the financial position of the Institute at 30 June 2005 and the results of its operations and cash flows for the year then ended in accordance with South African Statements of Generally Accepted Accounting Practice.

Jan 1, 2005

To the members of The South African Institute of Mining and Metallurgy I have audited the annual financial statements of The South African Institute of Mining and Metallurgy set out on pages 641 to 644 for the year ended 30 June 2006. These annual financial statements are the responsibility of the Institute?s Council members. My responsibility is to express an opinion on these annual financial statements based on my audit. Scope I conducted my audit in accordance with International Standards on Auditing. Those standards require that I plan and perform the audit to obtain reasonable assurance about whether the annual financial statements are free of material misstatement. An audit includes: ?examining, on a test basis, evidence supporting the amounts and disclosures in the annual financial statements, ?assessing the accounting policies used and significant estimates made by management, and ?evaluating the overall financial statement presentation. I believe that my audit provides a reasonable basis for my opinion. Audit opinion In my opinion, the annual financial statements present fairly, in all material respects, the financial position of the Institute at 30 June 2006 and the results of its operations and cash flows for the year then ended in accordance with generally accepted accounting practice appropriate to the Institute. Supplementary information The supplementary schedule does not form part of the annual financial statements and is presented as additional information. I have not audited this schedule and accordingly do not express an opinion on it.

Jan 1, 2006

By L. G. Austin

The paper summarizes the current state of development of simulation models for SAG and FAG mills, and gives the results of recent investigations of the physical processes occurring in autogenous grinding. The breakage process is treated as the sum of three regions of breakage actions: normal breakage caused by nipping of particles between media (steel balls or pebbles); abnormal breakage caused by media when the particle or lump is too big in relation to the media to be readily nipped; and self-breakage resulting from the chip¬ping fracture and abrasion of the tumbling action of rock lumps. Each region of breakage action has associated specific rates of breakage and primary progeny fragment distributions. A simplified form of the model was used to predict the performance of an 8 m diameter SAG mill with L/D = 0.5 grinding a copper ore, and predicted maximum capacity and minimum kWh/ton at about 6% ball load at 25% total filling. Two FAG mills of L/D = 2 were necessary to give the same capacity, and the simulations indicated a lower kWh/ton for these mills. For this ore, both systems were technically feasible.

Jan 1, 1987

By G. M. Dunn

Pressure leach autoclave circuits are employed in the leaching of ores, concentrates, mattes, alloys and intermediates for the recovery of metals into solution. Once the metals are extracted into solution, the value metals can be recovered by hydrometallurgical means such as by purification followed by electrowinning, hydrogen reduction, pyrohydrolysis, crystallization and other unit operations. In many of these integrated flowsheets the pressure leach step is pivotal to the recovery of the value metals from the host material. Furthermore, the autoclave circuit invariably is a high capital cost component of the plant and an area that is carefully scrutinized when debottlenecking and capacity increases are being considered. This paper identifies a unique proven way of increasing the capacity of existing or new exothermic pressure oxidative leach autoclave circuits by as much as two or three times.

Jan 1, 2009

By C. I. Ware

The phrase ?back to basics? is used to describe the fundamental principles and philosophies on which a successful mining operation is based. At Richards Bay Minerals (RBM), ?back-to-basics? (BTB) has been implemented as a continuous process to probe operational functions with a view to increase production without capital expenditure. It also ensures that the fundamentals of dredge mining are understood and adhered to. BTB is based on the principle that people drive organizations, necessitating an interactive implementation approach. At the RBM mine this entails a three-pronged approach, namely practical training, teamwork initiatives and the use of lean Six Sigma methodology. It is the latter on which this paper will focus. The lean Six Sigma methodology is successful in identifying, managing and documenting BTB projects, while team work initiatives are integral to successful project implementation. This paper describes two examples of how the Six Sigma methodology can be applied to a dredge mining operation. The first example focuses on the improvement of Mining Pond Echo (MPE) plant throughput by reducing the lost opportunity (non-production) due to tails downtime. The project was successful in increasing plant throughput by 4.5%. This was achieved by increasing the tails disposal system availability by running MPE as a four tails lines operation and focusing on causes of tails production downtime. Subsequently, the tails system at MPE is no longer the production bottleneck. Second, the Six Sigma methodology was successfully applied at Mining Pond Charlie (MPC) to increase the primary dredger throughput by 4.6% through focusing on the dredging technique and maintenance issues. This project highlighted the need for trend analyses to ensure an effective dredging technique, coupled with simple production documentation, which also ensures a focus on maintenance. Keywords: Back to basics, Six Sigma, training, teamwork, throughput improvement, tails, dredger.

Jan 1, 2007

By Y. Lizotte

This paper describes the design and implementation of the dispatching system at LAB Chrysotile Inc.'s Black Lake Mine Operation, Quebec, Canada. The initial system uses a computer in a passive role, to record and display information in ongoing operations. Simulation studies were undertaken at McGill University to assess various heuristic dispatching rules which can be program- med and inserted into the dispatching system. The computer can then suggest to the operator where a truck should be sent to maximize productivity or improve fleet efficiency. The study stresses the importance of considering the effects of implementing computerized systems on those individuals who must use these systems in their daily work. The roles of individuals from the industry and the university in this joint project are also highlighted.

Jan 1, 1987

By J. -M. Chautru

A geostatistical simulation of a typical mining site for polymetallic nodules in the North Pacific Ocean is presented. This is the first stage in the design of an industrial mining system. Two variables which have a major effect on the orebody's economic potential are considered, namely: the maximum slope of the ground inside a mining block of 50 x 100 m; and the average quantity of nodules on the same support. Two geostatistical problems have emerged in this study. The first is due to the lack of a change of support model for the maximum of a variable. A provisional solution, considering an experimentally accessible 'equivalent' support, is proposed. The second is due to a non-linear link between the two variables. To be able to take this into account in the simulation, we propose a new method based on the decomposition: X = E(X/Y) + Residue (X). Satisfactory results were obtained with this approach.

Jan 1, 1987

By B. Geelhoed

A generalization of Gy?s 1979 model for the variance of the fundamental sampling error has been proposed at WCSB2?2005 by Geelhoed. This generalized model can potentially lead to a better correspondence with actual sampling processes. However, a new parameter is required by the new model: ?the parameter for the dependent selection of particles?(Cij). It is important that this new parameter, which is at the basis of the new theory, is well understood in the sampling and blending community. In order to clarify the meaning of Cijand to prevent potential misinterpretation of Cij, we discuss the difference between Cij and an intuitively associated, but different, parameter: ?the parameter for the dependent selection of particle types?(Mij). In this contribution, the theoretical difference between both parameters is clarified. Simulations demonstrate that, numerically, the difference between Cij and Mij can be large. Some additional advantages of the approach which uses Cij are discussed: (i) the approach based on Cijis more general; (ii) in all cases where Mij is known, Cij can be determined as well, while the reverse is not true; (iii) an equation already exists that relates the sample variance to the value of Cij.

Jan 1, 2009

By E. L. Forner, G. M. Miller, J. Scheepers, A. J. du Toit

"The sizing, designing, and costing of copper electrowinning circuits requires an in-depth understanding of the fundamental relationships between circuit parameters and the practical operation requirements. The aim of this investigation was to optimize total copper electrowinning project cost by mapping the operating limits of key mechanical equipment. The model was compiled by mapping various cellhouse layouts in terms of number of cathodes per cell, crane productivity, stripping machine productivity, and rectifier–transformer (rectiformer) sizing using data tables for sensitivity analysis. These parameters were then collated and evaluated on a cost by size basis. The model provides an optimum band of operation for cellhouse productivity and project capital cost for a typical range of production throughputs, from 10 kt/a to 200 kt/a cathode copper. The information may be used as a high-level selection guide to assist with identifying a costeffective copper electrowinning circuit design for a specific production rate. The data was validated and compared with existing copper electrowinning cellhouses around the world that typically install no more than 84 cathodes per cell. IntroductionThe sizing, designing, and costing of copper electrowinning (EW) circuits require an indepth understanding of the fundamental parameters as well as the practical requirements to optimize cellhouse productivity and capital cost. Although a significant amount of work has been done designing new copper electrowinning circuits, an in-depth evaluation of world operating data reveals that the number of cathodes per cell, which affects cellhouse layout and productivity, is not consistent for a specific production rate (Anderson et al., 2009; Robinson et al., 2003, 2013). Based on this premise, Kafumbila (2017) suggested that there are unanswered questions, such as ‘why are the numbers of cathodes per cell different for copper production rates of 20 kt/a and 40 kt/a?’In this paper, data tables are employed to map the operating limits and costs of key Cu EW equipment. An overall Cu EW project cost map is then compiled by collating optimum cellhouse layout (number of cathodes per cell), optimum crane productivity, optimum"

Nov 1, 2018