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By M. Kumral

One of the most significant elements in solving the co-kriging equations is the matrix solver. In this paper, the singular value decomposition (SVD) as an equation solver is proposed to solve the co-kriging matrices. Given that other equation solvers have various drawbacks, the SVD presents an alternative for solving the co-kriging matrices. The SVD is briefly discussed, and its performance is compared with the banded Gaussian elimination that is most frequently used in co-kriging matrices by means of case studies. In spite of the increase in the memory requirement, the SVD yields better results.

Jan 1, 2012

By W van Drunick, S Naik

To date, Anglo Research has carried out several projects, based on the techniques developed in the AMIRA P9 (AMIRA International Limited), to develop comminution and flotation models for several Anglo Base Metals and, to a lesser degree, Anglo Platinum flotation plants. Plant optimization is thus achieved through steady-state sampling, model-fitting and simulation using the JK SimMet and JK SimFloat software packages. The surveys can vary depending on the needs of the plant/client. The survey can therefore include as little as a single piece of equipment, an entire milling/flotation circuit, or a complete circuit from primary comminution to final flotation concentrate (i.e. the ?integrated survey?). The presence of the AR team on-site usually precipitates in face-value observations that can lead to initial improvements. This stems from the knowledge-sharing on best practice that exists in parallel with the surveys. Numerous (reasonable) changes can then be simulated, thus indicating the optimization step most likely to result in the best efficiency improvements. The simulations can include changes in the flowsheet, ore characteristics, mill loads, grinding media size, change in grind, flotation residence time, air hold-up and several more. Plant surveys can result in process changes that provide the plant with either: higher plant tonnage, improved plant grind, additional flotation recovery and/or improved product grade. The additional benefit of performing an integrated plant survey is that the effects of an optimization change in the comminution circuit can be simulated using the flotation model. This paper describes a number of case studies where individual and integrated plant surveys were conducted by AR for Anglo Base Metals.

Jan 1, 2007

By A. C. Wingrove

The paper outlines the selection of a dewatered tailings backfill system for the Johannesburg Consolidated Investment Gold Division, and covers the following aspects: (i) 16 Shaft pilot testwork; (ii) engineering design problems relating to the Cooke 3 Shaft backfill operation; (iii) in-line mixing - applications with respect to the Randfontein Estates Gold Mine and Western Areas Gold Mine backfill operations; and (iv) pipeline friction losses.

Jan 1, 1988

By S. Özgen

In this study, the possibility of beneficiation of chromite tailings in the Uckopru/Fethiye-Turkey region by a combination of hydrocyclone and multigravity separator (MGS) was investigated. The two significant operational parameters of hydrocyclone, which were diameter of the apex and diameter of the vortex, and the three significant operational parameters of the MGS, which were drum speed, tilt angle, and wash water, were varied and the results were evaluated with the central composite rotatable design. In order to produce a chromite concentrate by hydrocyclone and MGS, mathematical model equations were derived by computer simulation programming, applying the least-squares method using Minitab 15. Second-order response functions were produced for the grade and recovery of chromite concentrates.

Jan 1, 2012

By H. H. McGregor

Introductory remarks by author When Mr R. C. J. Goode suggested preparation of a paper in the area of manpower utilization in South Africa, I was, while keen to accept his invitation, somewhat hesitant for two reasons. Firstly, I recognized the great difficulty of making a factual contribution, because of the lack of really relevant statistical information available, the fact that much of it is out of date, and the difficulty of researching and co-ordinating it and of evaluating a statistically sound resultant viewpoint. Experience in the actual preparation of this paper has done nothing to change my view in this respect. Secondly, it is obvious that a paper presented to a meeting of this Institute, by a member of it, would be expected to devote considerable attention to the subject in the mining industry. I am not directly employed by the mining industry, although my company has carried out extensive assignments for various sectors of it both in this country and in other parts of the world, since the 1939-45 war. I am more conscious than most of the tremendous technical and managerial skills at the disposal of the industry in this country, and consequently am equally conscious of the hazards of publishing facts and figures which might be taken to indicate any criticism of performance. I am aware that some of the information that I am about to present may indeed generate comment, and possibly even critical comment. I would like to be regarded therefore in presenting this information, as a member of the group, rather than an external critic. Under these circumstances, comment can only be constructive, and this is my earnest hope. The contribution of my paper, if contribution there is, will I hope be in the area of assessing labour productivity in mining, and in secondary industry in such a way that the performance of each against its own past results is comparable. This task has not for the present been to my knowledge attempted, and in advance I wish to take out authors' insurance against legitimate criticism from professional economists and others, by stating that I am well aware of possible short-comings in the arguments. Nevertheless I believe that under the circumstances I have, with the important assistance of several people, been able to take the subject further than has been the case in the past. Finally, I have related productivity in the mining industry and in secondary industry to a target of productivity in the Republic of South Africa. I was fortunate recently in being able to attend a series of lectures by a prominent economist in America. He introduced his subject by calling it 'A broad survey of macro-economics'. Perhaps I might be permitted to describe my paper, in the same idiom, as 'The macro-management of labour'.

Jan 6, 1970

By A. Sampson-Forsythe, P. Morissette, A. R. Punkkinen, D. R. Chinnasane

"The performance of ground support systems under dynamic loading is typically assessed in a qualitative and subjective manner. As a result, it is difficult to develop an explicit knowledge on the mechanisms of action and interaction of support elements subjected to rockbursts. This paper examines rockbursts that have occurred at Creighton, Copper Cliff, and Coleman mines since 2000, 2004, and 2006, respectively. The mines are located in the Sudbury Basin, in Ontario, Canada. The majority of pertinent information was obtained through on-site field assessments, seismic system records, and numerical elastic stress modelling. Passive monitoring is used to link the evolution of the frequency and severity of rockbursts to the evolution of mining and support practice at the three mine sites. Based on the collected data, ground support elements that enhanced the capacity of support systems to withstand dynamic loads are identified. IntroductionThe selection of appropriate mining methods, extraction sequences, rock mass de-stressing techniques, and ground support systems is of great importance in mitigating the level of rockburst-related risk. In burst-prone conditions, the design of support systems should account for the anticipated dynamic load demand and the capacity of the available support options. Furthermore, an economical design should, implicitly or explicitly, take into consideration the consequences of a rockburst and its impact on worker safety and mine productivity. Stacey (2012) has argued that we have a limited understanding of the mechanisms of rock mass behaviour in seismic conditions. This is compounded by a ‘lack of understanding of the mechanisms of action and interaction of support elements under dynamic loads’ (Stacey, 2012). Consequently, the design of support systems required to manage dynamic loads is usually based on experience. The assessment of the dynamic performance of ground support systems is typically subjected to qualitative (and sometimes subjective) interpretations from ground control personnel."

Jan 1, 2017

By R. M. G. Machunter

The use of testwork to establish an economically feasible separating plant has been a long established practice in the mineral processing industry. However, uncertainties in orebody characteristics and equipment/plant operation can have a significant impact on the separation performance of a given project. This paper explores the impact of uncertainties derived during testwork at key processing stages on the overall performance of mineral processing flowsheets. Case studies for both mineral sand and iron ore projects will be used to illustrate the concepts studied in this paper.

Jan 1, 2007

By S. Gqebe, A. Lewis, M. Rodriguez-Pascual

"Gravitational sedimentation of suspensions in various precipitation processes is hindered by colloidal stability. This is due to the high surface charge of the suspension and results in strong attraction/interaction between the ions on the particle surface and counter-ions in solution. Moreover, this strong interaction results in a charge build-up that renders the suspension stable. In order to induce gravitational sedimentation of these particles, a redistribution of ions close to the particle surface is required. We therefore sought to redistribute ions close to the particle surface by applying a magnetic field. This results in the reduction of interparticle electrostatic repulsive forces and a subsequent increase in the zeta potential of a suspension. For the purpose of this study, a copper sulphide suspension was used. Copper sulphide particles were exposed to a range of field strengths for set exposure times and their zeta potential was measured before and after exposure. All particles had an initial zeta potential value equal to or less than –40 mV prior to magnetic field exposure. A significant increase in zeta potential was observed, with values reaching a maximum of –16.5 mV when exposed to a 2 T field strength for 40 minutes. This is due to Lorentz ion shifts resulting from the Lorentz force exerted by the magnetic field on the particle surface. IntroductionMetal sulphide precipitation is a process for treating industrial waste streams with high residual concentration of mixed metal ions and acid mine drainage. This process has been reported to achieve higher metal removal compared with the industrially prevalent lime precipitation, due to the sparingly soluble nature of the metal sulphide precipitates formed. However, precipitation is governed by high levels of supersaturation which favour the formation of fine particles (Lewis, 2010). Consequently, some of the metal sulphide fines formed exhibit slow settling dynamics and thus tend to remain suspended in solution."

Jan 1, 2016

By E. J. Magri, A. Couble

Kriging estimates of geological resources are sometimes conditionally biased because the kriging plan contains too few samples. This may be done purposely in order to match the variance of the estimates to the true block dispersion variance. This work aims at evaluating the influence of conditional bias over the ultimate optimum pit design in relation to its shape, size and NPV (Net Present Value of profits). It has been restricted to two real case studies: a ‘carrot shaped’ gold porphyry in northern Greece and a manto-typeexotic copper deposit located in northern Chile. The methodology applied to each deposit consisted of generating a ‘real block model’ and four resource estimates by the use of conditional simulation and the application of four different kriging plans to the drillhole databases respectively. The estimation models vary in smoothness and conditional bias. Ultimate optimum pits were determined for the ‘real’ and the four different kriging models. Pit comparisons lead to the following conclusions: •In the worst case, conditional bias overestimated the project's NPV by 32% and 5% for the gold and copper deposits respectively. •The overestimation of high grades is more relevant than the underestimation of low grades. This resulted in a tonnage over-extraction of 148% and 1% for the gold and copper deposit respectively. This difference was attributable to the vastly different geometry of the deposits. •The smoothing effect of kriging, without or very little conditional bias, produced open pits that were different to the ‘true’ (ideal) ones and furthermore, underestimated the project's NPV by 10% and 6% for the gold and the copper deposits respectively. •Other factors that influence the optimum open pit design and to some extent control the effect of conditional bias are: the cut-off grade, the orebody geometry and distribution of grades within it and the amount of over-burden. Keywords: conditional bias, ultimate pit design

Jan 1, 2003

By K. Sinding

This paper discusses reasons for mining company mergers that have become the fashion, the role of the ?Juniors? and asks what the motives might really be. It examines changes in company concentration over the last 20 years in key mineral segments. Data at different stages of a project are examined to attempt to elucidate the role of the ?Juniors?. Areas for further research are suggested.

Jan 1, 2009

By A. M. Engelbrecht

Paper written on project work carried out in partial fulfilment of B Eng. (Chemical) Membrane processes are vital to a diverse range of technical and biological systems, which also feature in mineral processing applications such as the treatment of mine effluent and extraction of metals. In this study, the use of cellular automata to model a semi-permeable membrane that separates two compartments is considered. Cellular automata are simple models that enable the analyst to represent well-understood local effects, such as the chemical or steric interaction between molecules themselves and between molecules or particles and their environment, which can lead to very complex behaviour on a macroscopic scale. Various physical phenomena, including reverse osmosis, were simulated. Initial results for the effect of temperature, membrane structure and chemical properties of the solutes on the performance of the membrane appear promising. Keywords: cellular automata, dynamic modelling, filtration, membrane fouling, osmosis.

Jan 1, 2007

By R. Layton

Expert Systems Technology (EST) is becoming more and more widespread in both its range of applications and the public interest. It appears to be capable of performing tasks unmatched by other techniques. Within the mining industry a large body of unsolved problems now appear to have a solution. This paper examines the current state of EST both in the context of the history of Artificial Intelligence and current efforts at building mining expert systems. It provides recommendations for those wishing to get involved, and outlines the problems for those who believe that expert systems are capable of anything and everything. The paper also provides a detailed analysis of limitations of current EST that must direct research into more fundamental, commonsense areas than have been extensively covered before.

Jan 1, 1987

By P. G. Terrazas Prado

This paper presents the results of research on the development and application of a custom-made truck cycle and delay automated data collection system (TCD-ADCS) in a surface coal mining. Truck cycle and delay field data are locally stored in trucks and then synchronized and replicated through a wireless network into a centralized server containing an already-developed integrated production management system (IPMS). The system relies on motion sensing and distance travelled in order to automatically define the cycle starting/ending points, cycle time, position, and delay time. Connectivity and communication between loading equipment and trucks are also established. Communication between the equipment operators and TCD-ADCS system is via a user-friendly graphic interface. The hardware used for the development of this system consists of a rugged touch-screen personal computer, 2.4 GHz radio transmitter antenna, and a commercial GPS receiver. The system was developed, tested, and deployed at a surface coal mine in the USA. Keywords surface coal mining, truck and shovel, data collection, information systems.

Nov 1, 2013

By G. Lyman

The cross-belt sampler is a device that is very widely used even though it has not been ratified by the Standards associations. This paper is concerned with the bias testing of two cross-belt sampler designs against stopped belt samples and a cross-stream cutter at the belt end. The bias analysis is carried out using size distribution as the analyte and conventional t-testing and the Hotelling T squared test, which are compared for their effectiveness. The paper considers the issue of detectable bias and the statistical planning of bias tests.

Jan 1, 2009

One of the key issues facing gold producers is the management of cyanide and the implementation of the International Cyanide Management Code. Many operations now use cyanide destruction processes to ensure that the material being discharged to the tailings dam is compliant with regulatory requirements and the International Cyanide Management Code. One of the problems for operations is the quantification of both cyanide species and their reaction products throughout the leach and destruction circuits. Therefore methods have been developed utilizing high performance liquid chromatography (HPLC) to measure free cyanide, cyanide complexes of metals such as copper and iron, and other species formed from reactions in leaching and cyanide destruction, including cyanate, thiocyanate, and sulphur species (eg. sulphite, thiosulphate and sulphate). This enables a complete mass balance for cyanide and sulphur in both leaching and cyanide destruction. This paper outlines the methodology which has been developed and discusses the application of these methods in the fundamental research currently being conducted on the impact of sulphide minerals in cyanidation and cyanide destruction chemistry.

Jan 1, 2009

By A. Montini

The problems encountered in the design of control systems for milling cir- cuits when the model of the system and the model parameters are uncertain are discussed. Considering these uncertainty factors has led to the development of a technique that gives a quantitative assessment of real system stability, reveals the trade-offs between performance and stability and helps the designer in deciding what level of model complexity to use in the controller design. Furthermore, it allows for on- or off-line optimization of the milling circuit performance as it provides the base for the design of a controller which is stable over the plant operating range.

Jan 1, 1987

By J. M. Paull, J. B. See

The rate of reaction between different carbonaceous reducing agents and silicon monoxide gas was studied by the use of a technique developed in Norway by Tuset and Raaness. Argon carrier gas was used to pass a known fixed concentration of silicon monoxide gas through an I1 cm3 sample of precalcined reducing agent at 1650°c. Silicon monoxide gas was generated by the heating of a mixture of silica and silicon carbide, and the progress of the reaction was followed by monitoring the carbon monoxide in the off-gas with an infrared spectrometer. The reactivity of silicon monoxide gas towards a number of carbonaceous reducing agents (charcoal, Iscor coke, Lurgi char, and petroleum coke) was shown to be similar to results obtained with the carbon dioxide reactivity test. The silicon monoxide reactivity test was able to indicate the extent to which fines were generated when the reducing agent was converted to silicon carbide. Of the reducing agents studied, Lurgi char appeared to be the most suitable for the production of ferrosilicon because it has a high reactivity towards silicon monoxide gas and high strength when converted to silicon carbide. So that industry could be given some indication of the suitability of certain reducing agents for the production of ferrosilicon and silicon metal, a reactivity scale similar to that of Tuset and Raaness was constructed that compares the volume of silicon monoxide gas required by a reducing agent to reach a carbon monoxide content of 10 per cent in the off-gas during the conversion of the reducing agent to silicon carbide. This scale assists in the selection of those reducing agents that require less silicon monoxide gas for conversion to silicon carbide, and that give savings in material and power costs because less silicon monoxide gas need be generated in the furnace.

Jan 1, 1979

By H. H. McGregor

SYNOPSIS Changes in the national productivity (gross national product per head of the population) have been assessed in order to derive a target figure for the required annual increase. The conclusion reached IS compared with the targets of the economic development programme of the Republic. Productivity and management structure in the gold mining industry is then analyzed together with investment in plant, machinery and equipment for rock handling purposes. The conclusion is drawn that productivity improvement does not appear to have accorded with the massive expenditures in plant and equipment, and in augmented management. The productivity of the manufacturing and construction sectors of the economy has been examined. The principal difficulty is that the main avenue of approach is the value of product divided by the total labour force. This introduces inflationary questions, and the use of a suitable deflator becomes of prime importance. Severa1 different methods of assessing the productivity improvement in the industrial sector have been used with what is regarded as a comparatively high degree of compatibility. Improvements in productivity in the manufacturing industry up to 1966 appear, from the information available, to have substantially exceeded comparable figures for the mining industry. There is however evidence that thereafter productivity of the manufacturing industry has not maintained this satisfactory rate of increase. If the economy is to achieve the planned rate of expansion, there is no doubt that greater attention to this aspect will be required in the future than has been accorded to it in the past.

By G. Raspa

The paper describes a computer procedure for evaluating and selecting recoverable reserves in a mine worked by sublevel stoping. The boundaries of the volume to be mined are optimally defined by means of the 3-dimensional Lerchs-Grossmann algorithm, separately applied to both sides of the panels. The procedure, which has been developed for Masua Mine (Sardinia), also provides for smoothing the optimized boundaries, positioning the drilling drifts, interactive design of drilling fans and calculation of tonnage and grade of each volley. These tonnages and grades form the input of another procedure evolved for production planning.

Jan 1, 1987

By J. J. Cilliers, I. K. Craig, J. D. le Roux, K. Hadler

An analysis of the state-observability characteristics of a dynamic tank-to-tank model of a flotation bank indicates that the concentrate-flow rate of each tank can be estimated from accurate measurements of the pulp height in each tank and the final tailings flow-rate exiting the final tank. Therefore, there is an opportunity to construct an observer (model-based soft-sensor) which can estimate the concentrate flow-rate of tanks in a flotation bank. The concentrate flow-rate, i.e. mass pull, is generally measured by means of froth image analysers on industrial plants. A model-based soft-sensor will not only provide a means to validate froth image analyser results, but could potentially substitute them as they are less expensive to implement and maintain. Keywords: Concentrate flow-rate, estimation, flotation, modelling, observability, soft-sensor

Jan 1, 2020