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A General Meeting and Colloquium was held in Kelvin House, Johannesburg on Wednesday 29th September, 1971. The theme of the Colloquium was "The Ferro-alloy Industry". Prof D. D. Howat (President) was in the Chair. The meeting was attended by 106 delegates and was opened by the President at 10.05 a.m. OBITUARY The President: "It is my sad duty to announce the death of G. C. Needham, Fellow, who joined the Institute in 1966 and passed away on 27th September, 1971. As a mark of respect to the memory of the deceased and in sympathy with the bereaved I would ask you all to rise and observe a few moments silence." MEMBERSHIP The President: "I have much pleasure in announcing that the names of the following candidates, having been published in accordance with By-Law 5.2.2, Council has elected them to membership of the Institute. Fellows: Richard Lloyd Blandy, Brian Roger Borton, Brian Teversham, Peter Donald Dickson. Members: Frederick Brian Peacock, Peter John Stacey, Kenneth Niles Thanstrom, Byron J. Hayley, Ian Flemming Buchan, Abraham Hercules le Roux. Graduate: Ian William Coy. Students: Peter Boesley J ames, Kenneth Brian Perel. TRANSFERS From Member to Fellow: Cecil Eugene Fivaz, Peter Edwards. From Student to Graduate: Roy Stavely Traviss. From Student to associate: William Mitchell. I welcome the new members to the Institute and congratulate those members who have been transferred to a higher grade. COLLOQUIUM The first paper, presented by Mr S. Selmer-Olsen, Consulting Metallurgist, Amcor Limited, on 'Trends in Ferro Alloy Production' was published in the May issue of the Journal and comprised information and data relating to new developments in ferro alloy production in various parts of the world. This was followed by a paper-'Conductivity and Viscosity Properties of Slags produced in ferro-alloy manufacture' by D. 1. Ossin et al. This was a record of laboratory test work on slags containing both lime and magnesia, corresponding with the composition of slags encountered in the production of ferro chrome alloys when a dolomite flux is employed. The third paper-'Review of the work of the Pyrometallurgical Research Group of N.I.M. and Metallurgy Department, Wits.' presented by Dr P. R. Jochens, leader of the Research Group, outlined the progress made on ten different research projects presently under way in the Department of Metallurgy. These projects range from studies of the kinetics and mechanism of the reduction of chromite ores through the determination of the activities of MnO in slags to phase studies and melting point determinations in the alloy systems Cr-Fe-Si-C and Cr-Fe-Si. A new feature of this Colloquium was the introduction of the discussion panel composed of four or five individuals known to have special knowledge or interest in the subject under duscussion. Mr J. J. Coetzee was chairman of the first panel, Professor D. D. Howat of the second and Dr R. E. Robinson of the third. During the discussion of Mr Selmer-Olsen's paper an interesting contribution was made by Mr Jack Hayley of Transalloys (Pty.) Limited who pointed out that the lowest power cost in the U.S.A. was that from the TV A at 6 mils per unit (0,43 cents S.A.) while costs from other sources were 7 to 8 mils per unit (0,50 to 0,57 cents S.A.) He also referred to the use of 'pile sintering' of ore fines plus coke at certain ferro alloy plants in the V.S. and to the recent practice of 'graphitising' the paste used for Soderberg electrodes. The last session in the afternoon was devoted to a group discussion on 'Practical problems in Arc Furnace Operation', Mr H. R. Reid of Middelburg Steel Alloys (Pty) Limited occupying the chair, members of the panel being Mr J. Meintjies (Rand Carbide Limited), Mr J. Benn (Amcor) and Mr E. J. Jackson (Transalloys (Pty.) Limited). Mr Reid initiated the discussion by talking of the design and composition of electrode shoes, mentioning the use of the 85/15 Cu/Zn alloy and the comparison of hollow shoes and shoes cooled by tubes. Mr Meintjies discussed electrode management with particular reference to breakages, and dealt with casing and fin design and the welding of fins. Mr Benn dealt with aspects of closed top furnace operation with particular reference to the control of eruptions in the furnace and indicated that preheating of the raw materials might be well worth considering together with the development of a system for the detection of the water vapour present. Mr J ackson was concerned with shells, linings, refractories and tap holes. He deprecated the use of oxygen for opening the tap hole emphasising how uncontrolled use of oxygen led to loss of shape of the tap hole and quite severe burning out of the front hole resulting in time and labour in repairs. A notable feature of the Colloquium was the free discussion 'from the floor' of the hall. Many valuable and highly pertinent contributions were made spontaneously and usually in reply to some controversial topic raised by the discussion group.

By André de Jager, Henk Ludik

Navachab Mine experiences difficulties with pit wall stability in certain areas of the mine. The main reason for the instability is the fact that the geology comprises many joints and faults. Blasting, without impacting negatively on the stability of the pit walls, poses a major challenge. The mine has installed a technologically advanced seismic monitoring system with monitoring sensors positioned at various locations and depths throughout the pit. The electronic data recording system records all relevant information on a continuous basis with early warning signals in cases of potential danger. From the information recorded by this micro-seismic system it was established that the energy release into the high-wall is predominantly influenced by the mining rate, water content and mining tempo and to a lesser extent by the blasting operations. To limit the negative effects of blast vibrations, the use of Electronic Delay Detonators (EDDs) was introduced. The optimal delays were determined through signature trace analysis. The vibrations obtained during blasts initiated by means of electronic delay detonators were monitored and compared to those traditionally obtained when standard pyrotechnic delay detonators had been used. The measured vibration data indicated an improvement of 25% to 100% drop in vibration amplitude compared. The accuracy and programmability of EDDs presented huge potential for blast optimization in terms of limiting the vibrations without compromising fragmentation. The whole project was conducted over a twelve week period with some 4000 EDDs. The average size of a blast was in the order of 350 holes using about 40kg explosives per hole, which equates to 14,000 kg explosives over 12 different blasts. The paper deals in detail with the blast optimization process with regard to: - determining the rock response time; - establishing the signature traces; - analyzing the wave interference patterns; - predicting the direction of constructive and destructive wave interferences; - optimizing of the inter-hole and inter-row delay periods; - measuring the ground vibrations. The results obtained during electronic blasting are compared to those obtained during pyrotechnic blasting. Comparisons are being made with regard to the following: - ground vibration measurements; - pit wall stability measurements; - blast safety.

Jan 1, 2006

By M. Grodner

Ground Penetrating Radar (GPR) is an electromagnetic geophysical reflection technique that maps reflections associated with a change in electric properties of the target medium. It can thus be used to map the geometry of geological features and fractures as these can have different electromagnetic properties to intact rock. GPR was used successfully to determine the position and nature of the fractures in the tunnel sidewall, in the area of the simulated rockburst experiment. By comparing the radar scans acquired before with those acquired after the blast, it was possible to determine which fractures were reactivated by the blast and where new fractures were developed. It was found that the mining-induced fractures that formed during the development of the tunnel were re-activated by the simulated rockburst, as indicated by their increased reflectance on the radar scans. In addition, several new tunnel sidewall parallel fractures developed in the area of the blastholes. GPR thus clearly shows how and where the fracture pattern changed as a result of the blast and contributed to the understanding of the mechanisms of damage associated with the blast, and perhaps rockbursts in general.

Jan 1, 2001

By V. I. Ryaboy, V. P. Kretov, I. V. Ryaboy

Attachment of collectors containing thioamide groups to sulfide minerals is interpreted as interaction between NH-acids and sulfides acting as solid bases with the formation of a donor–acceptor reagent–mineral bond. As the acid function of the reagents increases, their sorption optimum is observed to shift to a less alkaline region. The developed concept has enabled us to propose a method for calculating optimal pH values for the sorption of reagents on mineral surfaces depending on the acidity of the reagents and the pH value of the medium. Our estimates correlate well with the experimental data. We studied the spectra of the reagents containing thioamide groups and the spectra of copper salts and their surface compounds on an oxidised copper film, chalcopyrite, and pyrite using the infrared (IR) spectroscopy. Some effective applications are described of reagents containing thioamide groups in the flotation of copper, copper-molybdenum, and gold ores, both separately and in combination with other collectors. It is shown that the flotation performance is maximised by adding two- and three-component collector combinations, including collectors containing thioamide groups. In this case, the increase in the recovery of copper, molybdenum, and gold is up to 2-5% compared to conventional process conditions. A new, high-performing reagent containing a thioamide group is proposed. A commercial pilot batch of the reagent was produced and sent for flotation tests in gold ore applications. Keywords: Thioamide reagents, dialkyldithiophosphate, collectors, flotation, arsenopyrite, chalcopyrite

Jan 1, 2020

By C. Birch

"The purpose of this study was to establish the impact of discount rates on cut-off grades for narrow tabular gold deposits as characterized by the goldfields of the Witwatersrand Basin in South Africa. There are various methods available for determining the cut-off grade, from simple breakeven calculations to sophisticated software packages that consider a variety of inputs to optimize the cut-off grade. For this study a simple financial model was created in Microsoft Excel® that links the ore flow, block listing, and the cash flow. This allows the cut-off grade to be optimized considering how the cost of capital and chosen discount rate affect the cash flow.The discounted cash flow (DCF) and resultant net present value (NPV) are a widely used valuation method for production properties according to the South African Code for the Reporting of Mineral Asset Valuation (SAMVAL Code). The financial model in this study utilizes the Solver function, as well as simple Microsoft Excel spreadsheet formulae to optimize the NPV. Solver was chosen as it is a standard feature in Excel and thus no additional software costs are incurred beyond the basic Microsoft Office suite. For the purpose of this study, just narrow tabular gold deposits of the Witwatersrand Basin were considered. An example of a typical ore block listing, as well as the costing figures, was obtained from an operating gold mine. The results obtained from the study financial model were compared to the current cut-off grades obtained from the mine using their proprietary optimizer program, and were found to be comparable. The methodology utilized for this study thus appears valid.The cut-off grade was optimized considering the cash flow, which includes the variable mineral resource royalty tax, the variable gold income tax, as well as the discount rate. By comparing the resultant NPVs using discount rates of zero, 9%, and 12%, the impact of the discount rate on cut-off grades, resultant life of mine, and average mining grades (AMG) could be compared for the example ore block listing. The South African Code for Reporting of Exploration Results, Mineral Resources and Mineral Reserves (SAMREC Code) does not require operations to state if a discount rate was considered in determining mineable reserves. Mining companies approach the question of applying discount rates in determining their cut-off grades, and thus mine planning strategy, in different ways. Due to the negative impact that optimizing purely on NPV has on the life of mine, some choose to optimize only on profit. Other companies have reverted to utilizing pay limits as their primary grade planning strategy. The calculated cut-off grade is then considered to be another planning indicator rather than a hard determination of mineable reserves."

Jan 1, 2016

By J. Böhlke, B. Friedrich, E. Hecker

The legislation for the disposal of heavy metals contaminated substances is still going to be tightened up in the future. The main criteria for the utilization or deposition of these residues are the content and the water solubility of these metals. Through this, the use of slags from the lead-and zinc-industry in road building may become limited or even not possible at all. From an economic point of view this would lead to Pb/Zn losses and costs for safe dumping. This paper investigates the feeding of the reducing agent via hollow electrode DC smelting and the yield of metal reduction. After carrying out thermodynamic calculations, the process window conditions for electric-arc furnace tests were determined. Doing this, the zinc could be reduced, evaporated and recovered as an oxidic intermediate product flue dust, while the lead was present either in flue dust or in metallic form. The zinc content in the final slag could be reduced by up to 90%. The slag product has undergone an eluation test which allows it to be used as building materials. Keywords: zinc reduction, lead reduction, hollow electrode, slag treatment, electric arc furnace

By J. J. Stacey

Large mining companies generally follow the distributed ownership corporate model, with a board of directors responsible for decisions that affect both shareholder value and stakeholders of the company. The board is simultaneously responsible for setting the culture and values of the corporation, which drive performance and priorities. Companies listed on the Johannesburg Securities Exchange (JSE) commit to sustainable development in various ways, either by virtue of implementing the King Code of Governance 2009 (King III) and/or through their own public reporting on social and environmental matters. Many mining companies make public statements regarding their support for environmental stewardship, ethical behaviour, and fair treatment of communities. It is a local, regional, and indeed, global phenomenon that companies fail to deliver on these statements. Research was carried out through the Institute of Directors of Southern Africa in 2007, and followed up in 2012, regarding directors? understanding of sustainable development issues, the relative priorities, what is needed for ?radical change? to effect sustainable development, and what enables or constrains the latter. Pertinent findings of both surveys are presented in this paper, and it is suggested that ?on-the-ground? performance may be indicative of the nature of leadership and decisions in the topmost ranks of the company. The results indicated that environmental concerns fall consistently below social issues. Financial capital ranked most important, and while environmental issues are recognized as being of strategic concern for the long-term, they ranked as being the lowest importance of all ?Five Capitals? (Financial, Manufactured, Social, Human, and Natural). Social capital ranked second lowest, with black economic empowerment being the only high-priority social issue. There is also evidence that certain companies within the mining sector fail to recognize their absolute dependence on natural resources. Much is made in academic and popular literature of the need for a new type of leadership for the radical shift to sustainable development: at company level this implies therefore a new type of director. The research found that only 14 per cent of directors felt that board decisions are consistent with their personal values; while intentions are strong to behave ethically and serve sustainable development, actions to give effect to these intentions lag significantly. Respondents indicated that the top impediments to courageous leadership for sustainable development related to personal issues of maintaining the image of being a director, fear of appearing weak, fear of being a lone voice, and bowing to board-colleague peer pressure.

Jan 1, 2014

By R. E. Gürtunca, D. J. Adams

Writen contribution by J.F.Curtls The subject mater of the paper is interesting in that, instead of 'numerical modeling based on elastic theory' being used for the prediction of energy release rate (ERR) in relation to various types of stope support, including backfil, use is made of stresses in the backfil in an atempt to corect the numerical modeling. Authors' reply to J. F. Curtis We thank Mr Curtis for his contribution to our paper. First of al, it should be emphasized that the object of the paper is not to address the validity of ERR as a tool for the assessment of seismic events or rockbursts, but to determine an in situ modulus for the rockmass with the aid of backfil measurements. Writen contribution by T.R. Stacey Although the authors of the above-mentioned paper have presented some good and interesting information, the title of the paper, and the recommendation that such an in situ modulis should be used for calculations of energy release rate (ERR), are viewed with some concern. The reasons for this concern are as follows. Authors' reply to T.R. Stacey Dr Stacey's comments on our paper are appreciated; we should like to address his concerns as follows.

Jan 1, 1991

By M. Bryson, J. Taguta

The Prieska deposit, mined between 1971 and 1991, is one of the world’s top thirty volcanogenic massive sulphide (VMS) base metal deposits. The Prieska Copper Mine in the Northern Cape Province was closed by Anglovaal when underground mining had extended to depths which did not allow for safe and economic extraction of the deposit at the time. The mine has a recorded historical production of over 1 Mt of zinc and 430 k tonnes of copper from 46.8 Mt of milled sulphide ore, achieving life-ofmine metal recoveries of 85% for copper and 84% for zinc into high quality concentrates (refer ORN ASX release 15 Nov 2019). Orion Minerals Ltd is currently investigating the feasibility of developing a new mine in the footprint of the historical Prieska Copper Mine, using the extensive remaining infrastructure, with the intent of extracting the unmined zinc-copper mineralisation from the Prieska deposit. This paper reports results on the flowsheet development philosophy on the hypogene ore, and challenges encountered in the process. This study initially failed to replicate historic copper and zinc recoveries employing the historic production flowsheet and reagent conditions unmodified on bench scale, as the copper and zinc were co-floating. Flowsheet modifications were therefore made to improve differential flotation and recovery, resulting in achieving comparable saleable products and recoveries from processing the hypogene ore on bench scale. Flotation variability test work on the hypogene ore focused on the use of the original flotation procedure and reagent suite using a sodium cyanide-zinc sulphate depressant system on the copper circuit, and it generated a saleable copper product of 20-26% Cu grade at 80-86% recovery. The zinc circuit generated a saleable zinc product grading at 48-55% Zn at 80-94% recoveries. Some zinc losses were due to the deportment of some zinc in sauconite. It is recommended that further test work may further improve the copper grades and recoveries. Keywords: Prieska, flotation, hypogene ore, flowsheet development, sulphide flotation, reagents

Jan 1, 2020

By J. H. E. Perry, V. H. Wiik

"The ore deposits of the Zambian Copperbelt occur in sedimentary strata that have been subjected to relatively mild, flexure-type folding. Unrolling serves to reconstruct the original depositional geometry of the folded sedimentary strata and is in common usage on the Copperbelt both for geological analysis of drill hole data and in routine ore reserve estimation.A computerized method of unrolling was introduced at Roan Consolidated Mines in 1969 based on a standard contouring program. A contour map of the geological structure is drawn from a regular grid of elevations, interpolated from the original, irregularly-spaced intersections. Unrolling is performed across this grid, perpendicular to one or two axes specified by the geologist. Each intersection is unrolled independently, and the new co-ordinates are subsequently processed to produce unrolled maps.The technique has been used successfully at RCM over the last two years in both the estimation of ore reserves and exploration planning."

Jan 1, 2014

By S. Rolseth, J. Thonstad

The traditional electrolyte for aluminium electrolysis is based on molten cryolite (Na3AlF6), acting as solvent for the raw material, alumina (Al2O3). Over the years there has been a trend to increase the content of excess aluminium fluoride (AlF3) to the cryolite-based electrolyte, in order to enhance the current efficiency of the process. In most cases one has ended up at 11?13 wt% excess AlF3because higher contents makes it difficult to control the heat balance of the process. This problem may be overcome if sensors are developed that will allow online control of electrolyte temperature and composition, and we may then see a surge towards still higher AlF3contents. In the development of new anode materials to replace the carbon anode with inert, oxygen-evolving anodes, focus is on anode corrosion, and a low electrolyte temperature is then highly desirable. While the conventional process operates at around 960°C, electrolyte temperatures as low as 750°C are being tested. This is achieved by having large excess contents of AlF3(40 wt%). The consequences of using such electrolyte compositions are discussed.

Jan 1, 2004

By I. V. Filippova, Y. Foucaud, M. Badawi, L. O. Filippov, S. Lebègue

To optimize the flotation of Ca-minerals, their separation contrasts were investigated by coupling experimental and theoretical techniques. We showed that they mainly rely on structural properties such as the Ca-Ca distance on their exposed surfaces but also on the ability to control the intermolecular interactions. An optimized composition of the carboxylic collector by calculating the collector-mineral and the intermolecular interactions was developed. Blending the saturated acids and non-ionic molecules with a fatty acid collector significantly increases the flotation selectivity between scheelite (CaWO4) and fluorite (CaF2). The theoretical results were validated by experimentally improving the separation contrast between Ca-minerals. After the tests of several depressants and collectors, the best depression of gangue Ca-minerals (fluorite, apatite and vezuvianite) was found by combining sodium silicate and sodium carbonate. Keywords: Ca Minerals, Fluorite, Scheelite, Carboxylic acids, Unsaturated Acid, Fatty acids

Jan 1, 2020

A localized nonlinear recoverable resource estimate technique has been applied using typical feasibility or new mining drilling data configurations drawn from a massive database from a mined-out area on a hydrothermal gold deposit. The results were then compared with the corresponding 8 m x 5 m grid grade-control data in order to determine the efficiency of the approach and the validity of the recoverable resource estimates for mine planning and financial forecasts.

Jan 1, 2014

By M. Pineda

Sublevel stoping (SLS) is one of the oldest and most used methods for underground mining. It relies heavily on the use of drilling and blasting techniques to remove the rock, and gravity to transport the broken rock to drawpoints located at the base of the stope, with LHDs to transport material from the drawpoints. Current SLS operations are based on the assumption of stable geometry of the stope. Thus, the stope design includes the definition of the geometry according to the orebody shape and geomechanical constraints to avoid instability, which may cause excessive dilution. Under some circumstances, dilution could enter the stope due to geotechnical instability, especially when large stope geometries are used. A review of current design and planning practices for large SLS operations indicates that no consideration is given to the material flow and the mixing that occurs after blasting. Material flow could have a large impacton the mixing of ore when grades are heterogeneous in the stope. In this paper, we discuss the influence of gravity flow on the design and planning of large sublevel stopes with and without vertical dilution, based on laboratory experiments. The outcomes of this investigation are used todevelop guidelines towards the design and planning of large SLS mines, which would complement the currently used geotechnical considerations.

Jan 1, 2015

By R. Hemp

This paper describes in broad outline the development of a computer programme for determining the effects of changes in various factors in the condenser water circuit on the operation of a cooling plant. The programme is used to obtain design figures which result in minimum total power consumption. This was done for a range of different upcast air quantities, and the implications of low air quantities for heat rejection are discussed.

By G. M. Evans, S. Mitra, A. V. Nguyen

As an alternative to the conventional flotation method, there has been continual research in an effort to enhance base metal ores and combustibles recovery using ultrasonics. These studies however were largely limited to the pre-treatment of ores for the removal of surface contaminants while the effect of ultrasonics on the bubble and pulp-phase interactions remained somewhat unexplored. Noting this deficiency, this study aimed to investigate the mechanistic effect of an ultrasonic field in an impeller less flotation cell specifically focusing on the bubble-particle interaction dynamics. A lab-scale flotation cell (capacity 1 litre) was designed, involving a vertically oriented ultrasonic probe (20 kHz, rated at 1.2 kW) and operated in the output power range from 1 to 20% with continuous liquid recirculation. Particle suspension was achieved by the combined action of recirculation and ultrasonic pulses. Interactions of coarse size glass ballotini particles (D32 = 314 μm) with bubbles (< 1 mm diameter) in the presence of a surfactant were studied, using high-speed imaging. Application of an ultrasonic pulse in the aqueous medium resulted in the generation of numerous microbubbles which increased with increasing input power and duration of the ultrasonic pulse time. Such periodic pulses introduced at a high level of turbulence in the pulp phase facilitated adequate bubble-particle contacts. Microbubbles played a key role in forming particle clusters which were observed to be floatable even in the absence of any carrier bubbles. When carrier bubbles were introduced, some of these particle clusters attached to the bubble surface and conveniently floated. It was noted that a favourable state of bubble-particle interaction was achievable to produce stable bubble-particles aggregates by suitably controlling the input power and period of the applied ultrasonic pulse. Keywords: Flotation, bubble-particle interactions, collision, attachment, detachment, ultrasonic pulse

Jan 1, 2020

By X. Cao, R. Wang, H. Han, Y. Hu, Z. Wei, W. Sun, H. Tang, J. Wang

Flotation reagents play a vital role in mineral flotation. In the past century, most studies focused on the modification of anion or cation collectors and the synergistic effect of mixed collectors, which have contributed to research. In this study, we reviewed brand-new reagents, metal-organic/inorganic complexes, with the functional group of metal ion, which are totally different from the traditional anion or cation collector and show absolute specificity for some minerals. For example, Pb-BHA complex collector was developed to realise the atmospheric flotation of scheelite due to the absolute specificity for calcium minerals. Calcium oleate collector was found to be the effective species in the flotation of calcium minerals, and has been employed to selectively separate fluorite from calcite. Selective adsorption of Al-Na2SiO3 polymer on calcite surfaces proved the self-assembly of H2SiO3 polymer using Al3+ had stronger selectively adsorption ability than Na2SiO3. Also that Fe3+-starch complex was a better depressant for iron minerals than caustic starch and contributed to a more efficient reverse flotation. In conclusion, metal ions are good templates for molecular assembly and can be used to control the structure of metal complexes and exhibit special properties, which provide possibilities for the design of new flotation agents. Keywords: Metal-organic/inorganic; flotation; collector; depressant

Jan 1, 2020

By D. Grabowski, Z. Pokryszka

A study carried out in the iron basin of Lorraine (North-East of France) highlighted the existence of under-oxygenated and noxious gas emissions (carbon dioxide, radon…) in vast built-up areas related to former mine workings. Site investigations showed that the gas flow was mainly due to natural thermal air circulation between old mines and external atmosphere. The main hazards associated with this flow of gas and its potential accumulation in confined volumes in buildings are asphyxiation and intoxication. A further study is in progress in order to better understand the origin of the gas generation within the old iron mine workings. Following the first hypothesis, the carbon dioxide emission is mainly due to the specific hydro-geo-chemical process associating the pyrite oxidation with the acid dissolution of carbonates. KEY-WORDS : gas, emission, iron mine, pyrite.

Jan 1, 2003

By J. Githiria, D. Wachira

The conventional truck and shovel haulage system has become expensive to operate in most mines due to current strict environmental conditions, increase in depth and size of open-pit mines, increase in labour costs, and fuel costs. These factors have motivated the search for alternative material haulage options in open-pit mines. In-pit crushing and conveying (IPCC) system has been regarded as a plausible alternative in material haulage systems. However, usage of IPCC has been limited to a few mines due to limited knowledge of IPCC performance, and other technical factors of the system. This paper investigates, and evaluates the productivity performance of four types of IPCC systems (fixed, semi-fixed, semi-mobile, and fully mobile IPCCs) using mine productivity index (MPi). Using a model developed by MATLAB, the MPi for the four systems is computed using input variables such as availability, utilisation, performance and number of trucks and shovels in a limestone quarry. The mine productivity index for fixed, semi-fixed, semi-mobile, and fully mobile IPCC is obtained as 67.13%, 69.02%, 70.52%, and 71.52% respectively. In conclusion, the fully mobile in-pit crushing and conveying system is the most appropriate IPCC in the quarry, due to its better productivity performance compared to the other three IPCC systems and the truck and shovel system currently in use.

Sep 1, 2021

By N. Moemise, M. B. Shongwe, P. A. Olubambi, M. M. Ramakokovhu

"Near-infrared (NIR) spectroscopy sorting technology is incorporated in an automated optical mineral sorter that can discriminate between materials using the differences in characteristics when exposed to near-infrared radiation. During September 2014 to April 2015, a pilot plant that utilized NIR technology to discriminate between kimberlite and waste materials was commissioned to determine the viability of including this technology in the diamond winning process flow sheet at Cullinan Diamond Mine. The plant was used to minimize the waste content in the size fraction -70+35 mm that reports to the crushing section and then to the dense media separation process. This paper describes the initial test work, conducted at Mintek, that led to the decision to conduct a pilot-scale study. The mineralogical characterization of the feed and product streams to establish the sorting criteria and the operational data obtained during the pilot plant campaign are described. The results indicated a good possibility of discriminating between the kimberlite and waste material using NIR technology. However, the consistency of discrimination was not good enough to avoid the risk of potential diamond loss. Furthermore, a lower than expected availability of the machine reduced the throughput capabilities. IntroductionUsing near-infrared spectroscopy (NIRS) technology for ore sorting is a new concept for the mineral processing and mining industry. NIRS has been used for decades in the laboratory for the identification of pure minerals, and has its roots in the recycling, food, and pharmaceutical industries (Salter and Wyatt, 1991; Robben et al., 2009). Ore sorting in itself is not a new concept; it was introduced during the Stone Age with handsorting being the first method to separate valuable materials from gangue (Wills and Napier-Munn, 2006; Sassos, 1985). However, over the years the scale of mining has increased and hand-sorting has become challenging to implement (Joensson, 2014).Sensor-based sorting is an advanced technology that can help overcome problems such as ore dilution experienced in mineral processing operations. The benefits are lower energy and water costs, reduced ore dilution, lower environmental impact, and improved profit margin (Mathew, 1974; Jonsson, 2014; Salter and Wyatt, 2009; Death et al., 2009). In sensor-based sorting, materials are mechanically sorted based on certain physical properties that are detected by a sensor (Dalm, 2013). Research has found that with NIR scanners it is possible to obtain a ‘fingerprint’ of a sample that is directly related to its mineralogical composition. According to Woutruba et al. (2009), molecules absorb NIR radiation by means of electronic and vibrational transitions. Nowadays, there are many sensors available in the market that utilize different material properties; the choice of a sensor is dependent on the mineralogy of the ore."

Jan 1, 2016