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By A. Mabentsela

A furnace freeze lining is necessary for safety and economic reasons in several smelting operations. The integrity of the freeze lining is put at risk by furnace power imbalances. Although numerous models have been derived to model the growth and depletion of the freeze lining due to power imbalances, no model exists for thermomechanical damage to the freeze lining. This study provides an initial pathway for modelling thermomechanical damage to the freeze lining in an ilmenite smelting furnace using information from the literature and experimental work. A methodology under the framework of continuum damage mechanics is proposed to model mechanical damage to the freeze lining due to phase changes, thermophysical changes, and constrained thermal expansion. Drill cores of solidified slag ingots were used to represent the freeze lining. The modified power law proved to be the best predictor of the softening response of the drill cores. Damage driving parameters were extracted from the raw data, and governing equations of the parameters with respect to temperature were derived for use in a finite element method (FEM) code.

Jan 26, 2023

By S. Banisi, S. Zare, M. Mahmoudi, M. Maleki-Moghaddam, M. Yahyaei

As the orebodies become more complex and lower grade, there is an increasing demand from crushing circuits for a finer product. When the product from a crushing circuit does not satisfy the requirements of the downstream processes, the cost of production increases. Thus, enhancing the performance of cone crushers through optimisation of their operating factors becomes important. One of the key factors affecting performance of cone crushers is the filling of the crushing chamber during the operation. The effect of varying the filling of the crushing chamber of a cone crusher was investigated. To assess the crusher performance, parameters such as crusher capacity, power utilisation, and reduction ratio were used. Extensive plant trials were conducted to obtain samples and operational data when the crusher chamber was 50% full (half-full) and 100% full, which is 300 mm above the top of the crusher chamber (super-choked condition). The results indicated a 62% difference in the crushing capacity when the crusher was operated in a super-choked condition compared to the half-full chamber level. In the super-choked condition, the size-specific energy at 12.7 mm was 20 % lower than that of the half-full condition. The Bond ball mill work index (BBWI) of crusher product indicated that the BBWI of the product of the super choked condition is 5.6% less than that of the product of half-full condition. This can be attributed to the generation of micro cracks in particles due to increase in the interparticle breakage when the crusher was operated in the super-choked mode. Keywords: Cone crushers, crushing efficiency, crushing chamber filling

Jan 1, 2020

By J. Madias, E. Benavidez, E. Brandaleze, L. Castella

Knowledge of the physical and chemical properties as well as the behaviour of the mould fluxes during melting, important in order to improve continuous casting operations. Lubrication and control of heat transfer in the mould are the more relevant functions of these materials. Values of physical properties like viscosity and surface tension at melting range temperatures are required, as much as the thermal behaviour under process conditions. The heat extraction from the liquid steel has an important effect in the final quality of products. Mould fluxes are constituted by different oxides, and may form glasses and crystal phases during cooling. The solidification rate and the chemical composition determine the proportion, type and crystalline morphology, which are responsible of the thermal transfer processes. In this paper, viscosity values are reported in the melting range temperatures calculated by means of the Riboud model and compared with fluidity results obtained by the inclined plane technique. Also the linear expansion of the mould fluxes at high temperatures was determined by dilatometry. The crystallization in two different fluxes was determined by DTA tests and correlated with the basicity index. Crystal phases were evaluated by scanning electronic microscopy on quenched samples at 1300°C. This information is relevant to increase the knowledge on the peritectic steel grades casting process in order to improve its quality. Keywords: mould fluxes, heat transfer, crystal phases, peritectic steels, thermal properties.

Jan 1, 2004

By L. Shoke

The aim of this study was to develop an in-house tensile testing procedure that would yield accurate and reproducible parameters as input material properties into computational models for numerical simulations of the mechanical behaviour of TM380 mild steel. To achieve this objective, we reviewed the ISO 6892:2009 tensile testing standard along with reported good practice guidelines. Tensile tests were conducted on a dog-bone shaped TM380 mild steel specimen with strain gauges attached on either side, to monitor alignment and measure strain, using three different types of tensile testing machines. Parameters quantified included yield stress, ultimate tensile strength, and modulus of elasticity. The values of these parameters were found to be in agreement with the values supplied by the manufacturer's specification and showed minimal variations between laboratories. Thus it can be concluded that the tensile test procedure used resulted in accurate and reproducible results. The strain values calculated as per standard were in disagreement with those determined from extensometer and strain gauges and resulted in lower elastic modulus values. This confirms that the current testing procedures require the use of long-range strain gauges or extensometer to determine the strain. A chemical analysis was conducted to verify the specification by the manufacturer. The specimen was found to be fairly homogeneous with minor sulphide inclusions. The micrographs reveal a pearlite and ferrite structure typical of mild steel, and the fractographs show a dimpled surface typical of ductile fracture, which is an attribute of mild steel.

Jan 1, 2013

By M. J. Makhula, R. M. S. Falcon, S. O. Bada, L. M. Falcon

"SynopsisThe combustion and co-combustion behaviour of macadamia nut shell, high-ash coal, and anthracite, along with their blends was studied using thermogravimetry. The reactivities of all samples were analysed in air, oxygen, and CO2 atmospheres and at different heating rates from 10 to 40°C/min. Macadamia shell was found to have a lower ash content, 0.36%, than coal with 27.49% ash. The calorific values were similar, 19.64 MJ/kg and 19.44 MJ/kg respectively. The differential thermogravimetric results indicate that as the heating rates increase the ignition, peak, and burnout temperatures increase significantly, leading to high combustion rates. The interaction between the fuels was evaluated using the weighted average model, and the results indicated that there is more synergetic interaction between 20% macadamia plus 80% coal under oxygen than in air and CO2 atmospheres. The results of the investigation provide the combustion and co-combustion characteristics of various samples and their blends and indicate their combustion compatibilities. IntroductionThe global macadamia nut industry is developing at a very rapid rate. South Africa is currently the world’s third largest producer, with a production of about 35 000 t as of 2012 (Department of Agriculture, Forestry and Fisheries, 2013), compared to 840 t produced in 1996. The greatest numbers of the macadamia nut farms in South Africa can be found in Mpumalanga, Limpopo, and KwaZulu-Natal provinces, with Mpumalanga as the largest producing area. There are many factors influencing the increased demand for macadamia nuts, the most important factor perhaps being their nutritional value (California Dried Fruit and Nuts, 2011; MPC, 2014) and their suitability as a feedstock for manufacturing cosmetics, bakery products, nut paste, chocolates, sauces, and ice-cream. As a fuel, macadamia shell has a high heating value ‘as-fired’ of about 20.71 MJ/kg (Vhathvarothai et al., 2013), which could in turn be used in drying the nust, and the shell could also be milled and applied as a fertilizer."

Jan 1, 2015

By R. R. M. Cousens, W. S. Garrett

Discussion: L. T. Campbell Pitt: When Mr Garrett and I discussed the design and construction of plugs and bulk head doors to resist great water pressures in mines about ten years ago, we visualized an emeregeny when there would be no time for site preparation. We could not however, anticipate a problem of such magnitude and urgency as the one described in the paper under discussion. The paper very clearly describes the flooding and the measures taken to save the mine. The complete flooding would have been a national disaster. The account of the combat between man and water reads like the account of a military operation. It was an endeavour which achieved success because there was a master plan, tenacity and, in fact, heroism. The paper is of necessity a long one. In my contribution I will mention some historical facts and factors that I believe have relevance to the flooding and the saving of the mine. It is of great satisfaction to me to have been one of the two initiators of a new approach to underground plug design and construction. The investigation was taken over by a Chamber of Mines Committee which combined our early work with further research and the resulting data had a significant bearing on the West Drie emergency plug designs. The final plug length was correctly based on the requirements to obviate leakage. A plug to have structural strength only would have been very much shorter but so ineffective as to have become a waste of labour, material, and in consequence, wasted the limited time available to prevent flooding of the whole mine. The figure of 75 lb per sq in. sheer stress provided a very ample margin, in my opinion, but under the very difficult site conditions and the limitations of plug material suitable for the very unusual construction, justified such a figure. There must have been considerable temptation to reduce the safety margin due to the urgency to complete and commission the plugs, but it is much to the credit of the directors of this operation that nothing less than a safe design was permitted. In about 1945 Blyvooruitzicht Gold Mining Company, which was then mining in to the West Driefontein area to assist in early development, decided to protect themselves from a possible inrush of water from the latter mine. A bulk head door was accordingly designed and installed on 2 level between 1945 and 1948 at 4,218 ft below surface. Since West Driefontein paid for it, Gold Fields consulting mechanical engineers collaborated with their colleagues of Rand Mines who completed their design after a few modifications were agreed. This door was never used to prevent an inrush into Blyvooruitzicht but the exercise was very useful to Gold Fields when the high pressure doors initially installed on 10 and 12 levels between Nos. 2 and 3 shafts to enable isolation of one section of the mine from another were designed. At that time the capacity of West Driefontein to cope with an inrush of water was comparatively small because the storage in stoped areas and the installed pump capacity were much less than in later years. These doors together with others of the same design were later moved to the lower levels served by sub vertical shafts. In addition, doors to prevent flood water entering the pump chambers on 18 level were installed at each end of that level, and designed for a head of 360 feet so that water would have to reach 16 level before the pumps were flooded. All these doors were called upon to hold water and it is reported that only a small plug in one of the doors and a 4 in. dia flanged pipe joint failed. The lesson is that in these cases the smallest details warrant as much attention as the major ones. That these were the only equipment failures when so much depended on equipment, is very much to the credit of design engineers, both of the Gold Fields head office and companies who supplied both mechanical and electrical equipment. Until I had read the paper I wondered why the policy of isolation by bulk head doors was not continued as the development moved eastward towards the Bank Compartment and particularly when it pierced the Bank dyke. The reasons have been given in the paper. It was unreasonable to expect provisions to be made to counter the remote contingency that the large installed pumping capacity and mine capacity to store water would be exceeded during a peak inrush. When pumps were being considered for West Driefontein, it was decided that the Gold Fields standard underground main pumps at that time of 1 million gallons per 24 hours would be too small. Three alternatives were considered. 1. Very large units that would require underground sub assembly and dismantling of both pump and motor. 2. The largest pump and motor that could be conveyed as a complete pump or motor from surface to the pump chamber. 3. Pumps of higher speed to reduce dimensions and weight. It was decided to adopt alternate 2 because of avoidance of transporting pumps in parts and assembling underground. Alternative 3 was not favoured because high speeds would have introduced problems of more exact rotor balancing. I believe the decision was correct and in the crisis enabled comparative easy transport of pumps and motors to surface for overhaul and, if required, transfer to other pump stations. The standard pump thus became a 10 stage 1,500 rpm pump with a capacity of approximately 2 million gallons per 24 hours against a static head that varied

Jan 3, 1969

By Y. R. Murthy, S. Angadi, A. K. Bhatnagar, S. K. Tripathy, L. O. Filippov

Dolomite is an essential raw material for the refractory industry, a flux in the iron and steel industry and also for the extraction of magnesium metal. Generally, particle size reduction, screening and classification are used for the preparation of the high-grade sized material for different applications, whereas low-grade fine fractions are not utilised. These fines or low-grade overburdens are dumped at the mine site for future utilisation, which creates environmental issues along with inadequate space management. In the present investigation, a detailed study was carried out to decrease the silica content of the low-grade dolomite fines from Gomardih , India, containing 28.6% CaO and 20.1% MgO along with 8.3% silica. Different process flow sheet options were evaluated with a combination of dry classifier, wet classifier, gravity concentrators as well as flotation. Different process variables were assessed along with mineralogical characterisation to optimise the process for efficient rejection of siliceous gangue minerals. Results indicated that dolomite, calcite and quartz are the major mineral phases present in the ore along with other minor minerals. It was concluded that two-stage flotation was an effective process for the reduction of silica up to below 1% after grinding to a particle size below 212 μm. A process flow sheet with a combination of gravitation air classifier and flotation can produce a concentrate with silica content below 4.5%. Keywords: Dolomite, flux, dry classification, flotation, characterisation, beneficiation

Jan 1, 2020

By I. Soto, E. Córdova, A. Anani

The new caving megaprojects that are planned to go into production in the next decade have scheduled horizontal developments at very high rates, which are difficult to achieve. Research has been conducted that seeks to model the construction times for underground developments to determine the feasibility of achieving the planned rates. However, these previous attempts do not consider all the operational aspects that make up the mine development cycle. Here, we present a discrete event simulation (DES) model that individualizes each unit operation of the development cycle to determine the construction rates that new projects will be able to attain. The developed model was applied to the New Mine Level (NML) of the El Teniente Division (DET). The results indicate that it would be impractical to achieve the advance rates scheduled in the original plans if the unit operations of the mine continue to be executed using the status quo. The metres developed after six years in the sections analysed can be significantly improved by changing the maintenance strategy for the equipment (457 metres increase), orepass availability (194 metres increase), and the initial planning sequence (1 598 metres increase). It is recommended that the mine implements a flexible maintenance strategy, defines a strategy to ensure and increase orepass availability to contractors, and makes use of current simulation tools for a more robust development sequence planning.

Oct 1, 2022

By P. S. G. Leon

One of the most difficult areas in concession contracts in resource-rich developing countries is achieving an equitable balance between the interests of investors, host states and, increasingly, mine and near mine communities. While some countries in the Andean region have resorted to outright or creeping expropriation of natural resource contracts under the guise of resource nationalism, others such as the Democratic Republic of the Congo (DRC), have claimed international best practice in the review (and setting aside) of important concession contracts.

Jan 1, 2011

By D. Fenn, A. du Kanda, D. Dukhan

"SynopsisGibb Consulting Services was contracted by Eskom Line Engineering Services to conduct an investigation to determine the absolute displacement to date and infer the current rate of displacement of unsurveyed colliery backfill.At the test site, where a 400 kV power line is to be constructed, neither the surface nor the backfill material had been monitored and it was not possible to state whether the surface will be subject to future settlement that may compromise surface infrastructure. Therefore indirect methods of estimating current and future displacements needed to be found to act as a proxy for a comprehensive long-term settlement monitoring exercise and provide a reasonable estimate for the settlement that has occurred in the decades of mining.The innovative solution was to recover essentially undisturbed core from backfill using a sonic drill rig and use the measured dry density values from the samples as a proxy for the rate and absolute displacement in the backfill.The success in obtaining an essentially undisturbed backfill core and the clear relationship of the backfill density with age and depth allowed the conclusion to be issued that the power line infrastructure can be constructed over the backfill; with a warning that once the water table recovers after mining ceases some collapse settlement may occur.With this method, the amount of settlement can be predicted and, if proven conclusively, provides a way to confidently release huge areas of currently waste ground for future surface infrastructural development.IntroductionIn coal mining, it is normal mining practice to backfill the newly mined-out voids with the excavated waste rock and soils. As there is no requirement for the mining companies to uniformly compact the spoil or accurately monitor surface or inter-backfill displacement, these backfilled voids are prone to differential compaction and consolidation settlement. They are therefore avoided as sites for future surface infrastructure work, especially for linear structures such as roads, railways, and power lines."

Jan 1, 2015

By F. J. N. Bruwer, T. R. Stacey

The research described considers whether the variability in coal material strength, as derived through a series of uniaxial compressive strength (UCS) tests, could be used to indicate the variability in coal pillar strength. The aim is to be able to use a distribution of UCS tests as input into the coal pillar strength calculation. This will allow the pillar design to be expressed in terms of a probability of failure rather than as the commonly used safety factor. To achieve this, the bulk strength factor associated with commonly used pillar strength formulae was replaced with a distribution of UCS results divided by an adjustment factor. The factor was determined so as to ensure that the resulting bulk strength does not deviate from the statistically determined bulk strength published in the original formulae. This approach enabled pillar strength distributions to be obtained using industry-accepted strength formulae, subsequently allowing for a probability of failure to be calculated for a specific pillar design. Using a regional coal material strength curve as a baseline, coalfields in which the coal is stronger than the regional mean can be identified and the pillar designs optimized. This is based on the stronger coals achieving lower probabilities of failure at similar safety factors. The research has considered actual UCS data from multiple mines in the Mpumalanga coalfields of South Africa, and has proved that the variability in material strength between coalfields could allow for some optimization using the proposed approach. Based on the data used in the study, a 2.78% increase in extraction could be achieved. However, further research will be required to validate the results of the study in an underground environment.

May 3, 2023

By M. Splaine, W. Davison, D. C. Atkinson

"Since 1964, Nchanga Consolidated Copper Mines, Ltd., has been developing and using production scheduling methods for optimizing its metallurgical operations in the short term (up to one year). Medium-range metallurgical planning has been possible only by successive evaluations of a single-year L.P. A modified version of Rosenbrock's direct search technique has now been developed to allow multi-year optimization of both mining and metallurgy for medium-range planning. The modifications to the search technique have produced a marked increase in computational efffciency for this heavily constrained problem in many variables and the system is a usable planning tool, given a reasonably powerful computer. The plans are 'optimum' in the sense that they yield the maximum present value of the operations.Each of the resulting five-yearly mine plans forms the basis for further detailed metallurgical evaluation by the established production scheduling system."

Jan 1, 2014

By S. T. L. Harrison, A. Kotsiopoulos, J. R. Amaral Filho, J. L. Broadhurst

The land disposal of voluminous fine-grained tailings from the processing of mined ore bodies poses a long-term risk to the surrounding environment and local communities, while also representing a loss of valuable natural resources; including water, land and mined minerals. To date, the development and practical implementation of alternative approaches and technologies for removing risk and reducing the burden associated with these wastes, particularly in South Africa, remains limited, and value recovery is largely limited to the extraction of precious metals. To this end, researchers at the University of Cape Town have developed a programmatic multi-phased approach to explore and develop opportunities for the valorisation of large-volume mine wastes, based on the innovation value chain. This paper outlines this conceptual approach and presents key outcomes from its application for the specific case of sulfide-bearing coal processing wastes from South African collieries. Through the application of a combination of qualitative and quantitative tools and methodologies, a number of potentially viable opportunities and processing routes for value recovery and bulk re-purposing of these wastes have been identified and tested on a laboratory scale. Studies have, however, also shown that there are several technical and non-technical factors currently constraining commercial application of these opportunities. Overcoming these constraints will require a commitment to innovative waste management approaches and effective multi-sectoral collaboration. Keywords: Coal processing wastes, physical separation, waste re-purposing and utilisation, technology transfer

Jan 1, 2020

By C. Massola, E. E. M. N. de Guzmán, M. G. Bergermana

The abrasiveness of a mineral or rock is an extremely important topic in the mining industry and is generally measured by the Bond abrasion index (AI). However, to determine such an index by the Bond test requires 1,600 g of sample with particle sizes ranging from ½” to ¾”, which are not available in certain situations, such as ore prospecting, drilling, and geometallurgical studies. In order to investigate the abrasiveness of smaller-sized sample materials, a modified LCPC test was developed, which allows testing fine materials (i.e., 1.0 mm or smaller) to predict wear in ore processing circuits and anticipate possible failures resulting from changes in abrasive characteristics of the ore being processed. The results for 16 different materials indicated a good correlation with the AI and the modified LCPC, resulting in a reliable alternative for the AI. Keywords: Bond Abrasion Index (AI), LCPC, abrasiveness

Jan 1, 2020

By C. Ndou, T. Mothupi, H. Mandende

The technological advances in efficient, rapid, and non-destructive hyperspectral core logging systems for systematic mineral mapping have led to the discovery and exploitation of new mineral deposits Hyperspectral imaging in the long-wave infrared range has been recently used successfully to identify various phosphatebearing minerals (monazite, xenotime, and britholite), with limited work on apatite associated with mafic-ultramafic layered intrusions. In this study we investigate the effectiveness of a hyperspectral imaging (HSI) system with long-wave infrared (LWIR) bandwidthsto identify apatite in the Upper Zone of the Bushveld Complex. The accuracy of the HSI results was validated by mineralogical and geochemical data. The two apatite-enriched zones detected by HSI suggesting widespread development of apatite throughout the uppermost 600 m of the Upper Zone. The lower apatite-enriched zone is approximately 40 m thick, while the upper apatite-enriched zone is about 23 m thick, consistent with previous thickness determinations by traditional logging and analytical methods. Spectral mixing observed in the response of apatite is ascribed either to the common association of apatite and olivine in these rocks, or to differences between the spatial resolution of the hyperspectral image and the size of apatite grains. The VNIR-SWIR wavelength region did not show prominent spectral features of apatite. Nonetheless, HSI in the LWIR range is effective in mapping apatite and should therefore be considered as an exploration tool. This research advances our knowledge of the reflectance spectroscopy of REE-bearing minerals, which makes it easier to detect, identify, and quantify REE-bearing silicate minerals by HSI.

Feb 6, 2023

By B. McFadzean, S. Pikinini, C. T. O’ Connor

Sperrylite (PtAs₂) comprises about 21% of the platinum group minerals (PGMs) in the Platreef ore and regularly reports to the tailings due to its poor floatability. Hence, improving its recovery will be of great economic value to the South African PGM industry. The reasons for its poor floatability are not yet clear. This paper seeks to understand the interactions occurring between PtAs₂ and common thiol collectors, viz. potassium normal butyl xanthate (PNBX), sodium normal dibutyl dithiophosphate (SNBDTP) and sodium normal mono butyl dithiocarbamate (SNBDTC). By understanding its interactions with these collectors, it is hypothesised that it will be possible to suggest ligands that may help improve the floatability of sperrylite. Mineral-collector interactions were studied by determining the molar energy of interaction using isothermal titration calorimetry and electrochemical techniques. The hydrophobicity of the mineral before and after adsorption of the collectors was determined by heat of immersion and its flotation response determined by microflotation tests. Microflotation tests using synthetic sperrylite at pH 9 showed low collectorless recovery of 34.8% and after adding the equivalent of one pseudo-monolayer of the PNBX collector, the recovery of 32.5% was obtained. Moreover, the addition of up to three pseudo-monolayers coverage of PNBX did not result in any increase in flotation recovery. A small recovery improvement was noted when synthetic plant water with the ionic strength of 0.0484 mol/L was used, but this did not hold for all collectors, with SNBDTP exhibiting higher recoveries in distilled water. Keywords: Sperrylite; flotation; recovery; adsorption energy; collectors; 2SPW (synthetic plant water)

Jan 1, 2020

By M. Khodadazadeh, K. G. van den Boogaart, T. Leißner, L. Tusa, J. Gutzmer, R. Gloaguen, M. Kern

Ore sorting is a technology that is increasingly used to process primary raw materials. Timeconsuming and expensive empirical state-of-the-art test work is carried out to assess whether the use of ore sorting for the enrichment of a particular ore makes technical and economic sense. With the innovative simulation-based approach presented here, it is possible to direct the selection of a suitable sensor based on quantitative mineralogical and textural data, thus avoiding much of the empirical studies. Required data can be collected quickly and cost-effectively using available methods of automated mineralogy. The obtained parameters such as mineral grain size distribution, modal mineralogy, mineral area and mineral density distribution have been utilised in this study to simulate the prospects of success of ore sorting, applying different types of sensors. Empirical tests with commercially available sensor systems have been conducted to experimentally validate the predictions of the simulations. The estimation of the target mineral grade can be further optimised by the use of machine learning algorithms for the integration of automated mineralogy data and sensor data. The approach can easily be adapted to other types of raw materials and thus has great potential to become a key technology for the optimisation of processing experiments. Keywords: Automated mineralogy, hyperspectral imaging, machine learning, ore sorting

Jan 1, 2020

By R. Burger, M. Masukawa

Cato Ridge Alloys (CRA) is a joint venture company between Assmang of South Africa, Mizushima Ferro Alloy Company (MZK) and Sumitomo Corporation from Japan. Negotiations for the formation of the company started in 1992 with the joint venture agreement signed on the 19th September 1996. MZK was to supply the technical know how for the production of Medium and Low Carbon FeMn while Assmang was to manage the day to day activities of the company. Sumitomo Corporation was to act as facilitator between Assmang and MZK and, together with Ore and Metal are responsible for the marketing of the refined products. The conceptual design of the plant started in December 1996 and the first charge of molten high carbon ferromanganese metal was charged on the 19th January 1998. Problems experienced during the initial startup period were addressed resulting in substantial operational improvements. A build-up in the stock of fine metal was addressed through the development of a process to remelt the fine metal, the development of a market for fine metal and the upgrading of the crushing and screening plant to reduce the generation of fine metal. The mass yield from High Carbon Ferromanganese to Refined Ferromanganese was increased through the implementation of statistical process control, changes to the blowing patterns and the development of a sampling device for taking samples during the process. Converter refractory consumption was reduced. This was achieved on the converter by improving the cooling of the converters with the installation of cooling fans and cooling fins. The heating schedule of the converters was changed for improved refractory life. Production schedules were modified to allow cooling of the refractory between low carbon erromanganese charges. Additional changes made to improve operations were: ? Changing from mehanite casting trays to metal fines beds. ? Installation of sonic horns in the baghouse to prevent the bridging of dust. ? Improved welding on the lance tips.

Jan 1, 2004

By F. Diot, S. K. Tripathy, L. O. Filippov, I. Filippova

Among different pre-treatment methods, a high voltage electric pulse was recently developed and is gaining popularity due to multi-benefits such as pre-weakening along the grain boundaries, as well as size reduction to improve the liberation characteristics. In this paper, the pre-treatment using high voltage electric pulse of lithium-bearing granite ore was studied to understand the morphology through texture, as well as the friability of the particles. To understand the phenomena, SELFRAG, a laboratory facility used for generating high voltage electric pulse and key operating variables were varied. The role of applied voltage (94.5-195.5 kV), number pulse (3-87), and the frequency of pulse (1.3-4.7 Hz) was varied to understand the liberation characteristics as well as energy consumption. Characterisation tools such as optical, and electron microscopy were used to describe the pre-weakening phenomena through textural features. Further, the energy required to break the particle to finer sizes as well as friability were determined and described. Keywords: Pre-treatment, high voltage electric pulse, lithium, liberation, grinding

Jan 1, 2020

By E. J. M. Jahnsen, I. Jauhari, T. Badrujaman, F. A. Stober, B. O. Wasmund, L. R. Nelson, T. Miraza, J. M. A. Geldenhuis, A. Taofik Hidyat

The role of dedicated operational support in the ramp-up and stabilisation of the FeNi-II furnace for ferro-nickel production at PT Antam?s smelter located in Pomalaa, Indonesia is described. The furnace was uprated to 32MW capability in a rebuild performed in 2005. This primarily involved installing a larger transformer, coupled with adoption of HATCH water-cooled copper plate, waffle and flanker coolers with integrated metal and slag tapblocks, HATCH air-cooled copper fin lower sidewall cooling and HATCH vertical sidewall binding system ? ?holddowns?. Following a smooth commissioning period, the progress in attaining the preliminary ramp-up target load of 24MW is described. This initial target was set by Antam, subject to some prevailing smelter equipment constraints, particularly kiln capacity. Stabilisation of the furnace operation is discussed, together with some of the specific commissioning and operational challenges surmounted by the joint Antam-HATCH team. These included: ?Mastering furnace integrity monitoring and operation with copper coolers, especially metal tapblock planned maintenance and repair strategies; ?Transition from traditional ?immersed electrode? to ?brush-arc? mode of operation approaching as closely as possible to the productive ?shielded-arc? mode of operation within existing equipment constraints; ?Reductant selection and control issues; ?Utilising the sophisticated furnace monitoring to provide detailed indication and warning of potentially destructive furnace upset conditions such as Si reversion and CO boils.

Jan 1, 2007