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By J. H. Zietsman, W. J. Leipoldt

"To be able to responsibly develop a multiphysics model of the steel belt sintering (SBS) process used to sinter chromite fines, it is important to have a comprehensive understanding of the process. This understanding was gained through a site visit, observation of the process in operation, and interaction with the operators. Material characterization will also reveal much about the process that is not yet fully understood. A well-defined and representative mass and energy balance will also give valuable insight into the process. The plan for the multiphysics model aims to combine a computational fluid dynamics (CFD) model with a discrete element method (DEM) model.To obtain a more accurate mass and energy balance representation of the SBS process, it was decided to develop a dynamic distributed parameter model of the mass and energy balance. This model will be used to gain better understanding of the SBS process so that a more complicated multiphysics model can be developed later. The reason for this is because the SBS process is very dynamic, with a large temperature distribution throughout the length of the process. In its current state, the mass and energy balance model is capable of handling solid and gas material packages and exchanging heat between these packages where they are mixed, and is able to model the heating of the gas by burning CO gas. The next step in the development of the model will involve enabling it to handle evaporatoin of liquid water, burning of solid carbon in the pellets, reduction of iron oxide in the pellets with the CO gas formed from carbon combustion, and then oxidation of the reduced iron in the oxygen-rich cooling zones."

Jan 1, 2014

By R. Heunis

The hazard of rock bursts and rock falls as experienced in South African gold mines is examined in the light of recent research findings. The problem areas include high fatality rates, losses in production and equipment, and a detrimental influence on the recruitment of labour. The nature of the hazard is analysed, and it is shown that rock bursts are strongly related to the spatial rate of energy release by mining but that rock falls are not. The role of blasting and geological discontinuities is discussed. Practical rock-burst control strategies are compared, including the use of stabilizing pillars, back-filling and, in particular, techniques for reducing the frequency and severity of accidents resulting from large rock bursts. The latest stope-support experiments and their potential implications to mining are consid~red. It is concluded that a better understanding of the rock-burst and rock-fall hazard has resulted from the industry's research efforts. The findings can be applied towards obtaining an improved underground environment for men and machines.

Jan 1, 1980

By C. Kirmanli

The purpose of this paper is to develop an expert system for hydraulic excavator and truck selection in surface mining. Hydraulic excavators and trucks are finding increasing applications in mining operations. Hydraulic excavators are extensively used especially when bringing electricity to rural areas is difficult and for small-scale mining. This paper describes an expert system, which selects the optimum hydraulic excavator truck configuration such that unit production cost is minimized and technical constraints such as geological, geotechnical and mining constraints are satisfied. The system has four modules: user interface, rules and an methods, databases and output module. The expert system in this study is developed within KappaPC shell. It supports object-orientated technology for the MS Windows environment. The software provides a very useful tool to practitioners, saving time and cost. Equipment selection is a recurring and expensive problem of mine planning and often involves interdisciplinary experts from different fields. It is very difficult and expensive to bring together all these experts. The capabilities of the expert system developed are illustrated in the paper. The software overcomes the difficulties of selecting the proper equipment for surface mining operations, which is very important, and results in substantial savings. Equipment databases for hydraulic excavators with 15-59 yd3 capacities and trucks with 35-360 tons are constructed and these databases are used to select the proper configuration. A case study is carried out for Soma Surface Coal mines in Turkey. Keywords: surface mining, expert systems, equipment selection, hydraulic excavators, diggability

Jan 1, 2009

By M. N. Mathabathe, A. S. Bolokang, C. W. Siyasiya, R. J. Mostert, G. Govender

The b-solidifying g-TiAl intermetallic alloys of nominal composition Ti-48Al (binary alloy), Ti-48Al-2Nb (ternary alloy), Ti-48Al-2Nb-0.7Cr (quaternary alloy), and Ti-48Al-2Nb-0.7Cr-0.3Si (quinary alloy) (in at.%) were developed. The materials produced were tensile tested at room temperature. The as-cast microstructures and fracture surfaces of the tensile tested specimens were examined using conventional metallographic methods. Microstructural examination indicated that the alloys were comprised of lamellar structures (a2+g) embedded in columnar dendritic cores in the as-cast condition. However, the quinary alloy contained a Ti5Si3 second phase. The alloys exhibited no detectable ductility during tensile deformation, indicating the brittleness of all the materials. The fracture surfaces revealed that the alloys failed by translamellar fracture with correspondingly few cleavage facets.

Apr 1, 2021

By J. W. van der Merwe, A. M. Maleka, V. J. Matjeke

The 10.5–12.5% chromium, titanium-stabilized ferritic stainless steel (FSS) plates used to fabricate coal line jumbo wagons is susceptible to undesirable chromium depletion during welding with 309L electrodes. In this work, non-stabilized FSS plates were welded using 308L welding electrodes. The objective was to weld non-stabilized FSSs using gas-shielded metal arc welding without causing sensitization. The welding process was optimized by lowering the heat input. Sensitization was assessed by rigorous etching techniques and anodic polarization scans. In addition, the welds were subjected to tensile testing, and their fracture surfaces were examined for intergranular cracking. Non-stabilized FSS plates were successfully welded using gas metal arc welding.

Apr 5, 2023

By M. Ye. Scheglov, G. I. Voiloshnikov, S. M. Ryakhovsky, V. E. Dementyev, V. N. Alekseev, N. S. Voiloshnikova

Irgiredmet has substantial experience on RIP and RIL technology for gold recovery, having started development of ion exchange technology in 1964. Irgiredmet specialists were involved in the majority of RIL and RIP projects in the former Soviet Union and Russia, and took part in commissioning of practically all plants using ion exchange technology. Laboratory and pilot plant tests were conducted to develop process design criteria for designing 15 RIP plants of the former USSR using bifunctional macroporous anionite AM-2B or its analogs. This paper is devoted to the laboratory, pilot plant testing and introduction of RIP technology conducted in cooperation with GC Pertopavlovsk. Medium base resin PuroLite S992 (PuroGold) was used as adsorbent. Some adsorption regularities and the affinity of resin to metal cyanide complexes were studied. Laboratory batch and continuous pilot tests on resin-in-pulp process were held for oxidised ores from Pioneer, Albyn and Malomyr mines (Amur region, Russia) owned by the Petropavlovsk company. A simplified flowsheet for gold elution and resin regeneration was developed. Alkaline cyanide solution was used as gold eluent and gold was recovered from eluates by electrowinning. Process design criteria were developed on the basis of the testwork results, and the plants were designed and constructed by GC Petropavlovsk. The RIP plant at Pioneer was commissioned in May 2008, at Malomyr in August 2010, and at Albyn deposit in December 2011. These plants are currently in operation at design performance at throughputs from 3 to 6.5 Mt/year. The primary gold ores of Pioneer and Malomyr deposits are refractory to cyanidation; Irgiredmet also completed continuous testwork on RIP technology using medium-base resin for pressure oxidation (POX) residues derived from their flotation concentrates. In 2019 a hydrometallurgical plant for the treatment of refractory gold concentrate after POX was commissioned at Pokrovsky mine (Amur region). Keywords: Gold ores, cyanidation, RIP, RIL –processes, ion exchange resin, medium base resin, adsorption, elution, electrowinning

Jan 1, 2020

By M. Bryson, G. Marap, M. Ntlhane, M. D. Hlahane

This study investigated flotation of phosphate from a low-medium grade 8-12% P2O5, 65-73% SiO2 sedimentary phosphate ore from Kropz Elandsfontein (herein referred to as Elandsfontein) in South Africa. Quantitative evaluation of minerals by scanning electron microscopy (QEMSCAN) was used to determine apatite grain size distribution, liberation and mineral association in the F2 horizon sample. The mineralogy indicated that apatite was liberated and for the Elandsfontein plant to operate at the design throughput, the flotation feed has to be milled to a coarse grind ranging between 300 μm and 425 μm. Reverse flotation process routes using varying reagent dosages, and flotation feed top sizes that could possibly yield a final product of 31% P2O5,10% SiO2 at a reasonable +70% P2O5 recovery were investigated. Based on the results, a split circuit of coarse (-300+212μm) flotation and fine (-212+20μm) flotation, was mostly preferred as compared to treating the whole ore. A final combined concentrate of 31% P2O5 and 10% SiO2 with P2O5 recovery of 84% could be produced from the reverse split circuit. The robustness of reverse flotation for both coarse and fine fractions was further investigated. Reverse flotation of the fines fraction was found to be robust and produced a final product of 31% P2O5. It was however more challenging to achieve the required product grade and recoveries on the coarser fraction (-425+212μm), suggesting that reverse circuit was not adequately robust at fractions coarser than 300μm. Keywords: Phosphate, sedimentary, reverse flotation, particle size

Jan 1, 2020

By I. J. Kotzé, R. T. Jones

Conventional PGM matte smelting requires the presence of a certain quantity of base metal sulphides in order to collect the platinum group metals in a molten sulphidic matte phase in the furnace. Furthermore, the quantity of chromium oxide in the feed materials is controlled in order to avoid the build-up of high-melting chromite spinels in the furnace. Mintek has developed a process for smelting difficult PGM-containing feed materials that contain low amounts of sulphur and/or high amounts of chromium oxide. A DC arc furnace is used to provide the appropriate conditions to generate an iron alloy that collects PGMs very effectively, leaving extremely low residual quantities of PGMs in the slag. Various feed materials have been treated successfully in furnace campaigns running at power levels up to 1.5 MW. The longest of these campaigns was run continuously for more than four months, treating more than two thousand tons of materials such as low-grade concentrates, revert tailings, and converter slag. The campaigns demonstrated the robustness and versatility of the process, and proved that it is possible to sustainably produce a PGM-containing alloy and discardable slags containing an average of less than 1.4 g/t of PGMs over the entire campaign. Keywords: DC arc, smelting, furnace, platinum, PGM, revert tailings, converter slag, ConRoast

Jan 1, 2004

By and M. V Roper, H. N. Engelbrecht

Quality control interventions emanate from process upsets and trends that move product quality beyond the natural variation expected in a stable process. The ability to detect upset conditions and react in an effective manner protects both resource utilisation and compliance to specifications. Product quality control on coal processing plants traditionally relies on the reference (combined sampler and laboratory) system to measure product qualities. The introduction of online analyser (OA) technology, applied in different configurations, creates a second source of measurement information for control decision making. The case study was done on the primary sample stream of the final product stream at Exxaro’s GG7 and 8 plants, part of the Grootegeluk complex. It explores the OLA system’s ability to meet the OEM performance guarantee, perform equally to the reference system without analytical delay time, and assesses the effort to achieve this performance in a by-line analyser (BLA) configuration. In the paper, a conceptual comparison of the two measurement systems is done and the theoretical and practical comparison of measurement performance is discussed. Results demonstrate that the OA outperformed the OEM’s performance guarantee and achieved similar levels of performance to the reference system without the response delay. Keywords: Online analyser (OLA), by-line analyser (BLA), coal quality measurement, measurement performance

Jan 1, 2020

By W. K. Loftus, H. S. Simpson

Discussion I. R. M. Cheston (Visitor): I should like to congratulate the authors on this interesting paper which graphically illustrates the overall effects of the gradual developments in diamond concentrating processes which have taken place over the past few years. These final stages of diamond concentration represent only a minor factor in the cost of diamond production but because of the shortage of highly trained people for this work, any easing of the burden on the sorting staff has an importance far beyond the immediate economic sphere. The search for the solution of problems posed by the economic and social conditions of industry is never-ending. The Diamond Research Laboratory is, even now, carrying out further work to improve still more the operation of general diamond recovery processes as described in the paper. Before looking at some of the latest developments in this field of final recovery, there are a few points arising from the paper on which I would like to comment. On page 321, reference is made to the X-ray sorters originally developed by the DRL. The paper gives a figure of 100 per cent recovery of diamonds from +7 mesh concentrates in two passes through the prototype machine. Not wishing to claim miraculous powers for our group, I would prefer to see this given as virtually 100 per cent recovery of all fluorescing diamonds. Firstly however much care is taken, there is bound to be an occasional operating loss. In the test work, 100 per cent recovery was made on many occasions but this was not always so. Secondly, although most diamonds fluoresce strongly under X-rays, some diamonds only fluoresce weakly. Type IIB diamonds, in fact hardly fluoresce at all, but the incidence of this special type of diamond is very low in most deposits. However, in operating the commercial X-ray machines, there is a certain background level of reflected radiation from other feed particles. Unless the diamond fluorescence is several times greater than this, it is not possible to achieve sufficient sensitivity in ejection. A certain small but variable proportion of diamonds from each deposit is always found to fluoresce too weakly to be recovered by the X-ray machine. Tests have shown, that for the De Beers mines, this proportion is considerably less than I per cent. These diamonds are nearly all dark brown or black in colour and therefore of low value. The degree of fluorescence does not, however, depend entirely on the colour or quality of the diamond and some of the brightest fluorescence comes from the lowest quality of boart diamonds. Investigations into the property of the diamond which causes this low fluorescence are being carried out. On page 322 it is suggested that zircon fluoresces in the same colour spectrum as the diamond. This is not quite accurate. The total light given out by zircon under X-rays is of the same order as that of diamond. However the zircon radiation has a much wider spectrum band than the diamond fluorescence. Reference is also made on page 322 to the effect of selective milling in small laboratory mills on diamonds. Perfect diamonds are very hard and very strong and are extremely difficult to break. Imperfect diamonds, which form the majority of diamonds recovered from most deposits, although hard, can be very brittle. Even under slight impact some of these diamonds may shatter to powder. Milling conditions must therefore be extremely closely controlled to minimize breakage, and even so, some breakage will always occur. As suggested in the paper, the necessary conditions are: the use of small balls, slow speed mills and very limited water addition. Tests elsewhere have suggested that the water content of the pulp in such a mill must be less than 25 per cent by weight of pulp to prevent diamond breakage reaching significant proportions. The skin flotation techniques described on page 323 operate on a very small scale. It is of interest to note that in West Africa a large-scale continuous skin flotation machine is used to recover the fine diamonds. In this operation the feed is dried and, after standing, is mixed with water and fed in a single layer onto a woven phosphor-bronze conveyor belt. This belt runs at a shallow angle into a water bath and as the particles are carried through the air-water-interface, the diamonds float off and over a weir into a collecting box. The bulk of the particles, being wettable, sink to the bottom of the tank and are continuously removed. If treated without prior drying, the diamond recovery is poor. If material is treated immediately after drying, a lot of the gangue particles also float. During standing, in the hot and humid atmosphere of West Africa, it is found that the gangue particles recover their wettability much faster than the diamond particles. Optimum selectivity is obtained after standing for approximately 24 hours. At the DRL we have been experimenting with optical filters to differentiate between the fluorescence of diamonds and zircon. By limiting the light transmission to the fairly narrow range emitted by diamonds, it is

Jan 4, 1970

By B. Hayen

The principal advantages of fibre optics as compared to copper wire are well known and include almost perfect electromagnetic isolation, light weight, small size, excellent transmission security and substantially better bandwidth/distance performance. The decreasing cost of the optical fibre technology (both fibre cable and equipment) has led to another generation of private networks, which provide much larger bandwidths, very high reliability and an increase of the maximum geographical coverage. The larger bandwidth allows to transport all types of information on a single network. Typical communication requirements are speech (audio), computer data, LAN info, control information, video, etc. OTN or ‘Open Transport Network’ is a transmission system based on the latest available technology in fibre optics. It is characterized by the dual ring approach, resulting in high network availability, and the integration of different types of services in one network. As such, it can fulfil almost all transmission requirements for voice, data, LAN, video and any special service required.

Sep 1, 2001

By C. C. Johnson

In the fourteen years that Rössing Uranium Limited has been in production, the metallurgical operations and controls on the leaching plant have evolved through four basic stages. Initially, the emphasis was placed on the achievement of consistent plant operation by overcoming severe startup difficulties. The second stage involved the attainment of the design operating targets, and also the commissioning of the ferric-leaching reactors in order to achieve a ferric ion concentration of more than 3,0 g/l. Improvements in control then became the priority, with the emphasis on consistently achieving the target concentrations of ferric ions, total iron, and terminal acidity. The latest phase has concentrated on the optimization of costs by means of adjustments to the historically established operating parameters in order to achieve large savings on consumables while maintaining the leaching efficiencies. Apart from the obvious incentive of reducing costs in an inflationary economy and a depressed uranium market, impetus for this work was given by a change in the type of ore from the open pit, which has the effect of reducing the extraction efficiency while increasing the consumption of consumable materials. These problems and their solutions are discussed in detail, and the importance to cost-effective optimization of an accurate, up-to-date cost-reporting structure is stressed.

Jan 1, 1990

By John Freer

The time 06h30 in midwinter is a little early to set out on an excursion from Johannesburg. Yet this was the hour that members, many accompanied by their wives, started to assemble in the parking lot adjacent to the squash courts at the Wanderers Club, Illovo, for a visit to Premier Diamond Mine at Cullinan. All fifty were checked in and aboard the coach by 07hOO. Coffee and sandwiches, served en route by Doris Gardner and Pam Binstead, were most welcome. IMM awards Given below are details of the trust funds, etc., to which applications are invited for grants, etc., payable in 1985. Application forms, which must be returned to the Secretary before 15th March, 1985, are available on request. Applicants should note that, in general, preference will be given to members of the Institution.

Jan 1, 1984

By J. A. Maritz, D. F. Malan

Pillar strength is affected by pillar shape, but this has largely been ignored in past research studies. Bord-and-pillar layouts are typically designed using empirical strength equations developed for square pillars. Owing to the poor quality of pillar cutting, many hard-rock pillars have an irregular shape and it is not clear how this affects pillar strength. Furthermore, the strength of rectangular pillars in comparison with square pillars is also difficult to quantify. The ‘perimeter rule’ is widely adopted for rectangular pillars, but its applicability for pillars with irregular shapes has never been tested. We used numerical modelling in this study to investigate the effect of pillar shape on strength. An analytical limit equilibrium model of a square and a strip pillar also provided useful insights. For slender pillars, the strength of a long rib pillar is essentially similar to that of a square pillar. In contrast, for rib pillars with a large width to height ratio, there is a substantial increase in strength. The study found that the perimeter rule should not be used for irregularly shaped pillars. Displacement discontinuity modelling, using a limit equilibrium approach, is proposed as an alternative to determine the strength of these pillars.

May 3, 2023

By T. Uysal

Various morphological parameters that affect the flotation recovery of sphalerite were modelled and optimized using the response surface method (RSM). The effects of roughness value, shape factor, and collector concentration were investigated using the central composite full design method. The results were evaluated by analysis of variance. The optimum roughening time was found to be 25minutes, the optimum roughness value was 2.9071 μm, and the optimum collector concentrationwas 0.001 M. Using these values, a flotation recovery of 98.01% was obtained. Similarly, in shapefactor studies, the optimum grinding time was 15 seconds, the optimum roundness value 0.7421, and the optimum collector concentration 0.0009 M, which resulted in a flotation recovery of 94.30%. The average error between the optimization results and the experimental results was estimated to be less than 6%, and the R2 values were greater than 90%. The study shows that RSM can be effectively applied in finding the economic optimum condition for obtaining maximum flotation recovery with minimum reagent consumption.

Sep 6, 2023

By J. Sjöberg, T. Savilahti, S. B. Umar

"Sublevel caving in Malmberget mine results in mining-induced surface deformation. One of the currently mined orebodies is the Printzsköld orebody. As mining deepens there is need to assess the behaviour of the cave formed in the subsurface above this orebody. Numerical analysis was used to assess the effects of extraction to deeper levels and perform strength parametric studies. Stress redistribution was studied, and the results showed high stress buildups in the hangingwall and the crown pillar. Two failure mechanisms have been identified – shear and tensile. Reducing cohesion by 50% increased the area of the yielded zone by more than 100% in the hangingwall.IntroductionThe Malmberget mine is owned and operated by the Luossavaara-Kiirunavaara AB (LKAB) mining company. Iron ore is extracted by large-scale sublevel caving. The mine comprises a total of 20 orebodies, about 10 of which are in production today (Figure 1). The mine is located in the municipality of Gallivare, about 100 km north of the Arctic Circle (Figure 2).Successful sublevel caving requires progressive caving of the orebody after initial blasting. This results in caving of the hangingwall, sometimes all the way to surface, resulting in surface deformation. As mining progresses to deeper levels a larger area is affected by deformation. Over the years, extraction from the Malmberget orebodies has led to deformation of the ground surface, affecting residential areas and existing infrastructure.Forecasting the caving process is not straightforward as it can be rapid or slow, depending on the rock mass conditions, stress conditions, the failure mechanisms at work, etc. Moreover, several of the orebodies in Malmberget are non-daylighting, which makes reliable caving analysis even more difficult, primarily since there is less available experience from such cases. The present study was designed to improve the understanding of the caving and deformation mechanisms at Malmberget, and in particularly for the Printzskold orebody"

Jan 1, 2017

By E. Pothas, P. R. Jochens, L. B. McRae, D. D. Howat

SYNOPSIS The phase equilibria, viscosities and sulphur capacities of titaniferous slags were determined in the composition range of CaO = 30 to 0 per cent, MgO = 0 to 30 per cent, SiO2 = 19.69 per cent, AI.O. = 13.12 per cent and TiO2 = 37.19 per cent. The phase equilibria were determined by high temperature microscopy, the viscosities were measured using a rotating outer cylinder viscometer and the sulphur capacities were evaluated from the results obtained by equilibrating the slag in a gas stream of CO, CO2 and SO2. The behaviour of these titaniferous slags under reducing conditions was examined. Possible use of the slags for aggregate, or slag-cement, and the possibility of extracting the TiO2 are discussed. CONTENTS INTRODUCTION PHASE EQUILIBRIA VISCOSITIES DISCUSSION OF THE PHASE EQUILlBRIA AND THE VISCOSITY VALUES EFFECT OF REDUCING CONDITIONS SULPHUR CAPACITY DISCUSSION OF THE SULPHUR CAPACITY VALUES POSSIBLE USES CONCLUSIONS ACKNOWLEDGEMENTS REFERENCES INTRODUCTION The latest phase in the exploitation of the mineral wealth of the Bushveld Igneous Complex is the erection of a plant by the Highveld Steel and Vanadium Corporation Limited near Witbank to produce steel and vanadium-rich slag from the titaniferous magnetites occurring in this rock formation. These titaniferous magnetites occur as segregations in the gabbro body and the TiO2 is mainly present within the structure of other constituent minerals but also occurs in smaller amounts as ilmenite and ulvospinel. The vanadium is thought to be present in the iron oxide phase due to isomorphous replacement of the iron. Until very recently, it was feared that the high titania content of these titaniferous magnetites would militate against their value as useful iron ores. However, the design of an integrated plant to produce both steel and vanadium-rich slag, and in which the iron-making process is conducted in submerged arc furnaces instead of in

By B. Aydin, A. S. Aloglu, S. Kahraman, E. Saygin

"The coal strength parameter is used in operations such as the selection and design of mechanical excavators and coal crushing/grinding equipment. However, coring or cutting prismatic specimens from coal for the standard strength tests is difficult, and sometimes not possible. For this reason a method for the indirect determination of coal strength from easy tests would be useful. In this study, the predictability of coal strength from the needle penetration test was investigated. This is a very easy and practical test method. Point load and needle penetration index (NPI) tests were carried out on coal specimens from Çayirhan coalfield in Turkey. The point load indexes were converted to the uniaxial compressive strength (UCS) values by using the general conversion factor. The UCS and NPI values were evaluated using regression analysis. A strong linear relationship was found between the two parameters. The conversion factor for the UCS-NPI ratio is 0.35 for the tested coal samples. It is concluded that the UCS of coal can be predicted from the NPI.IntroductionKnowledge of coal strength is important for the selection and design of mechanical excavators and coal crushing and grinding equipment. Uniaxial compressive strength of coal is used in designing pillar dimensions in room and pillar mining. Coals always contain bedding planes and cleats; they are also brittle and fragile. Therefore, coring or cutting prismatic specimens from coal for the standard strength tests is difficult, and sometimes not possible. For this reason, a method for the estimation of coal strength from easy tests would be useful.The needle penetration test is a nondestructive index test that is applicable both in the field and the laboratory and does not require any special sample preparation. The test has been used for the estimation of physical and mechanical properties of weak or soft rocks (Okada et al., 1985; Yamaguchi et al., 1997; Takahashi, Noto, and Yokokawa, 1988; Uchida et al., 2004; Aydan et al., 2006; Aydan, Watanabe, and Tokashiki, 2008; Aydan, 2012; Erguler and Ulusay, 2007; Park, Obara, and Kan, 2011; Ulusay and Erguler, 2012; Aydan and Ulusay, 2013; Aydan. Sato, and Yagi, 2014). This study investigates the predictability of coal strength from the needle penetration test."

Jan 1, 2017

By A. Chuma, K. J. Nyembwe, H. Simonsen, J. H. Potgieter

Different concentration techniques were evaluated for preconcentration of a mineral ore at a coarser size to avoid energy and resource wastage. Specifically, the aim was to reduce milling costs and energy required in the beneficiation of tin. In this study, cassiterite (0.17% Sn) was the mineral of interest in a pegmatite ore body associated with quartz (SiO₂ > 60%) and alumina (Al₂O3 > 20%). Three concentration techniques, namely dense media, shaking table, and flotation, coupled with characterization analysis, were used to assess the concentration response. The results confirmed that particle size and mineral liberation impact the separation process. High recovery and grade were obtained with gravity concentration methods (dense media and shaking table) for coarser (+300 to +212 μm) and intermediate (+150 to +53 μm) particle sizes. Lower recovery and grade were identified for much finer sizes (−53 to −38 μm). Flotation produced a high-grade product at a relatively low recovery and appeared to be only applicable to finer grains. Separation efficiency based on Schulz’s equation measured a segregation performance of 74.8% for dense medium separation and 60.7% for the shaking table for the coarse and intermediate particle sizes. Flotation only achieved a separation of 30%–40%. The results suggest that use of dense media separation as a rough preconcentration method prior to further grinding, and the utilization of a more advanced concentration technique for mineral recovery and upgrade, constitute a successful approach to improve process economics.

Apr 14, 2024

By Z. Luo, W. Chen, Y. Zhao, Y. Fu, L. Dong

The gas-solid dense-phase fluidised bed includes a complex multiphase fluid-particle system; different complex exchanges significantly affect the stability of the fluidised bed. To elucidate the characteristics of fluidisation in a gas-solid dense-phase fluidised bed, this study used experimental performance tests to obtain the static density characteristics, and the attachment and flow characteristic of the dense medium. The results indicate that the bulk density of the dense medium increases first and then decreases with the increase of particle size. The airflow rate difference is used to quantify the wall attachment characteristics of dense medium and the average pressure gradient in the axial direction of the bed is approximately 20 Pa/mm under the fluidisation results. At the same settlement location, with the decrease of fluidisation number, the settlement velocity of large and small particles becomes slower, the boundaries of settlement displacement and location probability are gradually disrupted, and the falling velocity of particles with a radius of 20 mm is faster than that of materials with a radius of 15 mm. This work also established a theoretical basis for regulating the stability and separation characteristics of gas-solid dense-phase fluidised bed. Keywords: Fluidised bed, different size particles, fluidisation characteristics, flotation bubbles, settling motion

Jan 1, 2020