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By H. Edinger

China?s engagement with the African continent has increased impressively in the past decade. Even though China is not the African continent?s largest stakeholder, the rapidly increasing engagement is evident in the huge number of Chinese migrants that have come to Africa in the wake of unprecedented trade and investment levels, as well as in increasing diplomatic and political interactions, which has taken most other commercial partners by surprise. All but four countries in Africa have adopted the ?One China?1 policy stance; and in so doing opened the door for new or strengthened commercial dealings with China, including increasing investments into Africa?s extractive industries. This has been particularly evident since the turn of the century, with a clear shift in China?s policy towards Africa elevating the continent in China?s foreign policy objectives. As such, Africa has become a strategic focus2 for Chinese outward bound and internationalizing companies, especially in the extractive industries. This planned shift in focus is based largely on geo-strategic and commercial needs and interests, rather than previous ideological ones.3

Jan 1, 2011

By Y. Rajpal

The Hedley and Grant pillar strength formula is widely used within the South African mining industry to calculate pillar strengths in bord and pillar mining layouts, and is currently being used at Bathopele Mine. Bathopele is an operation of Anglo American Platinum near Rustenburg, mining the UG2 reef at depths ranging from 40 m to 300 m below surface. The formula includes a parameter K, which is a downrated uniaxial compressive strength value of the rock, used to calculate the strength of a pillar. At Bathopele Mine, for the shallower areas Less than 150 m the value was 33 MPa, but this was increased to 44 MPa due to the fact that rock mass conditions improved and there were no incidence of failure in the shallower areas. Underground observations showed pillars to be stable with no signs of failure, and it was questioned whether the design was not still too conservative, resulting in sub-optimal extraction ratios and consequently a loss of revenue to the mine. A trial mining section was started at the mine where the pillars were reduced from 6 m x 6 m to 5 m x 5 m and the pillar behaviour was monitored for the onset of failure. Numerical modelling was conducted using the TEXAN code to back-analyse pillar stresses in order to find a more realistic value for K. Results from the trial section indicated that the pillar design was in fact too conservative, and the value for K was adjusted to 54 MPa for future designs. This paper details the findings from underground monitoring and numerical modelling results, and includes details for further calibration of the K value in order to further optimize the extraction of the orebody.

Jan 1, 2012

By D. B. Swanepoel

Hulamin Rolled Products (Ltd) developed a high Mn and Si containing alloy, EN 4017 as a scrap consuming alloy from the waste generated in producing their range of clad products for brazing of inter alia automotive heat exchangers. The multifaceted composition of this alloy (Al -1.2 wt% Si -1.1 wt% Mn -0.2 wt% Mg-0.26 wt% Cu) suggested that it might display some degree of strengthening via precipitate formation of the Mg2 Si-types. The aging isotherms constructed showed that EN 4017 with 0.19% Mg reached a lower peak strength (YS~210 MPa and UTS~260 MPa)compared to the EN 4017 material with 0.43% Mg (YS~270 MPa and UTS~325 MPa). The higher Mg variant of EN 4017 was comparable with the age-hardenable reference alloy EN 6061. Selected area electron diffraction (SAED) studies proved that the microstructure of age hardened EN 4017 contained a combination of ß', ß" and U2 phase after being aged at 175ºC for 65 h. The general microstructure contained precipitate free zones as well as grain boundary Si films, although these did not lead to significant embrittlement. The role of Mn dispersoids in the fracture mechanism of 4017 is also discussed. The article will compare the behaviour of EN 4017 with that EN6061. Keywords: Age-hardening, dispersoids, magnesium silicide, precipitate free zones

Jan 1, 2009

1. Book reviews Mill Operators' Conference. Parkville (Australia), Australasian Institute of Mining and Metallurgy, 1982. 425 pp. Reviewer: B. K. Loveday Off highway truck haulage. Newman Combined Group, the Australian Institute of Mining and Metallurgy and the Institute of Engineers in Australia. Sep. 1982. Reviewer: B. J. Vorster Environmental engineering in South African mines.Johannesburg, Mine Ventilation Society of South Africa, 1982. 974 pp. Reviewer: A. N. Brown Underground Operators Conference. West Coast Tasmania Branch. Australasian Institute of Mining and Metallurgy. Reviewer: D. R. Aspeling 2. New publications Electric steelimaking in the eighties: challenges and opportunities. Rotterdam, Balkema, 1982. 362 pp. $50.00 or £33. Tungsten: a review, by P. M. Harris and D. S. C. Humphreys. London, Institution of Mining and Metallurgy (Occasional Paper 2), 1983. Members: £3, nonmembers £6. The platinum industry - prospects in recovery. London, Shearson{American Express Ltd (St. Alphage House, Fore Street, London EC2Y 5DA), 1983. £75. The best of E&MJ mining and processing idea book' New York, Engineering and Mining Journal, 1983. 128 pp. Free with subscription to Engineering and Mining Journal. Mining 1983. Harlow (U.K.), Longman Group Limited, 1983. 500 pp. £39.50. Ooncise guide to world coalfields. London, World Coal Resources and Reserves Data Bank Service (14/15 Lower Grosvenor Place, London SW1W OEX), 1983. 380 pp. £45. 3. Canadian publications Asbestos, by G. O. Vagt, 9 pp. Ooal and Coke, by J. A. Aylsworth, 16 pp. Orude oil and natural gas, by R. L. Thomas, 12 pp. Phosphate, by G. S. Barry, 8 pp. Rhenium, by S. A. Hamilton, 3 pp. 4. Mintek reports Report 2102D The recovery of magnesite from dump fines from the Strathmore Mine. (First issued Feb. 1981.) Report 2106D The evaluation of drill cores and a bulk sample from a deposit of andalusite near Thabazimbi. (First issued Mar., 1981.) Report 2108D Evaluation of a grinding aid in batch grinding, classification, and gravity concentration. (First issued Jul. 1981.) Report 2109D The evaluation of an andalusite deposit from Kleinfontein, Groot Marico. (First issued Apr. 1981.) Report M7D The beneficiation of chromite ore from the Ma-l seam near Marikana. (First issued Nov. 1981.) Report M62 A preliminary investigation into the extraction of zinc by direct oxidative leaching of high-manganese sphalerite. Report M76 A mineralogical investigation of a refractory gold ore, and of a sulphide concentrate and calcined tailing from that ore. Report M85 List of unrestricted Mintek publications issued from 1966 to 1982. Report M97 Reduction in metal consumption by the use of alternating lines of higher and lower lifter bars in a rod mill. Report M98 Multivariable control and optimization of the operation of a milling circuit at East Driefontein Gold Mine. Report M101 The potentiality of heat-treated balls in the grinding of gold ores. X-ray diffraction The Southern Transvaal Section of the South Mrican Chemical Institute is to present a mini-course on 'X-ray Diffraction: Theory and Application' in Johannesburg on 18th and 19th October, 1983.

Jan 1, 1983

By J. Ndlovu, R. Hundermark

Keywords: Anglo Platinum, Polokwane Smelter, pyrometallurgy, metallurgy, platinum, platinum group metals, PGM, base metals, nickel, copper, sulphide smelting, electric furnace, Söderberg, electrode, matte, slag, flash drying, matte casting, crushing, granulation Anglo Platinum?s Polokwane Smelter is situated outside Polokwane, in the Limpopo Province of South Africa. Wet concentrate is received from various concentrators along the Eastern Bushveld Complex, with 60% of the total concentrate received being from UG2 reef and 40% from Merensky reef. The concentrate grade differs from 35 g/t to 110 g/t, and from this a PGM-rich nickel-copper matte is produced. The furnace matte produced is sent to the ACP converter in Rustenburg. The Anglo Platinum concentrators, from which concentrate is received, are Lebowa, Potgietersrus, Amandelbult, and Union, as well as the joint venture Modikwa. The concentrate is fed to two flash dryers that utilise coal-fired, fluidized-bed hot-gas generators to produce the hot gas that will drive off the moisture, leaving a fine bone-dry concentrate to feed to the furnace. The dry concentrate is pneumatically transferred to a storage silo before being transferred to the feed bins situated above the furnace. Lime, if required as a flux, may be transferred separately to the furnace feed bin by a pneumatic system. The concentrate and lime is fed from the feed bins onto airslides and into the furnace. The feed rate is automatically controlled, and the system is set up to optimize the power to feed ratio. The electric furnace is nominally rated at 68 MW and the power is transferred into the furnace using six 1.6 m diameter Söderberg electrodes. Concentrate is melted by energy generated when electric current passes through the electrodes and resistive slag layer. On melting, two immiscible phases form: slag and matte. Furnace matte, containing the bulk of the base metal sulphides and PGMs, is denser than slag and collects naturally at the bottom of the furnace. The furnace is constructed of a combination of refractory brick and water-cooled copper coolers. The furnace sidewalls and hearth are cooled by air drawn through the area by cooling fans. The hearth and matte zone are constructed from refractory bricks. The copper coolers reside only in the slag zone of the furnace along the entire perimeter of the furnace. One staggered row of plate coolers is installed above the waffle coolers along the perimeter of the furnace. Matte is tapped periodically through one of the two matte tapholes into 35-ton refractory-lined ladles, and cast into matte ingots on a casting machine. The cooled matte is discharged onto a concrete slab for cooling and then transferred by front-end loaders to the crushing plant. The matte is first crushed in a jaw crusher and then a Rhodax cone crusher to a size of 2 mm before it is loaded into tankers and sent to the ACP. The low-grade slag is tapped from the furnace through a water-cooled copper insert into a short water-cooled copper ?hot launder? which discharges into a granulation cold launder. The granulated slag slurry flows to three rake classifiers, from which the coarse slag is discharged onto a conveyor to dewatering silos. The dewatered slag from the silos is dumped. The water overflow from the classifiers reports to two thickeners where the water is clarified, and the thickener underflow is returned to the rake classifiers. The smelter is a zero-effluent plant and all the water from the slag silos where the slag is dewatered, as well as the storm water, is pumped to the process water dam from where it is pumped back into the plant for process water use. The off-gas from the furnace is drawn through a forced draught cooler and into a high temperature baghouse. The dust collected in the baghouse is pneumatically transferred into bins above the furnace and is fed via the concentrate airslides. The cleaned off-gas is then vented through the main stack.

Jan 1, 2006

By J. -Y. Jia, G. -B. Qiu, C. -G. Bai, D. -F. Chen

Due to the great importance of the smelting process, it is essential to establish a calculation model on the viscosity of the slag system containing titania. In this paper, the calculation models of mass action concentrations and viscosity for the CaO-SiO2-TiO2slag system have been established according to the coexistence theory of the slag structure, as well as the referenced viscosities ofCaO-SiO2-TiO2at different temperatures and TiO2compositions. With the two models, corresponding calculated programs are made by means of programming language Matlab5.3, and the curves of viscosity of the TiO2concentration (?TiO2/%) at 1400°C, (R=0.9~1.0) are plotted. The results show that mass action concentrations of TiO2increases with increasing percentage ofTiO2, while the viscosity of CaO-SiO2-TiO2system is decreased. The results show that the models are in good agreement with the experimental and referenced data. They also shows that the models are reasonable for the CaO-SiO2-TiO2slag system. Keywords: coexistence theory; CaO-SiO2-TiO2slag system; viscosity ; calculation models.

Jan 1, 2004

By S. P. Pereira

The mechanized mining cycle using loaders and shuttle cars had its peak in terms of usage in the mining industry during 1950 through 1960. In Brazil, this system is still used at underground coal mines in southern Santa Catarina coal basin. With the aim of investigating the benefits of a new mining scheme using the room and pillar method for these local mines, a computational simulator model was developed in order to investigate the mining cycle. This paper presents the methodology used to develop the simulator and the results that the simulation shows regarding impact of the proposed new scheme on mining productivity.

Jan 1, 2012

By J. Levin

Bond's Standard Work Index (SWi) indicates the grindability of an ore, and his Operating Work Index (OWI) indicates the performance of a grinding mil or circuit. The comparison of the two indices offers a measure of the efficiency of the grinding operation. Mil (or circuit) performance, particularly on the Witwatersrand, is often indicated by the index kilowatt -hours per tonne of minus 75 µm material produced (kWh/t minus 75µm or OE75)' The paper shows that a standard kWh/t minus 75 µm index (SE75) can be obtained from the standard Bond grindability test (which provides the SWi), and asks whether the two E75 indices can be used in the various ways in which the two Work Indices are used. For the answer, the paper presents averaged values for the standard grindability indices of the gold ores of the Witwatersrand, averaged values for the performance of grinding mils operating on those ores, and the results of laboratory grinding tests on a composite of several Witwatersrand ores. The particle-size indicator for the calculation of the Wi indices, the am size, is constant in its relation to the largest particles present, whereas the percentage minus 75 µm, the indicator of size for the E75 index, varies with the degree of grinding in its relation to the size of the largest particles. Because of this difference, the standard Work Index increases as the grind becomes finer, whereas the standard kWh/t minus 75 µ value decreases. The Wi and E75 indices nevertheless serve similar purposes when applied to moderately fine grinding-finer than 70 per cent minus 75 µm. Open circuit laboratory grinding tests revealed three stages in the grinding process, and credible values for the open circuit Work Index were obtained only from the second stage. The conversion of the open circuit Work Indices to the equivalent of close circuit indices by the application of Bonds open circuit inefficiency factor (a constant for grinds indicated by the d80 size) was of limited success; however, the development of a conversion factor related to particle-size should not be difficult. Initially difficulty was experienced in the calculation of the 0E75 indices from the results of the laboratory tests, but it was eventually considered that a constant value of the index derived from the results would be close to the true open-circuit index. The open-circuit grinding test could there fore be a convenient method for the detection of differences in the grindability of ores.

Jan 1, 1992

By F. Yang, T. Pan, T. Zhao, Z. Shao, D. Zuo

In this paper, the development and applications of robot technique is summarized, and the status and developing direction of China coal mine robotics. A description of the research meaning, frame and key technology of underground salvage robot is given. Keywords: coal mine, robot, special robot, salvage robot.

Jan 1, 2003

By H. Wagner

During the last few years a large number of pillars in different mines were investigated. Pillar conditions were evaluated using subjective, empirical, geophysical and numerical methods. A critical comparison of the different methods showed some interesting coherence. This paper concentrates on experiences using the p-wave velocities as an indicator of pillar conditions. Während den letzten Jahren wurde eine große Anzahl von Bergfesten in verschiedenen Bergwerken auf ihren Zustand hin untersucht. Hierzu wurden subjektive, empirische, geophysikalische sowie numerische Methoden angewandt. Dieser Vortrag beschäftigt sich mit den Erfahrungen beim Einsatz der p-Wellengeschwindigkeit zur Beschreibung des Festenzustandes. Le condition géotechnique d’une grand nombre des piliers des mines souterraines différentes sont examinées ces dernières années. On a appliqué des méthodes subjectives, empiriques, géophysiques et numériques. Ce rapport occupe aux expériences avec l’application de la vélocité des ondes de compression pour tracer le condition des piliers.

Jan 1, 2003

By J. Preussner, U. Glatzel, R. Völkl, S. Prins, M. Wenderoth

Platinum base alloys are very corrosion resistant and have got a high melting point. Similar to Ni-base superalloys, which are used for jet turbines, the hardening effect of the intermetallic L12Pt3Al phase is used to receive a material that is creep resistant at high temperatures. Chromium is added to the alloy system to stabilize the L12phase down to room temperature. With the right amount of nickel the misfit and shape of the precipitates can be controlled. Various alloy compositions have been melted and analysed. With scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) a microstructure can be observed, which is very similar to the one in Ni-base superalloys. To support alloy development with simulations, a thermodynamic database of the Pt-Al-Cr-Ni system is about to be established. The SEM and EDS measurements provide useful input to the thermodynamic optimization. Also many data from the literature have been used to receive the best approximation. The Cr-Pt binary phase diagram has been reassessed and the latest results of thermodynamic modelling are presented.

Jan 1, 2006

By S. Achilleoudes

This paper describes the various factors that contribute to the maximum design pressures acting on box fronts and how these factors influence the mass and economy of box front steelwork. The influence of material density, rock size and moisture content on the incidence of hang ups and mud rushes in the rock pass is also highlighted. The loads acting on any box front are a function of several different parameters. These include natural, operational and excavational parameters. A case study analysis was carried out using UG2 ore and a typical box front structure to demonstrate the relationship between the mass of the box front and the material pressures resulting from variations in the above parameters. Based on the results of this case study, the required design mass of a side mounted box front for a rock pass containing platinumUG2 increases in (close to) linear proportion to % overbreak and is also linearly proportional to the pressure on the face of the box front beyond saturated conditions. The mass of the box front structure also doubles with a 100%increase in over-break which emphasises that a box hole excavation that is as neat as possible will yield a lighter and more econimical box front structure.

Jan 1, 2005

By J. C. Jansen

The platinum mining industry has experienced a significant increase in fatal accidents. Mine accidents are in principle preventable, and there is enormous pressure on employers to reverse this trend. This paper reviews safety management systems (SMS) as well as behaviour-based safety (BBS). Based on the review, SWOT analyses are performed on the SMS and BBS processes and a model of an integrated safety management system (ISMS) is introduced. A number of fatal accidents is analysed to identify factors that contributed to accidents in the mining industry. Thereafter the potential weaknesses of an SMS of a platinum mine are exposed and the potential benefits of implementing the ISMS for this case study are demonstrated.

Jan 1, 2005

By J. Xiao, Y. Jiang, Y. Tanabashi, Z. Song

Modelling the effect of blasting-caused damage, anisotropy of rock masses and excavation sequence on deformational behaviour and stability of large-scale underground caverns is important in the design and information-oriented construction of the pumped storage power plant. A powerful three-dimensional numerical method that can be applied for that purpose is presented in this paper. Damaged range caused by blasting and mechanical properties of rock masses near to the walls of caverns are determined by using the back analysis approach in which three lines of the measurement results during the arch part excavation process were used to verified the simulations. Finally, applying the improved model and properties of rocks, the cavern stability and reinforcement effect of the preliminarily designed support system are also estimated for the safety in the bench excavation process. La création de modèles des effets relatifs aux dommages résultant des explosions, à l’anisotropie des masses rocheuses et à la séquence d’excavation quant au comportement à la déformation et à la stabilité des cavernes souterraines de grandes dimensions est une étape importante dans l’étude et la construction sur ordinateur de centrales hydrauliques à accumulation par pompage. Cet article traite d’une méthode numérique tri-dimensionnelle puissante applicable à cet effet. La gravité des dommages résultant des explosions et les propriétés mécaniques des roches à proximité des parois de la caverne sont déterminées par une analyse du fond dans laquelle les simulations sont vérifiées à l’aide de trois lignes de résultats de mesures prises durant le processus d’excavation de la partie arche. Finalement, la stabilité de la caverne et les effets du renforcement du système de support préalablement conçu sont estimés par application du modèle amélioré et des propriétés de la roche, pour application à la sécurité durant le processus d’excavation en gradins. Nachahmung der Wirkungen von durch Explosionen hervorgerufenen Schäden, Anisotropie der Gesteinsmassen und der Ausschachtungssequenz auf das Verformungsverhalten und die Stabilität großräumiger Untergrundhöhlen ist für das Design und den informationsorientierten Bau von Pumpenkraftwerken wichtig. Entsprechend der Vorgaben in dieser Arbeit kann ein leistungsfähiges, dreidimensionales numerisches Verfahren für diesen Zweck eingesetzt werden. Der durch Explosionen und die mechanischen Eigenschaften des Gesteins bedingte Schadensumfang im Bereich der Höhlenwände kann mit Hilfe eines retroversen Analyseansatzes bestimmt werden, bei dem die drei bei der Ausschachtung resultierenden Messlinien dazu genutzt wurden, die Simulationen zu bestätigen. Abschließend wurde außerdem durch Einsatz verbesserter Modelle und Gesteinseigenschaften die Auswirkungen vorläufig entworfener Unterstützungssystem auf die Höhlenstabilität und Verstärkungswirkungen hinsichtlich der Sicherheit bei Böschungsausschachtung abgeschätzt.

Jan 1, 2003

By R. Romano

Some topics, which difficult the effective use of RMR for dam foundations, are reviewed and a new geomechanics classification system, DMR (Dam Mass Rating), is proposed -as an adaptation of RMR- giving guidelines for several practical aspects in dam engineering and appraisal of dam foundation. On revise quelques problems qui ont fait difficile l’application du RMR pour les fondations des barrages. On propose un nouveau classification système, DMR (Dam Mass Rating)-comme un désarroi du RMR-qui donne recommendations pour quelques problèmes pratiques dans le projet et construction des barrages, et de ses fondations. Es werden einige die praxisgerechte Nutzung des RMR (Rock mass Rating) erschwerende Themen betrachtet und ein neues Geomechanisches Einteilungssystem, das DMR (Dam Mass Rating), eine Anpassung des RMR, vorgeschlagen. Daraus resultieren neue Richtlinien für verschiedene praktische Aspekte beim Dammbau und bei der Beurteilung von Dammunterbauten

Jan 1, 2003

By Y. G. Zhu, G. B. Zheng, X. X. Hu

Reverse flotation by cationic collectors is the classical method to reduce the silicon content in magnesite. But because of the low selectivity, there is a large loss of magnesite in the reverse flotation froth. To improve the efficiency of the collector, a novel collector named BK433 was developed in this paper. In order to determine the performance of the BK433 collector, a systematic experimental study was carried out with a high silicon magnesite in China. The suitable pH environment of slurry was confirmed, the depression effect of different depressants was investigated, and the flotation effect was compared with commonly used traditional collectors. The results show that the BK433 shows remarkable good selectivity and collection ability. After the 4 stages reverse flotation, the SiO2 content decreased from 3.76% to 0.25%, SiO2 impurity removal rate reached 94.69%. Meanwhile, the MgO content increased from 45.06% to 46.73%，the recovery of obtained concentrate (calculated by MgO) was 82.79%. Keywords: Magnesite, Desilicication, Reverse flotation, Collector

Jan 1, 2020

By Wynand Erasmus, Terry A. Jones

The Kelsey Centrifugal Jig (KCJ) utilizes the application of centrifugal force (and the resultant enhanced gravitational field) to conventional jigging technology principles to successfully process materials where the valuable constituent particulates are very fine and/or where there is a small specific gravity differential between these and the gangue minerals. The KCJ has been successfully employed in mineral sands applications in Australia for approximately 12 years. More recently, the KCJ has been tested and installed on zircon tailings dump retreatment projects in Australia and the USA, while being considered for similar projects in RSA, and is about to be installed in zircon tailings processing duties in India and Africa and in a tin removal duty in a rutile circuit in Australia. Extensive test work has been carried out on these applications and some typical performance data is presented in this paper. Information is also provided on the principles of operation of the KCJ and on the keys to a successful KCJ installation.

By Garry M. Johnston, Matthew L. Sutcliffe, Nicholas J. Welham

"The predominant current processes for the treatment of oxidized copper–cobalt ores use a reductive acid leach to bring the desired metals into solution. However, the indiscriminate nature of acid leaching results in a solution, akin to a metal soup, containing not only the Cu and Co but also an extensive suite of other metals. These other metals, notably Fe, Mn, Al, Ca, Mg and Si, all have to be eliminated from solution before the copper and cobalt can be recovered. Generally precipitation processes are used, but these tend to result in significant losses of copper and/or more usually cobalt from solution, leading to reduced recoveries. The AmmLeach® process uses ammonia-based chemistry to selectively leach the target metals, leaving the rest behind in the leach residue. This approach eliminates any need to clean the solution of unwanted metals and the consequent metal losses. After solid–liquid separation, the leach solution is immediately subjected to separation and concentration of the copper and cobalt using solvent extraction and electrowinning. INTRODUCTION The Copper Belt extends through the northern part of Zambia and the southern province of Katanga in the Democratic Republic of Congo (DRC) and contains the richest and highest grade deposits of copper and cobalt remaining in the world. Whilst there are a number of mines that produce sulphide concentrates, using froth flotation, the largest deposits are those where near-surface sulphides have been weathered over time to form oxides. The oxides cannot be concentrated by conventional physical means to give high recoveries. Despite this, a number of dense medium separation plants have been installed and used to produce a higher grade concentrate which is typically exported (while the rejects, typically 2 to 3% Cu are stockpiled for treatment at a later date). These plants generally have low recoveries and can only be used on the dwindling supply of high grade materials. In exporting the concentrate, little value adding is undertaken within the country, thus greatly reducing the economic benefits to the country. Recent changes to the regulations in the DRC will effectively ban the export of low value ores, concentrates and intermediates in favour of high value metals. This will necessitate mines to install new processing circuits in order to comply with these regulations. The head grade of ores currently being treated in the DRC is slowly decreasing as the extremely high grade materials are being selectively mined out. In many cases, the removal of a small volume of high grade materials leaves a much larger volume of economically marginal ore behind. This is due to a desire for short-term profits overtaking long-term prosperity. The remaining ore, which in many cases is still of relatively high value by world class standards, is likely to be only treatable by low cost heap leaching. There are some initial trials of heap leaching within the DRC, but implementation at a large scale has yet to be adopted."

Jan 1, 2015

By V. Yahorava

Resin-in-pulp (RIP) technology has recently often been considered for the direct recovery of base metals and uranium from dense pulps. Implementation of RIP will eliminate the requirement for any solid-liquid separation downstream of leaching and has the potential to combine the recovery and purification steps, hence reducing both capital and operating costs. The recovery of the valuable metal is expected to be higher when RIP is used, especially where the leached solids are difficult to settle or filter, and to wash. The main concerns about the use of RIP for uranium recovery from dense pulps are the impact of silica on the resin?s metallurgical performance and the operating costs that would be associated with resin loss. Although a number of resin manufacturers have been developing much improved RIP-grade resins, it is critical that the most cost-effective resin be selected. Mintek currently is doing a significant amount of work on silica fouling of RIP-grade strong-base resins in acidic leach liquors and the effect it has on the performance of the resin, including its durability. This paper describes the results of the test work done on silica fouling and its impact on plant design input data. Resin durability test work was done using various laboratory techniques, but durability was also evaluated on a relatively large scale using actual pumps, screens, and mechanical agitation. Based on the results generated, a preliminary economical evaluation was done to estimate the impact of resin loss on the overall economic viability of a specific application. Keywords: resin-in-pulp, silica fouling, resin loss, equilibrium, kinetics, elution, durability, mechanical strength, resistance to attrition.

Jan 1, 2009

By H. T. Ozkahraman

It is important to know the breakage mechanism in materials since this knowledge influences the results of subsequent grinding operations. There are two distinct failure mechanisms in breakage: one is tensile micro crack generation at low stresses, which leads to macroscopic failure by disintegration, and the other is formation of shear zones under heavier dynamic impact forces, which generates more fines as seen in crush zones in blasting. Tensile fracturing simply breaks the material into fragments. It is seen as the disintegration of the specimen into two or more separate fragments. This happens under the absence of lateral stresses and the material is free to expand. On the other hand, compressive-shear breakage produces finer fragments due to shear stresses. The first mechanism is observed in laboratory tensile and bending strength tests and the second mechanism is observed both in laboratory brittleness tests and in situ blasting operations under dynamic impact forces. The friability of rocks and ores can be determined by a brittleness test. A test apparatus to determine the friability value has been designed to suit limestone strength characteristics used in cement production. The friability and stored strain energy values of barite, marble, limestone and bauxite have been determined and compared with the corresponding Bond work index (Wi) and grindability index (G) of these materials. The physico-mechanical properties of the tested materials have also been determined to investigate their effect on friability and grinding. The relationships obtained between the indices were in surprisingly good agreement, with high correlations (0.99 and 0.97). The Bond work index and grindability index can therefore be estimated from the friability value, which can be determined more rapidly than the Bond test. But for certain rock types such as andesites the relationships does not hold. Key words: comminution, tensile stress, shear forces, brittleness test, strain energy.

Jan 1, 2010