Search Documents

By D. K. Chibwe, P. Taskinen

"Typical operation of industrial Peirce-Smith converters (PSCs) used in copper smelting results in several common phenomena such as excessive splashing, slopping, tuyere blockage, and low converter campaign life due to high tuyere line refractory erosion. These phenomena give rise to an inefficient operation from both a process and an energy perspective.This investigation presents numerical and physical models of flow patterns, mixing, solid-liquid mass transfer, and slag-matte phase distribution in a slice model of an industrial PSC. For physical simulations, a 0.2-scale cold model was developed. Water, kerosene, air, and sintered benzoic acid compacts were used to simulate matte, slag, injected gas, and solid additions into the PSC. The two- and three-dimensional numerical simulations of the three-phase system were carried out using volume of fluid (VOF) and realizable k- e (RKE) turbulence models to account for the multiphase and turbulence nature of the flow respectively. These models were implemented using the commercial computational fluid dynamics numerical code FLUENT.Both numerical and physical simulations were able to predict, in agreement, the mixing and dispersion characteristics of the system in relation to various blowing conditions employed in the investigation. Measurement of mass transfer characteristics conclusively indicated that fluid flow in the PSC is stratified. Both blowing configuration and volume of slag in the converters were found to have significant effects on mixing propagation, wave formation, and splashing.The splashing and wave motion in these converters are known to cause losses of metal/matte and potential production time due to the requirement for intermittent cleaning of the converter mouth, resulting in reduced process throughput. To prevent these losses and hence to increase process efficiency, we propose a combined blowing configuration using top lance and lateral nozzles. The numerical simulations were conducted on combined, as well as lateral, blowing conditions. In comparison, the recent results of the combined blowing concept were found to be encouraging."

Jan 1, 2014

THE THIRD INTERNATIONAL GEOCHEMICAL EXPLORATION SYMPOSIUM (Summary Account) This Symposium, co-sponsored by the Canadian Institute of Mining and Metallurgy and the Society of Economic Geologists, was held in Toronto, Canada in April, 1970. Over 700 delegates attended from 26 countries. Ninety papers were presented at the symposium and another 18 papers were read by title. The programme included: An Opening Session, Five General Sessions, a session on Remote Sensing Methods, a session on Geochemical Prospecting for Petroleum and Natural Gas, a session on Primary Halos and Lithogeochemical Methods, and a session on Statistics and Evaluation of Geochemical Data. The delegates were welcomed by Dr J. M. Harrison, President of the Canadian Institute of Mining and Metallurgy and Dr C. H. Smith, Regional Vice-President, North America of the Society of Economic Geologists. Dr D. R. Derry of Toronto delivered the opening address to the Symposium entitled 'Geochemistry-the link between ore genesis and exploration'. Dr Derry considered the various hypotheses on the origin of economic mineral deposits and expressed his belief that the next ten years will show evidence of an increased proportion of ore bodies that owe their origin, at some stage in time, to supergene agencies. He stressed that 'there are no sharp divisions between processes that form and destroy ore bodies at or near surface and those that form or destroy them at a depth of 20 kilometres in the earth's crust. The more we understand about the migration and concentration of metals the more accurately we can apply this knowledge to searching for unknown concentrations, whether at rock surface or at depth. To learn more about these processes of ore genesis we must rely on geochemical studies co-ordinated with field observations'. The five general sessions included accounts of progress in geochemical prospecting in different countries of the world, case histories describing the application of soil, stream sediment, geobotanical and biogeochemical techniques, papers on the behaviour of different elements under varied environmental conditions, discussions on analytical methods and the use of stable isotopes in mineral exploration. It is anticipated that the proceedings of the Symposium will be published late in 1970 or early in 1971 as a Special Volume of The Canadian Institute of Mining and Metallurgy. All registrants at the Symposium will receive a copy of this publication and copies will be available for purchase. At a special meeting called during the Symposium, charter members of the Association of Exploration Geochemists approved a constitution and elected an interim Council which will organize procedure and formulate policy during the coming year. The interim president of the Association is J. Alan Coope, Newmont Mining Corporation of Canada Limited, Toronto, Canada. More information on the constitution and membership in the Association will be distributed to learned societies and technical magazines in the near future. Membership will be open to exploration geochemists in all countries of the world. SOUTH AFRICAN COUNCIL FOR PROFESSIONAL ENGINEERS Report on Registration The Professional Engineers Act (Act 81 of 1968) came into force on the 14th February, 1969. At the time it was recognised that the success of the Act would depend in large measure on the extent to which engineers in South Africa would become registered professional engineers in terms of the provisions of the Act. The promulgation of the Act and its provisions relevant to registration were the subject of considerable publicity during 1969. This has resulted in a rate of application for registration far beyond the capacity of the very active committees set up for this purpose by the South African Council for Professional Engineers (SACPE). To give some idea of the task before these committees and before SACPE itself, which must ratify each case,

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

Proceedings of a General Meeting held at the Witbank Golf Club at 19h30 on 3rd November, 1977 Geomechanics colloquy The 27th Geomechanics Colloquy is to be held on 12th and 13th October, 1978, in the Salzburg Congress Hall. The themes of the four half-day sessions will be as follows: Conference on pneumoconiosis The Vth International Conference on Pneumoconiosis is to be held in Caracas (Venezuela) from 29th October to 3rd November, 1978.

Jan 1, 1978

By R. G. B. Pickering

Successful management of mining operations depend on the accurate and reliable measurement of performance as a monitoring instrument in a feedback and control loop. However, when changes are being considered, the probable effect of the change on bottom line results requires different measuring techniques incorporating an in depth understanding which can identify hot spots in the operation which exhibit strong sensitivity to change. The CSIR's Division of Mining Technology has therefore been devoting a considerable effort to the establishment of techniques which enable changes to be analysed in terms of their impact on the two key parameters describing mine performance, i.e. profitability and safety. This paper describes these techniques, outlines their application to some example situations and discusses planned enhancements. The first section of the paper addresses the profitability model, and this is followed by a section considering the mine safety model.

Jan 1, 1996

By F. Nakhaei, M. Le Roux, Q. P. Campbell, S. Botlhoko

The results of coal sink and float tests are plotted as washability curves. Analysis of these curves indicates the most effective method by which the coal can be cleaned. Sink and float experiments are samplingdependent, destructive, and use toxic chemicals. The present research introduces an alternative method based on a 3D imaging system called RhoVol, in which the density of individual particles is determined from mass and volume measurements. A quantitative error analysis was conducted on coal sample density measurements obtained by RhoVol, and the main factors influencing the errors identified and investigated. The results show that the drawback of this technique is related to its not being able to detect hidden concavities in the particle, resulting in an overestimation of particle volume. Furthermore, it is difficult to capture the impact of porosity and cracks on the volume of coal particles obtained from 3D silhouette images. This mismatch between the RhoVol data and sink and float test results has led to attempts to apply neural network (NN) and linear regression techniques to produce a fully reliable model for correction and estimation of coal density. The NN approach offers superior predictive capability over linear regression, and the estimated density distribution is in line with the sink and float analysis. The root mean square error in estimation of density using the NN model was less than 0.05 g/cm³.

Aug 2, 2022

By N. Naudé, J. de Villiers, C. P. Bergmann

It is proposed that the physical and chemical composition of individual mineral particles are an appropriate basis from which to model the performance of minerals processing equipment. Such a particle-based approach enables modelling across disciplines such as comminution, classification and flotation and automatically generates the traditional mass and chemistry balances. The general approach followed is to generate full grade-recovery curves for a separator by sampling product and tailings at varying mass yields. AutoSEM characterisation of each sample provides particle data that is used to reconcile mineral deportment and liberation to the measured size and assay data. In this way, partition surfaces can be generated and modelled. In this paper, an empirical model for the performance of a gravity spiral concentrator treating fine chromite ore is proposed. The model is based on the combination of two partition surfaces and is able to accommodate both forward and reverse gravity concentration effects per size fraction. The results show that this approach is well suited to represent spiral performance for the cases evaluated. The effect of two feed particle size distributions on the performance of the Multotec SC21 and SC25 spirals is demonstrated. Simulations are run in an Excel environment, linked to Python-enabled routines for enhanced data management and calculation speed. Keywords: Spiral concentrator, gravity separation, particle-based modelling

Jan 1, 2020

By C. S. Kucukkargoz, A. Bhalla

"The solid-state reduction of ilmenite concentrate with graphite was studied under argon atmosphere at temperatures between 1050°C and 1350°C. The rate of reduction increased with increasing temperature and decreasing particle size, with the maximum extent of reduction found to be 80% at 1350oC with a particle size in the range of -106 +90 µm. The activation energy for the reduction reaction was calculated to be 257 kJ/mole. The trivalent iron oxide was reduced first to divalent iron oxide and then to metallic iron. An annular ring of a partially reduced oxide phase containing metallic nuclei was formed around the core of ilmenite, which grew in size as the original ilmenite core shrank with progressive reduction. The reduction of titanium dioxide also took place during this stage, which produced the Magneli oxides in the form of TinO2n-1. The metallic phase had very high Fe and low Ti contents throughout the reduction, whereas the partially reduced oxide phase adjacent to the metallic phase was high in Ti and depleted in Fe. The metallic phase globules formed during this stage were small and are considered suitable only for leaching and not for other concentration processes. The core of the particle generally retained the composition of the original ilmenite. The purpose of this work was to remove iron and increase the titanium oxide content of the ilmenite to produce a high-titanium containing charge for subsequent smelting.IntroductionThe titanium-bearing minerals ilmenite (FeTiO3) and rutile (TiO2) are the primary natural raw materials used in industry to produce titanium metal and titanium-based products. The common titanium-bearing minerals are ilmenite, rutile, anatase, brookite, leucoxene, arizonite, and perovskite. Although the formula of ilmenite is commonly expressed as FeTiO3, the mineral can accommodate Mn and Mg, which are chemically bound in the form of (Fe,Mn,Mg)TiO3. Ilmenite concentrate can also contain Fe2O3 and Al2O3 in addition to the physically separable oxides such as SiO2 and CaO. The crystal structure of ilmenite is an ordered derivative of the corundum structure with a trigonal-rhombohedral symmetry. Fe2+ and Ti4+ ions occupy the octahedral sites, leaving the tetrahedral sites unoccupied. In each FeTiO3 unit, there are three O2- ions creating three octahedral sites, two of which are occupied by Fe2+ and Ti4+ (Wilson et al., 2005)."

Jan 1, 2017

By R. G. Diale, H. R. Chauke, T. M. Ledwaba, P. E. Ngoepe

FeCo alloys play an important role in soft magnetic materials with a wide range of technological applications due to their high saturation magnetization and Curie temperature. However, these alloys have low ductility at room temperature. The ductility can be improved by the ternary addition of elements such as V. A density functional theory supercell approach was used to generate B2 Fe50Co50-xVx (0 ≤ x ≤ 50) structures and the properties were evaluated at different atomic percentage compositions to determine the ductility at room temperature. The structures were fully optimized to obtain better equilibrium ground-state properties such as lattice parameters and thermodynamic properties for both binary and ternary systems. The stability of Fe50Co50- xVx was evaluated from the heats of formation, elastic properties, and phonon dispersion curves. Furthermore, magnetic strength was evaluated from magnetic moments. It was found that all structures are thermodynamically stable due to the negative heats of formation. The calculated Pugh’s ratio and Poisson’s ratio confirm that alloying with V effectively improved the ductility. It was also found that Fe50Co50-xVx showed a positive shear modulus for the entire concentration range investigated, in agreement with phonon dispersion curves. The ternary addition of V to the FeCo system resulted in reduced magnetic strength due to a decrease in magnetic moments. These findings reveal that B2 FeCo-V alloys can be used as components and actuators for the automotive industry.

Jun 10, 2024

By P. M. Solozhenkin, O. I. Solozhenkin

Currently lead nitrate is used as the recommended activator in Au-Sb flotation. However, due to high levels of hazard, the application of lead nitrate constitutes a potential risk for human health and ecosystems. To mitigate the harmful impact of activators on the environment, further research on activation by alternative reagents has been launched to promote the efficiency of antimony ores. In the present study, adsorption of lead, copper and zinc cations has been investigated by nuclear quadrupole resonance (NQR), which has revealed copper and zinc cations penetration into the mineral lattice, although lead cations remain adsorbed on the mineral surface. However, the combination of zinc and copper cations leads to preferential volumetric adsorption of zinc in the mineral lattice and further surface adsorption of copper which positively affects the activation process. It has been established that activation of stibnite can be achieved effectively with the mixture of Cu2+:Zn2+=1:1 as much as with lead cations in antimony ore flotation. As a part of this work, the computational modelling has been used in prognosis of reagent activity evaluation (PRAE) for stibnite and aurostibite flotation by sulfhydryl collectors. The lower PRAE value the stronger the ability of a collector to form a stable complex with a mineral. PRAE has shown a strong negative trend to complex formation on the mineral surface of aurostibite and stibnite. Based on these studies, several collectors have been proposed for effective flotation. To verify the feasibility of proposed collectors tetramethyl (ethyl) thiuram disulfides (TMTD and TETD) have been used for flotation of stibnite, sphalerite, pyrite and arsenopyrite. Flotation performance has been improved significantly with TMTD that allows the avoidance of lead nitrate application and increases the recovery of antimony by 8,16%. Keywords: Stibnite, aurostibite, activation, lead, copper, flotation reagents

Jan 1, 2020

By A. A. Rogozhin, S. I. Anufrieva, A. V. Kurkov

The results of development of technologies for flotation concentration of two types of complex beryllium ores are presented: beryllium-fluorite in apocarbonate metasomatites (Type I) and rare-earthberyllium in feldspar metasomatites (Type II). The researched samples of Type I ores contain a mineral complex that is difficult to separate by fatty acid flotation, including phenakite, bertrandite, fluorite, and carbonate minerals. The ores are characterised by an increased content of fluorite and carbonates. The sample of Type II ore contains such rare-earth minerals as bastnesite and orthite, and a beryllium mineral - cleiophane. The size of individualised grains of cleiophane does not exceed 0.04 mm, which significantly limits the possibility of extracting the mineral into the enrichment concentrates. For the Type I ores, a technological process for the extraction of fluorite using a phosphorus-containing reagent from the class of dialkylphenyl polyethylene glycol esters of phosphoric acid (DAPEGEPhA) has been developed. The use of DAPEGEPhA enables the production of a high-grade fluorite concentrate (95% CaF2). The production of commodity phenakite-bertrandite high-grade (10% BeO) flotation concentrate from the fluorite flotation tailings with using a fatty acid collector is based on binding calcium in the flotation pulp using soda, sodium hydroxide and sodium tripolyphosphate. The use of a combined collector based on fatty acids and DAPEGEPhA made it possible to produce a collective rare-earthberyllium- lithium concentrate with high REE extraction (88%) from the Type II ores. The concentrates obtained are suitable for production of commercial-grade hydrometallurgy products. Keywords: Beryllium ores, flotation, reagents, concentrates, hydrometallurgy products

Jan 1, 2020

By J. Petersen, K. Shaik

The traditional route utilised for the recovery of Platinum Group Minerals (PGMs) in South Africa involves the concentration of ore by flotation, followed by smelting to produce a PGM rich matte, which is then digested hydrometallurgically to solubilise base metals and Platinum Group Elements (PGE). HCl/Cl2 is conventionally used for PGE dissolution from concentrated material, which is an aggressive reagent associated with high maintenance costs as well as environmental concerns. Of interest is the leaching of PGMs directly from mineral ores, low grade concentrates and tailings in a cyanide-ferricyanide system as a more sustainable alternative. This system has shown favourable Pt recoveries among the Pt minerals, but with sperrylite (PtAs2) displaying highly refractory behaviour. The dissolution of sperrylite is investigated in a cyanide-ferricyanide system in the context of an electrochemical study involving OCP, chrono-amperometry and cyclic voltammetry. This approach allows the assessment of leaching characteristics as well as the investigation of surface passivation, which is believed to contribute to poor Pt recoveries. Some evidence is presented that such passivation is related to the formation of arsenide species on the mineral surface. Keywords: Sperrylite, PGMs, cyanide, ferricyanide, electrochemistry

Jan 1, 2020

By S. Fuchida, Y. O. Zubair, C. Tokoro

Mining of As-bearing minerals had resulted in the release of arsenic species predominantly As(III), which is known to be more toxic, and undue exposure to it is detrimental to human organ systems. Many materials have been examined for As(III) removal, but it is still challenging to advance sustainable materials for effective removal of As(III). In this paper, a more eco-friendly and superparamagnetic Fe0-Fe3O4 composite was synthesised and evaluated for heterogeneous catalytic oxidation and removal of As(III) with peroxymonosulfate (PMS, KHSO5). The kinetic removal studies showed that removal of As(III) was probably through a chemical process and the Elovich model best represented the experimental data. The removal capacity for As(III) on Fe0-Fe3O4 with PMS (1.76 mmol/g) is superior to that without PMS (0.83 mmol/g). Combined results from XPS and ESR showed that As(III) was fully transformed to As(V) through catalytic oxidation by Fe0-Fe3O4/PMS and afterwards enhanced its removal. The removal mechanism of arsenic was ascribed to the formation of outer-sphere (electrostatic attraction) and inner-sphere complexes. The adsorbent can be separated easily from water due to its excellent magnetisation (64.5 emu/g) and also has good reusability potential as more than 85% of the initial concentration of As(III) was immobilised after five consecutive cycles. Keywords: Arsenite, Fe0-Fe3O4 composite, catalytic oxidation, removal mechanism

Jan 1, 2020

By M. G. Maruma, L. A. Mampuru

"Mill liner wear is a major cost item in the mining industry and there is continuous research to prolong the life of the liners. Over the years it has become apparent that even though high-chromium white cast irons are highly efficient as abrasion-resistant materials, a combination of wear resistance and fracture strength remains difficult to achieve. Increasing the hardness of the high-chrome white cast iron (HCWCI), which improves the resistance to abrasion wear, is often accompanied by a deterioration in fracture strength. Operational conditions inside the mill require that the liner should be made of highly wear-resistant material with some fracture strength. Vanadium additions ranging from 0.2 to 3 wt% were made to HCWCI in an attempt to refine the microstructure. It was found that an increase in vanadium content promotes grain refinement. A content of 1.5-3 wt% gave the best results as measured by the maximum breaking strength.IntroductionOver the years it has become apparent that even though high-chromium white cast irons are highly efficient abrasion-resistant material, a combination of excellent wear resistance and fracture strength remains difficult to achieve. The exceptional wear resistance of highchromium white cast iron (HCWCI) is attributed to hard chromium carbides embedded in an austenitic/martensitic/pearlitic matrix. When the chromium contents exceed 12 wt%, interconnected MC3-type carbides of conventional cast irons are replaced by rodshaped and isolated M7C3 carbides (Powell, 1980), leading to an improvement in the impact toughness, ductility and fatigue resistance. However, the main M7C3 carbides in HCWCI are hard and brittle and can provide an easy path for crack propagation. This limits the applications of HCWCI, particularly in severe impact conditions. Most operations involving HCWCI are in crushing and grinding and the life of a part/liner is limited by its wear resistance. However, improving the wear resistance of HWCI comes at the cost of a significant reduction in fracture strength. Concerns about premature failure of HCWCI mill liners in the mining industries prompted a study to improve the wear resistance and mechanical properties of HCWCI."

Jan 1, 2016

By D. Marcotte, R. V. Dutaut

In most exploration or mining grade data-sets, the presence of outliers or extreme values represents a significant challenge to mineral resource estimators. The most common practice is to cap the extreme values at a predefined level. A new capping approach is presented that uses QA/QC coarse duplicate data correlation to predict the real data coefficient of variation (i.e., error-free CV). The cap grade is determined such that the capped data has a CV equal to the predicted CV. The robustness of the approach with regard to original core assay length decisions, departure from lognormality, and capping before or after compositing is assessed using simulated data-sets. Real case studies of gold and nickel deposits are used to compare the proposed approach to the methods most widely used in industry. The new approach is simple and objective. It provides a cap grade that is determined automatically, based on predicted CV, and takes into account the quality of the assay procedure as determined by coarse duplicates correlation.

May 1, 2021

By G. L. Dyer, R. D. Alorro, R. E. Browner

A potential new rare earth extraction process has been suggested (Lazo, et al., 2017) (Lazo, et al., 2018) based on converting the rare earth elements to solid phase rare earth oxalates in an oxalic acid leach. Oxalic acid consumption is a significant issue in the process, therefore to improve the viability of this proposed new extraction method, a process to recover oxalate from the leach solution and recycle oxalic acid is required. A review of the literature and confirmation through thermodynamic analysis of the potential options identified precipitation of calcium or ferrous oxalate as the best potential options. The use of metallic iron to both provide ferrous ions as a precipitant and reduce ferric ions in solution would provide the most economical option, however slow kinetics and unreacted iron created significant issues with this process. The direct use of ferrous ions, while faster and more efficient, produced a precipitate with relatively poor solid/liquid handling characteristics and would require an intermediate stage utilising calcium in regenerating the oxalate. Utilising calcium chloride and oxide created very similar precipitates with better physical properties than the ferrous oxalate and that a reasonable proportion of the oxalate could be recovered before neutralisation of the solution induced precipitation of other phases such as iron oxy-hydroxides and calcium phosphate. The produced calcium oxalate was easily converted to oxalic acid and gypsum via immersion in sulphuric acid. It was also found that there is a significant loss of oxalic acid due to factors other than rare earth oxalate precipitation during leaching. This leads to a maximum oxalate recovery in the range of 50 %.

Jan 1, 2020

By A. Golder, S. P. Dandapat, I. Roy

One of the consequences of large-scale opencast mining for coal is the disposal of an enormous volume of overburden material that needs to be removed. With the enlargement of opencast mines and associated high stripping ratios, the volume of overburden extraction is rising. Overburden from the initial mine cut has to be necessarily dumped outside the mining area until enough void is created inside the mine for back-filling operations. The quantity of overburden placed outside the mining area normally varies from 10% to 30% of the total overburden removal. The stability of these dumps placed outside the mining area is of prime importance from the point of view of smooth operations of the mines and safety of persons in and around the dumping area. Owing to increasing pressure on land use, mine operators do not have any other option other than to place the waste dumps very near to the surface edge of the pit, which may lead to failure of the topsoil benches of the working pit. This study identified major controlling parameters that influence a stable but economic combination of height and slope angle of external dumps located close to the edge of an open coal pit.

Nov 27, 2024

By K. Barani, F. Moradpouri, M. Godarzi

A sampling campaign carried out on the lead flotation circuit at Lakan lead-zinc processing plant demonstrated that the Pb recovery was only about 68-69%. Characterization of the Pb flotation tailing showed that 61.4% of the Pb is in the –37 μm size fraction, which is difficult to recover by flotation. Batch flotation experiments were carried out on a plant sample of the lead flotation feed and high-intensity conditioning (HIC) was used to improve flotation recovery. The results showed that increasing the collector conditioning time from 1 to 3 minutes significantly increases the Pb recovery from 42.5% to 57.3%. Further increases in conditioning time to 5 to 7 minutes decreased the Pb recovery. With a collector conditioning time of more than 3 minutes, due to the surface cleaning effect, increasing collector and frother dosage improved the flotation selectivity and recovery, even at higher collector dosages. The Pb recovery increased from 69.1% to 79.8% with increasing impeller speed from 600 to 1250 r/min. HIC increases the flotation kinetics and greatly improves the flotation recovery and concentrate grade.

Apr 2, 2022

By G. van Aswegen

The geometry and morphology of a set of low-angle fractures around a stope in a deep Witwatersrand gold mine are explained in terms of extension fractures forming under variable conditions of stress. Primary extension fractures (E1) form some distance ahead of an advancing stope along the s1, s2 plane. With stope advance, a couple of these fractures end up in a stress regime conducive to transpressional shear and a secondary set of extension fractures(E2) is formed at a high angle to the primary fractures. i.e. at a low angle to the stope. As the E2 fractures are undermined, they migrate into a stress regime of transtensional shear and a third set of extension fractures (E3) may develop between E2 fractures. These have sigmoidal shapes, being parallel to the E2 fractures at the E2 discontinuity where s3 is negative, and curved through the unfractured rock between E2 fractures where s3 is positive at the instant of fracturing. The fractures all display fractographic features characteristic of dynamic extension failure with striae indicative of the direction of rupture propagation and the local, instantaneous orientation of s1.

Jan 1, 2012

By B. k. Kenzhaliyev, M. A. Naimanbayev, Zh. A. Baltabekova, N. G. Lokhova

In research various desorbents were used to desorb the following rare-earth metals from Purosorb 140 cation exchanger, i.e. ammonium chloride; ammonium sulfate; a mixture of nitric acid and ammonium nitrate; a mixture of hydrochloric acid and ammonium chloride; a mixture of sulfuric acid and ammonium sulfate. It was established that a solution containing 30 g/dm3 of H2SO4 + 300 g/dm3 of (NH4) 2SO4 is the most optimal desorbing solution to desorb REMs from macroporous Purosorb 140 cation exchanger impregnated with rare-earth metals from industrial dihydrate wet-process phosphoric acid. It was established that the residual REM content in the cation exchanger decreased from 0.89 to 0.10 wt. % with an increase in the ammonium sulfate concentration from 10 to 400 g/dm3. Technological desorption regimes for rare-earth metals from cation exchanger were developed. The optimal conditions were determined to desorb rare-earth metals from the Purosorb 140 cation exchanger, particularly temperature 25°C; L:S ratio = (0.8 ÷ 1.1):1; duration = 1.0-1.5 hours. Keywords: Rare elements, sorption, cation exchangers, wet-process phosphoric acid, desorption

Jan 1, 2020