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By John Starkey

"The development of the Minnovex SAG Power Index (SPI) Test in Canada has created a new and accurate way to measure ore hardness in a SAG environment. Coupled with the standard Bond Ball Mill Work Index Test it is now possible to determine from these two relatively inexpensive laboratory tests, the amount of energy required to grind an ore from the primary crushed size to the desired liberation size. By testing multiple samples to discover where the hard and soft ore zones are located, the representative hardness distribution for the ore body can be determined and grinding equipment selected that is capable to meet production targets for all mining areas of the deposit.In the last century, it was deemed prudent to select up to 50-tonne samples of ore for Semi Autogenous Grinding (SAG) pilot plant tests and a second 5-tonne sample for metallurgical pilot plant work. The methods outlined in this paper show how the 50-tonne sample is no longer required for SAG design because it is better to measure the representative hardness distribution of the ore body than the hardness of a “chosen” representative sample. This is demonstrated to be true by the fact that the lower horizons of an ore zone cannot initially be accessed to recover 150mm pieces, and the bulk samples taken, rarely represent the desired design hardness of the ore. Median hardness will not yield a good result in most cases and a clear understanding of the location and extent of the hardest zones is imperative to achieve a truly successful grinding circuit design.This paper discusses two plants (Kubaka and Agnico Eagle) that have been designed using SPI and Bond with no pilot plant test backup. Both have been very successful in that they can grind design tonnage on the hardest ores in the mine. This guarantees that the mine’s profitability is protected in any mining sequence. It also allows the extra power to be converted to higher throughput on softer ores if additional cash flow is needed. The advantages from the owner’s point of view are dramatic. This procedure will be attractive as well when considering the costs for test work, and the samples for testing. Existing diamond drill core is normally used and this allows the inclusion of data from the deepest regions of the mine. In addition, it is also clear that the decision to use a crusher can now be made at the design stage of a project based on measured parameters and the estimated capital costs of alternative designs."

Jan 1, 2003

By S. M. Viduka

This paper presents a numerical investigation of solid separation in jigging device, which is a gravity separation method widely used in ore processing. Separation is recognized as being heavily dependent on fluid motion in the jig. This study explores the effects of the inlet time dependent velocity profile on jigging performance. Modelling of the liquid-solid system is performed through a combination of computational fluid dynamics (CFD) to simulate liquid flow and discrete element method (DEM) to resolve particle motion. The initial packing conditions consist of a binary-density particle system of 1130 particles each 1 cm in diameter. A variety of jigging profiles are implemented in jigging. The saw tooth pulsation profile is selected with three variations in both amplitude and frequency. The performance of each profile variant is compared in terms of solid flow patterns, separation kinetics, energy, and mean particle position. These quantitative comparisons demonstrate significant differences in the segregation rate, energy, and solid phenomena, helping find an alternative optimum operating setting for the system.

Sep 1, 2012

By Yang Xiao, Zhang Yimin, Bao Shenxu, Liu Chun

Stone coal is a unique vanadium-bearing resource in China. Many techniques, such as salt roasting-water leaching, blank roasting-acid leaching, direct acid leaching etc. have been developed for vanadium extraction from stone coal. The vanadium leaching rate can reach 74.9% for stone coal from Jiangxi, but only about 27% of vanadium is leached for Hubei ore by applying salt roasting-water leaching technique. This paper investigats the vanadium occurrence in stone coal by microscope observation and electron probe, and compares the minerals components of stone coal from Jiangxi and Hubei. Although most vanadium exist as an isomorphism by replacing Al(III) from dioctahedral structure in mica group minerals in stone coal from two regions, the free vanadium is remarkably abundant in Jiangxi stone coal than in Hubei stone coal, which results the fact that vandium is relatively readily extracted from former. Moreover, the content of calcite in Hubei stone coal is much higher than that in Jiangxi stone coal. Calcium can react with V2O5 to form water insoluble calcium vanadates during roasting and this may be the reasone why the water leaching rate of vanadium is low for Hubei ore. Acid leaching is more beneficial to the vanadium leaching but other extra methods, such as adding aid-leaching agent and/or increasing acid concentration is need for the ore where vanadium is embeded firmly. This study can effectively guide the selection of vanadium extraction techniques for stone coal from different regions.

Jan 1, 2014

By Darryel Boucher, Raymond Langlois, Neil Rowson, Kristian Waters

The Knelson Concentrator is a centrifugal gravity concentrator composed of a high speed rotating bowl into which a mineral slurry is fed. The rotational motion creates a centrifugal acceleration up to an equivalent of 200 G. Under this acceleration, particles enter fluidised riffles along the side of the bowl, with the fluidisation allowing for the substitution of dense material for less dense. The separation mechanism is not fully understood and questions remain on the optimal residence time, slurry feed parameters and bowl surface profile to achieve a better separation. The positron emission particle tracking (PEPT) technique has been applied to record the motion of a -1700+1180 µm particle of a quartz-gold matrix, labelled with 18F radioisotope while it undergoes concentration inside a 3" laboratory scale Knelson Concentrator (KC-MD3) operated at 60 G. The slurry used was composed of quartz and magnetite. Particle trajectories during the first stage of the concentration process where the heavier particles centrifuge through the increasingly dense slurry towards the riffles of the bowl are shown with respect to time. This work reveals new information on particle motion inside the Knelson Concentrator and the results will be used for validation of developed separation model as well as optimisation of a centrifugal concentrator’s performance.

Jan 1, 2014

By Charlene Gokhale

Geopolymerisation has emerged during the last few years as an industrial and ecological approach to construction and waste management. By utilizing waste materials and their reactive properties, it is now possible to create geopolymers systems that not only mechanically durable enough to be used as construction materials but are also potential stable immobilisation systems for toxic waste. Previous studies by Van Jaarsveld et al. (1997) and Van Jaarsveld et al. (1998) have reported on the numerous applications of geopolymers in the immobilisation of toxic metals. Research into the possible utilisation of geopolymers as an encapsulation media for organic waste has however been rare. This paper therefore provides an insight into the possible utilisation of geopolymers as a binder for hazardous organic materials.

Jan 1, 2003

By L. Pan

As an air bubble approaches a mineral surface, a thin liquid film (TLF) is formed in between. The excess pressure (p) in the film determines the kinetics of drainage, which is of critical importance in flotation. We have developed a new method of monitoring the kinetics for both stable and unstable wetting films and analyzed the results using the Reynolds lubrication theory. It has been found that initially a TLF is thinned by the Laplace pressure (pcur) due to changes in bubble curvature and subsequently by the disjoining pressure (?) created by the surface forces present in a wetting film. In the present work, we have derived an analytical expression for determining ? from the temporal and spatial profiles of TLFs on mineral surfaces. The results show that ? > 0 in a film formed on a hydrophilic surface and ? < 0 in a film formed on a surface hydrophobized by collector. Thus, the role of collector in flotation is to create a hydrophobic force and hence a negative disjoining present in wetting films. It is also found that smaller bubbles can create higher Laplace pressure, which helps the TLF drain faster.

Sep 1, 2012

By Ghislain Bournival, Seher Ata, Graeme J. Jameson

A common method to prevent bubbles from coalescing in a flotation cell is by the addition of surfactants, called frothers. The gas dispersion properties in a column were tested for solutions of 1-pentanol, tri(propylene glycol) methyl ether, and poly(propylene glycol) in the presence of sodium chloride. The dependency of surfactant on the gas holdup can be divided into regions. It seemed that for a sufficiently low concentration of surfactant, even a stronger surfactant could show a transition in gas holdup from constant/decreasing to increasing with concentration. This region, however, was not marked by a decrease in the average bubble size. In addition, PPG gave higher gas holdup values while averaging larger bubbles. On the other hand, sodium chloride mostly affected the gas holdup when the concentration was high enough to prevent bubble coalescence. Another parameter affecting the gas holdup was the superficial gas velocity. A linear dependency was found between the two under a bubbly flow regime. The current study showed that both surfactants and salt could slightly affect the influence of the superficial gas velocity on the gas holdup.

Jan 1, 2014

By D. J. Borrow, K. van Netten

"A fine coal tailings feed was selectively agglomerated using a concentrated water in oil emulsion binder consisting of 95% aqueous phase and 5% organic phase. The purpose of the study was to investigate a continuous system in plug flow, providing a rapid beneficiation technique with high selectivity and recovery. The development of the novel binder was undertaken in previous work in a batch system consisting of a high-speed blender. In this previous work, it was found that agglomeration could be achieved in 3 s, providing the binder was pre-dispersed. Furthermore, it was found that, depending on the feed, only ~1 wt% of oil was required to achieve agglomeration, some 10 times less than required in traditional oil agglomeration. In a more recent study, the technique was adapted into a continuous process. Due to the rapid speed of the process using the emulsion binder it was found that a simple flow constriction within a 1 inch pipe was sufficient to achieve the selective agglomeration observed in the batch system. In this previous study, a coal feed consisting of a flotation product was agglomerated at a superficial slurry velocity of 1.3 m/s using a partially closed ball valve as the flow constriction. In the current study, a feed consisting of fine coal tailings with an ash content of 50.1% was used to establish the influence of superficial slurry velocity on the agglomeration process. The superficial slurry velocity was varied between 1.3- 4.2 m/s, while maintaining a constant pressure drop of 100 kPa across the flow constriction. The flow constriction consisted of a partially closed ball valve. It was found that increasing the superficial slurry velocity across the flow constriction reduced the amount of organic liquid required to achieve agglomeration. Under the optimum conditions, a combustible recovery of 80.4% was achieved at a product ash content of 9.6%. This work demonstrates a valuable product can be rapidly produced from tailings material using the novel emulsion binder. INTRODUCTION A significant opportunity exists to recover fine coal from material that is currently classified as waste. This waste material, also called tailings, is currently considered not economic to process due to its high ash content, low solids concentration, and the fine size of the particles. Thus, for this opportunity to be realised, a process is required that is highly selective and has the ability to economically recover fine particles at high throughputs. The technique of oil agglomeration has previously been considered as a candidate for the recovery of fine coal, as it is highly selective and has no lower limit on the size of particle that can be recovered (Capes and Jonasson, 1989). However, the cost of the oil required as the binding agent in the process has proven to be a significant barrier to any long-term applications (Swanson, Nicol, and Bensley, 1977). Recently, however, Yoon and co-workers have developed an ultrafine coal separation process that utilizes an oil phase for the recovery of the hydrophobic coal particles and have implemented an oil recycle to greatly reduce the consumption and thus cost of the oil (Yoon et al., 2016)."

Jan 1, 2018

By Caibin Wu, Ali Lei, Ningning Liao, Jingsheng Ye

"The particle size distribution characteristics of ground product can influence the quality of the classification overflow and the next beneficiation indexes in an ore concentrator. Usually, the size distribution of ground product is considered to be determined by that of new ball mill feed. However, based on large amounts of data from industrial grinding circuit surveys, this paper has clearly shown that the size distribution of ground product should be determined by the size characteristics from classification underflow unless the circulating load was small, because the new feed is an important component and occupy a dominant position of mixed ore from belt feed and classification underflow. On the other hand, the correlation coefficient of the size distribution between ground product and classification underflow can be more than 0.99 when the relevance principle and its method are used. Meanwhile, their P80 value also keeps a synchronous correlation. The greater the capacity of classification underflow is, the higher the correlation of size distribution between the ground product and the mixed feed is. Furthermore, the correlation coefficient of the size distribution between ground product and classification overflow which is from primary or secondary can be 0.96. It is another discovery that the correlation coefficient is related to the type of classifier. The coefficient of size distribution of overflow and underflow from hydrocyclone is superior to that of spiral classifier, which can explain the reason why the hydrocyclone is widely used to replace the spiral classifier in concentrator.INTRODUCTION It is well knows that ball mill circuits closed with cyclones or spiral classifier such as a primary grinding circuit, a secondary grinding circuit and SAB mill have become an industry standard. Which grinding process employed will be determined by the P80 value of ground products. When the primary closed circuit ball mill or SAB that it is different throughout between the two processes was employed, a grinding fineness with -200mesh under 68% will be available. However, the secondary grinding circuit with the fineness of -200mesh above 80% can be conducted. Of course, the grinding fineness is determined by the grain size characteristics of the mineral."

Jan 1, 2018

By M. Kanuchová, J. Briancin, M. Achimovicová

"Faculty of Mining, Ecology, Process Control and Geotechnology, Technical University, Košice, Slovakia An industrial eccentric vibratory mill was used for direct and short-time mechanochemical reduction of ilmenite concentrate (FeTiO3) and anatase (TiO2) with magnesium metal powder in order to reduce Fe and Ti resp. and hereby to convert them to the more soluble phases suitable for further hydrometallurgical processing. X-ray diffraction analysis of FeTiO3 after 60 min of milling with Mg confirmed the presence of Fe0 and Mg2TiO4 phases and for TiO2 after 180 min of milling the new TiO and MgO phases have appeared. X-ray photoelectron spectroscopy has detected Fe0 (metal) and Mg2+ species which are corresponding to the product of FeTiO3 mechanochemical reduction. The product of TiO2 mechanochemical reduction has revealed XPS spectral lines corresponding to Ti2+, Ti4+ and Mg2+ species on its surface. Morphology of mechanochemically reduced samples was studied by scanning electron microscopy analysis. Subsequent leaching of mechanochemically reduced FeTiO3 and TiO2 was performed in dilute HCl and H2SO4 at 80oC and compared with mechanically activated samples. The recovery of Ti has reached 100% for FeTiO3 and 79% for TiO2 after 60 min of leaching. Based on this study the flowsheet for possible processing of natural refractory titanium ores patented by author was adapted and documented. INTRODUCTION Ilmenite (FeTiO3), along with rutile (TiO2) represents the most important titanium resource necessary for titanium industry, for production of titanium metal, alloys and pigment grade TiO2 which are becoming more important and versatile for various industries such as an aircraft and aerospace, navy, chemical, automotive, medical and offshore wind industries, for machine and plant engineering and architecture as well, mainly due to high corrosion resistance. Pigment grade TiO2 is utilizing in pigment, plastic, glass, paper and rubber industries (Zhang, 2011). There are obvious research efforts for development of the potential alternatives to the expensive thermo-chemical commercial processes of titanium raw materials processing. Zhang (2011) has summarized conventional thermo- a electrochemical processes which involved a combination of pyrometallurgical, hydrometallurgical and electrometallurgical technologies and highlighted the improved hydrometallurgical routes promising for commercial application in the future. Such improvement could also be mechanical activation of FeTiO3, TiO2 by high-energy milling which causes their structural disordering, the changes of physical and chemical properties, consequently and has a positive effect on the dissolution kinetics (Achimovicová et al., 2014a, 2017, Baláž, 2008). The various types of mills such as a planetary ball mill, a vertical ball mill, a drum mill, an attritor were used for mechanical activation of FeTiO3 as a pretreatment process for subsequent leaching (Achimovicová et al., 2014)."

Jan 1, 2018

By E. V. Zelinskaya

"Mineral and industrial raw material mining and preparation make a negative impact on the environment. The main types of impact are the land resources gathering, soil and water balance disturbance, surface-water, underground space and atmospheric air pollution, as well as the vast amount of solid and liquid waste production. Considerable attention in recent decades has been given to waste recycling. The task is to maximize the use of both newly formed and accumulated solid and liquid wastes. The mining and mining and smelting enterprises industrial waters are a very promising source of secondary hydromineralic raw materials. They have high concentrations of not only calcium, sodium, but also, for example, lithium, rubidium, heavy non-ferrous metals. In general, unfortunately, we have to state that today there is no wide practice of extracting valuable components from waste enrichment, as well as processing of man-made waters to extract metals from them. The quantity of extracted components from underground, and furthermore passing waters, is insignificant. At the same time there is a tendency to increased demand for rare metals: Sr, B, Br, I. This is explained by their wide use in many industries. For example, the consumption of lithium products is steadily increasing. The obtained results showed that in the liquid phase in connection with high salt content and a significant difference in the macro- and microcomponents contents, conditions are initially created for the microcomponents selective isolation possibility. The identified conditions realization is most possible in such technological processes as cryotechnology, sorption and ion flotation. There is an urgent need to expand research in this direction and to recognize as a publicly important task the mining and industrial waste processing full-scale introduction into the practice of operating mining and processing enterprises and iron and steel companies.INTRODUCTION Mineral and industrial raw material mining and preparation make a negative impact on the environment. The main types of impact are the land resources gathering, soil and water balance disturbance, surface-water, underground space and atmospheric air pollution, as well as the vast amount of solid and liquid waste production."

Jan 1, 2018

By Arun Appadurai

Pneumatic transport systems play a vital role in conveying discrete particles over a sizable distance with minimal energy consumption. However if such a system is not designed keeping particle physics in mind, it leads to intractable problems which could possibly assume dangerous proportions, including but not limited to expensive redesign of the entire system. This paper describes a novel method, which harnesses the powerful technique of Computational Fluid Dynamics (CFD) to investigate a problem occurring in rotary kilns using coal as a major fuel source. In some of the sites, a unique phenomenon of abnormally high CO emission was observed and owing to the highly random nature of occurrence, it was difficult to scientifically investigate the problem and its cause. Most of the published solutions for the high CO problem tend to concentrate on the incomplete combustion aspect of the kiln and resolve the situation by increasing the air supply thereby improving the stoichiometric ratio of combustion. This paper offers an alternate correlation that relates high CO emissions to the phenomenon of coal delivery fluctuations caused by the sub-standard operation of the coal transport system. A CFD model for the coal delivery pipe is validated by utilizing the actual process data sourced from the measurements taken from a functioning plant. The results of the model are used to derive correlative conditions that point to the unstable operating conditions of the coal delivery pipe prevalent in the industry. The conclusions are summarized into a series of recommendations for optimized design of coal delivery systems which are implemented in a pilot plant. The results irrevocably prove a statistically significant reduction in CO emissions without resorting to increased air supply and power consumption. Keywords:CFD, Pneumatic Conveying, Saltation Velocity, Particle Flow

Sep 1, 2012

By Kumar Ranjan, Kumari A. V. Asha, G. E. Sreedhar, Banerjee R. Raja, M. Narasimha, R. Shivakumar

In this paper, numerical simulation of magnetite, medium segregation and coal partitioning have been made in a 350 mm diameter cyclone. An attempt is made to assess the nature of impairment in efficiency in relation to the increasing amount of near gravity materials in coal. The CFD model approaches the Algebraic Mixture (ASM) model with the granular option and Reynolds stress model (RSM) to resolve the air core and turbulent mixing of the medium and coal particles. The partition characteristics of the DMC were modelled using both Lagrangian & Eulerian particle tracking for particles ranging in size from 0.5 to 8 mm and in density from 1200 to 2000 kg.m-3. Lagrangian frame work based Discrete Phase model used to simulate the coal particle trajectories inside the DMC and attempted to understand the residence time of different size and density coal particles. It was observed that coal particles having density near to separation-density (having fifty percent of probability to under flow and overflow) are exhibiting increased residence time than any density particles. As expected the smaller size coal particles shows higher residence time than the coarse coal particles. CFD simulations on effect of NGM mass fraction are simulated and analyzed using ASM model including for coal and magnetite. Coal particles with high NGM content show significant effect in misplacement of coal particles towards wrong products at all relative densities. The residence time of the particles increases because of its increased interaction with near dense particles. The effect of NGM fraction on overall cyclone performance as well as detailed flow assessment in terms of residence time distribution, NGM particle concentration profiles with respect to LZVV is presented.

Jan 1, 2018

By M. Blagojev, R. Tomanec

"Studies reported in this paper used polymetallic Pb-Zn-Sb-As-(Ag, Au) ore from Dražnja, Kosovo. The ore is comparatively rich in Zn (6.56%) and Pb (2.87%), but with high rates of Sb and As. Conventional lead and zinc concentration by flotation produced galena and sphalerite rich concentrate with high recovery, but with excessive As and Sb. After chemical analyses, which could not detect the reason for the excessive elements, ore minerals were identified under the ore microscope, their texture characterized, and degree of liberation of useful minerals was assessed. Microscopy of the mineral concentrates revealed complex intergrowths of galena and marmatite minerals mostly with sulphosalt minerals (boulangerite, jamesonite and bournonite) and also with arsenopyrite mainly responsible for the unsatisfactory quality of the concentrate. These complex sulphosalts, among other things have similar behaviour during the flotation concentration, and in spite of their interlocking with galena, therefore inadequate liberation, sulphosalts remain in the lead concentrate. Microscopic analyses indicated that a better galena concentration product is possible with a higher rate of mineral liberation, and then by selective floc flotation of some sulphosalt minerals. Purpose of this work was to show that only chemical analysis is not sufficient, according to that we solved the problem by precise mineral identification and time consuming mineral liberation measurements. INTRODUCTION The polymetallic Pb-Zn-Sb-As-(Ag, Au) ore body of Dražnja, Kosovo, fairly rich in Zn (6.56%) and Pb (2.87%) was repeatedly explored and once even worked. Mineralization at Draznja was primarily represented by sphalerite, galenite and marcasite/pirite. Some sections comprise massive sulphides, and others are lower grade zones of semi-massive sphalerite/galena or marcasite/pyrite dominant sulphides. The ore body II was formed in the southern gallery in the structure Çukë – Lajthishtë (with content of 3.16% Pb and 7.31% Zn). Pb-Zn ore with increased content of As, Sb sulphosalts is not rare phenomenon in the world. While previously treated as unprofitable, economical uninteresting ore, today with development processing and new reagents (organic, ecologic), are the topic of scientific papers. The examination of Pb-Zn ore with high content of sulphosalts we find in deposits as: The hydrothermal vein deposit of Harja in the Baia Mare area, contain a wide variety of sulphosalts [Cook, N. & Damian, G., 1997]; also the deposits Fankou Mine in Guangdong Province and the Dachang Mine in Guangxi Province, where the flotation concentration of galena and jamesonite takes place [Runqing Liu et al. 2015], [Zhang Ting, Qin Wen-Qing, 2015];. On a samples from Tibet in China flotation separation test of galena and jamesonite was conducted [Sun Wei, Han Haisheng, Tao Hongbiao, Liu Runqing, 2015]. According to history of investigation, the mineralized area of Dražnja has a long history of exploration and possible exploitation activities [Slowey, Galen, 2009]. Recent workings were carried out in three stages through the 20th century."

Jan 1, 2018

By Xinyang Xu, Chen Zhang, Lixia Li, Zhitao Yuan

"Density functional theory was employed to clarify the mechanisms of the activation of a quartz surface and its collection by the flotation method at the molecular level. The calculation results indicated that hydrogen bonds on the quartz surface (1 0 1) existed in pairs while in contact with water. The simulation was carried out to investigate the different effects of Ca2+ and Ca(OH)+ on a quartz surface with hydrogen bonds, and the results suggested that Ca(OH)+ most likely adsorbed onto and activated the quartz surface. Mulliken population analysis of the external oxygen atom of the quartz surface, calcium atom of Ca(OH)+, and the oxygen atom of oleate showed that there were electron transfer and the formation of a chemical bond between Ca1-O1 and Ca1-O3, which were indicative of strong interactions between the three atoms. In addition, the –OH of the Ca(OH)+ contributed to the activation, which suggested that the Ca(OH)+ group acted as a bridge between the surfaces of oleate and quartz.INTRODUCTIONFlotation is an effective separation method in mineral processing that takes advantage of the physicochemical differences between minerals and gangue, and the properties of the mineral surfaces play a key role in this process (Liu et al. 2016, Qin et al. 2017). In the reverse flotation process of iron ore, gangues are captured by cationic or anionic collectors and floated with air-bubbles as tailings, and the pre-depressed iron oxide minerals are left at the bottom as concentrates (Lima et al. 2013, Yianatos et al. 2015, Zhu et al. 2015). Quartz (SiO2) is one of the major gangues of hematite ores and cannot be easily removed. It is a naturally hydrophilic mineral, in which silicon is the cation in its crystal structure and has very limited solubility. Therefore, quartz must be activated, usually by metal ions, for its effective rejection as a float-product by reverse flotation (AIME. et al. 1976)."

Jan 1, 2018

By R. P. Bhagat

The paper reports results on sinterability of iron ores from the mines of Tata Steel Limited. The objective was to improve tumbler index (TI) of sinter and its reduction parameters, reduction degradation index (RDI) and reducibility (RI) while maintaining strand productivity same or to improve. Pot sintering experiments were carried out with Joda and Noamundi mines having LOI 3.8% and 2.9% respectively. Sinter basicity (CaO/SiO2) was varied in the 2.1 to 2.5 range and its MgO content was kept in the 1.4% to 1.8% range according to the blast furnace requirement. The ignition condition and vacuum was maintained according to the plant practice. The effect of variables namely, granulometric composition of ores vis-à-vis that of sinter mix, bed height, solid fuel, moisture content of green mix on the sintering indices was studied. The productivity with Noamundi ore (26 %+6.3 mm) was lower than that with Joda ore (45% +6.3 mm) at 4% coke in the mix and sinter basicity (CaO/SiO2) 2.1. However, with 4% coke (ash 22%) the RDI value was significantly high in case of Noamundi Ore, which decreased significantly to 29% with 5% coke. The size parameter of ore fines and its LOI content do influence the sintering speed and the sinter properties significantly. At 2.1 basicity ratio, the sinter with the Joda ore having coarsergranulometry had highest TI (=70.2%). The RDI (27%) in this case was inferior to that (23.2%) when Joda ores with finer size was sintered. Better RDI with finer sized ore could be attributed to better assimilation of CaO/ MgO with more balanced and uniformly distributed hematite minerals. The size parameter has been inter-influenced by the coke requirement. With the lower mean sized Joda ore the sinter RDI decreased significantly to 23% and the productivity improved to 42.9 T/(sq m*d) when the coke in the mix increased from 4% to 5%. An attempt to reduce the coke in the mix from 5% to 4% with respect to both the ores was not successful as it resulted higher RDI and lower strand productivity. The present study has revealed that sinter RDI improves (decreases) with decrease in the sintering time, while such correlation was absent between TI of sinter and speed of sintering. Corollary to this observation, one can take advantage of other stronger parameters to increase the sintering speed (and hence sinter productivity) without affecting the sinter strength. In the present study higher FeO sinters has displayed excellent RDI, however cold strength of sinter was not correlated with its FeO content. The TI and RI parameters of sinter improves marginally with increase in its MgO content while RDI got worsened. Keywords: LOI content, iron ore, reduction properties, sinter, noamundi, joda

Sep 1, 2012

By V. F. Petrov, E. P. Olberg, S. V. Petrov

"The study was carried out using process solutions produced during cyanidation of gold-bearing concentrates from a gold-processing plant. It was found that the water contained a significant portion of thiocyanate (7910.0 mg/L), cyanide was virtually not present. The metals occurred primarily as iron (355.0 mg/L) in the form of ferrocyanide. Cyanide recovery was conducted using an ozone treatment process with reactors developed by the Environmental Department of Irgiredmet. The process design ensured complete utilization (100%) of O3, thus equipment operation safety increased.The recovery of free cyanide from thiocyanate was 76.6%, which corresponded to 5.12 kg of NaCN (100%) per 1 m3 of solution. Recovered NaCN can be used for recycling in hydrometallurgical processes.The operating costs estimation showed that the production cost of a tonne of recovered cyanide was US$1288.7, considering the prices of energy and commercial sodium cyanide in Russia in 2017, i.e. recovered cyanide is cheaper than commercial cyanide by 55.8%.INTRODUCTION Depletion of oxidized gold-bearing ores readily amenable to cyanidation has shifted focus to large-scale processing of primary ores with high sulphide content. Primary ores processing flow sheets involve gravitational and/or flotation concentration with subsequent treatment of produced gold-bearing concentrates. Typically, concentrates reporting to cyanidation contain considerable amounts of sulphur that can interact with CN- and further formation of SCN-. The use of refractory gold liberation methods (bacterial liberation, ultra-fine grinding) provides activation of this side reaction up to complete consumption of free cyanide in a short period. This makes water recycling unviable and impractical.The interaction of the sulphur content in concentrates and cyanide contributes substantially to consumption of NaCN required for efficient gold recovery. Inappropriate consumption of the main reagent achieves dozens of kilogram per tonne of material to cyanidation, and reaches approximately 100% when gold is recovered from activated sulphide-containing products (e.g. by ultra-fine grinding)."

Jan 1, 2018

By L. E. Veki, S. M. Luukkanen, J. P. Karvonen, J. O. Leppinen

Today there is a consensus that xanthate adsorption on sulfide minerals is primarily controlled by redox reactions occurring at specific potentials on these semi-conductive minerals. Consequently, it is possible to control xanthate adsorption by controlling electrochemical conditions in the system by using oxidizing and reducing agents. The scope of this study was to investigate the possibilities to increase the selectivity of Cu-Fe-Zn ore flotation by applying electrochemical control in the conditioning of the flotation feed. In this work, mild steel grinding in a nitrogen atmosphere was used as the basis to provide a negative starting potential and minimize the amount of oxidation products on sulfide mineral surfaces. To study how different potential levels affect flotation results, a controlled conditioning procedure was utilized maintaining potential at a desired level by titrating the pulp with air. Xanthate adsorption kinetics during conditioning was examined by taking pulp samples for spectrophotometric analysis and laboratory flotation tests were conducted for samples that underwent the controlled conditioning procedure in the potential range of -200mV to +200mV vs. SHE. A clear correlation was detected between chalcopyrite recovery and the potential during controlled conditioning indicating that there was a constant increase in chalcopyrite recovery when the potential was shifted to more anodic values. It is possible that utilizing potential control in the conditioning stage, a smelter grade copper concentrate can be achieved directly in rougher flotation without cleaning stages. Conditioning in favorable conditions had significant positive effects on flotation selectivity of chalcopyrite. The improvement in copper concentrate grade being predominantly caused by the depression of pyrite. By applying the controlled conditioning procedure pyrite recovery in rougher flotation was reduced even low as under 1%, while in the tests without controlled conditioning, pyrite recovery varied between 7.5 – 65.7%. The result of this work indicate that affecting collector adsorption by electrochemical control in the conditioning stage can provide significant improvement in sulfide mineral flotation and industrial applications could lead to decreased chemical consumption, reduced equipment and maintenance costs.

Jan 1, 2018

By A. V. Neretin

This paper is a continuation and extention of the previous paper on energy-efficient placer mining methods which was presented in 2007 at the World Gold Conference in Cairns, Australia (Nere-tin, 2007a). The paper reports the results only on gravel processing as they were not fully discussed in the previous paper. It is common knowledge that placer gold mining requires processing of large tonnages of gold-bearing gravels by wash plants of different types. In Russia, gold-bearing gravels are mostly disintegrated and screened by the following types of wash plants: a water canon, a derocker or a scrubber trommel. Gold-bearing gravel processing is regarded as highly energy-intensive due to high energy consumption for transportation of large tonnage of material and high pressure water flow rate. The industries requiring a significant expenditure of energy normally estimate the process efficiency by energy consumption per product unit. In order to obtain quantitative data on energy consumption for gravel processing and to estimate placer mining costs, in 2003~2006 four placer gold mines located in the Irkutsk Region were thoroughly investigated through time and motion studies. At all these placer mines gravels were processed by a water canon, a derocker or a scrubber trommel. The objective of the study was to investigate the following parameters: ? wash plant throughput rate per hour; ? hourly diesel fuel and power consumption per cubic meter of gravel processed; ? volume per cent and shape of oversize material; ? different combinations of gravel processing methods. The results from this study were as follows: ? specific energy consumption per cubic metre of gravel processed for different combinations of gravel processing methods was estimated; ? a correlation between energy consumption and unit cost of gravel processing was determined; ? effect of yield and shape of oversize material on wash plant throughput rate per hour was de-fined; ? energy-efficient gravel processing methods were developed. Based on these results, an improved method of gold-bearing gravel processing was proposed. Implementation of this method at a placer mine saved US$ 123 000 in operating expenses only during a short-time Siberian placer mining season. At the same time, this method improved gravel disintegration, screening and processing operations used at the mine. Another advantage of the pro-posed method was higher gold recovery due to reduced yield of undersize material. In order to improve efficiency of gravel processing, a wash system including a derocker for primary gravel processing and a lightweight scrubber trommel was developed. There are two economic benefits of replacing water cannons with the proposed wash system. The first benefit includes lower operating costs for gravel processing due to lower specific energy consumption, while the second benefit is lower gold losses during slurrifying (disintegration and screening) and sluicing of the undersize material.

Jan 1, 2014

By Sashnee Raja, Mehdi Nemati, Ashley Sissing, Susan T. L. Harrison

"Extreme thermophiles, operating at 65 - 90°C, are finding increasing application in biohydrometallurgy These microorganisms have the advantage of exhibiting better oxidation kinetics in terms of reaction rate and extent of mineral solubilisation. These extreme thermophiles are Archae, characterised by a different cell envelope structure perceived to provide reduced structural strength in comparison to bacterial envelopes, and customised metabolic pathways.The active tank bioleaching process, used for high rate leaching, is conducted in a slurry bioreactor. Here sufficient energy dissipation is required to ensure suspension of the mineral phase as well as to sustain high rates of gas liquid mass transfer. It is well known that subjection to hydrodynamic stress of sufficient magnitude may alter the physiological state of a range of micro-organisms through changed viability (ability of the microbes to grow), metabolic activity and integrity.In this paper, we report on studies carried out to quantify the ability of the extreme thermophile Sulfolobus to withstand the hydrodynamic stress environment generated at high pulp densities in the slurry bioreactor. Both a pyrite system (as a model system) and a chalcopyrite system (as an application) were studied. In laboratory reactor systems, the nature of biological responses to stress induced at high pulp density have been identified in terms of ability of the microbes to grow, their metabolic activity and rate of leaching and cell integrity. Critical operating conditions within the laboratory reactor are identified and the mechanism mediating reduced performance considered."

Jan 1, 2003