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By Kal Sastry, Anshuman Prasad

This paper presents a population balance model (PBM) for describing the agglomeration process and select a suitable coalescence kernel that can simultaneously describe nucleation, layering and coalescence mechanisms. The PBM is solved numerically by making use of a size discretization procedure in order to simulate iron ore agglomeration in rotating drums where moist feed is added to preformed seeds. Subsequently, a comparison of computer simulation results with the previously published experimental data is provided. Finally, the paper discusses how the current approach can be further extended to the simulation of industrial iron ore agglomeration circuits operated in closed circuit.

Jan 1, 2003

By G. N. Jadhav

In India, bauxite deposits are concentrated in Central India, Western Ghats and Eastern Ghats. Bauxites from various regions in Gujarat were identified during the present investigations of geochemical mapping. Different types of Bauxites samples were collected from Kachchh, Jamnagar, Porbunder, Junagarh, Bhavnagar and Amreli areas of Gujarat state and were studied in detail for their geochemical signatures to plot the data on Geochemical map. Raw bauxites were characterized by using powder XRD, XRF, ICP and optical microscopy techniques (with the help of Model microscope having both transmitted and reflected light setups) and were later examined to grade their quality. Most of the bauxites from Kachchh region were of high-grade (gibbsitic) type; while those of Sourashtra region were of low-grade (lateritic / calcitic) types. Most of these bauxites were either of ferruginous/lateritic or of calcareous/calcitic types. Based on the mineralogical composition, such as gibbsite, hematite and/or goethite, Kaolinite and calcite minerals present in particular bauxites, the deposits were graded. Finally, the Geochemical mapping of Bauxites for Gujarat region was prepared and discussed.

Sep 1, 2012

By Hong Zhong, Shuai Wang, Xin Ma

"In this paper, we report a simple and effective process for producing a surfactant mixture of O-isopropyl-N-ethyl thionocarbamate (IPETC) and 4-(tert-butyl)benzyl mercaptan (BBSH). The composite collector was synthesized via one-pot reaction of sodium isopropyl xanthate, 4-tert-butylbenzylchloride and ethylamine using tert-butyl alcohol as solvent. The whole process for the synthesis of composite collector involves neither foul smelling reagents or intermediates, nor any by-products requires special treatment for disposal, and thus can be scaled up to an industrial level. The flotation response of chalcopyrite and pyrite independently with IPETC and BBSH collectors and with their mixture (the mole ratio of IPETC and BBSH is 1:1) was assessed. The microflotation results showed that the collecting ability of BBSH was slightly stronger than that of IPETC and that IPETC was more selective collector than BBSH against pyrite, and that the composite collector displayed a stronger collecting ability toward chalcopyrite than IPETC, and superior selectivity for chalcopyrite against pyrite than BBSH. The batch flotation results showed that composite collector exhibited better performance than IPETC and BBSH. It was demonstrated that the mixing of IPETC and BBSH would give rise to a synergistic effect significantly enhancing overall flotation performance. In addition, the adsorption mechanism of BBSH on the surface of chalcopyrite was conducted by adsorption test and infrared spectrum measurement, and the results showed that the interaction of BBSH on the chalcopyrite surface was dominated by the chemical adsorption, and the formation of a strong S-M bond plays a key role in the adsorption of mercaptans on minerals surfaces. The developed flotation reagents with special preparation method is the author’s original design, patented (patent of the People’s Republic of China) and have no analogues in the world of mineral processing. (Application number 201810100107.1, ""Alkyl thioether alcohol compounds, methods for their preparation and applications thereof "", China).1. INTRODUCTION Froth flotation is an essential method widely used in the mineral processing industry to selectively separate valuable minerals from gangues[1]. Worldwide, more than 109 tons of materials are treated annually by this method with the majority being metal sulfides and oxides[2]. Nowadays, the judicious utilization of complex sulfides to meet the ever-growing demand of mineral resources gains more attention, due to the gradual depletion of deposits with high grade, making imperative the development of new high-efficiency collectors and mixtures of collectors to process complex minerals. In comparison to individual collectors, the use of mixtures has several notable benefits including lower dosage requirements, improved selectivity, rates and recovery and an increase in the recovery of coarse particles[3-9]. Moreover, in terms of cost and environmental issues, using collector mixtures can reduce the total amount of agents used, thus reducing the overall effect on the environment and economic costs without affecting the flotation performance. Therefore, the search for high-efficiency mixtures of collectors is still interesting and relevant."

Jan 1, 2018

By L. A. Cisternas, R. I. Jeldres, C. Cruz, P. A. Robles

"Previous studies have shown that the floatability of chalcopyrite in seawater at highly alkaline conditions is significantly affected by the presence of clays. The reason is that the species of calcium and magnesium present in seawater under those conditions may act as a bridge between the surfaces of clay and chalcopyrite, generating massive aggregates that then depress. In this context, the objective of this work is to analyze the impact of pretreated seawater with low amount of calcium and magnesium ions on the recovery of a sulphide copper mineral with high kaolinite content as clay. The seawater pre-treatment is done by the addition of sodium hydroxide in a high carbon dioxide environment. The chemical reactions realized under these conditions lead to the formation and precipitation of calcium and magnesium species that are subsequently removed by vacuum filtration. The pre-treated seawater is then used in flotation tests at pH 11 for copper sulphide, where the mineral is synthetically prepared by mixtures of chalcopyrite, kaolinite, and quartz. When comparing the flotation results for different types of water, including seawater and pre-treated seawater, a significant effect is observed: as the seawater hardness decreases, which comprises the calcium and magnesium ions, the recovery of chalcopyrite is increased. However, the effect is markedly enhanced in the presence of kaolinite. Therefore, the results indicate that sodium hydroxide and carbon dioxide are able to remove different species of calcium and magnesium from seawater and could improve the chalcopyrite recovery with high kaolinite content. INTRODUCTIONIn many cases, mineral deposits are found in arid areas with little access to water resources. Water is a fundamental element to carry out the unit operations that achieved the separation of valuable minerals (especially in concentration operations). Seawater has acquired an interesting role in recent years (Cisternas and Moreno, 2014); in fact, it seems to be one of the few viable options to ensure the sustainability of the mining industry in arid zones. At present, there are numerous experiences of industries that use or have used this resource, either by submitting the seawater to a desalination treatment by reverse osmosis or by applying it directly, without desalting. The latter case may involve significant economic benefits (for example, by avoiding the investment of building a desalination plant) and in some cases some operational benefits. A positive aspect is that in general terms the foaming in the saline medium is much more efficient compared to fresh water (Quinn et al., 2014; Castro et al., 2010). Some reports show that the foaming doses required to achieve a certain quality of bubbles are remarkably reduced, reaching exceptional cases such as Xstrata's Raglan concentrator, where it did not even include foaming to carry out the operation. This fact is quite promising, considering that some researchers have stated that controlling the quality of bubbles and foam could float minerals through coarse particles. This would lead to multiple benefits, such as energy savings by avoiding excessive grinding and a lower presence of fine ore that causes major problems in water recovery operations by gravitation (such as thickening) and in tailings management. However, seawater also causes significant challenges in multiple operations (Jeldres et al., 2017, 2016; Castro et al., 2010), as for example in minerals with high clay content (Uribe et al., 2017). In fresh water, the presence of clays minerals in ores is already a major problem in the flotation stages since the operation becomes difficult to be controlled, and operators are commonly forced to increase the consumption of reagents because the collectors are deposited on the clays' surfaces reducing froth stability (Farrokhpay and Bradshaw, 2012). Sometimes the use of rheology-modifying reagents should also be incorporated since the pulps become more visc"

Jan 1, 2018

By A. N. Zagorodnyaya, T. N. Bukurov, Z. S. Abisheva, A. S. Sharipova

"This work presents the results of the development of a flowchart for the processing of copper production dusts resulting in the production of of lead sulphate, tribasic lead sulfate (TBLS), ammonium perrhenate, zinc, copper-cadmium cake.Dust having the following composition (wt. %): Pb 39.3, Zn 6.5, Cu 5.5, Stotal 10.8, As 1.05, SiO2 0.6, Cd 0.8, Bi 0.04, Ag 0.02, Re 0.03 was used in the work. Chemical and X-ray analyses indicated that lead, zinc and copper are generally present in dusts in the form of sulfates, various amounts of oxides, sulfides, silicates; sulfur (according to chemical analysis data) is present in the form of sulfates (~ 90%) and in the form of sulfides (~ 10%).Studies have been made on two-stage stripping of copper production dusts containing lead, zinc, copper, cadmium, rhenium in the form of various compounds, at first with soda solution, then with nitric acid solution. It has been indicated that the combination of the operations allows the recovery of 98% rhenium, 82% lead, 92% copper, and 96% zinc and cadmium each in the solution. Furthermore, at the stage of dust leaching with soda, 80% of rhenium and 0.01% of nonferrous metals each are recovered in the solution. Remaining quantities of all metals are recovered in nitric acid solution up to maximum values. Such behaviour of metals is caused by metal phase content in dusts and properties being formed during leaching of compounds. At the stage of dust leaching with soda solutions, carbonates with various compositions are formed due to the exchange reaction between nonferrous metal sulfates and sodium carbonate. The conversion of PbSO4 into PbCO3 is apparently occurs in the solid phase and the conversion of readily watersoluble zinc, copper, and cadmium sulfates into that of carbonate salts occurs in the liquid phase. Rhenium passes into solution due to the presence of rhenium greater quantity in dust in the form of readily soluble perrhenate. Some portion of the perrhenate is, probable, blocked by lead sulfate and liberated in the conversion of PbSO4 into PbCO3."

Jan 1, 2003

By Miguel Becerra, Daniel Jordán, Jorge Soto, Luis Torres

"Most SAG grinding operations currently use ball sizes between 5.5 and 6 inch maximum size. However, in most cases the use of this ball sizes hasn’t been justified by a phenomenological analysis of the real effect on the grinding process, but rather by trial and error. The analysis of the influence of ball sizes in SAG grinding hasn’t been developed in detail by considering the effect on process parameters inside the mill, grinding efficiency or internal classification. Historically a conventional grinding reference has been made on the empirical procedure developed by Azzaroni (1980). Further to Azzaroni’s methodology, Sepulveda (Sepúlveda, 2007) developed the SPEC methodology, incorporating the ball size effect on the grinding efficiency parameters using a population balance model included on Molycop tools spreadsheets.This paper demonstrates a detailed analysis at pilot scale of the ball size employed in SAG grinding and scaling that exists between the different levels. This analysis includes assessing the effect of balls sizes on parameters associated with grinding efficiency and its effect on the total fill level, product size distribution and specific energy consumption, among others. In a complementary way it develops a technical - economical evaluation from industrial data comparing two different ball sizes and its effect on the grinding process analysed integrally."

Jan 1, 2014

By Vishal Shukla, Ashok Kumar, Manas Ranjan, D. Chakraborty, Narayan Sharma

Jigging has a very important role in mineral processing Industry. Upgrading of Iron Ore by jigging has been an emerging trend. A detailed investigation is carried out to understand the influence of Jig feed granulometry and bed height during jigging operation. Noamundi jig plant data shows that variation in jig feed granulometry, feed quality and bed height are major contributors to fluctuation in jigging performance. At Noamundi the feed size (-10.0+0.5mm) fraction is used for fines jigging operation. To understand the effect of granulometrey on jig plant performance such as yield, separation efficiency and Fe recovery. In this context The performance of jigging was evaluated by daily average data from jig operation was used to study the influence of feed distribution on jigging performance .Coarser fraction (+6mm) has a positive influence , whereas fines fraction (-0.5mm) tends to lower performance . During Jigging rearrangements of Particles takes place due to an alternate expansion and compaction of Jig Bed .These particles are arranged by increasing density from top to bottom. During the particle stratification, Jig bed physically cut at desired horizontal particle density plant to separate the desired product. Investigation shows that optimum bed height is required at different Jig feed quality to achieve desired product quality, maximum separation efficiency and Fe recovery. This Paper will illustrate role of granulometry and Bed height control on Jigging plant performance.

Jan 1, 2014

By Grant C. Lukey, Jannie S. J. van Deventer

"The environmental effects of the mining and mineral industry include destruction of natural habitats, changes in river regimes and water tables, and other serious ecological impacts. In this century, it is likely that water will become a critical resource, and in most countries the mining industry competes for a share of this resource. The Kyoto Protocol may at first seem only relevant to the coal mining and power industry, however, it should not be forgotten that the mining and mineral industry is a significant consumer of power. Therefore the ratification of the Kyoto Protocol by most developed countries and the introduction of a carbon credit trading scheme will impact on the industry by potentially increased costs in utilities and waste discharges. It is clear therefore that the mining industry faces many challenges in the coming years. The mining industry?s commitment to sustainable development needs to continue to evolve, in order to meet these challenges effectively. With the advent of globalisation of the industry, it is now an opportune time for the industry to gain international agreement on how they want the industry to achieve sustainability in future years; such a progressive approach is necessary, otherwise government will force the industry to change, which may not necessarily be the best outcome for the industry.INTRODUCTIONThe Earth Summit in Rio de Janeiro in 1992 was an opportunity for world leaders to assemble and discuss strategies and initiatives that provide for further industrial growth without adverse effects on the environment. The World Summit on Sustainable Development held last year in Johannesburg, South Africa, was an opportunity to evaluate those initiatives implemented over the past 10 years, and to set a new and sustainable direction for the future. It is clear that industrial and technology development will continue at a rapid pace in order to serve the needs of a growing world population, but it is essential that the course of this development is well planned, well executed, and that it is sustainable. In reality, while government officials and politicians continue to debate policy and international protocols, the environment continues to suffer and the effects of climate change and global-warming become more real each day."

Jan 1, 2003

By M. Niinae

Electrokinetic soil remediation by electroosmosis and ionic migration is restricted to soluble sub-stances. At a higher pH, the soil particles sorb more heavy metals, such as cadmium, than at a lower pH and the precipitation reactions of heavy metals are promoted. Both mechanisms make heavy metals immobile, rendering clean up more difficult and electrokinetic extraction inefficient. There-fore, the acidification of soils is very important to increase the clean up efficiencies of heavy metals, such as cadmium by electrokinetic method from contaminated soils. In the present study, acidification of soils and cadmium transport are predicted with a numerical method in which electrical flow is coupled with hydraulic flow, and the sorption process in the soils is induced in the model. The effects of some factors such as electrode configuration, electric field strength and electrode spacing for saturated soils are investigated using this numerical model. The results obtained this study are summarized as follows: The two-dimensional electrode configurations containing cathode surrounded by three or more anodes rapidly acidify the soils and remove cadmium from soils compared with one-dimensional electrode configuration. However, two-dimensional electrode configurations develop spots of inactive electric field between cathodes. A larger electrode spacing increases the processing time required, and it was also found that a larger electric field strength reduced the processing time required.

Jan 1, 2014

By Marko Hilden

"A stochastic model of mineral texture is discussed and used to demonstrate that grain association within the intact texture has a significant effect on the liberation characteristics of breakage products. The majority of previous models have simulated texture and liberation of binary systems. This new model is able to simulate complex multi-component (multi-mineral) aggregate textures and their breakage products. Grain size distributions can be defined for each of several minerals. Mineral-mineral associations can be controlled by inserting mineral grains within grains of another mineral. Repeated Monte Carlo sampling of the aggregate is used and the liberation properties of the fragments are calculated. These are analysed to generate data in a similar form as reported by mineral liberation analysis systems, including density distributions, liberation distributions, and particle class distributions. Simulations results are presented where the model has been fitted to complex sulphide ores with four minerals. Comparison of the simulated particles and experimental data show that the model is able to reproduce similar particle class distributions as measured by QEMSCAN. The texture of real complex ores can be simulated and fitted to conventional mineral liberation analysis data. The model should provide a useful and practical means of modelling the effects of mineral texture on separation processes and in geometallurgical models."

Jan 1, 2014

By G. P. Karmakar, K. K. Chandan

"The drilling mud is an essential part of the drilling process, which plays a major role in keeping safe and efficient oil and gas well drilling. In the oil industry, bentonite clay dissolved in water produces the simplest type of drilling muds. Bentonite clay contains montmorillonite particles. These particles are dispersed uniformly in water and such dispersions are used in various industrial products like paints, ceramics, pesticides and drilling muds. The bentonite clay easily dissolves in water and increases the viscosity of the water, which is one of the most important properties of a drilling mud. Bentonite has the highest swelling capacity, which is responsible for building up of the viscosity of the clay-water system. The flocculation behavior of bentonite is one of the major concerns for the performance of the water-based drilling mud in the oil and gas well drilling process. The behavior of drilling mud greatly depends upon the quality and quantity of bentonite clay, as well as the additives that are used in their formulations. In this work, a comprehensive study has been carried out to find out the effect of added polyacrylamide (PAM) polymer, surfactant, pH and salt concentrations on the dispersion/ flocculation characteristics of bentonite clay-water system. It has been observed that the increase in PAM dosage reduces the residual turbidity and improves the settling rate of the bentonite particles. The flocculation rate has also been found to be better under higher pH conditions. The combined effect of salt concentration and PAM dosage improved the overall flocculation efficiency of the system.INTRODUCTIONIn the oil industry, bentonite clay dissolved in water produces simplest type of drilling muds. Bentonite clay containes montmorillonite particles. These particles are dispersed uniformly in water. Such dispersions are used in various industrial products like paints, ceramics, pesticides and drilling muds (Akther et al., 2007). The bentonite clay easily hydrates in water and increases the viscosity of the mud system (Razi et al., 2013; Meng et al., 2012). Bentonite clay in the drilling mud increases the viscosity which is one of the most important prop erties of a drilling mud. Bentonite has the highest swelling capacity, which is responsible for the building up viscosity of the clay-water system (Sonmez et al., 2013). The drilling mud is an essential part of the drilling process, which plays a major role in keeping a safe and efficient oil or gas well drilling (ASME, S. S. C., 2005). The flocculation behavior of bentonite is one of the major concerns for the performance of the water-based drilling mud in the oil or gas well drilling process. This behavior of drilling muds greatly depend upon the quality and quantity of bentonite clay, as well as the additives that are used in their formulations (Yu and Amanullah, 2005; Akther et al., 2007). Bentonite particles form aggregate under certain conditions including high temperature, and high concentration (Luckham and Rossi, 1999). If the quality of bentonite is not sufficient to accomplish intended viscosity of the muds, it is essential to add certain additives to increase the viscosity and prevent aggregation of the system (Razi et al., 2013). The anionic polymer bearing sample can build up inter-particle bonds between the polymer and clay particles. The addition of various additives like, polymers control the dispersion and enhance the viscosity of the mud by controlling the flocculation of montmorillonite particles in bentonite dispersion (Heller and Keren, 2002; Mahto and Sharma, 2004)."

Jan 1, 2018

By S. J. Ma

With the very effective depressant and collector developed by China Bluestar Lehigh Engineering Corp (hereinafter referred to as LEHIGH), satisfied results are obtained from laboratorial beneficiation tests on phosphate samples from Karatau, Republic of Kazakhstan by the direct flotation process. In this paper the effect of single factors on performance of flotation is studied and their applicable ranges are proposed. The final test results are described as follows: As the feed contains 23.20 % P2O5, and 3.96% MgO, a phosphate concentrate assaying 29.77%P2O5 and 1.54% MgO is produced, and the P2O5 recovery in concentrate is 88.28%. The beneficiation tests make it possible to simplify existing technology with fine grinding-desliming, followed by reverse & direct flotation system and consequently improve the concentrate grade and recovery for the future beneficiation plant

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 A. V. Rasskazova

"The oxidized and mixed ores are processed by heap leaching. Primary ores with high gold content are floated. In recent years mining of primary ores with the low gold content (up to 4 ppm) has increased. Extraction of gold from these ores by floatation is technologically ineffective. Gravity concentration is ineffective for fine gold particles because of their floatability. The research objective was assessment of the viability of processing gold-bearing ore with combined gravitational and hydrometallurgical methods and testing of recovery of metals from a gold-copper oxidized ore chloride-hypochlorite leaching solution. The advantage of chloride-hypochlorite lixiviant is the low cost of reagents which is produced by the electrochemical synthesis of NaCl solution with the addition of HCl. The adsorption of chlorine compounds by a mineral matrix and its ability to oxidize the refractory ore components and allows for the application of chloride-hypochlorite systems for gold recovery for both oxidized and primary ores. The complexity and problem in using a gold–chloride system is the strong adsorption of gold–chloride complexes onto mineral surfaces, such as goethite, quartz, and alumina. In preliminary testing, gold recovery from gravity circuit gold bearing concentrates processed by agitation leaching in chloride-hypochlorite solution, gold recovery has reached up 82% after 4 hours of leaching. Chloride-hypochlorite leaching of copper-gold oxidized ore with preliminary processing by sulfuric acid provided for 94 % gold recovery to solution. Understanding of ecological hazard of cyanides is the motive power of researches in the field of search non-cyanic chemistries to provide for technologically and economically effective solvents of gold. Soluble compounds of chlorine with a suitable oxidizer are one of the alternatives to cyanides. Basic researches of gold extraction by chloride-hypochlorite solution have shown high rates of gold recovery.INTRODUCTION Because of the continued and growing environmental concern for the use of cyanide for gold processing, interest for the use of non-cyanide lixiviants, especially with halides has renewed recently (Tran et al., 2001; Ferron et al., 2003; Bhaghalha, 2007). Leaching solutions based on halides (chloride, bromide and iodide) are viable alternative to cyanide (Kwang et al., 2008). The major disadvantage of the chlorine–chloride system is the high reactivity of chlorine in reaction with sulfide and gangue carbonate minerals. It is believed that only high grade materials may be treated by chlorine–chloride systems economically (Baghalha, 2007). Another important problem of the application of gold–chloride complex is that it tends to be rather unstable and may re-precipitate upon contact with a reductant, such as sulfidic minerals of ore. It is well known that Au(III)–chloride hydrolysis species are strongly adsorbed by goethite, quartz, and alumina (Machfsky et al., 1991). To minimize adsorption of gold–chloro complexes, it works best to minimize the adsorption time."

Jan 1, 2018

By Lucy van de Ruit, Megan Becker, Aubrey Mainza, Jenny Wiese

"UG2 chromitite ore is a complex, highly disseminated platinum ore from the Bushveld Complex in South Africa, with typical platinum group mineral (PGM) grain sizes below 15µm. The introduction of stirred mills to the platinum industry has enabled grinding to finer product sizes, which has improved liberation and recovery of the finely grained PGMs. However, reduction in particle size leads to an increase in chromite entrainment in the flotation concentrate, which has a negative impact on the subsequent smelting process. Factors such as particle size, froth structure, solids concentration and water recovery have all been identified as impacting entrainment, but whether particle shape also has a significant effect is unclear. The purpose of this study was to determine whether the recovery of chromite particles by entrainment during the flotation of UG2 ore is affected by particle morphology. A laboratory vertical stirred mill with inert ceramic media was used for grinding UG2 ore which was then floated in a batch flotation cell. Flotation feed and concentrate samples were analyzed using QEMSCAN to quantify the angularity and aspect ratio distributions of the particles. The stirred mill product was found to have relatively broad aspect ratio and angularity distributions, with the major mineral components (chromite and silicates) having very similar shape characteristics. Analysis of flotation feed and concentrate samples suggested that particle shape does not have a significant effect on chromite entrainment."

Jan 1, 2014

By Francis Pitard

"The optimization of metallurgical processes requires an in-depth understanding of the heterogeneity carried by any constituent of interest. It emphasizes that knowledge of the Theory of Sampling (TOS) is the necessary step to ensure that valuable and valid research programs, pilot plants, feasibility studies, plant design and plant operations have been set on solid foundations. Too many publications today are solely based on the properties of the sample, with no mention of how this sample relates to anything in the environment where it was collected. Unfortunately sampling is an error-generating process that leaves no apparent tracks of its shortcomings. Indeed, it is easier to track down analytical errors than sampling errors. Consequently, bad sampling practices plague the scientific community and the industry and are responsible for severe money losses, unsatisfactory science and processing, and sometimes litigation. A point-by-point strategy is presented addressing sampling problems in early stages of a project. Sampling system requirements for metallurgical accounting and process control are listed. The use of Chronostatistics is suggested to determine if sampling systems are performing satisfactorily and to identify the various types of process variability that may not be easily detected by a conventional inspection of available chronological data. This strategy will help engineering firms, manufacturers, managers and supervisors to provide, install, use and maintain key sampling systems located at very important points in a process. Equipped with the appropriate sampling and statistical tools it becomes easier to minimize reconciliation problems with the mine, with suppliers and with clients. Contrary to the beliefs of many people, good sampling systems are not expensive because in the long run they help to reduce hidden cost and better regulate plant productivity; they most certainly minimize the number of unnecessary meetings looking for solutions where there are none. The suggested strategy will help specialists to extract maximum information from the available data, as large investments and crucial decisions depend on it."

Jan 1, 2014

By S. F. Kaplan, A. S. Dolotov, V. N. Kovalev

"The proportion of refractory sulphide ores and concentrates in world gold mining industry is growing every year. Pressure oxidation of these materials (in autoclave) allows to oxidize gold hosting minerals. Traces of halides and pseudohalides present in the slurry liquids contribute to formation of complex gold compounds. Sorption-active carbon present in ores leads to irreversible adsorption of complex gold compounds and their loss. The objective of the research is to study gold extraction dependence on the concentration of chloride-, cyanide- and thiocyanate-ions in the slurry liquids during pressure oxidation. Double refractory flotation concentrate of the Bakyrchik deposit was used for the testwork. The research was planned on the basis of a full factorial experimental design with additional refining experiments. Ligand concentrations (0 – 1000 mg/l Cl-, 0 – 600 mg/l CN-, 0 – 1200 mg/l of SCN-), temperature (200 – 240 °?) and retention time (1 – 6 h) were used as variables of pressure oxidation process. It was determined that sulfide minerals oxidize much faster than ""organic"" carbon. Under the conditions of T = 240 ?C, t = 2 h, sulphide sulfur oxidation was 95.6%, while ""organic"" carbon oxidation was 46.1 %. Each of the examined ligands has a significant adverse impact on gold extraction. Analysis of the experimental data demonstrated that with a high degree of confidence (R2 = 0.883) gold extraction does not depend on the ligand type, but only on its concentration and the ""organic"" carbon oxidation degree. In case of complete oxidation of ""organic"" carbon, the presence of the ligand (L = Cl-, CNS-, CN-) in the liquids at a concentration of up to 20 millimole/L does not significantly affect gold extraction. The assumption that the main factor of preg-robbing in ???-CIL treatment of double refractory concentrates is the natural ""organic"" carbon sorption-active to gold has been confirmed. INTRODUCTION In recent decades, placer gold mining has been gradually declining and hardrock gold mining, including ""refractory"" gold mining, has been growing all over the world, as well as in the Russian Federation (http://www.miningworld.ru, 2015). One of the main reasons why gold ores are refractory is gold adsorption on natural carbonaceous materials (""organic carbon""). Only a few technologies are suitable for processing such ore concentrates (a significant amount of gold is contained in refractory hardrock ore both in Russia and worldwide) (Vorob'yev-Desyatovskiy N.V., Yepifanov A.V., 2014)."

Jan 1, 2018

High flotation of iron sulfide minerals at high pH values in copper ores is mainly due to the activation of these minerals by copper species dissolved from copper sulfide minerals during grinding. Several methods have been tested to reduce this copper activation during grinding and therefore to depress iron sulfide flotation. They include grinding the minerals at high pH values or with a less reactive medium such as high chrome, and addition of a thiol collector or copper complexant during grinding. The efficacy of these methods in the flotation of a copper ore was tested against more common methods of depression of iron sulfide flotation. The mechanism of iron sulfide depression in these methods was also investigated.

Jan 1, 2014

By Sydney Mantsho, Toni Streczynski, Manuel Gonzalez

"In 2013, the commissioning of the MillStar Stabilisation and FloatStar Stabilisation and Optimisation controllers were completed at the Cerro Bayo Silver (Ag) mine in Patagonia, Chile. The MillStar control system has stabilised the feed to the SAG mill as well as the density at the discharge end of the SAG mill and ball mill. The FloatStar Stabilisation and Optimisation controllers have successfully stabilised and optimised the flotation circuit to ensure consistent product quality within desired specifications.The mill feed is controlled utilising the MillStar Solids Feed controller. Additionally, the solids to liquid ratio into the SAG mill was controlled utilising the Mill Inlet Ratio controller in conjunction with the Solids Feed controller. The discharge end of the milling process is a highly interactive and complex system. The use of a Robust Nonlinear Model Predicative Controller (RNMPC) was ideally suited to control this section of the process. On the Cerro Bayo milling circuit, the RNMPC was used to control the mill discharge sump level and the primary cyclone feed density to produce a more consistent feed to the flotation circuit.Three levels of the FloatStar control system were installed, for flotation stability, concentrate flow stability as well as grade optimisation. The Level Stabiliser was used to stabilise the level control on 6 flotation banks. The Flow Optimiser was commissioned on the Rougher, Scavenger and Cleaner concentrate sumps to stabilise concentrate flow from the flotation cells. The Grade Recovery Optimiser was commissioned on the Roughers section. A number of instrumentation challenges were identified which limited the overall benefit derived from the system. Once these were addressed, the performance was optimised. The overall benefit provided by the system was observed in terms of the improvements in Ag recovery."

Jan 1, 2014

By Jaime Sepúlveda

"A broad diversity of critical operating conditions may influence, in very convoluted ways, the actual performance of any given mineral processing system, to the extent that it becomes nearly impossible to empirically determine the independent, decoupled impact of each condition. An effective approach to better understand the behaviour of such complex systems is via the extensive use of sufficiently detailed and reliable mathematical models, allowing the process analyst to explore and learn about the independent effect of all relevant operational conditions. Certainly, these tasks are greatly facilitated if the appropriate software tools - such as the Moly-Cop Tools software package - are readily available. Moly-Cop Tools 3.0 is a set of 63 easy-to-use EXCEL spreadsheets designed to help process engineers characterize and evaluate the operating efficiency of any given grinding circuit, following standardized methodologies and widely accepted evaluation criteria. Moly-Cop Tools 3.0 covers conventional and semiautogenous mills, crushers, HPGR’s, rod mills and vertimills, with the corresponding mass balance and parameter estimation routines; plus complementary spreadsheets regarding Bond’s Law calculations, grinding media selection and performance evaluations and other useful utility functions. As a relevant example of application, specifically focusing on semiautogenous grinding operations, the current publication describes how the models can help us learn and rationalise critical empirical observations such as the relationship between feed particle size and optimal ball filling, the role of the rocks as autogenous grinding media as well as the impact of feed size and discharge grate opening on the mill grinding capacity. Over the last 20 years, Moly-Cop Tools has gained wide acceptance around the mineral processing community in recognition to the quality of the mathematical models contained, their simplicity of application and ease of sharing of the calculations amongst all interested parties, since it is available free-of-charge with no restrictions to make as many copies as needed."

Jan 1, 2014